KR19990084235A - Wafer inspection system - Google Patents

Abstract

OBJECTIVE: To provide a wafer inspection system that can inspect a large number of wafers at the same time and determine good or bad.

Construction: Non-contacting a tray having a support block for stacking a plurality of wafers in parallel, a rotary drive means for rotating the tray at a low speed, and each wafer mounted on the support block and rotated on the side of the tray And a plurality of sensors for outputting a signal to be inspected by a signal, a signal processing and discriminating unit for processing a signal of the sensors to determine a defect of a wafer, and an output device for outputting the determination result in a form that a user can check. . The sensor outputs a signal including a leak when detecting a defective part of the wafer, and may employ a laser sensor, a photo sensor, an ultrasonic sensor, an infrared sensor, or an image sensor.

Efficient: As it realizes automated inspection by sensors while rotating a large number of wafers at low speed, it is possible to precisely inspect a large amount of wafers in a short time, and do not have to worry about operator's risk and equipment damage. Since it is output as a digital signal from the signal processing and determination unit, it can be used as a useful resource for implementing process automation.

Description

Wafer inspection system

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer inspection system, and more particularly, to a wafer inspection system capable of inspecting wafers for defects such as defects on the edges of the wafers or crystal defects on the wafer surface, while simultaneously inspecting a plurality of wafers. .

As is well known, the wafer serving as a base material for forming a semiconductor component is formed into a disc through a slicing process of thinly cutting an ingot made of silicon single crystal.

In the slicing process for manufacturing wafers, the inner portion of the annular saw blade coated with diamond powder on the surface is used to cut the ingot thinly to minimize the amount of single crystal silicon lost, while cutting with caustic after cutting. Clean saw blades and other damage from the city.

As such, crystal defects of the wafer generated in the slicing process have a fatal adverse effect on the fabrication of the semiconductor device. Thus, the wafer obtained through the slicing process is usually inspected to determine whether the wafer is emptied after cleaning or after polishing and cleaning.

In addition, wafers obtained through the slicing process often have defects in the edge portion due to the strong hardness of the material, and thus the edge portion of the wafer, which has been cut off due to such defects, may cause injury to workers or damage the equipment. There is concern.

Therefore, in order to prevent the above-mentioned damages and increase the yield of semiconductor products, the wafer is inspected. In the past, the wafer was unsuccessfully determined by visual inspection or microscopic examination, which made it difficult to determine the accuracy of the wafer. There was a problem that the work efficiency is very low because it was checked by one unit.

SUMMARY OF THE INVENTION An object of the present invention devised to solve the above-mentioned problem is to provide a wafer inspection system capable of inspecting a plurality of wafers at the same time to determine good or bad.

The present invention for achieving the above object is a tray having a support block for stacking a plurality of wafers in parallel, a rotary drive means for rotating the tray at low speed, and is installed on the side of the tray and loaded on the support block And a plurality of sensors for outputting a signal for non-contact inspection of each rotated wafer, a signal processing and discriminating unit for processing a signal of the sensors to determine a defect of the wafer, and a form in which the user can confirm the determination result. A wafer edge inspection system is provided, comprising an output device for outputting the data.

The sensor outputs a signal including a leak at the moment of detecting a defective part of the wafer, and employs one of a laser sensor, a photo sensor, an ultrasonic sensor, an infrared sensor, and an image sensor.

1 is a system configuration diagram according to an embodiment of the present invention;

2 is a plan view of a loaded state of a wafer according to an embodiment of the present invention;

3 is a signal waveform diagram of a sensor for explaining the detection principle of the present invention;

4 is a principle diagram of a laser sensor to which the present invention is applied as an embodiment;

5 is a block diagram showing a configuration of a signal processing and discriminating unit when employing a laser sensor in an embodiment of the present invention;

6 is a block diagram illustrating an AC photoelectric sensor applied in an embodiment of the present invention;

7 is a state diagram used of the image sensor applied in the embodiment of the present invention,

8 is a block diagram illustrating a signal processing and discriminating unit when an image sensor is employed in an embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

W-wafer M-rotation drive

2-tray 4-sensor

6-sensor mounting unit 8-signal processing and discriminating unit

9-output 22-support block

62-Guide rail

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

Referring to FIG. 1, a tray 2 is condensed on a drive shaft of a low speed motor used as the rotation driving means M, and a plurality of wafers W are horizontally loaded at a predetermined circumferential position of the tray 2. The support block 22 which forms the sandwich grooves at a predetermined distance in the longitudinal direction so as to be vertically installed is vertically installed.

A sensor mounting unit 6 is installed on the side of the tray 2, and a plurality of sensors 4 are provided on the sensor mounting unit 6 so as to face each wafer W loaded on the tray 2. It is installed at a certain distance in the longitudinal direction.

The sensor mounting unit 6 is mounted on the guide rail 62, and when the wafer W is inspected, the sensors 4 approach the wafer W loaded on the tray 2, and the wafer W ), It is possible to retract the sensors (4) from the wafer (W).

On the other hand, the sensor mounting unit 6 is electrically connected to the sensors 4 to process the detection signal of the sensor 4 by the signal processing and determining unit 8 for determining whether there is a defect of the wafer (W) And an output device 9 for displaying the discrimination result.

According to the present invention configured as described above, the wafer (W) is loaded on the tray (2), and then the sensor mounting unit (6) is pushed to approach the sensors (4) to the wafer (W) and then supported by driving the rotation driving means (M). The wafer W can be inspected by loading a detection signal of the sensor 4 while rotating the plurality of wafers W mounted on the tray 2 at a low speed so as to be fixed to the block 22.

