JPH06244273A - Magazine stand - Google Patents

Abstract

PURPOSE:To enable semiconductor wafers housed in a cassette to be successively unloaded from or reloaded in it by a method wherein a rotary table is turned by a prescribed angle with the rotating mechanism of a magazine stand when the semiconductor wafer is transferred in a working process. CONSTITUTION:Cassettes where a plurality of semiconductor wafers W are housed are placed in a cassette magazine at certain positions respectively, and a conveyer mechanism 20 is provided to loads or unloads the cassette magazine. A rotating mechanism 9 which rotates a rotary table 2 placed on a stationary base plate 1 of the cassette magazine in a rotatable manner and a horizontal-position retaining mechanism 9 which keeps a cassette shelf 3, which is provided onto the rotary table 2 of the cassette magazine in such a manner that it is movable as they are tilted, horizontal pushing it up are provided. An open-close mechanism is provided to open or close a cover 4 which is provided onto the rotary table 2 of the cassette magazine in a detachable manner covering the cassette shelf 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation device for a cassette magazine used for transporting semiconductor wafers in a process, that is, a magazine stand, and particularly to automation of work flow management and delivery to various processing devices. Regarding a magazine stand that can be supported.

[0002]

2. Description of the Related Art A semiconductor wafer used as a substrate for a semiconductor device is obtained by slicing, for example, a single crystal ingot of silicon or the like in the direction perpendicular to the rod axis, and then chamfering, lapping or etching the sliced product. ,
A mirror surface wafer is obtained by sequentially performing processing such as polishing.

In performing such various processes, the silicon wafers are classified according to various purposes such as type, ingot, resistance, oxygen concentration, and then about 25.
Processing is performed for each lot of about 0 sheets.

The reason why processing is performed in such a state that the lots are classified is that processing specifications differ according to various purposes, and when a defect occurs in a semiconductor device,
If the cause exists in the wafer, this is for verifying the process conditions and the like when the wafer was manufactured, and for providing the cause analysis and feedback to the process conditions and the like.

Therefore, it is important not only to divide the wafer into lots but also to verify the process conditions such as heat history at the time of pulling, and therefore the sliced order is managed by some method. There is a need.

Therefore, conventionally, a wafer accommodating jig called a cassette has been adopted, in which wafers are sequentially accommodated in the cassette, and the cassettes are divided into lots and conveyed in the processing process. Was there.

[0007] However, although such a cassette can usually store about 25 wafers, if one lot is large, the number is about 250. Therefore, about 10 cassettes are regarded as one unit in the processing step. Had to be transported. Therefore, in order to prevent the cassettes of different lots from being mixed, the cassettes of the same lot are further accommodated in a box called a container, and the containers are transported as a unit in the process.

[0008]

However, in the conventional wafer transfer method using the cassette and the container,
It involved various problems such as:

First, in a cassette containing about 25 wafers, if the number of wafers in one lot is about 250, the cassette is handled as a unit of about 10 cassettes as a unit. In some cases, it is not possible to accommodate all the cassettes in one lot, and in the end, one lot of wafers often covers several boxes.

On the contrary, in some cases, the number of wafers in one lot may be small. For example, even if the number of wafers in one lot is sufficient for one cassette, the number of wafers in another lot should not be mixed. Only the cassette was housed in one container to handle the process.

That is, cassettes of the same lot must be accommodated in one container without fail, and one or a plurality of containers are mounted on a hand truck for transportation in units of one lot.

When the handling of the cassette and the container is considered in order to avoid mixing between lots in this manner, there is a waste of transportation by the hand cart when the number of wafers in one lot is small.

On the other hand, depending on the processing steps, wafers of different lots may be processed together, and in such a case, containers of different lots may be stacked and stacked on the line side. Therefore, depending on the processing order, it may be necessary to take out the lower one of the stacked containers, and the work of extracting the desired container is extremely complicated, and moreover, the wafer is damaged when the stacking order of the containers is changed. There was also a risk of giving.

In addition to these problems, since all conventional wafer cassettes were handed over to each processing apparatus, it was thought that the wafers would be damaged each time they were handed over.

