Substrate processing apparatus and substrate processing method

Abstract

There are provided a substrate processing apparatus and a substrate processing method realizing an effective reduction of a voltage change of a substrate on an electrode to reduce the variation of incident energy of ions entering the substrate. The substrate processing apparatus includes: a first electrode holding a substrate on a main surface of the first electrode; a second electrode facing the first electrode; a RF power source applying to the first electrode a RF voltage whose frequency is equal to or higher than 40 MHz; and a pulse voltage applying unit applying to the first electrode a pulse voltage decreasing in accordance with a lapse of time, by superimposing the pulse voltage on the RF voltage.

1 . A substrate processing apparatus, comprising:
 a chamber;   a first electrode disposed in the chamber and holding a substrate on a main surface of the first electrode;   a second electrode disposed in the chamber to face the first electrode;   a RF power source applying to the first electrode a RF voltage whose frequency is equal to or higher than 40 MHz; and   a pulse voltage applying unit applying to the first electrode a pulse voltage decreasing in accordance with a lapse of time, by superimposing the pulse voltage on the RF voltage.   
     
     
         2 . The substrate processing apparatus according to  claim 1 ,
 wherein the pulse voltage applying unit comprises:
 a power source outputting a voltage periodically decreasing in accordance with the lapse of time; and 
 a first switching unit applying the voltage output from the power source, to the first electrode at a predetermined time interval. 
   
     
     
         3 . The substrate processing apparatus according to  claim 1 ,
 wherein the pulse voltage applying unit comprises:
 a plurality of power sources outputting voltages different from each other; and 
 a second switching unit selecting a voltage among the voltages output from the power sources at a predetermined time interval to apply the selected voltage to the first electrode. 
   
     
     
         4 . The substrate processing apparatus according to  claim 3 , further comprising:
 a voltage measuring unit measuring a voltage of the first electrode or a plasma measuring unit measuring a state of plasma; and   a switching instruction unit instructing the second switching unit to switch among the voltages output from the power sources, according to a result of the measurement by the voltage measuring unit or the plasma measuring unit.   
     
     
         5 . The substrate processing apparatus according to  claim 4 ,
 wherein the state of the plasma is electron density or electron temperature of the plasma.   
     
     
         6 . A substrate processing apparatus, comprising:
 a chamber;   a first electrode disposed in the chamber and holding a substrate on a main surface of the first electrode;   a second electrode disposed in the chamber to face the first electrode;   a RF power source applying to the first electrode a RF voltage whose frequency is equal to or higher than 40 MHz;   a pulse voltage applying unit applying a pulse voltage to the first electrode by superimposing the pulse voltage on the RF voltage;   a variable capacitance capacitor interposed between the first electrode and the pulse voltage applying unit and connected in series to the first electrode;   a voltage measuring unit measuring a voltage of the first electrode or a plasma measuring unit measuring electron density of plasma; and   a control unit changing electric charge capacitance of the variable capacitance capacitor according to a result of the measurement by the voltage measuring unit or the plasma measuring unit.   
     
     
         7 . A substrate processing apparatus, comprising:
 a chamber;   a first electrode disposed in the chamber and holding a substrate on a main surface of the first electrode;   a second electrode disposed in the chamber to face the first electrode;   a RF power source applying to the first electrode a RF voltage whose frequency is equal to or higher than 40 MHz; and   a pulse voltage applying unit applying to the first electrode a voltage having a waveform in which a first period and a second period are repeated, by superimposing the voltage on the RF voltage, the first period having a pulse group waveform including N 1  pieces of pulsed waveforms which are repeated with a break time t 1  and a frequency ω 1 , and the second period being a break time t 2  not including a pulsed waveform and longer than the break time t 1 .   
     
     
         8 . The substrate processing apparatus according to  claim 7 , further comprising:
 a voltage measuring unit measuring a voltage of the first electrode or a plasma measuring unit measuring electron density of plasma; and   a control unit controlling at least one of the number N 1 ,   the frequency ω 1 , and the break times t 1 , t 2  according to a result of the measurement by the voltage measuring unit or the plasma measuring unit.   
     
     
         9 . The substrate processing apparatus according to  claim 7 ,
 wherein the break time t 1  is given by the following expression:
     t 1<1/ω p  [second], 
   where   ωp (=e 2 N 0 /(ε 0 mi)) 1/2 : plasma ion frequency, where   e: electron elementary quantum   ε 0 : vacuum permittivity   mi: mass of ions   N 0 : plasma density   
     
     
         10 . A substrate processing apparatus, comprising:
 a chamber;   a first electrode disposed in the chamber and holding a substrate on a main surface of the first electrode;   a second electrode disposed in the chamber to face the first electrode;   a RF power source applying to the first electrode a RF voltage whose frequency is equal to or higher than 40 MHz;   a pulse voltage applying unit applying a pulse voltage to the first electrode by superimposing the pulse voltage on the RF voltage;   a variable resistor provided between the pulse voltage applying unit and the first electrode; and   a control unit controlling a resistance value R of the variable resistor.   
     
     
         11 . The substrate processing apparatus according to claim  1 ,
 wherein a voltage change of the substrate held on the first electrode in one pulse or in one pulse group is 50 volts or less.   
     
     
         12 . A substrate processing method, comprising:
 holding a substrate to be processed on an electrode disposed in a chamber;   applying to the electrode a RF voltage whose frequency is equal to or higher than 40 MHz; and   applying to the electrode a pulse voltage decreasing in accordance with a lapse of time, by superimposing the pulse voltage on the RF voltage.   
     
     
         13 . A substrate processing method, comprising:
 holding a substrate to be processed on an electrode disposed in a chamber;   applying to the electrode a RF voltage whose frequency is 40 MHz or higher; and   applying to the electrode a voltage having a waveform in which a first period and a second period are repeated, by superimposing the voltage on the RF voltage, the first period having a pulse group waveform including N 1  pieces of pulsed waveforms which are repeated with a break time t 1  and a frequency ω 1 , and the second period being a break time  2  not including a pulsed waveform and longer than the break time t 1 .