JP4422745B2 - Wafer position deviation detection apparatus and wafer position deviation detection method - Google Patents

Description

The present invention relates to a U E c positional deviation detecting system and the wafer position shift detecting method, in particular, reliably with as small number of sensors be wafer misalignment occurs in any direction in the wafer transfer apparatus provided in the wafer processing apparatus The present invention relates to an apparatus and a method that can be detected.

  As an apparatus for processing the surface of a wafer (hereinafter referred to as “surface processing apparatus”), an etching apparatus, a CVD apparatus, and a PVD apparatus are known. These apparatuses basically have a vacuum container (processing chamber) that forms a required decompressed space in which wafer surface processing is performed, an exhaust mechanism that places the vacuum container in a required decompressed state, and a vacuum container. A gas supply mechanism for supplying process gas, a power supply mechanism for supplying electric power into the vacuum vessel, a stage on which a wafer to be processed is placed, and a wafer is loaded into and loaded on the stage in the vacuum vessel A wafer transfer device is provided. A vacuum container that performs surface treatment of the wafer and a container provided with a wafer transfer device are provided adjacent to each other, and a gate valve is provided between them. A container provided with a wafer transfer device is generally called a separation chamber (or transfer chamber), and a plurality of vacuum containers for wafer processing are provided around it.

  In the above surface treatment apparatus, an operation for surface treatment of one wafer is performed as follows. First, a single wafer to be processed from the outside is loaded into a container provided with a wafer transfer device, and then the wafer is transferred into a vacuum vessel via a gate valve by the wafer transfer device. Mounted on top. Thereafter, the gate valve is closed and the vacuum vessel is sealed. In this state, the inside of the vacuum vessel is evacuated to a predetermined reduced pressure state by the evacuation mechanism, and then the process gas is introduced into the vacuum vessel by the gas introduction mechanism. The introduction amount of the process gas is set and maintained at an appropriate flow rate in relation to the reduced pressure state set in the vacuum vessel. Thereafter, power is supplied to the process gas by the power supply mechanism, plasma is generated with this power, and the surface treatment of the wafer on the stage is performed by the action of the plasma. When the surface treatment of the wafer is completed, the wafer is exchanged by the wafer transfer device. Wafer replacement is performed by removing the wafer whose surface treatment has been completed by the wafer transfer device from the stage, taking it out of the vacuum container, carrying it out of the surface treatment device, and then vacuuming the next wafer to be surface treated in the same manner as described above. It is performed so that it may be carried into a container. After exchanging the wafer as described above, the same operation as described above is repeated.

  A conventional example of a wafer transfer apparatus that loads a wafer into or out of the vacuum container in which the wafer surface treatment is performed will be described with reference to FIGS.

  FIG. 11 shows a plan view of a conventional wafer transfer apparatus, and FIG. 12 shows an example of its operation. This conventional wafer transfer apparatus has been used exclusively in the surface processing apparatus by the applicant. The wafer transfer apparatus includes a robot arm 101 and a gripping plate 102 with claws provided at the tip of the robot arm 101.

  The robot arm 101 has a configuration that rotates as a whole around a base (base member) 103. Reference numeral 103a denotes a base center portion that is the center of rotation. A drive device such as a motor (not shown) is installed below the base 103, and the position of the drive shaft of the motor coincides with the position of the base center portion 103a. The robot arm 101 includes an intermediate connecting portion 104, a parallel link pair 105 provided between the base 103 and the intermediate connecting portion 104, and a parallel link pair 107 provided between the intermediate connecting portion 104 and the grip plate attaching portion 106. It consists of. Both ends of each link of the parallel link pairs 105 and 107 are rotatably connected to the base 103, the intermediate connecting portion 104, and the grip plate attaching portion 106, respectively. By rotating the connecting portion (joint portion) in this way, a parallelogram link device is formed by the parallel link pair 105, the base 103, and the intermediate connecting portion 104, and the parallel link pair 107, the intermediate connecting portion 104, and the grip plate are attached. In part 106, another parallelogram link device is formed. The parallel link pair 105 forms a first arm, and the parallel link pair 107 forms a second arm. The grip plate 102 is fixed to the tip of the grip plate mounting portion 106. As shown by broken lines in FIGS. 11 and 12, the holding plate 102 has a bifurcated portion 102 a for mounting a circular wafer 108, and includes four claws 109 for pressing the mounted wafer 108 at four locations around it. ing. In a normal transfer state, the wafer 108 is gripped so as to be disposed on the gripping plate 102 and inside the four claws 109. In FIGS. 11 and 12, the wafer 108 mounted on the grip plate 102 is indicated by a broken line in order to clearly show the configuration of the robot arm 101.

