TW202041974A - Lithographic apparatus with thermal conditioning system for conditioning the wafer - Google Patents

Abstract

A lithographic apparatus receives radiation for imaging a pattern via projection optics onto a plurality of target areas on a substrate. Each target area receives a heat load through absorption of the radiation during imaging. The apparatus has thermal conditioning system to maintain the substrate at a spatially uniform, constant first temperature during the imaging. The thermal conditioning system has a heat sink operative to extract heat from the substrate; and a first heater system that supplies during the imaging, a first additional heat load to a part of the substrate. This part is the complement of the specific target area onto which the pattern is being imaged. The first additional heat load per unit area equals or exceeds a magnitude of the heat load per unit area.

Description

Lithography equipment with thermal regulation system for regulating wafer

The invention relates to a lithography device.

Thermally induced effect

The properties of physical substances tend to change in response to changes in temperature. Thermally induced changes in the properties of the physical components of the system can be critical to the performance of the system. In general, it is therefore preferable to thermally stabilize the system through controlled heating and/or controlled cooling of the components. This stabilization reduces the temperature-dependent changes in the components caused by the thermal load received from the environment of the components during the operation of the system. For example, the component may be thermally coupled to a heat sink that extracts heat from the component. Therefore, the components can achieve thermal equilibrium and use a constant spatially uniform temperature, thereby maintaining thermally induced deformation, which in turn remains constant and spatially uniform. Lithography System

The lithography system is an example of a system in which limiting thermally induced deformation is critical to the performance of the system. The lithography system is configured to image the pattern on a photosensitive resist ("resist") that covers the semiconductor wafer (or: semiconductor substrate). After imaging, the thus exposed resist is developed to form a mold for processing steps, where the next layer is created in the multilayer stack that ultimately forms the array of integrated electronic circuits. The lithography system includes a light source and a scanner (also known as: lithography equipment). The electromagnetic radiation generated by the light source is used in the scanner to project the pattern existing on the photomask (also known as patterning device, or reduction photomask) onto the resist layer on the wafer through projection optics . Actinic and non-actinic radiation

In practice, the electromagnetic radiation generated by the light source can include actinic radiation and non-actinic radiation. As is known, actinic radiation catalyzes the change of photoresist by, for example, breaking molecular bonds so that the pattern of the photomask can be printed into the photoresist. Non-actinic radiation does not produce such changes and therefore cannot be used to print patterns on photoresists. Non-actinic radiation is also called out-of-band (OOB) radiation. In particular, non-actinic radiation can cause undesired thermal loads on the wafer, and therefore can cause undesired thermally induced deformations during the imaging process. Thermally induced effects of anti-overlapping and focal points

The lithographic scanner has physical components whose functions are sensitive to thermal load, and their thermal conditions, such as thermally induced deformation, are critical to the performance of the scanner. The performance of the scanner can be expressed in terms of overlay and focus. The term "stacking" is an abbreviation of "stacking error", and indicates the degree to which successive layers in the integrated circuit chip are laterally displaced from each other. The overlap thus indicates the degree to which the pattern used to form a layer on the wafer is aligned with the layer previously formed in the wafer. Overlay is the horizontal distance between patterns, that is, the measured value in the wafer plane, and can be described as an orientation-dependent two-dimensional (vector) field. The term "focus" is an abbreviation of "focus error" and indicates the vertical deviation of the actual focal plane from the ideal focal plane during imaging. The important aspect of lithography maintains the uniformity of the size of the features generated on the surface of the substrate. The change in feature size is required to be a small fraction less than the predetermined nominal value. The key to achieving such performance is tight control of focus error. Overlay and focus control become more and more important

With each new generation of integrated circuits, the size of the features imaged on the wafer is further reduced by using actinic radiation with a shorter wavelength. Currently, extreme ultraviolet (EUV) lithography is used before the use of actinic radiation with 13.5 nm or even lower wavelengths. Therefore, tighter control of thermally induced effects in wafers becomes more and more important with each new generation of integrated circuits. ASML Background example

In order to outline some examples of efforts made in the field of lithography within the context of thermal control of wafers, refer to the following documents.

