Circuit board, method for manufacturing circuit board, and vibration device

Abstract

To provide a circuit board that can prevent a reduction in insulating performance in a through electrode, a method for manufacturing a circuit board, and a vibration device.SOLUTION: A circuit board 10 has: a semiconductor substrate 12 that includes a first surface 12a and a second surface 12b located on the opposite side of the first surface 12a; a through hole 13 that penetrates the first surface 12a and the second surface 12b; an organic insulating film 15 that is arranged on the first surface 12a and a side face 14 of the through hole 13; and a conductor 16 that is arranged on the opposite side of the organic insulating film 15 on the side face 14 of the through hole 13. The side face 14 of the through hole 13 has a first side face 14a that is connected with the first surface 12a and reduced in width from the first surface 12a toward the second surface 12b, and a second side face 14b that is connected with the second surface 12b from an end of the first side face 14a facing the second surface 12b.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a circuit board, a method for manufacturing a circuit board, and a vibration device. [Background technology]

[0002] For example, Patent Document 1 discloses a semiconductor device in which a through hole having a substantially vertical inner wall is provided in a silicon substrate, the through hole penetrating from one main surface to another main surface opposite the one main surface, an organic insulating layer is formed to cover the insulating layer formed on the inner wall of the through hole, and a conductive layer is formed inside the through hole. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-113466 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the through electrode described in Patent Document 1 has a through hole that is approximately vertical, so when attempting to form an organic insulating layer uniformly on the inner wall and one main surface of the through hole, the organic insulating layer becomes locally thin at the connection between the inner wall and one main surface of the through hole, resulting in a problem of reduced insulating function. [Means for solving the problem]

[0005] The circuit board includes a semiconductor substrate having a first surface and a second surface located opposite the first surface, a through hole penetrating the first surface and the second surface, an organic insulating film arranged on a side surface of the first surface and the through hole, and a conductor arranged on the organic insulating film opposite the side surface of the through hole, wherein the side surface of the through hole includes a first side surface connected to the first surface and narrowing from the first surface toward the second surface, and a second side surface connected to the second surface from an end of the first side surface on the second surface side.

[0006] a through hole disposed on the organic insulating film opposite the side of the through hole, the through hole having a rectangular shape in a planar view, a groove forming step of forming a bottomed groove in the first surface by wet etching, the groove having a first side that narrows toward the second surface; a through hole forming step of forming the through hole, the through hole having a second side that extends from an end of the first side facing the second surface toward the second surface, the through hole penetrating the first surface and the second surface; an organic insulating film forming step of forming the organic insulating film on the first surface and the first and second side surfaces of the through hole;

[0007] The vibration device includes the circuit board described above, a vibration element disposed on the first surface or the second surface of the circuit board and electrically connected to the conductor, and a lid joined to the circuit board so as to house the vibration element between the circuit board and the lid. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view showing a resonation device including a circuit board according to a first embodiment. [Figure 2] Cross-sectional view taken along line AA in Figure 1. [Figure 3] Enlarged view of part B in Figure 2. [Figure 4] Enlarged view of part C in Figure 2. [Figure 5] FIG. 2 is a flowchart showing a method for manufacturing a circuit board according to the first embodiment. [Figure 6] 5A to 5C are cross-sectional views illustrating a method for manufacturing a circuit board. [Figure 7] 5A to 5C are cross-sectional views illustrating a method for manufacturing a circuit board. [Figure 8]5A to 5C are cross-sectional views illustrating a method for manufacturing a circuit board. [Figure 9] 5A to 5C are cross-sectional views illustrating a method for manufacturing a circuit board. [Figure 10] 5A to 5C are cross-sectional views illustrating a method for manufacturing a circuit board. [Figure 11] 5A to 5C are cross-sectional views illustrating a method for manufacturing a circuit board. [Figure 12] 5A to 5C are cross-sectional views illustrating a method for manufacturing a circuit board. [Figure 13] 5A to 5C are cross-sectional views illustrating a method for manufacturing a circuit board. [Figure 14] FIG. 10 is a plan view showing a resonation device including a circuit board according to a second embodiment. [Figure 15] Cross-sectional view taken along line DD in Figure 14. [Figure 16] Enlarged view of part E in Figure 15. [Figure 17] FIG. 10 is a plan view showing a resonation device including a circuit board according to a third embodiment. [Figure 18] Cross-sectional view taken along line FF in Figure 17. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1. First embodiment First, the vibration device 1 having the circuit board 10 according to the first embodiment will be described with reference to Figures 1 to 4, taking as an example an oscillator in which a vibration element 3 is housed in an internal space S formed by a lid 2 and the circuit board 10. In FIG. 1, for the sake of convenience in explaining the internal configuration of the vibration device 1, the lid 2 is shown removed. Also, in FIGS. 1 and 2, the electrodes provided on the front and back surfaces of the vibration element 3 are not shown. Also, for the sake of convenience in explanation, the following plan views and cross-sectional views show three mutually perpendicular axes: the X-axis, the Y-axis, and the Z-axis. The direction along the X-axis is referred to as the "X-direction," the direction along the Y-axis as the "Y-direction," and the direction along the Z-axis as the "Z-direction." The arrow side of each axis is also referred to as the "plus side," and the side opposite the arrow as the "minus side." The plus side of the Z-direction is also referred to as the "upper," and the minus side of the Z-direction as the "lower."

