Film formation method, device manufacturing method, and film formation apparatus

Abstract

To provide a film formation method that enables flat film formation on a substrate having a through hole.SOLUTION: A film formation method according to the present invention includes a first step of placing a substrate 100 on a turntable 102 of a spin coating apparatus with one main surface 100a facing the turntable, and dropping first liquid having viscosity to the other main surface 100b of the substrate, a second step of holding the substrate in the same position until the dropped first liquid reaches the one main surface 100a side from the other main surface 100b side through a through hole 101, a third step of rotating the substrate 100 together with the turntable 102, and a fourth step of heating the first liquid together with the substrate 100.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a film formation method, a device manufacturing method, and a film formation apparatus. [Background technology]

[0002] In recent years, in the manufacture of three-dimensional semiconductor integrated circuit 3D implementation, micromachines (MEMS) such as semiconductor sensors, and quantum computer devices, attention has been focused on three-dimensional device structures with through-holes in the substrate. In such three-dimensional devices, in the lithography process after the through-holes are opened, the deterioration of the pattern dimensional accuracy due to the deterioration of the film thickness uniformity of the resist film caused by the presence of the through-holes is a problem. In some three-dimensional devices, it is possible to manufacture the devices by applying conventional manufacturing process techniques by blocking the inside of the through-holes using a CVD method or the like and flattening the substrate using a CMP technique or the like, but in micromachines, particularly devices with liquid flow paths and quantum computer devices, structures that utilize the through-holes themselves may be adopted, and in such devices, if the through-holes opened in the substrate are blocked and the device is manufactured, the through-holes must be opened again in the final stage, so blocking the through-holes is irrational from the viewpoint of the manufacturing process. Therefore, there is a demand for the development of a manufacturing process in which the manufacturing process can be continued while the through-holes are open after the through-holes are opened.

[0003] In recent years, quantum computers that use quantum bits to perform calculations have been attracting attention. As a method for realizing quantum bits, a superconducting circuit method that allows integration is particularly well known. In the superconducting circuit method, the energy levels of a harmonic oscillator formed using Josephson junctions are quantized at low temperatures to form quantum bits using a two-level system. In order to operate a quantum computer, many quantum bits are required, and many superconducting circuits that generate quantum bits are required, but the space for mounting circuits on a substrate is limited, and interference is likely to occur between circuits integrated on a substrate. As a means of solving this problem, a technology is sometimes used in which a ground pattern on the surface of a substrate and a ground pattern on the back of the substrate are connected by many through-substrate wirings in order to minimize the influence of microwave noise emitted from quantum bit elements (Patent Document 1).

[0004] Although the through-wires are sometimes formed after the formation of the superconducting circuit, plasma processing is required to form the through-holes (vias) for the through-wires, and this processing may damage the superconducting circuit, especially the Josephson junction portion. On the other hand, it is difficult to form the through-wires before the formation of the superconducting circuit. This is because it is difficult to form a film with sufficient film thickness uniformity on a substrate with through-holes formed therein, and the occurrence of variations in the resist film thickness in the portion where the Josephson junction is to be formed results in variations in the manufacture of the superconducting circuit.

[0005] In a substrate 10 having through holes 11 as shown in Fig. 11(a), when resist is spin-coated, the resist moves from the center of rotation toward the outer periphery of the substrate due to centrifugal force. At this time, when the flow of resist encounters the inner wall of the through holes 11 on the outer periphery of the substrate, it is influenced by gravity and flows into the through holes 11, in other words, toward the back side, so that the amount of resist supplied to the outer periphery side from the through holes 11 is reduced. As a result, as shown in Fig. 11(b) which is an enlarged cross section of the substrate 10, there is a problem that the film thickness of the resist film 12R on the substrate 10 from the through holes 11 to the outer periphery R of the substrate is thinner than the film thickness of the resist film 12C on the substrate 10 from the center C of the substrate to the through holes 11. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7133842 [Patent Document 2] Japanese Patent Application Publication No. 54-009919 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a film-forming method that makes it possible to improve the uniformity of the film thickness in a thin film coating film-forming method in which a liquid for forming a thin film is dropped onto a substrate having a through hole, and a device manufacturing method and film-forming apparatus that utilize the same. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention employs the following means.

[0009] (1) A film formation method according to one aspect of the present invention is a method for forming a film on one main surface of a substrate having a through hole, the method comprising: a first step of placing the substrate on a turntable of a spin coater with the one main surface facing the other main surface; and dropping a viscous first liquid onto the other main surface of the substrate; a second step of holding the substrate in the same state until the dropped first liquid reaches the one main surface side from the other main surface side through the through hole; a third step of rotating the substrate together with the turntable; and a fourth step of heating the first liquid together with the substrate.

