Patterning method

Abstract

This invention provides a patterning method that enables the patterning of metal films constituting through-wiring substrates with high precision, ease, and low cost. [Solution] The patterning method of the present invention comprises the steps of: immersing a through-wiring substrate 100 in a first resist 106 contained in a container 105; applying a second resist onto the first resist 106 adhering to the surface of the through-wiring substrate 100 and rotating the through-wiring substrate 100 using a spin-coating apparatus; heating the first resist 106 and the second resist to form a resist film; exposing and developing a predetermined portion of the resist film; etching the exposed portion of the first metal film 102; and removing the remaining portion of the resist film.

Description

Technical Field

[0001] The present invention relates to a method for patterning a metal film formed on the surface of a substrate having through holes.

Background Art

[0002] In recent years, semiconductor devices having a three-dimensional structure such as micro machines (MEMS) have attracted attention. In a semiconductor device having a three-dimensional structure, a plurality of through-wiring substrates on which various elements are mounted are stacked and electrically connected via through wirings. FIG. 1 is a cross-sectional view before patterning of one through-wiring substrate 100 among a plurality of through-wiring substrates constituting a semiconductor device. The through-wiring substrate 100 includes a substrate 101 having through holes 104, a first metal film 102 formed on the surface 101a of the substrate and the inner surface 104a of the through holes, and a second metal film 103 formed on the inner surface 104a of the through holes with the first metal film 102 interposed therebetween.

[0003] In the manufacturing process of a semiconductor device, patterning is performed on the first metal film 102 to form a predetermined circuit. In this patterning, due to the presence of the through holes 104, the following problems occur. It is difficult to uniformly apply a resist over the entire surface 100a of the through-wiring substrate and uniformly form a resist film. Also, in the development process, the developer flows into the through holes 104 and the opposite side of the processed surface of the through-wiring substrate 100, and the second metal film 103 formed there is eroded. Due to these problems, the accuracy of patterning the first metal film 102 deteriorates, and the electrical characteristics of the finally obtained elements vary for each through-wiring substrate 100 and also vary for each position on the through-wiring substrate 100. Also, it is necessary to perform the patterning process for each of the front side and the back side of the through-wiring substrate 100, which also poses a problem that an increase in the process cost is inevitable.

[0004] A method for applying resist to the surface of a substrate having through holes has been disclosed (Patent Document 1, etc.). A technique for simultaneously applying resist to both the front and back surfaces of a through-wiring substrate has also been disclosed. For example, a device is known that includes a dispenser for dropping resist onto the front (top) surface and a nozzle for blowing resist up from the back (bottom) surface, and performs simultaneous resist application to both the front and back surfaces while rotating the through-wiring substrate (Nanotec Double-Sided Simultaneous Coating Spinner SC300A). However, this device has difficulty filling the inside of all the through holes of the through-wiring substrate with resist, and is unsuitable for applying high-viscosity resists. In addition, a method for spray-coating resist onto both the front and back surfaces of a through-wiring substrate is known. However, even with this method, it is difficult to fill the inside of all the through holes from both the front and back surfaces without leakage, and it is extremely difficult to spray-coat easily and uniformly when the through-wiring substrate has a large diameter. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-258744 [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention has been made in view of the above circumstances, and aims to provide a patterning method that enables the patterning of metal films constituting through-wiring substrates to be performed easily, with high precision, and at low cost. [Means for solving the problem]

[0007] To solve the above problems, the present invention employs the following means.

[0008] (1) A patterning method according to one aspect of the present invention is a patterning method for a through-wiring substrate comprising a substrate having through holes, a first metal film formed on the surface of the substrate and the inner surface of the through holes, and a second metal film formed on the inner surface of the through holes, sandwiching the first metal film, comprising the steps of: immersing the through-wiring substrate in a first resist contained in a container; applying the second resist onto the first resist adhering to the surface of the through-wiring substrate and rotating the through-wiring substrate using a spin-coating apparatus; heating the first resist and the second resist to form a resist film; exposing and developing a predetermined portion of the resist film; etching the exposed portion of the first metal film; and removing the remaining portion of the resist film.

