JP2013076113A - Gas supply device and film deposition apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas supply device which can introduce a stabilized flow rate of gas into a treatment vessel without making the gas flow to the side of a vent pipe.SOLUTION: The gas supply device 40 which supplies a gas into a treatment vessel 4 storing a workpiece W to be deposited with a thin film is provided with a gas supply system 42 including: a gas passage 48 connected to the treatment vessel and through which a gas is made to flow; a flow rate control valve 64 inserted in the gas passage; an on-off valve mechanism 68 inserted in the gas passage on the downstream side than the flow rate control valve; a pressure detection part 74 of detecting the pressure in an intermediate gas passage 72 as a gas passage between the flow rate control valve and the on-off valve mechanism; and a valve control part 76 of controlling the pressure in the intermediate gas passage so as to be a fixed value of two or more times the pressure in the treatment vessel by controlling the flow rate control valve based on the detection of the pressure detection part.

Description

  The present invention relates to a film forming apparatus for forming a thin film on the surface of an object to be processed such as a semiconductor wafer and a gas supply apparatus used therefor.

  In general, in order to manufacture a semiconductor device, a desired device is manufactured by repeatedly performing various processes such as a film forming process, an etching process, an annealing process, and an oxidation diffusion process on a semiconductor wafer. Taking a film forming process as an example, with the recent demand for higher speed and higher integration of semiconductor devices, liquid or solid raw materials containing metals with good film quality characteristics tend to be used as process raw materials. Become.

  In this case, if the raw material is, for example, a liquid, the raw material whose flow rate is controlled by a liquid mass flowmeter is evaporated by a vaporizer to generate a raw material gas (Patent Document 1), or when the raw material is a solid or liquid, A raw material gas is generated by directly heating and vaporizing the raw material, and the flow rate of the raw material gas is controlled by a mass flow controller.

  When the source gas generated as described above is used for film formation, it is necessary to accurately control the deposited film thickness, and therefore the source gas is allowed to flow into the processing container before entering the film formation process. The flow rate of the source gas is stabilized by flowing directly to the exhaust side through a vent pipe (for example, Patent Document 2), and the valve is switched when the film formation process is started. It is made to flow into the processing container.

JP 2005-307233 A JP 2004-207713 A

  However, when the source gas is allowed to flow to the exhaust side through the vent pipe without being introduced into the processing vessel as described above, there is a problem that the source gas is wasted. In particular, in the case of an ALD (Atomic Layer Deposition) method in which a source gas and a reaction gas, for example, a nitriding gas are alternately and repeatedly flowed, and a thin film at an atomic level or a molecular level is stacked. As described above, in addition to the timing of introducing the raw material gas into the processing container, there is a problem that the time for flowing to the vent pipe to stabilize the flow rate increases, and as a result, the waste of the raw material gas further increases.

  Furthermore, when the raw material gas is allowed to flow to the vent pipe side as described above, this vent pipe is dedicated separately from the normal exhaust system for the processing vessel in order to prevent reaction by-products generated by the raw material gas. In some cases, it may be necessary to install a vacuum pump, and the cost of the apparatus increases.

  Therefore, as disclosed in Patent Document 1 described above, when a raw material gas is generated by vaporizing a liquid raw material in a vaporizer and this raw material gas is supplied into the processing vessel through the supply line, the supply line is in the middle. There is also a technique in which an orifice is provided in the chamber, and the flow rate of the liquid material is controlled by a liquid feed pump so that the pressure upstream of the orifice is constant, so that the gas flow rate introduced into the processing vessel is constant. Proposed.

  However, in this case, since the flow rate of the raw material in the liquid state is controlled, the pressure of the vaporized raw material gas is affected by a slight change in the flow rate, and the pressure of the raw material gas is kept constant. There was an inconvenience that it was difficult.

  The present invention has been devised to pay attention to the above problems and to effectively solve them. The present invention is a gas supply apparatus and a film forming apparatus capable of introducing a gas having a stabilized flow rate into a processing container without flowing the gas to the vent pipe side.

