PMMA As an etch mask for silicon micromachining a feasibility study.

Dhananjay Bodas, Sheetal J Patil, V N Krishnamurthy, S A Gangal


Silicon micromachining requires a proper etch mask, which can withstand the action of etchant during the fabrication of typical structures. Widely used etch mask materials are SiO2 , Si3N4, gold (Au), chromium (Cr) and boron diffusion. Deposition of these on substrates requires expensive equipment. Mihaela Ilie et al. [Proc. SPIE Materials and Device Characterization in Micromachining, 1998, 3512, 4221] reported PMMA as a mask layer on the backside during silicon etching by KOH solution. This etch mask is cheap and is easy to use. In the present work, PMMA is deposited on silicon substrate with a simple technique of spin-coating. The adhesion of spincoated film of PMMA on silicon wafer is an important parameter for its use as an etch mask, while etching in aqueous KOH solution for silicon micromachining. Pre- and posttreatments have been performed on silicon substrate and the mask layer to achieve greater adhesion of the mask material. Feasibility is demonstrated of the use of PMMA as etch mask.made to crystallize the thin films at as low a processing temperature as possible. The properties studied include dielectric measurements and hysteresis. Thin films of calcium-modified lead titanate (PCT) were also prepared by the sol gel technique and their pyroelectric characteristics were studied for use in infrared was coated. These results show that the crystalline quality and deposition rate can be controlled over a wide range by this method.


Silicon micromachining; etch mask; PMMA

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