JPH11106043A - Wafer transfer device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When a wafer position in a cassette is detected using an optical sensor, a light quantity decreases within an operation guarantee period of the optical sensor due to factors other than the average life, and the wafer position is detected. May not be possible. A light-reducing filter that interrupts the optical axis of the optical sensor is provided in the middle of the ascending path of the sensor mechanism and before the wafer is detected by the sensor. The degree of wear (deterioration) is determined. The replacement time is determined according to the degree of wear (deterioration).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer transfer device of a semiconductor manufacturing facility, and more particularly to a wafer transfer device provided with a wafer detection device for detecting the position of a wafer in a storage container for storing the wafer and the presence or absence of the wafer. .

[0002]

2. Description of the Related Art In a semiconductor manufacturing facility, a carry-in / out section for carrying in / out a wafer is provided outside a processing apparatus for performing an essential process (for example, a substrate processing apparatus for performing a process such as plasma etching on a wafer). FIG. 5 shows a schematic layout of the carry-in / out section.

As shown in FIG. 5, a wafer transfer section 2 is provided outside a substrate processing apparatus 1. The wafer transfer unit 2 includes a plurality of cassette mounting tables 5 on which a cassette 4 (storage container) storing the wafer 3 is mounted, and a centering unit 6 provided with a centering unit 6 for detecting an eccentric amount of the wafer 3 and performing alignment. 2a and a relay unit 2b on which a transfer robot 8 for transferring the wafer 3 moves. In the wafer standby section 2a where the cassette mounting table 5 is located, sensor elevating holes 7a and 7b are provided. The relay unit 2b is between the substrate processing apparatus 1 and the wafer standby unit 2a. The transfer robot 8 located at the relay section 2b has a structure capable of moving horizontally between each cassette mounting table 5 and the centering unit 6 and moving up and down from the lowermost part to the uppermost part in the cassette 4. doing. The operation of the transfer robot 8 is controlled by the controller 9.

The transfer robot 8 moves to the front of the cassette 4 facing the substrate processing apparatus 1, takes out the wafer 3, and transfers it to the centering unit 6. The transfer robot 8 takes out the wafer 3 whose center has been aligned by the centering unit 6 again, and transfers it to the substrate processing apparatus 1 from the loading port 1a. Further, the transfer robot 8 takes out the processed wafer 3 from the carry-out port 1b in the substrate processing apparatus 1 and stores it at the original position in the cassette.

The cassette 4 horizontally stores the wafers 3 at predetermined vertical intervals according to the diameter of the wafers by grooves provided on the inner peripheral edge. The transfer robot 8 inserts, for example, a U-shaped hand tip between the wafers in the cassette 4, holds the wafer 3 on the hand, and removes the wafer 3 from the cassette 4. Since the groove provided inside the cassette 4 is provided so as to accommodate the wafer 3 with a margin in the peripheral portion, the wafer 3
Are not strictly stored horizontally, and may be stored slightly obliquely when viewed from the front of the cassette (the side facing the transfer robot 8) depending on the storage state in the previous process. That is, the interval between the wafers is not strictly constant. In order for the transfer robot 8 to insert the hand between the wafers 3 without damaging the wafers 3, it is necessary to detect the storage positions of the wafers 3 in the individual cassettes 4. An outline of a wafer detection device for detecting a wafer position in the cassette 4 will be described below.

FIG. 6 is a schematic view of a wafer detecting device provided below the cassette mounting table. As shown in FIG. 6, the cassette mounting table 5 has a bottom portion 11a and a wall portion 11 of the wafer standby portion 2a.
It is fixed and held by b. A ball screw 12 is provided on the bottom 11a. A pulley 13 provided at a lower end of the ball screw 12 is linked with pulleys 15 and 16 by a belt 14. The pulleys 15 and 16 are provided with an encoder 17 and a motor 18, respectively. A guide rail 19 is provided on the wall 11b of the wafer standby section 2a in a vertical direction, and a guide 20 that can move up and down is connected to the guide rail 19. A plate 21 is fixed to the other end of the guide 20. The ball screw 12 passes through the guide 20. Plates 22 and 23 are fixedly provided at an end of the plate 21, and a light-emitting element 24 and a light-receiving element 25 are provided at upper ends of the plates 22 and 23 so as to face each other. Hereinafter, the light emitting side element 24 and the light receiving side element 25 are collectively called an optical sensor.

