System and method for monitoring and controlling gas plasma processes

• US 6,535,785 B2
• Filed: 10/31/2001
• Issued: 03/18/2003
• Est. Priority Date: 09/17/1997
• Status: Expired due to Term

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Johnson, Wayne, Parsons, Richard
• Primary Examiner(s): PATEL, RAMESH B
• Application Number:
  US09/984,760
• Publication Number:
  US 20020026251A1
• Time in Patent Office: 503 Days
• Field of Search: 700/121, 700/116, 700/117, 700/108, 700/110, 438/8, 438/9, 438/10, 438/11, 438/17, 438/711, 156/345, 156/346, 156/347, 156/348, 156/627.1, 354/622, 354/623, 354/647, 354/637, 354/638, 354/704
• US Class Current: 700/121
• CPC Class Codes: H01J 2237/332 Coating
• CPC Class Codes: H01J 2237/334 Etching
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32137 controlling of the discharge by modulation of energy
• CPC Class Codes: H01J 37/32146 Amplitude modulation, includes pulsing
• CPC Class Codes: H01J 37/32155 Frequency modulation
• CPC Class Codes: H01J 37/32165 Plural frequencies
• CPC Class Codes: H01J 37/32174 Circuits specially adapted for controlling the RF discharge
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32963 End-point detection
• CPC Class Codes: H01J 37/3299 Feedback systems

Abstract

A system and method for monitoring the conditions in a gas plasma processing system while varying or modulating the RF power supplied to the system, so that resulting signals of the electrical circuits of the system provide information regarding operational parameters of the system or the state of a process. Significant improvements in sensitivity and accuracy over conventional techniques are thereby achieved. In addition, the plasma processing system can be thoroughly tested and characterized before delivery, to allow more accurate monitoring of and greater control over a process, thereby improving quality control/assurance of substrates being produced by the system. The information obtained by the modulation technique can be displayed on a monitor screen, in order to allow an operator to accurately monitor the system/process and diagnose any problems with the system/process.

Claims

1. A plasma system comprising:

a power source;

a first plasma coupling element for providing power from said power source to a plasma;

a power varying controller for modulating at least one of an amplitude, a frequency, and a phase of said power to produce a modulation profile; and

a monitoring sensor for receiving said modulation profile of said first plasma coupling element, wherein said modulation profile is caused by said power varying controller.

2. The system as claimed in claim 1, wherein said monitoring sensor comprises a frequency sensor for measuring a first detected characteristic of a first component of said modulation profile at a first frequency and a second detected characteristic of a second component of said modulation profile at a second frequency;

said system further comprising;

a memory for storing stored data, said stored data including a first stored characteristic and a second stored characteristic, wherein said first stored characteristic corresponds to said first predetermined frequency and said second stored characteristic corresponds to said second predetermined frequency; and

a central processing unit which compares at least one of said first detected characteristic and said second detected characteristic to at least one of said first stored characteristic and said second stored characteristic, wherein said first detected characteristic, said first stored characteristic, said second detected characteristic and said second stored characteristic are each at least one of an amplitude and a phase.

3. The system as claimed in claim 1, further comprising a visual display for displaying at least one of:

an amplitude of a component of said modulation profile;

a phase of a component of said modulation profile;

a ratio of (1) a first amplitude of a first component of said modulation profile and (2) a second amplitude of said second component of modulation profile; and

a relative phase of a first component of said modulation profile with respect to a second component of said modulation profile, said relative phase being a difference of (1) a phase of said first component and (2) a phase of said second component.

4. The system as claimed in claim 1, wherein said monitoring sensor comprises a frequency sensor for measuring, at a detection time, a first detected characteristic of a first component of said modulation profile at a first predetermined frequency;

said system further comprising;

a memory for storing stored data, said stored data including first and second stored characteristics corresponding to said first predetermined frequency; and

a central processing unit which compares said first detected characteristic to said first and second stored characteristics, wherein all of said first detected characteristic and said first and second stored characteristics are at least one of an amplitude and a phase, wherein said first and second stored characteristics corresponds to first and second conditions of a process parameter of said plasma process, respectively, and wherein said process parameter is at least one of;

progress of the process;

ion density of the plasma;

gas mixture of the plasma;

gas pressure of the plasma;

proper assembly of an electrical component coupled to the plasma;

cleanliness of the chamber;

thickness of a coating on a surface within the chamber; and

quality of matching of a plasma coupling element to the power source.

5. The system as claimed in claim 1, wherein said plasma coupling element comprises at least one of:

an electrode;

an inductive coil;

a bias shield; and

an electrostatic chuck.

6. The system as claimed in claim 2, wherein said modulation profile includes a sideband component caused by said power varying controller, said sideband component occurring at a frequency corresponding to at least one of:

(a) a sideband frequency of a fundamental frequency of said power source; and

(b) a sideband frequency of a harmonic frequency of said fundamental frequency.

7. The system as claimed in claim 3, wherein said modulation profile includes a sideband component caused by said power varying controller, said sideband component occurring at a frequency corresponding to at least one of:

(a) a sideband frequency of a fundamental frequency of said power source; and

(b) a sideband frequency of a harmonic frequency of said fundamental frequency.

