Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-03-02
2001-10-30
Chaudhuri, Olik (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S749000, C438S033000
Reexamination Certificate
active
06309953
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a process for producing a semiconductor device with a roughened semiconductor surface.
Such a process is described, for example, in East German Patent DD 251 905 A3. That document discloses a process for producing a light-emitting semiconductor device having a III-V compound semiconductor body, in which the surface is roughened. Contact metallizations, which are formed of a gold-beryllium layer and a gold layer, are applied to subregions of the III-V compound semiconductor surface, for the purpose of making electrical contact.
A process is further known from German Published, Non-Prosecuted Patent Application DE 43 05 296 A1, corresponding to U.S. Pat. No. 5,429,954, in which the side surfaces of a mesa-etched LED semiconductor chip are roughened through the use of etching in order to improve output light coupling.
The roughening reduces the total reflection of the light radiation produced in the semiconductor device at the surface. As a consequence thereof, the radiated intensity, and therefore also the external quantum efficiency of the light-emitting semiconductor device, is increased.
However, the contact metallizations made of gold-beryllium and gold cause great difficulties in the production of those semiconductor devices.
Firstly, there are difficulties in automatic optical is detection of the gold metallizations. The reason therefor is an unfavorable contrast between the semiconductor surface and the gold contact surface. The camera systems conventionally used in chip assembly lines must be specially adjusted for that material combination. Without that adjustment, reasonably reliable automatic optical detection is not possible. However, any re-adjustment in chip assembly lines entails additional costs.
Great difficulties are also caused by the fact that the junction between the conventionally used gold bonding wire and a gold bonding pad only has low mechanical strength. That increases the risk of the connection wiring being torn off during the chip production, for example during encasing.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a process for producing a semiconductor device with a roughened semiconductor surface, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods of this general type.
With the foregoing and other objects in view there is provided, in accordance with the invention, a process for producing a semiconductor device, which comprises the following sequential steps: producing a semiconductor body having an Al
x
Ga
1−x
As layer with an upper surface, where x≦0.40; applying a contact metallization made of a non-noble metallic material to the Al
x
Ga
1−x
As layer; precleaning a semiconductor surface to produce a hydrophilic semiconductor surface; roughening the upper surface of the Al
x
Ga
1−x
As layer by etching with an etching mixture of hydrogen peroxide ≧30% and hydrofluoric acid ≧40% (1000:6) for a period of from 1 to 2.5 minutes; and re-etching with a dilute mineral acid.
With the objects of the invention in view there is also provided a process for producing a semiconductor device, which comprises the following sequential steps: producing a semiconductor body having an Al
x
Ga
1−x
As layer with an upper surface, where 0≦x≦1; applying a contact metallization made of a non-noble metallic material to the Al
x
Ga
1−x
As layer; precleaning a semiconductor surface to produce a hydrophilic semiconductor surface; and roughening the upper surface of the Al
x
Ga
1−x
As layer by etching with nitric acid 65% at temperatures of between 0° C. and 30° C.
In accordance with another mode of the invention, there is provided a process which comprises forming the contact metallization of aluminum or an aluminum-based alloy.
In accordance with a concomitant mode of the invention, there is provided a process which comprises additionally roughening at least sub-regions of lateral surfaces of the semiconductor body.
A contact metallization made of a non-noble metallic material such as, for example, aluminum or an aluminum-based alloy generally has better contrast with the semiconductor material than the known gold metallization. It therefore ensures reliable automatic optical detection with conventionally used optical detection systems. The mechanical strength of the connection between the aluminum bonding pads and gold bonding wires is significantly higher than that of a gold-gold connection. The use of non-noble metallic materials such as, for example, aluminum has the additional advantage that production of the contact metallizations does not require any special cycles outside the conventionally used production lines.
Other features which are considered as characteristic for the invent ion are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a process for producing a semiconductor device with a roughened semiconductor surface, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the a accompanying drawings.
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Patent Abstracts of Japan No. 63-249384 (Shiose), dated Oct. 17, 1988.
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Patent Abstracts of Japan No. 60-45648 (Hiroshi), dated Feb. 18, 1994.
Patent Abstracts of Japan No. 57-097686 (Kazuo), dated Jun. 17, 1982.
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Fischer Helmut
Lang Gisela
Nirschl Ernst
Sedlmeier Reinhard
Chaudhuri Olik
Doan Theresa
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
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