KR100869306B1 - Lithographic apparatus and device manufacturing method - Google Patents

Abstract

The invention provides a substrate table for holding a substrate, a projection system for projecting a patterned beam onto a target portion of the substrate; And a displacement measuring system configured to measure the position of the substrate table within three or more degrees of freedom. The displacement measuring system includes a first x-sensor configured to measure the position of the substrate table in a first direction, and first and second y-sensors configured to measure the position of the substrate table in a second direction. The displacement measuring system further comprises a second x-sensor, wherein the first and second x-sensors and the first and second y-sensors are positioned at each of the sensors relative to at least one grid plate. An encoder type sensor configured to measure. The displacement measuring system is adapted to determine three of the first and second x-sensors and the first and second y-sensors according to the position of the substrate table to determine the position of the substrate within three degrees of freedom. Optionally configured for use.

Description

Lithographic apparatus and device manufacturing method {LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD}

DESCRIPTION OF THE EMBODIMENTS Hereinafter, embodiments of the present invention will be described only by way of example, with reference to the accompanying schematic drawings in which corresponding reference numbers indicate corresponding parts.

1 shows a lithographic apparatus according to an embodiment of the invention;

2 shows a first embodiment of a measuring system according to the invention;

3 shows a second embodiment of a measuring system according to the invention; And

4 shows a third embodiment of a measuring system according to the invention.

FIELD The present invention relates to a lithographic apparatus and a method for manufacturing a device.

BACKGROUND A lithographic apparatus is a machine that applies a desired pattern onto a substrate, typically onto a target portion of the substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, alternatively referred to as a mask or a reticle, can be used to create a circuit pattern to be formed on a separate layer of the IC. This pattern can be transferred onto a target portion (eg, comprising part of one or several dies) on a substrate (eg, a silicon wafer). Transfer of the pattern is typically performed through 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. Conventional lithographic apparatus scans a pattern in a given direction ("scanning" -direction) through a so-called stepper through which each target portion is irradiated, and a radiation beam, by exposing the entire pattern onto the target portion at one time, while It includes a so-called scanner in which each target portion is irradiated by synchronously scanning the substrate in a direction parallel to the direction (direction parallel to the same direction) or anti-parallel direction (direction parallel to the opposite direction). It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

Positioning of the tables is one of the most demanding requirements of micro-lithography for liquid crystal display panel production as well as integrated circuits. For example, sub-100 nm lithography allows machines at an order of 1 nm in all six degrees of freedom (DOF) at speeds up to 3 m / s. There is a need for a substrate-positioning stage and a mask-positioning stage that match each other and have dynamic accuracy.

A popular approach to this required positioning requirement is that a coarse positioning module (e.g., XY table or gantry table) with a micrometer accuracy can be used to determine the stage positioning architecture. It is sub-divide by)), but it is cascaded into a fine positioning module that moves over the entire operating range. The fine positioning module serves to correct the residual error of the coarse positioning module with a few nanometers at the end, but only needs to accommodate a very limited range of movement. Actuators commonly used in such nano-positioning include piezoelectric actuators or voice-coil type electromagnetic actuators. The positioning in the fine module is generally derived at all 6 DOF, while the large range of operation is rarely required above 2 DOF, so the design of the schematic module is quite easy.

등의 "Integrated electro-dynamic multicoordinate drives(Proc. ASPE Annual Meeting, California, USA, 1996, p.456 내지 461)"에서 설명된 바와 같이 다수(최고 3) DOF 디바이스일 수 있다. 또한, 유사한 인코더들이 상업적으로, 예를 들어, Dr. J. Heidenhain GmbH에 의해 제조된 위치 측정 시스템 타입 PP281R으로 이용가능하다. 이러한 센서들은 어려움없이 서브-마이크로미터 레벨의 분해능을 제공할 수는 있지만, 절대적(absolute) 정확성과, 특히 긴 이동 범위에 걸친 열적 안정성(thermal stability)은 용이하게 달성할 수 없다.The micrometer accuracy required in coarse positioning can be easily achieved using relatively simple position sensors such as optical or magnetic incremental encoders. These are single axis devices using measurements at 1 DOF, or more recently

And multiple (up to 3) DOF devices, as described in " Integrated electro-dynamic multicoordinate drives (Proc. ASPE Annual Meeting, California, USA, 1996, p. 456-461). Similar encoders are also commercially available, e.g. Available as position measuring system type PP281R manufactured by J. Heidenhain GmbH. Such sensors can provide sub-micrometer level resolution without difficulty, but absolute accuracy and especially thermal stability over a long range of travel cannot be easily achieved.

On the other hand, the position measurement on the mask and substrate table at the end of the fine positioning module should be performed with the resolution of the sub-nanometer with nanometer accuracy and stability at all 6 DOF. This is typically done using redundant axes for additional calibration functions (e.g., calibration of interferometer mirror flatness on a substrate table) to measure displacement at all 6 DOF. Achieved using a multi-axis interferometer.

The disadvantage of this approach is that the stage is guided (turned back) into the range of the fine positioning module at every moment, and the position of the stage must be (re) calibrated in six degrees of freedom. This takes a considerable amount of time, resulting in reduced throughput of lithography.

As an alternative to interferometers, it is known to use optical encoders in combination with interferometers where possible. Such optical encoders are disclosed, for example, in US 2004/0263846 A1, which is incorporated herein by reference. The optical encoders described in this application use a grid plate that includes a grid pattern that is used to determine the position of the sensor with respect to the grid pattern. In one embodiment the sensor is mounted on a substrate table and a grid plate is mounted on the frame of the lithographic apparatus.

