JP2014154751A - Gas supply system and film deposition apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas supply system in which backflow of gas can be prevented when a flow of gas is switched between a gas supply line and a vent line.SOLUTION: There is provided a gas supply system 10 supplying gas required for film deposition processing to a processing vessel 4 performing the film deposition processing. The gas supply system 10 includes: a gas supply line 54 in which a first on-off valve V1 is interposed, and which supplies gas to the processing vessel; a vent line 56 in which a second on-off valve V2 is interposed, and which is branched from the gas supply line; and a valve control section 66 which, when switching a flow of gas from a processing vessel side to a vent line side, controls the second on-off valve to be opened after the lapse of a first predetermined time T1 during which pressure in the gas supply line becomes higher than pressure at the vent line side by bringing the first and second on-off valves into a simultaneously closed state and which, when switching the flow of gas from the vent line side to the processing vessel side, controls the first on-off valve to be opened after binging the first and the second on-off valves into the simultaneously closed state.

Description

  The present invention relates to a film forming apparatus for performing a film forming process on a semiconductor wafer made of a silicon substrate or the like, and a gas supply system used therefor.

  In general, in order to form a semiconductor integrated circuit such as an IC, various processes such as a film forming process, an etching process, an oxidation diffusion process, and an annealing process are performed on a semiconductor wafer made of a silicon substrate or the like. For example, taking the film forming process as an example among the above-described various processes, for example, depending on the type of film to be formed, in this film forming process, for example, a source gas and a reactive gas such as an oxidizing gas or a reducing gas are mixed in a vacuum atmosphere. A desired film type is formed on the wafer by reacting by heating in the processing container.

  During the film formation, the source gas and the reaction gas are supplied into a processing container in a reduced-pressure atmosphere (vacuum atmosphere) to cause both gases to react as described above. It is not something that has been introduced. For example, in order to stabilize the gas flow rate, gas may flow out from the gas source but may not be introduced into the processing container. In such a case, the gas discharged from the gas source via the gas supply line may be used. The gas is discarded without being introduced into the processing container by flowing toward the vent line provided so as to bypass the processing container by switching the flow in the middle.

  Moreover, in order to suppress the pressure fluctuation at the time of switching the gas supply into the processing container, the pressure in the vent line is adjusted (Patent Document 1).

  JP 2008-091651 A

  By the way, when the gas flow is switched between the gas supply line and the vent line, generally, the on-off valves provided on both lines are simultaneously operated from the open state to the closed state or vice versa. . However, in order to complete the opening / closing operation of this on-off valve, although it depends on the type of on-off valve, it takes a time of, for example, about 100 msec. In addition, there is a problem that the gas flows back from the vent line side to the gas supply line side to cause contamination.

  In particular, this back flow of gas tends to occur more often when the downstream side of the vent line is connected to the atmospheric pressure atmosphere side. In order to prevent this backflow, attempts have been made to provide a short period, for example, several hundreds of milliseconds, during which both the on-off valves are closed simultaneously, but this time is not optimized.

  In particular, when adopting a so-called ALD (Atomic Layered Deposition) method in which a raw material gas and a reactive gas are alternately and intermittently introduced into a processing container to form a thin film one by one, as described above The gas flow switching operation needs to be performed several tens to several hundreds of times in one film forming process, and an early solution of the above-described problems is desired.

  The present invention has been devised to pay attention to the above problems and to effectively solve them. An object of the present invention is to provide a gas supply system and a film forming apparatus capable of preventing a backflow of gas when switching a gas flow between a gas supply line and a vent line.

  According to a first aspect of the present invention, in a gas supply system for supplying a gas necessary for the film forming process to a processing container for performing the film forming process on the object to be processed, a flow rate is controlled by providing a first on-off valve. In addition, a gas supply line for supplying the gas to the processing vessel and a second on-off valve for disposing the gas are provided and branched from the gas supply line upstream of the first on-off valve. And when the gas flow is switched from the processing vessel side to the vent line side, the first and second on-off valves are closed at the same time, and the pressure on the vent line side is higher than that on the vent line side. The second on-off valve is controlled to be opened when a first predetermined time when the pressure on the gas source side in the gas supply line becomes large has passed, and the gas flow is controlled from the vent line side to the processing container. Switch to side And a valve control unit for controlling the first on-off valve to open after the first and second on-off valves are closed at the same time. Supply system.

