JPH0735514A - Film thickness measuring device - Google Patents

Abstract

PURPOSE:To provide a film thickness measuring device which does not cause deterioration of a sample during measurement. CONSTITUTION:A film thickness measuring device comprises a stage 11 for carrying thereon a sample 10 to be measured, a stereomicroscope 1 having a light source 12 for irradiating the sample 10 and the stage 11, and a camera 10 for picking up an image of the sample 10 so as to detect deflecting light from the outer surface of the sample 10, an image memory part 2 for storing therein a surface condition of the sample 10, as image data, detected by the camera 13, an image processing part 3 for processing the image data stored in the image memory part 2, a film thickness analyzing part 4 for analyzing a thickness of the sample 10 in accordance with the result of the process made by the image processing part 3, and a camera exposure control circuit 5 for controlling the camera 13 so that an input image has a suitable tone. Further, the film thickness analyzing part 4 incorporates a reference data table 41 exhibiting data indicating correlation among an averaged tone value previously obtained by experiments, a representative tone value and a film thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film thickness measuring device, and more particularly to a film thickness measuring device for detecting the reflected light from a sample to be measured and measuring the film thickness of the sample.

[0002]

2. Description of the Related Art A conventional film thickness measuring device is described in, for example, Japanese Patent Application Laid-Open No. 61-117404. As shown in FIG. 4, this film thickness measuring device includes a light source 52 for irradiating a measured sample 50 mounted on a stage 51, and a measured sample 50.
A camera 53 that captures an image and detects reflected light from the measured sample 50, an image storage unit 54 that stores image information input from the camera 53, and a wavelength analysis unit 55 that performs wavelength analysis from the input image information, A film thickness analysis unit 56 that analyzes the analyzed data to obtain the film thickness of the measured sample 50. The film thickness analysis unit 56 is provided with reference data indicating the relationship between the preliminary wavelength analysis data and the film thickness. Based on the wavelength analysis data obtained from the wavelength analysis unit 55, the film thickness analysis unit 56 searches for the reference data. Find the thickness.

As another conventional example, Japanese Patent Laid-Open No. 2-900
08 publication. This is to measure the thickness of the resist film applied on the substrate, heating the substrate, measuring the infrared energy intensity radiated from the resist film surface on the substrate at that time, to obtain in advance The film thickness of the resist film is obtained from the relationship between the infrared energy intensity and the resist film thickness.

[0004]

In the former example described above, there is a mechanism for inputting the sample surface state using a camera, and the image is saved in advance based on the wavelength distribution obtained by wavelength analysis of the input image. Since this is a method for obtaining the film thickness by searching the data of the correlation between the wavelength distribution and the film thickness, there is a drawback that a large amount of reference data is required and it takes time to obtain the film thickness of the sample.

Further, in the latter example, the principle of subjecting the sample to physical treatment and measuring the film thickness on the basis of the influence caused by it is used, so that the sample may be altered during the measurement. However, there is a drawback that it cannot be applied to all samples.

[0006]

A film thickness measuring apparatus of the present invention comprises a light source for irradiating the surface of a sample to be measured with light, a camera section for photographing reflected light from the sample to be measured, and a camera section for the camera section. A camera exposure control unit that controls exposure, an image storage unit that stores an image captured by the camera unit as image information, a background identification unit that identifies a background portion and a measured sample portion from the stored image information, and an identification unit. An average gray value calculation unit that calculates an average gray value of the range by cutting an arbitrary portion from the image information of the measured sample portion, and a gray histogram calculation unit that calculates a gray histogram of the image information of the cut range. A representative gray value calculation unit that calculates a typical gray value of the main part of the measured sample portion from the calculated gray histogram, the calculated average gray value, the representative gray value and It analyzes based on the reference data and a film thickness analyzer for determining the thickness of the sample to be measured.

[0007]

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing details of the image storage device 2 and the image processing device 3 of FIG. Further, FIG. 3 is a diagram showing a configuration example of reference data used for film thickness analysis.

As shown in FIG. 1, the film thickness measuring apparatus of the present invention photographs the stage 11 on which the sample 10 to be measured is placed, the sample 10 to be measured, the light source 12 for irradiating the stage 11 with light, and the sample 10 to be measured. Then, a stereoscopic microscope 1 having a camera 13 for detecting reflected light from the surface of the sample to be measured 10, an image storage section 2 for storing the surface state of the sample to be measured 10 photographed by the camera 13 as image information, and an image memory An image processing unit 3 for processing the image information stored in the unit 2, and an image processing unit 3
And a camera exposure control circuit 5 for controlling the camera 13 so that the shading of the input image falls within an appropriate range. . Further, the film thickness analysis unit 4 is provided with reference data 41, which is data indicating a correlation between an average gray value, a representative gray value, and a film thickness, which are previously obtained by an experiment.

