Exposure method, exposure apparatus, and method for producing article

Abstract

To provide a technique advantageous for precisely controlling multiple focus exposure.SOLUTION: An exposure method for performing a multiple focus exposure of exposing a photoresist layer by changing a distance between a substrate and a focal point of the projection optical system to a plurality of respective distances in an exposure apparatus having a projection optical system varies amounts of light for irradiating the photoresist layer according to the plurality of distances for the plurality of respective distances so that an evaluation index for evaluating a cross-sectional shape of an aperture formed on the photoresist layer after development falls in an allowable range.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an exposure method, an exposure apparatus, and an article manufacturing method.

Background Art

[0002] In a manufacturing process (lithography process) of a semiconductor device or the like, an exposure apparatus that transfers a pattern of a master onto a photoresist layer on a substrate by exposing the photoresist layer on the substrate through a projection optical system can be used. In the exposure apparatus, as one method of exposing the photoresist layer on the substrate, multi-focus exposure is known in which the distance between the substrate and the focus of the projection optical system is changed to expose the photoresist layer on the substrate (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, in an exposure apparatus, a substrate provided with a thick film photoresist layer may be used, and for such a substrate, multi-focus exposure can be performed from the viewpoint of improving the depth of focus. In this case, it is desirable to accurately control the multi-focus exposure so that the opening (pattern) formed in the photoresist layer on the substrate after development has a desired cross-sectional shape.

[0005] Therefore, an object is to provide a technique advantageous for accurately controlling multi-focus exposure.

Means for Solving the Problems

[0006] In order to achieve the above object, as one aspect of the present invention, an exposure method includes, in an exposure apparatus having a projection optical system, performing multi-focus exposure in which the distance between a substrate and the focus of the projection optical system is changed to each of a plurality of distances to expose a photoresist layer on the substrate, and adjusting the amount of light irradiated to the photoresist layer at each of the plurality of distances according to each of the plurality of distances so that an evaluation index for evaluating a cross-sectional shape of an opening formed in the photoresist layer after development falls within an allowable range.

[0007] A further object or another aspect of the present invention will be clarified by the preferred embodiments described below with reference to the accompanying drawings.

Advantages of the Invention

[0008] According to the present invention, for example, a technique advantageous for accurately controlling multi-focus exposure can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential for the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0011] In this specification and the accompanying drawings, directions are indicated in an XYZ coordinate system in which the direction parallel to the optical axis of the projection optical system is the Z direction. The directions parallel to the X-axis, Y-axis, and Z-axis in the XYZ coordinate system are the X direction, Y direction, and Z direction, respectively, and the rotations around the X-axis, Y-axis, and Z-axis are θX, θY, and θZ, respectively. The control and drive (movement) regarding the X-axis, Y-axis, and Z-axis respectively mean the control or drive (movement) regarding the direction parallel to the X-axis, the direction parallel to the Y-axis, and the direction parallel to the Z-axis. Also, the control or drive regarding the θX-axis, θY-axis, and θZ-axis respectively mean the control or drive regarding the rotation around the axis parallel to the X-axis, the rotation around the axis parallel to the Y-axis, and the rotation around the axis parallel to the Z-axis.

[0012] An embodiment according to the present invention will be described. FIG. 1 is a schematic diagram showing a configuration example of an exposure apparatus 100 in this embodiment. The exposure apparatus 100 is an apparatus that exposes a photoresist layer (photosensitive material layer) on a substrate to form a transfer image of a pattern of a reticle (mask) as a latent image pattern on the photoresist layer. The latent image pattern formed on the photoresist layer on the substrate can be converted into a pattern having a physical opening by a development process.

[0013] The light source unit LS includes a light source 101 and an elliptical mirror 102, and emits light. As the light source 101, a lamp, a laser, an LED, etc. can be used. The light emitted from the light source unit LS enters the first illumination optical system 104 and is shaped into a predetermined beam shape by the first illumination optical system 104. The light shaped by the first illumination optical system 104 is reflected by the mirror 105 and enters the second illumination optical system 106. The second illumination optical system 106 forms a secondary light source for illuminating the original plate 109 with a uniform illuminance distribution by an optical integrator (not shown). Note that the intensity of the light emitted from the light source unit LS can be controlled by the illumination system control unit 125 under the control of the main control unit 130.

[0014] On the optical path of the second illumination optical system 106, a wavelength selection unit 107 and a light detection unit 108 are provided. The wavelength selection unit 107 is a unit that selectively passes light of a wavelength used for exposing the substrate 114 among the light incident on the second illumination optical system 106. Specifically, the wavelength selection unit 107 has, for example, a plurality of wavelength plates that pass light of different wavelengths, and by changing the wavelength plate arranged in the optical path among the plurality of wavelength plates, light of a wavelength used for exposing the substrate 114 can be selectively passed. The plurality of wavelength plates can be arranged on, for example, a turret. The light detection unit 108 includes a photosensor 108a that detects the intensity of light and a half mirror 108b that reflects a part of the light incident on the second illumination optical system 106 and guides it to the photosensor 108a. The photosensor 108a outputs a signal according to the intensity of light. The light that has passed through the half mirror 108b illuminates the original plate 109. Note that the wavelength selection unit 107 and the light detection unit 108 can be controlled by the illumination system control unit 125 under the control of the main control unit 130.

