The background of the first invention will be described below.
In general, in order to fabricate a semiconductor integrated circuit, such as an IC or LSI, various deposition, oxidation and diffusion, and etching processes are repeatedly carried out for a semiconductor wafer. When the respective processes are carried out, it is required to transfer the semiconductor wafer between corresponding systems. In this case, as well known, in order to improve the yields, it is required to prevent particles and natural oxide films from adhering to the surface of the semiconductor wafer. Therefore, with the increase of the request for high scale down and high density integration, a closed treating-object housing box tends to be used for transferring the wafer. As shown in FIGS. 5 and 6, a treating-object housing box 2 has an opening portion 4 on one end thereof, and a substantially semi-circular box vessel 6 on the other end thereof. Multistage supporting protrusions 8 are provided on the inner wall of the box vessel 6, and the peripheral portions of semiconductor wafers W are mounted and supported thereon, so that the semiconductor wafers W can be housed therein on multiple stages at substantially even intervals. On the ceiling portion of the box vessel 6, a gripping handle 24 for holding the whole vessel is provided. Usually, one box can house therein about 25 or 13 wafers.
A rectangular hollow plate-shaped lid 10 is detachably mounted on the opening portion 4 of the box vessel 6. The interior of the box vessel 6 is evacuated in an airtight state to some extent, to be in an atmosphere of an inert gas, such as N2 gas, so that the wafers W housed therein do not contact outside air as much as possible.
The lid 10 is provided with two locking mechanisms 12. By releasing the locking mechanism 12, the lid 10 can be removed from the opening portion 10.
Specifically, as shown in FIG. 7, each of the locking mechanisms 12 has a rotatable disk-shaped locking plate 14 at the substantially center of the lid 10 in height directions. The locking plate 14 is formed with an elongated recessed key groove 16. Above and below the locking plate 14, there are provided a pair of rising and setting pins 20, each of which is connected to an arm 18 as a crank mechanism for converting a circular motion into a linear motion. By rotating the locking plates 14 by 90 degrees in normal and reverse directions, the upper and lower rising and setting pins 20 rise and set in vertical directions.
During locking, as shown in FIG. 6, the tips of the rising and setting pins 20 are inserted into and engaged with pin holes 22, which are formed in top and bottom edge portions for defining the opening portion 4 (only the bottom edge portion is shown in FIG. 6), to prevent the lid 10 from being removed from the opening portion 4. Therefore, if key members (not shown) are engaged with the corresponding key grooves 16 to be rotated by 90 degrees from a locked state shown in FIG. 7(A) to retract the rising and setting pines 20 by a distance ΔL as shown in FIG. 7(B) to pull them out of the pin holes 22 (see FIG. 6), the lid 10 is in an unlocked state.
In general, the above described housing box 2 is automatically transferred in a treatment system which includes an automatic transfer mechanism for the housing box, a stock region for temporarily stocking therein the housing box, and a treatment unit for treating semiconductor wafers. In addition, key members 26 are operated by automatic apparatuses having them, so that the lid 10 of the housing box 2 is automatically detached and attached by the above described process.
For example, such a treatment system is disclosed in Japanese Patent Laid-Open No. 4-180213, Japanese Patent Laid-Open No. 8-279546, Japanese Patent Laid-Open No. 11-274267, and the applicant's prior application (Japanese Patent Application No. 11-201000). To the interior of the system, an inert gas, such as N2 gas, or clean air having a high cleanliness factor is supplied.
Specifically, the interior of the above described treatment system is airtightly separated into a housing-box transfer area for receiving and temporarily stocking the housing box therein, and a wafer transfer area for transferring semiconductor wafers, which are taken out of the housing box after opening the housing box, to a wafer boat or the like to actually carry out a treatment. The housing-box transfer area is filled with clean air, and the wafer transfer area is filled with an inert gas, such as N2, for preventing natural oxide films from being produced.
The partition wall for separating both areas from each other has a door capable of being open and closed. This door is provided with one or two opening portions. The housing box is set so as to tightly contact the opening portions. Then, the housing box lid and the door are removed from the wafer transfer area to take shelter. In this state, the semiconductor wafers are fed into the wafer transfer area.
Referring to FIGS. 8 and 9, the state at this time will be described below.
