JPS63155636A - Automatic sticking system for semiconductor wafer - Google Patents

Abstract

PURPOSE:To detect an error of the operation of a turning means by a method wherein the volume to be turned which is preset at the turning means for positioning a semiconductor wafer is compared with the actually turned volume of the turning means. CONSTITUTION:When a semiconductor wafer 2 is sucked and held by an alignment table, a CPU detects the starting edge and the end edge of an orientation flat OF by using a pulse motor 24 and a photoelectric device PHSW 1. The CPU calculates the turned volume corresponding to an angle theta which is formed by the starting edge and the end edge of this OF in relation to the center of the semiconductor wafer 2. If the turned volume is within a reference value, the volume, to be turned, of one-half of this turned volume is set at the motor 24 and the motor is turned so as to position the OF. Said volume, to be turned, which is set at the motor 24 is compared with the actually turned volume. If there is a discrepancy, the motor 24 has been driven abnormally; as a result, an error is displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an automatic semiconductor wafer affixing apparatus used for affixing a semiconductor wafer to an adhesive tape in a pre-process of a semiconductor wafer scribing process.

<Prior Art> Generally, in a scribing process for semiconductor wafers, scribing is performed with the semiconductor wafer attached to an adhesive tape. The scribed semiconductor wafer is attached to adhesive tape and then cracked. Then, stretch the adhesive tape to separate the individual semiconductor elements,
This allows the semiconductor device to be easily handled in the next process, the bonding process.

Such a process of attaching a semiconductor wafer to an adhesive tape is performed as a pre-process of a semiconductor wafer scribing process. With the automation of semiconductor manufacturing lines in recent years,
It is desired to develop an automatic device for attaching semiconductor wafers to adhesive tape.

<Problems to be Solved by the Invention> The present invention has been developed in view of the above circumstances, and is a device for automatic affixing of semiconductor wafers. The present invention aims to provide an apparatus for automatic pasting of semiconductor wafers with the functions of:

Such objects of the present invention will become clearer in the detailed description of the present invention that follows.

Means for Solving the Problems> In order to achieve the above object, the present invention adopts the following configuration.

That is, the present invention provides an automatic semiconductor wafer attachment device that aligns a semiconductor wafer on which an orientation flat is formed and attaches it to an adhesive tape, comprising: a semiconductor wafer alignment unit that aligns the semiconductor wafer; an operation error detection section that detects an operation error of the semiconductor wafer alignment section, and the semiconductor wafer alignment section holds the semiconductor wafer in a state where the center of the semiconductor wafer and the center of rotation are aligned. , a rotation means for rotating the rotation means; an orientation flat end detection means for detecting an end of an orientation flat of a semiconductor wafer held and rotated by the rotation means; and an actual rotation amount (actual rotation amount) of the rotation means. until one end of the orientation flat is detected by the actual rotation amount detection means for detecting the rotation amount and the orientation flat end detection means.
a first rotation amount setting means for setting a first rotation amount for rotating the rotation means and applying the first rotation amount to the rotation means; and a first rotation amount setting means for setting the first rotation amount for rotating the rotation means; a second rotation amount setting means for setting a second rotation amount in a direction opposite to the first rotation amount and applying the second rotation amount to the rotation means until the other end of the orientation flant is detected by the end detection means; , the actual rotation amount of the rotating means rotated by being given the second rotation amount is set to a third rotation amount which is 1/2 of the actual rotation amount given by the actual rotation amount detection means; , a third rotation amount setting means for applying the third rotation amount to the rotation means, and the operation error detection section sets the actual rotation amount of the rotation means rotated by applying the third rotation amount to the actual rotation amount. Detecting an operation error of the rotation means of the semiconductor wafer alignment section based on comparing the actual rotation amount given by the detection means and a third rotation amount set in the third rotation amount setting means. It is characterized by

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic perspective view showing the overall configuration of the automatic semiconductor wafer attachment device according to the present embodiment, and FIGS. 2 to 9 are schematic diagrams of the configuration of each part of the automatic semiconductor wafer attachment device. It is.

FIG. 10 shows a semiconductor wafer 2 that is attached to an adhesive tape by an apparatus for automatic attachment of semiconductor wafers according to this embodiment.
, a frame 4 for holding the adhesive tape to which the semiconductor wafer 2 is attached, and a mount frame 6 which is the frame to which the semiconductor wafer 2 is attached.

An orientation flat OF, which is a flat cutout surface, is formed on the outer periphery of the semiconductor wafer 2 . An element pattern is formed on the semiconductor wafer 2 using this orientation flat OF as a reference.

The frame 4 is a ring-shaped metal plate or resin plate,
On its outer periphery, notches 48 and 4□ are formed, which are used when aligning the frame 4, which will be described later.

For automatic attachment of semiconductor wafers according to this embodiment, the apparatus separately supplies the semiconductor wafer 2 and the frame 4 from the wafer loader section and the frame loader section, respectively, and attaches them to the adhesive tape, and finally mounts the semiconductor wafers. -The frame 6 is stored in the unloader section.

The configuration of each part of this device will be explained below.

Reference numeral 8 (8, to 84) shown in FIG. 1 is a wafer cassette set in the wafer loader section. Wafer
The cassette 8 holds a plurality of semiconductor wafers 2 horizontally and stores them vertically at regular intervals. In this embodiment, there are two wafer loader sections: the left wafer rotor section has wafer cassettes 80, 8□, and the right wafer loader section has wafer cassettes 80, 8. ．． 84 can each be a cent. Each wafer loader section is configured to be movable in the vertical direction, and the wafer cassette 8
The semiconductor wafer 2 is supplied by detecting the semiconductor wafer 2 inside and pushing it out.

The wafer push mechanism provided in each wafer loader section is shown in FIG. That is, in the left webber loader section, there is a wafer pushing mechanism 10 driven by a motor.
The right wafer loader section is provided with a wafer pushing mechanism 12 driven by an air cylinder.

The semiconductor wafers 2 supplied from each wafer loader section are
This semiconductor wafer 2 is transported to a semiconductor wafer alignment section 14 for alignment.

The semiconductor wafer 2 is transported to the semiconductor wafer alignment section 14 by a transport belt 16 shown in FIG. This conveyor belt 16 is driven by a motor 18 in forward and reverse directions.