The motor 1 is controlled by the controller 9 shown in FIG.
When the drive 8 is driven, the ball screw 12 rotates via the pulley 16 and the belt 14, and the guide 20 moves up and down along the guide rail 19. Then, the plates 21, 22, and 23 (hereinafter, referred to as a sensor holding mechanism) fixed and held by the guide 20 move up and down. When the sensor holding mechanism rises, the light emitting side element 24 provided on the plate 22 projects from the sensor elevating hole 7a (FIG. 5) to the upper surface of the wafer standby part 2a.
Similarly, the light receiving side element 25 provided on the plate 23 projects from the sensor elevating hole 7b to the upper surface of the wafer standby unit 2a. The position (height) of the optical axis of the optical sensor provided on the plates 22 and 23 with respect to the cassette mounting table 5 can be calculated from an output signal from the encoder 17. The optical sensor and the sensor holding mechanism are collectively called a sensor mechanism.

FIG. 7 is a signal waveform diagram of each section for detecting a wafer position based on an output signal of a sensor mechanism in the conventional wafer detecting device shown in FIGS. 5 and 6. In FIG. 6, a plurality (two sets) of optical sensors are provided and the number of optical axes is also two. However, for convenience of explanation, the description will be simplified by using one optical axis.

[0009] As shown in FIG. 7, the reference position of the sensor holding mechanism is set as the drive origin of the motor 18, and the output signals (ON, OF) of the encoder obtained according to the drive of the motor 18 are obtained.
From F), the position of the sensor holding mechanism with respect to the ascending reference position can be obtained. The optical sensor output signal of the sensor mechanism indicates the state of light reception and light shielding. The lower and upper positions of the cassette mounting table 5 and the cassette 4
The position of the wafer held in the memory can be known. In the figure, the wafer position signal is obtained by inverting the optical sensor output signal.
Therefore, the controller 9 can detect the wafer position, the number of wafers, and the presence / absence of wafers by using the wafer position signal.

[0010]

When the position of a wafer is detected by using the above-mentioned transmission type optical sensor, the physical interruption of the optical axis of the optical sensor by the wafer is determined by the output of the light receiving element. I do. Even when the reflection type is used, the light reflected by the wafer is detected by the light receiving element. It is indispensable for the light emitting side element and the light receiving side element to operate normally regardless of the type of the optical sensor in order to detect the wafer position. However, the properties of the optical sensor, particularly the light emitting element, may be degraded for some reason.

For example, there is a case where the optical sensor does not operate normally and the position of the wafer cannot be detected due to a decrease in the light quantity of the light emitting side element. In this case, the transfer robot has to stop,
Since the loading of the wafer into the substrate processing apparatus is stopped, the process is interrupted. The light quantity shortage due to the average life can be dealt with by periodically replacing the optical sensor. However, when there is an electrical overload, static electricity, temperature, humidity, mechanical stress, or the like, the properties of the optical sensor deteriorate earlier than the average life. Depending on the environment in which the optical sensor is used, the amount of light may be reduced even within the life period (within the operation guarantee period).

An object of the present invention is to automatically detect a failure (abnormality) of an optical sensor that detects the position of a wafer stored in a storage container such as a cassette or the number of wafers or the presence or absence of a wafer. An object of the present invention is to provide a wafer transfer device.