[0015] A shutter 103 is provided between the light source unit LS and the first illumination optical system 104. The shutter 103 is driven by a drive unit 117 so as to be inserted into or removed from the optical path between the light source unit LS and the first illumination optical system 104. By driving the shutter 103 by the drive unit 117, the irradiation / non-irradiation of light to the photoresist layer on the substrate 114 is switched. That is, the start and end of the exposure of the photoresist layer on the substrate 114 are controlled. Note that the drive unit 117 can be controlled by the main control unit 130.

[0016] The original plate 109 is held by an original plate stage 110. The original plate stage 110 is configured to be movable in each of the X direction, Y direction, and Z direction, and is driven by a drive unit 119. That is, the original plate 109 held by the original plate stage 110 is driven in each of the X direction, Y direction, and Z direction by the drive unit 119. A pattern to be transferred to the photoresist layer on the substrate 114 is formed on the original plate 109. Note that the drive unit 119 can be controlled by the original plate control unit 126 under the control of the main control unit 130.

[0017] The projection optical system 111 projects an image of the pattern of the original plate 109 onto the photoresist layer on the substrate 114 at a predetermined magnification. The optical element 112 (for example, a lens) constituting the projection optical system 111 is configured to be movable along a direction (Z direction) parallel to the optical axis of the projection optical system 111, and can be driven by a drive unit 120. Thereby, the optical characteristics of the projection optical system 111, for example, the focal position of the projection optical system 111 can be changed (adjusted). Further, an aperture stop 113 is disposed on the pupil plane of the projection optical system 111 (the Fourier transform plane with respect to the plane (object plane) on which the original plate 109 is disposed). The diameter of the aperture of the aperture stop 113 can be controlled by a drive unit 121. Note that the drive units 120 to 121 can be controlled by the projection system control unit 127 under the control of the main control unit 130.

[0018] The substrate 114 is held by a substrate stage 115. The substrate stage 115 is configured to be movable in each of the X, Y, and Z directions and is driven by a drive unit 129. That is, the substrate 114 held by the substrate stage 115 is driven in each of the X, Y, and Z directions by the drive unit 129. A photoresist layer (photosensitive material layer) is provided on the substrate 114 by previously applying a photoresist (photosensitive material). Further, a mirror 116 for measuring the position of the substrate stage 115 is provided on the substrate stage 115. Note that the drive unit 129 can be controlled by a substrate control unit 128 under the control of a main control unit 130.

[0019] The focus measurement unit 122 measures the surface height (position in the Z direction) of the substrate 114. For example, the focus measurement unit 122 includes a light projector that projects light having a wavelength that does not expose the photoresist on the substrate 114 toward the substrate 114, and a light receiver that receives the light projected by the light projector and reflected by the substrate 114. The focus measurement unit 122 can measure the surface height of the substrate 114 based on the incident position of the light on the light receiving surface of the light receiver. Note that the focus measurement unit 122 can be controlled by a substrate control unit 128 under the control of a main control unit 130.

[0020] The height measurement unit 123 measures the position (height) of the substrate stage 115 in the Z direction. For example, the height measurement unit 123 includes a laser interferometer, and can measure the height of the substrate stage 115 by detecting the displacement of the mirror 116 in the Z direction by the laser interferometer. Further, the position measurement unit 124 measures the positions of the substrate stage 115 (that is, the substrate 114) in the X and Y directions. For example, the position measurement unit 124 includes a laser interferometer, and can measure the positions of the substrate stage 115 in the X and Y directions by detecting the displacements of the mirror 116 in the X and Y directions by the laser interferometer. Note that the height measurement unit 123 and the position measurement unit 124 can be controlled by a substrate control unit 128 under the control of a main control unit 130.

[0021] The main control unit 130 is configured by an information processing device (computer) including a processor such as a CPU (Central Processing Unit) and a storage unit such as a memory, and comprehensively controls each control unit 125 to 128. As a result, the main control unit 130 can control various processes performed by the exposure apparatus 100. In the exposure apparatus 100 of the present embodiment, the main control unit 130 and the control units 125 to 128 are provided individually, but the main control unit 130 and the control units 125 to 128 may be provided as one control unit.

[0022] In the exposure apparatus 100 configured as described above, in recent years, a substrate 114 provided with a thick photoresist layer may be used, and for such a substrate 114, multiple-focus exposure can be performed from the viewpoint of improving the depth of focus. Multiple-focus exposure is to perform multiple exposures on the photoresist layer on the substrate 114 by changing the Z-direction distance (hereinafter, may be referred to as "focus distance") between the substrate 114 and the focus of the projection optical system 111. For example, multiple-focus exposure can be performed by exposing the photoresist layer on the substrate 114 in each of a plurality of states where the focus distances are different from each other (that is, each of the plurality of focus distances). Alternatively, multiple-focus exposure may be performed by exposing the photoresist layer on the substrate 114 while continuously changing the focus distance.

[0023] In conventional multiple-focus exposure, regardless of the focus distance, the amount of light (hereinafter, may be referred to as "irradiation light amount") irradiated on the photoresist layer on the substrate 114 was kept constant. Therefore, for example, as the photoresist layer on the substrate 114 becomes thicker, it has been difficult to make the opening (pattern) formed in the photoresist layer on the substrate 114 after development have a desired cross-sectional shape. Therefore, in the present embodiment, the irradiation light amount in multiple-focus exposure is made different according to the focus distance so that an evaluation index for evaluating the cross-sectional shape of the opening formed in the photoresist layer on the substrate 114 after development falls within an allowable range. The irradiation light amount may be understood, for example, as a value (set value) set by the user via the user interface of the exposure apparatus 100.

