MORI (TM) high-density rf plasma source etching of polysilicon and metal films on wafers

Etching of patterned doped poly-Si and of patterned W or Al metal wafers with high selectivity, high anisotropy, and high rate is achieved using the newly developed MORI rf plasma source. The source operates at low pressure (typically 1 - 3 mtorr) and at 13.56 MHz while achieving high efficiency through the generation of an m equals 0 Whistler wave often referred to as the m equals 0 helicon wave. The chlorine etch selectivity of poly-Si to SiO 2 can exceed 100, the selectivity of poly-Si to photoresist can exceed 10, and the poly-Si etch rate ranges from 2500 A/m to about 4000 A/m, depending upon wafer characteristics. The uniformity is less than 2% (1 sigma) and the chlorine ion saturation current exceeds 15 mA/cm 2 above the wafer location. Uniform, anisotropic etching of Al-1% Si-0.5% Cu using pure Cl 2 or Cl 2 -(5-20%) BCl 3 at 1.5 - 3 mtorr achieves rates exceeding 6000 A/m with selectivity to photoresist (PR) of 9 and selectivity to oxide of 22 using a wafer rf bias power of 30 w at 13.56 MHz. Similarly excellent results are found in the etching of patterned W using SF 6 at 3 mtorr. Etch rates exceed 2500 A/m with selectivity to PR greater than 2 and selectivity to oxide greater than 10.