Delivery device and delivery method

Abstract

The present invention relates to a conveying apparatus and a conveying method. A substrate held by a conveying apparatus is appropriately detected in the conveying apparatus which conveys a plurality of substrates at the same time. A conveying apparatus which holds and conveys a first substrate and a second substrate in a manner of overlapping when viewed from above includes a first holding arm which holds the first substrate in a horizontal direction, a second holding arm which holds the second substrate in the horizontal direction, a first detection sensor which detects the presence or absence of the first substrate held by the first holding arm, and a second detection sensor which detects the presence or absence of the second substrate held by the second holding arm. At least the first detection sensor is constituted by a sensor which irradiates a light beam with the second holding arm as a reference surface, detects a difference in a light receiving position of a diffused reflection light from the reference surface and a diffused reflection light from the substrate, and thereby detects the presence or absence of the first substrate. A notch through which the light beam irradiated toward the second holding arm passes is formed at an inner end of a tip end portion of at least the first holding arm.

Description

Technical Field

[0001] This disclosure relates to conveying devices and conveying methods. Background Technology

[0002] Patent Document 1 discloses a plasma processing system comprising: a housing having an internal transfer device for feeding and unloading a workpiece; a receiving portion attached to the side of the housing and containing the workpiece; and a plasma processing apparatus for processing the workpiece. According to the plasma processing system described in Patent Document 1, windows are formed at relative positions on the upper and lower surfaces of the housing, and optical sensors for detecting the presence or absence of the workpiece are disposed on the outer side of these opposing windows.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Utility Model Application Publication No. 6-34253 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] The technology disclosed herein allows for the appropriate detection of substrates held in a transport apparatus that simultaneously transports multiple substrates.

[0008] Solution for solving the problem

[0009] One technical solution disclosed herein is a transport device that holds and transports a first substrate and a second substrate in an overlapping manner when viewed from above. The transport device includes: a first holding arm that holds the first substrate in a horizontal direction; a second holding arm that holds the second substrate in a horizontal direction; a first detection sensor that detects the presence or absence of the first substrate held by the first holding arm; and a second detection sensor that detects the presence or absence of the second substrate held by the second holding arm. At least the first detection sensor is composed of a sensor that illuminates a light beam with the second holding arm as a reference surface, detects the difference in the light-receiving positions of diffused reflected light from the reference surface and diffused reflected light from the substrate, thereby detecting the presence or absence of the first substrate. A notch is formed at at least at the inner end of the top portion of the first holding arm for the light beam illuminating the second holding arm to pass through.

[0010] The effects of the invention

[0011] According to this disclosure, in a transport apparatus that simultaneously transports multiple substrates, it is possible to appropriately inspect the substrates held in the transport apparatus. Attached Figure Description

[0012] Figure 1 This is a top view schematically illustrating a structural example of a vacuum processing apparatus according to an embodiment.

[0013] Figure 2 This is a three-dimensional diagram showing an example of the structure of a wafer transport mechanism.

[0014] Figure 3 This is a perspective view showing an example of a notch being formed in the lower picking section.

[0015] Figure 4 This is a longitudinal sectional view schematically illustrating an example of the structure of a wafer inspection mechanism according to an embodiment.

[0016] Figure 5 This is an explanatory diagram showing an example of the setup of a wafer inspection facility.

[0017] Figure 6 This is a flowchart illustrating the main steps of a wafer transport method according to an embodiment.

[0018] Figure 7 This is an explanatory diagram showing the main steps of the wafer transport method according to the implementation method.

[0019] Figure 8 This is a flowchart illustrating the main steps of a wafer transport method according to an embodiment.

[0020] Figure 9 This is an explanatory diagram showing the main steps of the wafer transport method according to the implementation method.

[0021] Figure 10 This is an explanatory diagram showing the effect of the notch formed in the lower picking section.

[0022] Figure 11 This is an explanatory diagram showing other structural examples of wafer inspection mechanisms.

[0023] Figure 12 This is an explanatory diagram showing other structural examples of wafer inspection mechanisms.

[0024] Figure 13 This is an explanatory diagram showing other structural examples of wafer inspection mechanisms.

[0025] Figure 14 This is a flowchart illustrating the main steps of the initialization process of the wafer transport mechanism.

[0026] Figure 15 This is an explanatory diagram illustrating an example of the initialization action of a wafer transport mechanism. Detailed Implementation

[0027] For example, in the manufacturing process of semiconductor devices, the interior of a processing module that houses a semiconductor wafer (substrate: hereinafter referred to as "wafer") is brought into a depressurized state, and various predetermined processing steps are performed on the wafer. These processing steps are performed using a vacuum processing apparatus equipped with multiple processing modules, in which multiple wafers, such as two wafers, are mounted longitudinally and transported simultaneously using a transport arm in order to shorten the time required for transporting the wafers.

[0028] In the case of transporting multiple wafers simultaneously, in order to properly feed and send wafers into and out of each processing module, it is necessary to independently determine and detect the presence or absence of wafers mounted on the transport arm.

[0029] The plasma processing system described in Patent Document 1 detects the presence or absence of wafers held inside a robotic arm (transfer arm) by illuminating light from a translucent sensor mounted outside the housing through a transparent window. However, Patent Document 1 does not describe the independent determination and detection of multiple substrates mounted on the transfer arm as described above. Furthermore, when using the translucent sensor disclosed in Patent Document 1 to independently detect the presence or absence of multiple wafers, there are difficulties due to spatial constraints such as the sensor's mounting position and angle, and there is room for improvement in this regard.

[0030] The technology disclosed herein was made in view of the above-described circumstances, and in a transport apparatus that simultaneously transports multiple substrates, the substrates held in the transport apparatus are appropriately inspected. Hereinafter, a vacuum processing apparatus equipped with the transport apparatus of this embodiment will be described with reference to the accompanying drawings. Furthermore, in this specification and the accompanying drawings, elements having substantially the same functional structure are labeled with the same reference numerals, thereby omitting repeated descriptions.

[0031] <Vacuum Processing Equipment>

[0032] First, the structure of the vacuum processing device will be explained. Figure 1 This is a schematic top view showing the general structure of the vacuum processing apparatus 1. In this embodiment, the vacuum processing apparatus 1 is described as an example having a COR (Chemical Oxide Removal) module and a PHT (Post Heat Treatment) module as processing modules. However, the module structure of the vacuum processing apparatus 1 disclosed herein is not limited to this and can be arbitrarily selected.

