JP2897368B2 - Method for forming bump structure of semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bonding technique for electrically connecting a semiconductor device main body and an external lead electrode, and in particular, relates to
The present invention relates to an improvement in a method for forming a bump structure of a semiconductor device in which one end of a wiring member connected to an external lead electrode is mounted on a bonding pad formed on a semiconductor substrate.

[Conventional technology]

As a semiconductor device, as shown in FIG. 10, a p-type silicon substrate (a) and an n ⁺ region (b) formed by ions such as phosphorus and arsenic implanted on the surface of the silicon substrate (a)
A source electrode (S), a gate electrode (G), and a source electrode (S) formed on the silicon substrate (a) via the insulating film (c).
A MOS type semiconductor device whose main part is constituted by a drain electrode (D) or the like, or a p-type silicon substrate (a) as shown in FIG. 11 and appropriate ions implanted into this silicon substrate (a) are formed. N-type region (N) and P-type region (P)
-N-type region (N) and its main components such as emitter electrode (E), base electrode (B) and collector electrode (C) formed on silicon substrate (a) via insulating film (d) A bipolar semiconductor device constituting a part is generally known.

By the way, when these semiconductor devices are mounted, it is necessary to electrically connect an internal circuit of the semiconductor device and an external circuit provided outside the semiconductor device. The so-called method is adopted.

That is, as shown in FIG. 12, a bonding pad composed of a conductive material such as aluminum on the surface of a silicon substrate (a) and having a base end connected to various electrodes (f) of a semiconductor element (e) group as shown in FIG. (G), and one end of a metal wire (i) is bonded onto the bonding pad (g) by a wire bonding machine (h) as shown in FIGS. 13 (A) to 13 (D); In this method, the other end is connected to an external lead electrode (i) to electrically connect an internal circuit of the semiconductor device and an external circuit provided outside the semiconductor device as shown in FIG. The portion other than the bonding pad (g) is defined by an insulating oxide film (k) such as SiO ₂ .

However, since the "thermocompression bonding method" is a method of connecting a metal wire (i) to each bonding pad (g), there is a disadvantage that the bonding process takes time in a semiconductor device having a large number of electrodes. In addition, there is a disadvantage that the connection strength between the bonding pad (g) and the metal wire (i) tends to fluctuate and the reliability thereof is poor.

Therefore, in recent years, as a method of solving these drawbacks,
As shown in FIGS. 15A and 15B, a bump (m) as a protruding electrode is formed on the bonding pad (g), and the bump (m) is used as a wiring member as shown in FIG. A bonding method called a “TAB method” for performing bonding by continuously fusing the metal foil (n) has been developed.

In this method, the metal foil (n) can be simultaneously fused to a plurality of bumps (m) as compared with the above-mentioned "thermocompression bonding method". This has the advantage that the length can be reduced and the adhesive strength does not vary.

By the way, the formation of bumps in the “TAB method” has been conventionally performed as follows.

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

Next, as shown in FIG. 17 (E), the photoresist (r) is removed, and an etching process is applied to Au (q) and the Ti-W alloy (p) exposed from the electrodeposited film (s). Are sequentially removed, and a heat treatment is performed to form bumps (m) as shown in FIG. 17 (F).

[Problems to be solved by the invention]

However, when the above-mentioned metal foil (n) is simultaneously fused to a plurality of mushroom-shaped bumps (m) formed by this plating method, the bump (m) depends on the temperature and pressure at the time of fusion.
However, there is a problem that the adjacent bumps (m) come into contact with each other to cause a short circuit.

On the other hand, when the thickness of the bump (m) is increased to increase its mechanical strength, the electrodeposited film grows in the width direction (ie, the horizontal direction) simultaneously with the thickness direction. There is a disadvantage that the size of the bump is larger than that of the bonding pad (g), and the occupation area of the bump (m) becomes large, which makes the semiconductor device unsuitable for miniaturization.

[Means for solving 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 method for forming a bump structure having a small occupation area and causing no short circuit.

That is, the present invention relates to a bump structure of a semiconductor device in which one end of a wiring member connected to an external lead electrode is mounted on a bonding pad formed on a semiconductor substrate, and the bump structure is provided on the bonding pad. And a conductive bump body, and an insulating auxiliary member covering the outer surface of the bump body, and wherein the head of the bump body protrudes upward from the insulating auxiliary member. In the forming method, an auxiliary member forming step of forming an insulating auxiliary member formed of a heat-shrinkable insulating material and having an opening corresponding to a bonding pad; and a step of applying a conductive paste into the opening of the insulating auxiliary member. A filling step of filling to form a bump body; and a heat shrinking step of thermally shrinking the insulating auxiliary member to project a head of the bump body. It is characterized by that.

