Wetting wave front control for reduced air entrapment during wafer entry into electroplating bath

{WETTING WAVE FRONT CONTROL FOR REDUCED AIR ENTRAPMENT DURING WAFER ENTRY INTO ELECTROPLATING BATH}

This application is entitled, pursuant to 35 USC §119(e), to inventor Ranjan et al., U.S. Provisional Patent Application No. 61/487,207, filed May 17, 2011, "Wetting Wave Front Control for Reduced Air Entrapment during Wafer Entry into Electroplating Bath" Priority is claimed on the basis of, and the entire contents of the above U.S. Provisional Patent Application are incorporated herein by reference.

The present invention relates to electroplating. More specifically, disclosed herein is a method and apparatus for reducing air bubbles during dosing of a wafer into an electrolyte.

Electroplating has many applications. One important application is the plating of copper on semiconductor wafers to form conductive copper wires to "wiring" individual components of an integrated circuit. Often this electroplating process serves, for example, as a step in a damascene fabrication procedure.

A persistent problem with today's wafer electroplating processes is the quality of the deposited metal film. Assuming that metal wire widths reach deep sub-micron ranges and that damascene trenches often have very high aspect ratios, the electroplated film must be very uniform (chemically and physically). The electroplated film should have a uniform thickness across the face of the wafer and should have a consistent quality across multiple batches of wafers.

Some wafer processing devices are designed to provide the required uniformity. As one example, SABER from Novellus Systems, Inc. of San Jose, California.^TM available in electroplating tools, and the clamshell apparatus described in US Pat. Nos. 6,156,167, 6,159,354 and 6,139,712, which are incorporated herein by reference. Clamshell devices have many advantages in addition to high wafer throughput and uniformity (e.g., wafer backside protection from contamination during electroplating, wafer rotation during electroplating process, and relatively small footprint for wafer transfer to electroplating baths (vertical immersion baths)) provides

There are many factors that can affect the quality of the electroplating process. In the context of the present invention, particular attention is paid to problems arising in the process of immersing a wafer in an electroplating bath. During wafer immersion with a plating electrolyte, air bubbles may be trapped on the underside of the plating (active side or plating surface) of the wafer. This is especially true when the wafer is immersed in a horizontal orientation (parallel to the plane defined by the surface of the electrolyte) along a vertical immersion trajectory.

Air bubbles trapped on the plating surface of the wafer can cause many problems. The bubbles prevent areas of the plated surface of the wafer from being exposed to the electrolyte, thus creating unplated areas. Depending on when the bubble is captured on the wafer and how long the bubble stays trapped on the wafer, the final plating defect may appear as an unplated area or as an area with reduced plating thickness.

Another problem associated with vertical immersion of horizontally oriented wafers is the multiple wetting fronts. When the wafer is immersed in this manner, the electrolyte contacts the wafer at two or more points, creating a plurality of wetting fronts when the wafer is immersed in the electrolyte. Where the individual wetting fronts meet, air bubbles can be trapped. Also, defects in the finished plating layer may propagate from a fine non-wetting area formed along a convergence line of a plurality of wetting wires.

Therefore, there is a need to improve the quality of the plated metal. An improved method and apparatus should reduce problems that may arise from bubble formation and multiple wet fronts during wafer immersion.

The methods described herein reduce air entrapment due to initial impact of the wafer and/or wafer holder in such a way that the electrolytic wetting wavefront is maintained throughout the immersion of the wafer (i.e., transverse to the wafer plating surface) while also minimizing air entrapment. In order to ensure that the wafer is moved (in such a way that the wavefront does not collapse during propagation through the

One embodiment is a method of immersing a wafer with an electrolyte in a plating bath, the method comprising the steps of (a) horizontally positioning the wafer at a first height above the electrolyte (the flat plating surface of the wafer is the electrolyte (parallel to the plane defined by the surface), (b) tilting the wafer at an angle such that the planar plating surface of the wafer is no longer parallel to the plane defined by the surface of the electrolyte, and (c) the electrolyte during the entire immersion of the wafer. moving the wafer into the electrolyte such that a wetting wave front is maintained.

One embodiment is a method of immersing a wafer with an electrolyte in a plating bath, the method comprising the steps of (a) horizontally positioning the wafer at a first height above the electrolyte (a plane in which the flat plating surface of the wafer is defined as the surface of the electrolyte) parallel to), (b) tilting the wafer by an angle so that the flat plating surface of the wafer is no longer parallel to the plane defined by the surface of the electrolyte, (c) pointing the wafer towards the electrolyte, defined as the surface of the electrolyte moving at a first speed along a trajectory substantially perpendicular to the plane being , the leading edge of the wafer enters the electrolyte), (e) accelerating the wafer from the second speed to the third speed (acceleration continues until a substantial portion of the flat plate-like plating surface of the wafer is immersed in the electrolyte); (f) decelerating the wafer from the third speed to a stationary state at a second height (either at the third speed, or during deceleration from the third speed to a stationary state, the flat plating surface of the wafer is completely immersed in the electrolyte ) is included. These velocities will also be referred to as translational wafer velocities or Z-velocities.

The methods described herein include rotating the wafer along an axis that is perpendicular to the planar plating surface of the wafer and passes through the center of the wafer. In certain embodiments, until about 25% to about 75% of the planar plating surface of the wafer is immersed in the electrolyte, and in some embodiments until about 50% of the planar plating surface of the wafer is immersed in the electrolyte. The deceleration from the speed to the second speed continues. During acceleration to the first speed, or during deceleration from the first speed, or from the first speed to the second speed, the leading edge of the wafer may enter electrolyte. In one embodiment, during deceleration from the third speed to rest, the wafer is completely immersed in the electrolyte. In certain embodiments, the total time taken for immersion, i.e., less than 300 milliseconds from when the leading edge of the wafer enters the electrolyte until the wafer is completely immersed in the electrolyte, is less than 200 milliseconds in another embodiment.

In one embodiment, the total time taken for immersion, i.e., less than 300 milliseconds from when the leading edge of the wafer enters the electrolyte until the wafer is fully immersed in the electrolyte, in another embodiment, less than 200 milliseconds. am.

In one embodiment, the first speed is between about 120 mm/s and about 300 mm/s, for example between about 120 mm/s and 200 mm/s. In some embodiments, a high speed of about 200-300 mm/s is used. In one embodiment, the second speed is between about 40 mm/s and about 80 mm/s. In one embodiment, the third rate is lower than the first rate. In one embodiment, the third speed is between about 100 mm/s and about 140 mm/s. Still other aspects of the first rate, the second rate and the third rate are mentioned in more detail below. In one embodiment, the wafer is tilted at an angle of 5 degrees or less (0 degrees not included). Different rotational speeds can be used during immersion or during electroplating. In certain embodiments, a rotation speed of about 10 rpm to 180 rpm for 200 mm wafers, about 5 rpm to 180 rpm for 300 mm wafers, and about 5 rpm to 150 rpm for 450 mm wafers is used during immersion.