[0009] (2) In the patterning method described in (1) above, it is preferable to immerse the through-wiring substrate in the first resist such that one main surface of the through-wiring substrate faces the bottom surface of the container.

[0010] (3) In the patterning method described in (2) above, in the process of immersing the through-wiring substrate in the first resist, it is preferable to float the through-wiring substrate on the surface of the first resist contained in the container, and then apply additional first resist to the through-wiring substrate from the side opposite to the first resist, so that the entire through-wiring substrate is covered with the first resist.

[0011] (4) In the patterning method described in either (1) or (2) above, it is preferable that the viscosity of the first resist is in the range of 4 cP or more and 100 cP or less.

[0012] (5) In the patterning method described in either (1) or (2) above, air bubbles in the through-holes may be sucked out and removed from the through-wiring substrate after it has been immersed in the first resist. [Effects of the Invention]

[0013] According to the present invention, the patterning of metal films constituting through-wiring substrates can be performed easily, with high precision, and at low cost. [Brief explanation of the drawing]

[0014] [Figure 1] This is a cross-sectional view of a through-wiring substrate to which the patterning method according to one embodiment of the present invention is applied. [Figure 2] (a) to (c) are cross-sectional views of a through-wiring substrate in each patterning process according to one embodiment of the present invention. [Figure 3] (a) and (b) are cross-sectional views of the through-wiring substrate in each patterning step of the same embodiment. [Figure 4] (a) to (c) are cross-sectional and perspective views of the through-wiring substrate in each patterning step of the same embodiment. [Figure 5] (a) to (c) are cross-sectional views of the through-wiring substrate in each patterning step of the same embodiment. [Figure 6] (a) and (b) are cross-sectional and perspective views of a through-wiring substrate in each process of the conventional patterning technology. [Figure 7] (a) to (c) are cross-sectional views of a through-wiring substrate in each step of the conventional patterning process. [Figure 8] (a) and (b) are cross-sectional and perspective views of a through-wiring substrate in each process of the conventional patterning technology. [Figure 9] (a) to (c) are cross-sectional views of a through-wiring substrate in each step of the conventional patterning process. [Figure 10] (a) and (b) are images and cross-sectional views of the surface of the through-wiring substrate after patterning according to Example 1 of the present invention. [Figure 11] This graph shows the distribution of line widths of the pattern formed by the patterning in Example 1. [Figure 12] (a) and (b) are images and cross-sectional views of the surface of the through-wiring substrate after patterning according to Comparative Example 1 of the present invention. [Figure 13]It is a graph showing the distribution of the line widths of the patterns formed by the patterning of Comparative Example 1.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, a patterning method according to an embodiment to which the present invention is applied will be described in detail with reference to the drawings. In the drawings used in the following description, for the sake of easy understanding of the features, the characteristic parts may be shown enlarged for convenience, and the dimensional ratios of each component etc. are not necessarily the same as the actual ones. Also, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and it can be appropriately changed and implemented without changing the gist thereof.

[0016] The patterning method according to an embodiment of the present invention is a method for patterning a predetermined metal film in a through-wiring substrate 100 as shown in FIG. 1. The through-wiring substrate 100 mainly includes a substrate 101 having through-holes 104, and a first metal film 102 and a second metal film 103 formed on the substrate 101. The first metal film 102 is formed on the surface (main surface and side surface) of the substrate 101a and the inner surface 104a of the through-hole by, for example, sputtering or the like. The second metal film 103 is formed on the inner surface 104a of the through-hole, sandwiching the first metal film 102 (on the first metal film 102), by, for example, vapor deposition or the like.

[0017] FIGS. 2 to 4 are diagrams for explaining each step of the patterning method of the present embodiment with respect to the through-wiring substrate 100. The patterning method mainly has the following steps A1 to A3.

