JP2003209159A - Wafer detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer detector capable of reliably detecting a wafer irrespective of reduction in an amount of received light of a light-receiving means in a structure of detecting the wafer by comparing the amount of received light of the light-receiving means opposing a light-emitting means with a threshold in a state that a detection arm is moved. <P>SOLUTION: When a threshold setting means 20 is notified of an opening of a detection arm provided with a light-emitting means 15 and a light-receiving means 16 from an arm control means 18, a light-emitting signal is outputted to the light-emitting means 15. Further, a threshold is set by multiplying the amount of received light of the light-receiving means 16 by a predetermined threshold constant. Thus, even if the amount of received light is small due to a fact that the detection arm is not accurately opened at a prescribed position, the threshold is set based on the amount of received light, thereby correctly detecting a wafer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer detection device for detecting a wafer by moving a detection arm so that a light projecting means and a light receiving means are opposed to each other.

[0002]

Conventionally, a wafer transfer device is provided as a device for picking up and transferring one wafer at a time from a wafer cassette accommodating a plurality of wafers. When the wafer is taken out by the apparatus, it is generally performed in advance to confirm whether or not the wafer is actually stored in each stage of the wafer cassette. For this reason, conventionally, for example, a wafer detection device including a sensor for detecting whether or not a wafer is stored in a wafer cassette by irradiating the wafer with light is provided together with the wafer transfer device.

As this type of wafer detection device, there is a type that detects a wafer by using a reflection type sensor. When a reflection type sensor is used, light from a light projecting means is absorbed depending on the surface treatment state of the wafer. In some cases, only a small amount of light enters the light receiving means. In order to solve such a problem, there is a system in which the light projecting element used in the light projecting means is designed to project light with two wavelengths so as to eliminate the absorption of light by the wafer. Is reflected in a direction different from that of the light receiving means, and there is a problem that it cannot be reliably detected.

In order to deal with such a problem, a transmission type sensor is used as a sensor of a wafer detection device used in a transfer device, and detection is performed by disposing the light projecting means and the light receiving means so as to face each other. It has been proposed, and as an example thereof, as shown in Japanese Unexamined Patent Publication No. 2000-36528, a light projecting means and a light receiving means are fixed so as to face each other on a detection arm which is fixed to project at the tip of a wafer transfer device. There are types. With such a configuration, the wafer transfer device moves the wafer from the inside of the wafer cassette by moving the wafer mounting unit into the wafer cassette and mounting the wafer after the detection of the wafer is completed when transferring the wafer. When the wafer is taken out and transferred to another wafer cassette or the like, the wafer placing section is rotated.

However, in the case of the type in which the detection arm is fixed to the tip of the wafer transfer device, the detection arm also turns along with the turning of the wafer mounting part, so that another transfer device is installed around the wafer transfer device. In order to prevent the detection arm from colliding with the transfer arm, the installation distance between the wafer transfer device and another transfer device must be large, which causes a problem of space saving.

Therefore, as disclosed in Japanese Unexamined Patent Publication No. 2001-210700, the detection arm opens from the storage position to the detection position only when the wafer is being detected, and the light projecting means and the light receiving means mounted on the detection arm face each other. There is one. In this case, since the wafer transfer device is rotated with the detection arm stored, the installation distance between the wafer transfer device and another transfer device can be suppressed as much as possible.

However, since the detection arm is moved each time the detection arm is detected, when the detection arm is moved to the detection position, the light projecting means and the light receiving means are always arranged to face each other in the same state. Although the optical axis does not shift, the light projecting means and the light receiving means located at the detection position may not be accurately positioned at the specified position due to the deviation of the tolerance of each mechanical component forming the detection arm. In such a case, since the reproducibility of the optical axis is lost, the amount of light received by the light receiving means in the wafer detection state varies from measurement to measurement, and the amount of light received should be compared with a predetermined threshold value. In the method of detecting a wafer, there is a risk of false detection.

In particular, when the light projecting means or the light receiving means is composed of an optical fiber, the optical fiber bends as the arm moves, so that the light projecting means and the light receiving means are always at the specified detection positions. Even if the optical axis is positioned and the optical axis is reproducible, if the bending state of the optical fiber changes as the arm moves, the reproducibility is eventually lost, and the light projection level of the light projecting means or The amount of light received by the light receiving means may change, resulting in erroneous detection.