The semiconductor wafer alignment unit 14 includes an alignment table 20 that receives and receives the semiconductor wafer 2 that has been transferred and aligns the orientation flat OF, and an alignment table 20 that aligns the center of the semiconductor wafer 2 with the alignment table 20.
A center alignment plate 22 for aligning the semiconductor wafer 2 so that the middle rc, sb, and center of the wafer 2 are aligned. , 22°, etc.

The alignment table 20 is equipped with a vacuum chuck for holding the semiconductor wafer 2 by suction. VLI is
The solenoid valve PUSWI that turns on/off the vacuum chuck is a pressure switch that detects a pressure drop within the vacuum chuck and turns on.

Further, this alignment table 20 is configured to be rotatable by a pulse motor 24 and configured to be movable in the vertical direction by an air cylinder 26.

Center alignment plate 22. , 22□ are provided at positions facing each other with the alignment table 20 at the upper limit position interposed therebetween. Each center alignment plate 22, . An arc-shaped reference surface corresponding to the outer shape of the semiconductor wafer 2 is formed on the opposing surface side of the semiconductor wafer 2 . Center alignment plate 22. ,22
□ is configured to be movable in the horizontal direction by a link mechanism driven by an air cylinder 28.

On both sides of the alignment table 20, conveyor belts 1
There is a wafer stopper 301°30□ for receiving and stopping the semiconductor wafer 2 conveyed on the wafer 6. Wafer stopper 30. ．． 30□ is swung by an air cylinder (not shown). When the semiconductor wafer 2 is supplied from the left wafer loader section, the right wafer stopper 30□ is used, and when the semiconductor wafer 2 is supplied from the right wafer loader section, the left wafer stopper 30□ 301 respectively rise and stop receiving the semiconductor wafer 2 that has been transported.

Reference numeral 32 shown in FIG.
In order to detect the edge of the orientation flat ○F of the semiconductor wafer 2 which is being held by suction and rotating,
This is an orientation flat end detection unit equipped with a set of transmission type photoelectric elements PH3WI, 2.3. As shown in FIG.
The light receiving section 38 and the light receiving section 38 are configured to be openable and closable by the air cylinder 34. The reason why such three sets of transmission type photoelectric elements PH3WI, 2.3 are used is to select and use appropriate photoelectric elements according to the size of the semiconductor wafer 2. The orientation flat end detection section 32 is open in a normal state, and is closed when detecting the end of the orientation flat 1-OF for positioning.

Reference numeral 40 shown in FIG. 1 and FIG.
A reversing fork is used to transfer the semiconductor wafer 2 whose OF has been aligned to the table 42. The reversing fork 40 is equipped with a vacuum chuck for suctioning and holding the semiconductor wafer 2 from the back side. VL2 is
The solenoid valve PUSW2 that turns on/off the vacuum chuck is a pressure switch that turns on when it detects a drop in the pressure inside the vacuum chuck.

The reversing fork 40 is driven by an air cylinder 44 to connect the alignment table 20 and the pasting table 4.
2, and is rotated upward by the motor 46, thereby inverting the semiconductor wafer 2 so that the back surface of the semiconductor wafer 2 faces upward. P.H.
3W4 is a photoelectric element for detecting whether the reversing fork 40 is in a predetermined position after performing a reversing operation.

As shown in FIG.
It includes a chuck table 48 and a frame chuck table 50 provided around the wafer chuck table 48. The wafer chuck table 48 is configured to be movable in the vertical direction by an air cylinder 49, and is biased upward by a compression coil spring 51. A protective film 52 is laid on the wafer chuck table 48. Reversing fork 4
The semiconductor wafer 2 transported by the wafer 2 is placed on the wafer chuck table 48 via the protective film 52 with its back side facing upward. Protective film 52
is used to prevent scratches from occurring on the surface of the semiconductor wafer 2.

Returning to FIG. 1, reference numeral 54 is a frame loader section. The frame loader section 54 includes a frame stocker 56 that stores a plurality of frames 4 in a stacked state, and a frame push-out mechanism that sequentially pushes out the frames 4 stored in the frame stocker 56 from below. This frame extrusion mechanism, as shown in Figure 4,
an extrusion plate 58 for extruding the frame 4;
It is composed of an air cylinder 60 that drives this horizontally.

The frame 4 supplied from the frame loader section 54 is
The frame positioning section 62
It is sent out to The frame feeding section includes a frame pusher 64 that engages with the inner peripheral surface of the frame 4 pushed out from the frame stocker 56 and feeds out the frame 4, and an air cylinder 66 for raising and lowering the frame pusher 64. , an air cylinder 68 for horizontally driving the frame bushing 64, and the like. In the normal state, frame pusher 64 is lowered.

When the frame 4 is pushed out from the frame stocker 56, the air cylinder 66 is driven to push up the frame pusher 64 and insert it into the frame 4, and then the air cylinder 68 is driven to push the frame pusher 64 up and into the frame 4. is sent out to the frame positioning section 62.

The frame positioning section 62 is provided with two positioning pins 70 (however, only one positioning pin 70 is shown in FIG. 4) for positioning the sent-out frame 4. This positioning pin 70 and the frame 4
The frame 4 is positioned by engaging the V-notches 44.4□. PH3W5 is a photoelectric element for detecting the positioned frame 4.

The positioned frame 4 is transported to the table 42 for pasting by the frame conveying section, and the pasting is carried out by the table 42.
It is placed on the frame chuck table 50 of No. 2. As shown in FIG. 5, the frame transport section includes a frame chuck arm 72 that holds the frame 4 by suction, an air cylinder 73 that raises this frame chuck arm 72, and a horizontal drive of the frame chuck arm 72. It is composed of an air cylinder 74, etc. for VL3 is a solenoid valve that turns on/off the frame chuck arm 72, and PUSW3 is a pressure switch that detects a drop in pressure within the frame chuck arm 72 and turns on.

The frame chuck table 50 attracts and holds the frame 4 transported by the frame transport section. Fifth
VL4 shown in the figure is a solenoid valve that turns on/off the frame chuck table 50, and PUSW4 is a solenoid valve that turns on/off the frame chuck table 50.
This is a pressure switch that detects a pressure drop within the chuck table 50 and turns on. Further, PH3W6 is a photoelectric element that detects the frame 4 on the frame chuck table 50.

Next, a tape supply/winding mechanism and an adhesive tape cutting mechanism will be explained based on FIGS. 1 and 6.