The International Application Publication No. WO 2018041491, which was filed by Cox et al., assigned to ASML and incorporated herein by reference, discloses an EUV lithography apparatus with a projection system that is configured to use light through a gap. The radiation beam patterned by the mask is projected onto the exposure area on the substrate held on the substrate stage. The lithography apparatus operates in a scanning mode, in which the photomask and substrate are scanned simultaneously during projection. The lithography device includes a cooling device positioned between the projection system and the substrate. The cooling device provides regionalized cooling of the substrate near the area where the patterned radiation beam is incident on the substrate through the slit. The amount of cooling provided by the cooling device is generally constant in the direction along the slit, for example, in a direction substantially perpendicular to the scanning direction. What may be required is to provide different amounts of cooling in the orientation along the direction of the gap. This is because the heating of the substrate caused by the patterned radiation beam may be different at different positions of the substrate in the direction along the slit in the exposure area E. The amount of heating of the substrate caused by the patterned radiation beam depends on the intensity of the radiation beam, and this can vary across the exposure area along the slit direction. Different parts of the photomask can have different reflectivities. This is because the spatial variation of reflectivity is determined by the nature of the pattern features on the photomask. Therefore, the lithography equipment also includes heating equipment having one or more radiation sources, such as infrared lasers, which are configured to provide illumination and heat one or more additional radiation beams of the substrate . One or more additional radiation beams can illuminate and heat at least a part of the exposed area, that is, the area of the substrate that receives the patterned radiation beam. The heating device further includes one or more sensors configured to sense infrared radiation from the substrate. The controller controls the infrared laser to adjust the power of its radiation beam as needed so as to selectively provide the required heating amount at different sections within the exposure area. Due to the operation of the infrared laser, the net heating of the substrate across the exposure area remains substantially constant. Therefore, the distortion of the substrate caused by the different heating amounts at different positions under the gap on the substrate in other ways is reduced.

US Patent 9,983,489, issued to Berendsen et al., assigned to ASML and incorporated herein by reference, discloses a method for compensating exposure errors in the exposure process of photolithography equipment. The method comprises: obtaining a dose measurement value indicating the IR radiation dose reaching the substrate level, wherein the dose measurement value is used to calculate the amount of IR radiation absorbed by the object during the exposure process; and using the dose measurement value to control the exposure Processed to compensate for exposure errors associated with IR radiation absorbed by the object during the exposure process. Examples of objects include: substrates, substrate tables, and mirrors for projection optics. Examples of the control of the exposure process include: controlling the heater to heat the mirror; controlling the thermal adjustment system to control the temperature of the substrate support of the lithography equipment.

US Patent 7,630,060, issued to Ottens et al., assigned to ASML and incorporated herein by reference, discloses a lithography apparatus that includes an illumination system for providing a radiation beam and for supporting patterning The supporting structure of the device. The patterning device is used to impart the radiation beam with the pattern in its cross section. The equipment also includes a substrate support for holding the substrate, and a projection system for projecting the patterned beam onto the target portion of the substrate. The equipment has an additional heating system to provide additional heating of the substrate. The substrate is additionally heated so that the substrate has a relatively constant thermal load. Here, the term "constant" means constant in time and/or position. The term "in addition" means to additionally illuminate the projection beam. Supplementary heating is preferably provided by supplemental lighting of the substrate using an additional lighting system. Additional heating, such as lighting, is assumed to heat the substrate without affecting, for example, resist patterning. Therefore, it may be advantageous to additionally illuminate the substrate in embodiments where additional illumination is used to use resist-insensitive radiation, such as infrared radiation. The feedforward system can control the dose of the supplemental lighting system based on the (known) heat generated by the patterned beam. Supplemental lighting systems may include, for example, lasers and/or "classical" radiation sources. The supplemental lighting system can, for example, uniformly irradiate the entire substrate surface, uniformly irradiate the gap, the gap in a patterned pattern, or the area around the gap. Here, the gap is the actual light projected on the substrate. Other supplementary lighting strategies are also possible. The advantage of supplementary heating is that the temperature of the substrate can be kept relatively stable during the lithography process. Therefore, the thermal expansion of the substrate remains constant in time and/or uniformly constant in position. Another advantage is that the substrate temperature can be controlled relatively easily. Therefore, the stacking error can be minimized because all the substrates can be exposed at the same temperature.

The U.S. Patent Application Publication 2018/0173116 filed by Koevoets et al., assigned to ASML and incorporated herein by reference discloses a scanning lithography apparatus with a projection system configured to project patterned radiation The beam is used to form an exposure area on the substrate held on the substrate stage. The lithography device further has a heating device for heating the substrate. The heating device includes a first heating element and a second heating element, and the first heating element and the second heating element are configured to heat the substrate area at the opposite end of the exposure area in the non-scanning direction of the lithography device. The heating device can heat the area overlapping with the exposure area. The heating device is advantageous because it prevents or reduces the distortion of the substrate at the ends of the exposure area in the non-scanning direction. This allows to improve the stacking performance of the lithography device. More specifically, the heating element delivers zoned heating to the substrate, which zone heating is used to heat the part of the substrate just outside the edge of the exposure area illuminated by the radiation beam. Therefore, the temperature of the substrate does not gradually decrease rapidly at the edge of the exposure area, but instead decreases slowly. This situation is advantageous because it reduces the distortion of the substrate that would otherwise be caused by the temperature drop. This situation enables the improvement of accuracy, that is, the improvement of the stacking performance of lithography equipment, and the pattern can be projected on the substrate using this improvement. The first heating element and the second heating element can be positioned above the substrate support and positioned at the opposite ends of the exposure area in the non-scanning direction of the lithography device. The heating elements may each include an LED array emitting infrared radiation, or two or more lasers emitting radiation of non-actinic wavelength.