[0033] like Figure 1As shown, the vacuum processing apparatus 1 has a structure in which the atmospheric section 10 and the depressurization section 11 are integrally connected by loading interlock modules 20a and 20b. The atmospheric section 10 has multiple atmospheric modules for performing desired processing on the wafer W under atmospheric pressure. The depressurization section 11 has multiple depressurization modules for performing desired processing on the wafer W under depressurized atmosphere.

[0034] The loading interlock module 20a temporarily holds the wafer W to be transferred from the loading module 30 (described later) of the atmospheric section 10 to the transfer module 60 (described later) of the decompression section 11. The loading interlock module 20a has multiple internal storage cabinets (not shown), such as two, thereby holding two wafers W internally at the same time.

[0035] The loading interlock module 20a is connected to the loading module 30 (described later) and the transfer module 60 (described later) via a gate (not shown) equipped with a gate valve (not shown). This gate valve ensures both airtightness and interconnectivity between the loading interlock module 20a, the loading module 30, and the transfer module 60.

[0036] The load interlock module 20a connects a gas supply section (not shown) for supplying gas and a gas exhaust section (not shown) for discharging gas, and is configured to switch the internal atmosphere to atmospheric pressure and depressurized pressure using the gas supply section and the exhaust section. That is, the load interlock module 20a is configured to appropriately transfer the wafer W between the atmospheric pressure section 10 and the depressurized pressure section 11.

[0037] Loading interlock module 20b temporarily holds wafer W for transfer from transfer module 60 to loading module 30. Loading interlock module 20b has the same structure as loading interlock module 20a. That is, it has a gate valve (not shown), a gate valve (not shown), an air supply section (not shown), and an exhaust section (not shown).

[0038] Furthermore, the number and configuration of the interlocking modules 20a and 20b are not limited to this embodiment and can be set arbitrarily.

[0039] The atmospheric section 10 includes: a loading module 30 equipped with a wafer transport mechanism 40 (described later), a loading port 32 for holding a front-opening wafer transport box 31 capable of storing multiple wafers W, a CST module 33 for cooling the wafers W, and a positioning module 34 for adjusting the orientation of the wafers W in the horizontal direction.

[0040] The loading module 30 includes an internal rectangular housing, the interior of which is maintained at atmospheric pressure. Multiple loading ports 32, for example three, are arranged on one side of the long side of the housing. Loading interlock modules 20a and 20b are arranged on the other side of the long side of the housing. A CST module 33 is provided on one side of the short side of the housing. A positioning module 34 is provided on the other side of the short side of the housing.

[0041] Furthermore, the number and configuration of the loading port 32, CST module 33, and positioning module 34 are not limited to this embodiment and can be designed arbitrarily. In addition, the type of atmospheric module provided in the atmospheric section 10 is not limited to this embodiment and can be selected arbitrarily.

[0042] The front-opening wafer transfer box 31 accommodates multiple wafers, for example, a batch of 25 wafers W. Furthermore, the interior of the front-opening wafer transfer box 31, placed in the loading port 32, is filled and sealed, for example, with atmosphere or nitrogen.

[0043] A wafer transport mechanism 40 for transporting wafers W is provided inside the loading module 30. The wafer transport mechanism 40 includes transport arms 41a and 41b for holding and moving the wafer W, a rotary table 42 supporting the transport arms 41a and 41b for rotation, and a rotary mounting stage 43 on which the rotary table 42 is mounted. The wafer transport mechanism 40 is configured to be movable in the longitudinal direction inside the housing of the loading module 30.

[0044] The decompression unit 11 includes a transfer module 60 for simultaneously transporting two wafers W to various processing modules, a COR module 61 for COR processing of the wafers W, and a PHT module 62 for PHT processing of the wafers W. The transfer module 60, COR module 61, and PHT module 62 are maintained in a decompression atmosphere. Furthermore, multiple COR modules 61 and PHT modules 62 are provided relative to the transfer module 60, for example, four COR modules 61 and two PHT modules 62.

[0045] The transfer module 60, serving as a transport device, includes an internal rectangular housing, which, as described above, is connected to the loading interlock modules 20a and 20b via gate valves (not shown). The transfer module 60 sequentially transports the wafer W fed into the loading interlock module 20a to a COR module 61 and a PHT module 62, and after applying COR and PHT treatments to the wafer W, it is then discharged to the atmosphere section 10 via the loading interlock module 20b.

[0046] The COR module 61 contains two stages 61a and 61b arranged horizontally to hold two wafers W. The COR module 61 performs COR processing on both wafers W simultaneously by arranging and holding them on stages 61a and 61b. Furthermore, the COR module 61 is connected to a gas supply unit (not shown) for supplying processing gas, purge gas, etc., and an exhaust unit (not shown) for discharging gas.

[0047] The PHT module 62 has two stages 62a and 62b arranged horizontally to hold two wafers W. The PHT module 62 performs PHT processing on both wafers W simultaneously by arranging and holding them on stages 62a and 62b. Furthermore, the PHT module 62 is connected to a gas supply unit (not shown) for supplying processing gas, purge gas, etc., and an exhaust unit (not shown) for discharging gas.

[0048] Furthermore, COR module 61 and PHT module 62 are connected to transmission module 60 via a gate (not shown) equipped with a gate valve (not shown). This gate valve ensures both airtightness and interconnectivity between transmission module 60 and COR module 61 and PHT module 62.

[0049] Furthermore, the number, configuration, and type of processing modules provided in the transmission module 60 are not limited to this embodiment and can be arbitrarily set.

[0050] The transfer module 60 contains a wafer transport mechanism 70 for transporting wafers W. The wafer transport mechanism 70 includes transport arms 71a and 71b arranged longitudinally (i.e., overlapping when viewed from above) to hold and move the two wafers W; a rotary table 72 supporting the transport arms 71a and 71b for rotation; and a rotary mounting stage 73 mounting the rotary table 72. Furthermore, the transfer module 60 contains a guide rail 74 extending along its length. The rotary mounting stage 73 is mounted on the guide rail 74 and configured to allow the wafer transport mechanism 70 to move along the guide rail 74.