[0024] The evaluation index is an index for evaluating (defining) the cross-sectional shape of an opening (hereinafter sometimes simply referred to as an opening) formed in the photoresist layer on the substrate 114 after development. The evaluation index may include at least one of a taper angle, a sidewall angle, a top dimension, a bottom dimension, and T / B. The taper angle is the taper angle of the cross-sectional shape of the opening. The sidewall angle is the angle of the side surface of the opening. The top dimension is the width (line width, CD width) of the opening on the surface of the photoresist layer, and may include topping in which the width of the opening on the surface of the photoresist layer is narrower than the width of the opening at the interface between the substrate 114 and the photoresist layer. The bottom dimension is the width (line width, CD width) of the opening at the interface between the substrate 114 and the photoresist layer, and may include footing in which the width of the opening at the interface between the substrate 114 and the photoresist layer is narrower than the width of the opening on the surface of the photoresist layer. The footing may be understood to include so-called trailing. T / B is the ratio of the width of the opening at the surface and the interface of the photoresist. That is, T / B is the ratio of the top dimension to the bottom dimension.

[0025] The focal length can be controlled (changed) by at least one of the relative driving of the substrate 114 and the projection optical system 111, the relative driving of the original plate 109 and the projection optical system 111, and the driving of the optical element 112 of the projection optical system 111. The relative driving of the substrate 114 and the projection optical system 111 can be performed, for example, by driving the substrate 114 (substrate stage 115) in the Z direction by the driving unit 129. The driving unit 129 is controlled by the substrate control unit 128 so that the substrate 114 is disposed at the position instructed by the main control unit 130. The relative driving of the original plate 109 and the projection optical system 111 can be performed, for example, by driving the original plate 109 (original plate stage 110) in the Z direction by the driving unit 119. The driving unit 119 is controlled by the original plate control unit 126 so that the original plate 109 is disposed at the position instructed by the main control unit 130. The driving of the optical element 112 of the projection optical system 111 can be performed, for example, by driving the optical element 112 in the Z direction by the driving unit 120. The driving unit 120 is controlled by the projection system control unit 127 so that the optical element 112 is disposed at the position instructed by the main control unit 130. Hereinafter, an example of changing the focal length by driving the substrate 114 (substrate stage 115) in the Z direction will be described.

[0026] The focal length may be controlled (changed) by changing the wavelength of the light emitted from the projection optical system 111. The change in wavelength can be performed by the wavelength selection unit 107. The wavelength selection unit 107 is controlled by the illumination system control unit 125 so that the light emitted from the projection optical system 111 has a desired wavelength. Also, the change in wavelength may be performed by the light source unit LS. For example, if the light source 101 is a laser light source, the wavelength may be changed by changing the position of the diffraction grating included in the light source unit LS by an actuator such as a piezo element. Alternatively, if the light source unit LS has a plurality of laser light sources that emit laser lights having different wavelengths, the wavelength may be changed by causing at least one of the plurality of laser light sources to emit laser light. Note that at least one of the driving unit 119, the driving unit 120, the driving unit 129, and the wavelength selection unit 107 may constitute a changing unit that changes the focal length.

[0027] The exposure light amount can be controlled (changed) by at least one of the intensity of the light irradiated on the photoresist on the substrate 114, the time for irradiating the photoresist layer on the substrate 114 with light, and the speed of changing the focal length. The intensity of the light irradiated on the photoresist on the substrate 114 can be controlled, for example, by changing the intensity of the light emitted from the light source unit LS. The intensity of the light emitted from the light source unit LS is controlled by the illumination system control unit 125 so as to be the intensity of the light instructed by the main control unit 130. The time for irradiating the photoresist layer on the substrate 114 with light can be controlled, for example, by driving the shutter 103 by the driving unit 117. The driving unit 117 is controlled by the main control unit 130 so that the shutter 103 is inserted into and removed from the optical path at a desired timing. The speed of changing the focal length can be controlled by at least one of, for example, the relative driving speed between the substrate 114 and the projection optical system 111, the relative driving speed between the original plate 109 and the projection optical system 111, and the driving speed of the optical element 112 of the projection optical system 111. The control of each driving speed can be the same as the control of the change in the focal length described above. Further, the speed of changing the focal length may be controlled (changed) by the speed of changing the wavelength of the light emitted from the projection optical system 111. The control of the speed of changing the wavelength can be the same as the control of the change in the wavelength described above. When the light source 101 is a laser light source, the control of the speed of changing the wavelength may be performed by changing the oscillation time for each wavelength, changing the wavelength presence probability for each pulse, and / or changing the intensities of a plurality of laser lights having different wavelengths from each other.

[0028] Hereinafter, an example of multi-focus exposure in the present embodiment will be described. In the following examples, as multi-focus exposure, an example of exposing the photoresist layer on the substrate 114 at each of a plurality of focal lengths will be described. The focal length may be understood as the focal position of the projection optical system 111 in the photoresist layer on the substrate 114, and hereinafter, for ease of explanation, it may be referred to as the "focal position".

