Gas supply system and gas supply method

Abstract

To provide a system for supplying gas, capable of stably and continuously supplying vaporized gas.SOLUTION: A system 100 for supplying gas includes: a first vaporization supply device 10A including a first vaporization part 12A, a first control valve 14A, a first diaphragm part 24A and a first pressure sensor 26A and for supplying the gas subjected to flow rate control; a second vaporization supply device 10B including a second vaporization part 12B, a second control valve 14B, a second diaphragm part 24B and a second pressure sensor 26B and for supplying the gas subjected to flow rate control; a control device 30; and a common flow passage 8 on the downstream side. The first vaporization supply device 10A alternately supplies the gas controlled into a first flow rate and a second flow rate smaller than the first flow rate to the common flow passage; and the second vaporization supply device 10B alternately supplies the gas controlled into a third flow rate and a fourth flow rate smaller than the third flow rate to the common flow passage and passes the gas at a fixed control flow rate to the common flow passage 8.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gas supply system and a gas supply method, and more particularly to a gas supply system and a gas supply method capable of continuously and stably supplying a gas generated using a vaporization supply device.

Background Art

[0002] In semiconductor manufacturing equipment, chemical plants, etc., various process gases such as raw material gases and etching gases are supplied to a process chamber. As a device for controlling the flow rate of the supplied gas, a mass flow controller (thermal mass flow controller) and a pressure type flow control device are known.

[0003] The pressure type flow control device can control the mass flow rate of various fluids with high precision by a relatively simple configuration combining a control valve and a throttle portion (for example, an orifice plate or a critical nozzle) on the downstream side thereof, and thus is widely used (for example, Patent Document 1). The pressure type flow control device has excellent flow control performance in that stable flow control can be performed even when the supply pressure on the primary side of the control valve fluctuates greatly.

[0004] In recent years, in the manufacture of semiconductor devices, HCDS (Si2Cl6: Hexachlorodisilane) gas has been used as a material for forming insulating films such as silicon nitride films (SiN x films) and silicon oxide films (SiO2 films). HCDS is a material that can be decomposed and reacted at low temperatures, enabling a low-temperature semiconductor manufacturing process at about 450 to 600°C.

[0005] However, since HCDS is a liquid (boiling point: about 144°C) at room temperature, liquid HCDS may be vaporized in front of the process chamber and then supplied. Patent Document 2 discloses a vaporization supply device applicable to HCDS and organometallic materials (for example, TEOS: tetraethyl orthosilicate).

[0006] In the above vaporization supply device, the liquid raw materials such as HCDS and organometals are pressure-fed from the raw material tank to the vaporization section and heated by a heater in the vaporization section. The raw material gas generated in the vaporization section is supplied to the process chamber after its flow rate is controlled using the control valve on the downstream side.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, when generating gas from a liquid raw material using a vaporizer and continuously supplying it, there was a case where the supply pressure on the upstream side of the pressure type flow control device decreased due to the gas consumption exceeding the gas generation amount in the vaporization section. In this case, it was difficult to appropriately control the flow rate and continuously flow the gas at a desired flow rate.

[0009] The present invention has been made to solve the above problems, and its main object is to provide a gas supply system and a gas supply method capable of stably supplying raw material gases such as HCDS gas and organometal gas generated using a vaporization supply device.

Means for Solving the Problems

[0010] The gas supply system according to an embodiment of the present invention includes a first vaporization unit having a raw material stored therein and a heater, a first control valve provided in a downstream flow path of the first vaporization unit, a first throttle portion provided in a downstream flow path of the first control valve, and a first pressure sensor that measures a gas pressure between the first control valve and the first throttle portion, and a first vaporization supply device that supplies gas with a controlled flow rate, a second vaporization unit having a raw material stored therein and a heater, a second control valve provided in a downstream flow path of the second vaporization unit, a second throttle portion provided in a downstream flow path of the second control valve, and a second pressure sensor that measures a gas pressure between the second control valve and the second throttle portion, and a second vaporization supply device that supplies gas with a controlled flow rate, a control device connected to the first vaporization supply device and the second vaporization supply device, and a common flow path that communicates with a downstream flow path of the first vaporization supply device and a downstream flow path of the second vaporization supply device, respectively. The first vaporization supply device alternately supplies gas controlled to a first flow rate and a second flow rate including zero, which is smaller than the first flow rate, to the common flow path. Further, the second vaporization supply device alternately supplies gas controlled to a third flow rate and a fourth flow rate including zero, which is smaller than the third flow rate, to the common flow path. The common flow path is configured to allow gas to flow at a constant control flow rate.