The present invention is about further improving the control of the exposure process in the lithography equipment plus others.

The present invention relates to a lithography device configured to receive radiation for imaging a pattern onto a plurality of target areas on a substrate via projection optics. Each specific target area of the target areas is used to receive a thermal load by absorbing at least part of the radiation during imaging on the specific target area. The lithography equipment includes a thermal regulation system. The thermal regulation system is configured to maintain the substrate at a spatially uniform and constant first temperature during the imaging period. The thermal conditioning system includes: a heat sink for extracting heat from the substrate; and a first heater system for supplying a spatially uniform first additional heat load to a portion of the substrate during the imaging period . This part is the complement of the specific target area on which the pattern is being imaged. A magnitude of the first additional heat load per unit area is equal to or exceeds a magnitude of the heat load per unit area.

At a uniform temperature in a space of the substrate, the pattern is imaged on a plurality of target areas independent of thermally induced deformation across the substrate.

In an embodiment, the thermal regulation system is configured to supply the first thermal load via irradiating the complement. To this end, the thermal conditioning system may include at least one of an LED and a scanning laser configured to supply the first additional thermal load.

In another embodiment, the thermal regulation system includes a second heater system for supplying a second additional heat load to a specific target area. This type of second additional heat load can be used when the heat load from imaging radiation per unit area is lower than the first additional heat load provided per unit area. The second heater system can be configured to supply a second additional heat load by irradiating a specific target area. For this purpose, the second heater system may include at least one of the following: a second LED and a second scanning laser configured to supply the second additional heat load.

In another embodiment, the lithography apparatus includes a pre-heating system that is configured to pre-heat the substrate to a substantially spatially uniform second temperature after imaging is started. The first temperature may be equal to the second temperature. The pre-heating system can be configured to pre-heat the substrate by irradiating the substrate. For this purpose, the pre-heating system includes at least one of the following: a third LED and a third scanning laser.

FIG. 1 is a schematic diagram of an extreme ultraviolet (EUV) lithography system. The extreme ultraviolet (EUV) lithography system includes a radiation source SO and a lithography device LA. The radiation source SO includes an EUV radiation source, such as a laser-generated plasma (LLP) EUV source or an electron-free laser (FEL). The lithography equipment LA includes an EUV scanner. The radiation source SO is configured to generate an EUV radiation beam B and supply the EUV radiation beam B to the lithography apparatus LA. The lithography equipment LA includes an illumination system IL, a support structure MT configured to support the patterning device MA (such as a photomask), a projection system (or: projection optics) PS, and a substrate support configured to support the substrate W WT.

The illumination system IL is configured to adjust the EUV radiation beam B before it is incident on the patterning device MA. In addition, the illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. The faceted field mirror device 10 and the faceted pupil mirror device 11 together provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution in the cross section. As a supplement or alternative to the faceted field mirror device 10 and the faceted pupil mirror device 11, the illumination system IL may also include other mirror surfaces or devices.

After this adjustment, the EUV radiation beam B interacts with the patterning device MA. Due to this interaction, a patterned EUV radiation beam B'is generated. The projection system PS is configured to project the patterned EUV radiation beam B′ onto a series of target areas of the substrate W one target area at a time. After the specific target area has been exposed to the radiation beam B', the substrate support WT is repositioned relative to the path of the radiation beam B'to position the next target area in the path of the beam B'. The projection system PS may include a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B′ onto the substrate W held by the substrate support WT. The projection system PS can apply the reduction factor to the patterned EUV radiation beam B', thus forming an image with features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 can be applied. Although the projection system PS is illustrated in the drawing of FIG. 1 as having only two mirror surfaces 13, 14, the projection system PS may include a different number of mirror surfaces (for example, six or eight mirror surfaces). For the sake of clarity, it is noted here that the lithography apparatus LA usually operates in a scanning mode, in which the support structure MT and the substrate support WT are scanned simultaneously, and the pattern imparted to the radiation beam B'is projected on the target area ( That is, a single dynamic exposure). The speed and direction of the substrate support WT relative to the support structure MT can be determined by the (reduced) magnification and image reversal characteristics of the projection system PS.

The substrate W may include a previously formed pattern. In this situation, the lithography apparatus LA aligns the image formed by the patterned EUV radiation beam B′ with the pattern previously formed on the target area for each target area.

