JPH01128549A - Manufacture of solder bump - Google Patents

Abstract

PURPOSE:To prevent the electric characteristic of a chip from deteriorating due to a decrease in moisture resistance by forming a solder deposited film on a pad with a metal mask, removing the mask, then removing by dissolving a resist, and forming a bump on the chip. CONSTITUTION:Pads 2 having 200mum of diameter and a thin gold layer having 1000Angstrom thereon are pattern-formed in a matrix state at a pitch of 400mum on a chip 1 formed on a wafer. After a positive type resist 9 is formed 2.5mum thick by a spin coating method on the wafer, it is selectively exposed, and then developed to expose only the pads 2. Then, after a metal mask 3 having 100mum of thickness is aligned, it is set in a vacuum depositing unit, and solder made of In-Pb alloy is deposited 30mum thick by a large-sized crucible. Thereafter, the wafer from which the mask 3 is removed is dipped in a boiling acetone for 1 min to remove the resist 9, thereby obtaining bumps 11.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method of manufacturing solder bumps on a flip-chip type semiconductor device, and the purpose is to manufacture solder bumps without adversely affecting the semiconductor device, and the manufacturing method is a method for manufacturing solder bumps on a flip-chip type semiconductor device. a step of coating a photosensitive resist film on the semiconductor substrate on which the pattern is formed;
A step of exposing and developing the resist film to expose only the electrode, a step of forming a solder deposition film on the electrode pad using a metal mask, and a step of dissolving and removing the resist after removing the metal mask. forming the solder bumps on the semiconductor chip.

[Industrial application field]

The present invention relates to a method for manufacturing solder bumps on flip-chip type semiconductor devices.

Due to the need to process a large amount of information at high speed, information processing devices are becoming smaller and larger in capacity.

Semiconductor devices such as ICs and LSIs are the main components of information processing devices, and improvements are being made in terms of both element configuration and exterior packaging in order to achieve smaller size and larger capacity.

In other words, by miniaturizing wiring patterns and miniaturizing semiconductor formation areas, unit elements are becoming smaller, and LS
Capacity is increasing from I to VLSI and from LSI to VLSI.

Further, advances in passivation technology have reduced the need for hermetically sealed packages, and flip-chip type semiconductor devices in which terminal electrodes are provided directly on semiconductor chips are about to be put into practical use.

The present invention relates to a method of forming solder bumps on this flip-chip type semiconductor device.

[Conventional technology]

A flip-chip type semiconductor device has a matrix of electrode pads (hereinafter referred to as pads) that connect the circuit to an external wiring board on the chip surface on which a pattern is formed, and solder bumps are placed on these pads. (hereinafter referred to as bumps) are formed, but the number of pads is large compared to the chip area, and the height of about 30 μm is required, making it difficult to ensure insulation between the bumps. It's bad.

For example, in the case of an LSI in which a total of 441 bumps, 21 of which are 200 μm in diameter, are formed on one side of a 10-square chip, the bump repetition pitch is 400 μm.
The spacing between bumps is only 200 μm.

Various methods have been tried to form such bumps, such as ■ solder vapor deposition method, ■ solder ball adhesion method, and ■ screen printing method, but the solder vapor deposition method is suitable for mass production processes.

That is, the solder ball bonding method is a method in which preformed solder balls are aligned with the pads of the chip and then heated and welded, but it requires a large number of steps and is not suitable for mass production.

In addition, the screen printing method cannot be said to be a practical method because the distance between the bumps is narrow, causing the pattern to collapse during the drying and baking stages, resulting in mutual short circuits.

From the above, it can be said that the solder vapor deposition method is the most suitable method.

Now, initially, as a method of forming bumps by vapor deposition, solder was directly vapor-deposited using a metal mask.

Here, the constituent material of the solder is indium-lead (In
-Pb) alloy, indium-tin (In-Sn) alloy.

Examples include tin-lead (Sn-Pb) alloys.

FIG. 2 is a cross-sectional view showing the process, and as shown in FIG. 2
are patterned in a matrix at regular intervals.

As shown in FIG. 3B, the metal mask 3 is accurately aligned and solder is deposited.

