Study on the sticking materials on tools in micromilling of single crystalline silicon

It is noticed some materials are stuck to micro tools in micromilling of single crystalline silicon and tool geometries have been changed greatly. Consequently, ductile-regime material removal cannot be realised sometimes even using the same micro tool and process parameters. Based on EDS analysis, elements of the sticking materials are identified. The dominant sticking materials are estimated as SiO2 and the sticking phenomenon has been explained in a chemical reaction way. Countermeasures to remove the sticking materials are proposed and examined. It is found that alkali solution can work well to remove these materials and the feasible removal time is one minute. Finally, an in-process interval cleaning method using alkali solution is proposed and verified in micromilling of the single crystalline silicon. By the proposed method, batch production of silicon substrate used in MEMS becomes possible from the micro cutter point of view.