After the substrate W has entered the scanner LA and has been positioned on the substrate support WT, the substrate W undergoes a measurement operation. The measurement operation is performed to obtain data representing both: the orientation of the target area in a plane perpendicular to the axis of the radiation beam B′ leaving the projection system PS, and the change in the elevation angle of the substrate W relative to the plane. The substrate W becomes exposed to the radiation beam B′ under the control of the data thus obtained in order to accurately print the pattern of the mask MA on the target area on the substrate W. The data can be used to control the position and orientation of the substrate support in six degrees of freedom, and/or control the projection optics, etc.

FIG. 2 is a diagram of a vertical cross-section of the exposure orientation 202 in the EUV scanner LA. The exposure position 202 is the area within the scanner LA where the wafer W becomes exposed to the radiation beam B′ in order to print the pattern of the mask MA on the target area 204 on the substrate W.

The scanner LA has a thermal regulation system configured to thermally regulate the substrate W.

The thermal conditioning system includes heat sinks 206 configured to extract heat from the substrate W. In the example shown, the heat sink 206 is received on the substrate support WT. The heat sink 206 contains, for example, a cooling system so that a cooling fluid flows through the cooling system, the cooling fluid extracting heat from the substrate W via thermal contact between the substrate W and the substrate support WT.

The thermal conditioning system includes a first heater system 208 for supplying a first additional heat load to the portion of the substrate W, which is the complement of a specific target 204 area, and the pattern is being imaged on the specific target area via the radiation beam B' on. That is, the first heater system 208 is supplying the first additional heat load to all of the substrate W, except for the target area 204 currently being exposed to the radiation beam B′.

The first heater system 208 includes an LED array in the example shown, which is configured to irradiate the substrate W with infrared light, which is absorbed by the substrate W to generate heat and thus thermally induced deformation. The operation of the first heater system 208 is explained with reference to the diagrams in FIGS. 3 and 4.

3 and 4 are diagrams showing parts of the exposure orientation 202 at different stages of moving the substrate W to the exposure position in plan view. When the target area of the substrate W exists under the gap, the feature indicated by reference numeral 302 schematically represents the gap, and the radiation beam B′ propagates from the projection system PS to the relevant target area on the substrate W through the gap. It is assumed that the substrate W has a spatially uniform temperature before the substrate W supported by the substrate support WT enters the exposure orientation 202. It is further assumed that the LEDs of the first heater system 208 are all turned off initially. Although the substrate support WT is moving the substrate W to the exposure position 202, the substrate W gradually becomes within the range of the first heater system 208. Once the substrate W becomes entirely within the range of the subset of LEDs, the LEDs of this subset are turned on. This situation results in the substrate W being irradiated by infrared light in a spatially uniform manner. This stage when the substrate W is completely within the range is illustrated in the diagram of FIG. 3. The turned-on LEDs are indicated in white, such as LEDs 208.1 and 208.2. The turned off LEDs are indicated in black, such as LEDs 208.3, 208.4, 208.5 and 208.6.

Although the substrate W is moving further in order to expose the substrate W toward the target area to be exposed (in a scanning pattern) to the position of the radiation beam B', some LEDs that are turned on are turned off, and other LEDs that are turned off are turned on to maintain Uniform irradiation of the substrate W, and thus maintain a uniform thermal load on the substrate W. In the diagram of FIG. 4, the LEDs 208.1 and 208.2 that were turned on in the diagram of FIG. 3 are now off, and the LEDs 208.5 and 208.6 that are turned off in the diagram of FIG. 3 are turned on in the diagram of FIG. 4 .

In the diagram of FIG. 3, the substrate W has not yet reached the position where the substrate W is under the gap 302, and the substrate W exists under the gap 302 in the diagram of FIG.

While the substrate W is within the range of the first heater system 208 but not yet under the gap 302, the substrate W receives a constant and spatially uniform thermal load. The heat load per unit time received from the first heater system 208 and the heat per unit area extracted from the substrate W via the heat sink 206 are controlled to be balanced with each other so that the substrate W is maintained at a constant and spatially uniform temperature.

Nowadays, when a target area such as the target area 204 is below the gap 302 to be exposed to the radiation beam B′, the target area is no longer covered by infrared radiation from the one or more LEDs of the first heater system 208. The reality is that the target area 204 receives the heat load through the reception of the radiation portion from the beam B'during the exposure. If the spatial density of the heat load per unit time received from the first heater system 208 for all practical purposes is equal to the spatial density of the heat load per unit time through the absorption of the radiation portion of the beam B', then the substrate W Will not experience changes in the net thermal load received, and therefore maintain a spatially uniform and temporally constant temperature during exposure.