  Thus, according to the present invention, when the gas flow is switched between the gas supply line and the vent line, the backflow of the gas can be prevented.

  According to a twelfth aspect of the present invention, there is provided a film forming apparatus that performs a film forming process on an object to be processed, a processing container that houses the object to be processed, a holding unit that holds the object to be processed, and an inside of the processing container. A film forming apparatus comprising: an exhaust system that exhausts the atmosphere of the gas; and a gas supply unit that includes the gas supply system according to any one of claims 1 to 11.

According to the gas supply system and the film forming apparatus according to the present invention, the following excellent operational effects can be exhibited.
When the gas flow is switched between the gas supply line and the vent line, the backflow of the gas can be prevented. Therefore, it is possible to prevent the film formation process from being contaminated.

It is a schematic block diagram which shows an example of the film-forming apparatus using the gas supply system which concerns on this invention. It is a timing chart which shows an example of the supply mode of each gas. It is a timing chart which shows the opening / closing operation | movement of the on-off valve of a gas supply system.

  Hereinafter, an embodiment of a gas supply system and a film forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings. 1 is a schematic configuration diagram showing an example of a film forming apparatus using a gas supply system according to the present invention, FIG. 2 is a timing chart showing an example of a supply mode of each gas, and FIG. 3 is an opening / closing valve of a gas supply system. It is a timing chart which shows operation.

  Here, as an example, a case where a silicon-containing film is formed by an ALD method using Si-containing gas as a source gas and ozone as an oxidizing gas as a reaction gas will be described. Here, a case where the gas supply system of the present invention is applied to a gas supply system that supplies ozone as a reaction gas will be described as an example.

  As shown in the figure, the film forming apparatus 2 includes a processing container 4 that accommodates a semiconductor wafer W that is an object to be processed, a wafer boat 6 that is an example of a holding unit that holds the semiconductor wafer W, and an inside of the processing container 4. An exhaust system 8 for exhausting the atmosphere of the gas, and a gas supply means 12 having a gas supply system 10 according to the present invention.

  Specifically, the processing container 4 is formed in a cylindrical shape with a ceiling with a lower end opened by quartz. In the processing container 4, a plurality of semiconductor wafers W supported in multiple stages by the wafer boat 6 made of quartz are accommodated. The opening at the lower end of the processing container 4 is hermetically closed through a sealing member 16 such as an O-ring by a lid portion 14 made of, for example, stainless steel. The wafer boat 6 is rotatably supported on the lid portion 14 via a heat retaining cylinder 18, and the lid portion 14 and the wafer boat 6 can be moved up and down integrally by an elevating mechanism 20, and a processing container. 4, the wafer W can be loaded and unloaded.

  A cylindrical heating means 22 containing a carbon wire heater or the like is provided around the processing container 4 so as to surround the processing container 4 so that the temperature of the wafer W can be controlled by heating. Further, an exhaust port 24 is provided in the lower side wall of the processing container 4, and the exhaust system 8 is connected to the exhaust port 24 so that the atmosphere in the processing container 4 can be evacuated, for example. . The exhaust system 8 has an exhaust passage 26 connected to the exhaust port 24.

  In the exhaust passage 26, a pressure adjusting valve 28 that adjusts the pressure in the processing vessel 4 from the upstream side to the downstream side, a vacuum pump 30, and a combustor 32 that burns combustible gas in the exhaust gas to make it harmless. Are connected to a factory duct 34 for exhausting the factory. Here, the pressure in the combustor 32 and the factory duct 34 on the downstream side of the vacuum pump 30 is almost atmospheric pressure. Depending on the gas type used here, a detoxifying device may be provided in place of the combustor 32.

  The processing container 4 is provided with a gas introduction part 36 for introducing various gases into the processing container 4. The gas introduction part 36 has a plurality of nozzles 36A, 36B, 36C. As these nozzles 36 </ b> A, 36 </ b> B, 36 </ b> C, for example, linear nozzles or distributed nozzles in which many holes are formed can be used. The gas supply means 12 for supplying the gas necessary for the film formation process to the processing container 4 supplies the reaction gas supply system 10 according to the present invention for supplying the reaction gas, and the source gas. A source gas supply system 40 and a purge gas supply system 42 for supplying a purge gas are provided.

