JP4150356B2 - Film forming apparatus and film forming method - Google Patents

Description

  The present invention relates to a film forming apparatus and a film forming method suitable for supplying a processing gas obtained by vaporizing a liquid material to a film forming apparatus such as a low pressure CVD (Chemical Vapor Deposition) apparatus.

  As one of the semiconductor manufacturing processes, there is a film forming process for forming a predetermined film on the surface of a semiconductor wafer (hereinafter referred to as “wafer”) W, and this process is performed using, for example, a low pressure CVD apparatus. This low-pressure CVD apparatus supplies a raw material in a gas state, advances a chemical reaction, and deposits a thin film on the wafer surface. A processing gas obtained by vaporizing a liquid raw material is used as a film forming gas in the apparatus. May be introduced.

  As an example of a film forming process using a processing gas obtained by vaporizing the liquid raw material, SiO2 using a processing gas obtained by vaporizing TEOS (Tetraethoxysilane) and an oxygen (O2) gas as a processing gas. There are examples of forming a film, and examples of forming a silicon nitride (Si3N4) film using a processing gas obtained by vaporizing Si2Cl6 as a processing gas and ammonia (NH3) gas.

  Here, as a liquid raw material vaporization system, a baking type or a VC (Vapor Control) type is known. In the baking type, a liquid raw material is introduced into a heating tank and heated to vaporize, and the VC type is a simple baking type, in which the liquid raw material is directly applied to a vaporizer and vaporized. The baking type includes TEOS having a vapor pressure of about 5.6 kPa (42 Torr) at about 85 ° C. and HCD (Si 2 Cl 6) having a vapor pressure of about 14.4 kPa (108 Torr) at about 85 ° C. It is suitable for vaporizing TEOS or BTBAS (SiH2 [NH (C4H9)] 2) having a vapor pressure of about 6.7 kPa (50 Torr) at about 85 ° C.

  By the way, the present inventors are considering using HEAD (hexaethylaminodisilane) having a vapor pressure of about 0.027 kPa (0.2 Torr) at about 85 ° C. and a low vapor pressure as a liquid raw material. However, vaporization systems such as baking type and VC type are suitable for those with high vapor pressure such as TEOS and BTBAS and high gas decomposition temperature, but low vapor pressure such as HEAD and decomposition temperature is low. A low liquid raw material cannot be sufficiently vaporized, and a sufficient supply amount for use as a processing gas cannot be secured. The baking type always holds the liquid material above a certain temperature, so it cannot be used for vaporizing a liquid material whose decomposition temperature is lower than the temperature of the heating tank, and the VC type has a fixed VC temperature. This is because it cannot be used for low vapor pressure. In the baking type, the raw material may change in quality because it keeps the liquid raw material at a high temperature for a long time. In the VC type, since the liquid raw material is always in high temperature contact in the vaporizer, the change is likely to occur. There is also a problem that the liquid material is liable to leak due to adhering to the valve and not closing.

  For these reasons, the present inventors are considering using a vaporization system that combines a vaporizer and a carrier gas. In this system, as shown in FIG. 8, a liquid source and a carrier gas are introduced into a vaporizer 11 from a liquid source storage tank 12 and a carrier gas source 13, respectively, and the liquid source is a carrier gas such as nitrogen (N2) gas. A mist is generated by collision with the gas and vaporized according to the principle of spraying to obtain a processing gas, and this processing gas is conveyed to the reduced pressure CVD apparatus 14 by a carrier gas. In this system, when supplying the processing gas to the low-pressure CVD apparatus 14, the valve V1 of the pipe 15 on the downstream side of the vaporizer 11 is opened, and after the supply of the processing gas is stopped, the valve V2 is opened and the exhaust pump is used. Residual components in the pipe 17 are removed by evacuating the interior of the pipe 17 on the path connecting the liquid source storage tank 12, the liquid source flow meter 16, and the vaporizer 11. In the figure, reference numeral 18 denotes a carrier gas flow meter.

  This system is suitable for vaporizing a low vapor pressure liquid raw material having a vapor pressure of 26.67 Pa (0.2 Torr) at about 85 ° C., for example, TEOS and BTBAS, and transports a processing gas using a carrier gas. Therefore, a sufficient amount of processing gas for film formation can be supplied to the low pressure CVD apparatus even with a liquid material having a low vapor pressure.

  Here, as a technique using a vaporization system in which a vaporizer and a carrier gas are combined, the technique of Patent Document 1 is proposed.

JP-A-8-17749

  However, in this system, even if the liquid raw material is vaporized by the vaporizer, the vapor component of the liquid raw material is in a state where the gas component of the liquid raw material and mist are mixed. 11, mist adheres to the inner wall of the pipe 15 connecting the vaporizer 11 and the low pressure CVD apparatus 14 on the downstream side of the gas 11 and is liquefied again. When re-liquefaction of mist occurs in this way, it changes in quality over time and solidifies, causing generation of particles. In addition, there is a problem that liquid raw material accumulates in front of the vaporizer 11 or in the vaporizer 11, thereby generating particles.

  The present invention has been made under such circumstances, and an object thereof is to supply a vaporizer and a film when a vaporized raw material gas obtained by vaporizing a liquid material having a low vapor pressure is supplied to a film forming apparatus. An object of the present invention is to provide a film forming apparatus and a film forming method that prevent the generation of particles by preventing the deposition of vaporized source gas mist in the supply path connecting the apparatuses.

