JPH0374506B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wafer handling method when processing a wafer, for example when implanting ions into the wafer in an ion implantation apparatus.

[Prior Art] FIG. 7 is a schematic plan view of an end station for explaining an example of a conventional wafer handling method. In this example, wafer handling is performed in the atmosphere. That is, a plurality of unimplanted wafers 2 are stored in advance in a cassette 7 of a loader 6 installed in the atmosphere, and after ion implantation, the disks 4 are transferred (pulled out) from the vacuum to the atmosphere.
The implanted wafer 2 loaded on the disk 4 is stored in the cassette 9 of the unloader 8 installed in the atmosphere, and the cassette 7 is placed on the disk 4.
An unimplanted wafer 2 is provided and mounted.

FIG. 8 is a schematic plan view of another end station for explaining another example of the conventional wafer handling method. In this example, the disk 4 is always in a vacuum, the cassettes 7 and 9 are in the atmosphere, and the wafers 2 are supplied and recovered through the airlock chamber 16. That is, the disk 4 is connected to a vacuum container 1 that communicates with an injection chamber (not shown) and is evacuated to a vacuum.
A direction control chamber 14 directly communicates with the vacuum vessel 12 without using a gate valve or the like. An aerodynamic chamber 16 is provided between the direction control chamber 14 and the atmosphere through gate valves 18 and 20, which is evacuated to a vacuum. A plurality of uninjected wafers 2 are stored in advance in the cassette 7 of the loader 6 installed in the atmosphere, and the disk 4
The implanted wafers 2 loaded in the wafers 2 are stored in the cassette 9 of the unloader 8 installed in the atmosphere via the direction control chamber 14 and the airlock chamber 16, and the unloaded wafers 2 are unloaded from the cassette 7 of the loader 6. The implanted wafer 2 is supplied to the disk 4 via the airlock chamber 16 and the direction control chamber 14 and mounted thereon.

[Problem that the invention seeks to solve]

The wafer handling method explained in FIG. 7 has the following problems.

Since the cassette 7 of the loader 6 and the cassette 9 of the unloader 8 are separate, the wafers 2 after implantation are collected in a different cassette 9 from the one when not implanted. However, depending on the operating conditions of the ion implanter, there may be cases where it is more convenient to collect the wafer 2 after implantation into the cassette 7 in which it was originally placed.
In such a case, an additional step of exchanging the wafers 2 between cassettes is required, which is very time-consuming and reduces the throughput (the number of wafers processed per unit time).

Since there is both a supply cassette 7 and a recovery cassette 9, not only may wafers run out in the cassette 7 during handling, but also the cassette 9 may become full of wafers. In such a case, it is necessary to replace the cassette 7 or 9, which requires a lot of effort, and the handling operation is suspended for the time required for these replacements, resulting in a corresponding reduction in processing capacity.

Generally speaking, the number of wafers 2 loaded onto the disk 4 is smaller than the number of wafers 2 stored in the cassettes 7 or 9 (for example, the former has 25 wafers and the latter has 14). ), it is not possible to process one cassette's worth of wafers 2 at one time. For this reason, one cassette is processed in several batches, or one lot is processed in several batches, but in that case, in the last process, if the number of wafers 2 does not reach the number of disks 4 installed, There is. In such a case, wafer 2
If the ion implantation is performed while there are some parts where the disk 4 is not attached, a problem will occur in the disk 4. For example, silicone rubber is laid at the attachment point of the wafer 2 on the disk 4 to improve heat conduction between the wafer 2 and the disk 4, and if ions are implanted there without the wafer 2 attached, the silicon rubber The rubber will be damaged. To prevent such problems from occurring, please
If there is a shortage of wafers 2 to be supplied, ions must be implanted after, for example, mounting a dummy wafer. In such a case, in the wafer handling method described in FIG. 7, the operator must attach the cassette containing the dummy wafers to the loader 6, which is very time consuming. Furthermore, sorting the dummy wafers collected by the unloader 8 must be done manually, which is troublesome.

On the other hand, in the end station shown in FIG. 8, a dummy station 10 is provided, and a dummy wafer 2d is supplied from a cassette 11 there.
Collection is now automatic, and the above-mentioned problems have been solved. However, since the cassette 7 of the loader 6 and the cassette 9 of the unloader 8 are separate, as in the case of FIG. 7, the above-mentioned problems still exist.