  First, the source gas gas supply system 40 includes a source gas gas supply line 44 connected to the source gas source side, and the downstream side of the source gas supply line 44 is connected to the processing gas. It is connected to a nozzle 36 </ b> A of a gas introduction part 36 provided in the container 4.

  A flow rate controller 46 such as a mass flow controller and a first on-off valve 48 are sequentially provided in the gas supply line 44 for the raw material gas from the upstream side toward the downstream side. A source gas vent line 50 is branched from the source gas supply line 44 upstream of the first on-off valve 48, and the source gas vent line 50 is downstream of the source gas vent line 50. An exhaust passage 26 between the pressure control valve 28 of the exhaust system 8 and the vacuum pump 30, that is, is connected to a vacuum atmosphere portion.

  A second opening / closing valve 52 is interposed in the middle of the source gas vent line 50. Accordingly, by switching the first and second on-off valves 48 and 52, the source gas can be flowed to the processing container 4 side or the source gas vent line 50 side can be switched and selected. It has become. Here, a silicon-containing gas such as trisdimethylaminosilane (3DMAS) can be used as the source gas.

  The reactive gas supply system 10 has a reactive gas supply line 54 connected to the reactive gas source, and the downstream side of the reactive gas supply line 54 is connected to the processing gas. It is connected to a nozzle 36 </ b> B of a gas introduction part 36 provided in the container 4.

  A flow rate controller 57 such as a mass flow controller and a first on-off valve V1 are sequentially provided in the gas supply line 54 for the reaction gas from the upstream side toward the downstream side. A reaction gas vent line 56 is branched from the reaction gas supply line 54 upstream of the first on-off valve V1, and the reaction gas vent line 56 is downstream of the reaction gas vent line 56. It is connected to the combustor 32 of the exhaust system 8, that is, the atmospheric pressure atmosphere portion.

  A second on-off valve V2 is interposed in the middle of the reaction gas vent line 56. Accordingly, by switching the first and second on-off valves V1 and V2, the reaction gas can be made to flow to the processing container 4 side or to the reaction gas vent line 56 side to be selected by switching. It has become.

  Then, on the upstream side of the first on-off valve V1 of the gas supply line 54 for the reaction gas, that is, on the gas source side, the gas supply line 54 for the reaction gas is formed in advance before the film forming process as will be described later. A pressure gauge 58 for measuring the pressure fluctuation is provided. The pressure gauge 58 may be removed during the actual film forming process if the pressure fluctuation in advance is obtained as described above. Here, ozone, which is a kind of oxidizing gas, is used as the reactive gas.

  As described above, the reason why the reactive gas is discarded not in the vacuum atmosphere portion of the exhaust passage 26 of the exhaust system 8 but in the combustor 32 that is the atmospheric pressure atmosphere portion is that when the reactive gas is discarded in the vacuum atmosphere portion, Here, since the gas is frequently switched by the ALD method, the raw material gas remaining in the vacuum atmosphere portion reacts with the reactive gas, causing an inconvenience that an unnecessary thin film adheres to the vacuum pump 30. This is to prevent the occurrence.

  The purge gas supply system 42 has a purge gas supply line 60 connected to the purge gas source, and a downstream side of the purge gas supply line 60 is provided in the processing vessel 4. The gas inlet 36 is connected to the nozzle 36C.

In the gas supply line 60 for purge gas, a flow rate controller 62 such as a mass flow controller and an open / close valve 64 are sequentially provided from the upstream side toward the downstream side. Here, an inert gas, for example, N ₂ gas is used as the purge gas. Note that a rare gas such as He may be used instead of the N ₂ gas.

  In order to control the opening / closing operation of each of the on-off valves 48, 52, 64, V1, V2, a valve control unit 66 made of, for example, a microcomputer is provided, and each of the on-off valves 48, 52, 64, V1, The switching operation of V2 is performed.