[0018] (Step A1) The through-circuit board 100 is immersed in the first resist 106 contained in container 105 in the following procedure. First, the through-circuit board 100 is floated on the surface of the first resist 106 contained in container 105. Then, an additional second resist 108 is applied to the through-circuit board 100 from the side opposite (above) the first resist 106, so that the entire through-circuit board 100 is covered with the first resist 106.

[0019] Specifically, as shown in Figure 2(a), half the amount of liquid first resist 106 (enough to fill about half the depth) is dropped into a petri dish-shaped container 105 using an application means 107 such as a dropper. Then, as shown in Figure 2(b), the through-wiring substrate 100 is placed on the surface of the liquid first resist 106. The liquid first resist 106 can then be allowed to flow in through the openings of the through-holes 104 that are in contact with the first resist 106, utilizing capillary action. Next, as shown in Figure 2(c), the remaining half of the liquid first resist 106, the second resist 108, is dropped onto the upper surface of the through-wiring substrate 100 using an application means 107 such as a dropper. As shown in Figure 3(a), the through-wiring substrate 100, which was on the first resist 106, is gradually immersed in the liquid first resist 106. In this case, immersion is preferably carried out by floating the through-wiring substrate 100 on the liquid surface 106a of the first resist 106 and allowing it to sink naturally by gravity.

[0020] In the process of immersing the through-wiring substrate 100 in the first resist, the rate at which the through-wiring substrate 100 sinks into the first resist 106 may be adjusted. In this case, it is necessary to ensure that the through-holes 104 are filled with the first resist 106 flowing in from one main surface 100a of the through-wiring substrate before the first resist 106 flows into the through-holes 104 from the other main surface 100b of the through-wiring substrate. However, if the through-wiring substrate 100 is pushed towards the bottom of the container to force it to sink, the first resist 106 may rapidly enter the through-holes 104, leaving air bubbles inside and preventing the through-holes 104 from being filled with the first resist 106.

[0021] The material of the first resist 106 is not particularly limited, but examples include resists such as TSMR-V90, AZ1500, and OFPR-800. When the through-wiring substrate 100 is immersed in the first resist 106, it is preferable that the viscosity of the first resist 106 be 100 cP or less, from the viewpoint of making it easier for the first resist 106 to flow into the through-holes 104. Furthermore, when the through-wiring substrate 100 is removed from the first resist 106, it is preferable that the viscosity of the first resist 106 be 4 cP or more, from the viewpoint of making it difficult for the first resist 106 to flow out of the through-holes 104.

[0022] The through-wiring substrate 100 is immersed in the first resist 106 such that one main surface 101a of the through-wiring substrate faces (is approximately parallel to) the bottom surface 105a of the container. The thickness direction of the substrate 101 through which the through-hole 104 penetrates is aligned with the vertical direction (the direction in which gravity acts). By immersing in this manner, the through-wiring substrate 100 has one main surface 100a side in contact with the first resist 106, while the other main surface 100b side is open to the atmosphere. Therefore, the first resist 106 can flow in only from the one main surface 100a side of the through-wiring substrate, and air can escape from the other open main surface 100b side, thus avoiding the problem of air bubbles remaining in the through-hole 104.

[0023] Furthermore, when immersing the through-wiring substrate 100 in the first resist 106, it is undesirable to tilt one main surface 100a of the through-wiring substrate relative to the bottom surface 105a of the container. If the through-wiring substrate 100 is immersed with one main surface 100a tilted, the other main surface 100b of the through-wiring substrate will also come into contact with the first resist 106, making it difficult for air to escape from the other main surface 100b, and potentially leaving air bubbles in the through-holes 104. In particular, if the through-wiring substrate 100 is immersed with one main surface 100a tilted 90 degrees relative to the bottom surface 105a of the container, the first resist 106 flows in evenly from both the one main surface 100a side and the other main surface 100b side, causing air bubbles to be trapped and remain in the center.

