JPH0494131A - Bump structure of semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To prevent short by constituting the title structure of a conductive bump body, which is erected on a bonding pad, and an insulating auxiliary member, which covers the sides, and projecting the head of the bump body above the insulating auxiliary member. CONSTITUTION:The primary part is constituted of a bump body 4, which is erected on the bonding pad 3 face of a silicon substrate 2 and is made of Pb/Sn solder paste, and a polyimide insulating auxiliary member 5, which covers the outside, and the head side of the bump body 4 is projecting above the insulating auxiliary member 5 face. The insulating auxiliary member 5 is attached to the outside of the bump body 4, and the mechanical strength increases, so it becomes for deformation to occur, and even if the fellow bump structures contact with each other, those are insulated and it does not cause short, and besides since the head of the bump body l4 is projecting about 5-10mum above the insulating member 5, it becomes possible to reliably a wiring member together.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bonding technique for electrically connecting a semiconductor device main body and an external extraction electrode, and particularly relates to a bonding technique for electrically connecting a semiconductor device main body and an external lead electrode. The present invention relates to a bump structure of a semiconductor device to which one end of a wiring member connected to an external extraction electrode is attached, and a method for forming the bump structure.

[Conventional technology]

As shown in FIG. 10, the semiconductor device includes a p-type silicon substrate (a) and an n region (b) formed by ions of phosphorus, arsenic, etc. implanted into the surface of the silicon substrate (a).
and a source electrode (S) and a gate electrode (G) formed on the silicon substrate (a) surface via an insulating film (C), and
An MO3 type semiconductor device, the main part of which is composed of a drain electrode (D), etc., and a p-type silicon substrate (a) as shown in FIG. N-type region (N) ・P-type region C
・N-type region (N) and emitter electrode (E) formed on the silicon substrate (a) via the insulating film (d)
2. Description of the Related Art A bipolar semiconductor device is generally known, whose main parts include a base electrode (B), a collector electrode (C), and the like.

By the way, when these semiconductor devices are mounted, it is necessary to electrically connect the internal circuit of the semiconductor device and the external circuit provided on the outside of this semiconductor device, and the thermocompression bonding method 1 is used as a bonding method for this purpose. A method called ``is adopted.

That is, in this method, as shown in FIG. 12, bonding pads are formed on the surface of a silicon substrate (a) and are made of a conductive material such as aluminum and whose base ends are connected to various electrodes (f) of a group of semiconductor elements (e). (g), one end of the metal wire (i) is bonded onto the bonding pad (g) using a wire bonding machine (h) as shown in FIGS. 13(A) to (D), and This is a method of electrically connecting the internal circuit of the semiconductor device and the external circuit provided outside the semiconductor device by connecting the other end to the external extraction electrode (j), as shown in FIG. Incidentally, the portion other than the bonding pad (g) is divided by a 5-ins continuous oxide film (k).

However, since this thermocompression bonding method 1 connects a metal wire (i) to each bonding pad (g), it has the disadvantage that the bonding process takes a long time in the case of a semiconductor device with a large number of electrodes. Moreover, there was a drawback that the connection strength between the bonding pad (g) and the metal wire (i) was likely to vary and its reliability was poor.

Therefore, in recent years, as a method to eliminate these drawbacks, the first
As shown in Figures 5 (A) and (B), a bump (m), which is a protruding electrode, is formed on the bonding pad (g), and the bump (m) is connected to the wiring member as shown in Figure 1. A bonding method called fTAB method 1 has been developed in which bonding is performed by continuously fusing metal foils (n) of 1 to 100 nm.

In this method, metal foil (
Since the method can fuse bonding method n), it has the advantage that the time required for the bonding process can be shortened and the adhesive strength does not vary.

By the way, bump formation in this 1rTAB method 1 has conventionally been performed as follows.

That is, as shown in FIG. 17(A), a Ti-W alloy (p) and Au (q) are sequentially deposited on the entire surface of the semiconductor substrate (a) with the bonding pad (g) exposed by sputtering. (see FIG. 17B), and the semiconductor substrate (a) except for the portion corresponding to the bonding pad (g).
After forming a photoresist (r) on the entire surface (see FIG. 17C), Au plating is applied to form a mushroom-shaped electrodeposited film (s) as shown in FIG. 17(D).