The above-described protective film 52 is pasted and supplied from a protective film supply reel 76 provided on one side of the table 42, and pasted and wound up by a protective film take-up reel 78 provided on the other side of the table 42. .

Reference numeral 80 is an adhesive tape supply reel that supplies adhesive tape 82 for pasting the semiconductor wafer 2. The adhesive tape 82 is set on the adhesive tape supply reel 80 in a state where it is overlapped with a separator 84 having the same width. The separator 84 is wound up separately from the adhesive tape 82 by a separator take-up reel 86 when the adhesive tape 82 is fed out with the adhesive side facing down.

The remainder of the adhesive tape 82 used for pasting the semiconductor wafer 2 is taken up by a residual tape take-up reel 88.

Reference numeral 90 denotes a pasting roller unit consisting of a plurality of rollers arranged in the vertical direction. As shown in FIG. 6, the adhesive tape 82 supplied from the adhesive tape supply reel 80 is applied to a roller unit 90 in a R S J shape, and is applied in parallel to the roller unit 90. The frame is then passed to the peeling roller unit 92 and wound onto the residue tape take-up reel 88.

As shown in FIG. 7, the pasting roller unit 90 is connected to the tip of an air cylinder 94 that horizontally drives the pasting roller unit 90. Furthermore, the peeling roller unit 92 is coupled to the cylinder body of the air cylinder 94. The pasting roller unit 90 and the peeling roller unit 92 are configured to slide on a rail 96 by means of cam followers provided above them. The rail 96 has air cylinders 9L provided at both ends thereof.
, 9B□, it is configured to be vertically movable. A rank and pinion mechanism 100 is provided at the bottom of the roller unit 90, and this rank and pinion mechanism 1
00 is driven by a motor 106 coupled via a brake 102 and a clutch 104.

The operations of the above-mentioned pasting roller unit 90 and peeling roller unit 92 will be explained with reference to FIGS. 7 and 8.

In the normal state, each roller unit 90, 92 is attached at the origin position to the left of the table 42, and the rail 9
6 is rising. Further, at this time, the brake 102 and the clutch 104 are released.

When pasting is performed, use an air cylinder 98°, 98□
is activated and the rail 96 is lowered. Then, a not-shown lever provided in connection with the peeling roller unit 92 operates to maintain the peeling roller unit 92 in a stopped state. In this state, when the air cylinder 94 is activated, only the roller unit 90 is driven in the horizontal direction, and the roller rolls while pressing the adhesive tape 82 on the table 42 downward, thereby creating an adhesive. tape 8
2 and the semiconductor wafer 2 are attached.

At this time, clutch 104 is released.

When peeling the residual tape from the frame 4 or the like after cutting the adhesive tape 82, the cock of the peeling roller unit 92 is released and the brake 102 is activated. In this state, when the air cylinder 94 is operated, the pasting roller unit 90 remains in a stopped state, so the peeling roller unit 92 and the air cylinder 94 move horizontally to the right as one. The peeling roller unit 92 peels off the residual tape by rotating the peeling roller while moving horizontally. FIG. 8 shows the position of each roller unit 90, 92 at the time when such a peeling operation is completed.

The return of each roller unit 90, 92 to its origin after the peeling operation is completed is performed as follows.

First, the air cylinders 9B, 98□ are operated to raise the rail 96. Raising the rail 96 in this way is done by each roller unit 90 during the return-to-origin operation.
This is because when the adhesive tape 92 rolls on the table 42, the residual tape peeled off by the above-described peeling operation will adhere to the frame 4 etc. again. As the rail 96 rises, the brake 102 is released and the clutch 104 is engaged. Then, when the motor 106 is operated and the rank-binion mechanism 100 is driven, the pasting roller unit 90 and the peeling roller unit 92 are integrally moved horizontally to the left and returned to the origin.

For pasting, an adhesive tape cutting mechanism 1 is provided above the table 42 for cutting the band-shaped adhesive tape 82 pasted by the above-described pasting operation into a circular shape along the frame 4.
08 is provided. This adhesive tape cutting mechanism 108
As shown in FIG.
0, a tape cutter 112 that is rotatably driven along the outer periphery of the presser plate 110, and the like. The pressing plate 110 and the tape cutter 112 are configured to be movable in the vertical direction as a unit.

Reference numeral 114 shown in FIG. 6 is a mount/frame chuck arm for ejecting the mount frame 6 from the attachment table 42. This mount/frame chuck arm 114 is attached to the peeling roller unit 92 described above. The mount/frame chuck arm 114 moves toward the table 42 side with the peeling operation of the peeling roller unit 92, and removes the mount/frame.
The frame 6 is held by suction, and the mount frame 6 is discharged and conveyed by the return-to-origin operation of the peeling roller unit 92 or the like. In addition, VL5 shown in FIG. 6 is a solenoid valve that turns on/off this mount/frame chuck arm 114, and PUSW5 is a solenoid valve that turns on/off the mount/frame chuck arm 114.
This is a pressure switch that detects a decrease in pressure within 14 and turns on.

The mount frame 6 suctioned and held by the mount frame chuck arm 114 is conveyed to the swing reversing unit 116 by the return-to-origin operation of each of the roller units 90 and 92. As shown in FIGS. 6 and 9, the swing reversing unit 116 includes a clamp mechanism 11 that holds the transported mount frame 6.
In addition to 8, there is also a swing mechanism 120 that swings the held mount frame 6 approximately 180 degrees in the horizontal direction, an inversion mechanism 122 that inverts the swung mount frame 6 so that the surface of the semiconductor wafer 2 faces up, and The mount frame is provided with a vertical drive mechanism 124 for lowering the mount frame to the heat tape 126. Note that the PH3W7 provided in the clamp mechanism 118 is a photoelectric element that detects the mount frame 6 clamped by the clamp mechanism 118.

The heat stage 126 is provided for the purpose of increasing tape tension by heating when using an adhesive tape using a heat-shrinkable film as a support.

As shown in FIG. 9, the mount frame 6 on the heat stage 126 is adjacent to the heat stage 126.
Mount frame extrusion mechanism 12 for extruding
8 and a transport table 130 for transporting the extruded mount frame 6 to a frame cassette 132 (132, to 1324) shown in FIG. The conveyance table 130 is configured to be movable in the horizontal direction by an air cylinder 131 shown in FIG. 9, and includes a conveyor belt 134 for conveying to the unloader section on the left side and a conveyor belt 134 for conveying to the unloader section on the right side. The mount frame 6 can be distributed to the belt 136.

