Substrate processing apparatus, quartz reaction tube and method of manufacturing semiconductor device

According to one aspect thereof, there is provided a substrate processing apparatus including: a reaction tube including an outer tube and an inner tube; a manifold connected to an open end of the reaction tube; a lid configured to close one end of the manifold; a first gas supply pipe configured to supply a cleaning gas; and a second gas supply pipe configured to supply a purge gas of purging a space inside the manifold. The reaction tube includes: an exhaust space; an exhaust outlet communicating with the exhaust space; a first exhaust port provided in the inner tube so as to face a substrate accommodated in the inner tube; and second exhaust ports through which the exhaust space communicates with the space inside the manifold. At least one of the second exhaust ports promotes gas exhaust in the exhaust space distanced away from the first exhaust port.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This non-provisional U.S. patent application claims priority under 35 U.S.C. § 119 of International Application No. PCT/JP2017/034542, filed on Sep. 25, 2017, in the WIPO, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The present disclosure relates to a substrate processing apparatus, a quartz reaction tube and a method of manufacturing a semiconductor device.

2. Description of the Related Art

In a heat treatment process of a substrate (also referred to as a “wafer”), which is one of manufacturing processes of a semiconductor device, a substrate processing apparatus such as a vertical type substrate processing apparatus may be used. For example, in the vertical type substrate processing apparatus, a plurality of substrates is charged (transferred) into a substrate retainer of the vertical the substrate processing apparatus and supported in a vertical direction by the substrate retainer. After the substrate retainer is loaded (transferred) into a process chamber of the vertical type substrate processing apparatus, a process gas is introduced into the process chamber while the plurality of the substrates is heated by a heater installed at an outside of the process chamber to thereby perform a substrate processing such as a film-forming process of forming a film on the plurality of the substrates. In addition, before the film attached to the process chamber is peeled off, a process such as a dry-cleaning process of removing the film attached to the process chamber may be performed. Conventionally, there is disclosed a technique of performing a cleaning process of the vertical type substrate processing apparatus using a double tube structure. In addition, there is disclosed another technique wherein, in order to improve an exhaust performance, an opening is provided in a part of a component such as a reaction tube of the vertical type substrate processing apparatus.

When the cleaning process of the process chamber is performed, various gases and various temperature conditions corresponding to the type of the film may be applied in order to effectively remove the film (target film) while suppressing the damage to components such as the process chamber. For example, it is possible to use a method of performing (repeating) a cycle including: (a) exposing the film to a first gas in order to modify (oxidize) the film so that the film can be easily removed; and (b) exposing the film to a second gas in order to remove the modified film after (a) is performed. In addition, when substances such as by-products generated due to the removal reaction of the second gas corrode the process chamber, the process chamber may be purged with an inert gas in order to quickly discharge (exhaust) the substances.

However, when a quartz reaction tube of the vertical type substrate processing apparatus is embodied by the double tube structure, a gas such as the process gas, the first gas and the second gas tends to stagnate in a space between an outer tube and an inner tube of the double tube structure. In such location where the gas tends to stagnate, a cleaning gas is supplied less and is exhausted slowly. As a result, the cleaning process may become incomplete or the time required for performing the cleaning process may be lengthened. In addition, by using the double tube structure, a gas such as a source gas may easily flow on the plurality of the substrates and a flow velocity of the gas such as the source gas flowing on the plurality of the substrates may be increased. However, an inert gas of purging a heat insulating space lower than a substrate processing position in the inner tube may easily flow into a substrate processing space of the process chamber. As a result, a thickness of the film formed on the substrate among the plurality of the substrates may vary depending on a vertical position where the substrate is disposed.

SUMMARY

Described herein is a technique capable of shortening a cleaning time.

According to one aspect of the technique of the present disclosure, there is provided a substrate processing apparatus including: a reaction tube including an outer tube with a closed end and an inner tube provide inside the outer tube, wherein the inner tube is configured to accommodate therein a substrate to be processed; a manifold of a cylindrical shape connected to an open end of the reaction tube; a lid configured to close one end of the manifold opposite to other end of the manifold connected to the reaction tube; a first gas supply pipe configured to supply a cleaning gas inside the reaction tube; and a second gas supply pipe configured to supply a purge gas of purging a space inside the manifold, wherein the reaction tube includes: an exhaust space formed between the outer tube and the inner tube into a C-shape in horizontal cross-section; an exhaust outlet formed on the outer tube and communicating with the exhaust space; a first exhaust port provided in the inner tube so as to face the substrate and configured to discharge a process gas; and a plurality of second exhaust ports formed along the exhaust space of C-shape, through which the exhaust space and the space inside the manifold communicate with each other, wherein at least one of the plurality of the second exhaust ports is configured to promote an exhaust of a stagnated gas in the exhaust space distanced away from the first exhaust port.

DETAILED DESCRIPTION

Embodiments

Hereinafter, one or more embodiments (hereinafter, simply referred to as “embodiments”) according to the technique of the present disclosure will be described with reference to the drawings.

As shown inFIG.1, a substrate processing apparatus1according to the embodiments described herein is configured as a vertical type heat treatment apparatus capable of performing a heat treatment process in manufacturing processes of a semiconductor integrated circuit (IC). The substrate processing apparatus1includes a process furnace2. The process furnace2includes a heater3. In order to uniformly heat the process furnace2, the heater3is constituted by a plurality of heater mechanisms. The heater3is of a cylindrical shape, and is installed perpendicular to an installation floor of the substrate processing apparatus1while being supported by a heater base (not shown) serving as a support plate. The heater3also functions as an activation mechanism (also referred to as an “excitation mechanism”) of activating (exciting) a gas such as a process gas described later by heat as described later.

A reaction tube4is provided on an inner side of the heater3. A reaction vessel (also referred to as a “process vessel”) is constituted by the reaction tube4. For example, the reaction tube4is made of a heat resistant material such as quartz (SiO2) and silicon carbide (SiC). The reaction tube4is of a cylindrical shape with an open lower end and a closed upper end. The reaction tube4is embodied by a double tube structure including an outer tube4A and an inner tube4B that are coupled to each other at a flange portion4C. The flange portion4C is provided at a lower portion of the reaction tube4. Upper ends of the outer tube4A and the inner tube4B are closed and a lower end of the inner tube4B is open. The flange portion4C protrudes outward from an outer periphery of the reaction tube4. An outer diameter of the flange portion4C is greater than an outer diameter of the outer tube4A. An exhaust outlet4D communicating with an inside of the outer tube4A is provided in the vicinity of the lower end of the reaction tube4. The reaction tube4including the above described components such as the outer tube4A and the inner tube4B is formed as a single body of a single material. The outer tube4A is relatively thick so as to withstand a pressure difference when the inside thereof is exhausted to vacuum.

A manifold5of a cylindrical shape or of a truncated cone shape is made of a metal or quartz, and is provided to support the lower end of the reaction tube4. An inner diameter of the manifold5is greater than an inner diameter of the reaction tube4(and an inner diameter of the flange portion4C). Thereby, an annular space described later is defined between the lower end of the reaction tube4(that is, the flange portion4C) and a lid19described later. The space (the annular space) and/or related components surrounding the space may be collectively referred to as a “furnace opening portion”.

The inner tube4B is provided with a main exhaust port4E and a plurality of supply slits4F. The main exhaust port4E is provided at the inner tube4B closer to a center of the reaction tube4than the exhaust outlet4D. The main exhaust port4E is configured to communicate with an inside and an outside of the inner tube4B on a side thereof. The main exhaust port4E is also referred to as a “first exhaust port4E”. The plurality of supply slits4F is provided at the inner tube4B at positions opposite to the main exhaust port4E. The main exhaust port4E is a single vertically elongated opening portion that opens to a region where a plurality of wafers including a wafer7is disposed. Each of the plurality of supply slits4F is a slit extending in a circumferential direction of the inner tube4B. The plurality of supply slits4F is arranged both in the horizontal direction and in the vertical direction so as to correspond to each of the plurality of wafers including the wafer7.

