JP2003166946A - Surface inspection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a sufficient irradiation light intensity and to enhance a detection accuracy in a surface inspection apparatus. <P>SOLUTION: In the surface inspection apparatus, the surface of a substrate 5 is irradiated with a laser beam 2, scattering reflected light due to the laser beam is detected, and a foreign substance is detected. The inspection apparatus is provided with an irradiation optical system 7 whose light source part 12 comprises a plurality of light emitting source and by which the surface of the substrate is irradiated with laser beams from the respective light emitting sources as luminous fluxes whose optical axes are mutually parallel. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface inspection apparatus for inspecting fine foreign matters on the surface of a substrate such as a semiconductor wafer or fine scratches such as crystal defects.

[0002]

2. Description of the Related Art A surface inspection apparatus irradiates a laser beam on the surface of a substrate and detects scattered reflection light generated by a foreign substance or a scratch to detect the foreign substance or the scratch. Although a gas laser (He, Ar, etc.) has been generally used as a light emission source in the surface inspection apparatus, recently, a laser diode (LD) has been used for reasons such as easy handling, safety, and long life. It is used.

FIG. 12 shows a conventional irradiation optical system using a laser diode as a light emitting source.

A laser beam 2 emitted from a light emitting source 1 is collimated by a collimator lens 3 into a parallel light beam, and an image forming lens 4 forms a surface of a substrate 5 such as a wafer (the image forming lens 4).
It is irradiated so that it may be focused on a point (focus point f).
The laser beam 2 is incident on the substrate 5 at an angle of θ. A scattered / reflected light detector (not shown) detects scattered / reflected light from a position deviated from the reflected light axis of the laser beam 2, for example, a direction substantially perpendicular to the paper surface.

The detection sensitivity and detection accuracy are related to the wavelength and intensity of the laser beam 2 with which the surface of the substrate is irradiated. The detection sensitivity can be improved by shortening the wavelength or increasing the intensity. Further, by expanding the irradiation range while keeping the intensity uniform, it is possible to improve the detection accuracy while maintaining the detection sensitivity.

[0006] In recent years, the surface inspection apparatus has a higher detection sensitivity,
In addition, the detection accuracy is required to be improved. For example, as the density of semiconductor elements is increased, the surface inspection apparatus is required to detect finer foreign matters and scratches on the wafer surface.

[0007]

As described above, the detection sensitivity and the detection accuracy are improved by increasing the irradiation light intensity, but when the laser diode is used as the light emitting source, the laser diode has various advantages. On the other hand, there is a problem that the amount of emitted light is smaller than that of a gas laser or the like, and there is a limit to increase the detection sensitivity by increasing the irradiation light intensity. Further, the shorter the wavelength of the irradiated laser beam is, the higher the detection sensitivity is. Therefore, it is desired to use a laser diode which emits a blue laser beam having a short wavelength. However, the blue laser diode has a problem that the emitted light amount is smaller than that of the red laser diode or the like, and the sufficient light amount required by the surface inspection apparatus cannot be obtained. Further, in order to shorten the inspection time, it is desirable that the irradiation range on the surface of the substrate is wide. However, if the irradiation range is widened, the intensity of the irradiation light beam is decreased, so that there is a problem that both the detection sensitivity and the detection accuracy decrease.

In view of the above situation, the present invention intends to obtain a sufficient irradiation light intensity in a surface inspection device to improve the detection accuracy.

[0009]

SUMMARY OF THE INVENTION The present invention is a surface inspection apparatus for irradiating a substrate surface with a laser beam and detecting scattered reflected light of the laser beam to detect foreign matter. The present invention relates to a surface inspection apparatus having a light source, and irradiating a laser beam from each of the light emitting sources onto a substrate surface as a light flux whose optical axes are parallel to each other. An optical member which has a lens and is provided corresponding to each light emitting source and makes a laser beam from the light emitting source enter the imaging lens, and an optical axis which is incident from the light emitting source to the imaging lens is formed into the image. The present invention relates to a surface inspection device parallel to the optical axis of a lens, a surface inspection device in which the light emitting sources are arranged in a matrix, and at least 1 on the optical axis entering the imaging lens from the light emitting sources. Optical axis tilt that tilts two optical axes It relates to a surface inspection apparatus provided with means,
Furthermore, the present invention relates to a surface inspection apparatus having a light source section in which a laser beam from at least one light emitting source is incident on the optical axis of the imaging lens at a predetermined angle.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

An outline of the surface inspection apparatus will be described with reference to FIG.