In addition, PH3W8 shown in FIG. 9 is heat stage 1.
A photoelectric element for detecting the mounting frame 6 on 26, P
H3W9 is a photoelectric element that detects the extrusion of the mount frame 6 on the heat stage 126, and PH3WIO is a photoelectric element that detects the reception of the mount frame 6 by the transport table 130.

The frame cassette 132 stores a plurality of mount frames 6 horizontally at equal intervals, and in this embodiment, four frame cassettes 1321 to 1324 can be set. Frame cassettes 1321.132° are placed in the left unloader section, and frame cassettes 132. ．． 1
324 are respectively set in the right unloader section. Each unloader section is configured to be movable in the vertical direction.

Reference numeral 138 shown in FIG. 1 is an operation panel. The operation panel 138 is provided with a three-digit, seven-segment LED that displays a code corresponding to the type of error in the device, operation keys, and the like. Further, reference numeral 140 is a patrol light that displays automatic driving operations, error occurrences, and the like.

Next, the configuration of the control system of the apparatus for automatically attaching semiconductor wafers according to this embodiment will be explained based on FIG. 11.

The control unit 142 uses the CPUI 44. ROMI 46°R
AM148. Operation panel controller 150. Sensor controller 152. Actuator controller 154.
It is composed of a pulse motor controller 156 and the like. The CPU 144 controls the entire device according to a processing program stored in the ROM 146. RAM14
8, data such as the size of the semiconductor wafer to be pasted and processing conditions are written. Operation panel controller 15
0 refers to the operation panel 138, the sensor controller 152 refers to a group of various sensors 158 such as pressure switches and photoelectric elements provided in this device, and the actuator controller 15
4 is a group 160 of various actuators 24 such as motors and air cylinders provided in this device, and a pulse motor controller 156 is a pulse motor 24 that rotationally drives the alignment table 20.
Each of these is to be regulated and distributed separately.

Next, the operation of the automatic semiconductor wafer bonding apparatus having the above-described configuration will be explained according to the operation flowchart shown in FIG.

When the apparatus is started with each part of the apparatus having returned to its original position and with the wafer cassette 8 and frame cassette 132 installed in the wafer loader section and unloader section, respectively, the wafer - The wafer loader section on one side with the cassette 8 mounted is lowered (step S2).

It is confirmed whether the semiconductor wafer 2 in the wafer cassette 8 has been detected by the wafer detector provided in the wafer loader section (step S4).

When the semiconductor wafer 2 is detected, the transport heald 16 is driven, and the detected semiconductor wafer 2 is pushed out from inside the wafer cassette 8 by the wafer pushing mechanism 10 or 12 provided in the wafer loader section (step S8 ). The extruded semiconductor wafer 2 is transferred to the conveyor belt 1
6 and is transported to the semiconductor wafer alignment section 14.

Then, the alignment table 20 is aligned with the semiconductor wafer 2.
It is confirmed whether the receipt has been received or not (step 510).

Confirmation that the semiconductor wafer 2 has been received is detected by a photoelectric element PH3WI1 provided near the alignment table 20, as shown in FIG. If the alignment table 20 does not pick up the semiconductor wafer 2 after a certain period of time has elapsed, an error display ■ is performed (step 512), the error display light of the patrol light 140 lights up, and the 7-segment LED of the operation panel 138 lights up.
will display the code corresponding to this error.

When it is confirmed that the alignment table 20 has received the semiconductor wafer 2, the alignment table 20 is raised (step 514). And center alignment plate 22. , 22□ are driven to determine the center of the semiconductor wafer 2 (step 516). Once the center of the semiconductor wafer 2 has been determined, the vacuum chuck of the alignment table 20 is operated to suck the semiconductor wafer 2 (step 818). and a pressure switch PUSWI provided in connection with the vacuum chuck.
Thus, it is confirmed whether the semiconductor wafer 2 is reliably attracted (step 520).

When the suction of the semiconductor wafer 2 is confirmed, the orientation flat OF of the semiconductor wafer 2 is aligned (step 524).

The procedure for aligning the orientation flat OF of the semiconductor wafer performed in this step will be described in detail later.

When the alignment of the orientation flat OF is completed, check again whether or not the semiconductor wafer 2 is attracted (
step 326). This is because the semiconductor wafer 2 may come off from the alignment table 20 during the alignment operation of the orientation flat OF.

If it is detected in this step S26 that the object is not attracted, the process proceeds to step S22 described above and an error display (2) is displayed.

By the way, after the above-described step 514 is completed, the process moves to step S16 and also moves to step 328. As a result, the reversing fork 40 moves forward and stops while being inserted below the semiconductor wafer 2 that is attracted to the alignment table 2o.

After the reversing fork 40 is inserted below the semiconductor wafer 2, the alignment table 2o is lowered (step 530). At the same time as the alignment table 20 is lowered, the suction of the alignment table 20 is released,
The vacuum chuck of the reversing fork 4o is activated. As a result, the semiconductor wafer 2 on the alignment table 20 is moved to the reversing fork 40 and held there by suction.

Then, it is checked whether the reversing fork 40 has reliably attracted the semiconductor wafer 2 (step 532). The presence or absence of suction is determined based on a detection signal from a pressure switch PUSW2 provided in connection with the vacuum chuck of the reversing fork 4o. If suction has not been performed, an error display (2) is performed (step 534), the error display light of the patrol light 140 lights up, and the 7-segment LED of the operation panel 138 displays a code corresponding to this error.

When the semiconductor wafer 2 is reliably attracted to the reversing fork 40, the reversing fork 40 is reversed (step 83).
6). Then, it is confirmed whether the reversing fork 40 is at a predetermined reversing position (step 538). Whether or not the reversing fork 40 is reversed is determined based on the detection signal of the photoelectric element PH3W4 provided in relation to the reversing fork 40. If the reversing fork 40 has not been reversed to the predetermined position, an error message ■ is displayed (step 540).
), the error indicator light on the patrol light 140 lights up, and the 7-segment LED on the operation panel 138 displays a code corresponding to this error.

If the reversing fork 40 is correctly reversed, the suction of the semiconductor wafer 2 is confirmed again (step 34).
1) If it is not absorbed, the above error message will be displayed.
(step 534).