  An example of the wafer transfer operation by the robot arm 101 will be described with reference to FIG. This operation shows the state in which the robot arm 101 existing at the most contracted position (leftward retracted position) extends the entire arm mechanism part to the right side while changing the positional relationship of the arm mechanism part in six stages (A to F). . By this operation, the position of the wafer 108 indicated by a broken line is shifted from the left side to the right side in the drawing. In this operation, as a matter of course, the position of the base 103 does not change, the parallel link pair 105 is rotated clockwise with respect to the base 103 and the parallel link pair 107 is rotated counterclockwise with respect to the intermediate connecting portion 104. In other words, the above-described operation is caused by changing the arm angle. The operation of the robot arm 101 is usually performed when a wafer for wafer processing is carried into a vacuum vessel. Further, the robot arm 101 can be moved backward by reversing the operation. In this way, the gripping plate 102, that is, the wafer 108 can be moved forward and backward by the expansion and contraction of the robot arm 101, whereby the wafer is carried in (introduced) and carried out (taken out) from the wafer processing vacuum vessel.

  When the wafer 108 is transferred by the robot arm 101 in the wafer transfer apparatus described above, there is no problem when the wafer 108 is placed at the correct position (normal position) on the holding plate 102. A misalignment may occur on the plate 102 and may occur. In such a case, a part of the wafer 108 rides on the claw 109 and is inclined. Note that the wafer 108 is in a normal position on the grip plate 102. The wafer 108 is surrounded by four claws 109, and the center of the wafer 108 and the center 110 (shown in FIG. 12A) determined by the four claws 109. Means a state in which they are arranged to match. Therefore, it is necessary to monitor whether the wafer 108 is always at the original normal position when the robot arm 101 transports the wafer and whether or not there is a problem of misalignment. In order to perform such monitoring, the wafer transfer apparatus shown in FIG. 11 and the like is provided with a device for detecting a positional deviation of the wafer.

  The wafer misalignment detection apparatus shown in FIG. 11 is formed by using one transmissive optical sensor 111. The transmissive optical sensor 111 is shown enlarged in FIG. The transmission type optical sensor 111 is provided with pipe portions 113 and 114 on one surface in front of the box-shaped container 112 at the upper and lower positions, and two optical fibers 115 are guided to the box-shaped container 112 so that the optical fiber 115 The leading ends protrude from the ends of the pipe portions 113 and 114. The tip positions 115a of the two optical fibers 115 coincide with each other in the vertical relationship. For example, a light projecting portion is provided at the tip 115 a of the upper optical fiber 115, and a light receiving portion is provided at the tip 115 a of the lower optical fiber 115. Light 116 (thin beam-like light beam) guided to the optical fiber 115 and emitted from the light projecting unit is received by the light receiving unit. Accordingly, when a light shielding object such as a wafer enters between the light projecting portion of the upper optical fiber 115 and the light receiving portion of the lower optical fiber 115, the light 116 is blocked. In this wafer misalignment detection apparatus, the presence or absence of a wafer is detected based on whether or not a part of the wafer exists between the light projecting unit and the light receiving unit, and thereby the wafer mounted on the grip plate 102 of the robot arm 101. The presence or absence of misalignment was detected. The transmissive optical sensor 111 having the above configuration is attached to a predetermined portion of the base 103. According to this, the wafer 108 when the robot arm 101 is in the most contracted state is detected. The state of the robot arm 101 when it is fully contracted is the state indicated by A in FIG.

  As described above, in the above-described conventional example described with reference to FIG. 11 and the like, the positional deviation of the wafer 108 on the grip plate 102 is detected using the single transmission type optical sensor 111 in the state when the robot arm 101 is contracted to the minimum. I was trying to do it.

Next, the literature of the conventional wafer position deviation detection mechanism will be described. For example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5 and the like shown below can be cited as documents of the wafer position deviation detection mechanism.

