Interferometric endpoint determination in a substrate etching process
First Claim
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1. A method of processing a substrate in a process zone, the method comprising:
- (a) selecting a wavelength of substrate reflected light that provides a local maximum of intensity, by reflecting light from the substrate while scanning through a sequence of successive wavelengths until a local maximum of an intensity of the substrate reflected light is detected;
(b) processing the substrate by exposing the substrate to an energized gas in the process zone while light having the selected wavelength is reflected from the substrate;
(c) detecting light reflected from the substrate which has the selected wavelength, and generating a signal; and
(d) evaluating the signal to determine an endpoint of the process.
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Abstract
In determining an endpoint of etching a substrate, light that is directed toward the substrate is reflected from the substrate. A wavelength of the light is selected to locally maximize the intensity of the reflected light at an initial time point of the etching process. The reflected light is detected to determine an endpoint of the substrate etching process.
35 Citations
18 Claims
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1. A method of processing a substrate in a process zone, the method comprising:
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(a) selecting a wavelength of substrate reflected light that provides a local maximum of intensity, by reflecting light from the substrate while scanning through a sequence of successive wavelengths until a local maximum of an intensity of the substrate reflected light is detected; (b) processing the substrate by exposing the substrate to an energized gas in the process zone while light having the selected wavelength is reflected from the substrate; (c) detecting light reflected from the substrate which has the selected wavelength, and generating a signal; and (d) evaluating the signal to determine an endpoint of the process. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of processing a substrate in a process zone, the method comprising:
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(a) determining a wavelength of light that provides a local maximum of intensity when light having the wavelength is reflected from the substrate, by scanning through a sequence of successive wavelengths of light directed onto, or reflected from, the substrate, and detecting a local maximum of an intensity of the light reflected from the substrate; (b) processing the substrate by exposing the substrate to an energized gas in the process zone while the substrate is exposed to light having the selected wavelength; (c) detecting light reflected from the substrate that has the selected wavelength and generating a signal; and (d) evaluating the signal to determine an endpoint of the process. - View Dependent Claims (10, 11, 12)
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13. A method of processing a substrate having a layer with a thickness, in a process zone, the method comprising:
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(a) determining a wavelength of light that provides a local maximum of intensity when light having the wavelength is reflected from the substrate, by calculating a wavelength of light based on a pathlength in the thickness of the layer on the substrate that provides a local maximum of intensity when light having the wavelength is reflected from the substrate; (b) processing the substrate by exposing the substrate to an energized gas in the process zone while the substrate is exposed to light having the selected wavelength; and (c) detecting light reflected from the substrate that has the selected wavelength and generating a signal; (d) evaluating the signal to determine an endpoint of the process. - View Dependent Claims (14, 15, 16, 17)
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18. A substrate etching method comprising:
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(a) placing a substrate in a process zone, the substrate comprising polysilicon exposed between features of a mask comprising silicon nitride; (b) providing an energized gas in the process zone that is capable of etching the polysilicon; (c) detecting an intensity of light that is reflected from the substrate at a wavelength of from about 200 to about 800 nm; and (d) evaluating the detected light intensity to determine an endpoint of etching of the substrate, whereby at an initial time during etching of the substrate, light having the wavelength generates a local maximum in intensity, when a first portion of light having the wavelength is reflected from the surface of the silicon nitride mask and another portion of the light is reflected from the interface between the silicon nitride mask and the polysilicon, and the interface and surface reflections of the light are substantially in phase upon emerging from the substrate.
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Specification