JP2003092338A - Detector for semiconductor wafer housing state - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detector which is capable of detecting abnormality in which plural wafers are stacked in a wafer housing container provided with a wafer housing slot, and has an improved detection rate of abnormalities such as cracks on a wafer or an obliquely inserted wafer. SOLUTION: The detector is provided with a means for projecting light beams 211a, 212a and 213a from a direction of the side of a wafer (W) housed in the wafer housing container (F), a means for receiving reflected light beams 211b, 212b and 213b, a means for measuring the quantity of the beams, a means for moving the beam projecting means and the beam receiving means along the slot of the wafer housing container, and a means for creating and recording correlated data of the quantity of the received beams by correlating the positions of the beam projecting means and the reflected beam receiving means with the quantity of the reflected beams.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection device for detecting and measuring the storage state of a wafer stored in a wafer storage container having a storage slot for placing a semiconductor wafer (hereinafter referred to as a wafer). In particular, the present invention relates to improvement of a method of measuring the presence or absence of a wafer and a method of detecting a position and an abnormality of a wafer.

[0002]

2. Description of the Related Art An example of a conventional wafer detection device is
Wafer is FOUP (Front Opening Un)
An explanation will be given taking as an example a case where the cassette is stored in an if Pod cassette.

FIG. 12 is a schematic diagram showing the manner of detection and measurement performed by a conventional wafer detection apparatus.
3 and FIG. 14 respectively show the mounting position of the sensor for measuring the presence or absence of the wafer in the conventional wafer detection device on the upper surface of the wafer,
It is the figure seen from the wafer side surface. FIG. 15 is a flow chart showing the procedure of the detection and measurement method of the conventional wafer detection device.

As shown in FIG. 12, a conventional wafer detection apparatus has a computer 120 which operates under program control.
And motor shafts 122a and 122b installed along the slots of the FOUP cassette (F) (shelves that hold peripheral portions of one main surface of the wafer), and motors for rotating the motor shafts 122a and 122b. 121, a sensor bracket 123a that is attached to the motor shaft 122a and moves by its axis rotation, a sensor bracket 123b that is attached to the motor shaft 122b and moves by its axis rotation, and is housed in a FOUP cassette attached to the sensor bracket 123a. Wafer (W)
The light emitting side sensor 101a which emits the light beam 111 from the side surface direction of the light beam 111 and the light beam 111 emitted from the light emitting side sensor 101a attached to the sensor bracket 123b.
It is configured to include a light-receiving side sensor 101b that receives light, and a sensor amplifier 101c that measures the amount of light received by the light beam 111 and sends the measured value to the computer 120.

Light emitting side sensor 101a and light receiving side sensor 1
As shown in FIGS. 13 and 14, 01b is attached to the sensor bracket 123a and the sensor bracket 123b so that the beam light travels along the wafer surface in a portion where the slot (S) of the FOUP cassette (F) does not have a frame. There is. In addition, the sensor bracket 123a and the sensor bracket 12
Since 3b moves at the same pitch in accordance with the movement of the motor 121, the light emitting side sensor 101a and the light receiving side sensor 101
The relative position of b is always constant.

The computer 120 issues a command to the motor 121. In addition, the command from the computer 120 controls the positions of the light emitting side sensor 101a attached to the sensor bracket 123a and the light receiving side sensor 101b attached to the sensor bracket 123b, and the light emitting side sensor 101a and the light receiving side sensor 101b. The function of creating and recording the association data of the received light amount by associating the position of the side sensor 101b with the received light amount of the sensor amplifier 101c, and the association data 2 to clarify the region where the light beam 111 is transmitted and the region where the light beam 111 is blocked are set. And associated data binarization means for converting into digitized data.

Further, the computer 120 registers the reference position of the wafer when the wafer is accommodated in the slot of the FOUP cassette. From the reference position of the wafer and the binarized data, the wafer is obliquely inserted, and the wafer crack is abnormal. And an anomaly analysis means for detecting the above, and a mapping data analysis means for calculating mapping data of the wafer slot position from the wafer reference position and the binarized data.

With this configuration, when the light emitting side sensor 101a and the light receiving side sensor 101b are moved and the light amount of the beam light 111 received by the light receiving side sensor 101b is measured,
If there is a wafer in the path of 11, the light beam 111 is blocked and the amount of received light approaches zero.
When there is no wafer in the path, the light beam 111 is transmitted and the amount of received light is the maximum value.

