JPH06258232A - Defect inspection device for glass substrate - Google Patents

Abstract

PURPOSE:To individually detect foreign matters such as particles existing on the front face and the back face of a glass substrate and to improve precision of detection. CONSTITUTION:In a defect inspection device for a glass substrate, scanning is carried out by irradiating a glass substrate with detecting light, and scattered light due to a foreign matter on the front face or the back face of the glass substrate is detected by an optical system, so that the number and the size of the foreign matters are detected. The detecting beam consists of the first laser beam L1 and the second laser beam L2, which cross each other at one point on the front face or the back face of a glass substrate G, detects the difference of amplitude between light receiving pulses by an optical system 14 and the generation of two light receiving pulses of approximately the same amplitudes at approximately constant time intervals, and consequently detects the foreign matters on the front face and the back face of the glass substrate G individually.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass substrate defect for detecting defects due to fine particles (dust), scratches, etc. (hereinafter, collectively referred to as foreign matter) existing on the front and back of the glass substrate. Regarding inspection equipment.

[0002]

2. Description of the Related Art The inventor has previously proposed Japanese Patent Application No. 4-313866.
We have proposed this type of defect inspection system for glass substrates. This inspection apparatus irradiates the surface of the glass substrate with detection light from the first light source, and scatters the light scattered by the fine particles on the front and back surfaces of the substrate within the vicinity of the critical angle of the total reflection of the substrate on the front surface side of the substrate. The first invention in which the fine particles on the front and back surfaces of the substrate are detected as defects by detecting with the first detection optical system arranged in Second irradiation of short-wavelength detection light and detection of scattered light by fine particles existing on the surface of the substrate by a second detection optical system arranged on the front surface side of the substrate to detect fine particles on the surface of the substrate as a defect Of the invention, etc.

In the above inspection device, theoretically, the first
The number of the fine particles present on the front and back surfaces of the substrate is detected by the invention of the above, and the number of the fine particles present on the front surface of the substrate is detected by the second invention. The number of fine particles present can be determined.

[0004]

However, in the first invention, the scattered light from the fine particles present on the back surface is emitted to the outside of the critical angle due to the influence of the refractive index of air, etc., and cannot be detected by the optical system. There are cases. Further, in the second aspect of the invention, since the intensity of the short wavelength detection light is relatively low, there is a problem in terms of detection sensitivity. If it is attempted to increase the detection sensitivity, the cost of the light source and the detection optical system becomes large, and the size is large. There was a problem of becoming. Therefore, it cannot be said that the detection accuracy of the number of fine particles existing on the front and back surfaces or the front surface of the substrate is necessarily high, and the number of fine particles existing on the back surface of the substrate cannot necessarily be detected accurately.

The present invention has been made in order to solve the above problems, and an object thereof is to make it possible to directly detect foreign matters such as fine particles existing on the front surface and the back surface of a substrate, respectively, and to improve the detection accuracy. It is to provide a significantly improved glass substrate defect inspection apparatus.

[0006]

In order to achieve the above object, the first invention is to scan the glass substrate while irradiating the glass with the detection light, and detect the scattered light due to the foreign matter on the front surface or the back surface of the glass substrate by the optical system. In the defect inspection apparatus for a glass substrate for detecting the number and size of the foreign matter, the detection light is composed of first and second laser beams intersecting at one point on the front surface or the back surface of the glass substrate. The difference between the amplitudes of the received light pulses due to the system and the occurrence of two received light pulses having substantially the same amplitude at substantially constant time intervals are detected to detect the foreign substances present on the front and back surfaces of the glass substrate, respectively. .

A second invention is a glass for scanning while irradiating a glass substrate with detection light and detecting scattered light due to foreign matter on the front or back surface of the glass substrate by an optical system to detect the number and size of the foreign matter. In the defect inspection apparatus for a substrate, the detection light is a detection light beam having a substantially inverted conical shape that converges at one point on the front surface or the back surface of the glass substrate, and the difference in the amplitude of the light reception pulse by the optical system, and a substantially constant light flux. This is to detect the occurrence of a light receiving pulse having a pulse width and detect the foreign substances existing on the front surface and the back surface of the glass substrate, respectively.