A disadvantage of optical encoder type sensors is that the sensor range of these sensors is in principle limited to the size of the grid plate. However, the size of such grid plates is physically limited due to the high resolution required for the grid. Thus, in practice, the size of the operating area of such a sensor is limited. Moreover, it is possible for holes / openings to be provided in the grid plate, for example in the opening through which the projection beam can be led. At the position of this hole / opening, the sensor cannot determine its position. In addition, the grid plate may be locally damaged, making it impossible to accurately determine the sensor position at this position.

It would be desirable to provide a high accuracy displacement measurement system for a lithographic apparatus that is configured to measure the position of the substrate table at every possible position that enables continuous measurement of the position of the substrate table.

According to one embodiment of the invention:

A substrate table holding the substrate;

A projection system for projecting the patterned beam onto a target portion of the substrate; And

A lithographic apparatus comprising a displacement measuring system configured to measure a position of the substrate table, the displacement measuring system mounted on the substrate table and mounted to at least two adjacent grid plates that are substantially stationary in a first direction. One or more encoder type x-sensors configured to measure the position of the substrate table relative to the displacement measurement system, wherein the displacement measurement system determines the position of the substrate table while crossing a crossing line between two or more adjacent grid plates. It is configured to measure continuously.

According to one embodiment of the invention:

A substrate table holding the substrate;

A projection system for projecting the patterned beam onto a target portion of the substrate; And

A lithographic apparatus is provided comprising a displacement measuring system configured to measure the position of the substrate table in six degrees of freedom (x, y, z, Rx, Ry, Rz), the displacement measuring system being:

One x-sensor configured to measure the position of the substrate table in a first direction,

Two y-sensors configured to measure the position of the substrate table in a second direction,

Three z-sensors configured to measure the position of the substrate table in a third direction, the displacement measuring system further comprising a second x-sensor and a fourth z-sensor; The 2 x-sensor and the first and second y-sensors are encoder type sensors configured to measure the position of the respective sensors relative to at least one grid plate, and the displacement measuring system measures the position of the substrate table in 6 degrees of freedom. Selectively use three of the first and second x-sensors and the first and second y-sensors, and three of the z-sensors, depending on the position of the substrate table to determine do.

According to one embodiment of the present invention, there is provided a device manufacturing method comprising projecting a patterned beam of radiation onto a substrate, the substrate at least onto a substrate table while projecting the patterned beam onto a target portion of the substrate. Supported by the substrate table, wherein the position of the substrate table includes at least one encoder type sensor mounted on the substrate table, and to measure the position of the substrate table relative to at least two adjacent grid plates that are substantially stationary in a first direction. Measured by a displacement measuring system configured, the displacement measuring system is configured to continuously measure the position of the substrate table while crossing a crossing line between the two adjacent grid plates.

1 schematically depicts a lithographic apparatus according to an embodiment of the invention. The apparatus comprises an illumination system (illuminator) IL, a patterning device (eg mask) MA configured to condition a radiation beam B (eg UV radiation or any other suitable radiation). ) And a mask support structure (eg, mask table) MT connected to the first positioning device PM configured to accurately position the patterning device according to certain parameters. In addition, the apparatus is configured to hold a substrate (eg, a resist-coated wafer) W and is connected to a second positioning device PW configured to accurately position the substrate according to predetermined parameters. Table (eg, wafer table) WT or " substrate support ". In addition, the apparatus is a projection configured to project a pattern imparted to the radiation beam B by the patterning device MA onto the target portion C (eg comprising at least one die) of the substrate W. System (eg, refractive projection lens system) PS.

The lighting 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, to direct, shape, or control the radiation. have.

The mask support structure supports the patterning device, i.e. bears its weight. This 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 maintained in a vacuum environment. The mask support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The mask support structure may be a frame or table, for example, which may be fixed or movable as required. The mask support structure can ensure that the patterning device is in a desired position with respect to the projection system, for example. Any use of the terms "reticle" or "mask" herein may be considered as synonymous with the more general term "patterning device".

As used herein, the term “patterning device” should be broadly interpreted to refer to any device that can be used to impart a pattern to a cross section of a radiation beam in order to create a pattern in a target portion of a substrate. The pattern imparted to the radiation beam does not exactly match the desired pattern in the target portion of the substrate, for example when the pattern comprises phase-shifting features or so-called assist features. Note that this may not be possible. In general, the pattern imparted to the radiation beam will correspond to a particular functional layer in the device to be created in the target portion, such as an integrated circuit.

The patterning device can be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in the lithography art and include various hybrid mask types, as well as mask types such as binary, alternating phase-shift, and attenuated phase-shift. One example of a programmable mirror array employs a matrix configuration of small mirrors, each of which can be individually tilted to reflect the incident radiation beam in a different direction. Inclined mirrors impart a pattern to the beam of radiation reflected by the mirror matrix.

The term "projection system" as used herein, if appropriate for the exposure radiation used, or for other factors such as the use of immersion liquid or the use of vacuum, refraction, reflection, catadioptric, It is to be broadly interpreted as encompassing any type of projection system, including magnetic, electromagnetic and electrostatic optical systems, or any combination thereof. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.

As shown herein, 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 the type as mentioned above, or employing a reflective mask).

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

The lithographic apparatus can also be constructed in such a way that, in order to fill the space between the projection system and the substrate, all or part of the substrate can be covered with a liquid having a relatively high refractive index, such as water. Immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques can be used to increase 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 placed between the projection system and the substrate during exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from a radiation source SO. For example, when the source is an excimer laser, the source and the lithographic apparatus may be separate entities. In this case, the source is not considered to form part of the lithographic apparatus, and the radiation beam is, for example, with the aid of a beam delivery system (BD) comprising a suitable directing mirror and / or beam expander, Passed from source SO to illuminator IL. In other cases, for example if the source is a mercury lamp, the source may be an integral part of a lithographic apparatus. The source SO and the illuminator IL may be referred to as a radiation system together with the beam delivery system BD as necessary.

