Lithographic apparatus and device manufacturing method

[0001] The present invention relates to level sensors, lithographic devices and methods for determining substrate height maps for use in lithographic processes.

[0002] A lithographic device is a machine that applies a desired pattern to a substrate, usually a target portion of the substrate. Lithographic equipment can be used, for example, in the manufacture of integrated circuits (ICs). In such cases, a patterning device, also called a mask or reticle, can be used instead to generate a circuit pattern to be formed on the individual layers of the IC. This pattern can be transferred to a target portion (eg, including part of one or several dies) on a substrate (eg, a silicon wafer). The pattern transfer is usually performed by imaging on a layer of a radiation sensitive material (resist) provided on the substrate. Generally, a single substrate contains a network of adjacent target portions that are sequentially given a pattern. Traditional lithographic equipment synchronizes the substrate with a so-called stepper, which illuminates each target area by exposing the entire pattern to the target area in one go, in parallel or antiparallel to a given direction (the "scan" direction). Includes a so-called scanner, in which each target portion is illuminated by scanning the pattern with a radiating beam in a given direction (the "scan" direction) while scanning. By imprinting the pattern on the substrate, it is also possible to transfer the pattern from the patterning device to the substrate.

[0003] The surface of the substrate on which the pattern is projected is usually not perfectly flat. In addition, the substrate may exhibit a thickness variation of a few microns. This variation in flatness and / or thickness of the substrate surface can result in inaccurate projection of the pattern, for example due to focus or imaging errors.

[0004] It has been proposed to provide level sensors and preferably incorporate them into lithographic equipment to compensate for variations in substrate non-flatness and / or thickness. Such level sensors can be used to determine the height map of the substrate before transferring the pattern onto the substrate, eg, projecting it. This height map can then be used to correct the position of the substrate while transferring the pattern to the substrate.

[0005] There is a desire to continuously increase the throughput of lithographic equipment. Therefore, it is desirable to reduce the time used to determine the height map of the substrate.

[0006] The time required to determine the height map using the level sensor can be reduced by using multiple measurement positions on the substrate. Such a level sensor is provided with a projection unit that projects a plurality of measurement beams onto a plurality of measurement positions on the substrate, preferably at the same time.

[0007] In many lithographic devices, the space available for the level sensor is relatively small, or the space available for the level sensor is located in a less favorable location within the lithographic device.

[0008] A potential drawback of level sensors with multiple measurement beams is that such level sensors can consume a relatively large amount of space.

[0009] It is desirable to provide a level sensor that can be more easily placed in the available space within the lithographic device, for example for use in a lithographic device.

[0010] According to an embodiment of the present invention, a level sensor configured to measure the height level of a substrate placed at a measurement position, the level sensor provides a plurality of measurement beams on the substrate. The board is equipped with a projection unit that projects to multiple measurement positions, a detection unit that receives the measurement beam after being reflected by the substrate, and a processing unit that calculates the height level based on the reflection measurement beam received by the detection unit. When placed in the measurement position, a level sensor is provided in which the projection unit and the detection unit are placed adjacent to the substrate.

[0011] According to an embodiment of the present invention, a lithography apparatus is provided with a lighting system configured to regulate a radiated beam and a pattern on the cross section of the radiated beam to form a patterned radiated beam. A support constructed to support a patterning device capable of being capable of, a substrate table constructed to hold the substrate, and a projection system configured to project a patterned emission beam onto a target portion of the substrate. A level sensor configured to measure the height level of a board on a board table placed at a measurement position, the level sensor projects multiple measurement beams onto multiple measurement positions on the board. It includes a unit, a detection unit that receives the measurement beam after being reflected by the substrate, and a processing unit that calculates the height level based on the reflection measurement beam received by the detection unit. When the substrate is placed in the measurement position, it is projected. A lithography apparatus is provided in which a unit and a detection unit are arranged adjacent to a substrate.

[0012] According to an embodiment of the present invention, a method of determining a height map of a substrate, in which a projection unit is used to project a measurement beam onto the substrate to allow the substrate to be measured at a measurement position. The substrate is placed in the measurement position, including a step of measuring the height, a step of receiving a reflected beam from the substrate using the detection unit, and a step of determining the height level based on the reflected beam received by the detection unit. If so, the projection unit and detection unit are placed adjacent to the substrate, and the step of repeating the measurement step at multiple measurement positions on the substrate and the step of determining the height map of the substrate based on the height level. And methods are provided that include.

