JP5990613B1 - Heating and cooling systems in lithographic apparatus - Google Patents

Abstract

A system for controlling the temperature of a patterning device in a lithographic apparatus is described. The system includes a cooling system and a heating system. The cooling system is configured to direct a gas flow along a first direction across the surface of the patterning device to remove heat from the patterning device before or during exposure of the patterning device. The heating system is configured to selectively heat a region on the surface of the patterning device before or during exposure of the patterning device. Selective heating and heat removal achieves a substantially uniform temperature distribution in the patterning. [Selection] Figure 2A

Description

Cross-reference to related applications
[0001] This application is related to US Application No. 14 / 662,138, International Application No. PCT / EP2013 / 0667615 and US Provisional Application No. 61 / 705,426, filed Mar. 18, 2015, The entirety is incorporated herein by reference.

  [0002] The present disclosure relates to systems and methods for controlling the temperature of an object, such as a reticle, in a lithographic apparatus.

  [0003] A 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 case, a patterning device, also referred to as a mask or a reticle, may be used to generate a circuit pattern formed on an individual layer of the IC. This pattern can be transferred onto a target portion (eg including part of, one, or more dies) on a substrate (eg a silicon wafer). Usually, the pattern is transferred by imaging on a radiation-sensitive material (resist) layer 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 a so-called stepper that irradiates each target portion by exposing the entire pattern onto the target portion at once, and simultaneously scanning the pattern in a certain direction ("scan" direction) with a radiation beam. Also included are so-called scanners that irradiate each target portion by scanning the substrate parallel or antiparallel 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.

  [0004] In a lithographic apparatus, a radiation beam can cause a thermal effect (eg, thermal expansion) in a reticle. These thermal effects may be due to absorption of the radiation beam at the non-transparent portion of the reticle and may cause, for example, alignment errors and / or overlay errors in the pattern formed on the substrate. To correct these errors due to reticle thermal expansion, current lithographic apparatus includes correction systems such as reticle or wafer alignment systems, magnification correction systems, feed forward systems for expansion prediction, lens correction systems, or combinations thereof. You can rely on However, due to the continuing trend of reducing device dimensions, these correction systems may not be able to provide the desired level of alignment and / or overlay accuracy that may be required for the development of reduced devices.

  [0005] Current lithographic apparatus can also achieve higher levels of alignment and / or overlay accuracy using a reticle cooling system in conjunction with one or more of the above correction systems. While these reticle cooling systems can help control reticle temperature and reduce thermal expansion due to absorption of the radiation beam, one disadvantage of current reticle cooling systems does not provide uniform cooling across the reticle That is. Non-uniform cooling of the reticle causes non-uniform thermal expansion of the reticle, resulting in non-uniform distortion of pattern features on the reticle. Such non-uniform thermal expansion of the reticle can adversely affect the alignment and / or overlay error correction process. For example, such non-uniform thermal expansion increases the complexity of the error correction process based on the expansion prediction system.

  [0006] Accordingly, it may be desirable to have a system and method for controlling reticle temperature without the above disadvantages.

  [0007] According to an embodiment, a system for controlling the temperature of a patterning device in a lithographic apparatus includes a cooling system and a heating system. The cooling system may be configured to direct a gas flow along a first direction across the surface of the patterning device to remove unwanted heat from the patterning device before or during exposure of the patterning device. . The heating system may be configured to selectively heat a region on the surface of the patterning device before or during exposure of the patterning device. Selective heating and heat removal can achieve a substantially uniform temperature distribution in the patterning device and achieve a reduced temperature rise in the patterning device.

  [0008] In another embodiment, a system for controlling the temperature of an object includes a cooling system, a thermal sensor array, and a heating system. The cooling system may be configured to induce a gas flow across the surface of the object. The thermal sensor array may be configured to dynamically measure the temperature distribution of the object. The heating system may be configured to selectively heat a region on the surface of the object based on the measured temperature distribution. Selective heating and heat removal can achieve a substantially uniform temperature distribution in the patterning device.

  [0009] In a further embodiment, the lithographic apparatus comprises an illumination system, a support, a substrate table, a projection system, a cooling system and a heating system. The illumination system may be configured to condition the radiation beam and the support may be configured to support a patterning device configured to impart a pattern to a cross section of the radiation beam to form a patterned radiation beam. . The substrate table may be configured to hold a substrate and the projection system may be configured to project a patterned radiation beam onto a target portion of the substrate. The cooling system may be configured to direct a gas flow along a first direction across the surface of the patterning device to remove unwanted heat from the patterning device before or during exposure of the patterning device. . The heating system may be configured to selectively heat a region on the surface of the patterning device before or during exposure of the patterning device. Selective heating and heat removal can achieve a substantially uniform temperature distribution in the patterning device.

  [0010] Further features and advantages, as well as the structure and operation of various embodiments, are described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Based on the teachings contained herein, additional embodiments will become apparent to those skilled in the art.