SUMMARY OF THE INVENTION Accordingly, a principal object of the present invention is to provide a wafer handling method in which wafers can be supplied and retrieved using the same cassette.

[Means for solving problems]

The wafer handling method of the first invention uses a cassette in which a plurality of unprocessed wafers are stored in advance, and a stocker capable of storing more wafers than the number of wafers stored in the cassette. All the wafers are transferred to the stocker to empty the cassette, the wafers are then taken out from the stocker for processing, and the processed wafers are returned to the original cassette.

The wafer handling method of the second invention includes a cassette in which a plurality of unprocessed wafers are stored in advance, a plurality of dummy wafers in advance, and further wafers in excess of the number of wafers stored in the cassette. Using a stocker that is available, first transfer all the wafers stored in the cassette to the stocker to empty the cassette, then remove the wafers from the stocker and supply them to the disk. If there is a shortage, supply dummy wafers to the disk,
The processed wafers are returned to the original cassette, and the dummy wafers are returned to the original stocker.

A wafer handling method according to a third aspect of the invention includes a plurality of cassettes each containing a plurality of unprocessed wafers in advance, and a pair of cassettes each containing a plurality of dummy wafers. Moreover, using a plurality of stockers capable of storing more wafers than the number of wafers stored in the pair of cassettes, first, all the wafers stored in each cassette are transferred to the pair of stockers and each cassette is emptied. Next, wafers are taken out from one stocker and supplied to the disk, and if there is a shortage of wafers to be supplied to the disk, either the stocker supplies dummy wafers to the disk by the insufficient number, or the other stocker supplies the insufficient number of wafers to the disk. Either supply the wafer to the disk,
After processing, the wafers are returned to the original cassette.
Dummy wafers are returned to the original stocker.

[Effect]

In the wafer handling method of the first invention, the wafers after processing are recovered into the original cassette.

In the wafer handling method of the second invention, dummy wafers are supplied to the disk by the number of wafers lacking, and the wafers after processing are collected into the original cassette, and the dummy wafers are collected into the original stocker.

In the wafer handling method of the third invention, when there is a shortage of wafers on the disk, dummy wafers are supplied for the shortage or wafers are supplied from another stocker, and the wafers after processing are collected into the original cassette. , the dummy wafer is recovered to the original stocker.

〔Example〕

FIG. 1 is a schematic plan view of an end station for explaining an example of the wafer handling method according to the present invention, and FIG. 2 is a schematic sectional view taken along the line - in FIG. 1. This example shows a case where wafers are handled in the atmosphere. That is, the pair of cassette 22A and stocker 26A (this is called stage A), the pair of cassette 22B and stocker 26B (this is called stage B), etc. are provided in the atmosphere, and the disk 4 is also used for taking out wafers 2. And when mounting, it is transferred (pulled out) from the vacuum to the atmosphere.

A plurality of unprocessed (unimplanted) wafers 2 (for example, 25 wafers) are stored in each of the cassettes 22A and 22B in advance. Cassette 22A, 22
Stocker 2 installed between B and disk 4
In each of 6A and 26B, a plurality of dummy wafers 2d, for example, the number of wafers 2 to be mounted on the disk 4 (for example, 9), are stored in advance in the upper part, and a pair of cassettes are stored in the lower part. 2
It is possible to store more wafers 2 (for example, 25 wafers) than the number stored in 2A and 22B.

The wafers 2 are taken out from the cassette 22A and the wafers 2 are collected therein by raising or lowering the cassette 22A in stages by a lifting mechanism 32A consisting of a motor or the like, and by rotating the conveyor belt 24A in the normal or reverse direction. It is done by folding. To explain this further, the cassette 22A has a plurality of shelves (25 in this example) on its inner surface that support both ends of the wafers 2 from below, and the plurality of wafers 2 are placed on the shelves. are placed at a predetermined distance from each other. The cassette 22A is provided so as to straddle the conveyor belt 24A, and the conveyor belt 24A is driven, for example, rotated in the forward direction, in step with the lowering of the cassette 22A from the raised position one step at a time. Depending on the case, cassette 2
The wafers 2 in 2A are placed one by one on the conveyor belt 24A starting from the one on the lower stage and are carried out. Conversely, by reversing the conveyor belt 24A at the same pace as the cassette 22A is raised step by step from the lowered position, the wafers 2 supplied on the conveyor belt 24A can be scooped up from below by the shelf. They are neatly stored in the cassette 22A in order from the top.