The illuminator IL may comprise an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. In general, at least the outer and / or inner radial extent (commonly referred to as -outer and -inner, respectively) of the intensity distribution in the pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components, such as the integrator IN and the condenser CO. The illuminator can be used to condition the radiation beam to have the desired uniformity and intensity distribution in the cross section of the radiation beam.

The radiation beam B is incident on a patterning device (eg mask MA) held on a mask support structure (eg mask table MT) and patterned by the patterning device. When the mask MA is crossed, the radiation beam B passes through the projection system PS to focus the beam on the target portion C of the substrate W. With the aid of the second positioning device PW and the position sensor IF (eg interferometer device, linear encoder or capacitive sensor), the substrate table WT is, for example, the path of the radiation beam B. It can be moved precisely to position different target portions C in it. Similarly, the first positioning device PM and another position sensor (not explicitly shown in FIG. 1) may be exposed, for example, after mechanical retrieval from a mask library or during scanning. It can be used to accurately position the mask MA with respect to the path of the beam B. In general, the movement of the mask table MT will be realized with the help of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which Forms a part of the first positioning device PM. Similarly, movement of the substrate table WT or "substrate support" can be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT may be connected or fixed only to the short-stroke actuator. The mask MA and the substrate W may be aligned using the mask alignment marks M1 and M2 and the substrate alignment marks P1 and P2. Although the illustrated substrate alignment marks occupy dedicated target portions, they may be located in the spaces between the target portions (these are known as scribe-lane alignment marks). Similarly, in situations where more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

The device shown may be used in one or more of the following modes:

1. In the step mode, the mask table MT or the "mask support" and the substrate table WT or the "substrate support" are basically kept stationary, while the entire pattern imparted to the radiation beam is subjected to the target portion C at once. Projected onto (ie, a single static exposure). The substrate table WT or " substrate support " is then shifted in the X and / or Y direction so that different target portions C can be exposed. The maximum size of the exposure field in the step mode limits the size of the target portion C imaged during a single static exposure.

2. In the scan mode, the mask table MT or "mask support" and the substrate table WT or "substrate support" are scanned synchronously while the pattern imparted to the radiation beam is projected onto the target portion C ( Ie, single dynamic exposure. The velocity and direction of the substrate table WT or "substrate support" relative to the mask table MT or "mask support" can be determined by the (de-) magnification and image reversal characteristics of the projection system PS. The maximum size of the exposure field in the scan mode limits the width (in the unscanned direction) of the target portion during a single dynamic exposure, while the length of the scanning operation determines the height (in the scanning direction) of the target portion.

3. In another mode, the mask table MT or "mask support" remains essentially stationary by holding a programmable patterning device, while the pattern imparted to the radiation beam is projected onto the target portion C. The substrate table WT or "substrate support" is moved or scanned. In this mode, a pulsed radiation source is generally employed, and the programmable patterning device is between the radiation pulses that continue after the substrate table WT or " substrate support " respectively moves or during the scan. Updated as needed. This mode of operation can be readily applied to maskless lithography using a programmable patterning device, such as a programmable mirror array of a type as mentioned above.

In addition, combinations and / or variations of the modes of use described above, or completely different modes of use may be employed.

2 shows a first embodiment of a displacement measuring system according to the invention. The displacement measuring system is generally indicated by using reference numeral 1. The displacement measuring system 1 has three degrees of freedom in the coplanar, i.e., the x-position, the y-position and the z-axis (Rz) (the z-axis is the axis perpendicular to the x and y axes shown in the figure). It is designed to measure the position of the substrate table 2 in a rotation about its angle.

The displacement measuring system 1 comprises four adjacent grid plates 3 mounted on a lithographic apparatus, for example on a frame or lens, such as a so-called metrology frame. The grid plate 3 is a flat plate disposed in substantially the same plane extending substantially in the directions of the x-axis and the y-axis. The four grid plates 3 are adjacent in such a way that at least one of each grid plate is arranged side by side or opposite to at least one of the other grid plates 3. At the same time, the four grid plates 3 cover substantially all the required positions of the substrate table 2, so that the measuring system 1 can continuously measure the position of the substrate table 2.

In this embodiment, the substrate table 2 is arranged below the grid plate 3. On the substrate table 2 two x-sensors 4 and 5 and two y-sensors 6 and 7 are arranged. The x-sensors 4 and 5 can measure the position of the substrate table in the x-direction. The y-sensors 6 and 7 can measure the position of the substrate table 2 in the y-direction. A pair of signals (x, x; x, y or y, y) of two x-sensors and two y-sensors can be used to determine the rotation about the z-axis (rotation in the xy plane) . Thus, using two x-sensors 4 and 5 and two y-sensors 6 and 7, three degrees of freedom (x, y, Rz) of the coplanar at all possible positions of the substrate table 2. It is possible to determine the position of the substrate table within. As a result, a high accuracy continuous measurement (nanometer or sub-nanometer resolution) of the substrate table 2 is possible.

The x-sensors 4 and 5 and the y-sensors 6 and 7 are of an encoder type capable of determining the position of each sensor with respect to the grid arranged on the grid plate 3. Each x- and y-sensor can be designed, for example, as described in US application US 2004/0263846 A1, which is incorporated herein by reference.

