Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Patent
1998-11-24
2000-11-21
Robinson, Ellis
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
428694SG, 156345, 118728, C23C 1456, C23C 1644, C23C 1602
Patent
active
061500062
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a component made of quartz glass, for use in the manufacture of semiconductors, with a rough surface which is formed by irregular, raised structural elements extending between a first, higher plane and a second, lower plane, whereby a plurality of the said structural elements has a substantially flat top surface extending in the first plane, the said top surface being bounded on all sides in a facet-like manner by substantially flat side surfaces which extend between the first and the second planes.
DISCUSSION OF PRIOR ART
The coating of substrates using so-called CVD processes is common in the manufacture of semiconductor components. As an example, layers of silicon oxide, silicon nitrate or silicon are deposited on silicon wafers. During this process the coating materials form deposits not only on the substrates but also on the walls of the processing chamber and on the apparatus arranged therein. Upon reaching a certain thickness these coats break off and thus cause particle problems. In order to avoid this the affected surfaces are cleaned from time to time.
The cleaning of the surfaces is costly in terms of time and money. In order to reduce these costs it is desirable to keep the time periods between consecutive cleaning steps as long as possible. However, especially during the CVD processes at higher temperatures, the difference between the thermal expansion coefficient of quartz glass and of the coating material leads to separation of the coats even at relatively small coat thicknesses.
It is known that roughened surfaces can hold thicker CVD layers. Sandblasting or chemical etching processes are commonly used to roughen quartz glass components. Even though sandblasting produces structures on the quartz glass surface which on the one hand contribute to a stronger bond of CVD layers, on the other hand this induces fractures in the component surface which in turn leads to separation of the CVD layers. Moreover, with sandblasting, a homogenous treatment of the entire surface of the component and maintenance of exact dimensioning is problematic.
As an alternative, the quartz glass component surfaces are roughened by chemical etching solutions. Etching of the surface frequently creates rounded surface structures, for example small round or oval grooves. In comparison with surfaces treated by sandblasting, such surfaces present reduced adhesiveness to CVD coats.
The published Japanese patent application No. JP 6-332956 describes a component of the kind indicated above. This document discloses an etching solution for the roughening of quartz glass surfaces which makes it possible to produce irregular, raised, substantially sharp-edged structural elements on a quartz glass component surface. When viewed from above, a granular morphology of a surface treated with the known acid solution is visible, with adjoining structural elements having mesa or truncated pyramid shapes. The structural elements extend between a higher level, for example the original surface of the component, and a lower level which is defined by for example the maximum etching depth. The dimensions of the structural elements have an average size from 5 mm to 15 mm. It is true that microfractures are not discernible in the quartz glass surface. But it has been shown that a surface so formed is not suitable for adherence of thick CVD layers.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a component made of quartz glass with a rough surface which is particularly suitable for adhesion of CVD coats.
According to the invention this object is accomplished on the basis of the above-described quartz glass component in that the average depth of surface roughness R.sub.a is between 0.1 .mu.m and 10 .mu.m and the magnitude of projection of the structural elements to the first plane has an average value between 30 .mu.m and 180 .mu.m.
It has been shown that the average roughness of the surface and especially the average size of the structural elements is decisive for a
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Becker Jorg
Hellmann Dietmar
Lebrun Gerard
Heraeus Quarzglas GmbH & Co. KG
Lee Laura L.
Robinson Ellis
Tiajoloff Andrew L.
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