Another embodiment is a method of immersing a wafer with an electrolyte of a plating bath, the method comprising the steps of (a) horizontally positioning the wafer at a first height above the electrolyte (the flat plating surface of the wafer is defined as the surface of the electrolyte (b) tilting the wafer at an angle of about 1 degree to about 5 degrees such that the flat plating surface of the wafer is no longer parallel to the plane defined by the surface of the electrolyte; rotating the wafer along an axis perpendicular to the planar plating surface and passing through the center of the wafer, (d) moving the wafer towards the electrolyte along a trajectory substantially perpendicular to the plane defined by the surface of the electrolyte, about 120 mm/s moving the wafer to a first speed of from about 300 mm/s to (e) decelerating the wafer to a second speed of from about 40 mm/s to about 80 mm/s (at the first speed, or at the first speed); During deceleration from to the second speed, the leading edge of the wafer enters the electrolyte, during deceleration from the first speed to the second speed, from about 40% to about 60% of the plate-like plating surface is immersed), (f) from the second speed, from about 100 mm/s to about 140 mm/s accelerating the wafer to a 3 speed (acceleration continues until at least about 75% of the flat plate plated surface of the wafer is immersed in the electrolyte), (g) from the 3rd speed to rest at a second height decelerating to the furnace (at the third speed, or during deceleration from the third speed to stationary, the flat plating surface of the wafer is completely immersed in the electrolyte). In one embodiment, the deceleration from the first rate to the second rate is continued until about 50% of the flat plating surface of the wafer is immersed in the electrolyte.

In some embodiments, any of the methods described herein are combined with active angle entry. In active angle acquisition, the tilt angle of the wafer is varied during wafer immersion to further minimize entrapment of air bubbles. In one embodiment, the leading edge of the wafer is in contact with the electrolyte at a first angle, and then, when the wafer is immersed, the tilt angle increases to a larger, second tilt angle, after which the tilt angle is , usually decreases to 0 degrees (parallel to the electrolyte). During the first, second, or third Z-velocities, a change in the tilt angle may occur. In another embodiment of active tilt control, the change in tilt angle comprises a first angle to a smaller angle and then decreasing the tilt angle to 0 degrees.

In general, active tilt angle control may be desirable not only in combination with Z-speed fluctuations, but also when the Z-speed varies in a conventional manner (acceleration to a constant speed and then decelerating to a standstill). . In one aspect, a method of immersing a wafer comprises the steps of contacting a leading edge of the wafer with an electroplating solution while tilting the wafer at a first angle with respect to a horizontal plane, and increasing the tilt angle to a second angle; Finally, it involves reducing the tilt angle, usually 0 degrees. In some embodiments, the first tilt angle and the second tilt angle are about 1-5 degrees.

In one embodiment, a method of immersing a wafer with a plating solution includes contacting a leading edge of the wafer with a plating solution at a first translational velocity while tilting the wafer relative to a horizontal plane, immersing the wafer partially in the plating solution slowing the wafer down to a second translational speed while remaining thereafter, and then increasing the speed of the wafer to a third speed before the wafer is fully immersed in the plating solution.

In one embodiment, a method for wafer immersion includes immersing the wafer at a very high Z-speed. In one embodiment, a method of immersing a wafer with a plating solution comprises plating a leading edge of the wafer in a direction towards the plating solution, with the wafer tilted relative to a horizontal plane, and at a first translational velocity of at least about 120 mm/s contacting the solution. For example, in some embodiments, the first translational velocity is about 120 mm/s, 300 mm/s, such as about 140 mm/s-300 mm/s, and in some cases about 200 mm/s-300 mm/s.

All methods described herein can be used in the context of a photolithographic process that can be performed before or after electroplating. In one of the embodiments, any method described herein comprises applying photoresist to a wafer, exposing the photoresist to light, patterning the resist and transferring the pattern to the wafer, selectively removing the photoresist from the wafer. including the step of removing In some embodiments, the photoresist is applied and patterned prior to electroplating and removed after electroplating.

In another aspect, an electroplating apparatus is provided. The apparatus includes a wafer holder configured to tilt the wafer during immersion into the plating solution, a chamber for holding the plating solution, and a controller constructed or designed to perform any of the wafer immersion methods described herein. For example, the controller may include program instructions for performing the steps of the described method. In one embodiment, as the wafer enters the solution, the controller includes instructions to transfer the tilted wafer, in a direction towards the plating solution, at a rate of at least about 120 mm/s. In one embodiment, when the wafer is immersed in the plating solution, the controller includes instructions to transfer the tilted wafer at a variable speed in a direction towards the plating solution. In one embodiment, the controller is configured to: (i) command to horizontally position the wafer at a first height above the electrolyte, wherein the planar plating surface of the wafer is parallel to a plane defined by the surface of the electrolyte; (ii) instructions to tilt the wafer by an angle such that the planar plating surface of the wafer is no longer parallel to the plane defined by the surface of the electrolyte; (iii) the electrolyte along a trajectory substantially perpendicular to the plane defined by the surface of the electrolyte; a command to move the wafer at a first speed toward obtained with the electrolyte), (v) instructions to accelerate the wafer from the second speed to the third speed (acceleration continues until a substantial portion of the flat plating surface of the wafer is immersed in the electrolyte), (vi) the third command to decelerate the wafer from speed to rest at a second height (at a third speed, or during deceleration from the third speed to rest, the flat plating surface of the wafer is completely immersed in the electrolyte. In one embodiment, the controller is configured to: (i) program instructions for contacting a leading edge of the wafer with a plating solution while tilting the wafer by a first angle with respect to the horizontal plane, then (ii) tilting the wafer at a second angle and (iii) a program command for decreasing the tilt angle of the wafer to 0 degrees.

In another aspect, a system comprising any of the plating apparatuses described herein and a stepper is provided.

In another aspect, a non-transitory computer machine-readable medium comprising program instructions for controlling an electroplating apparatus is provided. The non-transitory computer machine-readable medium may include program instructions comprising code for performing the steps of any of the methods described herein. For example, in one embodiment, the program instructions include: (i) code to horizontally position the wafer at a first height above the electrolyte (the planar plating surface of the wafer is parallel to the plane defined by the surface of the electrolyte) , (ii) a code that tilts the wafer by an angle such that the flat plating surface of the wafer is no longer parallel to the plane defined by the surface of the electrolyte, (iii) along a trajectory substantially perpendicular to the plane defined by the surface of the electrolyte a cord for moving the wafer at a first speed towards the electrolyte; obtained with electrolyte), (v) a cord that accelerates the wafer from a second speed to a third speed (acceleration continues until a substantial portion of the flat plating surface of the wafer is immersed in the electrolyte), (vi) the wafer is removed Code for decelerating from 3 speed to standstill at 2nd height (at 3rd speed, or during deceleration from the third speed to a stationary state, the flat plating surface of the wafer is completely immersed in the electrolyte.