  Here, when the flow of the reaction gas is switched from the processing container 4 side to the reaction gas vent line 56 side, the valve control unit 66 simultaneously switches the first and second on-off valves V1 and V2. A first predetermined time T1 (see FIG. 3) elapses in which the pressure on the gas source side in the gas supply line 54 for the reaction gas is larger than the pressure on the vent line 56 side for the reaction gas in the closed state. When the second on-off valve V2 is controlled to open, and the flow of the reaction gas is switched from the reaction gas vent line 56 side to the processing container 4 side, the first and second The first on-off valve V1 is controlled to be opened after the two on-off valves V1 and V2 are simultaneously closed.

  Accordingly, the reaction gas discarded to the reaction gas vent line 56 side is prevented from flowing back to the reaction gas supply line 54 side. The first predetermined time T1 is obtained in advance by, for example, flowing a gas into a processing container before performing a film forming process as will be described later. In the case of the present embodiment, the source gas gas supply system 40 is less likely to cause a back flow of the source gas, so that the valve operation as in the reaction gas system 10 is not necessary, and the normal valve operation is performed. I have to.

  The overall operation of the film forming apparatus 2 formed as described above is controlled by an apparatus control unit 70 formed of, for example, a computer. The apparatus control unit 70 controls the operation of the entire apparatus, and a computer program for performing this operation is stored in a storage medium 72 such as a flexible disk, a CD (Compact Disc), a hard disk, or a flash memory. Specifically, in response to a command from the apparatus control unit 70, supply of each gas is started, stopped, flow rate is controlled, process temperature and process pressure are controlled, and the like. At this time, the valve control unit 66 operates under the control of the device control unit 70.

  Next, an ALD film forming process performed using the film forming apparatus configured as described above will be described. First, a general operation of the film forming process will be briefly described. First, the wafer boat 6 holding the semiconductor wafers W is lowered from the inside of the processing container 4, that is, in an unloaded state and is in a standby state in a lower loading area.

  Here, when a thin film is formed on the semiconductor wafer W, the wafer boat 6 holds a plurality of, for example, about 50 to 150 unprocessed semiconductor wafers W in multiple stages. The processing container 4 is maintained at a process temperature or a temperature lower than that, and the wafer boat 6 is raised and inserted into the processing container 4, that is, loaded, and the lid 14 lowers the lower end of the processing container 4. The inside of the processing container 4 is sealed by closing the opening.

  Then, the inside of the processing container 4 is evacuated and maintained at a predetermined process pressure (vacuum atmosphere), and the electric power supplied to the heating means 22 is increased to increase the internal temperature and stably at a predetermined process temperature. maintain. Then, the respective gases are supplied from the source gas supply system 40, the reaction gas supply system 10 and the purge gas supply system 42 of the gas supply means 12, as shown in FIG. To form a silicon oxide film as a thin film on the semiconductor wafer W.

  Specifically, as shown in FIG. 2, a silicon-containing gas (FIG. 2A) and ozone (FIG. 2B) are intermittently supplied into the processing container 4. In FIG. 2, a portion where the pulse is raised indicates that gas is supplied into the processing container 4, and a portion where the pulse is not raised is discarded to the exhaust system 8 side through the vent lines 50 and 56. . That is, the raw material gas and the reaction gas are continuously flowing from the gas source side in order to stabilize the flow rates.

Further, in a portion where a pulse for gas supply does not stand, N ₂ gas, which is a purge gas, is supplied into the processing container 4 to promote discharge of residual gas in the container. The raw material gas and the reaction gas discharged to the exhaust system 8 are burned in the combustor 32 that is at almost atmospheric pressure, rendered harmless, and discharged to the factory duct 34 side. The period from the start of the source gas supply pulse to the start of the next supply pulse is one cycle, and it varies depending on the film thickness to be formed in one film formation process. About 100 cycles are performed.

  Here, the opening / closing operation of the first and second on-off valves V1, V2 of the gas supply system 10 for the reaction gas will be described with reference to FIG. FIG. 3A shows the fluctuation state of the pressure P1 on the gas source side of the reaction gas supply line 54. At this time, the pressure P3 of the reaction gas vent line 56 is slightly higher than the atmospheric pressure. It shows an almost constant value in the pressure (positive pressure) state. FIG. 3B shows a supply mode of ozone (reactive gas) to the processing container 4 and corresponds to FIG.

