JPH09260261A - Lithography equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithography equipment which can know the process and the cause when abnormality is generated, and automatically enables recovery from the abnormal state. SOLUTION: Image sensing means 71, 73, 75, 77 like TV cameras for watching are arranged in necessary parts of a process to be watched, image signals from the respective image sensing means are image-processed with an image-processing equipment 81, and abnormality is detected. A main control equipment 87 receives a signal of abnormality generation and result of analysis from the image-processing equipment, and performs automatic recovery as much as possible by using a wafer rejection equipment 43.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic apparatus used for manufacturing semiconductor integrated circuits and liquid crystal display devices.

[0002]

2. Description of the Related Art A lithographic apparatus is used in the manufacturing process of semiconductor integrated circuits and liquid crystal display devices. A lithographic apparatus is a resist coater that applies a photoresist to a substrate such as a wafer or a glass plate (hereinafter referred to as a wafer),
A projection exposure device that exposes and transfers a pattern of a photomask or reticle (hereinafter referred to as a reticle) onto a photosensitive substrate coated with a resist, a developing device that develops the exposed photoresist, and a wafer transfer that automatically transfers the substrate between the devices. It consists of devices.

In a lithographic apparatus, a resist coater, a projection exposure apparatus, and a developing apparatus are arranged in-line, and when wafers are automatically transferred by a wafer transfer apparatus while processing is continuously performed, and when each apparatus is arranged separately. In some cases, the steps of applying photoresist to the wafer, transferring the reticle pattern to the wafer, and developing the exposed wafer are processed in batches. Even in the case of batch processing, the handling of wafers in each device is carried out by using an automated device without human intervention. For example, in a projection exposure apparatus, a wafer cassette containing a predetermined number of wafers coated with photoresist is set in the apparatus,
The automatic wafer transfer device is used to take out the wafer from the wafer cassette, mount the wafer on the projection exposure apparatus, and store the exposed wafer in the wafer cassette.

Conventionally, the process monitoring in the photolithography apparatus, especially the abnormality detection in the wafer mounting process and the transfer process, has been performed.
A pressure sensor is provided in the vacuum exhaust system of the wafer loader or wafer transfer device that vacuum-adsorbs the wafer, or a position sensor is provided in the moving member, and the status set by the output signals of these sensors is monitored in the sequence management of each process. It was done by doing. For example, when the pressure of the exhaust system for vacuum-adsorbing the wafer on the wafer transfer arm is detected during execution of the wafer transfer sequence, and the pressure is higher than a predetermined value, the wafer is not properly mounted on the wafer transfer arm. Anomalies are detected because there is a possibility. Also, after the execution of a certain sequence,
If the status signal indicating that the moving member that should have moved to the predetermined position within the predetermined time has arrived at the predetermined position even at that time is not issued during the sequence execution, Assuming that an abnormality has occurred, the subsequent processing is stopped.

[0005]

The conventional abnormality detecting method only detects an abnormality in the state of the apparatus such as an error in the position of the moving member or an abnormality in the pressure of the vacuum exhaust system, and the abnormality has occurred. You cannot know the process or the cause. Therefore, the device merely notifies the position where the abnormality has occurred and the abnormal state, and when recovering from the abnormality, it is necessary for the operator to confirm the current state of the device and manually eliminate the abnormal state. Therefore, the apparatus remains stopped until the manual operation by the operator is performed, resulting in a significant decrease in work efficiency. Further, even if it is known that an abnormality has occurred, the cause cannot be known, so the cause of the abnormality cannot be fundamentally removed, and there is a possibility that the same cause will cause an abnormality again.

The present invention has been made in view of the above problems of the prior art. When an abnormality occurs, the process and cause of the abnormality can be known, and the recovery from the abnormal state is automatically performed. It is an object of the present invention to provide a lithographic apparatus capable of performing the above.

[0007]

According to the present invention, one or more image pickup means such as a television camera for monitoring is arranged in the whole process or a required place to be monitored, and the image signal from each image pickup means is subjected to image processing. The above object is achieved by performing image processing by the device. When an abnormality occurs, the image processing apparatus identifies the abnormal portion and analyzes the degree of the abnormality, that is, determines whether the abnormality can be automatically recovered. The main control device that manages the process receives an abnormality occurrence signal and a determination signal regarding automatic recovery from the image processing device, and attempts automatic recovery as much as possible. Since the automatic recovery function has a processing system independent of the processing steps to be monitored, that is, a processing system dedicated to the recovery, it becomes possible to deal with various situations more flexibly.

