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US 6,585,908 B2Granted
Shallow angle interference process and apparatus for determining real-time etching rate
AssigneeAxcelis Technologies, Inc.
InventorsAndre G. Cardoso, Alan C. Janos
Life of this patent
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Abstract
A process and apparatus for determining a real-time etching rate during a plasma mediated etching process. Real-time etching rate determination includes monitoring an interference pattern generated by a direct light beam and a reflected light beam from a wafer surface. A viewing angle for recording the interference pattern is nearly parallel to the wafer plane and at a fixed focal point on the layer to be removed. The direct light beam and reflected light beams are generated in situ during plasma processing.
Claims33
A process for determining a real-time stripping rate of a photoresist coating from a wafer, the process comprising:
- placing a wafer having a photoresist coating thereon into a plasma reaction chamber, wherein the reaction chamber includes a port;
- coupling an optical detector to the port, wherein the optical detector comprises receiving optics at a viewing angle nearly parallel to a plane of the wafer surface and, wherein the receiving optics are fixedly focused at a focal point on a surface of the photoresist;
- generating a plasma comprising reactive species and exposing the photoresist to the reactive species;
- monitoring interference signals received by the optical detector, wherein the interference signals are produced from a direct light beam and a light beam reflecting and refracting off the wafer, wherein the direct, reflected and refracted light beams are generated within the chamber and are at the same wavelength;
- extracting an interference pattern from the interference signals;
- and
- calculating a real time etching rate R from the interference signals according to the relationship:
- R=λ/(2T{square root over (n2−1)})
- wherein λ is the wavelength of the light beams generated in situ by the plasma or by a reaction between the photoresist and the reactive species or by an internal lamp used for heating the wafer;
- T is the time period interval between two consecutive minima in the interference pattern;
- and n is the refractive index of the photoresist measured at λ.
8 more elements
A process for determining a real-time etching rate, the process comprising:
- exposing a planar wafer having a reflective surface and a film coating thereon to a plasma;
- monitoring a focal point at a surface of the film coating and at a viewing angle nearly parallel to the wafer plane, wherein the step of monitoring comprises recording interference signals produced by a direct light beam, a reflected light beam and a refracted light beam of the same wavelength;
- and
- calculating a real time etching rate R from the interference signals according to the relationship:
- R=λ/(2T{square root over (n2−1)})
- wherein λ is the wavelength of the light beams;
- T is the time period interval between two consecutive minima in an interference pattern produced by the interference signals and n is the refractive index of the film coating measured at λ.
4 more elements
An apparatus for measuring a real time plasma etching rate, the apparatus comprising:
- a plasma reaction chamber containing a port;
- an in situ light source within the reaction chamber for illuminating a surface of the substrate, wherein the light source produces a direct light beam and a plurality of reflected and refracted light beams at the same wavelength;
- an optical detector coupled to the port and including receiving optics focused at the surface at an angle nearly parallel to the plane for receiving interference light signals produced by the direct, reflected and refracted light beams off the wafer;
- and
- computing means in communication with the receiving optics for computing a real time etching rate from the interference signals generated by the direct, reflected and refracted light beams, wherein the computing means calculates the real time etching rate based on an interference pattern generated from the interference signals, the refractive index of the material to be removed and a wavelength of the direct, reflected and refracted light beams.
2 more elements
An apparatus for measuring a real time plasma etching rate, the apparatus comprising:
- a plasma reaction chamber containing a port;
- a light source, wherein the light source comprises light emitted during an etching process and wherein the light source comprises a direct light beam and a plurality of reflected and refracted light beams at the same wavelength;
- receiving optics coupled to the port including an observation angle nearly parallel to a wafer plane and a focal point, wherein the focal point is set at a point on the wafer plane such that light contributing to an interference signals produced by the direct light beam and the plurality of reflected and refracted light beams, and received by the optics has a localized origin;
- and
- computing means in communication with the receiving optics for computing a real time etching rate from the interference signals generated by the direct, reflected and refracted light beams, wherein the computing means calculates the real time etching rate based on an interference pattern generated from the interference signals, the refractive index of the material to be removed and a wavelength of the direct, reflected and refracted light beams.
2 more elements
A process for determining a real-time etching rate, the process comprising:
- exposing a planar wafer having a reflective surface and a film coating thereon to a plasma;
- monitoring a surface of the film coating and at a viewing angle nearly parallel the wafer plane;
- recording interference signals produced by a direct light beam, a reflected light beam;
- and a refracted light beam of the same wavelength;
- and
- calculating a real time etching rate from the interference signals.
3 more elements
Dependencies are inferred from the claim text.