  Patent Document 1 relates to a semiconductor manufacturing apparatus, and is provided with a device that detects and prevents a wafer position shift when a wafer is placed on a stage in a processing container such as a dry etching apparatus. The wafer misalignment detection apparatus has a configuration in which three reflective sensors are provided along the edge of the wafer mounting surface of the stage to detect the three outermost positions of the wafer mounted on the stage. When any of the three reflective sensors cannot detect the reflected light, it is determined that a positional shift has occurred.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a position shift detection apparatus and method for efficiently and accurately detecting the position of a wafer and appropriately correcting the wafer transfer operation. In this misalignment detection, two optical sensors of transmission type or reflection type are arranged at predetermined positions, and the two optical sensors detect two locations on the circumference of the wafer to obtain the chord length of the circular wafer, Using the relationship between the length of the chord, the known radius of the wafer, and the three sides of the right triangle, the position of the center of the wafer is obtained, and the presence / absence of the wafer misalignment is thereby detected. Detection of two locations on the circumference of the wafer by the two optical sensors is performed only once at the same time.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a position shift detection device that detects a position shift before and after transporting a substrate and mounts the substrate at a desired position on the substrate stage when the substrate is mounted on the substrate stage. When the substrate is transported and placed on the substrate stage by the substrate transport device, the three outer edges of the substrate including the notches are detected by three sensors before the transport, and the notches are transported after the transport. The two substrate outer edge portions including the substrate are detected by two sensors, and the detection result before and after the substrate transfer is compared to calculate the positional deviation before and after the substrate transfer.

  Patent Document 4 discloses an apparatus for detecting an error in the position of a wafer. The wafer transfer device has a blade suitable for carrying the wafer, on which the wafer is mounted. This blade has a slot, and whether or not the wafer is misaligned on the blade is determined by providing one light detection sensor near the entrance of the processing chamber, and the light detection sensor passes the light to the reflector through the slot. Done by monitoring. The distance between the edge of the slot of the blade and the edge of the wafer is measured, and the position of the wafer with respect to the blade is measured based on this distance to detect the positional deviation of the wafer.

In Patent Document 5, a plurality of processing chambers are provided around a transfer chamber, an R-θ robot is provided in the transfer chamber, and a wafer is carried into or out of each processing chamber by this robot. When the wafer is loaded into the processing chamber, a sensor array (a plurality of optical sensors) that detects the relative position of the wafer or the like with respect to the target position is used to accurately position the wafer at the selected target position. It is arranged in alignment with each outer side of the upper surface wall and the lower surface wall.
Japanese Patent Laid-Open No. 7-201952 JP-A-10-223732 Japanese Patent Laid-Open No. 10-247681 JP-A-10-64971 JP-A-6-24284

  According to the conventional misregistration detection mechanism described with reference to FIGS. 11 to 13, one transmissive photosensor 111 is used, and a part of the outer edge of the wafer 108 creates a light shielding state in the photosensor. Therefore, even if a wafer misalignment occurs during transportation, it may be determined that the wafer is in a normal position as long as a part of the wafer blocks the light from the transmission optical sensor. was there. That is, since only one point on the outer edge of the wafer is detected by one transmission type optical sensor, even if the wafer 108 is displaced on the gripping plate 102, there is no change in position depending on the direction in which the displacement occurs. , May be detected by the optical sensor 111 and determined to be normal. As a result, the wafer on the grip plate 102 is transported with a positional deviation, and the possibility that the wafer is damaged increases. In the case where the wafer position shift is detected by using one optical sensor 111, it is considered that the occurrence of the above problems is fatal.

Further, the configuration for detecting the positional deviation of the wafer disclosed in each of the five patent documents mentioned above causes the same problem as described above when one optical sensor is used, and also uses three or more optical sensors. However, depending on the arrangement of the optical sensors, it is naturally possible to detect wafer positional deviations in all directions. However, a device that uses three or more optical sensors does not meet the desire to manufacture a device as inexpensively as possible. In view of the above, there is an increasing demand to increase the wafer misalignment detection performance, reliably detect wafer misalignment in all directions, and reduce the number of optical sensors as much as possible to reduce the manufacturing cost. .

An object of the present invention is to solve the above-described problems and meet the above-mentioned demands, and can detect a positional deviation reliably in any direction with respect to a normal position in a wafer processing apparatus. and to provide a wafer position deviation detecting system and the wafer position shift detecting how can be detected using an optical sensor.