[0010] (2) In the film forming method described in (1) above, in the first step, before dropping the first liquid, a second liquid made of a solvent that can improve the affinity of the liquid for forming a thin film with respect to the other main surface, the surface of the through hole, and the one main surface may be dropped onto the entire surface of the substrate.

[0011] (3) In the film forming method described above in (2), the solvent capable of improving the affinity of the second liquid may be a solvent of the first liquid.

[0012] (4) In the film forming method according to any one of (1) to (3) above, the rotation in the third step may be performed in a state where the other main surface side of the substrate is covered with a lid.

[0013] (5) In the film forming method described above in (4), the lid covering the other main surface side of the substrate may rotate in synchronization with the substrate.

[0014] (6) In the film forming method described in any one of (1) to (5) above, after the fourth step, the method may include a fifth step of placing the other main surface of the substrate so as to face a turntable of a spin coater and dripping a third liquid onto one of the main surfaces of the substrate, and a sixth step of heating the third liquid.

[0015] (7) In the film forming method described above in (6), it is preferable that the third liquid is the same as the first liquid.

[0016] (8) A device manufacturing method according to one embodiment of the present invention is a device manufacturing method using the film formation method described in either (6) or (7) above, in which a predetermined circuit is formed using a film formed by hardening the first liquid through the fourth step, and a film formed by hardening the third liquid through the sixth step.

[0017] (9) In the device manufacturing method described above in (8), the first liquid may be a copolymer, and the third liquid may be an electron beam resist.

[0018] (10) In the method for manufacturing a device described in (9) above, the solute of the first liquid may be a copolymer of methyl methacrylate and methacrylic acid (MMA / MAA copolymer), and the solvent of the first liquid may be ethyl lactate.

[0019] (11) In the method for manufacturing a device described in (9) above, a solute of the third liquid may be polymethyl methacrylate (PMMA) and a solvent of the third liquid may be chlorobenzene or anisole, or a solute of the third liquid may be methyl styrene / chloromethyl acrylate copolymer and a solvent of the third liquid may be anisole.

[0020] (12) In the method for producing a device according to any one of (8) to (11) above, the circuit may be a superconducting circuit having a Josephson junction.

[0021] (13) A film formation apparatus according to one embodiment of the present invention is a film formation apparatus used for the film formation method according to any one of (1) to (5) above, wherein at least a portion of a turntable of the spin coater facing the one main surface is free of irregularities on its surface. Effect of the Invention

[0022] According to the present invention, it is possible to provide a film formation method that enables formation of a thin film with improved film thickness uniformity in a thin film coating film formation method in which a liquid for forming a thin film is dropped onto a substrate having a through hole, a device manufacturing method utilizing the same, and a film formation apparatus. [Brief description of the drawings]

[0023] [Figure 1] 1A is a plan view of a substrate on which a film is formed by a film forming method according to an embodiment of the present invention, and FIG. [Diagram 2] 3A and 3B are plan views of a turntable used in the film forming method of the embodiment. [Diagram 3] 3(a) to 3(c) are cross-sectional views of a substrate and a spin coater in each step of the film formation method of the embodiment. [Figure 4] 3(a) to 3(c) are cross-sectional views of a substrate and a spin coater in each step of the film formation method of the embodiment. [Diagram 5] 3A to 3C are cross-sectional views of a substrate and a spin coater in each step of the film forming method of the embodiment. [Figure 6] 13(a) and 13(b) are enlarged images of a portion of the substrate after the fourth step and the sixth step in the film formation method of Example 1. [Figure 7] 13(a) and 13(b) are enlarged images of a portion of the substrate after the fourth step and the sixth step in the film formation method of Example 2. [Figure 8] 1 is an enlarged image of a portion of a substrate on which a film was formed by the film formation method of Comparative Example 1. [Figure 9] 10(a) to 10(h) are diagrams showing the distribution of electrical resistance values ​​in the thickness direction of chips cut out from the film-formed substrate of Comparative Example 1. FIG. [Figure 10] 4 is a diagram showing the distribution of electrical resistance values ​​in the thickness direction in a part of the film-formed substrate in Example 1. FIG. [Figure 11] 1A is a plan view of a substrate in which a through hole is formed according to a conventional technique, and FIG. 1B is an enlarged cross-sectional view of a portion of the portion indicated by line AA in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, a film forming method, a device manufacturing method, and a film forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the characteristics easier to understand, and the dimensional ratios of each component may not necessarily be the same as in reality. In addition, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them, and can be appropriately modified and implemented within the scope of the present invention.

