Patent Application
20120240857
The present application is based upon and claims the benefit of Japanese Patent Application No. 2010-219726, filed on Sep. 29, 2010, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a vertical heat treatment apparatus configured to perform heat treatment on multiple substrates loaded into a substrate holder in multiple stages by feeding a process gas.
2. Description of the Related Art
As a heat treatment apparatus to perform heat treatment such as a film deposition process on a substrate such as a semiconductor wafer (hereinafter referred to as “wafer”), a batch-type vertical heat treatment apparatus is known that loads a wafer boat, which is a substrate holder, with multiple wafers in multiple stages, accommodates this wafer boat in a reaction tube in an airtight manner, and feeds a process gas into the reaction tube in a vacuum atmosphere, thereby depositing thin films. This wafer boat has a disk-shaped top plate, a disk-shaped bottom plate, and support rods that are attached to the top plate and the bottom plate from their periphery sides at circumferentially spaced apart multiple points to connect the top plate and the bottom plate. Multiple slit-shaped grooves are so formed on the side surfaces of the support rods at intervals in a vertical direction as to face a region for receiving wafers. The wafers are received with their respective end portions supported in these grooves of the support rods. In the space between the peripheral portions of the wafers supported in the wafer boat and the inner wall of the reaction tube, gap regions are so formed in a circumferential direction as to correspond to regions where the support rods are provided.
As a method of feeding a process gas into this reaction tube, a cross-flow system may be employed so that a gas flow is formed horizontally on each wafer as illustrated in Japanese Laid-Open Patent Application No. 2009-206489. Specifically, for example, with a reaction tube having a double-tube structure of an inner tube and an outer tube, a vertically elongated slit-shaped exhaust opening is formed in the inner tube, and a vertically extending gas injector is so placed beside a wafer boat as to face the exhaust opening. Multiple gas ejection openings are so formed in the side wall of the gas injector as to correspond to the vertical positions of wafers, so that a gas flow heading from the gas ejection opening to the exhaust opening is formed on each wafer.
At this point, gap regions are formed in a circumferential direction between the peripheral portions of the wafers supported in the wafer boat and the reaction tube (inner tube) as described above. As a result of this configuration, the process gas ejected from the gas injector tends to flow more through these gap regions than through narrow regions between the wafers. This decreases the amount of gas fed to the wafers through the narrow regions between the wafers, thus reducing the efficiency of use of the process gas.
Japanese Laid-Open Patent Application No. 2010-73823 and Japanese Laid-Open Patent Application No. 61-136676 describe the techniques of circumferentially arranging wafers on a wafer disk or susceptor, and Japanese Laid-Open Patent Application No. 2000-208425 describes an apparatus that performs processing with wafers vertically stacked in layers. However, no description is given of the above-mentioned problem.
According to an aspect of the present invention, a vertical heat treatment apparatus includes a vertical reaction tube including a substrate holder and surrounded by a heating part, the substrate holder being configured to hold a plurality of substrates in multiple stages and to perform heat treatment on the substrates; and a process gas feed part provided in a lengthwise direction of the reaction tube and having a plurality of gas ejection openings formed at vertical positions corresponding to the respective substrates to feed a process gas onto the substrates held in the substrate holder, wherein the reaction tube has an exhaust opening formed therein at a position opposite to the gas ejection openings relative to a center of the reaction tube, and the substrate holder includes a plurality of circular holding plates stacked in layers at intervals and each having a plurality of substrate placement regions formed thereon; and a plurality of support rods supporting the holding plates, the support rods being provided in a circumferential direction of the holding plates to penetrate through the holding plates with outside positions of the support rods being at a same radial position as outer edges of the holding plates or at a radial position inside the outer edges of the holding plates relative to the center of the reaction tube.
