Mks Instruments, Inc.

Sylvie Charpenay

Peter Rosenthal

Joseph E Cosgrove

Peter A Rosenthal

Victor A Yakovlev

Jiazhan Xu

The method measures the temperature, emissivity, and other properties of relatively smooth surfaces radiating thermal energy, and is especially adapted for monitoring semiconductor fabrication processes. Temperature is determined by relating measured radiance to the predictions of the Planck radiation law, using knowledge of the emissivity determined from an analysis of the polarization of the thermally emitted radiance. Additional information regarding the properties of thin films, such as thickness and composition, can be computed from the emissivity or the ratio of the emissivities measured at two independent polarizations. Because the data are obtained from the intrinsic thermal radiance, rather than from an extrinsic light source, the measurement can be performed when it is inconvenient or impossible to provide a light source for reflectance measurements.

Thermal imaging for semiconductor process monitoring

The composition, free carrier concentrations, and other properties of thin films and graded layers embedded in film stack structures are measured by the method of the invention, which is based upon the application of two novel algorithms to extract the composition of a measured layer independently of the confounding effects of additional layers, and which can be effected even when calibration samples are not available with the same layered structure as the samples to be measured. The method uses sample model-based analysis algorithms to extract the dielectric function of the layer to be measured, combined with model-based analysis to relate the composition of the layer to its dielectric function. Because the dielectric function of a layer is a bulk spectral property of the material, and is inherently independent of the thickness of the layer, the composition of the material can be determined more easily and unambiguously from its dielectric function than from raw spectral quantities such as reflectance, ellipsometry, and transmittance, which spectral data are influenced strongly by the optical properties of the overlayers, the underlayers, and the substrate material. The method enables the measurement of layer composition with significantly fewer calibration samples, it allows product wafer analysis with structures that are significantly more complicated than the calibration samples, and it is intrinsically more reliable for transferring calibrations between tools even when the measurement geometry varies from tool-to-tool.

Growing community of inventors

Vernon, CT, United States of America

Sylvie Charpenay