[0011] The above gas supply system is typically configured such that the main gas supply path is switched by temporally shifting a period in which gas flows at the first flow rate through the first control valve of the first vaporization supply device and a period in which gas flows at the third flow rate through the second control valve of the second vaporization supply device.

[0012] In an embodiment, the second flow rate and the fourth flow rate are non-zero flow rates, and the first control valve and the second control valve are maintained in an open state so as not to be completely closed.

[0013] In one embodiment, during the period when the first vaporization supply device supplies gas to the common flow path at the first flow rate, the second vaporization supply device supplies gas to the common flow path at the fourth flow rate, and during the period when the second vaporization supply device supplies gas to the common flow path at the third flow rate, the first vaporization supply device is configured to supply gas to the common flow path at the second flow rate.

[0014] In one embodiment, the total flow rate of the first flow rate and the fourth flow rate is the same as the total flow rate of the second flow rate and the third flow rate.

[0015] In one embodiment, the first flow rate and the third flow rate are the same flow rate, the second flow rate and the fourth flow rate are the same flow rate, and the period in which the first vaporization supply device supplies gas to the common flow path at the first flow rate and the period in which the second vaporization supply device supplies gas to the common flow path at the third flow rate are repeatedly alternated a plurality of times.

[0016] In one embodiment, there is a overlapping period between the period in which the first vaporization supply device supplies gas to the common flow path at the first flow rate and the period in which the second vaporization supply device supplies gas to the common flow path at the third flow rate.

[0017] In one embodiment, the first vaporization section and the second vaporization section have the same shape and the same volume, and the length of the period in which the first vaporization supply device supplies gas to the common flow path at the first flow rate is the same as the length of the period in which the second vaporization supply device supplies gas to the common flow path at the third flow rate.

[0018] In one embodiment, the first vaporization supply device includes a first supply pressure sensor that measures the gas pressure upstream of the first control valve, and the second vaporization supply device includes a second supply pressure sensor that measures the gas pressure upstream of the second control valve. The gas flows at the first flow rate through the first control valve only when the output of the first supply pressure sensor is equal to or greater than a predetermined value, and the gas flows at the third flow rate through the second control valve only when the output of the second supply pressure sensor is equal to or greater than a predetermined value.

[0019] In one embodiment, the apparatus further includes a third vaporization section that stores a raw material and has a heater, a third control valve provided in a downstream flow path of the third vaporization section, a third throttle section provided in a downstream flow path of the third control valve, and a third pressure sensor that measures a gas pressure between the third control valve and the third throttle section. The apparatus further includes a third vaporization supply device that supplies gas with a controlled flow rate. The third vaporization supply device is connected to the control device and its downstream flow path communicates with the common flow path. The third vaporization supply device is configured to alternately supply gas controlled to a fifth flow rate and a sixth flow rate including zero, which is smaller than the fifth flow rate, to the common flow path, so that the gas flows through the common flow path at a constant control flow rate.

[0020] The gas supply method according to an embodiment of the present invention includes a first vaporization unit in which a raw material is stored and which has a heater, a first control valve provided in a downstream flow path of the first vaporization unit, a first throttle portion provided in a downstream flow path of the first control valve, and a first pressure sensor that measures a gas pressure between the first control valve and the first throttle portion; a first vaporization supply device; a second vaporization unit in which a raw material is stored and which has a heater, a second control valve provided in a downstream flow path of the second vaporization unit, a second throttle portion provided in a downstream flow path of the second control valve, and a second pressure sensor that measures a gas pressure between the second control valve and the second throttle portion; a second vaporization supply device; a control device connected to the first vaporization supply device and the second vaporization supply device; and a gas supply system including a common flow path in which a downstream flow path of the first vaporization supply device and a downstream flow path of the second vaporization supply device communicate with each other. The gas supply method is for flowing gas through the common flow path at a constant control flow rate, and includes: step (a) of flowing gas from the first vaporization supply device into the common flow path at a first flow rate and flowing gas from the second vaporization supply device into the common flow path at a fourth flow rate smaller than the first flow rate; and step (b) of, after step (a), flowing gas from the first vaporization supply device into the common flow path at a second flow rate smaller than the first flow rate and corresponding to the fourth flow rate and flowing gas from the second vaporization supply device into the common flow path at a third flow rate corresponding to the first flow rate. Step (a) and step (b) are repeatedly executed a plurality of times.

