Plasma reactor for processing substrates

• US 5,453,305 A
• Filed: 09/02/1993
• Issued: 09/26/1995
• Est. Priority Date: 12/13/1991
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Lee, Young H.
• Primary Examiner(s): Beck, Shrive
• Assistant Examiner(s): Talbot, Brian K.
• Application Number:
  US08/116,164
• Time in Patent Office: 754 Days
• Field of Search: 427/562, 427/563, 427/564, 427/570, 427/571, 427/575, 427/585, 156/643, 219/121.41, 219/121.44, 219/121.56, 219/121.59, 118/723 MR, 118/723 MA, 315/111.01, 315/111.11, 315/111.21, 315/111.31, 315/111.41, 315/111.51, 315/111.61, 315/111.71, 315/111.81, 315/111.91
• US Class Current: 427/562
• CPC Class Codes: B01J 19/126 Microwaves
• CPC Class Codes: B01J 19/129 Radiofrequency
• CPC Class Codes: B01J 2219/0894 Processes carried out in the presence of a plasma
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32192 Microwave generated discharge H01J37/32357, H01J37/32366, H01J37/32394, H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32587 Triode systems
• CPC Class Codes: H01J 37/32596 Hollow cathodes
• CPC Class Codes: H01J 37/32678 Electron cyclotron resonance

Abstract

A plasma reactor and method for forming a dense plasma from a gas is described incorporating a housing, a gas inlet to the housing, a pump for evacuating the housing, a magnetic coil to generate a magnetic field in the housing, a radio frequency power supply, an electrode or induction coil in the housing, a microwave power supply. The invention overcomes the problem of an upper plasma density limit independent of increases in microwave power.

Claims

1. A method for forming a plasma from a gas comprising the steps of:

holding said gas and said plasma to be formed in a housing,

admitting said gas having one or more gas species into said housing,

evacuating said housing to a pressure,

generating a magnetic field along a first axis in a first region within said housing,

applying first radio frequency power along a second axis to said gas and to said plasma in said first region, and concurrently with said step of applying first radio frequency power,

applying microwave power along a third axis to said gas and to said plasma in said first region, whereby electrons are excited to electron cyclotron resonance (ECR) in said first region,

said step of applying first radio frequency power includes the step of selecting the frequency of said first radio frequency power as a function of said magnetic field along said first axis and one of said gas species in said gas whereby ion cyclotron resonance (ICR) is obtained of said ions of said one of said gas species in said plasma.

2. The method of claim 1 wherein said step of applying first radio frequency power includes the step of first positioning in said first region a first electrode of nonmagnetic material, and

second positioning in said housing and outside said first region a second electrode of nonmagnetic material.

3. The method of claim 2 wherein said step of applying first radio frequency power includes the step of applying said first radio frequency power across said first and second electrodes.

4. The method of claim 2 wherein said step of applying first radio frequency power includes the step of selecting said first electrode having inner sidewall surfaces of a material whereby atoms of said material on said inner sidewall surfaces may be ionized in said plasma for deposition on a substrate.

5. The method of claim 4 further including the step of positioning said substrate between said first and second electrodes.

6. The method of claim 1 wherein said step of evacuating inlcudes the step of evacuating said housing below 1 mTorr.

7. The method of claim 1 wherein said step of generating includes the step of generating said magnetic field in the range from 1170 to 1430 gauss.

8. The method of claim 1 wherein said step of applying first radio frequency power includes the step of applying said first radio frequency power at a frequency in the range from 0.1 to 100 MHz.

9. The method of claim 1 wherein said step of applying first radio frequency power includes the step of applying said first radio frequency power in the range from 10 to 500 watts.

10. The method of claim 1 wherein said step of applying first radio frequency power includes the step of applying said first radio frequency power to said plasma in the range from 0.01 W/cm³ to 0.63 w/cm³.

11. The method of claim 2 further including the step of applying second radio frequency power to said second electrode.

12. The method of claim 2 wherein said step of first positioning includes the step of selecting said first electrode having cylindrical inner sidewalks concentric with said first axis.

13. The method of claim 1 further including the step of positioning an extraction grid adjacent said first region, and

applying a voltage to said extraction grid for removing ions from said first region in response to said applied voltage.

14. The method of claim 1 further including the step of positioning an extraction grid adjacent said first region,

applying a voltage to said extraction grid for a first time period to remove ions from said first region,

applying a voltage to said extraction grid for a second time period to repel ions from said first region, and

applying a voltage to said extraction grid for a third time period to remove ions from said first region whereby ions pass through said extraction grid in pulses.

15. The method of claim 14 further including the step of selecting an extraction grid having a plurality of holes therethrough wherein said holes have sidewalls and a longitudinal axis with respect to its sidewalls in a direction, a length and a width whereby ions passing therethrough correspond to said direction and ions striking said sidewalls impinge from an angle off from said predetermined direction and are neutralized.