[0024] Once the filling of the through-hole 104 is complete, the through-wiring substrate 100 is removed from the container 105 using a gripping means such as tweezers. As shown in Figure 3(b), the removed through-wiring substrate 100 has the first resist 106 adhering to its entire surface (main surface and sides) and the inner surface of the through-hole 104, and the inside of the through-hole 104 is filled with the adhering first resist 106. The first resist 106 adhering to the entire surface of the through-wiring substrate 100 has an uneven shape 106a.

[0025] If air bubbles remain on the through-wiring substrate surface 106b after immersion in the first resist 106, these bubbles may be removed by suction, for example, using a dropper or other suction device.

[0026] (A2 process) As shown in Figure 4(a), a second resist 108 is applied to the entire surface of the through-wiring substrate 100 using an application means 107 such as a dropper, in an amount sufficient to fill all recesses, onto the first resist 106 that has adhered to the entire surface of the through-wiring substrate 100. The material of the second resist 108 is the same as the material of the first resist 106. Hereinafter, the first resist 106 and the second resist 108 will be collectively referred to as resist, and the through-wiring substrate 100 covered with resist may be referred to as a resist through-wiring substrate 100A.

[0027] As shown in Figure 4(b), the resist through-wiring substrate 100A is rotated using a spin-coating apparatus (only the turntable 109 is shown). More specifically, the resist through-wiring substrate 100A is placed on the turntable 109, and the resist through-wiring substrate 100A is rotated together with the turntable 109. This rotation causes the applied second resist 108 to spread uniformly toward the outer periphery while filling the recesses of the first resist 106, so that the outermost surface, consisting of the first resist 106 and the second resist 108, can be flattened as shown in Figure 4(c). The application of the second resist 108 may be performed while the resist through-wiring substrate 100A is rotating, or it may be performed both before and during rotation.

[0028] The first resist and the second resist are heated and cured to form an integrated resist film 110. The heating is performed by placing the rotated resist through-wiring substrate 100A in a baking oven.

[0029] Furthermore, if the uneven surface of the through-wiring substrate 100 is small enough to be negligible after being removed from the container 105, the step of applying the second resist 108 may be omitted.

[0030] (A3 process) Exposure and development are performed on the resist through-wiring substrate 100A after heating. As shown in Figure 5(a), the portion of the resist film 110 that covers predetermined areas of the main surfaces 100a and 100b of the through-wiring substrate 100 is exposed, and then the first metal film 102 in the predetermined area is exposed by the developed resist 110A.

[0031] Exposure is performed on both main surfaces of the resist through-wiring substrate 100A. First, exposure is performed on one main surface facing the light source, and then on the other main surface, which is then reversed to face the light source. Development is performed by immersing the exposed resist through-wiring substrate 100A in a developer solution. The developer solution is made of a material that does not contain sodium (Na-free), which would affect the device characteristics, such as tetramethylammonium hydroxide (TMAH). The second metal film 103 is covered with the resist film 110 and protected from the developer solution.

[0032] As shown in Figure 5(b), a predetermined pattern 102A of the first metal film 102 is formed by etching (dry etching with a fluorocarbon gas, etc.) the first metal film 102 exposed on both main surfaces using the developed resist 110A as a mask. The etching is first performed on one main surface, and then on the other main surface, which is then inverted and faces the other.

[0033] By removing the pattern resist film 110A with a predetermined cleaning solution, the patterning is completed, and a through-wiring substrate 200 with the pattern 102A of the first metal film 102 exposed is obtained, as shown in Figure 5(c).

[0034] Figures 6-9 illustrate each step of the conventional patterning method for a through-wiring board 100. The conventional patterning method mainly consists of the following steps B1-B5.

