JPH11248617A - Contamination degree detecting method for substrate surface, and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and accurately measure a contamination degree on a surface of a large substrate of silicon wafer or quartz without destroying it. SOLUTION: This contamination degree detecting device consists of a flat cooling plate having a cooling function, on the surface of which small protuberances 4 are provided so that the inspected substrate 1 is placed on the protuberances 4, a beam irradiate device 6 which is located above the cooling plate with a space kept from it, so that a parallel beam 9 is irradiated toward the cooling plate and a scattered light observation camera 10 which is located in the space between the cooling plate and the beam irradiating device, and how the inspected surface of the substrate is contaminated is detected by a scattering ring 13 taken by the scattered light observation camera 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for cleaning large substrates such as silicon wafers and quartz.
In particular, the present invention relates to a technology for efficiently and accurately detecting minute contamination on the surface of a large-sized substrate.

[0002]

2. Description of the Related Art Silicon wafers and quartz are indispensable as substrates for various electronic devices, and when a minute contaminant layer exists on the surface of these substrates, they exhibit their intended functions as substrates. Therefore, detecting and removing the minute contaminant layer is a very important technique.

Conventionally, as a method of detecting contamination of a substrate, as shown in FIG. 1, a droplet 2 having a diameter of several millimeters is dropped on a substrate to be inspected, and its contact angle θ is measured. A method of detecting the degree of contamination from the magnitude of the contact angle θ is known. That is, there is a correlation between the contact angle θ of the droplet and the degree of contamination, and the higher the degree of contamination, the larger the contact angle θ. If carried out at the point, the contamination distribution in the surface of the substrate 1 can be known.

[0004]

The measurement of the contact angle θ of the droplet 2 is a technique capable of measuring the degree of contamination of the surface of the substrate 1 with high sensitivity. However, the measurement of multiple points on the surface of the substrate 1 is extremely time-consuming. It was troublesome and was not suitable for large substrates. or,
The measurement of the contact angle θ is extremely delicate, and it is inevitable that the measured value varies depending on the measurer, and there is a disadvantage that an inaccurate result is easily obtained.

On the other hand, there is a method of measuring the degree of contamination by chemical analysis such as ESCA or XPS. In this case, since the substrate 1 must be placed in a vacuum chamber, the surface state differs from that in the atmosphere. There were drawbacks. In addition, since the vacuum chamber is generally small, it is necessary to cut the substrate 1 to be measured into small pieces, so that the destructive inspection cannot be performed. In this case, there is also a problem that the measurement result is greatly affected by the electric conductivity of the substrate 1. On the other hand, with a particle counter using laser scattering of fine particles, it was impossible in principle to detect a fine organic contaminant layer by chemical adsorption, even though irregularities on the substrate 1 surface could be detected.

As described above, it was technically difficult to detect the degree of contamination on the surface of a substrate such as a silicon wafer or quartz. Focusing on the scattering ring generated by the scattered light, we determined a method to detect various types of contamination efficiently and with high accuracy, including the minute organic contamination layer, based on the form of this scattering ring, and developed a device for that purpose. It is proposed as an invention.

[0007]

According to the present invention, a large number of microdroplets are attached to the surface of a substrate to be inspected, and a parallel light beam is irradiated from above or below the substrate toward the microdroplets. Observe the scattering ring generated above or below the substrate by the scattered light from the microdroplets by optical means, and try to detect the state of contamination on the substrate surface from its diameter, ring width, ring distortion, and disappearance time of the scattering ring. A flat cooling plate having a cooling function, having a plurality of small projections on the surface, and mounting a substrate to be inspected on the small projections; A light irradiating device positioned at a distance from the cooling plate to irradiate parallel rays toward the cooling plate; and a scattered light observation camera movably positioned in a space between the cooling plate and the light irradiating device. ; By configuring the contamination degree detection device for the substrate surface from a, it solves St. the above problems.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is an explanatory view of an embodiment of the apparatus for detecting the degree of contamination of a substrate surface according to the present invention. In the figure, reference numeral 3 denotes a flat cooling plate which has a cooling function and has a cooling function. Is provided with a plurality of small projections 4, on which the substrate 1 to be inspected is placed.

Reference numeral 5 denotes a cooling plate control unit, which controls the cooling state of the cooling plate 3. On the other hand, above the cooling plate 3, a light beam irradiation device 6 directed toward the cooling plate 3 is positioned with a space therebetween. The light beam irradiation device 6 includes a light source 7 for generating light beams and a parabolic mirror 8, and can irradiate the cooling plate 3 with vertical parallel light beams 9.

