JP2024081398A - Manufacturing method of semiconductor circuit board and semiconductor circuit board - Google Patents

Abstract

To provide a manufacturing method of a semiconductor circuit board capable of suppressing occurrence of creeping discharge caused by a joint material.SOLUTION: A manufacturing method of a semiconductor circuit board includes a preparation step and a surface processing step. In the preparation step, prepared is a substrate joint body in which an insulative second substrate is joined onto a conductive first substrate and a metal plate is joined onto the second substrate via a conductive joint material. In the surface processing step, surface processing is performed by irradiating a portion, which is not overlapped with the metal plate, of the joint material provided in the substrate joint body with a laser beam.SELECTED DRAWING: Figure 4

Description

Embodiments of the present invention relate to a method for manufacturing a semiconductor circuit board and a semiconductor circuit board.

It is known that a semiconductor circuit board is used in a power module or the like, in which an insulating second board is bonded onto a conductive first board, and a metal plate is bonded onto the second board via a conductive bonding material. In such semiconductor circuit boards, it is necessary to suppress the occurrence of creeping discharge caused by the bonding material.

JP 2000-349400 A

The problem that the present invention aims to solve is to provide a manufacturing method for a semiconductor circuit board and a semiconductor circuit board that can suppress the occurrence of creeping discharge caused by bonding materials.

The manufacturing method of the semiconductor circuit board according to the embodiment includes a preparation step and a surface treatment step. In the preparation step, a substrate assembly is prepared in which an insulating second substrate is bonded onto a conductive first substrate, and a metal plate is bonded onto the second substrate via a conductive bonding material. In the surface treatment step, a surface treatment is performed by irradiating a laser beam onto a portion of the bonding material provided on the substrate assembly that does not overlap with the metal plate.

1A and 1B are cross-sectional views illustrating a semiconductor circuit substrate according to an embodiment. 2A and 2B are cross-sectional views showing a preparation step of the method for manufacturing a semiconductor circuit substrate according to the embodiment. 5A to 5C are plan views illustrating a surface treatment step in the method for manufacturing a semiconductor circuit substrate according to the embodiment. 5A to 5C are plan views illustrating a surface treatment step in the method for manufacturing a semiconductor circuit substrate according to the embodiment. 1 is a graph showing the relationship between the wavelength and absorptance of laser light in silver and copper. FIG. 13 is an explanatory diagram of an experimental example. 1 is an electron microscope photograph of a bonding material after irradiation with laser light in Experimental Example 1. 11 is an electron microscope photograph of the bonding material after laser light irradiation in Experimental Example 2. 13 is an electron microscope photograph of the bonding material after laser light irradiation in Experimental Example 3. 13 is an electron microscope photograph of the bonding material after laser light irradiation in Experimental Example 4.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing.
In this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals and detailed descriptions thereof will be omitted as appropriate.

1A and 1B are cross-sectional views illustrating a semiconductor circuit substrate according to an embodiment.
FIG. 1B is an enlarged view of a region R1 shown in FIG.
1A, a semiconductor circuit substrate 100 according to the embodiment includes a first substrate 10, a second substrate 20, a metal plate 30, and a bonding material 40. In this example, the semiconductor circuit substrate 100 further includes another metal plate 50, solder 60, and a sealing material 90.

The semiconductor circuit substrate 100 is, for example, an insulating circuit substrate. The semiconductor circuit substrate 100 is used, for example, in a power module.

The first substrate 10 is conductive. The first substrate 10 includes, for example, aluminum (Al). The first substrate 10 includes, for example, silicon carbide particle reinforced aluminum composite (AlSiC).

The second substrate 20 is provided on the first substrate 10. The second substrate 20 is insulating. The second substrate 20 includes, for example, ceramic. The second substrate 20 includes, for example, at least one of silicon nitride (Si ₃ N ₄ ) and aluminum nitride (AlN).

In the following description, the direction connecting the first substrate 10 and the second substrate 20 is referred to as the "stacking direction." For ease of description, the direction from the first substrate 10 to the second substrate 20 is referred to as the "upper" direction, and the direction from the second substrate 20 to the first substrate 10 is referred to as the "lower" direction.