The film forming apparatus of the present invention includes a storage tank for storing a liquid raw material,
A vaporizer connected to the downstream side of the storage tank via a liquid raw material supply path to vaporize the liquid raw material to obtain a vaporized raw material gas,
A mist separation unit provided on the downstream side of the vaporizer via a vaporized raw material gas supply path, for separating the processing gas and mist contained in the vaporized raw material gas, and discharging the separated mist;
A film formation processing unit that is provided on the downstream side of the mist separation unit via a processing gas supply path and performs a film formation process on the substrate using the processing gas sent from the mist separation unit;
A valve provided near the downstream side of the mist separation section in the processing gas supply path;
A purge gas supply path that is connected to the downstream side of the valve in the process gas supply path and supplies heated purge gas to remove deposits in the process gas supply path;
A cleaning liquid supply path for supplying a cleaning liquid to the mist separation unit via the vaporizer,
After the film forming process is performed, the purge gas heated from the purge gas supply path is supplied into the process gas supply path with the valve closed, and it is determined whether or not it is time to clean the mist separation unit. When the cleaning timing is determined, the cleaning liquid is supplied from the cleaning liquid supply path to the mist separation unit, and the cleaning liquid is discharged while the valve is closed . Further, the present invention determines whether or not it is time to purge the mist separating unit when it is determined that it is not time to clean as a result of determining whether or not it is time to clean the mist separating unit. When it is determined that it is time to perform, a purge gas may be supplied from a gas supply path connected to the vaporizer to the mist separation unit, and the purge gas may be discharged while the valve is closed.

  The mist separation part is configured by bending the air passage, and is configured such that the mist flowing upstream from the bent part is separated from the gas at the bent part in an attempt to proceed as it is by inertial force. For example, the gas source gas supply path is connected to the upper side, and a vertical cylindrical body having a processing gas supply path connected to the side surface of the lower end is formed.

  Furthermore, the mist separation unit is configured to include a mist reservoir for storing mist, and a discharge port for removing the mist stored in the mist reservoir, and the mist separation unit includes a discharge port for the mist separation unit. You may make it provide the suction path for removing the stored mist from a mist isolation | separation part.

The method of the present invention includes a step of obtaining a vaporized raw material gas by vaporizing a liquid raw material in a vaporizer,
Next, in the mist separation section provided on the downstream side of the vaporizer via the vaporized raw material gas supply path, the processing gas and the mist contained in the vaporized raw material gas are separated, and the separated mist is discharged from the discharge port. Process,
Next, a film forming process is performed on the substrate using the processing gas in a film forming processing unit provided via a processing gas supply path on the downstream side of the mist separating unit;
After the film formation process is performed, with the valve provided in the vicinity of the downstream side of the mist separation section in the processing gas supply path closed, the deposits in the processing gas supply path are removed downstream of the valve. In order to do so, a heated purge gas is supplied, and it is determined whether or not it is time to clean the mist separation unit. When it is determined that it is time to clean, the mist separation unit is passed through the vaporizer. Supplying a cleaning liquid, and discharging the cleaning liquid while the valve is closed .

  According to the present invention, when a liquid raw material is vaporized by a vaporizer to obtain a vaporized raw material gas containing a processing gas and mist, and the processing gas is supplied to the film forming apparatus, a mist separation unit on the downstream side of the vaporizer Since the process gas and the mist are separated at, and the separated mist is discharged, only the process gas passes through the process gas supply path connecting the vaporizer and the film forming apparatus, and the process Since the mist is prevented from adhering to the gas supply path, the generation of particles can be suppressed.

Embodiments of a film forming apparatus according to the present invention will be described below. FIG. 1 is a block diagram showing the main configuration of a film forming apparatus according to the present invention, in which 100 is a film forming apparatus for performing a predetermined film forming process on a substrate, for example, a wafer W, and 200 is the film forming apparatus. A gas supply system for supplying a predetermined processing gas. The film formation processing unit 100 is a low-pressure CVD apparatus in this example. For example, a wafer boat 120 loaded with a large number of wafers W is loaded into a vertical reaction tube 110 which is a reaction vessel (processing vessel). While heating with the heating means 130 provided in the outer side of the reaction tube 110, the inside of the reaction tube 110 is maintained to a predetermined vacuum degree via the vacuum pump 150 which is a vacuum exhaust means, and a reaction tube is supplied from the process gas supply path mentioned later. A predetermined processing gas is introduced into 110 and a predetermined film forming process is performed on the substrate.

  The gas supply system 200 uses, for example, a storage tank 2 for storing a liquid material having a low vapor pressure of, for example, 85.degree. C. and a vapor pressure of 26.67 Pa or less, and the liquid material from the storage tank 2 using a carrier gas. The vaporizer 3 vaporizes, the mist separation part 4 for separating the mist from the vaporized gas (vaporized raw material gas) of the liquid raw material vaporized by the vaporizer 3, and a piping system connecting them.

  The storage tank 2 is connected to the vaporizer 3 by a first supply path (liquid source supply path) 51, and the end of the supply path 51 on the storage tank 2 side is connected to the liquid source in the storage tank 2. The first supply path 51 is provided with a first valve V1, a liquid mass flow controller MC, and a second valve V2 in order from the upstream side (storage tank 2 side). . The storage tank 2 is connected to a pressurized gas supply path 21 having a valve Va. One end of the pressurized gas supply path 21 is above the liquid surface of the liquid raw material in the storage tank 2. It is provided so that it may be located in. The other end side of the pressurized gas supply path 21 is connected to a supply source 22 of pressurized gas, for example, N 2 gas, and when the liquid raw material is supplied from the storage tank 2 to the vaporizer 3, N 2 gas of about 1.0 kg / cm 2 is supplied to pressurize the liquid raw material, and by this pressurization, the liquid raw material is sent from the storage tank 2 to the vaporizer 3 on the downstream side. As the pressurized gas, an inert gas such as helium (He) gas or argon (Ar) gas can be used in addition to the N2 gas.