[0025] First Embodiment 1(a) is a plan view of a substrate (substrate on which a film is to be formed, a wafer) 100 on which a film is to be formed by a film formation method according to one embodiment of the present invention. The substrate 100 has two flat main surfaces 100a, 100b, and has one or a plurality of through-holes 101 penetrating in a thickness direction D. The constituent material of the substrate 100 is not particularly limited, and examples thereof include semiconductors such as silicon, sapphire, and glass. The shape, size, arrangement, etc. of the through-holes 101 are designed to match the circuit structure to be formed after film formation. Depending on the device to be manufactured, a film may be formed on the substrate 100 on one of the main surfaces 100a of which a thin film or insulating film for forming electrical wiring or superconducting wiring has already been formed.

[0026] The film formation method of this embodiment is a method for forming a film on one main surface 100a of a substrate 100 having a through-hole 101, and mainly includes the following first to sixth steps in order.

[0027] (first step) Fig. 1(b) is a cross-sectional view of the film forming apparatus with the substrate 100 set in the spin coater. Here, only the vicinity of the portion of the spin coater where the substrate 100 is placed is shown. First, as shown in Fig. 1(b), the substrate 100 is placed on the turntable 102 of the spin coater so that one main surface 100a on which a film is to be formed faces the turntable 102 (facing downward in this case). It is preferable that the surface of at least the portion of the turntable 102 of the spin coater facing the one main surface 100a is free of irregularities (is substantially flat).

[0028] 2(a) and (b) are plan views showing a configuration example of the turntable 102. The turntable 102 has a substrate support portion (pad) 102b for supporting the substrate 100 on a substantially flat surface 102a on the side where the substrate is placed. The substrate support portion 102b may be configured to be arranged axially symmetrically with respect to the rotation axis C of the turntable 102, as shown in FIG. 2(a). In addition, the heights of the substrate support portions 102 from the surface 102a of the turntable are all uniform so that the deposition surface of the substrate 100 is not tilted with respect to the rotation axis C, i.e., perpendicular to the rotation axis C, when the substrate 100 is placed thereon. The portion of one main surface 100a of the substrate other than the portion supported by the substrate support portion 102b is spaced apart from the surface 102a of the turntable.

[0029] If there is a recess in the center of the turntable for installing a screw to connect the turntable to the rotating shaft, the uniformity of the film thickness of the thin film formed near the center of the substrate on main surface 100b will deteriorate due to turbulence in the airflow near the recess, and a thick portion (convex portion) of the thin film formed by first liquid 103 will be formed at the opening of through hole 101 on the main surface 100b side near the center of the substrate, and the amount of first liquid 103 supplied to main surface 100a through through hole 101 at the center of the substrate will decrease, so it is desirable that the central portion of the turntable be flat.

[0030] One surface 102a of the turntable further includes substrate fixing portions (inner pins) 102c that prevent the substrate from slipping during rotation. The substrate fixing portions 102c are erected at positions close to the outermost periphery of the substrate when the substrate 100 is placed, and are configured so that the position of the top of the substrate fixing portions 102c is higher than the position of the deposition surface of the substrate 100. As shown in FIG. 2(b), by arranging some of the substrate fixing portions 102c in a line in one direction, the orientation flat portion of the substrate 100 can be fixed at the position of the some of the substrate fixing portions 102c.

[0031] A second liquid (not shown) having affinity may be dropped onto the other main surface 100b of the substrate. The second liquid may be dropped by moving the application position from the center to the outer periphery while rotating the substrate 100 together with the rotating table 102 using the function of a spin coater, or may be dropped while moving the application position over the entire surface using a liquid application nozzle or a dropper of the spin coater without rotating the substrate. A layer of the second liquid is arranged to cover substantially the entire surface of the other main surface 100b, substantially the entire surface of each through hole 101, and substantially the entire surface of one main surface 100a. Since the second liquid is a solvent that does not contain a solute, it has a lower viscosity than the first liquid 103 by the amount that it does not contain a solute, and can spread over the surface of the substrate 100. The second liquid is a solvent that can improve affinity, and when it is a solvent for the first liquid 103, the solute of the first liquid 103 and the solvent of the second liquid undergo a chemical reaction, and the solute of the first liquid 103 does not solidify to generate foreign matter or the like. Furthermore, if the second liquid is amphiphilic, having both hydrophobic and hydrophilic groups, even if the surface of substrate 100 has water molecules attached thereto and is hydrophilic, the second liquid will form a molecular layer on the surface of substrate 100, thereby improving affinity even in the case where first liquid 103 is a liquid that is difficult to apply to a hydrophilic substrate surface, such as electron beam resist or photoresist. Therefore, a monolayer or multiple molecular layers of the second liquid are formed on substantially the entire surface of the substrate 100, which promotes the spreading of the first liquid 103 applied in the next step over substantially the entire surface of the substrate 100.

