Single-crystal – oriented-crystal – and epitaxy growth processes; – Forming from vapor or gaseous state – With a step of measuring – testing – or sensing
Patent
1992-11-30
1995-02-07
Kunemund, Robert
Single-crystal, oriented-crystal, and epitaxy growth processes;
Forming from vapor or gaseous state
With a step of measuring, testing, or sensing
437250, 427 8, 427 9, 427 10, 20419233, 20429803, 117 86, 118712, 118688, C30B 2516
Patent
active
053873092
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE ART
The invention relates to a process for the spatially resolved measurement of the thickness of a thin film on a substrate, as well as to a device for performing the process.
Film thickness measurements are counted among the most significant auxiliary means in quality control during semiconductor manufacture, especially for checking individual process steps. Since the process environment, for example within a semiconductor-producing equipment, can vary greatly in spatial respects, it is particularly desirable to measure the film thickness over the entire wafer surface.
With increasing integration of components, the costs per wafer have risen considerably; for this reason, a complete check of each individual process step is the objective in order to recognize flawed parts as early as possible and to be able to sort these out.
STATE OF THE ART
A process for measuring the growth rate of an epitaxial layer on a substrate has been known from the technical publication by A. J. Spring Thorpe et al., "In Situ Growth Rate Measurements During Molecular Beam Epitaxie [sic!] Using an Optical Pyrometer", Applied Physics Letter, 55: 2138-2140 (1989).
This article describes measurement of the surface temperature of the substrate by means of an optical pyrometer during application of the layer. During this step, oscillations occur in the temperature which can be associated with the growth rate of the layer. However, it is not possible to measure, with this process, the absolute value of the layer thickness; furthermore, no spatial resolution over the area of the layer is possible.
One possibility of determining the thickness of layers resides in the interference of light beams reflected on the two surfaces of the layer. In an arrangement as disclosed, for example, in F. Kohlrausch, "Praktische Physik" [Practical Physics], vol. 1, 23rd edition, 1984, page 667, the phase difference of interfering beams is determined by their angle of inclination. Since all bundles of rays with the same angle of inclination are imaged independently of their point of origin during interference in the same image point, a locally resolved measurement of the layer thickness is not possible.
Moreover, the known interferometric methods for layer thickness determination are not directly suitable for measurement during production of the layer on account of the time required for the measurement and the necessary manipulating mechanisms.
Furthermore, a process for measuring the film thickness during application of the film has been known from DE 19 39 667 A1. In this process, the film thickness is determined by detecting the electromagnetic radiation emitted by the film.
Also, a process and apparatus for determining the layer thickness and the index of refraction of thin, transparent layers has been known from DE 24 48 294 A1.
DISCLOSURE OF THE INVENTION
The invention is based on the object of indicating a process permitting, during application of a film on a substrate, a spatially resolved measurement of the thickness of the film over the entire surface.
Furthermore, a device for carrying out this process is to be made available.
This object has been attained, according to the invention, by measuring and evaluating the intensity of two or more interfering electromagnetic bundles of rays which exhibit a phase difference after passing through differing path lengths in the film, and by providing that the thermal radiation of the substrate serves as the source of the electromagnetic radiation, and that all frequency proportions are filtered out of the continuous spectrum of the thermal radiation except for an approximately monochromatic proportion.
A bundle of rays emanating due to the thermal radiation from any desired point in the substrate is refracted on the interface between the substrate and the film and, after passing through the film, is separated on the vacant surface of the latter by partial reflection into a reflected and a transmitted component beam. The reflected beam, after reflection on the interface, is again separat
REFERENCES:
patent: 3620814 (1971-11-01), Clark et al.
patent: 5091320 (1992-02-01), Aspnes et al.
patent: 5096533 (1992-03-01), Igarashi
Bauer Norbert
Bobel Friedrich
Fraunhofer Gesellschaft zur Forderung der angewandten Forschung
Kunemund Robert
Paladugu Ramamohan Rao
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