The embodiments of the present invention will be described below with reference to the accompanying schematics showing the corresponding parts of the corresponding reference numerals, but this is merely an example.<figref num="1">[0014] It is a figure which shows the lithography apparatus by an embodiment of this invention.</figref><figref num="2">[0015] It is a side view of the level sensor according to the embodiment of the present invention.</figref><figref num="3">[0016] It is a schematic diagram of the projection grid (left side) and the obtained image (right side).</figref><figref num="4">[0017] It is a side view of the embodiment of the detection grid and the details of the detection grid.</figref><figref num="5">[0018] It is a top view of the embodiment of the level sensor having a plurality of measurement positions.</figref><figref num="6">[0019] FIG. 6 is a side view of an embodiment of a level sensor comprising a tilt measuring device.</figref><figref num="7">[0020] FIG. 6 is a top view of an embodiment of a beam delivery system for a level sensor having a plurality of measurement positions.</figref><figref num="8">[0021] FIG. 6 is a top view of a further embodiment of a beam delivery system for a level sensor having a plurality of measurement positions.</figref><figref num="9">[0021] FIG. 6 is a cross-sectional view of a further embodiment of a beam delivery system for a level sensor having a plurality of measurement positions.</figref><figref num="10">[0021] FIG. 6 is a side view of a further embodiment of a beam delivery system for a level sensor having a plurality of measurement positions.</figref>

[0022] FIG. 1 schematically shows a lithography apparatus according to an embodiment of the present invention. The device supports a lighting system (illuminator) IL configured to regulate the emission beam B (eg, UV radiation or any other suitable radiation) and a patterning device (eg, mask) MA. Includes a patterning device support structure (eg, mask table) MT connected to a first positioning device PM constructed and configured to accurately position the patterning device according to specific parameters. The device also supports a substrate connected to a second positioning device PW that is constructed to hold the substrate (eg, resist-coated wafer) W and is configured to accurately position the substrate according to specific parameters. Includes body (eg, wafer table) WT. In addition, the device is a projection system (eg, including) configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (eg, including one or more dies) of substrate W. , Refraction projection lens system) PS included.

Lighting systems include various types of optical components, such as refraction, reflection, magnetic, electromagnetic, electrostatic, etc., or any combination thereof, for inducing, shaping, or controlling radiation. You may be.

The patterning device support structure holds the patterning device in a manner depending on conditions such as the orientation of the patterning device, the design of the lithography apparatus, for example, whether or not the patterning device is held in a vacuum environment. This patterning device support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The patterning device support structure may be, for example, a frame or table, and may be fixed or movable as required. The patterning device support structure can ensure that the patterning device is in the desired position, eg, with respect to the projection system. When the term "reticle" or "mask" is used herein, the term can be considered synonymous with the more general term "patterning device".

[0025] As used herein, the term "patterning device" is broadly defined as any device that can be used to give a pattern to the cross section of a radiated beam, such as to generate a pattern on a target portion of a substrate. Should be interpreted as. It should be noted here that the pattern given to the radiated beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase shift features or so-called assist features. Generally, the pattern given to the radiated beam corresponds to a particular functional layer of the device generated in a target portion such as an integrated circuit.

The patterning device may be transparent or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography and include mask types such as binary masks, reternating phase shift masks, attenuated phase shift masks, and various hybrid mask types. Is done. As an example of a programmable mirror array, a matrix array of small mirrors is used, each of which can be individually tilted to reflect an incident radiation beam in different directions. The tilted mirror gives a pattern to the radiated beam reflected by the mirror matrix.

[0027] The term "projection system" as used herein refers to, for example, the exposure radiation used, or other factors such as the use of liquid immersion liquid or the use of vacuum, as appropriate, eg, refraction optical system, reflection optics. It should be broadly interpreted as covering any type of projection system, including systems, reflective refraction optical systems, magnetic optical systems, electromagnetic optical systems and electrostatic optical systems, or any combination thereof. When the term "projection lens" is used herein, it can be considered synonymous with the more general term "projection system".

[0028] As shown herein, the device is a transmissive type (eg, using a transmissive mask). Alternatively, the device may be of the reflective type (eg, using a programmable mirror array of the type mentioned above, or using a reflective mask).

[0029] The lithographic apparatus may be of the type having two (dual stage) or more substrate supports (and / or two or more patterning device supports). In such a "multistage" machine, additional supports may be used in parallel, or one or more supports may be spared while one or more other supports are used for exposure. The process can be carried out.

[0030] The lithographic apparatus may be of a type in which at least a part of the substrate is covered with a liquid having a relatively high refractive index such as water so as to fill the space between the projection system and the substrate. The immersion liquid can also be applied to other spaces in the lithographic apparatus, for example between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. As used herein, the term "immersion" does not mean that a structure such as a substrate must be submerged in a liquid, but that there is a liquid between the projection system and the substrate during exposure. ..