Four grid plates are used in this embodiment because the physical dimensions of the grid plate 3 are limited. It is in fact very difficult, or at least very expensive, to produce a grid plate of the size of an operating area with a grid with resolution to achieve the accuracy required for this application. Since the operating range used by the substrate table is substantially larger than the physical maximum size of this grid plate 3, the operating region is subdivided into four regions each having its own grid plate 3.

As described above, the grid plates 3 are arranged adjacently. This allows the sensor to take over from one grid plate 3 to another grid plate 3. During this sensor takeover, ie while the sensor first interacts with the first grid plate 3 and then with the second grid plate 3, another sensor may provide a signal that enables continuous measurement. Can be. If the first sensor is in the range of another grid plate 3, this sensor may again provide a signal indicating the position of the substrate table, possibly after re-initialization.

Subdivision of the operating area in four sub-regions, each with its own grid plate 3, makes it possible to cover all required positions of the substrate table 2 in a relatively efficient manner, but the grid plate 3 Crossings of the liver make it difficult to continuously measure the position of the substrate table 2 using a single sensor. In addition, the presence of a hole or opening (eg, an opening 8 that can accommodate a portion of the projection system at the center of four grid plates 3), or a damaged area within the grid plate 3, may be A single sensor of may cause it to be unable to measure the position of the substrate table 2 relative to one of the grid plates 3.

As explained above, three of the two x-sensors 4 and 5 and the y-sensors 6 and 7 make it possible to determine the position of the substrate table within three degrees of freedom of coplanarity. Thus, there is one extra sensor. This extra sensor can be used advantageously if one of the other sensors cannot be used out of the range of the grid plate 3. For example, one of the x-sensors or the y-sensors may be located just below the point of crossing from one grid plate 3 to another grid plate 3. In this case (for example, when the x-sensor 4 is positioned below the crossing line 3a between the two grid plates 3 when the substrate table 2 is moved in the x-direction) Each sensor cannot transmit a signal indicative of the x- or y-position of the substrate table 2. However, the other three sensors (in the example, x-sensor 5 and y-sensors 6 and 7) determine the position of the substrate table 2 within three degrees of freedom of coplanarity, thereby providing high accuracy. Continuous displacement / position measurements can be continued.

If the substrate table 2 is further moved in the x-direction, the first x-sensor 4 moves down another grid plate 3 (in this example, the grid plate 3 in the upper right of FIG. 2). do. The x-sensor 4 after re-initialization can then again provide a signal indicating the x-position of the substrate table 2. However, the y-sensor 6 can now be positioned below the crossing of the two grid plates 3. In such a situation this y-sensor 6 cannot be used to obtain a signal representing the y-position of the substrate table 2. However, since the x-sensor 4 is now located under one of the grid plates 3, the x-sensor 5 and the y-sensor ( In combination with 7) this x-sensor 4 can be used. Continuous control is obtained by selectively using a set of three sensors, each capable of properly determining a signal indicative of a position in the x- or y-direction. The selection of the respective x-sensors and y-sensors can be performed by the selection device. The selection / selection of each grid plate 3 depends on the position of the substrate table. If all four sensors can carry a signal, the extra signal can be used for calibration of the measuring system, for example.

The grid plates 3 in this embodiment are substantially rectangular plates, spaced apart from one another. The sides of these plates are oriented in the x- and y-directions. Therefore, it is preferable that two x-sensors 4 and 5 and two y-sensors 6 and 7 are spaced apart from one another in the x- and y-directions (within the x-y plane). In other words, the configuration of the x-sensors 4 and 5 and the y-sensors 6 and 7 in this embodiment of the substrate table 2 can be any of the four sensors 4, 5, 6 and 7. Nothing is arranged on the same line in the x-direction, and none of the four sensors 4, 5, 6 and 7 are arranged on the same line in the y-direction. In this way, only one of the four sensors will be out of range of the grid plate 3 in the case of crossing the crossing line 3a in the x-direction or the y-direction.

In an alternative embodiment, it is possible for the sides of the grid plates located relative to each other to be arranged in one or more other directions in the x-y plane, not in the x- and y-directions. These other directions are defined herein as the grid plate crossing line direction. In this case, the two x-sensors 4 and 5 and the two y-sensors 6 and 7 are preferably arranged in one or more of these crossing line directions with respect to each other.

Furthermore, in some theory within the operating range of the substrate table 2, at least one of the two x-sensors 4 and 5 and / or the y-sensors 6 and 7 is one of the grid plates 3. Note that it may be possible to not determine the position of each sensor relative to. For example, one x-sensor can be located below the crossing line of the grid plate 3 in the x-direction, while the other x-sensor can be located below the crossing line running in the y-direction. This situation is very undesirable because only two sensors lead to the positioning of the substrate table 2. As a result, the position of the substrate table 2 can no longer be derived within two degrees of freedom.

This undesirable situation can be avoided by providing more redundant sensors located on different positions of the substrate table 2. Another solution to this situation is that the substrate table 2 in this embodiment intersects only in one crossing line direction at a single time, or at least in a manner that may not be induced at locations known to not occur. It is to limit the movement of the table. Since the provision of more sensors will increase the weight and cost of the substrate table 2, the latter solution is generally preferred.

Therefore, in both solutions it is ensured that the measuring system will be able to determine the position of the substrate table 2 at every possible position of the substrate table 2 in the use of the lithographic apparatus. These positions include, for example, a range for exposure, a range moving from an exposure range to an exposure range, a range for exchanging the substrates, and a range for various functions, alignment, and the like.

