Dosimetry using optical emission spectroscopy/residual gas analyzer in conjunction with ion current

Abstract

The present invention generally provides methods and apparatus for controlling ion dosage in real time during plasma processes. In one embodiment, ion dosages may be controlled using in-situ measurement of the plasma from a mass distribution sensor combined with in-situ measurement from an RF probe.

1 . An apparatus for processing a substrate, comprising:
 a process chamber defining a process volume;   a conductive support pedestal positioned in the process volume;   a gas distribution assembly connected to a gas panel and positioned parallel the conductive support pedestal, wherein an RF plasma bias power supply is coupled between the gas distribution assembly and the conductive support pedestal;   a first sensor configured to monitor one or more attributes of a plasma generated in the process volume;   a second sensor configured to monitor one or more attribute of the RF plasma bias power supply; and   a controller coupled to the first and second sensors, wherein the controller is configured to receive and analyze signals from the first and second sensors.   
   
   
       2 . The apparatus of  claim 1 , wherein the first sensor is one of an optical emission spectrometer, a mass spectrometer and a residual gas analyzer. 
   
   
       3 . The apparatus of  claim 2 , wherein the second sensor is a RF voltage/current probe. 
   
   
       4 . The apparatus of  claim 2 , wherein the second sensor is a RF voltage/current probe connected to the RF plasma bias power supply. 
   
   
       5 . The apparatus of  claim 3 , wherein the controller is configured to monitor dosage of one or more ion species in the plasma generated in the process volume using measurements from the first sensor combined with measurements from the second sensor. 
   
   
       6 . The apparatus of  claim 1 , further comprises a toroidal plasma source in fluid communication with the process volume. 
   
   
       7 . An apparatus for processing a substrate, comprising:
 a plasma reactor having a process volume;   a first sensor configured to monitor one or more attributes of a plasma generated in the process volume by a RF bias power supply coupled to the plasma reactor;   a second sensor configured to monitor one or more attribute of a RF bias power supply; and   a controller coupled to the first and second sensors, wherein the controller is configured perform a process comprising:
 obtaining a value of the one or more attributes of the plasma from the first sensor; 
 obtaining a value of the one or more attributes of the RF bias power supply from the second sensor; and 
 determining a real time dose value of one or more ion species in the plasma from the value of the one or more attributes of the plasma and the value of the one or more attributes of the RF bias power supply. 
   
   
   
       8 . The apparatus of  claim 7 , wherein the one or more attributes of the RF bias power supply comprises a value of total ion current. 
   
   
       9 . The apparatus of  claim 8 , wherein the first sensor is one of an optical emission spectrometer, a mass spectrometer and a residual gas analyzer. 
   
   
       10 . The apparatus of  claim 8 , wherein the second sensor is a RF voltage/current probe connected to a feedpoint of the RF bias power supply. 
   
   
       11 . The apparatus of  claim 10 , wherein determining the real time dose value of the one or more ion species in the plasma comprises:
 determining a real time value of a ratio of the one or more ion species over total ions in the plasma using a real time value of the at least one attribute of the plasma measured by the first sensor;   determining a real time value of a total ion current near a feedpoint of the RF bias power supply measured by the second sensor coupled to the feed point of the RF bias power;   calculating a current value of the one or more ion species by multiplying the ratio of the one or more ion species in the plasma and the total ion current; and   integrating the current value of the one or more ion species over time.   
   
   
       12 . The apparatus of  claim 11 , wherein determining real time value of the total current comprises transforming the total ion current near the feedpoint of the RF bias power supply to a total ion current near a surface of the substrate. 
   
   
       13 . The apparatus of  claim 7 , wherein the method performed by the controller further comprises adjusting at least one attribute of the plasma reactor according to the real time dosage value of the one or more ion species in the plasma. 
   
   
       14 . An apparatus for processing a substrate, comprising:
 a process chamber defining a process volume;   a conductive support pedestal positioned in the process volume and configured to support the substrate during processing;   a gas distribution assembly positioned parallel the conductive support pedestal;   an RF plasma bias power supply coupled between the gas distribution assembly and the conductive support pedestal and configured to generate a plasma in the process volume;   a first sensor configured to monitor one or more attributes of the plasma generated in the process volume;   a second sensor configured to monitor one or more attribute of the RF plasma bias power supply; and   a controller coupled to the first and second sensors, wherein the controller is configured to apply a desired dose of a material to the substrate.   
   
   
       15 . The apparatus of  claim 14 , wherein the controller is configured to perform a process comprising:
 obtaining a value of an attribute of the ions of the material in the plasma using the first sensor;   obtaining a value of a total current of the RF bias power supply using the second sensor;   determining a real time dosage value of the material using the value of the attribute of the ions of the material and the value of the total current of the RF bias power supply; and   terminating the plasma when the real time dosage value is within an error range of the desired dose.   
   
   
       16 . The apparatus of  claim 15 , wherein the attribute of the ions of the material is a ratio of the ions of the material over total ions in the plasma. 
   
   
       17 . The apparatus of  claim 16 , wherein the first sensor is one of an optical emission spectrometer, a mass spectrometer and a residual gas analyzer. 
   
   
       18 . The apparatus of  claim 15 , wherein the second sensor is a RF voltage/current probe coupled to a feedpoint of the RF bias power supply and configured to measure voltage, current and phase of the RF bias power supply. 
   
   
       19 . The apparatus of  claim 18 , wherein the process performed by the controller further comprises transforming the total current of the RF bias power supply to a total ion current near a surface of the substrate. 
   
   
       20 . The apparatus of  claim 19 , wherein transferring the total current of the RF bias power supply to the total ion current near the surface of the substrate comprises:
 transforming the total current of the RF bias power supply from time domain to frequency domain;   correcting the total current of the RF bias power supply in frequency domain using calibration data of the second sensor; and   obtaining the total ion current near the surface of the substrate by transforming corrected total current in frequency domain to time domain.