[0011] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate the present invention and, together with the description, explain the principles of the invention and allow those skilled in the art to make the invention. To help you use it.
[0012] Figure 1 depicts a lithographic apparatus according to an embodiment of the invention. [0013] FIG. 2A is a schematic diagram of a first side view of an exemplary system comprising a reticle heating system and a reticle cooling system according to an embodiment. [0014] FIG. 2B is a schematic representation of a second side view of an exemplary system comprising a reticle heating system and a reticle cooling system according to an embodiment. [0015] FIG. 3 is a schematic top-down view of an exemplary system comprising a reticle heating system and a reticle cooling system according to an embodiment. [0016] FIG. 4 is a schematic diagram of an exemplary system including a thermal sensor array according to an embodiment. [0017] FIG. 5 is a schematic illustration of the formation of a resulting thermal profile with a reticle on a reticle stage during exposure, according to an embodiment. [0018] Figure 6 illustrates the formation of a steady thermal profile according to an embodiment. [0019] FIG. 7 is a schematic diagram of a reticle preheater system according to an embodiment. [0020] FIG. 8 illustrates the formation of a steady state thermal profile of a reticle in a preheater according to an embodiment. [0021] FIG. 9 is a schematic diagram of an exemplary system including a spatial distribution of thermal heaters, according to an embodiment. [0022] FIG. 10 illustrates the formation of a complex thermal profile using a system having a heater array, according to an embodiment.

  Embodiments will be described below with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical or functionally similar elements. In addition, the leftmost digit (s) of a reference number typically identifies the drawing in which the reference number first appears.

  [0024] A lithographic apparatus and device manufacturing method including embodiments that avoid problems with reticle heating is disclosed.

  [0025] References to "one embodiment," "an embodiment," "exemplary embodiment," and the like in the specification may mean that the described embodiment may include particular features, structures, or characteristics. However, not all embodiments may include a particular feature, structure, or characteristic thereof. Moreover, such phrases are not necessarily referring to the same embodiment. Also, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is explicitly explained that such feature, structure, or characteristic is brought about in the context of other embodiments. It is understood that this is within the knowledge of those skilled in the art. The following detailed description refers to the accompanying drawings that illustrate exemplary embodiments. The detailed description is not intended to be limiting and the scope of the embodiments is defined by the appended claims.

[0026] Figure 1 schematically depicts a lithographic apparatus 100 according to one embodiment of the invention. The lithographic apparatus 100 includes:
An illumination system (illuminator) IL configured to condition the radiation beam;
A support structure (eg mask table) constructed to support the patterning device (eg mask) MA and coupled to a first positioner PM configured to accurately position the patterning device according to certain parameters MT,
A substrate table (eg, a wafer table) constructed to hold a substrate (eg, resist-coated wafer) W and coupled to a second positioner PW configured to accurately position the substrate according to certain parameters WT,
A projection system (eg a refractive projection lens system) configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (eg comprising one or more dies) of the substrate W; PS.

  [0027] The illumination system may be a refractive, reflective, magnetic, electromagnetic, electrostatic, or other type of optical component, or any of them, to induce, shape, or control radiation Various types of optical components such as combinations can be included.

  [0028] The support structure supports the weight of the patterning device. The support structure 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 whether or not the patterning device is held in a vacuum environment. The support structure can hold the patterning device using mechanical, vacuum, electrostatic or other clamping techniques. The support structure may be, for example, a frame or table that can 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.”

  [0029] As used herein, the term "patterning device" refers to any device that can be used to provide a pattern in a cross section of a radiation beam so as to create a pattern in a target portion of a substrate. Should be interpreted widely. It should be noted that the pattern imparted to the radiation beam may not exactly match the desired pattern in the target portion of the substrate, for example if the pattern includes phase shift features or so-called assist features. . Typically, the pattern applied 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.

  [0030] The 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 halftone phase shift, as well as various hybrid mask types. One example of a programmable mirror array uses a matrix array of small mirrors, and each small mirror can be individually tilted to reflect the incoming radiation beam in various directions. The tilted mirror patterns the radiation beam reflected by the mirror matrix.

  [0031] As used herein, the term "projection system" refers to refractive, reflective, suitable for the exposure radiation used or for other factors such as the use of immersion liquid or vacuum. It should be construed broadly to encompass any type of projection system including catadioptric, magnetic, electromagnetic, and electrostatic optics, or any combination thereof. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.

  [0032] As shown herein, the lithographic apparatus is of a transmissive type (eg employing a transmissive mask). Further, the lithographic apparatus may be of a reflective type (for example, one employing the above-described programmable mirror array or one employing a reflective mask).

  [0033] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and / or two or more mask tables). In such “multi-stage” machines, additional tables can be used in parallel, or one or more tables are used for exposure while a preliminary process is performed on one or more tables. You can also

  [0034] Further, the lithographic apparatus is of a type capable of covering at least a part of the substrate with a liquid (eg, water) having a relatively high refractive index so as to fill a space between the projection system and the substrate. There may be. An immersion liquid may also be added to another space in the lithographic apparatus (eg, 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 the liquid, but simply the liquid between the projection system and the substrate during exposure. It means that.

  [0035] Referring to FIG. 1, the illuminator IL receives radiation from a radiation source SO. For example, if the radiation source is an excimer laser, the radiation source and the lithographic apparatus may be separate components. In such a case, the radiation source is not considered to form part of the lithographic apparatus, and the radiation beam is directed from the radiation source SO to the illuminator IL, eg, a suitable guiding mirror and / or beam extractor. Sent using a beam delivery system BD that includes a panda. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The radiation source SO and the illuminator IL may be referred to as a radiation system, together with a beam delivery system BD if necessary.