In addition, the inner tube4B is provided with a plurality of subsidiary exhaust ports (hereinafter, also referred to as “sub exhaust ports”)4G. The plurality of the sub exhaust ports4G is also referred to as a “plurality of third exhaust ports4G”. The plurality of the sub exhaust ports4G is provided at the inner tube4B closer to the center of the reaction tube4than the exhaust outlet4D and closer to a lower end opening of the reaction tube4than the main exhaust port4E. The plurality of the sub exhaust ports4G is configured to communicate with a process chamber6and an exhaust space S. The flange portion4C is also provided with a bottom exhaust port4H, a plurality of bottom exhaust ports4J and a nozzle introduction hole4K. The bottom exhaust port4H and the plurality of the bottom exhaust ports4J may be collectively referred to as a “plurality of second exhaust ports4H and4J”. The bottom exhaust port4H and the plurality of the bottom exhaust ports4J are configured to communicate with the process chamber6and a lower end of the exhaust space S. That is, the lower end of the exhaust space S is closed by the flange portion4C except where the bottom exhaust port4H and the plurality of the bottom exhaust ports4J are provided. The plurality of the sub exhaust ports4G, the bottom exhaust port4H and the plurality of the bottom exhaust ports4J are configured to mainly exhaust a shaft purge gas described later.

In a space between the outer tube4A and the inner tube4B (hereinafter, also referred to as the “exhaust space S”), one or more nozzles8configured to supply the process gas such as a source gas are provided corresponding to the positions of the plurality of the supply slits4F. As shown inFIG.4, the one or more nozzles8are constituted by nozzles8a,8b,8cand8d. Gas supply pipes9a,9band9cconfigured to supply the process gas (the source gas) are connected to the nozzles8a,8band8cthrough the manifold5, respectively.

Mass flow controllers (MFC)10a,10band10cserving as flow rate controllers (flow rate control mechanisms) and valves11a,11band11cserving as opening/closing valves are sequentially installed on flow paths of the gas supply pipes9a,9band9c, respectively, from the upstream sides to the downstream sides of the gas supply pipes9a,9band9c. Gas supply pipes12a,12band12cconfigured to supply an inert gas are connected to the gas supply pipes9a,9band9c, respectively, at the downstream sides of the valves11a,11band11c. MFCs13a,13band13cand valves14a,14band14care sequentially installed at the gas supply pipes12a,12band12c, respectively, from the upstream sides to the downstream sides of the gas supply pipes12a,12band12c. In the present specification, the components (elements) respectively connected to the nozzle8may also be collectively represented by a generic term. That is, for example, the gas supply pipes9a,9band9cmay be collectively referred to as a “gas supply pipe9”, and the MFCs10a,10band10cmay be collectively referred to as an “MFC10”. A process gas supply mechanism serving as a process gas supply system is constituted mainly by the gas supply pipe9, the MFC10and a valve11. In addition, a gas supply mechanism serving as a gas supply system is mainly constituted by the process gas supply mechanism, a MFC13and a valve14.

The nozzle8is provided in a nozzle chamber (that is, one of a plurality of nozzle chambers42described later) so as to extend straight from a lower portion of the reaction tube4to an upper portion of the reaction tube4. A nozzle hole or a plurality of nozzle holes8H configured to supply the gas such as the process gas may be provided on an upper end of the nozzle8or a side surface of the nozzle8. The plurality of the nozzle holes8H corresponds to the openings of the plurality of supply slits4F, respectively. The plurality of the nozzle holes8H is open toward the center of the reaction tube4. As a result, it is possible to inject (supply) the gas toward the plurality of the wafers including the wafer7through the inner tube4B.

An exhaust pipe15configured to exhaust an inner atmosphere of the process chamber6is connected to the exhaust outlet4D. A vacuum pump18serving as a vacuum exhaust apparatus is connected to the exhaust pipe15through a pressure sensor16and an APC (Automatic Pressure Controller) valve17. The pressure sensor16serves as a pressure detector (also referred to as a “pressure detection mechanism”) to detect an inner pressure of the process chamber6, and the APC valve17serves as a pressure controller (also referred to as a “pressure adjusting mechanism”). With the vacuum pump18in operation, the APC valve17may be opened or closed to exhaust (vacuum-exhaust) the process chamber6or stop the vacuum exhaust. With the vacuum pump18in operation, an opening degree of the APC valve17may be adjusted based on the pressure detected by the pressure sensor16, in order to control (adjust) the inner pressure of the process chamber6. An exhaust system (also referred to as an “exhaust mechanism”) is constituted mainly by the exhaust pipe15, the APC valve17and the pressure sensor16. The exhaust system may further include the vacuum pump18.

The lid19serving as a furnace opening cover capable of airtightly sealing a lower end opening of the manifold5is provided under the manifold5. The lid19is made of a metal such as SUS (stainless steel) and a nickel-base alloy, and is of a disk shape. An O-ring19A serving as a sealing part is provided on an upper surface of the lid19so as to be in contact with the lower end of the manifold5.

A cover plate20is provided on the upper surface of the lid19so as to protect a portion of the lid19inner than an inner periphery of the lower end of the manifold5. The cover plate20is made of a heat and corrosion resistant material such as quartz, sapphire and SiC, and is of a disk shape. Since the cover plate20does not require much mechanical strength, the cover plate20may be formed with a small thickness. In addition, according to the embodiments, the cover plate20does not have to be prepared independently of the lid19. For example, the cover plate20may be embodied by a film or a layer such as a nitride film coated on an inner surface of the lid19or a nitride film formed by modifying the inner surface of the lid19. The cover plate20may further include a wall extending along an inner surface of the manifold5from a circumferential edge of the cover plate20.

A boat21serving as a substrate retainer is configured to align the plurality of the wafers including the wafer7, for example, from 25 to 200 wafers in the vertical direction and configured to support the plurality of the wafers, while the plurality of the wafers is horizontally oriented with their centers aligned with each other. That is, the boat21supports (accommodates) the plurality of the wafers including the wafer7with predetermined intervals therebetween. The boat21is made of a heat resistant material such as quartz and SiC. It may be preferable for the reaction tube4to have a minimum inner diameter that allows the boat21to be safely loaded (transferred) into the reaction tube4and unloaded (transferred) out of the reaction tube4.

A heat insulating assembly22described later is disposed (provided) below the boat21. The heat insulating assembly22is embodied by a structure in which conduction or transmission of the heat tends to reduce in the vertical direction, and usually a cavity is provided in the heat insulating assembly22. It is possible to purge an inside of the heat insulating assembly22with the shaft purge gas. The upper portion of the reaction tube4where the boat21is disposed may be referred to as a “substrate processing region A”, and the lower portion of the reaction tube4where the heat insulating assembly22is disposed may be referred to as a “heat insulating region B”.

A rotating mechanism23configured to rotate the boat21is provided under the lid19opposite to the process chamber6. A gas supply pipe24of the shaft purge gas is connected to the rotating mechanism23. An MFC25and a valve26are sequentially installed at the gas supply pipe24from an upstream side to a downstream side of the gas supply pipe24. One purpose of a purge gas (that is, the shaft purge gas) is to protect an inside of the rotating mechanism23(for example, bearings) from the gas such as a corrosive gas used in the process chamber6. The purge gas is discharged (exhausted) from the rotating mechanism23along a shaft of the rotating mechanism23and is guided into the heat insulating assembly22.