[0035] (B1 process) As shown in Figure 6(a), the third resist 111 is applied to one main surface 100a of the through-wiring substrate 100. The application conditions are the same as in step A2. Hereafter, the through-wiring substrate 100 covered with the third resist 111 may be referred to as the resist through-wiring substrate 100B.

[0036] Next, as shown in Figure 6(b), the resist through-wiring substrate 100B is rotated using a spin-coating apparatus. This rotation causes the coated third resist 111 to spread toward the outer periphery, filling in the depressions on the main surface, and forming a flattened resurface. The coating of the third resist 111 may be performed while the resist through-wiring substrate 100B is rotating, or it may be performed both before and during rotation. The rotation conditions are the same as in step A2.

[0037] Next, the third resist 111 is heated and cured together with the resist through-wiring substrate 100B to form a resist film. The heating conditions are the same as those for step A2.

[0038] (B2 process) Exposure and development are performed on the resist through-wiring substrate 100B after heating. As shown in Figure 7(a), the developed resist film 112 is exposed to a portion of the third resist 111 that covers a predetermined area on one main surface 100d of the resist through-wiring substrate 100B, and then developed to expose the first metal film 102 in the predetermined area. The exposure and development conditions are the same as in step A3.

[0039] During development, the developer comes into contact with the resist film 112 on one main surface 100d of the resist through-wiring substrate, and also with the inner surface 104a of the through-hole and the exposed second metal film 103 formed on the other main surface 100e of the resist through-wiring substrate. Therefore, not only the exposed portion of the resist film 112, but also the exposed second metal film 103 that is not covered by the resist film 112 is immersed in the developer.

[0040] As shown in Figure 7(b), a predetermined pattern 102A of the first metal film 102 is formed by etching the first metal film 102 exposed on the main surface 100d side. The etching conditions are the same as those for step A3.

[0041] By removing the developed resist film 112 with a predetermined cleaning solution, the patterning on the main surface 100d side is completed, and a through-wiring substrate 100C with the pattern 102A of the first metal film 102 exposed is obtained, as shown in Figure 7(c).

[0042] (B4 process) The through-wiring substrate 100 is inverted, and as shown in Figure 8(a), the fourth resist 113 is applied to the other main surface 100e of the through-wiring substrate 100C. The application conditions are the same as in step B1. Hereafter, the through-wiring substrate 100C covered with the fourth resist 113 may be referred to as the resist through-wiring substrate 100D.

[0043] Next, as shown in Figure 8(b), the resist through-wiring substrate 100D is rotated using a spin-coating apparatus. This rotation causes the coated fourth resist 113 to spread toward the outer periphery, filling in the depressions on the main surface 100b, and forming a flattened outer surface. The coating of the fourth resist 113 may be performed while the resist through-wiring substrate 100D is rotating, or it may be performed both before and during rotation. The rotation conditions are the same as in step B1.

[0044] Next, the fourth resist 113 is heated and cured together with the resist through-wiring substrate 100D to form a resist film 114. The heating conditions are the same as those for step B1.

[0045] (B5 process) Exposure and development are performed on the resist through-wiring substrate 100D after heating. As shown in Figure 9(a), the developed resist film 114 exposes the portion of the fourth resist 113 that covers a predetermined area of ​​the main surface 100a of the through-wiring substrate 100, and is then developed to expose the first metal film 102 in the predetermined area. The exposure and development conditions are the same as in step B2. In this case as well, for the same reasons as in step B2, not only the exposed portion of the resist film 114 but also the second metal film 103 that is exposed and not covered by the resist film 114 is eroded by the developer.

[0046] As shown in Figure 9(b), a predetermined pattern 102A of the first metal film 102 is formed by etching the first metal film 102 exposed on the main surface 100e side. The etching conditions are the same as those for step B2.

[0047] By removing the developed resist film 114 with a predetermined cleaning solution, the patterning on the main surface 100e side is completed, and a through-wiring substrate 300 with the pattern 102A of the first metal film 102 exposed is obtained, as shown in Figure 9(c).

