JPH09330932A - Bump formation body and formation of bump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form single-layer or multilayer sprayed metal thick films in a short time by a method wherein the single-layer or multilayer sprayed metal thick films are selectively made to form on parts of an electronic component by a plasma spraying method and a bump is formed. SOLUTION: A photosensitive resist film 8 is pasted on the surface of an IC or LSI wafer subsequent to the end of a wafer process and thereafter, an exposure is performed in such a way as to open pad pattern parts to make openings 9 form in the pad parts in an area largish than a pad size. Then, Cr or Ti thin films are deposited as base metal layers 4 by a deposition method and the whole surface of the wafer is subjected to plasma spraying of Al powder by a plasma spraying method. Thereby, films are formed only on the layers 4 in the opening parts and Al sprayed thick films 6 are formed. After that, leaving as a sensitizing resist mask is intact, the whole surface of the wafer is performed a plasma spraying of Cu powder using the same plasma spraying device and Cu sprayed thick films 7 are made to deposit on the films 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bump forming body in which bumps are formed on an electronic component and a bump forming method.

[0002]

2. Description of the Related Art With the trend toward smaller, lighter and more sophisticated electronic equipment, there is an increasing demand for high-density packaging. Among various high-density mounting methods, a multi-chip module (MCM) that mounts a plurality of bare LSI chips (bare chips) on a circuit board is the most promising method. In order to put the MCM into practical use, it is essential to improve the level and cost of the flip chip connection technology for connecting a bare chip to a circuit board via bumps. The flip-chip connection technology is a technology for connecting a bare chip to the circuit board via bumps with the back side facing down, and it is an excellent method in which the connection area is within the area of the chip and high-density mounting is possible. Various materials, structures, formation methods, etc. are under development for bumps that play an important role in flip chips.

The bump forming method is roughly classified into two types. In the first method, a base metal layer (barrier metal layer for preventing metal diffusion) is simultaneously deposited on the pads of each chip on the LSI wafer, and then a solder layer (Sn, Pb) having a thickness of 10 to 50 μm is further deposited. ) Is attached to the solder bump method. The solder layer is formed by vacuum deposition (Japanese Patent Publication No. 63-4939), electrolytic plating (Japanese Patent Laid-Open No. 63-6860), or solder ball method (Japanese Patent Laid-Open No. 64-22049).
And so on. The vacuum deposition method has a low deposition rate, and Sn and P
Applying the alloy of b to a thickness of 10 μm or more is a problem in terms of process cost. Further, in the case of electrolytic plating, there are problems that the plating thickness varies depending on the electric field distribution, that the plating takes a long time, and that a common electrode for electrically connecting all pads is required. In the case of the solder ball method, solder balls having a uniform particle size are required, and it is difficult to insert the solder balls onto all the pads without fail. The second method is ball bonding with a gold wire to the pad to form a gold ball having a height of about 50 μm on the pad, which is characterized by the fact that a base metal layer is unnecessary and a normal LSI chip can be used. There is a problem that the time required to create the pads increases as the number increases.
Further, since the active element on the lower surface of the pad is destroyed by the impact during bonding, the active element cannot be arranged on the lower surface of the pad.

[0004]

It takes a long time to form a thick film having a thickness of 10 μm to 50 μm by the vapor deposition method or the plating method, which increases the process cost and makes it difficult to control the film thickness. The solder ball method is problematic in that it cannot cope with the reduction of the pad pitch due to the high integration in the future and the yield reduction due to an insertion error. In the ball bonding method, ball bonding is performed for each pad. Even with a high-speed bonder, the speed is 6 to 8 pads.