Effect of the Invention

[0021] According to the gas supply system and the gas supply method according to an embodiment of the present invention, the gas generated using the vaporization supply device can be stably supplied at a desired flow rate.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiment for Carrying Out the Invention

[0023] The applicant of the present application disclosed in Japanese Patent Application No. 2020 - 183375 a configuration capable of continuously supplying gas at a relatively large flow rate to the downstream side by temporally shifting the gases generated by vaporization supply devices provided in parallel on the upstream side with respect to a common flow path connected to a process chamber and sequentially supplying them from respective paths.

[0024] However, in the above configuration, while it is easy to flow a large flow rate of gas by not using a throttle part, the stability of flow rate control may not be sufficient. In particular, fluctuations in flow rate may occur when switching the flow path. Therefore, in the embodiment of the present invention, a pressure - type flow rate control device having a throttle part is used to control the flow of gas in each flow path, and the main gas supply path is sequentially switched to flow gas from the vaporization supply device in order, so as to stably supply gas.

[0025] Further, in one embodiment of the present invention, when sequentially switching the main gas supply path, the flow path that is not the main supply path is not completely closed, but rather a state of allowing some gas to flow is continued, that is, the control valve is maintained in a state where it is not completely closed. As a result, it has been found that fluctuations in the downstream pressure, particularly when switching the main supply path, can be suppressed, and gas supply can be performed more smoothly.

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the embodiments described below.

[0027] FIG. 1 shows a gas supply system 100 according to an embodiment of the present invention. The gas supply system 100 includes a plurality of vaporization supply devices connected in parallel to a common flow path 8 on the downstream side, here a first vaporization supply device 10A and a second vaporization supply device 10B. The first vaporization supply device 10A and the second vaporization supply device 10B are both connected to a control circuit 30 (or control device), and can be operated independently of each other by the control circuit 30.

[0028] The illustrated control circuit 30 is provided outside the first vaporization supply device 10A and the second vaporization supply device 10B, but is not limited thereto. For example, it may be built into one of the first vaporization supply device 10A or the second vaporization supply device 10B, or may be distributed and arranged in the first vaporization supply device 10A and the second vaporization supply device 10B.

[0029] The upstream sides of the first vaporization supply device 10A and the second vaporization supply device 10B are connected to, for example, a liquid raw material source 2 which is a liquid raw material stored in a liquid storage tank. In the present embodiment, the liquid raw material source 2 is commonly connected to both the first vaporization supply device 10A and the second vaporization supply device 10B. However, in other embodiments, the liquid raw material source 2 may be provided separately for the first vaporization supply device 10A and the second vaporization supply device 10B.

[0030] As liquid raw materials, for example, organometals such as HCDS (Si2Cl6), TEOS (tetraethyl orthosilicate), TMGa (trimethylgallium), and TMAl (trimethylaluminum) are used. In the following embodiments, an example of vaporizing and supplying HCDS will be described. The boiling point of HCDS is about 144°C, and the vapor pressure at 190°C is about 250 kPa abs.

[0031] The downstream sides of the first vaporization supply device 10A and the second vaporization supply device 10B communicate with the process chamber 4 via a common flow path 8. In the gas supply system 100, both the gas generated by the first vaporization supply device 10A and the gas generated by the second vaporization supply device 10B can be supplied to the process chamber 4. A vacuum pump 6 is connected to the process chamber 4, and the process chamber 4 and the communicating flow paths can be evacuated.

[0032] Next, with reference to FIGS. 1 and 2, the detailed configurations of the first vaporization supply device 10A and the second vaporization supply device 10B will be described. Note that FIG. 2 shows a specific configuration example of the vaporization supply device used as the first vaporization supply device 10A and the second vaporization supply device 10B, and corresponds to the vertical vaporization supply device also described in Patent Document 2.

[0033] As shown in FIG. 1, the first vaporization supply device 10A and the second vaporization supply device 10B each include first and second vaporization units 12A and 12B, and provided downstream of the first and second vaporization units 12A and 12B First and second pressure-type flow control devices 20A and 20B, First and second and first and second supply pressure sensors 16A and 16B that measure the supply pressure P0 on the upstream side of the pressure-type flow control devices 20A and 20B (that is, the pressure of the gas generated in the vaporization units 12A and 12B). Further, the first vaporization supply device 10A and the second vaporization supply device 10B of the present embodiment each have first and second liquid replenishment valves 18A and 18B disposed upstream of the first and second vaporization units 12A and 12B.

[0034] The first and second pressure-type flow control devices 20A and 20B include first and second control valves 14A and 14B, first and second throttle portions 24A and 24B provided on the downstream sides thereof, and first and second pressure sensors 26A and 26B for measuring the pressure (the pressure upstream of the throttle portion: upstream pressure or control pressure) P1 between them.