  First, immediately before starting the film forming process, the first on-off valve V1 is closed to prevent ozone from flowing into the processing container 4, and the second on-off valve V2 is opened to use ozone for the reaction gas. The flow rate is stabilized by flowing to the vent line 56 side.

  When the flow of the reaction gas is switched from the reaction gas vent line 56 side to the processing container 4 side, that is, when the point A1 and the reaction gas flow are switched from the processing container 4 side to the reaction gas vent line 56 side. That is, the point A2 is alternately and intermittently performed. At the point A1, the first on-off valve V1, V2 is simultaneously closed by closing the second on-off valve V2 first, and then the first on-off valve V1 is immediately opened to turn off the gas. The flow of the reaction gas is changed into the processing container 4 by switching the flow.

  Further, at the point A2, the first on-off valve V1 is closed first, thereby realizing the simultaneous closing state of the first and second on-off valves V1, V2, and then the second on-off valve V2 is turned on after a while. By opening, the flow of the gas is switched, and the reaction gas is caused to flow into the reaction gas vent line 56. When the gas flow is switched at points A1 and A2, a peak occurs in the pressure P1, and when the reaction gas is flowed to the processing container 4, the pressure P1 is in a reduced pressure state lower than the atmospheric pressure.

  Specifically, as described above, when the flow of the reaction gas is switched from the processing vessel 4 side to the reaction gas vent line 56, that is, at the point A2, the first and second on-off valves V1 and V2 are turned on. A first predetermined time in which the pressure P1 on the gas source side in the reaction gas supply line 54 becomes larger than the pressure P3 on the reaction gas vent line 56 side in the closed state (V1: closed) at the same time. When T1 elapses, the second on-off valve V2 is opened to switch the gas flow, and the reactive gas is allowed to flow to the reactive gas supply line 54 to be discarded.

  As described above, the reason why the first predetermined time T1 is set large is that the reaction gas flows into the evacuated processing container 4 until just before this, so that the pressure P1 is lower than the atmospheric pressure. In this state, when the open / close state of the first and second on-off valves V1 and V2 is switched at the same time in reverse, the reaction occurs from the reaction gas vent line 56 which is at a pressure P3 slightly higher than the atmospheric pressure. A backflow occurs toward the gas supply line 54 for gas. Therefore, in order to prevent this backflow, the first and second on-off valves V1 and V2 are kept closed for a long time, that is, for the first predetermined time until “pressure P1> pressure P3”. Only T1 is held, and then the second on-off valve V2 is opened to prevent the backflow.

  In this case, in order to realize “pressure P1> pressure P3”, it is only necessary to delay the opening operation of the second on-off valve V2 by the minimum time ΔT in which the pressures P1 and P3 are the same. The predetermined time T1> minimum time ΔT ”may be set. Regarding the actual setting of the first predetermined time T1, a safety margin is expected, and the opening / closing operation of the on-off valve usually requires about 100 msec. Therefore, a half-open state of about 100 msec occurs, and this safety is ensured. Therefore, the first predetermined time T1 is set longer than the minimum time ΔT.

  The length of the first predetermined time T1 is in the range of 5 to 10 sec, preferably in the range of 7 to 8 sec, depending on the process conditions and the length and diameter of the pipes forming the gas line. If the first predetermined time T1 is set longer than 10 seconds, the occurrence of backflow can be prevented, but this is not preferable because the throughput of the film forming process is reduced.

  The fluctuation state of the pressure P1 as described above is such that, before performing the actual film forming apparatus, a gas is flowed through the film forming apparatus 2 in advance in the same manner as during the film forming process, and the gas flow is changed between the processing container 4 side and the reaction gas. Is switched to the vent line 56 side, and the pressure P1 on the gas source side of the gas supply line 54 for the reaction gas at this time is measured by the pressure gauge 58. Since the pressure P3 in the reaction gas vent line 56 is substantially constant as described above, the minimum time ΔT is obtained, and the first predetermined time T1 in consideration of the safety margin is determined in advance. Become. As described above, at the point A2, an instruction to open the second on-off valve V2 is issued after a delay of the first predetermined time T1 with respect to the instruction to close the first on-off valve V1.