Engaging roux E c positional deviation detecting system and the wafer position shift detecting method in the present invention is configured as follows in order to achieve the above object.

A wafer misalignment detection apparatus according to the present invention includes an arm mechanism unit that performs expansion and contraction operations, a grip plate that is attached to a tip of the arm mechanism unit and places a wafer, a rotation mechanism unit that rotates the arm mechanism unit, A rotation mechanism unit and a base that supports the arm mechanism unit; a robot arm that includes first and second position-invariant photosensors on the base; and a first position when the wafer is in the first position. First combination result of detection result by optical sensor and detection result by second optical sensor, detection result by first optical sensor and detection by second optical sensor when wafer is in second position It is characterized in that the presence / absence of wafer misalignment is determined based on the second combination result with the result.

In the above-described wafer misalignment detection apparatus, the first and second photosensors are in a state where the first photosensor is shielded from light by the wafer and the second photosensor is in a light-receiving state when the arm mechanism is in the fully contracted state. The first optical sensor is in a light receiving state and the second optical sensor is in a light shielding state when the wafer is in the second position and the arm mechanism is in a specific state other than the most contracted state. The first optical sensor is in the light receiving state and the second optical sensor is in the light shielding state by the first wafer detection in the specific state, and the first optical sensor is shielded in the second wafer detection in the most contracted state. The wafer is determined to be in a normal position when the second optical sensor is in a light receiving state, and in other cases, it is determined that a positional shift has occurred.

In the wafer misalignment detection apparatus, both the first and second optical sensors have a U-shaped configuration having an opening, and the first optical sensor directs the opening toward the direction of expansion and contraction of the robot arm. The second photosensor is arranged with the opening directed in a direction orthogonal to the expansion and contraction direction.

A wafer misalignment detection method according to the present invention is a wafer misalignment detection method implemented by each of the above-described wafer misalignment detection devices, wherein the first optical sensor is a wafer when the arm mechanism is in a fully contracted state. The first light sensor is in the light receiving state and the second light sensor is in the light shielding state when the light is in the light shielding state, the second light sensor is in the light receiving state, and the arm mechanism is in a specific state other than the most contracted state. As a condition, it is determined that the wafer is in a normal position, and when the above condition is not satisfied, it is determined that the wafer is displaced.

As is apparent from the above description, according to the present invention, the wafer is obtained by using two small optical sensors and satisfying the predetermined positional relationship as described above in the combination of the light shielding state and the light receiving state in the two detection operations. since the state mounted in the gripping plate was made to determine whether the resulting position is or positional deviation normal, positional displacement in all directions can detect the, the cost further required to the light sensor in the low cost Can be realized.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a plan view showing an internal configuration of a wafer processing apparatus provided with a wafer misalignment detection apparatus according to the present invention, and FIG. 2 is a longitudinal sectional view of a main part of FIG. In FIG. 2, the illustration of the wafer misalignment detection device is omitted. 1 and 2 show a separation chamber (wafer transfer chamber) 11 for wafer transfer in a wafer processing apparatus 10 of a multi-chamber type. A wafer transfer device is provided inside the separation chamber 11, and the wafer transfer device is constituted by a robot arm 12. 1 and 2, a plan view and a side view of the robot arm 12 are shown. A wafer position deviation detecting device according to the present invention is attached to the robot arm 12. The configuration of the robot arm 12 itself is basically the same as that of the robot arm 101 described in the section of the prior art. The configuration of the wafer misalignment detection device attached to the robot arm 12 has a feature of the present invention. This wafer misalignment detection device has two optical sensors 13 and 14 (shown in FIG. 1) arranged in a predetermined positional relationship. ). The optical sensors 13 and 14 are, for example, transmissive optical sensors, and include a light projecting unit and a light receiving unit.