A boat elevator27is provided outside the reaction tube4vertically below the reaction tube4. The boat elevator27serves as an elevating mechanism (also referred to as a “transfer mechanism”) capable of elevating and lowering the lid19. When the lid19is moved upward or downward by the boat elevator27, the boat21placed on the lid19and the plurality of the wafers including the wafer7accommodated in the boat21may be transferred (loaded) into the process chamber6and be transferred (unloaded) out of the process chamber6. There may be provided a shutter (not shown) configured to close the lower end opening of the manifold5instead of the lid19while the lid19is being lowered to a lowest position thereof.

A temperature detector28is installed on an outer wall of the outer tube4A. The temperature detector28may be embodied by a plurality of thermocouples arranged in a vertical array. The state of electric conduction to the heater3may be adjusted based on the temperature detected by the temperature detector28such that the inner temperature of the process chamber6has a desired temperature distribution.

A controller29is constituted by a computer configured to control the entire part of the substrate processing apparatus1. The controller29is electrically connected to the components of the substrate processing apparatus1such as the MFCs10and13, the valves11and14, the pressure sensor16, the APC valve17, the vacuum pump18, the heater3, a cap heater34described later, the temperature detector28, the rotating mechanism23and the boat elevator27, and is configured to receive signals from the components described above or to control the components described above.

FIG.2schematically illustrates a vertical cross-section of the heat insulating assembly22. The heat insulating assembly22is constituted by a rotating table37, a heat insulator retainer38, a cylindrical portion39and a heat insulator40. The rotating table37serves as a bottom plate (that is, a support plate).

The rotating table37is of a disk shape. A through-hole through which a sub heater column33penetrates the rotating table37is provided at a center of the rotating table37. The rotating table37is placed on an upper end of a rotating shaft36, and is fixed to the cover plate20with a predetermined distance (gap) h1therebetween. A plurality of exhaust holes37A with a diameter (width) h2is provided at the rotating table37in a rotationally symmetrical arrangement in the vicinity of an edge of the rotating table37. The heat insulator retainer38and the cylindrical portion39are placed concentrically on an upper surface of the rotating table37and fixed by components such as screws. The heat insulator retainer38is configured to support the heat insulator40.

The heat insulator retainer38is of a cylindrical shape. A cavity through which the sub heater column33penetrates the heat insulator retainer38is provided at a center of the heat insulator retainer38. A flow path, whose cross-section is of annular shape, configured to supply the shaft purge gas upward in the heat insulating assembly22is provided between an inner periphery of the heat insulator retainer38and the sub heater column33. The heat insulator retainer38is provided with a pedestal38C of an outward-extending flange shape at a lower end of the heat insulator retainer38. An outer diameter of the pedestal38C is smaller than a diameter of the rotating table37. An upper end of the heat insulator retainer38is configured as a supply port38B of the purge gas. An upper end portion of the supply port38B expands in diameter so as to accommodate the sub heater column33protruding outward near the upper end portion of the supply port38B.

A plurality of reflecting plates40A and a plurality of heat insulating plates40B serving as the heat insulator40are coaxially arranged on a column of the heat insulator retainer38.

An outer diameter of the cylindrical portion39is set such that a gap G between the inner tube4B and the cylindrical portion39becomes a predetermined distance. The plurality of the heat insulating plates40B is provided on the column of the heat insulator retainer38at positions (heights) corresponding to the plurality of the sub exhaust ports4G. A cavity in which neither the plurality of the reflecting plates40A nor the plurality of the heat insulating plates40B is disposed is provided above the plurality of the heat insulating plates40B. As a result, with the plurality of the sub exhaust ports4G as a boundary, it is possible to maintain upper portions (that is, above the boundary) of components such as the heat insulating assembly22and the inner tube4B at a high temperature and lower portions (that is, below the boundary) of the components such as the heat insulating assembly22and the inner tube4B at a low temperature. Thereby, it helps to prevent by-products from adhering to components such as the inner tube4B in the gap G above the plurality of the sub exhaust ports4G where the purging effect by the purge gas is weak. For example, a vapor pressure of ammonium chloride which is one of the by-products is about 1000 Pa at 200° C. However, at temperatures lower than 200° C., the vapor pressure of the ammonium chloride decreases and the ammonium chloride condenses easily. Therefore, it is preferable that the temperature of the ammonium chloride is maintained higher than 200° C. or the ammonium chloride is purged by the purge gas. In a process performed at a medium or low temperature of 500° C. or lower, the plurality of the sub exhaust ports4G is preferably disposed at the positions (heights) of the plurality of the sub exhaust ports4G shown inFIG.3. However, in a process performed at a temperature higher than 500° C., the plurality of heat insulating plates40B may be installed on a plurality of plate supports38A provided on the column of the heat insulator retainer38in order to insulate a space between the boat21and the lid19throughout the entire heat insulating assembly22. It is preferable that the gap G is narrow in order to suppress the process gas and the shaft purge gas from passing therethrough. For example, the gap G preferably ranges from 7.5 mm to 15 mm. An upper end of the cylindrical portion39is closed by a flat plate, and the boat21is installed on the flat plate.

A casing (also referred to as a “body”)23A of the rotating mechanism23is airtightly fixed to a lower surface of the lid19. From an inside of the casing23A, an inner shaft23B of a cylindrical shape and an outer shaft23C of a cylindrical shape are arranged in this order coaxially in the casing23A. A diameter of the outer shaft23C is greater than that of the inner shaft23B. The outer shaft23C coupled to the rotating shaft36may be rotatably supported by bearings (not shown) interposed between the outer shaft23C and the casing23A. The inner shaft23B coupled to the sub heater column33is fixed to the casing23A so that it cannot rotate.

A sub heater column33is vertically inserted inside the inner shaft23B. For example, the sub heater column33is a quartz pipe configured to support the cap heater34concentrically at an upper end thereof. The cap heater34is configured by forming a circular tube in an annular shape, and a heating wire coil34B is accommodated in an inside of the cap heater34isolated from an outside of the cap heater34. The heating wire coil34B and a lead wire (not shown) of a temperature sensor (not shown) associated with the heating wire coil34B are taken out of the lid19through the sub heater column33.

The shaft purge gas introduced into the casing23A by the gas supply pipe24flows upward on an inner side and an outer side of the rotating shaft36. The purge gas supplied into the inner side the rotating shaft36flows upward along a flow path between the heat insulator retainer38and the sub heater column33. After the purge gas is ejected through the supply port38B, the purge gas flows downward in a space between the heat insulator retainer38and an inner wall of the cylindrical portion39, and is exhausted out of the heat insulating assembly22through the plurality of the exhaust holes37A. The purge gas supplied into the outer side the rotating shaft36flows between the rotating shaft36and the cover plate20while diffusing in a radial direction, and then joins the purge gas exhausted through the plurality of the exhaust holes37A to thereby purge the furnace opening portion.

FIG.3is a perspective view schematically illustrating the reaction tube4cut horizontally. In the inner tube4B is provided a plurality of supply slits4F configured to supply the process gas into the process chamber6. The supply slits4F are arranged in a lattice pattern. That is, for example, the number of the supply slits4F counted along the vertical direction (that is, the number of columns of the lattice pattern) is the same as the number of the wafers including the wafer7, and the number of the supply slits4F counted along the horizontal direction (that is, the number of rows of the lattice pattern) is three. A plurality of partition plates41extending in the vertical direction is provided so as to partition the exhaust space S between the outer tube4A and the inner tube4B. The partition plates41are arranged circumferentially between the supply slits4F or at both the ends of the supply slits4F. Sections separated from the exhaust space S by the plurality of the partition plates41constitutes the plurality of the nozzle chambers (also referred to as a “nozzle buffer”)42. As a result, the horizontal cross-section of the exhaust space S is of a C shape. In the vicinity of the substrate processing region A, only the plurality of the supply slits4F directly communicates with the plurality of the nozzle chambers (for example, three nozzle chambers)42and the inside of the inner tube4B.

