Pattern forming apparatus and pattern forming method

Abstract

We provide alignment mark detection technology. [Solution] The pattern forming apparatus comprises a holding unit for holding a substrate having a plurality of alignment marks, a stage having an upper surface on which the holding unit can be positioned, an optical unit positioned below the stage, and a control unit capable of controlling the operation of the stage and the optical unit. The optical unit is configured to output detection light and receive reflected light. The stage has a plurality of first transmitting units that can transmit detection light and reflected light. The control unit moves the stage so that the optical unit overlaps with one of the plurality of first transmitting units. The control unit irradiates the alignment marks from the back surface of the substrate with the detection light output from the optical unit via the first transmitting units and the holding unit. The control unit receives the reflected light reflected from the back surface of the substrate with the optical unit via the holding unit and the first transmitting units.

Description

TECHNICAL FIELD

[0001] This specification discloses a technique related to a pattern forming apparatus and a pattern forming method. BACKGROUND ART

[0002] Patent Document 1 discloses a pattern forming apparatus (exposure apparatus) provided with an optical system for detecting an alignment mark provided on the back surface of a substrate. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0003] PATENT DOCUMENT 1 Japanese Unexamined Patent Application Publication No. 2019-158926 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] A novel apparatus structure and detection method for detecting an alignment mark from the back surface side of a substrate are provided. MEANS FOR SOLVING THE PROBLEMS

[0005] The pattern forming apparatus (1) disclosed herein includes a holding unit (20) configured to hold a substrate (2) having a plurality of alignment marks (2m). The pattern forming apparatus includes a stage (10) having an upper surface (10u). The stage is configured to be movable in a direction parallel to the upper surface and to allow the holding unit to be placed on the upper surface. The pattern forming apparatus includes an optical unit (30) located below the stage. The optical unit is configured to output detection light (DL) and to receive reflected light (RL). The pattern forming apparatus includes a control unit (50) capable of controlling the operation of the stage and the optical unit. The stage has a plurality of first transparent sections (11) formed penetrating the stage in the thickness direction and configured to transmit detection light and reflected light. The control unit performs a process of moving the stage such that, when viewed from a direction perpendicular to the upper surface, the optical unit overlaps with one of the plurality of first transparent sections. The control unit performs the process of irradiating the alignment marks from the back surface (2b) of the substrate with the detection light output from the optical unit, via the first transmission unit and the holding unit. The control unit also performs the process of receiving the reflected light reflected from the back surface of the substrate with the optical unit, via the holding unit and the first transmission unit.

[0006] In the above configuration, the stage is equipped with multiple first transparent sections. By moving the stage, the optical section can be aligned with any one of the multiple first transparent sections. Then, detection light can be shone onto the alignment marks on the substrate from the back side of the substrate via the first transparent sections and the holding section. This makes it possible to detect the alignment marks from the back side of the substrate. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of the pattern forming apparatus 1. [Figure 2] This is a top view of the stage 10, the holding unit 20, and the substrate 2. [Figure 3] This is a cross-sectional view along line III-III in Figure 2. [Figure 4]This is a flowchart illustrating the exposure method using the pattern forming apparatus 1. [Modes for carrying out the invention]

[0008] (Outline configuration of pattern forming apparatus 1) Figure 1 shows a schematic configuration diagram of the pattern forming apparatus 1. The pattern forming apparatus 1 is an exposure apparatus for forming a mask pattern on a substrate 2. Figure 2 shows a top view of the stage 10, the holding unit 20, and the substrate 2. In Figure 2, the optical unit 30 located below the stage 10 is shown by a dotted line. Figure 3 shows a cross-sectional view along line III-III in Figure 2. In Figures 1-3, the z-direction is the direction perpendicular to the top surface 10u of the stage 10. The x-direction and x-direction are mutually orthogonal directions within the top surface 10u. In the case of identical parts that are repeatedly arranged, a representative reference numeral may be assigned to a part of them. The same applies to other drawings.

