Dual stage lithographic apparatus and device manufacturing method

RELATED APPLICATION

0001The present application is a Continuation In Part Application of U.S. application Ser. No. 11/101,631, filed on Apr. 8, 2005 now abandoned.

FIELD

0002The present invention relates to a multi stage lithographic apparatus and a method for manufacturing a device with the multi stage lithographic apparatus.

BACKGROUND

0003A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

0004There is an ongoing development in improving current lithographic apparatus. An aspect herewith is to increase the throughput (throughput is related to the number of substrates that can be processed in a certain time by a lithographic apparatus). For example, Dual Stage Lithographic apparatus generally have a larger throughput than Single stage apparatus since a substrate on a first substrate stage may be measured in a metrology station while another substrate on a second substrate stage is exposed in an exposure station on the basis of data measured previously in the metrology station. Another aspect is to improve the capability of lithographic apparatus to transfer patterns with smaller structures (but with a given quality) on substrates. For example, an Immersion lithographic apparatus is capable of transferring patterns with smaller structures in comparison with non-immersion lithographic apparatus (see for example EP 1486827, incorporated herein by reference).

0005In U.S. Pat. No. 5,969,441 (incorporated herein by reference) a Dual Stage lithographic apparatus is described that is provided with “H-drives” (see for example <figref idref="DRAWINGS">FIGS. 4</figref>, <b>5</b>: respective X-actuators <b>105</b> and <b>107</b> connected to respective sets of opposite Y-actuators <b>109</b>, <b>111</b> and <b>113</b>, <b>115</b>) for its substrate stages (substrate holders <b>11</b>, <b>13</b>). The described Dual Stage yields a relatively high throughput but a disadvantage is that the substrate stages need a “stage-swap” (according to the transition between <figref idref="DRAWINGS">FIG. 4</figref> and <figref idref="DRAWINGS">FIG. 5</figref> wherein substrate holder <b>11</b> is uncoupled from unit <b>25</b> and coupled to unit <b>27</b> and wherein substrate holder <b>13</b> is uncoupled from unit <b>27</b> and coupled to unit <b>25</b>) for passing each other while moving between the metrology station and the exposure station (column 16, lines 47–52). The apparatus has the disadvantage that the stage-swap takes time, thus yielding a decreased throughput.

0006In U.S. Pat. No. 6,341,007 (incorporated herein by reference) (see in particular <figref idref="DRAWINGS">FIGS. 2</figref>, <b>3</b>, <b>4</b>) a Dual Stage lithographic apparatus is described that is provided with one exposure station situated between two metrology stations. The substrates in the batch are measured alternately in the metrology stations before exposure in the exposure station. The stages can not pass each other while moving between the metrology stations and the exposure station (see <figref idref="DRAWINGS">FIG. 3</figref>). A disadvantage of this lithographic apparatus is that it requires two metrology stations. Therefore, there is a necessity of providing a double substrate conveying path. The extra metrology station and the extra conveying path yield an expensive lithographic apparatus. Furthermore, the system layout takes relatively much (floor)-space in the facrories (large footprint). A further disadvantage is that this concept yields problems of a logistics nature. Furthermore, the lithographic apparatus is not suitable for immersion lithographic applications such that it is not capable to project relatively small structures on the substrates.

SUMMARY

0007It is desirable to at least partially alleviate one of the mentioned disadvantages. In particular it is an aspect of the invention to provide a lithographic apparatus with a relatively high throughput and the capability of transferring patterns with relatively small structures on substrates.

0008In order to meet the desire the invention proposes a lithographic apparatus comprising:

0009a support constructed to support a patterning device, the patterning device being capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam;

0010a measuring system for measuring characteristics of substrates in a metrology station of the apparatus;

0011a projection system configured to project the patterned radiation beam onto a substrate in an exposure station of the apparatus;

0012a liquid confinement system for confining liquid between a final element of the projection system and the substrate;

0013a positioning system and at least two substrate stages constructed to hold substrates, wherein the positioning system is constructed for moving the stages between the metrology station and the exposure station, and wherein the positioning system is constructed for positioning one of the stages holding a substrate during exposure in the exposure station on the basis of at least one measured characteristic of that substrate;

0014wherein the stages are constructed and arranged for mutual cooperation in order to perform a joint scan movement for bringing the lithographic apparatus from a first situation, wherein the said liquid is confined between a first substrate held by the first stage of the said stages and the final element, towards a second situation, wherein the said liquid is confined between a second substrate held by the second stage of the two stages and the final element, such that during the joint scan movement the liquid is essentially confined within said space with respect to the final element. The joint scan movement yields an increased throughput compared to conventional immersion lithographic apparatus wherein a separate closing disc is used for confining the liquid between the transfer from the said first situation and the said second situation.