[0051] like Figure 2 As shown, the conveying arm 71a has a first arm 100 rotatably connected at one end relative to the rotary table 72, a second arm 110 rotatably connected at one end relative to the other end of the first arm 100, and a third arm 120a and a fourth arm 120b rotatably connected at the other end of the second arm 110. That is, the conveying arm 71a has a linkage arm structure that connects the three types of arms using two shafts.

[0052] Furthermore, an upper pick-up section 121a and a lower pick-up section 121b for holding wafers W are respectively connected to the other end of the third arm 120a and the other end of the fourth arm 120b. Moreover, the transport arm 71a uses the upper pick-up section 121a and the lower pick-up section 121b to hold and transport two wafers W simultaneously in a manner in which the two wafers W overlap when viewed from above.

[0053] In addition, such as Figure 2 and Figure 3 As shown, a notch 122 is formed at the inner end of the top portion of the lower pickup section 121b to allow the light beam Y irradiated from the lower wafer detection sensor 82 (described later) to pass through. Additionally, as... Figure 3 As shown, the shape of the notch 122 formed in the lower pickup section 121b is not particularly limited as long as the light beam Y passing through the notch 122 can reach the upper surface of the upper pickup section 121a.

[0054] The transport arm 71b has the same structure as the transport arm 71a. That is, the transport arm 71b has a linkage arm structure that connects three types of arms using two axes, configured to hold and transport two wafers W simultaneously in a manner that overlaps when viewed from above. In addition, a notch 122 is formed at the inner end of the top end of the lower pick-up section 121b of the transport arm 71b.

[0055] Furthermore, in the transfer module 60, the transfer arm 71a receives the wafer W held in the loading interlock module 20a and transfers it to the COR module 61. Additionally, the transfer arm 71a holds the wafer W that has undergone COR processing and transfers it to the PHT module 62. Furthermore, the transfer arm 71b holds the wafer W that has undergone PHT processing and sends it out to the loading interlock module 20b.

[0056] In addition, in the following description, the wafer held in the upper pick-up section 121a of the two wafers W held in the transport arm 71a or the transport arm 71b is sometimes referred to as the "upper wafer Wt", and the wafer held in the lower pick-up section 121b is referred to as the "lower wafer Wb".

[0057] In addition, in the decompression section 11, a plurality of wafer inspection mechanisms 80, totaling six in this embodiment, are provided corresponding to each COR module 61 and each PHT module 62. Each wafer inspection mechanism 80 can independently inspect two wafers W mounted on the wafer transport mechanism 70 (each pick-up part of the upper pick-up part 121a and the lower pick-up part 121b of the transport arm 71a or 71b).

[0058] Furthermore, the location of the wafer inspection mechanism 80 is not limited to the example shown in the figure. For example, it can also be set in a manner corresponding to the loading interlock modules 20a and 20b.

[0059] like Figure 4As shown, the wafer inspection mechanism 80 includes an upper wafer inspection sensor 81 for inspecting the upper wafer Wt mounted on the upper pickup unit 121a and a lower wafer inspection sensor 82 for inspecting the lower wafer Wb mounted on the lower pickup unit 121b.

[0060] The upper wafer inspection sensor 81, for example, is a ranging reflective sensor having a light-emitting part 81a and a light-receiving part 81b, and is disposed on the lower exterior of the housing constituting the transfer module 60. The upper wafer inspection sensor 81 illuminates a sensor beam (see reference) onto the top surface of the transfer module 60 through a light-transmitting window 83. Figure 4 The beam X is used as a reference surface to inspect the wafer W mounted on the transport arm 71a.

[0061] Specifically, the difference between the light-receiving positions of the diffused reflected light x1 from the top surface and the light-receiving positions of the diffused reflected light x2 from the wafer W and the light-receiving positions of the wafer W is detected, thereby determining whether the wafer W is mounted on the transport arm 71a.

[0062] Furthermore, the upper wafer inspection sensor 81 detects the presence or absence of the wafer W on the transport arm 71a by detecting the light-receiving positions of the diffused reflected light x1 and x2 from the top surface and the wafer W. However, when the light-receiving unit 81b receives both diffused reflected light and positive reflected light, it may falsely detect the presence or absence of the wafer W on the transport arm 71a. Specifically, the wafer W, which serves as the irradiation surface of the light beam X, has a mirror surface, so the light beam X irradiated at the wafer W undergoes positive reflection. Moreover, when the positive reflected light is received by the light-receiving unit 81b in addition to the diffused reflected light, it is impossible to properly detect the difference in light-receiving positions between the diffused reflected light x1 and the diffused reflected light x2, which may falsely detect the presence or absence of the wafer W.

[0063] Therefore, in this embodiment, the mounting angle of the upper wafer inspection sensor 81, in other words... Figure 5 The incident angle θx of the light beam X relative to the irradiated surface (in this embodiment, the tilt angle relative to the horizontal direction) needs to be such that the light-receiving unit 81b can receive at least a portion of the diffused reflected light x1 and x2 from the top surface of the transmission module 60 and the back surface of the wafer W, but does not receive the positive reflected light at the wafer W. This incident angle θx is preferably 20° to 70°, and more preferably 30° to 60°. When the incident angle is less than 20°, it is impossible to properly detect the diffused reflected light x1 and x2 using the light-receiving unit 81b. On the other hand, when the incident angle is greater than 70°, receiving the positive reflected light from the wafer W using the light-receiving unit 81b may result in the positive reflected light being mistakenly detected as diffused reflected light x1 and x2.

[0064] The lower wafer inspection sensor 82 is, for example, a ranging reflective sensor having a light-emitting part 82a and a light-receiving part 82b, and is located on the lower exterior of the housing constituting the transfer module 60. The lower wafer inspection sensor 82 illuminates a sensor beam (see reference) onto the back side (non-holding surface of the upper wafer Wt) of the upper pickup part 121a via a light-transmitting window 84. Figure 3 and Figure 4 The beam Y is used to detect the wafer W on the lower pickup section 121b, with the back side of the upper pickup section 121a as a reference surface.

[0065] Specifically, the light-receiving positions of the diffused reflected light y1 from the back of the upper pickup unit 121a and the diffused reflected light y2 from the wafer W, which are received by the light-receiving unit 82b, are detected to determine whether a lower wafer Wb is mounted on the lower pickup unit 121b.

[0066] In addition, the mounting angle of the lower wafer inspection sensor 82, in other words... Figure 5 The incident angle θy of the light beam Y relative to the irradiation surface (in this embodiment, the tilt angle relative to the horizontal direction) is preferably 20° to 70° and more preferably 30° to 60°, similar to that of the upper wafer detection sensor 81.