The thermal conditioning system further includes a second heater system 210 for supplying a second additional heat load to the target area 204 under the gap 302 for exposure to the radiation beam B′. The basic principle of the functionality for this is as follows. The first heater system 208 provides the space density of the heat load per unit time to the substrate W, and the space density matches the space density of the heat load per unit time provided to the substrate W by the radiation beam B′. The spatial density of the heat load per unit time supplied by the beam B'can vary with time and on a scale at different times. For example, it is finally determined that the magnitude of the parameter of the beam B′ generated by the absorbed heat at the target area 204 can be changed. As another example, different masks MA may reflect different amounts of radiation received from the source SO. As another example with varying heat load, different illumination modes (ie, different intensity distributions in the cross-section of the beam B) can be used to illuminate different masks MA. Examples of such illumination modes are: circular, dipole, quadrupole, hexapole, customer specific, polarized, unpolarized, etc. For some background information on lighting modes, please refer to the US 20180224715 filed for Voogd et al., assigned to ASML and assigned to ASML, or for Godfried et al., assigned to ASML and cited United States Patent Application Publication 20170293229 incorporated herein. As another example, the radiation from the source SO may include OOB radiation, such as infrared (IR) and deep ultraviolet (DUV) plus EUV. Part of the OOB radiation can become absorbed by the substrate W and can also cause undesired heat generation in the substrate W. This OOB radiation generation may depend on a set point such as the efficiency of the source SO. Therefore, if the thermal load supplied by the radiation beam B'to the substrate W changes with time, the spatial density of the thermal load supplied by the first heater system 208 and the radiation beam B'may be matched sufficiently accurately, so that it cannot The substrate W is maintained at a uniform and constant temperature in space. The first heater system 208 can then be controlled to adjust the additional heat load in order to restore balance. Another control option is provided by the second heater system 210 to be controlled so as to restore the balance of the spatial density of the heat load by supplying a second additional heat load to the target area 204 to compensate for the difference. In the diagrams of FIGS. 3 and 4, the second heater system 210 includes another LED array positioned near the gap 302. Regarding the LEDs in the second heater system 210, the LEDs 210.1 and 210.2 are clearly indicated. In the diagram of FIG. 3, the LED of the second heater system 210 is turned off, and in the diagram of FIG. 4, the LED is turned on.

The thermal conditioning system also has a controller 212 for controlling the first heater system 208 and the second heater system 210, and controlling the heat sink 206 as necessary to maintain the substrate W at a constant and spatially uniform temperature. To this end, the thermal conditioning system includes one or more sensors, such as temperature sensors and/or stress sensors at the substrate support WT, the sensor signals of which can be used as feedback inputs to the controller 212 . This control aspect of the thermal regulation system will be discussed in further detail with reference to FIG. 7.

The controller 212 can independently control individual LEDs (or scanning lasers) of the LEDs of the first heater system and/or the second heater system 210 so as to balance the local temperature difference at the substrate W. The controller 212 can also control the LED and/or the scanning laser to adjust the global heat generated at the substrate W. That is, the controller 212 can control the LED and/or the scanning laser in a common mode and superimpose the modulation of each of the LED and/or the scanning laser. The diagram in FIG. 2 shows the control options that the inventor 214 anticipates for the thermal regulation system.

As indicated with reference to the diagrams of FIGS. 3 and 4, the first heater system 208 can be controlled depending on: the position of the substrate W relative to the slit 302 and the speed of the substrate W relative to the slit 302. The position and speed determine which LEDs in the first heater system 208 are on and which LEDs are off. In addition: keeping all LEDs on all the time will cause several problems, such as: undesirable additional heat load supplied to the substrate support WT; the temperature of the substrate W is attributed to the portion of the substrate W that first enters the range of the first heater system 208 The gradient of the fact that it will receive more heat than the part that entered the range last. In addition, as mentioned above, the first heater system 208 can be controlled depending on the spatial density of the heat load supplied by the beam B′ to the relevant target area during its exposure. In this regard, the first heater system 208 and/or the second heater system 210 may also be controlled depending on the feed information about the upcoming exposure process change. For example, the second heater system 210 can be cut off, or its heat output can be reduced, while skipping the illumination of a specific target area on the substrate W.

As an alternative to the LED, the first heater system 208 and/or the second heater system 210 may use one or more scanning lasers or a hybrid combination of one or more scanning lasers and LEDs. For some background about scanning lasers, see, for example, the Wikipedia entries "Laser Scanning" and "Laser Illuminated Display". For completeness, it should be noted here that the first heater system 208 and the second heater system 210 may have their own heat sink (not shown in the drawing) or a common heat sink (not shown in the drawing) to facilitate Prevent undesired changes in the supplementary heat load from these heater systems 208 and 210 on the substrate W.

