JP2002083265A - Character recognition device for semiconductor wafer, and character recognizing optical unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a character recognition device, capable of improving the character recognition rate, even in a wafer which has been subjected to CMP. SOLUTION: In this character recognition device for semiconductor wafer for recognizing a identification character formed on a semiconductor wafer, this device comprises an infrared projecting optical system for projecting infrared rays to the area including the identification characters of the semiconductor wafer, an imaging optical system having an image-pickup element for receiving the infrared-ray transmitting the area including the identification character by the projection of the infrared-ray projecting optical system, and a character recognition means for processing the image taken by the image pick-up element to recognize the identified characters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a character recognition device for recognizing identification characters formed on a semiconductor wafer and an optical unit for character recognition attached to the character recognition device.

[0002]

2. Description of the Related Art In the manufacture of a semiconductor integrated circuit, in order to manage a large number of semiconductor wafers (hereinafter simply referred to as wafers) forming the semiconductor integrated circuit, a laser or the like is used on a wafer surface to form uneven identification characters (not shown). (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 a character recognition device of this type, an illumination unit provided on the device illuminates a wafer surface in an area including an ID number, and images reflected light from the wafer surface by an imaging device such as a CCD camera. A device that identifies an ID number based on an imaging signal is known. The projection of the illumination light onto the wafer surface includes bright-field illumination mainly using specularly reflected light from the wafer surface and dark-field illumination mainly using diffusely reflected light. By selectively switching the more advantageous one according to the formation state or the like and adjusting the light amount,
The number recognition rate was raised.

[0004]

However, a CMP method (Chemical Mecha) for flattening irregularities on the surface of a wafer.
In a wafer manufactured by the conventional method, the ID number stamped by a laser or the like is buried, which makes it difficult to read by a conventional character recognition method using reflected light.

[0005] In view of the above-mentioned drawbacks of the conventional device, the present invention provides a C
It is an object of the present invention to provide a character recognition device capable of improving a character recognition rate even on a wafer subjected to MP.

[0006]

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

(1) In a character recognition apparatus for a semiconductor wafer for recognizing identification characters formed on a semiconductor wafer, an infrared light projecting optical system for projecting infrared light to a region of the semiconductor wafer including the identification characters is provided. An image pickup optical system having an image pickup element for receiving infrared light transmitted through a region including the identification character by light emission of the infrared light projection optical system, and processing an image picked up by the image pickup element for identification. And character recognition means for recognizing characters.

(2) The infrared light projecting optical system of (1) is characterized by including a light source that emits infrared light in a wide band.

(3) In the character recognition device for a semiconductor wafer of (1), a shielding means for cutting the incidence of infrared light, which does not pass through the inside of the semiconductor wafer, on the image pickup device is provided.

(4) The shielding means of (3) is a shielding member disposed between the light source and the wafer, and arranged at a position near the identification character for shielding light that does not pass through the inside of the semiconductor wafer. There is a feature.

(5) In the character recognition device for a semiconductor wafer according to (4), the imaging optical system is arranged on a front surface side of the semiconductor wafer, and the device further comprises a device for recognizing the semiconductor wafer on which the identification characters are formed. A visible light projection optical system that projects visible bright field illumination light or visible dark field illumination light on the surface side, and projection by the visible light projection optical system and projection by the infrared projection optical system. And switching means for selectively switching between.

(6) a light projecting optical system for projecting infrared light to a region of the semiconductor wafer including the identification character, and a light receiving optical system for receiving the light beam of the infrared light transmitted through the semiconductor wafer;
Shielding means for cutting the incidence of infrared light that does not pass through the inside of the semiconductor wafer to the light receiving optical system.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an external view of the apparatus of the embodiment. Reference numeral 1 denotes a character recognition device main body. 2a, 2b are carriers 41a, 41 for accommodating a large number of semiconductor wafers 40.
b is a carrier mounting table for mounting b. Carrier mounting table 2
Fixed members (not shown) for positioning and fixing the carriers 41a and 41b are fixed to the upper surfaces of the carriers a and 2b, respectively. The carrier mounting tables 2a and 2b are moved up and down by a loader mechanism inside the main body, and the wafers 40 stored one by one in the slots in the carriers 41a and 41b 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, and is arranged in a positional relationship capable of detecting the orientation flat of the wafer 40 placed on the stage 5. As shown in FIG. 2, the wafer management ID number 50 on the wafer 40 is formed in a predetermined positional relationship with the orientation flat 40a. Therefore, by detecting the position of the orientation flat 40a, I
The position of D number 50 can be specified.

