The aim of bulk micromachining is to produce isolated and movable three-dimensional structures out of a silicon substrate. Examples of this type of basic structure for micromechanical systems, such as sensors and actuators, can include trenches, pits, bridges, or membranes. A main point of technical emphasis in bulk micromachining lies in the structuring of silicon using plasma etching or wet chemical etching in order to create trenches and deep pits. Fraunhofer IPMS has extensive experience and modern equipment for the manufacture of trenches using plasma etching techniques. Fraunhofer IPMS' technical expertise in bulk micromachining is emphatically applied to the development and production of MEMS scanners and pressure sensors.

Whereas structures are etched into the silicon substrate in bulk micromachining, in surface micromachining they are built onto the substrate, where substrates with pre-made CMOS circuits are commonly used. Therefore it is possible to monolithically integrate sensors or actuators with an electronic control system. Movable structures on CMOS wafers are manufactured through the use of sacrificial layer technologies. The elements that will be movable (such as springs or mirrors) are deposited and structured on the sacrificial layer using thin-film techniques. The sacrificial layer, in turn, will be introduced to the CMOS backplane. At the end of this process these structures are cleared from the sacrificial layer through isotropic etching, thus making them movable. In current projects within Fraunhofer IPMS, the organic sacrificial layers (such as polymers or coatings) used until now are being replaced with inorganic alternatives (e.g. SiO₂ or a-Si). Enhanced standard steps are thereby being introduced into sacrificial layer technologies, which will result in more stable processes and will make it possible to create structures of greater complexity.