  [0036] The illuminator IL may include an adjuster AD for adjusting the angular intensity distribution of the radiation beam. In general, at least the outer and / or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the illuminator pupil plane can be adjusted. In addition, the illuminator IL may include various other components such as an integrator IN and a capacitor CO. By adjusting the radiation beam using an illuminator, the desired uniformity and intensity distribution can be provided in the cross section of the radiation beam.

  [0037] The radiation beam B is incident on the patterning device (eg, mask MA), which is held on the support structure (eg, mask table MT), and is patterned by the patterning device. After passing through the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam on the target portion C of the substrate W. The substrate table is used, for example, to position various target portions C in the path of the radiation beam B using a second positioner PW and a position sensor IF (eg, interferometer device, linear encoder, or capacitive sensor). The WT can be moved accurately. Similarly, using the first positioner PM and another position sensor (not explicitly shown in FIG. 1a), for example after mechanical removal from the mask library or during a scan, the mask MA is emitted by the radiation beam B It is also possible to accurately position with respect to the path. In general, the movement of the mask table MT can be achieved by using a long stroke module (coarse positioning) and a short stroke module (fine positioning) that form part of the first positioner PM. Similarly, movement of the substrate table WT can also be achieved using a long stroke module and a short stroke module that 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 to a short stroke actuator only, or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks M1 and M2 and substrate alignment marks P1 and P2. In the example, the substrate alignment mark occupies the dedicated target portion, but the substrate alignment mark can also be placed in the space between the target portion (these are known as scribe line alignment marks). Similarly, if a plurality of dies are provided on the mask MA, the mask alignment mark may be placed between the dies.

  [0038] The example apparatus can be used in at least one of the modes described below.

  [0039] In step mode, the entire pattern applied to the radiation beam is projected onto the target portion C at once (ie, a single static exposure) while the mask table MT and substrate table WT remain essentially stationary. Thereafter, the substrate table WT is moved in the X and / or Y direction so that another target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged during a single static exposure.

  [0040] 2. In scan mode, the mask table MT and substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (ie, a single dynamic exposure). The speed and direction of the substrate table WT relative to the mask table MT can be determined by the (reduction) magnification factor and image reversal characteristics of the projection system PS. In the scan mode, the maximum size of the exposure field limits the width of the target portion during single dynamic exposure (non-scan direction), while the length of the scan operation determines the height of the target portion (scan direction). Determined.

  [0041] 3. In another mode, while holding the programmable patterning device, the mask table MT remains essentially stationary and the substrate table WT is moved or scanned while the pattern attached to the radiation beam is targeted. Project onto part C. In this mode, a pulsed radiation source is typically employed, and the programmable patterning device can also be used after each movement of the substrate table WT or between successive radiation pulses during a scan as needed. Updated. 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 described above.

  [0042] Combinations and / or variations on the above described modes of use or entirely different modes of use may also be employed.

  [0043] In the discussion that follows, problems with unintentional reticle heating that may be caused by absorption of exposure light (eg, radiation beam B) or any form of thermal energy in the chromium layer and / or reticle body of the reticle during exposure. Embodiment which avoids is shown. The amount of heat absorbed depends on the transmittance of the reticle. If active reticle cooling is not applied, the reticle temperature can be increased by approximately 6 ° C. relative to ambient temperature.

  [0044] As exposure light or any other thermal energy is absorbed by the reticle, thermal stresses may occur and thermal expansion may occur in the reticle. Thermal gradients and stresses can be generated by the relatively low thermal conductivity of typical reticle quartz materials. Such stress can lead to local reticle deformation. The fact that the reticle is generally clamped can lead to further higher order deformations. Some of this deformation can be corrected through the use of scan lens elements. However, even in such a situation, uncorrectable errors may remain. The remaining errors may be too great for future systems with extreme overlay specifications. Accordingly, new embodiments that avoid the problems associated with such unintentional reticle heating are desirable.

  [0045] According to certain embodiments, heat can be applied to portions of the reticle that are not in contact with the exposure light or have a lower temperature than other portions of the reticle. Some regions of the reticle may have a lower temperature than other regions due to the non-uniform cooling of the reticle surface described above. Some areas of the reticle, such as areas closer to the nozzle of the reticle cooling system, can cool faster than other areas away from the nozzle. Infrared (IR) light (or other suitable wavelength of light) on the surface of the reticle during scanning and exposure in one or more areas that are not in contact with exposure light or have a lower temperature than other areas of the reticle Heat can be applied by taking in. The intensity of the IR light can be modulated in time and space, so that the correct amount of heat can be captured at the desired location on the reticle. In this way, the entire reticle can be heated uniformly as the exposure process proceeds, minimizing thermal gradients, thermal stresses and thermal deformation.

  [0046] However, thermal stress can still be generated by the fact that the reticle is generally clamped. These stresses can be periodically relieved by unclamping the reticle and loosening the reticle. When relieving stress in this manner, the reticle can be clamped and aligned again as needed. Alternatively, the selective heating device may be spatially and temporally modulated to minimize the uncorrectable portion of thermally induced strain. This can result in a non-uniform temperature profile in the substrate, but can minimize uncorrected mask distortion.