The plurality of the partition plates41is connected to the inner tube4B. However, in order to avoid the stress caused by a temperature difference between the outer tube4A and the inner tube4B, the plurality of the partition plates41may not to be directly connected to the outer tube4A, and a slight gap may be provided between the plurality of the partition plates41and the outer tube4A. The plurality of the nozzle chambers42does not need to be completely isolated from the exhaust space S. One or more openings or gaps communicating with the exhaust space S and the plurality of the nozzle chambers42may be provided at the plurality of the nozzle chambers42, particularly at upper ends and lower ends of the plurality of the nozzle chambers42. Outer peripheral sides of the plurality of the nozzle chambers42may be partitioned by the outer tube4A. However, the configuration of the nozzle chambers42is not limited thereto. For example, a partition plate extending along an inner surface of the outer tube4A may be separately provided to constitute the outer boundary of the nozzle chambers42.

In the inner tube4B, the plurality of the sub exhaust ports (for example, three sub exhaust ports)4G is provided at such positions as to open toward a side surface of the heat insulating assembly22. One of the three sub exhaust ports4G is oriented in the same direction as the exhaust outlet4D, and is disposed at a height such that at least a part of an opening thereof overlaps a pipe of the exhaust outlet4D. In addition, the remaining two sub exhaust ports4G are arranged in the vicinity of both side portions of the plurality of the nozzle chambers42. Alternatively, the three sub exhaust ports4G may be arranged at positions that are spaced apart by 180 degrees on a circumference of the inner tube4B.

As shown inFIG.4, the nozzles8athrough8care installed in the three nozzle chambers42, respectively. The plurality of the nozzle holes8H opened toward the center of the reaction tube4is provided on the side surfaces of the nozzles8athrough8d, respectively. The gas ejected through the plurality of the nozzle holes8H is intended to flow from the plurality of supply slits4F into the inner tube4B, but a part of the gas may not flow directly into the inner tube4B.

As shown inFIG.1, the gas supply pipes9a,9band9cthrough the valves14a,14band14cof the gas supply system are connected to the nozzles8athrough8c, respectively. It is possible to supply different gases to the nozzles8athrough8cusing the gas supply system. Since the nozzles8athrough8care installed in independent spaces separated by the plurality of the partition plates41, it is possible to prevent the process gas supplied through the nozzles8athrough8cfrom being mixed in the plurality of the nozzle chambers42. It is also possible to discharge the stagnated gas in the plurality of the nozzle chambers42through the upper ends and the lower ends of the plurality of the nozzle chambers42to the exhaust space S. With the configuration described above, it is possible to prevent the process gas from being mixed in the plurality of the nozzle chambers42to form a film or to generate the by-products. Only inFIG.4is shown the nozzle (also referred to as a “purge nozzle”)8dthat can be installed as desired in the exhaust space S adjacent to the plurality of the nozzle chambers42along an axial direction (vertical direction) of the reaction tube4.

FIG.5is a bottom view schematically illustrating the reaction tube4. As described above, the flange portion4C is provided with the bottom exhaust port4H, the plurality of the bottom exhaust ports4J and the nozzle introduction hole4K serving as openings that connect the exhaust space S and a lower portion of the flange portion4C. The bottom exhaust port4H is a long hole provided at a location closest to the exhaust outlet4D, and each of the plurality of the bottom exhaust ports4J is a small hole. For example, the plurality of the bottom exhaust ports (for example, six bottom exhaust ports)4J is provided at six locations along the exhaust space S of a C shape. The nozzles8athrough8care inserted into the nozzle introduction hole4K through an opening of the nozzle introduction hole4K. As shown inFIG.1, the nozzles8athrough8cmay be closed by a nozzle introduction hole cover8S. For example, the nozzle introduction hole cover8S is made of quartz. When an opening of each of the plurality of the bottom exhaust ports4J is too large as will be described later, a flow velocity of the shaft purge gas passing therethrough may decrease, and the gas such as the source gas may enter the furnace opening portion from the exhaust space S by diffusion. Therefore, each of the plurality of the bottom exhaust ports4J may be configured as a hole with a reduced diameter at a center thereof (that is, a constricted hole).

FIG.6schematically illustrates discharge paths of the shaft purge gas. The shaft purge gas supplied through the gas supply pipe24flows in a radial direction through the gap h1between the rotating table37and the cover plate20while forming a diffusion barrier, and is discharged to the furnace opening portion. At the furnace opening portion, the purge gas suppresses the flow of the source gas into the furnace opening portion, dilutes the source gas that has entered the furnace opening portion by diffusion, and discharges the source gas with the flow of the purge gas. As a result, it is possible to prevent the by-products from adhering to the furnace opening portion or from deteriorating. For example, there are four discharge paths of the shaft purge gas as follows.

Path P1: the shaft purge gas enters the exhaust space S through the bottom exhaust port4H or the plurality of the bottom exhaust ports4J, and reaches the exhaust outlet4D.

Path P2: the shaft purge gas passes through the gap G between the inner tube4B and the heat insulating assembly22, enters the exhaust space S through the plurality of the sub exhaust ports4G, and reaches the exhaust outlet4D.

Path P3: the shaft purge gas enters the substrate processing region A through the gap G between the inner tube4B and the heat insulating assembly22, enters the exhaust space S through the main exhaust port4E, and reaches the exhaust outlet4D.

Path P4: the shaft purge gas enters the plurality of the nozzle chambers42through the nozzle introduction hole4K, crosses the substrate processing region A, enters the exhaust space S through the main exhaust port4E, and reaches the exhaust outlet4D.

The paths P3and P4through which the purge gas (that is, the shaft purge gas) flows into the substrate processing region A are not desirable for processing the substrate (that is, the wafer7) because a concentration of the process gas may decrease below the substrate processing region A so that an uniformity among the substrates (that is, the plurality of wafers including the wafer7) may be lowered. In particular, the reaction tube4of the embodiments has a feature that a pressure loss of the main exhaust port4E is small, so that the purge gas may be easily drawn into the paths P3and P4. If neither the nozzle introduction hole cover8S nor the plurality of the bottom exhaust ports4J is provided, the purge gas would flow exclusively through the path P4. Therefore, according to the embodiments, by enlarging an opening of each of the plurality of the sub exhaust ports4G and by reducing the gap G, the purge gas flows more easily through the path P2than through the path P3. In addition, by adjusting the opening of the nozzle introduction hole4K to be substantially small, for example, by closing the nozzle introduction hole4K by the nozzle introduction hole cover8S, it is difficult for the purge gas to flow through the path P4. When the process gas and the shaft purge gas are allowed to flow, a preferred pressure gradient is formed on a side surface of the cylindrical portion39due to the plurality of the sub exhaust ports4G. That is, on the side surface of the cylindrical portion39when the process gas and the shaft purge gas are flowing, according to the preferred pressure gradient, the pressure is high near a substrate processing region A and near a furnace opening portion, and the pressure is the lowest in the vicinity of the plurality of the sub exhaust ports4G. According to the preferred pressure gradient, it is possible to suppress both the flow of the shaft purge gas into the substrate processing region A by the path P3and the flow (diffusion) of the process gas into the furnace opening portion. When the supply of the shaft purge gas is excessive, a pressure loss in the paths P1and P2may increase, and the pressure gradient may be deteriorated.

The process gas such as a cleaning gas tends to stagnate at an innermost portion of the exhaust space S of a C shape since the innermost portion of the exhaust space S is in contact with and closed by the plurality of the nozzle chambers42. However, the process gas can be circulated in the exhaust space S and the furnace opening portion by the plurality of the bottom exhaust ports4J. When an amount of the shaft purge gas is large (that is, the pressure near the furnace opening portion is high), the shaft purge gas enters into the exhaust space S through the path P3to eliminate the stagnation of the process gas. Conversely, when the amount of the shaft purge gas is small, the process gas flows into or diffuses into the exhaust space S and is discharged through the bottom exhaust port4H. In both cases, it contributes to the exhaust of the stagnated gas in the exhaust space S. In addition, when an amount of the stagnated gas in the exhaust space S is very small, there is no problem because the stagnated gas in the exhaust space S is sufficiently diluted even if it enters the furnace opening portion.