[0010] As shown in FIGS. 1 and 2, the vibration device 1 includes a circuit board 10, a lid 2, and a vibration element 3.

[0011] The circuit board 10 has a rectangular shape in a plan view from the Z direction, and includes a semiconductor substrate 12 having a first surface 12a and a second surface 12b located opposite the first surface 12a, a through hole 13 penetrating the first surface 12a and the second surface 12b, an organic insulating film 15 disposed on the first surface 12a and a side surface 14 of the through hole 13, and a conductor 16 disposed on the organic insulating film 15 on the side opposite the side surface 14 of the through hole 13. The conductor 16 disposed in the through hole 13 serves as a through electrode 6. The semiconductor substrate 12 is a single crystal silicon substrate, more specifically, a (100) single crystal silicon substrate.

[0012] Furthermore, the circuit board 10 has an organic insulating film 15 provided on the first surface 12a of the semiconductor substrate 12, the organic insulating film 15 being connected to the organic insulating film 15 arranged on the side surface 14 of the through hole 13, and an SiN film 17, an SiO2 film 18, an SiN film 20, a circuit 21 including an oscillator circuit, and external terminals 11 stacked on the second surface 12b of the semiconductor substrate 12. An Al film 19 serving as wiring is formed in the SiO2 film 18.

[0013] The conductor 16 of the through electrode 6 penetrates the SiN film 17 and the SiO2 film 18 on the second surface 12b side of the semiconductor substrate 12 and is electrically connected to the Al film 19, and is electrically connected to the circuit 21 via the Al film 19. In addition, the vibration element 3 is mechanically and electrically bonded onto the through electrode 6 via a bonding member 5 such as a gold bump. Therefore, the vibration element 3 is electrically connected to the oscillation circuit of the circuit 21 and can oscillate.

[0014] The through hole 13 in which the through electrode 6 is formed is rectangular in plan view from the Z direction, and as shown in Figure 3, the side surface 14 of the through hole 13 has four first side surfaces 14a that are connected to the first surface 12a and narrow from the first surface 12a toward the second surface 12b, and four second side surfaces 14b that connect from the end of the first side surface 14a on the second surface 12b side to the second surface 12b.

[0015] The first side surface 14a is inclined at an angle θ of 54.7 degrees with respect to the first surface 12a and is a (111) plane of the single-crystal silicon substrate. The second side surface 14b is a surface perpendicular to the first surface 12a. Since the first side surface 14a of the through-hole 13 is formed between the first surface 12a and the second side surface 14b, when the organic insulating film 15 is formed on the first surface 12a and the side surface 14 of the through-hole 13, it is possible to prevent the organic insulating film 15 from becoming locally thin and its insulating function from deteriorating.

[0016] As shown in FIG. 4, the external terminal 11 is electrically connected to the Al film 19, which serves as wiring, via a through electrode 7 of a conductor 23 provided in a through hole 22 that penetrates the SiO2 film 18, the SiN film 20, and the circuit 21.

[0017] The lid 2 has a rectangular shape when viewed from above in the Z direction, and has a cavity on the surface facing the circuit board 10, forming an internal space S between the lid 2 and the circuit board 10 to house the vibration element 3. The lid 2 houses the vibration element 3 in the internal space S, and is joined to the circuit board 10 via a joining member 4. The internal space S is in a reduced pressure state, preferably closer to a vacuum. This reduces viscous resistance and improves the oscillation characteristics of the vibration element 3. The lid 2 is preferably made of the same material as the semiconductor substrate 12.