[0029] [Example 1] In Example 1, an example of controlling the taper angle in the cross-sectional shape of the opening formed in the photoresist layer after development will be described. FIG. 2 shows a cross-section of the photoresist layer after development in which multi-focus exposure is performed by the above-described exposure apparatus 100. In FIG. 2, the dotted line represents the focal position in the multi-focus exposure, and the size of the circle attached to each focal position represents the amount of irradiation light at each focal position. Further, the right figures in FIGS. 2(a) to 2(b) show the relationship (profile) between the focal position (focal length) and the irradiation light amount. In Example 1, an example of multi-focus exposure in which exposure is performed at four focal positions will be described, but the number of focal positions is not limited to four, and two or more focal positions may be used.

[0030] FIG. 2(a) shows the cross-sectional shape of the opening 201 formed in the photoresist layer 200 after development when conventional multi-focus exposure is performed. In the conventional multi-focus exposure, exposure is performed at a plurality (four) of focal positions 202 to 205, and the irradiation light amounts 206 to 209 are made constant (the same) at the plurality of focal positions 202 to 205.

[0031] In the conventional multi-focus exposure, the photoresist layer 200 on the substrate 114 is exposed at four focal positions 202 to 205 with the same irradiation light amounts 206 to 209, respectively. In this case, when exposure is performed at one focal position, even at a position (portion) of the photoresist layer 200 different from the one focal position, the energy of the defocused portion can be absorbed and a chemical reaction can proceed. For example, when exposure is performed at the focal position 205, the energy of the defocused portion is also absorbed by the surface (upper surface) of the photoresist layer 200, so that a chemical reaction can proceed on the surface of the photoresist layer 200 (that is, the integrated exposure amount on the surface can increase). As a result, since the integrated exposure amount in the upper part of the photoresist layer 200 is larger than the integrated exposure amount in the lower part, the cross-sectional shape of the opening 201 formed in the photoresist layer 200 after development has a taper angle.

[0032] Figure 2(b) shows the cross-sectional shape of the opening 211 formed in the photoresist layer 210 after development when performing multi-focus exposure in this embodiment (Example 1). In the multi-focus exposure of Example 1, exposure is performed at a plurality (four) of focal positions 212 to 215, and the irradiation light amounts 216 to 219 are made different according to the focal positions 212 to 215 so that the evaluation index falls within the allowable range (for example, so that the opening 211 has the target cross-sectional shape). In this case, it is preferable to make the irradiation light amounts 216 to 219 different according to the focal positions 212 to 215 so that the relationship between the focal position and the irradiation light amount becomes asymmetric with respect to the average position between the first focal position and the second focal position. The first focal position is the focal position 212 on the surface of the photoresist layer 210, and the second focal position is the focal position 215 at the interface between the substrate 114 and the photoresist layer 210. Also, since the focal position can be expressed as a focal length, it may be understood as "making the irradiation light amount different according to the focal position so that the relationship between the focal length and the irradiation light amount becomes asymmetric with respect to the average distance between the first focal length and the second focal length". The first focal length is the focal length when the focal point of the projection optical system 111 is on the surface of the photoresist layer 210. The second focal length is the focal length when the focal point of the projection optical system 111 is at the interface between the substrate 114 and the photoresist layer 210.

[0033] In the multi-focus exposure of Example 1, as the focal position is farther from the surface of the photoresist layer 210, that is, as the focal length becomes narrower, the irradiation light amount is increased. That is, the irradiation light amounts 216 to 219 are gradually increased so that the irradiation light amount 219 at the focal position 215 in the lower part of the photoresist layer 210 is larger than the irradiation light amount 216 at the focal position 212 in the upper part of the photoresist layer 210. As a result, the difference between the integrated exposure amount in the lower part and the integrated exposure amount in the upper part in the photoresist layer 210 is reduced, so that the cross-sectional shape of the opening 211 formed in the photoresist layer 210 after development becomes a steep angle (that is, the taper angle is reduced). That is, the cross-sectional shape of the opening 211 formed in the photoresist layer 210 after development can be accurately controlled.

[0034] Here, in Example 1, an example was shown in which the irradiation light amount was increased as the focal position was farther from the surface of the photoresist layer 210, that is, as the focal distance was narrowed. However, it is not limited thereto, and depending on the target cross-sectional shape of the aperture 211, the irradiation light amount may be decreased as the focal position is farther from the surface of the photoresist layer 210, that is, as the focal distance is narrowed. Further, in Example 1, an example in which the irradiation light amounts 216 to 219 were changed stepwise was shown. However, in the case of performing multi-focus exposure in which the photoresist layer on the substrate 114 is exposed while continuously changing the focal distance, the focal light amount may be continuously changed. Furthermore, in Example 1, the taper angle was used as an evaluation index, but it is not limited thereto, and other evaluation indexes such as sidewall angle and T / B may be used.

[0035] [Example 2] In Example 2, an example of controlling the footing in the cross-sectional shape of the aperture formed in the photoresist layer after development will be described. FIG. 3 shows a cross-section of the photoresist layer after development in which multi-focus exposure is performed by the above-described exposure apparatus 100. In FIG. 3, the dotted line represents the focal position in the multi-focus exposure, and the size of the circle attached to each focal position represents the size of the irradiation light amount at each focal position. Further, the right figures in FIGS. 3(a) to 3(b) show the relationship (profile) between the focal position (focal distance) and the irradiation light amount. In Example 2, an example of multi-focus exposure in which exposure is performed at four focal positions will be described. However, the number of focal positions is not limited to four, and two or more may be sufficient.