However, when each of the plurality of the bottom exhaust ports4J is increased in size and a conductance of the path of P1is increased too much, a maximum flow velocity of the shaft purge gas decreases in all paths including P1, and the process gas may easily enter the furnace opening portion by diffusion in a direction against the flow thereof.

In summary, it is preferable that a conductance of the path P4and a conductance of the path P3are set to be lower than both of the conductance of the path P1and a conductance of the path P2, and that upper limits of the conductance of the path P1and the conductance of the path P2are set such that the amount of the process gas enters into the furnace opening portion is below an allowable amount.

As shown inFIG.7, as described above, the controller29is electrically connected to the components of the substrate processing apparatus1such as the MFCs10,13and25, the valves11,14and26, the pressure sensor16, the APC valve17, the vacuum pump18, the heater3, the cap heater34, the temperature detector28, the rotating mechanism23and the boat elevator27, and is configured to control the components electrically connected thereto. The controller29is constituted by a computer including a CPU (Central Processing Unit)212, a RAM (Random Access Memory)214, a memory device216and an I/O port218. The RAM214, the memory device216and the I/O port218may exchange data with the CPU212through an internal bus220. The I/O port218is connected to the components described above. For example, an input/output device222such as a touch panel is connected to the controller29.

The memory device216is configured by components such as a flash memory and a hard disk drive (HDD). For example, a control program for controlling the operation of the substrate processing apparatus1or a program (for example, a recipe such as a process recipe and a cleaning recipe) configured to control the components of the substrate processing apparatus1according to the process conditions to perform a substrate processing such as a film-forming process is readably stored in the memory device216. The RAM214functions as a memory area (work area) where a program or data read by the CPU212is temporarily stored.

The CPU212is configured to read the control program from the memory device216and execute the read control program. In addition, the CPU212is configured to read the recipe from the memory device216according to an operation command inputted from the input/output device222. According to the contents of the read recipe, the CPU212is configured to control the components of the substrate processing apparatus1.

The controller29may be embodied by installing the above-described program stored in an external memory device224in a non-transitory manner into a computer. For example, the external memory device224may include a semiconductor memory such as a USB memory and a memory card, an optical disk such as a CD and a DVD and a hard disk drive (HDD). The memory device216or the external memory device224may be embodied by a non-transitory tangible computer readable recording medium. Hereafter, the memory device216and the external memory device224are collectively referred to as “recording media”. Instead of the external memory device224, a communication means such as the Internet and a dedicated line may be used for providing the program to the computer.

Hereinafter, an exemplary sequence of the substrate processing (film-forming process) of forming a film on the substrate (that is, the wafer7), which is a part of manufacturing processes of a semiconductor device, will be described. The exemplary sequence of the substrate processing is performed using the substrate processing apparatus1.

The exemplary sequence of the substrate processing will be described by way of an example in which a silicon nitride film (SiN film) is formed on the wafer7serving as the substrate by respectively supplying hexachlorodisilane (HCDS) gas serving as a first process gas (also referred to as the “source gas”) to the wafer7through the nozzle8aand ammonia (NH3) gas serving a second process gas (also referred to as a “reactive gas”) to the wafer7through the nozzle8b. In the following descriptions, the operations of the components constituting the substrate processing apparatus1are controlled by the controller29.

According to the exemplary sequence of the substrate processing (that is, the film-forming process) of the embodiments, the SiN film is formed on the wafer7by performing (repeating) a cycle a predetermined number of times (at least once). For example, the cycle may include: supplying the HCDS gas to the wafer7in the process chamber6; removing the HCDS gas (residual gas) from the process chamber6; supplying the NH3gas to the wafer7in the process chamber6; and removing the NH3gas (residual gas) from the process chamber6. The steps of the cycle are non-simultaneously performed. In the present specification, the exemplary sequence of the film-forming process according to the embodiments may be represented as follows:
(HCDS→NH3)×n=>SiN

<Wafer Charging and Boat Loading Step>

The plurality of the wafers including the wafer7is charged (transferred) into the boat21(wafer charging step). After the boat21is charged with the plurality of the wafers, the boat21charged with the plurality of the wafers is elevated by the boat elevator27and loaded (transferred) into the process chamber6(boat loading step). With the boat21loaded, the lid19seals the lower end opening of the manifold5via the O-ring19A. From a standby state before the wafer charging step, the valves14aand14bmay be opened to supply a small amount of the purge gas into the cylindrical portion39.

The vacuum pump18exhausts (vacuum-exhausts) the inner atmosphere of the process chamber6until the inner pressure of the process chamber6in which the plurality of the wafers including the wafer7is accommodated reaches a desired pressure (vacuum degree). In the pressure adjusting step, the inner pressure of the process chamber6is measured by the pressure sensor16, and the APC valve17is feedback-controlled based on the measured pressure. The purge gas is continuously supplied into the cylindrical portion39and the inner atmosphere of the process chamber6is continuously exhausted by the vacuum pump18until at least the processing of the wafer7is completed.

After the inner atmosphere (for example, oxygen) of the process chamber6is sufficiently exhausted from the process chamber6, the inner temperature of the process chamber6is elevated. The states of the electric conduction to the heater3and the cap heater34are feedback-controlled based on the temperature detected by the temperature detector28such that the inner temperature of the process chamber6has a desired temperature distribution suitable for performing a film-forming step described later. The heater3and the cap heater34continuously heat the process chamber6until at least the processing (the film-forming process) of the wafer7is completed. The time duration of supplying the electrical power to the cap heater34may not be equal to the time duration of supplying the electrical power to the heater3. Immediately before the start of the film-forming step, it is preferable that a temperature of the cap heater34reaches the same temperature as a film-forming temperature, and an inner surface temperature of the manifold5reaches 180° C. or higher (for example, 260° C.).

In addition, the boat21and the plurality of the wafers including the wafer7are rotated by the rotating mechanism23. The boat21is rotated by the rotating mechanism23via the rotating shaft36, the rotating table37, and the cylindrical portion39. Therefore, it is possible to rotate the plurality of the wafers including the wafer7without rotating the cap heater34. As a result, uneven heating is reduced. As a result, it is possible to uniformly heat the plurality of the wafers. The rotating mechanism23continuously rotates the boat21and the plurality of the wafers until at least the processing of the wafer7is completed.

After the inner temperature of the process chamber6is stabilized at a predetermined processing temperature, the film-forming step is performed by performing (repeating) a first step through a fourth step described below sequentially. In addition, before starting the first step, the valve26may be opened to increase the supply of the purge gas.

In the first step, the HCDS gas is supplied to the wafer7in the process chamber6. By opening of the valve11band the valve14a, the HCDS gas is supplied into the gas supply pipe9band the N2gas is supplied into the gas supply pipe12a. The flow rates of the HCDS gas and the N2gas are adjusted by the MFCs10band13a, respectively. The HCDS gas and the N2gas with the flow rate thereof adjusted respectively are supplied to the wafer7in the process chamber6through the nozzle8band8a, and are exhausted through the exhaust pipe15. By supplying the HCDS gas to the wafer7in the process chamber6, a silicon-containing layer having a thickness of, for example, less than one atomic layer to several atomic layers is formed as a first layer on an outermost surface of the wafer7.

After the first layer is formed, the valve11ais closed to stop the supply of the HCDS gas into the process chamber6. In the second step, by maintaining the APC valve17open, the vacuum pump18vacuum-exhausts the inner atmosphere of the process chamber6to remove the HCDS gas remaining in the process chamber6which did not react or which contributed to the formation of the first layer from the process chamber6. In addition, by maintaining the valve14aor the valve14bopen, the N2gas may be supplied to purge the gas supply pipe9, the reaction tube4or the furnace opening portion.