As described above, when handling semiconductor wafers, it is possible to verify the manufacturing history of each wafer and to prevent mixing between lots that have been divided into desired sections, and to prevent damage to the wafers and dust. There has been a strong demand for the development of a comprehensive flow management system that combines all of the manufacturing quality, production technology, and production control that can satisfy the original requirements in terms of quality such as adhesion prevention.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to efficiently transfer a wafer while preventing damage to the wafer and preventing mixing between lots. The purpose is to provide a magazine stand.

[0017]

In order to achieve the above object, the magazine stand of the present invention carries in and out of a cassette magazine in which cassettes for storing a plurality of semiconductor wafers are stored at fixed positions. A conveyor mechanism for carrying out, a rotating mechanism for rotating a rotary table rotatably mounted on the fixed base plate of the cassette magazine by a predetermined angle, and a cassette shelf tiltably provided on the rotary table of the cassette magazine. A horizontal holding mechanism for pushing up to keep the cassette shelf horizontal, and an opening / closing mechanism for opening and closing a removable cover provided on the rotary table of the cassette magazine so as to cover the cassette shelf. I am trying.

[0018]

The cassette for storing a plurality of semiconductor wafers is stored in the cassette shelf provided on the rotary table of the cassette magazine. Since the rotary table of the cassette magazine is rotatably provided with respect to the base plate, when the semiconductor wafer is transferred in the processing process, the rotary table of the magazine stand keeps the rotary table at a predetermined angle with the base plate fixed. By rotating the semiconductor wafers, the semiconductor wafers stored in the respective cassettes can be sequentially taken out or returned.

Further, since the cassette shelf provided on the rotary table of the cassette magazine is provided so as to be tiltable in the storage direction of the semiconductor wafer, the cassette shelf is tilted during the transportation and the semiconductor wafer is handed over. If the level is kept horizontal by the leveling mechanism of the magazine stand, it is possible to prevent the semiconductor wafer from popping out during transportation and to smoothly deliver the semiconductor wafer.

Since the cover of the cassette magazine is detachably provided on the rotary table so as to cover the cassette shelf, the cover should be attached during transportation and the magazine stand should be opened and closed only when the semiconductor wafer is transferred. If the cover is removed by the mechanism, it is possible to exert the dustproof effect during transportation without hindering the delivery work.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is a perspective view showing a cassette magazine according to an embodiment of the present invention, FIG. 2 (a) is a plan view showing the cassette magazine of the same embodiment, FIG. 2 (b) is a side view thereof, and FIG.
3A is a sectional view taken along the line AA of FIG.
2B is a sectional view taken along the line BB of FIG.

Cassette Magazine The cassette magazine M used in this embodiment has a base plate 1 made of a synthetic resin such as polyvinyl chloride, and is fitted with a rotary table 2 as shown in FIG. 3 (a). A recess 5 to be placed is formed.

An identification label 6 such as a bar code is attached to the back surface of the base plate 1 so that it can be collated with the identification label (not shown) attached to each cassette C.

For example, a host computer or the like can determine in which cassette magazine M a cassette C containing a particular semiconductor wafer W is stored, and in which cassette shelf 3 of the cassette magazine M is stored. It is possible to store and retrieve using. The bar code label 6 attached to the back surface of the base plate 1 has its information read by a bar code reader (not shown) arranged in each step or the like and output to a host computer or the like.

The material forming the base plate 1 is not limited to the synthetic resin, and a light metal such as aluminum can be used. Further, the structure for rotatably mounting the turntable 2 is not limited to the fitting structure by the recessed portion 6 formed in the base plate 1, but also the base plate 1
A fitting structure in which a convex part is formed on the rotary table 2 and a concave part is formed on the rotary table 2 side may be used. However, as will be described later, in this embodiment, the base plate 1 is made of polyvinyl chloride,
Since the rotary table 2 is made of aluminum, the structure shown in FIG. 3A is adopted in consideration of the workability of both.

The turntable 2 is made of aluminum and is fitted in the recess 6 formed in the base plate 1 as described above, but is rotatably provided with respect to the base plate 1. This is because the semiconductor wafers W are transferred from the cassette shelves 3 mounted on the rotary table 2 at equal intervals.
This is because the directions of the cassette shelves 3 are changed in order even when the base plate 1 is fixed to a conveyor or the like when sequentially taking out and returning.

