JPH11161735A - Device for recognizing character - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow even an inexperienced person to easily operate the setting of a device for obtaining optimal character recognition. SOLUTION: This device is provided with an adjusting means 20 for adjusting the angle of an illuminating light for illuminating an identification character applied on a semiconductor wafer and image pickup optimal systems 14-18 having an image pickup element 18 for image picking-up the illuminated identification character. Thus, the identification character can be recognized based on the output signal of the image pickup element 18. At that time, adjustment information obtained by the adjusting means 20 is stored, and the stored adjustment information is called so that the driving of the adjusting means 20 can be controlled based on the adjustment information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a character recognition device for recognizing a wafer management identification character or the like attached to the surface of a semiconductor wafer.

[0002]

2. Description of the Related Art In the manufacture of semiconductor integrated circuits, in order to manage a large number of semiconductor wafers (hereinafter simply referred to as "wafers") forming semiconductor integrated circuits, identification characters for management are formed by using a laser or the like on the surface of the wafer. (Hereinafter referred to as ID number). In order to selectively remove and rearrange wafers based on the ID numbers and to sort wafers of the same type, a character recognition device that automatically recognizes ID numbers is used.

As this type of character recognition device, an illumination unit provided on the device illuminates the vicinity of an ID number on a wafer, and the reflected light reflected therefrom is imaged by an imaging device such as a CCD camera. A device that identifies an ID number based on the imaging signal is known.

[0004] Incidentally, the ID number given on the wafer may be damaged as it passes through various manufacturing processes, or it may become difficult to recognize the ID number gradually due to various processing films during the manufacturing process. Also, the brightness of the input image tends to be unstable due to the influence of light from the outside. Conventionally, the operator himself has manually adjusted the illumination angle of the illumination unit with respect to the wafer so that the apparatus can accurately recognize the ID number in accordance with these situations. In addition, the optimum light amount has been readjusted again according to the illumination angle of the illumination unit.

[0005]

However, it is troublesome for the operator himself to make these adjustments manually.
In addition, skill is required to adjust to an optimum state according to the wafer in each step.

Further, the adjustment state once set needs to be changed when processing a wafer whose manufacturing process has changed. In order to return to the same adjustment state again, the previous setting is remembered and readjustment is performed, but this is troublesome and takes a lot of time.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the conventional apparatus, it is an object of the present invention to provide a character recognition apparatus capable of easily setting an apparatus for obtaining optimum character recognition even without a skilled person.

[0008]

Means for Solving the Problems In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) An illumination optical system for illuminating an identification character provided on a semiconductor wafer, and an imaging optical system having an image sensor for imaging the identification character illuminated by the illumination light of the illumination optical system. A character recognition device for recognizing the identification character based on an output signal of the image sensor, an adjustment means for adjusting an angle of illumination light of the illumination optical system with respect to the identification character on a semiconductor wafer; and an adjustment by the adjustment means. It is characterized by comprising storage means for storing information, calling means for calling the adjustment information stored in the storage means, and control means for driving and controlling the adjustment means based on the called adjustment information.

(2) The storage and recall means of (1) has a selection means for selectively retrieving one of the plurality of adjustment information stored in the storage means.

(3) In the character recognition device of (1),
The angle adjustment of the illumination light by the adjusting means is performed based on the position of the identification character on the semiconductor wafer.

(4) In the character recognition device of (1),
The imaging optical system is arranged coaxially with the optical axis of the illumination optical system, and the angle is changed together with the illumination optical system by the adjusting means.

(5) The illumination optical system of (4) is characterized in that it has a bright-field optical system arranged coaxially with the optical axis of the imaging optical system.

(6) In the character recognition device of (1),
The adjusting means includes a light amount adjusting means for adjusting the amount of illumination by the illumination optical system.

(7) The character recognition device according to (1), further comprising: a stage on which a semiconductor wafer is placed for positioning the identification character of the semiconductor wafer on the optical axis of the illumination optical system;
Transport means for transporting the semiconductor wafer between the stage and a carrier for accommodating the semiconductor wafer.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of the appearance of the apparatus of the embodiment. Reference numeral 1 denotes a character recognition device main body. Reference numerals 2a and 2b denote carrier mounting tables on which carriers 41a and 41b for accommodating a large number of semiconductor wafers 40 are mounted. Fixed members (not shown) for positioning and fixing the carriers 41a and 41b are fixed to the upper surfaces of the carrier mounting tables 2a and 2b, respectively. The carrier mounting tables 2a and 2b are provided with a loader mechanism 3 inside the main body.
4a, 34b to move up and down, and carriers 41a, 41b
The wafers 40 stored one by one in the internal slots are taken out or stored by the air tweezers 3.

