TWI803747B - Exposure device, and article manufacturing method - Google Patents

Abstract

The invention provides an exposure device and an article manufacturing method. It is advantageous to balance the correction performance and productivity of the optical performance of the projection optical system. The exposure device includes: a projection optical system for projecting the pattern of the mask onto the substrate; a supply unit for supplying a mixed gas obtained by mixing a plurality of gases with different refractive indices at a preset mixing ratio, that is, a set mixing ratio, to the projection optical system. The space between the optical elements inside the system; the control unit corrects the imaging characteristics of the projection optical system and exposes the aforementioned substrate by controlling and setting the mixing ratio. The control unit acquires a response characteristic indicating evolution of the imaging characteristics when the supply unit supplies the mixed gas at a fixed mixing ratio, and when the control unit sets the set mixing ratio as a target mixing ratio and exposes the substrate, During the transition period before the imaging characteristic changes to a stable state, the set mixture ratio is set to a value obtained by correcting the target mixture ratio according to the response characteristic, and the substrate is exposed.

Description

Exposure device, and article manufacturing method

The present invention relates to an exposure device and an article manufacturing method.

With the development of high integration of semiconductor devices in recent years, the requirements for the optical performance of the exposure device are also getting higher and higher. As an important factor that hinders the improvement of the optical performance of the exposure apparatus, the optical performance is affected by environmental changes such as air pressure changes inside and outside the projection optical system, temperature changes, and the like.

In response to such environmental changes, there is a method of supplying two or more types of gases with different refractive indices to the space in the projection optical system, and correcting lateral aberration by changing the mixing ratio of the gases to change the refractive index of the space (for example, Patent Document 1, 2). prior art literature patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 5-210049 Patent Document 2: Japanese Patent Application Laid-Open No. 5-144700.

The problem to be solved by the invention

When changing the mixing rate of the gas to correct the optical performance of the projection optical system, it takes a long time to replace the gas in the space of the projection optical system and stabilize the optical performance. Conventionally, the exposure device stops exposure and stands by until the optical performance becomes stable. Therefore, the downtime of the exposure apparatus is long and the productivity is lowered.

An object of the present invention is to provide, for example, an exposure apparatus that is advantageous in both correction performance and productivity of optical performance of a projection optical system. solutions to problems

According to a first aspect of the present invention, there is provided an exposure apparatus for exposing a substrate, wherein the exposure apparatus includes: a projection optical system for projecting a pattern of a mask onto the substrate; and a supply unit for supplying a mixed gas to the substrate. In the space between the optical elements inside the projection optical system, the mixed gas is obtained by mixing a plurality of gases with different refractive indices at a preset mixing ratio, that is, a set mixing ratio; The mixing ratio is set to correct the imaging characteristics of the projection optical system and to expose the substrate, and the control unit acquires a response characteristic representing the imaging characteristics when the supply unit supplies the mixed gas at a fixed mixing ratio. evolution (change), when the control section sets the set mixture ratio as the target mixture ratio and exposes the substrate, the control section sets the set mixture ratio to A value obtained by correcting the target mixture ratio based on the response characteristic is set, and the substrate is exposed.

According to a second aspect of the present invention, there is provided a method of manufacturing an article, which is characterized by comprising: a process of exposing a substrate by using the exposure device related to the above-mentioned first aspect; and a process of developing the exposed substrate, Herein, an article is manufactured from the aforementioned substrate that has been developed. The effect of the invention

According to the present invention, for example, it is possible to provide an exposure apparatus that is advantageous in both correction performance and productivity of optical performance of a projection optical system.

Embodiments will be described in detail below with reference to the drawings. In addition, the present embodiment below does not limit the invention related to the claims. Although some features were described in this embodiment, not all of these features are essential to the invention, and multiple features may be combined arbitrarily. In addition, in the drawings, the same reference numerals are assigned to the same or similar configurations, and repeated descriptions are omitted.

FIG. 1 is a diagram showing the configuration of an exposure apparatus 1 in the present embodiment. In one example, the exposure device 1 is an exposure device for exposing the pattern of the mask 3 to the substrate 10 in a step and repeat manner. However, the present invention can also be applied to a step and scan system and other exposure devices.

The illumination system 2 adjusts light from unillustrated light sources such as a mercury lamp with a wavelength of about 365 nm, a KrF excimer laser with a wavelength of about 248 nm, and an ArF excimer laser with a wavelength of about 193 nm, and illuminates the mask 3 . The photomask 3 is made of, for example, quartz glass, and a pattern (for example, a circuit pattern) to be transferred onto the substrate 10 is formed. The photomask stage 4 can hold the photomask 3, and adjusts at least one of the position and posture of the photomask 3 using, for example, a linear motor. The drive of the mask stage 4 is controlled by the control unit 25 .