0015In order to meet the desire the invention proposes a lithographic apparatus comprising:

0016a support constructed to support a patterning device, the patterning device being capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam;

0017a measuring system for measuring characteristics of substrates in a metrology station of the apparatus;

0018a projection system configured to project the patterned radiation beam onto a substrate in an exposure station of the apparatus;

0019a positioning system for positioning at least two substrate stages of the lithographic apparatus, wherein the stages are constructed to hold substrates;

0020a machine frame which is provided with a first part of a planar motor for cooperating with respective second parts of the planar motor in the respective stages, wherein the positioning system is constructed and arranged to control the planar motor for moving the stages between the metrology station and the exposure station and for moving each of the said stages in the exposure station in six degrees of freedom on the basis of at least one measured characteristic of the substrate on the stage, wherein the machine frame is constructed and arranged to allow the stages to pass each other while moving between the metrology station and the exposure station. Since the stages can pass each other there is no need for a “stage-swap”. In this way an apparatus is provided with a relatively high throughput while having only one metrology station and only one exposure station, and wherein the apparatus has a relatively small “footprint”.

0021In order to meet the desire the invention proposes a lithographic apparatus comprising:

0022a support constructed to support a patterning device, the patterning device being capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam;

0023a measuring system for measuring characteristics of substrates in a metrology station of the apparatus;

0024a projection system configured to project the patterned radiation beam onto a substrate in an exposure station of the apparatus;

0025a positioning system and at least two stages constructed to hold substrates, wherein the positioning system is constructed for moving the stages between the metrology station and the exposure station, and wherein the positioning system is constructed for positioning one of the stages holding a substrate during exposure in the exposure station on the basis of at least one measured characteristic of that substrate,

0026a machine frame having two essentially parallel guides extending in a first direction in a horizontal plane, wherein each guide is coupled to an element which can be moved along the guide by means of a motor, and wherein each element is coupled to a stage by means of a motor for moving the stage in a second direction directed in the horizontal plane and perpendicular to the first direction, wherein the positioning system is constructed and arranged for controlling the motors in order to move the stages in the plane, wherein the machine frame is constructed and arranged to allow the stages to pass each other while moving between the metrology station and the exposure station. Since the stages can pass each other there is no need for a “stage-swap”. In this way an apparatus is provided with a relatively high throughput while having only one metrology station and only one exposure station, and wherein the apparatus has a relatively small “footprint”.

0027In order to meet the desire the invention proposes a lithographic apparatus comprising:

0028a support constructed to support a patterning device, the patterning device being capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam;

0029a measuring system for measuring characteristics of substrates in a metrology station of the apparatus;

0030a projection system configured to project the patterned radiation beam onto a substrate in an exposure station of the apparatus;

0031a positioning system and at least two stages constructed to hold substrates, wherein the positioning system is constructed for moving the stages between the metrology station and the exposure station, and wherein the positioning system is constructed for positioning one of the stages holding a substrate during exposure in the exposure station on the basis of at least one measured characteristic of that substrate;

0032a base frame carrying a metro frame which supports the measuring system and the projection system, wherein the metro frame is dynamically isolated from the base frame, and wherein the measuring system comprises an encoder system extending in both the metrology station and the exposure station for measuring the position of the stages. The said encoder system for example reduces the need of frequent TIS alignments (aligning masks/reticles on the one hand with substrates on the other hand via Transmission Image Sensors such as described in EP 1510870, incorporated herein by reference, see in particular <figref idref="DRAWINGS">FIGS. 8A</figref>, <b>8</b>B). The reduction of the necessity of frequent TIS-alignments increases throughput of the lithographic apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

0033Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

0034<figref idref="DRAWINGS">FIG. 1A</figref> schematically depicts a lithographic apparatus according to an embodiment of the invention in a side-view;

0035<figref idref="DRAWINGS">FIG. 1B</figref> shows a stage of the lithographic apparatus according to <figref idref="DRAWINGS">FIG. 1A</figref>;

0036<figref idref="DRAWINGS">FIG. 2</figref> is a schematic side-view of a metrology station of the lithographic apparatus according to the invention;

0037<figref idref="DRAWINGS">FIG. 3</figref> is a schematic side-view of an exposure station of the lithographic apparatus according to the invention;

0038<figref idref="DRAWINGS">FIG. 4</figref> is a schematic top-view of a first embodiment of the drive and stage configuration of the dual stage immersion lithography apparatus according to <figref idref="DRAWINGS">FIG. 1A</figref>;

0039<figref idref="DRAWINGS">FIG. 5</figref> is a schematic top-view of the apparatus of <figref idref="DRAWINGS">FIG. 4</figref> showing a joint scan movement;

0040<figref idref="DRAWINGS">FIG. 6</figref> is a schematic top-view of a second embodiment of the drive and stage configuration of the dual stage immersion lithography apparatus according to <figref idref="DRAWINGS">FIG. 1A</figref>;

0041<figref idref="DRAWINGS">FIG. 7</figref> is a schematic top-view of the apparatus of <figref idref="DRAWINGS">FIG. 6</figref> showing a joint scan movement;

0042<figref idref="DRAWINGS">FIG. 8</figref> is a schematic top-view of a third embodiment of the drive and stage configuration of the dual stage immersion lithography apparatus according to <figref idref="DRAWINGS">FIG. 1A</figref>, wherein the lithographic apparatus performs a joint scan movement;

0043<figref idref="DRAWINGS">FIG. 9</figref> is a schematic side-view showing two substrate stages in a vertical cross section, wherein the stages perform a joint scan movement;

