Extremely highly selective phosphorus-doped polycrystalline silicon etching is achieved at the electron cyclotron resonance (ECR) position in a newly developed ECR plasma etching system. To characterize these etching results, the ion current density and the ion energy distribution in a ECR plasma are measured. Microwave power is absorbed completely at the ECR position. Therefore, the ECR position has maximum ion current density in an ECR plasma. Moreover, the mean ion energy and the width of ion energy distribution has minimum values at the ECR position. The ECR position in the ECR plasma can satisfy a high ion current density and a low ion energy at the same time. These characteristics correspond to the etching results.
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