JPH0694629A - Inspecting apparatus for crystal defect - Google Patents

Abstract

PURPOSE:To enable measurement of a crystal defect with a high throughput by providing a photosensor having a light-sensing surface being perpendicular to the direction of bending reflection which is different from the direction of regular reflection of a light beam on a complete specular surface and specific to a section gradient of the defect. CONSTITUTION:A scanning direction 9 of a laser beam being parallel to the orientation flat 6 of an Si wafer is made the direction of the axis X, while the direction of an oxidation-induced defect 5 being perpendicular to the orientation flat 6 is made the direction of the axis Y. On the occasion when beam scanning is executed in the direction of the axis X in which the defect 5 exists, an angle of incidence of an incident light 7 is made thetai. When the beam is cast on the defect 5 it is bent by an angle 2theta to the direction of the axis Y by a gradient theta (which is a section gradient of a crystal transformation defect and has uniformity) and reflected. By disposing light-sensing parts 10a and 10b on extensions of reflected lights 8a and 8b deviating by angles + or -2theta from a plane Y-Z in respect to an angle thetai of reflection on this plane, so that the light-sensing surfaces thereof are positioned perpendicularly thereto, only the reflected lights by the defect 5 can be sensed. As to a diffusedly reflected light by a particle or the like, it is advisable to provide a large light-sensing part additionally for receiving it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal defect inspection apparatus, and more particularly to an oxidation induced stacking F (hereinafter referred to as OSF) which appears on the surface of a silicon wafer.
For example, the present invention relates to a crystal defect inspecting apparatus effective for inspecting defects having a directional characteristic in its shape.

[0002]

2. Description of the Related Art Conventionally, in a crystal defect inspection apparatus for an object to be inspected such as a silicon wafer, there are the following methods.
There is a method in which the number of crystal defects is measured by image processing after imaging with an image sensor such as a D camera to obtain a digital image.

As the second method, there is a method in which the surface of the object to be inspected is scanned with a laser beam, the diffuse reflection component in the reflection component is caught by using a photomultiplier tube, and is treated and measured as a crystal defect.

[0004]

According to the above-mentioned method 1, the accuracy of the image information is high in distinguishing and measuring the original crystal defects and the particles, and the feature determination of the shape on the image to be inspected is performed. It has the advantage that it can be processed and the defect measurement accuracy is as high as 90% or more.

However, since the image processing is performed on the image for each visual field enlarged through the optical system, there is a problem that the throughput is extremely low. Although it depends on the magnification of the optical system, for example, in the case of inspecting the entire surface of an 8 ″ wafer with no gap, it takes tens to hundreds of hours to inspect each wafer.

Further, the above-mentioned second method has an advantage that the throughput is good because the output signal of continuous scanning by the laser beam can be processed in real time. For example, in the entire surface inspection of an 8 ″ wafer, the processing is completed in several minutes to several tens of minutes. However, it is difficult to distinguish between crystal defects and particles, and it is unsuitable to measure only defects. Not used for inspection.

As described above, while the conventional methods have their respective drawbacks, as a future trend of the object to be inspected represented by, for example, a wafer, the number of crystal defects generated is suppressed to a very small number as the memory capacity increases. Manufacturing technology is advanced, and 1M generation OSF density is 200 / cm ² The OSF density of the 16M generation is expected to shift to several pieces / wafer, although it was about the same level, and it is necessary to improve the throughput and the measurement accuracy in the full inspection in the future in terms of inspection performance. As a result, the technical difference between the conventional crystal defect inspection technique and the required wafer manufacturing technique is further widened as it is, and a significant improvement in the crystal defect inspection technique is desired. In view of the above point, the present invention has an object to provide a crystal defect inspection apparatus capable of highly accurate defect measurement with high throughput.

[0008]

The structure of the present invention which achieves the above object is a projector for irradiating an object to be inspected having crystal defects exposed on its surface with a light beam while irradiating it at a constant angle. And a light receiver having a light receiving surface perpendicular to a bending reflection direction peculiar to the cross-sectional gradient of the crystal defect different from the specular reflection direction on the mirror surface without the crystal defect of the light beam from the projector. And

[0009]

The angle of incidence and the angle of reflection of the light beam on a perfect mirror surface, which is essentially free from crystal defects, are equal, and if particles or the like are present on this mirror surface, diffuse reflection occurs, and further, crystal defects The crystal orientation depends on the plane orientation of the crystal plane, but the shape orientation is determined, and the cross-sectional gradient has a certain constant angle although there is a slight gradient error.