0044<figref idref="DRAWINGS">FIG. 10</figref> is a schematic vertical cross section of a first embodiment of the stages in <figref idref="DRAWINGS">FIG. 9</figref>;

0045<figref idref="DRAWINGS">FIG. 11</figref> is a schematic vertical cross section of a second embodiment of the stages in <figref idref="DRAWINGS">FIG. 9</figref>;

0046<figref idref="DRAWINGS">FIG. 12</figref> is a schematic vertical cross section of a third embodiment of the stages in <figref idref="DRAWINGS">FIG. 9</figref>;

0047<figref idref="DRAWINGS">FIG. 13</figref> is a schematic vertical cross section of a fourth embodiment of the stages in <figref idref="DRAWINGS">FIG. 9</figref>;

0048<figref idref="DRAWINGS">FIG. 14</figref> is a schematic vertical cross section of a fifth embodiment of the stages in <figref idref="DRAWINGS">FIG. 9</figref>.

DETAILED DESCRIPTION

0049<figref idref="DRAWINGS">FIG. 1A</figref> schematically depicts a lithographic apparatus according to one embodiment of the invention. The apparatus comprises:

0050an illumination system (illuminator) <b>2</b> configured to condition a radiation beam <b>4</b> (e.g. UV radiation).

0051a support structure (e.g. a mask table) <b>6</b> constructed to support a patterning device (e.g. a mask) <b>8</b> and coupled to a first positioner <b>10</b> configured to accurately position the patterning device in accordance with certain parameters;

0052a substrate table (e.g. a wafer table) WT constructed to hold a substrate (e.g. a resist-coated wafer) <b>14</b> and coupled (via a mirror block MB) to a second positioner <b>16</b> configured to accurately position the substrate in accordance with certain parameters; and

0053a projection system (e.g. a refractive projection lens system) <b>18</b> configured to project a pattern imparted to the radiation beam <b>4</b> by patterning device <b>8</b> onto a target portion C (e.g. comprising one or more dies) of the substrate <b>14</b>.

0054The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation.

0055The support structure supports, i.e. bears the weight of, the patterning device. It holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”

0056The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section such as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.

0057The patterning device may be transmissive 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, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.

0058The term “projection system” used herein should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.

0059As here depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).

0060The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and/or two or more mask tables). In such machines the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure.

0061The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the projection system and the substrate. An immersion liquid may 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. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.

0062Referring to <figref idref="DRAWINGS">FIG. 1A</figref>, the illuminator <b>2</b> receives a radiation beam from a radiation source <b>20</b>. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source <b>20</b> to the illuminator <b>2</b> with the aid of a beam delivery system <b>22</b> comprising, for example, suitable directing mirrors and/or a beam expander. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source <b>20</b> and the illuminator <b>2</b>, together with the beam delivery system <b>22</b> if required, may be referred to as a radiation system.

0063The illuminator <b>2</b> may comprise an adjuster <b>24</b> for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator <b>2</b> may comprise various other components, such as an integrator <b>26</b> and a condenser <b>28</b>. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.

0064The radiation beam <b>4</b> is incident on the patterning device (e.g., mask <b>8</b>), which is held on the support structure (e.g., mask table <b>6</b>), and is patterned by the patterning device. Having traversed the mask <b>8</b>, the radiation beam <b>4</b> passes through the projection system <b>18</b>, which focuses the beam onto a target portion C of the substrate <b>14</b>. With the aid of the second positioner <b>16</b> and position sensor <b>30</b> (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT of a wafer stage St can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam <b>4</b>. For this, known measure &amp; Control algorithms with feedback and/or feedforward loops may be used. Similarly, the first positioner <b>10</b> and another position sensor (which is not explicitly depicted in <figref idref="DRAWINGS">FIG. 1A</figref>) can be used to accurately position the mask <b>8</b> with respect to the path of the radiation beam <b>4</b>, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the mask table <b>6</b> may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner <b>10</b>. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner <b>16</b>. In the case of a stepper (as opposed to a scanner) the mask table <b>6</b> may be connected to a short-stroke actuator only, or may be fixed. Mask <b>8</b> and substrate <b>14</b> may be aligned using mask alignment marks M<b>1</b>, M<b>2</b> and substrate alignment marks P<b>1</b>, P<b>2</b>. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the mask <b>8</b>, the mask alignment marks may be located between the dies.

0065<figref idref="DRAWINGS">FIG. 1B</figref> shows a substrate stage St (also called substrate chuck) for the lithographic apparatus according to <figref idref="DRAWINGS">FIG. 1A</figref>. The stage St comprises the non-stationary parts of the second positioner <b>16</b>, a mirror block MB, and the substrate table WT mounted to the mirror block MB. In this example the mirror block MB is provided with interferometer-mirrors which are arranged for cooperation with interferometers for measuring the position of the mirror block MB.

0066The second positioner <b>16</b> is arranged for positioning the mirror block MB and the substrate table WT. The second positioner <b>16</b> comprises the short stroke module (which is provided with a short stroke motor ShM) and the long stroke module (which is provided with a long stroke motor LoM).

