Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-11-05
2001-04-24
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S688000, C438S742000
Reexamination Certificate
active
06221752
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority benefit of Taiwan application Serial no. 87113701, filed Aug. 20, 1998, the full disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a fabricating process of an integrated circuit, and more particularly, to a method of mending the erosion of a bonding pad caused by a residue on the bonding pad.
2. Description of the Related Art
When the main structure of an integrated circuit is formed, a protection layer is formed on the surface of the integrated circuit to protect the underlying devices or components of the integrated circuit. An ideal protection layer is formed with characteristics of uniform deposition, anti-cracking property, nonexistence of voids, resistance of penetration of moisture and alkaline ions, hardness, and strength of sustaining mechanical damage.
Silicon nitride and phospho-silicate glass (PSG) are commonly used for forming the protection layer. Silicon nitride which has a density higher than PSG is superior to resist the penetration of moisture and alkaline ions and to protect the integrated circuit from being damaged by an external mechanism. On the other hand, PSG contains phosphorous which has the gettering property, so that the moisture and alkaline ions can also be absorbed effectively to prolong the lifetime of the integrated circuit. Typically, a polyimide layer is formed after the formation of a silicon nitride layer for waterproofing.
The polyimide layer can be formed by a method of using one photo-mask or two photo-masks. The method of using one photo-mask is more straightforward and less time consuming than the method of using two photo-masks.
Aluminum is one of the most popular conductive materials applied in very large-scale integration (VLSI) currently. The aluminum has a good conductivity and adhesion, moreover, the cost of aluminum is low, and it is easily deposited and etched. Therefore, the bonding pad of an integrated circuit is often formed by aluminum.
In a conventional method, after the formation of a bonding pad on a substrate, a PSG layer is formed to cover the bonding pad and the substrate, and a silicon layer thicker than the PSG layer is formed on the PSG layer. For the purpose of protection, a polyimide layer is further formed on the silicon nitride layer. The polyimide layer can also function as a photo-resist layer for a photolithography process to define an opening penetrating through the silicon nitride layer and the PSG layer to expose the bonding pad. Since the polyimide can be removed in organic solution, after the etching process, a thorough cleaning process can not be performed by organic solution properly.
During the process of etching the silicon nitride layer and the PSG layer, an etchant containing fluorine is typically used. However, the fluorine cannot be properly cleaned away leaving residue on the surface of the bonding pad. With the residue of fluorine, the surface of the bonding pad is easily eroded affecting the profile and yield in the subsequent bonding process. Moreover, wafers being eroded sometimes fail the required quality and must be abandoned, causing waste.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method of mending the erosion of the bonding pad. The method reduces the waste of abandoning the wafers with eroded bonding pads. Therefore, the yield of the product is improved.
It is another object of the invention to provide a method of mending the erosion on a bonding pad on a wafer. While a bonding pad having a surface being eroded by halide from the etching process, the halide is removed from the surface of the bonding pad. The eroded bonding is stripped to expose the bonding pad which has not been eroded. A protection layer is formed on the exposed bonding pad.
In a preferred embodiment of the invention, a polyimide layer is formed as a photo-resist layer to define a passivation layer covering the bonding pad and the wafer. Being defined by etching process with etchant containing halide, a halide residue is left on a surface of the bonding which erodes the bonding pad. In the invention, the halide is removed from the surface followed by stripping the erosion part of the bonding bad. A protection layer is then formed to cover the bonding pad. It is often that when the bonding pad fails the quality inspection after being eroded, the whole wafer has to be abandoned. In addition, even the bonding pads with erosion pass the inspection, the profile thereof is deformed and the yield of the subsequent bonding process is seriously affected. As a result, the invention provides a method of mending the eroded bonding pad to minimize the waste of abandoned wafers, and to enhance the yield of fabrication process.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
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Chou Ta-Cheng
Kuo Wen-Pin
Lai Bruce
Bowers Charles
Huang Jiawei
J C Patents
Kielin Erik J
United Microelectronics Corp.
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