[0018] The vibration element 3 is disposed on the first surface 12a of the circuit board 10 and is mechanically and electrically connected to the conductors 16 of the pair of through electrodes 6 via a pair of bonding members 5 such as gold bumps. While the vibration element 3 of this embodiment is an AT-cut quartz crystal vibration element, it may also be an SC-cut quartz crystal vibration element or a BT-cut quartz crystal vibration element. Furthermore, the material of the vibration element 3 is not limited to quartz crystal, and may be, for example, a piezoelectric single crystal such as lithium niobate, lithium tantalate, lithium tetraborate, langasite, potassium niobate, or gallium phosphate.

[0019] As described above, in the circuit board 10 of this embodiment, the through hole 13 has the first side surface 14a between the first surface 12a and the second side surface 14b, with the angle θ relative to the first surface 12a being less than 90 degrees, so that when the organic insulating film 15 is formed on the first surface 12a and the side surface 14 of the through hole 13, it is possible to prevent the organic insulating film 15 from becoming locally thin and reducing its insulating function. Therefore, a resonator device 1 with high insulation between the semiconductor substrate 12 and the conductor 16 that becomes the through electrode 6 can be obtained, and with excellent reliability.

[0020] Next, a method for manufacturing the circuit board 10 according to the first embodiment will be described with reference to FIGS. As shown in FIG. 5, the method for manufacturing the circuit board 10 of this embodiment includes a circuit board preparation step, a groove formation step, a through-hole formation step, an organic insulating film formation step, a conductor formation step, and a singulation step.

[0021] 1.1.Circuit board preparation process First, in step S101, a large circuit substrate 10 having a semiconductor substrate 12 is prepared in order to simultaneously manufacture a plurality of circuit substrates 10. The semiconductor substrate 12 is a single crystal silicon substrate, more specifically, a (100) single crystal silicon substrate.

[0022] 1.2.Groove formation process In step S102, as shown in FIG. 6, a photosensitive resin 30 such as resist is applied to the first surface 12a and the circuit 21 of the semiconductor substrate 12, and openings are formed by photolithography at positions where the through-holes 13 will be formed. Then, as shown in FIG. 7, anisotropic wet etching of silicon is performed using an etchant such as KOH or TMAH to form a bottomed groove 31 that is rectangular in plan view and has a first side surface 14a that tapers toward the second surface 12b. The depth d of the groove 31 is preferably 0.1 μm to 3 μm, more preferably 0.2 μm to 2 μm. If the depth is less than this range, the overhang between the silicon substrate and the photosensitive resin 30 will be small, and a catalyst film 32 such as Au, which is deposited in a subsequent process, will connect between the silicon substrate and the photosensitive resin 30, preventing lift-off. On the other hand, if the thickness is greater than this range, thin portions of the catalyst film 32 will be formed at the edges, resulting in isolated particles, which will cause the problem of numerous small holes being created around the opening of the through-hole 13 during the subsequent MACE (Metal Assisted Chemical Etching) processing.

[0023] 1.3.Through hole formation process In step S103, as shown in Fig. 8, a catalyst film 32 made of Au or the like is formed on the photosensitive resin 30 and on the inner bottom surface of the groove 31 by evaporation or sputtering, and the catalyst film 32 on the photosensitive resin 30 and the photosensitive resin 30 on the circuit 21 are removed by lift-off. Thereafter, as shown in Fig. 9, a through hole 13 is formed by MACE, having a second side surface 14b extending from the end of the first side surface 14a on the second surface 12b side toward the second surface 12b, and penetrating the first surface 12a and the second surface 12b. After removing the catalyst film 32 on the inner bottom surface of the through hole 13, the SiN film 17 and the SiO2 film 18 are etched to expose the Al film 19 as the inner bottom surface of the through hole 13, as shown in Fig. 10.

[0024] 1.4. Organic insulating film formation process 11, a photosensitive organic insulating film 15 made of liquid SiO2 is applied to the first surface 12a and the first and second side surfaces 14a, 14b of the through-holes 13. Thereafter, the photosensitive organic insulating film 15 applied to the inner bottom surfaces of the through-holes 13 is removed by exposure and development, thereby exposing the Al film 19 as the inner bottom surfaces of the through-holes 13, as shown in FIG. 12. In this way, the organic insulating film 15 is formed on the first surface 12a and the first and second side surfaces 14a, 14b of the through-holes 13.

