JP2003282675A - Wafer mapping device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer mapping device that surely detects an abnormally housing state. <P>SOLUTION: This wafer mapping device inspects whether a wafer is normally housed or not in a wafer cassette 10 that houses a wafer 1 with a specified interval. The device comprises a light source 22 of a wide wavelength band that lights an end surface of the wafer, a projection optical system 24 that projects an image of the end surface of the wafer, an imaging device 25 that captures the projected image of the end surface of the wafer, a moving means 11 that causes the imaging device relative movement for an array direction of the wafer, and an image processor 26 that processes an output signal of the imaging device to detect a position of the end surface of the wafer. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer mapping device for inspecting whether a semiconductor wafer is normally accommodated in a wafer cassette.

[0002]

2. Description of the Related Art As shown in FIG. 1, a plurality of semiconductor wafers 1 used in a semiconductor manufacturing process are supplied to various kinds of processing equipment in a state where they are accommodated in a wafer cassette 10 and are fed one by one from the wafer cassette. After taking out and processing, the wafer cassette is returned to the inside of the wafer cassette, and the wafer cassette is collected when all the wafers in the wafer cassette have been processed.
The wafer handler automatically takes out and returns the wafer from the wafer cassette. Loading of wafers is performed assuming that a predetermined number of wafers are stored at a predetermined position in the wafer cassette.

The placement of the wafer 1 in the wafer cassette 10 may be performed manually or automatically. In any case, due to a work error, an apparatus error, a warp of the wafer, or the like, there may occur an abnormal accommodation in which the accommodation is not performed in a normal state. FIG. 2 is a diagram showing an example of an abnormal accommodation state. FIG. 2A shows a state in which there is a slot in which a wafer is not accommodated, and FIG. 2B shows a state in which two wafers are accommodated in one slot in an overlapping manner.
(C) shows a state in which one wafer is accommodated obliquely. The abnormal containment state does not always occur alone, but two or more abnormal containment states may occur in combination. Also,
When overlapping, the number of wafers is not limited to two, and three or more wafers may overlap.

As described above, in each process of the semiconductor manufacturing process, it is assumed that a predetermined number of wafers are stored in a predetermined position in the wafer cassette, and the abnormal storage state as shown in FIG. When this occurs, normal processing cannot be performed, and all the chips formed on one or more wafers may be defective. When such a problem occurs, the yield is significantly reduced.

Therefore, it is inspected whether or not the wafer is normally accommodated in the wafer cassette, and an apparatus therefor is called a wafer mapping apparatus. The wafer mapping device is realized as a single device and may be used alone, but may be provided in a device used in a semiconductor manufacturing process.

FIG. 3 is a diagram showing a general structure of a conventional wafer mapping apparatus. Reference numeral 13 is a proximity sensor, and the light output from the light source 14 such as a semiconductor laser or an LED is converged on the detection position by the lens 15, and the reflected light at the detection position is converged on the light receiving element 17 by the lens 16.
In this case, the inspection is performed by setting the positional relationship so that the end surface of the wafer 1 becomes the detection position. The light receiving element 17 outputs a large signal because the light reflected by the end face is emitted when the end face of the wafer exists, and the signal becomes small because the light is not emitted when the end face of the wafer does not exist. A moving member 12 provided with the proximity sensor 13 on the feed screw 11.
And the proximity sensor 13 is moved at a constant speed in the direction perpendicular to the surface of the wafer 1, that is, in the direction in which the wafers are arranged, the light receiving element 17 is placed at a position corresponding to the end face of the wafer.
Output changes. In this way, the presence / absence and the position of the end face of the wafer are detected.

[0007]

In the conventional wafer mapping device using the proximity sensor as described above, the light beam is focused on the detection position, so that a semiconductor laser or an LED which can be easily focused is used as the light source. Semiconductor laser and LE
D outputs monochromatic light having a narrow spectral width. There are various types of wafers 1, each having different spectral reflectance. For example, a silicon wafer has a similar reflectance over a wide wavelength range, but a compound semiconductor wafer has a low reflectance and a different spectral reflectance. Therefore, when a semiconductor laser or LED is used as a light source, there is a problem that the detection sensitivity of the proximity sensor greatly varies depending on the type of wafer, and there is a problem that the detection sensitivity of the proximity sensor must be set depending on the type of wafer. It was Also,
Depending on the type of wafer, the reflectance may be low, which may cause a problem that the end face cannot be detected with sufficient accuracy.

Further, when a semiconductor laser is used as a light source, the influence on the human eye becomes a problem when the laser beam is mistakenly seen depending on the class classified by the output of the laser used. It is necessary to take safety measures and there is a problem that the cost becomes high.