When the semiconductor wafer 2 is confirmed to be attracted, the reversing fork 4
0 is pasted and retreats to the table 42 side (step 542
). Then, the reversing fork 40 releases the suction of the semiconductor wafer 2 and transfers the transferred semiconductor wafer onto the wafer chuck table 48 covered with the protective film 52 (step 544). The semiconductor wafer 2 transferred to the wafer chuck table 48 has its back side facing up.

On the other hand, if the semiconductor wafer 2 is detected in step S4 described above, the process moves to step S8 and then to step 346. As a result, the frame 4 stored in the frame stocker 56 is pushed out by the frame push-out mechanism. Then, the frame pusher 64 provided in the middle of the conveyance path between the frame stocker 56 and the frame positioning section 62 rises (step 548), and moves forward while engaging the inside of the pushed-out frame 4 (step 550). . As a result, the frame 4 is sent out to the frame positioning section 62, and the notches 43 and 4 degrees of the frame 4 are moved to the frame positioning section 62.
The frame 4 is positioned by engaging with a positioning pin 70 provided in the frame 4 .

Then, it is confirmed whether the frame 4 has been reliably positioned (step 552). This is determined based on the detection signal of the photoelectric element PHS W 5 provided in the frame positioning section 62. If frame 4 is not aligned, an error message ■ is displayed (step 554).
), the error indicator light on the patrol light 140 lights up, and the 7-segment LED on the operation panel 138 displays a code corresponding to this error.

When the frame 4 has been positioned, the frame chuck arm 72 that transports the frame 4 to the table 42 descends to attach the frame 4 (stay 31 = tab 556), and adsorbs the positioned frame 4 (
step 858). Next, frame chuck arm 7
It is checked whether frame 2 has attracted frame 4 (step 560). This is determined based on the detection signal of the pressure switch PUSW3 provided in association with the frame chuck arm 72. If the frame 4 is not attracted, an error display ■ is displayed (step 562), and the error display light of the patrol light 140 lights up.
A seven segment LED on the control panel 138 will display a code corresponding to this error.

When it is confirmed that the frame 4 is attracted, the frame chuck arm 72 is raised (step 564).
). Then, it is checked again that frame 4 has been attracted (step 565), and if it has not been attracted, the above-mentioned error display (2) is performed (step 562). When adsorption of the frame 4 is confirmed, the frame chuck arm 72 moves to the attachment table 42 (step 5).
66). Then, the frame chuck arm 72 descends and transfers the frame 4 to the frame chuck table 50 (step 567).

When the transfer of the frame 4 is confirmed, the frame chuck table 50 is operated to suction and hold the placed frame 4 (step 570). Then, it is confirmed whether the frame chuck table 50 is reliably sucking the frame 4 (step 571). This is determined based on the detection signal of the pressure switch PUSW4 provided in relation to the frame chuck table 50.

If the frame 4 is not attracted, an error display (2) is performed (step 572), the error display light of the patrol light 140 lights up, and the 7-segment LED of the operation panel 138 displays a code corresponding to this error.

After confirming that the frame 4 is attracted to the frame/chuck table 50, the frame/chuck arm 7
In order to release the adsorption of the frame chuck arm 72 (step 573), the frame chuck arm 72 rises (step 574).

Through the above steps, the semiconductor wafer 2 and frame 4 are placed on the attachment table 42.

When the frame chuck arm 72 is raised, the pasting roller unit 90 is lowered (step 575). As a result, the adhesive tape 82 placed on the roller unit 90 also descends, and this adhesive tape 82 is attached to the wafer.
It comes into contact with the back surface of the semiconductor wafer 2 on the chuck table 48. When the pasting roller unit 90 is lowered, the pasting roller unit 90 moves horizontally toward the pasting table 42. As a result, pasting is performed by the roller unit 9.
0 is attached by a roller rolling over the adhesive tape 82 that is in contact with the back surface of the semiconductor wafer 2 and pressing lightly to attach the semiconductor wafer 2, the adhesive tape 82, and the frame 4 (step 576).

When the attachment of the semiconductor wafer 2, adhesive tape 82, and frame 4 is completed, the presser plate 110 and tape cutter 112 are lowered, and the presser plate 110 presses and holds the adhesive tape 82 on the frame 4. Then, by rotating the tape cutter 112 once around the presser plate 110, the adhesive tape 82 is cut so as to be slightly smaller than the outer shape of the frame 4 (step 8).
78).

When cutting of the adhesive tape 82 is completed, the wafer/chuck table 48 is lowered (step 580), the protective film take-up reel 78 is driven to take up the protective film 52, and a new protective film 52 is placed on the wafer/chuck table 48. (step 582).

On the other hand, when the cutting of the adhesive tape 82 is completed, the peeling roller unit 92 moves horizontally toward the adhesion table 42 side. As a result, the residue of the adhesive tape 82 stuck to the periphery of the frame 4 is peeled off from the frame 4 (step 584).

Once the adhesive tape has been peeled off, the mount/frame chuck arm 114 is lowered to eject the mount frame 6 on the table 42 (step 586).
. Adsorb the mount frame 6 (step 888)
. Then, it is confirmed whether the mount frame 6 has been reliably attracted (step 590). This is determined based on the detection signal of the pressure switch PUSW5 provided in connection with the mount/frame chuck arm 114. If the mount frame 6 is not attracted, an error message X is displayed (step 592), and the patrol light 14
0 error display light lights up and the operation panel 13
8 7-segment LEDs display the code corresponding to this error.

When it is confirmed that the mount frame 6 is attracted, the mount frame chuck arm 114 is raised (step 594). After the mount/frame chuck arm 114 is raised, check again whether the mount/frame 6 is attracted (step 595), and if it is not attracted, an error message X is displayed (step 592). When the suction of the mount frame 6 is confirmed, the pasting roller unit 90 and peeling roller unit 92, which have moved to the pasting table 42, return to their original positions (origins) (step 596). For pasting, the roller unit 90 and the peeling roller Uniso 1-92 return to their origin, and the mount/frame chuck arm 114 that has attracted the mount frame 6 also moves toward the swing reversing unit 116 (step 898). And mount
When the frame chuck arm 114 has moved to the position where one end of the mount frame 6 is inserted into the clamp mechanism 118 of the swing reversing unit 116, check again that the mount frame 6 is attracted (step 399).
, if it is not adsorbed, an error message X is displayed (step 592).