Next, a mapping method used in the conventional wafer detecting apparatus having the above structure will be described with reference to FIG. First, the computer 120 operates the motor 121 to move the light emitting side sensor 101a attached to the sensor bracket 123a and the light receiving side sensor 101b attached to the sensor bracket 123b from the top to the bottom of the FOUP cassette. Further, the computer 120 includes a light emitting side sensor 101a and a light receiving side sensor 101.
Each time b is moved, the value of the amount of received light is received from the sensor amplifier 101c, and the associated data of the amount of received light is created and recorded in association with the positions of the light emitting side sensor 101a and the light receiving side sensor 101b (step A1 in FIG. 15).

When the creation and recording of the association data are completed, the association data is binarized to clarify the region where the light beam 111 is transmitted and the light-shielded region (step A2 in FIG. 15).

Next, the binarized data is compared with the reference position of the wafer, and based on the following algorithm (A), the wafer is obliquely inserted into the slot over two or more slots (abnormality). 16), an abnormal wafer crack (FIG. 17) is detected (step A3 in FIG. 15), and slot position mapping data is created (step A4 in FIG. 15).

Algorithm (A) (A-1, A-
2, A-3 and A-4) are as follows. A-1: If there is no light-shielding portion in the range of the reference position of the wafer, there is no wafer at the slot position. A-2: If the light-shielding portion of the light beam exists in the range of the reference position of the wafer, the wafer exists at the slot position. A-3: However, when the light-shielding portion of the beam light is present across the reference positions of the two adjacent wafers, the wafer is obliquely inserted or the wafer cracking is abnormal. A-4: When there is a light-shielding portion other than the range of the reference position of the wafer, there is an abnormality such as damage of the FOUP cassette and inclusion of foreign matter.

[0013]

The first problem is that in the wafer measuring method and the wafer detecting algorithm by the sensor structure of the conventional apparatus, as shown in FIG. 18, two wafers are overlapped in one slot. Even if there is an abnormality in the two stacked sheets, the failure cannot be detected. The reason is that when two wafers are stacked in one slot and when the FOUP cassette or the slot is slightly tilted and the wafer is tilted as a result, the beam light is blocked. This is because there is not much difference. Similarly, even if three or more (plural) wafers overlap one slot, the defect cannot be detected.

The second problem is that in the wafer measuring method and the wafer detection algorithm using the sensor structure of the conventional apparatus, in the detection of a wafer crack, the wafer is only partially damaged as shown in FIG. That is, if the part of the part remains in a state of blocking the light beam, the defect cannot be detected.

Therefore, the first object of the present invention is to provide a FOU.
An object of the present invention is to provide an apparatus capable of detecting an abnormality in stacking a plurality of wafers stored in a P cassette.

A second object of the present invention is to reduce the detection error of an abnormal wafer crack stored in a FOUP cassette.

[0017]

In order to achieve the above object, a feature of the present invention is to detect and measure a storage state of a wafer stored in a wafer storage container having a slot for placing a wafer. In the apparatus, means for projecting a beam of light from a side surface direction of the wafer accommodated in the wafer container, means for receiving a reflected light of the beam of light,
A means for measuring the light quantity of the light beam received by the means for receiving the reflected light of the light beam, a means for projecting the light beam and a means for receiving the reflected light of the light beam are provided along the slot of the wafer container. A detection device for a wafer storage state having a plurality of sets of moving means.

Here, the detection device is further associated with the positions of the means for projecting the light beam and the means for receiving the reflected light of the beam and the received light amount of the reflected light of the beam to associate the received light amount. It is preferable to have means for creating and recording data. In this case, further, an abnormality analysis unit for detecting an abnormality of a plurality of the wafers, the oblique insertion of the wafers, and a crack of the wafer from the association data, and mapping data of the slot position of the wafer from the association data. And mapping data analysis means for calculating.

The means for moving is a motor shaft,
A sensor bracket that is coupled to the motor shaft and moves along the slot by rotation of the motor shaft, and a pair of the light projecting unit and the light receiving unit is attached to each sensor bracket. preferable.

Further, the means for projecting the light, the means for receiving the light, and the means for moving are provided so as to face a portion where the side surface of the wafer is exposed without the frame of the slot for forming the slot inside. That is, preferably, a plurality of them can be provided.