  The invention according to claim 1 is a gas supply apparatus for supplying a gas into a processing container that accommodates an object to be processed on which a thin film is formed, a gas passage connected to the processing container for flowing the gas, and the gas A flow control valve interposed in the passage, an on-off valve mechanism interposed in the gas passage downstream of the flow control valve, and the gas passage between the flow control valve and the on-off valve mechanism. A pressure detection unit for detecting a pressure in a certain intermediate gas passage, and controlling the flow rate control valve based on the detection of the pressure detection unit so that the pressure in the intermediate gas passage is twice the pressure in the processing vessel. A gas supply device comprising a gas supply system having a valve control unit that controls the constant value as described above.

  Thus, in a gas supply apparatus that supplies gas into a processing container that accommodates an object to be processed on which a thin film is formed, a gas having a stabilized flow rate is introduced into the processing container without flowing the gas to the vent pipe side. Is possible. Accordingly, it is possible not only to suppress wasteful consumption of gas, but also to eliminate the need for a dedicated vacuum pump for the vent pipe, and to reduce the apparatus cost.

  According to an eighth aspect of the present invention, there is provided a film forming apparatus for forming a thin film on an object to be processed. The heating means for heating, the gas introduction means for introducing gas into the processing container, the gas supply device according to any one of claims 1 to 4 connected to the gas introduction means, and the inside of the processing container A film evacuation system for evacuating the atmosphere, and an apparatus control unit for controlling the operation of the entire film formation apparatus.

According to the gas supply apparatus and the film forming apparatus of the present invention, the following excellent operational effects can be exhibited.
In a gas supply apparatus that supplies a gas into a processing container that accommodates an object to be processed on which a thin film is formed, a gas having a stabilized flow rate can be introduced into the processing container without flowing the gas toward the vent pipe. Therefore, it is possible not only to suppress wasteful consumption of gas, but also to eliminate the need for a dedicated vacuum pump for the vent pipe, and to reduce the apparatus cost.

It is a schematic block diagram which shows an example of the gas supply apparatus and film-forming apparatus of this invention. It is a timing chart which shows an example of the supply timing of each gas when performing the film-forming process by ALD method on a semiconductor wafer. It is a block diagram which shows a part of modified example of the gas supply apparatus of this invention.

Hereinafter, a preferred embodiment of a gas supply apparatus and a film forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings. Here, a case where a TiCl ₄ gas is used as a source gas, an NH ₃ gas is used as a reaction gas, and a titanium nitride film is formed as a thin film by an ALD method will be described as an example. FIG. 1 is a schematic configuration diagram showing an example of a gas supply apparatus and a film forming apparatus of the present invention. As shown in the figure, the film forming apparatus 2 of the present invention includes a processing container 4 formed into a cylindrical shape from, for example, aluminum, aluminum alloy, stainless steel or the like.

  An exhaust port 8 for exhausting the atmosphere in the processing container is provided at the bottom 6 of the processing container 4, and a vacuum exhaust system 10 is connected to the exhaust port 8. The vacuum exhaust system 10 has an exhaust passage 12 connected to the exhaust port 8, and the exhaust passage 12 has a valve opening degree for adjusting pressure from the upstream side to the downstream side. A pressure regulating valve 14 that can be adjusted, a trap mechanism 16 that removes reaction by-products and the like from the exhaust gas, and a vacuum pump 18 are sequentially provided. As a result, the atmosphere in the processing container 4 can be uniformly evacuated from the bottom peripheral portion.

  In the processing container 4, a holding unit 20 that holds an object to be processed is provided. Specifically, the holding means 20 includes a disk-shaped mounting table 24 provided at the tip of a support column 22 standing from the bottom 6 of the processing container 4. On the mounting table 24, for example, silicon A semiconductor wafer W such as a substrate can be placed thereon. The mounting table 24 is made of ceramic such as AlN. The mounting table 24 is configured to mount, for example, a semiconductor wafer W having a diameter of 300 mm. A heating means 26 such as a resistance heater is embedded in the mounting table 24 so that the semiconductor wafer W can be heated and maintained at a desired temperature. A heating lamp may be used as the heating means 26.

  In addition, the mounting table 24 presses the peripheral portion of the semiconductor wafer W and fixes the semiconductor wafer W on the mounting table 24, and the semiconductor wafer W is pushed up and down when the semiconductor wafer W is loaded and unloaded. A lifter pin is provided. In addition, a loading / unloading port 28 is provided on the side wall of the processing container 4, and a gate valve 29 that can be opened and closed airtightly when the semiconductor wafer W is loaded / unloaded is provided in the loading / unloading port 28.