Reference numeral 10 denotes a character recognition unit, the details of which will be described later, and is an ID number 50 of the wafer 40 mounted on the stage 5.
It has an illumination optical system for illuminating the vicinity, and an imaging optical system (light receiving optical system) for receiving reflected light from the wafer surface and transmitted light transmitted through the wafer to image the ID number 50.

Below the character recognition unit 10, a light source 20 for projecting infrared light from below (back side) the wafer 40 mounted on the stage 5, and a collimator for collimating the light beam from the light source 20 The lens 21 is placed, and constitutes an infrared light projecting optical system. The light source 20 is installed at a position where the ID number 50 can be illuminated from below when capturing and recognizing the ID number 50 by the character recognizing unit 10. Illumination light emitted from the light source 20 passes through the wafer 40 and performs character recognition. The light is received by the imaging optical system in the unit 10.

Since the wafer 40 has a property of transmitting infrared light, a light source that emits infrared light is used as the light source 20.
When a light source (e.g., an LED) that emits a single wavelength is used among the light sources that emit infrared light, character recognition may be performed if the film coated on the wafer 40 is a material that hardly transmits that wavelength. The amount of light received by the unit 10 is reduced. For this reason, it is preferable to use a light source that emits a luminous flux in a broadband infrared region, such as a halogen lamp or a tungsten lamp, and has a large amount of light. In this embodiment, a halogen lamp is used.

Reference numeral 22 denotes a shielding plate. The shielding plate 22 is the light source 2
0, and illumination light that is placed between the wafer 40 placed on the stage 5 and projected from outside the edge portion 40b (peripheral portion) of the wafer 40, in other words, illumination that does not pass through the inside of the wafer 40. It is installed to shield light.

FIGS. 3A and 3B are schematic views of the state in which the wafer 40 is mounted on the stage 5 when viewed from above and from the side. As shown in this figure, the end 22a which is the end of the shielding plate 22 is positioned so as to cover a part of the edge 40b of the wafer 40, and the illumination light projected from the outside of the edge 40b directly receives the imaging light. It is prevented from entering the system.

In this embodiment, since a halogen lamp is used as the light source 20, the diameter of light projected on the wafer 40 becomes large. For this reason, the illumination light projected from the outside of the edge portion 40b does not pass through the wafer 40 but directly enters the character recognition section 10 (imaging optical system). The light beam directly incident without passing through the wafer 40 naturally has a larger light amount than the light beam transmitted through the wafer 40, and thus becomes a major obstacle in recognizing the ID number 50. In the present embodiment, the use of the shielding plate 22 eliminates the illumination light flux that does not pass through the wafer 40 and suppresses the generation of a light flux that is an obstacle when recognizing the ID number.

In the present embodiment, the shielding plate 22 is used. However, the present invention is not limited to this, and only the ID number 50 may be illuminated or light emitted from outside (outer periphery) of the edge portion 40b may be eliminated. . For example, a slit may be provided in front of the light source 20 to illuminate only the ID number 50.
In the present embodiment, the shielding plate 22 is provided on the back side of the wafer 40.
This is because the illumination optical system (bright-field illumination optical system, dark-field illumination optical system) for illuminating the wafer surface is not obstructed. Therefore, when character recognition is performed using only transmitted light, the shielding plate 22 may be installed on either the front or the back of the wafer 40.