  First, a schematic configuration of a wafer processing apparatus related to a wafer misalignment detection apparatus according to the present invention will be described with reference to FIGS. The separation chamber 11 provided with the robot arm 12 has, for example, a substantially regular pentagonal planar shape, and processing chambers (vacuum containers) 15A to 15D are attached to the four side surfaces thereof as indicated by two-dot chain lines. Each processing chamber 15 </ b> A to 15 </ b> D includes a wafer stage 16. A wafer 17 to be processed is mounted on the wafer stage 16 in each processing chamber. Here, the contents of the surface treatment of the wafer performed in each processing chamber have a small relationship with the main part of the invention, and the description thereof will be omitted. Between each of the processing chambers 15 </ b> A to 15 </ b> D and the separation chamber 11, a gate valve 18 is provided for isolating each chamber and maintaining the respective sealing properties. The processing chambers 15A to 15D are formed as vacuum containers, and in order to process the surface of the wafer 17 mounted on the wafer stage 16, the inside of the processing chamber is in a required vacuum state (depressurized state), and a process is performed. Plasma is generated by introducing gas and power, and the surface of the wafer 17 is processed. For this reason, an exhaust device, a gas introduction device, a power supply device, and the like are attached to each processing chamber. However, these are well known and are omitted in FIG. A room 19 connected to the internal space of the separation chamber 11 is formed on the other side surface of the separation chamber 11, and two wafer tables 20 are arranged side by side. This wafer stage 20 is an intermediate wafer placement stage. As shown in FIG. 2, the wafer stage 20 is provided so as to be lifted and lowered as necessary by a lifting device 21.

  An external robot arm 22 for introducing the wafer 17 from the outside into the separation chamber 11 is provided outside the room 20 connected to the separation chamber 11. The wafer 17 introduced by the external robot arm 22 is mounted on the wafer table 20 in the raised state. In FIGS. 1 and 2, the members whose positions are changed by the movement are indicated by adding a dash to the original number.

  Next, the robot arm 12 will be described with reference to FIG. 1, FIG. 3, and FIG. 3 is a perspective view showing a wafer transfer operation state based on the robot arm 12. FIG. 3A shows a state where the robot arm 12 is contracted, and FIG. 3B shows a state where the robot arm 12 is extended. Yes. FIG. 4 is an enlarged plan view of a portion of the robot arm 12. 3A substantially coincides with FIG. The basic configuration is the same as that of the robot arm 101 as described above. That is, a base 31 is provided on the lower wall 11a of the separation chamber 11, and the base 31 is provided so as to freely rotate around its central axis by a driving device 32 provided on the lower side of the lower wall 11a. A first parallel link pair 33 is attached to the base 31, an intermediate connecting portion 34 is connected to the outer ends of the parallel link pair 33, and a second parallel link pair 35 is also attached to the intermediate connecting portion 34. A grip plate mounting portion 36 is provided at the outer end of the two parallel link pairs 35. In the intermediate connecting portion 34, the parallel link pair 33 is attached at the lower position, and the parallel link pair 35 is attached at the upper position. A grip plate 37 is fixed to the tip of the grip plate mounting portion 36. The entire robot arm 12 is rotated clockwise or counterclockwise by the driving device 32. The parallel link pair 33, the base 31, and the intermediate connecting portion 34 form a first parallelogram link device, and the parallel link pair 35, the intermediate connecting portion 34, and the grip plate attaching portion 36 form a second parallelogram link device. Is formed. The parallel link pair 33 forms a first arm, and the parallel link pair 35 forms a second arm. By operating the motor built in the base 31 and the motor built in the intermediate connecting portion 34, each connecting portion (joint portion) is rotated. By rotating the connecting portion in this way, the parallel link pair (first arm) 33 and the parallel link pair (second arm) 35 rotate, and the arm mechanism portion of the robot arm 12 as a whole is the length of the gripping plate 37. It expands and contracts in the direction (axial direction 38). The direction in which the gripping plate 37 advances and retreats is determined by the rotation of the robot arm 12 based on the driving device 32, and the expansion and contraction of the robot arm 12 is performed based on the rotation of the parallel link pairs 33 and 35 as shown in FIG. The grip plate 37 is moved back and forth.

  Based on the above-described configuration and operation, the robot arm 12 carries the unprocessed wafer 17 placed on the wafer stage 20 positioned in the middle into one of the processing chambers 15A to 15D, or processing chambers 15A to 15D. The wafer 17 processed in either of the above operations is carried out and placed on the wafer stage 20. When the wafer is loaded into the processing chamber, the robot arm 12 extends the arm portion toward the processing chamber, and when the wafer is unloaded from the processing chamber, the arm mechanism is contracted. Wafer loading (introduction) and unloading (unloading) are performed by the expansion and contraction of the robot arm 12. In the wafer transfer operation based on the robot arm 12 as described above, the wafer 17 needs to be in a normal position with the grip plate 37. That is, it is necessary to be placed between the four claws 39 in the grip plate 37. Whether or not the wafer is in the normal position on the holding plate 37 or whether or not a positional deviation has occurred is determined by an attached positional deviation detection device. Wafer position deviation means that a part of the wafer rides on the claw 39.