[0009] The pattern forming apparatus 1 mainly comprises a stage 10, a stage drive unit 12, a holding unit 20, an optical unit 30, a light source 40, a reflective mirror 41, a mask stage 42, a mask 43, a lens unit 44, and a control unit 50.

[0010] The substrate 2 is held on the holding surface 20s. The shape of the substrate 2 can vary. In this embodiment, the substrate 2 has a circular wafer shape. The material of the substrate 2 can also vary, such as Si, SiC, GaN, GaAs, AlO, etc. In this embodiment, the material of the substrate 2 is SiC.

[0011] A base layer 3 is deposited on the surface 2s of the substrate 2. A resist film 4 is deposited on the surface of the base layer 3. The resist film 4 is the film to be patterned by the pattern forming apparatus 1. The base layer 3 is the film on which various processes such as etching are performed using the patterned resist film 4.

[0012] Multiple alignment marks 2m are provided on the substrate 2. The alignment marks 2m are marks used to position the mask 43 and the substrate 2 during exposure. As shown in Figure 2, the alignment marks 2m are repeatedly arranged at predetermined intervals Px in the x direction and at predetermined intervals Py in the y direction. Furthermore, the position of the alignment marks 2m in the depth direction can vary. For example, the alignment marks 2m may be placed on the back surface 2b, the front surface 2s, or inside the substrate 2. In this embodiment, as shown in Figure 3, the alignment marks 2m are placed on the back surface 2b.

[0013] The stage 10 has an upper surface 10u. The upper surface 10u is configured to accommodate the holding part 20. The stage 10 is connected to the stage drive unit 12. The stage drive unit 12 is a mechanism that moves the stage 10 in directions parallel to the upper surface 10u (x, y directions) and in directions perpendicular to the upper surface 10u (z direction).

[0014] The stage 10 has multiple first transparent sections 11. The multiple first transparent sections 11 are formed to penetrate the stage 10 in the thickness direction (z direction) (see Figure 3). The multiple first transparent sections 11 are cylindrical in shape with a diameter R1 (see Figure 2). The first transparent sections 11 are parts that can transmit the detection light DL and reflected light RL, which will be described later. The material constituting the first transparent sections 11 can be various. In this embodiment, the material of the first transparent sections 11 is low thermal expansion glass.

[0015] The arrangement of the multiple first transparent sections 11 within the upper surface 10u can vary. In this embodiment, the multiple first transparent sections 11 are arranged at the center of the stage 10 and also arranged rotationally symmetrically around the outer circumference of the stage 10 (see Figure 2).

[0016] The arrangement positions and diameter R1 of the multiple first transparent sections 11 within the upper surface 10u should be determined in accordance with the arrangement of the alignment marks 2m. This will be explained in detail. Depending on the type of mask 43, the planar position of the alignment marks 2m may move in various ways. The planar position and diameter R1 of the first transparent section 11 should be determined so as to include the entire range of movement of the alignment marks 2m. This ensures that the alignment marks 2m are always superimposed on the first transparent section 11, even when the type of mask 43 is changed. Therefore, it becomes possible to detect the alignment marks 2m regardless of the type of mask 43.

[0017] The holding portion 20 is positioned on the upper surface 10u of the stage 10. The holding portion 20 has a holding surface 20s for holding the substrate 2. Various mechanisms may be used for holding the substrate 2. In this embodiment, the substrate 2 is held by a suction mechanism (not shown). The holding portion 20 is configured to be detachable from the stage 10. This makes it possible to replace the holding portion 20 if the holding surface 20s becomes worn or dirty.

[0018] The entire holding portion 20 is made of a material that transmits the detected light DL and the reflected light RL. That is, a material that can transmit the detected light DL and the reflected light RL is arranged on the entire surface of the holding portion 20. The materials that make up the holding portion 20 can vary. In this embodiment, the material of the holding portion 20 is low thermal expansion glass.

[0019] When viewed from a direction perpendicular to the upper surface 10u (z-direction), the holding portion 20 has an overlapping region with the first transmitting portion 11. This overlapping region functions as a second transmitting portion 22 that can transmit the detected light DL and the reflected light RL. In other words, the holding portion 20 has a plurality of second transmitting portions 22, each corresponding to a plurality of first transmitting portions 11.