[0048] Conventional patterning methods involve performing resist coating, spin coating, resist development, and resist removal twice each. In contrast, the patterning method of this embodiment involves performing resist coating, spin coating, resist development, and resist removal only once each, thereby reducing the number of steps.

[0049] As described above, the patterning method of this embodiment relates to the patterning of the first metal film 102 in a through-wiring substrate 100 comprising a substrate 101 having through holes 104, a first metal film 102 formed on both main surfaces of the substrate 101, and a second metal film 103 formed on the inner surface of the through holes 104. The second metal film 103 is made of a superconducting metallic material that is easily eroded by a Na-free developer.

[0050] According to the patterning method of this embodiment, in the process of patterning the first metal film 102, a resist film 110 can be formed to cover the entire surface of the through-wiring substrate 100 and the inner surface of the through-holes 104 before the development process. Since the development process can be performed with the second metal film 103 protected, it is possible to prevent the second metal film 103 from being eroded by the Na-free developer used in the development process. By maintaining the shape of the second metal film 103, subsequent process operations can be performed with high precision.

[0051] In the process of manufacturing superconducting qubits, strict conditions are imposed requiring a Na-free process to avoid the problem of Na acting as a mobile ion and significantly affecting the operation of MOS transistors. Nevertheless, as described above, the patterning method of this embodiment can realize a Na-free process and can therefore be applied to the process of manufacturing superconducting qubits.

[0052] In the patterning method of this embodiment, the entire through-wiring substrate 100 is immersed in resist, thereby simultaneously coating the entire surface of the through-wiring substrate 100 and the inner surfaces of the through-holes. This allows a resist film 110 covering the two main surfaces 100a and 100b and the inner surface 104a of the through-holes to be formed in a single photolithography process (resist coating, exposure, development, etching, and resist removal). Compared to the conventional method, where photolithography processes are performed separately for each main surface, the number of processes and the amount of resist required can be reduced, thus lowering costs.

[0053] Furthermore, in the patterning method of this embodiment, the rotational coating of the resist onto the surface of the through-wiring substrate 100 can be performed with the through-holes filled and the influence of surface irregularities reduced. Therefore, variations in the amount of resist coated and, consequently, the thickness of the formed resist film can be easily and significantly reduced across the entire surface of the through-wiring substrate 100.

[0054] When resist is applied by rotation to one main surface 100a of the through-hole substrate 100, it flows toward the outer edge, but some of it leaks out through the through-holes 104 toward the back side, preventing it from reaching the area beyond the through-holes 104. Therefore, it is difficult to uniformly apply the resist to the entire surface. In conventional patterning methods, the resist flowing toward the outer edge must be spread across the entire surface faster than it leaks out through the through-holes, which requires skilled techniques. However, the patterning method of this embodiment does not require such techniques.

[0055] Furthermore, in the patterning method of this embodiment, regardless of the position of the through-wiring substrate 100, all through-holes 104 are similarly filled with resist, and the resist is then applied to the surface by rotation. Therefore, regardless of the diameter of the through-wiring substrate 100, the resist can be applied uniformly over the entire surface, and consequently, a resist film of uniform thickness can be formed. Because the resist is applied uniformly to the entire surface of the through-wiring substrate 100 and to all the through-holes 104, subsequent processing can be carried out with high precision. [Examples]

[0056] The effects of the present invention will be made clearer by the following examples. However, the present invention is not limited to the following examples and can be modified as appropriate without altering its essence.

[0057] [Example 1] The patterning method (steps A1 to A3) of the above embodiment was performed on a through-wiring substrate. The substrate, first metal film, and second metal film constituting the through-wiring substrate were a 3-inch Si wafer, a TiN film, and an Al film, respectively. The Al film corresponding to the second metal film has the property of being eroded by a Na-free developer. Each step of the patterning method was carried out as follows.