The projection optical system 5 projects the pattern of the mask 3 onto the substrate 10 at a predetermined magnification (for example, 1/4 magnification). The substrate 10 is, for example, a substrate formed of a glass plate, a silicon wafer, or the like. A photosensitive agent 11 is coated on the surface of the substrate 10 . The projection optical system 5 includes a plurality of optical elements 6 (for example, optical elements such as lenses (lens), mirrors (mirror), and aperture diaphragms). At least one of the position, attitude, shape, and temperature of some of the optical elements 6 can be adjusted by the adjustment unit 7 .

The substrate stage 9 can hold the substrate 10, and at least one of the position and posture of the substrate 10 can be adjusted by, for example, a linear motor. The drive of the substrate stage 9 is controlled by the control unit 25 . The laser interferometer 14 is arranged near the substrate stage 9 , and measures the position of the substrate stage 9 by irradiating laser light on a bar mirror 12 arranged on the substrate stage 9 .

The exposure apparatus 1 has a supply unit 30 that supplies a mixed gas obtained by mixing a plurality of gases having different refractive indices to a space between optical elements inside the projection optical system 5 . In the supply unit 30 , the gas supply units 15 and 16 supply a plurality of types of gases having different refractive indices to the mixer 19 . The plurality of gases may be, for example, a plurality of gases selected from helium, nitrogen, oxygen, carbon dioxide, dry air, and the like. The gas supply volume regulators 17 and 18 adjust the gas supply volumes from the gas supply units 15 and 16, respectively. The mixer 19 mixes at least two different gases supplied from the gas supply units 15 and 16 , and supplies the mixed gas to the projection optical system 5 through the gas supply pipe 21 . The concentration measuring device 20 measures the concentration of each gas in the mixed gas. Such a supply unit 30 can supply a mixed gas mixed at a preset mixing ratio, that is, a set mixing ratio.

The mixed gas supplied to the projection optical system 5 diffuses into the space between the optical elements through the vent hole 8 provided in the adjustment part 7 supporting the optical element 6 . The air hole 8 may be a member not shown in the adjustment part 7 but in a member that fixedly supports the optical element 6 . The exhaust unit 22 exhausts gas from the projection optical system 5 through an exhaust pipe 24 . The exhaust pipe 24 is provided with an exhaust volume adjustment unit 23 that adjusts the exhaust volume to be exhausted from the exhaust unit 22 . The control unit 25 controls the exhaust volume adjustment unit 23 to adjust the exhaust volume based on the air pressure value measured by the barometer 26 to eliminate the air pressure difference inside and outside the projection optical system 5 .

The detector 13 detects the light transmitted from the projection optical system 5 . The detector 13 can include, for example, at least any one of an interferometer and a light intensity sensor. The control unit 25 can measure the wavefront aberration at each point within the exposure area of the projection optical system 5 based on the detection result of the detector 13 . In addition, the control unit 25 can also measure the distortion aberration of the projection optical system 5 according to the detection result of the detector 13 . Here, the distortion aberration indicates, for example, how much the actual image height on the image plane deviates from the ideal image height, and the distortion aberration can be measured at each point on the image plane (in the exposure area). In addition, any known structure can be applied to the detector 13 , and thus the description of the detailed structure and operation is omitted here.

The adjustment unit 7 adjusts the imaging characteristics, for example, adjusts at least one of the position, attitude, shape and temperature of some of the optical elements 6 of the projection optical system 5 . The adjustment unit 7 includes, for example, a mechanism for driving in the optical axis direction (Z direction shown in FIG. Or the mechanism that pulls the force of the optical element), the mechanism that heats or cools the optical element, etc. These drives in the adjustment unit 7 are controlled by the control unit 25 . However, it is sufficient that the adjustment unit adjusts imaging characteristics by at least one of driving the optical element 6 of the projection optical system 5 , driving the mask stage 4 , and driving the substrate stage 9 .