The metal plate 30 is provided on the second substrate 20. The second substrate 20 is located between the first substrate 10 and the metal plate 30 in the stacking direction. The metal plate 30 contains a metal. The metal plate 30 contains, for example, at least one of copper (Cu) and aluminum (Al). The metal plate 30 is smaller than the second substrate 20 in a planar view. The outer peripheral edge 30a of the metal plate 30 is located inside the outer peripheral edge 20a of the second substrate 20 in a planar view.

The bonding material 40 is provided between the second substrate 20 and the metal plate 30 in the stacking direction. The bonding material 40 bonds the second substrate 20 and the metal plate 30. The bonding material 40 is conductive. The bonding material 40 contains, for example, silver (Ag). The bonding material 40 is provided so that no gap is generated between the second substrate 20 and the metal plate 30. The bonding material 40 is provided in an area wider than the outer peripheral edge 30a of the metal plate 30.

1B, the bonding material 40 has a first portion 41 and a second portion 42. The first portion 41 overlaps with the metal plate 30 in the stacking direction. That is, the first portion 41 is located between the second substrate 20 and the metal plate 30 in the stacking direction. The first portion 41 contacts the second substrate 20 and the metal plate 30. The second portion 42 does not overlap with the metal plate 30 in the stacking direction. The second portion 42 contacts the second substrate 20. The second portion 42 does not contact the metal plate 30. The first portion 41 is located inside the outer peripheral edge 30a of the metal plate 30 in a plan view. The second portion 42 is located outside the outer peripheral edge 30a of the metal plate 30 in a plan view. The second portion 42 is a portion of the bonding material 40 that protrudes from the metal plate 30.

The second portion 42 is surface-treated by irradiation with laser light. Surface treatment by irradiation with laser light will be described later.

The other metal plate 50 is provided below the second substrate 20. The other metal plate 50 is located between the first substrate 10 and the second substrate 20 in the stacking direction. The other metal plate 50 includes a metal. The other metal plate 50 includes, for example, at least one of copper (Cu) and aluminum (Al). The other metal plate 50 is provided as necessary and can be omitted.

The solder 60 is provided under the other metal plate 50. The solder 60 is located between the first substrate 10 and the other metal plate 50 in the stacking direction. The solder 60 contains, for example, at least one of tin (Sn), silver (Ag), and copper (Cu). The solder 60 is provided as necessary and can be omitted.

The sealing material 90 seals the solder 60, the other metal plate 50, the second substrate 20, the bonding material 40, and the metal plate 30, which are layered on the first substrate 10. The sealing material 90 contains a gel-like resin.

Hereinafter, a method for manufacturing a semiconductor circuit substrate according to an embodiment will be described.
2A and 2B are cross-sectional views showing a preparation step of the method for manufacturing a semiconductor circuit substrate according to the embodiment.
FIG. 2B is an enlarged view of a region R2 shown in FIG.
3 and 4 are plan views showing a surface treatment step in the method for manufacturing a semiconductor circuit substrate according to the embodiment.
As shown in FIGS. 2A, 2B, 3, and 4, the method for manufacturing a semiconductor circuit substrate according to the embodiment includes a preparation step and a surface treatment step.

In the method for manufacturing a semiconductor circuit board according to the embodiment, a preparation step is first performed. As shown in FIG. 2(a), in the preparation step, a substrate assembly 80 is prepared. The substrate assembly 80 has a structure in which a second substrate 20 is bonded onto a first substrate 10, and a metal plate 30 is bonded onto the second substrate 20 via a bonding material 40.

The preparation process includes, for example, a first process of bonding a metal plate 30 onto the second substrate 20 via a bonding material 40 and bonding a metal plate 50 onto the second substrate 20 via the bonding material 40, and a second process of bonding the second substrate 20 onto the first substrate 10. When using a substrate that is sold with the metal plate 30 and the metal plate 50 bonded to the second substrate 20 (for example, a SiN substrate with copper clad on both sides), the first process may be omitted.