[0058] (A1 process) The through-wiring circuit board was immersed in the first resist in the container. TSMR-V90 liquid (viscosity approximately 27 cP) was used as the first resist.

[0059] (A2 process) After step A1, the substrate was removed from the container, and a second resist was applied to the surface of the through-wiring substrate to which the first resist had adhered. The same resist used as the first resist was applied as the second resist. After the application of the second resist, the through-wiring substrate was rotated using a spin-coating apparatus to flatten the surface. The rotation speed was set to 500-1500 rpm, and the rotation time was set to 30-60 s. After surface flattening, heating was performed at 100-150°C for 10-15 minutes to obtain a resist-coated through-wiring substrate in which a resist film was formed on the entire surface and inside the through-holes.

[0060] (A3 process) After step A2, a predetermined area of ​​the resist film was exposed by irradiating it with ultraviolet light through a mask. Subsequently, the resist through-wiring substrate was immersed in a developer solution to remove the exposed portion of the resist film. A 2.38% TMAH liquid was used as the developer solution. After removing the exposed portion of the resist film, the exposed portion of the first metal film was dry-etched with CF4 plasma to form a pattern of the first metal film. Finally, the remaining resist film was removed using a cleaning solution to obtain a through-wiring substrate with the first metal film pattern exposed.

[0061] [Comparative Example 1] The conventional patterning method (steps B1 to B4) described above was applied to a through-wiring substrate. The substrate, first metal film, and second metal film constituting the through-wiring substrate were the same as in Example 1. Each step of the patterning method was performed as follows.

[0062] (B1 process) A third resist was applied to one main surface of the through-wiring substrate, the substrate was rotated to flatten the third resist, and then it was heated to form a resist film. The same resist used for the third resist was the same as that used for the first and second resists. The rotation and heating conditions were the same as those for process A2.

[0063] (B2 process) The resist film formed in step B1 was exposed and developed to expose a predetermined portion of the first metal film. The exposed portion of the first metal film was dry-etched to form a pattern of the first metal film. By removing the remaining resist film using a cleaning solution, a through-wiring substrate with the pattern of the first metal film exposed on one main surface was obtained. The conditions for exposure, development, etching, and cleaning were the same as in step A3.

[0064] (B3 process) The fourth resist was applied to the other main surface of the through-wiring substrate after the B2 process. The through-wiring substrate was rotated to flatten the fourth resist, and then heated to form a resist film. The rotation and heating conditions were the same as in the B1 process.

[0065] (B4 process) The resist film formed in step B3 was exposed and developed to expose a predetermined portion of the first metal film. The exposed portion of the first metal film was dry-etched to form a pattern of the first metal film. By removing the remaining resist film using a cleaning solution, a through-wiring substrate with the pattern of the first metal film exposed was obtained on the other main surface. The conditions for exposure, development, etching, and cleaning were the same as in step B2.

[0066] The through-wiring substrate after step A2 in Example 1 and the through-wiring substrate after step B2 in Comparative Example 1 were compared by observing the same pattern areas.

[0067] Figure 10(a) is an image of a comparison pattern in the through-wiring substrate of Example 1. Figure 10(b) is an image of the cross-sectional structure in the dashed-dotted line portion S1 of this image. From the image in Figure 10(a), it can be seen that the resist film 110 covers the entire surface of the through-wiring substrate and fills the inside of the through-holes, as shown in the image in Figure 10(b).

[0068] The width W of the linear pattern P shown in Figure 10(a) was measured for each position (each chip) on the wafer. Specifically, the width W of the same pattern P formed was measured at predetermined distances from the edges E1 and E2 in each of the two orthogonal directions (vertical and horizontal). Figure 11 is a graph showing the measurement results. From this graph, it can be seen that the width W of the pattern P is approximately the same (about 5 μm in this case) at all positions in any direction on the wafer, and there is almost no variation.