[0067] Furthermore, as described above, the light beam Y emitted from the projection section 82a of the lower wafer inspection sensor 82 passes through the notch 122 formed at the inner end of the top part of the lower pickup section 121b and illuminates the back side of the upper pickup section 121a.

[0068] The vacuum processing apparatus 1 described above is equipped with a control unit 90. The control unit 90 is, for example, a computer equipped with a CPU, memory, etc., and has a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the wafer W in the vacuum processing apparatus 1. Furthermore, the program storage unit also stores a program for controlling the operation of the drive systems of the various processing modules, transport mechanisms, etc., described above, and for implementing the wafer processing described later in the vacuum processing apparatus 1. Alternatively, the program may be stored on a storage medium H that can be read by a computer, and loaded into the control unit 90 from that storage medium H.

[0069] The vacuum processing apparatus 1 of this embodiment is configured as described above. Next, a wafer processing method including the substrate transport method of this embodiment will be described. Figure 6 and Figure 7 This is a flowchart and explanatory diagram showing the main steps of the method for transporting wafer W from the transport arms 71a and 71b of the wafer transport mechanism 70 relative to various processing modules. Furthermore, Figure 8 and Figure 9 This is a flowchart and explanatory diagram showing the main steps of the transport method for transporting wafer W from various processing modules relative to the transport arms 71a and 71b of the wafer transport mechanism 70.

[0070] <Wafer Processing Methods>

[0071] First, a front-opening wafer transfer box 31, which holds multiple wafers (e.g., 25 wafers in a batch), is fed into the loading port 32. With the front-opening wafer transfer box 31 positioned in the loading port 32, the wafer transport mechanism 40 accesses the front-opening wafer transfer box 31 and retrieves two wafers W from it. After the two wafers W delivered from the front-opening wafer transfer box 31 are aligned horizontally by the positioning module 34, they are transported to the storage cabinet (not shown) of the loading interlock module 20a.

[0072] When the two wafers W are transported to the loading interlock module 20a, the interior of the loading interlock module 20a switches from atmospheric pressure to depressurized pressure, and then connects with the interior of the transfer module 60. Next, the two wafers W are sequentially handed over to the upper pick-up section 121a and the lower pick-up section 121b of the transport arm 71a, and then sent into the transfer module 60.

[0073] Alternatively, when transferring the wafer W from the loading interlock module 20a to the transport arm 71a, a detection can be performed to determine whether the transfer of the wafer W to the transport arm 71a is appropriate. In this case, the method for detecting the transfer of the wafer W is not particularly limited; for example, it can be performed using a detection sensor (not shown) installed inside the loading interlock module 20a, or as described above, by providing a wafer detection mechanism 80 corresponding to the loading interlock module 20a. The details of the detection method using the wafer detection mechanism 80 will be described later.

[0074] The wafer transport mechanism 70, holding two wafers W, then moves to a COR module 61. Next, the two wafers W held in the transport arm 71a are transferred from the upper pick-up section 121a and the lower pick-up section 121b to the stages 61a and 61b of the COR module 61, respectively.

[0075] When transferring wafer W from transport arm 71a to COR module 61, as described above, firstly, wafer transport mechanism 70 is moved to a position between the transfer module 60 and COR module 61 for transferring wafer W (hereinafter sometimes referred to as the "first initialization position"). Figure 6 Step S1).

[0076] When the wafer transport mechanism 70 moves to the first initialization position of the COR module 61, the wafer inspection mechanism 80, which is provided corresponding to the COR module 61, detects the case where two wafers W are mounted on the transport arm 71a of the wafer transport mechanism 70. Figure 6 Step S2). Specifically, as Figure 7 As shown in (a), the light beams X and Y emitted from the light-projecting section 81a of the upper wafer detection sensor 81 and the light-projecting section 82a of the lower wafer detection sensor 82, respectively, are diffused and reflected at the lower wafer Wb. Therefore, the diffused and reflected light x2 and y2 are received in the light-receiving sections 81b and 82b, and by detecting the light-receiving positions of the diffused and reflected light x2 and y2, the case where at least the lower wafer Wb is mounted on the lower pickup section 121b is detected.

[0077] Here, as Figure 7 As shown in (a), the upper wafer detection sensor 81 detects the case where at least the lower wafer Wb is mounted on the transport arm 71a by detecting the diffused reflected light x2 from the lower wafer Wb on the light beam X from the projection section 81a. In other words, when both the upper wafer Wt and the lower wafer Wb are mounted on the transport arm 71a, the light beam X is reflected by the lower wafer Wb before reaching the upper wafer Wt, therefore, it is not possible to independently detect the case where the upper wafer Wt is mounted on the upper pickup section 121a. However, according to this embodiment, as described above, when transferring the wafer W from the loading interlock module 20a, the wafer Wt is mounted on the upper pickup section 121a before the lower pickup section 121b. Furthermore, as described later, when transferring the wafer W relative to the processing module, the lower wafer Wb is mounted on the lower pickup section 121b before the upper pickup section 121a. That is, the transport method according to this embodiment is also as follows. Figure 7 and the following Figure 9 As shown, the transport operation of wafer W is controlled so that a state is not formed where only the lower wafer Wb is held in the transport arm 71a. When the lower wafer Wb is held in the lower pick-up section 121b, the upper wafer Wt is always held in the upper pick-up section 121a. Therefore, in this embodiment, even when the upper wafer Wt cannot be independently detected by the upper wafer detection sensor 81, it is possible to simulate the detection of the case where the upper wafer Wt is mounted in the upper pick-up section 121a.

[0078] Next, the lower pick-up section 121b of the transport arm 71a accesses the COR module 61, and the lower wafer Wb is transferred from the lower pick-up section 121b to the COR module 61. Figure 6 Step S3).

[0079] When transferring the lower wafer Wb from the lower pick-up section 121b, the lower wafer detection sensor 82 detects whether the lower wafer Wb has been properly transferred from the lower pick-up section 121b relative to the COR module 61. Figure 6 Step S4). Specifically, as Figure 7 As shown in (b), by receiving at least a portion of the diffused reflected light y1 from the back side of the upper pickup unit 121a of the light beam Y emitted from the light projection unit 82a of the lower wafer detection sensor 82 using the light receiving unit 82b, the detection is performed when the lower wafer Wb is not held in the lower pickup unit 121b, that is, when the lower wafer Wb is properly handed over to the COR module 61.

