Method and Apparatus for Measuring Process Parameters of a Plasma Etch Process

• US 20130016344A1
• Filed: 07/14/2011
• Published: 01/17/2013
• Est. Priority Date: 07/14/2011
• Status: Abandoned Application

• Current Assignee: Andrew Weeks Kueny, Larry Bullock, Mark Anthony Meloni
• Original Assignee: Andrew Weeks Kueny, Larry Bullock, Mark Anthony Meloni
• Inventors: Kueny, Andrew Weeks, Meloni, Mark Anthony, Bullock, Larry
• Application Number:
  US13/183,240
• Publication Number:
  US 20130016344A1
• Time in Patent Office: Days
• US Class Current: 356/217
• CPC Class Codes: G01J 1/4257 applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam monitoring arrangements for lasers in general H01S3/0014
• CPC Class Codes: G01J 3/027 Control of working procedures of a spectrometer; Failure detection; Bandwidth calculation
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/433 Modulation spectrometry; Derivative spectrometry
• CPC Class Codes: H01J 37/32926 Software, data control or modelling
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32972 Spectral analysis

Abstract

A configurable hybrid superheterodyne spectrum analyzer for deriving process state parameters from detected modulated light emitted by a plasma receives and conditions the electric signals converted from the modulated light for subsequent superheterodyne mixing at a specific intermediate frequency (IF) that is lower than the frequency of the modulated light. Signal conditioning includes filtering noise, aliasing and DC and/or amplifying or de-amplifying the signal. Once mixed, the superheterodyne signal is further filtered by an IF filter to define the signal bandwidth characteristics relevant to the process state parameters. The IF filter may configurably employ multiple filter functions such as Gaussian filtering of increasing widths and/or comb filtering for multiple passbands in the frequency spectrum. Finally, the IF mixed and filtered signal is digitized with respect to the specific intermediate frequency using an IF digitizer. The processed signal is then passed to a signal analyzer for derivation of process state parameters. The system may further include a controller for receiving information from the signal analyzer regarding signal processing requirements and then actively configuring one or all of the signal conditioner filter, signal conditioner amplifier, IF filter and IF digitizer to meet those requirements.

Claims

1. A plasma parameter measurement system for deriving at least one parameter from a modulated light component emitted by a plasma, comprising a plasma light detector for detecting plasma light emissions being generated from the plasma, an optical sensor for converting the detected plasma light to a light signal, a signal processor preparing the light signal for analysis and a signal analyzer for determining at least one parameter from the processed extracted modulated signal, wherein the signal processor comprises:

a superheterodyne assembly for receiving the light signal and a reference signal at an intermediating frequency and mixing the light signal and the reference signal to produce a superheterodyned signal at a down-converted intermediate frequency;

an intermediating frequency filter for filtering the superheterodyned signal across one or more bandwidths relevant to the at least one process state parameter; and

an intermediating frequency digitizer for digitizing the filtered superheterodyned signal at a sample rate.

2. The plasma parameter measurement system as in claim 1, wherein the signal processor further comprises:

a conditioning filter for filtering a passband of frequencies of the light signal; and

a low noise amplifier for altering a level of intensity of the light signal.

3. The plasma parameter measurement system as in claim 1, wherein the superheterodyne assembly further comprises:

a reference oscillator for generating a reference frequency; and

a phase locked loop synthesizer for locking a phase and frequency of the reference signal at the intermediate frequency based on the reference frequency.

4. The plasma parameter measurement system as in claim 1, wherein the intermediating frequency filter further comprises:

a filtering function of increasing spectral widths for filtering passbands of frequencies of the superheterodyned signal.

5. The plasma parameter measurement system as in claim 1, wherein the intermediating frequency filter further comprises:

a comb filtering function for filtering multiple passbands of frequencies of the superheterodyned signal.

6. The plasma parameter measurement system as in claim 1, wherein the intermediating frequency filter further comprises:

a comb filtering function for filtering multiple passbands of frequencies of the superheterodyned signal; and

a filtering function of increasing widths for the filtering multiple passbands frequencies.

7. The plasma parameter measurement system as in claim 1, wherein the signal processor further comprises:

a controller for controlling the sample rate of the intermediating frequency digitizer.

8. The plasma parameter measurement system as in claim 2, wherein the signal processor further comprises:

a controller for controlling the passband of frequencies of the light signal of the conditioning filter.

9. The plasma parameter measurement system as in claim 2, wherein the signal processor further comprises:

a controller for controlling the level of intensity of the light signal of the low noise amplifier.

10. The plasma parameter measurement system as in claim 1, wherein the signal processor further comprises:

a post processor for processing the filtered superheterodyned signal.

11. The plasma parameter measurement system as in claim 1, wherein the post processor further comprises:

a Fast Fourier Transform for isolating bandwidths within filtered superheterodyned signal.

12. The plasma parameter measurement system as in claim 1, wherein the post processor further comprises:

Goertzel algorithms for isolating bandwidths within filtered superheterodyned signal.