08 Aug. CMOS-integrated light modulators
The Fraunhofer Institute for Photonic Microsystems IPMS develops area light modulators consist of arrays of micromirrors on semiconductor chips, with the number of mirrors varying from a few hundred to several million depending on the application. Implementing 1-axis and 2-axis tilting mirrors as well as sinking mirrors are monolithically integrated on CMOS backplanes. In most cases, this requires a highly integrated application specific electronic circuit (ASIC) as the basis for the device architecture to enable individual analog deflection of each micromirror. In addition, Fraunhofer IPMS develops the electronics and software to control the mirror array. Depending on the application, the individual mirrors can be tilted or deflected vertically to create a surface pattern, for example to image defined structures. High-resolution tilted mirror arrays with up to 2.2 million individual mirrors can be used as highly dynamic programmable masks for optical microlithography in the ultraviolet spectral range, according to the developers. Mirror dimensions are 10 μm or larger, according to the researchers. By tilting the micromirrors, the structural information is transferred to a high-resolution photoresist at a high frame rate. The developers see further areas of application in semiconductor inspection and metrology, as well as in laser printing, marking and material processing.
High light yield thanks to light redistribution
One Fraunhofer IPMS development is a CMOS-integrated micromirror array with two tilting axes per mirror and an associated technology platform. The device consists of 512 x 320 individually addressable mirrors with 48 μm pixel size. The optical operating principle is based on spatially resolved redistribution of light. This can be used to redirect light beams or to generate and control 2-D intensity profiles and patterns with variable intensity. Because light redistribution occurs instead of masking, higher light output is possible, according to the researchers. This development is expected to open up new possibilities in the semiconductor industry, microscopy – especially for biomedical applications – and laser materials processing such as laser ablation and engraving, among others.
SLM chip with control electronics. Image: Fraunhofer IPMS
One million micromirrors individually deflected
Another SLM technology from Fraunhofer IPMS is a matrix device with about one million micromirrors with an optically active area of 33 × 8 mm². The matrix is said to be reprogrammable at a frequency of 2 kHz, with each torsion-mounted micromirror being given an individual deflection. Based on this device configuration, application-specific customer needs can be taken into account for further developments, according to the developers. A customer evaluation kit is available to customers for exploring new applications. The kit consists of a matrix with 256 x 256 individual mirrors (64k), control electronics and software. Another current development at the institute is to implement sunken mirrors on the 64k platform.
Mirror array with one million individual mirrors. Image: Fraunhofer IPMS / Sven Döring
Customer Evaluation Kit: SLM chip with 256 x 256 micro mirrors and control electronics. Image: Fraunhofer IPMS
Further information about the area light modulators from the Fraunhofer IPMS
Source and image: www.ipms.fraunhofer.de