  [0047] According to an embodiment, the method of intentionally and selectively heating one or more regions of the reticle can allow the temperature distribution in the reticle to be maintained in a substantially uniform spatial distribution. With such a temperature profile, the resulting reticle deformation includes a simple magnification that can be normally corrected without using a complex system including, for example, a lens manipulator. Any remaining small non-uniform heat distribution (and corresponding non-uniform thermal expansion / deformation) can be compensated by existing reticle heating solutions.

  [0048] IR light having a wavelength of about 1500 nm, 2000 nm or more can be absorbed by a general reticle quartz material, and therefore is used intentionally and in various embodiments of the invention to select a reticle. Heat can be generated to heat automatically. One advantage of this method is that it does not rely on the presence of an absorber (eg, a Cr layer) outside the imaging area on the reticle.

  [0049] The optical heating system includes a plurality of radiation sources configured to generate a plurality of radiation beams to heat the patterning device before and / or during exposure of the patterning device, and the patterning device And a controller configured to modulate the intensity of the radiation from the plurality of radiation sources at least once to produce a desired thermal pattern in the patterning device by maintaining a constant temperature profile over time. In some embodiments, a thermal sensor array may be included to determine the temperature distribution of the patterning device.

  [0050] In an embodiment, the plurality of radiation sources may be arranged along a plane substantially perpendicular to the radiation beam during operation of the patterning device, and receive and emit each radiation beam from the radiation source. A plurality of optical systems are provided that are configured to provide a beam to the patterning device.

  [0051] The controller further varies the intensity of the radiation of the plurality of radiation sources based on at least one of a sensed thermal distribution of the patterning device and a thermal pattern in which the heat flux entering and exiting the patterning device is balanced. May be configured.

  [0052] In certain embodiments, the radiation source may include multiple lasers or light emitting diodes (LEDs) to carry IR light to multiple locations on the reticle surface. In a further embodiment, a single high power laser can be used. In a single laser embodiment, multiple light beams can be generated to provide IR light using beam splitters and optical switches as needed. Laser light can be carried from the laser source through the optical fiber to the reticle and can be directed to various positions on the reticle surface using mirrors or optical switches.

  [0053] FIG. 2A illustrates a first side view of a system 200 comprising a reticle heating system and a reticle cooling system according to an embodiment. In this example embodiment, system 200 may be part of a lithographic apparatus having a structure and functionality similar to lithographic apparatus 100 described above with reference to FIG. The reticle heating system may include a laser system 201, a plurality of optical fibers 202, an optical system 204, and an optical device 208. As described above, the reticle heating system may be configured to intentionally and selectively heat the reticle 210. In this example embodiment, the optical fiber 202 can carry light (eg, IR radiation) from the laser system 201 to the optical system 204. The optical system 204 is configured to project / focus the beam 206 onto a region of the reticle 210 that is selected to be heated, eg, via a mirror 208 (or other optical device) along the Z axis. May be. A portion of the IR radiation beam 206 can be absorbed on the top surface 212 of the selected area of the reticle 210. The absorbed radiation can generate heat. In the exemplary embodiment, beam 206 may include a plurality of beams, each of the plurality of beams corresponding to each of a plurality of optical fibers 202. In another example, the mirror 208 and the optical system 204 can be placed on a fixed frame (“fixed world”) 214 of the illuminator IL.

  [0054] FIG. 2A shows the laser system 201 as a heat source and the optical fiber 202 as a heating element for convenience, but other heat sources and / or heating elements may be used without departing from the spirit and scope of the present disclosure. It should be noted that it is obvious to those skilled in the art. For example, an LED or LED array may be used as a heat source and / or a heating element and may be configured to provide a radiation beam 206 to heat the reticle 210. Further, it will be appreciated by those skilled in the art that other projection / focus systems other than optical system 204 and mirror 208 may be used to direct radiation beam 206 onto reticle 210 without departing from the spirit and scope of the present disclosure. it is obvious. In another embodiment, the radiation beam 206 can be directed onto the reticle 210 from the LED or optical fiber 202 without using a focusing system.

  [0055] According to certain embodiments, a reticle cooling system (described in further detail below with reference to FIG. 2B) has a gas flow 230 directed across the top surface 212 of the reticle 210, for example, along the Y axis. It may be configured as follows. The gas stream 230 can help reduce the temperature of the reticle 210 that can be unintentionally heated by absorbing some energy from the exposure light 218 (such as the radiation beam B described above with reference to FIG. 1). . Such a decrease in reticle temperature can help reduce the thermal expansion of reticle 210 and the heating of gas around reticle 210. This reduction in thermal expansion and a reduction in the temperature of the gas around the reticle 210 reduces image distortion. In some embodiments, the characteristics (eg, temperature, pressure, or flow rate) of the gas stream 230 may be adjusted dynamically to achieve the desired temperature of the reticle 230. In some embodiments, the gas of the gas stream 230 may comprise helium or consist essentially of helium. In some embodiments, the gas stream 230 may include a very clean and dry gas or air.