In the third step, the NH3gas is supplied to the wafer7in the process chamber6. The valves11aand14bare controlled in the same manner as the valves11band14ain the first step. The flow rates of the NH3gas and the N2gas are adjusted by the MFCs10aand13b, respectively. The NH3gas and the N2gas with the flow rate thereof adjusted respectively are supplied to the wafer7in the process chamber6through the nozzle8band8a, and are exhausted through the exhaust pipe15. The NH3gas supplied to the wafer7reacts with at least a portion of the first layer (that is, the silicon-containing layer) formed on the wafer7in the first step. As a result, the first layer is modified (nitrided) into a second layer containing silicon (Si) and nitrogen (N), that is, a silicon nitride layer (SiN layer).

After the second layer is formed, the valve11ais closed to stop the supply of the NH3gas into the process chamber6. Similar to the second step, the vacuum pump18vacuum-exhausts the inner atmosphere of the process chamber6to remove the by-products or the NH3gas remaining in the process chamber6which did not react or which contributed to the formation of the second layer from the process chamber6.

By performing the cycle wherein the first step through the fourth step described above are performed non-simultaneously (without overlapping) in order a predetermined number of times (n times), the SiN film having a predetermined composition and a predetermined thickness is formed on the wafer7.

For example, the process conditions for the exemplary sequence of the substrate processing are as follows:

Processing Pressure (the inner pressure of the process chamber): 10 Pa to 4,000 Pa;

Flow rate of the HCDS gas: 1 sccm to 2,000 sccm;

Flow rate of the NH3gas: 100 sccm to 10,000 sccm;

Flow rate of the N2gas (to the nozzles): 100 sccm to 10,000 sccm; and

Flow rate of the N2gas (to the rotating shaft): 100 sccm to 500 sccm

By selecting suitable values within these process conditions described above, it is possible to perform the substrate processing (film-forming process) properly.

A thermally decomposable gas such as the HCDS may form a film of the by-products on a surface of metal more easily than on a surface of quartz. The film of the by-products containing materials such as silicon oxide (SiO) and silicon oxynitride (SiON) may be easily adhered to a surface exposed to the HCDS gas (and the ammonia gas), particularly when the temperature of the surface is 260° C. or lower.

<Purging and Returning to Atmospheric Pressure Step>

After the film-forming step is completed, by opening the valves14aand14b, the N2gas is supplied into the process chamber6through each of the gas supply pipes12aand12b, and then the N2gas supplied into the process chamber6is exhausted through the exhaust pipe15. The inner atmosphere of the process chamber6is replaced with the N2gas (that is, the inert gas) (substitution by inert gas), and thus the gas such as the source gas remaining in the process chamber6or the reaction by-products remaining in the process chamber6are removed (purged) from the process chamber6(purging step). Thereafter, the APC valve17is closed, and the N2gas is filled in the process chamber6until the inner pressure of the process chamber6reaches a normal pressure (returning to atmospheric pressure step).

Thereafter, the lid19is lowered by the boat elevator27and the lower end of the manifold5is opened. The boat21with the processed wafers including the wafer7charged therein is unloaded out of the reaction tube4through the lower end of the manifold5(boat unloading step). Then, the processed wafers including the wafer7are transferred (discharged) from the boat21(wafer discharging step).

When the film-forming process described above is performed, a film nitrogen may be formed on heated surfaces of components (members) in the reaction tube4by depositing deposits such as the SiN film containing nitrogen. For example, the film may be formed on an inner wall of the outer tube4A, a surface of the nozzle8a, a surface of the inner tube4B and a surface of the boat21. Therefore, a cleaning process is performed when an amount of the deposits (that is, an accumulated thickness of the film formed on the heated surfaces of the components) reaches a predetermined amount (thickness) before the deposits are peeled off or fall off.

The cleaning process is performed by supplying, for example, F2gas serving as a fluorine-based gas into the reaction tube4. Hereinafter, an example of the cleaning process according to the embodiments will be described with reference toFIGS.8and11. In the following descriptions, the operations of the components constituting the substrate processing apparatus1are controlled by the controller29.

First, the substrate processing apparatus1described above is provided (prepared).

For example, the shutter (not shown) is moved to open the lower end opening of the manifold5(shutter opening step). Then, the boat21without accommodating the plurality of the wafers (hereinafter, also referred to as an “empty boat21”) is elevated by the boat elevator27and loaded (transferred) into the reaction tube4(boat loading step).

The vacuum pump18vacuum-exhausts the inner atmosphere of the reaction tube4such that an inner pressure of the reaction tube4reaches a desired pressure. The vacuum pump18continuously exhausts the inner atmosphere of the reaction tube4until at least the cleaning process is completed. The heater3heats the reaction tube4such that an inner temperature of the reaction tube4reaches a desired temperature (also referred to as a “second temperature”). For example, in order to prevent a temperature of an exhaust gas from excessively rising (elevating) in accordance with an etching reaction, the second temperature may be set lower than the temperature of the wafer7(also referred to as a “first temperature”) in the film-forming step described above. In the pressure and temperature adjusting step S120, the boat21is rotated by the rotating mechanism23. The rotating mechanism23may continuously rotate the boat21until at least the cleaning process is completed.

In a gas cleaning step (also referred to as a “cleaning gas supply step”) S130, the valves11band14aare controlled in the same manner as the valves11band14ain the first step of the film-forming step. A flow rate of the F2gas serving as the cleaning gas is adjusted by the MFC10b. The F2gas with the flow rate thereof adjusted is supplied into the reaction tube4through the gas supply pipe9band the nozzle8b. By supplying the N2gas through the gas supply pipe12b, it is possible to dilute the F2gas with the N2gas, and as a result, it is possible to control a concentration of the F2gas supplied into the reaction tube4. In the gas cleaning step S130, a small amount of the N2gas may be supplied through the gas supply pipes12aand24to purge the nozzle8a, the shaft (that is, the rotating shaft36) and the furnace opening portion. In addition, a gas such as hydrogen fluoride (HF) gas, hydrogen (H2) gas and nitrogen monoxide (NO) gas may be added to the F2gas.

In the gas cleaning step S130, the APC valve17is appropriately controlled to adjust the inner pressure of the reaction tube4to a predetermined pressure. For example, the predetermined pressure of the reaction tube4may range from 1,330 Pa to 101,300 Pa, preferably, from 13,300 Pa to 53,320 Pa. The flow rate of the F2gas supplied into the reaction tube4is adjusted by the MFC10ato a predetermined flow rate. For example, the predetermined flow rate of the F2gas may range from 100 sccm to 3,000 sccm. The flow rate of the N2gas supplied into the reaction tube4is adjusted by the MFC13ato a predetermined flow rate. For example, the predetermined flow rate of the N2gas may range from 100 sccm to 10,000 sccm. For example, the time duration of supplying the F2gas into the reaction tube4(that is, a gas supply time of the F2gas), may be set to a predetermined time ranging from 60 seconds to 1,800 seconds, preferably, from 120 seconds to 1,200 seconds. The temperature of the heater3is adjusted (set) such that the inner temperature of the reaction tube4may become a predetermined temperature (also referred to as the “second temperature”). For example, the second temperature may range from 200° C. to 450° C., preferably, from 200° C. to 400° C.

When the inner temperature of the reaction tube4is less than 200° C., the etching reaction of the deposits may not easily proceed. Conversely, when the inner temperature of the reaction tube4is greater than 450° C., the etching reaction may become intense and the components (members) in the reaction tube4in the reaction tube4may be damaged.