[0035] The first and second control valves 14A and 14B are feedback-controlled based on the outputs of the first and second pressure sensors 26A and 26B, respectively, whereby the upstream pressure P1 can be maintained at a pressure corresponding to a desired flow rate. The first and second pressure-type flow control devices 20A and 20B may include downstream pressure sensors (not shown) for measuring the pressures on the downstream sides of the throttle portions 24A and 24B. The downstream pressure sensors may be provided in each of the first and second pressure-type flow control devices 20A and 20B, or a single common one may be provided.

[0036] Hereinafter, when there is no particular need to distinguish, the first vaporization supply device 10A and the second vaporization supply device 10B are simply referred to as the vaporization supply device 10, the first and second vaporization portions 12A and 12B are simply referred to as the vaporization portion 12, the first and second pressure-type flow control devices 20A and 20B are simply referred to as the pressure-type flow control device 20, the first and second control valves 14A and 14B are simply referred to as the control valve 14, the first and second throttle portions 24A and 24B are simply referred to as the throttle portion 24, the first and second pressure sensors 26A and 26B are simply referred to as the pressure sensor 26 or the upstream pressure sensor 26, the first and second supply pressure sensors 16A and 16B are simply referred to as the supply pressure sensor 16, and the first and second liquid replenishment valves 18A and 18B are simply referred to as the liquid replenishment valve 18.

[0037] When the pressure-type flow control device 20 satisfies the critical expansion condition P1 / P2 ≥ approximately 2 (where P1 is the upstream pressure, P2 is the downstream pressure which is the pressure on the downstream side of the throttle portion 24, and approximately 2 is for nitrogen gas), the flow velocity of the gas passing through the throttle portion 24 is fixed at the speed of sound, and the mass flow rate is determined by the upstream pressure P1 regardless of the downstream pressure P2. Flow control is performed using this principle. When the critical expansion condition is satisfied, the flow rate Q is given by Q = K1·P1 (where K1 is a constant depending on the fluid type and fluid temperature).

[0038] Also, when a downstream pressure sensor for measuring the pressure on the downstream side of the throttle portion 24 (downstream pressure P2) is provided, even when the above critical expansion condition is not satisfied, based on the upstream pressure P1 and the downstream pressure P2, Q = K2·P2 m (P1 - P2) n (where K2 is a constant depending on the fluid type and fluid temperature, and m, n are exponents derived based on the actual flow rate), the flow rate Q can be calculated.

[0039] The pressure-type flow control device 20 adjusts the opening degree of the control valve 14 by feedback control so that the flow rate Q calculated based on the measured upstream pressure P1 (or the upstream pressure P1 and the downstream pressure P2) approaches the input set flow rate. Thereby, gas can flow at the set flow rate to the downstream side of the throttle portion 24. The flow rate obtained by the above calculation may be displayed externally as a flow rate output value.

[0040] The vaporization section 12 of the vaporization supply device 10 is provided with a heater 13a (see Figure 2), and can heat the vaporization chamber 12a (see Figure 2) where the liquid raw material is stored to vaporize the liquid raw material. The liquid raw material is vaporized until the supply pressure P0 reaches the vapor pressure corresponding to the heater set temperature. For example, when HCDS is heated to 190°C by the heater, HCDS vaporizes until the supply pressure P0 reaches approximately 250 kPa which is the vapor pressure at that temperature, and then reaches a saturated state and the supply pressure P0 is maintained at approximately 250 kPa.

[0041] The supply pressure sensor 16 is provided for measuring the supply pressure P0. As the supply pressure sensor 16, for example, a pressure sensor of a type that measures pressure from the magnitude of the strain generated in the diaphragm is used. The supply pressure sensor 16 can be used to confirm whether the supply pressure P0 is sufficiently greater than the upstream pressure P1 corresponding to the rated flow rate.

[0042] As shown in FIG. 2, the vaporization supply device 10 may have a preheating unit 11 having a heater on the upstream side of the liquid replenishing valve 18. The preheating unit 11 is provided to assist vaporization in the vaporization unit 12. By preheating the liquid raw material L in the preheating chamber 11a formed as an expansion portion from the flow path in advance, the required amount of heat in the vaporization unit 12 can be reduced, and a decrease in the material temperature during vaporization can be suppressed.