When adhesion of the mount frame 6 is confirmed, the clamp mechanism 118 of the swing reversing unit 116 closes and clamps the mount frame 6 (step 3100).
. Then, it is confirmed whether the mount frame 6 is securely clamped (step 5102). This is due to the photoelectric element P H provided in the clamp mechanism 118.
The determination is made based on the detection signal of SW7. mount·
If the frame 6 is not clamped, an error display XI is performed (step 5104), the error display light of the patrol light 140 lights up, and the 7-segment LED of the operation panel 138 displays a code corresponding to this error.

After confirming that the mount frame 6 is clamped, the swing reversing unit 116 swings approximately 180 degrees in the horizontal direction (Step 51o6), and confirms that the mount frame 6 is clamped again (Step 51).
07). If it is not clamped, an error display XT is performed (step S104). When the clamping of the mount frame 6 is confirmed, the mount frame 6 is turned over so that the front surface of the semiconductor wafer 2 is facing upwards (step 3108). Then, check once again whether the mount frame 6 is clamped (step 5IO9), and if it is not clamped, an error display XI is displayed (step 5104).

Once the clamping of the mount frame 6 is confirmed, it is confirmed that there is no other mount frame 6 on the heat stage 126 (step 3110). This is performed based on the detection signal of the photoelectric element PH3W3 provided on the heat stage 126. If there is another mount frame 6 on the heat stage 126, an error display X■ is displayed (step 311.1>, the error display light of the patrol light 140 lights up, and the 7-segment LED of the operation panel 138 indicates this error. Display the corresponding code.

When it is confirmed that there is no other mount frame 6 on the heat stage 126, the swing reversing unit 116 descends (step 5112), and when the mount frame 6 reaches above the heat stage 126, the clamp mechanism 118 is released. (Step 5113). This moves the mount frame 6 to the heat stage 126.

Mount frame 6 transferred to heat stage 126
is heated here (step Sll4). This causes the adhesive tape on the mount frame 6 to contract, increasing the tape tension.

However, if such slack removal is not required, this step 5114 is omitted.

(Hereinafter, blank space) After heating the mount frame 6, the mount
The frame pushing mechanism 128 operates to push out the mount frame of the heat stage 126J (step 5l16). Then, it is confirmed whether the mount frame 6 has been pushed out from the heat stage 126 (
Step 5l18). This is determined based on the detection signal of the photoelectric element PH3W9 provided at the end of the heat stage 126. If the mount frame 6 has not been pushed out, an error message will be displayed (step 31).
20) The error display light of the patrol light 140 lights up, and the 7-segment LED of the operation panel 138 displays a code corresponding to this error.

The mount frame 6 pushed out from the heat stage 126 rides on a transport table 130 for transporting to the unloader section. Then, the photoelectric element PH3WIO provided on the transport table 130 confirms whether or not the mount frame 6 has been received by the transport table 130 (steso 7''5122). If the reception is not received, an error display XIV is performed (step 5124), and the error display light of the patrol light 140 lights up, and the 7-segment LED of the operation panel 138 displays a code corresponding to this error.

If the mount frame 6 is not supported on the transport table 130, the mount frame 6 is transported to the unloader section and stored in the frame cassette 132 placed in the unloader section (step 5126).
). When the photoelectric element provided in the unloader section detects that the mount frame 6 has been stored in the frame cassette 132, the unloader section moves up one pitch to accommodate the next mount frame 6. (step 5128).

As described above, after aligning the semiconductor wafer 2 supplied from the wafer loader section in a predetermined direction, the adhesive tape 8
A series of operations for attaching the semiconductor wafer 2, such as attaching the semiconductor wafer 2 to the frame cassette 132 and storing the mount frame 6 with the semiconductor wafer 2 attached thereto in the frame cassette 132, are automatically performed.

Next, the alignment operation of the orientation flat OF in the automatic semiconductor wafer attachment apparatus described above will be explained in detail.

As described above, the element patterns formed on the semiconductor wafer 2 are arranged with the orientation flat OF as a reference. Therefore, in order to easily align the semiconductor wafer 2 in the scribing process, it is necessary to attach the orientation flat OF to the adhesive tape in a predetermined direction. For this purpose, first, the orientation flat ○F formed on the semiconductor wafer 2 is detected, and then the orientation flat OF is aligned.

However, the semiconductor wafer 2 to be attached to the adhesive tape has a shape other than the normal shape shown in FIG. 13(a).
The semiconductor wafer 2 has chips 2I on a part of its periphery as shown in the same figure (bl), and cracks as shown in the same figure (C). Therefore, -43= If the chipped or cracked semiconductor wafer 2 is detected as an orientation flat OF, the semiconductor wafer 2 will be incorrectly aligned and attached to the adhesive tape, which is inconvenient. .

For these reasons, it is required to detect the true orientation flat OF of the semiconductor wafer 2.

In FIG. 13 [a], O8 indicates the start end of the orientation flat OF, and OE indicates the end of the orientation flat ○F. However, as shown in Figure 14, the orientation flat O
Photoelectric element PH5WI (P
H3W2. PH3W3) is alignment table 2
Since the orientation flat OF is located slightly inside the radius of the semiconductor wafer 2 from the center of the orientation flat OF, the starting end O8 and the ending end OE of the orientation flat OF referred to here are
As shown in Figure 3+d+, it refers to a location located slightly inside the end of the actual orientation flat OF (the x mark in Figure 3(d)).

By the way, step S24 in the operation flowchart shown in FIG. This includes determining operational errors.

The pulse motor 24 normally rotates by a rotation amount equal to the set rotation amount, but if it does not rotate by an amount equal to the set rotation amount due to some abnormality, the orientation flat OF cannot be correctly aligned. The determination of the operation error of the pulse motor 24 performed in the step is performed in order to determine such an operation error of the pulse motor 24 and to more correctly position the orientation flat OF.

Hereinafter, the semiconductor wafer 2
The procedure for detecting the true orientation flat OF, positioning it, and determining an operation error of the pulse motor 24 will be explained based on FIGS. 14 and 15.

