Metal treatment – Compositions – Heat treating
Patent
1982-03-10
1984-02-21
Hearn, Brian E.
Metal treatment
Compositions
Heat treating
29576T, 432 18, H01L 21322, H01L 21324
Patent
active
044328095
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention generally relates to the manufacture of silicon semiconductor wafers and more particularly to a method of reducing oxygen precipitation in silicon wafers.
The manufacture of semiconductor devices (e.g., transistors) on the surface of a silicon wafer is well known in the art. Present day efforts have concentrated on device miniaturization to achieve high device density. As the size of semiconductor devices shrink, it becomes extremely important to eliminate impurities at the surface of the silicon wafer where the devices are formed. For example, the presence of even minute amounts of metal impurities at the surface of the semiconductor wafer can cause shorting of devices or degradation of device operation.
One method of achieving an impurity free zone at the surface of a silicon wafer is by using ultra pure environments and inert equipment for all semiconductor processing steps. It will be recognized, however, that the introduction of some impurities is almost inevitable as the silicon wafer undergoes various manufacturing processes.
A second method of achieving an impurity free surface zone is by utilizing the phenomenon known as "gettering". Gettering occurs when a defect or impurity is deliberately introduced into the semiconductor crystalline structure. The defect or impurity acts as an internal trap for any subsequent impurities introduced into the semiconductor by attracting subsequent impurities thereto.
A common method of obtaining gettering is by forming a region of precipitated oxygen inside the silicon wafer. The internal precipitation region acts as a trap for any impurities introduced into the surface of the silicon wafer during subsequent processing. The impurities are attracted to the internal precipitation region and drawn away from the wafer surface thus ensuring an impurity free device region. An example of a method for producing a silicon wafer having a high internal getter density and a surface layer free from precipitated oxygen may be found in IBM Technical Disclosure Bulletin, Vol. 19, No. 4, September 1976, p. 1295 to Biedermann. Disclosed is a high temperature wafer annealing process for dissolving precipitated oxygen near the surface and diffusing the oxygen off the wafer.
From the above description it will be realized that gettering will only be effective if the internal gettering region does not extend near the wafer surface. If the internal gettering reigion extends near the surface impurities introduced in subsequent processing steps will not be drawn away from the surface by the gettering region. Moreover, the precipitated oxygen in the gettering region near the surface will act as an impurity and have an adverse effect on device operation.
Unfortunately, high temperature (i.e., greater than about 800.degree. C.) processing of a silicon wafer causes interstitial (dissolved) oxygen in the wafer to precipitate, thereby enlarging the internal gettering region. Each high temperature processing step precipitates more oxygen until the internal gettering region extends into the device region, and degrades device operation. Precipitation during high temperature processing is particularly a problem with silicon wafers having a high (e.g., greater than about 33 parts per million) interstitial oxygen content, as greater amounts of oxygen precipitates with each high temperature step, and enlarges the internal gettering region into the device region.
The prior art has heretofore not found a way to reduce oxygen precipitation during high temperature processing steps. For example, the surface diffusion method disclosed in the above-mentioned IBM Technical Disclosure Bulletin to Biedermann will only successfully diffuse low concentrations of precipitated oxygen near the wafer surface. When the internal gettering region extends near the wafer surface, the resultant high precipitated oxygen concentration cannot be diffused out. As a consequence of these problems, wafers with a high interstitial oxygen content were heretofore discarded, or used for producing low p
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Chye Patrick W.
Hearn Eric W.
Kulkarni Murlidhar V.
Markovits Gary
Bigel Mitchell S.
Hearn Brian E.
International Business Machines - Corporation
Schiavelli Alan E.
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