JP3348168B2 - Crystal defect detection method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a crystal internal defect by a laser beam, wherein the crystal is used to detect a crystal defect existing near the crystal surface by using total reflection. The present invention relates to a defect detection method and its device.

[0002]

2. Description of the Related Art Semiconductor crystals have the property of transmitting infrared light. Conventionally, utilizing this property, a crystal defect existing in the crystal has been detected by a method as shown in FIG. That is, in FIG. 7, reference numeral 71 denotes a wafer of a semiconductor crystal or the like to be detected, 72 denotes an objective lens, and 73 denotes a C lens.
A sensor such as a CD sensor or a photodiode array, which receives an infrared laser beam B from a side wall surface 75 of a wafer 71 and scatters light from a crystal defect d present on a passage of the incident infrared laser beam B. Is focused by the objective lens 72 and formed on the sensor 73 to detect a crystal defect existing in the crystal.

[0003]

A crystal defect exists in any part of a crystal. However, in general VLSI
What is problematic in the production of such a device is a crystal defect existing in a depth range of about several microns from the crystal surface 74.
Particularly, in the production of MOS devices, the existence of defects near the very surface becomes a problem. Therefore, it is desirable to be able to detect crystal defects existing within this range as accurately as possible, but this is difficult with the above-described conventional method.

That is, the side wall surface 75 of the wafer 71 from which a crystal defect is to be detected must be flat in order to efficiently receive the infrared laser beam B. In an actual defect inspection, the wafer 71 is cleaved using the cleavage of the crystal to obtain a flat side wall surface 75.
However, even if the central portion of the cleaved side wall surface 75 is flat, the peripheral ridgeline 76 portion has a jagged or uneven surface, the corner is crushed, or the corner is chipped, and a complete plane is obtained. Was difficult. Therefore, even if the infrared laser beam B is irradiated from the vicinity of the ridgeline 76 in order to examine a crystal defect at a shallow place of several microns or less in the vicinity of the crystal surface 74, irregular reflection occurs at the ridgeline portion. It is difficult to make the light beam incident on the surface.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. An object of the present invention is to improve the position detection accuracy in the depth direction of a defect near the crystal surface, which is the most important in the manufacture of VLSI and the like. Another object of the present invention is to provide a crystal defect detection method and apparatus capable of reliably and accurately detecting a crystal defect near a crystal surface.

[0006]

In order to achieve the above-mentioned object, a method for detecting a crystal defect according to the present invention comprises the steps of: directing an infrared laser beam from a crystal side wall surface into a crystal so as to be totally reflected at the crystal surface; Incident at an incident angle, the scattered light of the infrared laser beam from a crystal defect existing near the position of the total reflection point on the crystal surface is orthogonal to the scanning plane of the infrared laser beam parallel to the depth direction from the crystal surface. A crystal defect near the crystal surface is detected by detecting with an observation optical system arranged on the side.

[0007] A crystal defect detection device according to the present invention comprises:
An infrared laser light source for injecting an infrared laser beam from the crystal side wall surface into the crystal so as to be totally reflected at the crystal surface at a predetermined angle of incidence, and the incident infrared laser beam being parallel to a depth direction from the crystal surface. An observation optical system arranged on the side orthogonal to the scanning surface, and detecting the scattered light of the infrared laser beam from the crystal defect existing near the position of the total reflection point on the crystal surface by the observation optical system. This is to detect nearby crystal defects.

[0008]

The detection principle of the present invention will be described with reference to FIGS. FIG. 1 is a view for explaining the principle of the present invention, FIG. 2 is a plan view of a crystal part for explaining an incident path of an infrared laser beam to the crystal, and FIG. 3 is a crystal defect image formed on a sensor. .

1 and 2, reference numeral 1 denotes a wafer such as a semiconductor crystal, 2 denotes a crystal surface, 3 denotes an objective lens, and 4 denotes a C lens.
It is a sensor such as a CD sensor or a photodiode array. In the case of the present invention, the infrared laser beam B is applied from the crystal side wall surface 5 toward the crystal surface 2 at a predetermined incident angle so as to be totally reflected at the crystal surface 2.

The incident infrared laser beam B is totally reflected on the crystal surface 2 as shown in the figure. At this time, if a crystal defect d exists at the position of the total reflection point, a part of the infrared laser beam B is It is scattered by this crystal defect d. Therefore, the objective lens 3 and the sensor 4 are provided just above the total reflection point, and the scattered light from the crystal defect d is condensed by the objective lens 3, and as shown in FIG. The defect image d is formed.