As shown in FIG. 2(b), when bonding the metal plate 30 onto the second substrate 20 via the bonding material 40, the bonding material 40 is provided over an area wider than the outer peripheral edge 30a of the metal plate 30. In other words, after bonding, the bonding material 40 has a portion (first portion 41) that overlaps with the metal plate 30 and a portion (second portion 42) that does not overlap with the metal plate 30. The second portion 42 is the portion of the bonding material 40 that protrudes from the metal plate 30.

As shown in FIG. 2(a), if there is a second portion 42 of the bonding material 40 (a portion that protrudes from the metal plate 30) in the substrate bonded body 80, creeping discharge may occur, as indicated by the dashed arrow.

Therefore, in the method for manufacturing a semiconductor circuit board according to the embodiment, a surface treatment process is performed after the preparation process. As shown in Figs. 3 and 4, in the surface treatment process, a portion (second portion 42) of the bonding material 40 provided on the substrate bonded body 80 that does not overlap with the metal plate 30 is irradiated with laser light to perform surface treatment.

3 shows the second portion 42x that is not irradiated with laser light (i.e., surface treatment has not been performed). FIG. 4 shows the second portion 42y that is irradiated with laser light (i.e., surface treatment has been performed). Also, in FIG. 3 and FIG. 4, the area to be irradiated with laser light is shown by a dashed line. The laser light is irradiated to an area including at least the outer peripheral edge 42a of the second portion 42. The outer peripheral edge 42a of the second portion 42 is the boundary between the second portion 42 and the second substrate 20 in a plan view. The laser light is irradiated, for example, to the entire second portion 42. Also, the laser light is irradiated to the second portion 42 along the outer peripheral edge 30a of the metal plate 30, for example. The outer peripheral edge 30a of the metal plate 30 is the boundary between the metal plate 30 and the second portion 42 in a plan view.

As shown in Figures 3 and 4, by performing surface treatment by irradiating the second portion 42 with laser light, the shape of the outer peripheral end 42a of the second portion 42 becomes gentler. In other words, by performing surface treatment by irradiating the second portion 42 with laser light, the unevenness of the shape of the outer peripheral end 42a of the second portion 42 becomes smaller. This reduces the extreme outward protrusion of the outer peripheral end 42a of the second portion 42, which causes creeping discharge, and suppresses the occurrence of creeping discharge caused by the second portion 42 (bonding material 40).

In an embodiment, at least a portion of the second portion 42 may be removed by surface treatment. For example, at least a portion of the second portion 42 can be removed by adjusting the output or wavelength of the laser light. By removing at least a portion of the second portion 42, the occurrence of creeping discharge caused by the second portion 42 can be more reliably suppressed.

The laser device that irradiates the laser light used for surface treatment is, for example, a pulsed laser device that oscillates a pulsed output at a constant repetition frequency (pulse width). The pulse width is preferably several picoseconds. In other words, the laser light is preferably irradiated from a so-called picosecond laser device. By performing surface treatment with laser light irradiated from a picosecond laser device, damage to the second substrate 20 and the metal plate 30 can be suppressed.

The wavelength of the laser light used for the surface treatment is preferably selected based on, for example, the material of the metal plate 30 and the material of the joining material 40. The wavelength of the laser light used for the surface treatment is preferably a wavelength at which the absorption rate of the joining material 40 is greater than the absorption rate of the metal plate 30.

FIG. 5 is a graph showing the relationship between the wavelength of laser light and the absorptance in silver and copper.
In FIG. 5, the relationship between the wavelength of the laser light and the absorptance in silver is shown by a solid line, and the relationship between the wavelength of the laser light and the absorptance in copper is shown by a dashed line.
5, when the wavelength of the laser light is in the range of 300 nm or more and 400 nm or less, the absorptance in silver is higher than the absorptance in copper. When the wavelength of the laser light is about 355 nm, the difference between the absorptance in silver and the absorptance in copper is the largest.

