JP2684408B2 - Wafer transfer method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a wafer transfer method.

(Prior Art) For semiconductor devices such as ICs and LSIs, a wafer cut out from an ingot is sequentially subjected to surface treatment, thermal oxidation treatment, impurity diffusion treatment, film deposition treatment, etching treatment, etc. It is manufactured through a number of processes. In these manufacturing steps, the semiconductor wafer is repeatedly subjected to the heat treatment a plurality of times.

Generally, a multi-stage furnace, for example, a four-stage furnace, which is stacked up and down, is used as a heating furnace for heat treatment of a semiconductor wafer.
A multi-stage pedestal is provided in front of the furnace port, and various automatic devices for handling wafers are mounted on the pedestal.

When loading and unloading the semiconductor wafer into and from the heating furnace, a dedicated wafer boat is operated. Usually, one boat holds up to 200 wafers per lot.

On the other hand, when the semiconductor wafer is transferred from the previous process to the heating furnace, a dedicated cassette (also called a carrier) is used. Usually, one cassette (also called a carrier) is used. Normally, one cassette holds up to 25 semiconductor wafers per lot. Therefore, wafers are transferred from a plurality of cassettes for one port.

By the way, when handling a wafer, it is forbidden for the operator's hand to directly touch the wafer to prevent contamination. Therefore, a dedicated automatic wafer transfer device
It is installed as an auxiliary facility of the heating furnace near the furnace opening, and this wafer transfer device automatically transfers wafers from the cassette to the boat.

Generally, semiconductor device manufacturers do not inspect all wafers that have undergone heat treatment, and
A method is used in which three monitoring wafers (referred to as monitor wafers) are sampled from a port and the state of the film thickness of the film formed on the surface of these monitor wafers is inspected. Then, if the inspection result of the monitor wafer is acceptable, the product wafer is also treated as acceptable.
Therefore, the wafers are arranged in one boat at predetermined positions in the intermediate portions on both sides of the wafer arrangement.

Conventionally, when transferring such monitor wafers to a predetermined position on the boat, one monitor wafer is put in advance in the cassette, and the monitor wafers are collectively transferred together with the product wafers from the cassette by the wafer transfer device. It was automatically transferred to the boat.

(Problems to be Solved by the Invention) However, in the conventional method, the product wafer cannot be fully accommodated in one cassette because the monitor wafer is already accommodated in the cassette. For example, when only one monitor wafer is previously stored in the cassette, only 24 product wafers can be stored. Therefore, there is a problem that the amount of product wafers that can be handled per cassette is limited, and the efficiency of the process as a whole is lowered.

Instead of mechanically transferring the monitor wafer by the wafer transfer device, an operator may manually transfer the monitor wafer to the port, but the monitor wafer is contaminated or damaged and the cleanliness of the room deteriorates. The inconvenience occurs.

Furthermore, one cassette does not always accommodate 25 wafers in full, and if there are wafers falling out of the cassette, if these wafers are transferred to the boat as is, the wafers will have a fixed pitch on the boat. However, there is a problem that they are not arranged continuously and are subjected to non-uniform heat treatment.

An object of the present invention is to provide a wafer transfer method capable of transferring a product wafer in a cassette unit onto a boat without contaminating the wafer to be heat-treated when the monitor wafer is heat-treated together with the product wafer. To do.

Further, another object of the present invention is to provide a wafer transfer method capable of continuously arranging product wafers in a cassette, which are dropped out, on a boat at a constant pitch. .

〔The invention's effect〕

(Means for Solving the Problems) According to the invention of claim 1, a first step of sandwiching a plurality of monitor wafers accommodated in a cassette by a sandwiching means and taking them out from the cassette, and the sandwiched monitor wafers are mounted on a boat. A second step of transporting the monitor wafers upward, a third step of transferring all of the monitor wafers from the clamping means onto the boat so that the monitor wafers are arranged at predetermined positions on the boat, and the clamping means. The port and monitor wafer 1
The cassette is moved by a relative distance of an integral multiple of the pitch, and the required number of monitor wafers among the plurality of monitor wafers arranged on the boat are left on the boat, and the required number of monitor wafers are held by the holding means. And a fifth step of transferring a plurality of wafers from another cassette to the port after the fourth step, and a wafer transfer method characterized by the above.

