Thin Films - Microreactors Made of Glass and Silicon - Microreactors in Organic Chemistry and Catalysis, Second Edition (2013)

Microreactors in Organic Chemistry and Catalysis, Second Edition (2013)

3. Microreactors Made of Glass and Silicon

3.5. Thin Films

In thin film technology there is a distinction between physical vapor deposition (PVD) and chemical vapor deposition (CVD), a combination of types is available. All methods work in vacuum. The most important physical processes are evaporation and the sputtering. The material is introduced into the system as a solid (target). With an energy introduced into the target, they resolve atoms and molecules form a layer on the substrate. The layer thickness achieved is in the micrometer range. The layer composition substantially corresponds to that of the target. It can be pure metals, alloys, or dielectrics.

The chemical vapor deposition is characterized by at least one reaction at the surface of the work piece to be coated. In this process, reaction must have at least one gaseous starting compound and two reaction products – of which at least one in the solid phase.

An important process is the LPCVD (low pressure CVD) at a working temperature of 500–1000 °C and a working pressure of 0.01–10 mbar. With the thermally activated process, frequently silicon dioxide, silicon nitride, and polysilicon can be produced. For heat-sensitive substrates or materials, the PECVD (plasma enhanced CVD) is applied. It ignites the plasma above the wafer; it can either be inductive (inductively coupled PECVD ICPECVD) or capacitive (capacitance-coupled PECVD). The CVD process is carried out at temperatures between 200 and 500 °C. See Refs [6, 10, 11] for more details.