According to an aspect of the present invention, a vertical heat treatment apparatus includes a vertical reaction tube including a substrate holder and surrounded by a heating part, the substrate holder being configured to hold a plurality of substrates in multiple stages and to perform heat treatment on the substrates; and a process gas feed part provided in a lengthwise direction of the reaction tube and having a plurality of gas ejection openings formed at vertical positions corresponding to the respective substrates to feed a process gas onto the substrates held in the substrate holder, wherein the reaction tube has an exhaust opening formed therein at a position opposite to the gas ejection openings relative to a center of the reaction tube, the substrate holder includes a plurality of circular holding plates stacked in layers at intervals and each having a substrate placement region formed thereon; and a plurality of support rods supporting the holding plates, the support rods being provided in a circumferential direction of the holding plates to penetrate through the holding plates with outside positions of the support rods being at a same radial position as outer edges of the holding plates or at a radial position inside the outer edges of the holding plates relative to the center of the reaction tube, and a clearance between the outer edges of the holder plates and an inner wall surface of the reaction tube is smaller than a clearance between an upper surface of the substrate supported on a first one of the holding plates and a lower surface of a second one of the holding plates immediately above and opposite the first one of the holding plates.
According to an aspect of the present invention, a vertical heat treatment apparatus includes a vertical reaction tube including a substrate holder and surrounded by a heating part, the substrate holder being configured to hold a plurality of substrates in multiple stages and to perform heat treatment on the substrates; and a process gas feed part provided in a lengthwise direction of the reaction tube and having a plurality of gas ejection openings formed at vertical positions corresponding to the respective substrates to feed a process gas onto the substrates held in the substrate holder, wherein the reaction tube has an exhaust opening formed therein at a position opposite to the gas ejection openings relative to a center of the reaction tube, and the substrate holder includes a plurality of circular holding plates stacked in layers at intervals and each having a plurality of substrate placement regions formed thereon; and a plurality of support rods supporting the holding plates, the support rods being provided in a circumferential direction of the holding plates to penetrate through the holding plates with outside positions of the support rods being at or inside positions 3 mm outward relative to outer edges of the holder plates in a radial direction of the reaction tube.
Accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention, in which:
As a heat treatment apparatus that performs heat treatment such as a film deposition process on wafers, a batch-type vertical heat treatment apparatus is known that loads a wafer boat with approximately 100 to approximately 150 wafers in multiple stages, accommodates this wafer boat in a reaction tube in an airtight manner, and feeds a process gas into the reaction tube in a vacuum atmosphere, thereby depositing thin films. This wafer boat has a disk-shaped top plate, a disk-shaped bottom plate, and support rods that are attached to the top plate and the bottom plate from their periphery sides at circumferentially spaced apart multiple points to connect the top plate and the bottom plate. Multiple slit-shaped grooves are so formed on the side surfaces of the support rods at intervals in a vertical direction as to face a region for receiving wafers. The wafers are received with their respective end portions supported in these grooves of the support rods. In the space between the peripheral portions of the wafers supported in the wafer boat and the inner wall of the reaction tube, gap regions are so formed in a circumferential direction as to correspond to regions where the support rods are provided.
As a method of feeding a process gas into this reaction tube, a cross-flow system may be employed. Specifically, for example, with a reaction tube having a double-tube structure of an inner tube and an outer tube, a vertically elongated slit-shaped exhaust opening is formed in the inner tube, and a vertically extending gas injector is so placed beside a wafer boat as to face the exhaust opening. Multiple gas ejection openings are so formed in the side wall of the gas injector as to correspond to the vertical positions of wafers, so that a gas flow heading from the gas ejection opening to the exhaust opening is formed on each wafer.
At this point, gap regions are formed in a circumferential direction between the peripheral portions of the wafers supported in the wafer boat and the reaction tube (inner tube) as described above. As a result of this configuration, the process gas ejected from the gas injector tends to flow more through these gap regions than through narrow regions between the wafers. This causes the amount of gas fed to the wafers through the narrow regions between the wafers to be less than a set value, so that the degradation of productivity (film deposition rate) and of the uniformity of film thickness and a coverage characteristic in the plane may be caused. Further, the discharge of a process gas without contribution to film deposition increases the amount of use of the process gas, thus causing an increase in cost.
In recent years, consideration has been given to a process of depositing, for example, an alumina (Al2O3) film on a silicon carbide (SiC) substrate or a silicon (Si) substrate for solar batteries, which are, for example, approximately 4 inches (100 mm) in diameter, instead of a common wafer of 12 inches (300 mm) in size. Further, consideration has been given as well to a process of manufacturing a light-emitting diode (LED) device by depositing a gallium nitride (GaN) film on a wafer by metal organic chemical vapor deposition (MO-CVD) using, for example, a sapphire substrate of 100 mm in outside diameter as the wafer.
