Thomas D. Raymond

High-speed noninterferometric nanotopographic characterization of Si wafer surfaces

We present a high-speed silicon wafer metrology tool capable of resolving surface features in the nanometer height range. This tool uses a high performance Shack-Hartman sensor to analyze the wavefront of a beam of light reflected from a silicon wafer surface. By translating the wafer to analyze small portions of the wafer in each camera frame and then continuously piecing the frames together, we can retain sub-millimeter spatial resolution while rapidly analyzing large apertures. This tool is particularly effective for resolving features near the wafer edge. We will describe the measures required to obtain this level of resolution. We also compare data taken with this device to that taken with the National Institute of Standards and Technology X-ray optics Calibration Interferometer (XCALIBIR). Finally, we show measurements of a variety of typical and atypical 200 mm diameter wafer samples.

Optical Flatness Metrology for 300 mm Silicon Wafers

The National Institute of Standards and Technology (NIST) is developing two interferometric methods for measuring the thickness, thickness variation, and flatness of free‐standing and chucked silicon wafers with diameters up to 300 mm. The “eXtremely accurate CALIBration InterferometeR” (XCALIBIR) is a precision phase measuring interferometer with an operating wavelength of 633 nm and a test beam of 300 mm diameter. XCALIBIR is used to evaluate the flatness of chucked wafers. NIST’s Infrared Interferometer (IR2) is a phase measuring interferometer that operates at 1.55 μm and is used to measure the thickness variation of free‐standing 300 mm silicon wafers.