The present invention has been made in view of the above circumstances, and an object of the present invention is to compare the amount of light received by a light-receiving means facing a light-projecting means with a detection arm moved, with a threshold value. It is an object of the present invention to provide a wafer detection device capable of reliably detecting a wafer regardless of a reduction in the amount of light received by the light receiving means in a structure for detecting a wafer.

[0010]

A wafer detection device of the present invention is provided on at least one detection arm movable between a storage position and a detection position protruding from the storage position.
A light projecting unit and a light receiving unit that form an optical axis along the surface direction of the wafer by facing each other while the detection arm moves to the detection position, and the amount of light received by the light receiving unit is below a predetermined threshold value. In this case, in the wafer detection device provided with the determination means for determining that the wafer has been detected, the threshold value is set based on the amount of light received by the light receiving means when the detection arm is located at the detection position and no wafer is present. The setting means for setting is provided (Claim 1). With such a configuration, when the detection arm moves to the detection position protruding from the storage position, the light projecting unit and the light receiving unit face each other and form an optical axis along the surface direction of the wafer.

Here, the setting means sets the threshold value based on the amount of light received by the light receiving means when the detection arm is located at the detection position and no wafer is present. As a result, even if the amount of light received by the light receiving unit fluctuates due to the detection arm being located at the detection position in an abnormal state, the threshold value is set accordingly, so the determination unit determines that the amount of light received by the light receiving unit is When it falls and falls below a predetermined threshold value, it can be reliably determined that a wafer is detected.

In the above structure, the setting means may set a numerical value obtained by multiplying the received light amount by a predetermined threshold constant as a threshold value (claim 2). According to such a configuration, the setting unit sets a numerical value obtained by multiplying the amount of received light by a predetermined threshold constant as the threshold, so that the threshold can be easily set.

Further, the detection arm is provided so as to be opened and closed between a storage position and a detection position, and either or both of the light projecting means and the light receiving means provided in the detection arm are constituted by an optical fiber. (Claim 3). According to such a configuration, when the detection arm is opened from the storage position to the detection position, either or both of the optical fiber forming the light projecting means and the light receiving means provided in the detection arm is greatly curved. become. At this time, the smaller the curved diameter of the optical fiber, the more easily light leaks, so even if the detection arm is correctly positioned at the detection position, the light receiving amount of the light receiving means is reduced, but the threshold value is based on the light receiving amount. The wafer can be surely detected by setting the above.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. 2 is a side view showing the wafer transfer device, and FIG. 3 is a plan view thereof. 2 and 3, in the wafer transfer device 1, the base 2 is provided with the elevating part 3 so as to be able to elevate and lower, and the lower arm 4 is provided on the upper surface of the elevating part 3 so as to be rotatable, and the tip of the lower arm is provided. The upper arm 5 is provided so as to be rotatable, and a bifurcated wafer mounting portion 6 is provided at the tip of the upper arm 5.

On the other hand, a wafer storage device 7 is arranged so as to face the wafer transfer device 1. This wafer storage device 7
Is provided with a wafer cassette 9 on the upper surface of the cassette table 8. A plurality of wafers 10 are stored in the wafer cassette 9 at a predetermined interval, and the wafer transfer device 1 takes out the wafer 10 stored in the wafer cassette 9 by the wafer mounting unit 6 and transfers it to a predetermined position. It has become.

Here, a wafer detection device 11 is provided at a portion of the upper arm 5 of the wafer transfer device 1 opposite to the wafer mounting portion 6. In the wafer detection device 11, the first and second detection arms 12 and 13 are provided on the base 14 so as to be opened and closed by an actuator (not shown), and the light projection means 15 and the light reception means 16 are provided at the tips of the detection arms 12 and 13. Are fixed to each other. Each of the detection arms 12 and 13 is located at an open detection position when detecting the wafer 10 stored in the wafer cassette 9, and the light projecting means 15 and the light receiving means 16 face each other at the detection position. At the same time, when the wafer detection is completed, the wafer is closed and placed in the storage position.