In some embodiments, the program instructions include (i) code for contacting a leading edge of the wafer with a plating solution while tilting the wafer at a first angle to a horizontal plane, followed by (ii) tilting the wafer at a second angle a code to increase, and then (iii) a code to decrease the tilt angle of the wafer to zero degrees.

Applicable to substrates other than semiconductor wafers, and not limited to any particular size of the substrate, when a wafer is used, the specific parameters described herein depend on the size of the wafer being immersed in the electrolyte. The method described herein works with, for example, 200 mm, 300 mm, and 450 mm diameter wafers.

These and other features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.

1A is a cross-sectional view of a typical bubble capture scenario. 1B is a cross-sectional view of a bubble removal scenario using axial electrolyte flow. 1C is a cross-sectional view along the vertical immersion path (z-axis) of a wafer with a tilted orientation (from the plane defined by the surface of the electrolyte). 1D is a cross-sectional view along a vertical immersion path (z-axis) including a wafer holder of a wafer with an inclined orientation (from the plane defined by the surface of the electrolyte). 2A-2D schematically depict wafers at various stages during the immersion process into electrolyte. 3 is a graph of a conventional trapezoidal immersion Z-velocity profile. 4 is a cross-sectional view of an angled wafer immersion using a trapezoidal Z-velocity profile. 5A is a process flow diagram illustrating a method of an aspect described herein in accordance with one embodiment of the present invention. 5B is a process flow diagram illustrating a method of an aspect described herein in accordance with another embodiment of the present invention. 6 is a graph of the immersion method described herein. 7 is a cross-sectional view of oblique immersion using the immersion method described herein. 8 is a diagram showing wet-wire propagation on the wafer plating surface after initial entry of the wafer into electrolyte and the same wet-wire propagation on the other half of the wafer plating surface when conventional trapezoidal Z-speed immersion is used. 9 shows wet front propagation on the wafer plating surface after initial acceptance of the wafer into electrolyte and the same wet front propagation on the other half of the wafer plating surface when the Z-rate immersion method described herein is used. 10 is a graph showing the improved film quality of wafers using the methods described herein as compared to a conventional trapezoidal Z-speed immersion profile.

<b>summary</b>

As outlined above in the background section, during immersion of the wafer into the plating electrolyte, air bubbles may be trapped on the plating underside (plating surface) of the wafer. This is especially true when the wafer is immersed along a vertical immersion trajectory in a horizontal orientation (orientation parallel to the plane defined by the electrolyte surface). 1A, a typical bubble-trapping scenario occurring in an electroplating system 101 is shown. In the vessel 105, a horizontally oriented wafer 103, along the vertical Z-axis, is lowered towards the electrolyte and eventually immersed in the electrolyte. By vertical immersion of the horizontally oriented wafer 103 , air bubbles 109 are trapped on the underside (plating surface) of the wafer 103 .

Air bubbles trapped on the plating surface of the wafer can cause many problems. The bubbles prevent areas of the plated surface of the wafer from being exposed to the electrolyte, thus resulting in unplated areas. The final plating defect may appear as an unplated region or a region with reduced plating thickness, depending on when the bubble is captured on the wafer and the length of time the bubble stays trapped in the wafer. In the inverted (inverted) configuration, the buoyancy forces tend to lift the air bubble onto the active surface of the wafer. These bubbles are difficult to remove from the wafer surface because the plating cell has no intrinsic means to lead the bubbles to the only path around the wafer edge, away from the wafer surface. Typically, the wafer 103 rotates about an axis passing through its center and perpendicular to the plating surface. Also, while this rotation assists in dislodging the bubbles through centrifugal force, many of the smaller bubbles remain attached to the wafer. Thus, while horizontal wafer orientation (particularly associated with a vertical immersion trajectory) has many advantages from a hardware configuration and throughput standpoint, it is technically leads to problems that are difficult to solve. One way to facilitate the removal of trapped air bubbles is to use an electrolyte flow directed perpendicularly towards the plating surface of the wafer. This may assist in dislodging air bubbles. As in the scenario 102 shown in FIG. 1B , a plating solution flows out of a conduit 111 perpendicular to the plating surface of the wafer at a speed sufficient to expel trapped air bubbles. As indicated by the arrows from conduit 111 , most of the flow is directed to the center of wafer 103 . When the flow impinges on the surface of the wafer, the flow redirects across the wafer surface, pushing the bubble toward the side of the wafer 103, as indicated by the dashed arrow. This helps to remove not only air bubbles generated during immersion, but also air bubbles that form or reach the surface during electroplating. Unfortunately, the radial non-uniformity of forced convection in these systems can result in non-uniform plating profiles. This is because the electroplating rate is a function of the local fluid velocity, for example, forced convection in a system as shown in FIG. 1B causes a non-uniform velocity profile across the wafer surface.

One way to solve many of the problems described above is to use angled wafer immersion. That is, when the wafer is introduced into the electrolyte along a vertical path (along the Z-axis), the wafer is tilted with respect to the plane defined by the surface of the electrolyte. 1C shows this immersion scenario 112 in which the wafer 103 is immersed into the electrolyte 107 along the Z-axis while the wafer is tilted relative to the surface of the electrolyte (in this example, tilted by an angle θ). do. When inclined immersion is used, air bubbles that would otherwise be trapped in the wafer can escape into the atmosphere without being captured further, with the aid of buoyancy, since the wafer is tilted. Also, a single wet front is established, so there is no problem with wet front convergence. Inclined wafer immersion is described in greater detail in Jonathan Reid et al., May 31, 2001, U.S. Patent No. 6,551,487, "Methods and Apparatus for Controlled-Angle Wafer Immersion," which is incorporated herein by reference. To reduce bubble formation, rotational speed can compensate for oblique immersion.

Another problem is that conventional wafer holders typically have some means and associated hardware for positioning and rotating the wafer as well as supporting the wafer along the perimeter of the wafer. 1D, when the vertical immersion path is used, the components of the wafer holder 170, in particular the leading edge, are brought into contact with the electrolyte before the wafer itself, which is This is because at least a portion of the wafer holder extends beyond the perimeter of the wafer and protrudes from the wafer plating surface. Around the perimeter of the wafer, due to the shape of the leading edge of the wafer holder extending beyond the plating surface, air bubbles are trapped when the leading edge of this wafer holder collides with the electrolyte. While certain wafer holders, such as the clamshell devices described above, are shaped and constructed to minimize these problems, at least some of these problems exist.