That is, in the lithographic apparatus according to the present invention, the image pickup means for monitoring a predetermined process portion in the apparatus, the abnormality detection means for detecting the abnormality of the process by using the output of the image pickup means, and the abnormality for recovering the abnormality A recovery means and a management means for managing the process are provided, and the management means is characterized in that when the abnormality detection means detects an abnormality in the process, the abnormality recovery means performs the abnormal recovery. The abnormality detecting means includes an image processing means.

If the monitor means for displaying the image picked up by the image pickup means is provided, the progress status of the process, the status in the event of an abnormality, the progress status of the abnormal recovery operation, and whether the abnormal recovery is properly performed or not. Can be easily confirmed. Further, if the storage means for storing the image signal output by the image pickup means is provided, the cause of the abnormality is clarified by reproducing the image signal when the abnormal state occurs, which is useful for improving the arrangement, structure or sequence of the device unit. be able to.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to a wafer transfer mechanism to a projection exposure apparatus which constitutes a part of a lithographic apparatus. The projection exposure apparatus 10 includes an illumination system 11,
The pattern of the reticle 13 including the reticle 13, the projection optical system 15, and the wafer stage 17, which is uniformly illuminated by the illumination system 11, is transferred by the projection optical system 15 to a predetermined area of the wafer W placed on the wafer stage 17. . The wafers W coated with the photoresist are stored one by one in a shelf in the wafer cassette 21. The wafer W taken out of the cassette 21 is transferred to the pre-alignment apparatus 50 by the first wafer transfer apparatus 30 and pre-aligned by the pre-alignment apparatus 50 so that the orientation flat of the wafer is in a predetermined direction, and then, The projection exposure apparatus 1 by the second wafer transfer device 60
It is mounted on the wafer stage 17 of 0.

The wafers in the wafer cassette 21 are taken out one by one from the shelf of the cassette 21 by the movable arm 25 of the wafer take-out device 23. The arm 25 is movable in the vertical direction (Z direction), and is also movable back and forth in a direction (X direction) connecting the entrance and the back of the cassette 21. The arm 25 is extended to a space below a wafer in the cassette 21. The wafer W is taken out from the cassette 21 by inserting the wafer W into the cassette 21 and then raising the arm 25 slightly to place the wafer on the arm 25, and then retracting the arm 25 in the X direction and pulling it out of the cassette 21.

The wafer W taken out from the wafer cassette 21 is in a standby state below the first wafer transfer device 30.
It is placed on the pair of arms 33a and 33b of the carrier table 31. The arms 33a and 33b of the transfer table 31 of the first wafer transfer device 30 are provided with suction holes 35a and 35b connected to a vacuum exhaust device (not shown). Hold by adsorption. The carrier 31 is driven in the direction of the pre-alignment apparatus 50 (Y direction) from the position of the wafer cassette 21 by the lead screw 37 which is rotationally driven by the drive motor 38.
Then, when the carrier table 31 reaches the position of the pre-alignment apparatus 50, the suction holes 35a, 3 of the arms 33a, 33b.
The vacuum suction of the wafer W by 5b is released, and the lifting means 39
By lowering the wafer transfer device 30 as a whole, the wafer W on the arms 33a and 33b is placed on the rotary table 51 of the pre-alignment device 50.

The rotary table 51 has a suction hole on the surface thereof, which is connected to an evacuation device, and sucks and holds the wafer transferred from the transfer table 31 of the first wafer transfer device 30. The pre-alignment device 50 is, for example, Japanese Patent Laid-Open No. 63-280.
As described in Japanese Patent No. 435, the rotary table 5
1. An illumination light source and a CCD linear sensor (not shown) arranged above and below the wafer mounted on the wafer 1 are sandwiched. The peripheral shape of the entire wafer is detected by causing the illumination light source to emit pulsed light in synchronism with the rotation of the rotary table 51 to detect the image of the peripheral portion of the wafer by the CCD linear sensor, and the orientation flat of the wafer becomes parallel to the Y direction. The rotary table 51 is stopped at the position.

