Coating processes – Measuring – testing – or indicating – Thickness or uniformity of thickness determined
Patent
1996-04-19
1999-11-09
Padgett, Marianne
Coating processes
Measuring, testing, or indicating
Thickness or uniformity of thickness determined
427 8, 427523, 427566, 427561, 20419213, 20429803, 118718, 118720, 118723VE, 118691, B05D 300, C23C 1400, C23C 1600, B05C 1100
Patent
active
059809752
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to manufacturing methods and apparatus for thin-film-coated substrates involving optical coatings for optical filters, such as anti-reflection filters, interference filters, half mirrors and band-pass filters; anti-reflection coatings for various display devices; and other thin film products used for semiconductors, optical disks, etc.
BACKGROUND ART
There are two conventional methods of manufacturing optical filters and other thin-film-coated substrates based on techniques such as vacuum evaporation and sputtering. One comprises the measurement of the thickness of the thin film produced and control of the film coating process based on the results of such measurement, while the other provides no such control, and both are widely used.
The method that does not incorporate thin film thickness measurement aims to achieve the desired thickness by, for example, controlling the film formation time while keeping the conditions of the film formation atmosphere and speed constant. In the case of producing a thin film while moving the substrates to be coated, the desired film thickness may be obtained by controlling their moving speed.
With such a thin-film-coated substrate manufacturing method, it is not possible to check whether the thin film being produced would satisfy the required specification until the film coating process is completed, as the film thickness is not measured during the process. A thin film production apparatus normally operates in a vacuum so that it is not desirable to frequently take out the substrate on which a thin film is being produced to measure its thickness. Therefore, where more than one thin film is generated, measurement is not carried out until the production of all thin films is complete.
However, operating conditions of thin film production apparatus, such as film formation speed, are generally susceptible to fluctuations, and these have quite frequently caused the film thickness to fluctuate, resulting in the production of coatings that do not meet the specifications. Therefore, with thin film production methods in which film thickness measurement was not used, it was difficult to sustain the yield above a certain level.
As a result, the control of the film coating process through the measurement of film thickness began to be practiced. Taking the production of anti-reflection coatings and other optical coatings over plane substrates, such as glass plates, as an example, conventional methods of manufacturing thin-film-coated substrates in which the film thickness is measured and the film coating process is controlled based on the results of such measurements are explained with reference to the accompanying drawings.
FIG. 7 is a schematic diagram which shows the thin-film-coated substrate manufacturing process as viewed in a direction parallel to the substrate surface and perpendicular to the direction of the movement of the substrates. Inside a vacuum vessel 16, a thin film material 3 is placed, with the film-forming particle flux generating element 2 pointing upwards in the diagram. Electrons are ejected from an electron gun 6, and travel to the film-forming particle flux generating element 2 due to the effect of a magnetic field, not shown on the diagram. On collision with the element, they heat it, thereby generating a film-forming particle flux 5. The film-forming particle flux axis 9, i.e. the axis of the film-forming particle flux 5 (representing the direction in which film-forming particles are generated in the highest density), points upwards in the diagram. A film formation monitoring plate 8 is placed on the film-forming particle flux axis 9 or in its vicinity, and a film thickness measuring device 7, which optically measures the thickness of the thin film formed on the film formation monitoring plate 8, is located above it. An arrangement is made so that a thin film is formed on the underside of each of the group of substrates to be coated 1 through exposure to the film-forming particle flux 5 in the vicinity of the film-for
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Nomura Fumiyasu
Saito Takeshi
Padgett Marianne
Toray Industries Inc.
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