  Further, when the flow of the reaction gas is switched from the reaction gas vent line 56 side to the processing vessel 4, that is, at the point A1, the first and second on-off valves V1 and V2 are closed at the same time as in the point A2. (V2: closed), and immediately after that, specifically, when the second predetermined time T2, which is much shorter than the first predetermined time T1, has elapsed, the first on-off valve V1 is opened. The gas flow is switched so that the gas flows to the processing container 4 side.

  In this case, since the inside of the processing container 4 is always evacuated to a reduced pressure or a vacuum state, the pressure P2 in the processing container 4 is always smaller than the pressure P3, and accordingly, the first on-off valve V1. There is no risk of backflow even if the door is opened. Therefore, the first on-off valve V1 may be opened after confirming that the second on-off valve V2 is reliably closed. At this time, as described above, since the opening / closing operation of the opening / closing valve usually requires about 100 msec, a half-open state of about 100 msec occurs. Accordingly, the second predetermined time T2 is set in the range of 200 to 500 msec, preferably in the range of 300 to 400 msec in consideration of the safety of this amount. That is, the length of the second predetermined time T2 is set to a length that does not cause the first and second on-off valves V1, V2 to be in a half-open state at the same time.

  As described above, the first predetermined time T1 is set to a value considerably larger than the second predetermined time T2. As described above, at the point A1, the instruction to open the first on-off valve V1 is issued after a delay of the second predetermined time T2 with respect to the instruction to close the second on-off valve V2. As a result, it is possible to optimize and minimize the time length of the first and second on-off valves V1 and V2 when the gas flow direction is switched, and to prevent the backflow of gas. It becomes possible.

  As described above, according to the present invention, when the gas flow is switched between a gas supply line, for example, a reaction gas supply line and a vent line, for example, a reaction gas vent line, the gas backflow is reduced. Can be prevented. Accordingly, it is possible to prevent the formation of a contaminated thin film on the semiconductor wafer during the film forming process.

  In the above embodiment, in order to obtain the fluctuation pattern of the pressure P1 shown in FIG. 3A, the reaction gas was actually passed through the film forming apparatus and measured by the pressure gauge 58. The process conditions of the film formation process, for example, the flow rate of the gas, the process pressure, and the design values such as the length and the inner diameter of the piping forming each line of the gas supply system 10 of the reactive gas are shown in FIG. You may make it obtain | require the fluctuation pattern of the pressure P1 shown to A).

  Further, in the above embodiment, the case where the downstream side of the reaction gas vent line 56 is connected to the combustor 32 which is an atmospheric pressure atmosphere portion provided in the exhaust system 8 is described as an example, but the present invention is not limited thereto. The downstream side of the reaction gas vent line 56 is connected to a detoxifying device (not shown), which is an atmospheric pressure atmosphere portion provided separately and independently from the exhaust system 8, and is burned here and then discharged from the factory duct 34. You may make it discharge.

  Furthermore, in the above-described embodiment, the case where the present invention is applied to the reaction gas supply system 10 has been described as an example. However, the present invention is not limited to this, or instead, the pressure P1 of the gas supply line is changed to the vent line. When a fluctuation larger than the pressure P3 occurs, the downstream side of the vent line 56 is connected to the vacuum atmosphere portion (the portion in the exhaust passage 26 that is in the vacuum atmosphere) with respect to the gas supply system 40 of the source gas. Thus, the present invention may be applied. The present invention can be applied not only to a film forming apparatus using plasma but also to a single wafer type film forming apparatus for processing semiconductor wafers one by one.

In addition, although trisdimethylaminosilane (3DMAS) is used as the silicon-containing gas here, the silicon-containing gas is not limited to DCS gas, and the silicon-containing gas is dichlorosilane (DCS). , Hexachlorodisilane (HCD), monosilane [SiH ₄ ], disilane [Si ₂ H ₆ ], hexamethyldisilazane (HMDS), tetrachlorosilane (TCS), disilylamine (DSA), trisilylamine (TSA), Vista butyl One or more gases selected from the group consisting of aminosilane (BTBAS), bisdiethylaminosilane (BDEAS), diisopropylaminosilane (DIPAS), and trisdimethylaminosilane (3DMAS) can be used.

