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In a close collaboration the team of Micromotion, micro resist technology, BESSY, and LSU-CAMD have successfully mastered the challenges of LIGA production of ultra-precision microparts for Micro Harmonic Drive® gears. The complementary expertise ranging from design and application know-how to process research and technical support resulted in high quality LIGA microparts and superior Micro Harmonic Drive® gears taking advantages of the free 2D design capability and material choice. It is also an excellent example that through contributions from partners with different background and expertise LIGA precision parts can be produced with high quality and yield and for a market competitive price.

At present the Micro Harmonic Drive is the world’s smallest backlashfree micro gear. Its favourable properties such as high repeatability, high torque capacity, low mass of inertia and high degree of efficiency are proved applied in different applications for semiconductor manufacturing, measuring machines, aerospace and other industries. However for high precise assembly applications often linear adjustments of a few nanometres are required. The common solution for positioning in the nanometres range is the use of piezoelectric effect actuators. The drawbacks are the need for a closed loop control system, overshooting during positioning, local wear, short travel ranges and loss of position without power supply. To overcome these obstacles the advantages of the Micro Harmonic Drive are exploited together with a stepper motor, an eccentric drive and monolithic flexure hinges are combined in a compact unit, called Nanostage. With this setup a travel range of 40 microns and a resolution < 3 nm is achieved. The single sided and double sided repeatability was measured in an open loop control system with < 5 nm and < 10 nm respectively.

Poly-methylmethacrylate (PMMA), a positive resist, is the most commonly used resist for deep X-ray lithography (DXRL)/LIGA technology. Although PMMA offers superior quality with respect to accuracy and sidewall roughness but it is also extremely insensitive. In this paper, we present our research results on SU-8 as negative resist for deep X-ray lithography. The results show that SU-8 is over two order of magnitude more sensitive to X-ray radiation than PMMA and the accuracy of the SU-8 microstructures fabricated by deep X-ray lithography is superior to UV-lithography and comparable to PMMA structures. The good pattern quality together with the high sensitivity offers rapid prototyping and direct LIGA capability. Moreover, the combinational use of UV and X-ray lithography as well as the use of positive and negative resists made it possible to fabricate complex multi-level 3D microstructures. The new process can be used to fabricate complex multi-level 3D structures for MEMS, MOEMS, Bio-MEMS or other micro-devices.