The control unit 25 comprehensively controls the operation of each part of the exposure apparatus 1 . The control unit 25 can be constituted by a computer including a CPU and a memory. In this embodiment, the control unit 25 functions as a control unit that corrects the imaging characteristics of the projection optical system 5 and exposes the substrate by controlling the set mixing ratio set in the supply unit 30 . In addition, the control unit 25 calculates the adjustment amount of the optical element 6 and the adjustment amount of the substrate stage 9 by the adjustment portion 7 based on the detection result of the detector 13, and calculates the adjustment amount of the optical element 6 and the adjustment amount of the substrate stage 9 according to the calculated adjustment amount of the optical element 6 The adjustment amount controls the adjustment unit 7 and the substrate stage 9 .

Hereinafter, the exposure process of the optical performance (imaging characteristic) of the projection optical system 5 in this embodiment is demonstrated. The index representing imaging characteristics includes a plurality of aberration components. For example, the imaging characteristic may include at least one of spherical aberration, lateral aberration, distortion aberration, field curvature, astigmatism, and coma aberration. Here, in order to show a specific example, spherical aberration, which is the first aberration component among the plurality of aberration components, is set as a correction target. Furthermore, as other aberration components other than the first aberration component, it is assumed that a magnification aberration and a distortion aberration are generated.

In the correction processing in the present embodiment, the control section 25 acquires in advance a response characteristic indicating evolution of imaging characteristics when the mixed gas is supplied by the supply section 30 at a fixed mixing ratio. When the control unit 25 sets the set mixing ratio to the target mixing ratio to expose the substrate, the control unit 25 sets the setting mixing ratio to the target mixing ratio according to the response characteristic during the transition period before the imaging characteristic changes to a stable state. The corrected values are determined and the substrate is exposed. FIG. 2 is a flowchart showing a specific example of such exposure processing. In S101 , the control section 25 acquires a response characteristic indicating evolution of imaging characteristics when the mixed gas is supplied by the supply section 30 at a fixed mixing ratio. Here, the data of such response characteristics are obtained by pre-measurement or simulation, and are stored in the memory of the control unit 25 .

In this embodiment, the response characteristics may include response characteristics respectively related to spherical aberration, lateral aberration, and distortion aberration. Figure 3 shows examples of these response characteristics. The response characteristic referred to here means the evolution of aberration (the change of aberration with respect to the replacement time) when the mixed gas is supplied from the supply unit 30 at a fixed mixing ratio. (a) is an example of response characteristics of spherical aberration, (b) is an example of response characteristics of lateral aberration, and (c) is an example of response characteristics of distortion aberration. Even if the purge gas is supplied into the projection optical system, the entire space cannot be replaced immediately, and such a response characteristic is exhibited. For example, as shown in (a), spherical aberration has an unsteady state period (transition period) before it becomes a stable state. The obtained data of each response characteristic are stored in a memory (not shown) of the control unit 25 .

In S102, the control unit 25 measures a change in the amount of aberration due to exposure. For example, along with exposure, the projection optical system 5 absorbs exposure energy, so that imaging characteristics vary (exposure aberration). Then, the control unit 25 applies the detection result of the detector 13 to a predetermined prediction formula to predict the variation of the imaging characteristic (here, spherical aberration), thereby determining the correction amount. Alternatively, the control unit 25 may measure a change in aberration with respect to exposure heat generated under each lighting condition based on the detection result of the detector 13 . In addition, the control unit 25 measures the atmospheric pressure of the space in which the projection optical system 5 is installed using the barometer 26 .

In S103, the control unit 25 obtains a refractive index for compensating the aberration change amount obtained in S102, and determines a target mixing ratio corresponding to the refractive index. The correspondence relationship between the refractive index and the target mixing ratio is prescribed in advance by a mathematical formula or a table. In addition, the control unit 25 may calculate the amount of spherical aberration caused by the influence of the change in the atmospheric pressure based on the value of the atmospheric pressure measured in S102, and add it to the correction amount. As a method of determining the amount of spherical aberration caused by changes in atmospheric pressure, there is, for example, a method of obtaining the product of the pressure sensitivity coefficient and the pressure change amount, wherein the product of the pressure sensitivity coefficient and the pressure change amount is used to measure the spherical image The difference is calculated by the amount of change relative to the change in air pressure.

For example, the mixing ratio is determined as follows. The amount of change in the spherical aberration with respect to the change in the mixing ratio of the mixed gas (that is, the change in the refractive index) is proportional to that shown in FIG. 4 . Based on this relationship, the proportionality constant of the amount of spherical aberration with respect to the refractive index of the lens space of the projection optical system can be calculated by optical simulation. In addition, the control unit 25 may estimate the amount of spherical aberration generated by the projection optical system 5 due to exposure heat under the lighting conditions used for exposure based on the change in aberration measured in S102, and calculate the amount of spherical aberration generated by the projection optical system 5. added to the calibration volume.