As a wafer mapping apparatus which does not cause the above problems, there is a transmission method for detecting whether or not the light beam is blocked by the wafer, but there is a problem that the structure is complicated and the cost is high. is there.

The present invention solves the above problems,
An object of the present invention is to realize a wafer mapping device that can reliably detect an abnormal accommodation state.

[0011]

In order to achieve the above object, the wafer mapping apparatus of the present invention uses a wide wavelength band light source such as a white light source as an illumination light source, and the end faces of at least two wafers as light receiving elements. It is characterized by using a one-dimensional image sensor (linear sensor) or a two-dimensional image sensor (area sensor) capable of simultaneously detecting the images.

That is, the wafer mapping apparatus of the present invention is a wafer mapping apparatus for inspecting whether the wafers are normally accommodated in the wafer cassette which accommodates the wafers at a predetermined interval, and illuminates the end surface of the wafer. An illumination light source in a wide wavelength range, a projection optical system that projects an image of the end surface of the wafer, an imaging device that captures a projected image of the end surface of the wafer, and the imaging device relative to the array direction of the wafer. It is characterized by comprising a moving means for moving and an image processing section for processing the output signal of the image pickup device to detect the position of the end face of the wafer.

According to the present invention, a light source in a wide wavelength range such as a white light source is used as an illumination light source, and a one-dimensional image sensor or a two-dimensional image sensor used as an optical element also has a wide wavelength sensitivity range. Even if the spectral reflectance differs depending on the type, it can be detected in any of the detectable wavelength ranges.

Further, since the image is captured by the one-dimensional image sensor or the two-dimensional image sensor, the position and width of the end face can be accurately detected, and the detection accuracy of the abnormal accommodation state of the wafer in the wafer cassette is improved.

It is desirable that a white light source is used as an illumination light source and a replaceable optical filter is provided so that an inspection can be performed at an appropriate wavelength according to the type of wafer.

The image processing unit binarizes the output signal of the image pickup device, detects the interval between adjacent wafers and the width of the end face of each wafer, and determines whether the detected interval and width are within a predetermined range. . If the distance between adjacent wafers is outside the predetermined range, the wafers are missing or obliquely accommodated, and if the width of the end face of the wafer is outside the predetermined range, two or more wafers are overlapped.

The distance between adjacent wafers is the amount of movement when the image pickup devices are moved relative to the arrayed wafers by the moving means so that the end faces of the adjacent wafers are detected at the same position in the image pickup device. To detect from.

[0018]

FIG. 4 is a diagram showing the configuration of a wafer mapping apparatus according to an embodiment of the present invention. As shown,
This device includes a detection head 21 and an image processing & control unit 26.
And a monitor 27. The detection head 21 includes an incandescent lamp 22 having a reflecting mirror, an optical filter 23, a projection lens 24, and a one-dimensional image sensor 25. The light from the incandescent lamp 22 is reflected by the reflecting mirror coated with the multilayer film, passes through the optical filter 23, and is reflected by the optical filter 23.
The end faces of one or more wafers 1 are obliquely illuminated. Although the irradiated light has a wide wavelength range in this embodiment, the material (surface color, reflectance, surface condition) of the wafer cassette 10 to be inspected.
Wafer 1 in consideration of damage to wafers and wafers (photosensitivity, etc.)
The wavelength range of the illumination light is appropriately set by selecting the optical filter to be used according to the state of the end face and the reflectance. The projection lens 24 projects the image of the end surface of the wafer 1 onto the one-dimensional image sensor 25. The one-dimensional image sensor 25 is arranged such that the arrangement direction of the light receiving cells is the arrangement direction of the wafer 1, that is, the direction perpendicular to the surface of the wafer 1, and at least two wafers 1 which are normally accommodated are arranged.
One-dimensional image sensor 2 to capture the image of the end face of the
The projection magnification of the projection lens 24 is set with respect to the length of the light receiving surface of No. 5.

The detection head 21 is attached to a moving member (not shown) provided on the feed screw 11, and is movable in the arrangement direction of the wafers 1. One-dimensional image sensor 25
Output signal is sent to the image processing unit 26, where it is processed to detect the position of the end face of the wafer 1 and inspect whether it is normally accommodated. Further, information about the detected position of the end surface of the wafer 1 is displayed on the monitor 27, or the position information is displayed on the wafer loading / unloading machine.