According to a second aspect of the present invention, a first step of holding a predetermined number of wafers contained in the cassette by a holding means and taking them out of the cassette, and a plurality of groove portions for holding the held wafers. A second step of transporting the wafer onto a boat provided with a wafer, and a third step of transferring all the wafers from the holding means to the groove of the boat so that the wafers are arranged at predetermined positions on the port, This third
When there is a groove portion where the wafer is not held in the wafer transfer area on the boat by the holding means in the process,
The fourth step of sandwiching the wafers arranged on the boat by the sandwiching means so that the wafers held in the groove portion on the subsequent stage of the groove portion become the head, and the groove portion not holding the wafers and the sandwiching means. A wafer transfer method comprising: a fifth step of moving the holding means and the boat relative to each other so as to correspond to the head of the held wafer, and transferring the wafer onto the boat. Is what you get.

(Operation) In the present invention, the monitor wafers are arranged on the port at a predetermined pitch interval in the first to fourth steps, and between the monitor wafers arranged at the predetermined pitch interval in the fifth step. , Transfer the other product wafers from the cassette. Therefore, monitor wafers are arranged on the boat for each lot of product wafers.

Also, if there is a missing wafer in the cassette,
In the fourth step, since the wafers are moved on the ports by the pitch corresponding to the slip-outs, the wafers are continuously arranged at a constant pitch on the boat.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

A horizontal four-stage furnace (not shown) for heat-treating, for example, oxidation / diffusion treatment of silicon wafers is installed, and a boat stand (not shown) is provided so as to communicate with the insertion port of each furnace. There is. Each shelf of the gantry is equipped with a soft landing device (not shown) having a quartz fork. The soft landing device has a mechanism for sliding the fork along the length of the shelf (X-axis direction).

An elevator device (not shown) having an arm for transferring to a port and a fork is provided on the front side of the heat treatment furnace.

A wafer transfer table for transferring the wafers in the cassette to the boat is provided along the lowest shelf of the gantry.

As shown in FIG. 1, the wafer transfer table 11 has a cassette stage 12 for mounting a large number of wafer cassettes 2 and a boat stage 15 for mounting a boat. These stages 12 and 15 are on the same line and in the same elevation, and are installed in series so that their lengths are along the X axis. The cassette 2 and the boat 4 are placed on the stage 12 and the stage 15, respectively, so that the pattern formation surface of the wafer W is along the Y axis. In addition, cassette 2
In the wafer loading portion of the boat 4, a large number of grooves are formed at a predetermined pitch interval and along the edge curve of the wafer W. Are to be retained.

The loading device 13 for loading the wafer W from the cassette 2 to the boat 4 is a wafer transfer table.
It is provided on the front side of 11. This loading device 13
A panel backed up by a computer system
14 is provided, and the necessary data can be input by keying on the panel 14.

As shown in FIG. 2, the lower mechanism of the loading device 13 constitutes an X-axis moving mechanism, and the two guide shafts 23a and 23b and the ball screw 2 are parallel to each other along the X-axis.
With 4. A slide table 22 is provided so as to straddle the guide shafts 23a and 23b, and supports the upper mechanism of the loading device 13. The ball screw 24 is screwed into a nut on the slide table 22, one end of the screw 24 is connected to the drive shaft of the pulse motor 25, and the other end is rotatably attached to the frame of the table 11. .

The switch of the pulse motor 25 is connected to the motor drive circuit 26, the circuit 26 is connected to the controller 27, and the controller 27 is backed up by the computer system. That is, when a predetermined signal is output from the computer system to the circuit 26 via the controller 27, the motor 25 is driven in response to this, and the table 22 slides in the X-axis direction.

Next, the upper mechanism of the loading device 13 will be described with reference to FIGS. 3 and 4.