[0005]

In the present invention, in order to solve the above problems, bumps are formed by selectively forming a single-layer or multi-layer sprayed metal thick film on a part of an electronic component by a plasma spraying method. To form. In addition, a metal thick film exhibiting superplasticity is selectively formed by a plasma spraying method on a part of the electronic component, and is formed to obtain a constant bump forming body.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a cross-sectional view of a bump forming body formed by the bump forming method of the present invention. FIG. 1A shows a single-layer sprayed thick film, and Al or Cu can be used as a metal material. (B) is based on two layers of an Al sprayed thick film and a Cu sprayed thick film. The bumps are formed in an array or line on the pads provided on the surface of the Si chip. 1
Is a Si wafer, 2 is a vapor deposited Al formed on the wafer
The thin pad 3 is a passivation film such as SiN. The size of the opening of the SiN film is the pad size. Further, 4 is a base metal layer and 5 is an Al or Cu sprayed thick film. In the case of a two-layer thick film, 6 is an Al sprayed thick film and 7 is a Cu sprayed thick film. By interposing the sprayed Al between the vapor-deposited Al forming the pad and the Cu sprayed thick film, the adhesion of the bump to the pad can be increased.

FIG. 2 is a process drawing of a bump having a two-layer structure of an Al sprayed film and a Cu sprayed film. I after completion of wafer process
After the photosensitive resist film 8 is attached to the surface of the C or LSI wafer (FIG. 2A), the pad pattern portion is exposed so as to be exposed, so that the pad portion is opened with an area slightly larger than the pad size (see FIG. 2b) In addition,
The thickness of the photosensitive resist film 8 is approximately the same as the required bump height. As the underlying metal layer 4, a Cr or Ti thin film is deposited by evaporation to a thickness of about 1 μm (FIG. 2c). After that, the entire surface of the wafer is A
l Plasma spraying of powder is performed. As the characteristics of the sprayed thick film,
Since the sprayed particles are repelled on the elastic surface (photosensitive resist mask film), the film is formed only on the underlying metal layer in the opening (FIG. 4c), and the Al sprayed thick film 6 is formed.
The thickness of the Al sprayed thick film 6 was about 20 μm. Thereafter, with the photosensitive resist mask as it is, the same plasma spraying device is used to plasma spray Cu powder onto the entire surface of the wafer to deposit a Cu sprayed thick film 7 (FIG. 2d). The thickness of the Cu sprayed thick film 7 is about 50 μ from the optimum pad height condition.
m. The process of FIG. 2 includes a process of forming a pattern of a photosensitive resist, but if it can be used with bumps of the same size as the pad size, it is not shown in the figure but normal IC, LSI
The pad forming resist pattern in the final step of the wafer process can be used as it is as a mask for the sprayed thick film, whereby the steps (FIGS. 2a to 2c) can be omitted. In the above description, the bumps are collectively formed on a wafer basis, but it is also possible to divide the wafer into chips and form the bumps on a chip basis.

Generally, in the flip-chip mounting, the uniformity of the height of the bump-formed body is important and is generally required ± 1 μm.
Planarization is performed to obtain m. Although not shown, the bump surface is flattened by pressing a flat plate against the bumps on the wafer (FIG. 2e). Then, the photosensitive resist film 8 is removed to complete the flip chip bumps (FIG. 2f). Recently, many LSIs coated with a polyimide film for chip protection have been manufactured. In such a case, no photoresist is needed. A polyimide overcoat replaces the photoresist. In this case, of course, it is not necessary to remove the polyimide protective film last.

The plasma spraying process enables high-speed film formation, and a thick film having a thickness of 10 μm or more can be obtained at high speed. Further, it is advantageous in that it is binderless and does not require a baking process after deposition. In plasma spraying, the velocity of the raw material particles is high, and since they collide with the pad portion at a high speed, the sprayed thick film is deposited by breaking through the surface oxide film of the Al film forming the pad, and the sprayed thick film is the Al film on the pad. Allows low contact resistance electrical connection to the membrane. When an Al thick film formed by plasma spraying is used, the Al on the wafer is
Since it is the same metal as the thin film, there is no influence of metal diffusion and a low contact resistance can be obtained. Therefore, an underlayer is not always necessary, and the process can be simplified. Since the plasma spray method does not form a film on the photosensitive resist, the sprayed thick film at the opening is not stripped during the resist removal process, and it is possible to form a thick film only on the pad with high accuracy. Become.

Further, according to the present invention, since no force is applied to the base on which the bump is attached unlike wire bonding, it is possible to form a bump even in an LSI having an active element under the bump.

