METHOD OF ETCHING MATERIALS WITH ELECTRON BEAM AND LASER ENERGY
We disclose a method of electron-beam induced of etching the surface of a specimen in a charged-particle beam instrument, where the charged-particle beam instrument has first and second laser beams, an electron beam, and a gas-injection system for applying etchant gas to the surface. Etching is accomplished by applying a photolytic pulse from the first laser to the surface; applying a pyrolytic pulse from the second laser to the surface; and, applying an etchant gas to the surface at least during the pyrolytic pulse. Two or more alternating pyrolytic laser pulses and photolytic laser pulses may be applied to the surface. The stage supporting the specimen may be tilted relative to the axis of the electron beam before applying the electron beam to the surface of the specimen. The electron beam is applied to the surface of the specimen during the time the etchant gas is present at the surface.
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This application claims the priority of U.S. Provisional Application Ser. No. 61/151,687, filed Feb. 11, 2009, which provisional application is incorporated by reference into the present application.
CO-PENDING APPLICATIONSThis application is related to co-pending applications Ser. No. 12/211,638, titled “Methods for electron-beam induced deposition of material inside charged-particle microscopes,” filed Sep. 16, 2008, and Ser. No. 12/399,579, titled “Method and apparatus for precursor delivery system of irradiation beam instruments,” filed Mar. 6, 2009.
BACKGROUND1. Technical Field
This disclosure relates to systems and methods for the inspection and modification of surfaces and microscopic and nanostructures in charged-particle beam instruments; in particular for the inspection and edit of integrated circuits, semiconductor wafers and photolithographic masks and optical beam analytical methods. Examples of charged-particle beam instruments are focused ion-beam microscopes (FIB's) and scanning electron microscopes (SEM's). Typical modern FIB's include an ion beam, an electron beam and ports for additional instruments, such as gas injectors, manipulators and x-ray analyzers.
2. Background Art
Certain techniques for use of an electron beam in charged-particle beam instruments for etching or depositing material are known. Some techniques are described in U.S. Pat. No. 6,753,538 B to Musil, et al., which patent is incorporated by reference into this application, but which is not admitted to be prior art by inclusion in this Background section. The electron-beam induced etch method is frequently used for editing the microscopic and nanostructures receiving the most attention in industry and research. The simultaneous use of optical energy together with the electron beam aids navigation to the area of interest, the monitoring of the process, and enhances the rate or selectivity of the etch process. As was shown lately in the art, the deposition and etch processes can be significantly improved by changing the temperature of the specimen surface being processed.
Typically, the surface is imaged by the electron beam (120) scan of the charged-particle beam instrument and the area of interest (110) on the specimen surface (100) is located by known means. Existing contamination on the surface (100) may be cleaned by application of a photolytic laser pulse (240).
In the preferred embodiment, our method of etching the surface (100) of a specimen in a charged-particle beam instrument comprises applying a photolytic pulse (240) from a second laser (140) to the area of interest (110), applying a pyrolytic pulse (230) from a first laser (130) to the surface (100) to heat the surface (100); applying an etchant gas (180) to the surface (100) at least during the pyrolytic pulse (230). In other embodiments, there can be two or more alternating pyrolytic laser pulses (230) and photolytic laser pulses (240), and optional additional pulses (245) as shown in
At any point after application of the etchant gas (180), the surface (100) may be imaged to determine if the etching of the surface (100) is completed; and, if the etching of the surface (100) is not completed, then the application of the pyrolytic laser pulse (230), the photolytic laser pulse (240) and the application of the etchant gas (180) may be repeated. The photolytic laser pulse (240) will increase the rate of etching by removing contamination products from the area of interest (110) and help prevent the condensation of these products at the surface (100). It is advisable to turn off the flow of etchant gas (180) and the electron beam (120) during the photolytic pulse (240) to avoid interactions between them that could interfere with the etching process.