The upper mechanism of the loading device 13 has a lift mechanism for lifting the wafer, a chuck mechanism for holding the wafer, and an elevating mechanism for elevating the chuck mechanism. The lift mechanism has a first cylinder 16 having a rod 17 protruding and retracting in the Z-axis direction. The chuck mechanism has a gear box 20 having two pairs of rods 19 protruding and retracting in the Y-axis direction. The lifting mechanism has a second cylinder 21 that is connected to the casing of the cylinder of the chuck mechanism and that has a rod 21a that projects and retracts in the Z-axis direction.

A wafer receiving member 18 is provided at the tip of the rod 17 of the lift mechanism. Grooves having the same pitch as the wafer holding grooves on the inner surface of the cassette 2 are formed on the upper surface of the receiving member 18.

The gearbox 20 of the chuck mechanism has a plurality of motors (not shown) and a plurality of reduction gears (not shown). Each of these cylinders has a pair of rods 19
It is connected to. Wafer chuck members 19a, 19b are provided at the tips of the rods 19 of each pair, and the wafer chuck members 19a, 19 at the rod tips approach and separate (open and close) when the rods 19 project and retract. Grooves having the same pitch as the wafer holding grooves of the cassette 2 are formed on the opposing surfaces of the wafer chuck members 19a and 19b.

In the chuck mechanism, one rod 19 penetrates the wafer chuck member 19b so that the chuck member 19b and the other chuck member 19a do not interfere with each other.

Next, a case where the wafer W is transferred from the cassette 2 to the boat 4 will be described in detail with reference to FIGS. 5A to 5F.

(I) Five wafer cassettes, as shown in FIG. 5A.
2M, 2A, 2B, 2C, 2D and one boat 4 are placed on the respective predetermined positions of the stages 12 and 15. The cassette 2M is a monitor wafer dedicated cassette for accommodating a plurality of, for example, three monitor wafers MW. This monitor wafer dedicated cassette 2M is composed of first to fourth product wafer dedicated cassettes 2A, 2
Along with B, 2C, and 2D, they are mounted on the cassette stage 12 in one row.

The boat 4 on the stage 15 has a plurality of dummy wafers DM, for example, five dummy wafers DM, accommodated in a front portion and a rear portion thereof in advance at a predetermined pitch. The first to fourth product wafer dedicated cassettes 2A, 2B, 2C and 2D each accommodate 25 product wafers W.

The initial data is input to the computer by operating the keyboard of panel 14. The monitor data MW and the product wafer W on the boat 4 are included in this initial data.
And data on the relative positions of the cassettes 2M, 2A, 2B, 2C, 2D and the board 4 and the like.

A start signal is sent from the computer to the controller 27, the loading device 13 is slid in the X-axis direction, and the wafer chuck members 19a and 19b are positioned directly above the cassette 2M.

(II) Supply compressed air to the cylinder 16 of the lift mechanism,
The member 18 lifts the mower wafer MW in the cassette 2M to the height of the wafer chuck members 19a and 19b. Then, the chuck members 19a and 19b are brought close to each other to sandwich the monitor wafer MW.

Next, the push-up member 18 is lowered to leave the three monitor wafers MW between the chuck members 19a and 19b.

(III) The loading device 13 is slid from the cassette stage 12 to the boat stage 15 and stopped at a predetermined position on the front side of the boat 4. Then, the second cylinder 21
The rod 21a is moved in and out, and the monitor wafer MW is moved to the boat 4
The upper edge is lowered to a predetermined position, and the lower edge of the monitor wafer MW is inserted into the groove of the boat 4. At this time, the chuck members 19a and 19b and the monitor wafer M are detected by a sensor (not shown).
The second cylinder is detected while detecting the approach of W to the boat 4 and avoiding the collision of the monitor wafer MW with the boat 4 based on this.
21 operation is stopped. The chuck members 19a and 19b are opened to transfer the three monitor wafers MW after the dummy wafer row of three onto the boat 4 as shown in FIG. 5B.

(IV) Next, as shown in FIG. 5C, the chuck member 19
With a and 19b opened, the boat 4 is moved to the rear surface side of the boat 4 by a distance that is an integral multiple of the monitor wafer MW on the boat 4, for example, one pitch. Then, the chuck members 19a and 19b are closed, and the rear two of the three monitor wafers MW on the boat are clamped by the chuck members 19a and 19b.

