Apparatus and method for controlling etch depth
First Claim
1. A method for etching a feature having a feature depth in a layer of a wafer, the method comprising:
- etching to a first depth of the feature at a first etching rate;
etching from the first depth to a second depth at a second etching rate, the second etching rate being slower than the first etching rate;
optically determining when the second depth has reached the feature depth; and
stopping etching the feature, wherein the wafer is a crystalline silicon wafer, wherein the feature is etched into the crystalline silicon wafer.
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Abstract
An apparatus and method for etching a feature in a wafer with improved depth control and reproducibility is described. The feature is etched at a first etching rate and then at a second etching rate, which is slower than the first etching rate. An optical end point device is used to determine the etching depth and etching is stopped so that the feature has the desired depth. Two different etching rates provides high throughput with good depth control and reproducibility. The apparatus includes an etching tool in which a chuck holds the wafer to be etched. An optical end point device is positioned to measure the feature etch depth. An electronic controller communicates with the optical end point device and the etching tool to control the tool to reduce the etch rate part way through etching the feature and to stop the etching tool, so that that the feature is etched to the desired depth.
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Citations
16 Claims
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1. A method for etching a feature having a feature depth in a layer of a wafer, the method comprising:
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etching to a first depth of the feature at a first etching rate;
etching from the first depth to a second depth at a second etching rate, the second etching rate being slower than the first etching rate;
optically determining when the second depth has reached the feature depth; and
stopping etching the feature, wherein the wafer is a crystalline silicon wafer, wherein the feature is etched into the crystalline silicon wafer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for etching a feature having a feature depth in a layer of a wafer, the method comprising:
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etching to a first depth of the feature at a first etching rate;
etching from the first depth to a second death at a second etching rate, the second etching rate being slower than the first etching rate;
optically determining when the second depth has reached the feature depth; and
stopping etching the feature, wherein the method is part of a process for shallow trench isolation.
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Specification