[0031] Referring to FIG. 1, the illuminator IL receives a radiated beam from the source SO. The radiation source and the lithographic apparatus may be separate components, for example, when the radiation source is an excimer laser. In such cases, the source is not considered to form part of the lithography equipment and the radiated beam is illuminated from the source SO with the help of a beam delivery system BD equipped with, for example, a suitable induction mirror and / or beam expander. Passed to IL. In other cases, for example, if the source is a mercury lamp, the source may be an integral part of the lithographic apparatus. The radiation source SO and the illuminator IL can be referred to as a radiation system together with the beam delivery system BD, if desired.

The illuminator IL may include an adjuster AD configured to adjust the angular intensity distribution of the radiated beam. In general, the outer and / or inner radial range of the intensity distribution on the pupil plane of the illuminator IL (commonly referred to as σ-outer and σ-inner, respectively) can be adjusted. The illuminator IL may also include various other components such as an integrator IN and a capacitor CO. The illuminator IL may be used to adjust the radiated beam to obtain the desired uniformity and intensity distribution over its cross section.

[0033] The radiation beam B is incident on the patterning device (eg, mask) MA held on the patterning device support structure (eg, mask table) MT and is patterned by the patterning device. The radiated beam B across the patterning device MA passes through the projection system PS, which focuses the beam on the target portion C of the substrate W. With the help of a second positioning device PW and position sensor IF (eg, interferometer device, linear encoder or capacitive sensor), the substrate table WT may be positioned, eg, various target portions C, in the path of the radiation beam B. You can move accurately. Similarly, for the path of the radiated beam B, such as after mechanical removal from the mask library or during scanning, using a position sensor (not specified in FIG. 1) separate from the first positioning device PM. The patterning device MA can be accurately positioned. In general, the movement of the patterning device table MT can be achieved with the help of a long stroke module (coarse motion positioning) and a short stroke module (fine motion positioning) that form a portion of the first positioning device PM. Similarly, the movement of the substrate support WT can be realized by using the long stroke module and the short stroke module forming the portion of the second positioner PW. For steppers (as opposed to scanners), the patterning device table MT may be connected or fixed only to the short stroke actuator. The patterning device MA and the substrate W can be aligned using the patterning device alignment marks M1 and M2 and the substrate alignment marks P1 and P2. The substrate alignment mark as shown occupies a dedicated target portion, but may be located in the space between the target portions (well known as a scribe lane alignment mark). Similarly, in situations where multiple dies are provided on the patterning device MA, the patterning device alignment marks are placed between the dies.

[0034] The illustrated lithography apparatus can be used in at least one of the following modes. 1. In step mode, the patterning device support MT and the substrate support WT are basically kept stationary, while the entire pattern applied to the radiated beam is projected onto the target portion C in one go (ie, simply). (I static exposure). The substrate support WT is then moved in the X and / or Y directions so that another target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C where the image is formed with a single static exposure. 2. In scan mode, the patterning device support MT and substrate support WT are scanned synchronously while the pattern given to the emitted beam is projected onto target portion C (ie, single dynamic exposure). The velocity and direction of the substrate support WT with respect to the "patterning device support MT" can be determined by the enlargement (reduction) and image inversion characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width of the target area (in the non-scan direction) in a single dynamic exposure, and the length of the scan operation determines the height of the target area (in the scan direction). 3. In another mode, the patterning device support MT holds the programmable patterning device and is essentially kept stationary, moving or scanning the substrate support WT while targeting the pattern given to the radiated beam. Project to C. In this mode, a pulsed source is typically used to update the programmable patterning device as needed each time the substrate support WT is moved or between successive emission pulses during scanning. This mode of operation is readily available for maskless lithography using programmable patterning devices such as the types of programmable mirror arrays mentioned above.

[0035] Combinations and / or variants of the above-mentioned usage modes, or completely different usage modes are also available.

[0036] FIG. 1 shows the possible positions of the level sensor 1 according to the embodiment of the present invention in the lithography apparatus. The substrate support WT and the substrate W supported on the substrate support WT are shown by dotted lines at the measurement positions of the substrate. At this measurement position, the height level of the substrate W can be determined.

Level Sensor [0037] FIG. 2 shows a level sensor entirely indicated by reference numeral 1. The level sensor 1 is configured to determine the height map of the substrate 2. This height map can be used to correct the position of the substrate while projecting the pattern onto substrate 2. Although the level sensor can be placed in a separate device, it is desirable to incorporate it in a lithographic device as shown in Figure 1.

[0038] The level sensor 1 includes a projection unit 3, a detection unit 4, and a processing unit 5. The projection unit 3 includes a radiation output unit 6 (eg, a radiation source or an outlet connected to the radiation source somewhere else) and a projection grid 7. The radiation output unit 6 can be any suitable radiation source or can be connected to it. This is a broadband light source or preferably connected to it, but polarized or unpolarized laser beams can also be used. The radiation output unit 6 provides a measurement beam guided by the projection grid 7.