The wafer storage container has a diameter of 200.
It may be a wafer cassette for placing semiconductor wafers of mm or more. Also in this case, the wafer cassette may be a FOUP cassette.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a wafer detecting apparatus of the present invention will be described by taking a case where a wafer is stored in a FOUP cassette as an example. FIG. 1 (A) is a perspective view schematically showing how a wafer detection state of a wafer detecting apparatus according to an embodiment of the present invention is detected and measured, and FIG. 1 (B) shows its measurement system. FIG.

FIG. 2 and FIG. 3 are views of the mounting position of a sensor for measuring the presence / absence of a wafer in the wafer detection apparatus according to the embodiment of the present invention, as viewed from the top surface and the side surface of the wafer. FIG. 4 is a flow chart showing the procedure of the detection and measurement method of the wafer detection device of the present invention.

Referring to FIG. 1, a wafer detecting apparatus according to an embodiment of the present invention is implemented in a computer 220 operated by program control and a slot of a FOUP cassette (for holding a peripheral portion of one main surface of a wafer). A motor shaft 222a, a motor shaft 222b, and a motor shaft 222c installed along a plurality of shelves arranged in the axial direction with the same shape and pitch, and the motor shaft 222a and the motor shaft 222.
b and the motor 22 for rotating the motor shaft 222c
1, a sensor bracket 223a attached to the motor shaft 222a and moved by the rotation of the shaft, and a motor shaft 2
The sensor bracket 223b mounted on the motor shaft 222b and moved by its shaft rotation, and the sensor bracket 22 mounted on the motor shaft 222c and moved by its shaft rotation.
3c and F attached to the sensor bracket 223a.
A light projecting side sensor 201a for projecting a beam light 211a from the side surface direction of the wafer housed in the OUP cassette;
The light receiving side sensor 201b which is attached to the sensor bracket 223a and receives the beam reflected light 211b reflected by the beam light 211a hitting the wafer side surface, and the light receiving amount received by the light receiving side sensor 201b are measured, and this value is sent to the computer 220. The sensor amplifier 201c and the beam light 212 is attached to the sensor bracket 223b from the side surface of the wafer housed in the FOUP cassette.
a light emitting side sensor 202a for emitting a, a light receiving side sensor 202b attached to a sensor bracket 223b for receiving the beam reflected light 212b reflected by the beam light 212a hitting the side surface of the wafer, and a light receiving side sensor 202b.
The amount of light received by the computer 220 is measured, and this value is calculated by the computer 220.
To send to the sensor amplifier 202c and the sensor bracket 22
3c, a light-projecting side sensor 203a that projects a beam light 213a from a side surface direction of a wafer housed in a FOUP cassette, and a beam reflection that the beam light 213a is attached to a sensor bracket 223c and reflected on the wafer side surface. The light-receiving side sensor 203b receives the light 213b, and the sensor amplifier 203c that measures the amount of light received by the light-receiving side sensor 203b and sends the measured value to the computer 220.

The computer 220 issues a command to the motor 221. In addition, a command from the computer 220 includes a light emitting side sensor 201a and a light receiving side sensor 201b attached to the sensor bracket 223a, and a light emitting side sensor 202 attached to the sensor bracket 223b.
a and the light receiving side sensor 202b, and the sensor bracket 22
The function of controlling the positions of the light emitting side sensor 203a and the light receiving side sensor 203b attached to the 3c, the positions of the light emitting side sensor 201a and the light receiving side sensor 201b, and the light receiving amount of the sensor amplifier 201c are associated with each other to obtain association data. A function of creating and recording, a function of creating and recording association data by associating the positions of the light emitting side sensor 202a and the light receiving side sensor 202b with the light receiving amount of the sensor amplifier 202c, and the light emitting side sensor 203a and the light receiving side sensor 203.
It has a function of creating and recording by associating the position of b with the amount of light received by the sensor amplifier 203c.

Further, the computer 220 registers the reference position of the wafer when the wafer (W) is accommodated in the slot of the FOUP cassette (F), and a plurality of wafers are superposed from the reference position of the wafer and the association data. It has a data analysis means for detecting an abnormality of a wafer oblique insertion and a wafer crack, and an association data analysis means for calculating mapping data of a wafer slot position from the wafer reference position and the association data.