  4 in which only the robot arm 12 is enlarged is shown, in particular, a plan view of the wafer misalignment detection apparatus, and FIG. 5 is a side view of the wafer misalignment detection apparatus. With reference to FIGS. 4 and 5, the wafer misalignment detection apparatus will be described. Although the wafer misalignment detection device is fixed to the base 31, the illustration of the wafer misalignment detection device is omitted in FIG. In the present embodiment, the misregistration detection device that detects misregistration of the wafer 17 that occurs during conveyance is configured using two optical sensors 13 and 14. The positional deviation detection device includes a mounting plate 51 fixed to the base 31 and two optical sensors 13 and 14 fixed on the mounting plate 51 in a predetermined positional relationship. The mounting plate 51 is held horizontally, and its surface is parallel to the surface of the wafer 17 to be transferred. When the robot arm 12 performs an expansion / contraction operation, the gripping plate 37 moves in the axial direction 38, but the mounting plate 51 has a configuration in which the longitudinal direction extends toward the axial direction 38. . The optical sensor 13 is provided on the rear side in the axial direction 38 with respect to the mounting plate 51, and the optical sensor 14 is provided on the front side in the axial direction 38. The installation positions of the optical sensors 13 and 14 are determined so that the wafer 17 and the optical sensors 13 and 14 are in a predetermined positional relationship when the robot arm 12 is in the most contracted state (at the time of the minimum contraction). . The condition to be satisfied regarding the positional relationship is given based on the operation state of the optical sensors 13 and 14 corresponding to the position of the wafer 17, and details thereof will be described later.

  The optical sensors 13 and 14 are transmissive optical sensors, in which an optical fiber 52 is wired in a U-shaped frame shown in FIGS. And a light receiving portion is formed at the lower end. In the U-shaped frame of the optical sensors 13 and 14, an opening for allowing the wafer to pass is formed between the light projecting portion and the light receiving portion at the tip. A light beam 53 passes between the leading ends of the U-shaped frame. When the light beam 53 is blocked, the light is blocked. Otherwise, the light is received. The optical fiber 52 drawn from the rear side of the optical sensors 13 and 14 in the U-shaped frame is drawn to the lower side of the mounting plate 51, and further extended downward along the column plate 55 via the coupler 54. . In FIG. 5, reference numeral 56 denotes the height position of the transferred wafer.

  In the above description, the wafer 17 is assumed to have a diameter of 200 mm, for example, and the dimensions of the mounting plate 51 and the arrangement positions of the optical sensors 13 and 14 on the mounting plate 51 are set in order to detect the wafer 17. In addition, as shown in FIGS. 4 and 5, the arrangement state of the optical sensors 13 and 14 having the U-shaped frame is such that the U-shaped frame of the rear side optical sensor 13 is in the axial direction (stretching direction of the robot arm). 38 and is open toward the front (right side in FIG. 4) (the opening is directed in the axial direction 38), and the front photosensor 14 has a U-shaped frame orthogonal to the axial direction 38. 4 and is open toward the upper side in FIG. 4 (the opening is oriented in the direction perpendicular to the axial direction 38).

