JPH0332220B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention automatically processes silicon wafers placed on a silicon wafer boat (a storage unit storing silicon wafers in the shape of a shelf) or on the stage of various processing equipment. The present invention relates to a suction method when suctioning with a suction hand of a conveying device.

<Conventional technology> When silicon wafers are subjected to various treatments or their performance is measured using a measuring device, the silicon wafers placed on a shelf in a boat are sucked into the suction hand of an automatic transfer device and processed. A conveyance device for conveying a device to a stage has already been proposed by the present inventor in Japanese Patent Application Laid-Open No. 62-93112 and the like.

Silicon wafers used for ICs, etc. are extremely sensitive to distortion, scratches, and dust, and are easily distorted and scratched, so care must be taken when storing them or transporting them using automatic transport equipment. Requires attention.

<Problems to be Solved by the Invention> For this purpose, silicon wafers are placed horizontally in a boat, for example, with their back sides facing up and their edges supported at two or three places to prevent dust from getting on the surface. When handling a silicon wafer placed on a silicon wafer, a suction hand is used to suction the back surface, which is the top surface, in order to avoid touching the surface, and suction power is also required when suctioning to avoid applying shock to the silicon wafer. I keep it to a minimum.

However, when picking up a silicon wafer with the suction hand of an automatic transfer device, ideally the suction hand should be stopped slightly above the silicon wafer (for example, 0.1 mm above the surface) and the suction operation should be started in this state. It is best to suction the silicon wafer to the underside of the suction hand using light suction.
There may be variations or large errors in the position of the silicon wafer placed on the boat or stage,
If the silicon wafer was placed at a slight incline for some reason, there was a risk that the suction hand would push the silicon wafer and damage it, or that it would not be able to be suctioned.

<Means for Solving the Problems> The present invention has been made to solve the above-mentioned problems, and a silicon wafer placed horizontally on a boat or the like is transported by a suction hand of an automatic transfer device.
To provide a method of suctioning a silicon wafer that can surely suction it without damaging it by pressing it.

To this end, in the suction method of the present invention, an automatic transfer device equipped with a suction hand having suction holes on the lower surface, a sensor for detecting the suction state, and an elevating mechanism for raising and lowering the suction hand is used to hold a silicone placed horizontally. In the suction method in which the wafer is suctioned by a suction hand, a reference position is set directly above the silicon wafer, and when the silicon wafer placement position shifts to the highest position due to an error, the silicon wafer directly below it is The distance to the wafer is set as a certain descending distance h, the first step is to position the suction hand at the reference position, and the second step is to start the suction operation while lowering the suction hand horizontally by the descending distance h. In the third step, the suction hand is raised to the reference position again, and at this time, it is detected whether or not the suction hand is suctioning the silicon wafer, and in the fourth step, it is detected that the suction hand is not suctioning the silicon wafer. , the descending distance h
The distance obtained by adding the minute distance a to the above is set as the new descending distance h, and the above steps 1 to 3 are performed again. If the suction hand cannot pick up the silicon wafer, the steps 1 to 4 above are repeated multiple times. It is composed of

<Function> In this silicon wafer adsorption method,
Descending distance h from the reference position to the silicon wafer
is set in advance to be the distance when the error in the placement position of the silicon wafer is at the highest position, that is, when the silicon wafer is placed at the highest position. Even if the position of the silicon wafer is shifted upward when the silicon wafer is lowered by the lowering distance h from the reference position, it is possible to prevent the suction hand from pressing against the silicon wafer and damaging it. If the silicon wafer is tilted or shifted to a low position,
Each time the suction hand descends to pick up a silicon wafer, it approaches the silicon wafer by a small distance (for example, 0.1 mm), and the suction hand descends reliably to a position where it can pick up the silicon wafer without pressing it. By using the minimum suction force, it is possible to adsorb and transport the silicon wafer without giving any impact to the silicon wafer.

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

FIG. 1 shows an automatic transfer device equipped with suction hands for transferring silicon wafers. To explain the general structure of the conveyance device with reference to this figure, a horizontal moving part 2 is disposed on the upper part of the main body 1 so that it can rise and rotate, and a carriage 3 is inside the horizontal moving part 2 with its upper part protruding upward. Arranged so that it can be moved horizontally. A suction hand 5 is horizontally attached to the carriage 3 via a rotating shaft 4.