To assist in bubble rupture, sonication as described in Bryan Buckalew et al., US Pat. No. 7,727,863, "Sonic Irradiation During Wafer Immersion," may be used. In one embodiment, sonication, such as described in US Pat. No. 7,727,863, is used in conjunction with the methods described herein. In one embodiment, sonication is used for the first 50 ms (milliseconds) or more after the wafer collides with the electrolyte. In one embodiment, sonication is used for the first 100 ms or more after the wafer collides with the electrolyte. In one embodiment, sonication is used during the first 150 ms or more after the wafer collides with the electrolyte. In one embodiment sonication is used while the entire wafer is immersed in the electrolyte. Also, as plating methods become more sophisticated, for example, requiring thinner and higher quality plated layers, air entrapment can become an issue, even when using, for example, inclined wafer immersion. For example, when using a conventional immersion process, when an inclined wafer holder loaded with wafers enters the plating solution, air is misplaced under the wafer, resulting in at least partial air entrapment. Due to incomplete initial wetting of the wafer due to air entrapment on the wafer surface occurring at the wafer entrance, the adsorption of plating additive molecules onto the wafer surface is poor. Due to the absence of uniform additive adsorption and poor wetting properties, poor filling behavior, pitting or loss metal defects may occur on the surface of the wafer. The inventors of the present invention have discovered that the novel immersion process can lower the defect rate of the plated layer of the wafer, for example, by further reducing the amount of air entrapment compared to the gradient immersion used with conventional immersion methods.

2A-2D show perspective views outlining the parameters referred to in connection with the immersion methods described herein. FIG. 2A shows that, depending on the apparatus used, the wafer 240 must travel a linear distance 246 in the plating bath 242 before entering the plating electrolyte 244 . 2B shows that the wafer 240 is tilted by an angle in a horizontal plane (parallel to the electrolyte surface). A preferred angle is from about 1 degree to about 5 degrees, in certain embodiments from about 3 degrees to about 5 degrees. These ranges enable the aforementioned benefits of oblique immersion while keeping the footprint of the device to a minimum. The wafer can be tilted along its vertical trajectory to the electrolyte as long as it is tilted even after receiving it into the electrolyte. When the wafer is introduced in the horizontal direction, the leading edge of the wafer, which receives the electrolyte, makes one wetting wire rather than a plurality of wetting wires. In certain embodiments, the angle at which the wafer is tilted during an immersion protocol is changed. In these embodiments, the "swing speed," ie, the rate at which the wafer is tilted from the horizontal plane to θ, can be controlled so as not to create turbulence and thus induce unwanted air entrapment. As with all events in high throughput environments, if the swing speed is too low, the throughput will be low, and if the swing speed is too high, turbulence can result. In one embodiment, the swing speed of the wafer is about 0.25 to 10 degrees per second. In another embodiment, the swing speed is about 0.25 to 1.5 degrees per second. In another embodiment, the swing speed is about 0.5 to 1 degree per second.

In one embodiment, the tilt angle is set prior to immersion and remains constant during the immersion process. The methods described herein include horizontally positioning the wafer over the electrolyte, and tilting the wafer from a horizontal plane, these steps may be performed in any order as long as the wafer remains tilted after it has entered the electrolyte. The step of tilting the wafer may be performed while moving the wafer along its Z-axis trajectory, or prior to moving it along the Z-axis.

In some embodiments, the tilt angle is actively changed during immersion of the wafer. Due to this, entrapment of air bubbles can be reduced. Active tilt angle control can be used independently of, or in conjunction with, Z-speed fluctuations to reduce air bubble entrapment. In some embodiments, the leading edge of the wafer is contacted with the plating solution with the wafer tilted by a first angle from the horizontal plane, after which the degree of tilt of the wafer increases to a second angle, after which, for example, decreases to 0 degrees. In another embodiment, the leading edge of the wafer is in contact with the plating solution with the wafer tilted by a first angle in the horizontal plane, after which the tilt angle decreases to a smaller tilt angle before finally decreasing to 0 degrees.

2C shows that the wafer can be rotated during immersion. Like tilting, wafer rotation can be implemented at any point along the vertical trajectory of the wafer into the electrolyte as long as it is rotating even after entry into the electrolyte. 2D shows the wafer 240 tilted or rotated when immersed in the electrolyte 244 . In one embodiment, for wafer immersion, the rotation speed is about 10 rpm to 180 rpm for a 200 mm diameter wafer, about 5 rpm to 180 rpm for a 300 mm wafer, and about 5 rpm to about 150 rpm for a 450 mm wafer. Different rotational speeds can be used for immersion (first rotational speed) and plating (second rotational speed), and also for post-plating (additional plating speed). For example, the wafer may spin at a certain rate to recover the electrolyte from the wafer after removing the wafer from the plating bath, for example, when rinsing the electrolyte from the plated wafer. These are described more specifically in US Pat. No. 6,551,487 (mentioned above), along with exemplary hardware for performing the gradient dipping method. 3 is a graph of a conventional oblique immersion protocol, wherein the vertical trajectory velocity, "Z-velocity" is shown along the y-axis and the wafer holder position along the x-axis. On the x-axis, the wafer holder position relative to the electrolyte surface is reported, where the positive distance (in millimeters) is the position above the electrolyte, 0 is the electrolyte surface, and the negative distance is the position below the electrolyte surface. This profile represents wafer immersion using a clamshell wafer holder with any connected hardware extending along the perimeter of the wafer in contact with the electrolyte prior to the wafer itself.

In the immersion protocol of Figure 3, assuming that the wafer is already tilted from the horizontal plane and maintains that angle during immersion, the wafer is moved from a resting position above the electrolyte towards the electrolyte along the Z-axis. In this example, the wafer also rotates during immersion. The wafer holder is started in an entry position above the surface of the plating solution, accelerated above the surface of the electrolyte to a constant Z-velocity in the range of, for example, 70-110 mm/s, and moves towards the electrolyte. The wafer encounters the solution at this Z-speed, and while the majority of the wafer is immersed up to about 4-7 mm above the final (plating) position, the Z-speed remains constant, where the wafer holder begins to decelerate and the plating stop in position. This immersion Z-velocity profile takes the shape of an approximately trapezoid, often referred to as a "trapezoidal" Z-velocity curve.

