Measurement of critical dimensions of etched features

A method of characterizing a semiconductor wafer etch process, the method comprising:

• 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.

A method of forming and utilizing a test mark that is indicative of a critical dimension of an etched feature, the method comprising:

• 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.