Plasma processing method

• US 6,231,774 B1
• Filed: 12/18/1998
• Issued: 05/15/2001
• Est. Priority Date: 12/19/1997
• Status: Expired due to Term

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Saito, Susumu
• Primary Examiner(s): DANG, THI D
• Application Number:
  US09/215,165
• Time in Patent Office: 879 Days
• Field of Search: 216/60, 438/9, 204/298.32, 204/298.03, 204/192.13, 204/192.33
• US Class Current: 216/60
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge

Abstract

Plasma P that is caused to fluctuate by a magnet 128 is generated inside a reaction chamber 102 of an etching apparatus 100. The signal of the fluctuating plasma light detected at a photosensor unit 136 via a detection window 134 is sampled over a constant sampling cycle with a arithmatic control unit 120 to obtain data strings. A plurality of hypothetical fluctuation cycles are hypothesized and the step for calculating the moving average values during the individual hypothetical fluctuation cycles using the data strings is repeated, then arithmetic processing is performed on the moving average values calculated for the individual repetition timings to create moving average value data for each of the hypothetical fluctuation cycles to ascertain approximate expressions corresponding to the individual hypothetical fluctuation cycles. In addition, deviation quantities between data strings of the individual moving average values and the corresponding approximate expressions during a given period are calculated, and the hypothetical fluctuation cycle corresponding to the smallest deviation quantity is determined as the fluctuation cycle of the plasma P. Based upon the fluctuation cycle thus determined, the data string of the moving average value is ascertained from the data strings of the sampling signal to determine the endpoint for the processing.

Claims

1. A plasma processing method for performing plasma processing on an object placed inside a reaction chamber by forming an electric field within said reaction chamber into which a processing gas is introduced and generating plasma that fluctuates over a given fluctuation cycle, comprising:

(a) a step for obtaining sampling data by sampling plasma light of said plasma with a constant sampling period;

(b) a step for hypothesizing a plurality of hypothetical fluctuation cycle, calculating a moving average values over each period corresponding to each of the hypothetical fluctuation cycles based upon said sampling data and obtaining a moving average value data for each of said hypothetical fluctuation cycles;

(c) a step for obtaining an approximate expression corresponding to each of said hypothetical fluctuation cycles based upon said moving average value data for each of said hypothetical fluctuation cycles;

(d) a step for ascertaining a deviation quantity between said moving average value data and a corresponding approximate expression for each of said hypothetical fluctuation cycles at one or two or more time points; and

(e) a step for ascertaining a hypothetical fluctuation cycle having the smallest deviation quantity among said deviation quantities to determine said hypothetical fluctuation cycle as said fluctuation cycle of said plasma.

2. A plasma processing method according to claim 1, further comprising:

(f) a step for calculating a moving average value using said sampling data for a period corresponding to said fluctuation cycle of said plasma obtained in step (e); and

(g) a step for determining an endpoint for plasma processing based upon said moving average value data calculated in step (f).

3. A plasma processing method according to claim 1, wherein:

a maximum value of said hypothetical fluctuation cycle is an anticipated upper limit value of said fluctuation cycle and a minimum value of said hypothetical fluctuation cycles is an anticipated lower limit value of said fluctuation cycle.

4. A plasma processing method according to claim 1, wherein:

said hypothetical fluctuation cycles are integer multiples of said sampling cycle.

5. A plasma processing method according to claim 1, wherein:

said hypothetical fluctuation cycles are not integer multiples of said sampling cycle.

6. A plasma processing method according to claim 5, wherein:

in step (b), numerical processing is performed on said sampling data to obtain pseudo sampling data corresponding to said hypothetical fluctuation cycle and said moving average values are calculated based upon said sampling data and said pseudo sampling data.

7. A plasma processing method according to claim 6, wherein:

in step (b), weighting is implemented on said sampling data and said pseudo sampling data to calculate said moving average values.

8. A plasma processing method according to claim 1, wherein:

in step (e), deviation quantities between the moving average values and the corresponding approximate expressions over a period extending, at least anticipated maximum value of the fluctuation cycle, are obtained for each hypothetical fluctuation cycle.

9. A plasma processing method according to claim 1, wherein:

a rotating magnetic field that causes plasma to fluctuate with a given rotation cycle is formed within said vacuum container.

10. A plasma processing method for performing plasma processing on an object placed inside a reaction chamber by forming an electric field within said reaction chamber into which a processing gas is introduced and generating plasma that fluctuates over a given fluctuation cycle, comprising:

(a) a step for obtaining sampling data by sampling plasma light of said plasma with a constant sampling period, with said fluctuation cycle not restricted to be an integer multiple of said sampling cycle;

(b) a step for calculating moving average values for said fluctuation cycle based upon said sampling data; and

(c) a step for determining an endpoint of plasma processing based upon change in said moving average values.

11. A plasma processing method according to claim 10, wherein:

in step (b), numerical processing is performed on said sampling data to obtain pseudo sampling data corresponding to said fluctuation cycle and said moving average values are calculated based upon said sampling data and said pseudo sampling data.

12. A plasma processing method according to claim 11, wherein:

in step (b), weighting is implemented on said sampling data and said pseudo sampling data to calculate said moving average values.

13. A plasma processing method according to claim 10, wherein:

a rotating magnetic field that causes plasma to fluctuate over a given rotation cycle is formed within said vacuum container.