Meanwhile, as illustrated in FIG. 2, the wafer W is typically formed with a flat surface Wf on one side of the circumference.

When the wafer W to be inspected is loaded on the tray 2, the flat surface Wf is brought into close contact with the end of the clamping groove 222 so that the wafer rotated by the rotation driving means M at the time of inspection ( Make sure to give W) the correct orientation. This stacking method is for preventing the detection error of the sensor 4, and may also be used to motivate the detection of the missing position of the wafer W electrically.

The defect of the wafer (W) can be known by the signal output from the sensor (4). That is, when the wafer W is good, the signal of the sensor 4 appears as a substantially flat waveform except for the synchronization signal as shown in FIG. 3A, and when the wafer W has a defect, the signal of FIG. Like b, it appears as a mixed waveform of leak components.

As described above, the sensors 4 output a signal having a waveform distinguished from the normal part at the defective part of the wafer W, and the sensor 4 employs a laser sensor, a photo sensor, an infrared sensor, an ultrasonic sensor, or an image sensor. can do.

As described above, the present invention can be implemented in various embodiments of various kinds of sensors which can be adopted to implement the present invention and the signal processing and discriminating unit 8 connected thereto.

First, an embodiment in which a laser sensor is employed as the sensor 4 will be described.

As shown in FIG. 4, the laser sensor includes a light transmission system 422 for emitting a laser light, a scanning mirror 424 for scanning the laser light in a straight line on the surface of the wafer W, and a laser reflected on the wafer W. It consists of a light receiving system 426 that receives light, and detects diffraction images caused by microstructures such as crystal defects, roughness, and scratches on the edges of the surface of the wafer W.

In the case of employing a sensor for measuring an analog quantity, such as a laser sensor, the plurality of sensors 4 may include an amplifier 842, a multiplexer 844, an A / D converter 846, and an interface as shown in FIG. And a signal processing and discriminating unit 8 composed of 848 and personal computer 850. The personal computer 850 recognizes a signal having a leak component to determine how many wafers W are placed on the tray 2, and the user can know the result of the determination through the output device 9. Since it is output as, it is possible to accurately find a defective wafer having defects while inspecting a plurality of wafers W at a time. Here, of course, a small microcomputer made of a single chip may be used instead of the personal computer 850.

As described above, the sensor for measuring the analog amount may be a photo sensor in addition to the laser sensor.

In the case of using the photosensor, in order to avoid the interference of natural light, as shown in FIG. 6, the oscillation circuit 442 and the photodiode 444 as the light emitting portion, and the phototransistor 446, the filter 448, the amplifier as the light receiving portion. An alternating current photo sensor composed of a 450, a detection circuit 452, and a level interface 454 is adopted to be connected to the input terminal of the multiplexer 844 of FIG. When the wafer W is inspected using the AC photoelectric sensor, leakage occurs in the AC signal as shown in the drawing, and the personal computer 850 uses the leakage component. The goodness of the wafer W is inspected.

Also, as the sensor 4, image information about the wafer W rotated by one-dimensional scanning is obtained by using an image sensor 462 composed of photodiode arrays or solid-state image pickup devices arranged in a row as shown in FIG. can do. When the image sensor 462 is employed in this manner, the signal processing and discriminating unit 8 for processing the obtained image information can be implemented with a circuit as shown in FIG. That is, in this embodiment, the image information output from the image sensor 462 is stored in the pattern memory 466 in the frame unit through the preprocessing circuit 862 in units of frames, and then loaded into the microprocessor 468. Acquisition of the image information, and the two-dimensional image information loaded into the microprocessor 468 is compared with the data of the memory 470 stored as a setting reference value, and the result can be confirmed by the user through the output device 9. By outputting in such a form, it is possible to determine whether the wafer W is unsatisfactory.

On the other hand, although not shown, when the ultrasonic sensor is employed in the sensor 4, the defect of the wafer (W) can be detected by the change in the amount of attenuation of the ultrasonic wave reflected from the rotating wafer (W).

In the case where an infrared sensor is employed in the sensor 4, the wafer W is provided with a separate infrared lamp for irradiating infrared light, so that the wafer W is lost due to the change in the amount of infrared rays reflected from the wafer W. Can be detected.

Thus, the sensor 4 which detects the defect of the wafer W is somewhat affected by the defect of the edge part of the wafer W in the slicing process, or the crystal defect of the surface of the wafer W caused by poor polishing or cleaning. The signal waveform is changed, and the signal processing and discriminating unit 8 amplifies the minute waveform change and then determines whether the wafer W is defective by the amplified signal.

As can be seen from the above description, the present invention implements an automated inspection by sensors while rotating a plurality of wafers at a low speed, so that a large amount of wafers can be inspected precisely in a short time, and workers' risk and equipment damage are concerned. There is a useful effect that you do not have to.

In addition, since the test result of the present invention is output as a digital signal from the signal processing and determining unit, it can be utilized as a useful resource for implementing process automation.

Claims (2)

A tray having a support block for stacking a plurality of wafers in parallel; Rotary drive means for rotating the tray at a low speed; A plurality of sensors installed on the side of the tray and outputting a signal for non-contact inspection of each wafer loaded and rotated on the support block; A signal processing and discriminating unit which processes a signal of the sensors to determine a defect of a wafer; Wafer edge inspection system comprising an output device for outputting the determination result in a form that can be confirmed by the user. The sensor outputs a signal including a leak at the moment of detecting a defective part of the wafer, and employs one of a laser sensor, a photo sensor, an ultrasonic sensor, an infrared sensor, and an image sensor.