8. The system as claimed in claim 4, wherein said modulation profile includes a sideband component caused by said power varying controller, said sideband component occurring at a frequency corresponding to at least one of:

(a) a sideband frequency of a fundamental frequency of said power source; and

(b) a sideband frequency of a harmonic frequency of said fundamental frequency.

9. The system as claimed in claim 1, further comprising a second plasma coupling element coupled to said plasma.

10. The system as claimed in claim 9, wherein said modulation profile includes a sideband component caused by said power varying controller, said sideband component occurring at a frequency corresponding to at least one of:

(a) a sideband frequency of a fundamental frequency of said power source; and

(b) a sideband frequency of a harmonic frequency of said fundamental frequency.

11. A method of controlling a plasma system, the method comprising the steps of:

providing a power source;

providing a plasma coupling element;

providing power from said power source to a plasma;

modulating at least one of an amplitude, a frequency, and a phase of said power in order to produce a modulation profile of said plasma coupling element; and

receiving said modulation profile.

12. The method as claimed in claim 11, further comprising the steps of:

measuring a first detected characteristic of a first component of said modulation profile at a first frequency;

measuring a second detected characteristic of a second component of said modulation profile at a second frequency;

storing stored data, said stored data including a first stored characteristic and a second stored characteristic, wherein said first stored characteristic corresponds to said first frequency and said second stored characteristic corresponds to said second frequency; and

comparing at least one of said first detected characteristic and said second detected characteristic to at least one of said first stored characteristic and said second stored characteristic, wherein said first and second detected characteristics and said first and second stored characteristics are at least one of an amplitude and a phase.

13. The method as claimed in claim 11, further comprising the steps of displaying at least one of:

an amplitude of a component of said modulation profile;

a phase of a component of said modulation profile;

a ratio of (1) a first amplitude of a first component of said modulation profile and (2) a second amplitude of a second component of said modulation profile; and

a relative phase of a first component of said modulation profile with respect to a second component of said modulation profile, said relative phase being a difference of (1) a phase of said first component and (2) a phase of said second component.

14. The method as claimed in claim 11, further comprising the steps of:

processing a first substrate;

measuring a first detected characteristic of a component of said modulation profile at a frequency corresponding to a first value of a process parameter, and wherein said process parameter is at least one of;

(1) progress of a process;

(2) ion density of the plasma;

(3) mixture of the plasma;

(4) gas pressure of the plasma;

(5) proper assembly of an electrical component coupled to the plasma;

(6) cleanliness of the chamber;

(7) thickness of a coating on a surface within the chamber; and

(8) quality of matching of a plasma coupling element to the power source;

storing said first detected characteristic;

processing a second substrate;

measuring a second detected characteristic of a component of said modulation profile at said frequency corresponding to a second value of said process parameter;

storing said second detected characteristic;

processing a third substrate;

measuring a third detected characteristic of said modulation profile at said frequency; and

comparing said third detected characteristic to said first and second detected characteristics in order to analyze said modulation profile for said third substrate, wherein said first, second and third detected characteristics are at least one of an amplitude and a phase.

15. The method as claimed in claim 12, wherein said step of varying comprises modulating at least one of an amplitude, a frequency, and a phase of said power in order to provide a sideband component of said modulation profile of said plasma coupling element, wherein said sideband component is at a frequency corresponding to at least one of:

(a) a sideband frequency of a fundamental frequency of said power source; and

(b) a sideband frequency of a harmonic frequency of a fundamental frequency of said power source.

16. The method as claimed in claim 14, wherein said step of varying comprises modulating at least one of an amplitude, a frequency, and a phase of said power in order to provide a sideband component of said modulation profile of said plasma coupling element, wherein said sideband component is at a frequency corresponding to at least one of:

(a) a sideband frequency of a fundamental frequency of said power source; and

(b) a sideband frequency of a harmonic frequency of a fundamental frequency of said power source.

17. A plasma system comprising:

a power source;

a first plasma coupling element for providing power from said power source to a plasma;

a power varying controller for modulating at least one of an amplitude, a frequency, and a phase of said power to produce a modulation profile; and

a monitoring sensor for receiving the modulation profile,

wherein the modulation profile includes a sideband component caused by the modulation at a frequency corresponding to at least one of;

(a) a sideband frequency of a fundamental frequency of said power source; and

(b) a sideband frequency of a harmonic frequency of said fundamental frequency.

18. In a method of controlling a power source for a plasma coupling element of a plasma system, the improvement comprising:

modulating at least one of an amplitude, a frequency, and a phase of power delivered by a power source to a plasma coupling element in order to produce a modulation profile;

receiving said modulation profile; and

controlling said power source based on said modulation profile,

wherein said modulation profile includes a sideband component caused by the modulation, at a frequency corresponding to at least one of;

(a) a sideband frequency of a fundamental frequency of said power source; and

(b) a sideband frequency of a harmonic frequency of a fundamental frequency of said power source.