  Next, the operation of the robot arm 12 having the above-described configuration will be described, and the wafer position deviation detection method according to the present invention will also be described. In this description, FIGS. 7 to 10 are referred to together with the above-described drawings. FIG. 7 shows a transitional state in which the robot arm 12 performs a transport operation as indicated by an arrow 57 and transports the wafer 17 in a state where the wafer 17 is mounted on the gripping plate 37. The direction of the arrow 57 coincides with the direction of the axial direction 38 described above. Further, the wafer 17 is shown by a broken line in order to clearly show the shape of the holding plate 37. When the robot arm 12 is in the most extended state (for example, state F in FIG. 12), the grip plate 37 and the wafer 17 mounted thereon are in a state of entering the inside of the processing chamber. In the state where the robot arm 12 is most contracted, the outer edge of the wafer 17 is engaged with the two transmissive optical sensors 13 and 14. 8 and 9 show two states in which the robot arm 12 is contracted in the axial direction 38 and the gripping plate 37 and the wafer 17 are retracted. The positional relationship shown in FIG. 8 indicates the positional relationship related to the first detection state of the wafer 17. At this time, the rear side optical sensor 13 is in a light receiving state, and the front side optical sensor 14 is in a light shielding state. The positional relationship shown in FIG. 9 indicates the positional relationship related to the second detection state of the wafer 17. At this time, the rear side optical sensor 13 is in a light shielding state, and the front side optical sensor 14 is in a light receiving state. The positional relationship shown in FIG. 9 is the positional relationship created when the robot arm 12 is in the most contracted state, and the positional relationship shown in FIG. 8 was created with the robot arm 12 slightly extended from the most contracted state. It is a positional relationship. The positional relationship that creates a state in which the rear side optical sensor 13 shown in FIG. 9 is in a light shielding state (which is turned on) and the front side optical sensor 14 is in a light receiving state (which is turned off) is referred to as a reference position. To do.

  The positional relationship between the wafer 17 and the two transmission optical sensors 13 and 14 generated by the operation of the robot arm 12 (that is, the wafer transfer device) shown in FIGS. 8 and 9 is controlled by the control device. Made by doing. Since a computer is used as the control device and is well known, it is not shown here. The positional deviation detection of the wafer 17 according to the present embodiment is performed by using the two optical sensors 13 and 14 and creating the two states shown in FIGS.

  The method for detecting the positional deviation of the wafer is as follows. When the wafer 17 that has been subjected to the surface treatment is taken out of any of the processing chambers 15A to 15D, the robot arm 12 receives the wafer 17 with its gripping plate 37 in an extended state, and performs a contraction operation. At this time, it is a problem whether the wafer 17 is in a normal position on the grip plate 37 or whether or not a positional deviation has occurred. Therefore, the presence / absence of misalignment is detected. In a state where the wafer 17 is mounted on the grip plate 37, the robot arm 12 performs a contraction operation and moves the wafer 17 to the left in FIG. Then, the operation of the robot arm 12 is temporarily stopped at the position shown in FIG. At this time, if the wafer 17 is in a normal position without causing a positional shift with respect to the holding plate 37, the rear transmission optical sensor 13 is in a light receiving state and the front transmission optical sensor 14 is in a light shielding state. The first position detection of the wafer 17 is performed based on the positional relationship shown in FIG. 8, and the wafer 17 is placed on the grip plate 37 at a normal position, that is, at a position between the four claws without riding on the claws 39. That is confirmed.

  Next, the robot arm 12 is operated, further contraction operation is performed, and the wafer 17 is moved to the reference position. At this position, as shown in FIG. 9, if the wafer 17 is in a normal position, the rear transmission optical sensor 13 is in a light shielding state and the front transmission optical sensor 14 is in a light receiving state. In this way, the second position detection of the wafer 17 is performed based on the positional relationship shown in FIG. 9, and it is confirmed whether or not it is a normal position.

  As described above, in the method of detecting the wafer position deviation according to the present embodiment, the position of the wafer 17 is confirmed using the two transmissive optical sensors 13 and 14 in two steps as shown in FIGS. I have to. Thus, it is possible to detect how far the wafer 17 mounted on the gripping plate 37 is out of the normal position with respect to the gripping plate 37. Moreover, even if a positional deviation occurs in any direction, it is possible to detect all using two optical sensors.

  FIG. 10 shows the direction of misalignment of the wafer 17 that may occur on the gripping plate 37, and the comparison of detection performance between the conventional method and the method according to the present invention (according to this embodiment) with respect to the misalignment in each direction. It is. As the misalignment occurrence direction, eight directions of the vertical direction, the horizontal direction, and a direction located between them are shown in FIG. The conventional method is a misregistration detection apparatus configured using one optical sensor shown in FIG. As apparent from FIG. 10, according to the conventional method, as the wafer shift direction, it is not possible to detect the position shift in the left direction, the upper left direction, the lower direction, the lower right direction, and the lower left direction in FIG. On the other hand, it has been proved that the displacement of all directions can be detected by the method of the present embodiment. Further, there is an advantage that the wafer position shift in all directions can be detected by using the two minimum optical sensors 13 and 14.