FIG. 3 is a sectional view of the second embodiment of the present invention. The same film as in FIG. 1 is given the same number. Reference numeral 10 is a plasma sprayed thick film made of a superplastic material. In the present invention, zinc / 22Al was used as a material because of its superplasticity and superplastic temperature. The superplastic temperature of zinc / 22Al is about 250 ° C., which is convenient for forming on a Si wafer. The manufacturing process in this case is shown in FIG. After the wafer process is completed, the pad pattern portion is exposed so that it is opened, so that an opening 9 (FIG.
a) Allow. The underlying metal layer 4 is made of Cr or T by vapor deposition.
An i thin film is deposited to a thickness of about 1 μm (FIG. 4b). Then, using a plasma spraying device, zinc / 22
Thermal spraying of Al powder is performed. As a result, as a characteristic of the sprayed film formation, the sprayed particles are repelled on the elastic surface, so that the film is formed only on the underlying metal layer 4 in the opening (FIG. 4c). After the thermal spray film formation, the photosensitive resist 8 is removed (Fig. 4d).
Then, the wafer is held at a superplastic temperature, an intaglio (not shown) engraved in a desired shape is aligned with the pad position, and the wafer is pressed against the wafer with a desired pressure. Since the superplastic thick film 9 is faithfully plastically deformed according to the plate due to the characteristics of the superplastic material, a desired bump shape can be collectively obtained. When the chip is connected to the substrate by the conductive resin or solder, the convex shape as shown in FIG. 3, that is, the bump shape of the two-step protrusion type, is used to collect the conductive resin on the protrusion of the first step. As a result, extra resin or solder does not spread and high-precision mounting is possible. As a material exhibiting superplasticity, bismuth / S other than this example
It is considered that n alloy, lead / Sn alloy, Mg / Al alloy, etc. can be used, but bismuth / Sn and lead / Sn have too low superplasticity temperature, and Mg / Al has too high superplasticity temperature. Difficult to use.

[0013]

Although the above description is limited to the case of using a Si wafer, when plasma spraying is used, a thick film of any material can be formed on any material, so that bumps can be formed on general electronic components. . For example, bumps can be made on chip resistors, chip inductors, chip capacitors and other components. The outermost layer of the terminal portion of the current chip component is covered with solder. It is naturally possible to form a metal sprayed thick film on this. Some chip parts have Ni or sintered silver as an underlayer of the solder layer, and in such a case, it is not necessary to attach an outer solder layer. It is also possible to attach bumps. As for the thermal spray material,
Noble metals such as gold and silver and non-metals other than Al and Cu are also possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a bump according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a bump forming method according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a structure of a bump according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a bump forming method according to a second embodiment of the present invention.

[Explanation of symbols]

 1 Si Wafer 2 Pad Made of Al Thin Film 3 Passivation Film 4 Base Metal Layer 5 Al or Cu Sprayed Thick Film 6 Al Sprayed Thick Film 7 Cu Sprayed Thick Film 8 Photosensitive Resist Film 9 Pad Opening 10 Thickness Made of Superplastic Material film

Claims (8)

[Claims] 1. A bump-formed body having bumps formed of a single-layer or multi-layered sprayed metal thick film. 2. The bump forming body according to claim 1, wherein the sprayed metal thick film is an Al sprayed thick film or a Cu sprayed thick film. 3. The bump forming body according to claim 1, further comprising a bump in which an Al sprayed thick film and a Cu sprayed thick film are sequentially laminated. 4. A bump forming body having bumps formed of a formed superplastic sprayed metal thick film. 5. A bump forming method, characterized in that a single-layer or multi-layer sprayed metal thick film is selectively formed on a part of an electronic component by a plasma spraying method. 6. The bump forming method according to claim 5, wherein the sprayed metal thick film is Al or Cu. 7. The bump forming method according to claim 1, wherein an Al sprayed thick film and a Cu sprayed thick film are sequentially formed as the metal thick film. 8. A bump forming method, wherein a metal thick film exhibiting superplasticity is selectively formed on a part of an electronic component by a plasma spraying method, and is formed.