Micromachining is divided into two categories: surface and bulk. In surface micro-machining, layers are added to the substrate and are patterned to create structures. Bulk micromachining uses various techniques to remove pieces of the substrate to create a pattern in the substrate. Most MEMS devices are created using both types of micromachining.
Surface micromachining entails growing, depositing, or coating thin films on a substrate and then patterning the films with a dry or wet etching process. Surface micromachining provides finer, more detailed structures in comparison to bulk micromachining.
To enable high-quality surface micromachining, Brewer Science offers anti-reflective coatings, sacrificial layers, planarizing coatings, and optical coatings.
Brewer Science® anti-reflective coatings improve the photolithographic process, enabling fine resolution of photoresist features.
Brewer Science® sacrificial layer materials allow the patterned deposition of metals, oxides, and inorganics. Typically the sacrificial layer is placed under a photoresist so that the photoresist can be removed after deposition.
As structures on the substrate become more three-dimensional (3-D), photoresist uniformity over the structures becomes more difficult. Brewer Science® leveling materials fill in the structures to create a flat surface for the photoresist. Once the photoresist has accomplished its task, it and the leveling material are normally removed.
Brewer Science® optical coatings provide transparent films that are spin-applied and offer either high or low refractive indices.
- ARC® bottom anti-reflective coatings
- Level™ M10 planarizing material
- GF and WGF planarizing materials
Bulk micromachining is a process of removing pieces of the substrate. This process can be done using a wet process (alkaline or acidic etching) or it can be done using gas particles to “sandblast” the surface (deep reactive ion etching, DRIE). In wet processes, areas of the wafer are masked to prevent the etchants from reaching the surface. These areas will remain intact after the wet etch. Typical masking materials are inorganic films or spin-applied organics. The inorganic films, such as silicon nitride or silicon oxide, are chemically vapor deposited.
Organic films, such as Brewer Science® ProTEK® coatings, are spin-applied. These films can be used as either blanket coatings to protect one side of the wafer or are exposed to UV light to pattern them.