In this case, the first and second detection arms 12
And 13 are normally located in the storage position.
This is because when the wafer mounting portion 6 is swung as shown in FIG. 4, when the detection arms 12 and 13 are located at the detection positions as shown by the broken lines in FIG. This is because it may cause a collision with a device located around the device.

FIG. 1 is a functional block diagram of the wafer detector 11. In FIG. 1, the CPU 17 can communicate with the arm control means 18. The arm control means 18 controls the pivoting operation of the lower arm 4 and the upper arm 5 of the wafer transfer apparatus 1 and the opening / closing operation of the first and second detection arms 12 and 13, as well as the elevating operation of the elevating part 3. When the first and second detection arms 12 and 13 are opened to detect the wafer 10, the CPU 17 is notified of the detection start signal, and when the CPU 17 is notified of the scan start signal, the elevating unit It is designed to move up and down.

The CPU 17 drives the light projecting means 15 at a predetermined cycle to project light from the light projecting means 15 and, based on the light receiving signal from the light receiving means 16, the wafer 10
To detect. That is, as shown in FIG.
Judgment means 1 as a function executed based on a program
9 and threshold value setting means 20, and the judging means 1
Reference numeral 9 determines the detection of the wafer 10 by comparing the amount of light received by the light receiving means 16 with a threshold value set by the threshold value setting means 20 as described later.

Here, the threshold value setting means 20 receives the light projected from the light projecting means 15 by the light receiving means 16 with the first and second detection arms 12 and 13 opened, and receives the light. The abnormality detection and the threshold value setting are performed based on the light receiving amount of the means 16, and the method of setting the threshold value based on the light receiving amount in this manner is a feature of the present embodiment. .

Next, the operation of the above configuration will be described. The arm control means 18 is provided on the opposite side of the wafer mounting portion 6 as shown in FIG. 6 in order to detect the wafer 10 prior to carrying the wafer 10 on the wafer mounting portion 6. The wafer detector 11 is swung so as to face the wafer cassette 9.

Subsequently, as shown in FIG. 7, the first and second detection arms 12 and 13 of the wafer detection device 11 are opened.
As a result, the first and second detection arms 12 and 13 are opened and positioned at the detection position, so that the light projecting unit 15 and the light receiving unit 16 face each other. Such a light projecting means 1
5 and the light receiving means 16 face each other, the optical axis formed between the light projecting means 15 and the light receiving means 16 comes along the surface direction of the wafer 10 housed in the wafer cassette 9. At this time, the arm control means 18 outputs a detection start signal to the wafer detection device 11 when the first and second detection arms 12 and 13 are opened.

FIG. 5 shows the CPU 17 of the wafer detector 11.
The detection operation of is shown. In FIG. 5, CPU1
When the detection start signal is input from the arm control means 18 (S1), the light emitting element 7 outputs a light projection signal to the light projection means 15 (S2). As a result, the light projecting means 15 projects light, and the projected light enters the light receiving means 16.
A light receiving signal is input from 6. In this case, since the wafer 10 is not present on the optical axis between the light projecting means 15 and the light receiving means 16, the light receiving means 16 is the light projecting means 1.
The light from 5 will be received as it is.

By the way, the first and second detection arms 12
Since the respective mechanical parts including 13 and 13 have a tolerance, the light projecting means 15 located at the detection position due to deviation of the tolerance or the like.
In some cases, the light receiving means 16 and the light receiving means 16 are not accurately located at the specified detection position. Therefore, since the reproducibility of the optical axis between the light projecting means 15 and the light receiving means 16 is lost, the amount of light received by the light receiving means 16 in the detection state of the wafer 10 varies from measurement to measurement. The conventional method of detecting a wafer by comparing the amount of received light with a predetermined threshold value may cause erroneous detection.

Therefore, in this embodiment, erroneous detection is prevented as follows. That is, the CPU 17 of the wafer detection device 11 stores the received light amount a from the light receiving means 16 as shown in FIG. 5 (S4), and after calling the initial set received light amount b (S5), the detection arms 12 and In order to determine whether the installation state of 13 is normal, the received light amount a
Is compared with the initial setting received light amount b (S6). This initial setting light receiving amount b is set to determine whether the light receiving means receives light in a normal state of the detection arms 12 and 13 based on the light receiving amount received by the light receiving means 16.