Rotating table 2 with respect to base plate 1
The specific structure for rotating is as follows.
That is, as shown in FIG. 2 (a) and FIG. 3 (a),
First, the base plate 1 is provided with four through holes 7. The ball bearings 8 of the magazine stand S penetrate the four through holes 7 to push up the rotary table 2, whereby the rotary table 2 is moved to the base plate 1. Emerge from. Further, a through hole 10 through which the rotary shaft 9 penetrates is formed in the center of the base plate 1, and the rotary table 2 is further provided.
An engaging hole 12 that engages with a pin 11 formed at the tip of the rotary shaft 9 is formed on the back surface of the.

As the ball bearing 8 moves up, the rotating shaft 9 also moves up, passes through the through hole 10 and the pin 11 engages with the engaging hole 12, and then the rotating shaft 9 is rotated by a predetermined angle. By doing so, the rotary table 2 supported by the ball bearing 8 rotates smoothly. When the rotary table 2 is rotated by a predetermined angle, the ball bearing 8 and the rotary shaft 9 are lowered to mount the rotary table 2 on the base plate again. The ball bearing 8 described above
The support structure of the rotary table 2 by the rotary table 2 and the rotary structure of the rotary table 2 by the rotary shaft 9 are specific examples, and the cassette magazine M used in the magazine stand of the present invention.
Then, other means may be adopted.

On the rotary table 2, there is formed a cassette shelf 3 capable of further storing a plurality of cassettes C containing a plurality of semiconductor wafers W. For example, in the embodiment shown in FIGS. 1 and 2, 12 for a 6 inch wafer.
Cassettes (= 300 wafers), 8 inch wafers can be stored in 8 cassettes (= 200 wafers) on the rotary table 2 in 4 equal parts (ie 9 wafers).
Each cassette shelf 3 is formed at an interval of 0 °, and in the case of a cassette for 8 inches, two cassettes C (three cassettes in the case of 6 inches) can be stacked on one cassette shelf 3. It has become.

In this embodiment, in particular, the reference position of the semiconductor wafer W in each cassette C is kept constant and, for example, as shown in FIG.
The h ₁ and h ₂ shown in (b) are made constant regardless of the specifications of the wafer W and the cassette C, so that the handling robot R can accurately hold the semiconductor wafer W.

However, when the storage pitch of the wafers W in the cassette C is different, as in the case of a 6-inch wafer and an 8-inch wafer, the bar code information of the cassette magazine M or the cassette C is output to the handling robot R. This is dealt with by changing the operation trajectory mode of the handling robot R.

The cassette shelf 3 is structurally shown in FIG.
As shown in FIG. 3B and FIG. 3B, the cassette shelf 3
The frame 15 includes a side frame 13 and a mounting plate 14 for mounting the cassette C, and these are pivotally rotatably attached to a bracket 15 fixed on the rotary table 2.

Since the semiconductor wafer cassette C used in this embodiment has a structure in which the semiconductor wafers W are horizontally inserted at a predetermined pitch as shown in FIG. The semiconductor wafer may fall off due to vibration at the time. Therefore, when mounting the cassette shelf 3 on the rotary table 2,
If the cassette shelf 3 is provided so as to be tiltable, and in particular, the cassette shelf 3 is lowered backward as shown by the solid line in FIG. 3B, it is possible to prevent the semiconductor wafer from falling off during transportation.

However, it can be said that it is preferable to incline the cassette shelf 3 rearward and downward during transportation, but when the semiconductor wafer W is transferred to a processing apparatus or the like, it is preferable that the cassette shelf 3 is horizontal. It may be appropriate in terms of scratching W. Therefore, in this embodiment, a through hole 16 through which the push-up pin 17 rising from the magazine stand S penetrates is bored in the base plate 1 and the rotary table 2, and the push-up pin 17 penetrates the through-hole as shown in FIG. 3B. Push the cassette shelf 3 horizontally through 16
This attitude is maintained when the semiconductor wafer W is delivered.

Cassette magazine M used in this embodiment
Has a cylindrical dustproof cover 4 as shown in FIGS. 1 and 2, and is set so as to cover each cassette C stored in the cassette shelf 3. The side surface and the ceiling surface of the dust-proof cover 4 are made of transparent synthetic resin such as polycarbonate, and the lower end edge is provided with a collar portion 4a for reinforcement and opening / closing of the cover by a magazine stand. The collar portion 4a is formed at a position where it does not hinder the delivery of the semiconductor wafer to the processing apparatus, and is further provided with a hole 18 into which the pin 19 of the opening / closing mechanism provided in the magazine stand S is inserted.