Next, referring to FIG. 2, the image storage unit 2
Is an original image storage unit 21 that stores an image of a state in which the measured sample 10 is placed on the stage 11, a background storage unit 22 that stores an image of a state in which the measured sample 10 is not placed on the stage 11, and a processing target. It is composed of a storage unit 23.

The image processing unit 3 inputs data from the original image storage unit 21 and the background storage unit 22 of the image storage unit 2, and a background correction unit 31 for correcting the shading of the background portion and a background correction unit 31. An average value calculation unit 32 that calculates the average of the light and shade based on the output data, a histogram calculation unit 33 that obtains the light and shade distribution, and a representative light and shade that obtains the most representative light and shade value of the processing target image from the obtained light and shade distribution data Value calculator 34
And a temporary storage unit 35 that temporarily stores the data from the processing target storage unit 23.

Next, the operation of this embodiment will be described with reference to the drawings.

First, the image projected from the camera 13 is input to the background storage unit 22 of the image storage unit 2 with the sample 10 to be measured not placed on the stage 11. Then, the sample 10 to be measured is placed on the stage 11, and the image projected from the camera 13 is input to the original image storage unit 21 of the image storage unit 2.

Here, the background correction unit 31 is the original image storage unit 2.
1 and the contents of the background storage unit 22 are input, and the difference between these is calculated to correct the shading of the background portion. The corrected image is output to the processing target storage unit 23. At this time, in the image stored in the processing target storage unit 23, when the number of pixels having the minimum or maximum density becomes equal to or larger than the reference number, the camera exposure control circuit 5 controls the operation of the camera 13. The number of pixels having the minimum or maximum value is reduced to the reference value. After that, the image is again input from the camera 13 to the original image storage unit 21 and the background storage unit 22.

The image processing unit 3 specifies a processing range for obtaining the average gray value and the representative gray value from the processing target storage unit 23, and transfers the image information of the range to the temporary storage unit 35.
The average value calculation unit 32 inputs the image of the processing range from the temporary storage unit 35, calculates the average of the grayscale values, and outputs it as the average grayscale value data to the film thickness analysis unit 4.

Similarly, the histogram calculating section 33 inputs the image information of the processing range from the temporary storage section 35, calculates the distribution of the gradation values, and calculates the gradation distribution data as the representative gradation value calculating section 34.
Output to. The representative shade value calculation unit 34 obtains a shade value having the maximum distribution from the inputted shade distribution data, and outputs it as the representative shade value data to the film thickness analysis unit 4. The film thickness analysis unit 4 inputs the average gray value data and the representative gray value data from the image processing unit 3. Then, the corresponding reference data is retrieved from the reference data 41 provided in advance. As shown in FIG. 3, the retrieved reference data is composed of an average gray value a, a representative gray value m, and a film thickness value d in that state. The film thickness value d is uniquely determined by the lightness and darkness of the surface as shown in equation (1).

D = f (a, m) (1) Here, the function f is a function determined by the material of the sample and the film of the sample.

Thus, the film thickness analyzing section 4 can obtain the film thickness of the sample from the average gray value data, the representative gray value data and the reference data.

[0019]

As described above, the film thickness measuring apparatus of the present invention uses the gray value of the reflected light from the sample to be measured as the reference data for analyzing the film thickness of the sample to be measured. This has the effect of simplifying the data structure and facilitating search and analysis at high speed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing details of an image storage unit 2 and an image processing unit 3 in FIG.

FIG. 3 is a diagram showing a configuration example of reference data used for film thickness analysis.

FIG. 4 is a configuration diagram showing a conventional example.

[Explanation of symbols]

 1 Stereoscopic Microscope 2,54 Image Storage Section 3 Image Processing Section 4,56 Film Thickness Analysis Section 5 Camera Exposure Control Circuit 10,50 Measured Sample 11,51 Stage 12,52 Light Source 13,53 Camera 21 Original Image Storage Section 22 Background Storage unit 23 Processing target storage unit 31 Background correction unit 32 Average gray value calculation unit 33 Gray histogram calculation unit 34 Representative gray value calculation unit 35 Temporary storage unit 41 Reference data 55 Wavelength analysis unit

Claims (1)

[Claims] 1. A light source for irradiating the surface of a sample to be measured with light, a camera section for photographing reflected light from the sample to be measured, a camera exposure control section for controlling exposure of the camera section, and the camera section. An image storage unit that stores the image captured by the device as image information, a background identification unit that identifies a background portion and a measured sample portion from the stored image information, and an arbitrary image information from the identified image information of the measured sample portion. An average gray value calculation unit that cuts out a portion and calculates the average gray value of the range,
A grayscale histogram calculation unit that calculates a grayscale histogram of the image information in the clipped range, and a representative grayscale value calculation unit that calculates a typical grayscale value of the measured sample main part from the calculated grayscale histogram, A film thickness measuring device, comprising: a film thickness analyzing unit that analyzes the film based on the average gray value, the representative gray value, and reference data provided in advance to obtain a film thickness of a sample to be measured.