[0036] FIG. 3(a) shows the cross-sectional shape of the aperture 301 formed in the photoresist layer 300 after development in the case of performing conventional multi-focus exposure. In the conventional multi-focus exposure, exposure is performed at a plurality (four) of focal positions 302 to 305, and the irradiation light amounts 306 to 309 are made constant (the same) at the plurality of focal positions 302 to 305.

[0037] In conventional multi-focus exposure, the photoresist layer 300 on the substrate 114 is exposed at four focal positions 302 to 305 with the same exposure light amount 306 to 309, respectively. In this case, depending on the adhesion between the substrate 114 and the photoresist layer 300 and the light transmittance of the substrate 114, trailing A may occur at the lower part of the photoresist layer 300. Trailing A refers to a phenomenon in which the bottom dimension of the opening 301 formed in the cured photoresist layer 300 becomes smaller than the target value due to the remaining photoresist.

[0038] Figure 3(b) shows the cross-sectional shape of the opening 311 formed in the developed photoresist layer 310 when multi-focus exposure of this embodiment (Example 2) is performed. In the multi-focus exposure of Example 2, as in Example 1 above, exposure is performed at a plurality (four) of focal positions 312 to 315, and the exposure light amounts 316 to 319 are made different according to the focal positions 312 to 315 so that the evaluation index falls within the allowable range. Also in this case, as in Example 1 above, the exposure light amounts 316 to 319 may be made different according to the focal positions 312 to 315 so that the relationship between the focal position and the exposure light amount becomes asymmetric with respect to the average position between the first focal position and the second focal position.

[0039] In the multi-focus exposure of Example 2, the exposure light amounts at a plurality of focal positions are partially changed. That is, the exposure light amounts at a part of the plurality of focal positions 312 to 315 are made different from the exposure light amounts at other parts. When eliminating trailing A, as shown in Figure 3(b), the exposure light amount 319 at the focal position 315 is made larger than the exposure light amounts 316 to 318 at the other focal positions 312 to 314. As a result, the remaining photoresist at the lower part of the photoresist layer 310 is reduced, so that trailing is eliminated (reduced) in the cross-sectional shape of the opening 311 formed in the developed photoresist layer 310. That is, the cross-sectional shape of the opening 311 formed in the photoresist layer 310 after development can be accurately controlled.

[0040] Here, in Example 2, an example of partially changing the irradiation light amount at a plurality of focal positions to eliminate skirt pulling was shown. Skirt pulling is an example of footing, which is an abnormal shape of the opening that occurs at the interface between the substrate 114 and the photoresist layer. Examples of footing include, for example, cases where the light transmittance of the substrate 114 is low, the photoresist in the vicinity of the substrate 114 is overexposed, and the bottom dimension becomes larger than the target value. In this case, the irradiation light amount 319 at the focal position 315 may be made smaller than the irradiation light amounts 316 - 318 at the other focal positions 312 - 314. Also, in Example 2, an example of partially changing the irradiation light amount performed at a plurality of irradiation positions was shown, but in the case of performing multi-focus exposure in which the photoresist layer on the substrate 114 is exposed while continuously changing the focal length, the focal light amount may be temporarily changed. Furthermore, in Example 2, footing (skirt pulling) was used as an evaluation index, but it is not limited thereto, and other evaluation indexes such as taper angle, sidewall angle, and T / B may be used.

[0041] [Example 3] In Example 3, an example of controlling topping in the cross-sectional shape of the opening formed in the photoresist layer after development will be described. FIG. 4 shows a cross-section of the photoresist layer after development that has been exposed by the above-described exposure apparatus 100. In FIG. 4, the dotted line represents the focal position in the exposure, and the size of the circle attached to each focal position represents the size of the irradiation light amount at each focal position. Also, the right figures in FIGS. 4(a) - (b) show the relationship (profile) between the focal position (focal length) and the irradiation light amount. Note that in Example 3, an example of multi-focus exposure with exposure performed at two focal positions will be described, but the number of focal positions is not limited to two and may be three or more.

[0042] FIG. 4(a) shows a cross-sectional shape of an opening 401 formed in a photoresist layer 400 after development when conventional exposure is performed. In FIG. 4(a), an example of performing exposure with an irradiation light amount 406 at one focal position 402 located at the boundary between a substrate 114 and the photoresist layer 400 is shown as the conventional exposure. In the conventional exposure, topping B may occur when the irradiation light amount 406 is insufficient. Topping B refers to an abnormal shape of the opening that occurs on the surface of the photoresist layer after curing. For example, it is a phenomenon in which the top dimension of the opening 401 formed in the cured photoresist layer 400 becomes smaller than the target value.

[0043] FIG. 4(b) shows a cross-sectional shape of an opening 411 formed in a photoresist layer 410 after development when multi-focus exposure of the present embodiment (Example 3) is performed. In the multi-focus exposure of Example 3, as in Examples 1 to 2 described above, exposure is performed at a plurality (two) of focal positions 412 to 413, and the irradiation light amounts 416 to 417 are varied according to the focal positions 412 to 413 so that the evaluation index falls within the allowable range. Also in this case, as in Examples 1 to 2 described above, the irradiation light amounts 416 to 417 may be varied according to the focal positions 412 to 413 so that the relationship between the focal position and the irradiation light amount becomes asymmetric with respect to the average position between the first focal position and the second focal position.