As shown in FIGS. 2 and 3, the light projecting side sensor 201a is designed so that the beam light 211a is directed toward the center of the wafer around the wafer (W) without the frame of the slot (S) of the FOUP cassette (F). Is attached to. Further, the light emitting side sensor 201a is attached so that the beam light 211a strikes the wafer side surface at an angle of θ ° with respect to a plane parallel to the wafer surface.

The light receiving side sensor 201b is mounted on the opposite side of the light projecting side sensor 201a with the plane parallel to the wafer surface as a reference, with the light receiving direction facing the wafer center. Also,
It is attached at a light-receiving angle of −θ ° with respect to a plane parallel to the wafer surface.

Light emitting side sensor 202a and light emitting side sensor 2
03a also has beam lights 212a and 213a on a portion of the FOUP cassette where there is no slot frame, like the light emitting side sensor 201a.
Is oriented so as to face the center of the wafer and is attached to the side surface of the wafer at an angle of θ ° with respect to a plane parallel to the wafer surface. Further, the light-receiving side sensor 202b and the light-receiving side sensor 203b also have a light-receiving direction on the opposite side of the light-projecting side sensor 202a and the light-projecting side sensor 203a with respect to the plane parallel to the wafer surface, like the light-projecting side sensor 201b. It is attached so that the light receiving angle is −θ ° with respect to the plane parallel to the wafer surface with the center facing.

The light emitting side sensor 201a and the light receiving side sensor 201b, and the light emitting side sensor 202a and the light receiving side sensor 20.
2b, the light emitting side sensor 203a and the light receiving side sensor 203b are separately attached so as to measure different wafer side surfaces.

When the light emitting side sensor and the light receiving side sensor are moved with this structure and the light amount of the light beam received by the light receiving side sensor is measured, the light amount is as follows. (A) When the light beam hits a portion of the side surface of the wafer that is perpendicular to the wafer surface, the light amount of the reflected light beam received by the light-receiving side sensor becomes the strongest (FIG. 5). (B) The farther the angle of the beam light from the side surface of the wafer is from the right angle with the wafer surface, the weaker the light amount of the beam reflected light received by the light receiving side sensor is (FIG. 6). (C) When the light beam hits the wafer surface, the light amount of the light beam reflected by the light-receiving side sensor becomes zero (FIG. 7). (D) When the beam light does not hit the wafer, the light amount of the beam reflected light received by the light receiving side sensor becomes zero (FIG. 8).

Further, since the side surface of the wafer has chamfered portions at both ends, when the amount of beam reflected light received by the light receiving side sensor on one wafer is measured, the change in the amount of received light is shown in FIG. It becomes like. Further, when the light receiving amount of the beam reflected light received by the light receiving side sensor is measured in a state where the two wafers are overlapped, the change in the light receiving amount is shown in FIG.
It becomes like. From this, the following can be said regarding the relationship between the amount of received beam reflected light and the slot position of the wafer. (E) The amount of received beam reflected light is highest at the central portion of the wafer and low at both ends of the wafer (FIG. 9). (F) When the amount of received beam reflected light is zero, no wafer exists in that region (FIG. 9). (G) When two wafers are overlapped, there is a valley in the amount of received light between the wafers (FIG. 10).

Even when there is an error in the distance from the side surface of the wafer housed in the FOUP cassette to the light emitting side sensor and the light receiving side sensor, the beam light has a width as shown in FIG. Within the range, it is possible to receive the beam reflected light that hits the side surface of the wafer. In this case as well, the total amount of received light decreases, but peaks and valleys of the amount of received light occur, so the same can be said as from (a) to (g) above.

The wafers stored in the FOUP cassette are positioned by abutting the FOUP cassette, and the above error is within a range that can be dealt with by the beam width of a general sensor.

Next, a method of detecting and measuring the wafer placement state by the wafer detecting apparatus of the embodiment of the present invention having the above structure will be described.

First, the computer 220 issues a command to the motor 221, and the light emitting side sensor 201a and the light receiving side sensor 201b mounted on the sensor bracket 223a are
The light emitting side sensor 202a and the light receiving side sensor 202b attached to the sensor bracket 223b, and the light emitting side sensor 2 attached to the sensor bracket 223c.
03a and the light-receiving side sensor 203b are moved downward from the top of the FOUP cassette.