However, performing this process with these substrates loaded in multiple stages in a wafer boat causes a relative increase in apparatus cost because these substrates are smaller in size than 12 inch wafers. Further, the vertical dimension of the wafer boat (heat treatment apparatus) is limited by, for example, the ceiling surface of a clean room. Therefore, it is difficult to increase the number of substrates to be loaded into the wafer boat (the number of slots) in order to reduce the apparatus cost.
According to an aspect of the present invention, a vertical heat treatment apparatus is provided that improves the efficiency of use of a process gas in performing heat treatment in a reaction tube by feeding multiple substrates loaded in stages in a substrate holder with the process gas from their sides.
In the following, a description is given of a vertical heat treatment apparatus according to an embodiment of the present invention, which is suitable for improving the efficiency of use.
A description is given, with reference to
The reaction tube 12 has a double-tube structure of an outer tube 12a and an inner tube 12b contained in the outer tube 12a. Each of the outer tube 12a and the inner tube 12b is formed to be open on the bottom side. The outer tube 12a is an example of a first reaction tube, and the inner tube 12b is an example of a second reaction tube. The inner tube 12b has a horizontal ceiling surface. The outer tube 12a has a ceiling surface curved outward to substantially define a cylindrical shape. The inner tube 12b has a side surface curved outward along a lengthwise direction of the inner tube 12b on one end side, so that gas injectors 51 to be described below, which form a gas feed part, are contained in this outward curved portion of the inner tube 12b. Further, as illustrated in
Process gases fed from the gas injectors 51 into the inner tube 12b are discharged through this exhaust opening 16 to a region between the inner tube 12b and the outer tube 12a. Each of the outer tube 12a and the inner tube 12b has its lower end formed into a flange shape and is supported from the bottom side in an airtight manner by a flange part 17, which has a substantially cylindrical shape open at an upper and a lower end. That is, the outer tube 12a is hermetically supported by an upper end surface of the flange part 17, and the inner tube 12b is hermetically supported by a projection part 17a that horizontally projects inward from the inner wall surface of the flange part 17. The inner tube 12b is, for example, 330 mm in inside diameter.
An exhaust opening 21 is so formed in the sidewall of the flange part 17 as to communicate with the region between the inner tube 12b and the outer tube 12a. This exhaust opening 21 connects to an evacuation passage 22 via an evacuation port 21a. A vacuum pump 24 is connected to the evacuation passage 22 via a pressure control part 23 such as a butterfly valve. A lid body 25 having a substantial disk shape is provided under the flange part 17 so that the peripheral edge portion of the lid body 25 is circumferentially in hermetic contact with a flange surface that is the lower end portion of the flange part 17. The lid body 25 is configured to move upward and downward with the wafer boat 11 with an elevation mechanism such as a boat elevator (not graphically illustrated).
Referring to
Next, a description is given in detail of the wafer boat 11. As illustrated in
In this example, the five support rods 32 are arranged at equal intervals. As illustrated in
The clearance t between the outer edges of the holder plates 31 and the inner wall surface of the inner tube 12b as illustrated in
In each of the holder plates 31, substrate placement regions 33 for placing the wafers W are arranged so that the peripheral portions of the wafers W on the outer edge side of the holder plate 31 are positioned on the outer edge of the holder plate 31. Accordingly, when viewed in a radial direction of the reaction tube 12, the outer edges of the wafers W and the peripheral surfaces of the support rods 32 are aligned on the border line of the holder plate 31 (that is, the circumference of a circle concentric with and equal in diameter to the holder plate 31). That is, according to an aspect of this embodiment, the radial position of the outer edge of the holder plate 31 is the same as the radial positions of the peripheries (outside positions OP in
Further, the substrate placement regions 33 are formed so that the surfaces of the wafers W placed in the substrate placement regions 33 are vertically at the same position as the surface of the holder plate 31, that is, the upper surfaces of the wafers W and the upper surface of the holder plate 31 are in the same plane. Specifically, the distance between the surfaces of the substrate placement regions 33 and the lower surface of the holder plate 31 that faces the surfaces of the substrate placement regions 33 is determined to be, for example, 8 mm to 10 mm in accordance with the thickness (for example, 0.5 mm to 2 mm) of the wafers W accommodated in these substrate placement regions 33.
