Enhanced selectivity over a photoresist film and process optimization for reactive ion etching of NiCr

• NiCr films are patterned by RIE though a photoresist mask using Cl2/BCl3/SF6.
• The selectivity over the photoresist is increased by 4.4–8.3 times by adding SF6.
• The impact of various gas mixtures, pressures, and RF powers are studied.
• Optimum etch parameters are found.

A high-selectivity patterning technology of NiCr thin films was first suggested in this paper. NiCr thin films were etched through a photoresist mask using a gas combination of Cl2/BCl3/SF6 in a reactive ion etching (RIE) system. The impact of various gas mixtures, pressures, and RF powers were studied and optimum etch parameters were found, based on NiCr etch rate, resist etch rate, and non-uniformity on 6 in. diameter wafers. The photoresist etch rate was decreased by 3.4–7 times and the selectivity of NiCr over photoresist was increased by 4.4–8.3 times by introducing a small amount of SF6 in Cl-based plasma, which made it possible to pattern NiCr films using a standard lithographic resist as mask. Optimized NiCr etch rate and uniformity were achieved in low pressure (⩽20 mtorr), with high BCl3 concentration (BCl3:Cl2:SF6 = 90 sccm:10 sccm:5 sccm), at a RF power of 700 W.

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