[0080] Alternatively, when detecting the handover of the lower wafer Wb (step S4), the detection of whether the upper wafer Wt is indeed held in the upper pickup unit 121a can also be performed simultaneously. As described above, when the lower wafer Wb is mounted in the lower pickup unit 121b, the upper wafer Wt in the upper pickup unit 121a cannot be directly detected using the upper wafer detection sensor 81. Therefore, by confirming the reception of the diffused reflected light x2 by the light receiving unit 81b at the moment the lower wafer Wb is handed over to the COR module 61, the situation where the upper wafer Wt is mounted in the upper pickup unit 121a can be appropriately detected according to the different light receiving positions of the diffused reflected light x1.

[0081] When the lower wafer Wb is transferred to the COR module 61, the upper pick-up section 121a of the transport arm 71a then accesses the COR module 61, and the upper wafer Wt is transferred from the upper pick-up section 121a. Figure 6 Step S5).

[0082] When the upper wafer Wt is transferred from the upper pick-up section 121a, the upper wafer detection sensor 81 is used to detect whether the upper wafer Wt has been properly transferred from the upper pick-up section 121a relative to the COR module 61. Figure 6 Step S6). Specifically, as Figure 7 As shown in (c), by using the light receiving section 81b to receive at least a portion of the diffused reflected light x1 from the top surface of the transfer module 60 of the light beam X irradiated from the light projection section 81a of the upper wafer detection sensor 81, the case where the upper wafer Wt is not held in the upper pickup section 121a, that is, the case where the upper wafer Wt is properly transferred to the COR module 61, is detected.

[0083] When two wafers W are placed on stages 61a and 61b of COR module 61 respectively, the gate valve (not shown) of COR module 61 is closed to perform COR processing on the two wafers W.

[0084] When the COR process of COR module 61 is completed, the gate valve (not shown) is opened to transfer the two wafers W from the stage 61a and 61b of COR module 61 to the transport arm 71a of wafer transport mechanism 70.

[0085] When transferring wafer W from COR module 61 to transfer arm 71a, firstly, wafer transfer mechanism 70 is moved to the first initialization position, that is, the position for transferring wafer W between the transfer module 60 and COR module 61. Figure 8 Step P1).

[0086] When the wafer transport mechanism 70 moves to the first initialization position of the COR module 61, the wafer detection mechanism 80, which is provided corresponding to the COR module 61, detects cases where no wafer W is mounted on the transport arm 71a of the wafer transport mechanism 70. Figure 8 Step P2). Specifically, as Figure 9 As shown in (a), the light beams X and Y, respectively emitted from the light-emitting section 81a of the upper wafer detection sensor 81 and the light-emitting section 82a of the lower wafer detection sensor 82, are diffused and reflected on the top surface of the transfer module 60 and the back surface of the upper pickup section 121a. As a result, at least a portion of the diffused and reflected light x1 and y1 is received in the light-receiving sections 81b and 82b, thereby enabling detection even when the wafer W is not mounted on the transport arm 71a.

[0087] Next, the upper pick-up section 121a of the conveyor arm 71a accesses the COR module 61, transferring the upper wafer Wt to ​​the upper pick-up section 121a. Figure 8 Step P3).

[0088] When the upper wafer Wt is transferred to the upper pickup unit 121a, the upper wafer detection sensor 81 detects whether the upper wafer Wt has been properly transferred to the upper pickup unit 121a. Figure 8 Step P4). Specifically, as Figure 9 As shown in (b), the case of transferring the upper wafer Wt to ​​the upper pickup unit 121a is detected by detecting the change in the light-receiving position of the diffused reflected light x1 from the top surface of the transfer module 60 received by the light-receiving unit 81b due to the mounting of the upper wafer Wt to ​​the light-receiving position of the diffused reflected light x2 from the upper wafer Wt.

[0089] When the upper wafer Wt is transferred to the upper pick-up unit 121a, the lower pick-up unit 121b of the transport arm 71a then accesses the COR module 61 and transfers the lower wafer Wb to the lower pick-up unit 121b. Figure 8 Step P5).

[0090] When the lower wafer Wb is transferred to the lower pickup unit 121b, the lower wafer detection sensor 82 is used to detect whether the lower wafer Wb has been properly transferred to the lower pickup unit 121b. Figure 8 Step P6). Specifically, as Figure 9 As shown in (c), the situation where the lower wafer Wb is handed over to the lower pickup unit 121b is detected by detecting the change in the light-receiving position of the diffused reflected light y1 from the back side of the upper pickup unit 121a, which is detected by the light-receiving unit 82b, to the light-receiving position of the diffused reflected light y2 from the lower wafer Wb due to the mounting of the lower wafer Wb.

[0091] When the two wafers W are transferred to the transport arm 71a, the wafer transport mechanism 70 then moves to the first initialization position of a PHT module and transfers the two wafers W to the stage 62a and 62b of the PHT module 62, respectively.

[0092] The method of wafer W handover relative to PHT module 62 and Figure 6 and Figure 7 The method of transferring wafer W relative to COR module 61 is the same. That is, as described above, wafer transport mechanism 70 moves to the first initialization position of PHT module 62 ( Figure 6 Step S1), after confirming the holding state of wafer W ( Figure 6 In step S2), the lower pickup unit 121b and the upper pickup unit 121a sequentially access the PHT module 62 to transfer the lower wafer Wb and the upper wafer Wt. Figure 6 Steps S3 and S5). Furthermore, at this time, it is checked whether the lower wafer Wb and upper wafer Wt are properly transferred from the lower pick-up unit 121b and the upper pick-up unit 121a. Figure 6 Steps S4 and S6).

[0093] When placing two wafers W onto stages 62a and 62b of the PHT module 62 respectively, the gate valve (not shown) of the PHT module 62 is closed to perform PHT processing on the two wafers W.

[0094] When the PHT processing of PHT module 62 is completed, the gate valve (not shown) is opened, and the two wafers W are transferred from the stage 62a and 62b of PHT module 62 to the transport arm 71b of wafer transport mechanism 70.

