Negative ion control for dielectric etch

摘要

Apparatus, methods, and computer programs for semiconductor processing in a capacitively-coupled plasma chamber are provided. A chamber includes a bottom radio frequency (RF) signal generator, a top RF signal generator, and an RF phase controller. The bottom RF signal generator is coupled to the bottom electrode in the chamber, and the top RF signal generator is coupled to the top electrode. Further, the bottom RF signal is set at a first phase, and the top RF signal is set at a second phase. The RF phase controller is operable to receive the bottom RF signal and operable to set the value of the second phase. Additionally, the RF phase controller is operable to track the first phase and the second phase to maintain a time difference between the maximum of the top RF signal and the minimum of the bottom RF signal at approximately a predetermined constant value, resulting in an increase of the negative ion flux to the surface of the wafer.

主权项

1. A capacitively-coupled plasma chamber, comprising:
a bottom radio frequency (RF) signal generator coupled to a bottom electrode, the bottom RF signal set at a first frequency at a first phase; a top RF signal generator coupled to a top electrode, the top RF signal set at the first frequency at a second phase, the top electrode being at a predetermined distance from the bottom electrode; and an RF phase controller configured to determine the first phase of the bottom RF signal and configured to calculate a predetermined value as a travel time required for negative ions formed near a top plasma sheath of the plasma to travel the predetermined distance towards the bottom electrode, wherein the RF phase controller is further configured to set a value of the second phase of the top RF signal generator based on the predetermined value, wherein the RF phase controller is configured to set the second phase to maintain a time difference between a maximum of the top RF signal and a minimum of the bottom RF signal at approximately the predetermined value.