Since the reflection on the mirror surface or the diffuse reflection of particles or the like and the determination of the shape orientation and the sectional gradient due to the crystal defect are distinguished by the reflection direction of the light beam, the light beam having only the crystal defect is formed. The signal can be taken out and the measurement can be performed in real time.

[0011]

Embodiments of the present invention will now be described with reference to FIGS. FIG. 2 is a schematic configuration diagram of a crystal defect inspection apparatus according to an embodiment of the present invention, and a silicon wafer will be described as an example of the inspection object.

In FIG. 2, a rotatable inspection stage 1
A wafer 4 is adsorbed on the surface 2, and the surface 3 of the wafer 4 is irradiated with a laser beam while being scanned by the light projecting unit 1. The laser beam reflected on the surface 3 of the wafer 4 is received by the light receiving section 2 and then output to the processing section 13.

The light projecting section 1 includes a laser head 1a, a reflecting mirror 1b for reflecting the laser beam from the laser head 1a, a polygon mirror 1d having a driving section 1c for scanning the laser beam from the reflecting mirror 1b, and a scan lens. The laser beam is emitted while scanning the surface 3 of the wafer 4 at a constant angle θ _i . On the other hand, the light receiving section 2 that receives the reflected light from the wafer 4
Has a condenser lens 2b and a light receiver 2a.

In such a schematic structure, the narrowed laser beam is irradiated while being scanned on the surface 3 of the wafer 4, and the incident angle θ _i and the reflection angle θ _{o on the} mirror-finished wafer surface 3.
And are equally distributed. Therefore, the reflected laser beam can be received by arranging the light receiving section 2 in the traveling direction of the reflected laser beam and arranging the light receiving surface (condensing lens 2b) perpendicular to the traveling direction.

In the present embodiment, the OSF exposed and present on the surface 3 of the wafer 4 is a crystal dislocation defect and has a constant orientation and cross-sectional gradient in terms of shape, and this OSF has a laser beam. It is noticed that the reflected laser beam bends in a certain direction due to the constant cross-sectional gradient when irradiated with. That is, if the light receiving section 4 is placed in the bending direction of the laser beam, only the reflected laser beam corresponding to the OSF can be received.

The OSF on the wafer 4 is shown in FIG.
This will be described below. As described above, the OSF 5 of the wafer 4
Is a crystal dislocation defect. Therefore, when the orientation of the orientation flat 6 which is the cutting on the wafer 4 is set to 0 °, the generation state of the OSF 5 varies depending on the crystal plane orientation, and as shown in FIG. The relationship of 90 ° in FIG.
The plane orientation (111) has the relationship of 120 ° in FIG. 3B, and the plane orientation (511) has the relationship of 105 ° in FIG. 3C.

The cross section of the OSF 5 shown in FIG. 3 is shown in FIG.
As shown in (b), it has a constant angle θ. That is, looking at the AA cross section of the OSF 5 shown in FIG.
As shown in FIG. 4B, there is a slope of θ with respect to the flat mirror surface, and this slope is constant. Therefore, when the laser beam is applied to this gradient, the laser beam is bent and reflected by the angle θ.

This situation will be described with reference to FIG. A laser beam scanning direction 9 parallel to the orientation flat 6 of the wafer 4 is defined as an X-axis direction, and an OSF direction perpendicular to the orientation flat 6 is defined as a Y-axis direction. Now, when the laser beam is scanned in the X-axis direction in which the OSF 5 exists, the incident light 7 is made to the wafer 4 at an incident angle θ _{i with} respect to the vertical Z-axis of the wafer 4, and the optical path is along the Y-axis direction. On the flat mirror surface wafer (when there is no OSF etc.), the laser beam is reflected at a reflection angle θ _i in the YZ plane.

However, the OS existing on the wafer 4
When the laser beam is incident on F5, as shown in FIG. 1 (a) or 1 (b), it is reflected by being bent at an angle 2θ with respect to the Y-axis direction due to the gradient θ, and reflected light 8a or 8b.
Occurs. That is, the laser beam scanned along the Y-axis direction in the X-axis direction is reflected along the Y-axis direction as it is on the mirror surface without the OSF, but when it hits the OSF 5, the cross-sectional gradient θ causes an angle difference. It will deviate by 2θ from the Y-axis direction.

Therefore, in FIG. 1C, the light receiving surface is vertically positioned on the extension line of the reflected lights 8a and 8b which deviate from the reflection angle θ _i on the YZ plane by ± 2θ. If the light receiving portions 10a and 10b are arranged, only the light reflected by the OSF 5 can be received.