0067The long stroke motor LoM comprises a stationary part LMS that can be mounted to a stationary frame or a balance mass (not shown) and a non-stationary part LMM that is displaceable relative to the stationary part. The short stroke motor ShM comprises a first non-stationary part SMS (that may be mounted to the non-stationary part LMM of the long stroke motor) and a second non-stationary part SMM (that may be mounted to the mirror block MB).

0068It should be noted that the mask table <b>6</b> and the first positioner <b>10</b> (see <figref idref="DRAWINGS">FIG. 1A</figref>) may have a similar structure as depicted in <figref idref="DRAWINGS">FIG. 1B</figref>.

0069A so-called dual stage (multi stage) machine may be equipped with two (or more) stages as described. Each stage can be provided with an object table (such as the substrate table WT). In such an arrangement, a preparatory step such as the measurement of a height map of the substrate disposed on one of the object tables can be performed in parallel with the exposure of the substrate disposed on another object table. In order to expose a substrate that previously has been measured, the stages may change position from the measurement location to the exposure location (and vice versa). As an alternative, the object tables can be moved from one stage to an other.

0070The apparatus depicted in <figref idref="DRAWINGS">FIG. 1A</figref> could be used in at least one of the following modes: <ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0071">1. In step mode, the mask table <b>6</b> and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT is then shifted in the X and/or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.</li><li id="ul0001-0002" num="0072">2. In scan mode, the mask table <b>6</b> and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the mask table <b>6</b> may be determined by the (de-)magnification and image reversal characteristics of the projection system <b>18</b>. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion.</li><li id="ul0001-0003" num="0073">3. In another mode, the mask table <b>6</b> is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.</li></ul>

0074Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

0075<figref idref="DRAWINGS">FIG. 4</figref> is a schematic top-view of an embodiment of a drive and stage configuration of the lithographic apparatus schematically shown in <figref idref="DRAWINGS">FIG. 1A</figref>. The part is defined by a plane indicated in <figref idref="DRAWINGS">FIG. 1A</figref> by the line LL. The lithographic apparatus comprises a first metrology station <b>32</b>.<b>1</b>, a second metrology section <b>32</b>.<b>2</b> and an exposure station <b>34</b> which is situated between the metrology stations <b>32</b>.<b>1</b>, <b>32</b>.<b>2</b>.

0076In <figref idref="DRAWINGS">FIG. 2</figref> a schematic side view of a metrology station <b>32</b> is provided. The metrology station is supported by a base frame <b>36</b> which carries a metro frame <b>38</b>. The base frame <b>36</b> may be placed directly on the floor in a factory. The base frame <b>36</b> and the metro frame <b>38</b> are dynamically isolated by isolation means <b>40</b> (the isolation means <b>40</b> may be passive isolation means such as airmounts, active isolation means such a pneumatic pistons or combinations thereof). Due to the dynamical isolation, it is prevented that vibrations or other disturbance movements in the base frame transfer into the metro frame (the disturbances will at least be reduced to a relatively large amount). The metro frame and elements which are connected to it are sometimes called the “silent world”.

0077<figref idref="DRAWINGS">FIG. 2</figref> also shows a (substrate) stage <b>42</b> holding a substrate <b>14</b> and a measuring system <b>44</b> comprising a height measurement sensor <b>46</b> and a position sensor <b>30</b>. In this example, the position sensor <b>30</b> is capable of measuring the position of the stage <b>42</b> in six degrees of freedom. The measuring system <b>44</b> is carried by the metro frame and is therefore part of the silent world. The sensors <b>46</b>, <b>30</b> may be used for measuring a characteristic (height map) of the substrate <b>14</b> held by the stage <b>42</b>. The height map is used later during exposure in the exposure station <b>34</b>.

0078The position sensor <b>30</b> for measuring the position of the stage <b>42</b> may be an interferometer sensor <b>48</b>.<b>1</b> which is capable of directing interferometer measurement beams <b>50</b> towards interferometer mirrors <b>52</b> attached to the stage <b>42</b>. As an alternative, the position sensor may be an encoder system <b>48</b>.<b>2</b> for measuring the position of the stage <b>42</b>. However, it is noted here that combinations of interferometers and encoders, whereby the interferometer system measures different parameters than the encoder are also possible.

0079In the presented example of <figref idref="DRAWINGS">FIG. 2</figref> the encoder system <b>48</b>.<b>2</b> is an encoder plate which is attached to the metro frame <b>38</b>. The stage <b>42</b> is provided with encoder heads <b>54</b> which are capable of cooperating with the encoder plate <b>48</b>.<b>2</b> for measuring the position of the stage <b>42</b>. Note that the encoder plate is provided with a cut-away to let the height measurement sensor <b>46</b> directing a light measurement beam through the cut-away on the surface of the substrate <b>8</b> for measuring the height of the surface of the substrate. Preferably, each corner (at or near each corner) of the upper surface of the stage <b>42</b> is provided with an encoder head <b>54</b>. The position of the stage can be measured at any location under the cut-away with the encoder system <b>48</b>.<b>2</b>.