  The vaporizer 3 is connected to the mist separation unit 4 through a second supply path (vaporized raw material gas supply path) 52, and a carrier gas, for example, N2 gas supply source 24 is connected through a carrier gas supply path 23. Thus, N2 gas as a carrier gas is supplied to the vaporizer 3. In the carrier gas supply path 23, a first mass flow controller M1 and a valve Vb are provided in this order from the carrier gas supply source 24 side, and a carrier gas having a predetermined flow rate is supplied to the vaporizer 3. . Here, as the carrier gas, for example, an inert gas such as He gas or argon gas can be used in addition to the N2 gas.

  Next, an example of the vaporizer 3 will be described with reference to FIG. 2. In the figure, reference numeral 31 denotes a vaporizer main body, and the vaporizer main body 31 is made of a thin disk-shaped metal plate configured to be bent inside. Divided into two by the valve body 32, the lower space is configured as a vaporization chamber 33. In the figure, reference numeral 34 denotes a liquid source introduction path for supplying a liquid source to the vaporizing chamber 33. The first supply path 51 is connected to the other end of the liquid source introduction path 34 and is pumped. The incoming liquid material is discharged from a valve port 34 a formed on one end side of the liquid material introduction path 34.

  In the figure, reference numeral 35 denotes a carrier gas introduction path for supplying a carrier gas to the vaporizing chamber 33. The carrier gas supply path 23 is connected to the other end side of the carrier gas introduction path 35, and the carrier gas Is introduced into the vaporizing chamber 33 through a gas inlet 35a formed on one end side of the carrier gas introducing passage 35. In the figure, reference numeral 36 denotes a gas discharge path for discharging the vaporized raw material gas obtained by vaporizing the liquid source, and the other end side of the discharge path 36 is connected to the second supply path 52.

  The valve body 32 functions to control the flow rate by opening and closing the valve port 34a. For example, the valve body 32 is pressed by the tip of the drive shaft 38 by electromagnetic actuator means 37. The opening and closing of the valve port 34a and the valve opening degree can be controlled. Further, the entire vaporizer 3 is heated to a predetermined temperature by a heater (not shown), and the liquid raw material is easily vaporized by heating, and the vaporized raw material gas in a vaporized state is prevented from being reliquefied.

  In the vaporizer 3, the inside of the vaporizing chamber 33 is in a reduced pressure atmosphere by evacuation on the film forming apparatus (reduced pressure CVD apparatus) 100 side, and the pumped liquid material flows out from the valve port 34a and is reduced in pressure. Mist vaporization and vaporization occur simultaneously due to adiabatic expansion in the vaporization chamber 33 of the atmosphere, and vaporized raw material gas is generated. This vaporized raw material gas is carried by the carrier gas and passes through the gas discharge path 36 and the second supply path 52. Are discharged and conveyed to the mist separation unit 4 in the next process. Therefore, in this vaporizer 3, even a liquid raw material having a low vapor pressure and a low decomposition temperature is sufficiently misted and vaporized to obtain a vaporized raw material gas, which is smoothly transferred to the next process by the carrier gas. The

  The mist separation unit 4 is connected to a low-pressure CVD apparatus that forms the film formation processing unit 100 by a third supply path (processing gas supply path) 53 having a third valve V3. Here, the piping system such as the first supply path 51, the second supply path 52, and the third supply path 53 is constituted by a so-called 1/8 inch stainless steel pipe having an inner diameter of 1 mm and an outer diameter of 3 mm, for example. The second supply path 52 is set to a length of, for example, about 3 cm in order to introduce the vaporized raw material gas from the vaporizer 3 into the mist separation unit 4 in a stable state so as not to be reliquefied. Has been.

  The mist separating section 4 is arranged to extend in the vertical direction, and includes a pipe 41 made of a vertical cylindrical body having an inner diameter larger than that of the first supply path 51 and the second supply path 52. The second supply path 52 is connected to the upper end of the path 41, and the third supply path 53 is connected to the side surface of the lower end of the pipe 41 at an angle of approximately 90 degrees with respect to the mist separation section 4. Has been. As a result, a vent path extending downward and then bent into a substantially L-shape is formed, and a mist discharge path 42 is connected to the bottom, and a connection region between the mist discharge path 42 and the pipe 41 is a mist. It becomes the discharge port 43. The mist discharge passage 42 is provided with a mist discharge valve Vm for discharging mist in the vicinity of the bottom of the pipe 41, whereby the mist discharge port 43 is opened and closed. An exhaust pump 44 serving as an exhaust means is connected to the other end side of the mist discharge path 42, and the mist discharge path 42 and the exhaust pump 44 constitute a suction path.

