Optics: measuring and testing – By polarized light examination – Of surface reflection
Reexamination Certificate
1999-05-11
2001-07-31
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By polarized light examination
Of surface reflection
C356S432000
Reexamination Certificate
active
06268916
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to measurement of samples and in particular, to a system for a non-destructive measurement of properties of a sample. This invention is particularly useful for non-destructive measurement of dose of a dopant in a semiconductor material.
In semiconductor manufacturing, it is frequently desirable to obtain information concerning the properties of a semiconductor material in a sample such as a wafer during or after processing. For example, it may be desirable to obtain an indication of the dose of a dopant in a semiconductor material such as silicon.
One system for measuring dose is proposed in U.S. Pat. No. 4,952,063. As described in this patent, a thermal wave is generated in a material by causing periodic localized heating of the material by focusing an intensity modulated pump beam of light on a spot of the sample surface. A probe beam is directed towards the spot of the sample surface to sense changes in the indices of refraction induced by the pump beam. The output of the detector is processed to analyze reflected light signals that are in phase with the modulation of the pump beam in order to detect changes in reflectivity of the sample. Such reflectivity measurements are then used to determine dopant concentration, residue deposits and defects of samples.
While the system described in U.S. Pat. No. 4,952,063 may be useful for certain dose measurements, it has many disadvantages. Thus, for some dopant concentrations, the change in reflectivity measured may correspond to different values of the dopant concentration so that the dopant concentration cannot be uniquely identified from the change in reflectivity. The change in reflectivity may also be too small to be measured for some dopant concentrations.
Spectroscopic ellipsometry is used to measure the damage profile at high doses. For wafers implanted at low doses, spectroscopic ellipsometry may not be adequate.
In U.S. Pat. No. 5,536,936, a spectroscopic ellipsometer is used to measure the ellipsometric parameter values of the sample in the presence of and in the absence of excitation of the sample. The technique in U.S. Pat. No. 5,536,936, however, lacks adequate sensitivity for measuring the change in ellipsometric parameters caused by excitation of the sample.
None of the above described systems is entirely satisfactory. It is, therefore, desirable to provide an improved system for non-destructive measurement of samples, which avoids the above-described difficulties or disadvantages.
SUMMARY OF THE INVENTION
As noted above, when a pump beam of radiation is supplied to a sample, energy of the beam is absorbed by the sample, thereby causing the physical properties of the sample to change. The change in the physical properties of the sample causes changes in the ellipsometric parameters of the sample. By detecting the change in one or more ellipsometric parameters of the sample caused by the pump beam, physical properties of the sample can be measured. To increase measurement sensitivity, the pump beam is modulated at a first modulation frequency. Physical properties of the sample are thus also modulated at the first frequency. A polarized probe beam is supplied to the sample and modified by the sample to provide a modified beam. Where the pump beam is modulated at the first frequency, the probe beam is also caused by the sample to be modulated at such frequency. A polarization state of radiation in the probe beam is modulated at a second frequency before detection. The modified beam is detected to provide an output. The output is processed to provide information or indication related to a signal at a frequency substantially equal to the difference between the first and the second frequencies or the harmonics thereof in any combination. A change in one or more ellipsometric parameters is derived from such information or indication. Such change is a measure of the physical properties of the sample. By deriving from the detected output signal information of a signal at a difference frequency, the technique of this invention provides adequate sensitivity to obtain a measurable change in one or more ellipsometric parameters of the sample caused by the pump beam.
In a related aspect of the invention, it may be desirable to measure dose of a dopant in a semiconductor wafer, the profile of such dopant, and also measure the film thickness and/or index of refraction information of the wafer by means of the same instrument. Preferably, the instrument includes a device for measuring dose of a dopant in the wafer and a second device for measuring film thickness and/or index of refraction information of the wafer.
REFERENCES:
patent: 4255971 (1981-03-01), Rosencwaig
patent: 4521118 (1985-06-01), Rosencwaig
patent: 4522510 (1985-06-01), Rosencwaig et al.
patent: 4679946 (1987-07-01), Rosencwaig et al.
patent: 4854710 (1989-08-01), Opsal et al.
patent: 4952063 (1990-08-01), Opsal et al.
patent: 5042952 (1991-08-01), Opsal et al.
patent: 5074669 (1991-12-01), Opsal
patent: 5149978 (1992-09-01), Opsal et al.
patent: 5206710 (1993-04-01), Geiler et al.
patent: 5228776 (1993-07-01), Smith et al.
patent: 5298970 (1994-03-01), Takamatsu et al.
patent: 5536936 (1996-07-01), Drevillon et al.
patent: 5608526 (1997-03-01), Piwonka-Corle et al.
patent: 5706094 (1998-01-01), Maris
patent: 6008906 (1999-12-01), Maris
“A New Method of Photothermal Displacement Measurement by Laser Interferometric Probe Its Mechanism and Applications to Evaluation of Lattice Damage in Semiconductors,” S. Sumie et al.,Jpn. J. Appl. Phys., vol. 31, Part 1, No. 11, Nov. 1992, pp. 3575-3583.
“Effects of ambient gas on photo-acoustic displacement measurement by laser interferometric probe,” S. Sumie et al.,J. Appl. Phys., vol. 74, No. 11, Dec. 1, 1993, pp. 6530-6533.
“Characteristics of photoacoustic displacement for silicon damaged by ion implantation,” H. Takamatsu et al.,J. Appln. Phys., vol. 78, No. 3, Aug. 1, 1995, pp. 1504-1509.
“Analysis of lattice defects induced by ion implantation with photo-acoustic displacement measurements,” S. Sumie,J. Appl. Phys., vol. 76, No. 10, Nov. 15, 1994, pp. 5681-5689.
“Photodisplacement Measurement by Interferometric Laser Probe,” H. Takamatsu et al.,Japanese Journal of Applied Physics, vol. 29, No. 12, Dec. 1990, pp. 2847-2850.
“Photoellipsometry determination of surface Fermi level in GaAs (100),” Y. Xiong et al.,J. Vac. Sci. Technol. A, vol. 11, No. 4, Jul./Aug. 1993, pp. 1075-1082.
“Photoellipsometry: a modulation spectroscopy method applied to n-type GaAs,” Y. Xiong et al.,Thin Solid Films, 234 (1993), pp. 399-401.
“Modulated ellipsometric measurements and transfer-matrix calculation of the field-dependent dielectric function of a multiple quantum well,” J. Zettler et al.,Physical Review B, Dec. 15, 1992, pp. 955-962.
Ellipsometric measurement of the Kerr magnetoopic effect, H. Minden,Applied Optics, vol. 18, No. 6, Mar. 15, 1979, pp. 813-817.
Ion Dose Monitor PA-400, Ion Implant Dose Measurement Systems, product brochure for Kobelco, Kobe Steel Ltd., 4 pages.
International Search Report dated Aug. 4, 2000.
Chen Xing
Lee Shing
Nikoonahad Mehrdad
Font Frank G.
Kla-Tencor Corporation
Skjerven Morrill & MacPherson LLP
Smith Zandra
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