[0095] The method of transferring wafer W from PHT module 62 to transport arm 71b and Figure 8 and Figure 9 The method of transferring wafer W from COR module 61 relative to transport arm 71a is the same. That is, as described above, wafer transport mechanism 70 moves to the first initialization position of PHT module 62 ( Figure 8Step P1), after confirming the holding state of wafer W ( Figure 8 In step P2), the upper pickup unit 121a and the lower pickup unit 121b sequentially access the PHT module 62, and connect the upper wafer Wt and the lower wafer Wb. Figure 8 Steps P3 and P5). Furthermore, at this time, it is checked whether the upper wafer Wt and lower wafer Wb are properly transferred from the upper pick-up unit 121a and the lower pick-up unit 121b. Figure 8 Steps P4 and P6).

[0096] Then, the gate valve (not shown) of the loading interlock module 20b is opened, and the two wafers W are transported to the storage cabinet (not shown) of the loading interlock module 20b by the wafer transport mechanism 70.

[0097] When two wafers W are transported to the loading interlock module 20b, the interior of the loading interlock module 20b switches from a reduced pressure atmosphere to an atmospheric pressure atmosphere, and then connects with the interior of the loading module 30. Next, the two wafers W are transferred to the wafer transport mechanism 40, cooled by the CST module 33, and then housed in the front-opening wafer transfer box 31 of the loading port 32. This completes the series of wafer processing steps in the vacuum processing apparatus 1.

[0098] <Effects of the substrate inspection method in this embodiment>

[0099] As described above, the transfer module 60 of this embodiment includes a ranging reflective sensor, serving as an upper wafer detection sensor 81 and a lower wafer detection sensor 82 for detecting the wafer W mounted on the transfer arms 71a and 71b of the wafer transport mechanism 70. Therefore, compared to using a transmissive sensor as the wafer inspection mechanism, which is also disclosed in Patent Document 1, the space required for such a wafer inspection mechanism can be eliminated. Specifically, since it is not necessary to arrange the light-emitting and light-receiving parts of the light beam relative to each other as with a transmissive sensor, the spatial constraints related to the installation of the wafer inspection mechanism can be reduced.

[0100] Furthermore, according to this embodiment, a notch 122 is formed at the inner end of the top end of the lower pickup portion 121b used to hold the lower wafer Wb, for allowing the light beam Y irradiated from the lower wafer detection sensor 82 to pass through. Thus, as... Figure 10 As shown, compared to the case where the notch 122 is not formed, the margin M between the outer end We of the lower wafer Wb mounted on the lower pickup section 121b and the center of the beam Y can be set to be larger.

[0101] As described above, for the lower wafer Wb mounted on the lower pickup unit 121b, the light beam Y irradiated from the lower wafer detection sensor 82 detects the presence or absence of the lower wafer Wb by detecting the difference in the light-receiving positions at the light-receiving portion 82b of the diffused reflected light y1 from the back surface of the upper pickup unit 121a and the diffused reflected light y2 from the lower wafer Wb. Here, if the lower wafer Wb is mounted with a position offset relative to the lower pickup unit 121b, or if the mounting position of the lower wafer Wb is offset during transport, the lower wafer detection sensor 82 may falsely detect the presence or absence of the lower wafer Wb. Specifically, since the lower wafer Wb is mounted with a position offset relative to the lower pickup unit 121b, and the light beam Y does not properly irradiate the lower wafer Wb, it is possible that the diffused reflected light y1 from the back surface of the upper pickup unit 121a may be received even though the lower wafer Wb is mounted.

[0102] In this regard, according to this embodiment, the reference plane of the beam Y of the lower wafer detection sensor 82 is set to the back side of the upper pickup section 121a, and a notch 122 is formed at the inner end of the top end of the lower pickup section 121b, thereby setting a larger margin M between the outer end of the lower wafer Wb and the center of the beam Y. In other words, the range of false detection of positional offset relative to the lower wafer Wb can be set smaller (increasing the range that the beam Y can illuminate relative to the lower wafer Wb), thus improving the reliability of positional offset relative to the lower wafer Wb during transport.

[0103] Furthermore, in this embodiment, the mounting angles of the upper wafer inspection sensor 81 and the lower wafer inspection sensor 82, in other words, the incident angles θx and θy of the light beams X and Y relative to the irradiation surface, are set to angles such that at least a portion of the diffused reflected light x1 and y1 from the top surface of the transfer module 60 and the back surface of the upper pickup unit 121a can be received by the light-receiving units 81b and 82b, while the positive reflected light from the wafer W cannot be received by the light-receiving units 81b and 82b. Therefore, the light-receiving units 81b and 82b can appropriately detect the differences in the light-receiving positions of the diffused reflected light x1 and y1 and the diffused reflected light x2 and y2, that is, the presence or absence of the wafer W on the transport arm can be appropriately detected.

[0104] In addition, in the above embodiments, the wafer inspection mechanism 80 (upper wafer inspection sensor 81 and lower wafer inspection sensor 82) is located outside and below the transfer module 60, but the location of the wafer inspection mechanism 80 is not limited to this.

[0105] Specifically, for example, it could also be, such as Figure 11As shown, the upper wafer detection sensor 81 and the lower wafer detection sensor 82 are respectively disposed on the upper exterior of the transfer module 60. In this case, for example, the upper wafer detection sensor 81 can illuminate the light beam X using the upper surface of the lower pickup section 121b as a reference surface, and the lower wafer detection sensor 82 can illuminate the light beam Y using the bottom surface of the transfer module 60 as a reference surface. Furthermore, in this case, in order to improve the reliability of positional offset relative to the upper wafer Wt during transport, a notch 122 may be formed at the inner end of the top end of the upper pickup section 121a.

[0106] Furthermore, with the upper wafer detection sensor 81 and the lower wafer detection sensor 82 respectively located above and outside the transfer module 60, when both the upper wafer Wt and the lower wafer Wb are mounted on the transport arm 71a, the light beam Y is positively reflected by the upper wafer Wt before reaching the lower wafer Wb. Therefore, it is impossible to independently detect the case where the lower wafer Wb is mounted on the lower pickup unit 121b. From this perspective, when the upper wafer detection sensor 81 and the lower wafer detection sensor 82 are located above and outside the transfer module 60, it is desirable to control the transport operation of the wafer W so that a state is not formed where only the upper wafer Wt is held on the transport arm 71a, and when the upper wafer Wt is held on the upper pickup unit 121a, the lower wafer Wb is necessarily held on the lower pickup unit 121b. Therefore, even when the mounting of the lower wafer Wb cannot be detected independently using the lower wafer inspection sensor 82, it is possible to simulate the detection of the case where the lower wafer Wb is mounted on the lower pickup unit 121b.