  The pipe 41 constituting the mist separating section 4 is made of a so-called 3/8 inch stainless steel pipe having an inner diameter of 8 mm and an outer diameter of 10 mm, for example, and the length of the pipe is set to about 120 mm, for example. Yes. The mist discharge passage 42 is formed of a so-called 3/8 inch stainless steel pipe similar to the piping system of the first to third supply passages 51 to 53, for example. For this reason, the pipe 41 has a larger inner diameter than the second supply path 52, the third supply path 53, and the discharge path 42 connected to the mist separator 4. The reason why the inner diameter of the pipe 41 of the mist separation unit 4 is made larger than that of the piping system is that the gas flow rate is slow and the surface area of the heating pipe is large, so that the mist is easily vaporized. Further, since the discharge path 42 is connected to the pipe line 41 in the direction of gravity (vertical direction), a wall surface part 45 with which the vaporized raw material gas collides is formed at the bottom part of the pipe line 41. And the mist discharge valve Vm form a mist reservoir 46.

  Further, the third supply path 53 connected to the pipe line 41 is in a gravitational direction (with respect to the pipe line 41) at a position not in contact with the mist M so that the mist M stored in the mist reservoir 46 is not drawn. It is connected at an angle of approximately 90 degrees to the pipe 41 in this direction (in the vertical direction), and in this example, is connected so as to form a bent gas flow path.

  The mist separation unit 4 is provided with cleaning liquid supply means 6 for supplying a cleaning liquid to the pipe 41 in order to clean the inside of the pipe 41 including the mist reservoir 46. The cleaning liquid supply means 6 is connected to the upper portion of the pipe 41 and includes a cleaning liquid supply path 61 having a cleaning liquid supply valve Vc, and a cleaning liquid tank 62 connected to the cleaning liquid supply path 61 for storing the cleaning liquid. It is configured. As the cleaning liquid, for example, a solvent for dissolving a liquid raw material or a solidified liquid raw material, for example, an alcohol-based chemical liquid such as ethanol or hexane is used. The cleaning liquid supplied from the cleaning liquid tank 62 through the cleaning liquid supply path 61 into the pipe 41 is discharged through the mist discharge path 42 by opening the mist discharge valve Vm.

  In the third supply path 53, a third valve V3 is provided in the vicinity of the mist separation unit 4, and a second mass flow controller M2 is provided to form a vaporized raw material gas in a state in which re-liquefaction is prevented. In order to guide to the processing unit 100, the distance from the third valve V3 to the film forming processing unit 100 is set to be as short as about 20 cm, for example. In practice, the upstream side of the third valve V3 of the third supply path 53 is very short, and the third valve V3 is connected to the outlet of the mist separation unit 4. If this is not done, the upstream side of the third valve V3 becomes a dead zone, and mist accumulates in that region.

  Further, in the region from the downstream side of the valve V3 of the third supply path 53 to the film forming processing unit 100, a heating means such as a tape heater is provided around the pipe in order to heat the vaporized raw material gas and prevent reliquefaction. As a result, the vaporized raw material gas is supplied to the film forming unit 100 while being heated to about 120 ° C., for example.

  Further, this film forming apparatus is provided with a purge gas supply means 7 as shown in FIG. This purge gas supply means includes a purge gas supply path 71 having one end connected to the upstream side of the valve Vb of the carrier gas supply path 23 and the other end connected to the downstream side of the third valve V3 of the third supply path 53. The purge gas supply path 71 is provided with a third mass flow controller M3, a heating unit 72, and a valve Vd in order from the upstream side.

  In the heating unit 72, for example, a heater made of a resistance heating wire is wound around the outside of the tubular body, and the inside of the tubular body is filled with particles made of ceramics, for example, so that a purge gas flows through the inside of the tubular body. It is configured. The particles are heated to a predetermined temperature by a heater, and the purge gas is heated to a predetermined temperature by passing the purge gas therethrough. Thus, in the region of about 150 cm upstream of the valve Vd, the purge gas is heated to, for example, about 120 ° C. The heated purge gas is ventilated through the piping, and the film formation processing unit 100 is evacuated. Exhausted.

  Further, in the gas supply system 200, a cleaning branch path 63 having a valve Vf, one end side of which is connected to the cleaning liquid supply path 61 and the other end side thereof is connected between the valve Vb of the carrier gas supply path 23 and the vaporizer 3. One end side is connected to the downstream side of the first valve V1 of the first supply path 51 and upstream of the liquid mass flow controller MC, and the other end side is connected to the downstream side of the valve Vm of the mist discharge path 42. A branch path 54 having a valve Ve may be provided.

  A film forming method performed in such a film forming apparatus will be described with reference to FIG. 3. First, a mist discharge valve Vm in the mist discharge path 42, a valve Vc in the cleaning liquid supply path 61, a valve Vd in the purge gas supply path 71, The valve Ve of the branch path 54 is closed, the first valve V1 and the second valve V2 of the first supply path 51, the third valve V3 of the third supply path 53, the valve Va of the pressurized gas supply path 21, and the carrier gas. The valve Vb of the supply path 23 is opened to perform the film forming process (Step S1).

  That is, in the gas supply system 200, N2 gas, which is a pressurized gas, is supplied into the storage tank 2 via the pressurized gas supply path 21, and the liquid raw material, for example, HEAD in the storage tank 2 is supplied to the first tank by this pressurization. Via the supply path 51, it is pumped to the vaporizer 3 with the flow rate adjusted by the liquid mass flow controller MC. At this time, the temperature of the liquid raw material flowing through the first supply path 51 is set to about 40 ° C., for example.