(V) As shown in FIG. 5D, chuck members 19a, 19b
The two monitor wafers MW are lifted in the state of being sandwiched by, and then they are moved in the X-axis direction and stopped immediately above the MW dedicated cassette 2M on the cassette stage 12. Next, the chuck members 19a and 19B are lowered to move the monitor wafer M
The edge of W is inserted into the groove of the dedicated cassette 2M, the chuck members 19a and 19b are opened, and the two monitor wafers MW are returned to the positions shifted by one bit in the dedicated cassette 2M.

(VI) As shown in FIG. 5E, in the first cassette 2A
All of the 25 product wafers W are lifted together by the member 18, and these are sandwiched by the chuck members 19a and 19b.
To the right of the monitor wafer MW on the boat 4. Subsequently, similarly to this, the product wafer W in the second cassette 2B is transferred to the right of the previously transferred product wafer W on the boat 4.

(VII) As shown in FIG. 5F, two monitor wafers M
The W is transferred from the dedicated cassette 2M to the right of the product wafer W on the boat 4. With the chuck members 19a and 19b open, the monitor wafer MW is moved by one pitch, and only one of the two monitor wafers MW is clamped and returned to the dedicated cassette 2M.

(VIII) Thereafter, the operation substantially similar to the above-mentioned operation is repeated to transfer the product wafers W from the third cassette 2C and the fourth cassette 2D onto the boat 4 in sequence.

(IX) After the wafer transfer is completed, the boat 4 is transferred to the delivery position, and is transferred to the shelf of the furnace to be used while holding the boat 4 by the arm of the elevator device, the boat 4 is transferred to the fork, and the soft landing device is used. Insert the boat 4 into the furnace. Then, heat treatment is performed at a predetermined temperature and for a predetermined time.

In this way, only one monitor wafer MW transferred from the dedicated cassette 2M onto the boat 4 is left on the boat 4 and the other monitor wafers MW are sandwiched by the chuck members 19a and 19b. Therefore, it is not necessary to put the monitor wafer MW together with the product wafer W in the cassettes 2A, 2B, 2C and 2D in advance. Therefore, 25 product wafers W can be accommodated in one cassette 2.

The present invention is not limited to the above-mentioned first embodiment. For example, in the above-described first embodiment, one monitor wafer MW is arranged between the group of product wafers W, but it is also possible to arrange two or more moita wafers MW between the group of product wafers W.

Further, in the first embodiment, the wafer chuck members 19a,
Although the wafers MW and W are moved by moving 19b, they may be moved relatively. For example, the wafers MW and W may be moved by moving them on the wafer transfer table 11 side. Good.

Further, by using the wafer transfer device of the above-described embodiment, the product wafer W can be transferred from the cassette 2 to the boat 4 at a predetermined pitch even when the wafer, for example, the product wafer W is missing from the cassette 2.

Hereinafter, with reference to FIGS. 6A to 6E, a wafer transfer method when the product wafer W is missing from the cassette 2 will be described. The first embodiment and the second embodiment
The description of the parts common to those of the first embodiment will be omitted.

(I) As shown in FIG. 6A, four wafer cassettes are used.
2A, 2B, 2C and 2D are placed on the cassette stage 12 at predetermined positions. Each of the first cassette 2A, the third cassette 2C, and the fourth cassette 2D contains 25 product wafers W. For example, 23 product wafers W are stored in the second cassette 2B.
Is housed. In this case, the wafer W is missing in the first and second wafer holding grooves of the second cassette 2B.

Compressed air is supplied to the cylinder 16 of the lift mechanism,
Thus, the product wafer W in the cassette 2A is lifted to the height of the wafer chuck members 19a and 19b. Then, the chuck member 1
The product wafer W is sandwiched by bringing 9a and 19b close to each other.

(II) As shown in FIG. 6B, chuck members 19a, 19b
The product wafer W is moved in the X-axis direction while being sandwiched by
The product wafer W is transferred to a predetermined position on the boat 4.