Next, as shown in FIG. 17(E), a photoresist (
r) is removed and subjected to etching treatment to form an electrodeposited film (
After sequentially removing Au (Q) and Ti-W alloy (p) exposed from s), heat treatment was performed to form bumps (m) as shown in FIG. 17(F). .

[Problem to be solved by the invention]

However, when the metal foil (n) is simultaneously fused to a plurality of mushroom-shaped bumps (m) formed by this plating method, the bumps (m) are deformed due to the temperature and pressure during fusion. There is a problem in that adjacent bumps (m) may come into contact with each other, causing a short circuit.

On the other hand, if the thickness of the bump (m) is increased to increase its mechanical strength, the electrodeposited film will grow in the width direction (i.e. horizontal direction) as well as in the thickness direction.
There is a problem that the width of the bump (m) is larger than that of the bonding pad (g), and the area occupied by the bump (m) becomes large, making it unsuitable for miniaturization of semiconductor devices.

[Means to solve the problem]

The present invention has been made in view of the above problems, and an object of the present invention is to provide a bump structure that occupies a small area and does not cause short circuits, and a method for forming the same.

That is, the invention according to claim 1 is based on a bump structure of a semiconductor device in which one end of a wiring member that is arranged on a bonding pad formed on a semiconductor substrate and connected to an external extraction electrode is attached, It is composed of a conductive bump body erected above, and an insulating auxiliary member covering the outer surface of the bump body, and the head of the bump body protrudes upward from the insulating auxiliary member. It is characterized by the presence of

In the invention according to claim 1, any conductive material or insulating material suitable for the method for forming the bump body may be used as the conductive material constituting the bump body and the insulating material constituting the insulating auxiliary member. can. The latter insulating auxiliary member may be provided individually corresponding to the - bump body, or an insulating layer may be formed on the entire surface of the semiconductor device except for the area where the bump body is formed, and this insulating The layer may also serve as an insulating auxiliary member for each bump structure. In addition, when the above-mentioned insulating auxiliary member is constituted by an insulating layer that covers the entire surface of the semiconductor device, the above-mentioned insulating film can be used as a barrier layer from the external atmosphere in the semiconductor element and a buffer layer against external stress. Moreover, there is an advantage that the formation thereof can be simplified compared to a configuration in which the insulating auxiliary members are provided individually.

Next, the inventions according to claims 2 to 4 relate to a method suitable for forming the bump structure described in the invention according to claim 1, and the invention according to claim 2 comprises: heat-shrinkable insulation an auxiliary member forming step of forming an insulating auxiliary member made of a material and having an opening at a portion corresponding to the bonding pad; and a filling step of filling the opening of the insulating auxiliary member with conductive paste to form a bump body. and a heat shrinking step of heat shrinking the insulating auxiliary member to protrude the head of the bump body.

In the invention according to claim 2, the heat-shrinkable insulating material may be an insulating material that causes its volume to shrink due to the volatilization phenomenon of the solvent contained in the material and the thermosetting phenomenon of the material, such as a photosensitive material. Polyimide resin, polyamide resin, silicone resin, fluororesin, etc. can be used.

Further, as the conductive paste constituting the bump body, a heat-resistant material that can be filled into the opening of the insulating auxiliary member can be applied, such as Pb/Sn solder paste, I
Metal pastes such as n/Pb solder paste can be used;
Further, as a method for filling these metal pastes, a screen printing technique using a screen plate can be applied.

In addition, the invention according to claim 3 includes: forming an auxiliary member forming an insulating auxiliary member made of an insulating material and having an opening in a portion corresponding to a bonding pad; and an etching step of anisotropically etching only the surface side of the insulating auxiliary member to protrude the head of the bump body. It is something to do.

In the invention according to claim 3, the insulating material is preferably a photosensitive insulating material in consideration of the work of forming the insulating auxiliary member, such as photosensitive polyimide resin, photoresist material, siloxane resin, etc. The conductive paste that can be used and constitutes the bump body is as follows:
The metal pastes listed in the invention according to claim 2 can be applied.