Further, the computer 220 uses the light emitting side sensor 2
01a, the light receiving side sensor 201b, and the light emitting side sensor 202a
And the light receiving side sensor 202b, and the light emitting side sensor 203a and the light receiving side sensor 203b are moved every time the sensor amplifier 20 is moved.
1c, sensor amplifier 202c, and sensor amplifier 203
The value of the amount of received light is received from c and the positions of the light emitting side sensor 201a and the light receiving side sensor 201b and the sensor amplifier 201c are received.
Light receiving amount, light emitting side sensor 202a and light receiving side sensor 20
2b and the amount of light received by the sensor amplifier 202c, and the relation between the positions of the light emitting side sensor 203a and the light receiving side sensor 203b and the amount of light received by the sensor amplifier 203c are created and recorded (step in FIG. 4). B1).

When the creation and recording of the association data are completed, the computer 220 compares the individual association data with the wafer reference position, and based on the following algorithm (B), stacks a plurality of wafers, obliquely inserts wafers,
Abnormality of wafer crack is detected (step B2 in FIG. 4) and slot position mapping data is created (step B3 in FIG. 4).

Algorithm (B) (B-1, B-
2, B-3, B-4, B-5 and B-4 ') are as follows. B-1: If the beam reflected light is not detected in the range of the reference position of the wafer, there is no wafer at the slot position. B-2: When the beam reflected light is detected within the range of the reference position of the wafer, the wafer exists at the slot position. B-3: When two or more peak values of the beam reflected light are detected within the range of the reference position of one wafer, an abnormality of stacking a plurality of wafers has occurred (when there are two peak values, it is 2 If three sheets are stacked, three sheets will be stacked, and if n locations will be stacked, n sheets will be stacked.) B-4: When the beam reflected light is detected by one light receiving side sensor and the beam reflected light is not detected by the other two light receiving side sensors within the range of the reference position of the same wafer, or when the beam is detected by the two light receiving side sensors When the reflected light is detected and the beam reflected light is not detected by the other one light receiving side sensor, the wafer is obliquely inserted or the wafer is broken. B-5: When the beam reflected light is detected outside the range of the reference position of the wafer, an abnormality such as breakage of the FOUP cassette or mixing of foreign matter has occurred.

The above embodiment has been described by using an example in which there are three sets of the light emitting side sensor, the light receiving side sensor, the sensor amplifier, the sensor head and the motor shaft. By setting 4 to the following B-4 ', it is possible to handle all cases of two or more sets. B-4 ′: When the beam reflected light is detected by one light receiving side sensor and the beam receiving light is not detected by any one of the other light receiving side sensors within the range of the reference position of the same wafer, the wafer is obliquely inserted, Or, an abnormality of wafer crack has occurred.

In the above embodiment, the wafer storage container is described as an example of a FOUP cassette, but this storage container has a diameter of 200 mm or more, for example, 20 wafers.
The present invention is suitably applied to any wafer storage container having a wafer storage slot, such as a wafer cassette for storing 0 mm wafers or 300 mm wafers.

[0042]

The first effect of the present invention is to perform wafer mapping by detecting the peak value of the beam reflected light,
It is possible to detect an anomaly in which multiple wafers are stacked in a wafer cassette, and if this anomaly cannot be detected and subsequent processing is continued, it is expected that the wafer will be damaged or scattered. That is, it is possible to prevent deterioration of the device quality due to the above.

The second effect of the present invention is to detect the wafers from a plurality of directions, so that it is possible to detect abnormalities in the oblique insertion of the wafer and abnormalities in the cracking of the wafer, which are also possible in the conventional technique. Abnormality can be detected even if a wafer is cracked in which only a part of the wafers stored in the cassette is damaged. If this abnormality cannot be detected and subsequent processing is continued, the wafer is expected to occur. That is, it is possible to prevent the deterioration of the device quality due to the damage and scattered wafers.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a detection device according to an embodiment of the present invention.

FIG. 2 is a top view showing how to install a sensor in the detection device according to the embodiment of the present invention.

FIG. 3 is a side view showing how to install the sensor in the detection device according to the embodiment of the present invention.