3 shows a second embodiment of the measuring system 10 according to the invention. In this embodiment the measurement system is configured to determine the position of the two substrate tables 11 and 12 with a high level of accuracy. To obtain the position of the substrate tables 11 and 12 within six degrees of freedom, sensors of the same quantity and shape are mounted on each substrate table 11 and 12. Substrate tables 11 and 12 are located below one or both of the two grid plates 13. These grid plates 13 are substantially full of the substrate tables 11 and 12 so that the measurement system 10 can continuously determine the position of the substrate tables 11 and 12 with a high level of accuracy within six degrees of freedom. Cover the operating area. The position of each substrate table 11 and 12 because the substrate tables 11 and 12 are both located directly below the grid plate 13 used to determine the position of each substrate table within six degrees of freedom. Is not hindered by the other substrate tables 12 and 11. Therefore, the measurement system 10 according to the invention is very suitable for determining the position of a substrate table in a so-called "dual stage lithographic apparatus" having two substrate tables.

As described for the embodiment of FIG. 2, each substrate table 11 and 12 represents the position of each substrate table 11 and 12 within (coplanar) three degrees of freedom (x, y, Rz). To determine, it includes two x-sensors 14 and 15 and two y-sensors 16 and 17. Since three degrees of freedom can be determined based on the three sensor signals, one of the two x-sensors and the two y-sensors is redundant. Moreover, each substrate table 11 and 12 includes four z-sensors 18 to determine the position of the substrate table at the z position. Three degrees of freedom of these four z-sensors 18 can be used to determine further degrees of freedom, i.e., x-position, rotation about the x-axis (Rz) and rotation about the y-axis (Ry).

Encoder type x-sensors 14 and 15 and y-sensors 16 and 17 may be of the type described herein in connection with the embodiment of FIG. 2. The z-sensor 18 is preferably an interferometer, but may be configured in any suitable form as described below in this specification.

Since there are four z-sensors 18 provided on each of the substrate tables 11 and 12, one of the z-sensors is redundant. Thus, one of two x-sensors 14 and 15 and two y-sensors 16 and 17 and one of four z-sensors 18 will determine its position relative to the grid plates 13. If not, the position of the substrate tables 11 and 12 can still be determined with six degrees of freedom.

Also, in order to be able to cross over the crossing line 13a in the x-direction as shown in FIG. 3, the x-sensors 14 and 15 and the y-sensors 16 and 17 are Each of the four sensors 14, 15, 16 and 17 are arranged in such a way that they are spaced apart from each other in the xy plane in a direction perpendicular to the direction of the crossing line 13a from the other three, in which the direction of the electrons and the latter direction is the x-direction. Also, in order to be able to cross the crossing line in the y-direction, each of these four sensors 14, 15, 16 and 17 are spaced apart from each other in the direction perpendicular to the y-direction of this crossing line. . Note that the latter arrangement with respect to the sensors 14, 15, 16 and 17 is not strictly necessary because there is no crossing line in the y-direction in this embodiment.

Also for the same reasons, one of the four z-sensors 18 is spaced apart from the other z-sensor 18 in the x-y plane in a direction perpendicular to the x-direction and in a direction perpendicular to the y-direction, respectively. In this way, the maximum one of the z-sensors 18 is the grid plate when the crossing line in the x-direction or y-direction (the latter does not exist in the embodiment shown in FIG. 3) is crossed. It would not be possible to determine its position with respect to the grid grid on (13).

The x-sensors 14 and 15, the y-sensors 16 and 17 and the z-sensor 18 are advantageously arranged at the corners of the inner rectangle and the outer rectangle, whereby one x-sensor ( 14 or 15), one y-sensor 16 or 17 and two z-sensors 18 arranged at opposite corners are arranged at four corners of each rectangle. Moreover, the z-sensors of the inner rectangle are arranged at a corner different from the z-sensors of the outer rectangle. Using this configuration, each of the two x-sensors and the two y-sensors is in the xy plane in a direction perpendicular to the x-direction and in a direction perpendicular to the y-direction from the other x-sensors and y-sensors. Spaced apart, and each z-sensor 18 is also spaced apart from the other z-sensors 18 in the xy plane in a direction perpendicular to the x-direction and in a direction perpendicular to the y-direction. Moreover, this configuration requires a relatively small amount of space on the substrate tables 11 and 12. In this configuration the x and y sensors are preferably arranged in the maximum distance configuration so that the Rz measurement can be performed most accurately.

4 shows a third embodiment of the measuring system 21 according to the invention, which uses encoder-type sensors to measure the position of the substrate. In this embodiment the grid grating is formed by a large number of grid plates 23 (only three are shown by reference numeral 23 for simplicity) covering the entire operating area of the substrate table 22. Grid plates are indicated by dashed lines. The grid plate 23 may be, for example, a wafer on which a grid grating is provided. These wafers are limited in size (typically 300 mm), but the grating can be provided on the wafer with very high accuracy using a lithographic exposure process. However, because the size of the grid plate 23 is limited, another configuration of sensors on the substrate table 22 to be described may be desirable.

The substrate table 22 has 6 sets of 2 sensors (2 sets in each corner), 2 total, so that the substrate table 22 includes redundant sensors for each sensor present on the substrate table 22. Four x-sensors 24 and 25, four y-sensors 26 and 27, and six z-sensors 28.

At each of the three corners of the substrate table 22, the substrate table 22 includes two x-sensors 24 and 25 or two y-sensors 26 and 27, and two z-sensors 28, Each set includes two sensor sets comprising one x-sensor 24 or 25 or one y-sensor 26 or 27, and one z-sensor 28. All four sensors are preferably arranged in an area smaller than that of one grid plate 23. If one of the four sensors on the corner of the substrate table 22 is unable to determine its position relative to the grid grid, the corresponding other of the four sensors may be used to determine the position of the substrate table 22. . For example, if one of the x-sensors 24 and 25 is located below the crossing line, the other x-sensors 25 and 24 can be used to determine the x-position of the substrate table 22.

