Semiconductor device manufacturing: process – Formation of electrically isolated lateral semiconductive... – Having substrate registration feature
Reexamination Certificate
1999-05-19
2001-04-17
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Formation of electrically isolated lateral semiconductive...
Having substrate registration feature
C438S427000, C438S700000, C438S975000, C216S011000
Reexamination Certificate
active
06218264
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a calibration standard for the profilometry in the sub-nanometer range, especially for the Atomic Force Microscope/Scanning Tunneling Microscope (AFM/STM) profilometry and to a method of producing said calibration standard.
BACKGROUND OF THE INVENTION
Nanometrology stands for the measurement technology necessary to investigate, to develop and to verify the measuring features of instruments and of material standards with an uncertainty best given in units of nanometers. For the calibration of different probe systems and different measuring instruments reference standards are asked for.
2-D AFM profilometry uses specially shaped ultrafine silicon tips with a diameter of typically about 250 nm. The absolute measuring preciseness solely depends on the exact knowledge of the tip diameter which usually is determined by a high resolution SEM with a measuring accuracy of 3 to 5%.
With a tip diameter of 250 nm this leads to a measuring preciseness worse than about 7.5 nm. Within the electron microscope, depending on the rest gas concentration, the tip is more or less contaminated and thus its diameter is changed indefinitely during measuring. To improve the measuring accuracy the tip should be calibrated directly before and after the measurement with a gauge.
Other common solutions also focus on the application of single-crystal silicon technology.
A standard reference material (SRM) consisting of a silicon wafer with a silicon dioxide film of uniform thickness is described in SPIE Vol.661, “Film thickness and refractive index Standard Reference Material calibrated by ellipsometry and profilometry” by G. A. Candela et.al. The silicon dioxide film contains windows used for stylus profilometry measurements with a mechanical depth very nearly the same as the oxide thickness. The depth is not exactly the same as the oxide thickness due to native oxide forming in the window with an average thickness of about 2 nm. This affects the accuracy of the measurement.
In Metrologia, 1991/92, Vol.28, pp.443-453, “Nanometrology at the PTB” by H. Kunzmann, a reference scale in the sub-nanometer range is derived from a silicon single crystal epitaxially grown by chemical gas transfer. With high probability the surface of this crystal is plane within one lattice plane and it is proposed to use the steps which are small-integer multiples of lattice plane distances for the calibration of probe systems for nanometrology. These steps are results of the epitaxial processes and they could be used to manufacture step-height gauges, but only if the technology of epitaxial growth could be brought under well-defined metrological control. Although realizing accuracies in the sub-nanometer range, this solution only covers 1-D displacement metrology.
SUMMARY OF THE INVENTION
In accordance with the present invention, a calibration standard and method for calibrating is described comprising a supporting structure of single crystal material with at least one pair of different kinds of structures, the structures including at least a trench and a raised line having substantially the same width.
The invention further provides an array of structures wherein the widths are different between selected structures in said array.
It is therefore an object of the invention to provide a calibration standard for 2-D and 3-D profilometry with an accuracy in the range of 1 nm and better.
The invention also comprises methods of producing a calibration standard and the use of the standard for measuring features in the sub-nanometer range.
REFERENCES:
patent: 6016684 (2000-01-01), Scheer et al.
patent: 0 536 827 A1 (1992-09-01), None
patent: 3 206 905 (1991-09-01), None
patent: WO 93/14377 (1993-07-01), None
T. Ohmi et al., “Calibration of height in atomic force microscope images with subnanometer scale silicon dioxide steps”, Appl. Phys. Lett., vol. 61, No. 20, pp. 2479-2481, Nov. 16, 1992.
M. Anders et al., “Potentiometry for thin-film structures using atomic force microscopy”, J. of Vacuum Science & Technology, A8, No. 1, pp. 394-399, Jan./Feb. 1990.
G. A. candela et al., “Film thickness and refractive index Standard Reference Material calibrated by ellipsometry and profilometry”, SPIE, vol, 661, pp. 402-407, Optical Testing and Metrology (1986).
Hatsuzawa et al., “Critical Dimension Measurements by Electron and Optical Beams for the Establishment of Linewidth Standards”, Proc. IEEE 1992 Int. Conf. on Microelectronic Test Structures, vol. 5, pp. 180-184, Mar. 16-19, 1992.
Gehrtz et al., “Scanning tunneling microscopy of machined surfaces”, J. Vac. Sci. Technol. A, vol. 6, No. 2, pp. 432-435, Mar./Apr. 1988.
H. Kunzmann, “Nanometrology at the PTB”, Metrologia, vol. 28, pp. 443-453, 1991/1992.
Bartha Johann W.
Bayer Thomas
Greschner Johann
Nonnenmacher Martin
Nonnenmacher Regine
Fourson George
International Business Machines - Corporation
Nonnenmacher Regine
Pham Thanh V.
Trepp Robert M.
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