In the present invention, as the heat-shrinkable insulating material, an insulating material which causes volume shrinkage due to a volatilization phenomenon of a solvent contained in the material and a thermosetting phenomenon of the material can be used, for example, a photosensitive polyimide resin. , A polyamide resin, a silicone resin, a fluororesin, or the like can be used. Also,
The insulating auxiliary member made of this insulating material may be provided individually corresponding to one bump body, or an insulating layer is formed on the entire surface of the semiconductor device except for a portion where the bump body is formed, A configuration in which the insulating layer also individually serves as an insulating auxiliary member of the bump structure may be employed.
When the insulating auxiliary member is formed of an insulating layer covering the entire surface of the semiconductor device, the insulating coating can be used as a barrier layer from an external atmosphere and a buffer layer against external stress in the semiconductor element. ,
Moreover, there is an advantage that the formation can be simplified as compared with the configuration in which the insulating coatings are individually provided.

Further, as the conductive paste constituting the bump body, a heat-resistant material that can be filled in the opening of the insulating auxiliary member can be used, for example, Pb / Sn solder paste, In / Pn
A metal paste such as a solder paste can be used, and a screen printing technique can be applied as a method for filling the metal paste.

The dimension control in the height direction of the bump body is performed by appropriately adjusting the thickness of the insulating auxiliary member.

[Action]

According to the present invention, it is possible to reliably form a bump structure including a conductive bump main body erected on a bonding pad and an insulating auxiliary member that covers an outer surface of the bump main body. Since the bump main body is formed of a conductive paste without using the electrodeposition method, the horizontal expansion of the bump main body can be prevented, and the area occupied by the bump main body can be reduced.

In the case where such a bump structure is formed, the deformation of the bump structure when a wiring member such as a metal foil is fused is difficult to occur, and even if the deformation occurs, the adjacent bump structure may be deformed. Even if the bodies come into contact with each other, they are insulated by the insulating auxiliary member and do not cause a short circuit, and since the head of the bump main body projects above the insulating auxiliary member, Wiring members such as metal foil can be reliably fused.

〔Example〕

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

First Embodiment In this embodiment, the present invention is applied, and a bump structure (1) according to the embodiment includes a bonding pad (3) on a silicon substrate (2) as shown in FIGS. A bump body (4) formed on the surface and formed of a Pb / Sn solder paste, and a polyimide insulating auxiliary member (5) attached to the bump body (4) and covering the outer surface thereof. Its main part is formed, and the head side of the bump body (4) projects upward by about 5 to 10 μm above the surface of the insulating auxiliary member (5).

The bonding pad (3) is formed of aluminum, and is covered with a surface protection film (6) of a plasma nitride film (SiN _x ) except for a central portion thereof, and has a Ti-W alloy on its surface. A film (7) and an Au film (8) are formed.

According to the bump structure (1) according to this embodiment, the insulating auxiliary member (5) is provided on the outer surface of the bump body (4).
Since the mechanical strength is increased by an amount corresponding to the mounting of the bumps, the deformation is less likely to occur when the wiring member is fused to the head of the bump body (4), and the bumps are slightly deformed and adjacent bumps are formed. Even if the structures (1) come into contact with each other, they are insulated by the insulating auxiliary member (5) and do not cause a short circuit, and the head side of the bump body (4) is 5 to 5 times wider than the insulating auxiliary member (5). Since it protrudes upward by about 10 μm, it is possible to reliably fuse the wiring member.

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

[Method of Forming Bump Structure] This method is a method of forming a bump structure according to the first embodiment.

First, as shown in FIG. 3A, a plasma nitride film (Si
The bonding pad (3) made of aluminum exposed from the surface protective film (6) of N _x ) is sputter-etched to remove a natural oxide film formed on the surface thereof, and Ti-W is formed by sputtering. After continuously depositing the alloy film (7) and the Au film (8) (see FIG. 17B), a photoresist (r) is selectively applied to a 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 FIG. 3D), and a heat-shrinkable photosensitive film is formed on the entire surface. A conductive polyimide resin (provimid 348, manufactured by Ciba-Geigy Japan Co., Ltd.) (5 ') is applied by a spin coating method to a thickness of about 70 μm, and further through a photomask (M) as shown in FIG. 3 (E). After exposing the exposed portion to a solvent-insoluble type by irradiating light, the unexposed portion is dissolved and removed with a developing solution (trade name: QZ3301 manufactured by Nippon Ciba Geigy Co., Ltd.), and a rectangular shape is formed as shown in FIG. The insulating auxiliary member (5) having the opening (9) is formed.