In the example of Figure 3, the leading edge of the wafer holder starts 40 mm above the electrolyte surface. The wafer is accelerated towards the electrolyte along the Z-axis until it reaches a velocity of about 100 mm/s at a distance of about 30 mm above the electrolyte surface. Thereafter, the Z-velocity remains constant at about 100 mm/s until the leading edge of the wafer holder is in contact with the electrolyte (where the x-axis is zero, indicated by dashed line 300). Shortly thereafter, the leading edge of the wafer itself is in contact with the electrolyte (about -2 mm on the x-axis, indicated by dashed line 305 ). At about -10 mm of the x-axis, approximately half of the wafer is immersed in the electrolyte. At about -15 mm of the x-axis, the wafer is fully immersed in the electrolyte (indicated by dashed line 310 ). Just before this point, the Z-speed decreases at 100 mm/s used during most of the immersion. The following edge of the wafer holder is fully immersed at about -16 mm (indicated by dashed line 320 ). The deceleration continues until the leading edge of the wafer holder is about 18 mm below the surface of the electrolyte (-18 mm on the x-axis), which is a typical plating depth.

There are some problems with the Z-speed immersion protocol. 4 shows a cross-sectional view of a wafer immersion process 400 using a trapezoidal Z-velocity profile. The wafer holder 420 holds the wafer 415 . Wafer 415 is rotated, immersed in electrolyte 410 along a Z-axis trajectory as described with respect to FIG. 3 , and held in plating bath 405 . This diagram shows a snapshot in which the wafer is about half immersed in electrolyte. The related problem can be divided into two major problems.

The first problem is that the Z-speed when the wafer collides with the solution does not ensure sufficient removal of air trapped at the wafer edge, which (ultimately) causes a pit defect on the leading side of the wafer. may lead to incomplete wetting of As the wafer holder collides with the surface of the electrolyte, shear and normal stresses (to the surface of the electrolyte) can build up in any air pockets trapped at the wafer edge. Also, portions of the wafer holder that extend beyond the perimeter of the wafer, for example beyond the wafer plating surface in the Z-direction, may enhance air entrapment. By collision with the electrolyte surface, the pressure inside the bladder can increase significantly. If the impact velocity is insufficient, the air pockets may stay in place or split into smaller air pockets, resulting in poor wetting of the wafer surface. It has been found that a minimum Z-axis velocity of about 120 mm/s to about 300 mm/s is required upon impact to cause sufficient pressure build-up to expel the air pockets. As shown in FIG. 4 , when the wafer holder collides with the electrolyte surface, in the plating cell 405 , the displaced electrolyte flows over the weir (indicated by 425 ), while the electrolyte below the wafer plating surface, as shown in FIG. 4 , It forms a wetting wave front that propagates along the surface of the wafer, as indicated by the horizontal dotted arrow. The leading edge 430 of the wet wavefront is also shown in FIG. 4 .

A second problem with current trapezoidal profiles is that a single wetting wavefront is formed, which eventually ruptures as it travels along the interface between the surface of the electrolyte and the wafer plating surface. This is analogous to a beach wave that, after reaching its peak, breaks (collapses) due to the loss of energy to continue propagating the wave. This wave collapse causes the formation of large amounts of air bubbles in the electrolyte, after which the air bubbles adhering to the wafer surface result in voids and missing metal defects. Thus, a constant Z-velocity through most of the immersion of the wafer in a trapezoidal profile, without fluctuations, causes the build-up of waves in the first cycle of wafer immersion and the collapse of the waves later in the immersion.

Although not necessarily, when the wave velocity does not closely match the velocity of the underlying bulk solution through which the wave propagates, the wetting wave front tends to disintegrate. Depending on the liquid properties and the geometry of the cell containing the plating solution, the wave collapses when the velocity difference between the wave and the bulk solution is greater than the cutoff value. It has therefore been found that a variable speed wafer entry profile during wafer immersion is required to control the formation and propagation of the wave to prevent the wavefront from collapsing.

<b>Way </b>

A method for immersing a wafer with the electrolyte of a plating bath is described herein. Generally, the method described herein comprises the steps of positioning a wafer in a horizontal direction to a first height above an electrolyte, wherein the planar plating surface of the wafer is parallel to the plane defined by the surface of the electrolyte, and (b) the wafer; tilting the wafer by an angle so that the planar plating surface of the plate is no longer parallel to the plane defined by the surface of the electrolyte; moving into In one embodiment, the wafer is tilted by an angle of 5 degrees or less. In one embodiment, the wafer is tilted at an angle of about 1 degree and about 5 degrees. In some embodiments, the wafer is tilted at an angle of about 3 to 5 degrees. In a more specific embodiment, the method comprises introducing the wafer into the electrolyte at a specified rate (acceleration, constant rate, or deceleration) sufficient to minimize entrapment of air on the wafer surface near the leading edge entering the electrolyte. includes The wafer Z-velocity is slowed down to a sufficient rate to maintain the wet wavefront, ie, to prevent the wave from collapsing during immersion. After the first portion of the wafer is immersed, the deceleration is stopped at the second speed, and the acceleration is implemented again so that the wavefront does not collapse. Acceleration is maintained up to a third speed and then decelerated again until it stops at the last part of the Z-velocity profile is used. When the backside of the wafer is immersed, i.e., a tapering region of the wafer is being immersed, and thus a wetting wavefront propagates across this tapering region for full immersion, a final deceleration is used to minimize bubble formation can do. The wafer is fully immersed at any point between the point at which the third speed is reached and the deceleration until it stops.

5A shows an aspect of a method 500 for performing such immersion. Assuming the wafer is approximately positioned over the electrolyte and tilted before the wafer enters the electrolyte, the wafer is moved (505) at a first speed towards the electrolyte along a Z-axis trajectory. The wafer may also be rotated as described herein. Once the first (Z) speed is reached, the wafer then decelerates 510 from the first speed to a second (Z) speed. At the first speed, or during deceleration to the second speed, the leading edge of the wafer enters the electrolyte and, optionally, the wafer rotates during entry. In one embodiment, the first speed is between about 120 mm/s and 300 mm/s, in another embodiment, between about 120 mm/s and about 175 mm/s, and in another embodiment, about 120 mm/s. /s to 160 mm/s. In some embodiments, a high speed of about 200-300 mm/s is used. In one embodiment, when the wafer enters the electrolyte at a first rate, the Z-rate is held constant between about 10 ms and about 80 ms starting from when the leading edge of the wafer contacts the surface of the electrolyte, and In an embodiment of , the first speed is maintained for about 50 ms before deceleration to the second speed.

In one embodiment, the leading edge of the wafer enters the electrolyte during deceleration from the first speed to the second speed. In one embodiment, the second speed is from about 40 mm/s to about 110 mm/s, in another embodiment from about 50 mm/s to about 70 mm/s, and in another embodiment from about 55 mm/s /s to about 65 mm/s. Once the leading edge of the wafer has been immersed in the electrolyte, the first portion of the wafer is immersed. In one embodiment, the deceleration from the first rate to the second rate is continued until about 25% to about 75% of the planar plating surface of the wafer is immersed with the electrolyte, and in another embodiment, wafer plating The deceleration continues until about 50% of the surface is submerged.