[0039] The projection grid 7 comprises a periodic grid, i.e., a pattern having a periodic structure, so that the radiation intensity of the measurement beam has a periodic structure. The left side of FIG. 3 shows an example of such a projection grid with a periodic structure. The measurement beam having periodic radiant intensity is guided toward the measurement position 8 via the optical reflector 9. The substrate is placed at this measurement position 8. Another optical element can be provided to guide the measurement beam towards substrate 2. At the measurement position 8, the measurement beam is reflected on the substrate 2 and travels to the detection unit 4 via the second optical reflector 10 and possibly another optical element. The detection unit 4 includes a detection grid 11 and three detectors 12a, 12b, and 12c.

[0040] The detection grid 11 has a periodic structure as shown in FIG. This periodic structure comprises an array of three segments 13a, 13b, 13c per period. The top surface of each segment within the array of segments has a different angle with respect to the angle of incidence of the measurement beam 14. As a result, the measurement beam is divided into three measurement beam sections 14a, 14b, 14c by three segments, each measuring one of the three detectors 12a, 12b, 12c, eg, a photodiode or radiation intensity. Guided to one of the other factors that can be.

[0041] Since the structure of the segments in the array of segments is periodic, each segment 13a, 13b, 13c in each array of segments is associated with a portion of the measurement beam received by that segment, detector 12a. , 12b, 12c. Therefore, all first segments 13a direct the radiation of the measurement beam towards the first detector 12a, the second segment 13b of the periodic structure directs towards the second detector 12b, and the period. The third segment 13c of the structure guides towards the third detector 12c.

[0042] The measured radiant intensity is received by the processing unit 5, and the height level of substrate 2 is estimated based on the radiant intensity received by different detectors, as described below in an exemplary embodiment. can do.

[0043] With reference to FIG. 3 again, the periodic structure shown on the left side of FIG. 3 is composed of a rhombus having a length L of about 30 μm and a width W of about 4 μm. Since the NA of the imaging optical system used for the level sensor is small, the periodicity in the width direction of the projection grid is not resolved, and the periodicity in the length direction L of the projection grid 7 is resolved. Note that in the alternative embodiment, the periodicity can also be resolved in the width direction.

On the right side of FIG. 3, the projected image resulting from this periodic structure on substrate 2 is shown. The image of FIG. 3 shows that the projected image has periodicity in the length direction of the projection grid 7. This image is reflected on the upper surface of the substrate 2 and directed toward the detection unit 4. The intensity distribution received by the detection grid 11 of the detection unit 4 can be estimated by the sinusoidal intensity distribution, which depends on the image length variables x and shifts caused by the height of the substrate.<maths num="1"><img file="JP5487144B2_D0001.tif" /></maths>In this equation, the pitch of the sinusoidal change is chosen to be equal to 2π. The image shift s is determined by the height of the substrate. Determine this shift s and calculate the height of the substrate at each measurement position 8 taking into account parameters A and B, which are also unknown variables.

[0045] Figure 4 shows, for illustration, a spatial image AI of a sinusoidal intensity distribution above the three segments 13a, 13b and 13c. Segments 13a, 13b, 13c each receive another part of the intensity distribution. Since the angles of the segments 13a, 13b, 13c are different, each part of the intensity distribution is guided to each of the detectors 12a, 12b, 12c. The intensity of the radiation received by the detectors 12a, 12b, 12c is guided to the processing unit 5 to determine the height level of the substrate at measurement position 8.

[0046] The radiation intensities D1, D2 and D3 received by each of the detectors 12a, 12b and 12c can be expressed by the following relational expressions.<maths num="2"><img file="JP5487144B2_D0002.tif" /></maths>Orthogonal signals can be derived from these three equations with three unknown variables.<maths num="3"><img file="JP5487144B2_D0003.tif" /></maths>With these two orthogonal signals, the value s can be found for any value of s, so there is no linearity error and no dead zone with zero sensitivity to changes in substrate height. As a result, the level sensor 1 is suitable for determining the height of the substrate in a relatively large height range of more than ± 5 μm, or even ± 10 μm. Therefore, the need for closed loop height control during height level measurements can be eliminated.

[0047] In a further embodiment, the detection grid can include four or more segments per period of the measurement beam. In the embodiment shown in FIG. 4, the segments 13a, 13b, and 13c each have the same length ls. In an alternative embodiment, the segments can have different lengths as long as the length of the complete array of segments corresponds to the period of the image of the measurement beam projected onto the detection grid 11.