The image processing section 26 is provided with an input means for inputting setting information, and the wafer cassette 1 to be inspected.
Setting information such as an appropriate position, an appropriate detection width, a binarization parameter, and a gray scale are input according to 0 and the accommodated wafer 1. The image processing unit 26 compares the output signal of the one-dimensional image sensor 25 with the binarization parameter,
After digitizing, it is determined based on these setting information whether the accommodation state of the wafer is normal. The proper position indicates the range of the interval P between adjacent wafers when they are normally housed, and the proper detection width indicates the allowable range of the width of one wafer.

The detection head 21 is sequentially moved to a position where the images of the end faces of the two wafers 1 can be simultaneously captured to generate a binarized signal, and a wafer interval P and a wafer width, which will be described later, are sequentially stored, and are normally stored. If it is not stored normally, it is judged what kind of state it is. In the present embodiment, the feed screw 11 moves the detection head 21 with respect to the wafer cassette 10.
It is also possible to move.

FIG. 5 is a diagram showing an example of a binarized signal obtained by binarizing the output signal of the one-dimensional image sensor 25.
(A) is a binarized signal when the wafer 1 is normally accommodated, and the binarized signal has two pulse-shaped “high” portions, and the interval between the two “high” portions is Each high in P
The widths of the portions are W1 and W2. If normal, the interval P
Is within the range set at the proper position, and the width W1,
W2 is also within the range set by the proper detection width. Interval P
Is the one-dimensional image sensor 25 where the end face of the adjacent wafer is
5, the detection head 21 is moved by the feed screw 11 so as to be detected at the same position in FIG.
(B) is a binarized signal when one wafer 1 is missing, and there is only one "high" portion, and there is no "high" portion that should be at the other position indicated by the broken line. FIG. 5C shows a binarized signal when two wafers 1 are overlapped,
The width of the "high" part is widened or two adjacent "high" parts are detected. FIG. 5D shows a binarized signal when the wafer 1 is inclined, and the interval P ′ between the two “high” portions is different from the normal interval P. Interval P ′ is wafer 1
May be smaller or larger than the interval P depending on which side is inclined. Referring to FIGS. 6 and 7,
The binarized signal when the wafers are accommodated obliquely will be described.

FIG. 6A shows a case where one wafer is accommodated at an angle when the wafer is supported on both sides of the drawing, and reference numerals b to i indicate one-dimensional image sensors. 6B shows an image range, and FIGS. 6B to 6E and 7F to 7H show binarized signals in the image ranges b to h in FIG. 6A. . In the image area, the end faces of two wafers are captured. After the image range b is captured, the wafer is moved vertically by the arrangement pitch of the wafer to capture the image range c, and then the image range is sequentially shifted in the order of the image range d to capture the image.

In the image areas b and f, there is only one "high" portion as shown in FIGS. 6B and 7F, and one wafer is used.
Although it is the same as the case where one sheet is missing, the determination results of other image ranges are also determined, so it is possible to determine whether the sheet is obliquely accommodated or missing.

In the case of (D) and (E) of FIG. 6 and (G) and (H) of FIG. 7, the interval between the two "high" portions is different from the normal interval P, and In C), three "high" parts appear. When such a binarized signal appears, it is understood that there is a wafer accommodated obliquely, and therefore a warning indicating an abnormality is displayed on the monitor 27. In the case of the image range i shown in FIG. 6A, a normal binarized signal is obtained.

As shown in FIG. 6A, when the wafer is supported on both the left and right sides, if it is only detected that the wafer is oblique, the left side position and the image range f as in the image range b-d. It can be detected by capturing only at the center position or the right position like -h. But 1
If the detection head 21 is moved up and down at only one position to capture an image, it is desirable to capture at the central portion. This is because there are two directions in which the wafer is inclined, and in any case, the deviation of the interval is similarly large, so that the determination error is small.

Not only is the detection head 21 moved up and down at one position, but images are captured at a plurality of positions.
The determination may be performed by combining those results.
In this case, not only the determination error is reduced, but also the oblique direction when the object is obliquely accommodated can be detected. However, in this case, the feed screw 11 is attached to the wafer cassette 10.
On the other hand, a mechanism for relatively moving the feed screw 11 in the direction perpendicular to the axis is required and the inspection time becomes long.

FIG. 8 shows a case where the image of the end surface of the wafer is captured by changing the position. The feed screw 11 can be moved in the direction perpendicular to the axis, for example, the position shown by A-C. Then, at each position, the detection head 2 is moved by the feed screw 11.
The operation of moving 1 in the wafer arrangement direction (axial direction of the feed screw) and capturing an image at a predetermined position is repeated. In this case, at the positions shown by B and C, the end face of the wafer becomes oblique with respect to the optical axis of the projection lens 24, and the image value of the end face decreases. Therefore, it is desirable that the direction of the moving member 12 holding the detection head 21 can be changed so that the optical axis of the projection lens 24 is perpendicular to the end surface of the wafer even at the positions B and C. .