Reference numeral 7 denotes a control unit which switches illumination optical systems (bright-field illumination optical system, dark-field illumination optical system, infrared light projection optical system), adjusts the amount of light, and controls the orientation flat.
Various settings necessary for character recognition, such as the setting of the position and angle of the D number, are performed, and a preset one is called. The control unit 7 includes a small monitor 7a, and displays whether the recognition result of the ID number is correct, the current setting state, and the like. Reference numeral 8 denotes a monitor that displays the state of the ID number and the like on the wafer 40 imaged by the character recognition unit 10. The operator sets the character recognition unit 10 so that the apparatus can appropriately perform character recognition while watching the monitor 8. I do.

Next, the configuration of the character recognition unit 10 will be described with reference to FIGS. FIG. 4 is a schematic configuration diagram showing an outline of the optical system of the character recognition unit 10 and its periphery.

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 optical system for projecting illumination light from a direction perpendicular to the wafer surface along the optical axis L1 by a light source 11 such as an LED and a collimator lens 12, and a plurality of illumination optical systems sandwiching the optical axis L1. And a dark-field illumination optical system for projecting illumination light onto the wafer surface from an oblique direction by a light source 13 such as an LED. The imaging optical system includes a half mirror 14 arranged on the optical axis L1, a mirror 15 for changing the optical path,
The camera includes a focus lens 16, an aperture 17, and a CCD camera 18. The CCD camera 18 has sensitivity in the visible light region and the infrared light region.

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, reaches the imaging surface of the CCD camera 18 via the mirror 15, the focus lens 16, and the diaphragm 17, and is bright-field imaged by the CCD camera 18. Is obtained. On the other hand, of the light reflected from the wafer 40 by the illumination light of the light source 13, the light irregularly reflected by the unevenness of the ID number 50 reaches the imaging surface of the CCD camera 18 via the same optical path,
A dark-field image is obtained by the CCD camera 18.

In the infrared light projecting optical system, the divergent light emitted from the light source 20 is converted into a parallel light beam by the collimator lens 21, and the illumination light is projected from the vertical direction to the back surface of the wafer along the optical axis L1. While the infrared light is transmitted through the back surface of the wafer 40, only the light beam parallel to the optical axis L1 reaches the imaging surface of the CCD camera 18 via the same optical path as described above.
A transmitted image is obtained by light projected from the back surface of the wafer 40 by the camera 18.

In FIG. 4, reference numeral 6a denotes an LED of the orientation flat detector 6, and 6b denotes its CCD (light receiving element). The position angle of the orientation flat of the wafer 40 and the presence or absence of eccentricity are detected based on the output of the CCD 6b. Is done.

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

After the carrier 41a in which the wafer 40 is stored and the empty carrier 41b are set on the mounting tables 2a and 2b, respectively, an illumination optical system to be used is selected by the control unit 7 (here, bright field illumination). It is assumed that the optical system has been selected), and an OK button is pressed to instruct the apparatus to start operation. Further, the control circuit 30 drives the air tweezers 3 by the air tweezers moving mechanism 31 and
The wafer 40 is taken out from a and transferred onto the stage 5. The position of the wafer 40 placed on the stage 5 is detected by the orientation flat detector 6, and the stage rotation mechanism 35 is driven based on the detection signal so that the ID number 50 is positioned on the optical axis L1. The stage 5 is rotated.

When the wafer 40 is placed at a predetermined position, the control unit 30 first turns on the illumination light source 11 to illuminate the wafer surface including the ID number. The specularly reflected light from the wafer surface illuminated by this illumination light is transmitted to the CCD via the above-described optical system.
The light enters the camera 18. The output signal from the CCD camera 18 is digitally converted by the A / D converter 38, and then is taken into the frame memory 36a as a bright field image. The bright field image captured in the frame memory 36a is sent to the image processing unit 37. The image processing section 37 obtains character recognition data of ID number 50 based on the image data.

When the wafer 40 is manufactured by CMP or the like, it becomes difficult to obtain data for character recognition from the reflected light on the surface. In this case, the control unit 7 selects the infrared light projecting optical system, and performs the same operation as described above. When the infrared light projecting optical system is selected, the control unit 30 turns on the light source 20 for infrared light illumination and projects the wafer 40 from the back surface.