For completeness, it should be noted here that the set of turned-on LEDs of the first heater system 208 can produce a spatially non-uniform lighting pattern in the plane of the substrate W to a certain extent. This can be attributed to the shape and intensity distribution of the area of the plane illuminated by the turned-on LED. However, in the scanner LA, each target part is irradiated by scanning the pattern of the mask MA in a given direction ("scanning" direction) through a projected radiation beam B (see Fig. 1) while being parallel to Or scan the substrate W antiparallel to the given direction synchronously. That is, the substrate W is moving under the LED of the first heater system 208 and under the gap 302 at this step, and the illumination pattern generated by the LED is blurred in the coordinate system that is stationary with respect to the substrate W. The blur therefore tends to balance the non-uniformity in the illumination pattern and the uniformity of the resulting heat generation in the substrate W. Similar considerations can be applied to the use of the scanning laser in the first heater system 208. Also, similar considerations can be applied to the second heater system 210.

In the diagrams of Figures 2, 3 and 4, the first heater system 208 and the second heater system 210 are drawn as multiple entities (LED and/or scanning laser ), the infrared beams have a relatively small incident angle on the substrate W with respect to the direction perpendicular to the substrate W. For the sake of clarity, it should be noted here that the magnitude of the incident angle may depend on a design option of several factors. One such factor is, for example, the volume available in the scanner LA. Another such factor is, for example, a way in which the first heater system 208 and the second heater system 210 themselves may need to be thermally adjusted in order to minimize the thermal load on components other than the substrate W in the scanner LA.

5 is a diagram illustrating the use of a scanning laser 502 in a plane perpendicular to the substrate W within the context of the present invention. The scanning laser 502 is a laser device that generates a laser beam 504 whose direction can be controlled. In the figure, the laser beam 504 is shown twice, once when it is incident on the substrate W perpendicularly, and once when it is incident on the substrate W in the shown plane according to a non-zero angle θ. By changing the direction of the laser beam 504 in this plane, different parts of the substrate W can be irradiated. The magnitude of the irradiated surface area of the substrate W depends on the angle θ. The width of the surface area irradiated by the vertically incident beam 504 is indicated by "X ₁ ". The width of the surface area irradiated by the beam 504 irradiating the substrate W at an angle θ is indicated by "X ₂ ". The width X ₂ and the width X ₁ accord with: X ₂ =X ₁ /cosθ. That is, the irradiated area depends on the angle at which the laser beam 504 irradiates the substrate W. By controlling the intensity of the laser beam 504 according to the angle θ, that is, by changing the intensity as the reciprocal of cos θ, a spatially uniform thermal load can be generated regardless of the direction of the beam 504.

The above discusses the angle-dependent control of the intensity of the beam 504 in a specific plane perpendicular to the substrate W. If the direction of the beam 504 is controlled in two planes perpendicular to the substrate W and perpendicular to each other, the intensity is controlled to two angles depending on one angle in one plane to provide a spatially uniform thermal load.

If the scanning laser 502 supplies the pulsed beam 504, that is, the scanning laser delivers laser energy in discrete pulses instead of continuously delivering laser energy, the duty cycle and/or repetition rate of the pulses can be controlled according to the angle so that Generate a uniform thermal load in space. Under this condition, the intensity can be kept constant. Angle-dependent control of intensity and a combination of repetition rate and duty cycle are also feasible.

The speed at which the direction of the beam 504 can be changed and therefore the speed at which different surface areas of the substrate W can be irradiated is much higher than the speed of heat propagation through the substrate W. Therefore, and for all practical purposes, using the scanning laser 502 for a strong heating load on the substrate W has the same thermal effect as the strong heating load for a stationary LED array discussed above with reference to FIGS. 2 and 3.

6 is a diagram of another position 602 outside the exposure position 202 at the scanner LA. The other orientation 602 of the scanner is, for example, the measured orientation within the scanner. At the measurement orientation, the substrate W undergoes a measurement operation as discussed earlier in order to obtain data to control the exposure of the target area on the substrate W at the exposure orientation. Alternatively or in addition, the other orientation may be a substrate handler (or: wafer handler) or a load lock. The substrate handler is an electromechanical integrated module designed to move the substrate into and out of the (vacuum) center of the scanner LA via a load lock. The load lock is a device used to transfer substrates between two or more environments, where different conditions prevail, for example, different pressures, different temperatures, different gas compositions, and so on. In EUV scanners, the load lock is used to transfer the substrate from an environment with ambient pressure to another environment with a much lower pressure, which is called "vacuum" for all practical purposes. For more background information on substrate handlers, see, for example, US Patent 9,885,964 issued to Westerlaken et al., assigned to ASML and incorporated herein by reference. For more background on load locks, see, for example, US Patent 7,878,755 issued to Klomp et al., assigned to ASML and incorporated herein by reference.