0080<figref idref="DRAWINGS">FIG. 3</figref> is a schematic side view of an exposure station <b>34</b>. The exposure station <b>34</b> is supported by the base frame <b>36</b>. The base frame carries the metro frame <b>38</b>, the metro frame <b>38</b> is dynamically isolated from the base frame <b>36</b> by the isolation means <b>40</b>. The projection system <b>18</b> is supported by the metro frame <b>38</b> via supporting members <b>56</b> (the supporting members <b>56</b> may also be dynamical isolation means). In this example the metro frame <b>38</b> carries the position sensor <b>30</b> (an interferometer <b>48</b>.<b>1</b> and/or an encoder system <b>48</b>.<b>2</b>, whereby it is noted that the encoder system <b>48</b>.<b>2</b> is provided with a cut away for the projection system <b>18</b>). However, it is noted that the position sensor <b>30</b> may also be carried by the projection system <b>18</b> (or, equivalently, by a frame attached to the projection system <b>18</b>).

0081If the position sensor <b>30</b> is an encoder plate <b>48</b>.<b>2</b>, then this encoder plate may extend both in the exposure station <b>34</b> and the metrology station <b>32</b>. In an advanced embodiment there is only one encoder plate which extends completely from the metrology station <b>32</b> to the exposure station <b>34</b>.

0082A reticle stage or mask stage <b>6</b> is located above the projection system <b>18</b>. The position of the reticle stage and the position of the mask/reticle are measured by a measuring system <b>60</b>. The measuring system <b>60</b> cooperates with the position sensor <b>30</b> in order to align the mask/reticle with the substrate <b>14</b> under the projection system <b>18</b>. Aligning the mask/reticle to the substrate is usually performed according to zero point sensors and TIS-alignment techniques (see for a description EP 1510870). For applying the TIS-alignment it is required that the position of the substrate with respect to the base frame <b>36</b> is known within a certain accuracy (rough indication as starting point for the fine TIS measurements) such that the substrate is in the capture range of the TIS sensor.

0083Generally, interferometer sensors measure relative positions (by counting fringes). In order to obtain absolute position measurements via the interferometer sensor the interferometer sensors can be “zerod” by means of a so-called zeroing-operation, which means that a reference point is defined in order to obtain absolute position measurements. Defining such a reference point is of special interest in a multi-stage apparatus, since in such an apparatus it frequently occurs that one stage eclipses another stage yielding a loss of an already defined reference point. If this happens it may be necessary to define a new reference point (according to a new zeroing operation) has to be defined which costs time and reduces throughput. However, the application of the encoder plate may yield an absolute measurement system which reduces or even eliminates the necessary zeroing operations which is beneficial for throughput. Furthermore, if the encoder plate has a high accuracy, the frequency of TIS-alignments itself may also be reduced or even eliminated (at least partly replaced by the encoder measurements), such that the throughput of the corresponding apparatus is further increased.

0084As shown in <figref idref="DRAWINGS">FIG. 4</figref>, the stages holding substrates can be exchanged between, on the one hand, the metrology stations <b>32</b>.<b>1</b>, <b>32</b>.<b>2</b> and, on the other hand, the exposure station <b>34</b>. This will be described in more detail hereinafter. <figref idref="DRAWINGS">FIG. 4</figref> schematically depicts two guides <b>62</b>.<b>1</b>, <b>62</b>.<b>2</b> which extend in a first direction (the X-direction) in a horizontal plane. The guides <b>62</b> may be attached to the base frame <b>36</b>, but it is preferred to attach the guides <b>62</b> to a machine frame which is completely separated (thus no dynamical coupling) from the said base frame <b>36</b>, the metro frame <b>38</b> and the projection lens <b>18</b>.

0085Each guide <b>62</b> is coupled to elements <b>64</b> which can be moved along the guide <b>62</b> in the first direction (X-direction) by means of a motor of the positioning system. In the configuration of <figref idref="DRAWINGS">FIG. 4</figref> each stage <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b> is coupled to two elements <b>64</b>. Each stage can be moved in the horizontal plane in the Y-direction (which is essentially perpendicular to the first direction) by motors in the elements <b>64</b>. In a preferred embodiment the motors in the guides <b>62</b> and/or in the elements <b>64</b> cooperate with balance masses in order to reduce effects of reaction forces. The stages <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b> may be supported by the base frame <b>36</b> via an air bearing which yields a dynamical isolation of the base frame <b>26</b> and the stages <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b>. It is noted that as an alternative of the described drive configuration a planar motor configuration may be applied.