Storing the wafers 2 in the stocker 26A and taking out the wafers 2 and dummy wafers 2d from the stocker 26A is carried out by raising or lowering the stocker 26A step by step using an elevating mechanism 34A consisting of a motor, etc., and driving the conveyor belt 24A. It is done by folding. To explain this further, Stotzker 2
The cassette 6A has almost the same structure as the above-mentioned cassette 22A except that it is open at the front and rear in the direction of movement of the wafers 2, and is installed so as to straddle the conveyor belt 24A. By driving the conveyor belt 24A at the same pace as the wafers 24A are raised step by step, for example by rotating them in the forward direction, the wafers 2 supplied from the cassette 22A onto the conveyor belt 24A are scooped up from below on a shelf. The dummy wafers 2d are sequentially stored in the lower part of the stocker 26A starting from the upper stage. Conversely, by rotating the conveyor belt 24A in the forward direction at the same pace as the stocker 26A is lowered one step at a time from the raised position, the wafers 2 in the stocker 26A are transferred one by one to the conveyor belt 24A, starting from the lower step. It is placed on top and carried out toward the disk 4. The same applies to the unloading of the dummy wafer 2d. Note that when the stocker 26A is fixed without being raised or lowered, there is a space S larger than the thickness of the wafer 2 between the conveyor belt 24A and the stocker 26A or the wafer 2, etc. stored therein (see FIG. 2). If the conveyor belt 24A is driven in this state, the wafer 2 placed on the conveyor belt 24A will pass through the stocker 26A.

Wafer 2 or dummy wafer 2 to disk 4
The loading and unloading of the discs d is carried out by raising the conveyor belt 30 by a lifting mechanism 38 consisting of an actuator or the like, rotating the conveyor belt 30 in the forward or reverse direction, and rotating the disk 4 in stages. be exposed. The cassette 22B and the stocker 26B are also similar to those described above, but when transporting the wafer 2 or dummy wafer 2d from them, the elevating mechanism 36 consisting of an actuator, etc.
The conveyor belt 28 is raised by.

Next, a wafer handling method in the end station will be explained. First, the two cassettes 22A and 22B containing uninjected wafers 2 are mounted on the highest device, and the wafers 2 are taken out one by one from the lower side of the cassette 22A and placed directly below the dummy wafers 2d in the stocker 26A. All the wafers 2 in the cassette 22A are transferred to the stocker 26A by loading them sequentially toward the lower stage. Similarly, all the wafers 2 in the cassette 22B are transferred to the stocker 26B, and the cassettes 22A and 22B are temporarily emptied.

Next, the wafers 2 are sequentially unloaded from the bottom of the stocker 26A (the wafers 2 there were originally stored in the top of the cassette 22A), are supplied to the disk 4, and are loaded from position _P1 on the disk 4. The wafers 2 are sequentially mounted at position _P9 , and then the disk 4 is placed in a high vacuum implantation chamber (not shown) to perform ion implantation.

After ion implantation, the disk 4 is returned to the atmosphere and the implanted wafer 2 is moved to position P ₁ on the disk 4.
It passes through the above-mentioned space S of the stocker 26A, is recovered to the top of the original cassette 22A (that is, to the original position), and is then removed from the stocker 26A.
The next wafer 2 in 6A is mounted on the disk 4 at position _P1 . Do the same thing at position P ₂ of disk 4 ~
After reaching position _P9 , the second ion implantation is performed.
In this case, the wafers 2 after implantation are recovered in the same cassette as when they were supplied, and in the same location therein (that is, in the same order in which they were previously stored).

When the wafer 2 in the stocker 26A runs out,
This is detected by, for example, a photo sensor, and the unimplanted wafer 2 is supplied to the disk 4 from, for example, the stocker 26B. When the cassette 22A is full of implanted wafers 2, this is detected by, for example, a photo sensor, and the implanted wafers 2 from the disk 4 are automatically collected into the cassette 22B, and a signal to replace the cassette 22A is sent. is emitted.