In each of the holder plates 31, a cut 34 is formed in the center part of each substrate placement region 33 and its region on the peripheral side of the holder plate 31 relative to the center part in order to have the wafers W transferred to and from an external transfer arm 60 schematically illustrated in
At the time of placing the wafers W in the wafer boat 11, with the wafer boat 11 moved downward to a position below the reaction tube 12, the transfer arm 60 supporting a wafer W moves downward from above the substrate placement region 33 to pass through the cut 34 to below the substrate placement region 33, so that the wafer W is placed in the substrate placement region 33. Further, the wafer boat 11 is caused to rotate on the vertical axis so that another substrate placement region 33 faces the transfer arm 60 side, and a wafer W is placed in the substrate placement region 33 in the same manner. After thus placing five wafers W on the holder plate 31 by causing the wafer boat 11 to intermittently rotate, the transfer arm 60 is caused to move, for example, downward, so that five wafers W are placed on the holder plate 31 positioned below the previous holder plate 31 in the same manner. At the time of unloading the wafers W from the wafer boat 11, the wafer boat 11 and the transfer arm 60 are driven in reverse order to that at the time of placing the wafers W in the wafer boat 11. Transfer arms 60 may be arranged in multiple stages to have multiple wafers W transferred to and from the wafer boat 11 at the same time.
The gas injectors 51 are formed of, for example, quartz, and are disposed along a lengthwise direction of the wafer boat 11. In the sidewalls of the gas injectors 51, the gas ejection openings 52 are so formed at multiple positions in a vertical direction as to face the wafer boat 11 side. These gas ejection openings 52 are so arranged as to correspond to the vertical positions of the wafers W accommodated in the wafer boat 11. That is, each of the gas ejection openings 52 is so positioned as to correspond to a space between one holder plate 31 and another holder plate 31 (or the top plate 37) immediately above and opposite the one holder plate 31. The gas injectors 51 are inserted into the inner tube 12b through the sidewall of the flange part 17 on one end side, and are connected through valves 53 and flow rate control parts 54 to gas reserve sources 55 where process gases are reserved on the other end side. As illustrated in
These gas injectors 51a through 51d are connected to the gas reserve sources 55a through 55d of trimethyl aluminum (TMA) gas, which is a first process gas, ozone (O3) gas, which is a second process gas, tetrakis-ethyl-methyl-amino-hafnium (TEMAH) gas, which is a third process gas, and nitrogen (N2) gas, which is a purge gas, respectively. The gas ejection openings 52 of the gas injectors 51 are oriented to the exhaust opening 16. However, if the support rods 32 may affect the uniformity of film thickness, the gas ejection openings 52 of the gas injectors 51 may not be oriented to the exhaust opening 16, and specifically, may be oriented to positions slightly away from the exhaust opening 16 horizontally.
This vertical heat treatment apparatus includes a control part 56 (
Next, a description is given of operations of the vertical heat treatment apparatus according to this embodiment. First, the wafer boat 11 is moved downward to below the reaction tube 12. While causing the wafer boat 11 to intermittently rotate as described above, five wafers W are placed on each of the holding plates 31 with the transfer arm 60. Then, the wafer boat 11 in which, for example, 750 (5×150) wafers W are placed is inserted into the reaction tube 12, and the lower surface (flange surface) of the flange part 17 and the upper surface of the lid body 25 are caused to come into hermetic contact.
Next, the reaction tube 12 is evacuated to a vacuum by evacuating the atmosphere (gas atmosphere) inside the reaction tube 12 with the vacuum pump 24, and while causing the wafer boat 11 to rotate on the vertical axis, heating is performed with the heater 13 so that the wafers W in the wafer boat 11 become, for example, 300° C. in temperature. Then, while causing the pressure inside the reaction tube 12 to be controlled to a process pressure with the pressure control part 23, TMA gas is fed into the reaction tube 12 from the gas injector 51a.