Next, a preferred embodiment of the magazine stand S of the present invention used when the semiconductor wafer W is transferred to a processing apparatus or the like using the cassette magazine M will be described. 4 is a plan view showing a magazine stand according to the present invention, and FIG. 5 is a sectional view taken along the line C-C of FIG.

The magazine stand S of this embodiment comprises a belt conveyor 20 for transferring the cassette magazine M from the transport vehicle, a rotating mechanism for rotating the rotary table 2 of the cassette magazine M, and a cassette shelf of the cassette magazine M. A horizontal maintaining mechanism for maintaining 3 horizontally, an opening / closing mechanism for opening / closing the dustproof cover 4 of the cassette magazine M, and a handling robot R for loading / unloading the semiconductor wafer W into / from the cassette C are provided.

Belt conveyor The belt conveyor 20 is provided around a plurality of rotating rollers 21 and has a pair of belts 22 rotated by a drive motor (not shown), and carries the base plate 1 in and out in the direction of the arrow in FIG. As shown in FIG.
A stopper pin 23 whose position can be freely adjusted is provided as shown in FIG. 3, and the stopper pin 23 performs positioning in the moving direction.

As shown in FIG. 4, positioning plates 25 having positioning rollers 24 are provided on both sides of the conveyed base plate 1, and at least one of the positioning rollers 24 (and / or Alternatively, the positioning plate 25) is movably provided so that the positioning in the left-right direction is performed.

The presence or absence of the cassette magazine M is detected by the photoelectric sensor 26 (see FIG. 5) provided below the base plate 1, and the belt conveyor 20 is stopped when the cassette magazine M is transported to a fixed position. Also,
When the loading of the cassette magazine M is completed, the belt conveyor 20 is entirely lowered by being supported by the guide pins 43 and the bushes 44 and by operating one fluid cylinder 42, so that the belt conveyor 20 faces the base plate 1 at a position where it does not come into contact. ing.

Two guide poles 30 are provided between an upper plate 28 and a lower plate 29 fixed to the frame 27 of the magazine stand S of the rotary mechanism of the rotary table.
A guide bush 31 is slidably inserted into each of the above. A movable plate 32 is fixed to these guide bushes 31, and a tip of a rod 34 of a fluid cylinder 33 attached to the lower plate 29 is fixed to the movable plate 32.

Therefore, when the fluid cylinder 33 is driven to raise the rod 34, the movable plate 32 rises while the guide bush 31 slides along the guide pole 30.

A speed reducer 35 connected to the output shaft of a rotary motor (not shown) is fixed to the movable plate 32, and the rotary shaft 9 is fixed to the upper plate 28 via the speed reducer 35. The bearing bush 36 is provided so as to penetrate therethrough, whereby the rotating shaft 9 is vertically movable and rotatable with respect to the upper plate 28. In addition, the speed reducer 35
Four ball bearings 8 each having a ball 8a at its tip are fixed to the plate 37 fixed to the plate 37, and the ball bearings 8 rise together with the rotating shaft 9 as the movable plate 32 rises.

A fluid cylinder 38 is fixed to an upper plate 28 of the horizontal mechanism of the cassette shelf, and a push-up pin 17 at the end of the rod is formed in the base plate 1 and the rotary table 2 of the cassette magazine M. The bottom of the cassette shelf 3 is pushed up by penetrating therethrough to keep the cassette shelf 3 horizontal.

Since the horizontal mechanism for maintaining the cassette shelf 3 by the fluid cylinder 38 is necessary only when the semiconductor wafer W is taken in and out of the cassette C, for example, the position where the handling robot R is installed (FIG. 4). (See) only.

Dustproof Cover Opening / Closing Mechanism In the magazine stand S of this embodiment, a pin 19 is inserted into the hole 18 of the dustproof cover 4 shown in FIG. While the semiconductor wafer W is taken in and out by pushing up the dustproof cover 4, the dustproof cover 4 is attached again when the access to the semiconductor wafer W is completed and dust or the like adheres to the semiconductor wafer W. Prevent.

Specifically, as shown in FIG. 5, rack and pinion gear boxes 39 corresponding to the number of holes 18 are fixed to the upper plate 28, and the rack-formed pins 19 are attached to the rack and pinion mechanism. Up and down by. At this time, in order to equalize the ascending and descending speeds of the pins 19 and suppress the inclination of the dustproof cover 4 supported by the pins 19, there is one motor that drives the pinion in the gear box 39, and each gear is Box 3
9 are connected by a rotation transmission member (not shown) so as to be synchronized.