  On the other hand, N2 gas, which is a carrier gas, is supplied from the carrier gas supply path 23 to the vaporizer 3 with the flow rate adjusted by the first mass flow controller M1. Here, since the inside of the reaction tube 110 is evacuated to a predetermined degree of vacuum in the film forming unit 100, the gas in the gas supply system 200 is vented downstream by opening each valve provided in the supply path. I will do it. Thus, the liquid source and the carrier gas are introduced into the vaporizer 3 at a flow rate ratio of, for example, HEAD: N 2 = 0.1 sccm: 100 sccm, and the liquid source is vaporized as described above to obtain a vaporized source gas. . At this time, the temperature of the vaporization source gas in the vaporization chamber 33 is set to about 100 ° C., for example. As described above, the vaporizer 3 is sufficiently misted even in the case of a liquid material having a low vapor pressure and a low decomposition temperature of 85.degree. And vaporization are performed to obtain a vaporized raw material gas containing a processing gas component and mist.

  The vaporized raw material gas is conveyed to the mist separation unit 4 via the second supply path 52 by the carrier gas. Since the mist separation unit 4 is in a state in which the mist discharge valve Vm is closed and the mist discharge port 43 is closed, when the vaporized raw material gas containing the processing gas component and mist is introduced into the mist separation unit 4, the mist separation unit 4 When venting the bent air passage inside, the processing gas is passed through the bent air passage as it is by the inertial force, but the mist flows from the upstream side of the bent part and tries to proceed as it is by the inertial force. It falls by gravity at the bent part and is separated from the gas.

  Thus, the mist in the vaporized raw material gas falls in the pipe 41 and accumulates in the mist reservoir 46, while the process gas is flowed by the second mass flow controller M2 via the bent third supply passage 53. The film is conveyed to the film formation processing unit 100 in an adjusted state. Further, mist may be generated when the vaporized raw material gas collides with the inner wall of the wall surface portion 45 of the pipe line 41 forming the mist reservoir portion 46. In this case, the mist is also stored in the mist reservoir portion 46. Here, the temperature of the vaporized raw material gas in the mist separation unit 4 is set to about 105 ° C. At this time, since the third supply path 53 is heated as described above, re-liquefaction of the processing gas component of the vaporized raw material gas is prevented.

  In the film forming unit 100, first, a predetermined number of wafers W are mounted on the holder 120, and are loaded into the reaction tube 110 maintained at a predetermined temperature, for example, and the reaction tube 110 is evacuated to a predetermined degree of vacuum. . Then, after stabilizing the inside of the reaction tube 110 at a predetermined temperature and a predetermined pressure, a processing gas obtained by vaporizing HEAD as a processing gas and NH 3 gas (not shown) are supplied from the third supply path 53. Then, a film forming process for forming a silicon nitride film on the wafer W is performed.

  After completing the film forming process in this way, a purge process is performed downstream of the third valve V3 in the third supply path 53 (step S2). That is, the valves V1 and V2 of the first supply path 51, the valve V3 of the third supply path 53, the valve Va of the pressurized gas supply path 21, and the valve Vb of the carrier gas supply path 23 are closed, and the valve of the purge gas supply path 71 is closed. Vd is opened, the reaction tube 110 is evacuated by the vacuum pump 150, and the purge gas supply path 71 and the third supply path 53 are heated to purge the carrier gas supply source 24 with N2 gas, which is purge gas, from the purge gas supply path 71. To be supplied to the third supply path 53.

  As a result, N2 gas heated to a predetermined temperature, for example, 120 [deg.] C., flows to the downstream side of the valve V3 of the third supply passage 53, and this heated N2 gas is applied to the inner wall surface of the third supply passage 53. Residues of the processing gas adhering and adhering matters such as solid components in which the processing gas has changed are pushed out to the film forming unit 100 and removed. Here, since the valve V3 is provided in the vicinity of the outlet of the mist separation section 4, the supply path 53 on the downstream side of the mist separation section 4 is cleaned by the purge with this N2 gas. For example, this purge process may be performed every time the film forming process is performed in the film forming process unit 100, or may be performed periodically every time the film forming process is performed a predetermined number of times.

  After the third supply path 53 is purged with N2 gas in this way, it is determined whether or not it is time to supply the cleaning liquid to the mist separation unit 4 and perform cleaning (step S3), and the timing when cleaning is not performed. If so, the process proceeds to step S4. If it is time to perform the process, the process proceeds to step S6. Here, the cleaning of the mist separation unit 4 is performed periodically, for example, after the film formation process in the film formation processing unit 100 is performed a predetermined number of times.

  If the process proceeds to step S4, it is further determined whether or not it is time to purge the mist separation unit 4, and if it is time to purge, the process proceeds to step S5, and if it is time not to purge, step S1. Return to. When the process proceeds to step S5, the valve Vd is closed, the valves Vb and Vm are opened, and the exhaust pump 44 is operated. As a result, N2 gas, which is a purge gas, is supplied from the carrier gas supply source 24 to the mist separation unit 4 via the carrier gas supply path 23 and the vaporizer 3 and is discharged via the mist discharge path 42.

  Thus, by purging N2 gas in the vaporizer 3 and the mist separation unit 4, the liquid raw material remaining in the vaporizer 3 and the mist separation unit 4 can be completely removed, and the process reproducibility is improved. It is possible to improve and further suppress the generation of particles. For example, the purge process may be performed every time the film forming process is performed in the film forming process unit 100, or may be performed periodically every time the film forming process is performed a predetermined number of times.