[0043] A heater (not shown) for heating the preheating unit 11 from the side, a heater 13a for heating the vaporization unit 12 from the side and the bottom surface, and a heater 13b for heating the pressure type flow control device 20 and its downstream flow path from the side and the bottom surface can each operate independently. Typically, the heater temperature of the preheating unit 11 is set lower than the heater temperature of the vaporization unit 12, and the heater temperature of the pressure type flow control device 20 is set higher than the heater temperature of the vaporization unit 12.

[0044] The heater provided in each part is composed of, for example, a heat transfer member and a heating element fixed thereto. As the heat transfer member, for example, a thick aluminum plate is used, and as the heating element, for example, a cartridge heater is used. In addition to this, a jacket heater can also be used as the heater.

[0045] Also, as shown in FIG. 2, the vaporization supply device 10 of the present embodiment includes a stop valve 17 provided downstream of the control valve 14, a purge three-way valve 19a provided between the liquid replenishing valve 18 and the vaporization unit 12, and a purge three-way valve 19b provided downstream of the stop valve 17. The stop valve 17 is used to reliably stop the supply of gas from the vaporization supply device 10. As the liquid replenishing valve 18 and the stop valve 17, an AOV (air-operated valve) or the like is preferably used. Further, the purge three-way valves 19a and 19b are also composed of an AOV or the like and are used to switch and flow the purge gas. In the purge three-way valve 19a, when the valve body is closed, the inlet of the purge gas is closed and the flow path of the liquid raw material is communicated, and when the valve body is opened, the inlet of the purge gas is opened and communicates with the inside of the vaporization unit, and the purge gas can flow. In the purge three-way valve 19b, when the valve body is closed, the inlet of the purge gas is closed and the downstream of the stop valve 17 and the process chamber are communicated, and when the valve body is opened, the inlet of the purge gas is opened and communicates with the process chamber, and the purge gas can flow.

[0046] In the vaporization supply device 10 shown in FIG. 2, a vertical configuration is adopted, the vaporization unit 12 is provided above the preheating unit 11, and a pressure type flow control device 20, a stop valve 17, etc. are provided above the vaporization unit 12. However, the vaporization supply device 10 is not limited to the above vertical configuration, and may have a configuration in which the preheating unit 11, the vaporization unit 12, and the pressure type flow control device 20 are arranged in a row in the horizontal direction, and may be configured in any manner.

[0047] As described above, the control valve 14 of the pressure type flow control device 20 is a valve (proportional valve) that can be adjusted to an arbitrary opening degree, and its opening degree is feedback-controlled based on the output of the pressure sensor 26. As the control valve 14, for example, a piezo element-driven valve (sometimes referred to as a piezo valve) is used. The piezo valve can change the pressing force of the diaphragm valve body 14a against the valve seat by controlling the drive voltage applied to the piezo element, and thereby can open to an arbitrary opening degree. As the throttle portion 24, for example, an orifice plate or a critical nozzle is used.

[0048] In the vaporization supply device 10 described above, the liquid raw material L is supplied from the liquid raw material source 2 to the vaporization unit 12 or the preheating unit 11 of the vaporization supply device 10. The liquid raw material L is pressure-fed, for example, by supplying pressurized inert gas to the liquid storage tank and extruding the liquid raw material L at a constant pressure. The supply amount of the liquid raw material L to the vaporization unit 12 can be adjusted by controlling the opening and closing time of the liquid replenishing valve 18 or the like.

[0049] Also, in the vaporization unit 12, the raw material gas G is generated by heating the liquid raw material L using a heater. By generating gas with the control valve 14 closed, the supply pressure P0 rises to the vapor pressure. Thereafter, if the control valve 14 is opened, the raw material gas G can flow to the downstream side of the vaporization supply device 10.

[0050] FIG. 3 is a graph showing the change in the supply pressure P0 when the control valve 14 is opened for one pulse for a predetermined period (here, 1 second) according to the valve control signal SV based on the set flow rate from the state where the supply pressure P0 is maintained at the vapor pressure (here, 246 kPa abs) in the vaporization supply device 10.

[0051] As can be seen from FIG. 3, when the control valve 14 is opened, the gas accumulated upstream flows out to the downstream side. At this time, the supply pressure P0 decreases with time from the initial pressure. This is because the amount of gas flowing out through the control valve 14 is larger than the amount of gas generated in the vaporization unit 12. Then, when the gas supply for one pulse is completed and the valve control signal SV returns to 0%, the control valve 14 is closed, the gas generation in the vaporization unit 12 proceeds, and the supply pressure P0 recovers.