A third invention is a glass for scanning while irradiating a glass substrate with detection light, and detecting scattered light by foreign matter on the front or back surface of the glass substrate by an optical system to detect the number and size of the foreign matter. In the defect inspection apparatus for a substrate, the detection light is composed of first and second laser beams intersecting at a point on the front surface or the back surface of the glass substrate, and the optical system uses only one of these laser beams. Based on the number of the received light pulses and the number of the received light pulses obtained by the optical system using both the laser beams, the foreign substances existing on the front surface and the back surface of the glass substrate are respectively detected.

[0009]

In the first invention, when the first and second laser beams are irradiated from the surface side of the glass substrate and these beams are crossed at one point on the surface, foreign matter such as fine particles existing on the surface The amplitude of the received light pulse detected by is increased. Further, the light receiving pulse due to the foreign matter present on the back surface has a smaller amplitude than the light receiving pulse due to the foreign matter on the front surface,
Moreover, two beams are detected at almost constant time intervals due to the beam crossing angle and the scanning speed. By discriminating these light receiving pulses, it is possible to individually detect a foreign substance existing only on the front surface and a foreign substance existing only on the back surface.

In the second invention, for example, when the detection light beam is irradiated from the surface side of the glass substrate and focused on one point on the surface, the amplitude of the light receiving pulse detected by the foreign matter such as fine particles existing on the surface is growing. Further, the light receiving pulse due to the foreign matter on the back surface has a smaller amplitude than the light receiving pulse due to the foreign matter on the front surface, and has a substantially constant pulse width due to the beam crossing angle and the scanning speed. By discriminating these light receiving pulses, it is possible to individually detect a foreign substance existing only on the front surface and a foreign substance existing only on the back surface.

In the third invention, for example, when the first and second laser beams are irradiated from the back surface side of the glass substrate and these beams are crossed at one point on the front surface, the first and second laser beams are provided. The number of light-receiving pulses obtained using only one of the beams indicates the number of all foreign substances existing on the front surface and the back surface, and the number of light-receiving pulses obtained using both the first and second laser beams is It is the sum of the number of foreign matter present and the number of foreign matter present on the back surface doubled. By using this relationship, it is possible to individually detect the foreign substance existing only on the back surface and the foreign substance existing only on the front surface.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the configuration and operation of an embodiment of the first invention. First, in (a), L ₁ and L ₂ are the first and second laser beams, respectively. The laser light sources (not shown) are arranged so that the points intersect at one point on the surface of the glass substrate G. The laser beam L
The strengths of ₁ and L ₂ are the same. Moreover, the thickness of the glass substrate G is exaggerated and drawn for convenience.

Above the substrate G, the lenses 11, 12 and the photodetector 13 are arranged in the direction in which the optical axis is orthogonal to the substrate G.
A detection optical system 14 is arranged. This optical system 1
As is well known, 4 is for detecting scattered light of a laser beam passing through fine particles and converting it into a pulse signal, and detecting the number and size (particle diameter) of fine particles by the number and amplitude of this signal.

Here, the laser light source and the detection optical system 14 integrally scan two-dimensionally over the glass substrate G, thereby detecting foreign matters such as fine particles existing on the front and back of the glass substrate G. However, here, for convenience of description, the laser light source and the detection optical system 14 are fixed,
The operation of this embodiment will be described below on the assumption that the glass substrate G moves relatively at the speed v as shown in the drawing.