FIG. 14 shows the center alignment provisional 22. ．． The semiconductor wafer 2 centered by 22□ is aligned and
A state in which the table 20 has been adsorbed is shown. The end of the orientation flat OF is provided with a photoelectric element PH3W that is appropriately selected according to the size of the semiconductor wafer 2.
L, 2.3. In this figure, only the photoelectric element PH3WI is shown for convenience. The output of the photoelectric element PH3WI is directly given to a pulse motor controller 156 that controls the pulse motor 24. The pulse motor controller 156 is configured to stop the pulse motor 24 in response to a detection signal from the photoelectric element PH3WI. Further, based on the command from the CPU 144, the pulse motor controller 156
The amount of rotation is outputted to the pulse motor 24 as a number of pulses, and the remaining amount of rotation when the pulse motor 24 is in a stopped state is given to the CPU 144 as the number of remaining pulses.

FIG. 15 is a flowchart showing the detection of the orientation flat OF, the alignment procedure, and the determination of an operation error of the pulse motor 24. The following explanation will be based on this.

In step S20 shown in FIG. 12, when it is confirmed that the semiconductor wafer 2 is suctioned and held on the alignment table 20, the CPU 44 controls the pulse motor 2.
4 by 360 degrees counterclockwise (first rotation amount) N.

is set (step 3130). This amount of rotation is expressed by the number of pulses for driving the pulse motor 24. In this embodiment, the rotation amount N0 is set to 1024 pulses. The CPU 144 outputs this rotation amount N0 to the pulse motor 24 via the pulse motor controller 156 (steer knob S132).

Thereby, the semiconductor wafer 2 is rotated by the pulse motor 24. And orientation franc)O
When the start end O8 of F is detected by the photoelectric element PH3Wl, the detection signal is sent to the pulse motor controller 156.
is applied, and the pulse motor 24 stops.

After completing step 5132, the CPU 144 monitors whether the pulse motor 24 has stopped (step S
134).

After confirming that the pulse motor 24 has stopped, the CPU
144 sets a rotation amount (second rotation amount) - No for rotating the pulse motor 24 360 degrees clockwise (step 5136), and outputs this to the pulse motor 24 via the pulse motor controller 156 (step 3138).
). As a result, the semiconductor wafer 2 is rotated clockwise. And the terminal O of the orientation flat OF
When E is detected by the photoelectric element PH3WI, the detection signal is given to the pulse motor controller 156, and the pulse motor 24 is stopped.

When the CPU 144 confirms that the pulse motor 24 has stopped (step 5140), it reads the remaining number of pulses N1 at that time (step 3142).

Then, by subtracting this remaining number of pulses N, from the initially set rotation amount N, (1024 pulses),
The rotation amount corresponding to the angle θ between the end ○S of the orientation flat OF and the center of the semiconductor wafer 2 (
No−N, ) is calculated.

Once the rotation amount (No N+) is calculated, it is detected whether or not it is within the range of predetermined reference rotation amounts A and B (step S144). The reference rotation amounts A and B are determined in relation to the positional variations in the orientation flat OF, as shown in FIG. 16. That is,
The reference rotation amount A is the rotation amount corresponding to the angle θ1 formed between the edge of the orientation flat OF located farthest from the center 0 of the semiconductor wafer 2 and the center 0 of the semiconductor wafer 2 . Further, the reference rotation amount B is the angle θ formed between the end of the orientation flat OF2 located closest to the center 0 of the semiconductor wafer 2 and the center O of the semiconductor wafer 2.
This is the amount of rotation corresponding to 2.

For example, a semiconductor device H2 as shown in FIG. 13(b)
When the chip 21 is detected by the photoelectric element PH3WI, the amount of rotation (No N
l) becomes smaller than the reference rotation NA. Also, the 13th
When a cracked portion of the semiconductor wafer 2 as shown in Fig. C1 is detected by the photoelectric element P HS W 1, the amount of rotation (No Nl ) corresponding to the angle θ4 shown in Fig.
becomes larger than the reference rotation amount B.

In this way, the rotation amount (No-Nl) is the reference rotation amount A,
When it is outside the range of B, the photoelectric element PH3W1 determines that it has not detected the true orientation flat OF, displays an error display Xv indicating this (step 3146), and the error display light of the patrol light 140 lights up. At the same time, the 7-segment LED on the operation panel 138 displays a code corresponding to this error.

True orientation flat O is achieved by the above steps.
When F is detected, the detected orientation flat OF is aligned.

Based on the rotation amount (No-N,) calculated by reading the remaining number of pulses N, in step 5142, the CPU 144 determines the rotation amount (No-Nl) to rotate the pulse motor 24 counterclockwise by (No Nl)/2. 3
The rotation amount) is set (step 5148), and outputted to the pulse motor 24 via the revolution motor controller 156 (step 5150). As a result, the semiconductor wafer 2 rotates counterclockwise by (No - Nl)/2 and stops.

After confirming that the pulse motor 24 has stopped (step 5152), the remaining number of pulses N3 is read (step S154). Then, it is checked whether this remaining pulse number N is zero (step S]56). As long as the pulse motor 24 is operating normally, the pulse motor 24 should be rotated counterclockwise by (No Nl )/2, and the remaining number of pulses N3 should be zero. If this remaining number of pulses N is not zero, it means that the pulse motor 24 has operated abnormally, so an error display XVI is displayed without indicating this (step S158), and the error display light of the patrol light 140 is turned on. At the same time, the 7 segment I of the operation panel 138.

ED will display the code corresponding to this error.

If the remaining number of pulses N3 is zero, the orientation flat OF is correctly positioned perpendicular to the direction connecting the center of the alignment table 20 and the photoelectric element P HS W 1.

The above steps complete the alignment of the orientation flat OF. However, semiconductor wafer 2
8! Depending on the species, the semiconductor wafer 2 may be rotated an additional 906 or 1800 times to complete the final alignment.

Next, we will briefly explain the recovery process that is performed when an error occurs in the automatic attachment of semiconductor wafers according to the above-described embodiment.

When any of the above-mentioned errors occurs, each mechanical section that is a process subsequent to the location where the error occurs continues its operations and stops after completing its respective operation cycle. On the other hand, the one location 52 where the error occurred and each mechanical section corresponding to the preceding process stop when the error occurs. Based on the above-mentioned error display, the operator removes the workpiece (for example, the semiconductor wafer 2 or the frame 4) where the error occurred, or
Take appropriate measures such as setting the cassette correctly.

Then, each mechanical section corresponding to the process preceding the error occurrence point is returned to its origin, and the apparatus is restarted.