[0052] In this way, each vaporization supply device 10 can flow gas at a desired flow rate in pulses even when the gas consumption exceeds the gas generation amount. Therefore, if a plurality of vaporization supply devices 10 are prepared and connected in parallel, and gas supply is sequentially performed from the vaporization supply devices 10 at staggered times, it is possible to continuously supply gas at a controlled flow rate. In the present embodiment, the pulsed gas supply operation from the first vaporization supply device 10A and the pulsed gas supply operation from the second vaporization supply device 10B are alternately repeated. More specifically, the control circuit 30 performs operation control so as to temporally shift the opening period of the first control valve 14A and the opening period of the second control valve 14B, whereby the gas from the first vaporization unit 12A and the gas from the second vaporization unit 12B are sequentially flowed into the common flow path 8.

[0053] FIG. 4 is a graph showing the flow rate input signal, the flow rate output signal, and the pressure on the downstream side of the throttle portion (downstream pressure P2) for controlling the operations of the control valves 14A and 14B in each of the first vaporization supply device 10A and the second vaporization supply device 10B. IN(1) and OUT(1) indicate the flow rate input signal (command signal from an external device) to the first vaporization supply device 10A and the flow rate output signal (signal corresponding to the actual flow rate) output from the first vaporization supply device 10A. Further, IN(2) and OUT(2) indicate the flow rate input signal to the second vaporization supply device 10B and the flow rate output signal output from the second vaporization supply device 10B. Further, P2 indicates the output of the downstream pressure sensor provided on the downstream side of the throttle portion 24. The flow rate input signal and the flow rate output signal indicate those when the flow rate is given at a ratio with the rated flow rate being 100%.

[0054] As shown in Fig. 4, pulse-like flow input signals IN(1) and IN(2) are alternately sent to the first vaporization supply device 10A and the second vaporization supply device 10B. As a result, gas is alternately sent to the common flow path 8 from the first vaporization supply device 10A and the second vaporization supply device 10B. Thereby, gas can be continuously supplied to the process chamber 4 at a flow rate corresponding to a certain control flow rate (here, 100% flow rate). In the example shown in Fig. 4, in each of the vaporization supply devices 10A and 10B, an operation of alternately flowing gas at 100% flow rate and 0% flow rate, that is, a pulse-like opening / closing operation, is alternately performed.

[0055] In Fig. 4, the main reason why the flow input signals IN(1) and IN(2) are rectangular wave signals while the flow output signals OUT(1) and OUT(2) are not is that when driving the control valves 14A and 14B based on the flow input signal at the rising edge, in order to prevent overshoot, actually, the opening operation of the control valves 14A and 14B is performed by a somewhat gentle first-order lag system control. Also, since the control valves 14A and 14B are feedback-controlled (PID control) based on the measured upstream pressure P1, there is a somewhat time delay in the opening adjustment. For this reason, the flow output signal as shown in the figure is obtained without a sharp flow rise.

[0056] Also, at the falling edge, even if the control valves 14A and 14B are rapidly closed, the outflow of the gas remaining between the control valves 14A and 14B and the throttle portions 24A and 24B occurs. For this reason, the gas flow rate (and the upstream pressure P1) does not suddenly become zero but decays exponentially. In the pressure-type flow control devices 20A and 20B, the flow output signals OUT(1) and OUT(2) are generated based on the outputs of the first and second pressure sensors (upstream pressure sensors) 26A and 26B and correspond to the upstream pressure P1.

[0057] Also, it can be seen that during the period when the flow rate input signals IN(1) and IN(2) are zero, the flow rate output signals OUT(1) and OUT(2) take non-zero values (here, values below 10% of the flow rate). The reason for this is that even when the control valves 14A and 14B of either flow path are closed, the other is open, and gas is flowing on the downstream side of the throttle portions 24A and 24B. Therefore, in the closed flow path, the upstream pressure P1 between the throttle portions 24A and 24B and the control valves 14A and 14B does not decrease to zero.

[0058] In this way, in the gas supply system 100, first, from the state where both control valves 14A and 14B are closed and the supply pressure P0 (see FIG. 3) is maintained at a sufficiently high pressure, first, only the first control valve 14A is pulsed open for a predetermined period (here, 1 second). At this time, gas flows to the downstream side of the first control valve 14A, and the supply pressure P0 decreases as the gas is consumed. On the other hand, during this period, the second control valve 14B remains closed, and no gas flows from the second vaporization supply device 10B.

[0059] Next, when the opening period of the first control valve 14A ends, the first control valve 14A is closed, and only the second control valve 14B is pulsed open for a predetermined period (here, 1 second). At this time, gas flows to the downstream side of the second control valve 14B, and the supply pressure P0 in the second vaporization supply device 10B decreases. On the other hand, during this period, since the first control valve 14A remains closed, no gas flows from the first vaporization supply device 10A, and the supply pressure P0 in the first vaporization supply device 10A can recover to the pressure at which the next pulsed gas supply is performed.