In this case, vacuum evaporation is carried out by heating a large crucible by resistance, so a metal mask is attached to the underside of the wafer. Due to the expansion caused by heating, a gap is created between the metal mask 3 and the chip 1, and when the metal mask 3 is removed from the wafer after vapor deposition, the nozzles 4 are not aligned with each other as shown in FIG. There is a problem that the thin solder 5 bridges the gap.

In order to solve this problem, as shown in FIG. 3(A), a photosensitive polyimide film 6 is coated on the position excluding the pad 2, and after aligning the metal mask 3 thereon, a photosensitive polyimide film 6 is coated as shown in FIG. 3(A). The solder 7 is vapor-deposited. (See Figure B) Next, by removing the metal mask 3 and then removing the polyimide film 6, it is possible to form a perfect bump with no solder bridges.

However, although a hydrazine-based etching solution is used to remove the polyimide film 6, it has a strong reducing effect, so it is necessary to thoroughly rinse the chip with water after removing the polyimide film 6. There is concern that this may lead to deterioration of the characteristics of

[Problem that the invention seeks to solve]

As mentioned above, when forming bumps on a flip chip type IC by solder vapor deposition, it is necessary to use hydrazine to remove the polyimide film, and for that purpose, sufficient water washing is necessary. The problem is that the characteristics of

[Means for solving problems]

The above problem is caused by the process of forming bumps on pads patterned on a semiconductor chip to form a flip-chip type semiconductor device, which involves applying a photosensitive resist film onto a semiconductor substrate patterned with pads. a step of exposing and developing the resist film to expose only the electrode pad; a step of forming a solder deposition film on the pad using a metal mask; and after removing the metal mask, This problem can be solved by dissolving and removing the resist to form bumps on the chip.

[Effect]

The present invention uses photoresist in place of the polyimide used up to now.

In other words, photoresist is inferior to polyimide in terms of heat resistance, but it has a heat resistance of 120 to 150°C, and since it is heated through a metal mask during vapor deposition,
It can fully withstand vapor deposition treatment.

Therefore, the present invention uses a photoresist as a mask material to eliminate solder bridging, thereby eliminating the need for washing with water and thereby preventing deterioration of the electrical characteristics of the chip due to a decrease in moisture resistance.

〔Example〕

FIG. 1 is a sectional view showing the manufacturing process of a solder bump according to the present invention.

That is, on the chip l formed on the wafer, the diameter is 200 μm and 1000 gold n on the surface as before.
u) Pads 2 each having one Fj layer are patterned in a matrix with a pitch of 400 μm.

(The above is A in the same figure) After forming a positive resist (product name 1300-31 Shupley East Co., Ltd.) 9 on the wafer to a thickness of 2.5 μm by the spin code method as shown in CB in the same figure. After selective exposure using the same conventional method, development was performed to expose only the pad 2 portion.

(The above is C in the same figure) Next, after aligning the metal mask 3 with a thickness of 100 μm as in the conventional method, it is placed in a vacuum evaporation device, and solder made of In-Pb alloy is applied to a thickness of 30 μm using a large crucible. It was deposited to a thickness of . (The above is D in the same figure) Next, metal mask 3
The wafer from which the resist was removed was immersed in boiling acetone for 1 minute to remove the resist 9, thereby making it possible to obtain a hump 11 as shown in FIG.

〔Effect of the invention〕

According to the present invention, since washing with water is not required, it is possible to eliminate deterioration of chip characteristics due to moisture absorption, and it is also possible to obtain an IC chip in which the bumps are completely insulated from each other.

Note that the above formation method can also be applied to the case of forming solder bumps on a ceramic circuit board.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a manufacturing process of a solder bump according to the present invention, FIG. 2 is a sectional view showing a conventional manufacturing process, and FIG. 3 is a sectional view showing another conventional manufacturing process. In the figure, 1 is the chip, 2 is the pad, 3 is the metal mask, 4.11 is the bump, 7.10 is the solder,
9 is a resist.

Claims (1)

[Claims] The process of forming a flip-chip type semiconductor element by forming solder bumps on electrode pads patterned on a semiconductor chip is performed by exposing the semiconductor substrate on which the electrode pads are patterned. a step of exposing and developing the resist film to expose only the electrode pad; a step of forming a solder vapor deposition film on the electrode pad using a metal mask; A method for manufacturing a solder bump, comprising: removing the mask and then dissolving and removing the resist to form a solder bump on a semiconductor chip.