[0044] In the multi-focus exposure of Example 3, similar to the multi-focus exposure of Example 1, as the focal position moves away from the surface of the photoresist layer 210, that is, as the focal length decreases, the irradiation light amount is increased. Also, the multi-focus exposure of Example 3 can be considered to partially change the irradiation light amounts at a plurality of focal positions, similar to the multi-focus exposure of Example 2. Specifically, in the multi-focus exposure of Example 3, exposure is performed when there is a focal position 412 on the surface of the photoresist layer 400 and when there is a focal position 413 at the interface between the substrate 114 and the photoresist layer 400. Then, the irradiation light amount 416 at the focal position 412 is made smaller than the irradiation light amount 417 at the focal position 413. As a result, since the integrated exposure amount in the upper part of the photoresist layer 410 increases, topping B is eliminated (reduced) in the cross-sectional shape of the opening 411 formed in the photoresist layer 410 after development. That is, the cross-sectional shape of the opening 411 formed in the photoresist layer 410 after development can be accurately controlled.

[0045] Here, in Example 3, an example in which the irradiation light amount is varied according to the focal position is shown in order to eliminate the phenomenon in which the top dimension among toppings becomes smaller than the target value. Among the examples of toppings, for example, there may be a case where the top dimension becomes larger than the target value. Even in this case, it is preferable to vary the irradiation light amount according to the focal position so that the top dimension becomes the target value. Also, in Example 3, an example in which the irradiation light amounts performed at a plurality of irradiation positions are partially changed is shown, but in the case of performing multi-focus exposure in which the photoresist layer on the substrate 114 is exposed while continuously changing the focal length, the focal light amount may be temporarily changed. Furthermore, in Example 3, topping is used as an evaluation index, but it is not limited thereto, and other evaluation indexes such as a taper angle, a sidewall angle, and T / B may be used.

[0046] [Control Example 1 of Multi-Focus Exposure] Next, Control Example 1 of multi-focus exposure (exposure method) in this embodiment will be described. FIG. 5 is a flowchart showing Control Example 1 of multi-focus exposure in this embodiment. In Control Example 1, multi-focus exposure in which the photoresist layer on the substrate 114 is sequentially exposed at each of a plurality of focal lengths will be described. The flowchart in FIG. 5 can be executed by the main control unit 130.

[0047] In step S11, the main control unit 130 determines n focal lengths F(1) to F(n). "n" is a natural number of 2 or more. For example, the main control unit 130 can determine n focal lengths F(1) to F(n) by dividing the photoresist layer that can be provided on the substrate 114 in the thickness direction. The number "n" of focal lengths can be set according to the formation accuracy of the openings in the photoresist layer after development. The number "n" of focal lengths and / or the formation accuracy can be set by the user via, for example, the user interface of the exposure apparatus 100. As described above, the focal length may be understood as the focal position of the projection optical system 111 in the photoresist layer on the substrate 114.

[0048] In step S12, the main control unit 130 determines the irradiation light amounts E(1) to E(n) at each of the n focal lengths F(1) to F(n). For example, when performing multi-focus exposure with a constant irradiation light amount with respect to the focal length, the main control unit 130 acquires reference information indicating the cross-sectional shape of the aperture that can be formed in the photoresist layer. Then, based on the reference information, the main control unit 130 determines the relationship between the focal length and the irradiation light amount that can keep the evaluation index within the allowable range. Specifically, the cross-sectional shape of the reference information is compared with the target cross-sectional shape, and the irradiation light amount is decreased in the part where the target cross-sectional shape is smaller than the cross-sectional shape of the reference information, and the irradiation light amount is increased in the part where the target cross-sectional shape is larger than the cross-sectional shape of the reference information. Thereby, based on the relationship, the main control unit 130 can determine the irradiation light amounts E(1) to E(n) at each focal position F(1) to F(n), that is, the relationship between the focal length and the irradiation light amount. Here, the reference information can be obtained by an experiment using the exposure apparatus 100 or by a simulation using the main control unit 130 or an external device before starting the flowchart of FIG. 5.

[0049] In step S13, the main control unit 130 sets "i", which indicates the number of exposure times in the multi-focus exposure, to "1" (that is, sets it to "i = 1"). Next, in step S14, the main control unit 130 relatively drives the focus of the substrate 114 and the projection optical system 111 so as to be at the focal length F(i), and in that state, exposes the photoresist layer on the substrate 114 with the irradiation light amount E(i). The start and end of the exposure can be controlled by driving the shutter 103 by the driving unit 117. Also, since the control of the focal length F(i) and the control of the irradiation light amount E(i) are as described above, the description here is omitted.

[0050] In step S15, the main control unit 130 determines whether or not n exposures have been performed in the multi-focus exposure. If n exposures have been performed in the multi-focus exposure, the process ends. On the other hand, if n exposures have not been performed in the multi-focus exposure, the process proceeds to step S16, and the main control unit 130 adds "1" to "i", which indicates the number of exposure times in the multi-focus exposure, and then executes step 104.

[0051] [Control Example 2 of Multi-Focus Exposure] Next, a second control example of multi-focus exposure (exposure method) in the present embodiment will be described. FIG. 6 is a flowchart showing the second control example of multi-focus exposure in the present embodiment. In the second control example, multi-focus exposure for exposing a photoresist layer on the substrate 114 while continuously changing the focal length will be described. The flowchart of FIG. 6 can be executed by the main control unit 130.