In the case of the present invention, unlike the conventional detection method, the infrared laser beam B does not hit the ridge of the crystal side wall 5 and is scattered, and the beam diameter of the infrared laser beam B is freely reduced. Therefore, the range of the detection depth from the crystal surface 2 can be adjusted by adjusting the beam diameter. Therefore, it is possible to reliably and accurately detect a crystal defect near the crystal surface, which has been difficult with the conventional method.

In FIG. 1, if the incident position of the infrared laser beam B is scanned in the Z (vertical) direction, the total reflection point on the crystal surface 2 can be moved in the Z direction. If the incident position of the infrared laser beam B is moved in the X direction or the incident angle on the side wall surface 5 is changed, the position of the total reflection point on the crystal surface 2 can be scanned in the Y direction. Therefore, by controlling the incident position and the incident angle of the infrared laser beam B, crystal defects can be detected on the entire surface of the crystal surface 2.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a block diagram of one embodiment of the crystal defect detection device of the present invention, and FIG. 5 is a plan view of a wafer and an infrared laser light source.

4 and 5, reference numeral 1 denotes a semiconductor crystal wafer to be detected, 2 denotes a crystal surface, 3 denotes an objective lens, 4 denotes a CCD sensor of an infrared TV camera 6, and 5 denotes an infrared laser beam B. A crystal side wall surface, 7 is a moving stage for placing and positioning the wafer 1, 8 is an infrared laser light source, 9 is an infrared laser light emitted from the infrared laser light source 8, which is narrowed down to a predetermined beam diameter. It is a laser beam stop lens for giving an incident angle. For example, as shown in FIG. 5, the incident angle of the infrared laser beam B with respect to the wafer 1 can be freely changed by passing the infrared laser beam B through the periphery of the laser beam stop lens 9. The same or equivalent parts as those in FIG. 1 are denoted by the same reference numerals.

Reference numeral 10 denotes a Z-axis moving motor for moving the moving stage 7 in the Z (up and down) direction.
Is an X-axis moving motor for moving the moving stage 7 in the X direction (see FIG. 5), and 12 is a Y-axis moving motor for moving the moving stage 7 in the Y direction (see FIG. 5). The moving stage 7 on which the wafer 1 is mounted is moved by three motors in X, Y,
It can move freely in the three axial directions of Z.

Numeral 13 denotes a lens barrel length fine-tuning motor for adjusting the focus of the objective lens 3 to the CCD sensor 4, and numeral 14 a focus adjusting motor for adjusting the focus of the objective lens 3 to the position of the total reflection point 15 of the infrared laser beam B. Motor,
By controlling these motors, the focus of the objective lens 3 can be adjusted to a desired position.

Reference numeral 16 denotes an A / D converter for converting an image signal read from the CCD sensor 4 of the infrared TV camera 6 into digital data; 17 a computer for detecting a crystal defect; Is a frame memory for storing the obtained image data of the crystal defect for one screen, and 20 is a crystal memory based on the crystal defect image data stored in the frame memory 19. A monitor device 21 for displaying a defect image is a motor controller that drives and controls each motor under the control of the computer 17.

Next, the operation of the above embodiment will be described. First, the wafer 1 on which a crystal defect is to be detected is placed on the moving stage 7. And the infrared laser light source 8
Is turned on, and the detection start position is input to the computer 17 from the keyboard 18. The motor controller 21 controls the motor 1 under the control of the computer 17.
0, 11 and 12 to move the moving stage 2 to X, Y, Z
The position is controlled so that the infrared laser beam B incident from the infrared laser light source 7 is totally reflected at the specified coordinate position on the crystal surface 2.

In this state, the focusing motor 14 is driven to focus the objective lens 3 on the infrared laser beam B.
Is adjusted to match the position of the total reflection point 15, the lens barrel length fine adjustment motor 13 is driven, and the image forming position of the objective lens 3 is adjusted to C.
Adjustment is made so as to match on the CD sensor 4.

After completion of the above positioning and focusing, when a command to start a detection operation is given from the keyboard 18, the computer 17 starts the operation of detecting a crystal defect existing near the crystal surface 2 as follows. .

That is, the infrared laser beam B incident at a predetermined angle from the side wall surface 5 of the wafer 1
When there is a crystal defect at the position of the total reflection point 15 of the infrared laser beam B, a part of the infrared laser beam B is scattered by the crystal defect. The scattered light from the crystal defect is condensed by the objective lens 3 and forms an image on the CCD sensor 4 as shown in FIG.