[0069] Figure 12(a) is an image of the comparison pattern on the through-wiring substrate of Comparative Example 1. Figure 12(b) is an image of the cross-sectional structure in the dashed-dotted line portion S2 of this image. From the image in Figure 12(a), as shown in the image in Figure 12(b), it can be seen that there are areas on the surface of the through-wiring substrate that are not covered with the resist film, and in the subsequent etching process, the first metal film 102 of the pattern that should have been preserved is lost, resulting in a defective first metal film pattern 102B. It can be seen that there is almost no resist film inside the through-holes, and that the second metal film 103 is exposed to the resist developer.

[0070] The width W of the linear pattern P shown in Figure 12(a) was measured for each position (each chip) on the wafer. Specifically, the width W of the same pattern P formed was measured at predetermined distances from the edges E1 and E2 in each of the two orthogonal directions (vertical and horizontal). Figure 13 is a graph showing the measurement results. From this graph, it can be seen that the width W of the pattern P is not uniform in any direction on the wafer, and is generally quite varied.

[0071] The uniform width of the patterns obtained by the patterning method of the present invention is thought to be due to the uniform application of resist to the entire surface and within all through-holes of the through-wiring substrate, and the subsequent processes being carried out with sufficient precision. As a result, it is thought that the patterns P are formed as designed and have almost the same width W at any position on the wafer.

[0072] Conversely, the inconsistent width of patterns obtained using conventional patterning methods is thought to be due to the fact that the resist is not uniformly applied to the surface and through-holes of the through-wiring substrate, and subsequent processes are not performed with sufficient precision. As a result, the pattern P is not formed as designed, and the width W of the pattern P varies from position to position. [Explanation of Symbols]

[0073] 100, 100C, 200, 300... Through-hole wiring boards 100a, 100d, 200a... One main surface of a through-hole wiring board 100b, 200b... The other main surface of the through-hole wiring board. 100A, 100B, 100D... Through-wall wiring boards 101... Circuit board 101a...Surface of the substrate 102...first metal film 102A...Pattern of the first metal film 102B... Pattern of the first metal film with defects 103...Second metal film 104, ...through hole 104a...Inner surface of through hole 105...container 105a...Bottom of the container 106...First Resistance 106a...Liquid level of the first resist 106b... Irregularities of the first resist 107... Coating method 108...Second registration 109... Rotating stand 110... Resist film 110A... Developer-developed resist film 111...Third Resistance 112...Developed third resist film 113...Fourth Registration 114...Developed fourth resist film

Claims

1. A method for patterning the first metal film in a through-wiring substrate comprising a substrate having through holes, a first metal film formed on the surface of the substrate and the inner surface of the through holes, and a second metal film formed on the inner surface of the through holes, sandwiching the first metal film, The process involves immersing the through-wiring substrate in a first resist contained in a container, The process includes applying a second resist onto the first resist attached to the surface of the through-wiring substrate, and rotating the through-wiring substrate using a spin-coating apparatus. A step of heating the first resist and the second resist to form a resist film, A step of exposing and developing a predetermined portion of the resist film, The process of etching the exposed portion of the first metal film, A patterning method characterized by comprising the step of removing the remaining portion of the resist film.

2. The patterning method according to claim 1, characterized in that the through-wiring substrate is immersed in the first resist such that one main surface of the through-wiring substrate faces the bottom surface of the container.

3. In the process of immersing the through-wiring substrate in the first resist, After floating the through-wiring substrate on the surface of the first resist contained in the container, The patterning method according to claim 2, characterized in that an additional first resist is applied to the through-wiring substrate from the side opposite to the first resist, with the through-wiring substrate in between, so that the entire through-wiring substrate is covered with the first resist.

4. The patterning method according to either claim 1 or 2, characterized in that the viscosity of the first resist is in the range of 4 cP or more and 100 cP or less.

5. The patterning method according to either claim 1 or 2, characterized in that, after immersing the through-wiring substrate in the first resist, air bubbles in the through-holes are sucked out and removed.

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