[0052] In step S21, the main control unit 130 determines n focal lengths F(1) to F(n). Next, in step S22, the main control unit 130 determines the irradiation light amounts E(1) to E(n) at each of the n focal lengths F(1) to F(n). Thereby, the relationship between the focal length and the irradiation light amount that can keep the evaluation index within the allowable range can be determined. Note that steps S21 to S22 are the same as steps S11 to S12 in the flowchart of FIG. 5, so the description here is omitted.

[0053] In step S23, the main control unit 130 determines the change rate V(t) of the focal length and the light intensity I(t) with respect to time t. For example, the main control unit 130 generates the change rate V(t) of the focal length and the light intensity I(t) for realizing the relationship based on the relationship between the focal length and the irradiation light amount. Here, in the second control example, an example of determining both the change rate V(t) of the focal length and the light intensity I(t) is shown, but it is not limited thereto, and only one of the change rate V(t) of the focal length and the light intensity I(t) may be determined. For example, when the change rate V(t) of the focal length is constant, only the light intensity I(t) may be determined, or when the light intensity I(t) is constant, only the change rate V(t) of the focal length may be determined.

[0054] In step S24, the main control unit 130 drives the substrate stage 115 by the driving unit 129 to place the substrate 114 at the exposure start position. Next, in step S25, the main control unit 130 executes multi-focus exposure based on the focus distance change speed V(t) and the light intensity I(t) determined in step S23. Specifically, the main control unit 130 changes the focus distance in accordance with the focus distance change speed V(t) and changes the intensity of the light emitted from the projection optical system 111 in accordance with the light intensity I(t). At this time, the main control unit 130 causes the focus measurement unit 122 to measure the surface height of the substrate 114 in real time, and performs feedback control of the driving unit 129 that drives the substrate stage 115 based on the measurement result. Thereby, the focus distance can be changed at an accurate speed. In addition, the main control unit 130 causes the light detection unit 108 to detect the light intensity in real time, and performs feedback control of the light intensity emitted from the light source unit LS based on the detection result. When changing the intensity of the light emitted from the light source unit LS over time, a laser or an LED may be used as the light source 101 of the light source unit LS.

[0055] As described above, in the multi-focus exposure of the exposure apparatus 100 according to the present embodiment, the irradiation light amount is made different according to the focus distance so that the evaluation index falls within the allowable range. Thereby, the multi-focus exposure can be accurately controlled so that the cross-sectional shape of the opening formed in the photoresist layer after development becomes the target cross-sectional shape.

[0056] <Embodiment of a method for manufacturing an article> The article manufacturing method according to an embodiment of the present invention is suitable for manufacturing articles such as microdevices like semiconductor devices and elements having fine structures. The article manufacturing method of the present embodiment includes an exposure step of exposing a substrate using the above-described exposure apparatus (exposure method) (a step of forming a pattern on the substrate), a processing step of processing the substrate exposed in the exposure step, and a manufacturing step of manufacturing an article from the substrate processed in the processing step. The processing step may include a step of developing the substrate exposed in the exposure step. Further, such an article manufacturing method includes other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). The article manufacturing method of the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article as compared with the conventional method.

[0057] <Other Embodiments> The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiment to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. Further, it can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0058] <Summary of Embodiments> The disclosure of this specification includes at least the following exposure method, exposure apparatus, and article manufacturing method. (Item 1) An exposure method of performing multi-focus exposure in an exposure apparatus having a projection optical system, the method including changing the distance between a substrate and the focus of the projection optical system to each of a plurality of distances and exposing a photoresist layer on the substrate, wherein the amount of light irradiated to the photoresist layer at each of the plurality of distances is made different according to each of the plurality of distances so that an evaluation index for evaluating a cross-sectional shape of an opening formed in the photoresist layer after development falls within an allowable range. (Item 2) When the distance when the focus of the projection optical system is on the surface of the photoresist layer is defined as the first distance, and the distance when the focus of the projection optical system is at the interface between the photoresist layer and the substrate is defined as the second distance, the amount of light is varied according to each of the plurality of distances such that the relationship between the distance and the amount of light becomes asymmetric with respect to the average distance between the first distance and the second distance. The exposure method according to item 1, wherein: (Item 3) Based on the information indicating the cross-sectional shape obtained when the amount of light is constant with respect to the distance, determine the relationship between the distance and the amount of light that can keep the evaluation index within the allowable range, and vary the amount of light based on the relationship. The exposure method according to item 1 or 2, wherein: (Item 4) In the multi-focus exposure, the amount of light is increased or decreased as the distance becomes narrower. The exposure method according to any one of items 1 to 3, wherein: (Item 5) In the multi-focus exposure, the amount of light is partially changed. The exposure method according to any one of items 1 to 3, wherein: (Item 6) The evaluation index includes at least one of the taper angle of the cross-sectional shape, the angle of the side surface of the opening, the width of the opening on the surface of the photoresist layer, the width of the opening at the interface between the substrate and the photoresist layer, and the ratio of the width of the opening between the surface and the interface. The exposure method according to any one of items 1 to 5, wherein: (Item 7) The distance is controlled by at least one of the relative drive between the substrate and the projection optical system, the relative drive between the reticle having the pattern transferred to the substrate and the projection optical system, and the drive of the optical elements of the projection optical system. The exposure method according to any one of items 1 to 6, wherein: (Item 8) The distance is controlled by changing the wavelength of the light emitted from the projection optical system. The exposure method according to any one of items 1 to 7, wherein: (Item 9) The exposure method according to any one of Items 1 to 8, wherein the amount of light is controlled by at least one of the intensity of light irradiated on the photoresist layer, the time for irradiating the photoresist layer with light, and the speed of changing the distance. (Item 10) The exposure method according to any one of Items 1 to 9, wherein the multi-focus exposure exposes the photoresist layer in each of a plurality of states where the distances are different from each other. (Item 11) The exposure method according to any one of Items 1 to 9, wherein the multi-focus exposure exposes the photoresist layer while changing the distance. (Item 12) An exposure step of exposing a substrate using the exposure method according to any one of Items 1 to 11, A processing step of processing the substrate exposed in the exposure step, A manufacturing step of manufacturing an article from the substrate processed in the processing step, An article manufacturing method characterized by including the above. (Item 13) An exposure apparatus for exposing a photoresist layer on a substrate, A projection optical system, A changing unit that changes the distance between the substrate and the focus of the projection optical system, A control unit that controls multi-focus exposure for exposing the photoresist layer on the substrate by changing the distance to each of a plurality of distances by the changing unit, The control unit varies the amount of light irradiated on the photoresist layer at each of the plurality of distances according to each of the plurality of distances so that an evaluation index for evaluating the cross-sectional shape of the opening formed in the photoresist layer after development falls within an allowable range. An exposure apparatus characterized by this.