  On the other hand, when the routine proceeds to step S6, the valve Vd is closed, the valves Vc and Vm are opened, and the exhaust pump 44 is operated. As a result, the mist stored in the mist reservoir 46 is discharged to the outside of the apparatus via the mist discharge path 42, and the cleaning liquid is supplied to the mist separation section 4 from the cleaning liquid supply path 61. Here, since the cleaning liquid is a solvent that dissolves the liquid raw material and the solidified liquid raw material, the mist adhering to the inner wall of the pipe 41 of the mist separation unit 4 is washed away, and the mist is temporarily liquefied. Even if the part is transformed into a solid component, it is dissolved and removed by the cleaning liquid.

  Further, in the cleaning process, the second valve V2, the valve Ve, and the valve Vf are opened and the exhaust pump 44 is operated, so that the cleaning liquid is supplied to the cleaning branch path 63, the vaporizer 3, the liquid mass flow controller MC, the first supply path 51, You may make it flow through the branch path 54 and the mist discharge path 42, and remove deposits, such as a liquid raw material adhering to these inner walls, and the solidification component of a liquid raw material.

  In such a film forming apparatus, since the mist separation unit 4 is provided on the downstream side of the vaporizer 3, the mist can be separated from the vaporized raw material gas, and in the third supply path 53 on the downstream side of the mist separation unit 4. The adhesion of mist is prevented. As a result, re-liquefaction of mist can be prevented, and as a result, generation of particles is reduced.

  At this time, the mist separating section 4 is constituted by a pipe 41 extending in the vertical direction, and a third supply path 53 is connected to the pipe 41 so as to form a substantially L shape. The mist is separated from the gas by gravity at the bent portion by forming a flow path for the bent processing gas and providing the mist reservoir 46 in the direction of gravity, so that the mist can be reliably separated with a simple separation structure. It can be carried out. Further, since the structure is simple, the process can be stably performed for a long period of time, and a stable process gas can be supplied. Furthermore, there is an advantage that operation and maintenance are easy.

  Furthermore, the temperature control of each process in the storage tank 2, the vaporizer 3, the mist separation part 4, and the 3rd supply path 53 is carried out from the upstream side toward the downstream side, and a liquid raw material (vaporization raw material gas, processing gas) Therefore, the liquid raw material can be vaporized more reliably. At this time, the third supply path 53 is heated by a heater, and the processing gas flowing through the third supply path 53 is heated to, for example, 120 ° C., so that it is supplied to the film forming processing unit 100 in a state in which reliquefaction is suppressed, Generation of particles can be prevented.

  Furthermore, for example, every time a film forming process is performed or a predetermined number of film forming processes are performed, the purge gas is vented to the downstream side of the valve V3 of the third supply path 53. The processing gas remaining on the downstream side of the valve V3 is pushed out by the purge gas and removed. By venting the heated purge gas here, not only the processing gas but also the deposits with altered processing gas can be removed. As a result, when the next film forming process is performed, since the deposit is not present on the downstream side of the valve V3 of the third supply path 53, the generation of particles can be further suppressed, and the process can be performed. Reproducibility can be improved. Moreover, the downstream side of the valve V3 of the supply path 53 can be quickly dried by ventilating the heated purge gas, and the reproducibility can be improved.

  At this time, since the purge gas is supplied through a supply path different from the supply path from the vaporizer 3, the uniformity and reproducibility of the film thickness can be improved. When the N2 gas is purged in the supply path from the vaporizer 3, if the liquid raw material remains in the vaporizer 3 or the mist separation section 4, the liquid raw material is supplied to the third supply by purging the N2 gas. In some cases, it may adhere to the channel 53 and is supplied as a processing gas during the next run, which may deteriorate the uniformity of the film thickness, deteriorate the reproducibility, or cause generation of particles. is there.

  Furthermore, for example, every time a film forming process is performed or every time a predetermined number of film forming processes are performed, the purge gas is supplied to the vaporizer 3 and the mist separating unit 4 via the carrier gas supply pipe 23 in the supply path connecting them. By aeration, the liquid raw material remaining inside these can be removed. As a result, when the next lot is processed, the inside thereof is always in a dry state without any deposits, so the reproducibility of the processing can be improved. In this case, since the purge gas is supplied into the vaporizer 3 and the mist separation unit 4 through a supply path different from the supply path to the film formation processing unit 100, the purge area is the vaporizer 3 and the mist separation unit 4. These purges can be efficiently performed, and the deposits in these regions can be completely removed in a short time.

  Furthermore, after the mist is discharged from the mist separating section 4 by suction at a predetermined timing, the mist separating section 4 is washed, so that it adheres to the inside of the pipe 41 and the area near the mist collecting section 46 even after the mist is discharged. When the mist or the attached mist is changed and the next lot is processed, the inside of the mist separation unit 4 is always in a state in which the attached matter does not exist, so that generation of particles is further suppressed. And reproducibility of processing can be improved.

  Next, another example of the mist separation unit 4 will be described. In the example shown in FIG. 4, the second supply path 52 and the third supply path 53 are connected to the upper side of the pipe 41, and the mist discharge path 42 is connected to the bottom of the pipe 41. Also in the example, the mist reservoir 46 is formed by the wall surface 45 at the bottom of the pipe 41 and the mist discharge valve Vm. In such a configuration, the processing gas component in the vaporized raw material gas is ventilated downstream via the third supply path 53 by the bent vent path formed in the pipe line 41, and the mist is While trying to advance as it is by the inertial force while ventilating in the air passage, it is separated from the gas by gravity at the bent portion and falls to the mist reservoir 46, so that the processing gas component and the mist can be separated and processed Only the gas component can be supplied to the film forming unit 100.

