Void free filling of TSV vias by bottom up copper electroplating for wafer level MEMS vacuum packaging

Through silicon via (TSV) is an emerging technology for MEMS packaging for MEMS packaging. 370μm deep TSV vias with diameter of 60μm were filled by bottom up copper electroplating with copper methylsulfonate and methane sulfonic acid as base electrolyte. Insulating layer of the wafer was silicon nitride deposited by LPCVD. The TSV vias filling processes include electroplating to fill the vias and wet etching to remove the seed layer and adhesion layer. Patterned photoresist mask was adopted to obtain ideal electroplating results and protect the copper in the vias during the wet etching process. The copper filled wafer with silicon nitride was bonded with Pyrex_7740 glass having cavities by anodic bonding. The results of Helium pressure tests showed that the leak rate was less than 3*10^-9 Pa·m³/s. The results suggested the potential of TSV application in wafer level MEMS vacuum packaging.