First, as shown in FIG. 1A, it is assumed that fine particles D ₁ and D ₃ are on the front surface of the glass substrate G and fine particles D ₂ and D ₄ are on the back surface. First, in the state of FIG.
Since the fine particles D _{1 on the} surface are at the intersections of the beams L ₁ and L ₂ ,
The scattered light is detected by the optical system 14 to generate a light receiving pulse as indicated by P _a in FIG. Next, when the glass substrate G moves relatively to the state shown in FIG. 1B, the fine particles D ₂ on the back surface are detected only by the beam L ₂ and the light receiving pulse P as shown by P _b in FIG. _A received light pulse whose amplitude is smaller than a is detected.

Thereafter, in the state of FIG. 1C, the fine particles D ₂ on the back surface are detected only by the other beam L ₁ this time, and are substantially the same as the light receiving pulse P _b as indicated by P _c in FIG. A light receiving pulse having an amplitude is detected. At this time, the time interval Δt between the light receiving pulses P _b and P _c is determined by the crossing angle of the beams L ₁ and L ₂ and the scanning speed (relative moving speed of the glass substrate G).
It is determined by and and is a value unique to the system.

Further, in the state of FIG. 1D, the fine particles D ₄ on the back surface are detected by the beam L ₂ to generate a light receiving pulse P _d , and immediately after that, in the state of FIG. 1E, the fine particles D ₃ on the front surface.
There beam L _1, is detected by the L ₂ caused a light pulse P _e, 1 particles D ₄ beam L ₁ backside of the state of (f)
To generate a light receiving pulse P _f . Here, as shown in FIG. 2, the time interval between the light receiving pulses P _d and P _f is Δt as described above, and the amplitudes of these pulses P _d and P _f are almost the same as the light receiving pulses P _b and P _c. It is clear.

Therefore, as is apparent from FIG. 2, the received light pulse due to the fine particles on the surface of the glass substrate G has a large amplitude, and each pulse is randomly generated.
The light receiving pulse due to the fine particles on the back surface of the glass substrate G has a small amplitude, and the two pulses forming the pair of pulses have substantially the same amplitude, and the time interval Δt is substantially constant. Therefore, in the signal processing circuit after the optical system 14, for example, a first discrimination level V _r1 as shown in FIG. 2 is set, and the signal level of the received light pulse is discriminated by this discrimination level V _r1 to thereby determine the surface. It is possible to detect the number of light receiving pulses by the fine particles, that is, the number of fine particles on the surface, and it is possible to detect the size of the fine particles by the magnitude of the amplitude.

Further, a second discrimination level V _r2 lower than the discrimination level V _r1 is set, and the received light pulse whose amplitude is higher than this level and lower than the first discrimination level V _r1 has a time interval Δt. When a pair of (two) received light pulses is detected, it can be determined that the pair of received light pulses is due to one particle on the back surface, and therefore the second discrimination level V _r2 and the time interval Δt. The number of fine particles on the back surface can be detected by detecting the number of such a pair of light-receiving pulses (two light-receiving pulses correspond to one fine particle) using. Further, the size of the fine particles can be detected to some extent.

According to the present invention, as in the other embodiment shown in FIG. 3, each laser light source (not shown) is arranged so that the laser beams L ₁ and L ₂ intersect at one point on the back surface of the glass substrate G. The same can be applied to the case in which they are arranged. In this case, the light receiving pulse by _one fine particle (for example, D ₁ ) on the front surface has a small amplitude, and a pair of them are detected at a time interval Δt, and the light is received on the back surface. One received light pulse by one certain fine particle (for example, D ₂ ) is detected with a large amplitude. In this case, the setting of the waveform diagram of the light receiving pulse and the discrimination level and the like can be easily imagined, and thus detailed description thereof will be omitted.

Next, an embodiment of the second invention will be described. FIG. 4 shows a schematic configuration of this embodiment. In this embodiment, the detection light beam from the light source 16 is converted into a substantially inverted conical detection light beam L ₃ by the condenser lens 15, and this light beam L ₃ is made into glass. The optical system 14 detects scattered light from the fine particles by irradiating the surface of the substrate G so that the light is focused at one point. As the condenser lens 15, one having a large diameter and a short focal length is used.