Another object of the present invention is to provide a wafer transfer apparatus provided with a control means for judging replacement time according to the degree of wear (deterioration) of the optical sensor.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is characterized by a mounting table on which a storage container for storing a wafer is mounted, and a loading / unloading of the wafer from the storage container. A robot hand, a sensor mechanism having an optical sensor for detecting a wafer in the storage container, and a drive mechanism for vertically moving the sensor mechanism from below the mounting table to the upper surface of the storage container; A wafer detecting means for detecting the position of a wafer in the storage container by moving the optical sensor up and down by the movement of the optical sensor. A light-reducing filter provided at a location where light is blocked, and the degree of wear (deterioration) of the optical sensor is determined based on the output of the light sensor of the light passing through the light-reducing filter, and the replacement time is determined according to the degree of wear (deterioration). In providing the control unit with that function.

Another feature of the present invention is that the control means determines whether or not the total number of wafers stored in the storage container can be detected based on the optical sensor output of the light passing through the neutral density filter, and Another object of the present invention is to have a function of determining replacement of an optical sensor when the total number cannot be detected.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A wafer transfer apparatus according to one embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a view showing an example of a lower portion of a cassette mounting table of a wafer transfer apparatus according to the present embodiment, and the same parts as those of the conventional example shown in FIG.

FIG. 2 is a signal waveform diagram of each part in the present embodiment. As in the conventional example, in FIG. 1, a plurality of (two sets) optical sensors are provided and the number of optical axes is also two. However, for convenience of explanation, the description is simplified by using one optical axis.

As shown in FIG. 1, several types of neutral density filters 30 are provided below the cassette mounting table 5 and above the vertical movement start position of the optical sensor along the movement path of the sensor mechanism. In this embodiment, for example, the dimming rate is 60%,
%, 20% filters 31, 32, 33 are provided in the vertical direction. The numerical value in the neutral density filter 30 indicates the rate of decrease in the amount of light after passing through the filter. The amount of light decreases by 60% when the light passes through the filter 31 with the neutral density of 60%. This shows that the light amount after passing is 40. The larger the numerical value of the extinction ratio, the smaller the amount of light after passing through the filter.

When the sensor holding mechanism (plates 21, 22, 23) ascends with the ascending reference position as the drive origin, as in the conventional example, the optical axes of the optical sensors provided on the plates 22, 23 first cause the dimming rate to be 60%. Then, the light passes through a filter 32 having a light reduction rate of 40% and a filter 33 having a light reduction rate of 20% in this order. Further, when the sensor holding mechanism is raised, the optical axis is blocked by the end face of the cassette mounting table 5, and then the wafer position in the cassette 4 (not shown) is detected above the cassette mounting table 5. FIG. 1 shows a state in which the sensor holding mechanism has risen to above the cassette mounting table 5.

Hereinafter, a procedure for detecting the position of the wafer while confirming the performance of the light emitting side element where the performance is most likely to deteriorate will be described. It is assumed that the optical sensor outputs a binary signal of ON when the output signal of the light receiving side element is above the threshold value and OFF when the output signal is below the threshold value. When the light emission amount of the light emitting side element 24 is normal, the optical sensor output signal is always ON until the light is shielded by the end surface of the cassette mounting table 5 even if the optical axis passes through the filter 30. However, if the light emission amount of the light emitting side element 24 is reduced for some reason, for example, as shown in FIG.
It is turned off when the output signal of the optical sensor passes through the filter 31 having the dimming rate of 60%. If the amount of light emission is slightly reduced, the dimming rate is 40
The optical sensor output signal is turned on when the light passes through the% filter 32 and the filter 33 with the extinction ratio of 20%. That is, it can be seen that light can be received by the light receiving side element 25, but the light emission amount of the light emitting side element 24 is reduced.

The control contents of the controller in the embodiment shown in FIGS. 1 and 2 will be described with reference to FIGS. 3 and 4.