[0020] The optical unit 30 is arranged on the lower side (-z direction side) of the stage 10. The optical unit 30 is arranged at a position facing the lower surface 10b of the stage 10. By moving the stage 10 in the xy directions with the driving device 52, the position of the optical unit 30 in the xy directions relative to the stage 10 can be changed. The optical axis of the optical unit 30 extends upward (in the +z axis direction) from the optical unit 30. The optical unit 30 includes an output unit (not shown) that outputs detection light DL, and a light receiving unit (not shown) that receives reflected light RL. For the light receiving unit, for example, a photoelectric conversion element such as a camera or a sensor can be used.

[0021] The wavelength region of the detection light DL can be variously set according to the material of the substrate 2. The wavelength region of the detection light DL is preferably set to a range that transmits through the substrate 2. In the present example, the wavelength region of the detection light DL is set within the range of 500 nm to 850 nm (so-called near-infrared light). Thereby, when the substrate 2 is composed of SiC or Si, the detection light DL can be transmitted through the substrate 2. Accordingly, even when the alignment mark 2m is formed on the inner side of the substrate 2, the alignment mark 2m can be detected.

[0022] The light source 40 irradiates light of a wavelength that exposes the resist film 4. The mask stage 42 is arranged between the light source 40 and the lens unit 44. The mask stage 42 supports the mask 43. The exposure light EL emitted from the light source 40 is irradiated onto the mask 43 via the reflection mirror 41. A circuit pattern or the like corresponding to a desired semiconductor device is formed on the mask 43. The exposure light EL irradiated onto the mask 43 is irradiated onto the substrate 2 via the lens unit 44.

[0023] The control unit 50 is the part that controls the operation of each part of the pattern forming apparatus 1. The control unit 50 has a CPU and memory unit (not shown). The stage drive unit 12, optical unit 30, light source 40, etc. are connected to the control unit 50. Image data from the optical unit 30 and drive performance information from the stage drive unit 12 are input to the control unit 50. Based on the various information that is input, the control unit 50 controls the optical unit 30 and the stage drive unit 12.

[0024] (Exposure method) The exposure method using the pattern forming apparatus 1 will be explained using the flowchart in Figure 4. In step S10, the substrate 2 is held in the holding unit 20. At this time, alignment is performed so that the alignment mark 2m overlaps on at least one of the multiple first transparent units 11. In the example in Figure 2, the alignment mark 2m overlaps on all five first transparent units 11.

[0025] In step S20, the stage drive unit 12 moves the stage 10 in the x and y directions so that the optical unit 30 overlaps with one of the multiple first transmission units 11. In the example in Figure 2, the optical unit 30 overlaps with the first transmission unit 11 located at the center of the stage 10.

[0026] In step S30, the optical unit 30 outputs detection light DL. The detection light DL passes through the first transmission section 11 of the stage 10 and the second transmission section 22 of the holding section 20 (see Figure 3). The detection light DL is then irradiated onto the alignment mark 2m from the back surface 2b of the substrate 2. The irradiated detection light DL is reflected as reflected light RL. The reflected light RL passes through the second transmission section 22 and the first transmission section 11 and enters the optical unit 30.

[0027] In step S40, the optical unit 30 receives reflected light RL. This captures the alignment mark 2m. The captured data is transmitted to the control unit 50.

[0028] In step S50, the control unit 50 determines whether or not the alignment mark 2m has been imaged for all of the multiple first transmission units 11. If the determination is negative (S50: NO), the process proceeds to step S60, where a first transmission unit 11 from which the alignment mark 2m has not yet been imaged is selected. The process then returns to step S20, where the alignment mark 2m is imaged using the selected first transmission unit 11.

[0029] On the other hand, if imaging of the alignment marks 2m is completed for all first transmission sections 11 (S50: YES), the process proceeds to step S70. In step S70, the control unit 50 calculates the relative positions of the stage 10 and the substrate 2 in the x and y directions.