When a <b (when the amount of received light is smaller than the initially set amount of received light) (S6: NO), for example, when each of the detection arms 12 and 13 is opened, for example, each detection arm 1 is detected.
It is determined that the light receiving means 16 is receiving light when the movements of the detection arms 12 and 13 are abnormal, such as when the light receiving means 16 receives light when the opening of 2 and 13 is incomplete. Is output (S17), and then the stop output is output (S18).

On the other hand, when a ≧ b (when the amount of received light is equal to or greater than the initially set amount of received light) (S6: YES), the light receiving means 16 is operated while the detection arms 12 and 13 are normally moved.
It is determined that the light is being received by and the threshold setting constant α is read from the memory (S7). The threshold value setting constant α is the ratio of the threshold value to the amount of received light. And a
A threshold value is obtained by calculating × α = β, and the obtained β is set as a new threshold value and stored in the memory (S9). That is, the smaller the amount of light received by the light receiving means 16, the smaller the threshold value is set. In this case, wafer 1
The reason why the threshold value (relatively larger than the zero level) is set to detect 0 is that the wafer 10 is different from the effective light diameter formed between the light projecting means 15 and the light receiving means 16.
This is because the thickness dimension is smaller, and even if the wafer 10 is positioned on the optical axis, the light receiving means 16 is in the light receiving state and is not completely in the light shielding state.

When the threshold value setting is completed as described above, the CPU 17 outputs a scan start signal to the arm control means 18 (S10). As a result, the arm control means 18 causes the detection arms 12 and 13 as shown in FIG.
Is moved to the wafer cassette 9 and positioned at the detection start position. In this state, therefore, the light projecting means 15 and the light receiving means 16 are provided.
The wafer 10 comes to be positioned on the optical axis formed by.

Here, the CPU 17 inputs a light receiving signal from the light receiving means 16 (S11) and stores the received light amount a1 in the memory (S12). Subsequently, the CPU 17 calls β (S13), compares a1 with β (S14), and
When 1 <β (when the amount of received light is smaller than the threshold value) (S14: NO), it is determined that the wafer 10 is not detected and a non-detection signal is output (S19). Also, a1 ≧ β
If (the amount of received light is greater than or equal to the threshold value) (S14: Y
ES), it judges that the wafer 10 is detected and outputs a detection signal (S15). Then, the above-described operation is repeated until it is notified from the arm control means 18 that a predetermined amount has been scanned (S16: NO), and when notified (S1).
6: YES), and ends the detection operation.

According to such an embodiment, the light emitting means 15 and the light receiving means 16 are provided at the tips of the respective detection arms 12 and 13 of the wafer detection device 11, and the respective detection arms 12 and 13 are positioned at the detection position. In the configuration for detecting the wafer 10 stored in the wafer cassette 9 in the above state,
Since the threshold value is set on the basis of the amount of light received by the light receiving means 16 when the wafer 10 is not present, this is the case where the amount of light received is reduced because the detection arms 12 and 13 are displaced from the detection positions. However, the wafer 10 can be reliably detected. Moreover, since the threshold value is set by multiplying the amount of light received by the light receiving means 16 by a predetermined threshold constant, the threshold value can be easily set.

(Second Embodiment) Next, the second embodiment of the present invention will be described.
Embodiments of the present invention will be described with reference to FIGS. 9 and 10.
The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. The second embodiment is characterized in that the light projecting means and the light receiving means are composed of optical fibers. In FIG. 9 showing the plane of the wafer transfer apparatus 1, first and second
Heads of a side-view type light-projecting optical fiber 21 and a light-receiving optical fiber 22 are fixed to the detection arms 12 and 13, respectively.
With the optical fibers 21 and 22 in the detection position.
Heads face each other to form an optical axis.
These optical fibers 21 and 22 constitute a light projecting means and a light receiving means, and when light from a light projecting element (not shown) provided in the base 14 is projected from the light projecting optical fiber 21, Light enters the light-receiving optical fiber 22 and enters a light-receiving element (not shown) provided in the base 14.