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

Next, as shown in FIG. 4, Pb / Pb / Pb / is formed by a screen printing technique using a screen plate (11) having a substantially L-shaped opening (10) in which a portion corresponding to the bonding pad (3) is opened. Opening (9) of insulating auxiliary member (5) as shown in FIG. 3 (G) by applying Sn solder paste
Is filled with the above Pb / Sn solder paste (12), and
After drying, a polishing treatment is performed to remove the Pb / Sn solder paste (12) applied on the surface of the insulating auxiliary member (5) (FIG. 3H).
reference). In this case, since the excess Pb / Sn solder paste (12) applied on the surface of the insulating auxiliary member (5) can be easily removed by polishing, the shape of the opening (10) of the screen plate (11) is As shown in FIG. 4, a substantially L-shaped pattern corresponding to the arrangement of the bonding pads (3) is sufficient and does not require so precise alignment accuracy.

Next, the insulating auxiliary member (5) composed of the photosensitive polyimide resin is subjected to heat treatment in two stages under a temperature condition of about 140 ° C. and about 400 ° C. The solvent is volatilized and the resin is thermoset, and the volatilization phenomenon of the solvent and the thermosetting phenomenon of the resin cause volume contraction of the insulating auxiliary member (5).
Due to this volume contraction, the insulating auxiliary member (5) becomes 30 μm.
As shown in FIG. 3 (I), Pb / Sn
The head of the bump body (4) made of solder paste
The bump structure (1) according to the first embodiment protrudes upward by about 5 to 10 μm from the insulating auxiliary member (5).

According to this forming method, the bump structure (1) according to the first embodiment can be surely formed, and the bump body (4) is formed by the Pb / Sn solder paste.
During the heat treatment of the insulating auxiliary member (5), the bump body (4) melts and spreads slightly in the horizontal direction, but its spread is small and its occupied area can be reduced. There is no need to provide a new one.

Therefore, there is an advantage that the bump structure (1) having a small occupied area and causing no short circuit can be easily formed.

◎ Second Embodiment In the bump structure (1) according to this embodiment, the insulating auxiliary member constituting a part of each bump structure (1) is the fifth.
As shown in the figure, the structure is substantially the same as the bump structure according to the first embodiment except that it is also used by an insulating layer (50) made of polyimide resin formed on the entire surface of the semiconductor device.

That is, as shown in FIG. 5, the bump structure (1) is formed on the entire surface of the semiconductor device and has a rectangular opening (51) at a portion corresponding to each bonding pad (3). A layer (50) and a bump body (4) made of a Pb / Sn solder paste filled in the rectangular opening (51) and having a head side projecting about 5 to 10 μm above the surface of the insulating layer (50). The main part is constituted by (1) and (2), and the insulating auxiliary member of each bump structure (1) is also used by the insulating layer (50).

Also, similarly to the bump structure of the first embodiment, the bump structure (1) is unlikely to be deformed when the wiring member is attached, and the bump body (4) of each bump structure (1) is formed of an insulating layer ( Since each of the rectangular openings (51) provided in the bump structure (50) is partitioned, a short circuit between the bump structures (1) does not occur, and the head side of the bump body (4) is formed on the insulating layer (50). ) Since it protrudes about 5 to 10 μm above the surface, it is possible to reliably fuse the wiring member.

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

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

[Method of Forming Bump Structure] This method is a method of forming a bump structure according to the second embodiment.

That is, as shown in FIG. 6A, an insulating layer (50) made of a polyimide resin and having a rectangular opening (51) at a position corresponding to each bonding pad (3).
Is uniformly formed on the entire surface of the semiconductor device, and a Pb / Sn solder paste is applied by a screen printing technique to form a solder paste in the opening (51) of the insulating layer (50) as shown in FIG. 6 (B). (12) is filled, and then dried and polished to remove excess solder paste (12) applied on the insulating layer (50) (see FIG. 6C).

Next, RIE using an etching material for polyimide resin
After the treatment, only the surface side of the insulating layer (50) is etched to form a bump structure (1) as shown in FIG. 6 (D).

Also in this forming method, the bump structure (1) according to the second embodiment can be reliably formed, and since the bump body (4) is formed by the Pb / Sn solder paste, the insulating auxiliary member (5) is 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 newly provide a connection material during mounting. .

Therefore, there is an advantage that the bump structure (1) having a small occupied area and causing no short circuit can be easily formed.