When the wafer pre-alignment is completed,
The vacuum suction of the wafer by the rotary table 51 is released,
The wafer on the rotary table 51 is the second wafer transfer device 6
It is placed on the arms 63a and 63b of the carrier table 61 of 0. The pair of arms 63a and 63b of the transfer table 61 have suction holes 65 that are vacuum-exhausted by a vacuum exhaust device (not shown).
a, 65b, and sucks and holds the wafer placed on the arms 63a and 63b. The carrier 61 is a drive motor 68.
The wafer is moved in the Y direction by the lead screw 67 that is driven to rotate and reaches the wafer stage 17 of the projection exposure apparatus 10 that is moving to the wafer transfer position, and then the vacuum of the wafer is generated by the suction holes 65a and 65b of the arms 63 and 63b. The suction is released and the second wafer transfer device 60 is slightly lowered by the elevating means 69 to place the wafer on the arms 63a and 63b on the wafer stage 17. Wafer stage 17 on which wafer W is placed
Is moved to a position below the projection optical system 15, and after performing a predetermined alignment, the image of the reticle 13 is exposed.

From the wafer cassette 21 to the projection exposure apparatus 10
Image pickup devices 71, 73, 75, 77 such as TV cameras are arranged above the wafer transfer path reaching the wafer stage 17 and sequentially monitor the transfer state of the wafer W. The image output of each of the image pickup devices 71, 73, 75, 77 is supplied to the image processing device 81. In addition, the image output of each imaging device is a monitor 8 so that the operator can observe the situation inside the device.
3 and is stored in the image storage device 85 such as a video recorder. The image processing device 81 sequentially analyzes the input image, grasps the progress of the process, and detects an error.

In this way, when the operation abnormality occurs, the image processing apparatus 81 can identify the abnormal portion and analyze the degree of abnormality.
And outputs the result to main controller 87. The main control device 87, which has received the signal from the image processing device 81, performs the abnormal recovery operation when the automatic recovery is possible, and stops the device when the automatic recovery is impossible. The abnormality recovery operation is performed by, for example, the wafer rejection device 43.
The wafer rejection device 43 includes a rejection arm 41 that is movable in the Z direction and movable back and forth in the X direction, and the wafer W transferred by the transfer table 31 of the first transfer device 30 is picked up by the rejection arm 41. , And stores them in the empty shelves of the wafer recovery box 45 located on the opposite side. The images before and after the occurrence of the abnormality stored in the image storage device 85 can be used for analyzing the cause of the abnormality.

FIG. 2 is a view of the wafer transfer mechanism of FIG. 1 viewed from above. In the figure, rectangular areas A, B, surrounded by broken lines,
C and D represent the imaging visual fields of the imaging devices 71, 73, 75 and 77, respectively. That is, in the imaging device 71, the wafer stored in the wafer cassette 21 is taken out from the cassette 21 by the movable arm 25 of the wafer taking-out device 23,
The process transferred to the first wafer transfer device 30 is monitored. The image pickup device 73 monitors a part of the wafer transfer process by the first wafer transfer device 30, and the image pickup device 75 a part of the wafer transfer process by the first wafer transfer device 30 or the wafer rejection device 43. Monitor the recovery work of. The imaging device 77 also monitors the wafer transfer process from the first wafer transfer device 30 to the pre-alignment device 50, the pre-alignment process, and the wafer transfer process from the pre-alignment device 50 to the second wafer transfer device 60. To do. However, as shown in FIGS. 1 and 2, it is not necessary to monitor the entire wafer transfer path from the beginning to the end, and it is possible to omit the monitoring in a portion of low importance for abnormality monitoring, for example, the visual field B. In that case, the imaging device 73 becomes unnecessary.

The abnormality detection by the image processing device 81 can be performed, for example, by a method in which the operation of each device is modeled and stored, and the model and the actual operation are sequentially compared to detect an error. For example, the movement of the wafer W in the visual field A monitored by the image pickup device 71 is a combination of the linear movement in the X direction by the movable arm 25 of the wafer take-out device 23 and the linear movement in the Y direction by the first wafer transfer device 30. is there. Therefore, the wafer removal device 23 and the first
When the wafer transfer device 30 of FIG. 3 is operating as designed, the wafer W in the field of view A has two contours 91 and 92 so that the contour of the wafer is in contact with the two curves 91 and 92. , 92 to move in the strip-shaped area 90. However, when a wafer cannot be taken out from the wafer cassette 21 due to an obstacle in the wafer take-out device 23, or the transfer position of the wafer from the movable arm 25 of the wafer take-out device 23 to the carrying table 31 is shifted, the arm of the carrying table 31 is displaced. If the wafer is not properly placed on the wafers 33a and 33b, the movement path of the wafer is as shown in FIG.
It will protrude from the strip-shaped region 90 shown in FIG. If the wafer is not properly placed on the transfer table 31 of the first transfer device, the wafer cannot be transferred properly, or even if it is transferred, the transferred wafer is normally placed on the rotary table 51 of the pre-alignment device 50. An abnormal situation occurs such that it cannot be placed on the.