When the operator who receives this removes the cassette 22A in which the implanted wafers 2 have been collected and attaches the cassette 22A in which the unimplanted wafers 2 are stored, the wafer 2 stocker 26 as described above
The transfer to A is automatically performed and a standby state is entered. During this time, in parallel, the supply of wafers 2 from stocker 26B, ion implantation, and collection of wafers 2 to cassette 22B are performed.

When using dummy wafers due to insufficient wafers to be supplied to disk 4, stocker 26A, 2
The dummy wafer 2d in the upper part of 6B is supplied to the disk 4, and after ion implantation, the dummy wafer 2d is transferred to the original (that is, the same as when it was supplied) stocker 2.
6A, 26B. For this purpose, for example, the source of supply of the dummy wafers 2d, the number of supplied wafers, etc. are stored in the control means.

In this case, if there are two or more stages consisting of a pair of cassette and stocker (Figures 1 and 2 show an example of two stages), the disk 4
When there is a shortage of wafers 2 to be supplied to a stage, there are various ways of supplying dummy wafers 2d from the stage concerned or supplying wafers 2 from other stages, and a typical example is shown in FIG. When the number of wafers mounted on disk 4 is M (for example, 9), and the number of wafers stored in each stage is N (for example, 25),
FIG. 3a shows a case where each time there is a shortage of wafers to be supplied from one stage to the disk 4, the insufficient number of dummy wafers are supplied from that stage. For example, during ion implantation, nine wafers 2 are supplied to the disk 4 from the stocker 26A of stage A, and during ion implantation, seven wafers 2 and two dummy wafers 2d are supplied from the stocker 26A. . Next, the wafer 2 or dummy wafer 2d is supplied from stage B in the same manner.

On the other hand, FIG. 3b shows a case where when there is a shortage of wafers 2 supplied from one stage, the insufficient number of wafers 2 are supplied from other stages, and dummy wafers 2d are supplied all at once after ion implantation. shows.

Which of the above methods is used depends on the injection conditions and the like. For example, if you want to change the implantation conditions for each cassette, use the method shown in Figure 3a, and if you want to continuously implant ions into a large number of wafers under the same conditions, use the method shown in Figure 3b. .

The wafer handling method described above provides the following effects.

The wafer 2 after implantation is collected into the same cassette in which it was supplied. Therefore, the conventional step of exchanging wafers between cassettes is not necessary, and the associated effort can be saved, and processing capacity can be improved. Furthermore, as in the above-described example, the wafers 2 after implantation can not only be collected into the same cassette in which they were supplied, but also can be collected into the same cassette in the same order. The main advantage of doing so is that when different types of wafers 2 are stored in one cassette, if the wafers 2 after implantation are recovered in the same order as the original, there is no need to replace the wafers. This means that post-processing becomes much easier.

The cassettes on the loader side and the cassettes on the unloader side are not separate as in the past, but the wafers 2 after implantation are collected into the original cassette, so the number of cassettes can be half of the conventional number, which makes it easier to replace cassettes. The frequency and effort are also halved compared to the conventional method, which also improves processing capacity.

As in the above example, the stockers 26A, 26
If the dummy wafers 2d are stored in B in advance, when there is a shortage of wafers 2 to be supplied to the disk 4, the dummy wafers 2d can be stored without having to obtain them.
d can also be automatically supplied and collected.

Furthermore, as in the above example, if two pairs of cassettes and stockers are used (in other words, two stages), while the cassette in one stage is being replaced, the wafers 2 can be transferred from the other stage to the disk 4. can be supplied. Therefore, it is possible to eliminate interruptions in ion implantation due to wafer breakage during handling, thereby further improving throughput. Of course, there may be three or more stages.

Note that some end stations carry the wafers 2 one by one into the implantation chamber, implant ions, and then carry them out without using the disk 4 as described above. The wafer handling method of the invention can be used. In that case, there is only one stage, and there is no need to store the dummy wafer 2d in the stocker. Even in such a case, the effects described above and above can be obtained.

Next, a case where wafers are handled in a vacuum will be described. FIG. 4 is a schematic plan view of another end station for explaining another example of the wafer handling method according to the present invention, and FIG. 5 is a schematic sectional view taken along the line - in FIG. 4. 1st
Components equivalent to those in the figures and FIG. 2 are given the same reference numerals and their explanations will be omitted.