  Further, the example shown in FIG. 5 is an example in which the pipe line 41 constituting the mist separating unit 4 is arranged obliquely with respect to the direction of gravity, and the second supply path 52 is connected to the upper side of the pipe line 41, A mist discharge path 42 having a mist discharge valve Vm is connected to the lower side of the pipe line 41 in the direction of gravity, and a mist reservoir 46 is constituted by the vicinity of the connection region of the discharge path 42 and the mist discharge valve Vm. Further, a third supply path 53 is connected to the upper side of the pipe line 41 in the direction of gravity, thereby forming a bent ventilation path for the process gas to vent.

  Even in such a configuration, the process gas component of the vaporized raw material gas is vented downstream by the bent air passage, and the mist is trying to advance by the inertial force while ventilating in the air passage. The gas is separated from the gas by gravity and falls to the mist reservoir 46, whereby the processing gas component and the mist can be separated, and only the processing gas component can be supplied to the film forming processing unit 100.

  Furthermore, the configuration shown in FIG. 6 connects the second supply path 52 and the mist discharge path 42 provided with the mist discharge valve Vm to the bottom of the pipe 41, and the third supply to the upper side of the pipe 41. This is an example in which a spiral member 81 constituting a spiral ventilation path is provided in the pipe line 41 by connecting the path 53. In such a mist separation unit 4, when the vaporized raw material gas is supplied into the pipe 41, this vaporized raw material gas spirals along the spiral member 81. At this time, the mist is generated by centrifugal force. It adheres to the surface of the spiral member 81. The mist adhering to the spiral member 81 falls along the spiral member 81 by gravity, and is stored in a mist reservoir 46 formed in the vicinity of the bottom of the conduit 41 and the mist discharge valve Vm. It is discharged at the timing.

Next, examples performed to confirm the effects of the present invention will be described.
(Example 1)
Using the above-described film forming apparatus, HEAD is used as the liquid source, N2 gas is used as the carrier gas, NH3 gas is introduced into the film forming unit 100 as another processing gas, and the temperature in the reaction vessel 110 is set to 350 ° C. to 500 ° C. The reaction vessel 110 is adjusted to 26.6 Pa to 133 Pa (0.2 Torr to 1 Torr), a silicon nitride film is formed on the wafer W, the number of particles having a particle size of 0.13 μm or more in the film, and The film thickness was measured for each run (Run 1 to Run 17). A maximum of 97 particles were counted. Here, between each run, the purge process of the 3rd supply path 53 by the heated N2 gas and the purge process of the vaporizer 3 and the mist separation part 4 were performed by the N2 gas.

The result is shown in FIG. In the figure, the left vertical axis represents the number of particles, and the right vertical axis represents the film thickness. The horizontal axis shows runs 1 to 17, and there are three data for each run. The left side is data on the upper region of the wafer boat 120, the center is data on the central region of the wafer boat 120, and the right side is data. Data on the lower area of the wafer boat 120 is shown. In the figure, the solid line indicates the film thickness on the wafer W at each run, and the dotted line indicates the film thickness of the thin film adhering to the reaction vessel 110 and the wafer boat 120, respectively.
(Comparative Example 1)
In a film forming apparatus using the conventional vaporization system shown in FIG. 8, HEAD is used as a liquid source, N 2 gas is used as a carrier gas, and NH 3 gas is introduced into the film forming unit 100 as another processing gas, A silicon nitride film is formed on the wafer W under the same conditions as in Example 1, and the number of particles having a particle size of 0.13 μm or more and the film thickness in the film are determined for each run (Run 1 to Run 21). It was measured. The result is shown in FIG.

  According to the results of Example 1 and Comparative Example 1, in the film forming apparatus provided with the gas supply system of the present invention, the number of particles having a particle size of 0.13 μm or more is 100 or less, and the conventional vaporization system is used. It was recognized that the number of particles decreased dramatically.

  Further, the film thickness for each run is substantially constant, and it is recognized that the variation in Example 1 is smaller than that in Comparative Example 1, and the gas supply system of the present invention improves the reproducibility of the process. It was confirmed that an almost constant film thickness was ensured for each run and stable treatment could be performed.

  Further, in Example 1 described above, the in-plane uniformity of the film thicknesses of the run 5, run 6, and run 7 was measured, and the values were almost the same for each run. Reproducibility was recognized for each run.

  Further, in the above-described film forming apparatus, HEAD is used as the liquid source, N 2 gas is used as the carrier gas, and the vaporizer 3 is supplied at a flow ratio of HEAD: N 2 = 0.1 sccm: 100 sccm and supplied to the film forming unit 100. The processing gas flow rate was observed over 100 minutes, but it was found that the processing gas flow rate was stable at 0.1 sccm, and the processing gas obtained by vaporizing the liquid raw material by the gas supply system of the present invention. It was confirmed that can be supplied to the film forming unit 100 at a stable flow rate.