For this reason, when the material of the metal plate 30 is copper and the material of the bonding material 40 is silver, the wavelength of the laser light used for the surface treatment is preferably 300 nm or more and 400 nm or less, and more preferably about 355 nm. With such a wavelength, the surface treatment of the second portion 42 (bonding material 40) can be efficiently performed while suppressing damage to the metal plate 30.

The method for manufacturing a semiconductor circuit board according to the embodiment may further include a sealing step after the surface treatment step. In the sealing step, for example, a part of the substrate assembly 80 (solder 60, another metal plate 50, second substrate 20, bonding material 40, and metal plate 30) is sealed with a sealing material 90. This produces the semiconductor circuit board 100 according to the embodiment.

Experimental examples will now be described.
FIG. 6 is an explanatory diagram of an experimental example.
FIG. 7 is an electron microscope photograph of the bonding material after irradiation with laser light in Experimental Example 1.
FIG. 8 is an electron microscope photograph of the bonding material after irradiation with laser light in Experimental Example 2.
FIG. 9 is an electron microscope photograph of the bonding material after irradiation with laser light in Experimental Example 3.
As shown in FIG. 6, in Experimental Examples 1 to 3, a sample having a structure in which a copper metal plate 30 was bonded to an aluminum nitride second substrate 20 via a silver bonding material 40 was prepared. Next, at four points of this sample, a part of the second portion 42 was irradiated with laser light under the conditions of Experimental Examples 1 to 3 below. In FIG. 6, the region irradiated with the laser light is indicated by a dashed line. As shown in FIG. 6, in Experimental Examples 1 to 3, a part of the second portion 42 was irradiated with laser light along a direction perpendicular to the outer peripheral edge 30a of the metal plate 30. Results of photographing the region R3 with an electron microscope after irradiation with laser light are shown in FIG. 7 to FIG. 9.

In Experimental Examples 1 to 3, the laser light was irradiated under the following conditions.
(Common conditions)
Wavelength: 532 nm
Pulse width: 15 picoseconds Beam diameter: 33 μm
Focus position: 294.5 mm from the end of the scanner lens to the bottom of the plate, plate thickness assumed to be 1.5 mm (Experimental Example 1)
Atte: 82%
Output: 0.9318W
Repetition: 200kHz
Speed: 100 mm/s
Number of irradiations: 1 (Experimental Example 2)
Atte: 90%
Output: 0.3166W
Repetition: 200kHz
Speed: 100 mm/s
Number of irradiations: 1 (Experimental Example 3)
Atte: 91%
Output: 0.2397W
Repetition: 200kHz
Speed: 100 mm/s
Number of exposures: 1

As shown in Figures 7 to 9, the shape of the outer peripheral edge 42a is gentler in the second portion 42y irradiated with the laser light than in the second portion 42x not irradiated with the laser light. In other words, the shape of the outer peripheral edge 42a is less irregular in the second portion 42y irradiated with the laser light than in the second portion 42x not irradiated with the laser light. From this, for example, if the shape of the outer peripheral edge 42a is less irregular, it can be determined that surface treatment has been performed by irradiating with laser light.

In addition, as shown in Figures 7 to 9, the second portion 42y irradiated with the laser light has smaller irregularities in the stacking direction than the second portion 42x not irradiated with the laser light. From this, for example, if the irregularities in the stacking direction of the second portion 42 are smaller, it can be determined that surface treatment has been performed by irradiating with laser light.

In addition, as shown in Figures 7 to 9, a striped pattern is formed in the second portion 42y irradiated with the laser light by surface treatment using the laser light irradiation. From this, for example, if a striped pattern is formed in the second portion 42, it can be determined that surface treatment using the laser light irradiation has been performed.

FIG. 10 is an electron microscope photograph of the bonding material after irradiation with laser light in Experimental Example 4.
In the fourth experimental example, laser light irradiation was performed in the same manner as in the first experimental example, except that the output of the laser light was made larger than that in the first experimental example.