Further, as an etching means for etching only the surface side of the insulating auxiliary member to make the head of the bump body protrude, RIE (reactive ion etching) method or the like can be applied.

Furthermore, the invention according to claim 4 includes: forming an auxiliary member forming an insulating auxiliary member made of an insulating material and having an opening at a portion corresponding to the ponding pad; The present invention is characterized by comprising an electrodeposition step of electrodepositing a metal material to form a bump body with a protruding head.

In the invention according to claims 2 to 4, the dimension of the bump body in the height direction is controlled by suitably adjusting the thickness of the insulating auxiliary member.

[Effect]

According to the invention according to claim 1, the bump structure is composed of a conductive bump body erected on the bonding pad, and an insulating auxiliary member covering the outer surface of the bump body. Therefore, deformation of the bump structure when wiring members such as metal foils are fused is less likely to occur, and even if deformation occurs and adjacent bump structures contact each other, they will not be insulated by the insulating auxiliary member. Moreover, since the head of the bump body protrudes above the insulating auxiliary member, wiring members such as metal foil can be reliably fused to the head of the bump body. becomes.

On the other hand, according to the invention according to claim 2, there is provided an auxiliary member forming step of forming an insulating auxiliary member made of a heat-shrinkable insulating material and having an opening at a portion corresponding to the bonding pad; 3. A filling step of filling a conductive paste into the opening of the bump body to form a bump body, and a heat shrinking step of heat-shrinking the insulating auxiliary member to protrude the head of the bump body, Claim 3 According to the invention according to the invention, there is provided an auxiliary member forming step of forming an insulating auxiliary member made of an insulating material and having an opening in a portion corresponding to a bonding pad, and applying a conductive paste into the opening of the insulating auxiliary member. The method further comprises: a filling step of filling the bump body to form a bump body; and an etching step of anisotropically etching only the surface side of the insulating auxiliary member to protrude the head of the bump body; According to the invention, an auxiliary member forming step of forming an insulating auxiliary member made of an insulating material and having an opening in a portion corresponding to a bonding pad, and a step of electrodepositing a metal material within the opening of the insulating auxiliary member. and an electrodeposition step of forming a bump body with a protruding head thereof, whereby the bump structure according to claim 1 can be reliably formed, and the bump structure according to claims 2 to 3 can be reliably formed. In the invention, since the bump body is formed from a conductive paste without using an electrodeposition method, it is possible to prevent the bump body from spreading in the horizontal direction and reduce its exclusive area.On the other hand, in the invention according to claim 4, Although the bump body is formed by the electrodeposition method, its horizontal spread can be suppressed by the inner wall surface of the opening of the insulating auxiliary member. It becomes possible to reduce the size.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

◎First Embodiment This embodiment is an application of the invention according to claim 1, and the bump structure (1) according to the embodiment is bonded to a silicon substrate (2) as shown in FIGS. Pad (3)
It consists of a bump body (4) erected on the surface and formed of Pb/Sn solder paste, and an insulating auxiliary member (5) made of polyimide attached to this bump body (4) and covering its outer surface. The main part is composed of the bump body (4
) head side is 5 to 10 μm from the surface of the insulating auxiliary member (5)
It protrudes upward to some extent.

The bonding pad (3) is made of aluminum, and is covered with a surface protection film (6) of plasma nitride film (SiN) except for the central part, and a Ti-W alloy is coated on the surface of the bonding pad (3). Film (7) and Au film (8)
is formed.

According to the bump structure (1) according to this embodiment, its mechanical strength is high due to the fact that the insulating auxiliary member (5) is attached to the outer surface of the bump body (4). When the wiring member is fused to the head of the bump body (4), deformation is unlikely to occur, and even if slight deformation occurs and adjacent bump structures (1) come into contact with each other, the insulating auxiliary member ( 5) will not cause a short circuit due to insulation, and since the head side of the bump body (4) protrudes approximately 5 to IO μm above the insulating auxiliary member (5), the wiring member can be reliably fused. becomes possible.