Further, in order to accurately capture the image of the end surface of the wafer, the projection lens 24 needs to be focused on the end surface of the wafer, so that the output of the one-dimensional image sensor becomes the sharpest. It is desirable to adjust the detection head 21 for the end face of the wafer.

The three detection heads 21 are connected to A, B and C.
Alternatively, the image of the end surface of the wafer may be simultaneously captured at the three positions. In this case, three detection heads are required and the moving member for holding them needs to be large, which increases the cost, but the inspection time can be shortened as compared with the case where the inspection head is moved to three locations.

Further, in the above embodiment, the end faces of the two wafers are projected onto the one-dimensional image sensor, but the number of elements of the one-dimensional image sensor is sufficiently large and a high resolution image can be obtained. In this case, the end faces of three or more wafers may be projected on the one-dimensional image sensor.

Further, in the above embodiment, the number of detecting heads is two.
Although the image is captured by stopping at the position where the end faces of the wafers are projected onto the one-dimensional image sensor, the image may be captured at a predetermined position while moving the detection head at a constant speed. In this case, in order to accurately detect the width and position of the end face, it is necessary that the movement amount of the detection head during the read cycle of the one-dimensional image sensor is sufficiently small.

Further, although the one-dimensional image sensor is used as the image pickup means in the above embodiment, it is also possible to use a two-dimensional image sensor (area sensor). If a two-dimensional image sensor is used, an image of the end face can be captured with a width equal to or larger than a predetermined width. Can also be detected. However, since the end surface of the wafer is curved, it is not possible to focus on the entire image range, so image processing or the like is necessary.

[0034]

As described above, according to the present invention,
In the wafer mapping device, the abnormal accommodation state can be reliably detected.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a wafer cassette that accommodates semiconductor wafers.

FIG. 2 is a diagram showing an example of an abnormally accommodated state of a wafer in a wafer cassette.

FIG. 3 is a diagram showing a configuration of a conventional example of a wafer mapping device.

FIG. 4 is a diagram showing a configuration of a wafer mapping apparatus according to an embodiment of the present invention.

FIG. 5 is a diagram showing an example of a detection signal in an abnormal accommodation state in the embodiment.

FIG. 6 is a diagram showing a relationship between an image range and a detection signal when there is a wafer accommodated obliquely in the embodiment.

FIG. 7 is a diagram showing a detection signal corresponding to an image range when there is a wafer accommodated obliquely in the embodiment.

FIG. 8 is a diagram illustrating a case where images of three end faces of different wafers are captured.

[Explanation of symbols]

1 ... Wafer 10 ... Wafer cassette 11 ... Feed screw 21 ... Detection head 22 ... Illumination light source 23 ... Optical filter 24 ... Projection lens 25 ... Imaging device (one-dimensional image sensor) 26 ... Image processing unit

Continued front page    F term (reference) 2F065 AA02 AA12 AA22 BB02 CC19                       FF04 GG02 GG24 JJ02 JJ03                       JJ25 JJ26 QQ04                 5F031 CA02 FA01 FA11 JA02 JA04                       JA06 JA13 JA14 JA23 JA25                       JA27 JA32 JA36 LA12

Claims (6)

[Claims] 1. A wafer mapping device for inspecting whether wafers are normally accommodated in a wafer cassette that accommodates wafers at predetermined intervals, and an illumination light source in a wide wavelength range for illuminating an end face of the wafer, A projection optical system for projecting an image of the end face of the wafer; an image pickup device for capturing the projected image of the end face of the wafer; moving means for moving the image pickup device relative to the array direction of the wafer; An image processing unit that processes an output signal of the apparatus to detect the position of the end surface of the wafer. 2. The wafer mapping device according to claim 1, wherein the imaging device is a one-dimensional image sensor. 3. The wafer mapping device according to claim 1, wherein the imaging device is a two-dimensional image sensor. 4. The wafer mapping device according to claim 1, wherein the illumination light source includes a white light source and a replaceable optical filter. 5. The wafer mapping device according to claim 1, wherein the image processing unit binarizes an output signal of the imaging device, and detects an interval between adjacent wafers and a width of an end face of each wafer. Then, the wafer mapping device that determines whether the detected interval and width are within a predetermined range. 6. The wafer mapping device according to claim 5, wherein the image processing units are arranged such that the edge surfaces of adjacent wafers are detected at the same position in the image pickup device. A wafer mapping device for detecting an interval between adjacent wafers based on a moving amount by the moving means when the wafer is moved relative to the wafer.