The wet etch SiO2 in HF acid is a traditional process in wafer fab. But there is a special problem for this process, which is that there is still natural SiO2 on silicon wafer after wet etching, which will make ohm contact between metal and Si bad. In back-metallization process this is a main technical problem. At present the most of companies can solve it via shortening process time and increasing annealing temperature. But there will be some negative effects on process capacity and quality.

     In MEMS technology SiO2 (or PSG) is a standard sacrificial layer which can be easily remove in HF acid. But there is the adhesion between the Si and structure layer due to the surface tension of water in this kind of release process. In order to solve this problem the high cost will needed.

     The equipments of HF vapor etcher designed and made by MST can solve above problems very well. Its basic principle is that HF acid is changed to vapor via N2 bubble and etches SiO2.

After etching all of resultant and residue will be removed by N2 and the surface of Si wafer will be clean and dry which can directly be metalized without other clean process. For MEMS release process it can overcome the adhesion problem.

     The HF vapor etcher made by MST are special for MEMS release and back metallization process with two types of R&D and productive, which can meet the different users.

       The details for equipments and process: http://www.szmst.com/en/tech.asp?menuid=156

     experimental tpye: "HF vapor etcher(MHHF-01AR).pdf"

     productive tpye: "HF vaor etcher(MHHF-01AP).pdf"