  It should be noted that by changing the mounting positions of the optical sensors 13 and 14 in the above-described embodiment, an allowable amount of wafer deviation can be adjusted, and a change in wafer dimensions can be accommodated. In the above-described embodiment, the optical sensor is configured as a transmission type, but it is needless to say that the optical sensor can be configured as a reflection type. Further, the optical sensor is not limited to one using an optical fiber. It is also possible to use a light emitting element or a light receiving element. Moreover, a silicon substrate is preferable as a wafer to be detected for displacement, and a transparent substrate is not a target. Further, regarding the positional deviation detection method, the process is not particularly shown using a flowchart or the like, but it is clear in the explanation of the configuration and operation of the above-mentioned apparatus, and the summary explanation is given in the column of means for solving the problem. Has been done.

The present invention is an apparatus for processing the surface of a semiconductor wafer, such as an etching apparatus or a CVD apparatus, and is used for detecting a wafer position shift.

It is a top view which shows the internal structure of the wafer processing apparatus with which the wafer position shift detection apparatus which concerns on this invention is applied. It is a vertical side view which shows the internal structure of the wafer processing apparatus with which the wafer position shift detection apparatus of this invention is applied. 4A and 4B are perspective views showing a wafer transfer operation state by the robot arm of the present invention, where A shows a state where the robot arm is contracted and B shows a state where the robot arm 12 is extended. It is a top view of the robot arm of the present invention. It is a partial side view which shows the principal part structure of the wafer position shift detection apparatus of this invention. It is a perspective view of the transmissive optical sensor of the present invention. It is a top view which shows one process of operation | movement of the robot arm of this invention. It is a top view which shows the 1st detection state by the wafer position shift detection apparatus of this invention. It is a top view which shows the 2nd detection state (reference position) by the wafer position shift detection apparatus of this invention. It is a figure for demonstrating the effectiveness of the wafer position shift detection apparatus of this invention. It is a top view of the robot arm of the conventional wafer conveyance apparatus. It is a top view which shows the operation example of the conventional robot arm. It is a perspective view of the conventional optical sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wafer processing chamber 11 Separation chamber 12 Robot arm 13, 14 Optical sensor 17 Wafer

Claims (4)

An arm mechanism that performs expansion and contraction,
A grip plate that is attached to the tip of the arm mechanism and on which a wafer is placed;
A rotating mechanism for rotating the arm mechanism;
A base that supports the rotation mechanism and the arm mechanism;
First and second photosensors that are position invariant on the base;
Having a robot arm with
A first combination result of a detection result by the first photosensor and a detection result by the second photosensor when the wafer is in a first position;
A second combination result of a detection result by the first photosensor and a detection result by the second photosensor when the wafer is in a second position;
And determining whether or not the wafer is misaligned based on the wafer. The first and second optical sensors are configured such that when the arm mechanism portion is in a fully contracted state, the first optical sensor is in a light shielding state with the wafer and the second optical sensor is in a light receiving state, The first photosensor is in a light receiving state and the second photosensor is in a light shielding state when the arm mechanism is in a specific state other than the most contracted state in the second position. Has been placed,
In the first wafer detection in the specific state, the first optical sensor is in a light receiving state and the second optical sensor is in a light shielding state, and in the second contraction state, the first optical sensor is in the light receiving state. The wafer is determined to be in a normal position when the second light sensor is in a light-shielding state and the second photosensor is in a light-receiving state, and in other cases, it is determined that a positional shift has occurred. The wafer positional deviation detection apparatus as described. The first and second optical sensors both have a U-shaped configuration having an opening, and the first optical sensor is disposed with the opening directed toward the extending and contracting direction of the robot arm, The wafer position deviation detection device according to claim 2, wherein the second optical sensor is arranged with the opening directed in a direction orthogonal to the expansion and contraction direction. A wafer misalignment detection method implemented by the wafer misalignment detection apparatus according to any one of claims 1 to 3,
When the arm mechanism portion is in the fully contracted state, the first photosensor is in a light shielding state with the wafer and the second photosensor is in a light receiving state,
The wafer is in a normal position on condition that the first optical sensor is in a light receiving state and the second optical sensor is in a light shielding state when the arm mechanism is in a specific state other than the most contracted state. Judge that there is,
When the condition is not satisfied, it is determined that the wafer is displaced.
A wafer positional deviation detection method characterized by the above.

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