[0022] In this embodiment, for example, there are fine particles D ₁ on the surface of the substrate as shown in FIG. 4, if the back surface of the substrate has fine D _2, as shown in FIG. 5, the light receiving pulse P by the fine particles D ₁ of the surface ₁ has a large amplitude, and the received light pulse P ₂ due to the fine particles D ₂ on the back surface has a small amplitude due to the attenuation of the detected light beam L ₃ . Moreover, the light receiving pulse P ₂ by the rear surface of the fine particle D ₂ is for a period Δt which fine particles D ₂ by the relative movement of the glass substrate G is flowing through the detection light beam L ₃ on the back of the glass substrate G, is that level It becomes "High". That is, the light receiving pulse P ₂ having a pulse width of the period Δt
Is obtained.

Therefore, as shown in FIG. 5, the first and second discrimination levels V _r1 and V _r2 are set, and the signal level of the light receiving pulse is discriminated by the first discrimination level V _r1 to detect the light received by the fine particles on the surface. The number of pulses, that is, the number of particles on the surface can be detected, and the size of the particles can be detected by the magnitude of the amplitude.

Further, a second discrimination level V _r2 lower than the discrimination level V _r1 is set, and the received light pulse whose amplitude is above this level and below the first discrimination level V _r1 and whose pulse width is approximately Δt. When the light receiving pulse is detected, it can be judged that this light receiving pulse is due to one particle on the back surface. Therefore, such a light receiving pulse is obtained using the second discrimination level V _r2 and the period Δt. The number of fine particles on the back surface can be detected by detecting the number of particles.
At the same time, the size of the particles can be detected to some extent. Also in this embodiment, the glass substrate G as shown in FIG.
It is possible to make the substantially inverted conical detection light beam L ₃ converge at one point on the back surface of the above, and to distinguish the fine particles on the front and back sides by the difference in the detection pulse.

FIG. 6 schematically shows an embodiment of the third invention. In the figure, 17 is a first laser light source,
18 is a second laser light source, 19 is these laser light sources 1
This is a sensor unit provided with 7, 18 and a detection optical system 14. The sensor unit 19 can scan in both directions a and b in the figure. In this embodiment, unlike the previous embodiments, the sensor unit 19 itself moves, but the glass substrate G may move in the same manner as described above. Further, the laser light sources 17 and 18 are arranged so that the first and second laser beams L ₁ and L ₂ intersect at one point on the surface of the glass substrate G.

The operation of this embodiment will be described below. Also in this embodiment, if the laser light sources 17 and 18 are turned on to irradiate the first and second laser beams L ₁ and L ₂ , then the first and second laser beams are substantially emitted.
Since it is the same as that of the invention described above, the fine particles on the front and back of the glass substrate G can be individually detected.

The following methods are also available as other detection methods. That is, first, the laser light source 17 is turned on, and the sensor unit 19 is scanned in the a direction in a state where only the first laser beam L ₁ is irradiated. Thereby, the scattered light due to the fine particles existing on both the front surface and the back surface of the glass substrate G is generated by the optical system 14.
And the total number of fine particles existing on the front and back sides is detected from the received light pulse.

Then, the laser light sources 17 and 18 are turned on, and the sensor unit 19 is scanned in the direction b while the first and second laser beams L ₁ and L ₂ are being emitted. Then, as described with reference to FIG. 2, if attention is paid only to the number of light receiving pulses, the pulse number is (the number of fine particles on the front surface + the number of fine particles on the back surface × 2).
Becomes Therefore, the number of fine particles present on the back surface can be detected by subtracting the number of detection pulses during scanning in the a direction from the number of detection pulses during scanning in the b direction.
Furthermore, by subtracting this number of fine particles from the number of detection pulses during scanning in the a direction, the number of fine particles present on the surface can also be detected.

