Methods and apparatuses for effectively reducing gas residence time in a plasma processing chamber

Patent metadata

Field	Value
Publication number	US-9299541-B2
Application number	US-201213436728-A
Country	US
Kind code	B2
Filing date	Mar 30, 2012
Priority date	Mar 30, 2012
Publication date	Mar 29, 2016
Grant date	Mar 29, 2016

Abstract

Methods and apparatuses for controlling plasma generation in a plasma processing chamber to reduce an effective residence time of by-product gases or to control in real time the concentration of certain polymer pre-cursors or reaction by-products in the plasma processing chamber are disclosed. The gas residence time is “effectively” reduced by reducing the plasma reaction for at least a portion of the process time. Thresholds can be provided to control when the plasma reaction is permitted to proceed at the full rate and when the plasma reaction is permitted to proceed at the reduced rate. By reducing the rate of plasma by-product generation at least for a portion of the process time, the by-product gas residence time may be effectively reduced to improve process results.

First claim

What is claimed is:

1. A plasma processing system having at least one plasma processing chamber for processing a substrate, comprising: a lower electrode for supporting said substrate; a chamber ceiling disposed above said lower electrode such that a plasma processing region exists between an upper surface of said substrate and said chamber ceiling during said processing; a plasma generation power source for providing energy to generate a plasma in said plasma processing region from supplied reactant gas; a light emitting apparatus for emitting a first light into said plasma processing region; a light receiving apparatus for receiving a second light, said second light representing an altered version of said first light after said first light passes through said plasma processing region; and
a controller configured to analyze said second light to ascertain whether a parameter of said second light equals or exceeds a first threshold indicative of a first concentration of by-product gases resulting from a reaction of the plasma with an exposed surface of the substrate or equals or falls below a second threshold indicative of a second concentration of the by-product gases, wherein said controller controls an effective gas residence time of by-product gases on the upper surface of the substrate by adjusting the plasma generation energy level between a full mode of plasma generation and a reduced mode of plasma generation by sending a first signal for reducing an amount of plasma generation energy to a plasma generation energy level associated with the reduced mode of plasma generation provided by said plasma generation power source if said parameter of said second light equals or exceeds said first threshold, said controller sends a second signal for increasing said amount of plasma generation energy provided by said plasma generation power source to a plasma generation energy level associated with the full mode of plasma generation if said parameter of said second light equals or falls below said second threshold, wherein the plasma generation energy level associated with the reduced mode of plasma generation is sufficiently low as to minimize or stop the reaction of the plasma with exposed surfaces of the substrate such that the concentration of by-product gases reduces over time in the reduced mode of plasma generation, and wherein the plasma generation energy level associated with the full mode of plasma generation is sufficiently high as to increase the reaction of the plasma with exposed surfaces of the substrate to a full level in which the concentration of by-product gases increases over time in the full mode of plasma generation.

2. The plasma processing system of claim 1 wherein the plasma processing chamber is a narrow-tap chamber in which a gap between an upper surface of said lower electrode and said chamber ceiling is less than 10% of a diameter of said substrate and the effective residence time of the by-product gases is reduced by selecting the first threshold and the second threshold to reduce the effective residence time of the by-product gases compared with continuous operation in the full mode of plasma generation.

3. The plasma processing system of claim 1 wherein said light emitting apparatus is configured to emit a broad spectrum light.

4. The plasma processing system of claim 1 wherein said light emitting apparatus is configured to emit a laser light.

5. The plasma processing system of claim 1 wherein said chamber ceiling represents a dielectric window.

6. The plasma processing system of claim 1 wherein said light emitting apparatus is a light source with a collimator.

7. The plasma processing system of claim 1 wherein said light receiving apparatus is an optical emission spectroscopy meter.

8. The plasma processing system of claim 1 wherein the controller limits a total time in which the plasma generation power source is continuously in the full mode so as to reduce an effective residence time of a plasma byproduct constituent to be shorter than a steady state residence time which is an amount of time it would take a plasma constituent to physically travel from above the substrate to a region outside the substrate (the normal gas residence time), wherein the effective residence time is calculated by multiplying the normal gas residence time by a fraction of time in which the plasma generation power source is in the full mode.

9. The plasma processing system of claim 8 , wherein the effective residence time is no more than about 25% of the normal gas residence time.

10. The plasma processing system of claim 1 , wherein the plasma generation energy level associated with the reduced mode of plasma generation is sufficiently low as to minimize the reaction of the plasma with exposed surfaces of the substrate, while ensuring that the plasma is not completely extinguished.

11. The plasma processing system of claim 1 , wherein the chamber is configured to maintain a constant flow of the supplied reactant gas between the reduced mode and the full mode.

12. A plasma processing system having at least one plasma processing chamber for processing a substrate, comprising: a lower electrode for supporting said substrate; a plasma generation power source for providing energy to generate a plasma from supplied reactant gas, said plasma is generated in a plasma processing region above said substrate; a light emitting apparatus configured to emit a first light into said plasma processing region; a light receiving apparatus configured to receive a second light, said second light representing an altered version of said first light after said first light passes through said plasma processing region, wherein said second light results after a by-product gas absorbs some portion of wavelength of the first light; and
a controller configured to analyze said second light and in response regulate a plasma generation energy level, the controller ascertaining whether a parameter of said second light equals or exceeds a first threshold indicative of a first concentration of the by-product gas, resulting from a reaction of the plasma with an exposed surface of the substrate, or equals or falls below a second threshold indicative of a second concentration of the by-product gas, wherein said controller sends a first signal to reduce an amount of plasma generation energy to a plasma generation energy level associated with a reduced mode of plasma generation provided by said plasma generation power source if said parameter equals or exceeds said first threshold, and wherein said controller sends a second signal for increasing said amount of plasma generation energy to a plasma generation energy level associated with a full mode of plasma provided by said plasma generation power source if said parameter equals or falls below said second threshold, wherein the plasma generation energy level associated with the reduced mode of plasma generation is sufficiently low as to minimize or stop the reaction of the plasma with exposed surfaces of the substrate, and wherein the plasma generation energy level associated with the full mode of plasma generation is sufficiently high as to increase the reaction of the plasma with exposed surfaces of the substrates to a full level, and wherein the plasma generation energy levels associated with the reduced mode and the full mode are sufficiently low and high, respectively, as to ensure that in the full mode, the concentration of by-product gas increases over time, and that in the reduced mode, a concentration of by-product gas is decreased over time with respect to a concentration of by-product gas provided by the full mode.

13. The plasma processing system of

Assignees

• Fischer Andreas
• Lam Res Corp

Inventors

• Fischer Andreas

Classifications

• H01J37/32972 Primary

  Spectral analysis · CPC title

• H10P50/242

  of Group IV materials · CPC title

• H05H1/24

  Generating plasma {(nuclear fusion reactors G21B1/00; gas-filled discharge reactors H01J37/32)} · CPC title