Plasma processing with enhanced charge neutralization and process control

Abstract

A plasma processing apparatus includes a platen that supports a substrate for plasma processing. A RF power supply generates a multi-level RF power waveform at an output having at least a first period with a first power level and a second period with a second power level. A RF plasma source having an electrical input that is electrically connected to the output of the RF power supply generates at least a first RF plasma with the first RF power level during the first period and a second RF plasma with the second RF power level during the second period. A bias voltage power supply having an output that is electrically connected to the platen generates a bias voltage waveform that is sufficient to attract ions in the plasma to the substrate for plasma processing.

1 . A plasma processing apparatus comprising:
 a. a platen that supports a substrate for plasma processing;   b. a RF power supply that generates a multi-level RF power waveform at an output, the multi-level RF power waveform having at least a first period with a first power level and a second period with a second power level;   c. a RF plasma source having an electrical input that is electrically connected to the output of the RF power supply, the RF plasma source generating at least a first RF plasma with the first RF power level during the first period and a second RF plasma with the second RF power level during the second period; and   d. a bias voltage power supply having an output that is electrically connected to the platen, the bias voltage power supply generating a bias voltage waveform that is sufficient to attract ions in the plasma to the substrate for plasma processing.   
   
   
       2 . The plasma processing apparatus of  claim 1  wherein the plasma processing apparatus comprises a plasma etching apparatus. 
   
   
       3 . The plasma processing apparatus of  claim 1  wherein the plasma processing apparatus comprises a plasma deposition apparatus. 
   
   
       4 . The plasma processing apparatus of  claim 1  wherein the plasma processing apparatus comprises a plasma doping apparatus. 
   
   
       5 . The plasma processing apparatus of  claim 1  wherein at least one of the first and the second power levels are substantially constant during respective ones of the first and the second periods. 
   
   
       6 . The plasma processing apparatus of  claim 1  wherein the second RF power level is chosen so that the plasma in the second period has enough electrons to at least partially neutralize charge accumulating on the substrate during the second period, thereby reducing charging effects on the substrate. 
   
   
       7 . The plasma processing apparatus of  claim 1  wherein a relative timing of the RF power waveform and the bias voltage waveform is chosen to at least partially neutralize charge accumulating on the substrate. 
   
   
       8 . The plasma processing apparatus of  claim 1  wherein the bias voltage waveform is substantially synchronized to the multi-amplitude RF power waveform. 
   
   
       9 . A plasma processing apparatus comprising:
 a. a platen that supports a substrate for plasma processing;   b. a RF power supply that generates a multi-level RF power waveform at an output, the multi-level RF power waveform having at least a first period with a first power level and a second period with a second power level;   c. a RF plasma source having an electrical input that is electrically connected to the output of the RF power supply, the RF plasma source generating a first RF plasma with the first RF power level during the first period and a second RF plasma with the second RF power level during the second period; and   d. a bias voltage power supply having an output that is electrically connected to the platen, the bias voltage power supply generating a bias voltage waveform that is synchronized to the RF power waveform and having at least a first bias voltage during a first period with a potential that is sufficient to attracts ions in the plasma to the substrate for plasma processing and a second bias voltage during a second period.   
   
   
       10 . The plasma processing apparatus of  claim 9  wherein at least one of the first and the second RF power levels are substantially constant during respective ones of the first and the second periods. 
   
   
       11 . The plasma processing apparatus of  claim 9  wherein at least one of the first and second RF power level, the first and second bias voltage, and the first and second period is chosen to achieve at least one of a predetermined process rate and a predetermined process profile. 
   
   
       12 . The plasma processing apparatus of  claim 9  wherein the second bias voltage has a potential that assists in neutralizing charge accumulating on the substrate. 
   
   
       13 . The plasma processing apparatus of  claim 9  wherein the second RF power level is chosen so that the plasma in the second period has enough electrons to at least partially neutralize charge accumulating on the substrate during the second period, thereby reducing charging effects on the substrate. 
   
   
       14 . The plasma processing apparatus of  claim 9  wherein the second bias voltage is substantially at ground potential. 
   
   
       15 . The plasma processing apparatus of  claim 9  wherein the bias voltage waveform is substantially synchronized to the multi-amplitude RF power waveform. 
   
   
       16 . The plasma processing apparatus of  claim 15  wherein the pulses in the RF power waveform are substantially aligned in time with the pulses in the bias voltage waveform. 
   
   
       17 . The plasma processing apparatus of  claim 15  wherein the pulses in the RF power waveform are displaced in time relative to the pulses in the bias voltage waveform. 
   
   
       18 . The plasma processing apparatus of  claim 9  wherein a relative timing of the RF power waveform and the bias voltage waveform is chosen to at least partially neutralize charge accumulating on the substrate. 
   
   
       19 . The plasma processing apparatus of  claim 9  wherein a frequency of the RF power waveform in the first period is different from a frequency of the RF power waveform in the second period. 
   
   
       20 . A plasma processing apparatus comprising:
 a. a platen that supports a substrate for plasma processing;   b. a RF power supply that generates a multi-amplitude RF power waveform at an output having a first power level during a first period, a second power level during a second period, and a third power level during a third period;   c. a plasma source having an electrical input that is electrically connected to the output of the pulsed power supply, the plasma source generating a first plasma with the first power level during a first period and a second plasma with the second power level during a second period, and substantially extinguishing the plasma during the third period; and   d. a bias voltage power supply having an output that is electrically connected to the platen, the bias voltage power supply generating a bias voltage waveform having a first voltage during a first period and a second voltage during a second period, the first voltage being sufficient to attract ions in the plasma to the substrate for plasma processing.   
   
   
       21 . The plasma processing apparatus of  claim 20  wherein the bias voltage waveform is substantially synchronized to the multi-amplitude RF power waveform. 
   
   
       22 . The plasma processing apparatus of  claim 20  wherein the second RF power level is sufficient to maintain the plasma with enough electrons to at least partially neutralize charge accumulating during the second period, thereby reducing charging effects on the substrate. 
   
   
       23 . The plasma processing apparatus of  claim 20  wherein a relative timing of the multi-amplitude RF power waveform and the bias voltage waveform is chosen to at least partially neutralize charge accumulating on the substrate. 
   
   
       24 . A plasma processing apparatus comprising:
 a. a platen that supports a substrate for plasma processing;   b. a RF power supply that generates a RF power waveform at an output, the RF power waveform having at least a first period and a second period;   c. a RF plasma source having an electrical input that is electrically connected to the output of the RF power supply, the RF plasma source generating a first RF plasma during the first period and a second RF plasma during the second period; and   d. a bias voltage power supply having an output that is electrically connected to the platen, the bias voltage power supply being synchronized to the RF power waveform and having a first bias voltage during a first period that is sufficient to attracts ions in the plasma to the substrate for plasma processing and a second bias voltage during a second period.   
   
   
       25 . A plasma processing apparatus comprising:
 a. a means for generating a pulsed plasma with a first power level during a plasma processing period, and a second power level during a charge neutralization period; and   b. a means for generating a bias voltage waveform having a first voltage for extracting ions from the plasma during the plasma processing period and a second voltage during a second period that allows electrons in the plasma to at least partially neutralize charge accumulating on a substrate during plasma processing.