Real time etch measurements and control using isotopes
First Claim
1. A method for determining characteristics of an etching process while etching a solid thin film with a reactive gas to produce etch products, comprising the steps of:
- depositing at least one layer of isotopically enriched material at a known location during growth of the solid thin film;
while etching the thin film in an etch reactor, directing an ion beam on to a surface to be analyzed so as to form ions and neutral molecules from the surface;
analyzing the ions or the neutral molecules by a mass spectrometer detecting the isotopically enriched material and producing an output data stream; and
determining the characteristics of the etching process from the output data stream of the spectrometer and the known location of at least one layer of the isotopically enriched material.
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Abstract
A method is provided for determining etching characteristics during gas phase etching of thin film materials such as semiconductors during manufacture of devices. Etch end point, rate of etching, uniformity of etching and uniformity of growth of thin films can be determined. Isotopically enriched materials are deposited in layers which may be only a few nanometers thick at selected locations during growth of the thin films. The isotopes are removed during gas phase etching, carried by gas into an analysis chamber, condensed on a surface, and analyzed for isotopical composition. Mass spectroscopy of recoiled ions is a preferred detection technique.
24 Citations
31 Claims
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1. A method for determining characteristics of an etching process while etching a solid thin film with a reactive gas to produce etch products, comprising the steps of:
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depositing at least one layer of isotopically enriched material at a known location during growth of the solid thin film; while etching the thin film in an etch reactor, directing an ion beam on to a surface to be analyzed so as to form ions and neutral molecules from the surface; analyzing the ions or the neutral molecules by a mass spectrometer detecting the isotopically enriched material and producing an output data stream; and determining the characteristics of the etching process from the output data stream of the spectrometer and the known location of at least one layer of the isotopically enriched material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of determining the uniformity of growth during formation of first and second layers of a solid thin film, comprising the steps of:
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depositing at least one uniform layer of isotopically enriched material at a known location during growth of the solid thin film; while etching the thin film in an etch reactor, directing an ion beam on to a surface to be analyzed so as to form ions and neutral molecules from the surface; analyzing the ions or the neutral molecules by a mass spectrometer detecting the isotopically enriched material and producing a first output data stream; depositing a first and a second layer of a solid thin film for which uniformity of deposition is to be determined, the first and second layers having differing amounts of isotopically enriched material; etching from the second to the first layer while directing an ion beam on to a surface to be analyzed so as to form ions and neutral molecules from a surface being etched; analyzing the ions or the neutral molecules from the surface being etched by a mass spectrometer detecting the isotopically enriched material and producing a second output data stream; and deconvolving the data from the first and the second output data stream to determine the uniformity of growth of the second layer over the first layer.
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14. A method for controlling an etching process while etching a solid thin film with a reactive gas, comprising the steps of:
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depositing at least one layer of isotopically enriched material at a known location during growth of the solid thin film; while etching the thin film in an etch reactor, directing an ion beam on to a surface to be analyzed so as to form ions and neutral molecules from the surface; analyzing the ions or the neutral molecules by a mass spectrometer detecting the isotopically engineered material and producing an output data stream; and applying the output data stream to a controller to control the etching process. - View Dependent Claims (15, 16)
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17. A method for determining an etch depth in a solid thin film being etched with a reactive gas, comprising the steps of:
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depositing a layer of isotopically enriched material at a known location during growth of the solid thin film; placing the solid thin film in an etch reactor having an inlet gas conduit and an outlet gas conduit; introducing into the inlet gas conduit a reactive gas so as to etch the solid thin film and produce a reaction product; directing a gas containing the reaction product from the outlet gas conduit into an analysis chamber; condensing the reaction product entering the analysis chamber on to a sample block in the chamber to produce a surface of condensed reaction product; bombarding the surface of the condensed reaction product to produce bombardment products and collecting the bombardment products in a mass spectrometer for analysis; and observing the signal from the mass spectrometer apparatus to detect the presence of the layer of isotopically engineered material and determine the location of etching. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A method for etching a thin film, comprising the steps of:
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depositing a layer of isotopically engineered material during growth of the solid thin film; placing the solid thin film in an etch reactor having an inlet gas conduit and an outlet gas conduit and means for controlling at least one etch rate parameter; introducing into the inlet gas conduit a reactive gas so as to etch the solid thin film and produce a reaction product; directing a gas containing the reaction product from the outlet gas conduit into an analysis chamber; condensing the reaction product entering the analysis chamber onto a sample surface in the chamber to produce a surface of condensed reaction product; bombarding the surface of the condensed reaction product to produce bombardment products and collecting the bombardment products in a mass spectrometer apparatus for analysis; and detecting the signal from the mass spectrometer apparatus to detect the presence of the layer of isotopically engineered material at the level of etching and adjusting an etch rate parameter in response to the detected signal. - View Dependent Claims (28, 29)
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30. A method for determining etch rate of a thin film, comprising the steps of:
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depositing first and second layers of isotopically engineered material at a known distance apart during growth of the solid thin film; placing the solid thin film in an etch reactor having an inlet gas conduit and an outlet gas conduit; introducing into the inlet gas conduit a reactive gas so as to etch the solid thin film and produce a reaction product; directing a gas containing the reaction product from the outlet gas conduit into an analysis chamber; condensing the reaction product entering the analysis chamber onto a sample holder in the chamber to produce a surface of condensed reaction product; bombarding the surface of the condensed reaction product to produce bombardment products and collecting the bombardment products in a mass spectrometer apparatus for analysis; observing the signal from the mass spectrometer apparatus to detect the presence of the first layer of isotopically engineered material; continuing to etch until the second layer of isotopically engineered material is detected; and from the time between etching of the first and second layers and the known distance apart, calculate the etch rate between the first and second layers.
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31. A method for determining the uniformity of etching of a thin film, comprising the steps of:
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depositing a layer of isotopically engineered material during growth of the solid thin film; placing the solid thin film in an etch reactor having an inlet gas conduit and an outlet gas conduit; introducing into the inlet gas conduit a reactive gas so as to etch the solid thin film and produce a reaction product; directing a gas containing the reaction product from the outlet gas conduit into an analysis chamber; condensing the reaction product entering the analysis chamber onto a sample holder in the chamber to produce a surface of condensed reaction product; bombarding the surface of the condensed reaction product to produce bombardment products and collecting the bombardment products in a mass spectrometer apparatus for analysis; and observing the signal from the mass spectrometer apparatus to determine the shape of the signal as the layer of isotopically engineered material is etched.
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Specification