(III) As shown in FIG. 6C, 23 product wafers W in the second cassette 2B are transferred onto the boat 4.

(IV) Next, as shown in FIG. 6D, the chuck member 19
2 of the product wafer W on the boat 4 with a and 19b open
The boat 4 is moved to the rear side by the pitch. That is, the second
In the process of transferring the product wafer W from the cassette 2B of the above, in the wafer transfer area on the boat 4 by the chuck members 19a and 19b, the product wafer immediately behind the two groove portions where the product wafer W is not held. W is the chuck member 19a, 19
Be at the beginning of b. Then, the chuck members 19a, 1
9b is closed, and the 23 product wafers W on the boat are clamped by the chuck members 19a and 19b and lifted.

(V) As shown in FIG. 6E, chuck members 19a, 19b
Is moved to the front side of the boat 4 by two pitches of the product wafer W, and is lowered, and the chuck members 19a and 19b are opened and transferred onto the boat 4. Next, the product wafers W are sequentially transferred onto the boat 4 from the third and fourth cassettes 2C and 2D.

As a result, the product wafers W are continuously placed on the boat 4 at a constant pitch.

The effects of this embodiment will be described below in a comprehensive manner.

According to the present invention, the monitor wear MW and the product wafer W can be automatically loaded onto the boat 4 from different cassettes 2 without mixing the monitor wafer MW with the product wafer W in the same cassette in advance. Therefore, the product wafers W can be fully accommodated in one cassette, the product wafers W can be transferred on the boat in units of one cassette, and the product yield can be improved. Further, since the operator does not manually transfer the wafer, the contamination of the wafer is prevented and the cleanliness can be improved.

Further, even if the product wafer W in the cassette is missing, it can be appropriately dealt with. Therefore, the operating rate of the device could be significantly improved.

〔The invention's effect〕

As described above, according to the present invention, it is not necessary to put monitor wafers in the carrier of product wafers one by one, so that one carrier can accommodate, for example, 25 product wafers. Therefore, the product wafers can be transferred to the boat on a carrier-by-carrier basis, and the yield and cleanliness can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a wafer transfer apparatus for explaining an embodiment of the method of the present invention, and FIG. 2 is a perspective view schematically showing an X-axis moving mechanism in the lower portion of FIG. 1, FIG. Figure 4 shows the first
FIG. 5 is an explanatory view of a wafer clamping operation by the apparatus shown in FIG. 5, FIG. 5 is an explanatory view of a transfer operation by the apparatus shown in FIG. 1, and FIG. 2 ... Cassette, 4 ... Boat 19 ... Wafer chuck

Claims (2)

(57) [Claims] 1. A first step of sandwiching a plurality of monitor wafers contained in a cassette by a sandwiching means and removing them from the cassette, a second step of transporting the sandwiched monitor wafers onto a boat, and the monitor. A third step of transferring all of the monitor wafers from the holding means onto the boat so that the wafers are arranged at predetermined positions on the boat, and the holding means and the port are an integer of one pitch of the monitor wafer. A relative distance by a double distance, leaving a required number of monitor wafers on the boat among a plurality of monitor wafers arranged on the boat, and clamping the required number of monitor wafers by the clamping means and returning them to the cassette; A wafer transfer method comprising four steps and a fifth step of transferring a plurality of wafers from another cassette to the port after the fourth step. 2. A first step of pinching a predetermined number of wafers contained in the cassette by a pinching means to take them out of the cassette, and a plurality of groove portions for holding the pinched wafers. Second to carry on the boat
A step, a third step of transferring all of the wafers from the holding means to the groove of the boat so that the wafers are arranged at predetermined positions on the port, and the holding means on the boat in the third step. When there is a groove portion in the wafer transfer area where the wafer is not held, the wafer arranged on the boat is sandwiched so that the wafer held in the groove portion on the subsequent stage of the groove portion becomes the head. The fourth step of holding the wafer by the holding means, and the holding means and the boat are relatively moved so that the groove portion where the wafer is not held and the head of the wafer held by the holding means correspond to each other, and the fourth step is performed. A wafer transfer method comprising: a fifth step of transferring a wafer.