The horizontal moving part 2 is attached to the tip of a cylinder 6 erected on an elevating plate 7 which is disposed in the main body 1 so as to be movable up and down, and the elevating plate 7 is rotatably arranged in the main body 1. The ball screw 8 is screwed into a ball screw 8, and the ball screw 8 is rotationally driven by a step motor 9. As the step motor 9 is driven, the horizontal moving section 2, that is, the suction hand 5 of the carriage 3 moves up and down. Although not shown in the drawings, a motor for rotationally driving the cylinder 6 is disposed inside the main body 1, and a motor for driving the carriage 3 is attached to the elevating plate 7.

Pulleys are disposed at both ends and in the center of the horizontal moving section 2, and a driving wire is placed between these pulleys, with a portion of the wire being connected to the carriage 3.
A central pulley is attached to a rotating shaft passing through the cylinder 6, and this pulley is rotationally driven by a motor within the main body 1, so that the carriage 3 moves on the horizontal moving section 2. Further, within the carriage 3, a motor for reversing the suction hand is disposed so as to rotate the rotary shaft 4, and the suction hand 5 is reversed by this motor.

As shown in FIGS. 3 and 4, an air passage 10 is provided in the suction hand 5, a suction hole 11 is provided on the lower surface of the suction hand 5 as an opening of this air passage, and the end of the air passage is It is connected to an inlet of a vacuum pump (not shown) or the like. In addition, a pressure sensor 12 for detecting the intake pressure is installed in a part of the air passage.
is installed, and when the detected pressure of this pressure sensor 12 falls below a certain value, it is detected that the suction hand 5 has suctioned the silicon wafer 15 to its lower surface. In order to turn on and off the intake air from the suction hole 11, an electromagnetic valve 22 shown in FIG. 2 is installed in the air passage 10 and the like.

The automatic conveyance device having the above configuration is controlled by a control circuit including the CPU 20 as a main part, and as shown in FIG.
A drive signal for suction on/off outputted from the CPU 20 is sent to the electromagnetic valve 22 via the drive circuit 21, and a signal for raising and lowering the suction hand 5 is sent to the drive circuit 23.
3 rotates a step motor 9 for raising and lowering.

On the other hand, the silicon wafer 15 is stored in a boat in a clean room, and the boat is shown in FIG.
As shown in FIG. 4, grooves 17 are provided at regular intervals on three support pillars 16 that are erected, and the wafer 15 is placed horizontally with its back side facing up and its edges caught in the grooves 17. It is placed there.

Next, a method of adsorbing a silicon wafer using such an automatic transfer device will be explained based on the flowchart shown in FIG.

When taking out and transporting a silicon wafer placed in a boat, the automatic transport device first moves the suction hand 5 in its original position to the silicon wafer 1 to be taken out in the boat, as shown in FIG.
5 to the reference position directly above (step
100). The distance from this reference position to the silicon wafer 15 is h (for example, 2 to 3 mm).
, and the distance h is preset to the distance with the highest error when the silicon wafer is placed at the highest position, that is, when the silicon wafer is placed at the highest position. .

Next, in step 110, the electromagnetic valve 22 is opened, and suction starts from the suction hole 11 of the suction hand 5, and the suction operation is started. And step
At step 120, the lifting step motor 9 is rotated to lower the horizontal moving unit 2, thereby lowering the suction hand 5 by a distance h (Fig. 3), and then at step 130, the step motor 9 is rotated in the reverse direction. Then, the suction hand 5 is raised by a distance h, that is, to the reference position.

At this time, if the silicon wafer 15 is placed in the groove 17 in a proper state, when the suction hand 5 descends, the silicon wafer 15 will be placed in the suction hole 17.
The suction hand 5 is attached to the silicon wafer 1.
5 is adsorbed to its lower surface, it rises to the reference position.

The suction state of the suction hand 5 is determined in step 140, and if the detection signal of the pressure sensor 12 is below a certain pressure, it is assumed that the silicon wafer 15 has been suctioned, and the process then proceeds to step 150.

In step 150, the suction hand 5 holding the silicon wafer 15 by suction is moved to a predetermined original position by moving the carriage 3, etc., and in step 160, after confirming that the silicon wafer 15 is suctioned and held, The silicon wafer is transported to a stage or the like of a processing device (not shown).

On the other hand, if the silicon wafer 15 is deformed, or for some reason the silicon wafer 15 is placed at an angle, and a gap larger than expected occurs between the suction hand 5 and the silicon wafer 15, suction fails. , this is detected by the pressure sensor 12, and the process proceeds from step 140 to step 170. In step 170, distance h is replaced by a constant minute distance a (for example,
0.1mm) is added to set a new distance h.