At this point, the gas ejection openings 52 are positioned beside the wafers W, and the regions between the holder plates 31 of the wafer boat 11 are wider than the region between the outer edges of the holder plates 31 and the inner wall surface of the inner tube 12b. Therefore, as illustrated in
Next, the feeding of the TMA gas is stopped, and as illustrated in
Thereafter, as illustrated in
According to this embodiment, in a vertical heat treatment apparatus that performs heat treatment on substrates held in a substrate holder by ejecting process gases from gas ejection openings formed at vertical positions corresponding to the substrates, multiple circular holder plates are stacked in layers to hold multiple substrates on each holder plate, and support rods supporting the peripheral edge portions of these holder plates are so provided as to not project from the outer edges of the holder plates. This makes it possible to reduce the gap between the holder plates and a reaction tube. As a result, it is possible to reduce the amount of a process gas that passes outside the holder plates and therefore does not contribute to a process. Therefore, it is possible to make effective use of a process gas, that is, it is possible to improve the efficiency of use of a process gas. Further, multiple substrates are placed on each of the holder plates. Therefore, compared with the case of placing one substrate on each holder plate, it is possible to reduce the footprint of the apparatus per substrate. Therefore, it is possible to reduce the cost of the apparatus.
More specifically, according to this embodiment, in the vertical heat treatment apparatus that performs heat treatment on the wafers W held in the wafer boat 11 by ejecting process gases from the gas ejection openings 52 formed at vertical positions corresponding to the wafers W, the circular holder plates 31 are stacked in layers to hold multiple wafers W on each holder plate 31, and the support rods 32 supporting the peripheral edge portions of these holder plates 31 are so provided as to not project from the outer edges of the holder plates 31. Accordingly, it is possible to reduce the gap between the holder plates 31 and the reaction tube 12. Therefore, it is possible to reduce the amount of a process gas that passes outside the holder plates 31 and therefore does not contribute to a process. Therefore, it is possible to make effective use of a process gas, that is, it is possible to feed a process gas onto the surfaces of the wafers W with efficiency. Further, making effective use of a process gas allows prompt deposition of a thin film. Therefore, it is possible to improve productivity. Further, since each of the wafers W is fed with a sufficient amount of a process gas, it is possible to obtain a thin film of uniform thickness in the plane of the wafer W. Further, even if depressions such as grooves or holes are formed on the surface of the wafer W, the process gas spreads inside the depressions. Therefore, it is possible to obtain a thin film of a high coverage characteristic without feeding a large amount of a process gas. Further, the holder plates 31 support the outer edge regions of the wafers W, and unlike plate-shaped holder plates, allow film deposition on the backsides of the wafers W. Accordingly, it is possible to prevent the warpage of the wafers W in the thickness directions (vertical directions).
Since multiple wafers W are placed on each of the holder plates 31, compared with the case of placing one wafer W on each holder plate 31, it is possible to reduce the footprint of the apparatus per wafer W. Therefore, it is possible to reduce the cost of the apparatus. In general, the conventional apparatus has slots each containing a single wafer on a holder plate provided in multiple stages. According to this embodiment, the number of wafers W placed on each holder plate 31 is, for example, five. According to the apparatus configuration of this embodiment, the throughput of the apparatus is quintupled, while the footprint of the apparatus (the outside diameter of the reaction tube 12) is no more than approximately tripled. Therefore, even if the vertical dimension of the vertical heat treatment apparatus (the wafer boat 11) is limited by, for example, the ceiling surface of a clean room, it is possible to increase the number of wafers W that may be processed with the vertical heat treatment apparatus. Therefore, it is possible to reduce the cost of the apparatus for processing a single wafer W. That is, according to this embodiment, it is possible to cause an approximately severalfold increase in the number of wafers W that may be processed at a time. Further; in this example, five wafers W having a size of 100 mm in diameter are circumferentially arranged on each of the holder plates 31. Therefore, it is possible to use apparatuses (the reaction tube 12 and the heating furnace body 14) for common 300 mm wafers, and the process conditions and the apparatus operating conditions that have been established for 300 mm wafers may be used as they are.