As shown in FIG. 10, in the second portion 42y irradiated with the laser light, a portion of the second portion 42 is removed by the surface treatment by irradiating with the laser light. From this, for example, if at least a portion of the second portion 42 is removed, it can be determined that the surface treatment by irradiating with the laser light has been performed.

The embodiment may include the following configurations:

(Configuration 1)
a preparation step of preparing a substrate assembly in which an insulating second substrate is bonded onto a conductive first substrate, and a metal plate is bonded onto the second substrate via a conductive bonding material;
a surface treatment process for performing a surface treatment on a portion of the bonding material provided on the substrate bonded body that does not overlap with the metal plate by irradiating the portion with a laser light;
A method for manufacturing a semiconductor circuit substrate comprising the steps of:

(Configuration 2)
2. The method of claim 1, wherein the second substrate comprises ceramic.

(Configuration 3)
3. The method for manufacturing a semiconductor circuit substrate according to claim 2, wherein the second substrate includes at least one of silicon nitride and aluminum nitride.

(Configuration 4)
the metal plate includes copper;
The method for manufacturing a semiconductor circuit substrate according to any one of configurations 1 to 3, wherein the bonding material contains silver.

(Configuration 5)
5. The method for manufacturing a semiconductor circuit substrate according to claim 4, wherein the wavelength of the laser light is 300 nm or more and 400 nm or less.

(Configuration 6)
6. The method for manufacturing a semiconductor circuit substrate according to any one of configurations 1 to 5, wherein the laser light is emitted from a picosecond laser device.

(Configuration 7)
A conductive first substrate;
an insulating second substrate provided on the first substrate;
A metal plate provided on the second substrate;
a conductive bonding material provided between the second substrate and the metal plate and bonding the second substrate and the metal plate;
Equipped with
The bonding material has a first portion overlapping the metal plate and a second portion not overlapping the metal plate,
The second portion of the semiconductor circuit substrate is surface-treated by irradiation with laser light.

As described above, the embodiment provides a method for manufacturing a semiconductor circuit board and a semiconductor circuit board that can suppress the occurrence of creeping discharge caused by the bonding material.

Although an embodiment of the present invention has been illustrated above, this embodiment is presented as an example and is not intended to limit the scope of the invention. This new embodiment can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the gist of the invention. This embodiment and its variations are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

10: First substrate 20: Second substrate 20a: Outer peripheral edge 30: Metal plate 30a: Outer peripheral edge 40: Joining material 41: First portion 42: Second portion 42a: Outer peripheral edge 42x: Second portion not irradiated with laser light 42y: Second portion irradiated with laser light 50: Another metal plate 60: Solder 80: Substrate assembly 90: Sealing material 100: Semiconductor circuit substrate

Claims (7)

a preparation step of preparing a substrate assembly in which an insulating second substrate is bonded onto a conductive first substrate, and a metal plate is bonded onto the second substrate via a conductive bonding material;
a surface treatment process for performing a surface treatment on a portion of the bonding material provided on the substrate bonded body that does not overlap with the metal plate by irradiating the portion with a laser light;
A method for manufacturing a semiconductor circuit substrate comprising the steps of: The method for manufacturing a semiconductor circuit board according to claim 1, wherein the second substrate includes ceramic. The method for manufacturing a semiconductor circuit board according to claim 2, wherein the second substrate includes at least one of silicon nitride and aluminum nitride. the metal plate includes copper;
The method for manufacturing a semiconductor circuit board according to claim 1 , wherein the bonding material contains silver. The method for manufacturing a semiconductor circuit board according to claim 4, wherein the wavelength of the laser light is 300 nm or more and 400 nm or less. The method for manufacturing a semiconductor circuit board according to claim 1, wherein the laser light is emitted from a picosecond laser device. A conductive first substrate;
an insulating second substrate provided on the first substrate;
A metal plate provided on the second substrate;
a conductive bonding material provided between the second substrate and the metal plate and bonding the second substrate and the metal plate;
Equipped with
The bonding material has a first portion overlapping the metal plate and a second portion not overlapping the metal plate,
The second portion of the semiconductor circuit substrate is surface-treated by irradiation with laser light.

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