Using positive dc offset of bias rf to neutralize charge build-up of etch features

Abstract

Apparatus, systems and methods for plasma etching substrates are provided that achieve dissipation of charge build-up on a substrate being plasma etched to avoid notching or twisting in high aspect ratio contents and similar features. Charge build-up on a substrate being etched by plasma etching can be dissipated by a method for etching a substrate, the method comprising: providing a plasma processing chamber comprising a chamber enclosure and a substrate support adapted to support a substrate within the chamber enclosure; supporting a substrate on the substrate support; forming a plasma within the chamber enclosure such that a surface of the substrate is in contact with the plasma; etching the substrate by generating a negative bias on the substrate surface relative to the plasma; and intermittently changing the bias on the substrate surface to positive relative to the plasma. The present method can be integrated into known plasma processing systems.

1 . An etching apparatus, comprising:
 a plasma processing chamber comprising a chamber enclosure and a substrate support within the chamber enclosure;   a plasma generator coupled to the plasma processing chamber;   an RF voltage power source configured to cause a negative bias, relative to a plasma in the plasma processing chamber, to form across a surface of a substrate on the substrate support to etch an opening in the substrate;   a DC power supply configured to apply a constant positive DC voltage to the substrate support, and to cause the negative bias on the substrate surface to change to a positive bias, relative to the plasma, on the substrate surface; and   a control operably coupled between the DC power supply and the substrate support, the control configured to selectively establish and preclude electrical connection between the DC power supply and the substrate support.   
     
     
         2 . The etching apparatus of  claim 1 , wherein the plasma generator is decoupled from a bias of the substrate. 
     
     
         3 . The etching apparatus of  claim 1 , wherein the plasma generator includes a device selected from the group consisting of an electron cyclotron resonance source, an inductively coupled plasma source, a surface wave plasma source, a helicon wave plasma source, and a capacitive coupled plasma source. 
     
     
         4 . An etching apparatus, comprising:
 a plasma processing chamber comprising a chamber enclosure and a substrate support within the chamber enclosure;   a plasma generator coupled to the plasma processing chamber;   an RF voltage power source configured to cause a negative bias, relative to a plasma in the plasma processing chamber, to form across a surface of a substrate on the substrate support to etch an opening in the substrate; and   a function generator configured to apply a waveform signal to the substrate support, wherein the waveform signal is selected to intermittently cause the negative bias on the substrate surface to change to a positive bias relative to the plasma.   
     
     
         5 . An etching apparatus, comprising:
 a plasma processing chamber comprising a chamber enclosure and a substrate support within the chamber enclosure;   a plasma generator coupled to the plasma processing chamber;   an RF voltage power source configured to cause a negative bias, relative to a plasma in the plasma processing chamber, to faun across a surface of a substrate on the substrate support to etch an opening in the substrate; and   a function generator operably coupled with the substrate support and configured to apply a series of pulses alternating between a positive voltage and a voltage that is less than the positive voltage, including a zero voltage, to the substrate support at an amplitude, frequency and duration selected to intermittently cause the negative bias on the substrate surface to change to a positive bias relative to the plasma.   
     
     
         6 . The etching apparatus of  claim 5 , wherein the series of pulses from the function generator form a waveform pattern. 
     
     
         7 . The etching apparatus of  claim 6 , wherein the waveform pattern is a sinusoidal waveform pattern. 
     
     
         8 . The etching apparatus of  claim 6 , wherein the waveform pattern is a triangular waveform pattern. 
     
     
         9 . The etching apparatus of  claim 6 , wherein the waveform pattern is a square waveform pattern. 
     
     
         10 . The etching apparatus of  claim 6 , wherein the waveform pattern is a repetitive waveform pattern or a single-shot waveform pattern. 
     
     
         11 . The etching apparatus of  claim 5 , further comprising a filter configured to isolate the function generator from an RF signal of the RF voltage power source. 
     
     
         12 . The etching apparatus of  claim 4 , further comprising an amplifier configured to amplify the waveform signal. 
     
     
         13 . The etching apparatus of  claim 4 , further comprising a patterned mask on the substrate configured to shield at least a portion of the substrate from the plasma. 
     
     
         14 . The etching apparatus of  claim 4 , wherein the chamber enclosure is connected to ground (zero volts). 
     
     
         15 . The etching apparatus of  claim 1 , further comprising a matchbox configured to match an impedance of the plasma to an output impedance of the RF voltage power source. 
     
     
         16 . The etching apparatus of  claim 15 , wherein the match box includes a shunt capacitor and a series inductor. 
     
     
         17 . The etching apparatus of  claim 15 , wherein the match box is configured to automatically match the impedance of the plasma to the output impedance of the RF voltage power source. 
     
     
         18 . The etching apparatus of  claim 15 , wherein the match box includes a manual control for tuning the match box. 
     
     
         19 . The etching apparatus of  claim 1 , wherein the control is a switch configured to alternate between an open position and a closed position.