After reaching the second rate, there may be a period of time during which the Z-rate is maintained at the second rate. In one embodiment, the second Z-velocity is held constant for about 50 ms to about 120 ms, and in one embodiment, about 100 ms. In one embodiment, the Z-velocity is accelerated ( 515 ) to the third speed without staying at the second speed, ie, upon reaching the second speed. In one embodiment, the third rate is lower than the first rate. In one embodiment, the third speed is from about 100 mm/s to about 140 mm/s, in another embodiment from about 120 mm/s to about 140 mm/s, and in another embodiment from about 130 mm/s /s to about 140 mm/s.

In one embodiment, during acceleration from the second rate to the third rate, a substantial portion of the wafer is immersed in the electrolyte. For purposes of this disclosure, a "substantial portion" of the wafer is defined as the aforementioned first portion being immersed during deceleration from the first speed to the second speed, and the wafer surface being immersed during acceleration from the second speed to the third speed. means the total area of the wafer plating surface including the second portion of After reaching the third (Z) speed, the Z-speed decelerates 520 from the third speed to a stop. At the third speed, or during deceleration from the third speed to rest, the flat plating surface of the wafer is completely immersed in the electrolyte. In one embodiment, the flat plating surface of the wafer is completely immersed in the electrolyte during deceleration from the third speed to rest. After the wafer is fully immersed in the electrolyte, method 500 is performed. In certain embodiments, the wafer is immersed during plating to a depth of about 15 mm to about 35 mm, in another embodiment to a depth of about 15 mm to about 20 mm, and in yet another embodiment, about 16 mm to a depth of about 18 mm. As mentioned previously, as an option, the rotational speed of the wafer can be varied from the speed used during immersion to a speed more suitable for electroplating.

For example, the total time taken for immersion can be important because, during immersion, one portion of the wafer is exposed to the electrolyte and the other is not. Depending on the plating conditions, the thickness of the seed layer, etc., it may be important to immerse the wafer as quickly as possible. This needs to be balanced with the need to reduce air entrapment. In one embodiment, the total time taken for immersion (i.e., from when the leading edge of the wafer enters the electrolyte until the wafer is completely immersed in the electrolyte) is less than 300 milliseconds, in another embodiment , less than 250 milliseconds, and in another embodiment less than 200 milliseconds. In one embodiment, acceleration and deceleration may be compared. In one embodiment, the range of acceleration and deceleration, independently of each other, is about 0.1 m/s² and about 7.5 m/s², in another embodiment, about 1.5 m/s² to about 6 m/s², in another embodiment, about 2.5 m/s² to about 4 m/s²am.

5B shows a process flow 501 for one embodiment of an immersion protocol that uses active tilt angle control to reduce air bubble entrapment. This convention can be combined with the process shown in Figure 5A and can also be used independently, eg with a conventional Z-velocity profile. In the embodiment shown in FIG. 5B , the process begins at operation 535 of tilting the wafer by a first angle, tilting the wafer by a first angle at operation 540 and, optionally, rotating the wafer, is brought into contact with the plating solution. Then, in operation 545, the tilt angle is increased to a second angle while the wafer is immersed, and then, in operation 550, the tilt angle is reduced, typically to zero degrees. As mentioned earlier, this sequence can be combined with the process sequence described in Figure 5A. For example, an increase in the tilt angle may occur at any of the first, second, or third Z-velocities. In some embodiments, the tilt angle is about 1-5 degrees before the tilt angle decreases to zero. In one specific example, the wafer is first tilted at 1.4 degrees, and the leading edge of the wafer is in contact with the plating solution with the wafer tilted at 1.4 degrees. During this time the Z-speed may be the first speed or the wafer may be decelerated to the second speed. The tilt is then increased to 4 degrees and the Z-velocity can be accelerated to a third speed. And finally, the wafer tilt is reduced to 0 degrees, and the wafer becomes horizontally oriented. In another embodiment, the process shown in Figure 5B is used with a conventional trapezoidal Z-velocity profile. In these examples, it is shown to reduce bubble entrapment. In some embodiments, after the wafer is contacted with the electroplating solution at a first angle, and finally before reducing the tilt angle to zero degrees, the tilt angle of the wafer is reduced to a smaller tilt angle (not zero degrees).

6 is a graph of an immersion method as described in the process shown in FIG. 5A. As shown in Figure 3, the y-axis shows the Z-velocity of the wafer holder and the x-axis shows the wafer holder position relative to the electrolyte surface. Also, in this example, a clamshell wafer holder was used. The conventional trapezoidal Z-velocity profile described in connection with FIG. 3 is superimposed on FIG. 6 for comparison. In this example, assuming that the wafer is tilted at an angle as described above, the leading edge of the (clamshell) wafer holder starts at a position about 30 mm from the electrolyte surface. The wafer moves towards the electrolyte along the Z-axis and is accelerated to about 150 mm/s. At this first speed, the wafer holder contacts the electrolyte surface (indicated by dashed line 600 ), and deceleration from the first speed to the second speed (in this example, about 60 mm/s) begins. At about 2 mm the leading edge of the wafer touches the electrolyte (indicated by dashed line 605 ). In this example, during the first deceleration step, approximately half of the wafer is immersed. In one embodiment, about half of the wafer is immersed simultaneously when the second speed is reached. Upon reaching the second speed, the Z-speed of the wafer is accelerated once again from the second speed to a third speed (in this example, about 130 mm/s). During this acceleration step, all but a small portion of the remaining unimmersed portions of the wafer are immersed. When the third speed is reached, a deceleration phase begins, approximately at which time the wafer plating surface is completely immersed with a small portion of the wafer holder immersed (indicated by dashed line 610 ). During the final deceleration from the third speed to rest, the final portion of the wafer holder is submerged (indicated by dashed line 620 ). Z-motion continues until the wafer has reached the desired plating depth (in this example, about 18 mm below the electrolyte surface) (-18 mm on the graph).

7 is a cross-sectional view of oblique immersion using the immersion method described herein. FIG. 7 is similar to FIG. 4 , but in FIG. 7 , the illustrated immersion 700 utilizes the Z-velocity profile of the present invention described above. In this illustration, the wet wavefront 705 of the electrolyte is stable and does not collapse unlike with conventional immersion methods.