[0025] 1.5. Conductor formation process 13, in step S105, a conductor 16 is formed on the side of the organic insulating film 15 opposite to the side surface 14 of the through hole 13 by a sputtering method, a plating method, a paste filling method, or the like. This completes the through electrode 6 having a tapered upper portion and a vertical lower portion.

[0026] 1.6.Singulation process In step S106, the large circuit board 10 on which the through electrodes 6 are formed is divided into individual pieces using a dicing device or the like.

[0027] By the method for manufacturing circuit board 10 of the present embodiment described above, it is possible to manufacture circuit board 10 having through electrodes 6 each having a tapered upper portion and a vertical lower portion. Because the upper portions of through electrodes 6 are tapered, when organic insulating film 15 is formed on first surface 12a and side surface 14 of through hole 13, organic insulating film 15 is locally thinned at the connection portion between first surface 12a and side surface 14 of through hole 13, and a decrease in insulating function can be prevented.

[0028] 2. Second embodiment Next, a resonation device 1a including a circuit board 10a according to a second embodiment will be described with reference to FIGS. 14, for the convenience of explaining the internal configuration, the lid 2 is removed. Also, in FIGS. 14 and 15, electrodes provided on the front and back surfaces of the vibration element 3 are not shown.

[0029] The circuit board 10a of this embodiment is similar to the circuit board 10 of the first embodiment, except that the configuration of the insulating films provided on the first surface 12a and on the side surfaces 14 of the through holes 13 is different from that of the circuit board 10 of the first embodiment. The following description will focus on the differences from the first embodiment described above, and similar items will be denoted by the same reference numerals and their description will be omitted.

[0030] As shown in Figures 14 and 15, the vibration device 1a of this embodiment has a circuit board 10a, a lid 2 joined to the circuit board 10a so as to house the vibration element 3 between the lid 2 and the circuit board 10a, and the vibration element 3 arranged on the first surface 12a of the circuit board 10a and electrically connected to the conductor 16.

[0031] 16 , the circuit board 10a includes a semiconductor substrate 12 having a first surface 12a and a second surface 12b located opposite the first surface 12a, a through hole 13 penetrating between the first surface 12a and the second surface 12b, an organic insulating film 15 disposed on the first surface 12a and a side surface 14 of the through hole 13, a conductor 16 disposed on the side of the organic insulating film 15 opposite the side surface 14 of the through hole 13, and an inorganic insulating film 15a disposed between the side surface 14 of the through hole 13 and the organic insulating film 15. In other words, the inorganic insulating film 15a and the organic insulating film 15 are disposed between the side surface 14 of the through hole 13 and the conductor 16.

[0032] With this configuration, the insulation between the conductor 16 that becomes the through electrode 6 and the semiconductor substrate 12 can be further improved, and the same effects as those of the circuit board 10 of the first embodiment can be obtained.

[0033] 3. Third embodiment Next, a resonation device 1b including a circuit board 10b according to a third embodiment will be described with reference to FIGS. 17, for the convenience of explaining the internal configuration, the lid 2 is removed. Also, in FIGS. 17 and 18, electrodes provided on the front and back surfaces of the vibration element 3 are not shown.

[0034] The circuit board 10b of this embodiment is similar to the circuit board 10 of the first embodiment except that the positions of the through electrodes 6 and 7 are different from those of the circuit board 10 of the first embodiment and that the vibration element 3 is mounted on a circuit 21. The following description will focus on the differences from the first embodiment described above, and similar items will be denoted by the same reference numerals and their description will be omitted.

[0035] As shown in Figures 17 and 18, the vibration device 1b of this embodiment has a circuit board 10b, a lid 2 joined to the circuit board 10b so as to house the vibration element 3 between the circuit board 10b, and the vibration element 3 arranged on the second surface 12b of the circuit board 10b and electrically connected to the conductor 23.

