Fabrication of high-yield Si micro-diaphragms using electrochemical etch-stop in TMAH/IPA/pyrazine solution

This paper presents the fabrication of high-yield Si micro-diaphragms using electrochemical etch-stop method in TMAH/IPA/pyrazine solution. When IPA was added TMAH solution, the flatness of etching front is improved and undercutting is reduced, but the etch rate of (100) Si is decreased. The (100) Si etch rate is improved with addition of pyrazine. The (100) Si etch rate of 0.8/min which is faster by 13% than pure TMAH 20 wt.% solution is obtained using TMAH 20 wt.%/pyrazine 0.5 g and the etch rate of (100) Si is decreased with more additive quantity of pyrazine. Addition of pyrazine to TMAH 25 wt.% solution, the flatness variations of etching front is not observed and undercutting ratio is reduced about 30-50%. Addition of pyrazine to TMAH increases the etch rate of (100) Si, thus the elapsed time for etch-stop was shortened. I-V curves of n- and p-type Si in TMAH/IPA/pyrazine solution were obtained. OCP (Open Circuit Potential) and PP (Passivation Potential) of n- and p-type Si were also obtained, and applied potential was selected between n- and p-type Si's PP. 801 Si micro-diaphragms having 20 thick were fabricated on 5 inches Si wafer using electrochemical etch-stop method in TMAH/IPA/pyrazine solution. The average thicknesses of micro-diaphragms were 20.03 and standard deviation was ±0.26.