Endpoint detector for plasma etching

• US 5,888,337 A
• Filed: 05/17/1996
• Issued: 03/30/1999
• Est. Priority Date: 05/20/1995
• Status: Expired due to Term

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Saito, Susumu
• Primary Examiner(s): Smith, Lynette F.
• Assistant Examiner(s): Brumback, Brenda G.
• Application Number:
  US08/649,324
• Time in Patent Office: 1,047 Days
• Field of Search: 156/345, 204/298.32, 204/192.33, 356/356, 356/349, 356/363, 438/9
• US Class Current: 156/345.25
• 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 37/32972 Spectral analysis

Abstract

An endpoint detector for plasma etching comprises a photo detecting section for receiving an emission spectrum of plasma due to etching gas from a process chamber for providing plasma etching to a processing object so as to detect a specific waveform of the received emission spectrum, a calculating section for detecting an endpoint of an etching process based on a detecting signal sent from the photo detecting means, the photo detecting section comprises a first optical system for detecting light having a specific wavelength from the emission spectrum received from the process chamber so as to be photoelectrically transferred, and a second optical system for detecting a part of the emission spectrum so as to be photoelectrically transferred before light having a specific wavelength is extracted from the emission spectrum by the first optical system, and the calculating section reduces drift of an electrical signal, which is based on light having a specific wavelength extracted from the first optical system, based on an electrical signal, which is based on light extracted from the second optical system, so as to detect the endpoint of the etching process.

Claims

1. An plasma etching endpoint detector, for detecting an endpoint of a plasma etching process, said endpoint detector coupled to a process chamber which provides etching plasma to a processing object via a pair of parallel plate electrodes, said endpoint detector comprising:

photo detecting means for receiving an emission spectrum of said plasma, and for transmitting first and second detecting signals based on said received emission spectrum;

calculating means, coupled to said photo detecting means, for detecting said endpoint of said etching process based on said first and second detecting signals received from said photo detecting means;

wherein said photo detecting means comprises;

a first optical system, coupled to said calculating means, for detecting first-order diffracted light having a specific wavelength from the emission spectrum, for photoelectrically transferring said detected light, and for transmitting said first detecting signal, said first optical system, including,

a condenser lens for converging the emission spectrum,

an incident slit provided at a focal position of said condenser lens,

a diffraction grating for receiving said emission spectrum passed through said incident slit, and for diffracting said first-order diffracted light, wherein a light-receiving angle of said diffraction grating is variable,

an emission slit provided after said diffraction grating for receiving said first-order diffracted light, and

a first light-receiving sensor for receiving the first-order diffracted light from said diffraction grating passing through said emission slit, and for transmitting said first detecting signal, and

a second optical system for detecting a predetermined wave band of the emission spectrum, for photoelectrically transferring said detected part of the emission spectrum, and for transmitting said second detecting signal, said second optical system, including,

dispersing means, provided in an optical path formed between said incident slit and said diffraction grating, for extracting a part of the emission spectrum passing through said incident slit, and

a second light-receiving sensor for receiving the part of emission spectrum extracted by said dispersing means, and for transmitting said second detecting signal; and

wherein said calculating means reduces drift in said first detecting signal received from the first optical system based on said second detecting signal received from said second optical system, to detect the endpoint of the etching process.

2. The endpoint detector according to claim 1, wherein said condenser lens comprises an aberration corrected lens.

3. The endpoint detector according to claim 1, wherein a slit direction of said incident slit and that of said emission slit are provided to be parallel to said pair of parallel plate electrodes.

4. The endpoint detector according to claim 3, wherein said incident slit is positioned between a plane including one parallel plate electrode of said pair of parallel plate electrodes and a plane including the other electrode of said pair of parallel plate electrodes.

5. A plasma etching device, for a plasma etching process of a processing object, comprising:

a process chamber for providing a plasma etching process to said processing object;

gas introducing means coupled to said process chamber for introducing etching gas to said process chamber;

a pair of electrodes provided in said process chamber for generating plasma due to etching gas in said process chamber;

a high frequency power source for applying a high frequency voltage to said pair of electrodes;

photo detecting means optically coupled to said process chamber for receiving an emission spectrum of said plasma, and for transmitting first and second detecting signals based on said received emission spectrum;

calculating means, coupled to said photo detecting means, for detecting an endpoint of said etching process based on said first and second detecting signals received from said photo detecting means, and for transmitting a calculation signal; and

control means coupled between said calculating means and said high frequency power source for controlling a drive of said high frequency power source based on said calculation signal received from said calculating means;

wherein said photo detecting means comprises;

a first optical system, coupled to said calculating means, for detecting first-order diffracted light having a specific wavelength from the emission spectrum, for photoelectrically transferring said detected light, and for transmitting said first detecting signal, said first optical system, including,

a condenser lens for converging the emission spectrum,

an incident slit provided at a focal position of said condenser lens,

a diffraction grating for receiving said emission spectrum passed through said incident slit, and for diffracting said first-order diffracted light, wherein a light-receiving angle of said diffraction grating is variable,

an emission slit provided after said diffraction grating for receiving said first-order diffracted light, and

a first light-receiving sensor for receiving the first-order diffracted light from said diffraction grating passing through said emission slit, and for transmitting said first detecting signal, and

a second optical system for detecting a predetermined wave band of the emission spectrum, for photoelectrically transferring said detected part of the emission spectrum, and for transmitting said second detecting signal, said second optical system, including,

dispersing means, provided in an optical path formed between said incident slit and said diffraction grating, for extracting a part of the emission spectrum passing through said incident slit, and

a second light-receiving sensor for receiving the part of emission spectrum extracted by said dispersing means, and for transmitting said second detecting signals; and

wherein said calculating means reduces drift in said first detecting signal received from the first optical system based on said second detecting signal received from said second optical system, to detect the endpoint of the etching process.