[0059] The invention is not limited to the above embodiments, and various changes and modifications are possible without departing from the spirit and scope of the invention. Therefore, claims are attached to disclose the scope of the invention.

Description of Symbols

[0060] 100: Exposure apparatus, 109: Original plate, 110: Original plate stage, 111: Projection optical system, 114: Substrate, 115: Substrate stage, 130: Main control unit

Claims

Claim 1 An exposure method for performing multi-focus exposure in an exposure apparatus having a projection optical system, the method comprising changing the distance between a substrate and the focus of the projection optical system to each of a plurality of distances and exposing a photoresist layer on the substrate, wherein the amount of light irradiated onto the photoresist layer at each of the plurality of distances is varied according to each of the plurality of distances so that an evaluation index for evaluating the cross-sectional shape of an opening formed in the photoresist layer after development falls within an allowable range. Claim 2 When the distance when the focus of the projection optical system is on the surface of the photoresist layer is defined as a first distance and the distance when the focus of the projection optical system is at the interface between the photoresist layer and the substrate is defined as a second distance, the amount of light is varied according to each of the plurality of distances so that the relationship between the distance and the amount of light is asymmetric with respect to the average distance between the first distance and the second distance. The exposure method according to claim 1, characterized in that. Claim 3 Based on information indicating the cross-sectional shape obtained when the amount of light is constant with respect to the distance, a relationship between the distance and the amount of light that can keep the evaluation index within the allowable range is determined, and the amount of light is varied based on the relationship. The exposure method according to claim 1, characterized in that. Claim 4 In the multi-focus exposure, the amount of light is increased or decreased as the distance becomes narrower. The exposure method according to claim 1, characterized in that. Claim 5 In the multi-focus exposure, the amount of light is partially changed. The exposure method according to claim 1, characterized in that. Claim 6 The evaluation index includes at least one of a taper angle of the cross-sectional shape, an angle of a side surface of the opening, a width of the opening on the surface of the photoresist layer, a width of the opening at the interface between the substrate and the photoresist layer, and a ratio of the width of the opening between the surface and the interface. The exposure method according to claim 1, characterized in that. Claim 7 The distance is controlled by at least one of relative driving of the substrate and the projection optical system, relative driving of a reticle having a pattern transferred to the substrate and the projection optical system, and driving of an optical element of the projection optical system. The exposure method according to claim 1, characterized in that. Claim 8 The exposure method according to claim 1, characterized in that the distance is controlled by changing the wavelength of light emitted from the projection optical system.

9. The exposure method according to claim 1, characterized in that the amount of light is controlled by at least one of the intensity of light irradiating the photoresist layer, the time for irradiating the photoresist layer with light, and the speed of changing the distance.

10. The exposure method according to claim 1, characterized in that the multi-focus exposure exposes the photoresist layer in each of a plurality of states where the distances are different from each other.

11. The exposure method according to claim 1, characterized in that the multi-focus exposure exposes the photoresist layer while changing the distance.

12. An exposure step of exposing a substrate using the exposure method according to any one of claims 1 to 11, A processing step of processing the substrate exposed in the exposure step, A manufacturing step of manufacturing an article from the substrate processed in the processing step, An article manufacturing method characterized by including the above.

13. An exposure apparatus for exposing a photoresist layer on a substrate, A projection optical system, A changing unit that changes the distance between the substrate and the focus of the projection optical system, A control unit that controls multi-focus exposure for exposing the photoresist layer on the substrate by changing the distance to each of a plurality of distances by the changing unit, The control unit varies the amount of light irradiating the photoresist layer at each of the plurality of distances according to each of the plurality of distances so that an evaluation index for evaluating the cross-sectional shape of the opening formed in the photoresist layer after development falls within an allowable range. An exposure apparatus characterized by this.

Images