[0030] In step S80, exposure is performed. Specifically, the control unit 50 drives the stage drive unit 12 so that the pattern of the mask 43 is projected onto a predetermined position on the substrate 2 based on the relative position calculated in step S70. The control unit 50 also drives the light source 40 to generate exposure light EL. The exposure light EL irradiated onto the mask 43 is irradiated onto the substrate 2 via the lens unit 44. That is, the pattern of the mask 43 is transferred to the substrate 2. Thereafter, the control unit 50 drives the stage drive unit 12 to repeatedly position the substrate 2 and drive the light source 40, thereby obtaining a substrate 2 with the desired pattern transferred onto it.

[0031] (Configuration of the first transmission unit 11 and the stage drive unit 12) It is preferable that the refractive indices of the first transmission section 11 and the second transmission section 22 are approximately the same. For example, the refractive indices can be made the same by using the same material for both the first transmission section 11 and the second transmission section 22. The effects are explained below. At the boundary BD between the first transmission section 11 and the second transmission section 22, the detected light DL and reflected light RL have an angle of incidence and an angle of refraction (see Figure 3). If the refractive indices of the first transmission section 11 and the second transmission section 22 are different, the angle of incidence and the angle of refraction will be different (Snell's Law). As a result, problems such as distortion of the detected image of the alignment mark 2m may occur, making accurate positioning difficult. Therefore, by making the refractive indices of the first transmission section 11 and the second transmission section 22 approximately the same, the angle of incidence and the angle of refraction can be made approximately the same for the detected light DL and the reflected light RL. This makes it possible to obtain a more accurate detected image of the alignment mark 2m.

[0032] The thermal expansion coefficients of the first transparent section 11 and the second transparent section 22 are preferably low. Specifically, it is more preferable that the thermal expansion coefficient is in the range of -30 ppb / K to +30 ppb / K. An example of such a material is low thermal expansion glass made of glass-ceramic composite material. The effects are explained below. During exposure of the pattern forming apparatus 1, the stage 10 and the holding section 20 may be heated by the heat generated from the exposure light EL and the stage drive unit 12. If the thermal expansion coefficients of the first transparent section 11 and the second transparent section 22 are relatively high, thermal expansion may cause misalignment or internal stress in the first transparent section 11 and the second transparent section 22. As a result, accurate positioning may become difficult. Therefore, by making the thermal expansion coefficients of the first transparent section 11 and the second transparent section 22 relatively low, misalignment and internal stress can be suppressed, making it possible to position them more accurately. Robustness against thermal expansion can be given to positioning accuracy.

[0033] (effect) In the technology described herein, the stage 10 can be moved to align any one of the first transmissive parts 11 with the optical part 30 (S20). Then, detection light DL can be irradiated onto the alignment mark 2m from the back surface 2b of the substrate 2 via the first transmissive part 11 and the second transmissive part 22 (S30), and reflected light RL can be received (S40). This makes it possible to detect the alignment mark 2m from the back surface 2b side of the substrate 2.

[0034] Problems can arise when alignment marks are placed on the surface of a substrate. For example, consider a case where epitaxial growth, mask formation, and ion implantation are repeatedly performed alternately using alignment marks formed by steps. In this case, if the surface of the single crystal substrate has an off-angle, epitaxial growth may occur anisotropically, and crystal growth may occur only on one side of the step of the alignment mark. As a result, the position of the alignment mark in the planar direction shifts as crystal growth progresses. However, using the technology described herein, it is possible to detect alignment marks placed on the back surface of the substrate. Since crystal growth does not occur on the back surface, it is possible to suppress the positional shift of the alignment mark.

[0035] The holding portion 20 needs to have a region corresponding to the first transparent portion 11 of the stage 10 made of a material that transmits detection light DL and reflected light RL. Such a structure can be realized by making the holding portion 20 of an impermeable material such as metal, forming a through hole in the region corresponding to the first transparent portion 11, and fitting a transparent material into the through hole. However, since the holding portion 20 is made of a composite material, the structure becomes complex. Also, if there are variations in the position of the first transparent portion 11, it is necessary to make different holding portions 20 to correspond to each variation. Therefore, in the technology of this specification, the entire holding portion 20 is made of a material that transmits detection light DL and reflected light RL. In other words, the holding portion 20 is made of a single transparent material. As a result, the structure of the holding portion 20 can be simplified compared to the above structure in which the holding portion 20 is made of a composite material, making it possible to make the holding portion 20 lighter, thinner, and lower in cost. Also, even if there are variations in the position of the first transparent portion 11, it is possible to accommodate them with a single holding portion 20.

