Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1999-12-14
2001-12-11
Lund, Jeffrie R. (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S725000, C118S728000, C065S355000, C065S356000
Reexamination Certificate
active
06328807
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a deposition process for planar lightwave devices and particularly to an improved apparatus and method for depositing thin films onto a substrate.
2. Technical Background
A key step in the manufacturing of planar optical components is the deposition of thin films onto a substrate. Planar optical components require that the deposited doped thin glass films have uniform properties when used as planar waveguides for optical components used, for example, in the telecommunication industry.
The soot/glass deposition rate by the flame hydrolysis deposition (FHD) process is thermophoretically dominated and, it was discovered, is adversely influenced by variations in the substrate temperature. Typically, a silica, si, sapphire or other wafer substrate is held in a vacuum chuck which is rotated and a line-flame burner translated with respect to the chuck to provide a uniform coating of doped glass material onto the substrate. It was discovered, however, that the uniformity of the thickness of a film coating utilizing such a process varied over the surface of the resultant wafer-shaped coated substrate as did the index of refraction despite the rotation as well as the translation in X-Y directions of the substrate relative to the flame during the FHD process. This discovery of a pattern of thickness variations and index of refraction variations lead to experimental testing of the temperature of a chuck exposed to a line-flame translated across the chuck and the resultant discovery that significant temperature variations occur during the exposure of the chuck, and a wafer substrate attached to the chuck, to a line-flame burner. As a result of the discovery of the pattern of thickness variations and index of refraction variations and the resultant correlation of such variations with variations in the temperature of the chuck, the source of the problem of film thickness and index of refraction variations was discovered.
SUMMARY OF THE INVENTION
The method and apparatus of the present invention overcomes the thickness non-uniformities of the flame hydrolysis deposition (FHD) process by providing a holder for a substrate which is heated to a predetermined temperature selected to maintain the substrate temperature relatively constant during the FHD process. As a result, the thickness of a thin film applied to the substrate is relatively uniform as is the index of refraction of the resultant core material deposited on the substrate. In one embodiment of the present invention, a chuck receives a disk-shaped wafer substrate and includes an electrical heater for maintaining the chuck temperature at from about 700° C. to about 900° C. In another embodiment, a gas heater is positioned on a side of the chuck opposite the substrate wafer to heat the chuck to substantially the same temperature range. In either embodiment, a chuck is rotated with respect to a line-flame burner which introduces a vaporized mixture of organometallic material into the line-flame burner for depositing a thin film of from about 5 to 6.5 microns of doped glass onto the wafer substrate.
The method of the present invention includes heating a wafer-holding chuck to a predetermined temperature while holding a substrate wafer in the chuck and flame hydrolysis depositing soot/glass onto the substrate. Although the present invention is described in the environment of a flame hydrolysis deposition, other deposition techniques may also benefit from the system of the present invention.
Additional features and advantages of the invention will be set forth in the detailed description which follows and will be apparent to those skilled in the art from the description or recognized by practicing the invention as described in the description which follows together with the claims and appended drawings.
It is to be understood that the foregoing description is exemplary of the invention only and is intended to provide an overview for the understanding of the nature and character of the invention as it is defined by the claims. The accompanying drawings are included to provide a further understanding of the invention and are incorporated and constitute part of this specification. The drawings illustrate various features and embodiments of the invention which, together with their description serve to explain the principals and operation of the invention.
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Boek Heather D.
Boylan Elizabeth A.
Huang Haibo
Laborde Pascale
Lewis Gary L.
Corning Incorporated
Lund Jeffrie R.
Price Heneveld Cooper DeWitt & Litton
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