FIG. 4 is a flowchart showing a procedure of a method for detecting and measuring a wafer storage state in the detection device according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating a relationship between a wafer side surface angle and a light receiving state in the detection device according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating a relationship between an angle of a wafer side surface and a light receiving state in the detection device according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating a relationship between an angle of a wafer side surface and a light receiving state in the detection device according to the embodiment of the present invention.

FIG. 8 is a diagram illustrating a relationship between a wafer side surface angle and a light receiving state in the detection device according to the embodiment of the present invention.

FIG. 9 is a diagram showing a result of measuring the amount of received light with respect to one wafer in the detection device according to the embodiment of the present invention.

FIG. 10 is a diagram showing a result of measuring the amount of received light when two wafers are stacked in the detection apparatus according to the embodiment of the present invention.

FIG. 11 is a diagram illustrating how light is received depending on the distance from the sensor to the side surface of the wafer in the detection device according to the embodiment of the present invention.

FIG. 12 is a configuration diagram showing a conventional detection device.

FIG. 13 is a top view of how to install a sensor in a conventional detection device.

FIG. 14 is a side view showing how to install a sensor in a detection device of the related art.

FIG. 15 is a flowchart showing a procedure of a method for detecting and measuring a wafer storage state in a conventional detection device.

FIG. 16 is a schematic diagram for explaining the state of the wafer diagonally facing in the detection device of the related art.

FIG. 17 is a schematic diagram for explaining a state of a wafer crack in a conventional detection device.

FIG. 18 is a schematic diagram for explaining detection of an abnormal state of stacking of a plurality of wafers and wafer inclination in a detection device of the related art.

FIG. 19 is a schematic diagram for explaining a state of a wafer crack in a conventional detection device.

[Explanation of symbols]

101a Light emitting side sensor 101b Light receiving side sensor 101c sensor amplifier 111 beam light 120 computers 121 motor 122a motor shaft 122b motor shaft 123a Sensor bracket 123b sensor bracket 201a Light emitting side sensor 201b Light receiving side sensor 201c sensor amplifier 202a Light emitting side sensor 202b Light receiving side sensor 202c sensor amplifier 203a Emitter side sensor 203b Light receiving side sensor 203c sensor amplifier 211a beam light 211b Beam reflected light 212a beam light 212b Beam reflected light 213a beam light 213b Beam reflected light 220 computers 221 motor 222a Motor shaft 222b Motor shaft 222c motor shaft 223a Sensor bracket 223b Sensor bracket 223c sensor bracket W wafer F FOUP cassette S slot

Claims (6)

[Claims] 1. A detection device for detecting and measuring a storage state of a semiconductor wafer stored in a wafer storage container provided with a slot for placing a semiconductor wafer, wherein a side surface of the semiconductor wafer stored in the wafer storage container. Means for projecting the light beam from a direction, means for receiving the reflected light of the light beam, means for measuring the light amount of the light beam received by the means for receiving the reflected light of the light beam, and the light beam A semiconductor wafer storage state detection device comprising a plurality of sets of means for projecting light and means for receiving the reflected light of the beam along a slot of a wafer storage container. 2. The detection device is further associated with the positions of the means for projecting the light beam and the means for receiving the reflected light of the beam and the received light amount of the reflected light of the beam, to associate data of the received light amount. 2. The semiconductor wafer storage state detection device according to claim 1, further comprising means for creating and recording the. 3. The detection device further comprises abnormality analysis means for detecting a plurality of semiconductor wafers stacked from the association data, oblique insertion of the semiconductor wafers, and cracks in the semiconductor wafer, and the association data. 3. The semiconductor wafer storage state detection device according to claim 2, further comprising: mapping data analysis means for calculating mapping data of the slot position of the semiconductor wafer. 4. The means for moving comprises a motor shaft and a sensor bracket which is coupled to the motor shaft and moves along the slot by rotation of the motor shaft, and the means for projecting light to each sensor bracket. The semiconductor wafer storage state detection device according to claim 1, further comprising a pair of means for receiving light. 5. The means for projecting light, the means for receiving light, and the means for moving are opposed to a position where a side surface of the semiconductor wafer is exposed without a frame of the slot for forming the slot inside. The semiconductor wafer storage state detection device according to claim 1, wherein the detection device is provided. 6. The semiconductor wafer storage state detection device according to claim 5, wherein a plurality of the light projecting means, the light receiving means, and the moving means are provided.