JPH0772092A - Method and apparatus for detecting crystal defect - Google Patents

Abstract

PURPOSE:To provide a detecting method for surely and accurately detecting a crystal defect in the vicinity of a crystal surface which enhances a positional detecting accuracy in the depthwise direction of the crystal defect in the vicinity of the crystal surface which is most important in manufacturing of a VLSI or the like. CONSTITUTION:An infrared laser beam B is made incident on a crystal toward its inside at a predetermined angle of incidence from a side wall face 5 so as to be totally reflected at a surface 2 of the crystal. A scattered light of the infrared laser beam B from a crystal defect (d) present at a total reflection point on the crystal surface 2 is detected by observation optical systems 3, 4 arranged orthogonally to a scattering face by the infrared laser beam, thereby, the crystal defect in the vicinity of the crystal surface is detected.

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 defect existing in the vicinity of the crystal surface is detected by utilizing total reflection. The present invention relates to a defect detection method and apparatus.

[0002]

2. Description of the Related Art Semiconductor crystals have a property of transmitting infrared rays. Conventionally, by utilizing this property, crystal defects existing in the crystal have been detected by the method shown in FIG. That is, in FIG. 7, 71 is a wafer such as a semiconductor crystal as a defect detection target, 72 is an objective lens, and 73 is C.
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 existing on a passing path of the incident infrared laser beam B. Was collected by the objective lens 72 and focused on the sensor 73 to detect crystal defects existing in the crystal.

[0003]

The crystal defects are present in every part of the crystal. However, in general, VLSI
A problem in manufacturing such as is a crystal defect existing in a depth range of several microns from the crystal surface 74.
In particular, the presence of defects near the pole surface is a problem in the manufacture of MOS devices. Therefore, it is desirable to be able to detect the crystal defects existing within this range as accurately as possible, but this is difficult when the above-mentioned conventional method is used.

That is, in order to efficiently enter the infrared laser beam B, the wafer 71, which is a target for detecting crystal defects, must have a flat side wall surface 75. In the actual defect inspection, the wafer 71 is cleaved by utilizing the cleaving property of the crystal, and the flat side wall surface 75 is obtained.
However, even if the central portion of the cleaved side wall surface 75 is flat, the peripheral ridge line 76 has uneven jagged edges, crushed corners, or lacked corners to obtain a perfect plane. Was difficult. Therefore, even if the infrared laser beam B is irradiated from the vicinity of the ridge line 76 in order to investigate a crystal defect at a shallow position near the crystal surface 74, which is a few microns or less, irregular reflection occurs at the ridge line portion, and the infrared laser beam B is generated in the crystal. It was difficult to make the beam incident on the beam.

The present invention has been made to solve the above problems, and an object thereof is to improve the accuracy of detecting the position in the depth direction of defects near the crystal surface, which is the most important in manufacturing VLSI and the like. It is an object of the present invention to provide a crystal defect detection method and apparatus capable of reliably and accurately detecting crystal defects near the crystal surface.

[0006]

In order to achieve the above object, a crystal defect detecting method according to the present invention is designed such that an infrared laser beam is directed from a crystal side wall surface into a crystal so as to be totally reflected on the crystal surface. Crystals that are incident at an incident angle and are detected by an observation optical system arranged on the side orthogonal to the scanning surface of the infrared laser beam to detect the scattered light of the infrared laser beam from the crystal defect existing at the position of total reflection on the crystal surface. This is to detect crystal defects near the surface.

Further, the crystal defect detecting apparatus according to the present invention is
Observation that the infrared laser beam is incident from the side wall of the crystal toward the inside of the crystal at a predetermined incident angle so as to be totally reflected on the crystal surface, and the infrared laser beam is placed on the side orthogonal to the scanning surface of the incident infrared laser beam. Equipped with an optical system,
By detecting the scattered light of the infrared laser beam from the crystal defect existing at the position of the total reflection point with the observation optical system, the crystal defect near the crystal surface is detected.

[0008]

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

In FIGS. 1 and 2, 1 is a wafer such as a semiconductor crystal, 2 is a crystal surface, 3 is an objective lens, and 4 is C.
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 incident from the crystal side wall surface 5 toward the crystal surface 2 with a predetermined incident angle so as to be totally reflected on 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 this total reflection point, a part of the infrared laser beam B will be generated. It is scattered by this crystal defect d. Therefore, the objective lens 3 and the sensor 4 are provided directly above the total reflection point, the scattered light from the crystal defect d is condensed by the objective lens 3, and the crystal is formed on the sensor 4 as shown in FIG. The defect image d is formed.

In the case of the present invention, the infrared laser beam B does not hit the edge line of the crystal side wall surface 5 and is scattered unlike the conventional detection method, and the infrared laser beam B has its beam diameter narrowed freely. Therefore, the detection depth range from the crystal surface 2 can be adjusted by adjusting the beam diameter. Therefore, it becomes possible to reliably and accurately detect a crystal defect near the crystal surface, which was 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. Further, the position of the total reflection point on the crystal surface 2 can be scanned in the Y direction by moving the incident position of the infrared laser beam B in the X direction or changing the incident angle on the side wall surface 5. Therefore, by controlling the incident position and the incident angle of the infrared laser beam B, the crystal defect 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 detecting apparatus of the present invention, and FIG. 5 is a plan view of a wafer and an infrared laser light source portion.