The four sensors at each corner are advantageously arranged in such a way that all four sensors arranged at a single corner are spaced apart from each other in the x-y plane in a direction perpendicular to each other in the x-direction and the y-direction. In addition, the x-sensor or y-sensor at one corner is aligned with the z-sensor at the other corner, for example up to two sensors when the crossing line in the x-direction is crossed by the substrate table. Crosses this line simultaneously, one of which is an x- or y-sensor and the other is a z-sensor.

Additional sensors may be provided on the substrate table 22 for even more redundancy of the measurement system 21 and, as a result, greater robustness. In particular, an additional two x-sensors and an additional two z-sensors may be provided at the fourth corner of the substrate table 22.

In addition, the x-, y- and z-sensors may be designed as described for the embodiment of FIGS. 2 and 3.

Typical systems used in the present invention employ an interference reading (encoder) head within 2 DOF and interpolation up to a factor of 20,000 for each axis, up to 2 [mu] m. It includes a grid grid having a period.

For the measurement of the remaining 3 DOF, i.e. z, Rx, and Ry, it can have optical triangulation, fiber optic back-scatter, and very short optical paths (in air) to A wide range of displacement sensing technologies can be employed, including very less sensitive interferometer sensors, capacitive or inductive sensors.

Currently, capacitive and optical sensors are preferred over other measurement principles, although others may be appropriate in some applications of the present invention. The use of inductive sensors for Zerodur chucks is problematic because conductive targers are required for the sensor. On the other hand, pneumatic proximity sensors (air micrometers) are disadvantageous in that they apply a limited force on the target, as well as limited resolution and working distance.

Whether interferometric or triangulation, optical sensors can be designed with relatively large (millimeter) operating distances, which facilitates assembly tolerance. Compared to capacitive sensors, they generally have a higher bandwidth and can be configured as an absolute distance sensor. Absolute sensors, however, are disadvantageous for long-term stability problems due to mechanical drift (thermal or other factors) requiring periodic calibration.

On the other hand, capacitive sensors can be designed as absolute sensors with very high stability. Moreover, distance measurement is performed over a relatively large target surface, which allows to somewhat reduce the effects of localized non-flatness of the target surface.

Nano-positioning system based encoders provide an advantageous alternative to interferometers and are simpler to implement. For example, by the fact that the measuring grid in the xy plane is permanently fixed on a dimensionally stable and thermally insensitive metrology frame in the long term when implemented with zero-CTE material such as Zerodur, Better measurement stability can be achieved. This greatly facilitates the stringent requirement for environmental control of the area immediately around the optical path of the interferometer beam, especially in the case of lithographic projection apparatus employing wavelengths of 157 nm or less. Such devices require purging with a gas that does not absorb the beam (strongly absorbed in the air), and the present invention substantially eliminates the need for an air shower by the length of the interferometer beam. Can reduce the consumption.

In addition, the mask position relative to the projection optics can be measured within the encoder solution without resorting to differential configurations. Placing the readhead directly on top of the projection optics places more demands on thermal dissipation, but links with active cooling or remote light sources and fiber optics. Techniques for minimizing this, such as detectors, are already available and are already deployed in state-of-the-art interferometer systems.

In addition, the nano-positioning system based encoder can be arranged as follows: a first sensor head is disposed on the substrate table and a first grating is mounted on the projection system or frame. In one embodiment, such a frame is at least substantially stationary with respect to the projection system, which means that the relative displacement of the portion of the frame to which the projection system and the first grating are attached can be ignored. If this cannot be achieved, it is understood that the displacement of the frame relative to the projection system is also measured. In addition, to ensure that relative displacement is virtually negligible, the displacement of the frame relative to the projection system is measured even when the frame is considered substantially stationary.

The first sensor head may be mounted on top of the substrate table toward a first grating mounted on a projection system or frame. The sensor head and the first grating are arranged in such a way that during all movement of the substrate table the first sensor head and the first grating can cooperate to measure the displacement of the substrate table relative to the projection system.

Also in this configuration, the measurement system may include a first z-sensor. The z-sensor and the first grating cooperate to determine the displacement of the substrate table with respect to the projection system in a third measurement direction perpendicular to the plane defined by the first measurement direction and the direction of the lines of the first grating. For example, when the first measurement direction is in the x-direction and the sensor head sends a polarized radiation beam to the first grating in the z-direction, the lines of the first grating extend in the y-direction. In that case the plane defined by the first measurement direction and the direction of the lines of the first grating is the x-y plane. In that case the third measuring direction is the z-direction since it is a direction perpendicular to the x-y plane. Therefore, in this situation the first grating is used not only to measure the displacement of the substrate table with respect to the projection system in the x-direction, but also to measure the displacement of the substrate table with respect to the projection system in the z-direction.

The z-sensor may be an interferometer, and it is understood that the first grating has a reflective surface that interacts with the interferometer. The grating comprises, for example, two mutually parallel reflecting surfaces due to the nature of the grating. In this case, the difference in the optical length path between the reflection at the first surface and the reflection at the second surface (or between the reflection surfaces) is preferably N times the wavelength of the interferometer beam, where N is a positive integer (1, 2, 3, 4, ...).

Alternatively, the z-sensor can be a capacitive sensor. For functionality, capacitive sensors require a short distance, such as a few millimeters from the capacitive sensor in the measurement direction, and require an electrically conductive counter plate. By making all or part of the first grating electrically conductive, the first grating acts as a counter plate for the capacitive sensor. Such a grating can be used with capacitive line sensors by connecting lines to each other and connecting them to ground.