The light emitted from the light source 20 illuminates the back surface of the wafer 40 and is transmitted to the front surface of the wafer 40, and a part of the light is incident on the CCD camera 18. The output signal from the CCD camera 18 is converted into a digital signal by the A / D converter 38, and is taken into the frame memory 36 as a transmission image in synchronization with the lighting of the light source 20. The transmitted image data taken into the frame memory 36 is sent to the image processing unit 37. The image processing section 37 obtains character recognition data of ID number 50 based on the image data.

As described above, when the ID number is difficult to recognize with the reflected light (bright-field illumination light and dark-field illumination light) on the front surface of the wafer, character recognition can be performed by transmitted light from the back surface of the wafer. On the other hand, if the reflected light on the wafer surface can be used to increase the character recognition rate rather than using the transmitted light from the back surface, switching to an illumination optical system using reflected light is possible. I just need. Such selection can be made appropriately depending on the state of the wafer to be recognized.

Further, by using the infrared light projecting optical system, not only the ID number stamped on the wafer surface but also the character recognition of the ID number stamped on the back surface of the wafer can be dealt with.

[0037]

As described above, according to the present invention, the character recognition rate can be improved even if the wafer is subjected to CMP by irradiating the illumination light from the back surface of the wafer and using the transmitted light. .

[Brief description of the drawings]

FIG. 1 is an external view of an apparatus according to an embodiment.

FIG. 2 is a diagram showing details of a wafer 40;

FIG. 3 is a schematic view of a state in which a wafer 40 is mounted on a stage 5 when viewed from above and from the side.

FIG. 4 is a schematic configuration diagram showing an outline of an optical system of the character recognition unit 10 and its periphery.

FIG. 5 is a block diagram showing a control system.

[Explanation of symbols]

 Reference Signs List 1 apparatus main body 5 stage 7 control unit 8 monitor 10 character recognition unit 11 light source 13 light source 18 CCD camera 20 light source 22 shielding plate 30 control circuit 36 frame memory 37 image processing unit 38 A / D converter 40 wafer

Claims (6)

[Claims] 1. A semiconductor wafer character recognition device for recognizing identification characters formed on a semiconductor wafer, comprising: an infrared light projecting optical system for projecting infrared light onto a region of the semiconductor wafer containing the identification characters; An imaging optical system having an imaging element for receiving infrared light transmitted through a region including the identification character by the projection of the infrared light projection optical system; and an identification character processing the image captured by the imaging element. Character recognition means for recognizing
A character recognition device for a semiconductor wafer, comprising: 2. The character recognition device for a semiconductor wafer according to claim 1, wherein the infrared light projecting optical system includes a light source that emits broadband infrared light. 3. The semiconductor wafer character recognition device according to claim 1, further comprising shielding means for cutting infrared light that does not pass through the inside of the semiconductor wafer from entering the image pickup device. Character recognition device. 4. The shielding means according to claim 3, wherein the shielding means is a shielding member disposed between the light source and the wafer and arranged at a position near the identification character for shielding a light projecting through the inside of the semiconductor wafer. A character recognition device for a semiconductor wafer, comprising: 5. The semiconductor wafer character recognition device according to claim 4, wherein the imaging optical system is disposed on a front surface side of the semiconductor wafer, and the apparatus further comprises a surface of the semiconductor wafer on which the identification characters are formed. A visible light projection optical system that projects visible bright field illumination light or visible dark field illumination light to the side, and a projection by the visible light projection optical system and a projection by the infrared projection optical system. A character recognition device for a semiconductor wafer, comprising: switching means for selectively switching. 6. A light projecting optical system for projecting infrared light to a region including an identification character of a semiconductor wafer, a light receiving optical system for receiving a light beam of the infrared light transmitted through the semiconductor wafer, and the semiconductor wafer An optical unit for character recognition, comprising: shielding means for cutting the incidence of infrared light that does not pass through the inside of the light receiving optical system.