[0060] Thereafter, in the same manner, the operation of opening the first control valve 14A for a predetermined period and the operation of opening the second control valve 14B for a predetermined period are alternately and sequentially repeated. As a result, the supply of gas from the first vaporization section 12A and the supply of gas from the second vaporization section 12B are alternately switched and repeatedly performed, and gas can be continuously supplied to the process chamber 4.

[0061] Next, the gas supply operation of another mode will be described. FIG. 5 shows an example in which the opening degrees of the control valves 14A and 14B are alternately controlled to the opening degrees corresponding to 90%-10% flow rates, different from the example shown in FIG. 4. Hereinafter, the main flow rate (here, 90% flow rate) may be referred to as the first flow rate or the third flow rate, etc., and the sub-flow rate (here, 10% flow rate) left open so as not to completely close the control valves 14A and 14B may be referred to as the second flow rate or the fourth flow rate, etc. The main flow rate is sufficiently larger than the sub-flow rate. The sub-flow rate is assumed to include a 0% flow rate as in the example shown in FIG. 4. Also, the supply path through which gas is flowing at the main flow rate may be referred to as the main supply path.

[0062] As can be seen by comparing FIG. 4 and FIG. 5, when the opening degree of the control valve 14 is adjusted at 90%-10% flow rates, the fluctuation of the downstream pressure P2 at the time of switching the main supply path is suppressed. This is considered to be because the flow rate instability at startup could be suppressed by not performing the operation of completely closing the control valve 14. The control valve 14 (especially the piezo valve) is configured such that in the fully closed state, the valve body is strongly pressed against the valve seat by a biasing means such as a spring in order to counteract the upward push of the valve body by the gas pressure. Therefore, there is a possibility of causing flow instability immediately after the valve is opened.

[0063] Therefore, as shown in FIG. 5, in order to supply gas with a more stable flow, it is considered effective to also slightly open the control valve 14 on the non-main supply path side when switching the main supply path and flowing gas alternately. However, if it is opened too much, the recovery of the supply pressure P0 will be delayed due to an increase in gas consumption. From this perspective, the sub-flow rate is preferably set to 0% flow rate to 30% flow rate, more specifically, 5% flow rate to 20% flow rate.

[0064] Note that FIG. 5 shows an example of a 90%-10% flow rate as a combination of the main flow rate (the first flow rate or the third flow rate) and the sub-flow rate (the second flow rate or the fourth flow rate), but it is not limited to this. For example, it may be 80%-20% flow rate or 85%-15% flow rate.

[0065] Also, when the desired flow rate is the rated flow rate, typically, the sum of the main flow rate and the sub-flow rate is set to the rated flow rate (100% flow rate). However, it is not limited to this. Needless to say, when the desired control flow rate is lower than the rated value, the total flow rate may be adjusted to match the control flow rate. Furthermore, when the actual gas flow rate decreases, for example, when switching the main supply amount, even if the control flow rate is the rated flow rate, the gas may be supplied alternately at 100%-10% flow rate, that is, controlled to flow at a total of 110% flow rate. The main flow rate and the sub-flow rate may be set arbitrarily, and different main flow rate - sub-flow rate settings may be used for the vaporization supply devices 10A and 10B respectively, or the main flow rate - sub-flow rate setting may be changed during gas supply.

[0066] In the above-described embodiment, the length of the period during which the first vaporization supply device 10A flows gas at the main flow rate is set to be the same as the length of the period during which the second vaporization supply device 10B flows gas at the main flow rate (here, 1 second). This is because the first vaporization section 12A and the second vaporization section 12B have the same shape and the same volume, and the gas generation capabilities and the characteristics of the decrease in the supply pressure P0 during valve opening are set to be equivalent. However, it is not limited to this, and when the gas generation capabilities of the vaporization sections 12 are different, for example, the lengths of the periods during which the first vaporization supply device 10A flows gas at the main flow rate and the second vaporization supply device 10A flows gas at the main flow rate may be different.

[0067] Further, when performing continuous gas supply by combining the pulsed gas supplies from the plurality of vaporization supply devices 10 as described above, the supply pressure P0 during the period when the control valve 14 is open is required to be equal to or higher than a predetermined value (for example, 150 kPa abs). And for this reason, the supply pressure P0 immediately before the opening of the control valve 14 is also required to be sufficiently large.