At the other position 602, the substrate W is pre-heated to a spatially uniform and constant pre-heating temperature using the pre-heating system 604. The pre-heating system 604 may, for example, use an LED array or one or more scanning lasers or a combination of one or more LEDs and one or more scanning lasers to be similar to that of the first heater system 210 or the second heater system 210 Way to implement.

The constancy and uniformity of the preheating temperature promote the control of the first heater system 208 and the second heater system 210. It should be noted here that, in fact, the spatial uniformity of the preheating temperature of the substrate is more important than its constancy, because the non-uniformity is more difficult to compensate than the deviation of the temperature value.

Assume that the other orientation 602 is the measurement orientation in the scanner LA. During and after measuring the properties of the substrate W, the size of the substrate W preferably does not change. Therefore, the spatially uniform preheating temperature of the substrate W is preferably the same as the spatially uniform temperature, and at the spatially uniform temperature, the substrate W is maintained at the exposure orientation. If the substrate W is only subjected to thermal load via absorption of radiation from the source SO, the spatially uniform temperature of the substrate W at the exposure side is preferably equal to or greater than the local temperature that the substrate W will locally adopt in the target area. Therefore, the temperature of the substrate W can be kept constant and uniform independently of the thermal load of exposure.

The pre-heating of the substrate W can be performed before the measurement operation is performed in order to eliminate the effect of the spatial variation of the thermally induced deformation on the data, and the spatial variation is extracted for the result of the measurement operation that controls the exposure process. If the constant spatially uniform preheating temperature is different from the constant spatially uniform temperature of the substrate W generated by the thermal conditioning system at the exposure orientation 202, this difference can be taken into account by the exposure process. Since the preheating temperature of the substrate W and the temperature of the substrate W generated by the thermal conditioning system are both constant and spatially uniform, the shape of the substrate W at the preheating temperature and the substrate W at the exposure position 202 are at this temperature The shapes are the same, except for the uniform scaling factor. This zoom factor can then be used to determine the orientation of the target area for the exposure process, providing the orientation of the target area generated by the measurement operation. If necessary, the uniform preheating temperature of the substrate W can be set to a bit higher than the uniform temperature of the substrate W during exposure so as to take into account the heat loss during the travel of the substrate W from the preheating position to the exposure position. However, this situation implies that the heat loss and therefore the resulting change in the thermally induced deformation of the substrate W needs to be calibrated and takes into account thermal regulation control.

As another option, the pre-heating system 604 above the substrate W can be moved from the measurement side 602 to the exposure side 202 together with the substrate support WT. When the substrate W becomes within the range of the first heater system 208, the first heater system 208 can take over.

In short, therefore, the temperature of the substrate W preferably always remains uniform and constant in the presence of the scanner LA.

The control of the thermal regulation system via the controller 212 is explained with reference to FIG. 7. The diagram in FIG. 7 shows the portion 702 of the substrate support WT carrying the substrate W in the diagram in FIG. 2. Please refer to the reference numeral 702 in the diagram of FIG. 2.

The substrate support WT includes a module 704 that carries actuators (not shown), which are controlled to position the substrate W for exposure and measurement. The module 704 accommodates a substrate stage 706 for carrying a substrate W. The substrate stage 706 interfaces with the substrate W via a plurality of protrusions, and two of the plurality of protrusions are clearly indicated by reference numerals 708 and 710. The substrate stage 706 is interfaced with the module 704 via a plurality of other protrusions, two of which are clearly indicated by reference numerals 712 and 714. The substrate W is clamped to the substrate stage 706 via an electrostatic clamp (not shown in the figure). The substrate stage 706 is clamped to the module 704 via another electrostatic clamp (not shown in the figure). For some background on electrostatic clamps, see, for example, US Patent 9,366,973 issued to Ockwell et al., assigned to ASML and incorporated herein by reference.

The substrate stage 706 of the substrate support WT has one or more temperature sensors, such as temperature sensors 716, 718, and 720 positioned between the protrusions at the side of the substrate stage 706, which side faces in operation Substrate W. One or more temperature sensors 716 to 720 can be used to control the first heater system 208 and/or the second heater system 210 and/or the pre-heating system 604. The temperature sensors 716 to 720 are used to sense the temperature of the substrate W. Therefore, the influence of the temperature of the substrate stage 706 on the sensing is preferably limited by thermally isolating the temperature sensors 716 to 720 from the substrate stage 706.

The sensor signal from one of the temperature sensors 716 to 720 represents the local temperature as sensed by this temperature sensor. The control is implemented by maintaining the sensor signals from the temperature sensors 716 to 720 all at a constant and all representing the same temperature, also known as the temperature set point. The first heater system 208, the second heater system 210, and the pre-heating system 602 are each controlled to generate more local heat in the substrate W when the local temperature as sensed drops below the temperature set point, and when such Locally less heat is generated when the sensed local temperature rises above the temperature set point.