Third Embodiment The bump structure (1) according to this embodiment is substantially the same as the bump structure according to the first embodiment except that the bump body (4) is formed by plating. is there.

That is, as shown in FIGS. 7 and 8, this bump structure (1) is erected on the surface of the bonding pad (3) of the silicon substrate (2) and is formed of a bump body (4) formed by Au plating. ) And a polyimide insulating auxiliary member (5) attached to the bump body (4) and covering the outer surface thereof, the main part of which is constituted. The head side of the bump body (4) is an insulating auxiliary member. (5) Mushrooms are projected upward by about 5 to 10 μm from the surface.

Also in the bump structure (1) according to this embodiment, the mechanical strength is increased by the amount of the insulating auxiliary member (5) attached to the outer surface of the bump body (4). (4) When the wiring member is fused to the head, the deformation is less likely to occur, and even if the deformation occurs slightly and the adjacent bump structures (1) come into contact with each other, the insulating auxiliary member (5) And the short side is not caused by the insulation, and the head side of the bump body (4) protrudes about 5 to 10 μm above the insulating auxiliary member (5), so that the wiring member can be securely fused. It becomes possible.

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

[Method of Forming Bump Structure] This method is a method of 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) are formed at a portion corresponding to the bonding pad (3) through a process similar to the forming process according to the first embodiment. ), And an insulating auxiliary member (5) made of polyimide resin having a rectangular opening (9) is formed at this position (see FIG. 9B).

Next, a bump body (4) having a mushroom-shaped head is grown in the opening (9) of the insulating auxiliary member (5) by Au plating to form a bump structure as shown in FIG. 9 (C). (1) is formed.

In this forming method, the bump body (4) is formed by a plating method. However, the horizontal extension can be suppressed by the inner wall surface of the opening (9) of the insulating auxiliary member (5). The occupied area can be reduced.

Therefore, there is an advantage that the bump structure (1) having a small occupied area and causing no short circuit can be easily formed.

〔The invention's effect〕

According to the present invention, it is possible to reliably form a bump structure including a conductive bump main body erected on a bonding pad and an insulating auxiliary member that covers an outer surface of the bump main body. The spread of the bump body in the horizontal direction can be prevented, and the area occupied by the bump body can be reduced.

Therefore, there is an effect that a bump structure having a small occupied area and causing no short circuit can be easily formed.

[Brief description of the drawings]

1 to 9 show an embodiment 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 II-II of FIG. 3 (A) to 3 (I) are process diagrams of forming a bump structure according to the first embodiment, FIG. 4 is a partially enlarged plan view of a screen plate used during the formation, and FIG. 5 is a second embodiment. FIGS. 6A to 6D are perspective views of a bump structure according to an example, FIGS. 6A to 6D are process diagrams of 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. FIG. 8 is a sectional view taken along the line VIII-VIII of FIG. 7, and FIGS. 9 (A) to 9 (C) are views showing the steps of forming a bump structure according to the third embodiment, respectively. And FIG. 11 are schematic structural views of a semiconductor device, FIG. 12 is a perspective view of a bonding pad, FIGS. 13 (A) to (D) are explanatory views of the steps of the thermocompression bonding method, and FIG. 15 (A) is a perspective view of a conventional bump structure, FIG. 15 (B) is a sectional view taken along the line BB of FIG. 15 (A), and FIG.
FIG. 16 is an explanatory view of a method of fusing a metal foil to a bump structure,
17 (A) to 17 (F) are process charts for forming a conventional bump structure. [Description of Symbols] (1) Bump structure (2) Silicon substrate (3) Bonding pad (4) Bump body (5) Insulating auxiliary member

Continuation of the front page (72) Inventor Hitoshi Kojima 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. Ebina Works (56) References JP-A-2-28932 (JP, A) JP-A-62-173740 (JP) , A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/60

Claims (1)

(57) [Claims] 1. A bump structure for a semiconductor device, wherein one end of a wiring member connected to an external lead electrode is mounted on a bonding pad formed on a semiconductor substrate, the bump structure standing on the bonding pad. Forming a bump structure having a conductive bump body and an insulating auxiliary member covering the outer surface of the bump body, and wherein the head of the bump body protrudes upward from the insulating auxiliary member. A method of forming an auxiliary auxiliary member formed of a heat-shrinkable insulating material and having an opening corresponding to a bonding pad; and filling a conductive paste in the opening of the auxiliary auxiliary member. And a heat shrinking step of thermally shrinking the insulating auxiliary member to project the head of the bump body. A method for forming a bump structure of a semiconductor device.