Apparatus and Method for Monitoring a Thickness of a Silicon Wafer with a Highly Doped Layer

摘要

Apparatus for monitoring a thickness of a silicon wafer with a highly-doped layer at least at a backside of the silicon wafer is provided. The apparatus has a source configured to emit coherent light of multiple wavelengths. Moreover, the apparatus comprises a measuring head configured to be contactlessly positioned adjacent the silicon wafer and configured to illuminate at least a portion of the silicon wafer with the coherent light and to receive at least a portion of radiation reflected by the silicon wafer. Additionally, the apparatus comprises a spectrometer, a beam splitter and an evaluation device. The evaluation device is configured to determine a thickness of the silicon wafer by analyzing the radiation reflected by the silicon wafer by an optical coherence tomography process. The coherent light is emitted multiple wavelengths in a bandwidth b around a central wavelength wc.

主权项

1. An apparatus for monitoring a thickness of a silicon wafer with a highly-doped layer at least at a backside of the silicon wafer, the apparatus comprising:
a light source configured to emit coherent light of multiple wavelengths, a measuring head configured to be contactlessly positioned adjacent the silicon wafer comprising the backside from which a portion is to be removed and configured to illuminate at least a portion of the silicon wafer with the coherent light of multiple wavelengths and configured to receive at least a portion of radiation reflected by the silicon wafer, a spectrometer configured to receive at least a portion of the radiation reflected by the silicon wafer and measure the partial intensities of the radiation reflected by the silicon wafer as a function of wavelength, a beam splitter coupled to the measuring head, the light source and the spectrometer, an evaluation device configured to determine a thickness of the silicon wafer by analyzing the radiation reflected by the silicon wafer using an optical coherence tomography process, wherein the light source is configured to emit coherent light at multiple wavelengths with a bandwidth b around a central wavelength wc, the bandwidth b having limits that are defined such that a wavelength for which an optical absorption coefficient of the highly-doped layer of the silicon wafer is a minimum lies within the bandwidth b.