  The processing container 4 is provided with gas introduction means 30 for introducing gas into the processing container 4. Specifically, the gas introduction means 30 includes a shower head 32 provided on the ceiling of the processing container 4. The shower head 32 is integrally formed with the ceiling board 34, and is formed of, for example, aluminum or aluminum alloy.

  The shower head 32 is formed in a circular shape so as to face the entire upper surface of the mounting table 24, and a processing space S is formed between the shower head 32 and the mounting table 24. The shower head 32 introduces various gases into the processing space S in a shower shape, and a plurality of injection holes 36 for injecting gas are formed on the injection surface on the lower surface of the shower head 32.

  A gas introduction port 38 for introducing gas into the shower head 32 is provided on the upper portion of the shower head 32. The structure of the gas introducing means 30 is not limited to the shower head 32, and may be any structure, for example, a structure like a simple nozzle. The processing container 4 is provided with a gas supply device 40 that is a feature of the present invention. Specifically, the gas supply device 40 includes a source gas supply system 42 that supplies a source gas, a reaction gas supply system 44 that supplies a reaction gas, and a purge gas supply system 46 that supplies a purge gas. .

  First, the source gas supply system 42 has a gas passage 48 for flowing the source gas toward the processing container 4. The distal end, that is, the upstream side of the gas passage 48 is connected to the gas source 50, and the downstream side is connected to the gas introduction port 38 of the shower head 32. Here, the gas source 50 has a raw material storage tank 52, and the raw material 54 is stored in the raw material storage tank 52.

The raw material 54 is in a liquid or solid state, and here, TiCl _{4 which} is liquid at room temperature is used. The raw material storage tank 52 is provided with a raw material heater 58 and a raw material pressure gauge 60 for measuring the pressure of the generated raw material gas. By heating and vaporizing the raw material 54, the raw material gas at a constant pressure is supplied. It is supposed to be generated. The gas inlet 62 at the tip of the gas passage 48 is located in the upper space of the raw material storage tank 52 in order to flow the generated raw material gas.

  A flow rate control valve 64 such as a mass flow controller is interposed on the upstream side of the gas passage 48 in order to control the flow rate of the flowing gas. The flow rate control valve 64 has an actuator 66 for controlling the valve opening, and the flow rate of gas flowing therethrough can be adjusted. As the actuator 66, a piezoelectric element such as a piezoelectric element is used. An open / close valve mechanism 68 is interposed in the gas passage 48 on the downstream side of the flow control valve 64.

  As the on-off valve mechanism 68, an on-off valve 70 that selectively realizes an open state and a closed state is used here. The on-off valve 70 is set so that the flow passage area in the open state is smaller than the cross-sectional area of the gas passage 48, thereby exhibiting the orifice function. Therefore, the flow path area in the open state can define the gas flow rate. Specifically, as will be described later, the pressure on the upstream side of the on-off valve 70 is set to be a constant value that is twice or more the pressure on the downstream side, and the on-off valve 70 is in the open state. When it becomes, it functions as a sonic nozzle. In this case, the gas flow rate is determined depending on the flow path area when the on-off valve 70 is open and the pressure in the intermediate gas passage 72.

  The gas passage 48 between the flow control valve 64 and the on-off valve mechanism 68 is an intermediate gas passage 72, and a pressure detector 74 including a pressure gauge is provided to detect the pressure in the intermediate gas passage 72. ing. And in order to adjust the valve opening degree of the flow control valve 64, the valve control part 76 which consists of microcomputers etc. is provided, and this valve control part 76 is based on the detected value of the said pressure detection part 74, and is based on the said value. By controlling the flow rate control valve 64, the pressure in the intermediate gas passage 72 is set to a constant value that is twice or more the pressure in the processing vessel 4 (process pressure), that is, the pressure on the downstream side of the on-off valve mechanism 68. It is trying to become.

  In this case, the valve control unit 76 operates under the control of the device control unit to be described later, and the set value of the process pressure and the pressure in the intermediate gas passage 72 may be determined in advance or instructed by the device control unit. You may do it.