  [0056] In a further embodiment, the reticle stage / chuck 216 supports the reticle 210 and moves the reticle 210 under the exposure beam 218, for example, along the X axis to image the reticle (not shown). It may be configured to expose above. The exposure beam 218 can be absorbed by the chromium layer 220 at the bottom of the reticle. Further, by moving the chuck 216 and the reticle 210, the radiation beam 206 is focused on the moving portion of the reticle top surface 212 and heat is applied to the entire top surface.

  [0057] The laser of the laser system 201 introduces energy only where the beam 206 is needed, eg, only in areas of the reticle 210 that have a lower temperature than the image area of the reticle 210 or lower than other areas of the reticle 210. Can be modulated. The laser light can be modulated in various ways. For example, in addition to on / off modulation, the pulse width and intensity per pulse can be modulated to provide more accurate energy control. This modulation can be performed by a controller that can be an integral part of the laser system 201. In another embodiment, the controller may be separate from the laser system 201.

  [0058] The beam 206 can be controlled in terms of position, intensity, and modulation so that a desired amount of energy (heat) can be introduced at a desired location on the reticle 210 in response to the absorption profile of the reticle 210. Such beam control can be calibrated or estimated using transmission data and models. Dynamic control can also be obtained using feedback during the exposure / heating process using a thermal sensor (described below with reference to FIG. 4) at the reticle stage 216.

  [0059] FIG. 2B illustrates a second side view of a system 200 "comprising a reticle heating system and a reticle cooling system according to an embodiment. In this example embodiment, system 200 '' may have a structure and function similar to system 200 described above with reference to FIG. 2A. Therefore, the difference between the system 200 and the system 200 '' will be described. Similar components between system 200 and system 200 '' are similarly numbered, and only those features that are useful for explaining the differences or describing the disclosed embodiments are described.

  [0060] According to an example of this embodiment, the reticle cooling system may include a gas nozzle 232 and a gas extraction unit 234. The gas nozzle may include a gas inlet 208 and the gas extraction unit 234 may include a gas outlet 209. The gas outlet 209 may be positioned on the opposite side of the gas inlet 208 with respect to the reticle 210. Each of gas inlet 208 and gas outlet 209 may be positioned so as to be in close proximity, eg, adjacent, to the same surface (eg, top surface 212) of reticle 210. Gas inlet 208 and gas outlet 209 may be positioned to provide gas flow 230 across reticle 210. The gas stream 230 can travel from the gas inlet 208 substantially parallel to the top surface 212 of the reticle 210. The gas outlet 209 may be configured to extract the gas stream 230 when the gas stream 230 reaches the opposite side of the reticle 210. The gas stream 230 extracted by the gas outlet 209 can return to be recirculated to the gas inlet 208 after the gas in the gas stream 230 has been thermally reconditioned.

  [0061] In an embodiment, the gas extraction unit 234 may be integrated or coupled with a fixed purge plate 203 that is positioned above the reticle 210 and may remain stationary during operation of the lithographic apparatus. The fixed purge plate 203 is a non-movable component of the lithographic apparatus, and can partially define a pressurized environment containing clean gas in the region between the reticle 210 and the bottom surface of the fixed purge plate 203. In another embodiment, the gas extraction unit 234 may be integral with the reticle stage 216. In another embodiment, the gas inlet 208 may be integral with the reticle stage 216. For example, reticle stage 216 may form gas nozzle 232 or be directly coupled to gas nozzle 232. In further embodiments, the gas inlet 208 may be separate from the reticle stage 216, for example, a separate gas nozzle 232 that passes through the opening 205 defined by the reticle stage 216 shown in FIG. 2B. The gas nozzle 232 and the gas inlet 208 can move to travel substantially in accordance with the reticle stage 216, for example, by attaching the nozzle 232 to a moving frame that travels in accordance with the reticle stage.

  [0062] FIG. 3 shows a top-down view of a system 300 comprising a reticle heating system and a reticle cooling system according to an embodiment. In this example embodiment, system 300 may have a structure and function similar to system 200 and system 200 ″ described above with reference to FIGS. 2A and 2B. Therefore, the differences between system 200, system 200 '' and system 300 will be described. Similar components between system 200, system 200 ″, system 300 are similarly numbered, and only those features that are useful for explaining the differences or describing the disclosed embodiments are described.

  In the example of this embodiment, each of the plurality of optical fibers 202 may be individually controlled and selectively turned on / off. According to an example, such control can be performed using the controller of the laser system 201. Optical system 204 (eg, a lens array) can be used to direct beam 206 from optical fiber 202 to reticle 210 along the Z axis via mirror 208 (not shown). During exposure, the exposure light 218 can heat the reticle by being partially absorbed by the reticle's chromium 220 layer.

  [0064] According to an embodiment, the plurality of optical fibers 202 is cooled faster than the optical fiber set 311 is in an area on the reticle 210, eg, an area 306 outside the chrome layer 220 or other areas on the reticle 210. It can be individually controlled to be turned on to selectively illuminate the area near the resulting gas nozzle 232. In another embodiment, the plurality of optical fibers 202 corresponds to an area where the optical fiber set 312 is away from the area on the reticle 210, eg, the area 310 above the chrome layer 220 or the gas nozzle 232 that does not need to be heated. It can be controlled individually so that it is turned off. In this way, only selected areas such as area 306 are exposed with IR light and consequently heated.