An address number of 1 is set in advance on the cassette mounting table 5 in accordance with the number of the cassette mounting tables 5 (here, three).
The controller performs the following processes in parallel according to the individual cassette mounting tables 5. For convenience of explanation, an explanation will be given taking the address number 1 of the cassette mounting table 5 as an example. In addition, the symbol S in the figure is an abbreviation of a step, and the symbol “S
"1" indicates step 1.

First, address number 1 is selected in "START", and 1 is substituted in next cassette information "NEXT" in step 1. When the next cassette information “NEXT” is 1, it indicates that the cassette 4 can be mounted on the cassette mounting table 5. In step 2, it is determined whether “NEXT = 1”, that is, whether or not the next cassette can be placed.

In step 3, the address number 1 of the cassette mounting table 5 to be worked is stored, and the motor 18 of the corresponding address number, that is, the motor 18 of the cassette mounting table 5 to be worked is driven. The driving of the motor 18 causes the sensor mechanism to move up from the ascending reference position which is the driving origin. In step 4, the optical sensor moves up to the lower surface of the cassette mounting table 5. During this time, the light beam of the optical sensor passes through the neutral density filter.
In step 5, it is determined whether or not the optical sensor output signal at the time of passing through the filter 31 having the dimming rate of 60% is ON. If the optical sensor is ON at the time of passing through the filter 31 having the smallest light amount after passing, it is determined that the optical sensor is operating normally, and the process proceeds to step 6 according to the arrow Y, and the next cassette information “NEX”
Substitute 1 for "T".

Next, the process proceeds to step 7, where the cassette is placed on the cassette mounting table to be worked, and then to step 8. In step 8, the motor 18 is further driven to detect the positions of the lower surface and the upper surface of the cassette mounting table 5, and subsequently, the positions of the first and second wafers 3 from the bottom. The sensor mechanism moves up to the uppermost stage of the loaded cassette 4 and detects all the wafer positions stored in the cassette 4, and then moves down to the ascending reference position which is the driving origin. When the sensor mechanism returns to the driving origin, the operation of the transfer robot 8 is controlled in step 9.
The operation control of the transfer robot 8 in the step 9 is the same as that of the conventional example, and has no direct relation to the present invention, so that the detailed description is omitted. When the processing of all the wafers stored in the cassette 4 is completed in step 10, it is determined that the processing in units of cassettes has been completed, and in step 11, processing from a previous process (not shown) is awaited. Determine. If there are no unprocessed cassettes, a series of processing ends (proceeding to "END"). If there is an unprocessed cassette, the process returns to step 2.

If there is an unprocessed cassette, the process proceeds from step 2 to step 5. If the light quantity of the light emitting side element 24 has decreased to some extent or more, in step 5, the output when passing through the filter 31 having the dimming rate of 60% is turned off, and the process proceeds to "A".

"A" The following contents are shown in FIG. In step 20, the output at the time of passing through the filter 32 having a light reduction rate of 40% is determined. If the output is ON, the process proceeds to step 21 according to the arrow of Y, and the filter 33 having the dimming rate of 20% is used.
Determine the output when passing. If the output is also ON in step 21, the output of the light emitting side element 24 is slightly reduced but the output is low enough not to affect the wafer position detection. "Replacement" is displayed to prompt the operator (operator) for scheduled inspection and maintenance, and "1" is substituted into the next cassette information "NEXT" in step 23 to indicate that the next cassette can be placed. That is, the process returns to step 7 shown in FIG. Proceed to step 11 and return to step 2 again if there is an unprocessed cassette. Next cassette information "NEX
Since "T" is 1, "replacement required" is displayed, but wafers can be processed by mounting a cassette.