  Here, for example, the process pressure is set to about 1 to 3 Torr, the pressure in the intermediate gas passage 72 is set to about 30 Torr, the pressure in the gas source 50 is set to about 131 Torr, and upstream of the gas passage 48. The pressure gradually increases as you go. The intermediate gas passage 72 and the gas source 50 are temperature-controlled at about 80 ° C., and the processing vessel 4 has a wall surface at about 170 ° C. and the mounting table 24 at about 450 ° C. In addition, the entire gas passage 48 is provided with passage heating means 78 for heating in order to prevent the flowing gas from being liquefied or solidified. Here, it is heated to about 80 ° C., for example.

  A vent pipe 80 is branched from the middle of the intermediate gas passage 72, and a vent pipe on-off valve 81 is interposed in the middle. The downstream side of the vent pipe 80 is connected to the exhaust passage 12 of the vacuum exhaust system 10.

Next, the reaction gas supply system 44 is formed in substantially the same manner as the source gas supply system 42. That is, the reaction gas supply system 44 has a gas passage 82 for flowing the reaction gas toward the processing container 4. The tip of the gas passage 82, that is, the upstream side is connected to the gas source 84, and the downstream side is connected to the gas introduction port 38 of the shower head 32. Here, the gas source 84 has a reaction gas tank 86, and a high-pressure reaction gas is stored in the reaction gas tank 86. Here, NH ₃ which is a nitriding gas is used as the reaction gas. This reaction gas is made to flow at a constant pressure by a regulator (not shown).

  A flow rate control valve 88 such as a mass flow controller is interposed on the upstream side of the gas passage 82 in order to control the flow rate of the flowing gas. The flow rate control valve 88 has an actuator 90 that controls the valve opening, and the flow rate of gas flowing therethrough can be adjusted. As the actuator 90, a piezoelectric element such as a piezoelectric element is used. An open / close valve mechanism 91 is interposed in the gas passage 82 on the downstream side of the flow control valve 88.

  As the on-off valve mechanism 91, an on-off valve 92 that selectively realizes an open state and a closed state is used here. The on-off valve 92 is set so that the flow path area when opened is smaller than the cross-sectional area of the gas passage 82, thereby exhibiting an orifice function. Therefore, the flow path area in the open state can define the gas flow rate. Specifically, the pressure on the upstream side of the on-off valve 92 is set to be a constant value more than twice the pressure on the downstream side. When the on-off valve 92 is opened, the sonic nozzle It is supposed to function as. In this case, the gas flow rate is determined depending on the flow path area when the on-off valve 92 is open and the pressure in the intermediate gas passage 94.

  The gas passage 82 between the flow control valve 88 and the on-off valve mechanism 91 is the intermediate gas passage 94, and a pressure detector 96 comprising a pressure gauge is provided to detect the pressure in the intermediate gas passage 94. It has been. In order to adjust the valve opening degree of the flow control valve 88, a valve control unit 98 made of, for example, a microcomputer is provided, and the valve control unit 98 is based on the detection value of the pressure detection unit 96. By controlling the flow rate control valve 88, the pressure in the intermediate gas passage 94 is set to a constant value that is twice or more the pressure in the processing vessel 4 (process pressure), that is, the pressure downstream of the on-off valve mechanism 91. It is trying to become.

  In this case, the valve control unit 98 operates under the control of the device control unit which will be described later, and the process pressure and the set value of the pressure in the intermediate gas passage 94 may be determined in advance or instructed by the device control unit. You may do it.

Here, for example, the process pressure is set to about 1 to 3 Torr, the pressure in the intermediate gas passage 94 is set to about 100 Torr, and the pressure sequentially increases toward the upstream side of the gas passage 82. A vent pipe 100 is branched from the middle of the intermediate gas passage 94, and a vent pipe on-off valve 102 is interposed in the middle. The downstream side of the vent pipe 102 is connected to the exhaust passage 12 of the vacuum exhaust system 10. NH ₃ is supplied after being heated to about 150 ° C. by a heating source (not shown).

  Next, the purge gas supply system 46 is formed in the same manner as the reaction gas supply system 44. That is, the purge gas supply system 46 has a gas passage 104 for flowing the purge gas toward the processing container 4. The distal end, that is, the upstream side of the gas passage 104 is connected to the gas source 106, and the downstream side is connected to the gas introduction port 38 of the shower head 32. Here, the gas source 106 has a purge gas tank 108, and a high-pressure purge gas is stored in the purge gas tank 108.