[0032] In this state, a viscous first liquid 103 is applied to the other main surface 100b of the placed substrate. The application of the first liquid 103 may be performed by using the function of a spin coater to move the application position from the center to the outer periphery while rotating the substrate 100 together with the turntable 102, or may be performed without rotating the substrate by moving the application position over the entire surface using a liquid application nozzle or dropper of the spin coater. FIG. 3(a) is a cross-sectional view showing the state of the substrate 100 immediately after application of the first liquid 103. The other main surface 100b is entirely covered with a layer of the first liquid 103.

[0033] (Second process) Next, the substrate is held in the same state without moving until the applied first liquid 103 reaches one main surface 100a of the substrate from the other main surface 100b side of the substrate through the through holes 101. Fig. 3(b) is a cross-sectional view showing a state in which the first liquid 103 has reached one main surface 100a side, the through holes 101 are filled with the first liquid 103, and the first liquid 103 has spread to one main surface 100a. In addition, if there is no through-hole 101 in the center of the substrate 100, it is desirable to hold the first liquid 103 until it reaches the center of the substrate 100 in order to apply the first liquid 103 to the center of the substrate 100.

[0034] (Third step) Next, the function of the spin coater is used to rotate the substrate 100 together with the rotating table 102. As a result, the first liquid 103 protruding from the openings of each through-hole 101 spreads along one main surface 100a of the substrate, forming a thin film made of the first liquid 103 with a thickness determined by the viscosity of the first liquid, the rotation speed, the rotation time, etc. The rotation in the third step may be performed in a state where the other main surface 100b side of the substrate is covered with a lid 104 adjacent to the other main surface 100b.

[0035] At this time, on the other main surface 100b, along a normal N (see Figure 1(a)) that connects the center of the substrate 100 and each through hole 101 and perpendicularly intersects with a tangent T to the outer periphery, a portion of the first liquid 103 that has flowed from the center of the substrate 100 due to the centrifugal force generated during rotation is bent in its moving direction in each through hole 101 toward the lower side of each through hole 101 (the back side / main surface 100a side) due to gravity, etc. That is, the flow of first liquid 103 collides with the side wall of the inner wall of each through hole 101 in the outer circumferential direction of substrate 100, and as a result, a certain amount of first liquid 103 determined by centrifugal force, the diameter of through hole 101, and gravity is diverted to main surface 100a via each through hole 101, and on main surface 100b, the supply amount of first liquid decreases in the region from each through hole 101 to the outer circumferential direction of the substrate on normal line N connecting the center of substrate 100 and each through hole 101, and the thickness of the thin film formed in that region becomes thinner than that of the region from each through hole 101 to the center of the substrate on normal line N connecting the center of substrate 100 and each through hole 101. On the other hand, on main surface 100a, first liquid 103 is supplied from each through hole 101 provided in substrate 100, and therefore first liquid 103 is also supplied from main surface 100b through each through hole 101 to the region toward the outer periphery of substrate 100 on normal line N connecting the center of substrate 100 and each through hole 101. As a result, the ratio of the film thickness of the first liquid in the region toward the center of each through hole 101 on normal line N connecting the center of substrate 100 and each through hole 101 to the film thickness of the first liquid in the region toward the outer periphery of each through hole 101 can be improved compared to the case of main surface 100b coated using the same method as the conventional coating method. Therefore, the thin film 103 formed from the first liquid on one main surface 100a can have a better thickness uniformity than the thin film 103 formed on the other main surface 100b.

[0036] FIG. 3(c) illustrates a case where the lid 104 is placed in the third step. The lid 104 is supported by a lid support portion (outer pin) 102d erected on one surface 102a of the rotating table. The rotation of the substrate 100 in the third step is preferably performed in such a state that the other main surface 100b side of the substrate is covered with the lid 104, is substantially sealed by the lid 104 separated from the lid support portion 102d, and the lid 104 covering the other main surface 100b side of the substrate rotates in synchronization with the substrate 100. In this state, the wind received by the first liquid 103 in the middle of spreading can be reduced. Therefore, the first liquid 103 can spread uniformly on one main surface 100a without being biased by the pressure generated by receiving the wind. The lid 104 covering the other main surface 100b side of the substrate may be configured to rotate in synchronization with the substrate 100.