The upper limit and the lower limit of the pin 19, that is, the positioning of the dust cover 4 in the raised position (open position) and the lowered position (set position in the cassette magazine),
This is performed by detecting a predetermined position of the pin 19 with a proximity switch or the like.

Handling Robot As shown in FIG. 4, the magazine stand S according to the present embodiment.
Is provided with a handling robot R for loading and unloading the semiconductor wafer W stored in the cassette C with respect to a processing device such as chamfering, lapping, etching, and polishing. It also has a multi-axis arm that meets the requirements of each machining process.

In FIG. 5, "40" is the cassette C.
A photoelectric sensor for detecting the presence or absence of the semiconductor wafer W in the cassette magazine M, and a through hole 41 (FIG. 2) formed in the base plate 1 and the rotary table 2 of the cassette magazine M.
The detection light is applied to the semiconductor wafer W housed in the cassette C through (see (a)). Therefore, if no semiconductor wafer W is stored in the cassette C, the reflected light is not returned to the photoelectric sensor 40. Therefore, by outputting the result to the handling robot R, useless work is prevented in advance. can do.

Next, the operation will be described. First, the single crystal ingot is sliced in the direction perpendicular to the axis of the rod, the obtained plurality of semiconductor wafers W are divided into predetermined lots, and then stored in the cassette C in the order of slicing. And
Cassette C of the same lot is one cassette magazine M
To be installed on.

In the present embodiment, considering that the number of semiconductor wafers in one lot is usually about 250 to 300 (8 inch is 200 or less), 12 cassettes (= 300 wafers of 6 inch wafers). Wafers), 8 inch wafers are set to 8 cassettes (= 200 wafers), so 6 inch wafers can be a maximum of one cassette magazine, and even 8 inch wafers can be a maximum. One cassette magazine is enough.

Particularly, in order to prevent the semiconductor wafers of different lots from being mixed in the process, it is preferable that all the cassettes C stored in one cassette magazine M are the cassettes C of the same lot.

Further, since the cassette shelf 3 provided on the rotary table 2 is provided so as to be tiltable in the storage direction X of the semiconductor wafer W, the cassette C tilts backward and downward during transportation, and vibration during transportation. For example, the semiconductor wafer W can be prevented from jumping out of the cassette C.

In this way, the cassette C is placed on the cassette shelf 3.
After storing the cassette magazine M, the cassette magazine M is conveyed to a target processing step using an automatic carrier or the like, and the magazine stand S described above is provided at the entrance of each processing step. Then, the cassette magazine M transferred from the automatic transport vehicle is fed by the belt conveyor 20 until it hits the stopper pin 23 for positioning, and the positioning roller 24 performs left-right positioning.

By the way, when the cassette magazine M is delivered, the barcode mark 6 attached to the back surface of the base plate 1 is read, and information about the semiconductor wafer W carried into the processing step is transferred to the host computer. Sent.

When the positioning of the cassette magazine M is completed, the belt conveyor 20 is stopped and the work of taking out the semiconductor wafer W is started. In this case, first, the dustproof cover 4 is pushed up so that the handling robot R can access the semiconductor wafer.

That is, a motor (not shown) is operated to synchronously raise each pin 19 via the gear box 39 of the rack and pinion. As the pins 19 rise, the tips of the pins fit into the holes 18 formed in the collar portion 4a of the dust cover 4, and the pins 19 rise further, so that the dust cover 4 starts to rise. The upper limit of the dustproof cover 4 is detected by detecting a predetermined position of the pin 19 with a proximity sensor or the like, and the motor is stopped by outputting this to the motor. In this way, the dustproof cover 4 is opened, and the operation of the handling robot R on the semiconductor wafer W stored in the cassette C is started.

When the semiconductor wafer W is loaded and unloaded by the handling robot R, the rotary table 2 is rotated so that the cassette shelf 3 in which the target cassette C is stored is located at a position facing the handling robot R.

That is, first, the fluid cylinder 33 is operated. As a result, the movable plate 32, the speed reducer 35, the rotary shaft 9, and the ball bearing 8 are integrally raised, the rotary shaft 9 passes through the through hole 10 of the base plate 1, and the tip end thereof is the engaging hole of the rotary table 2. Engage 12.