[0048] The angle of the top surface of the segment is about -15 °, 0 ° and 15 ° with respect to the principal plane of the detection grid 11. Any other suitable angle can be applied to each of the segments. The angular difference must be large enough to divide the measurement beam into three identifiable beam sections that can be directed to three separate detectors 12a, 12b, 12c so that the intensity difference between the three beam sections can be determined. It doesn't become.

Since the height level of the substrate 2 is measured in an open loop and can be measured in a relatively large height range, the level sensor 1 simultaneously measures the height level at a plurality of measurement positions 8. Suitable for. Various methods can be applied to position the measurement position 8 of the level sensor 1 at various positions on the substrate 2.

[0050] In certain embodiments, the substrate 2 can be moved along the level sensor 1 in a scanning operation. Since the height control of the closed loop is not required, this operation can be performed at a constant speed, thereby eliminating the need to accelerate the substrate support supporting the substrate 2 while determining the height level of the substrate. In a further embodiment, the level sensor 1 can move beyond the substrate 2 while the substrate is stationary. In a further embodiment, both the level sensor 1 and the substrate can be moved to obtain an optimal path for moving the measurement position across the surface of the substrate.

[0051] In one embodiment, the level sensor is provided with a movable radiation guidance device configured to guide the measurement beam to various positions on the substrate without moving the entire level sensor and / or the substrate. Can be done. With such a level sensor, it is possible to measure at least the height of a part of the substrate, for example, the line of the measurement position, without having to move the entire level sensor and / or the substrate. In such an embodiment, it is possible to reduce the required or complex movements of the board with respect to the level sensor in order to obtain a height map of the entire board.

[0052] FIG. 5 shows a further embodiment of the level sensor 101. In the level sensor 101 of FIG. 5, the same or similar features as those of the embodiment of FIG. 2 are indicated by the same reference number.

[0053] The level sensor 101 is configured to measure the height of the substrate at various measurement positions 108 spaced apart on a line crossing the width of the substrate 2. For each measurement position 108, the level sensor 101 includes the component of the level sensor shown in FIG. Therefore, each measurement position 108 is associated with a projection unit with a radiation output unit 6 and a projection grid 7, and a detection unit with a detection grid 11 and some detectors (not shown). Further, the optical elements 9 and 10 are provided to guide the measurement beam from the projection unit to the measurement position, reflect it on the substrate 2, and then guide the measurement beam from the measurement position to the detection unit.

[0054] In the illustrated embodiment, one radiation output unit 6, one detection grid 11, and a set of three or more detectors are provided for each measurement position 108. There is one projection grid 7 and a set of optical elements 9 and 10 at every measurement position. The projection grid 7 and the optical elements 9 and 10 thus extend along the measurement position 108.

[0055] In an alternative embodiment, one detection grid 11 may be provided for use at all measurement positions 8. Also, additional or alternative, one or more components, such as projection grids, detection grids, etc., may be provided at a plurality of measurement positions 8, but not all.

The level sensor shown in FIG. 5 is configured to measure the height of the substrate at 12 measurement positions 8. The entire width of the substrate can be covered by this line at measurement position 8. If desired, a different number of measurement positions 8 can be provided. The measurement position 8 can also be arranged in a configuration other than along a single line as shown in the embodiment of FIG.

The structure of the level sensor 1 as shown in FIG. 2 is particularly suitable for use with a level sensor having a plurality of measurement positions. This is because the level sensor can measure the height of the surface of the substrate 2 in a relatively large height range. Generally, the height range of such magnitudes of measurement is greater than the usual variation in substrate thickness and / or flatness. Since the measurement range is large in this way, it is possible to eliminate the need for height control of the closed loop. As a result, the level sensor of FIG. 5 is used to measure the height of the substrate at a plurality of measurement positions 8 without having to correct the position of the substrate due to the height difference of the substrate at various measurement positions. It can be measured at the same time.

[0058] A plurality of measurement positions 8 can be moved along the substrate to obtain height information of a plurality of positions on the substrate 2. This operation can be obtained by the operation of the level sensor 101, the operation of the substrate 2, and / or the operation of the radiation guide element of the level sensor 101, for example, the operation of the optical elements 9 and 10. A combination of these operations can be used to obtain a height map of the substrate 2 used for substrate correction operations during the actual lithography process.

Tilt measuring device [0059] FIG. 2 shows a level sensor 1 capable of measuring the height of a substrate with relatively high accuracy. Level sensors can provide reliable measurements within ± 5 μm, or even ± 10 μm, and in some cases even larger height ranges. However, when the image of the projection grid is out of focus with respect to the detection grid, the level sensor may be sensitive to the tilt of the substrate around the x-axis. Although this effect is small, it can be taken into account when measuring the tilt of substrate 2 and determining the height map of the substrate. Correcting the height determined by taking into account the tilt of the substrate can further improve the accuracy of the height map. Next, an example of a level sensor capable of measuring the inclination of the substrate will be described.