In thus making effective use of a process gas, the clearance t between the outer edges of the holder plates 31 and the inner wall surface of the inner tube 12b is such a small value that allows the wafer boat 11 to rotate inside the inner tube 12b, and is specifically 3 mm to 8 mm, and preferably, 5 mm to 8 mm. Accordingly, when viewed in a radial direction of the reaction tube 12, the outside positions OP (
In the above-described example, five wafers W are placed on each of the holder plates 31, while three wafers W may be placed on each of the holder plates 31 as illustrated in
Further, as the wafers W, in addition to those of 100 mm in size as described above, common-size wafers W of 300 mm in diameter may be used. Furthermore, even when the wafers W are, for example, angular wafers of polysilicon for solar batteries, it is possible to form a laminar flow of gas between the holder plates 31 by forming the substrate placement regions 33 corresponding to the outer shape of the wafers W in the holder plates 31. Therefore, it is possible to perform a uniform process irrespective of the outer shape of the wafers W, and it is possible to make effective use of a process gas and reduce the cost of the apparatus.
Further, in the above-described example, a thin film is deposited using atomic layer deposition (ALD), according to which a process gas for an atomic layer or a molecular layer is caused to adsorb to the surfaces of the wafers W, and then this process gas is oxidized to form a reaction product. On the other hand, a thin film may also be formed by chemical vapor deposition (CVD). In this case, for example, the above-described TMA gas and O3 gas are fed into the reaction tube 12 at the same time.
Further, the vertical heat treatment apparatus of this embodiment is applied to a film deposition method for depositing a thin film on the surfaces of the wafers W. On the other hand, the vertical heat treatment apparatus of this embodiment may also be applied to the case of performing thermal oxidation of silicon (Si) at the surfaces of the wafers W by feeding, for example, O2 gas or H2O gas as a process gas.
Further, the gas ejection openings 52 may be formed into a slit shape in the lengthwise direction of the wafer boat 11. Further, instead of the double-tube structure of the reaction tube 12, a duct-shaped gas feed part and a duct-shaped exhaust part each elongated in the lengthwise direction of the wafer boat 11 may be provided on the exterior of the reaction tube 12 in an airtight manner, and the gas ejection openings 52 and exhaust openings 16a may be formed at multiple positions in a vertical direction in the reaction tube 12 on opposite sides so as to communicate with the gas feed part and the exhaust part, respectively.
Furthermore, the cut 34 is formed in each of the holder plates 31 to have the wafers W transferred to and from the wafer boat 11. On the other hand, for example, through holes may be formed at, for example, three points in each of the substrate placement regions 33, and a transfer mechanism having three pins so provided as to be movable upward and downward, which is not graphically illustrated, may be provided below the wafer boat 11. In this case, for example, the wafer boat 11 is positioned below the reaction tube 12, and when a wafer W is transferred to a position above the substrate placement region 33 with the transfer arm 60, the three pins move upward from below the wafer boat 11 through the through holes of the holder plates 31 to receive the wafer W from the transfer arm 60. Then, the transfer arm 60 is retracted and the pins are moved downward, so that the wafer W is placed in the substrate placement region 33. Thereafter, the wafers W are successively placed on the holder plates 31 below. At the time of extracting the wafers W from the wafer boat 11, the wafers W are successively transferred to the transfer arm 60 with those on a lower side in the wafer boat 11 first.
In the above-described examples, after depositing a reaction product of alumina and a reaction product of hafnium oxide in layers on the surfaces of the wafers W, these reaction products may be further deposited in layers as required to form a thin film of a laminated structure. Further, the present invention may also be applied to a process for manufacturing an LED device by depositing a gallium nitride (GaN) film on the wafers W by MO-CVD using sapphire substrates of, for example, 100 mm in outside diameter as the wafers W.
Further, in the above-described examples, multiple wafers W are placed on each of the holder plates 31, while the wafers W may be placed one on each of the holder plates 31 as illustrated in
According to an embodiment of the present invention, it is possible to reduce the gap between a holder plate and a reaction tube and to reduce the amount of a process gas passing outside the holder plate, so that it is possible to improve the efficiency of use of the process gas.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiment shown and described herein. Accordingly, various modifications may be made without departing from the sprit or scope of the general inventive concept as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-219726 | Sep 2010 | JP | national |