  [0065] The intensity of the IR light is selected and controlled by the controller of the laser system 201 so that the amount of heating outside the exposure area is the same as the heating in the pattern area 220, for example, as a result of the exposure beam 218 at 193 nm. Can do.

  [0066] The thermal sensor array can be configured to monitor the temperature of each position on the reticle 210 during or between exposures. According to an embodiment, the information provided by these thermal measurements is used to control the intensity of each IR beam in the plurality of optical fibers 202 to accurately correct the thermal gradient by the laser controller of the laser system 201. can do.

  [0067] FIG. 4 illustrates a system 400 that includes an array of thermal sensors 402 according to an embodiment. In this example embodiment, system 400 may have the same structure and function as system 200, system 200 ″, and system 300 described above with reference to FIGS. 2A, 2B, and 3. Therefore, differences between the system 200, the system 200 '', the system 300, and the system 400 will be described. Similar components between system 200, system 200 ″, system 300, and system 400 are similarly numbered, and only those features that are useful for explaining the differences or the disclosed embodiments are described.

  In this example embodiment, the thermal sensor 402 array is configured to monitor the temperature of the reticle 210 based on the light 404 reflected from the reticle surface 212 via the mirror 406. In this embodiment, the thermal sensor 402 may be positioned so that the IR light 206 used to heat the reticle does not reach the sensor 402.

  [0069] According to certain embodiments, the IR laser of the laser system 201 used for heating can be controlled (eg, modulated and synchronized) by the thermal sensor 402 via the controller of the laser system 201. Alternatively, the sensor can only be activated when the IR heating laser is not on. A feedback loop (not shown) may be provided to tune the IR laser and sensor during the scan.

  [0070] In further embodiments, a cooling mechanism can be provided to remove heat (eg, "air shower"). Use of such a cooling mechanism can be employed to ensure that the final temperature of the reticle is not too high.

  [0071] In a further embodiment, a reticle “preheater” may be employed to imprint reticle 210 with an initial thermal profile (or “fingerprint”). This can be done by loading reticle 210 onto a dummy stage that creates an environment that mimics heat loss from reticle 210 on stage 216. The reticle 210 can then be heated by a 2D heater having a spatial distribution of heating elements that is programmable in x and y to produce a spatial temperature profile. The thermal profile can be selected to correspond to the temperature pattern that results from exposure. Once heated, the reticle 210 may then be transported to the reticle stage 216 within a short time (eg, within 60 seconds). This can result in a small shift of heat in the reticle 210. However, once exposure begins, the thermal pattern remains stable (because the thermal profile is selected to correspond to the steady thermal pattern produced by exposure). Using this method, a heat distribution can be established in a certain time, thereby eliminating the need for complex correction mechanisms such as those involving scan lens elements.

  [0072] FIG. 5 schematically illustrates a reticle 502 on a reticle stage during exposure, along with the resulting thermal profile 508 formation. The reticle 502 is positioned on the chuck 504, and the exposure light 506 heats the reticle with a chrome pattern. This results in heating of the reticle. The volume surrounded by the pellicle frame 512 and the pellicle 514 is also heated.

  FIG. 6 shows a steady state 600 that occurs after a long exposure of the reticle. Heat 602 generated by the exposure diffuses through the reticle. Radiation and convection 604 is generated by removing heat from the reticle. Some heat 606 may flow through the clamp. Heat inflow is balanced by the heat flux exiting the system. The resulting heat distribution in the reticle usually does not change much with continuous exposure.

  [0074] FIG. 7 shows an exemplary preheater 700 disposed on a reticle (on a reticle head or "Turret"). Preheater 700 includes a heater 702 disposed on reticle 704. In this example, the reticle is on dummy clamp 706. The main purpose of these clamps is to approximate the thermal conductivity that the reticle experiences with an actual reticle stage clamp. Airflows 708 and 710 above and below the reticle mimic the flow that the reticle experiences during exposure on the reticle stage. These airflows contribute to simulating the reticle stage environment during exposure.

  [0075] The heater 702 includes a 2D light array that generates a wavelength of approximately 193 nm (eg, 240 nm LED). Light of such a wavelength may be absorbed by the chrome pattern. Alternatively, an IR LED or laser can be used to generate a 2D thermal pattern. IR radiation at 2 micron wavelength is absorbed directly into quartz. With such absorption, heat may be absorbed on the reticle along with the chrome pattern. This method has the advantage that no assumptions about the spatial distribution of the chrome pattern need be made.

  [0076] The heater 702 may be configured to generate a spatially dependent thermal pattern by controlling the intensity of individual light sources. Intensities 714 and 716 can be selected to be lower than intensity 712 above the image area. This allows the heat to be taken directly into the reticle where it is needed rather than waiting for the heat to diffuse from the image area to the outside perimeter of the exposure area (which may be a long time). .

  [0077] FIG. 8 shows a reticle state 800 in the preheater after thermal equilibrium is established. After some heating, a thermal profile 802 can be established at the reticle. This thermal profile roughly corresponds to that created after a long exposure with a balanced heat flux in and out of the reticle.

  [0078] A desired thermal profile can be determined via measurement, calibration and modeling. The required correction to the reticle pattern resulting from the provided temperature profile can also be determined by measurement, calibration and modeling. The theoretical model may include the measured optical properties of the reticle as input. Such optical properties can include measured absorption and transmission of light obtained by scanning the reticle with a small image area and spot sensor.