In the figure, reference numeral 5 denotes a substrate which is an object to be inspected such as a wafer, and the surface inspection apparatus mainly comprises a scanning drive mechanism section 6, an irradiation optical system 7 and a detection system 8.

Further, the scanning drive mechanism section 6 comprises a substrate holding section 9 for holding the substrate 5, the substrate holding section 9 is rotatably supported by a rotation driving section 10, and the rotation driving section 1
0 is adapted to be linearly moved in the radial direction parallel to the rotating surface of the substrate 5 by the linear drive mechanism section 11.

The irradiation optical system 7 is a deflection optical member 1 such as a light source section 12 for emitting a laser beam 2 as an inspection light and a mirror for directing the laser beam 2 from the light source section 12 onto the substrate 5.
3, 14 and a lens group 15 for focusing the laser beam 2 on the surface of the substrate 5 and the like. The detection system 8 includes light receiving detectors 16 and 17 having a detection optical axis that intersects the optical axis of the laser beam 2 with which the surface of the substrate 5 is irradiated.

The surface inspection of the substrate 5 is performed by irradiating the laser beam 2 on the surface of the substrate 5 from the irradiation optical system 7 while the substrate 5 is rotated by the rotation driving unit 10, and further by the straight line. The rotation drive unit 10 is moved in the radial direction by the drive mechanism unit 11.

Thus, the irradiation points of the laser beam 2 are concentric circles by stepwise feeding at a required pitch for each rotation of the substrate 5 or by continuously feeding the rotation driving unit 10 at a predetermined speed. , Or while drawing a locus of a spiral circle, the substrate 5 moves from the center to the outer edge, and the entire surface of the substrate 5 is scanned by the laser beam 2.

When the laser beam 2 scans the surface of the substrate 5, if there is a foreign substance or a scratch, the laser beam 2 is scattered and reflected. The scattered reflected light is detected by the light receiving detectors 16 and 17 of the detection system 8 arranged at a predetermined position,
By processing the signals from the light receiving detectors 16 and 17 by an arithmetic processing unit (not shown), foreign matter and scratches are detected.

FIG. 2 shows an outline of the irradiation optical system 7 of the surface inspection apparatus of the present invention, in which the deflecting optical members 13, 14 and the like are omitted.

The light source unit 12 includes two sets of light emitting sources 1a and 1b.
Laser beams 2a, 2 from the light emitting sources 1a, 1b
b is made into a parallel light flux by the collimating lenses 3a and 3b, respectively, and is formed by the single imaging lens 4 on the substrate 5
It is designed to be focused on the surface of. The optical axes of the collimating lenses 3a and 3b and the imaging lens 4 are parallel to each other, and the laser beams 2a and 2b emitted from the light emitting sources 1a and 1b are irradiated by the imaging lens 4 at the same irradiation point. It is designed to be focused on 18. The laser beams emitted from the light emitting sources 1a and 1b may have the same wavelength or different wavelengths. In a transparent film or the like, the reflectance of the surface changes depending on the wavelength, so the detection sensitivity is affected. By varying the wavelength, the influence of the reflection state on the surface of the substrate 5 on the wavelength is reduced. The same irradiation point 18 exists on the focal plane of the imaging lens 4 or in the vicinity thereof.

The laser beams 2a and 2b from the light emission source 1a and the light emission source 1b are condensed at the same irradiation point 18 by the imaging lens 4, so that the light quantity distribution of the laser beam 2 at the irradiation point 18 is converged. Is shown by the solid line in FIG.
The amount of light at the irradiation point 18 increases. Incidentally, in FIG. 3, what is indicated by a broken line is the light quantity distribution of the laser beams 2a and 2b alone.