Around this time, the ball bearing 8 passes through the through hole 7 of the base plate 1 and pushes up the back surface of the rotary table 2 to slightly lift the rotary table 2 from the base plate 1. Operate the rotation motor from this state,
After rotating the rotary shaft 9 by a predetermined angle via the speed reducer 35, the rod 34 of the fluid cylinder 33 is lowered to mount the rotary table 2 on the base plate 1 again. As a result, the target cassette shelf 3 rotates to the position facing the handling robot R.

Then, the fluid cylinder 38 attached to the upper plate 28 is operated to raise the push-up pin 17. As a result, the tip of the push-up pin 17 passes through the through holes 16 of the base plate 1 and the rotary table 2 and pushes up the bottom surface of the cassette shelf 3. Since the stroke of the push-up pin 17 is set so that the cassette shelf 3 becomes horizontal, the semiconductor wafer W stored in the cassette C of the cassette shelf 3 accessed by the handling robot R can be smoothly handled. In addition, it will be kept horizontal during the work.

When the loading / unloading of the semiconductor wafer W by the handling robot R is completed, the next cassette shelf C is rotated to the position facing the handling robot R. At this time, the push-up pin 17 is once lowered. When the work for all the cassettes C on the rotary table 2 is completed, the pins 19 are lowered to close the dustproof cover 4, and the belt conveyor 20 is operated in the reverse direction (delivery direction) to eject the cassette magazine M.

Incidentally, in some processing steps, the above-mentioned handling robot for the magazine stand may be omitted and the cassette may be manually taken out or returned from the cassette magazine. However,
Even in such a process, the magazine stand and the cassette magazine of the present invention effectively function in preventing mixing between lots and efficient transport.

It should be noted that the embodiments described above are provided for facilitating the understanding of the present invention, and not for limiting the present invention. Therefore, each element disclosed in the above-described embodiments is intended to include all design changes and equivalents within the technical scope of the present invention.

For example, the structure of the cassette magazine used in the magazine stand of the present invention is not limited to the embodiment shown in FIGS. 1 to 3, and includes at least a base plate, a rotary table, a cassette shelf and a cover. It suffices to do so, and it can be appropriately changed according to the intended processing step. Further, the processing step in which the magazine stand of the present invention is used is not limited only to the above-mentioned steps such as chamfering of semiconductor wafers, lapping, etching, polishing, etc. Any process can be applied.

[0067]

As described above, according to the present invention, there is provided a magazine stand capable of efficiently transporting semiconductor wafers while preventing damage to the semiconductor wafers and preventing mixing between lots. You can Further, automation of such semiconductor wafer delivery work can be expected.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cassette magazine according to an embodiment of the present invention.

FIG. 2A is a plan view showing the cassette magazine of the embodiment, and FIG. 2B is a side view of the same.

FIG. 3A is a sectional view taken along the line AA of FIG.
2B is a sectional view taken along the line BB of FIG.

FIG. 4 is a plan view showing a magazine stand according to the present invention.

5 is a cross-sectional view taken along the line CC of FIG.

[Explanation of symbols]

 1 ... Base plate 2 ... Rotating table 3 ... Cassette shelf 4 ... Dust-proof cover 8 ... Ball bearing 9 ... Rotating shaft 17 ... Push-up pin 19 ... Pin 20 ... Belt conveyor W ... Semiconductor wafer C ... Cassette M ... Cassette magazine S ... Magazine stand R … Handling robot X… Semiconductor wafer storage direction

Claims (1)

[Claims] 1. A conveyor mechanism for loading and unloading the cassette magazine (M) with respect to a cassette magazine (M) in which a cassette (C) housing a plurality of semiconductor wafers (W) is stored at a fixed position, A rotary mechanism for rotating a rotary table (2) rotatably mounted on a fixed base plate (1) of the cassette magazine (M) by a predetermined angle, and a rotary mechanism on the rotary table (2) of the cassette magazine (M). A horizontal holding mechanism that pushes up the tiltable cassette shelf (3) to keep the cassette shelf (3) horizontal, and the cassette shelf (3) on the rotary table (2) of the cassette magazine (M). A magazine stand comprising an opening / closing mechanism for opening / closing a removable cover (4) provided so as to cover the magazine stand.