  [0079] FIG. 9 illustrates a further embodiment 900 that includes a spatial distribution of thermal heaters. In this example, the heater may be a resistance element. In this embodiment, the plate (eg, PCB board) may include horizontal 902 and vertical 904 interconnects that are equidistant. Each of the small surface mount resistors 906 may be connected to one of a vertical 904 interconnect and a horizontal 902 interconnect. All vertical interconnects are connected to a voltage supply on one side and can be individually switched on 908 or off 910.

  [0080] Similarly, the horizon switch can be turned on 912 and off 914. The heater array may be placed on a reticle that needs to be preheated. Since the reticle image pattern is generally rectangular, it is simply a matter of selecting the appropriate group of horizontal and vertical interconnects connected to the power supply to produce the desired thermal pattern. In this way, a low resolution “thermal image” can be generated. In FIG. 9, since the lower left part of the heater is “on” and the rest is “off”, only the upper part (lower left rectangular area 916) of the “high temperature” register is heated. With such a simple scheme, the rectangular image area can be heated uniformly.

  [0081] Since registers are typically long-lived, such embodiments are expected to be robust. Even if some resistors fail, the generation of thermal “holes” is not a big problem as a result. The thermal time constant for compensating the resulting “hole” is so short that the final result can be ignored. Of course, the system can be more reliable by using two (or more) parallel registers for each node. So if one fails, half of the heat source remains.

  [0082] Implementing the control system for the embodiments disclosed herein is fairly straightforward. As will be apparent to those skilled in the art, one or more drivers can be used and the switch can be implemented with standard digital logic.

  [0083] FIG. 10 illustrates the formation of a complex thermal profile using a system such as the thermal array of FIG. For example, assume that a particular reticle has non-uniform optical properties (ie, transmission and absorption). FIG. 10 shows a state 1000 where the reticle has a region 1002 (upper right) with 75% absorption and a remaining region 1005 with 25% absorption. In this example, region 1002 experiences three times as much heat absorption as region 1004. This non-uniform heating profile can be compensated using multiple multiplexed “thermal images” 1006 and 1008. In this example, thermal image 1006 is turned on for 1/3 time and thermal image 1008 is turned on for 2/3 time. Corresponding thermal resistor array patterns are shown schematically at 1010 and 1012 respectively.

  [0084] More elaborate patterns can be generated by dividing the array into more rectangular patterns. Further embodiments can include a driver for each register, as is done with LCD displays. A further advantage of such an embodiment is that it relates to the placement of edges that need not be highly accurate. Low resolution is sufficient because high spatial frequency errors (eg caused by lost registers) spread with a small time constant.

  [0085] Although specific reference is made herein to the use of a lithographic apparatus in IC manufacturing, a lithographic apparatus described herein may include integrated optical systems, guidance patterns and detection patterns for magnetic domain memories, It should be understood that other applications such as the manufacture of flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads and the like may be had. As will be appreciated by those skilled in the art, in such other applications, the terms “wafer” or “die” as used herein are all more general “substrate” or “target” respectively. It may be considered synonymous with the term “part”. The substrate described herein can be used, for example, before or after exposure, such as a track (usually a tool for applying a resist layer to the substrate and developing the exposed resist), a metrology tool, and / or an inspection tool. May be processed. Where applicable, the disclosure herein may be applied to substrate processing tools such as those described above and other substrate processing tools. Further, since the substrate may be processed multiple times, for example, to make a multi-layer IC, the term substrate as used herein may refer to a substrate that already contains multiple processing layers.

  [0086] Although specific reference has been made to the use of embodiments of the present invention in the context of optical lithography as described above, it will be appreciated that the present invention may be used in other applications, such as imprint lithography. However, it is not limited to optical lithography if the situation permits. In imprint lithography, the topography within the patterning device defines the pattern that is created on the substrate. The topography of the patterning device is pressed into a resist layer supplied to the substrate, whereupon the resist is cured by 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.

  [0087] As used herein, the terms "radiation" and "beam" refer to ultraviolet (UV) (eg, wavelengths of 365 nm, 355 nm, 248 nm, 193 nm, 157 nm, or 126 nm, or about these wavelengths) ), And extreme ultraviolet (EUV) (e.g., having a wavelength in the range of 5-20 nm), and all types of electromagnetic radiation, including particulate beams such as ion beams and electron beams.

  [0088] The term "lens" may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic, and electrostatic optical components, depending on the context. .

  [0089] 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 invention may be in the form of a computer program comprising a sequence of one or more machine-readable instructions representing the methods disclosed above, or a data storage medium (eg, semiconductor memory, magnetic A disc or an optical disc).

  [0090] The "Summary" and "Summary" sections describe one or more exemplary embodiments of the invention contemplated by the inventor, but not all, so that the invention and the appended claims It is not intended to limit the scope of

  [0091] Embodiments of the invention have been described using functional building blocks that illustrate implementations of specific functions and their relationships. In the present specification, the boundaries of these functional building blocks are arbitrarily defined for convenience of explanation. Alternative boundaries can be defined as long as certain functions and their relationships are properly implemented.