0086In the configuration of <figref idref="DRAWINGS">FIG. 4</figref> the stages can not pass each other. Therefore, the working sequence of the lithographic apparatus which belongs to this configuration is as follows. A substrate <b>14</b>.<b>1</b> is provided on the first stage <b>42</b>.<b>1</b> via a first substrate convey path to the first metrology station <b>32</b>.<b>1</b>. Then this substrate is measured (see <figref idref="DRAWINGS">FIG. 2</figref>, measurement system <b>44</b>, generation of a height map) in the metrology station <b>32</b>.<b>1</b> while being scanned in the horizontal plane (the stage <b>42</b>.<b>1</b> is moved in the horizontal plane for this). The position of the stages <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b> is, in the example of <figref idref="DRAWINGS">FIG. 4</figref>, measured by an interferometer system <b>48</b>.<b>1</b>. Next the stage is transferred to the exposure station <b>34</b> in order to expose the substrate <b>14</b>.<b>1</b> held by the stage <b>42</b>.<b>1</b>. The exposure is based on the measured height map of the substrate <b>14</b>.<b>1</b>, wherein the stage <b>42</b>.<b>1</b> holding the substrate is positioned by the positioning system. (It is noted that the said motors are capable of positioning the stage in six degrees of freedom, however within a limited range, under the projection system <b>18</b>). At the same time, the other stage <b>42</b>.<b>2</b> is in the second metrology station <b>32</b>.<b>2</b> and holds a substrate <b>14</b>.<b>2</b> which is measured. The substrate <b>14</b>.<b>2</b> has been supplied via a second substrate convey path. After the exposure of substrate <b>14</b>.<b>1</b> has been performed the stage <b>42</b>.<b>1</b> with the exposed substrate moves to the first metrology station <b>32</b>.<b>1</b>, the exposed substrate <b>14</b>.<b>1</b> is conveyed via the first substrate convey path, and a new substrate to be measured is loaded on the stage <b>42</b>.<b>1</b> via the first substrate convey path. At the same time the substrate <b>14</b>.<b>2</b> held by the stage <b>42</b>.<b>2</b> is exposed. The sequence continues in this way. It is clear that the configuration requires a double substrate convey path.

0087It is noted that the beams of the interferometers sometimes have to bridge relatively great distances between the interferometer system and the interferometer-mirror attached to the stage (see <figref idref="DRAWINGS">FIG. 4</figref>, interferometer beams in the X-direction). This decreases the accuracy of the measurement in this direction, since pressure variations in the air disturb the interferometer measurement beam (this effect increases with an increased distance). Application of the discussed encoder system <b>48</b>.<b>2</b> alleviates this disadvantage and may yield higher measurement accuracies.

0088<figref idref="DRAWINGS">FIG. 6</figref> schematically depicts another dual stage concept in a top-view defined by the line LL in <figref idref="DRAWINGS">FIG. 1</figref>. In this concept stages with substrates <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b> can be exchanged between the metrology station <b>32</b> and the exposure station <b>34</b>. The concept is provided with two guides <b>62</b>.<b>1</b>, <b>62</b>.<b>2</b> which extend in a first direction (the X-direction) in a horizontal plane. The guides <b>62</b> may be attached to the base frame <b>36</b>, but it is preferred to attach the guides <b>62</b> to a machine frame which is completely separated (thus no dynamical coupling) from the said base frame <b>36</b>, the metro frame <b>38</b> and the projection lens <b>18</b>. Each guide <b>62</b> carries an element <b>64</b> which can be moved along the guide <b>62</b> in the first direction (X-direction) by means of a motor (part of and) controlled by the positioning system. In this example the elements <b>64</b> are T-elements which are part of a so-called “T-drive”. Each stage <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b> is coupled to one T-element <b>64</b>, wherein the T-element <b>64</b> can move the stage to which it is coupled in the Y-direction by a motor which may be present in the element <b>64</b>. The motor is (preferably part of and) controlled by the positioning system. In a preferred embodiment the motors in the guides <b>62</b> and/or in the elements <b>64</b> cooperate with balance masses in order to reduce effects of reaction forces. It is noted that the stages <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b> may be supported by the base frame <b>36</b> via a dynamically isolating air bearing.

0089The dual stage concept according to <figref idref="DRAWINGS">FIG. 6</figref> allows the stages <b>42</b>.<b>1</b> and <b>42</b>.<b>2</b> to pass each other while being moved between the metrology station <b>32</b> and the exposure station <b>34</b>. This concept based on the T-drives does not require a stage swap (in contrast to the H-drive concept described in U.S. Pat. No. 5,969,441). Therefore a relatively high throughput can be achieved since a continuous transfer movement of the stages is possible without a stop for a swap.

0090As an alternative of the depicted “T-drive system” (guides <b>62</b>.<b>1</b>, <b>62</b>.<b>2</b> and T-elements <b>64</b> in <figref idref="DRAWINGS">FIG. 6</figref>) a planar motor configuration can be used. According to the planar motor configuration the lithographic apparatus is provided with a machine frame with coils and/or magnets (the first part of the planar motor) for cooperating with magnets and/or coils in the said stages <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b> (the respective second parts of the planar motor) such that the positioning system can move each of the said stages <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b> between the metrology station <b>32</b> and the exposure station <b>34</b>. Such a planar motor can also be used to position the stages in the exposure station <b>34</b> in six degrees of freedom. The machine frame may be part of the base frame <b>36</b> (then the coils and/or magnets) are integrated in the base frame <b>36</b>, or the machine frame is separated (dynamically isolated) from the base frame <b>36</b>. The planar motor is under control of the positioning system.