Therefore, there is an advantage that poor connection of the wiring member to the bump structure (1) and short-circuit phenomena between the bump structures (1) can be reliably prevented.

``Method 1 for Forming a Bump Structure'' This forming method is an application of the invention according to claim 2 as the method for forming the bump structure according to the first embodiment.

First, as shown in FIG. 3(A), a plasma nitride film (Si
The aluminum bonding pad (3) exposed from the surface protection film (6) of N, ) is subjected to sputter etching treatment to remove the natural oxide film formed on its surface.
And, the Ti-W alloy film (7) and A were formed by sputtering method.
After continuously depositing the u film (8) (see Figure 3C)
, a photoresist (r) is selectively formed on the portion corresponding to the bonding pad (3) (see FIG. 3C).
.

Next, the Au film (8) and the Ti-W alloy film (7) exposed from the photoresist (r) are removed by etching means (see Figure 3), and a heat-shrinkable photosensitive polyimide is coated on the entire surface. Resin (manufactured by Nippon Ciba-Geigi Co., Ltd., trade name Propimid 348) (5') was applied to a thickness of approximately 70 μm using a spin coating method, and then irradiated with light as shown in Figure 3 (E) through a photomask (M). After changing the exposed area to a solvent-insoluble type, the unexposed area is dissolved and removed using a developer (manufactured by Nippon Chiba Gaiki Co., Ltd., product name QZ3301) to form a rectangular opening as shown in FIG. 3(F). An insulating auxiliary member (5) having (9) is formed.

Incidentally, at this stage, the photosensitive polyimide resin has not yet been thermally cured.

Next, as shown in FIG.
) opening in the shape of an abbreviation (1
Pb/Sn solder paste is applied by screen printing technique using a screen plate (11) having a diameter of 0) to form an opening (
9) is filled with the above Pb/Sn solder paste (12), and polished after drying to form an insulating auxiliary member (5).
The Pb/Sn solder paste (12) applied on the surface is removed (see FIG. 3H). In this case, the excess Pb/Sn solder paste (12) applied on the surface of the insulating auxiliary member (5) can be easily removed by polishing, so the shape of the opening (10) of the screen plate (11) is As shown in FIG. 4, an abbreviated pattern corresponding to the arrangement of the bonding pads (3) is sufficient, and very precise alignment accuracy is not required.

Next, the insulating auxiliary member (5) made of the photosensitive polyimide resin was heat-treated in two stages under temperature conditions of about 140°C and about 400°C,
The solvent in the photosensitive polyimide resin is volatilized and the resin is thermally cured, causing volumetric contraction of the insulating auxiliary member (5) due to the volatilization of the solvent and the thermosetting phenomenon of the resin. Due to this volumetric contraction, the insulating auxiliary member (5)
Since the film is reduced by about 0 μm, the bump body (4) made of Pb/Sn solder paste is
) The head protrudes upward by about 5 to 10 μm from the insulating auxiliary member (5), forming the bump structure (1) according to the first embodiment.

According to this formation method, the bump structure (1) according to the first embodiment can be reliably formed, and since the bump body (4) is formed of Pb/Sn solder paste, the insulating auxiliary member ( During the heat treatment in step 5), the bump body (
4) Although it melts and spreads slightly in the horizontal direction, the spread is small and the occupied area can be reduced, and during mounting,
There is no need to newly provide connection material.

Therefore, it has the advantage that the bump structure (1) which occupies a small area and does not cause short circuit can be easily formed.

◎Second Example In the bump structure (1) according to this example, the insulating auxiliary member constituting a part of each bump structure (1) is
As shown in A, the bump structure and the path according to the first embodiment are the same except that they are also used by an insulating layer (50) made of polyimide resin formed over the entire surface of the semiconductor device.

That is, this bump structure (1) is formed on the entire surface of the semiconductor device as shown in FIG. layer (50), and an insulating layer (50) filled in the rectangular opening (51) and on the head side thereof.
Pb/S protrudes above the surface by about 5 to 10μm
The main part thereof is composed of a bump body (4) made of n-solder paste, and the insulating layer (50) also serves as an insulating auxiliary member of each bump structure (1).