As this purge gas, N ₂ which is an inert gas is used here. A rare gas such as Ar may be used as the purge gas. This purge gas is made to flow at a constant pressure by a regulator (not shown). Note that the pressure of the purge gas may not be controlled, or may be kept flowing during film formation. According to this, it is possible to prevent the source gas from returning to the upstream side.

  A flow rate control valve 110 such as a mass flow controller is interposed on the upstream side of the gas passage 104 to control the flow rate of the flowing gas. This flow control valve 110 has an actuator 112 for controlling the valve opening, and the flow rate of gas flowing therethrough can be adjusted. As the actuator 112, a piezoelectric element such as a piezoelectric element is used. An open / close valve mechanism 112 is interposed in the gas passage 104 on the downstream side of the flow control valve 110.

  As the on-off valve mechanism 112, an on-off valve 114 that selectively realizes an open state and a closed state is used here. The on-off valve 114 is set so that the flow path area in the open state is smaller than the cross-sectional area of the gas passage 104, thereby exhibiting an orifice function. Therefore, the flow path area in the open state can define the gas flow rate. Specifically, the pressure on the upstream side of the on-off valve 114 is set to be a constant value that is twice or more than the pressure on the downstream side. When the on-off valve 114 is opened, the sonic nozzle It is supposed to function as. In this case, the gas flow rate is determined depending on the flow path area when the on-off valve 114 is open and the pressure in the intermediate gas passage 116.

  The gas passage 104 between the flow control valve 110 and the on-off valve mechanism 112 serves as the intermediate gas passage 116, and a pressure detector 118 including a pressure gauge is provided to detect the pressure in the intermediate gas passage 116. It has been. In order to adjust the valve opening degree of the flow control valve 110, a valve control unit 120 made of, for example, a microcomputer is provided. The valve control unit 120 is based on the detection value of the pressure detection unit 118. By controlling the flow rate control valve 110, the pressure in the intermediate gas passage 116 is set to a constant value that is twice or more the pressure in the processing vessel 4 (process pressure), that is, the pressure on the downstream side of the on-off valve mechanism 112. It is trying to become.

  In this case, the valve control unit 120 operates under the control of the device control unit, which will be described later, and the set values of the process pressure and the pressure in the intermediate gas passage 116 may be determined in advance or instructed by the device control unit. You may do it.

  Here, for example, the process pressure is set to about 1 to 3 Torr, the pressure in the intermediate gas passage 116 is set to about 100 Torr, and the pressure sequentially increases toward the upstream side of the gas passage 104. A vent pipe 122 is branched from the middle of the intermediate gas passage 116, and a vent pipe opening / closing valve 124 is interposed in the middle. The downstream side of the vent pipe 122 is connected to the exhaust passage 12 of the vacuum exhaust system 10.

  In order to control the overall operation of the film forming apparatus 2, the apparatus control unit 126 includes, for example, a computer or the like. For example, an instruction for controlling the process pressure, the process temperature, and the supply amount of each gas, Instructions for opening and closing each on-off valve are given. The device control unit 126 has a storage medium 128 for storing a computer program necessary for the control. The storage medium 128 is composed of, for example, a flexible disk, a CD (Compact Disc), a hard disk, a flash memory, or a DVD.

<Description of deposition method>
Next, a film forming method performed using the film forming apparatus configured as described above will be described with reference to FIG. FIG. 2 is a timing chart showing an example of the supply timing of each gas when a film formation process is performed on a semiconductor wafer by the ALD method. Here, as described above, here, a case where TiCl ₄ gas is used as a source gas, NH ₃ gas is used as a reaction gas, and a titanium nitride film is formed as a thin film by an ALD method will be described as an example.

  First, on the mounting table 24 in the processing container 4, for example, a semiconductor wafer W having a diameter of 300 mm is loaded. At this time, the gas passages 48, 82, and 104 of the gas supply systems 42, 44, and 46 of the gas supply device 40 in the processing container 4 are evacuated by the vacuum exhaust system 10 before the semiconductor wafer W is loaded. And maintained at a low pressure. During this initial evacuation, the vent open / close valves 81, 102, and 124 of the vent pipes 80, 100, and 122 provided in the gas supply systems 42, 44, and 46 are opened to promote evacuation. When the initial evacuation is completed in this way, the vent open / close valves 81, 102, and 124 are closed, and the vent pipes 80, 100, and 122 are not used during the subsequent film forming process.

