ECR position etching for high selectivity and high-rate N⁺ poly-Si patterning

A novel electron cyclotron resonance (ECR) plasma etching technology is described that produces simultaneously highly selective, high-rate, and anisotropic n⁺ poly-Si etching at a low acceleration voltage. ECR position etching for n⁺ poly-Si pattern fabrication is discussed. In this technology, a substrate is located at the ECR position in a plasma chamber, and etching is carried out without RF bias power. Due to the low ion energy, high ion current and highly collimated ion flux at the ECR position, n ⁺ poly-Si etching with a high selectivity and a high rate can be realized. The n⁺ poly-Si etching rate at the ECR position is 3300 A/min, and an anisotropic etching profile is realized by using Cl2 etching gas. The selectivity ratio of n⁺ poly-Si to SiO₂ etching is 260. These etching characteristics are explained by low ion energy, high ion current density and highly collimated ion flux at the ECR position.