The F2gas may be supplied into the reaction tube4continuously or intermittently. When the F2gas is supplied into the reaction tube4intermittently, the APC valve17may be closed to contain the F2gas in the reaction tube4. By intermittently supplying the F2gas into the reaction tube4, it is possible to generate (form) pressure fluctuations in the reaction tube4, and as a result, the F2gas is diffused everywhere in the reaction tube4including each section of the plurality of the nozzle chambers42. In addition, it is possible to control the amount of the by-products (or the grain size of the by-products) such as ammonium fluoride (NH4F) and tetrafluorosilane (SiF4) in the reaction tube4to prepare an environment in which the etching reaction easily proceeds. As a result, it is possible to suppress the amount of the F2gas used in the gas cleaning step S130, and it is also possible to reduce the cost of the cleaning process.FIG.8shows an example in which the F2gas is intermittently supplied into the reaction tube4to generate the pressure fluctuation in the reaction tube4.

Instead of the F2gas, a fluorine-based gas such as chlorine fluoride (ClF3) gas, nitrogen fluoride (NF3) gas, HF gas, a mixed gas of the F2gas and the HF gas, a mixed gas of the ClF3gas and the HF gas, a mixed gas of the NF3gas and the HF gas, a mixed gas of the F2gas and H2gas, a mixed gas of the ClF3and the H2gas, a mixed gas of the NF3gas and the H2gas, a mixed gas of the F2gas and NO gas, a mixed gas of the ClF3gas and the NO gas and a mixed gas of the NF3gas and the NO gas may be used as the cleaning gas. Instead of the N2gas, for example, a rare gas such as argon may be used as the inert gas.

After the gas cleaning step S130is completed, the valve10ais closed to stop the supply of the F2gas into the reaction tube4. The heater3heats the reaction tube4such that the inner temperature of the reaction tube4reaches a desired temperature (also referred to as a “third temperature”). The temperature elevating step S140will be described by way of an example in which the third temperature is higher than the second temperature, that is, an example in which the inner temperature of the reaction tube4is changed (elevated) from the second temperature to the third temperature. The heater3continuously heats the reaction tube4to the third temperature until a multistage purge step S150described later is completed.

By setting (adjusting) the third temperature higher than the second temperature, it is possible to promote the desorption of the cleaning gas and other adsorbed gases, and it is possible also to promote the sublimation of the particle source from the surfaces of the components in the reaction tube4, for example, a very small (about several A) compound of a solid material generated by the reaction between the deposits and the cleaning gas (hereinafter, also referred to as a “residual compound”).

More preferably, the third temperature is set higher than the temperature of the wafer7(that is, the first temperature) in the film-forming step. However, when the inner temperature of the reaction tube4is greater than 630° C., the components in the reaction tube4may be damaged by the heat.

The temperature of the heater3is adjusted (set) such that the inner temperature of the reaction tube4may satisfy the conditions described above. For example, the temperature of the heater3is set to the third temperature ranging from 400° C. to 630° C., preferably, from 550° C. to 620° C.

The multistage purge step (also referred to as a “pressure swing purge”) S150is performed with the inner temperature of the reaction tube4set to the third temperature. In addition, the multistage purge step S150may be started with the start of the temperature elevating step S140. In the multistage purge step S150, the following first purge step S160and second purge step S170are sequentially performed.

In the first purge step S160, a first purge is performed. That is, the reaction tube4is purged while the inner pressure of the reaction tube4is periodically varied within a first pressure range described later. Specifically, the first purge is performed by performing (repeating) a cycle two or more times (twice or more). The cycle of the first purge includes: elevating the inner pressure of the reaction tube4by supplying the purge gas into the reaction tube4(also referred to as a “first pressure elevating step”); and lowering the inner pressure of the reaction tube4by strengthening the exhaust of the inner atmosphere of the reaction tube4(also referred to as a “first pressure lowering step”).

In the first pressure elevating step, with the APC valve17slightly open, the valves14a,14band26are opened to supply the N2gas into the reaction tube4. For example, the flow rates of the N2gas controlled (adjusted) by the MFCs13a,13band25, respectively, are set to be within a range from 1,000 sccm to 50,000 sccm. For example, a maximum inner pressure of the reaction tube4is set to a pressure ranging from 53,200 Pa to 66,500 Pa.

When the first pressure elevating step is performed with the APC valve17fully closed, it is possible to increase a range of the pressure swing may be increased. However, the particles such as the residual compound may easily flow back (diffuse) from the exhaust pipe15into the reaction pipe4.

In the first pressure lowering step performed after the first pressure elevating step, the APC valve17is fully opened. For example, while maintaining the valves14a,14band26open, the flow rates of the N2gas controlled (adjusted) by the MFCs13aand13b, respectively, are reduced within a range from 50 sccm to 500 sccm. For example, a minimum inner pressure of the reaction tube4is set to a pressure ranging from 300 Pa to 665 Pa.

The range of the pressure swing in the first purge step S160, that is, a differential pressure between the maximum inner pressure of the reaction tube4in the first pressure elevating step and the minimum inner pressure of the reaction tube4in the first pressure lowering step is, for example, may range from 52,535 Pa to 66,101 Pa. Due to the differential pressure, a flow of the gas such as the N2gas is generated throughout the reaction tube4when the N2gas is discharged, and as a result, it is possible to promote the diffusion and the exhaust of the materials such as the cleaning gas and the residual compound sublimated.

After the first purge step S160is completed, the second purge step S170is performed. In the second purge step S170, the concentration of a gas such as the residual cleaning gas is lowered. Therefore, a second purge step S170(simply referred to as a “second purge”) is performed by changing (varying) the inner pressure of the reaction tube4periodically with a range smaller than the range of the pressure swing in the first purge step S160. That is, the reaction tube4is purged by the second purge. Process conditions other than the inner pressure of the reaction tube4in the second purge step S170are the same as the first purge step S160.

<Temperature Lowering and Returning to Atmospheric Pressure Step: S180>

After the multistage purge step S150is completed, the inner temperature of the reaction tube4is lowered by adjusting the output of the heater3(temperature lowering step). That is, the inner temperature of the reaction tube4is changed (lowered) from the third temperature to the first temperature. By maintaining the valves14a,14band26open, the N2gas is supplied into the reaction tube4. Thereby, the inner atmosphere of the reaction tube4is filled with the N2gas (substitution by inert gas), and the inner pressure of the reaction tube4is returned to the normal pressure (returning to atmospheric pressure step).

Thereafter, the lid19is lowered by the boat elevator27and the lower end of the manifold5is opened. The empty boat21is unloaded out of the reaction tube4through the lower end of the manifold5(boat unloading step). When the cleaning process including the steps S100through S190described above is completed, the film-forming process described above may be resumed.

In the cleaning process described above, the N2gas is supplied at a constant rate through the nozzles8aand8band the gas supply pipe24in the multistage purge step S150. However, the N2gas may be supplied at periodically changing rates. For example, the gas such as the residual gas and the N2gas (that is, the purge gas) may be stirred and mixed by repeating: an operation of reducing the flow rate of the N2gas supplied through the gas supply pipe24and discharging (exhausting) the residual gas in the exhaust space S to the furnace opening portion through the plurality of the bottom exhaust ports4J along with the purge gas being supplied through the nozzles8aand8b; and an operation of conversely increasing the flow rate of the N2gas supplied through the gas supply pipe24and pushing out the residual gas in the furnace opening portion through the plurality of the bottom exhaust ports4J or the plurality of the sub exhaust ports4G along with the shaft purge gas.