In the case of an example of a conventional system shown in FIG. 8, two stages of upper and lower mounting tables 30A and 30B capable of being integrally moved in vertical directions are provided on the side of the housing-box transfer area of the opening portion 28 of a partition wall 26, and a treating-object housing box 2 is mounted thereon to be fixed. An opening/closing mechanism 34 for removing the lid 10 and a door 32 for opening and closing the opening portion 28 is provided for substantially simultaneously removing the lid 10 and the door 32 and for causing them to take shelter upwards or downwards while holding them. The opening/closing mechanism 34 is provided with a key portion (not shown) which is inserted into the key groove shown in FIG. 6 to be rotated to carry out locking and unlocking.
After the carrying-out of the wafers in one of the housing boxes is completed, the lid 10 and the door 32 are mounted again. Thereafter, the mounting tables 30A and 30B are caused to integrally slide upwards in, e.g., the shown embodiment, and the wafers are carried out of the housing box 2, which newly faces the opening portion 28, in the same manner as that described above.
Furthermore, the reason why the two housing boxes 2 are thus set is that the wafer carrying-in/out efficiency is improved.
On the other hand, in the case of an example of a conventional system shown in FIG. 9, the partition wall 26 is provided with upper and lower openings 28A and 28B which are provided with doors 32A and 32B for opening and closing them, respectively. Inside of the housing-box transfer area of the openings 28A and 28B, mounting tables 30A and 30B are fixedly mounted, respectively. Inside of the wafer transfer area of the openings 28A and 28B, two opening/closing mechanisms 34A and 34B are provided so as to correspond to the openings 28A and 28B, respectively. In the same manner as that described above, the lid 10 and the door 32A or 32B are removed from the housing box, which is set on each of the openings 28A and 28B, by means of the opening/closing mechanisms 34A and 34B. Furthermore, these opening/closing mechanisms are disclosed in Japanese Patent Laid-Open No. 11-274267, which has been described above as the prior art, and so forth.
By the way, in the above described examples of conventional systems, two housing boxes can be set in the vicinity of one or two openings, so that it is possible to fed the wafers into the wafer transfer area to greatly improve the transfer efficiency of the wafers to the wafer boat.
However, in the case of the example of the conventional system shown in FIG. 8, the two mounting tables 30A and 30B are provided so as to be slidable in vertical directions. Therefore, there is a problem in that it is required to ensure a large space for three housing boxes in this portion.
In the case of the example of the conventional system shown in FIG. 9, it is sufficient to provide a space for only two housing boxes. However, in this case, there is a problem in that it is required to provide two opening/closing mechanisms 34A and 34B which have a complicated structure and which are relatively expensive, so that the costs are high.
In particular, in the case of the opening/closing mechanisms 34A and 34B shown in FIG. 9, the structure must be complicatedly devised in order to avoid the interference of the opening/closing mechanisms with each other, so that higher costs are caused.
The background of the second invention will be described below.
In the fabrication of semiconductor devices, various treatments, such as oxidation, diffusion and CVD, are carried out with respect to semiconductor wafers serving as objects to be treated. As systems for carrying out such treatments, so-called vertical heat treatment systems are widely utilized.
As such a vertical heat treatment system, from the standpoint of the improvement of throughput, there is known a vertical heat treatment system which uses two wafer boats serving as holders for holding a plurality of semiconductor wafers and wherein semiconductor wafers are transferred with respect to one wafer boat while heat treatment is carried out with respect to the other wafer boat.
The conventional heat treatment system has a housing which is separated into front and rear portions by a partition wall to define a carrier transfer area and a loading area in which a vertical heat treatment furnace having an opening in its bottom is provided. The loading area includes: a boat elevator which is a lifting mechanism moved in vertical directions for carrying a wafer boat in and out of the heat treatment furnace; a holder mounting portion comprising two boat mounting portions which are arranged in the front and rear portions of one side portion of the housing; a boat transfer mechanism which is a holder transfer mechanism for transferring the wafer boat between the boat mounting portion and the boat elevator; and a wafer transfer mechanism which is a treating-object transfer mechanism for transferring semiconductor wafers with respect to the wafer boat supported on the boat mounting portion.
This vertical heat treatment system has a motion space region in which the wafer transfer mechanism and the boat transfer mechanism overlap with each other. When the semiconductor wafers are transferred, the boat transfer mechanism is moved to a sheltered position below the motion space region, and when the wafer boat is transferred, the wafer transfer mechanism is moved to a sheltered position above the motion space region.
The sheltered position of the wafer transfer mechanism is thus arranged upwards in the vertical heat treatment system with the above described construction. Therefore, when the wafer boat is carried out of the heat treatment furnace, the wafer transfer mechanism is easy to have the influence of heat from the bottom end opening of the heat treatment furnace and the wafer boat after the heat treatment, and the temperature of the wafer transfer mechanism at the sheltered position sometimes reaches to 150° C., so that it is difficult to stably operate the system for a long term due to the failure of the control apparatus in the wafer transfer mechanism and so forth.