The image data of the crystal defect image d formed on the CCD sensor 4 is sequentially read for each pixel by a CCD sensor reading circuit (not shown), and is converted into digital data by the A / D converter 16. After that, it is input to the computer 17. Computer 17 uses this C
The image data of the crystal defect image sent from the CD sensor 4 is written to the corresponding address position in the frame memory 19.

Next, for example, the Z-axis moving motor 11 is driven, and the moving stage 7 is sequentially moved in the Z (up and down) direction at a predetermined pitch, for example, in units of pixels of the CCD sensor 4, and the same as described above at each position. The operation of detecting a crystal defect is performed, and image data of the crystal defect existing at each position is stored in the frame memory 19. When the scanning of the infrared laser beam B is completed over the entire width of the wafer 1 in the Z direction in this manner, a crystal defect image in the Z direction near the crystal surface 2 can be obtained.

Next, the X-axis moving motor 11 is driven to sequentially move the moving stage 7 in the X direction (see FIG. 5) at a predetermined pitch, for example, in units of pixels of the CCD sensor 4, so that the total reflection point 15 The position in the Y direction is sequentially changed, and at each Y position, the same operation of detecting a crystal defect along the Z direction as described above is performed.

By scanning the entire surface of the crystal surface 2 in this manner, the frame memory 19 stores image data of crystal defects on the entire surface of the crystal surface 2. Therefore, if the image data stored in the frame memory 19 is displayed on the monitor device 21, for example, as shown in FIG. 6, images of all crystal defects existing within a predetermined depth range from the crystal surface can be obtained. it can.

[0026] Incidentally, the embodiment focusing of the movement and the lens movement stage 2 was to automatically perform Te <br/> by a respective motor 1 0-1 4, may be performed manually Of course. Also, semiconductor crystal is taken as an example,
As long as the crystal is transparent to a laser, the crystal is not limited to a semiconductor crystal, and can be applied to another crystal.

[0027]

As described above, according to the method and apparatus of the present invention, an infrared laser beam is incident from the side wall surface of the crystal toward the inside of the crystal at a predetermined incident angle so as to be totally reflected by the crystal surface. Detection of crystal defects near the crystal surface by detecting the scattered light of the infrared laser beam from the crystal defects existing near the position of the total reflection point on the surface from the direction perpendicular to the depth direction from the crystal surface with the observation optical system As a result, it is possible to improve the position detection accuracy in the depth direction of a defect near the crystal surface, which is the most important in manufacturing such as a VLSI, and to reliably and accurately detect a crystal defect near the crystal surface. .

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a plan view of a crystal part for describing an incident path of an infrared laser beam to a crystal in the present invention.

FIG. 3 is a diagram showing a crystal defect image formed on a sensor.

FIG. 4 is a block diagram of one embodiment of a crystal defect detection device according to the present invention.

FIG. 5 is a plan view of a wafer and an infrared laser light source part in FIG. 4;

FIG. 6 is a view showing a defect image near the crystal surface obtained by the method of the present invention.

FIG. 7 is a diagram illustrating the principle of a conventional method.

[Explanation of symbols]

 Reference Signs List 1 wafer 2 crystal surface 3 objective lens 4 sensor 5 crystal side wall B infrared laser beam d crystal defect

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shuji Nango Kirin 1st Building, Ratok System Engineering Co., Ltd. 540, Waseda Tsurumaki-cho, Shinjuku-ku, Tokyo (56) References JP-A-4-12254 (JP, A JP-A-6-140488 (JP, A) JP-A-1-151243 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/84-21/958 H01L 21 / 64-21/66

Claims (2)

(57) [Claims] 1. An infrared laser beam is incident from a crystal side wall surface into a crystal at a predetermined incident angle so as to be totally reflected on a crystal surface, and infrared rays from a crystal defect existing near a position of a total reflection point on the crystal surface. The scattered light of the laser beam from the crystal surface
A crystal defect detection method, wherein a crystal defect near a crystal surface is detected by detection with an observation optical system arranged on a side orthogonal to a scanning plane of the infrared laser beam parallel to a depth direction . 2. An infrared laser light source for injecting an infrared laser beam from a crystal side wall surface into a crystal at a predetermined incident angle so as to be totally reflected on the crystal surface, and an infrared laser beam incident on the crystal surface from the crystal surface.
An observation optical system arranged on a side orthogonal to a scanning plane parallel to the depth direction, wherein the observation optical system detects scattered light of an infrared laser beam from a crystal defect existing near a position of a total reflection point on a crystal surface. A crystal defect in the vicinity of the crystal surface.