[0060] FIG. 6 shows a level sensor of FIG. 2 further comprising a tilt measuring device 20. The tilt measuring device 20 is arranged to receive at least a portion of the reflected measurement beam and is configured to supply a tilt signal representing the tilt of the substrate with respect to the nominal plane 21 about the x-axis (Rx). The tilt measuring device 20 is connected to the processing unit 5 to correct the height level measured by the level sensor 1 and supplies a tilt signal to the processing unit 5, if necessary.

In the level sensor 1, the measurement beam reflected by the substrate 2 is received by the optical element 10. The optical element 10 is a partial retroreflector that reflects a major portion of the measurement beam, eg, 80% of the radiation intensity, towards the detection unit 4.

The rest of the measurement beam is transmitted through a partial reflector and is used to detect the tilt of the substrate within the tilt measurement device 20. The rest of the measurement beam is shown in FIG. 6 as the tilt measurement beam 22.

[0063] The tilt measurement beam 22 is received by the beam splitting device 23. The beam splitting device 23 is configured to split the tilt measurement beam into two parts, each part guided by one of the two tilt detectors 24, 25. The beam splitting device 23 comprises two wedges arranged facing each other. The portion of the tilt measurement beam received by the lower wedge is guided by the tilt detector 24, and the portion of the tilt measurement beam received by the upper wedge is guided by the tilt detector 25. The two wedges of the beam splitting device 23 are separated in a tilt-sensitive direction.

[0064] Comparing the ratio of the relative amounts of radiation received by the two tilt detectors 24, 25 represents the tilt of the substrate. For example, when the substrate is tilted as shown by the arrow T in FIG. 6, the portion of the tilt measurement beam 22 received by the upper wedge increases and the portion received by the lower wedge decreases. The difference in the amount of radiation received by the two tilt detectors 24 and 25 can be normalized to determine the small difference in the intensity of the radiation received by the tilt detectors 24 and 25. As a result of comparing the amount of radiation received by the respective tilt detectors 24 and 25 in this way, a small fluctuation in the tilt of the substrate 2 is detected.

The tilt measuring device of FIG. 6 is just one example of a tilt sensor that can be used to measure the tilt of a substrate and correct the height determined by the tilt measuring device 20. Any other tilt measuring device 20 capable of measuring the tilt of the substrate can be applied. Generally, it is desirable to measure the inclination about an axis perpendicular to the plane on which the measurement beam of the level sensor travels. In the illustrated embodiment, the measurement beam travels in the yz plane, and thus the measured tilt is the tilt of the substrate about the x-axis (Rx).

[0066] The tilt measuring device 20 as shown in FIG. 6 can be constructed to be very compact and is therefore applicable to level sensor systems for multiple measurement positions as shown in FIG. Are suitable. In such a level sensor, an inclination measuring device 20 can be provided for each measurement position of a plurality of measurement positions, and the inclination variable of the substrate can be measured for each measurement position 8. Therefore, for each measurement position 8, the level sensor 101 can be provided. The height determined by can be corrected with respect to the inclination of the substrate 2.

Measurement Beam Delivery System [0067] FIG. 5 shows a top view of a level sensor 101 configured to measure the height level of substrate 2 at multiple measurement positions 8. The level sensor 101 offers the possibility of simultaneously measuring the height of substrate 2 at various measurement positions 8. This level sensor also offers the possibility of an open loop scan of the measurement position along the surface of substrate 2. If desired, the tilt of the substrate 2 is measured with one or more tilt measuring devices to correct the height measured by the level sensor 1, and for any of the effects of the tilt of the substrate 2, if any. Can also correct the measured height.

[0068] While this level sensor offers the possibility of determining the height map of substrate 2 quickly and accurately, a level sensor as shown in FIG. 5 requires significant space above substrate 2. Sometimes. Such a space is not always available on the substrate in the lithographic apparatus.

[0069] In order to use the space available in the lithographic apparatus more efficiently, FIG. 7 shows an alternative beam in which the measurement beam is supplied at a plurality of measurement positions on the substrate and the plurality of measurement positions 8 are arranged on a line. The delivery method is shown. The substrate 2 is arranged at the measurement position. That is, at least one of the measurement positions 8 of the level sensor is located somewhere on the substrate 2 so that the height measurement of the substrate 2 can be performed.