Thus, a desired irradiation light intensity can be obtained even when the amount of light emitted from the light emitting source alone is small.

In the above embodiment, the number of light emitting sources is two, but it is also possible to use a large number of light emitting sources of three or more.

FIG. 4 shows a second embodiment, and shows a case where a large number of light emitting sources 1a ... 1n are used.

1n are provided for the respective light emission sources 1a ... 1n, and the collimator lenses 3 are provided.
2n is made to enter one imaging lens 4 via a ... 3n, and the optical axes of the collimating lenses 3a ... 3n are made parallel to the optical axis of the imaging lens 4. It was done.

In this embodiment, all the laser beams 2a are
2n is condensed at one point of the irradiation point 18, and as shown in FIG. 5, the irradiation light intensity at the irradiation point 18 is about n times that of the single light emitting source 1. In FIG. 5, the vertical axis represents light intensity and the horizontal axis represents space.

Although the plurality of light emitting sources 1 are arranged in one row in FIG. 4, they may be arranged in a matrix of a plurality of rows.

Since the light source section 12 has a plurality of light emitting sources 1, it is possible to adjust the light quantity distribution at the irradiation point 18.

FIG. 6 shows a third embodiment in which the light emitting sources 1a and 1b are provided at separate positions.

The light emitting source 1a and the collimating lens 3a provided corresponding to the light emitting source 1a are provided at a position intersecting with the optical axis of the imaging lens 4, for example, on an optical axis orthogonal to each other, and from the light emitting source 1a. The emitted laser beam 2a is reflected by the reflecting mirror 21a in parallel with the optical axis of the imaging lens 4 and guided to the imaging lens 4.

The light emitting source 1b and the collimating lens 3b are also arranged in the same manner. The laser beam 2b emitted from the light emitting source 1b is reflected by the reflecting mirror 21b, and the imaging lens 4 is formed.
The light is incident on the imaging lens 4 in parallel with the optical axis of.

By the image forming lens 4, the light emitting sources 1a, 1a
The laser beams 2a and 2b emitted from b are focused on the irradiation point 18.

In the third embodiment, when the number of light emitting sources 1 is three or more, the light emitting sources 1 and the collimating lens 3 may be arranged on the radiation centered on the optical axis of the imaging lens 4.

As shown in FIG. 7, when the optical axis of the collimator lens 3 is tilted with respect to the optical axis of the imaging lens 4, the irradiation point 18 moves. Therefore, when the optical axes of the collimating lenses 3a and 3b are tilted as shown in FIG. 8, the irradiation points 18a and 18b of the light emitting sources 1a and 1b are displaced, and the light amount distribution at the irradiation point 18 is indicated by the solid line in FIG. Like a trapezoid. For example, when the irradiation points 18a and 18b are displaced in a direction intersecting the scanning direction with each other, the range (width) having the predetermined light intensity is widened while maintaining the light intensity. The amount of movement in the radial direction can be increased, the number of rotations of the substrate 5 can be reduced when scanning the entire surface, the detection accuracy can be improved while the detection sensitivity is stable, and the inspection time can be shortened.

As means for inclining the optical axis of the collimator lens 3, a wedge prism 19 is inserted on the optical axis of the collimator lens 3 as shown in FIG.
9 is rotated appropriately.

By adjusting the light quantity distribution at the irradiation point 18, the irradiation light intensity is increased when accuracy is required, and the irradiation range is widened when inspection efficiency is required. It is possible to match the inspection situation.

Incidentally, as described in the third embodiment,
The reflecting mirrors 21a and 21b function as deflection optical members and also as means for tilting the optical axis. That is, by tilting the reflecting mirrors 21a and 21b, it is possible to tilt the optical axis that enters the imaging lens 4 from the light emitting sources 1a and 1b.