  As described above, when the semiconductor wafer W is loaded into the processing chamber 4 that has been initially evacuated and placed on the mounting table 24, the processing chamber 4 is sealed. Then, the temperature of the semiconductor wafer W is raised to a predetermined process temperature by the heating means 26 provided on the mounting table 24, and this temperature is maintained. At the same time, the respective gases are introduced into the treatment space S from the injection holes 36 of the shower head 32 which is the gas introduction means 30 provided on the ceiling portion of the treatment container 4 in the order shown in FIG.

In this case, in the gas supply device 40, TiCl ₄ gas which is a raw material gas is supplied to the shower head 32 by the raw material gas supply system 42, and NH ₃ gas which is a reactive gas (nitriding gas) is supplied to the shower head by the reactive gas supply system 44. N ₂ gas, which is a purge gas, is supplied to the shower head 32 by the purge gas supply system 46.

An example of the supply timing of each of the above gases is shown in FIG. 2, in which TiCl ₄ (FIG. 2 (A)) as a source gas and NH ₃ gas (FIG. 2 (B)) as a reaction gas are alternately used. The supply is intermittently repeated to provide a pulsed supply mode. Then, during the period in which the source gas supply stop period and the reaction gas supply stop period overlap, the purge gas N ₂ gas is supplied (FIG. 2C), and the residual gas in the processing container 4 is discharged. Is promoting. During the supply of the raw material gas adsorbed TiCl ₄ gas is on the surface of the semiconductor wafer W, and, during the supply of the reaction gas reacts with NH ₃ gas TiCl ₄ gas adsorbed on the semiconductor wafer W is a reactive gas As a result, a titanium nitride film (TiN) having a thin atomic level or molecular level is formed by nitriding. By repeating this operation, the thin films are stacked, and a titanium nitride film having a desired thickness can be obtained by repeating the necessary number of times (cycles). Here, as a modification, the purge gas may be constantly flowed during film formation as described above instead of intermittently (FIG. 2D). When this purge gas is always flowed, not only the pressure fluctuation in the processing vessel 4 can be suppressed, but also the raw gas such as TiCl ₄ and NH ₃ is prevented from interdiffusing to the gas passages 48 and 82 side, and the gas It is possible to prevent a thin film from being deposited in the passages 48 and 82.

Here, one cycle is from the start of the source gas supply period to the start of the next source gas supply period. As an example, the source gas supply period T1 is about 0.6 seconds, the reaction gas supply period T2 is about 0.3 seconds, and the purge period T3 is about 0.2 seconds. In addition, as an example of the supply amount of each gas, TiCl ₄ gas is about 250 sccm / second, NH ₃ gas is about 2 liter / minute, and N ₂ gas is about 5 liter / minute. The process pressure is in the range of 1 to 10 Torr, and is set in the range of 1 to 3 Torr here. Moreover, process temperature is about 300-600 degreeC. In addition, the supply mode of each gas by the ALD method shown in FIG. 2 is merely an example, and is not limited to this.

<Gas supply>
Here, the supply of each gas will be described in detail. First, the raw material gas will be described. In the raw material storage tank 52 that is the gas source 50 of the raw material gas supply system 42, the raw material heater 58 is used to heat and vaporize TiCl ₄ that is the liquid raw material 54 to generate the raw material gas. Yes. The pressure of the raw material gas in the raw material storage tank 52 is detected by a raw material pressure gauge 60. By controlling the raw material heater 58 based on the detected value, the raw material gas is maintained at about 131 Torr, for example. In this case, the raw material 54 is heated to about 80 ° C., for example. This raw material gas flows through the gas passage 48 and intermittently opens and closes the shower head 32 by opening and closing the on-off valve 70 of the on-off valve mechanism 68 provided in the middle according to the pulse timing of FIG. Introduced.