In the lithographic projection system according to the invention, the number of interferometers used to measure the displacement of the substrate table with respect to the projection system is reduced. In this way the cost of the measurement system and the substrate table is reduced. It is understood that displacements of the substrate table relative to the projection system in the first and second directions are measured using a sensor head or read head. In this embodiment, the lithographic apparatus is equipped with a measuring system comprising a first sensor head and a second sensor head. For this purpose, the first grating may comprise not only a first group of mutually parallel lines extending perpendicular to the first measurement direction, but also a second group of mutually parallel lines extending perpendicular to the second measurement direction. The first grating may be provided with a checkered pattern used in connection with the first and second sensor heads. In that case the transition between the light and dark areas of the checkered pattern takes over the role of parallel lines of the grating. Alternatively, there may be a separate second grating for use by the second sensor head. The first and second sensor heads are preferably integrated into a single sensor unit.

In another embodiment, the measurement system is adapted to measure the displacement of the substrate table with respect to the projection system within all three degrees of freedom of the plane defined by the first and second measurement directions by using the sensor head. . This means that when this plane is the x-y plane, the translational displacement of the substrate table in the x- and y-directions and the rotational displacement about the axis in the z-direction are measured using the sensor heads.

For this purpose, the measurement system in this embodiment comprises first, second and third sensor heads. Two of these sensor heads are used to measure the displacement of the substrate table in the first measurement direction and the other encoder is used to measure the displacement of the substrate table in the second measurement direction. Of course, it can also be used in the other way around. The sensor heads are arranged at known relative distances, and any rotation of the substrate table about the axis center extending in the third measuring direction can be determined based on the sensor head measurements.

Each sensor head can be associated with its own grating, which means that in that case the measuring system comprises first, second and third gratings. However, in certain embodiments, two or more sensor heads share a grating suitable for measuring in two directions, for example due to the presence of a checkered pattern.

Using the sensor heads as described above, it is understood that a measuring system which measures displacements of the substrate table relative to the projection system in all three degrees of freedom of the plane defined by the first and second measuring directions is used without a z-sensor. do. In that case the sensor heads are mounted on the substrate table.

In another alternative embodiment, the measurement system is provided with first, second and third z-sensors. These z-sensors are arranged at known relative positions so that any rotation of the substrate table about the first and second measuring directions can be determined by the measurements. All z-sensors preferably interact with the grating to measure displacements of the substrate table relative to the projection system. This induces the measurement system to make position measurements within six degrees of freedom (6 DOF).

The measurement system for determining the position of the substrate table has been described herein. However, this measuring system can be used for any other movable object whose position is to be determined with a high level of accuracy. In this aspect the measurement system can be used successfully for the determination of the position of the patterning device support in the lithographic apparatus. In particular, the system can be used to position the patterning device support at a high level of accuracy, within six degrees of freedom. In addition, all features of the described measurement system can be applied to measurement systems for other movable objects, such as patterning device supports.

In this specification, although reference is made to a specific use of the lithographic apparatus in IC fabrication, the lithographic apparatus described herein includes integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid crystals. It should be understood that other applications may be present, such as the manufacture of displays (LCDs), thin film magnetic heads, and the like. As those skilled in the art relate to these alternative applications, any use of terms such as "wafer" or "die" herein may be considered synonymous with the more general term "substrate" or "target portion", respectively. Will understand. The substrate referred to herein may be processed before or after exposure, for example in a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), or a metrology and / or inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. In addition, the substrate may be processed more than once, for example, to produce a multi-layer IC, so the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

While specific reference has been made to specific uses of embodiments of the present invention in connection with optical lithography, it is to be understood that the present invention may be used in other applications, for example imprint lithography, and is not limited to optical lithography if the specification allows. Will understand. Topography in a patterning device in imprint lithography defines a pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate on which 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 therein after the resist has cured.

As used herein, the terms "radiation" and "beam" refer to ultraviolet (UV) radiation (e.g., having a wavelength of 365, 248, 193, 157 or 126 nm) and (e.g., 5 to 20 nm). Encompasses all forms of electromagnetic radiation, including extreme ultraviolet (EUV) radiation having wavelengths in the range, as well as particle beams such as ion beams or electron beams.

The 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.

While 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 present invention relates to a computer program comprising one or more sequences of machine-readable instructions for implementing a method as disclosed above, or to a data storage medium on which such computer program is stored (e.g., semiconductor memory, magnetic Or an optical disc).

The above description is for illustrative purposes, not limitation. 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.

According to the invention, there is provided a lithographic apparatus comprising a displacement measuring system for the continuous measurement of the position of a substrate table.

Claims (25)