The following processing is processing when exposing the substrate by setting the set mixing ratio to the target mixing ratio determined here.

In S104 , the control unit 25 determines the allowable range (correctable range) of each of the lateral aberration and the distortion aberration which are other aberration components in the replacement of the mixed gas. Such a correctable range may be prescribed in advance in an exposure recipe.

In S105 , the control unit 25 starts air supply and exhaust control of the projection optical system 5 . Specifically, the control unit 25 adjusts the gas supply volume regulators 17 and 18 in accordance with the target mixing ratio determined in S103 to adjust the flow rate of the gas flowing into the mixer 19 . The gas mixed by the mixer 19 is supplied to the projection optical system 5 while the exhaust volume is adjusted by the exhaust volume adjustment unit 23 so that no pressure difference between inside and outside the projection optical system 5 occurs. Thereby, spherical aberration is corrected.

In S106, the control part 25 carries in (loads) the board|substrate to be exposed by the conveyance mechanism which is not shown in figure. The loaded substrate is held by the substrate stage 9 .

In S107 , the control unit 25 determines whether or not the current point of time is in the transition period before the imaging characteristic (here, spherical aberration) turns to a stable state. In the case of the transient period, in S108, the control unit 25 sets the set mixture ratio to a value obtained by correcting the target mixture ratio according to the response characteristic. Specifically, the aberration amount corresponding to the current time is calculated from the response characteristic of the spherical aberration obtained in S101 ((a) of FIG. 3 ), and the target mixture ratio is calculated using the correction amount corresponding to the aberration amount. Correction. In this way, in the present embodiment, the target mixture ratio of the air-fuel mixture is actively corrected.

However, in the case where such an active correction of the mixture ratio is performed, other aberration components may be newly generated, and thus may need to be corrected as well. The other aberration components are corrected by the adjustment unit 7 within its correctable range. Then, in S109, the control unit 25 determines whether or not other aberration components are within the allowable range (correctable range) determined in S104. When the other aberration components are within the allowable range, in S110 the control unit 25 controls the adjustment unit 7 to correct the other aberration components. When the change of other aberration components exceeds the correctable range of the adjustment unit 7, the exposure is stopped (S111) until the adjustment unit 7 can perform correction. At this time, the supply of the mixed gas may be continued until it reaches a correctable range, and the exposure by the exposure apparatus 1 may be stopped during this period. If the current time point is after the transition period, that is, in the period of the steady state ("No" in S107), then in S112, the control unit 25 sets the set mixture ratio to the target mixture determined in S103. Compare.

Thereafter, in S113, the control unit 25 performs exposure on the substrate. After the exposure is completed, in S114, the control unit 25 controls the transport mechanism to unload the substrate (unload). In S115, the control unit 25 judges whether or not there are substrates to be processed later. If there are substrates left after that, return to S102 and repeat the process. When the processing of all the predetermined substrates is completed, this processing ends.

In the above-mentioned example, it was described that the mixed gas is supplied for correcting spherical aberration, but the correction target may be lateral aberration, distortion aberration, curvature of field, astigmatism, coma aberration, and the like. In addition, in the above example, the other aberration components to be corrected by the adjustment unit 7 are lateral aberration and distortion aberration, but they may be spherical aberration, curvature of field, coma aberration, and the like.

According to the above processing, as long as the other aberration components (magnification aberration and distortion aberration) do not exceed the correctable range of the adjustment unit 7 , desired spherical aberration can be obtained without stopping the exposure processing. Accordingly, it is possible to balance the correction performance of the optical performance of the projection optical system with productivity.

<Embodiments of the article manufacturing method> The article manufacturing method according to the embodiment of the present invention is suitable for manufacturing articles such as microdevices such as semiconductor devices and elements having a precise structure. The article manufacturing method of this embodiment includes a process of forming a latent image pattern on a photosensitive agent coated on a substrate using the above-mentioned exposure device (process of exposing the substrate); and developing the substrate on which the latent image pattern is formed in the above-mentioned process. process. In addition, the manufacturing method includes other known processes (oxidation, film formation, evaporation, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). Compared with conventional methods, the article manufacturing method of this embodiment is advantageous in at least one of article performance, quality, productivity, and production cost.

The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, claims are appended in order to disclose the scope of the invention.