[0037] (Fourth step) Next, the first liquid 103 supplied in the through-hole 101, on the other main surface 100b, and on the one main surface 100a is heated together with the substrate 100 using a heating means 105 such as a hot plate. FIG. 4(a) is a diagram showing a state in which the first liquid 103 is cured by heating, and the first thin films 103A, 103C, and 103B are formed on the one main surface 100a, the other main surface 100b, and in the through-hole 101, respectively. The heating means 105 illustrated in FIG. 4(a) is flat, and micro-projections 105b are provided on the surface 105a on the side where the substrate 100 is heated. Therefore, the substrate 100 can be supported by the micro-projections 105b and heated without contacting the heating means 105.

[0038] (Fifth step) Next, the substrate 100 is placed on the rotating table 102 in a state in which it has been upside down in the first to third steps, so that the other main surface 100b faces the rotating table 102. Fig. 4(b) is a diagram showing the state in which the substrate 100 is placed. At this time, one main surface 100a of the substrate faces away from the rotating table 102 (facing upward), and becomes the surface on which a film is to be formed.

[0039] While the substrate 100 is stationary or rotating, a third liquid 106 serving as a raw material for film formation is dropped onto one main surface 100a of the substrate, and then the substrate 100 is rotated together with the turntable 102 to apply the third liquid 106. As the third liquid 106, for example, a liquid that can be cured at a temperature equal to or lower than the melting temperature of the first liquid 103 and has an etching rate with respect to a predetermined etching solution smaller than that of the first liquid 103 can be used. When the same liquid as the first liquid 103 (liquid having the same composition) is used as the third liquid 106, the thickness uniformity of the coating film that can be formed with the first liquid 103 can be further improved compared to when it is formed as a single layer (when the third liquid 106 is not applied). When forming a Josephson junction to be used in a quantum computer device or the like, the first liquid 103 is assumed to be a liquid whose solute is a copolymer of methyl methacrylate / methacrylic acid (MMA / MAA copolymer) and whose solvent is ethyl lactate, and the third liquid 106 is assumed to be an electron beam resist whose solute is methyl styrene / chloromethyl acrylate copolymer and whose solvent is anisole, or whose solute is polymethyl methacrylate resin (Poly Methyl Methacrylate: PMMA) and whose solvent is chlorobenzene or anisole.

[0040] 4(c) is a cross-sectional view showing the state of the substrate 100 immediately after application of the third liquid 106. The first liquid 103 formed up to the fourth step substantially fills the through-hole 101, and the through-hole 101 is substantially blocked, so that the third liquid 106 can be applied to the substrate 100 in the same manner as when it is applied to a substrate having no through-hole formed therein.

[0041] (Sixth step) Next, the third liquid 106 supplied onto the first thin film 103A of the first liquid 103 is heated together with the substrate 100 using the heating means 105 such as a hot plate. FIG. 5 is a diagram showing a state in which the third liquid 106 is cured by heating, and a second thin film 106A made of the cured third liquid 106 is formed on the first thin film 103A. As the heating means 105, for example, one having a configuration similar to that shown in FIG. 4(a) can be used. Since each through hole 101 is substantially blocked by the first liquid 103B, the thickness uniformity of the second thin film 106A can be improved compared to a case in which each through hole 101 is not substantially blocked by the first liquid 103B.

[0042] (Pretreatment process) Before the first step, the substrate 100 may be subjected to a pretreatment such as a dehydration bake treatment to improve wettability.

[0043] In the dehydration bake process, the substrate is dehydration baked at a temperature above the boiling point of water using a hot plate or the like, and finally cooled. Regarding cleaning processes, in general semiconductor manufacturing processes such as IC and LSI manufacturing processes, not only the organic solvent cleaning process mentioned above but also a wide variety of other methods are used. For this reason, I think there is no need to write about it specifically. On the other hand, regarding dehydration bake, it is known that if water molecules adhere to the surface of the substrate 100, the surface of the substrate 100 becomes hydrophilic, and the adhesion and coatability with organic liquids such as photoresist deteriorates. Dehydration bake is performed to remove the water molecules adsorbed from such a hydrophilic substrate surface and make it hydrophobic, which has good adhesion and coatability with organic liquids.

