CHEMNITZ – 14th May 2007 – MEMS fabrication technologies cause tolerances in device dimensions and consequently on key parameters like the resonant frequency. In contrast to these manufacturing tolerances industrial applications require defined conditions.

Therefore 3D-Micromac AG has developed an industrial-applicable laser-trimming tool to overcome these tolerances. The processing of Silicon in particular Micro Mirror Devices (MMD) by ultra-short pulse is accompanied by a very small heat affected zone and causes a minimum of stress into the material. The trimming of all MMDs on a wafer to a certain frequency value is performed by selective ablation of material. The reported technology promises an increasing yield and maximizes the efficiency in MEMS production because a post fabrication tuning of the resonant frequency by software is no longer necessary.

The main goal is to trim all mirror elements on a wafer. Additional trimming elements at frequency influencing mirror components enable a trimming of mirrors to a certain frequency value. The laser cutting of trimming elements at the torsion spring effects a frequency decrease because of lowering beam stiffness while the removal of mass trimming elements at the mirror plate increases frequency by mass reduction. The contamination with particles is reduced by processing in fine vacuum and bonding and reflecting areas of the MMD remain clean.

The new laser-tool, which has been developed in collaboration with the Center for Microtechnologies of Technical University of Chemnitz, enables the measurement and trimming of MMDs on a wafer and simplifies the industrial use.

Femtosecond laser sources suit the application as well as picosecond laser sources but a picosecond laser workstation is the first choice because of its higher repetition rate for the development of a suitable system for industrial use.

The laser trimming technique is not limited to Silicon Micro Mirror Devices. It also fits all kinds of sensors and actuators and suits a large variety of materials, for instance ceramics.

Frequency trimming of MEMS devices is a promising approach to overcome these manufacturing tolerances, to tune sensors and actuators for certain operating conditions and it promises an increasing yield in MEMS technology.