As the light source 7, monochromatic light such as white light or laser light is used. Further, a camera 1 for scattered light observation is provided in a space between the cooling plate 3 and the light beam irradiation device 6.
Numeral 0 is positioned so as to be movable up and down in the direction of the cooling plate 3, and the scattered light observation camera 10 is connected to a monitor device 11 and an image processing device 12, respectively.

The apparatus for detecting the degree of contamination on the substrate surface has the structure described above, and the substrate 1 to be detected is
Is placed on the small projections 4 of the cooling plate 3 and the substrate 1 is slowly cooled to near 0 ° C. This cooling rate can be arbitrarily controlled by the cooling plate controller 5. Since the substrate 1 does not directly contact the cooling plate 3 but only contacts the small protrusions 4, there is no possibility that the surface of the substrate 1 is contaminated by the cooling plate 3. The substrate 1 is cooled by the cooling of the cooling plate 3, and water vapor in the air is condensed on the surface of the substrate 1 to form a droplet group composed of minute droplets 2. The size of the droplet 2 is several microns to several hundred microns.

In such a situation, when the light source 7 of the light beam irradiation device 6 located above is turned on, the parallel light beam 9 reflected by the parabolic mirror 8 becomes the substrate 1 on which the microdroplets 2 are formed. Irradiated perpendicular to the surface. Then, as shown in FIG. 3, a scattering ring 13 is generated by a light scattering phenomenon from a droplet group including the minute droplets 2. This scattering ring 13
Are visible from an observation point above the substrate 1. And
Since the scattering ring 13 has a characteristic morphological characteristic according to the state of contamination of the substrate 1, this state is captured by the camera 10 for observing the scattering ring, and the image information is visually displayed on the monitor device 10. Together with the image processing device 1
2, the contamination state of the substrate 1 is detected by comparing the data accumulated in advance and analyzing the relationship between the contamination state and the form of the scattering ring 13.

The relationship between the state of contamination on the surface of the substrate 1 and the scattering ring 13 is as follows. When white light is used as the light source 7, a circular ring having a width as shown in FIG. When monochromatic light is used, it is observed as a narrow ring with a narrow width, and when two or more types of laser light with different wavelengths are used, it is observed as a double clear ring. Scatter ring 1
The state of contamination on the surface of the substrate 1 is sensitively reflected on the distortion of the diameter, ring width and ring shape of the substrate 3.

FIG. 3 shows an example of a scattering ring when white light is incident. The outside of the scattering ring is blue and the inside is red, and the relationship between the width of the scattering ring and the degree of contamination is shown in FIG. The result is as shown in the graph of FIG. That is, as the degree of contamination increases, the diameter of the scattering ring 13 increases, and its width also increases.

Therefore, the degree of contamination on the surface of the substrate 1 can be quantified from the relationship shown in FIG. Also, substrate 1
If the degree of contamination on the surface is constant and uniform, the scattering ring 13 becomes a perfect circle, so if the scattering ring 13 is distorted, it means that the part has a different degree of contamination than other regions.

Therefore, by continuously changing the observation position, that is, the position of the camera 10 up and down, the scattering ring 13 in the entire region of the substrate 1 can be observed, and the distribution of contamination in the surface of the substrate 1 can be analyzed. FIG. 5 shows a situation in which the scattering ring 13 is enlarged while the camera 10 is raised as described above.

The generation and growth of fine droplets due to the condensation of water vapor on the substrate 1 are shown in FIG. 6 (a) → (b) → (c) when the substrate surface is clean, and when the substrate is contaminated. 7 (a) → (b) → (c). That is, when the surface of the substrate 1 is clean, the contact angle of the droplet 2 is small, so that the droplet shape is quickly distorted due to aggregation, and the scattering ring 13 disappears quickly with this, but the surface of the substrate 1 is contaminated. In this case, since the contact angle of the droplet 2 is large and the droplet 2 continues forever as shown in FIG. 7, the scattering ring 13 does not easily disappear.

Accordingly, the degree of contamination of the substrate 1 can be detected from the relationship between the time until the scattering ring 13 disappears and the degree of contamination. In the case where distortion is present in the substrate 1, the distortion affects the shape of the scattering ring and hinders accurate measurement of the degree of contamination. However, as shown in FIG. A transparent plate 14 having a high degree of flatness is placed on the surface of the substrate 1, and the entire surface is scanned with a laser beam 15 from above. Accumulate the scattering ring 13
When the distortion is analyzed from the roundness of the substrate 1, the initial distortion of the substrate 1 can be corrected by using the correction data as correction data.