[0044] As the wettability improvement process, a solvent (such as ethyl lactate) of the liquid used in film formation is applied to the entire surface of the substrate 100, including the inner wall surface of the through-hole 101, in the following procedure. First, the substrate 100 is installed, taking into consideration the installation state of the substrate in the following first step, and the solvent of the first liquid 103 is applied to one main surface 100a of the substrate and the inside of the through-hole 101. Next, the substrate 100 is rotated to dry the applied solvent. Next, the substrate 100 is inverted and reinstalled so that the other main surface 100b faces upward as shown in FIG. 1(b), and the solvent of the first liquid 103 is applied to the other main surface 100b. Next, the substrate 100 is rotated to dry all the applied solvent. In this process, the liquid to be applied is a solvent for first liquid 103, and since it does not contain any solutes, it has a lower viscosity than first liquid 103. Therefore, this solvent can cover almost the entire surface of substrate 100, including the inner walls of all through-holes 101, with organic molecules that constitute the solvent, and can improve the wettability of first liquid 103 to be applied in the subsequent process.

[0045] By carrying out the wettability improvement treatment, the wettability of the first liquid 103 applied from the first step to the third step is improved on the entire surface of the substrate 100 including the inner wall surface of the through hole 101, and therefore the supply time of the first liquid 103 can be shortened. In particular, the effect of smooth wetting and spreading into the through hole 101 and improving the flow efficiency of the first liquid 103 makes it possible to supply the first liquid 103 to one main surface 100a of the substrate via the through hole 101 regardless of the design such as the size (hole diameter, length) and arrangement of the through hole.

[0046] As described above, in the film formation method of this embodiment, liquid is supplied to the film formation surface (one main surface 100a) of the substrate 100 via the through holes 101 with the substrate 100 facing downward. The liquid supplied downward via the through holes 101 spreads onto the film formation surface starting from the openings of the through holes 101, and therefore spreads evenly across the entire one main surface 100a of the substrate, regardless of the distance from the rotation center (rotation axis C) of the substrate 100. Therefore, regardless of the size, arrangement, etc. of the through holes 101, the liquid can be supplied evenly across the entire film formation surface, and a flat film can be formed by hardening the liquid. In addition, on one of the main surfaces 100a, when the substrate is rotated, the first liquid 103 is also supplied from the main surface 100b side through each through hole 101 to the region toward the outer periphery of the substrate 100 on the normal line N connecting the center of the substrate 100 and each through hole 101. As a result, the ratio of the film thickness of the first liquid in the region toward the center of each through hole 101 on the normal line N connecting the center of the substrate 100 and each through hole 101 to the film thickness of the first liquid in the region toward the outer periphery of each through hole 101 can be improved compared to when coating is performed by the conventional method in which the one of the main surfaces 100a is the upper surface. According to the film formation method of this embodiment, the film thickness uniformity can be improved even though the film formation surface of the substrate has the through hole 101, so that in the subsequent processes, production variations caused by film thickness variations can be prevented, and a decrease in yield can be prevented.

[0047] Various devices can be manufactured using the film forming method of this embodiment. That is, a predetermined circuit can be formed using a film formed by hardening the first liquid 103 through the fourth step and a film formed by hardening the third liquid 106 through the sixth step. For example, after forming a thin film made of a conductive material on the surface of the substrate 100, a resist is used as the third liquid 106, and a wiring pattern (circuit (e.g., a superconducting circuit with a Josephson junction)) of a predetermined device is formed on the second thin film 103A hardened through the fourth step by using a lithography method and an etching method. Subsequently, by repeating such steps, a predetermined device can be manufactured.

[0048] Since a through hole can be formed in the substrate at the initial stage of device manufacturing, and then a resist film can be applied in the lithography process without significantly reducing the uniformity of the resist film thickness, the problem of the delicate parts of the device being damaged by a through hole forming process such as a long-term high-temperature plasma treatment after the formation of the delicate parts of the device can be avoided. For example, by forming a resist pattern using the film formation method of this embodiment, a device structure including a superconducting circuit can be formed without exposing it to high-temperature plasma for a long period of time, and a superconducting quantum bit substrate can be manufactured without damaging delicate Josephson junctions. EXAMPLES

[0049] The effects of the present invention will be more clearly understood by the following examples. Note that the present invention is not limited to the following examples, and can be modified as appropriate without departing from the spirit and scope of the present invention.

[0050] Example 1 Two layers of electron beam resist consisting of MMA / MAA copolymer and Methyl Styrene / Chloromethyl Acrylate Copolymer were formed on one main surface of a substrate having a through hole by using the film forming method of the above embodiment. The substrate used was a silicon substrate having through holes with diameters of 150 μm and 1000 μm.