The air tweezers 3 suck and hold the wafer 40 by suction portions 3a of substantially U shape formed on both sides of the arm.
It can be moved in the directions A and B in the figure according to the drive path 4. The suction part 3a is provided with a small hole, and the small hole passes through the inside of the air tweezers 3 and is connected to a suction device (not shown) via a vacuum tube, a solenoid valve, and the like. By operating the suction device, the wafer 40 is held by suction.

Reference numeral 5 denotes a character recognition stage which is rotated and moved up and down by a pulse motor (not shown). The stage 5 is also provided with a small hole having the same function as the suction section 3a, and thereby holds the wafer 40 by suction.

Reference numeral 6 denotes an orientation flat (Orientat) of the wafer 40.
ori Flat detector for detecting ional flat).
The orientation flat detector 6 includes an LED, a light receiving element, and the like.
They are arranged in a positional relationship in which the orientation flat of the wafer 40 placed on the stage 5 can be detected. As shown in FIG. 2, the ID number 50 for wafer management on the wafer 40 is
It is formed in a predetermined positional relationship with respect to a. Therefore, the position of the ID number 50 can be specified by detecting the position of the orientation flat 40a.

Reference numeral 10 denotes a character recognition unit whose details will be described later. The character recognition unit 10 has an ID number 50 of the wafer 40 mounted on the stage 5.
It has an illumination system for illuminating the vicinity and an imaging optical system for receiving reflected light from the wafer surface and imaging the ID number 50. The optical system of the character recognition unit 10 has an arrow C
It is installed so that it can be tilted in the direction.

Reference numeral 7 denotes a control unit.
0 tilt angle adjustment, switching of illumination system (bright field illumination system, dark field illumination system), light quantity adjustment, ID for orientation flat
Various settings required for character recognition, such as the position and angle setting of numbers, are performed, and preset settings are called. The control unit 7 includes a small monitor 7a, and displays whether or not the recognition result of the ID number on the wafer is present, a current setting state, and the like. 8
Is a monitor that displays the state of the ID number and the like on the wafer 40 captured by the illumination unit 10, and the operator sets the character recognition unit 10 so that the apparatus can appropriately perform character recognition while watching the monitor 8. .

Next, the configuration of the character recognition unit 10 will be described with reference to FIGS. FIG. 3 is a schematic configuration diagram showing an outline of an optical system, an angle adjusting mechanism, and the periphery thereof of the character recognition unit 10.

The optical system of the character recognition unit 10 is an optical system housing 19.
And comprises an illumination optical system and an imaging optical system.
The illumination optical system includes a bright-field illumination light source 11 such as an LED, a collimator lens 12 disposed on the illumination optical axis L1, and a dark-field illumination light source 13 such as an LED disposed with the illumination optical axis L1 interposed therebetween. . The imaging optical system includes a half mirror 14 arranged on the illumination optical axis L1, a mirror 15 for changing an optical path, a focus lens 16, an aperture 17, and a CCD camera 18.

The illumination light emitted from the light source 11 is converted into a parallel light beam by the collimator lens 12, passes through the half mirror 14, and illuminates the vicinity of the ID number 50 on the wafer 40. The divergent light emitted from the light source 13 also illuminates the vicinity of the ID number 50 on the wafer 40. The light source 13 is located on the wafer 4
It is set so as to illuminate evenly above 0. Light source 11
The optical axis of the specularly reflected light from the wafer 40 by the illumination is changed by the half mirror 14 and reaches the imaging surface of the CCD camera 18 via the mirror 15, the focus lens 16, and the diaphragm 17. Further, the wafer 40 by the illumination light of the light source 13
Of the reflected light from above, the reflected light along the optical axis L1 reaches the imaging surface of the CCD camera 18 via the same optical path.

Reference numeral 20 denotes an angle adjustment mechanism for changing the angle of the character recognition unit 10. The optical system housing 19 having the above-described optical system is supported by a support arm 21. The support arm 21 is held so as to be rotatable (in the direction of arrow C in FIG. 1) about a rotation shaft 23 of a holding unit 22 provided in the apparatus main body 1. The rotation of the support arm 21 is performed by a pulse motor disposed in the holding unit 22, and the angle of the optical axis L <b> 1 of the optical system housing 19 with respect to the wafer 40 is adjusted by controlling the rotation of the pulse motor. In addition, the rotating shaft 2
The rotation axis of 3 is for the wafer 4 mounted on the stage 5.
The arrangement is set so as to be on the same line as the top surface. Therefore, even if the rotation angle of the support arm 21 is changed, the ID number 50 assigned to the wafer 40 is always located on the optical axis of the illumination optical system and the imaging optical system described above.

In FIG. 3, reference numeral 6a denotes an LED of the orientation flat detector 6, and 6b denotes its CCD (light receiving element).
Based on the output of the CCD 6b, the position angle of the orientation flat of the wafer 40 and the presence or absence of eccentricity are detected.