Therefore, in the present invention, if the wafer W that has been normally delivered and normally transferred does not pass, if the operation of taking out the wafer from the cassette 21 fails, or to the transfer table 31. The area within the field of view A through which the wafer W passes is determined in advance as the wafer movement prohibited areas 94 and 95 only when a positional deviation that causes a hindrance to the subsequent steps occurs when the wafer is mounted on the image processing apparatus. It is stored in 81. The image processing device 81 performs image processing on the signal output from the image pickup device 71 to sequentially obtain the position of the wafer within the field of view A, and the wafer W moves in the motion prohibited area 94,
It is determined whether or not 95 has been passed. If the wafer W has not passed through the motion prohibited areas 94 and 95 in the field of view A, a status signal indicating that the wafer is normally handled is sent to the main controller 87.

When it is found that the wafer W bites into the motion prohibited area 95 and moves as a result of the image processing in the image processing apparatus 81, for example, as shown in FIG. A signal indicating the occurrence of an abnormality is sent to the control device 87, the degree of the abnormality is determined, and the determination result is sent to the main control device 87.

For example, when the image processing device 81 determines that the degree of wafer positional deviation is within a range that does not hinder the transfer to the first transfer device 30, the image processing device 81 causes the main control device 87. A signal indicating that automatic recovery is possible. Receiving the signal of automatic recovery, main controller 87 commands first wafer transfer device 30 to transfer the wafer to a position in front of wafer rejection device 43 and then stops the wafer, and then to wafer rejection device 43. Command the reject arm 41 to transfer 31
The upper wafer is picked up and stored in a vacant shelf of the wafer recovery box 45 to perform the abnormality recovery operation. On the other hand, when it is determined that it is difficult to stably place the wafer on the transfer arms 33a and 33b of the first transfer device 30 because the degree of positional deviation of the wafer is significant, the image processing device 81 causes the main control device 87 to operate.
A signal to the effect that automatic recovery is not possible. Upon receiving a signal indicating that automatic recovery is impossible, main controller 87 immediately stops the operation of wafer unloading device 23 and first transfer device 30, issues an alarm, and waits for the operator to manually perform abnormal recovery. The criterion for determining whether automatic recovery is possible is preset in the image processing device 81.

The wafers recovered in the wafer recovery box 45 are
The wafer cassette 21 is again collected by the operator.
Inserted into the lithographic process. The operating condition of the device or the condition where the device is automatically performing abnormal recovery can be monitored by the monitor 83 at any time.
Further, even when the abnormal recovery has to be performed manually, the operator can grasp the rough condition by the monitor 83, and therefore the abnormal recovery can be quickly performed. Since the history of the occurrence of the abnormality is stored in the image storage device 85 such as a video device, it can be used for clarifying the cause of the abnormality by reproducing and analyzing it. Can be adjusted or modified so that the same cause does not occur again.

Although only the modeling of the device operation in the visual field A of the image pickup device 71 has been described here, the modeling is similarly performed in the visual fields B, C and D of the other image pickup devices 73, 75 and 77. The image processing device 81 performs abnormality detection based on the model set for each field of view.

In the above example, an example in which the operation of the apparatus is modeled by the movement area of the wafer when the abnormality is detected by the image processing apparatus 81 has been described. However, the model using the timing of the work sequence is used as the model by the movement area of the wafer. Can also be added.

FIG. 5 illustrates an example thereof. In this example, the image pickup devices 71, 75 and 77 shown in FIG. 1 are used,
The image pickup device 73 for monitoring the visual field B shown in FIG. 2 is omitted. FIG. 5A shows an imaging visual field A by the imaging device 71, and FIG. 5B shows an imaging visual field C by the imaging device 75. In the visual field area A of the image pickup device 71, the timing detection line 97 is set together with the wafer motion prohibition areas 94 and 95 described in FIG. 3, and in the visual field area C of the image pickup device 75, the wafer motion prohibition area 101, The timing detection line 105 is set together with 103.