[0051] As a pretreatment step, the substrate was rotated at 500 rpm for 60 seconds, while 20 mL of isopropyl alcohol (IPA) was sprayed onto the substrate surface to be cleaned. The substrate was then rotated at 2000 rpm for 30 seconds to dry the cleaning solution. The substrate was then dehydrated and baked at 110°C for 180 seconds using a hot plate or the like, and naturally cooled.

[0052] In the first step, the substrate was rotated at 500 rpm for 60 seconds, while 20 mL of ethyl lactate was sprayed onto the substrate surface as the second liquid. The substrate was then rotated at 2000 rpm for 30 seconds to dry the second liquid. Next, 5 mL of a solution of methyl methacrylate / methacrylic acid copolymer (MMA / MAA copolymer) in ethyl lactate was dripped onto the entire surface of the substrate as the first liquid.

[0053] Next, in a second step, the substrate was held stationary until the dropped first liquid reached one of the main surfaces of the substrate through the through holes from the other main surface of the substrate.

[0054] In the third step, the other main surface of the substrate was covered with a lid disposed adjacent thereto, and the substrate was then rotated at 1000 rpm for 60 seconds to form a thin film on one main surface of the substrate.

[0055] Next, in the fourth step, the first liquid supplied into the through-holes, onto the other main surface, and onto one of the main surfaces was heated and cured on a hot plate together with the substrate.

[0056] In the fifth step, 2 ml of an anisole solution of Methyl Styrene / Chloromethyl Acrylate Copolymer was applied as the third liquid. The substrate was rotated at 1000 rpm for 60 seconds in the fifth step.

[0057] Finally, in the sixth step, the third liquid supplied onto the first thin film was heated and cured together with the substrate using a hot plate again.

[0058] Fig. 6(a) is an enlarged image of a portion of the substrate on which a first layer was formed after the fourth step by the film formation method of Example 1. Fig. 6(b) is an image of a second layer formed on the first layer in Fig. 6(a). In both images of Fig. 6(a) and (b), the periphery of the through hole is displayed with a substantially uniform interference color, and it can be seen that a substantially uniform film is formed on both the first and second layers.

[0059] A Manhattan-type Josephson junction pattern was drawn on the two-layer electron beam resist and developed. Then, the lower aluminum film was deposited, followed by tunnel oxidation and the deposition of the upper aluminum film, and the resist film and aluminum film unnecessary for the Josephson junction were removed by the lift-off method, forming the Josephson junction.

[0060] Example 2 Film formation was carried out in the same manner as in Example 1, except that in the third step, the rotation of the substrate was set to 2000 rpm for 60 seconds.

[0061] FIG. 7(a) is an enlarged image of a portion of the substrate on which the first layer was formed after the fourth step by the film forming method of Example 2. FIG. 7(b) is an image of the substrate on which the second layer was formed on the first layer in FIG. 7(a). In the images of FIG. 7(a) and (b), the periphery of the through-hole is displayed in an interference color with a higher uniformity than the periphery of the through-hole in FIG. 6(a) and (b), and it can be seen that the total film thickness uniformity of the first and second layers is further improved. From a comparison of FIG. 6(a) and (b) with FIG. 7(a) and (b), it can be seen that the higher the rotation speed of the substrate, the wider the range of the first liquid can be uniformly supplied on one main surface of the substrate, and the more uniform the film can be formed.

[0062] (Comparative Example) A film was formed on one of the main surfaces of the same substrate as in Example 1 by using a conventional spin coating method. That is, with one of the main surfaces facing away from the turntable (upper side), the same first liquid as in Example 1 was applied to the entire one of the main surfaces while rotating the substrate, and then heated. The substrate was rotated at 2000 rpm for 60 seconds. The amount of the first liquid applied was 5 ml.

[0063] Figure 8 is an enlarged image of a portion of a substrate on which a film was formed using a conventional film formation method. From this image, it can be seen that areas of different colors are randomly distributed around the through-holes, resulting in a non-uniform film.

[0064] In the comparative example, a Manhattan-type Josephson junction was also formed by the same process as in Example 1. As the measurement results of the resistance value of the Josephson junction when the target value of the electric resistance was set to 5 kΩ, the area of ​​the Josephson junction and the oxidation time of the tunnel oxide film were set, the measurement data of the comparative example is shown in Figures 9(a) to (h) and the measurement data of Example 1 is shown in Figure 10.

