In　this　paper,　based　on　the　relationships　of　the　etch-rate　with　the　feature　widths　(FWs)　from　2μm　to　100μm　and　the　results　of　the　etch-rate　changing　with　etch-time　for　a　particular　FW,　which　were　obtained　by　our　experiments,　a　possible　etching　process　model　was　proposed.　When　the　etch-time　was　relatively　short,　it　was　a　reaction　limited　process.　With　the　etch-time　going　on,　the　fresh　reactive　gas　was　difficult　to　diffuse　through　the　etching　trench　to　the　fresh　reaction　interface,　the　etch-rate　decreased,　which　was　called　the　residual　removing　limited　process.　Our　mathematic　fitting　results　proved　the　above　etching　model　and　pointed　out　that　for　the　reaction　limited　process,　the　etch　depth　linearly　increase　with　the　etch　time.　When　the　etch　process　was　dominated　by　the　residual　removing　limited　process,　the　etch-rate　decreased.　©　The　Electrochemical　Society.