The disk 4 is housed in a vacuum container 12 that communicates with an injection chamber (not shown) and is evacuated to a vacuum. During wafer handling, the disk 4 is rotated in stages as shown by the solid line in FIG. During injection, it is rotated and translated as indicated by the broken line (reference numeral 4') in FIG. A transfer chamber 42 directly communicates with the vacuum container 12 without using a gate valve or the like. Cassettes 40A, 40B which are evacuated to vacuum are provided between the transfer chamber 42 and the atmosphere, and cassette doors 44A, 44B and gate valves 46A, 46B are provided on both sides of the cassettes, respectively.
The aforementioned cassettes 22A and 22B are housed in cassette chambers 40A and 40B, respectively, and stockers 26A and 26B are both housed in a transfer chamber 42. Furthermore, the aforementioned conveyance belts 24A and 24B are divided into conveyance belts 23A and 27A and conveyance belts 23B and 27B, respectively, in this example.

Next, a wafer handling method in the end station will be explained with reference to FIG. In step 1, the cassette door 44A,
44B is opened, and the cassettes 22A and 22B containing uninjected wafers 2 are mounted on the end station. In step 2, the cassette doors 44A, 44B are closed, and in step 3, the cassette chambers 40A, 40B are evacuated. In step 4, the gate valves 46A and 46B are opened, and in step 5, the wafer 2 is transferred to the cassette 22.
Transfer everything from A and 22B to stockers 26A and 26B. In step 6, the stocker 26
Nine wafers 2 are supplied from A and mounted on the disk 4, and in step 7, ions are sequentially implanted into the wafers 2. In step 8, the implanted wafer 2 is collected into the cassette 22A, and
Nine unimplanted wafers 2 are supplied from the stocker 26A to the disk 4, and ions are implanted in step 9. In step 10, the implanted wafers 2 are collected into the cassette 22A, and seven unimplanted wafers 2 are supplied to the disk 4 from the stocker 26A (in this example, the wafers 2 are loaded into the cassette 22A,
Since the number of wafers 2 stored in 22B is 25, only 7 uninjected wafers 2 remain on one stage at the time of third loading).
The missing two cards are Stotzker 26 on the other stage.
Supplied from B. After ion implantation in step 11, in step 12, the seven implanted wafers 2 are collected into the original cassette 22A, and the two wafers 2 are collected into the original cassette 22B.
Nine unimplanted wafers 2 are supplied to the disk 4 from the stocker 26B. In step 13,
At the same time as ion implantation, the gate valve 46A is closed. In step 14, the wafer 2 is loaded and unloaded in the same manner as described above, and nitrogen gas or the like is injected into the cassette chamber 40A to open the cassette chamber 40A.
Bring A to atmospheric pressure (vent). In step 15, ions are implanted and the cassette door 4 is
4A, and in step 16 open cassette 22A.
exchange. That is, the cassette 22A containing the implanted wafers 2 is removed, and the cassette 22A containing the unimplanted wafers 2 is attached. After that, the same operation as above is repeated. Then, in step 27, the remaining three wafers 2 are supplied from the stocker 26A to the disk 4, and dummy wafers 2d are supplied from the stocker 26A to compensate for the shortage.
Supply 6 pieces. The wafer 2 and dummy wafer 2d at this time are collected in the original cassette 22A and the original stocker 26A in step 29.
That is, in this example, the method of supplying the dummy wafers shown in FIG. 3b is adopted.

As described above, in this wafer handling method, handling is performed in a vacuum, so compared to the handling method explained in FIGS. 1 and 2, in which the disk 4 is moved in and out between the vacuum and the atmosphere. , processing power is further improved. Of course,
It goes without saying that the effects described in FIGS. 1 and 2 can also be obtained. Further, although there is a conventional handling method using an end station in which a loader cassette and an unloader cassette are housed separately in two cassette chambers, the wafer handling method of the present invention differs from that conventional example. In comparison, the number of cassette chambers can be reduced by half, and therefore the vacuum can be reduced by half.
The processing capacity improves accordingly.