1: Exposure device 2: Lighting system 3: mask 5: Projection optical system 9: Substrate carrier 10: Substrate 25: Control Department 30: Supply Department

[ Fig. 1 ] is a diagram illustrating a configuration of an exposure apparatus in an embodiment. [ Fig. 2 ] is a flowchart showing exposure processing accompanying correction of the optical performance of the projection optical system in the embodiment. [ Fig. 3 ] is a graph showing an example of response characteristics of aberrations in gas mixture replacement. [ Fig. 4 ] is a graph showing a proportional relationship between the amount of change in spherical aberration and the change in the mixing ratio of the mixed gas.

1: Exposure device

2: Lighting system

3: mask

4: Mask carrier

5: Projection optical system

6: Optical components

7: Adjustment department

8: Air vent

9: Substrate carrier

10: Substrate

11: Sensitizer

12: Bar mirror

13: Detector

14:Laser interferometer

15,16: Gas supply part

17,18: Air supply regulator

19: Mixer

20: concentration measuring device

21: Air supply piping

22: exhaust part

23: Displacement adjustment part

24: Exhaust piping

25: Control Department

26: Barometer

30: Supply Department

Claims (12)

An exposure device for exposing a substrate, the exposure device is characterized in that it has: a projection optical system, which projects the pattern of the mask onto the aforementioned substrate; a supply unit for supplying a mixed gas obtained by mixing a plurality of gases having different refractive indices at a preset mixing ratio as a set mixing ratio to a space between optical elements inside the projection optical system; who; and a control section that corrects the imaging characteristics of the projection optical system and exposes the substrate by controlling the set mixing ratio, The control unit acquires a response characteristic representing evolution of the imaging characteristic when the mixed gas is supplied by the supply unit at a fixed mixing ratio, When the control unit sets the set mixing ratio as the target mixing ratio and exposes the substrate, the control unit sets the set mixing ratio to be based on the response characteristic during a transition period before the imaging characteristic becomes a stable state. The value obtained by correcting the aforementioned target mixing ratio is then exposed to the aforementioned substrate. The exposure device according to claim 1, wherein, After the elapse of the transition period, the control unit sets the set mixture ratio to the target mixture ratio and exposes the substrate. The exposure device according to claim 1, wherein, It also has an adjustment unit that adjusts the aforementioned imaging characteristics, The control section corrects the first aberration component, which is the imaging characteristic, among the plurality of aberration components by controlling the set mixing ratio, The adjustment unit corrects other aberration components other than the first aberration component, which are the imaging characteristics, in response to the change of the set mixture ratio by the control unit during the transition period. The exposure device as described in Claim 3, further comprising: a reticle carrier holding the aforementioned reticle; and a substrate stage holding the aforementioned substrate, The adjustment unit adjusts the imaging characteristics by performing at least one of driving the optical elements of the projection optical system, driving the mask stage, and driving the substrate stage. The exposure device according to claim 3, wherein, When the correction amount of the other aberration component exceeds the correctable range of the adjustment unit, the control unit stops exposing the substrate until the adjustment unit can perform correction. The exposure device according to claim 3, wherein, The aforementioned imaging characteristics include at least one of spherical aberration, lateral aberration, distortion aberration, curvature of field, astigmatism, and coma aberration. The exposure device according to claim 3, wherein, The aforementioned first aberration component is spherical aberration, and the aforementioned other aberration components are lateral aberration and distortion aberration. The exposure device as claimed in item 7, wherein, The foregoing response characteristics include response characteristics respectively related to spherical aberration, magnification aberration, and distortion aberration. The exposure device according to claim 1, wherein, The aforementioned plurality of gases are a plurality of gases selected from helium, nitrogen, oxygen, carbon dioxide, and dry air. The exposure device according to claim 1, wherein, There is also a barometer that measures the atmospheric pressure of the space in which the aforementioned projection optical system is disposed, The control unit obtains an amount of change in the imaging characteristic due to the influence of a change in atmospheric pressure based on the value of the atmospheric pressure measured by the barometer, and obtains a correction amount for the imaging characteristic based on the amount of change. The exposure device according to claim 1, wherein, There is also a detector that detects the light transmitted through the aforementioned projection optical system, The control unit obtains a change amount of the imaging characteristic due to absorption of exposure energy by the projection optical system using the detector, and obtains a correction amount of the imaging characteristic based on the change amount. A method of manufacturing an article, comprising: A process for exposing a substrate using the exposure apparatus according to any one of claims 1 to 11; and A process of developing the exposed substrate, Here, an article is produced from the developed substrate described above.

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