We have found it usually desirable to tilt the stage (105) supporting the surface (100) relative to the axis of the electron beam (120) before applying the electron beam (120) to the surface of the specimen. As shown in the configuration depicted in
Step 425 represents the application of the pyrolytic laser pulse (230) and the electron beam (120). At step 430, the flow of gas (180) is stopped, and the photolytic laser pulse (240) is applied at step 435. At step 440, the surface (100) may be imaged to determine the progress of the etching process. At step 445, if the cleaning-heating-gas-electron beam cycle must be repeated to complete etching, the process returns to step 410; else, the etching process is complete at step 450.
None of the description in this application should be read as implying that any particular element, step, or function is an essential element which must be included in the claim scope; the scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke paragraph six of 35 U.S.C. Section 112 unless the exact words “means for” are used, followed by a gerund. The claims as filed are intended to be as comprehensive as possible, and no subject matter is intentionally relinquished, dedicated, or abandoned.
Claims
1. A method of etching the surface of a specimen in a charged-particle beam instrument, where the charged-particle beam instrument has first and second laser beams, an electron beam, and a gas-injection system for applying etchant gas to the surface, the method comprising:
- applying a photolytic pulse from the first laser to the surface;
- applying a pyrolytic pulse from the second laser to the surface; and, applying an etchant gas to the surface at least during the pyrolytic pulse.
2. The method of claim 1, comprising two or more alternating pyrolytic laser pulses and photolytic laser pulses.
3. The method of claim 1, further comprising:
- imaging the surface after the application of the etchant gas to determine if the etching of the surface is completed; and, if the etching of the surface is not completed, then, repeating the application of the photolytic laser pulse, the pyrolytic laser pulse and the application of the etchant gas.
4. The method of claim 1, further comprising:
- applying the electron beam to the surface of the specimen during the application of the etchant gas.
5. The method of claim 4, where the charged-particle beam instrument further comprises a stage supporting the specimen, the method further comprising:
- tilting the stage supporting the specimen relative to the axis of the electron beam before applying the electron beam to the surface of the specimen; and,
- applying the electron beam to the surface of the specimen during the time the etchant gas is present at the surface.
6. The method of claim 5, where the energy of the electron beam is selected to substantially maximize secondary electron emission from the surface.
7. The method of claim 1, where the charged-particle beam instrument further comprises a stage supporting the specimen, the method further comprising:
- applying the electron beam to the surface of the specimen both during the time the etchant gas is present at the surface and during the time the pyrolytic laser beam is applied to the surface.
8. The method of claim 7, further comprising:
- tilting the stage supporting the specimen relative to the axis of the electron beam before applying the electron beam to the surface of the specimen; and,
- applying the electron beam to the surface of the specimen during the time the etchant gas is present at the surface.
9. The method of claim 8, where the energy of the electron beam is selected to substantially maximize secondary electron emission from the surface.
10. A method of etching the surface of a specimen in a charged-particle beam instrument, where the charged-particle beam instrument has a stage supporting the specimen, an electron beam, a pyrolytic laser beam, and a gas-injection system for applying etchant gas to the surface, the method comprising:
- tilting the stage supporting the specimen relative to the axis of the electron beam;
- applying the etchant gas to the surface; and,
- applying the pyrolytic laser beam to the surface; and,
- applying the electron beam to the surface of the specimen during the time the etchant gas is present at the surface and during the time the pyrolytic laser beam is applied to the surface.
11. The method of claim 10, where the energy of the electron beam is selected to substantially maximize secondary electron emission from the surface.
Type: Application
Filed: Feb 11, 2010
Publication Date: Aug 12, 2010
Applicant: OMNIPROBE, INC. (Dallas, TX)
Inventors: Lyudmila Zaykova-Feldman (Dallas, TX), Herschel M. Marchman (Dallas, TX), Thomas M. Moore (Dallas, TX)
Application Number: 12/704,167