Apparatus for monitoring substrate biasing during plasma processing of a substrate

• US 6,367,413 B1
• Filed: 05/26/2000
• Issued: 04/09/2002
• Est. Priority Date: 06/15/1999
• Status: Expired due to Term

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Jones, William D., Sill, Edward L., Baldwin, Craig T.
• Primary Examiner(s): Mills, Gregory
• Assistant Examiner(s): ALEJANDRO MULERO, LUZ L
• Application Number:
  US09/580,824
• Time in Patent Office: 683 Days
• Field of Search: 118/723.E, 118/723.ER, 118/728, 118/712, 118/723.I, 118/723.IR, 118/723.MW, 118/723.ME, 118/723.MR, 118/723.MA, 118/723.AN, 156/345, 315/111.21, 315/111.31, 361/225, 361/233, 361/234, 361/235
• US Class Current: 118/723.00E
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32174 Circuits specially adapted for controlling the RF discharge
• CPC Class Codes: H01J 37/32706 Polarising the substrate

Abstract

A processing system for processing a substrate with a plasma comprises a processing chamber configured for containing a plasma and a substrate support. Electrodes are coupled to the substrate support and an RF power source is coupled to each of the electrodes for biasing the electrodes to create a DC bias on a substrate positioned on the supporting surface. A first comparator having first and second inputs is electrically coupled to one of the electrodes with an isolating device being coupled between the first and second inputs to isolate the first input from the bias on the one electrode. The comparator has an output reflective of a voltage difference between the first and second inputs. A second comparator has a first input coupled to the first electrode and a second input coupled to the second electrode, and has an output reflective of a voltage difference between the first and second inputs resulting from the bias difference between the first and second electrodes.

Claims

1. A processing system for processing a substrate with a plasma comprising:

a processing chamber configured for containing the plasma;

a substrate support within the chamber having a supporting surface for supporting the substrate proximate the plasma;

at least first and second electrodes coupled to the substrate support, the electrodes each being positioned proximate the supporting surface and being electrically isolated from one another;

an RF power source coupled to each of the electrodes for biasing the electrodes, the biased electrodes developing a DC bias thereon and operable for creating a DC bias on the substrate positioned on the supporting surface;

a first comparator having first and second inputs electrically coupled to one of the electrodes to measure the DC bias of the electrode, an isolating device being coupled between the first input and the second input and operable for isolating the first input from the DC bias on the one electrode created by the RF power source, the comparator having an output reflective of a voltage difference between the first and second inputs resulting from the electrode DC bias created by the RF power source;

a second comparator having a first input coupled to the first electrode and a second input coupled to the second electrode, the comparator having an output reflective of a voltage difference between the first and second inputs of the second comparator resulting from the DC bias difference between the first and second electrodes;

wherein the relative RF-created DC bias levels on the first and second electrodes may be monitored so that the DC bias levels may be optimally adjusted.

2. The processing system of claim 1 further comprising a first capacitor electrically coupled between the RF power source and at least one of the electrodes;

the first capacitor having a variable capacitance for varying the DC bias created on the substrate by the at least one electrode relative to the DC bias created on the substrate by at least one of the other electrodes of the electrodes, the varied DC bias thereby varying the effect of a plasma on one portion of the substrate relative to the effect of the plasma on another portion of the substrate.

3. The processing system of claim 2 further comprising a second capacitor coupled to another of said electrodes such that the DC bias created by the electrodes may be varied relative to each other.

4. The processing system of claim 1 wherein the substrate support is formed of a dielectric material and the electrodes are embedded in the dielectric material.

5. The processing system of claim 1 further comprising a DC power source coupled to the electrodes, the DC power source operable for creating a DC potential difference between the two electrodes for electrostatically clamping a substrate to the supporting surface of the substrate support.

6. The processing system of claim 1 wherein at least one of the inputs of the first comparator is coupled to the electrode through a voltage dividing circuit, the voltage dividing circuit having a variable resistor which may be adjusted to vary a voltage level at the comparator input.

7. The processing system of claim 1 wherein at least one of the inputs of the second comparator is coupled to a respective electrode through a voltage dividing circuit, the voltage dividing circuit having a variable resistor which may be adjusted to vary a voltage level at the comparator input.

8. The processing system of claim 7 further comprising an automatic adjustment device coupled to the variable resistor for automatically varying the resistance of the variable resistor, the automatic adjustment device being coupled to the output of the second comparator such that the resistance is varied based upon said output of the second comparator.

9. The processing system of claim 8 further comprising a disabling switch operably coupled to the RF power source and the automatic adjustment device, the disabling switch operable for disabling the automatic adjustment device when RF power is delivered to the electrodes by the RF power source.

10. The processing system of claim 7 further comprising a third comparator having a first input coupled to the first electrode and a second input coupled to the second electrode, the third comparator having an output reflective of a voltage difference between the first and second inputs of the third comparator resulting from the bias difference between the first and second electrodes.

11. The processing system of claim 1 wherein said isolating device is a diode.

12. A processing system for processing a substrate with a plasma comprising:

a processing chamber configured for containing the plasma;

a substrate support within the chamber having a supporting surface for supporting the substrate proximate the plasma;

first and second electrodes coupled to the substrate support, the electrodes each being positioned proximate the supporting surface and being electrically isolated from one another;

a DC power source coupled to the electrodes, the DC power source operable for creating a DC potential difference between the two electrodes for electrostatically clamping the substrate to the supporting surface of the substrate support;

an RF power source coupled to each of the electrodes simultaneously with the DC power source for biasing the electrodes, the RF biased electrodes developing a DC bias thereon and operable for creating a DC bias on the substrate positioned on the supporting surface;

a first comparator having first and second inputs each electrically coupled to one of the electrodes to measure the DC bias of the electrode, an isolating device being coupled between the first input and the second input and operable for isolating the first input from the DC bias on the one electrode created by the RF power source, the comparator having an output reflective of a voltage difference between the first and second inputs resulting from the electrode DC bias created by the RF power source;

at least one of the first comparator inputs being coupled to one of the electrodes through a voltage dividing circuit including a variable resistor which may be adjusted to vary a voltage level at the comparator input;

a second comparator having a first input coupled to the first electrode and a second input coupled to the second electrode, the second comparator having an output reflective of a voltage difference between the first and second inputs of the second comparator resulting from the bias difference between the first and second electrodes;

at least one of the second comparator inputs being coupled to one of the electrodes through a voltage dividing circuit including a variable resistor which may be adjusted to vary a voltage level at the comparator input;

wherein the relative RF-created DC bias levels on the first and second electrodes may be monitored so that the DC bias levels may be optimally adjusted.

13. The processing system of claim 12 further comprising an automatic adjustment device coupled to the variable resistor which is coupled to the second comparator for automatically varying the resistance of the variable resistor, the automatic adjustment device being coupled to the output of the second comparator such that the resistance is varied based upon said output.

14. The processing system of claim 13 further comprising a disabling switch operably coupled to the RF power source and the automatic adjustment device, the disabling switch operable for disabling the automatic adjustment device when RF power is delivered to the electrodes by the RF power source.

15. The processing system of claim 12 further comprising a third comparator having a first input coupled to the first electrode and a second input coupled to the second electrode, the third comparator having an output reflective of a voltage difference between the first and second inputs of the third comparator resulting from the bias difference between the first and second electrodes.

16. The processing system of claim 12 wherein said isolating device is a diode.