[0070] For each measurement position 8, a radiation output unit 6, a projection grid 7, a detection grid 11 and three detectors (not shown) are provided. These components of such a level sensor correspond to the components used in the level sensors shown in FIGS. 2 and 5. However, the radiation output unit 6 and the projection grid 7 are provided on one side adjacent to the substrate 2, and the detection grid 11 and the detector are provided on the other side adjacent to the substrate 2. Although different components can be placed at different heights relative to substrate 2, in the illustrated embodiment all components are placed at a higher height level than substrate 2.

The advantage of this arrangement is that there are no components placed on top of board 2, and all components on one side of board 2 are placed close to each other, resulting in all components in the lithographic apparatus. The space required is relatively small.

Note that the term "adjacent" is used to indicate a position outside the board when projected vertically from the main plane of the board. The terms "above" or "below" indicate a position within the substrate when projected vertically from the main plane of the substrate.

[0073] FIGS. 8, 9 and 10 show further embodiments in which the space required for the measurement beam of the level sensor can be further reduced. In the embodiments of FIGS. 8, 9 and 10, reflection bars 30 and 31 are provided on the substrate 2. The reflection bars 30 and 31 are provided with inclined reflection surfaces 30a and 31a, respectively (see FIG. 9 showing a diagram along line AA of FIG. 8).

[0074] The angles of the slopes 30a, 31a are preferably equal to the horizontal plane and oriented towards the surface of the substrate. The angle is selected so that the measurement beam received by the reflection bar 30 in a substantially horizontal plane is reflected toward the measurement position 8 on the substrate 2. The measurement beam is reflected at the measurement position 8 and returns toward the reflection bar 31. The reflected beam is received on the reflection bar 31 at substantially the same height as that reflected by the reflection bar 30. The measurement beam is guided from the reflection bar 31 to the detection unit 4 substantially horizontally.

[0075] Another optical element may be provided in the detection unit 4 in order to detect a signal representing the height of the substrate 2. These signals can be used to determine the height of the substrate 2 at measurement positions within the detection unit 4 or within any other suitable location. The components of the level sensor can correspond to the components of the embodiments described above, but any other suitable level sensor device can also be used.

[0076] The components of the sensor are indicated by the projection unit 3 and the detection unit 4. The projection unit 4 is configured to provide a plurality of measurement beams to measure height levels at various measurement positions 8 on the substrate 2. The measurement beam is provided at substantially the same height and is guided to the reflection bar 30. All reflected measurement beams are received by the reflection bar 31 at substantially the same height and guided towards the detection unit 4.

[0077] The advantage of the measurement beam delivery device of the embodiments shown in FIGS. 8, 9 and 10 is that the measurement beam can be maintained at a relatively low height level relative to substrate 2, while at the same time the projection unit 3 And the detection unit 4 is arranged adjacent to the substrate, and the space available for providing these units 3 and 4 can be increased.

[0078] In the embodiments shown in FIGS. 8, 9 and 10, only three measurement positions 8 are shown. In practice, more measurement positions 8, eg, more than 50 measurement positions, can be placed in a line or in any other suitable configuration. In addition, the substrate 2 can be moved to move the measurement position 8 across the surface of the substrate, determine the height level of the substrate across the surface of the substrate, and move to determine the height map of the substrate. The operation can be achieved by the operation of the level sensor and / or the operation of the substrate, or any other suitable method.

It should be noted that the projection unit 3 and the detection unit 4 may be partially or wholly placed on the substrate within the measurement position when using the reflection bars 30 and 31.

[0080] Further, the projection unit 3 and / or the detection unit 4 of the embodiments of FIGS. 7, 8, 9 and 10 may have different optical path lengths of the measurement beams between different measurement beams, if necessary. It can be equipped with a compensator that compensates for everything.

It should also be noted that the measurement beam of the level sensor may be a parallel beam. The advantage of using a parallel beam (eg, a laser beam) is that the feasibility of the level sensor is improved.

Although the text specifically mentions the use of lithographic devices in the manufacture of ICs, it should be understood that the lithographic devices described herein have other uses as well. For example, this is the manufacture of integrated optical systems, induction and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads and the like. In the light of these alternative uses, the use of the terms "wafer" or "die" herein is considered synonymous with the more general terms "base" or "target portion", respectively. Those skilled in the art will recognize that this is acceptable. The substrates described herein are treated, for example, with a track (usually a tool that applies a layer of resist to the substrate and develops the exposed resist), metrology tools and / or inspection tools before or after exposure. be able to. As appropriate, the disclosures herein can be applied to these and other substrate processing tools. Further, the substrate can be processed multiple times, for example to produce a multilayer IC, and thus the term substrate as used herein can also refer to a substrate that already contains a plurality of treated layers.

Although the use of embodiments of the present invention in the field of optical lithography has been specifically mentioned, the present invention may also be used in other fields, such as the field of imprint lithography, in some contexts and is limited to optical lithography. Please understand that it will not be done. In imprint lithography, topography within a patterning device defines a pattern created on a substrate. The topography of the patterning device is imprinted in the resist layer supplied to the substrate, and the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is removed from the resist, leaving a pattern inside as the resist cures.

