JPH04363611A - Optical measuring deveice - Google Patents

Abstract

PURPOSE:To obtain an optical measuring device where a standard sample applicable over a wide range is mounted without using a plurality of standard sample with various kinds of thicknesses by mounting the standard sample where a thin inclined film with a film thickness varied continuously is formed onto a substrate. CONSTITUTION:A standard sample where a thin inclined film 2' with a film thickness varied continuously is formed is mounted onto a substrate 1. The standard sample may be the one obtained by laminating two of objects where the thin inclined film 2' is formed on the substrate 1. With one standard sample, accurate inspection and calibration can be made over a wide range, which is highly efficient. Also, by using the standard sample with the film thickness changing continuously, an accurate measurement can be made in any film thickness. The standard sample, where two objects with the thin inclined film 2' is formed on the substrate 1 are laminated, can be especially applied to a phase plate.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical measuring device that optically measures film thickness, level differences, etc. by utilizing the interference effect of light.

0002

2. Description of the Related Art When manufacturing or using a non-contact type film thickness measuring device, it is necessary to perform accuracy checks and calibrations before the final process or before use. To this end, accuracy tests and calibrations were performed using standard samples with known film thicknesses. Specifically, for example, the film thickness of the measured object is determined by irradiating the measured object with polychromatic light and comparing it with a standard sample exhibiting the same wavelength as the specific wavelength reflected by light interference at the measured point. Measure.

FIG. 8 is an explanatory diagram showing the structure of a conventional standard sample. As shown in the figure, a number of standard samples A, B, and C having various film thicknesses a, b, and c are prepared by changing the amount of film deposited, and the non-contact film thickness measuring device is calibrated.

[0004] The film thickness uniformity of conventional standard samples must be excellent at about ±5%, and it is necessary to measure, evaluate, and calibrate each sample using a large number of samples with different film thicknesses. there were. This standard sample includes thermal oxide films of various thicknesses, SiO2 on a substrate such as a Si wafer or glass.
, Si3N4, Poly-Si, etc., were formed by sputtering, CVD, etc., and the thickness of each thin film was precisely measured to various thicknesses.

[0005]

[Problem to be Solved by the Invention] However, in conventional standard samples of various thicknesses, the film thicknesses are not continuously uniform, so it is difficult to obtain film thicknesses that are not found in the standard samples, that is, to form a single standard sample. If the measured value is between the thickness of another standard sample, the film thickness of the measured value may be overlooked, or accurate measurement may be difficult, causing problems in film thickness calibration and inspection.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical measuring device equipped with a standard sample that can be applied over a wide range without using a plurality of standard samples of various thicknesses.

[0007]

[Means for Solving the Problems] As a result of intensive research, the present inventors have found that, by using a standard sample in which a sloped thin film with a continuously changing film thickness is formed instead of a conventional standard sample, The present inventors have discovered that accuracy inspection and configuration can be performed without using a plurality of standard samples, and have accomplished the present invention. Accordingly, the present invention provides an optical measuring device characterized in that a standard sample is mounted on a substrate, in which a sloped thin film with a continuously changing film thickness is formed. Further, the standard sample to be mounted on the optical measuring device of the present invention may be a standard sample in which two substrates each having an inclined thin film formed thereon are bonded together.

[0008]

[Operation] In the present invention, accuracy can be inspected and calibrated over a wide range using one standard sample, which is efficient. Moreover, by using a standard sample whose film thickness changes continuously, accurate measurements can be made at any film thickness. The tilted thin film mounted on the optical measuring device of the present invention has a uniform thickness on a substrate, for example, and its thickness is continuously changed by varying the etching processing time. Dry etching may be performed by continuously moving the mask, but a method in which the thin film on the substrate is immersed together with the substrate at a regular rate in an appropriate etching solution is better.
It is simple and does not require special means.

Furthermore, by controlling the speed at which the thin film is immersed in the etching solution, it is possible to curve the surface of the inclined thin film, for example, into a concave or convex surface. Note that a standard sample made by bonding two substrates with a tilted thin film formed thereon may be particularly useful as a phase plate. As shown in FIG. 9, the current phase plate is made by pasting together two inclined films, and by changing the thickness of one, the phase difference between the incident light and the outgoing light is changed. (Phase difference=n×
1/λ, n: refractive index, λ: wavelength) As this phase plate, 0
．． In the invention according to claim 2, which uses a tilted thin film having a thickness of about 0.05 to 10 μm, a very slight and precise phase difference can be generated.

0010

[Embodiment] The details of the method for manufacturing a standard sample installed in the optical measuring device of the present invention will be described below, using a thermal oxide film wafer as an example. First, a Si wafer was thermally oxidized using a conventional method. FIG. 1 is a cross-sectional view showing a thermal oxide film formed on a Si wafer. As shown in the figure, a thermal oxide film 2 is mounted on a substrate 1 of a Si wafer 10. The thickness of the thermal oxide film 2 is determined according to the required maximum thickness of the tilted thin film. For example, if the required maximum thickness of the tilted thin film is 5000 Å, the thickness of the thermal oxide film 2 is required to be 5000 Å or more than 5000 Å. .

