Voltage waveform generator for ion energy control in plasma processing

A voltage waveform generator (1107) for a plasma assisted processing apparatus comprises an output node (510), a switch node (511) electrically coupled to the output node, and a multilevel voltage source converter (1101) coupled to the switch node, which is configured to apply a sequence of monotonically descending voltage levels at the switch node, each of the voltage levels being applied for a respective predetermined time period such that a pitch defined by the voltage levels and the respective predetermined time periods corresponds with a negative voltage slope of a portion of a tailored voltage waveform at the output node. The tailored voltage waveform controls an ion energy on an exposed surface of a substrate processed by plasma generated ions. The multilevel voltage source converter comprises a T-type converter (1111) in series with at least one H-bridge cell (1112).