Apparatus for controlling plasma size and position in plasma-activated chemical vapor deposition processes comprising rotating dielectric

• US 5,230,740 A
• Filed: 12/17/1991
• Issued: 07/27/1993
• Est. Priority Date: 12/17/1991
• Status: Expired due to Term

• Current Assignee: Advanced Refractory Technologies, Inc.
• Original Assignee: Crystallume Co.
• Inventors: Pinneo, John M.
• Primary Examiner(s): Hearn, Brian E.
• Assistant Examiner(s): BASKIN, JONATHAN
• Application Number:
  US07/809,288
• Time in Patent Office: 588 Days
• Field of Search: 315/111.21, 315/111.41, 333/157, 333/159, 333/99 PL, 11/723, 11/715, 156/345
• US Class Current: 118/723.0MW
• CPC Class Codes: H01J 37/32192 Microwave generated discharge H01J37/32357, H01J37/32366, H01J37/32394, H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32256 Tuning means
• CPC Class Codes: H01J 37/32266 Means for controlling power transmitted to the plasma
• CPC Class Codes: H01J 37/3299 Feedback systems

Abstract

A block of dielectric material having a long axis and a short axis and having low losses at a selected microwave frequency and a dielectric constant selected to produce a desired degree of phase modulation is mounted on a rotatable shaft in an orientation perpendicular to the long and short axes and arranged inside a waveguide feeding a CVD reactor containing a plasma species The block is spun by a rotational force applied to the shaft at an angular acceleration such that the two axes of the block successively intersect the axis of the waveguide within the decay period of the plasma species. The frequency of phase modulation can be varied by changing the angular acceleration of the shaft, and the amplitude of the phase modulation can be varied by changing the ratio of block length to thickness and/or by selecting a material with higher dielectric constant. The incident microwave power may be modulated as a function of angular position of the spin shaft. By moving the apparent plasma and modulating the applied microwave power, a customized temperature profile may be achieved over a desired substrate area.

Claims

1. Apparatus for imparting a regular variation to the relative phase of microwave energy generated in a microwave source and traveling in a waveguide comprising:

a block of dielectric material, rotatably mounted in a fixed position on a shaft in said waveguide, said shaft positioned on an axis centered in said waveguide, said block of dielectric material comprising a solid having a height, a width, and a thickness, said thickness being different from said width, and wherein said fixed position on said shaft is an axis comprising the locus of points defining the center of said width and thickness;

rotating means for rotating said shaft; and

modulating means, coupled to said microwave source and responsive to said rotating means, for modulating the microwave energy output of said source as a function of the orientation of said block in said waveguide.

2. The apparatus of claim 1 wherein said rotating means rotates at a constant rotational speed.

3. The apparatus of claim 1 wherein said block is rectangular in shape.

4. The apparatus of claim 1 wherein the thickness of said block has a cross-sectional shape selected to impart a selected motion profile to a plasma.

5. Apparatus for controlling the position of a plasma within a microwave-enhanced CVD reactor including a reaction chamber, said apparatus comprising:

a first waveguide communicating with said reaction chamber;

a second waveguide communicating with said reaction chamber, said second waveguide being oriented in opposing relation to said first waveguide with respect to said reaction chamber, said first and second waveguides having substantially the same lengths;

microwave energy source means for propagating first and second microwave energy to said reaction chamber through said first and second waveguides, said first and second microwave energy being substantially in phase with each other and substantially equal in magnitude, to create a standing wave in said reaction chamber resulting from the combination of said first and second microwave energy;

a first block of dielectric material, rotatably mounted in a fixed position on a first shaft in said first waveguide, said first shaft positioned on an axis centered in said first waveguide, said first block of dielectric material shaped such that it presents different thicknesses along the axis of said first waveguide a different angular positions of said first shaft, wherein said fixed position on said first shaft is an axis comprising the locus of points defining the center of said width and thickness of said first block of dielectric material;

a second block of dielectric material, rotatably mounted in a fixed position on a second shaft in said second waveguide, said second shaft positioned on an axis centered in said second waveguide, said second block of dielectric material shaped such that it presents different thicknesses along the axis of said second waveguide at different angular positions of said second shaft, wherein said fixed position on said second shaft is an axis comprising the locus of points defining the center of said width and thickness of said second block of dielectric material;

rotating means for rotating said first and second shafts;

means for operating said first and second phase-altering means to control the position of the maxima of said standing wave within said reaction chamber.

modulating means, responsive to said means for rotating said first and second shafts, coupled to said microwave source, for modulating the microwave energy output of said microwave energy source means as a function of the orientation of said first and second blocks in said first and second waveguides.

6. The apparatus of claim 5 wherein said rotating means rotates at a constant rotational speed.

7. The apparatus of claim 5 wherein said block is rectangular in shape.

8. The apparatus of claim 5 wherein the thickness of said first and second blocks each have a cross-sectional shape selected to impart a selected motion profile to a plasma in said reaction chamber.