  Furthermore, the source gas is not limited to the silicon-containing gas, and an organometallic compound gas can be used. Examples of the organometallic compound gas include trimethylaluminum (TMA), tetrakisdimethylaminohafnium (TDMAH), and tetrakisethyl. One or more gases selected from the group consisting of methylaminohafnium (TEMAH), tetrakisethylmethylaminozirconium (TEMAZ), and tetrakisdimethylaminotitanium (TDMAT) can be used. In this case, as the reaction gas, one gas selected from the group consisting of a nitriding gas, an oxidizing gas, and a reducing gas can be used.

  Although the semiconductor wafer is described as an example of the object to be processed here, the semiconductor wafer includes a silicon substrate and a compound semiconductor substrate such as GaAs, SiC, GaN, and the like, and is not limited to these substrates. The present invention can also be applied to glass substrates, ceramic substrates, and the like used in display devices.

2 Deposition device 4 Processing vessel 6 Wafer boat (holding means)
DESCRIPTION OF SYMBOLS 10 Gas supply system of reaction gas 12 Gas supply means 22 Heating means 32 Combustor 34 Factory duct 40 Gas supply system of raw material gas 42 Gas supply system of purge gas 54 Gas supply line for reaction gas 56 Vent line for reaction gas 58 Pressure Total 66 Valve control unit T1 First predetermined time T2 Second predetermined time V1 First on-off valve V2 Second on-off valve W Semiconductor wafer (object to be processed)

Claims (12)

In a gas supply system that supplies a gas necessary for film formation to a processing container that performs film formation on an object to be processed.
A gas supply line for supplying the gas whose flow rate is controlled by interposing a first on-off valve to the processing container;
A vent line branched from the gas supply line upstream of the first on-off valve with a second on-off valve interposed to discard the gas;
When switching the gas flow from the processing vessel side to the vent line side, the first and second on-off valves are closed at the same time, and the gas in the gas supply line is more than the pressure on the vent line side. Controlling the second on-off valve to be open when a first predetermined time when the pressure on the source side becomes large has elapsed,
When switching the gas flow from the vent line side to the processing container side, the first on-off valve is opened after the first and second on-off valves are simultaneously closed. A valve controller to control;
A gas supply system comprising: The gas supply system according to claim 1, wherein a downstream side of the vent line is connected to an exhaust system side of the processing container. The gas supply system according to claim 2, wherein the downstream side of the vent line is connected to an atmospheric pressure atmosphere portion of the exhaust system. The gas supply system according to claim 2, wherein a downstream side of the vent line is connected to a vacuum atmosphere portion of the exhaust system. The gas supply system according to claim 1, wherein a downstream side of the vent line is connected to a detoxifying device for an atmospheric pressure atmosphere portion. The gas supply according to any one of claims 1 to 5, wherein the first predetermined time is obtained based on a process condition of the film forming process and a design value of each line of the gas supply system. system. The first predetermined time is obtained in advance by actually flowing the gas and switching the gas flow between the processing container side and the vent line side and measuring the pressure on the gas source side of the gas supply line. The gas supply system according to any one of claims 1 to 5. The gas supply system according to any one of claims 1 to 7, wherein the first predetermined time is within a range of 5 to 10 seconds. In order to make the first and second on-off valves closed at the same time, the second on-off valve until the first on-off valve or the second on-off valve shifts from an open state to a closed state through a half-open state. The gas supply system according to any one of claims 1 to 8, wherein a predetermined time is required. The gas supply system according to claim 9, wherein the second predetermined time is in a range of 200 to 500 msec. The gas supply system according to any one of claims 1 to 10, wherein the gas is at least one of a source gas and a reaction gas. In a film forming apparatus for performing a film forming process on an object to be processed,
A processing container for containing the object to be processed;
Holding means for holding the object to be processed;
An exhaust system for exhausting the atmosphere in the processing vessel;
Gas supply means having the gas supply system according to any one of claims 1 to 11,
A film forming apparatus comprising:

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