Similarly to the bump structure of the first embodiment, this bump structure (1) is also difficult to deform at times when wiring members are attached, and the bump body (4) of each bump structure (1) is made of an insulating layer. Since the bump structures (1) are partitioned by rectangular openings (51) provided in the bump structures (50), short circuits between the bump structures (1) will not occur. 50) Since it protrudes upward from the surface by about 5 to 10 μm, it becomes possible to reliably fuse the wiring member.

Therefore, there is an advantage that poor connection of the wiring member to the bump structure (1) and short-circuit phenomena between the bump structures (1) can be reliably prevented.

Furthermore, since the entire surface of the semiconductor device is covered with the insulating layer (50), it has the advantage that the insulating layer (50) can be used as a barrier layer from the external atmosphere in the semiconductor element and as a buffer layer against external stress. .

r Bump Structure Forming Method 1 This forming method is an application of the invention according to claim 3 as a forming method of the bump structure according to the second embodiment.

That is, as shown in FIG. 6(A), an insulating layer (50) is made of polyimide resin and has a rectangular opening (51) at a portion corresponding to each bonding pad (3).
) is uniformly formed over the entire surface of the semiconductor device, Pb/Sn solder paste is applied using screen printing technology to form openings (51) in the insulating layer (50) as shown in FIG. 6(B).
The inside is filled with solder paste (12), and then, after drying, polishing is performed to remove excess solder paste (12) applied on the insulating layer (50) (see FIG. 6C).

Next, RIE using etching material for polyimide resin.
A bump structure (1) as shown in FIG. 6(D) is formed by etching only the surface side of the insulating layer (50).

Also, in this formation method, the bump structure (1) according to the second embodiment can be reliably formed, and since the bump body (4) is formed of Pb/Sn solder paste, the insulating auxiliary member (5) can be reliably formed. ) During the heat treatment, the bump body (4) melts and spreads slightly in the horizontal direction, but the spread is small and the occupied area can be reduced, and there is no need to provide additional connection material during mounting. .

Therefore, it has the advantage that the bump structure (1) which occupies a small area and does not cause short circuit can be easily formed.

◎Third Embodiment The bump structure (1) according to this embodiment is similar to the bump structure according to the first embodiment except that the bump body (4) is formed by the plating method. It is.

That is, as shown in FIGS. 7 and 8, this bump structure (1) is erected on the bonding pad (3) surface of the silicon substrate (2) and has a bump body (4) formed of Au plating. ), and an insulating auxiliary member (5) made of polyimide that is attached to the bump body (4) and covers its outer surface.
), and the head side of the bump body (4) protrudes above the surface of the insulating auxiliary member (5) in a mushroom shape by about 5 to IO μm.

Also in the bump structure (1) according to this embodiment, an insulating auxiliary member (5) is provided on the outer surface of the bump body (4).
Since the mechanical strength of the bump body (4) increases as the wiring member is attached, deformation is less likely to occur when the wiring member is fused to the head of the bump body (4). Even if the structures (1) come into contact with each other, they are insulated by the insulating auxiliary member (5) and will not cause a short circuit, and the head side of the bump body (4) is 5 to Since it protrudes upward by about IO μm, it is possible to reliably fuse the wiring member.

Therefore, there is an advantage that poor connection of the wiring member to the bump structure (1) and short-circuit phenomena between the bump structures (1) can be reliably prevented.

``Method 1 for forming a bump structure'' This forming method is an application of the invention according to claim 4 as a method for forming a bump structure according to the third embodiment.

That is, as shown in FIG. 9(A), a Ti-W alloy film (7) and an Au film (
8) is selectively deposited and has a rectangular opening (9) in this area.
5) (see Figure 6C).

Next, Au plating treatment was performed to form the insulating auxiliary member (5).
) inside the opening (9) of the bump body (
4) to form a bump structure (1) as shown in FIG. 9(C).

In this formation method, the bump body (4) is formed by the plating method, but its horizontal spread can be suppressed by the inner wall surface of the opening (9) of the insulating auxiliary member (5). The exclusive area can be reduced.

Therefore, it has the advantage that the bump structure (1) that occupies a small area (and does not cause short circuits) can be easily formed.

