Adjusting DC bias voltage in plasma chamber

• US 6,221,782 B1
• Filed: 04/06/1999
• Issued: 04/24/2001
• Est. Priority Date: 12/15/1994
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Pu, Bryan Y., Carducci, James D., Wu, Robert W., Lee, Evans Y., Shan, Hongching, Welch, Michael D., Luscher, Paul E., Blume, Richard
• Primary Examiner(s): Utech, Benjamin L.
• Assistant Examiner(s): Tran, Binh X
• Application Number:
  US09/287,701
• Time in Patent Office: 749 Days
• Field of Search: 438/710, 438/714, 438/726, 438/729, 438/731, 438/733, 156/345
• US Class Current: 438/710
• CPC Class Codes: H01J 37/32477 characterised by the means for protecting vessels or internal parts, e.g. coatings
• CPC Class Codes: H01J 37/32623 Mechanical discharge control means
• CPC Class Codes: H01J 37/32706 Polarising the substrate
• CPC Class Codes: H01J 37/32834 Exhausting

Abstract

A method of adjusting the cathode DC bias in a plasma chamber for fabricating semiconductor devices. A dielectric shield is positioned between the plasma and a selected portion of the electrically grounded components of the chamber, such as the electrically grounded chamber wall. The cathode DC bias is adjusted by controlling one or more of the following parameters: (1) the surface area of the chamber wall or other grounded components which is blocked by the dielectric shield; (2) the thickness of the dielectric; (3) the gap between the shield and the chamber wall; and (4) the dielectric constant of the dielectric material. In an apparatus aspect, the invention is a plasma chamber for fabricating semiconductor devices having an exhaust baffle with a number of sinuous passages. Each passage is sufficiently long and sinuous that no portion of the plasma within the chamber can extend beyond the outlet of the passage. By blocking the plasma from reaching the exhaust pump, the exhaust baffle reduces the deposition of unwanted particles on exhaust pump components. The exhaust baffle also reduces the cathode DC bias by reducing the effective surface area of the electrically grounded chamber wall which couples RF power to the plasma.

Claims

1. A method of adjusting the DC bias voltage at a first electrode in a semiconductor processing plasma chamber, comprising the steps of:

(a) providing a vacuum chamber having an electrically conductive wall;

(b) mounting a first electrode inside the vacuum chamber so as to be electrically insulated from the wall;

(c) maintaining inside the chamber a gas pressure low enough to permit formation of a plasma;

(d) applying RF electrical power between the first electrode and the chamber wall, the power being sufficient to form a plasma inside the chamber;

(e) positioning a dielectric shield between the plasma and a portion of said wall so as to block direct contact between the plasma and said portion of the wall; and

(f) adjusting the DC bias at the first electrode by adjusting at least one of the parameters within the group consisting of

(i) the area of said portion of the wall blocked by the shield,

(ii) the thickness of the shield,

(iii) the spacing between the shield and the wall, and

(iv) the dielectric constant of the shield.

2. A method according to claim 1, further comprising the step of mounting a semiconductor substrate on the first electrode.

3. A method according to claim 1, wherein the positioning step further comprises positioning the shield close enough to the wall to prevent the formation of plasma between the shield and the wall.

4. A method of adjusting the DC bias voltage at a first electrode in a semiconductor processing plasma chamber, comprising the steps of:

providing a plasma chamber having first and second electrodes, the two electrodes being electrically insulated from each other;

forming a plasma inside the chamber;

applying RF electrical power between the first electrode and the second electrode so as to create a DC bias voltage at the first electrode relative to the second electrode;

positioning a dielectric shield between the plasma and a portion of the second electrode so as to block direct contact between the plasma and said portion of the second electrode; and

adjusting said DC bias voltage by adjusting the area of said portion of the second electrode blocked by the shield.

5. A method according to claim 4, further comprising the step of mounting a semiconductor substrate on the first electrode.

6. A method according to claim 4, wherein:

the step of providing a plasma chamber further comprises providing the chamber with an electrically conductive wall, wherein the second electrode includes the electrically conductive wall;

the step of applying RF power comprises providing said RF power between the first electrode and the electrically conductive wall; and

the step of positioning a shield comprises positioning the shield between the plasma and said portion of the electrically conductive wall.

7. A method according to claim 6, further comprising the step of:

connecting the electrically conductive wall to an electrical ground;

wherein the step of applying RF power comprises providing said RF power between the first electrode and the electrical ground.

8. A method of adjusting the DC bias voltage at a first electrode in a semiconductor processing plasma chamber, comprising the steps of:

providing a plasma chamber having first and second electrodes, the two electrodes being electrically insulated from each other;

forming a plasma inside the chamber;

applying RF electrical power between the first electrode and the second electrode so as to create a DC bias voltage at the first electrode relative to the second electrode;

positioning a dielectric shield between the plasma and a portion of the second electrode so as to block direct contact between the plasma and said portion of the second electrode; and

adjusting said DC bias voltage by adjusting the dielectric constant of the shield.

9. A method according to claim 8, wherein:

the dielectric shield has a first dielectric constant; and

the step of adjusting the dielectric constant of the dielectric shield comprises the step of replacing the dielectric shield with a second dielectric shield having a second dielectric constant different from said first dielectric constant.

10. A method according to claim 8, further comprising the step of mounting a semiconductor substrate on the first electrode.

11. A method according to claim 8, wherein:

the step of providing a plasma chamber further comprises providing the chamber with an electrically conductive wall, wherein the second electrode includes the electrically conductive wall;

the step of applying RF power comprises providing said RF power between the first electrode and the electrically conductive wall; and

the step of positioning a shield comprises positioning the shield between the plasma and said portion of the electrically conductive wall.

12. A method according to claim 11, further comprising the step of:

connecting the electrically conductive wall to an electrical ground;

wherein the step of applying RF power comprises providing said RF power between the first electrode and the electrical ground.