Measurement of critical dimensions of etched features
First Claim
1. A method of determining a critical dimension associated with an etch process comprising:
- forming a test mark in a device, wherein the test mark is formed at least in part by imaging overlapping, angularly offset lines in a resist that covers a selected layer to define the test mark and thereafter etching at least the selected layer to form the test mark;
detecting at least a portion of the test mark to determine a geometric parameter of the test mark; and
approximating a critical dimension of interest based at least in part on the determined geometric parameter of the test mark.
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Abstract
A test mark, as well as methods for forming and using the test mark to facilitate the measurement of the critical dimensions of etched features in semiconductor and other wafer level processing is described. The test marks may be used to characterize, calibrate and/or monitor etch performance. Test marks are defined by imaging (typically at partial exposures) overlapping, angularly offset lines in a resist that covers a layer to be etched. The lines preferably have line widths that are equal (or related) to a critical dimension of interest. After the resist is developed and otherwise processed, the layer is etched as appropriate, thereby creating the test marks. The test marks are then imaged to facilitate the determination of a geometric parameter of each mark. Most commonly, the geometric parameter determined relates to the area of the mark and/or the length of its major dimension. These parameters can then be used to approximate a critical dimension of interest based at least in part on the determined geometric parameter of the test mark.
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Citations
30 Claims
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1. A method of determining a critical dimension associated with an etch process comprising:
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forming a test mark in a device, wherein the test mark is formed at least in part by imaging overlapping, angularly offset lines in a resist that covers a selected layer to define the test mark and thereafter etching at least the selected layer to form the test mark; detecting at least a portion of the test mark to determine a geometric parameter of the test mark; and approximating a critical dimension of interest based at least in part on the determined geometric parameter of the test mark. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of characterizing a semiconductor wafer etch process, the method comprising:
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forming a test mark in a semiconductor wafer, wherein the test mark is formed at least in part by imaging overlapping, angularly offset straight lines in a resist that covers a selected layer to define the test mark and thereafter etching at least the selected layer to form the test mark, wherein the angular offset is in the range of approximately 0.2 to 10 degrees; detecting at least a portion of the test mark to determine a geometric parameter of the test mark indicative of at least one of the length of the test mark or an area of at least a portion of the test mark; and approximating a critical dimension of interest based at least in part on the determined geometric parameter of the test mark.
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22. A method of forming and utilizing a test mark that is indicative of a critical dimension of an etched feature, the method comprising:
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making a first partial lithographic exposure to define a first line in a resist positioned over a layer of interest, wherein the partial exposure is at a reduced power level relative to a power level used to define other features in the resist; making a second partial lithographic exposure to define a second line in the resist, wherein the second line overlaps, but is angularly offset from the first line; developing and stripping the resist to define a resist test feature; etching the layer of interest, whereby the etching forms a test marks defined by the resist test feature; and imaging at least a portion of the test mark to facilitate the determination of a geometric parameter of the test mark. - View Dependent Claims (23, 24, 25)
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26. An etching machine comprising:
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an etch chamber suitable for etching wafers; a detector configured for detecting a geometric characteristic selected from the group consisting of the area or length of etched test marks defined on wafers that are created during an etch process in the etch chamber, wherein the test marks are somewhat diamond shaped marks formed at least in part by imaging overlapping, angularly offset straight lines in a sacrificed resist that covered the selected layer to define the test marks and thereafter etching at least the selected layer to form the test marks, wherein the test marks are sized and positioned in a manner so that detection of the geometric parameter facilitates approximation of a critical dimension of interest based at least in part of the detected geometric parameter of the test mark. - View Dependent Claims (27, 28, 29)
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30. A wafer comprising a multiplicity of test marks formed in a selected etched layer, wherein the test marks are somewhat diamond shaped marks formed at least in part by imaging overlapping, angularly offset straight lines each having a width indicative of a critical dimension of interest in a sacrificed resist that covered the selected layer to define the test marks and thereafter etching at least the selected layer to form the test marks, wherein the angular offset is in the range of approximately 0.2 to 10 degrees, the test marks being sized and positioned in a manner to facilitate detection of a geometric parameter of the test marks in order to approximate the critical dimension of interest based at least in part of the detected geometric parameter of the test mark.
Specification