As is well known, the film thickness uniformity of a Si oxide film formed by thermal oxidation is very excellent, and the film thickness variations were not strictly measured here. FIG. 2 is an explanatory diagram showing an apparatus for performing etching processing. As shown in the figure, the Si wafer 10 on which film growth had been completed was fixed to a holder 11, and the holder 11 was suspended by a nylon thread 12.

Si wafer 1 fixed with holder 11
A liquid tank 14 holding an etching liquid 13 for Si oxide film was placed below the substrate. Usually this liquid contains HF-NH4F
Use a type of chemical. Not limited to Si oxide film, 1000 Å
It is preferable to use an etching solution that is controlled at an etching rate of approximately 1/min and does not generate bubbles.

The other end of the thread 12 is connected to a pulse motor 15.
It is connected to a device that moves the position more precisely. The descending speed of the pulse motor 15 was controlled by a computer, and the speed was adjusted to achieve the desired angle of inclination.

Using the above system, the wafer 10 was immersed in the etching solution 13, and after the immersion was finished, it was taken out and cleaned. If it is desired to reduce the film thickness over the entire surface after dipping, the entire surface is further etched until a predetermined film thickness is reached.

FIG. 3 is a schematic sectional view showing the structure of a standard sample according to an embodiment of the present invention, and corresponds to the section AB in FIG. Moreover, FIG. 4 is a diagram showing the relationship between the AB cross section of the standard sample and the film thickness of the inclined thin film when the falling speed is kept constant. As shown in the figure, if the descent speed is kept constant,
The etching depth of the thin film changed continuously due to the difference in etching treatment time, and a standard sample 10' having a tilted thin film 2' with a constant slope was obtained.

[0016] In the above, the Si oxide film was taken as an example, but the film is not limited to this film, and PSG, Si3 N4, P
Of course, it can also be applied to other films such as oly-Si. For PSG, a suitable etching solution can be obtained using dilHF or the like. Si3N4 with concHF or hot phosphoric acid,
Poly-Si can be etched using Cicaculin (Kanto Kagaku Co., Ltd.), but the etching rate is approximately 100 Å/min, and it is necessary to perform the immersion process multiple times or to sufficiently reduce the rate of descent.

FIG. 5 is a schematic sectional view showing the structure of a standard sample according to another embodiment of the present invention, and corresponds to the section AB in FIG. Moreover, FIG. 6 is a diagram showing the relationship between the AB cross section of the standard sample and the film thickness of the inclined thin film. As shown in FIGS. 5 and 6, by gradually increasing the immersion speed in the etching solution, a standard sample 20 having a concave inclined thin film 22 is obtained. Further, as shown in FIG. 7, when the speed of immersion in the etching solution is gradually lowered, a standard sample 30 having a convex inclined thin film 32 is obtained.

[0018] In the non-contact type film thickness measuring device equipped with the standard sample as described above, calibration and accuracy inspection were carried out efficiently. In addition, there were no film thicknesses that could not be calibrated or inspected, and accurate measurements were possible.

[0019]

As described above, according to the present invention, it is possible to calibrate a wide range of film thicknesses and test accuracy using one standard sample, which is efficient. In addition, since we use a standard sample whose film thickness changes continuously, there is no film thickness that cannot be calibrated or inspected.
Accurate measurements can be made at any film thickness.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a thermal oxide film mounted on a Si wafer.

FIG. 2 is an explanatory diagram showing an apparatus that performs etching processing.

FIG. 3 is a schematic cross-sectional view showing the configuration of a standard sample according to an example of the present invention.

[Figure 4] A-B of the standard sample when the descent speed is constant
FIG. 3 is a diagram showing the relationship between the cross section and the thickness of the inclined thin film.

FIG. 5 is a schematic cross-sectional view showing the configuration of a standard sample according to another example of the present invention.

FIG. 6 is a diagram showing the relationship between the AB cross section of the standard sample and the inclined thin film.

FIG. 7 is a cross-sectional view showing the configuration of a standard sample according to yet another example.

FIG. 8 is an explanatory diagram showing the configuration of a conventional standard sample.

FIG. 9 is a conceptual diagram of a conventional phase plate.

[Explanation of symbols]

1 Board 2 Thin film 2', 22, 32 Inclined thin film 10 Wafer 11 Holder 12 Thread 13 Etching liquid 14 Liquid tank 15 Pulse motor

Claims (2)

[Claims] 1. An optical measuring device characterized in that a standard sample is mounted on a substrate, in which a sloped thin film with a continuously changing film thickness is formed. 2. The optical measuring device according to claim 1, further comprising a standard sample in which two sheets of the inclined thin film formed on the substrate are bonded together.