Using Positive DC Offset of Bias RF to Neutralize Charge Build-Up of Etch Features

• US 20100213172A1
• Filed: 05/11/2010
• Published: 08/26/2010
• Est. Priority Date: 02/23/2006
• Status: Active Grant

• Current Assignee: Aaron R. Wilson
• Original Assignee: Aaron R. Wilson
• Inventors: Wilson, Aaron R.
• Granted Patent: US 8,419,958 B2
• Time in Patent Office: Days
• US Class Current: 216/67
• CPC Class Codes: H01J 37/32706 Polarising the substrate
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/6833 Details of electrostatic chucks
• CPC Class Codes: H02N 13/00 Clutches or holding devices using electrostatic attraction, e.g. using Johnson-Rahbek effect

Abstract

Apparatus, systems and methods for plasma etching substrates are provided. The invention achieves 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 readily integrated into known plasma processing systems.

Claims

1. A method for etching a substrate, comprising:

generating a plasma within a processing chamber to contact a surface of a substrate situated on a support within the chamber;

etching the substrate to form an opening by providing an RF voltage signal to the processing chamber to impose a negative bias on the surface of the substrate relative to the plasma;

generating a constant DC voltage signal that is positive relative to the plasma at an amplitude, frequency and duration effective to cause the negative bias on the substrate surface imposed by the RF voltage signal to change to a positive bias on the substrate surface relative to the plasma; and

selectively operating a control to switch between an open position that precludes electrical communication between the constant DC voltage signal and the substrate support and a closed position that establishes electrical communication between the constant DC voltage signal and the substrate support to intermittently supply the constant DC voltage signal to the substrate support to cause the negative bias on the substrate surface imposed by the RF voltage signal to change to a positive bias on the substrate surface relative to the plasma.

2. The method of claim 1, wherein selectively operating the control delivers a pulsed positive DC voltage signal ranging from a positive voltage to a less positive voltage including a zero voltage.

3. The method of claim 1, wherein the constant DC signal is a waveform pattern signal.

4. The method of claim 3, wherein the waveform pattern is a sinusoid waveform pattern.

5. The method of claim 3, wherein the waveform pattern is a triangle waveform pattern.

6. The method of claim 1, wherein selectively operating the control supplies the constant DC voltage signal to the substrate support to decrease charge build-up within the opening.

7. The method of claim 1, wherein plasma generation is decoupled from substrate bias.

8. The method of claim 1, wherein the plasma is generated by a plasma source selected from the group consisting of 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.

9. A method for etching a substrate, comprising:

etching a surface of substrate to form an opening by providing an RF voltage signal in the presence of a plasma to impose a negative bias on the surface of the substrate relative to the plasma; and

selectively operating a control to intermittently supply a constant positive DC voltage signal to the substrate support at an amplitude, frequency and duration effective to cause the negative bias on the substrate surface imposed by the RF voltage signal to change to a positive bias on the substrate surface relative to the plasma, wherein the control is switched between an open position that prevents and a closed position that permits electrical communication between the constant DC voltage signal and the substrate support.

10. A method for etching a substrate, comprising:

forming a plasma within a processing chamber to contact a surface of a substrate situated within the chamber;

etching the substrate to form an opening by providing an RF voltage signal to the processing chamber to generate and impose a negative bias on the substrate surface relative to the plasma, the bias varying from negative to positive relative to the plasma, wherein ions in the plasma etch the substrate when the bias is negative; and

selectively operating a control to intermittently deliver a positive DC voltage signal as a pulsed signal ranging from a positive voltage to a less positive voltage including a zero voltage at an amplitude, frequency and duration effective to cause the negative bias on the substrate surface imposed by the RF voltage signal to change to a positive bias on the substrate surface relative to the plasma.

11. 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 processing chamber;

an RF voltage power source configured to generate and impose a negative bias across a surface of a substrate supported by the substrate support relative to a plasma to etch an opening in the substrate;

a DC power supply in selectable electrical communication with the substrate support, the DC power supply configured to generate a constant positive DC voltage signal to the substrate support when the DC power supply is in electrical communication with the substrate support to cause the negative bias on the substrate surface imposed by the RF voltage power source to change to a positive bias on the substrate surface relative to the plasma; and

a control to switch between an open position that precludes electrical communication between the constant DC voltage signal and the substrate support and a closed position that establishes electrical communication between the constant DC voltage signal and the substrate support.

12. The apparatus of claim 11, wherein plasma generation is decoupled from substrate bias.

13. The apparatus of claim 11, wherein the plasma generator is configured for generating a plasma source selected from the group consisting of 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.

14. 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 processing chamber;

an RF voltage power source configured to generate and impose a negative bias across a surface of a substrate supported by the substrate support relative to a plasma to etch an opening in the substrate;

a DC power supply in selectable electrical communication with the substrate support, the DC power supply configured to generate a pulsed positive DC voltage signal to the substrate support when the DC power supply is in electrical communication with the substrate support, the pulsed DC voltage signal ranging from a positive voltage to a less positive voltage including a zero voltage at an amplitude, frequency and duration to intermittently cause the negative bias on the substrate surface imposed by the RF voltage power source to change to a positive bias on the substrate surface relative to the plasma; and

a control operable to preclude and establish electrical communication between the DC voltage signal and the substrate support.

15. 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 processing chamber;

an RF voltage power source configured to generate and impose a negative bias across a surface of a substrate supported by the substrate support relative to a plasma to etch an opening in the substrate; and

a function generator power supply in electrical communication with the support substrate and configured to generate a pulsed positive DC voltage signal to the substrate support ranging from a positive voltage to a less positive voltage including a zero voltage at an amplitude, frequency and duration to intermittently cause the negative bias on the substrate surface imposed by the RF voltage power source to change to a positive bias on the substrate surface relative to the plasma.

16. The apparatus of claim 15, wherein the function generator is configured to pulse the positive DC signal in a waveform pattern signal.

17. The apparatus of claim 16, wherein the waveform pattern is a sinusoid waveform pattern.

18. The apparatus of claim 16, wherein the waveform pattern is a triangle waveform pattern.

19. 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 processing chamber;

a function generator power supply in electrical communication with the support substrate and configured to generate a variable voltage signal; and

a filter operable to convert the variable voltage signal to an RF signal, wherein the RF signal imposes a bias, relative to the plasma, across a substrate supported by the substrate support.