Measurement of multiple patterning parameters
Methods and systems for evaluating the performance of multiple patterning processes are presented. Patterned structures are measured and one or more parameter values characterizing geometric errors induced by the multiple patterning process are determined. In some examples, a single patterned target and a multiple patterned target are measured, the collected data fit to a combined measurement model, and the value of a structural parameter indicative of a geometric error induced by the multiple patterning process is determined based on the fit. In some other examples, light having a diffraction order different from zero is collected and analyzed to determine the value of a structural parameter that is indicative of a geometric error induced by a multiple patterning process. In some embodiments, a single diffraction order different from zero is collected. In some examples, a metrology target is designed to enhance light diffracted at an order different from zero.
1. A semiconductor wafer, comprising:
a diffractive metrology target including a first set of structures having a first grating pitch generated by a first patterning step of a multiple patterning process and a second set of structures generated by a subsequent patterning step of the multiple patterning process, the second set of structures offset from the first set of structures by a fraction of the first grating pitch, the first set of structures and the second set of structures generated by the first patterning step and the subsequent patterning step of the multiple patterning process include at least two different pitches; and
a nominal device structure corresponding to the diffractive metrology target, the nominal device structure including a third set of structures having a third grating pitch generated by the first patterning step of the multiple patterning process and a fourth set of structures generated by the subsequent patterning step, the fourth set of structures offset from the first set of structures by a fraction of the third grating pitch, the third set of structures and the fourth set of structures generated by the first patterning step and the subsequent patterning step of the multiple patterning process include a uniform pitch.
2. The semiconductor wafer of claim 1 , wherein the diffractive metrology target is located in a scribe line of the semiconductor wafer.
3. The semiconductor wafer of claim 1 , wherein the nominal structure is located within a die of the semiconductor wafer.
4. The semiconductor wafer of claim 1 , wherein the diffractive metrology target and the corresponding nominal structure have the same overlay.
5. The semiconductor wafer of claim 1 , wherein an overlay of the diffractive metrology target is offset by a known amount from an overlay of the nominal structure.