Very high aspect ratio silicon trench with nearly vertical sidewall profile had been demonstrated by inductively coupled plasma (ICP) etching. This silicon trench with aspect ratio more than 30 and vertical sidewall were basically fabricated by STS ASE™ technology and controlled at proper process parameters. We controlled the appropriate platen power and reaction gas to solve the problem of more positive profile at high aspect ratio trench and avoid the bowing formation on the sidewall simultaneously. Different feature sizes for silicon trench were designed to study the aspect ratio dependent etching properties. The 2.2 μm wide trench etched had aspect ratio of 33 and etching rate of 1.8 μm/min while the 5.0 μm wide trench had aspect ratio of 20 and etching rate of 2.5 μm/min.
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