〔Effect of the invention〕

According to the invention according to claim 1, deformation of the bump structure when wiring members such as metal foils are fused is less likely to occur, and even if deformation occurs and adjacent bump structures come into contact with each other, The insulating auxiliary member provides insulation so that no short circuit occurs, and furthermore, it becomes possible to reliably fuse a wiring member such as metal foil to the head of the bump body.

Therefore, it is possible to reliably prevent poor connection of the wiring member to the bump structure and short circuit between the bump structures.

On the other hand, according to the inventions according to claims 2 to 4, the bump structure described in claim 1 can be reliably formed, and the horizontal expansion of the bump body can be prevented, and the area can be reduced exclusively. .

Therefore, it is possible to easily form a bump structure that occupies a small area and does not cause short circuits.

[Brief explanation of drawings]

1 to 9 show embodiments of the present invention, FIG. 1 is a perspective view of a bump structure according to the first embodiment, FIG. 2 is a sectional view taken along the line ■-■ of FIG. 1, 3(A) to (1) are process diagrams for forming the bump structure according to the first embodiment, FIG. 4 is a partially enlarged plan view of the screen plate used during the formation, and FIG. A perspective view of a bump structure according to an example, FIG.
) to (D) are process diagrams for forming a bump structure according to a second embodiment, and FIG. 7 is a perspective view of a bump structure according to a third embodiment.
Figure 8 is a sectional view taken along the line ■-■ of Figure 7, and Figures 9 (A) to (C
10 and 11 are schematic configuration diagrams of a semiconductor device, FIG. 12 is a perspective view of a bonding pad, and FIG. 13 ( A) to (D) are process explanatory diagrams of the thermocompression bonding method, FIG. 14 is a perspective view of a bonding pad after bonding, FIG. 15(A) is a perspective view of a conventional bump structure, and FIG. 15(B) ) is a cross-sectional view taken along line B-B of FIG. 15(A), FIG. 16 is an explanatory diagram of the method of fusing metal foil to the bump structure, and FIGS. 17(A) to (F) are conventional bump structures. It is a diagram of the body formation process. [Explanation of symbols] (1) Bump structure (2) Silicon substrate (3) Bonding pad (4) Bump body (5) Insulating auxiliary member Fig. 3 Figure 2 Figure Figure 4 Figure Figure Figure Figure 10 Figure 11 Figure Figure 12 Figure 13 (A) (B) (C) (D) Figure 15 (A) Figure 15 Figure (B) Figure 14 Figure 16 (A) (F) Figure 17

Claims (4)

[Claims] (1) In a bump structure of a semiconductor device to which one end of a wiring member placed on a bonding pad formed on a semiconductor substrate and connected to an external extraction electrode is attached, a conductive bump structure provided upright on the bonding pad is attached. A semiconductor device comprising: a bump main body; and an insulating auxiliary member covering an outer surface of the bump main body, the head of the bump main body protruding upward from the insulating auxiliary member. Bump structure. (2) In the method for forming a bump structure described in claim (1), an insulating auxiliary member is formed of a heat-shrinkable insulating material and has an opening at a portion corresponding to a bonding pad. a filling step of filling the opening of the insulating auxiliary member with a conductive paste to form a bump body; and heat-shrinking the insulating auxiliary member to protrude the head of the bump body. A method for forming a bump structure, comprising the steps of: heating and shrinking. (3) In the method for forming a bump structure described in claim (1), an auxiliary member forming an insulating auxiliary member made of an insulating material and having an opening at a portion corresponding to a bonding pad. a filling step of filling the opening of the insulating auxiliary member with a conductive paste to form a bump body, and anisotropically etching only the surface side of the insulating auxiliary member to form the head of the bump body. A method for forming a bump structure, comprising: an etching step for protruding the bump structure. (4) In the method for forming a bump structure described in claim (1), an auxiliary member forming an insulating auxiliary member made of an insulating material and having an opening at a portion corresponding to a bonding pad. Formation of a bump structure comprising: a forming step; and an electrodeposition step of electrodepositing a metal material in the opening of the insulating auxiliary member to form a bump body with a protruding head. Method.