The operation of the apparatus having the above configuration will be described with reference to the block diagram of the control system shown in FIG.

First, the transfer of the wafer 40 and the character recognition unit 10
The registration of settings such as angle adjustment will be described. When the power of the apparatus is turned on, the control unit 30 initializes the state of the character recognition unit 10 to make it usable. The carrier 41a in which the wafer 40 is stored and the carrier 41b in which the wafer 40 is not stored are set on the mounting tables 2a and 2b, respectively.
When the OK button of the control unit 7 is pressed, the control circuit 30
Drives the air tweezers moving mechanism 31 to insert the air tweezers 3 below the lowermost (or designated) wafer 40 in the carrier 41a, and to hold the wafer 40 by suction. After that, the air tweezers moving mechanism 31 is driven to transfer the wafer 40 onto the stage 5. When the wafer 40 is positioned on the stage 5, the control unit 30 activates the stage vertical movement mechanism 32 to move up the stage 5 to suck and receive the wafer 40. When the wafer 40 is sucked, the controller 30 operates the stage rotation mechanism 35 to rotate the stage 5. When the rotation starts, the orientation flat detector 6 detects orientation flat and eccentricity.

In the orientation flat detection, a shadow of the wafer edge is projected from an illumination light source 6a located below the surface of the wafer 40 on the orientation flat detection unit 6 to a CCD 6b radially mounted above the wafer 40. As the wafer 40 rotates, the CCD 6b detects a change in the shadow, and based on the information, the control unit 30 performs data processing using an algorithm for calculating the orientation angle of the orientation flat 50, and based on the result, determines the position angle of the orientation flat 50. obtain.

The detection of the eccentricity is also processed by using an algorithm for calculating the eccentric position based on the position data of the shadow of the wafer 40 when the stage 5 is rotated. When the eccentricity is detected, the controller 30 drives the stage 5 and the air tweezers 3 to replace the position of the wafer 40 on the stage 5 so that the center of the wafer 40 and the center of the stage 5 are aligned to eliminate the eccentricity.

When the eccentricity is eliminated by replacing the wafer 40, the control unit 30 performs the same operation again, and detects the orientation flat position angle and checks whether or not there is eccentricity. If the eccentricity is less than the reference value, the I
The stage 5 is rotated by a predetermined angle so that the position of the D number 50 is located on the optical axis L1 of the character recognition unit 10. Thus, the ID number 50 illuminated by the illumination light source 11 or the illumination light source 13 is captured by the CCD camera 18, and the image is displayed on the monitor 8.

The image from the CCD camera 18 is taken into the frame memory 36 and then subjected to image processing by the image processing section 36 to perform character recognition. The control unit 30
A character portion is cut out based on the image data binarized by the image processing unit 36, and the ID number 50 is recognized by a similarity method in which this is compared with a dictionary of character fonts stored in advance.

In this character recognition, if the ID number 50 is scratched or the like or if the film is partially applied to the ID number 50 due to the film processing in the semiconductor manufacturing process,
The reflected light from the ID number 50 illuminated by the illumination light source 11 or 13 may not be captured by the CCD camera 18 and the character recognition may not be properly determined. In this case,
The operator operates a switch of the control unit 7 to adjust the angle of the character recognition unit 10 so that the image of the ID number 50 displayed on the monitor 8 can be most clearly observed. That is, the angle of the illumination optical axis L1 with respect to the ID number 50 is changed, and the reflected light from the ID number 50 is
At the best. The illumination optical system includes a light source 11 using specular reflection light and an illumination light source 1 using diffuse reflection light.
3, the light source can be selectively used depending on the condition of the wafer by using only one of them or combining both light sources. Also, the optimum light amount of each light source is adjusted.

If the character recognition result of the ID number 50 is determined to be good by adjusting the angle of the character recognition unit 10 or the like, OK is displayed on the small monitor 7a. The operator operates a switch of the control unit 7, and at this time, the setting state of the character recognition unit 10 such as angle adjustment is stored in the memory 38. When OK is instructed by the control unit 7, the wafer for which the ID number 50 has been recognized is housed from the stage 5 at the designated position of the carrier 41 b by the air tweezers 3.

The setting such as the angle adjustment of the character recognition unit 10 is performed in advance for each wafer lot in the semiconductor manufacturing process, and the setting state of a plurality of patterns is stored in the memory 38.

Next, the recognition of the wafer ID number in the actual production line will be briefly described. The carriers 41a and 41b in which the wafers 40 are stored are placed on the mounting tables 2a and 2b.
To transfer the wafer and recognize the ID number. At this time, the setting state of the character recognition unit 10 is stored in the memory 3
8 is selected from the patterns stored in the memory. When the setting is completed, the character recognition is started by the start switch of the control unit 7.