  Here, as described above, the pressure in the intermediate gas passage 72 positioned between the flow control valve 64 and the on-off valve mechanism 68 is detected by the pressure detection unit 74, and the valve control unit 76 detects the flow control valve 64. By adjusting the valve opening degree, the pressure is controlled to be a constant value that is twice or more the pressure on the downstream side of the on-off valve mechanism 68.

  Here, the pressure on the downstream side of the on-off valve mechanism 68 is about 1 to 3 Torr that is the same as the process pressure, and is maintained at a constant value that is twice or more of this pressure, for example, about 30 Torr. In this case, the pressure difference is provided, and the flow passage area of the valve opening when the on-off valve 70 is open is a predetermined size smaller than the cross-sectional area of the gas passage 48. The function will be demonstrated.

  Therefore, when the on-off valve 70 is in the open state, it becomes a sonic nozzle and can flow a gas (raw material gas) with a constant flow rate stably without depending on the downstream pressure. In other words, during the supply period of the pulsed source gas, a constant amount of source gas that flows stably over the length of the supply period T1 does not depend on the downstream pressure and does not use a vent pipe. Will be able to. At this time, the insufficient raw material gas in the intermediate gas passage 72 is sequentially supplied from the upstream side by adjusting the flow rate control valve 64.

Therefore, in the conventional gas supply apparatus, immediately before starting the supply of the raw material gas, the raw material gas was unnecessarily flowed into the vent pipe in order to stabilize the flow rate. Thus, it is not necessary to flow the source gas through the vent pipe, and it is possible to eliminate waste of gas (source gas). The gas supply mode as described above is executed similarly in the reactive gas supply system 44 and the purge gas supply system 46 because the similar on-off valve mechanisms 91 and 112 are provided. Therefore, it is possible to prevent wasteful consumption of the reaction gas (NH ₃ ) and the purge gas (N ₂ ).

  As described above, in the present invention, in the gas supply device 40 that supplies gas into the processing container 4 that accommodates the target object on which a thin film is formed, for example, the semiconductor wafer W, the gas is stable without flowing to the vent pipe side. The gas having the flow rate thus changed can be introduced into the processing container 4. Therefore, it is possible not only to suppress wasteful consumption of gas, but also to eliminate the need for a dedicated vacuum pump for the vent pipe, and to reduce the apparatus cost.

<First Modification Example and Second Modification Example>
Next, a modified embodiment of the gas supply device of the present invention will be described. FIG. 3 is a block diagram showing a part of a modified embodiment of the gas supply apparatus of the present invention, FIG. 3 (A) shows the first modified embodiment, and FIG. 3 (B) shows the second modified embodiment. . In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In the first modified embodiment shown in FIG. 3A, a certain capacity is provided in order to temporarily store gas in the middle of the intermediate gas passage 72 that is a part of the gas passage 48 of the source gas supply system 42. A buffer tank 130 is interposed. In this case, not only can the same effect as described above with reference to FIG. 1 be exhibited, but also the overall capacity in the intermediate gas passage 72 including the capacity of the buffer tank 130 increases. Even if the source gas flowing during film formation becomes large, it becomes possible to cope with this. The embodiment in which the buffer tank 130 is provided can be similarly applied to the other reaction gas supply system 44 and the purge gas supply system 46. In the above case, if the buffer tank 130 is not provided, the supply amount of the raw material gas may fluctuate or a large amount of gas cannot be supplied in a short time.

  In the second modified embodiment shown in FIG. 3B, an on-off valve 132 and an orifice 134 different from the on-off valve 70 described above are used as the on-off valve mechanism 68 interposed in the gas passage 48 of the source gas supply system 42. Are provided in series. The opening area (flow path area) of the orifice hole of the orifice 134 is configured to define the flow rate of the source gas. That is, the orifice 134 exhibits an orifice function similar to that when the previous on-off valve 70 shown in FIG. On the other hand, the opening / closing valve 132 of the second modified embodiment is set so that the flow path area in the opened state is substantially the same as or close to the cross-sectional area of the gas passage 48, for example. Unlike the orifice 134, the orifice function is set so as not to exhibit.