When the light emission amount of the light emitting side element further decreases, the output of the light passing through the filter 32 having the light reduction rate of 40% is turned off in step 20, and according to the arrow N, step 31 is performed.
Proceed to. At step 31, "Warning: Replacement required" is displayed and an alarm for warning is given. At step 32, the output when passing through the filter 33 having a dimming rate of 20% is determined.
When the output is ON, the output of the light emitting side element is considerably reduced and does not affect the wafer position detection for one cassette, but may affect the wafer position detection for the next cassette. It is determined that there is, and step 3 is performed according to the arrow of Y.
Go to 3 and substitute 0 for the next cassette information “NEXT”
This indicates that the next cassette cannot be placed. Thereafter, the process returns to "B", that is, step 7 shown in FIG. In steps 7 to 11, the position of the wafer is detected, and the processing is completed for the wafer stored in the currently working cassette.
When the process returns to step 2, the next cassette information "NEXT" is 0, and the process proceeds to step 12. In step 12, it is determined whether or not the optical sensor has been replaced. If the optical sensor has not been replaced, the process proceeds to step 13, in which the cassette mounting table of address number 1 is removed from the work target, and the address number is other than 1 (here, 2 and 2). The processing is performed on the cassette mounting table of 3). When the replacement of the optical sensor is completed, the cassette mounting table of the address number 1 is returned to the work target, and the process returns to step S3.

Referring back to FIG. If the output at the time of passing through the filter 33 having the dimming rate of 20% determined in step 32 is OFF, the process proceeds to step 33 to determine whether or not the replacement of the optical sensor has been completed. If the optical sensor has been replaced, the process proceeds to step 23, and the next cassette information “NEXT” is set to 1
And returns to step 7 shown in FIG. If the replacement of the optical sensor has not been completed, it is determined that the next cassette cannot be placed, and in step 34, 0 is substituted for the next cassette information "NEXT". Return to

As a result of the determination in step 2, step 12
If the optical sensor has not been replaced, the process proceeds to step 13 to remove the cassette mounting table of the address number 1 from the work target and use the cassette mounting tables other than the address number 1 (here, 2 and 3). A wafer transfer process is performed.

In step 20, the extinction ratio is 40%.
If the output after passing through the filter 32 is ON, the output after passing through the filter 33 having a dimming rate of 20% will not normally be OFF in step 21, but if the output is OFF, It is determined that some abnormality has occurred in the neutral density filter, and the process proceeds to step 25 as a filter error in step 24.

In step 25, it is determined whether or not the filter has been replaced. If the filter has been replaced, the process proceeds to step 23. If the filter has not been replaced in step 25, 0 is substituted for the next cassette information "NEXT" in step 26, and the process returns to step C, that is, step 2 shown in FIG.

If the filter has not been replaced, the cassette mounting table having the address number 1 is removed from the work in step 13, and the wafer transfer processing is performed using the cassette mounting tables other than the address number 1 (here, 2 and 3). I do.

In the present embodiment, three types of light-reducing filters are provided, and when the optical axis of the optical sensor is turned off when passing through the filter 31 having a light-reducing rate of 60%, the controller 5 displays the light sensor replacement display. Only when the optical sensor is turned off when passing through the filter 32 with a dimming rate of 40%, the display of the optical sensor replacement is performed, but only one cassette is processed. At that point, the cassette was removed from the work target without placing it.However, a filter other than the above-described light attenuation rate may be used depending on the type and durability of the optical sensor to be used. One type or more types may be used.

If the output signal is OFF when the light passes through the filter 31 having a light reduction rate of 60%, "replacement required" or "warning: replacement required" is displayed in the following steps.
When the output signal is OFF when passing through the 0% filter 32 (the output of the light emitting side element is considerably reduced and does not affect the wafer detection for one cassette, but may affect the wafer detection for the next cassette. As described above, in addition to generating an alarm (warning sound) as described above, the display is made to blink, or when the output signal when the light passes through the filter 33 with the dimming rate of 40% is ON (the output of the light emitting side element). Is slightly reduced, but the output is reduced so as not to affect the wafer detection).

Further, in the present embodiment, the dimming filter is provided so that the optical axis of the optical sensor passes in descending order of the dimming rate due to the elevation of the sensor holding mechanism. However, the order may be changed. In this case, the order of the steps shown in FIGS. 3 and 4 may be changed as needed.