[0107] In addition, for example, such as Figure 12 As shown, alternatively, the upper wafer detection sensor 81 can be positioned above the outside of the transfer module 60, and the lower wafer detection sensor 82 can be positioned below the outside of the transfer module 60. In this case, for example, the upper wafer detection sensor 81 can illuminate the light beam X using the upper surface of the lower pickup section 121b as a reference surface, and the lower wafer detection sensor 82 can illuminate the light beam Y using the back surface of the upper pickup section 121a as a reference surface. Furthermore, in this case, to improve the reliability of positional offset relative to the upper wafer Wt and lower wafer Wb during transport, a notch 122 can be formed at the inner end of the top portion of each of the upper pickup section 121a and the lower pickup section 121b.

[0108] Furthermore, in the above embodiments, the upper wafer detection sensor 81 and the lower wafer detection sensor 82 are both composed of a ranging reflective sensor, but it is also possible that the upper wafer detection sensor 81 and the lower wafer detection sensor 82 are composed of other types of detection sensors.

[0109] Specifically, for example, such as Figure 13As shown, the upper wafer detection sensor 181 can also be composed of a transmissive sensor, and the lower wafer detection sensor 82 can be composed of a ranging reflective sensor. In this case, the upper wafer detection sensor 181, being a transmissive sensor, detects that no wafer W is mounted on the transport arm 71a when the light beam X irradiated from the light-emitting section 181a is received by the light-receiving section 181b. On the other hand, if the light beam X is blocked by the wafer W and is not received by the light-receiving section 181b, it detects that at least one wafer W is mounted on the transport arm 71a.

[0110] Thus, by using at least one of the upper wafer inspection sensor 81 and the lower wafer inspection sensor 82 constituting the wafer inspection mechanism 80 as a ranging reflective sensor, multiple wafers W mounted on the transport arm can be independently determined and inspected. Furthermore, compared to using only a transmissive sensor as the wafer inspection mechanism, the spatial constraints related to the arrangement of this wafer inspection mechanism are reduced. Moreover, by setting the reference plane illuminated by the beam of the ranging reflective sensor to either the upper pickup section 121a or the lower pickup section 121b, and forming a notch 122 in the other pickup section, the reliability of the positional offset of the wafer inspection mechanism relative to the wafer W can be improved.

[0111] Furthermore, in the above embodiments, when the wafer W mounted on the transport arms 71a and 71b is fed into or out of the processing module, the wafer inspection mechanism 80 detects the presence or absence of the mounted wafer W (wafer inspection operation). However, the timing of this wafer inspection operation is not limited to the above embodiments. For example, the wafer inspection mechanism 80 may detect the presence or absence of the wafer W mounted on the transport arms 71a and 71b when the holding state of the wafer W on the transport arms 71a and 71b is unclear due to an emergency stop of the vacuum processing device 1 (initialization operation).

[0112] Figure 14 and Figure 15 This is a flowchart and explanatory diagram showing the main steps of the initialization operation of the wafer transport mechanism 70. Furthermore, the following explanation uses the case where the initialization operation of the wafer transport mechanism 70 is performed at the first initialization position of a PHT module 62 as an example; however, as long as the "second initialization position" described later can be set, the initialization operation can be performed at the first initialization position of any processing module. Additionally, the following explanation uses the case where the initialization operation of the transport arm 71a (confirmation of the holding state of the wafer W) is performed as an example; however, the initialization method for the transport arm 71b is performed using the same method as the initialization operation of the transport arm 71a.

[0113] In the initialization operation of the wafer transport mechanism 70, firstly, the wafer transport mechanism 70, whose holding state of the transport arm 71a relative to the wafer W is unclear, is moved to the first initialization position of a PHT module 62. Figure 14 Step U1).

[0114] Next, using the lower wafer inspection sensor 82 of the wafer inspection mechanism 80, which is provided corresponding to the PHT module 62, it is detected whether the lower wafer Wb is held in the lower pick-up section 121b of the transport arm 71a. Figure 14 Step U2). Specifically, a beam Y is irradiated from the projection unit 82a onto the back side of the upper pickup unit 121a. The light receiving unit 82b determines whether the lower wafer Wb is mounted based on the difference between the light receiving position of diffused reflected light y1 from the back side of the upper pickup unit 121a (as a reference) and the light receiving position of diffused reflected light y2 from the back side of the lower wafer Wb. More specifically, if diffused reflected light is detected at the light receiving position of diffused reflected light y1 (as a reference), it is determined that the lower wafer Wb is not mounted; if diffused reflected light y2 is detected at a position offset from the light receiving position (as a reference), it is determined that the lower wafer Wb is mounted.

[0115] Next, the upper wafer inspection sensor 81 of the wafer inspection mechanism 80 is used to detect whether the upper wafer Wt is held in the upper pick-up section 121a of the transport arm 71a.

[0116] Here, as described above, normally when both the upper wafer Wt and the lower wafer Wb are mounted on the transport arm 71a, the beam X is positively reflected by the lower wafer Wb before reaching the upper wafer Wt. Therefore, it is not possible to independently detect the case where the upper pick-up unit 121a is equipped with the wafer Wt.

[0117] Therefore, in the initialization operation of this embodiment, the wafer transport mechanism 70 is rotated about the vertical axis by the movement of the rotary table 72 or the transport arm 71a. Figure 14 Step U3). Thus, by rotating the wafer transport mechanism 70 about the vertical axis, as... Figure 15 As shown, the wafer transport mechanism 70 is positioned such that the light beam X emanating from the upper wafer detection sensor 81 does not touch the lower wafer Wb but irradiates the upper wafer Wt (hereinafter referred to as the "second initialization position").

[0118] When the wafer transport mechanism 70 is moved to the second initialization position, it is then detected whether the upper wafer Wt is held in the upper pick-up section 121a of the transport arm 71a. Figure 14Step U4). Specifically, a beam X is irradiated onto the top surface of the transmission module 60 from the projection section 81a. The light-receiving section 81b determines whether the wafer Wt is mounted based on the difference between the light-receiving position of the diffused reflected light x1 from the top surface (as a reference) and the light-receiving position of the diffused reflected light x2 from the back surface of the upper wafer Wt. More specifically, if diffused reflected light is detected at the light-receiving position of the reference diffused reflected light x1, it is determined that the wafer Wt is not mounted; if diffused reflected light x2 is detected at a position offset from the light-receiving position of the reference, it is determined that the wafer Wt is mounted.