  [0092] The above description of specific embodiments fully discloses the general nature of the invention, and thus requires a person of ordinary skill in the art to apply undue experimental work by applying knowledge in the art. Without departing from the general concept of the present invention, such specific embodiments can be easily modified and / or adapted for various applications. Accordingly, such adaptations and modifications are intended to be included within the meaning and scope of equivalents of the disclosed embodiments based on the teachings and guidance presented herein. The expressions or terms in this specification are for purposes of illustration and are not intended to limit the present invention, so the terms or expressions herein are to be interpreted by those skilled in the art in light of the teachings and guidance. Please understand that it should be done.

  [0093] The breadth and scope of the present invention is not limited by any of the above-described exemplary embodiments, but is only defined by the appended claims and their equivalents.

Claims (16)

A system for controlling the temperature of a patterning device in a lithographic apparatus,
The system includes a cooling system that directs a gas flow along a first direction across the surface of the patterning device to remove heat from the patterning device before or during exposure of the patterning device; A heating system that selectively heats a region on the surface of the patterning device before or during exposure of the patterning device;
The cooling system comprises a gas nozzle including a gas inlet for supplying the gas stream to the surface of the patterning device;
The heating system includes a plurality of radiation sources that generate a plurality of radiation beams, a focus system that directs the plurality of radiation beams along a second direction on the surface of the patterning device, and the surface of the patterning device A controller for adjusting the intensity of the plurality of radiation beams to form a desired thermal pattern thereon,
The controller adjusts the intensity of the plurality of radiation beams to selectively heat a region near the gas nozzle that can be cooled faster than other regions on the surface of the patterning device;
The system wherein the selective heating and heat removal achieves a substantially uniform temperature distribution in the patterning device.   The system of claim 1, further comprising a thermal sensor that measures a temperature distribution at two or more locations of the patterning device. The system of claim 2 , further comprising a controller that adjusts an amount of heat provided to a selected region on the surface of the patterning device based on the measured temperature distribution. The first direction is perpendicular to the second direction, according to any one of claims 1 to 3 system. The system according to claim 1, wherein the plurality of radiation sources are individually controllable. The heating system, the controls to the spatial temperature distribution of the patterning device to approximate the steady state temperature distribution, according to any one of claims 1 to 5 system. The cooling system comprises a gas extraction unit comprising a gas outlet to extract the gas stream, the system according to any one of claims 1 to 6. The system of claim 7 , wherein the gas outlet is positioned opposite the patterning device relative to the gas inlet. A movable stage for holding the patterning device;
A fixed purge plate positioned above the movable stage, wherein the gas outlet is coupled to an opening in the fixed purge plate;
The system according to claim 7 or 8 , further comprising: A system for controlling the temperature of an object,
The system includes a cooling system that induces a gas flow across the surface of the object to remove heat from the object, a thermal sensor array that dynamically measures temperature distribution at two or more locations of the object, and a measurement A heating system that selectively heats a region on the surface of the object based on the temperature distribution
The cooling system comprises a gas nozzle including a gas inlet for supplying the gas flow to the surface of the object;
The heating system includes a plurality of radiation sources that generate a plurality of radiation beams, a focus system that directs the plurality of radiation beams on the surface of the object, and a desired thermal pattern on the surface of the object. A controller for adjusting the intensity of the plurality of radiation beams to
The controller adjusts the intensity of the plurality of radiation beams to selectively heat a region near the gas nozzle that can be cooled faster than other regions on the surface of the object;
The system wherein the selective heating and heat removal achieves a substantially uniform temperature distribution in the object. The system of claim 10 , further comprising a controller that adjusts an amount of heat provided to a selected region on the surface of the object based on the measured temperature distribution. The cooling system comprises a gas extraction unit comprises a gas outlet for extracting the gas flow system according to claim 10 or 11. An illumination system for adjusting the release elevation beam, a support constructed to support a patterning device for forming a cross-section imparted to patterned radiation beam a pattern in the radiation beam, a substrate table constructed to hold a substrate, the patterned radiation beam the A projection system that projects onto a target portion of a substrate; and a gas flow in a first direction across the surface of the patterning device to remove heat from the patterning device before or during exposure of the patterning device A cooling system that guides along, and a heating system that selectively heats a region on the surface of the patterning device prior to or during exposure of the patterning device;
The cooling system comprises a gas nozzle including a gas inlet for supplying the gas stream to the surface of the patterning device;
The heating system includes a plurality of radiation sources that generate a plurality of radiation beams, a focus system that directs the plurality of radiation beams along a second direction on the surface of the patterning device, and the surface of the patterning device A controller for adjusting the intensity of the plurality of radiation beams to form a desired thermal pattern thereon,
The controller adjusts the intensity of the plurality of radiation beams to selectively heat a region near the gas nozzle that can be cooled faster than other regions on the surface of the patterning device;
The lithographic apparatus, wherein the selective heating and heat removal achieves a substantially uniform temperature distribution in the patterning device. The lithographic apparatus according to claim 13 , further comprising a thermal sensor for measuring a temperature distribution at two or more locations of the patterning device . The lithographic apparatus according to claim 14 , further comprising a controller for adjusting an amount of heat provided to a selected region on the surface of the patterning device based on the measured temperature distribution. 16. A lithographic apparatus according to any one of claims 13 to 15, wherein the first direction is perpendicular to the second direction.