Finally, in the examples shown in FIGS. 1 and 2 and the examples shown in FIGS. 4 to 6, the end station has a disk 4, has two stages, and uses a dummy wafer 2d. However, the present invention is not limited thereto, and the above-mentioned effects can be obtained by the handling method (first invention) using a cassette and a stocker, and furthermore, the above-mentioned effects can be obtained by using the disk 4 and the dummy wafer 2d. Handling method (second invention)
The above-mentioned effects can be obtained, and the above-mentioned effects can also be obtained by using a handling method including a plurality of stages (third invention).

〔Effect of the invention〕

As described above, in the first invention, a cassette and a stocker are used, and the wafers after processing are collected into the original cassette. Therefore, the conventional step of exchanging wafers between cassettes is not necessary, and the associated effort can be saved, and processing capacity can be improved. In addition, there is no need to replace both the cassette on the loader side and the cassette on the unloader side as in the past, but only one cassette needs to be replaced, so the frequency and effort for replacing cassettes is halved compared to the conventional method. It is possible to improve processing capacity even when

In the second invention, in addition to the first invention,
Since dummy wafers can be automatically supplied to the disk, in addition to the effect of the first invention, when there is a shortage of wafers to be supplied to the disk, dummy wafers can be quickly supplied without requiring human labor. It will be done.

In the third invention, in addition to the second invention,
By using multiple pairs of cassettes and stockers, it is possible to eliminate interruptions in ion implantation due to wafer breakage during handling, so in addition to the effects of the second invention, processing capacity can be further improved. This effect can also be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view of an end station for explaining an example of the wafer handling method according to the present invention. Figure 2 shows the line -
FIG. FIG. 3 is a diagram for explaining how to supply a wafer or dummy wafer to a disk. FIG. 4 is a schematic plan view of another end station for explaining another example of the wafer handling method according to the present invention. FIG. 5 is a schematic cross-sectional view taken along line - in FIG. 4. FIG. 6 is a diagram for explaining the wafer handling operation in the end station shown in FIGS. 4 and 5. FIG. FIG. 7 is a schematic plan view of an end station for explaining an example of a conventional wafer handling method. 8th
The figure is a schematic plan view of another end station for explaining another example of the conventional wafer handling method. 2...Wafer, 2d...Dummy wafer, 4...
Disk, 12... Vacuum container, 22A, 22B...
...Cassette, 26A, 26B...Stocker.

Claims (1)

[Claims] 1. A wafer handling method when processing wafers, which includes a cassette in which a plurality of unprocessed wafers are stored in advance, and a stocker capable of storing more wafers than the number of wafers stored in the cassette. First, all the wafers stored in the cassette are transferred to the stocker to empty the cassette, and then the wafers are carried out from the stocker for processing.
A wafer handling method characterized by collecting the processed wafers into the original cassette. 2. The wafer handling method according to claim 1, wherein the wafers after processing are collected in the same order as the cassette in which they were stored in advance. 3 A wafer handling method in which multiple wafers are loaded onto a disk and processed one after another, using a cassette in which multiple unprocessed wafers are stored in advance and a cassette in which multiple dummy wafers are stored in advance. Then, using a stocker that can store more wafers than the number of wafers stored in the cassette, first, all the wafers stored in the cassette are transferred to the stocker to empty the cassette, and then the wafers are taken out from the stocker. At that time, if there is a shortage of wafers to be supplied to the disk, dummy wafers are supplied to the disk by the insufficient number of wafers, and the processed wafers are returned to the original cassette, and the dummy wafers are returned to the original stocker. A wafer handling method characterized by: 4. A wafer handling method for loading a plurality of wafers onto a disk and processing them one after another, in which a plurality of cassettes, each containing a plurality of unprocessed wafers in advance, are paired with the cassette. First, the wafers stored in each cassette are stored using a plurality of stockers which are made up of a stocker, which has a plurality of dummy wafers stored in advance, and which can store more wafers than the number of wafers stored in the paired cassettes. All the wafers are transferred to the pair of stockers to empty each cassette, and then the wafers are taken out from one stocker and supplied to the disk. If there is a shortage of wafers to be supplied to the disk at this time, the stocker is filled with the insufficient number of wafers. Either supply dummy wafers to the disk or supply the insufficient number of wafers to the disk from another stocker, and then collect the processed wafers into the original cassette, and return the dummy wafers to the original stocker. A wafer handling method characterized by: