Real time surface morphology analysis of semiconductor materials and devices using 4D interference microscopy

Abstract

Recently, 4D microscopy (3D + t) has been demonstrated in confocal, near field, digital holographic and scanning interference microscopy. The last technique is of particular interest to semiconductor materials and device analysis because of its nanometric axial resolution over a large depth of field. In our first prototype system based on scanning white light interferometry we recently demonstrated real time 3D measurement of non-periodic movement at a rate of 5 i/s over 2 μm using a high speed CCD camera (250 i/s) and FPGA based image processing. In the present work we report on a second prototype based on a higher performance CMOS camera having a frame rate of 500 i/s at full frame and up to 16,000 i/s at reduced frame size. Results are shown of a 3D measurement rate of 18 i/s over a depth of 8 μm using post-processing. Different algorithms are being modeled in VHDL for performing the processing on a more complex FPGA based board in real time. It is reasonable to expect 3D image rates of tens and hundreds of images per second depending on the frame size and scanning depth. This will open the way for performing new types of high speed surface morphology characterization in semiconductor materials and device development.