FIGS. 5 (a) and 5 (b) are plan views of the incident light 7 and the reflected light 8a, 8b by the OSF 5, showing the bending angle 2θ by the gradient θ and the light receiving parts 10a, 1.
At 0b, there is a margin for the reflected bending angle, and an opening of ± θ _k is provided. By doing so, even if there is a slight gradient error, it can be dealt with. Further, the OSF of FIG. 5A and the OSF of FIG. 5B indicate different orientation OSFs depending on the plane orientation, but in order to detect as the Y orientation OSF, the inspection stage 12 is used. By rotating the wafer 4 itself, FIG.
In the cases of (a) and (b), the Y orientation OSF 5 can be detected by rotating the orientation flat 6 by 90 °.

Although FIGS. 1 and 5 show an example in which a laser beam is incident in a direction perpendicular to the gradient θ of the OSF 5 (in the OSF direction), FIG. 6 shows the laser beam along the θ gradient of the OSF 5. The figure shows the case of incidence.

In this case, when the incident light 7 is close to the normal to the surface of the gradient θ as shown in FIG. 6A, θ _i − with respect to the Z axis.
When it has a reflection angle of θ and is distant from the normal line of the surface of the gradient θ as shown in FIG. 6B, it has a reflection angle of θ _i + θ with respect to the Z axis. Therefore, as shown in FIG.
As shown in FIG. 5, c and 8d do not coincide with the detection direction, and the reflected light does not reach the light receiving portions 10a and 10b. Therefore, in order to detect the OSF5, the Y-direction OSF is detected.
As a result, it becomes necessary to set the wafer position and consider the orientation characteristic.

FIG. 7 shows particles and the like existing on the surface of the wafer 4, and FIG. 7A shows a flaw on the wafer surface.
7B shows dirt and FIG. 7C shows particles. In this case, unlike the OSF, the directions of the reflected lights 8e, 8f, and 8g by the laser beam are not fixed, and typical diffused reflection occurs. When the light intensity of the reflected light 8e, 8f, 8g is equivalent to that of the Y-directional OSF, the light receiving unit 10
It is impossible to distinguish whether the light received at a and 10b is OSF or noise due to particles or the like.

Therefore, in consideration of such a case, a larger light receiving portion 10c may be added in addition to the light receiving portions 10a and 10b as shown in FIG. 8 so as to receive diffused reflected light. Reference numeral 11 represents a mask of the light receiving unit 11c. The output waveform of such an arrangement structure is as shown in FIG.
In the case of only SF5, the light receiving section 10a shown in FIG.
A peak is generated in any of 10b and no output is generated in the light receiving section 10c. In addition, it is found that noise such as particles causes noise because only a peak occurs in the light receiving unit 10c as shown in FIG. 9B. Further, when peaks occur in all the light receiving portions 10a, 10b, 10c as shown in FIG. 9C, it can be determined that the particles are large particles and the like, and noise can be determined.

[0026]

As described above, it is possible to receive the reflected light of only the OSF on the wafer by utilizing the plane orientation of the crystal of the OSF and the constant cross-sectional gradient.
It is possible to obtain an inspection apparatus having high SF measurement accuracy and good throughput through real-time processing by scanning a laser beam.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for detecting an OSF.

FIG. 2 is a schematic configuration diagram of the entire crystal defect detection device.

FIG. 3 is an azimuth diagram of OSF generation on a wafer.

4A and 4B are a plan view and a cross-sectional view of an OSF.

FIG. 5 is a diagram showing the plane of FIG. 4 together with a rotated state.

FIG. 6 is a reflection state diagram of an anisotropic orientation OSF.

FIG. 7 is an irregular reflection state diagram due to noise factors.

FIG. 8 is a configuration diagram of a light receiving unit for noise determination.

FIG. 9 is a waveform diagram showing an example of an output signal from the light receiving unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting part 2, 10a, 10b, 10c Light receiving part 3 Wafer surface 4 Wafer 5 OSF 6 Orient flat 7 Incident light 8a, 8b, 8c, 8d, 8e, 8f, 8g Reflected light 9 Scanning direction 12 Inspection stage 13 Processing part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masato Nozawa No. 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation Fuchu factory

Claims (1)

[Claims] 1. A mirror surface which is provided with a light projector for irradiating an object to be inspected having crystal defects exposed on the surface with a light beam while irradiating the light beam at a constant angle, the mirror surface having no crystal defects of the light beam. 2. A crystal defect inspection apparatus including a photodetector having a light receiving surface perpendicular to a bending reflection direction specific to the cross-sectional gradient of the crystal defect different from the specular reflection direction in FIG.