Process for etching a transparent workpiece including backside endpoint detection steps
First Claim
1. A method of defining a pattern on a mask comprising a transparent substrate having top and bottom surfaces, comprising:
- defining a photoresist pattern on said top surface of said mask, said pattern including a periodic structure having a periodic spacing between elements of the structure;
placing said mask on a support pedestal in a plasma reactor chamber and generating a plasma in said chamber to etch said top surface of said mask through openings in said photoresist pattern;
transmitting light through said pedestal and through said bottom surface of said mask;
viewing through said support pedestal light reflected from said periodic structure and detecting an interference pattern in said reflected light; and
determining from said interference pattern a depth to which periodic structure has been etched in said top surface.
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Accused Products
Abstract
A method is provided for defining a pattern on a workpiece such as a transparent substrate or mask or a workpiece that is at least transparent within a range of optical wavelengths. The method includes defining a photoresist pattern on the top surface of the mask, the pattern including a periodic structure having a periodic spacing between elements of the structure. The method further includes placing the mask on a support pedestal in a plasma reactor chamber and generating a plasma in the chamber to etch the top surface of the mask through openings in the photoresist pattern. The method also includes transmitting light through the pedestal and through the bottom surface of the mask, while viewing through the support pedestal light reflected from the periodic structure and detecting an interference pattern in the reflected light. The method further includes determining from the interference pattern a depth to which periodic structure has been etched in the top surface.
81 Citations
17 Claims
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1. A method of defining a pattern on a mask comprising a transparent substrate having top and bottom surfaces, comprising:
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defining a photoresist pattern on said top surface of said mask, said pattern including a periodic structure having a periodic spacing between elements of the structure; placing said mask on a support pedestal in a plasma reactor chamber and generating a plasma in said chamber to etch said top surface of said mask through openings in said photoresist pattern; transmitting light through said pedestal and through said bottom surface of said mask; viewing through said support pedestal light reflected from said periodic structure and detecting an interference pattern in said reflected light; and determining from said interference pattern a depth to which periodic structure has been etched in said top surface. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of defining a pattern on a mask comprising a transparent substrate of quartz having top and bottom surfaces and an opaque layer on said top surface, comprising:
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defining a photoresist pattern on said opaque layer, said pattern including a periodic structure having a periodic spacing between elements of the structure; placing said mask on a support pedestal in a plasma reactor chamber and generating a plasma in said chamber to etch said opaque layer through openings in said photoresist pattern; sensing through openings in said support pedestal light transmitted through said transparent substrate, and monitoring said light for a change that indicates completion of etching of said opaque layer, and halting the etching of said opaque layer in response to said change; placing said mask on a support pedestal in a plasma reactor chamber and generating a plasma in said chamber to etch said transparent substrate through openings in said opaque layer; transmitting light through said pedestal and through said bottom surface of said transparent substrate; viewing through said support pedestal light reflected from said periodic structure and detecting an interference pattern in said reflected light; and determining from said interference pattern a depth to which periodic structure has been etched in said top surface. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification