Nanoimprint on Silicon for Opto-Electronic Applications

For the development of a novel optical sensor technology, diffraction grating microstructures were manufactured on a silicon surface. The principle of operation of the sensor technology is based on rotatory encoder technology, developed at Hahn-Schickard. It is based on a convolution of a Gaussian laser beam at a diffraction grating, generating sine and cosine signals resulting from the movement of the diffraction grating. Applying this approach to silicon is new and places technological challenges, which are overcome using a proprietary nanoimprint lithography (NIL) process. The process development, which was done on bulk silicon, is discussed, and its capability of producing operational optical grating microstructures is verified by moving the bulk silicon chips with the grating over an opto-electronic module using a piezo stage in an automated control and data acquisition setup. The noise measured in a 16-bit setup was below 2.8 nm RMS, and the linearity error was 100 nm RMS. Compared to the traveled distance (320 µm), this is less than 350 ppm. Furthermore, the chips with the grating were refined to a MEMS-accelerometer chip by introducing etched spring structures. This setup then was verified using different miniaturized interpolator boards.