  In other words, the on-off valve 132 only operates to start or stop the flow of the raw material gas, and does not operate to limit the gas flow rate. Also in this case, the same effects as those described above with reference to FIG. 1 can be exhibited. Further, the order of the orifice 134 and the on-off valve 132 may be exchanged here, or the second modified example and the first modified example may be combined. In general, the conductance of the on-off valve has a variation such as an error between manufacturers. By providing the orifice 134 as described above, the total conductance variation between the on-off valve 132 and the orifice 134 can be reduced.

  In the above embodiment, the case where the characteristic configuration of the present invention is applied to all the gas supply systems 42, 44, 46 of the gas supply device 40 has been described as an example. The characteristic configuration of the present invention may be applied to a part of the gas supply systems 42, 44, 46, for example, one or two gas supply systems. In addition to the baking method in which the gas source 50 generates the source gas, a bubbling method in which the gas is generated by bubbling with a carrier gas, a method in which the source gas is pressurized and stored in the tank, etc. Such a method may be adopted.

Further, the configuration on the processing container 4 side described here is merely an example, and the present invention can be applied to processing containers of any configuration, and also to a film forming apparatus using plasma. The present invention can be applied. Furthermore, although the case where TiCl ₄ which is a metal-containing gas is used as an example is described here, another metal-containing gas may be used.

Examples of the raw material include halogen-based raw materials such as SnCl ₂ , t-butyliminotris (diethylamino) tantalum, tetraethylhafnium, trimethylaluminum, bisethylcyclopentadienylruthenium, bis (6-ethyl-2,2-dimethyl). It is also possible to use an MO-based material such as (-3,5-decanedionato) copper or an organic Si-based material such as tetramethylsilane, trimethylsilane, or dimethyldimethoxysilane.

  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.

DESCRIPTION OF SYMBOLS 2 Film-forming apparatus 4 Processing container 10 Vacuum exhaust system 20 Holding means 24 Mounting stand 26 Heating means 30 Gas introduction means 32 Shower head 40 Gas supply apparatus 42 Raw material gas supply system 44 Reaction gas supply system 46 Purge gas supply system 48,82,104 Gas passage 50, 84, 106 Gas source 54 Raw material 64, 88, 110 Flow rate control valve 68, 91, 112 On-off valve mechanism 70, 92, 114 On-off valve 74, 96, 118 Pressure detection unit 76, 98, 120 Valve control unit 126 apparatus control unit 130 buffer tank 134 orifice W semiconductor wafer (object to be processed)

Claims (8)

In a gas supply apparatus that supplies gas into a processing container that accommodates an object to be processed on which a thin film is formed,
A gas passage connected to the processing vessel for flowing gas;
A flow control valve interposed in the gas passage;
An on-off valve mechanism interposed in the gas passage downstream of the flow control valve;
A pressure detector that detects a pressure in an intermediate gas passage that is the gas passage between the flow control valve and the on-off valve mechanism;
A valve control unit that controls the flow rate control valve based on the detection of the pressure detection unit to control the pressure in the intermediate gas passage to be a constant value that is twice or more the pressure in the processing container;
A gas supply apparatus comprising: a gas supply system including: 2. The gas supply device according to claim 1, wherein the on-off valve mechanism is formed of an on-off valve, and an open flow path area of the on-off valve defines the flow rate of the gas. 2. The on-off valve mechanism comprises an orifice and an on-off valve made in series, and an opening area of an orifice hole of the orifice is configured to define a flow rate of the gas. Gas supply device. The gas supply device according to any one of claims 1 to 3, wherein a buffer tank is interposed in the intermediate gas passage. The gas supply device according to any one of claims 1 to 4, wherein a passage heating means for heating the gas passage to prevent liquefaction or solidification of the gas is provided. The gas supply apparatus according to any one of claims 1 to 5, wherein a gas source of the gas is connected to an upstream side of the gas passage. The said gas is a metal containing gas, The liquid or solid raw material used as the said metal containing gas is stored in the said gas source, The Claim 1 thru | or 6 characterized by the above-mentioned. Gas supply device. In a film forming apparatus for forming a thin film 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;
Heating means for heating the object to be processed;
Gas introduction means for introducing gas into the processing vessel;
The gas supply device according to any one of claims 1 to 4, connected to the gas introduction means,
An evacuation system for evacuating the atmosphere in the processing vessel;
An apparatus controller for controlling the operation of the entire film forming apparatus;
A film forming apparatus comprising:

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