In recent years, it has been also requested to increase the diameter of the semiconductor wafer in order to improve the yields of chips per one semiconductor wafer. For example, it has been requested that a semiconductor wafer having a diameter of 12 inches (300 mm) is heat-treated.
However, with the increase of semiconductor wafers, the width, length and height of the vertical heat treatment system increase, so that the floor area and ceiling height for the installation of the heat treatment system also increase. Therefore, the production costs and maintenance costs of the vertical heat treatment system increase, so that it is required to miniaturize the vertical heat treatment system.
The background of the third invention will be described below.
As one of systems for heat-treating objects to be treated, such as semiconductor wafers (which will be hereinafter referred to as wafers), in a semiconductor fabricating processes, there is a vertical heat treatment system for carrying out a batch treatment. In this system, a plurality of wafers serving as objects to be treated are held on a holder (boat) while being stacked, and this holder is carried in a vertical heat treatment furnace for carrying out heat treatment, e.g., CVD (Chemical Vapor Deposition) and oxidation.
The vertical heat treatment system has a holder mounting portion (holder supporting mechanism, boat stage) for supporting thereon the holder. The objects to be treated are transferred to and held in the holder which is supported on the holder mounting portion. Thereafter, the holder mounting portion, in which the objects to be treated are held, is housed in the heat treatment chamber of the vertical heat treatment system, and the objects to be treated are heat-treated.
When the objects to be treated are heat-treated, the positional relationship between the interior of the heat treatment chamber and the objects to be treated is important. Since the temperature distribution and the concentration distribution of atmospheric gas exist in the heat treatment chamber, it is required to arrange the objects in the heat treatment chamber so that the centers of these distributions corresponds to the center of the wafers serving as the objects to be treated. If the heat treatment is carried out in a state that these centers do not correspond, the thickness values of the films formed on the objects are ununiform.
In order to make the positional relationship between the heat treatment chamber and the objects constant, it is effective to make the positional relationship between the holder and the objects constant.
There are some cases where the position shift occurs when the holder (boat) is mounted on the holder mounting portion (holder supporting mechanism, boat stage), and there is some possibility that the position error causes errors in the position relationship between the objects and the holder when the objects are transferred.
The background of the fourth invention will be described below.
As one of systems for heat-treating objects to be treated, such as semiconductor wafers (which will be hereinafter referred to as “wafers”), in a semiconductor fabricating processes, there is a vertical heat treatment system for carrying out a batch treatment. In this system, a plurality of wafers are held on the multiple stages of a holder, such as a wafer boat, and this holder is carried in a vertical heat treatment furnace for carrying out various heat treatments, such as diffusion, oxidation or CVD (Chemical Vapor Deposition).
In recent years, in order to surely inhibit contamination due to particles and natural oxide films on the wafers from being produced in a region called a loading area for carrying wafers in and out of the heat treatment furnace in such a vertical heat treatment system, a closed type system or the like has been put to practical use wherein the loading area is separated as an airtight region which is isolated from outside air, to form an atmosphere of an inert gas, such as nitrogen gas, to carry the wafers in and out.
By the way, the heated wafers after the heat treatment are carried in the above described loading area from the heat treatment furnace, and the temperature of the loading area is high, so that it is required to provide a cooling mechanism. This cooling mechanism is provided for mainly protecting a filter or the like for purifying the interior of the area, from heat. Therefore, in view of the suppression of the flying of particles in the area, the cooling mechanism is provided in the vicinity of an intake hole, i.e., relatively below the loading area.
However, the above described conventional cooling mechanism has the following problems. That is, in recent years, in order to further improve the productivity of semiconductor devices, the size of wafers serving as objects to be treated is being changed from a diameter of 8 inches (about 200 mm) to a relatively large diameter of 12 inches (about 300 mm). When wafers of this large size are carried out of a large-diameter heat treatment furnace which heat-treated the wafers, a large amount of heat is emitted from a throat, and the temperature of the loading area suddenly rises due to a large amount of radiation simultaneously emitted from the large-diameter wafers and the wafer boat, so that there is a problem in that various control parts including electrical parts provided in the area are damaged.
Moreover, this phenomenon that the temperature in the loading area suddenly rises to the high temperature causes a more serious problem in the case of the closed type (inert gas purging box type) system for circulating an inert gas in the area.