Further, in the above embodiment, the scattering ring is observed from the incident light side. However, the opposite is applied to a transparent substrate such as a plate glass or quartz, which tends to have a weaker scattering intensity on the incident light side. Observation may be made from the transmission side.

Further, since the position of the camera 10 is moved up and down, the surface of the substrate 1 is not scanned, but the position of the camera 10 is fixed as shown in FIG. May be performed while moving. This method is suitable for measuring the degree of contamination in a chamber or a clean room in which environmental conditions such as humidity and temperature are controlled.

In the above embodiment, condensation of water vapor by cooling was used as a method for generating a group of fine droplets. However, a fine mist generator or a steam generator using an ultrasonic vibrator was used to generate fine droplets. May be generated.

[0022]

The present invention has the structure as described above, and detects the degree of contamination of the substrate surface from the form of the scattering ring, and can detect only a small amount of organic contamination on the substrate surface due to chemical adsorption with high sensitivity. Instead, the presence of fine particles attached to the substrate surface can be detected with high sensitivity.

The present invention is also applicable to the uniformity evaluation of ultra-thin layers such as oil floating on the water surface and LB (Langmuir Blodgett) films, and enables non-destructive evaluation of large-area substrates at high speed. There is no limitation on the type of the material, and it has versatility that it can be applied to flat substrates made of most materials, and is extremely practical.

[0024]

[Brief description of the drawings]

FIG. 1 is an enlarged view of a droplet dropped on a substrate surface.

FIG. 2 is an explanatory view of an embodiment of a substrate surface contamination degree detecting apparatus according to the present invention.

FIG. 3 is a plan view of an example of a scattering ring generated by irradiation of parallel rays.

FIG. 4 is a graph showing the relationship between the shape of a scattering ring and the state of contamination.

FIG. 5 is a plan view of an example of the scattering ring showing a state of the scattering ring which expands as the camera is raised.

FIG. 6 is a plan view of the substrate, showing a state in which droplets gather over time on a clean substrate.

FIG. 7 is a plan view of a substrate showing a state in which droplets gather over time on a contaminated substrate.

FIG. 8 is an explanatory view showing a method for correcting initial distortion of a substrate.

FIG. 9 is an explanatory diagram showing a method of moving the substrate in the horizontal direction and scanning the entire surface thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Droplet θ Contact angle 3 Cooling plate 4 Small projection 5 Cooling plate controller 6 Light irradiation device 7 Light source 8 Parabolic mirror 9 Parallel light 10 Camera 11 Monitor device 12 Image processing device 13 Scattering ring 14 Transparent plate 15 Laser Light 16 Transportation

Claims (7)

[Claims] 1. A method in which a large number of microdroplets are attached to the surface of a substrate to be inspected, and a parallel light beam is irradiated toward the microdroplets from above or below the substrate, and scattered light from the microdroplets is used. The degree of contamination of the substrate surface is characterized by observing the scattering ring generated above or below the substrate by optical means, and detecting the state of contamination of the substrate surface from its diameter, ring width, ring distortion, and disappearance time of the scattering ring. Detection method. 2. A flat cooling plate having a cooling function and having a plurality of small projections on its surface, on which a substrate to be inspected is mounted; and A beam irradiator positioned at a space and configured to irradiate a parallel beam toward the cooling plate; a scattered light observation camera positioned vertically movable in a space between the cooling plate and the beam irradiator; Wherein the contamination state of the substrate surface to be inspected is detected from the scattering ring captured by the scattered light observation camera. 3. The contamination distribution in the substrate surface is detected by continuously changing the observation position of the scattering ring up and down and observing the scattering ring in the entire region of the substrate. A method for detecting the degree of contamination on the substrate surface. 4. The degree of contamination on the substrate surface according to claim 1, wherein the flatness of the substrate is measured in advance by the Newton ring method, and the initial distortion of the substrate is corrected as background data. Detection method. 5. The method according to claim 1, wherein the substrate is cooled to form fine droplets on the surface of the substrate. 6. The observation position of the scattering ring is fixed,
2. The method according to claim 1, wherein the scattering ring is observed because the substrate is moved in the lateral direction. 7. The method according to claim 1, wherein the formation of the microdroplets is performed by spraying a mist.