  In the present invention, as the low vapor pressure liquid raw material, in addition to HEAD, for example, Ta (OC2H5) 5 having a vapor pressure at 140 ° C. of 40 Pa or less, TDEAH (HF {N (C2H5)} 4) or the like can be used, and in addition to the process of forming a silicon nitride film using the process gas obtained by vaporizing HEAD as the process gas and the NH3 gas, Ta (OC2H5 ) It can be applied to a process of forming a Ta2O5 film using a processing gas obtained by vaporizing 5 and an O3 gas. The mist separation unit 4 may be configured to include a heating unit for heating the pipe line 41. In this case, the mist separation unit 4 suppresses reliquefaction of the vaporized raw material gas, promotes mist vaporization, and reduces the amount of mist. It is possible to reduce and increase the amount of processing gas. Further, as the film forming unit, a single wafer type film forming apparatus may be used in addition to the batch type low pressure CVD apparatus.

It is a longitudinal section showing an example of a film deposition system concerning the present invention. It is sectional drawing which shows an example of the vaporizer | carburetor and mist separation part which are used for the said film-forming apparatus. It is a flowchart which shows the film-forming method performed with the said film-forming apparatus. It is sectional drawing which shows the other example of the said mist isolation | separation part. It is sectional drawing which shows the other example of the said mist isolation | separation part. It is sectional drawing which shows the other example of the said mist isolation | separation part. It is a characteristic view which shows the result of the Example and comparative example which were performed in order to confirm the effect of this invention. It is a piping diagram which shows the conventional vaporization system.

Explanation of symbols

W Semiconductor wafer 100 Deposition apparatus 110 Reaction tube 120 Wafer boat 130 Heating means 150 Vacuum pump 200 Gas supply system 2 Reservoir 21 Pressurized gas supply path 3 Vaporizer 4 Mist separation part 42 Mist discharge path 44 Exhaust pump 51 First Supply path (liquid raw material supply path)
52 Second supply path (vaporization source gas supply path)
53 3rd supply path (process gas supply path)
6 Cleaning liquid supply means 61 Cleaning liquid supply path 7 Purge gas supply means 71 Purge gas supply paths V1 to V3 Valve Vm Mist discharge valve

Claims (9)

A storage tank for storing liquid raw materials;
A vaporizer connected to the downstream side of the storage tank via a liquid raw material supply path to vaporize the liquid raw material to obtain a vaporized raw material gas,
A mist separation unit provided on the downstream side of the vaporizer via a vaporized raw material gas supply path, for separating the processing gas and mist contained in the vaporized raw material gas, and discharging the separated mist;
A film formation processing unit that is provided on the downstream side of the mist separation unit via a processing gas supply path and performs a film formation process on the substrate using the processing gas sent from the mist separation unit;
A valve provided near the downstream side of the mist separation section in the processing gas supply path;
A purge gas supply path that is connected to the downstream side of the valve in the process gas supply path and supplies heated purge gas to remove deposits in the process gas supply path;
A cleaning liquid supply path for supplying a cleaning liquid to the mist separation unit via the vaporizer,
After the film forming process is performed, the purge gas heated from the purge gas supply path is supplied into the process gas supply path with the valve closed, and it is determined whether or not it is time to clean the mist separation unit. When the cleaning timing is determined, the cleaning liquid is supplied from the cleaning liquid supply path to the mist separation unit, and the cleaning liquid is discharged while the valve is closed. Membrane device. As a result of determining whether or not it is time to clean the mist separation unit, when it is determined that it is not time to clean, it is determined whether or not it is time to purge the mist separation unit, and it is determined that it is time to purge. The purge gas is supplied from the gas supply path connected to the vaporizer to the mist separator when the gas is supplied, and the purge gas is discharged while the valve is closed. Deposition device. The mist separation part is configured by bending the air passage, and configured so that the mist flowing upstream from the bent part is separated from the gas at the bent part in an attempt to proceed as it is by inertia force. The film forming apparatus according to claim 1 or 2, characterized in that: The mist separator section, the claims together with the vaporized raw material gas supply passage on the upper side is connected, characterized in that the side to the processing gas supply path of the lower end portion is constituted by the cylindrical portion of the connected vertical 3. The film forming apparatus according to 3 . The mist separation unit includes a mist reservoir for storing mist,
The film forming apparatus according to claim 1 , further comprising: a discharge port that removes the mist stored in the mist reservoir. 6. The film forming apparatus according to claim 1, wherein a suction path for removing the mist stored in the mist collecting part from the mist separating part is provided at the discharge port of the mist separating part. .   6. The film forming apparatus according to claim 1, wherein the purge gas supply path is provided with heating means for supplying purge gas. A step of vaporizing a liquid raw material in a vaporizer to obtain a vaporized raw material gas;
Next, in the mist separation section provided on the downstream side of the vaporizer via the vaporized raw material gas supply path, the processing gas and the mist contained in the vaporized raw material gas are separated, and the separated mist is discharged from the discharge port. Process,
Next, a film forming process is performed on the substrate using the processing gas in a film forming processing unit provided via a processing gas supply path on the downstream side of the mist separating unit;
After the film formation process is performed, with the valve provided in the vicinity of the downstream side of the mist separation section in the processing gas supply path closed, the deposits in the processing gas supply path are removed downstream of the valve. In order to do so, a heated purge gas is supplied, and it is determined whether or not it is time to clean the mist separation unit. When it is determined that it is time to clean, the mist separation unit is passed through the vaporizer. Supplying a cleaning liquid, and discharging the cleaning liquid while the valve is closed . As a result of determining whether or not it is time to wash the mist separation unit, when it is determined that it is not time to wash, determining whether or not it is time to purge the mist separation unit;
9. The method of claim 8 , further comprising: supplying a purge gas to the mist separation unit when the purge timing is determined in this step, and discharging the purge gas while the valve is closed. The film-forming method of description.

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