One embodiment is a method of immersing a wafer into an electrolyte in a plating bath, the method comprising the steps of (a) horizontally positioning the wafer at a first height above the electrolyte (the flat plating surface of the wafer is (parallel to the plane defined by the surface of the electrolyte); and (b) tilting the wafer at an angle of about 1 degree to about 5 degrees such that the planar plating surface of the wafer is no longer parallel to the plane defined by the surface of the electrolyte. (c) rotating the wafer along an axis that is perpendicular to the planar plating surface of the wafer and passes through the center of the wafer; and (d) along a trajectory substantially perpendicular to the plane defined by the surface of the electrolyte. , moving the wafer towards the electrolyte at a first rate of from about 120 mm/s to about 300 mm/s, and (e) decelerating the wafer to a second rate of from about 40 mm/s to about 80 mm/s. step (during deceleration from the first speed or from the first speed to the second speed, the leading edge of the wafer enters the electrolyte; about 40% to about 60% of the plate-like plating surface is immersed during deceleration from the first speed to the second speed; and (f) at the second speed, from about 100 mm/s to about 140 mm/s. accelerating the wafer to a third rate (acceleration continues until at least about 75% of the planar plating surface is immersed in the electrolyte), and (g) decelerating, at the third rate, to a standstill at a second height step (either at the third speed, or during deceleration from the third speed to rest, the flat plating surface of the wafer is completely immersed in the electrolyte). In one embodiment, the deceleration from the first rate to the second rate is continued until about 50% of the flat plate plated surface of the wafer is immersed in the electrolyte. In one embodiment, the leading edge of the wafer enters the electrolyte during deceleration to the second speed. In another embodiment, the third rate is lower than the first rate. In one embodiment, (c) is a rotation speed of about 10 rpm to 180 rpm for a 200 mm wafer, a rotation speed of about 5 rpm to 180 rpm for a 300 mm wafer, and a rotation speed of about 5 rpm to 150 rpm for a 450 mm wafer include In one embodiment, the wafer is completely immersed in the electrolyte during deceleration from the third speed to rest. In one embodiment, the total time taken for immersion (ie, from when the leading edge of the wafer enters the electrolyte until the wafer is fully immersed in the electrolyte) is less than 300 milliseconds.

One embodiment is a method of immersing a wafer with a plating solution, the method comprising the steps of (a) contacting a leading edge of the wafer with a plating solution at a first translational velocity while tilting the wafer relative to a horizontal plane, and thereafter (b) slowing the wafer to a second translational speed with the wafer partially immersed in the plating solution, and (c) increasing the speed of the wafer to a third speed before the wafer is fully immersed in the plating solution. includes

Another embodiment is a method of immersing a wafer with a plating solution, the method comprising: with the wafer tilted relative to a horizontal plane, the leading edge of the wafer at a first translational velocity of at least about 120 mm/s in a direction toward the plating solution contacting the portion with a plating solution.

The method described herein allows the electrolytic wetting wavefront to be maintained throughout the immersion of the wafer (i.e., the wavefront is wafer plating) in such a way that air entrapment due to initial impact of the wafer and/or wafer holder is reduced, and while also minimizing air entrapment. Describes wafer entry into electrolyte that allows the wafer to be moved in such a way that the wavefront does not collapse while propagating across the surface.

<b>Device</b>

Another aspect of the invention is an apparatus configured to effect the methods described herein. Suitable apparatus includes hardware for performing process operations in accordance with the present invention, and a system controller having instructions for controlling the process operations.

A suitable apparatus for performing the methods described herein should provide for wafer movement at a speed, angle, rotation, swing speed, acceleration, deceleration suitable for the described embodiments. The rotation drive components of these devices provide a wide range of wafer holder rotation speeds and Z-speeds (constant or not), at the stated tilt angles, from the point at which the leading edge of the wafer meets the electrolyte until the wafer is fully immersed; Wafers can be immersed in 300 milliseconds. In one embodiment, the rotating means of the wafer holder may rotate the wafer at a speed of about 1 rpm to about 600 rpm. In one embodiment, an actuator for moving the wafer holder along the Z-axis provides linear bidirectional motion at a rate of 0 to about 300 millimeters/second. The wafer holder must also be capable of tilting the wafer as described. A preferred example of a wafer holder is the clamshell device described in US Pat. Nos. 6,156,167 and 6,139,712, although other wafer holder components may be used to implement the methods described herein. When a clamshell is used as a wafer holder component of a device, other components include positioning elements for the clamshell, since the clamshell has the necessary electrical contacts, fixed and rotating components, and the like.

One embodiment is a plating apparatus comprising: (a) a wafer holder configured to tilt a wafer from a horizontal direction during immersion into the plating solution; (b) a chamber for holding the plating solution; (c) ) a controller constructed or designed to transfer the tilted wafer in a direction toward the plating solution at a rate of at least about 120 mm/s as the wafer enters the plating solution. In one embodiment, the wafer speed is between about 140 mm/s and 300 mm/s. In one embodiment, the wafer speed is at least about 120 mm/s when the leading edge of the wafer contacts the plating solution. For example, the wafer holder may be a clamshell wafer holder from Novellus Systems, Inc. of San Jose, CA. The controller may be, for example, a commercially available controller modified to suit the needs of the methods described herein. One example of such a controller is a controller sold by IAI America, Inc. of Torrance, California.

In one embodiment is a plating apparatus comprising: (a) a wafer holder configured to tilt a wafer from a horizontal plane during immersion into the plating solution; (b) a chamber for holding the plating solution; (c) and a controller constructed or designed to transfer the tilted wafer at a variable speed in a direction toward the plating solution when the wafer is immersed in the solution. In one embodiment, at a first speed, the leading edge of the tilted wafer is in contact with the plating solution, then the speed of the wafer is slowed down to a second speed with the wafer partially immersed in the plating solution, and finally The controller is designed or configured such that the speed of the wafer is increased to a third speed before it is fully immersed.

One embodiment is a plating apparatus comprising: (a) a wafer holder configured to tilt a wafer from a horizontal plane during immersion into the plating solution; (b) a chamber for holding the plating solution; Tilt the wafer by 1 angle, then contact the leading edge of the wafer with plating solution while tilting the wafer at the first angle, increase the tilt angle to a second angle, and then decrease the tilt angle to 0 degrees and a controller having program instructions for it.

Embodiments of the present invention may utilize various processes involving data stored on or transmitted through one or more computer systems. Embodiments described herein also relate to apparatus for performing these operations, such as computers and microcontrollers. These apparatus and processes can be used to control wafer positioning parameters of the methods described above and apparatus designed to perform the methods. The control device may be a general purpose computer specially configured for the required purpose, or optionally activated or reset by a computer program and/or data structure stored in the computer. The processes presented herein are not inherently related to any particular computer or other device. Specifically, various general purpose machines may be used with programs written in accordance with the teachings herein, or it may be more convenient to construct more specialized apparatus to perform and/or control the required method steps.