As is clear from the description of the embodiments above, in the automatic attachment of semiconductor wafers according to the present invention, the rotating means of the semiconductor wafer positioning unit constituting the apparatus rotates the alignment table 20 in the embodiments and It corresponds to the pulse motor 24 that causes However, it goes without saying that the rotating means is not limited to this.

Further, the orientation flat end detection means includes the photoelectric elements PHSW1 to PHSW3 in the embodiment.
It corresponds to However, it is sufficient to have at least one photoelectric element for detecting the end of the orientation flat. Further, the orientation flat end detection means is not limited to a photoelectric element, but may be other detection means such as a proximity switch.

Further, the actual rotation amount detection means for detecting the actual rotation amount (actual rotation N) of the rotation means corresponds to the pulse motor controller 156 in the embodiment. In the embodiment, the pulse motor controller 156 outputs the remaining number of pulses, but the actual rotation amount of the pulse motor 24 can be determined by subtracting this remaining number of pulses from the set rotation amount. Means for outputting the number of remaining pulses is also included in the actual rotation amount detecting means according to the present invention. However, it goes without saying that the actual rotation amount detection means includes a device that measures and outputs the actual rotation amount using, for example, a rotary encoder.

The first rotation amount setting means, the second rotation amount setting means, and the third rotation amount setting means that constitute the semiconductor wafer alignment section correspond to the control section 142 in the embodiment.

Further, the operation error detection unit is the control unit 142 in the embodiment.
It corresponds to In the embodiment, an operation error of the pulse motor 24 is detected by detecting whether the remaining number of pulses given from the pulse motor controller 156 is zero, but this is because the actual rotation amount is not the set rotation amount. This is equivalent to comparing with , and is included in the operation error detection section according to the present invention.

<Effects of the Invention> As is clear from the above description, the automatic attachment of semiconductor wafers according to the present invention uses a rotation amount set to be applied to the rotation means for aligning the semiconductor wafer,
Since an operation error of the rotation means is detected based on a comparison with the actual rotation amount of the rotation means rotated each time the set rotation amount is given, the semiconductor wafer is are not misaligned.

Therefore, according to the present invention, a semiconductor wafer can be correctly aligned and attached to an adhesive tape.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing the overall configuration of a semiconductor wafer automatic pasting apparatus according to an embodiment of the present invention, and FIG. 2 is a configuration of the semiconductor wafer alignment section and the surrounding area of the reversing fork in the embodiment. FIG. 3 is a configuration diagram of the orientation flat end detection section in the above embodiment, and FIG.
The figure is a block diagram of the frame loader section and the surroundings of the frame positioning section in the embodiment, FIG. 5 is a block diagram of the frame transport section and its periphery in the embodiment, and FIG. 6 is the adhesive tape supply system and the adhesive tape in the embodiment. 7 and 8 are diagrams illustrating the structure and operation of the pasting roller unit and peeling roller unit in the above embodiment; FIG. 9 is a diagram illustrating the structure around the heat stage in the embodiment; FIG. 10 is an explanatory diagram of the semiconductor wafer, frame, and mount frame used in the embodiment, FIG. 11 is a block diagram schematically showing the configuration of the control system in the embodiment, and FIG. 12 is a diagram showing the configuration of the control system in the embodiment. FIG. 13 is an explanatory diagram of the need to detect the true orientation flat in the embodiment, FIG. 14 is an explanatory diagram of alignment of the orientation flat in the embodiment, and FIG. 15 is an illustration of the necessity of detecting the true orientation flat in the embodiment. FIG. 16 is an explanatory diagram of the reference rotation amount set for orientation flat alignment in the embodiment. 2... Semiconductor wafer, OF... Orientation flat, 4... Frame, 6... Mount frame, 8... Wafer cassette, 14... Semiconductor wafer positioning section, 20... Alignment table, 24... Pulse motor, 32... Orientation flat end detection section, 40... Reversing fork, 4
2... Paste on table, 48... Wafer/chuck table, 50... Frame/chuck table, 5
4... Frame loader section, 62... Frame positioning section, 72... Frame chuck arm, 82...
...Adhesive tape, 90...Pasting is done using a roller unit, 9
2...Peeling roller unit, 10 days...Adhesive tape cutting machine! , 114... Mount frame chuck arm, 116... Swing reversing unit, 118...
・Clamp mechanism, 126... Heat stage, 128
...Mount frame extrusion mechanism, 130...
Transport table, 132...Frame cassette, 13
8... Control panel, 140... Patrol light, 142...
・Control unit, 144...CPU, PH3WI to PH3W
I1...Photoelectric element, PUSW1 to PUSW5...
Pressure switch.

Claims (1)

[Scope of Claims] An automatic semiconductor wafer affixing device that aligns a semiconductor wafer on which an orientation flat is formed and affixes it to an adhesive tape, the device comprising: a semiconductor wafer positioning unit that aligns the semiconductor wafer; an operation error detection section that detects an operation error of the semiconductor wafer alignment section, the semiconductor wafer alignment section holding the semiconductor wafer in a state where the center of the semiconductor wafer and the center of rotation are aligned; a rotating means for rotating this;
Orientation flat end detection means for detecting an end of an orientation flat of a semiconductor wafer held and rotated by the rotation means; and actual rotation amount detection means for detecting an actual rotation amount (actual rotation amount) of the rotation means. , a first rotation amount setting means for setting a first rotation amount for rotating the rotation means until one end of the orientation flat is detected by the orientation flat end detection means, and applying the first rotation amount to the rotation means; 1st
Setting a second rotation amount for rotating the rotation means rotated by the rotation amount setting means in a direction opposite to the first rotation amount until the other end of the orientation flat is detected by the orientation flat end detection means. and a second rotation amount setting means for applying the second rotation amount to the rotation means, and an actual rotation amount of the rotation means rotated by being given the second rotation amount is given from the actual rotation amount detection means; and third rotation amount setting means for setting a third rotation amount that is 1/2 of the actual rotation amount and applying it to the rotation means, and the operation error detection unit is provided with the third rotation amount. The actual rotation amount of the rotation means rotated by the rotation is given from the actual rotation amount detection means, and is based on comparing this actual rotation amount with a third rotation amount set in the third rotation amount setting means. An automatic semiconductor wafer pasting apparatus characterized in that an operation error of the rotating means of the semiconductor wafer positioning section is detected.