delete delete In a lithographic apparatus: A substrate table holding the substrate; A projection system for projecting the patterned beam onto a target portion of the substrate; And A displacement measuring system configured to measure the position of the substrate table, The displacement measuring system is one or more first encoder type x− mounted on the substrate table and configured to measure the position of the substrate table relative to two or more adjacent grid plates that are substantially stationary in a first direction. And a sensor, wherein the displacement measuring system is configured to continuously measure the position of the substrate table while crossing a crossing line between the two or more adjacent grid plates, The displacement measuring system comprises a second encoder type x-sensor mounted on the substrate table and configured to measure the position of the substrate table relative to the two or more adjacent grid plates in the first direction, the displacement And a measurement system is configured to selectively use one of the first and second x-sensors according to the position of the substrate table to determine the position of the substrate table in the first direction. Device. The method of claim 3, wherein The displacement measuring system is configured to measure the position of the substrate table within three or more degrees of freedom (x, y, Rz) of the coplanar, the displacement measuring system being: Further comprising first and second encoder type y-sensors mounted on the substrate table and configured to measure the position of the substrate table relative to the at least two adjacent grid plates in a second direction, The displacement measuring system is adapted to determine the position of the substrate table within the three degrees of freedom, the first and second x-sensors, and the first and second y-sensors according to the position of the substrate table. Lithographic apparatus, characterized in that it is configured to selectively use three of them. The method of claim 4, wherein And the respective x-sensors and y-sensors are spaced apart from the other x-sensors and the y-sensors in at least a direction perpendicular to the direction of the crossing line. The method of claim 4, wherein And the respective x-sensors and y-sensors are spaced apart from the other x-sensors and y-sensors in a direction perpendicular to at least the first and / or second direction. The method of claim 4, wherein The displacement measuring system comprises four z-sensors for measuring the position of the substrate table in a direction perpendicular to the first and second directions, the displacement measuring system having another three degrees of freedom (z, Rx). , Ry) to selectively use three of the four z-sensors according to the position of the substrate table to determine the position of the substrate table. The method of claim 7, wherein And each of the four z-sensors is spaced apart from the other z-sensors in at least a direction perpendicular to the direction of the crossing line. The method of claim 7, wherein And each of the z-sensors is spaced apart from the other three z-sensors in a direction perpendicular to at least the first and / or second direction. The method of claim 7, wherein And the z-sensors are interferometers. The method of claim 7, wherein Each corner of the substrate table is equipped with one of the four z-sensors, and each of the corners is also provided with the first x-sensor, the second x-sensor, the first y-sensor and the second. Lithographic apparatus characterized in that one of the y-sensors is mounted. The method of claim 7, wherein The two x-sensors, two y-sensors and four z-sensors are arranged at the corners of the inner and outer rectangles, each rectangle having one x-sensor, one y-sensor and two z-sensors And the z-sensors are disposed on opposite corners of the inner rectangle and on two other opposite corners of the outer rectangle. The method of claim 3, wherein The lithographic apparatus comprises two or more substrate tables, each of which is equipped with one or more x-sensors. The method of claim 7, wherein At each of the three or more positions of the grid plate, two sensor sets are arranged, each sensor set comprising one x-sensor or one y-sensor, and one z-sensor. Lithographic apparatus. The method of claim 3, wherein And the dimension of the at least one grid plate in the first and second directions is smaller than the dimension of the substrate table in the first and second directions. The method of claim 3, wherein And each of the at least two grid plates is a wafer provided with a grid grating. In a lithographic apparatus: A substrate table holding the substrate; A projection system for projecting the patterned beam onto a target portion of the substrate; And A displacement measuring system configured to measure the position of the substrate table in six degrees of freedom (x, y, z, Rx, Ry, Rz), the displacement measuring system comprising: One x-sensor configured to measure the position of the substrate table in a first direction, Two y-sensors configured to measure the position of the substrate table in a second direction, and A three z-sensor configured to measure the position of the substrate table in a third direction, the displacement measuring system further comprising a second x-sensor and a fourth z-sensor The first and second x-sensors and the first and second y-sensors are encoder type sensors configured to measure the position of the respective sensors relative to at least one grid plate, the displacement measuring system having six degrees of freedom. Three of the first and second x-sensors and the first and second y-sensors, and three of the z-sensors, depending on the position of the substrate table to determine the position of the substrate table within A lithographic apparatus, characterized in that it is configured to selectively use a dog. delete delete In the device manufacturing method: Projecting a patterned beam of radiation onto a substrate, wherein the substrate is supported on a substrate table while projecting the patterned beam onto at least a target portion of the substrate, the position of the substrate table being: Measured by a displacement measurement system comprising one or more encoder type sensors mounted on the substrate table and configured to measure the position of the substrate table relative to two or more adjacent grid plates that are substantially stationary in a first direction, The displacement measuring system is configured to continuously measure the position of the substrate table when crossing the crossing line between the two or more adjacent grid plates, The displacement measuring system comprises a second encoder type sensor mounted on the substrate table and configured to measure the position of the substrate table relative to the two or more adjacent grid plates in the same direction as the first encoder type sensor. And when one of the encoder type sensors is located at a position where the position with respect to the two adjacent grid plates cannot be determined, the position of the substrate table is determined based on the signal of the other encoder type sensor. Device manufacturing method. The method of claim 20, The displacement measuring system is configured to measure the position within three or more degrees of freedom (x, y, Rz), the displacement measuring system being: First and second x-sensors configured to measure the position of the substrate table in a first direction, A first and a second y-sensor configured to measure the position of the substrate table in a second direction, The x-sensors and the y-sensors are encoder type sensors configured to measure the position of the respective sensors relative to the two or more adjacent grid plates, The first and the second x-sensor, and the first and the second, when one of the x-sensors or y-sensors is located at a position that cannot determine its position relative to at least one grid plate. and the position of the substrate table within three degrees of freedom is determined based on the other three signals of the y-sensor. The method of claim 21, Movement of the substrate table is limited in such a way that only one of the two x-sensors and two y-sensors can be located at a position where each sensor is known to be unable to determine its position relative to the one or more grid plates. Device manufacturing method characterized in that. The method of claim 21, The position of the substrate is measured within six degrees of freedom, and the displacement measuring system further comprises four z-sensors configured to measure the position of the substrate table in a third direction, one of the z-sensors Is located at a position where the position with respect to the at least one grid plate cannot be determined, the above in another three degrees of freedom (z, Rx, Ry) based on the other three signals of the four z-sensors. A device manufacturing method, characterized in that the position of the substrate table is determined. The method of claim 3, wherein And said at least two grid plates cover all possible positions of said substrate table to enable continuous positioning of said substrate table. The method of claim 20, And said two adjacent grid plates cover all possible positions of said substrate table to enable continuous measurement of positions of said substrate table.

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