METHOD AND APPARATUS FOR DETECTING PLASMA UNCONFINEMENT

• US 20090272402A1
• Filed: 05/02/2008
• Published: 11/05/2009
• Est. Priority Date: 05/02/2008
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Kim, KeeChan, Bailey, Andrew D. III, Kim, Yunsang
• Granted Patent: US 8,257,503 B2
• Time in Patent Office: Days
• US Class Current: 134/1.200
• CPC Class Codes: G01N 21/68 using high frequency electric fields
• CPC Class Codes: H01L 21/67028 for cleaning followed by drying, rinsing, stripping, blasting or the like
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring

Abstract

A method for detecting plasma unconfinement in a reaction chamber during a bevel edge cleaning operation is provided. The method initiates with selecting a wavelength associated with expected by products of a bevel edge clean process. The method includes cleaning the bevel edge area of a substrate and monitoring the intensity of the selected wavelengths during the cleaning for deviation from a threshold wavelength intensity. The cleaning is terminated if the deviation from the threshold wavelength intensity exceeds a target deviation.

Claims

1. A method for detecting plasma unconfinement in a reaction chamber during a bevel edge cleaning operation, comprising:

selecting a wavelength associated with expected by products of a bevel edge clean process;

cleaning the bevel edge area of a substrate;

monitoring the selected wavelengths during the cleaning for deviation from a wavelength intensity; and

terminating the cleaning if the deviation from the wavelength intensity exceeds a target deviation.

2. The method of claim 1, wherein the by products include silicon fluoride and carbon monoxide.

3. The method of claim 1, wherein the wavelength is monitored externally through a quartz window of the reaction chamber.

4. The method of claim 1, wherein cleaning the bevel edge area includes striking a plasma proximate to a peripheral edge of the substrate.

5. The method of claim 4, wherein the plasma is a CF₄ based plasma.

6. The method of claim 4, wherein an inert gas flows through a center area of the reaction chamber and towards the bevel edge.

7. A method for preventing plasma unconfinement in a reaction chamber during an edge cleaning process, comprising:

processing a semiconductor substrate in a processing chamber, the processing depositing by products on a peripheral edge of the substrate;

performing an edge cleaning process to remove the deposited by products, the edge cleaning process including,

striking a plasma confined to the peripheral edge region of the substrate;

monitoring confinement of the plasma to the peripheral edge region, the monitoring including,

tracking a wavelength signal during the edge cleaning process; and

determining whether the plasma remains confined based on fluctuation of the tracked wavelength signal.

8. The method of claim 7, wherein the by products include silicon fluoride and carbon monoxide.

9. The method of claim 7, wherein the wavelength is monitored internally within the chamber through an optical emission spectrometer sensor integrated into the reaction chamber.

10. The method of claim 7, wherein the process chamber is an etch chamber.

11. The method of claim 7, wherein the plasma is a CF₄ based plasma.

12. The method of claim 7, wherein an inert gas flows through a center area of the reaction chamber and towards the bevel edge during the edge cleaning process.

13. The method of claim 7, wherein determining whether the plasma remains confined based on fluctuation of the tracked wavelength signal includes,

tracking deviation of the wavelength signal over a time period;

identifying a maximum wavelength signal, a minimum wavelength signal and an average wavelength signal during the time period.

14. The method of claim 13, further comprising:

subtracting the minimum wavelength signal from the maximum wavelength signal and dividing a result by the average wavelength signal; and

comparing a result of the dividing to a threshold value to determine whether the plasma is confined for the time period.

15. The method of claim 14, wherein if the result of the dividing is greater than the threshold value then the edge cleaning process is terminated.