Single-crystal – oriented-crystal – and epitaxy growth processes; – Forming from vapor or gaseous state – With decomposition of a precursor
Reexamination Certificate
1997-02-06
2001-05-15
Kunemund, Robert (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Forming from vapor or gaseous state
With decomposition of a precursor
C117S092000, C117S103000, C117S105000, C117S953000, C117S955000, C117S954000
Reexamination Certificate
active
06231668
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to calibrated scales and a method for manufacturing such scales, and more particularly to scales for use for calibrating very sensitive microscopes, such as electron microscopes.
RELATED TECHNOLOGY
The following articles have to do thematically with the present invention and are based on related art.
1. Technical data sheets from the firms Leitz (Wetzlar) and Zeiss (Oberkochen). The technical data sheets include a description of metal patterns in the micrometer range (0.5 &mgr;m to 10 &mgr;m), which are lithographically defined on substrates. When objects are measured in the nanometer range, these patterns can be scaled, it then being necessary, however, to take substantial errors into account.
2. Technical data sheets from the firm LOT (Darmstadt). The technical data sheets from the firm LOT describe patterns that are produced lithographically in semiconductor materials. Numbered among these are, for example, line- or cross-lattice structures in silicon, which can be defined with the help of holographic methods. In this case, the lines are spaced apart by 300 nm or 700 nm;
3. Technical data sheets from the firm Plano (Marburg). The technical data sheets from the firm Plano describe patterns fabricated using electron beam methods and aluminum vapor deposition on silicon substrates. The aluminum tracks produced have a thickness as well as minimal width of 500 nm.
The scales described under numbers 2 and 3 must also be scaled before they can be used in the nanometer range. This has its inherent drawbacks.
The following articles are mentioned as examples of analysis methods based on X-ray diffractometry and are hereby incorporated by reference herein:
1. Appl. Phys., 56(1984), p. 1591. Speriosu, V. S.; Vreeland, T., Jr.: “X-ray Rocking Curve Analysis of Superlattices”;
2. Springer, Proceedings in Physics 13, Les Houches, France. Quillec, M.: “Structural Characterization of Superlattices by X-ray Diffraction”;
3. Phys. stat. sol. (a), 105(1988), p. 197. Baumbach; Brühl; Pietsch; Terauchi: “Characterization of AlGaAs/GaAs-Superlattices and Thin Layers by X-ray Diffraction”.
The following sources contain model calculations, which can be used to evaluate the experimental data of the analysis methods, and are hereby incorporated by reference herein:
1. Acta Cryst., A42(1986), p. 539-545. Bartels, W. J.; Hornstra, J.; Lobeek, D. J.: “X-Ray Diffraction of Multilayers and Superlattices”,
2. J. phys. soc. Japan, 26(1969), no. 5, p. 1239 Tagaki, S.: “A Dynamical Theory of Diffraction for a Distorted Crystal”;
3. Journal of Crystal Growth, 44(1978), p. 513-517. Hornstra, J.; Bartels, W. J.: “Determination of the Lattice Constant of Epitaxial Layers of III-V-Compounds”;
The model equations are based on a formulation published in 1986 (1) for calculating the reflectivities of Bragg reflections, which is based on the Tagaki-Taupin formalism (2) of the dynamic theory of X-ray diffraction, and on a treatise on the lattice constants when working with strained epitaxy layers of III-V semiconductors (3).
Epitaxial methods can be used, such as molecular-beam epitaxy, to deposit semiconductor heterostructures, i.e., layers which vary in composition and thickness, one after another on a semiconductor substrate. Examples of the extensive literature on this subject are:
1. Springer Publishers, Berlin 1984, p. 88. Springer Series in Solid-State Sciences, vol. 53 Weimann, G., et al.: “Two-dimensional Systems, Heterostructures and Superlattices”;
2. J. of Cryst. Growth. 105(1990), p. 1-29. Tsang, W. T.: “Progress in Chemical Beam Epitaxy”;
3. H. C. Freyhardt (Editor), Springer Publishers 1980. Ploog, K.: “Growth, Properties and Application”;
4. Thin Solid Films, 205(1991), pp. 182-212. Adomi K., et al.: “Molecular Beam Epitaxial Growth of GaAs and Other Compound Semiconductors”.
These four references are also incorporated by reference herein.
What all the named literature sources on epitaxial methods have in common is that the individual layer thicknesses are able to be determined from the growth rates and from various in-situ control methods, such as RHEED and ellipsometry. However, they do not attain the accuracy achieved by the present invention.
Some early pioneer works are cited as examples from the voluminous literature on characterizing semiconductor heterostructures, mostly on the basis of photoluminescence, and as a further example of an analysis method:
1. “Festkörperprobleme” [Advances in Solid State Physics], vol. XV (1975), p. 21., Dingle, R.: “Confined Carrier Quantum States in Ultrathin Semiconductor Heterostructures”;
2. Reviews of Modern Physics, 54 (1982), p. 437. Ando, T.; Fowler, A. B.; Stem, F.: “Electronic properties of two-dimensional systems.”
These two references are also incorporated by reference herein.
The experimental data ascertained from the “photoluminescence” analysis method are evaluated, for example, by simulating photoluminescence spectra, as described by the following article, which is also incorporated by reference herein:
IEEE J. Quantum Electron., 26(1990), p. 2025. Jonsson, B.; Eng, S. T.: “Solving the Schrödinger Equation in Arbitrary Quantum-Well Potential Profiles Using the Transfer Matrix Method”.
SUMMARY OF THE INVENTION
The present invention is directed to the calibration of a spacial scale (spatial coordinates) of technical devices, which work on the basis of high-resolution and ultrahigh-resolution imaging processes. These are imaging processes based on particle flows, such as scanning electron microscopy, scanning transmission electron microscopy, or scanning probe microscopy (atomic force microscopy, scanning tunneling microscopy).
The technical task at hand is to manufacture and calibrate a scale which will enable the technical devices mentioned above to be calibrated with very high precision. The invention achieves this objective by enabling scales to be manufactured and calibrated in the nanometer range.
More particulary, the present invention provides a method for manufacturing and calibrating a scale in the nanometer range for technical devices which are used for the high-resolution or ultrahigh-resolution imaging of structures characterized in that:
a to construct the scale, at least two different crystalline or amorphous materials are used for the heterolayer structure, which are easily distinguished from one another by their contrast when they are imaged using high-resolution or ultrahigh-resolution imaging methods; that
b the different crystalline or amorphous material layers used are deposited by means of a material deposition method in the deposition direction, one after another in alternating sequence onto a substrate material, as a heterolayer sequence, until the entire layered stack is obtained; that
c the heterolayer sequence is characterized experimentally using an analysis method that is sensitive to the layer thicknesses of the heterolayer sequence, the applied analysis method being independent of the high-resolution or ultrahigh-resolution imaging methods used in the technical devices for which the scale is manufactured; that
d the experimental data obtained from the analysis method are evaluated and recorded, to make it possible to define the spacings between equivalent hetero-interfaces; and that
e subsequently, right after the step according to point b or the step according to point c, the heterolayer structure of the various materials is exposed by splitting open the heterolayer sequence in the deposition direction.
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Deckman et al., Microfabrication of molecular scale microstructures, Appli
Betz Walter
Goebel Rainer
Hillmer Hartmut
Loesch Rainer
Poecker Armin
Deutsche Telekom AG
Kenyon & Kenyon
Kunemund Robert
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