The spatial density of the temperature sensor at the substrate stage 706 is selected so that the magnitude of the deformation of the substrate W due to the uncertainty of the sensing temperature is acceptable for the accuracy of the exposure process, that is , The imaging of the pattern on the substrate W is accurate.

The substrate stage has one or more stress sensors, such as stress sensors 722 and 724, positioned between the protrusions at the side of the substrate stage 706, which side faces the module 704 in operational use. The stress sensors 722 and 724 include, for example, strain gauges, and can be used to determine whether the substrate table 706 is experiencing global deformation (as opposed to only a single local deformation). If the global deformation is being sensed, the controller 212 adjusts the global irradiation by the first heater system 208 and/or the second heater system 210 in response to the deformation so as to generate a stable thermal condition of the substrate W.

10: Faceted field mirror device 11: Faceted pupil mirror device 13: Mirror 14: Mirror 202: Exposure orientation 204: Target area 206: Heat sink 208: First heater system 208.1: LED 208.2: LED 208.3: LED 208.4: LED 208.5: LED 208.6: LED 210: second heater system 210.1: LED 210.2: LED 212: controller 214: inventor 302: gap 502: scanning laser 504: laser beam 602: another direction 604: pre-heating system 702: part/reference number 704: module 706: substrate stage 708: reference number/protrusion 710: reference number/protrusion 712: reference number/protrusion 714: reference number/protrusion 716: temperature Sensor 718: Temperature sensor 720: Temperature sensor 722: Stress sensor 724: Stress sensor B: Extreme ultraviolet (EUV) radiation beam B': Patterned extreme ultraviolet (EUV) Radiation beam IL: Illumination system LA: lithography equipment/scanner MA: patterning device/mask MT: support structure PS: projection system/projection optics SO: radiation source W: substrate WT: substrate support X ₁ : Width X ₂ : width

The present invention is further explained by means of examples and with reference to the accompanying drawings, in which: Figure 1 is a diagram of an EUV lithography system including a radiation source and a scanner; Figure 2 is a diagram of the exposure position in the scanner; 3 and 4 are diagrams of different states of the substrate moving to the exposure position of the exposure position; Figure 5 is a diagram illustrating the use of a scanning laser to control the additional thermal load generated on the substrate; Figure 6 is a diagram of the measurement orientation of the scanner; and Fig. 7 is a diagram of a part of a substrate support carrying a substrate. The same illustrated element symbols or the same reference acronyms in the drawings indicate similar or corresponding parts.

208.1: LED

208.2: LED

208.3: LED

208.4: LED

208.5: LED

208.6: LED

210.1: LED

210.2: LED

302: Gap

W: substrate

WT: substrate support

Claims (10)

A lithography device configured to receive radiation for imaging a pattern on a plurality of target areas on a substrate via projection optics, wherein: Each specific target area of the target areas is used to receive a thermal load by absorbing at least part of the radiation during imaging on the specific target area; The lithography equipment includes a thermal regulation system; The thermal conditioning system is configured to maintain the substrate at a spatially uniform and constant first temperature during the imaging period; The thermal regulation system includes: A heat sink for extracting heat from the substrate; and A first heater system for supplying a first additional heat load to a portion of the substrate during the imaging period, This part is the complement of the specific target area on which the pattern is being imaged; and A magnitude of the first additional heat load per unit area is equal to or exceeds a magnitude of the heat load per unit area. Such as the lithography device of claim 1, wherein the thermal regulation system is configured to supply the first thermal load by irradiating the complement. Such as the lithography apparatus of claim 2, wherein the thermal regulation system includes at least one of the following: an LED and a scanning laser configured to supply the first additional thermal load. The lithography equipment of 2 or 3, wherein the thermal regulation system includes a second heater system for supplying a second additional heat load to the specific target area. Such as the lithography apparatus of claim 4, wherein the second heater system is configured to supply the second additional heat load by irradiating the specific target area. The lithography apparatus of claim 5, wherein the second heater system includes at least one of the following: a second LED and a second scanning laser configured to supply the second additional thermal load. The lithography apparatus of 2 or 3, which includes a pre-heating system configured to pre-heat the substrate to a substantially spatially uniform second temperature before starting the imaging. Such as the lithography device of claim 7, wherein the first temperature is equal to the second temperature. The lithography apparatus of claim 7, wherein the pre-heating system is configured to pre-heat the substrate by irradiating the substrate. Such as the lithography device of claim 9, wherein the pre-heating system includes at least one of the following: a third LED and a third scanning laser.

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