System and method for monitoring and controlling gas plasma processes

• US 6,351,683 B1
• Filed: 04/19/2000
• Issued: 02/26/2002
• Est. Priority Date: 09/17/1997
• Status: Expired due to Fees

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Johnson, Wayne, Parsons, Richard
• Primary Examiner(s): Grant, William
• Assistant Examiner(s): PATEL, RAMESH B
• Application Number:
  US09/508,105
• Time in Patent Office: 678 Days
• Field of Search: 700/108, 700/110, 700/116, 700/117, 700/121, 438/8, 438/9-10, 438/11, 438/17, 438/711, 156/345-348, 156/627.1, 324/622, 324/623, 324/647, 324/637, 324/638, 324/704
• 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 response signal; and

a monitoring sensor for receiving the response signal, including a sideband component caused by the modulation, at a frequency corresponding to 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.

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 response signal at a first frequency and a second detected characteristic of a second component of said response signal 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 and said first stored characteristic are both one of an amplitude and a phase, and wherein said second detected characteristic and said second stored characteristic are both one of an amplitude and a phase.

3. 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 response signal 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 one of an amplitude and a phase, wherein said first stored characteristic corresponds to a first condition of a process parameter of said plasma process, and said second stored characteristic corresponds to a second condition of said process parameter of said plasma process, and wherein said process parameter is 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.

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

an electrode;

an inductive coil;

a bias shield; and

an electrostatic chuck.

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

6. A plasma processing system comprising:

a power source;

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

a power varying controller for modulating at least one of an amplitude, a frequency and a phase of the power to produce a response signal; and

a monitoring sensor for receiving the response signal and calculating a phase difference of a first component of said response signal and a second component of said response signal;

wherein said response signal includes a sideband component caused by said power varying controller, said sideband component occurring at a frequency corresponding to 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. 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 response signal; and

receiving said response signal, including a sideband component caused by the modulation, at a frequency corresponding to 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.

8. The method as claimed in claim 7, further comprising the steps of:

measuring a first detected characteristic of a first component of said response signal at a first frequency;

measuring a second detected characteristic of a second component of said response signal 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 one of an amplitude and a phase.

9. The method as claimed in claim 7, further comprising the steps of:

processing a first substrate;

measuring a first detected characteristic of a component of said response signal at a frequency corresponding to a first value of a process parameter, and wherein said process parameter is 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 response signal 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 response signal at said frequency; and

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

10. 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 applied from a power source to a plasma coupling element to produce a response signal;

receiving the response signal; and

calculating a phase difference of a first component of said response signal and a second component of said response signal;

wherein receiving said response signal, including a sideband component caused by the modulation, at a frequency corresponding to 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.