0091According to an embodiment of the lithographic apparatus according to the invention there is provided an immersion liquid <b>66</b> between a final optical (lens) element of the projection system <b>18</b> and a target portion of the substrate <b>14</b> (<figref idref="DRAWINGS">FIG. 3</figref>). The application of immersion fluid yields the advantage that during exposure smaller structures of patterns can be transferred from the reticle or mask to substrates <b>14</b> than in a comparable system without immersion fluid. The lithographic apparatus has a liquid confinement system for confining liquid between a final element of the projection system and the substrate. The liquid confinement system comprises a so-called immersion hood <b>68</b> (see <figref idref="DRAWINGS">FIG. 9</figref>). The immersion fluid may be kept in place during illumination by the immersion hood <b>68</b>. The immersion hood <b>68</b> may comprise a mechanical contact-seal and/or may also comprise a contact-less seal which operation is based on guiding a pressure-gas-flow towards the fluid to be confined (combinations are possible).

0092After exposure of a substrate the stage holding it has to move away, for example towards a metrology station. Since it is desired that the immersion fluid <b>66</b> is kept in its space under the final element of the projection system <b>18</b>, special measures have to be taken before the stage can be moved away from its position under the space of the immersion liquid <b>66</b>. A possibility is to use a separate closing disc or a separate small closing stage (unable to hold a substrate) which closes the space at the bottom, until a stage holding a substrate to be exposed takes the place of the closing disc/closing stage.

0093However, the said closing disc/closing stage yields extra take-over operations which cost valuable time and which appear to decrease the throughput of the lithographic apparatus significantly.

0094Therefore, it is an aspect of the invention to prevent the necessity of a closing disc (or closing stage) and to provide a lithographic apparatus wherein the stages are constructed and arranged for mutual cooperation in order to perform a joint scan movement for bringing the lithographic apparatus from a first situation, wherein the said liquid is confined between a first substrate held by the first stage of the said stages and the final element, towards a second situation, wherein the said liquid is confined between a second substrate held by the second stage of the two stages and the final element, such that during the joint scan movement the liquid is essentially confined within said space with respect to the final element.

0095The said joint scan movement of the stages <b>42</b>.<b>1</b> and <b>42</b>.<b>2</b> is illustrated schematically in <figref idref="DRAWINGS">FIG. 9</figref> (the arrows <b>71</b> indicate the direction of movement of the stages with respect to the projection system <b>18</b>). The joint scan movement is performed such that the liquid <b>66</b> stays confined in its space under the final lens element <b>70</b>. At the bottom of the space the stages <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b> confine the liquid <b>66</b>. At the sides it is the immersion hood (which preferably stays in an essentially fixed position with respect to the projection system <b>18</b>) which confines the liquid <b>66</b>.

0096In an advanced embodiment the respective first stage <b>42</b>.<b>1</b> and second stage <b>42</b>.<b>2</b> have respective immersion cross edges <b>72</b>.<b>1</b>, <b>72</b>.<b>2</b> (situated at or near a side of the relevant stage, see <figref idref="DRAWINGS">FIG. 9</figref>), wherein the immersion cross edges are constructed and arranged to cooperate with each other during the joint scan movement. Preferably each immersion cross edge <b>72</b> comprises one or more essentially plane and smooth surface(s). Thus, it is possible to perform the said joint scan movement in such a way that a well-defined space is obtained between plane surfaces of different immersion cross edges (for example a space defined by parallel surfaces). In <figref idref="DRAWINGS">FIG. 9</figref> an example is provided wherein the cooperating immersion cross edges of the stages define a space with a mutual distance D during the joint scan movement.

0097A different shape of the immersion cross edges <b>72</b>.<b>1</b>, <b>72</b>.<b>2</b> is shown in <figref idref="DRAWINGS">FIG. 10</figref>. In <figref idref="DRAWINGS">FIG. 10</figref> the stage <b>42</b>.<b>1</b> shows an immersion cross edge with respectively a vertical plane A, a horizontal plane B and a vertical plane C. These planes are constructed to cooperate with respective planes D, E, F of the immersion cross edge <b>72</b>.<b>2</b>.

0098The lithographic apparatus according to the invention may comprise a control system (using a feedback and/or a feedforward loop) that may be fed with position measurements (actually the term position measurement may include position, velocity, acceleration and/or jerk measurements) of the stages (the measurements may be performed by the measurement system <b>44</b>) for calculating setpoint-signals for the relevant motors. The motors are controlled during the joint scan movement of the stages by the positioning system according to the setpoint-signals such that the mutual constant distance D between the planes of the respective immersion cross edges corresponds to a pre-determined function. The pre-determined function may be chosen such that the space between the immersion cross edges functions a liquid channel character (see below for further description).

0099According to an embodiment of the lithographic apparatus, the positioning system is constructed and arranged to control the motors for moving the stages such that stage <b>42</b>.<b>1</b> pushes the stage <b>42</b>.<b>2</b> gently during the joint scan movement. Herewith, a control system (using a feedback and/or a feedforward loop) of the positioning system is fed with position measurements (actually the term position measurement may include position, velocity, acceleration and/or jerk measurements) of the stages (performed by the measurement system <b>44</b>) and calculates setpoint-signals for the relevant motors. Next, motors are controlled by the positioning system according to the setpoint-signals such that the mutual constant distance D between the planes of the respective immersion cross edges is essentially zero.