FIG.9schematically illustrates a modeled exhaust path in the reaction tube4. The modeled exhaust path is simplified. For example, a fluid resistance (hereinafter simply referred to as “resistance”) for the process gas ejected through the main exhaust port4E to flow downward in the exhaust space S is included in a resistance of the main exhaust port4E. A resistance for the purge gas ejected through the plurality of the sub exhaust ports4G or the plurality of the bottom exhaust ports4J to flow in a lateral direction in the exhaust space S is included in a resistance of the plurality of the sub exhaust ports4G or a resistance of the plurality of the bottom exhaust ports4J. Referring toFIG.9, the shaft purge gas from the gas supply pipe24is supplied substantially uniformly over an entire circumference of the furnace opening portion. In addition, most of the process gas from the nozzle8is usually sucked into the exhaust outlet4D through the plurality of the supply slits4F and the main exhaust port4E. A portion closer to the exhaust outlet4D corresponds to the exhaust space S rather than the main exhaust port4E, the plurality of the sub exhaust ports4G, the bottom exhaust port4H and the plurality of the bottom exhaust ports4J.

Since the plurality of the sub exhaust ports4G and the bottom exhaust port4H are distanced apart from a main exhaust path of the process gas, a pressure in the vicinity of the exhaust outlet4D is low and the gas is drawn toward the exhaust outlet4D. Therefore, the plurality of the sub exhaust ports4G forms an upward flow of the shaft purge gas flows in a lower portion of the gap G, and the bottom exhaust port4H functions as a drain of discharging the surplus shaft purge gas in the furnace opening portion which remains there or has already contributed to diluting the process gas.

A conductance of main exhaust port4E, a conductance of the gap G and the flow rate of the shaft purge gas flow rate may be set so that an inner pressure of the inner tube4B of the main exhaust port4E is substantially the same as or slightly lower than an inner pressure of the main exhaust port4E. Since the conductance and the pressure difference (total pressure) are both small at an upper portion of the gap G, the movement of gas molecules is suppressed. That is, although there is a concentration difference of the gas such as the purge gas in the vertical direction in the gap G, the amount of the gas advection or the gas diffusion is small because a cross-sectional area of the gap G is small and the distance (length) of the gap G is long. In the lower portion of the gap G, the diffusion barrier is formed by the upward flow of the purge gas, so that the process gas having diffused to the plurality of the sub exhaust ports4G is exhausted along with the flow of the purge gas toward the exhaust outlet4D.

Since there is no other highly resistant locations in a path along which the purge gas flows from the plurality of the bottom exhaust ports4J to the lower end of the exhaust space S, the flow rate of the purge gas is determined by the conductance of the plurality of the bottom exhaust ports4J itself set to be relatively small. By ejecting the purge gas into the lower end of the exhaust space S, it is possible to generate the gas advection and the gas stirring in a blocked portion (for example, the innermost portion) of the exhaust space S whose cross section is of a C shape. As a result, it is possible to effectively purge the process gas and the cleaning gas having stagnated at the blocked portion. When the flange portion4C is provided without the plurality of the bottom exhaust ports4J, it may be difficult to purge the blocked portion of the exhaust space S, which is a dead end, and it may require many times of repetition of performing the pressure swing described above.

When a conductance of the nozzle introduction hole4K is set to a significant value larger than substantially zero (0), a gentle flow in the vertical direction is generated in the plurality of the nozzle chambers42. In particular, when the upper ends of the plurality of the nozzle chambers42are also opened slightly, it is possible to facilitate gas replacement in the plurality of the nozzle chambers by42the gentle flow in the vertical direction while suppressing the influence on the gas distribution in the substrate processing region A. In general, from the viewpoint of preventing the source gas from entering the furnace opening portion, it is preferable to set the flow rate of the shaft purge gas such that the shaft purge gas flows slightly upward through the nozzle introduction hole4K. When the bottom exhaust port4H and the plurality of the bottom exhaust ports4J are provided excessively, a higher flow rate of the shaft purge gas may be required.

When the nozzle8is configured to supply a gas other than the source gas, it is easy to increase the conductance of the nozzle introduction hole4K. For example, when the nozzle8is configured to supply the same kind of purge gas (N2) as the shaft purge gas, the purge gas may flow upward or downward through the nozzle introduction hole4K by controlling the flow rates (or pressures) of both purge gases. In general, the flow rate of the shaft purge gas is set equal to or greater than a predetermined value. Therefore, when the purge gas from the nozzle8is increased, as indicated by a thick arrow inFIG.3, the purge gas overflowing from the plurality of the nozzle chambers42flows to the furnace opening portion through the nozzle introduction hole4K, then flows into the exhaust space S through a nearby sub exhaust port among the plurality of the sub exhaust ports4G or a nearby bottom exhaust port among the plurality of the bottom exhaust ports4J, and may contribute to the purging of the stagnated gas in the exhaust space S.

According to the embodiments, it is possible to provide at least one or more of the following effects.

(a) By providing the plurality of the sub exhaust ports4G, the purge gas that has flowed into the inner tube4B is allowed to spontaneously flow into the exhaust space S between the outer tube4A and the inner tube4B. Therefore, it is possible to reduce the flow rate of the purge gas that flows into the substrate processing region A.

(b) By providing the bottom exhaust port4H, the plurality of the bottom exhaust ports4J and the plurality of the sub exhaust ports4G, it is possible to improve the exhaust efficiency of the cleaning gas with respect to the exhaust space S.

Other Embodiments

While the technique is described by way of the above-described embodiments, the above-described technique is not limited thereto. The above-described technique may be modified in various ways without departing from the gist thereof. For example, the embodiments are described by way of an example in which the outer tube4A and the inner tube4B of the reaction tube4are formed as a single body. However, the reaction tube4is not limited thereto. The outer tube4A and the inner tube4B may be provided as separate components and mounted on the manifold5. When the outer tube4A and the inner tube4B are provided as the separate components, openings between the exhaust space and the furnace opening portion in the vicinity of open ends of the outer tube4A and the inner tube4B correspond to the bottom exhaust port4H and the plurality of the bottom exhaust ports4J. Alternatively, the outer tube4A, the inner tube4B and the manifold5may be made of quartz as a single body.

Hereinafter, a modified example of the embodiments will be described.FIG.10is a bottom view schematically illustrating a reaction tube400of a substrate processing apparatus according to the modified example of the embodiments described herein. The descriptions of the embodiments described above are incorporated herein by reference. According to the modified example, the inner tube4B includes a plurality of bulges401that expands outward. Each of the plurality of the bulges401provides a space for installing additional nozzles or sensors inside thereof. The plurality of the bulges401continue to expand outward from a lower end to an upper end of the inner tube4B while maintaining the same shape.

Since the exhaust space S is locally narrowed by the plurality of the bulges401, the gas is likely to stagnate as it is. According to the modified example, the plurality of the sub exhaust ports4G is provided at the inner tube4B further behind a bulge among the plurality of the bulges401farthest from the main exhaust port4E, at least one of the plurality of the bottom exhaust ports4J is provided at the flange portion4C, and at least one of the plurality of the bottom exhaust ports4J is provided with respect to the exhaust space S interposed between the plurality of the bulges401. According to the modified example, a width of the narrowing of the exhaust space S by t the plurality of the bulges401is preferably wider than the gap G.

The embodiments are described by way of an example in which a cleaning process of cleaning the reaction tube is performed after the film-forming process of forming the film on the substrate. However, the above-described technique is not limited thereto. For example, the above-described technique may be effectively applied to processes, for example, a modification process such as an oxidation process and a nitridation process, a diffusion process and an etching process when the by-products are generated, the surface of the reaction tube is eroded, or a precoat film is formed to protect the reaction tube.

Instead of a manufacturing apparatus of a semiconductor device (that is, the substrate processing apparatus described above), the above-described technique may be preferably y applied to a film-forming apparatus of forming a film using a gaseous source.

According to some embodiments in the present disclosure, it is possible to improve the gas stagnation in the gap of the double tube (that is, the gap between the inner tube and the outer tube), to shortening the cleaning time, and to improve the film uniformity between the plurality of the substrates.