ETCHING METHOD AND PLASMA PROCESSING APPARATUS

An etching method includes providing a substrate on a substrate support in a chamber of a plasma processing apparatus. The etching method further includes etching the substrate with plasma generated in the chamber, thereby forming a recess in the substrate. In the etching, an electrical bias is supplied to the substrate support, to attract ions from the plasma into the substrate. In the etching, at least one of a bias frequency, which is a reciprocal of a time length of a waveform cycle of the electrical bias, and a pulse duty ratio of a pulsed electrical bias is modified to maintain an ion energy flux to the substrate.