0100According to a preferred embodiment of the lithographic apparatus, the positioning system is constructed and arranged to control the motors for moving the stages such that during the joint scan movement the said mutual distance D is larger than zero but smaller that 1 millimeter. A favorable mutual distance D appears to be between 0.05 and 0.2 millimeter. A distance D in this distance-range is especially favorable if one of the stages is provided with a channel system <b>74</b> leading to and from an opening the immersion cross edge, wherein the channel system <b>74</b> is constructed and arranged for generating a flow of gas and/or liquid along the immersion cross edge during the joint scan movement. The generation of this flow is of importance to reduce the chance that bubbles (bubbles deteriorate the projection of patterns on the substrate) are generated in the immersion liquid <b>66</b>. A stable and well controlled distance D results in a stable and well favorable flow thereby avoiding the generation of bubbles in the immersion liquid during the joint scan movement.

0101The application of a channel system <b>74</b> may yield (during the joint scan movement) a gas flow from under the stages <b>42</b> (see for example <figref idref="DRAWINGS">FIG. 11</figref> with indication G) and a liquid flow from above the stages (see for example <figref idref="DRAWINGS">FIG. 11</figref> with indication L). Then a mixture of gas and liquid will be drained away via the channel system <b>74</b> (see indication L/G). Flexible tubes may be connected to the (channel system <b>74</b> of the) stage for further transport of the mixture L/G.

0102In the example of <figref idref="DRAWINGS">FIG. 11</figref> each stage (<b>42</b>.<b>1</b> respectively <b>42</b>.<b>2</b>) has a channel system (<b>74</b>.<b>1</b> respectively <b>74</b>.<b>2</b>), wherein each channel system leads to an opening in a plane surface of the immersion cross edge (<b>72</b>.<b>1</b> respectively <b>72</b>.<b>2</b>). In the example of <figref idref="DRAWINGS">FIG. 10</figref> only the stage <b>42</b>.<b>2</b> is provided with a channel system <b>74</b>, wherein the channel system <b>74</b> has three openings in the surface E of the immersion cross edge <b>72</b>.<b>2</b>. Little arrows in the channel system <b>74</b> show the direction of the flow during the joint scan movement.

0103<figref idref="DRAWINGS">FIG. 10</figref>, <b>13</b>, <b>14</b> show a configuration wherein the stages <b>42</b>.<b>1</b>, <b>42</b>.<b>2</b> are provided with a water gutter <b>76</b>.<b>1</b>, <b>76</b>.<b>2</b> under the immersion cross edges <b>72</b>.<b>1</b>, <b>72</b>.<b>2</b>. The water gutter is capable of catching liquid possible dripped along the immersion cross edge before, during and after the joint scan movement. Application of only one water gutter attached to only one of the stages is in principle sufficient for only catching liquid during the joint scan movement.

0104The said interferometer system <b>48</b>.<b>1</b> uses interferometer-mirrors attached to the stages for position measuring. In the example of <figref idref="DRAWINGS">FIG. 4</figref> it does not make sense for the interferometer system <b>48</b>.<b>1</b> to have interferometer mirrors <b>52</b> on the stages at the sides of the immersion cross edges. However, for the drive and stage configuration in <figref idref="DRAWINGS">FIG. 6</figref>, it may be advantageous to have an interferometer-mirrors <b>52</b> at the stages at the sides of the immersion cross edges (for example to have relative short distances of the interferometer beam, which generally yields relative high measurement accuracies). This also holds for the configuration of <figref idref="DRAWINGS">FIG. 8</figref>, for example in the situation whereby the stage <b>42</b>.<b>1</b> visits the exposure station <b>34</b> (the immersion cross edge is at the side of the positive X-direction, and in the left X-direction is a relatively long interferometer beam path). In these case it is preferred that the stages are provided with an interferometer-mirror <b>52</b> at the immersion cross edge. It is noted that the chance on contamination (liquid flow) and or damage arising during the joint scan movement is greater than for the other interferometer-mirrors. Therefore it is advantageous to stagger the interferometer-mirror with respect to the immersion cross edge as indicated in <figref idref="DRAWINGS">FIG. 12</figref>. As an alternative the interferometer-mirrors <b>52</b> are placed it in a protective niche of the stage, as indicated in <figref idref="DRAWINGS">FIG. 13</figref>. Another alternative is to place the interferometer-mirror <b>52</b> below the said water gutter <b>76</b> which catches liquid (and possible contamination). <figref idref="DRAWINGS">FIG. 14</figref> shows an example of a combination of the mentioned measures whereby the interferometer-mirrors are both staggered with respect to the immersion cross edge <b>72</b> and placed at a level under the water gutter <b>76</b>. In this way the interferometers stay clean and undamaged which yield a reliable performance of the measurement system.

0105Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion”, respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

0106Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

0107The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365, 355, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-14 20 nm), as well as particle beams, such as ion beams or electron beams.

0108The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

0109While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein.

0110The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.