[0065] In Figure 9, the resistance values ​​of the Josephson junctions vary widely, from 539 Ω to 560.896 kΩ. Even excluding the points where the resistance values ​​are significantly different, the main distribution of resistance values ​​varies from the 3 kΩ to 6 kΩ range. On the other hand, in Figure 10, although there are some Josephson junctions in the 2 kΩ and 6 kΩ range, the majority of resistance values ​​are within the 4 kΩ to 5 kΩ range.

[0066] In general, in a Manhattan-type Josephson junction, the variation in the junction area caused by the variation in the thickness of the electron beam resist in electron beam lithography is considered to be small, but on the other hand, if the resist thickness varies in the tunnel oxidation process, the area of ​​the resist opening changes, and the amount of contaminant gas released from the opening surface also depends on the release area, so that the variation in the resist thickness causes the variation in the resistance value of the Josephson junction. From this point of view, it can be said that the variation in the thickness of the electron beam resist formed in Example 1 is smaller than the variation in the resist thickness in the comparative example.

[0067] Similarly, in the case of a grease gun type Josephson junction, which is one of the methods for forming a Josephson junction, the resist film thickness has a large effect on the junction area of ​​the grease gun type Josephson junction, so that if the variation in the resist film thickness is large, the variation in the resistance value of the Josephson junction also becomes large. Therefore, even in the process of forming a grease gun type Josephson junction, by forming a Josephson junction using the coating method described in the above embodiment, the variation in the resistance value of the Josephson junction can be made smaller than when the conventional technology is used. [Explanation of symbols]

[0068] 100... Substrate 100a: One main surface of a substrate 100b... Other main surface of substrate 101...Through hole 103A, 103B, 103C...First thin film 102 Rotating table 102a...One side of the turntable 102b...Board support part 102c... Board fixing part 102d...Lid support part 103...first liquid 104 Lid body 105...Heating means 106...Third liquid C Rotation axis D: Board thickness

Claims

1. A method for forming a film on one main surface of a substrate having a through hole, comprising the steps of: a first step of placing the substrate on a rotation table of a spin coater so that the one main surface faces the other main surface of the substrate, and dropping a first liquid having viscosity onto the other main surface of the substrate; a second step of holding the substrate in the same state until the dropped first liquid reaches the one main surface side from the other main surface side through the through hole; a third step of rotating the substrate together with the turntable; and a fourth step of heating the first liquid together with the substrate.

2. 2. The method of claim 1, further comprising the step of dropping a second liquid, the second liquid being made of a solvent capable of improving the affinity of a liquid for forming a thin film on the other main surface, the surface of the through hole, and the one main surface, over the entire surface of the substrate before dropping the first liquid in the first step.

3. 3. The film forming method according to claim 2, wherein the solvent capable of improving the affinity of the second liquid is a solvent of the first liquid.

4. 4. The film forming method according to claim 1, wherein the rotation in the third step is performed in a state where the other main surface side of the substrate is covered with a lid.

5. 5. The film forming method according to claim 4, wherein the lid covering the other main surface side of the substrate rotates in synchronization with the substrate.

6. The method for forming a film according to any one of claims 1 to 3 and 5, further comprising: a fifth step of, after the fourth step, placing the other main surface of the substrate so as to face a rotation table of a spin coater and dripping a third liquid onto one main surface of the substrate; and a sixth step of heating the third liquid.

7. 7. The film forming method according to claim 6, wherein the third liquid is the same as the first liquid.

8. A method for manufacturing a device using the film formation method according to claim 6, comprising the steps of: A method for manufacturing a device, comprising forming a predetermined circuit using a film formed by hardening the first liquid through the fourth step, and a film formed by hardening the third liquid through the sixth step.

9. 9. The method for manufacturing a device according to claim 8, wherein the first liquid is a copolymer, and the third liquid is an electron beam resist.

10. 10. The method for manufacturing a device according to claim 9, wherein the solute of the first liquid is a copolymer of methyl methacrylate and methacrylic acid (MMA / MAA copolymer), and the solvent of the first liquid is ethyl lactate.

11. 10. The method for manufacturing a device according to claim 9, wherein a solute of the third liquid is polymethyl methacrylate (PMMA) and a solvent of the third liquid is chlorobenzene or anisole, or a solute of the third liquid is methyl styrene / chloromethyl acrylate copolymer and a solvent of the third liquid is anisole.

12. The method for producing a device according to any one of claims 8 to 11, characterized in that the circuit is a superconducting circuit having a Josephson junction.

13. A film forming apparatus for use in the film forming method according to any one of claims 1 to 3 and 5, A film forming apparatus, characterized in that a surface of at least a portion of a rotation table of the spin coater facing the one main surface is free of irregularities.

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