Then, the process returns to step 120 again, and the suction hand 5 is lowered from the reference position by a new distance h, and in step 130, the suction hand 5 is raised again by the distance h from the reference position. Then, in step 140,
It is determined again whether or not the suction hand 5 has suctioned the silicon wafer 15. If the suction hand 5 has suctioned the silicon wafer 15, the process proceeds to step 150 in the same way as above and moves the suction hand 5 to its original position. At step 170, the minute distance a is added to the distance h, and the operations from step 120 to step 140 are repeated.

In this way, by repeating steps 120 to 140 and step 170, the distance h that the suction hand 5 descends from the reference position becomes a minute distance.
If the silicon wafer 15 cannot be picked up immediately due to deformation or poor posture, the suction hand 5 can safely pick up the silicon wafer 15 without pressing it.

On the other hand, if the suction is not possible, repeat this operation up to three times and then proceed from step 180.
190, close the electromagnetic valve 22 and close the suction hole 1.
At step 200, the suction hand 5 is returned to its original position, and at step 210, it is recognized that no silicon wafer is placed on that shelf in the boat. Then, move the suction hand 5 to the reference position of the next silicon wafer,
The process moves on to the adsorption process.

Note that the distance h and the minute distance a described above can be set to arbitrary values, and the number of repetitions when suction fails can also be set to an arbitrary number. Furthermore, the suction method described above can also be used when suctioning a silicon wafer placed on a stage of a processing device or the like.

<Effects of the Invention> As explained above, according to the silicon wafer suction method of the present invention, a suction hand having a suction hole on the lower surface, a sensor for detecting the suction state, and a lifting mechanism for raising and lowering the suction hand are provided. In a suction method in which an automatic transfer device suctions a horizontally placed silicon wafer using a suction hand, a reference position is set directly above the silicon wafer, and the silicon wafer placement position is the highest position as an error. The distance from the reference position to the silicon wafer directly below it when it deviates from the reference position is set as a fixed descending distance h, and the first step is to position the suction hand at the reference position, and the second step is to lower it while starting the suction operation. The suction hand is lowered horizontally by a distance h, and as a third step, the suction hand is raised again to the reference position. At this time, it is detected whether or not the suction hand is suctioning a silicon wafer. As a fourth step, the suction hand is When it is detected that the suction hand is not suctioning the silicon wafer, the distance obtained by adding the minute distance a to the descending distance h is set as the new descending distance h, and the above steps 1 to 3 are performed again, so that the suction hand is not suctioning the silicon wafer. When the wafer could not be adsorbed, the above-mentioned first to fourth steps were repeated a plurality of times.

Therefore, the descending distance h from the reference position to the silicon wafer is the distance when the error in the silicon wafer placement position is the highest position, that is, the silicon wafer is placed at the highest position. Therefore, when the suction hand is lowered by the descending distance h from the reference position for the first time, even if the position of the silicon wafer is shifted upward, the suction hand will not press against the silicon wafer and damage it. This can be prevented. In addition, if the silicon wafer is tilted or shifted to a low position, the suction hand will approach the silicon wafer by a minute distance each time it descends to suction the silicon wafer, and the suction hand will move closer to the silicon wafer. The silicon wafer can be reliably lowered to a suction position without being pressed, and the silicon wafer can be suctioned and transported using the minimum suction force without giving any impact to the silicon wafer.

[Brief explanation of drawings]

The figures show one embodiment of the present invention, in which Figure 1 is a front view of an automatic conveyance device, Figure 2 is a block diagram of a control system,
FIG. 3 is a front view showing the suction state of the suction hand, FIG. 4 is a plan view thereof, and FIG. 5 is a flowchart of a silicon wafer suction process. 5... Suction hand, 12... Pressure sensor, 15
...Silicon wafer.

Claims (1)

[Scope of Claims] 1. An automatic transfer device equipped with a suction hand having a suction hole on the lower surface, a sensor for detecting the suction state, and an elevating mechanism for raising and lowering the suction hand picks up a silicon wafer placed horizontally. In the suction method using the suction hand, a reference position is set directly above the silicon wafer, and when the silicon wafer placement position deviates to the highest position due to an error, a position immediately below the reference position is set. The distance to the silicon wafer is set as a certain descending distance h, the first step is to position the suction hand at the reference position, and the second step is to horizontally move the suction hand by the descending distance h while starting the suction operation. In the third step, the suction hand is raised again to the reference position, and at this time, it is detected whether or not the suction hand is suctioning the silicon wafer.In the fourth step, the suction hand is suctioning the silicon wafer. When it is detected that the suction hand is not able to suction the silicon wafer, the distance obtained by adding the minute distance a to the descent distance h is set as the new descent distance h, and the above first to third steps are performed again, and if the suction hand cannot suction the silicon wafer, A silicon wafer adsorption method characterized by repeating the first to fourth steps described above multiple times.