[0036] Although embodiments of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness.

[0037] (modified version) The material constituting the first permeable portion 11 may be air. In other words, the first permeable portion 11 may be a cavity.

[0038] The components of the technology disclosed herein are listed below. [Configuration 1] A holding part (20) is configured to hold a substrate (2) having multiple alignment marks (2m), A stage (10) having an upper surface (10u), wherein the stage is configured to be movable in a direction parallel to the upper surface and to be able to arrange the holding portion on the upper surface, An optical unit (30) located below the stage, configured to output detection light (DL) and receive reflected light (RL), A control unit (50) capable of controlling the operation of the stage and the optical unit, A pattern forming apparatus (1) comprising, The stage has a plurality of first transparent portions (11) formed to penetrate the stage in the thickness direction and configured to transmit the detected light and the reflected light, The control unit, A process of moving the stage such that, when viewed from a direction perpendicular to the upper surface, the optical part overlaps with one of the multiple first transparent parts, The process involves irradiating the alignment mark from the back surface (2b) of the substrate with the detection light output from the optical unit, via the first transmission unit and the holding unit. A process in which the reflected light reflected from the back surface of the substrate is received by the optical unit via the holding unit and the first transmitting unit, A pattern forming apparatus that performs this operation. [Configuration 2] The holding portion comprises at least one second permeable portion (22), The pre-detection light is irradiated onto the back surface of the substrate through the first and second transmission sections. The pattern forming apparatus according to configuration 1, wherein the reflected light is incident on the optical section through the second and first transmission sections. [Configuration 3] The pattern forming apparatus according to configuration 2, wherein the refractive indices of the first transparent portion and the second transparent portion are substantially the same. [Structure 4] The pattern forming apparatus according to configuration 2 or 3, wherein the thermal expansion coefficients of the first permeable portion and the second permeable portion are in the range of -30 ppb / K to +30 ppb / K. [Composition 5] A pattern forming apparatus according to any one of configurations 1-4, wherein, when viewed from a direction perpendicular to the upper surface, a material capable of transmitting the detected light and the reflected light is arranged across the entire surface of the holding portion. [Composition 6] The pattern forming apparatus according to any one of configurations 1 to 5, wherein the holding portion is configured to be detachably attached to the stage. [Composition 7] The pattern forming apparatus according to any one of configurations 1-6, wherein the detection light has a wavelength range of 500 nm to 850 nm. [Structure 8] A holding part configured to hold a substrate having multiple alignment marks, A stage having an upper surface, wherein the stage is configured to be movable in a direction parallel to the upper surface and to be able to position the holding portion on the upper surface, An optical unit located below the stage, configured to output detection light and receive reflected light, A control unit capable of controlling the operation of the stage and the optical unit, A pattern forming method using a pattern forming apparatus comprising: The stage has a plurality of first transparent portions formed to penetrate the stage in the thickness direction and configured to transmit the detected light and the reflected light, The pattern formation method is, The process involves holding the substrate in the holding portion such that, when viewed from a direction perpendicular to the upper surface, the alignment marks overlap on at least one of the plurality of first transparent portions, The process involves moving the stage such that, when viewed from a direction perpendicular to the upper surface, the optical part overlaps with one of the multiple first transparent parts, The process involves irradiating the alignment mark from the back surface of the substrate with the detection light output from the optical unit, via the first transmission unit and the holding unit. The process of receiving reflected light reflected from the back surface of the substrate with the optical unit via the holding unit and the first transmitting unit, A pattern forming method comprising the following:

[0039] According to configuration 2, the detected light and reflected light can pass through the holding part.