<b>patterning</b><b> Method/Device:</b>

The apparatus/processes described herein may be used in combination with a lithographic patterning tool or process (eg, a lithographic patterning tool or process for the manufacture or fabrication of semiconductor devices, displays, LEDs, photovoltaic panels, etc.). Typically, though not necessarily, these tools/processes will be used or practiced together in a common manufacturing facility. In general, lithographic patterning of a film comprises the steps of (1) applying a photoresist to a work member (i.e., a substrate) using a spin-on or spray-on tool, ( 2) curing the photoresist using a hot plate or furnace or UV curing tool; (4) developing the resist to selectively remove the resist and patterning using a tool (eg, a wet bench), (5) using a dry or plasma assisted etch tool to deposit the resist pattern into the underlying film or transferring to a work member, (6) removing the resist using a tool (eg, an RF or microwave plasma resist stripper), each step capable of using a plurality of possible tools. becomes In one embodiment, a lithography tool patterns the wafer to form vias and trenches, which vias and trenches may be filled using a copper electrodeposition tool. The method herein can be used, for example, to immerse a wafer having a copper seed layer into an electrolytic bath, wherein features on the wafer are filled with, for example, copper. In addition, the method comprises one or more steps (1)-(6) described above.

<b>example</b>

The present invention will be further understood by reference to the following examples, which are by way of example only. The scope of the present invention is not limited to the exemplary embodiments, and the above examples are merely for describing aspects of the present invention. Any method that is functionally equivalent is within the scope of the present invention. From the detailed description and accompanying drawings, various modifications of the present invention, in addition to those described herein, will become apparent to those skilled in the art. Incidentally, such modifications are within the scope of the appended claims. For example, it will be appreciated by those skilled in the art that certain materials will become available as equivalents and/or alternatives to the materials described herein, even if they are not currently available.

<b>Example 1</b>

The wetting behavior of wafers was studied using the method described herein in which the wafer was immersed in a plating solution and using a clamshell (see previous description) wafer holder. In this study, a 300 mm wafer was used. A wafer was immersed in electrolyte using a conventional trapezoidal Z-velocity profile, for example as described in FIGS. As described, the wafer is tilted, rotated, and then immersed. After that, conventional immersion vs. The wafer surface quality resulting from the improved immersion was compared.

Wafers immersed using trapezoidal Z-speed immersion showed evidence of increased air entrapment and showed collapse of the wetting fracture surface with respect to wafers immersed using the improved method. Wafers immersed using conventional trapezoidal Z-speed immersion had a much higher level of unwetted area on the plating surface.

Fig. 8 shows wet front propagation in a snapshot (left) of the plating surface of the wafer immediately after initial entry of the wafer into electrolyte, when conventional trapezoidal Z-speed immersion is used, and later over the other half of the wafer plating surface. The same wet front propagation in the snapshot (right) is shown. The direction of wetting wavefront propagation in FIG. 8 is indicated by a dashed arrow, ie from the top left of the wafer surface to the bottom right of the wafer surface (as shown). In this example, at 100 mm/s (at a constant rate) the wafer holder/wafer was taken as electrolyte. The contact line 800a indicates a wet wire where the electrolyte meets the wafer. The portion of the wafer to the left of line 800a is the immersed portion of the wafer after impact with the electrolyte. In the region 805 where the wafer collides with the electrolyte, there is evidence of air entrapment and poor wetting is observed. For example, a non-wetted region 805 is left on the wafer after immersion. For example, by indexing the wafer and tracking which part collides with the electrolyte first, the impact area can be determined. Also, non-wetted areas on the surface of the wafer (after immersion) are evidence of bubbles 810 moving with the wetting wavefront 800a during immersion. Since the velocity is maintained at a substantially constant 100 mm/s, the wet front builds up and eventually collapses, as shown by 800b, and a large amount of air bubbles with the wavefront (some left behind the wafer surface) are formed.

9 shows wetline propagation in a snapshot (left) to the wafer plating surface after initial acquisition of the wafer into electrolyte, when the improved Z-rate immersion method described herein is used, and the other half of the wafer plating surface. Shows the same wet front propagation in a later snapshot (right) for . In this example, at 150 mm/s (with deceleration in this example) the wafer holder/wafer was taken as electrolyte. To the left of the wetting line 800a, air entrapment is minimized using these methods, as is evident by the few non-wetting areas in the impingement area. Also (after immersion) there are few bubbles as the wetting wire 905 propagates across the wafer surface, as is evident by the few wetting areas across the entire plating surface. These tests show that higher initial intake rates lower air entrapment and improve wetting.

In this example, after entry of the wafer into the electrolyte at 150 mm/s, the Z-speed gradually decreases to about 60 mm/s until about half of the wafer is immersed in solution. In order for the wet front to remain in a stable shape and not collapse, the deceleration described results in a gradual reduction in fracture front construction. Since the volume of the wafer holder immersed in solution increases by the power of the vertical displacement, further reduction in the Z-velocity well beyond the immersion of the first half of the wafer does not prevent final wave collapse. Nevertheless, the intensity of the wave collapse is still low compared to the conventional trapezoidal profile shown in FIG. 8 . However, when, for example, during immersion of the second half of the wafer the Z-velocity is accelerated after reaching a second velocity (eg, the local velocity minimum in the Z-velocity curve as in FIG. 6 ), wavefront collapse is harmed. lose This is indicated by reference numeral 900b. Z-velocity acceleration during immersion of the backside of the wafer increases the bulk velocity of the plating solution located below the wet wavefront across the bulk solution, thus reducing the difference between the bulk solution velocity and the wave velocity, avoiding wavefront collapse minimized enough for Figure 9 shows that the wavefront 900b has much less voiding and foaming in the wafer. These results are supported by actual electroplating studies performed after immersion as previously described. These electroplating studies are described in Example 2.

<b>Example 2</b>

10 is a graph showing improved wafer film quality when using the method described herein compared to a trapezoidal Z-rate immersion profile. Immersion, using a conventional trapezoidal Z-velocity profile (labeled "100Z/trapezoid" in FIG. 10) compared to a Z-velocity profile according to the examples described herein (labeled "Get XL" in FIG. 10) Electroplating was performed in the tool using a plurality of patterned wafers. Defect counts related to air bubbles and poor wetting are reflected in the total number of margin voids (MV) of the metrology tool. The edge void total (average of 0.55 runs) decreased from 19 or more using a conventional trapezoidal Z-velocity profile (100 mm/s) to less than 1 when using a Z-velocity profile according to the description associated with FIG. 6 . .

While the present invention has been described in connection with several preferred embodiments, it is not intended to be limited to the details provided above. Many variations of the preferred embodiment described above can be used. Accordingly, the present invention should be broadly interpreted with reference to the following claims.