[0119] Thus, in the vacuum processing apparatus 1 of this embodiment, by rotating the wafer transport mechanism 70 around the vertical axis at a first initialization position of a processing module, the wafer transport mechanism 70 can be moved to a second initialization position where the beam X irradiates the upper wafer Wt without touching the lower wafer Wb. Therefore, even when the holding state of the transport arms 71a and 71b on the wafer W is unclear, it is possible to independently detect whether the wafer W is mounted on the upper pickup section 121a and the lower pickup section 121b.

[0120] Furthermore, the vacuum processing apparatus 1 of this embodiment differs from conventional vacuum processing apparatuses in that it has two initialization positions for the wafer transport mechanism 70. That is, in conventional vacuum processing apparatuses, the initialization position of the wafer transport mechanism 70 for transporting and inspecting wafer W is only the first initialization position described above, but in this embodiment, a second initialization position is set for independently inspecting the wafer Wt.

[0121] Additionally, for example, in Figure 14 In the detection of the wafer holding state of the lower pickup unit 121b shown in step U2, if it is determined that the lower wafer Wb is not mounted on the lower pickup unit 121b, it is not necessary to move the wafer transport mechanism 70 to the second initialization position in the detection of the upper wafer Wt in step U3. That is, since the lower wafer Wb is not mounted on the lower pickup unit 121b, the upper wafer Wt can be directly illuminated by the beam X from the upper wafer detection sensor 81 even without moving the wafer transport mechanism 70 to the second initialization position.

[0122] Furthermore, the structure of the vacuum processing apparatus 1 for the wafer W transport method (inspection method) using the technology of this disclosure is not limited to the above-described embodiments. That is, as long as multiple wafers W are transported and processed simultaneously using a wafer transport mechanism, the wafer W transport method (inspection method) of this disclosure can be applied to any processing system.

[0123] The embodiments disclosed herein should be considered illustrative rather than restrictive in all respects. The above embodiments may be omitted, substituted, or modified in various ways without departing from the appended claims and their spirit.

Claims

1. A conveying device that holds and conveys a first substrate and a second substrate in a manner that, when viewed from above, overlaps the first substrate and the second substrate, wherein, The conveying device includes: The first holding arm holds the first substrate in the horizontal direction; The second holding arm holds the second substrate in the horizontal direction; A first detection sensor detects the presence or absence of the first substrate held by the first holding arm; and The second detection sensor detects the presence or absence of the second substrate held by the second holding arm. At least the first detection sensor comprises a sensor that illuminates a light beam using the second holding arm as a reference surface, and detects the difference in the light-receiving positions of the diffused reflected light from the reference surface and the diffused reflected light from the substrate, thereby detecting the presence or absence of the first substrate. A notch is formed at the inner end of at least the tip of the first retaining arm to allow the light beam illuminating the second retaining arm to pass through. The tilt angle of the light beam emitted from the first detection sensor relative to the horizontal direction is set to an angle that allows the light-receiving part to receive diffused reflected light from the reference surface without allowing the light-receiving part to receive positively reflected light from the first substrate. The first detection sensor and the second detection sensor are disposed on a first side in the vertical direction of the first holding arm, and the second holding arm is disposed on a second side in the vertical direction of the first holding arm opposite to the first side. The second detection sensor uses the inner wall surface of the housing constituting the conveying device as a reference surface to irradiate a light beam and detect the presence or absence of the second substrate.

2. The conveying device according to claim 1, wherein, The tilt angle is between 20° and 70°.

3. The conveying device according to claim 2, wherein, The tilt angle is between 30° and 60°.

4. The conveying device according to any one of claims 1 to 3, wherein, At least one of the first detection sensor and the second detection sensor is a ranging reflective sensor.

5. The conveying device according to any one of claims 1 to 3, wherein, The second detection sensor is composed of a transmission type sensor.

6. A transport method comprising a method for transporting substrates in a transport apparatus in which a first substrate and a second substrate are held and transported in a manner in which the first substrate and the second substrate overlap when viewed from above, wherein, The conveying device includes: The first holding arm holds the first substrate in the horizontal direction; The second holding arm is disposed above the first holding arm and holds the second substrate in the horizontal direction; A first detection sensor detects the presence or absence of the first substrate held by the first holding arm; and The second detection sensor detects the presence or absence of the second substrate held by the second holding arm. At least the first detection sensor comprises a sensor that illuminates a light beam using the second holding arm as a reference surface, and detects the difference in the light-receiving positions of the diffused reflected light from the reference surface and the diffused reflected light from the substrate, thereby detecting the presence or absence of the first substrate. The first and second detection sensors are disposed on a first side in the vertical direction of the first holding arm, and the second holding arm is disposed on a second side in the vertical direction of the first holding arm opposite to the first side. The second detection sensor illuminates a light beam using the inner wall surface of the housing constituting the conveying device as a reference surface to detect the presence or absence of the second substrate. The conveying method includes the following steps: The first substrate held in the first holding arm is transferred between the first holding arm and the processing device attached to the conveying device; The holding state of the first holding arm on the first substrate is confirmed using the first detection sensor; The second substrate, held in the second holding arm, is transferred between the second holding arm and the processing device; and The second detection sensor is used to confirm the holding state of the second holding arm on the second substrate. The tilt angle of the light beam irradiated from the first detection sensor relative to the horizontal direction is set to an angle that allows the light-receiving part to receive diffused reflected light from the reference surface without allowing the light-receiving part to receive positive reflected light from the first substrate.

7. The conveying method according to claim 6, wherein, A notch is formed at the inner end of at least the tip of the first retaining arm. When the first substrate is detected using the first detection sensor, the light beam is irradiated onto the second holding arm in a manner that passes through the notch.

8. The conveying method according to claim 6 or 7, wherein, When the substrate is fed into the processing device, the first substrate is fed in before the second substrate is fed in. When the substrate is discharged from the processing device, the second substrate is discharged before the first substrate is discharged.

9. The conveying method according to claim 6 or 7, wherein, At least one of the first detection sensor and the second detection sensor is composed of a ranging reflective sensor.

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