Now, when the first and second detection arms 12 and 13 are opened from the storage position shown in FIG. 9 to the detection position shown in FIG. 10, the bending diameters of the optical fibers 21 and 22 are reduced accordingly. Here, since the optical fibers 21 and 22 have a property that light easily leaks to the outside when the curved diameter becomes small, even if the first and second detection arms 12 and 13 are correctly positioned at the detection position. However, the amount of light received by the light-receiving optical fiber 22 may decrease.

However, in the present embodiment, as in the first embodiment, the threshold value is determined based on the amount of light received by the light receiving optical fiber 22 when the first and second detection arms 12 and 13 are open. Since the value is set, the wafer 10 can be reliably detected regardless of the decrease in the amount of light received by the light-receiving optical fiber 22.

The present invention is not limited to the above embodiments, but can be modified or expanded as follows. Even when the wafer is completely shielded by the wafer when the wafer is positioned on the optical axis between the light projecting means and the light receiving means and the light receiving quantity of the light receiving means becomes zero, it is based on the light receiving quantity of the light receiving means. You may make it set a threshold value. The detection arm may be configured to be slid forward to move to the detection position protruding from the storage position. Either one of the detection arms may be movably provided, and the detection arm may be provided with either one of the light projecting means and the light receiving means.

[0035]

As is apparent from the above description, according to the wafer detecting apparatus of the present invention, the setting arm causes the detection arm to be located at the detection position and the wafer is not present. Since the threshold value is set, in the configuration in which the wafer is detected by comparing the light receiving amount of the light receiving means facing the light projecting means with the threshold value while the detection arm is moved, the light receiving amount of the light receiving means is detected. There is an excellent effect that the wafer can be surely detected regardless of the decrease of.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an overall configuration according to a first embodiment of the present invention.

FIG. 2 is a side view of a wafer transfer device and a wafer storage device.

FIG. 3 is a plan view of a wafer transfer device and a wafer storage device.

FIG. 4 is a view corresponding to FIG. 3 showing a swivel state of the wafer mounting portion.

FIG. 5 is a flowchart showing the operation of the CPU of the wafer detection device.

FIG. 6 is a view corresponding to FIG. 3 showing a wafer detection device facing a wafer cassette.

FIG. 7 is a view corresponding to FIG. 6 showing the first and second detection arms in an open state.

FIG. 8 is a diagram corresponding to FIG. 6 showing a state where the wafer is moved to a wafer detection position.

FIG. 9 is a view corresponding to FIG. 6 showing a second embodiment of the present invention.

FIG. 10 is a view corresponding to FIG. 7.

[Explanation of symbols]

1 is a wafer transfer device, 6 is a wafer mounting unit, 7 is a wafer storage device, 11 is a wafer detection device, 12 is a first detection arm, 13 is a second detection arm, 15 is a light projecting means, and 16 is a projection device. Light means, 17 is a CPU (determination means, setting means), 18
Is an arm control means, 21 is a light projecting optical fiber (light projecting means), and 22 is a light receiving optical fiber (light receiving means).

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01H 35/00 H01H 35/00 V H03K 17/78 Q H03K 17/78 G01V 9/04 A F term (reference) ) 5F031 CA02 DA01 FA01 FA07 FA11 GA36 GA43 GA47 GA49 JA02 JA05 JA13 JA22 JA45 5G055 AA01 AA03 AB01 AC01 AD09 AE28 AG11 5J050 AA05 BB18 CC00 EE31 EE35 EE39

Claims (3)

[Claims] 1. A wafer provided on at least one detection arm movable between a storage position and a detection position protruding from the storage position, the detection arms facing each other in a state of being moved to the detection position. Wafer detection including a light projecting unit and a light receiving unit that form an optical axis along the surface direction, and a determination unit that determines that a wafer is detected when the amount of light received by the light receiving unit falls below a predetermined threshold value. In the apparatus, the wafer detection apparatus further comprises setting means for setting the threshold value based on the amount of light received by the light receiving means when the detection arm is located at the detection position and no wafer is present. 2. The wafer detector according to claim 1, wherein the setting unit sets a numerical value obtained by multiplying the amount of received light by a predetermined threshold constant as a threshold. 3. The detection arm is provided so as to open and close between a storage position and a detection position, and either or both of a light projecting means and a light receiving means provided in the detection arm are made of an optical fiber. The wafer detection device according to claim 1, wherein the wafer detection device is a wafer detection device.