Systems for measuring stresses in line features formed on substrates
View Patent ↗Methods and systems for evaluating stresses in line features formed on substrates. Stresses may be computed from measured curvature information based on simple analytical functions. The curvature information can be obtained optically by, e.g., a coherent gradient sensing method, to obtain a full-field measurement of an illuminated area.
1. A system, comprising:
a detection module having a radiation source to produce a probe beam, a beam-guiding element to direct said probe beam to a reflective surf ace of a substrate with line features to produce a reflected probe beam, a radiation-processing module to manipulate said reflected probe beam to produce a radiation output, and a radiation detection unit to convert said radiation output to produce a curvature signal having curvature information of an area of the reflective surface based on said reflected probe beam; and
a processing module coupled to receive and process said curvature signal and operable to compute stresses of each line feature on said substrate from an analytical function of curvatures in two different directions of the substrate corresponding to the location of the line feature.
2. The System as in claim 1 , wherein said processing module is operable to:
extract information of a surface spatial gradient of an illuminated area on the substrate;
process the surface spatial gradient information to simultaneously measure a first curvature of the substrate along a longitudinal direction of the line feature and a second curvature of the substrate at the same location along a transverse direction perpendicular to the longitudinal direction; and
compute the stresses on the line feature based on measured first and second curvatures.
3. The system as in claim 1 , wherein Bald processing module is operable to:
compare the computed stresses on the line feature to an acceptable maximum stress; and
generate an indicator when a computed stress on the line feature exceeds the acceptable maximum stress.
4. The system as in claim 1 , wherein said radiation source includes a laser.
5. The system as in claim 1 , wherein said radiation-processing module includes two optical gratings.
6. A system comprising:
a first mechanism to extract information of a surface spatial gradient of an illuminated area on a substrate from an radiation image pattern obtained from a reflection of radiation from the illuminated area;
a second mechanism to process the surface spatial gradient information to simultaneously measure a first curvature of the substrate along a longitudinal direction of at least one line feature and a second curvature of the substrate at the same location along a transverse direction perpendicular to the longitudinal direction; and
a third mechanism to compute the stresses on the line feature based on measured first and second curvatures according to an analytical function.
7. The system as in claim 6 , wherein the first mechanism is operable to perform a spatial differentiation on an interference pattern produced from the reflection to extract the information of the surface spatial gradient within the illuminated area.
8. The system as in claim 7 , wherein the first mechanism comprises two optical diffraction gratings in series along an optical path to perform the spatial differentiation.
9. The system as in claim 1 , wherein said radiation-processing module is configured to optically perform a spatial shearing on the reflected probe beam so that the radiation output carries surface spatial gradient information within an area on the reflective surface illuminated by the probe beam.