As described above, the wafer 40 is taken out of the carrier 41a by the air tweezers 3, and
Conveyed up. After the position of the orientation flat is detected by the orientation flat detection unit 6 and the eccentricity is corrected, the stage 5 rotates and the ID number 50 portion of the wafer 40 is placed at a predetermined position of the character recognition unit 10. When the rotation of stage 5 stops,
Character recognition by the character recognition unit 10 is performed. The recognition result is displayed on the small monitor 7a. If the recognition result is not good, a desired pattern is selected from the patterns in the setting state of the character recognition unit 10 registered in advance. The control unit 30 adjusts the angle of the illumination optical axis and the light source based on the information on the selected pattern. The operator checks the state of the ID number 50 captured by the CCD camera 18 on the monitor 8 and selects the best pattern. Since the operator only has to select from the setting states stored in advance, the setting state can be set so that the character recognition can be easily performed even by a non-expert. Further, even when the process of the wafer changes, the state can be easily changed to an appropriate state. The wafer whose ID number 50 can be recognized is stored in the designated position of the carrier 41b by the air tweezers 3.

As described above, in this embodiment, since the angle is changed by pairing the illumination optical system and the image pickup optical system, coaxial dark-field character recognition using a bright-field light source is always performed even when the angle changes. This makes it possible to expand the setting conditions for character recognition as compared with, for example, moving only the imaging optical system.

In the present embodiment, the character recognition unit performs recognition based on preset conditions, and if the recognition result is not good, the operator selects another condition from among the registered settings each time. However, it is possible to further reduce the burden on the operator by automatically changing the setting conditions until the recognition result becomes good on the device side.

Further, in the present embodiment, the angle is changed for the illumination optical system and the imaging optical system as a pair. However, the imaging optical system may be moved only the illumination optical system without changing the angle. In this case, coaxial dark field character recognition using a bright field light source cannot be performed, but since reflected light from the wafer is obtained when the angle of the illumination optical system is changed, character recognition is performed in comparison with a conventional device. Setting conditions are expanded.
Actually, the illumination optical system and the imaging optical system are separated, and only the angle of the illumination optical system is changed.Also, the illumination optical system and the imaging optical system are not separated, and only the dark field optical system of the illumination optical system is used. It can be driven.

[0041]

As described above, according to the present invention,
Even an unskilled person can easily perform settings for obtaining optimum character recognition, and can improve the character recognition of the apparatus.

[Brief description of the drawings]

FIG. 1 is an external view of a character recognition device.

FIG. 2 is a diagram showing a positional relationship between an ID number on a semiconductor wafer and an orientation flat;

FIG. 3 is an optical system diagram showing an optical system and the like of a character recognition unit.

FIG. 4 is a main part configuration diagram of a control system of the apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Character recognition apparatus main body 3 Air tweezers 5 Stage 7 Control part 10 Character recognition part 19 Optical system housing 20 Angle adjustment mechanism 30 Control circuit 37 Image processing part

Claims (7)

[Claims] An illumination optical system for illuminating an identification character provided on a semiconductor wafer, and an imaging optical system having an image sensor for imaging the identification character illuminated by illumination light of the illumination optical system, In a character recognition device for recognizing the identification character based on an output signal of the image sensor, an adjustment means for adjusting an angle of illumination light of the illumination optical system with respect to the identification character on a semiconductor wafer, and adjustment information by the adjustment means Character recognition, comprising: storage means for storing the adjustment information; calling means for calling the adjustment information stored in the storage means; and control means for driving and controlling the adjustment means based on the called adjustment information. apparatus. 2. The character recognizing device according to claim 1, wherein said memory calling means has a selecting means for selectively calling one of a plurality of adjustment information stored in said memory means. 3. The character recognition apparatus according to claim 1, wherein the adjustment of the angle of the illumination light by said adjustment means is performed based on the position of said identification character on a semiconductor wafer. 4. The character recognition device according to claim 1, wherein the imaging optical system is disposed coaxially with an optical axis of the illumination optical system.
A character recognition device characterized in that the angle is changed together with the illumination optical system by the adjusting means. 5. The character recognition device according to claim 4, wherein the illumination optical system has a bright field optical system arranged coaxially with an optical axis of the imaging optical system. 6. A character recognition apparatus according to claim 1, wherein said adjusting means includes a light amount adjusting means for adjusting an illumination light amount by said illumination optical system. 7. The character recognition device according to claim 1, further comprising: a stage on which a semiconductor wafer is placed for positioning an identification character of said semiconductor wafer on an optical axis of said illumination optical system; And a transfer means for transferring the semiconductor wafer to and from a carrier.