[0036] The circuit board 10b has a through electrode 7 which is a conductor 23 provided in a through hole 22 that is electrically connected to an internal terminal 24 provided on a circuit 21 on the second surface 12b side of the circuit board 10b, and a through electrode 6 which is a conductor 16 provided in a through hole 13 that is electrically connected to an external terminal 11 provided on an organic insulating film 15 on the first surface 12a side of the circuit board 10b. The circuit board 10b also has a semiconductor substrate 12 which has a first surface 12a and a second surface 12b located opposite the first surface 12a, a through hole 13 which penetrates between the first surface 12a and the second surface 12b, an organic insulating film 15 which is arranged on the first surface 12a and a side surface 14 of the through hole 13, and a conductor 16 which is arranged on the organic insulating film 15 on the side opposite to the side surface 14 of the through hole 13.

[0037] The lid 2 houses the vibration element 3 in the internal space S, and is joined via a joining member 4 onto the circuit 21 on the second surface 12b side of the circuit board 10b. The vibration element 3 is mechanically and electrically bonded onto an internal terminal 24 provided on the second surface 12b of the circuit board 10b via a bonding member 5 such as a gold bump.

[0038] With this configuration, it is possible to obtain the same effects as the circuit board 10 of the first embodiment. [Explanation of symbols]

[0039] 1, 1a, 1b... vibrating device, 2... lid, 3... vibrating element, 4... bonding member, 5... bonding member, 10, 10a, 10b... circuit board, 11... external terminal, 12... semiconductor substrate, 12a... first surface, 12b... second surface, 13... through hole, 14... side surface, 14a... first side surface, 14b... second side surface, 15... organic insulating film, 15a... inorganic insulating film, 16... conductor, 17... SiN film, 18... SiO2 film, 19... Al film, 20... SiN film, 21... circuit, 22... through hole, 23... conductor, 24... internal terminal, 30... photosensitive resin, 31... groove, 32... catalyst film, S... internal space, θ... angle.

Claims

1. a semiconductor substrate having a first surface and a second surface opposite the first surface; a through hole penetrating the first surface and the second surface; an organic insulating film disposed on the first surface and a side surface of the through hole; a conductor disposed on the opposite side of the through hole from the side surface of the organic insulating film, The side surface of the through hole is a first side surface connected to the first surface and narrowing in width from the first surface toward the second surface; a second side surface that is perpendicular to the first surface and is connected to the second surface from an end of the first side surface on the second surface side, a depth of the first side surface from the first surface is 0.1 μm or more and 3 μm or less; a depth of the second side surface to the second surface is greater than a depth of the first side surface from the first surface; Circuit board.

2. the semiconductor substrate is a single crystal silicon substrate, The through hole has a rectangular shape in a plan view. The circuit board according to claim 1 .

3. The single crystal silicon substrate is a (100) single crystal silicon substrate. The circuit board according to claim 2 .

4. an inorganic insulating film between the side surface of the through hole and the organic insulating film; The circuit board according to any one of claims 1 to 3.

5. The second surface has a circuit electrically connected to the conductor. The circuit board according to any one of claims 1 to 4.

6. a single crystal silicon substrate having a first surface and a second surface opposite the first surface; a through hole penetrating the first surface and the second surface; an organic insulating film disposed on the first surface and a side surface of the through hole; a conductor disposed on an opposite side of the through hole from the side surface of the organic insulating film, a circuit board preparation step of preparing the circuit board having the single crystal silicon substrate; a groove forming step of forming, in the first surface by wet etching, a groove with a bottom that is rectangular in plan view and has a first side surface whose width decreases toward the second surface and a depth from the first surface of 0.1 μm to 3 μm; a through-hole forming step of forming the through-hole that penetrates the first surface and the second surface, the through-hole having a second side surface that is perpendicular to the first surface and extends from an end of the first side surface on the second surface side toward the second surface, the depth of the second side surface to the second surface being greater than the depth of the first side surface from the first surface; an organic insulating film forming step of forming the organic insulating film on the first surface and the first and second side surfaces of the through hole; a conductor forming step of forming the conductor on the side of the organic insulating film opposite to the side of the through hole, A method for manufacturing a circuit board.

7. In the through hole forming step, the through holes are formed by a MACE method. The method for manufacturing a circuit board according to claim 6 .

8. The single crystal silicon substrate is a (100) single crystal silicon substrate. The method for manufacturing a circuit board according to claim 6 or 7.

9. The circuit board according to any one of claims 1 to 5; a vibration element disposed on the first surface or the second surface of the circuit board and electrically connected to the conductor; a lid joined to the circuit board so as to house the vibration element between the lid and the circuit board, Vibration device.

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