[0084] As used herein, the terms "radiation" and "beam" are used not only for particle beams such as ion beams or electron beams, but also for ultraviolet (UV) radiation (eg, 365 nm, 248 nm, 193 nm, 157 nm or 126 nm). It covers all types of electromagnetic radiation, including (or have wavelengths around these) and extreme ultraviolet light (EUV) radiation (eg, having wavelengths in the range of 5 nm to 20 nm).

[0085] The term "lens" can refer to any one or a combination of various types of optical components, including refraction, reflection, magnetic, electromagnetic and electrostatic optical components, if circumstances permit.

Although the specific embodiment of the present invention has been described above, it is understood that the present invention can be practiced by a method different from the description. For example, the present invention is a computer program that includes one or more sequences of machine-readable instructions that describe the methods disclosed above, or a data storage medium that internally stores such computer programs (eg, semiconductor memory, etc.). It can take the form of a magnetic or optical disk).

[0087] The above description is exemplary and not limiting. Therefore, it will be apparent to those skilled in the art that the invention as described can be modified without departing from the scope of the following provisions. 1. A level sensor configured to measure the height level of a substrate placed at a measurement position, wherein the level sensor projects a plurality of measurement beams onto a plurality of measurement positions on the substrate. A detection unit that receives the measurement beam after being reflected by the substrate, and a processing unit that calculates a height level based on the reflection measurement beam received by the detection unit. A level sensor in which the projection unit and the detection unit are arranged adjacent to the substrate when the substrate is arranged at the measurement position. 2. The level sensor according to Clause 1, wherein the measurement position is located on a line. 3. The level sensor according to Clause 2, wherein when projected onto the main plane of the substrate, the measurement beam is not perpendicular to the line in which the measurement position is located. 4. The level sensor according to Clause 3, wherein during the projection, the measurement beam travels non-parallel to the line in which the measurement position is located. 5. The level sensor according to any one of the above clauses, wherein the measurement beam is a parallel beam. 6. Receive the plurality of measurement beams from the projection unit, receive the first reflection bar arranged so as to guide the measurement beam to the substrate, and receive the plurality of reflection measurement beams from the projection unit. The level sensor according to Clause 1, comprising a second reflection bar arranged to direct the measurement beam to the detection unit. 7. The level sensor according to clause 6, wherein the first reflection bar is configured to receive the plurality of measurement beams from the projection unit in a plane substantially parallel to the main plane of the substrate. 8. The first reflection bar comprises an inclined reflective surface that reflects the plurality of measurement beams toward the substrate, and the second reflection bar directs the plurality of reflection measurement beams toward the detection unit. The level sensor according to Clause 6, which has a sloping reflective surface that reflects. 9. The level sensor according to clause 6, wherein the second reflection bar directs the plurality of measurement beams from a plane substantially parallel to the main plane of the substrate to the detection unit. 10. The level sensor according to Clause 9, wherein the first and second reflection bars are point symmetric. 11. The level sensor according to Clause 9, wherein the first and second reflection bars are placed on the substrate that determines the height map. 12. The level sensor according to Clause 1, wherein the projection and / or detection unit comprises a compensator that compensates for the difference in optical path length of the beams between different measurement beams. 13. The projection unit includes a radiation output unit that provides a measurement beam, and a projection grid that receives the measurement beam and is arranged so as to give the measurement beam a periodic radiation intensity, and the detection unit comprises the reflection. The level sensor according to Clause 1, comprising a detection grid arranged to receive the measurement beam and a detector arranged to receive the measurement beam. 14. The level sensor according to Clause 1, further comprising a tilt measuring device arranged to receive at least a portion of the reflection measuring beam and configured to provide a tilt signal representing the tilt of the substrate with respect to a nominal plane. .. 15. A lithography system built to support a lighting system configured to regulate the radiated beam and a patterning device that can pattern the cross section of the radiated beam to form a patterned radiated beam. A support, a substrate table constructed to hold the substrate, a projection system configured to project the patterned radiation beam onto a target portion of the substrate, and the substrate placed at the measurement position. With a level sensor configured to measure the height level of a substrate on a table, the level sensor comprises a projection unit that projects a plurality of measurement beams onto a plurality of measurement positions on the substrate, and the substrate. A detection unit that receives the measurement beam after reflection and a processing unit that calculates a height level based on the reflection measurement beam received by the detection unit are provided, and when the substrate is arranged at the measurement position, the said A lithography apparatus in which a projection unit and the detection unit are arranged adjacent to the substrate. 16.