In FIG. 4, collimating lenses 3a ... 3
When the optical axis of n is gradually tilted away from the optical axis of the imaging lens 4, the light amount distribution shown in FIG. 11 is obtained at the irradiation point 18. 1n and collimating lenses 3a ... 3n are arranged in a matrix, the optical axes of the collimating lenses 3a ... 3n are gradually inclined for each column, and the collimating lens 3b for each row.
When the optical axes of 3 m are parallel, the light amount distribution shown in FIG. 11 is obtained for each column, and the light amounts of all columns are condensed at the same position, so that the light amount distribution shown in FIG. 11 corresponds to the number of rows. Only the polymerized light intensity distribution and light intensity are obtained, and the desired light intensity is obtained.
Moreover, the laser beam 2 having a wide irradiation range can be obtained.

[0038]

As described above, according to the present invention, in the surface inspection apparatus for irradiating the surface of the substrate with the laser beam and detecting the scattered reflected light of the laser beam to detect the foreign matter, a plurality of light source units are provided. Since it is equipped with an irradiation optical system for irradiating the substrate surface with the laser beams from the respective light sources as luminous fluxes whose optical axes are parallel to each other, it is sufficient to use a light source with a small amount of emitted light. The amount of irradiation light can be obtained, and the detection accuracy can be improved.

Further, since the optical axis inclining means for inclining at least one optical axis is provided on the optical axis which is incident on the imaging lens from the light emitting source, the light quantity at the irradiation point irradiated by the plurality of light emitting sources. The distribution can be adjusted to a light amount distribution according to the inspection state. Further, since the range having the predetermined light intensity is widened while maintaining the light intensity, the detection accuracy is improved, and the number of rotations when the entire surface is scanned can be reduced and the inspection time can be shortened.

[Brief description of drawings]

FIG. 1 is a skeleton view showing a basic configuration of a surface inspection device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an irradiation optical system of the surface inspection device.

FIG. 3 is a diagram showing a light quantity distribution at an irradiation point in the irradiation optical system.

FIG. 4 is an explanatory diagram of an irradiation optical system according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a light amount distribution at an irradiation point of an irradiation optical system in the second embodiment.

FIG. 6 is an explanatory diagram of an irradiation optical system according to a third embodiment of the present invention.

FIG. 7 is an explanatory diagram of an irradiation optical system according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram of an irradiation optical system according to the embodiment of the present invention.

9 is a diagram of a light amount distribution at an irradiation point of the irradiation optical system shown in FIG.

FIG. 10 is an explanatory diagram of a modified example of the irradiation optical system according to the embodiment of the present invention.

FIG. 11 is an explanatory diagram of another light amount distribution obtained in the embodiment of the present invention.

FIG. 12 is an explanatory diagram showing an irradiation optical system of a conventional surface inspection apparatus.

[Explanation of symbols]

1 light source 2 laser beam 5 substrates 6 Scan drive mechanism 7 Irradiation optical system 8 detection system 12 Light source 15 lens groups 18 irradiation points 19 wedge prism

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G051 AA51 AB01 AB02 BA01 BA10                       BB01 BB09 CA01 CB01 CB05                       DA08                 4M106 AA01 BA05 CA41 CA46 DB08                       DB12

Claims (5)

[Claims] 1. A surface inspection apparatus for irradiating a substrate surface with a laser beam and detecting scattered light of the laser beam to detect foreign matter, wherein a light source section has a plurality of light emission sources, A surface inspection apparatus comprising: an irradiation optical system that irradiates a laser beam from a light emitting source onto a substrate surface as a light flux having optical axes parallel to each other. 2. The illuminating optical system has one imaging lens, and has an optical member which is provided corresponding to each light emitting source and causes a laser beam from the light emitting source to enter the imaging lens. The surface inspection apparatus according to claim 1, wherein an optical axis of the light incident on the imaging lens from the light source is parallel to the optical axis of the imaging lens. 3. The surface inspection apparatus according to claim 1, wherein the light emitting sources are arranged in a matrix. 4. The surface inspection apparatus according to claim 2, wherein at least one optical axis inclining means for inclining an optical axis is provided on an optical axis which is incident on the imaging lens from the light emitting source. 5. The surface inspection apparatus according to claim 2, further comprising a light source unit in which a laser beam from at least one light emitting source is incident on the optical axis of the imaging lens at a predetermined angle.