Although the case where the output of the optical sensor is ON / OFF binary has been described, an optical sensor that generates a continuous analog output may be used. In this case, the output of the optical sensor is compared with an appropriate threshold value by the controller, and the above-described O
Signals corresponding to N and OFF may be formed.

As described above, according to the present embodiment,
The provision of the neutral density filter allows the light amount of the optical sensor provided on the cassette mounting table to be detected before the wafer position is detected. The wafer transfer process can be performed using another cassette mounting table without mounting the cassette. In addition, since the replacement of the optical sensor is displayed according to the degree of decrease in the amount of light, the replacement of the optical sensor can be performed systematically, and whether or not to detect the position of the wafer stored in the cassette in accordance with the degree of decrease in the amount of light. Therefore, it is possible to prevent the operation from being stopped during the position detection of the wafer stored in one cassette. Therefore, the processing can be terminated in units of one cassette.

[0040]

According to the present invention, the optical axis of the optical sensor passes through the neutral density filter while the sensor mechanism is being raised and is located below the cassette, and the optical sensor of the optical sensor is based on the light amount of the light beam passing through the neutral density filter. By judging the degree of wear (deterioration) and determining the replacement time according to the degree of wear (deterioration), a failure (abnormality) of the optical sensor is detected and the optical sensor is detected before detecting a wafer in the storage container. It is possible to obtain a wafer transfer device that can be replaced and does not stop the operation of the wafer transfer robot itself or the processing of the substrate processing apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a wafer position detecting device according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram of each part in the embodiment shown in FIG.

FIG. 3 is a flowchart showing control contents of a controller in the embodiment shown in FIGS. 1 and 2;

FIG. 4 is a flowchart showing control contents of a controller in the embodiment shown in FIGS. 1 and 2;

FIG. 5 is a diagram showing a schematic layout of a conventional substrate processing apparatus.

6 is a diagram showing a wafer position detecting means in the substrate processing apparatus shown in FIG.

FIG. 7 is a signal waveform diagram of each part of the wafer detection device in the conventional example shown in FIGS. 5 and 6.

[Explanation of symbols]

1. substrate processing apparatus 1a.
b ... Unloading port 2 ... Wafer transfer unit 2a ... Wafer standby unit 2
b relay unit 3 wafer 4 cassette 5 cassette mounting table 6 centering unit 7a, 7b sensor elevating hole 8 transport robot 9
Controller 11a Bottom 11b Wall 12 Ball screw 13, 15, 16 Pulley 14 Belt 17 Encoder
DESCRIPTION OF SYMBOLS 18 ... Motor 19 ... Guide rail 20 ... Guide 21, 22, 23 ... Plate 24 ... Light emitting side element 25 ... Light receiving side element 30 ... Dimming filter 31 ... Filter with 60% dimming rate 32 ... Filter with 40% dimming rate 33 ... Dimming rate 2
0% filter

Claims (2)

[Claims] A mounting table for mounting a storage container for storing a wafer thereon, a robot hand for loading and unloading a wafer from the storage container,
A sensor mechanism having an optical sensor for detecting a wafer in the storage container, and a drive mechanism for vertically moving the sensor mechanism from below the mounting table to the upper surface of the storage container, and the optical sensor A wafer detecting device for detecting the position of a wafer in a storage container by moving up and down, wherein the optical axis of the optical sensor is blocked at a position before the wafer is detected while the sensor mechanism is being lifted. And a function of judging the degree of wear (deterioration) of the optical sensor based on the output of the optical sensor of the light that has passed through the filter, and judging the replacement time according to the degree of wear (deterioration). A wafer transfer device provided with control means. 2. The wafer transfer device according to claim 1, wherein the control means determines whether or not the total number of wafers stored in the storage container can be detected based on an optical sensor output of light passing through the neutral density filter. And a function of determining whether to replace the optical sensor when the total number of wafers cannot be detected.