In this embodiment, the sensor unit 19 is set to a, b.
Although it is configured to reciprocate in both directions, a sensor unit having only the first laser light source and a sensor unit having the first and second laser light sources are prepared, and these are simultaneously scanned in only one direction. However, the same effect can be obtained. In this case, it is possible to simplify the drive unit for the sensor unit and shorten the measurement time.

In the above embodiment, the case where the fine particles are exclusively present as the defects of the glass substrate has been described, but the present invention is also applicable to the detection of scratches on the front and back surfaces.

[0031]

As described above, the first to third inventions are
Since the foreign matter is detected by focusing on the difference in the amplitude of the received light pulse due to the foreign matter on the front surface or the back surface of the glass substrate, the time interval of the same amplitude pulse, the pulse width, etc., the foreign matter existing only on the front surface and the back surface are detected. The existing foreign substances can be detected individually, and the number and size of them can be accurately measured. Therefore, the detection accuracy can be improved as compared with the conventional inspection apparatus. In particular, in the first or second invention, since foreign matter on the front and back can be detected simultaneously by only scanning in one direction, the inspection can be speeded up, and since the device configuration is simple, the size and weight can be reduced and the cost can be reduced. Can be planned.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of the first invention.

FIG. 2 is a waveform diagram of a light receiving pulse showing the operation of the embodiment of FIG.

FIG. 3 is a schematic explanatory view showing another embodiment of the first invention.

FIG. 4 is a schematic explanatory view showing an embodiment of the second invention.

5 is a waveform diagram of a light receiving pulse showing the operation of the embodiment of FIG.

FIG. 6 is a schematic explanatory view showing an embodiment of the third invention.

[Explanation of symbols]

11, 12 Lens 13 Photodetector 14 Detection Optical System 15 Condenser Lens 16 Light Source 17 First Laser Light Source 18 Second Laser Light Source 19 Sensor Part L ₁ First Laser Beam L ₂ Second Laser Beam L ₃ Detected Luminous Flux D _{1 to} D ₄ fine particles G glass substrate

Claims (3)

[Claims] 1. A defect inspection for a glass substrate, wherein scanning is performed while irradiating the glass substrate with detection light, and scattered light due to foreign matter on the front or back surface of the glass substrate is detected by an optical system to detect the number and size of the foreign matter. In the device, the detection light is composed of first and second laser beams intersecting at one point on the front surface or the back surface of the glass substrate, and the difference in the amplitude of the light receiving pulse by the optical system, and at a substantially constant time interval. A defect inspection apparatus for a glass substrate, characterized in that it detects the occurrence of two light-receiving pulses of substantially the same amplitude to detect foreign substances present on the front and back surfaces of the glass substrate, respectively. 2. A defect inspection for a glass substrate, wherein scanning is performed while irradiating the glass substrate with detection light, and scattered light due to foreign matter on the front or back surface of the glass substrate is detected by an optical system to detect the number and size of the foreign matter. In the device, the detection light is composed of a detection light flux having a substantially inverted conical shape that converges at one point on the front surface or the back surface of the glass substrate, and has a difference in amplitude of light receiving pulses by the optical system, and a substantially constant pulse width. A defect inspection apparatus for a glass substrate, which detects the occurrence of a light reception pulse to detect foreign substances existing on the front surface and the back surface of the glass substrate, respectively. 3. A defect inspection for a glass substrate, wherein scanning is performed while irradiating the glass substrate with detection light, and light scattered by foreign matter on the front or back surface of the glass substrate is detected by an optical system to detect the number and size of the foreign matter. In the device, the detection light is composed of first and second laser beams intersecting at a point on the front surface or the back surface of the glass substrate, and a light reception pulse obtained by the optical system using only one of these laser beams. And the number of received light pulses obtained by the optical system using both of the laser beams and foreign matter existing on the front surface and the back surface of the glass substrate, respectively. apparatus.