[0040] According to configuration 3, the angle of incidence and the angle of refraction can be made approximately the same at the boundary between the first transmission portion and the second transmission portion.

[0041] According to configuration 4, even when the first and second permeable parts are heated, displacement and internal stress can be suppressed.

[0042] According to configuration 5, the structure of the holding part can be simplified, making it possible to reduce the weight, thinness, and cost of the holding part.

[0043] According to configuration 6, the retaining part can be replaced if it becomes worn or dirty.

[0044] According to configuration 7, when the substrate is made of SiC or Si, the detection light can be transmitted through the substrate.

[0045] According to configuration 8, alignment marks can be detected from the back side of the circuit board. [Explanation of symbols]

[0046] 1: Pattern forming apparatus 2: Substrate 2m: Alignment mark 2b: Back side 10: Stage 10u: Top side 11: First transmission section 22: Second transmission section 30: Optical section 50: Control section DL: Detection light RL: Reflected light

Claims

1. A holding part (20) is configured to hold a substrate (2) having multiple alignment marks (2m), A stage (10) having an upper surface (10u), wherein the stage is configured to be movable in a direction parallel to the upper surface and to be able to arrange the holding part on the upper surface, An optical unit (30) located below the stage, configured to output detection light (DL) and receive reflected light (RL), A control unit (50) capable of controlling the operation of the stage and the optical unit, A pattern forming apparatus (1) comprising, The stage has a plurality of first transparent portions (11) formed to penetrate the stage in the thickness direction and configured to transmit the detected light and the reflected light, The control unit, The process of moving the stage such that, when viewed from a direction perpendicular to the upper surface, the optical part overlaps with one of the multiple first transparent parts, The process involves irradiating the alignment mark from the back surface (2b) of the substrate with the detection light output from the optical unit, via the first transmission unit and the holding unit. A process in which the reflected light reflected from the back surface of the substrate is received by the optical unit via the holding unit and the first transmitting unit, A pattern forming apparatus that performs this operation.

2. The holding portion comprises at least one second permeable portion (22), The pre-detection light is irradiated onto the back surface of the substrate through the first and second transmission sections. The pattern forming apparatus according to claim 1, wherein the reflected light is incident on the optical section through the second and first transmission sections.

3. The pattern forming apparatus according to claim 2, wherein the refractive indices of the first transparent portion and the second transparent portion are substantially the same.

4. The pattern forming apparatus according to claim 2, wherein the thermal expansion coefficients of the first permeable portion and the second permeable portion are in the range of -30 ppb / K to +30 ppb / K.

5. The pattern forming apparatus according to any one of claims 1 to 4, wherein, when viewed from a direction perpendicular to the upper surface, a material capable of transmitting the detected light and the reflected light is arranged over the entire surface of the holding portion.

6. The pattern forming apparatus according to claim 1, wherein the holding portion is configured to be detachably attached to the stage.

7. The pattern forming apparatus according to claim 1, wherein the detection light has a wavelength range of 500 nm to 850 nm.

8. A holding part configured to hold a substrate having multiple alignment marks, A stage having an upper surface, wherein the stage is configured to be movable in a direction parallel to the upper surface and to be able to position the holding portion on the upper surface, An optical unit located below the stage, configured to output detection light and receive reflected light, A control unit capable of controlling the operation of the stage and the optical unit, A pattern forming method using a pattern forming apparatus comprising: The stage has a plurality of first transparent portions formed to penetrate the stage in the thickness direction and configured to transmit the detected light and the reflected light. The pattern formation method is, The process involves holding the substrate in the holding portion such that, when viewed from a direction perpendicular to the upper surface, the alignment marks overlap on at least one of the plurality of first transparent portions, The process involves moving the stage such that, when viewed from a direction perpendicular to the upper surface, the optical section overlaps with one of the multiple first transparent sections. The steps include: irradiating the alignment mark from the back surface of the substrate with the detection light output from the optical unit via the first transmission unit and the holding unit; The process of receiving reflected light reflected from the back surface of the substrate with the optical unit via the holding unit and the first transmitting unit, A pattern forming method comprising the following:

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