4 and 5, 1 is a semiconductor crystal wafer to be detected, 2 is a crystal surface, 3 is an objective lens, 4 is a CCD sensor of an infrared TV camera 6, and 5 is an infrared laser beam B. Crystal side wall surface, 7 is a moving stage for mounting and positioning the wafer 1, 8 is an infrared laser light source, 9 is an infrared laser light radiated from the infrared laser light source 8 and a predetermined beam diameter It is a laser beam diaphragm lens for giving an incident angle. For example, as shown in FIG. 5, the incident angle of the infrared laser beam B on the wafer 1 can be freely changed by passing the infrared laser beam B through the peripheral portion of the laser beam diaphragm lens 9. In addition, the same or equivalent portions as those in FIG. 1 are denoted by the same reference numerals.

Reference numeral 10 is a Z-axis moving motor for moving the moving stage 7 in the Z (vertical) direction, and 11 is a moving stage 7.
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 placed is moved by X, Y, and
It is designed so that it can move freely in the three Z directions.

Reference numeral 13 is a lens barrel length fine adjustment motor for adjusting the focus of the objective lens 3 to the CCD sensor 4, and 14 is focus for adjusting the focus of the objective lens 3 to the position 15 of the total reflection point of the infrared laser beam B. A motor,
The focus of the objective lens 3 can be adjusted to a desired position by controlling these motors.

Reference numeral 16 is an A / D converter for converting the image signal read from the CCD sensor 4 of the infrared TV camera 6 into digital data, 17 is a computer for detecting crystal defects, and 18 is a computer 17 for various purposes. A keyboard for inputting the operation command of No. 1, a frame memory 19 for storing the obtained image data of the crystal defect of one screen, and a crystal 20 based on the image data of the crystal defect stored in the frame memory 19. A monitor device 21 displays a defect image, and a motor controller 21 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 which is the target of crystal defect detection is placed on the moving stage 7. And the infrared laser light source 8
The power of is turned on and the detection start position is input from the keyboard 18 to the computer 17. The motor controller 21, under the control of the computer 17,
0, 11, 12 are driven 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 by moving by a specified amount in the three axis directions.

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

After completion of the above-mentioned alignment and focusing, when a command for starting the detecting operation is given from the keyboard 18, the computer 17 starts the detecting operation of the crystal defects existing in the vicinity of the crystal surface 2 as follows. .

That is, the infrared laser beam B incident from the side wall surface 5 of the wafer 1 at a predetermined angle is applied to the crystal surface 2
However, if there is a crystal defect at the total reflection point 15 position of the infrared laser beam B, a part of the infrared laser beam B is scattered by the crystal defect. Then, the scattered light from the crystal defect is condensed by the objective lens 3 and imaged 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 out pixel by pixel by a CCD sensor readout circuit (not shown) and converted into digital data by the A / D converter 16. Then, it is input to the computer 17. The computer 17 uses this C
The image data of the crystal defect image sent from the CD sensor 4 is written in the corresponding address position of the frame memory 19.

Then, for example, the Z-axis moving motor 11 is driven to move the moving stage 7 in a predetermined pitch, for example, in the Z (vertical) direction in units of pixels of the CCD sensor 4, sequentially, and at each position, the same as described above. The crystal defect detection operation is performed, and the 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 over the entire width of the wafer 1 in the Z direction is completed in this way, a crystal defect image along the Z direction near the crystal surface 2 can be obtained.

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

By scanning the entire crystal surface 2 in this manner, image data of crystal defects on the entire crystal surface 2 is stored in the frame memory 19. 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, an image of all crystal defects existing within a predetermined depth range from the crystal surface can be obtained. it can.

In the above embodiment, the motors 11 to 14 and 16 are used to move the moving stage 2 and focus the lens.
Although it is automatically performed by the above method, it may be manually performed. Further, although the semiconductor crystal is taken as an example, any crystal other than the semiconductor crystal can be applied as long as it is a crystal transparent to the laser.

[0027]

As described above, according to the method and apparatus of the present invention, the infrared laser beam is directed to the inside of the crystal from the side wall surface of the crystal so as to be totally reflected on the crystal surface, and the total reflection point is obtained. Since the observation optical system detects the scattered light of the infrared laser beam from the crystal defect existing at the position, the crystal defect near the crystal surface is detected. It is possible to improve the position detection accuracy in the depth direction of the defect,
Crystal defects near the crystal surface can be detected reliably and accurately.

[Brief description of drawings]

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

FIG. 2 is a plan view of a crystal portion for explaining an incident path of an infrared laser beam on a crystal according to the present invention.

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

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

5 is a plan view of the wafer and the infrared laser light source portion in FIG.

FIG. 6 is a diagram 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]

 1 Wafer 2 Crystal Surface 3 Objective Lens 4 Sensor 5 Crystal Sidewall Surface B Infrared Laser Beam d Crystal Defect

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoya Ogawa 1-5-1, Mejiro, Toshima-ku, Tokyo Gakuin-in University (72) Inventor Nanshi 540, Kirin 1st Building, Tsurumaki-cho, Waseda, Shinjuku-ku, Tokyo Ratok System Engineer Ring Co., Ltd.

Claims (2)

[Claims] 1. An infrared laser from a crystal defect existing at a position of total reflection on the crystal surface, which is an infrared laser beam incident from the side wall of the crystal toward the inside of the crystal so as to be totally reflected on the crystal surface. A crystal defect detecting method, characterized in that a crystal defect near a crystal surface is detected by detecting scattered light of the beam with an observation optical system arranged on a side orthogonal to a scanning surface of the infrared laser beam. 2. An infrared laser light source which makes an infrared laser beam incident at a predetermined incident angle from the side wall surface of the crystal into the crystal so as to be totally reflected on the crystal surface, and is orthogonal to a scanning surface of the incident infrared laser beam. With the observation optical system arranged on the side, the crystal defect near the crystal surface is detected by detecting the scattered light of the infrared laser beam from the crystal defect existing at the position of the total reflection point on the crystal surface by the observation optical system. A crystal defect detection device characterized by the above.