The image processing device 81 sends a wafer passage signal to the main control device 87 when the tip of the wafer passes the timing detection line 97 or 105. The wafer take-out device 23, the first wafer transfer device 30, the second wafer transfer device 60, etc. are sequence-controlled by the main controller 87, and when the wafer transfer is normally performed, each device in the device is The time when the wafer passes through the position is almost fixed. In other words, the passing time of the wafer is monitored at a certain position in the apparatus, and if the wafer does not pass that position even at the scheduled time, it is assumed that some abnormality has occurred. It is used for abnormality detection.

In the example of FIG. 5, the time Δt required for the wafer to move between the timing detection lines 97 and 105 by the first wafer transfer device 30 is obtained in advance and stored in the main controller 87. Time t ₁ from the image processing device 81
When the signal that the wafer has passed through the timing detection line 97 is sent to the main controller 87, the main controller 87 causes the time t ₂ = t ₁ + Δt.
First, it is checked whether or not a signal indicating that the wafer has passed through the timing detection line 105 is sent from the image processing device 81, and when the wafer passage signal is not sent, it is determined to be abnormal. This time t ₂ may have a certain allowable time width.

By using the model utilizing the timing of the work sequence as described above, it is possible to check the abnormality in the wafer transfer route which is not monitored by the image pickup device. The abnormality determination using the timing of this work sequence can be used together with the abnormality determination using the movement region of the wafer.

The present invention is not limited to the wafer transfer mechanism in the projection exposure apparatus that constitutes the lithography apparatus, but also detects an abnormality in the resist coater or the developing apparatus, or transfers the wafer from the resist coater to the projection exposure apparatus, and the projection exposure apparatus. It is also applicable to other units such as transfer of a wafer from a developing device to a developing device.

[0030]

According to the present invention, it is possible to reduce the stop of the main body due to the operation abnormality in each step in the lithographic apparatus, and it is possible to reduce the manufacturing cost.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example in which the present invention is applied to a wafer transfer mechanism for a projection exposure apparatus.

FIG. 2 is a top view of FIG. 1;

FIG. 3 is a diagram showing an example of modeling of device operation in a field of view A.

FIG. 4 is an explanatory view of a wafer moving in a field of view.

FIG. 5 is a diagram illustrating another example of modeling the operation of the apparatus.

[Explanation of symbols]

W ... Wafer, 10 ... Projection exposure apparatus, 11 ... Illumination system, 13
... reticle, 15 ... Projection optical system, 17 ... Wafer stage, 21 ... Wafer cassette, 23 ... Wafer take-out device, 25 ... Movable arm, 30 ... First wafer transfer device,
31 ... Conveyance stand, 33a, 33b ... Arm, 35a, 35
b ... suction hole, 37 ... lead screw, 38 ... drive motor, 3
9 ... Elevating means, 41 ... Rejection arm, 43 ... Wafer rejection device, 45 ... Wafer collection box, 50 ...
Pre-alignment device, 51 ... Rotating table, 60 ... Second wafer transfer device, 61 ... Transfer table, 63a, 63b ...
Arm, 65a, 65b ... suction hole, 67 ... lead screw,
68 ... Drive motor, 69 ... Elevating means, 71, 73, 7
5, 77 ... Imaging device, 81 ... Image processing device, 83 ... Monitor, 85 ... Image storage device, 87 ... Main control device, 94,
95 ... Wafer movement prohibited area, 97 ... Timing detection line, 101, 103 ... Wafer movement prohibited area, 105
... Timing detection line

Claims (5)

[Claims] 1. An image pickup device for monitoring a predetermined process portion in the apparatus, an abnormality detection device for detecting an abnormality in the process using an output of the image pickup device, an abnormality recovery device for recovering the abnormality, and a process. A lithographic apparatus comprising: a managing unit that manages, wherein the managing unit performs an abnormal recovery by the abnormal recovering unit when the abnormal detecting unit detects an abnormal process. 2. The lithographic apparatus according to claim 1, wherein the abnormality detecting unit includes an image processing unit. 3. The lithographic apparatus according to claim 1, wherein the recovery means has a processing system independent of the step. 4. The lithographic apparatus according to claim 1, further comprising monitor means for displaying an image picked up by said image pickup means. 5. The lithographic apparatus according to claim 1, further comprising a storage unit that stores an image signal output by the image pickup unit.