[0068] For this reason, the control circuit 30 may be configured to open the first control valve 14A from closed to open to allow gas to flow from the first vaporization section 12A only when the output of the first supply pressure sensor 16A is equal to or higher than a predetermined value, and similarly, to open the second control valve 14B from closed to open to allow gas to flow from the second vaporization section 12B only when the output of the second supply pressure sensor 16B is equal to or higher than a predetermined value. Also, when the output of the supply pressure sensor 16 drops to a predetermined threshold value during gas supply, the control valve 14 may be configured to automatically close to recover the supply pressure P0.

[0069] Hereinafter, a gas supply system 200 according to another aspect will be described with reference to FIGS. 6 and 7. FIGS. 6 and 7 show the configuration of the gas supply system 200 according to another aspect and the drive signals of the control valves 14A, 14B, and 14C applied thereto. Note that the same reference numerals are assigned to the same elements as those in the embodiment shown in FIG. 1, and detailed descriptions thereof are omitted.

[0070] In another embodiment of the gas supply system 200 shown in FIG. 6, in addition to the first vaporization supply device 10A and the second vaporization supply device 10B, a third vaporization supply device 10C is provided. The third vaporization supply device 10C also communicates with the common flow path 8, and the first to third vaporization supply devices 10A, 10B, and 10C are connected in parallel on the upstream side of the common flow path 8.

[0071] The third vaporization supply device 10C also has a third vaporization section 12C having a heater, a third supply pressure sensor 16C, a third pressure type flow control device 20C provided on the downstream side thereof, and a liquid replenishment valve 18C for controlling the supply of liquid to the third vaporization section 12C, similar to the first and second vaporization supply devices 10A and 10B. The third pressure type flow control device 20C is composed of a third control valve 14C, a third throttle section 24C, and an upstream pressure sensor (third pressure sensor) 26C disposed therebetween. The control circuit 30 is connected to the first to third vaporization supply devices 10A, 10B, and 10C.

[0072] As shown in FIG. 7, in the gas supply system 200 of the present embodiment, the control valves 14A, 14B, and 14C are operationally controlled so as to sequentially supply gas at the main flow rate for a predetermined period with a time shift. In the illustrated example, first, a period A1 in which gas flows at the main flow rate (here, 80% flow rate) through the first control valve 14A is provided, then a period B1 in which gas flows at the main flow rate through the second control valve 14B is provided, and then a period C1 in which gas flows at the main flow rate through the third control valve 14C is provided. During the period in which gas is flowing at the main flow rate through a predetermined control valve, gas is flowing at the sub flow rate (here, 10% flow rate) through the other control valves.

[0073] Thereafter, a period A2 is provided during which the first control valve 14A is set to the main flow rate again at the timing of switching the third control valve 14C from the main flow rate to the sub-flow rate. Subsequently, a period B2 during which the second control valve 14B is set to the main flow rate again and a period C2 during which the third control valve 14C is set to the main flow rate are provided in sequence. In this way, by sequentially and repeatedly switching the main supply path to supply gas from the first to the third vaporization supply devices 10A, 10B, and 10C, it is possible to continuously supply gas to the process chamber 4 at a controlled flow rate.

[0074] Also, as shown in FIG. 7, in this embodiment, ramp control is adopted when each control valve 14 is opened, and control is performed such that the target opening degree of the control valve increases with time. Further, the opening operation of the control valve 14 by this ramp control is executed overlappingly before the other control valves are turned off, and an overlapping period OL is provided at the timing of switching the main supply path. During the overlapping period OL, gas can flow at the main flow rate through two control valves.

[0075] In this way, a slight overlapping period may be provided for the opening and closing operation of the control valve 14. The inventor has confirmed that a fluctuation suppression effect of the downstream pressure P2 can be expected even by providing a slight overlapping period. Therefore, there is a possibility of supplying gas more stably.

[0076] The period when the control valve 14 starts to open, that is, the opening degree control of the valve at the time of flow rate startup, is not limited to the above-described ramp control, and various controls such as control in which the target value increases in a quadratic function or a first-order lag can be adopted. Also, similar to the time of flow rate startup, various controls such that the target opening degree gradually decreases can be adopted at the time of flow rate shutdown.

[0077] As described above, embodiments of the present invention have been explained, but various modifications are possible. For example, in order to replenish the liquid raw material inside the vaporization unit 12, the supply pressure P0 may be monitored using the supply pressure sensor 16, and when the supply pressure P0 after the recovery period falls below a predetermined threshold value, the liquid replenishment valve 18 may be opened for a predetermined period. Also, the liquid raw material may be replenished based on the value of the liquid level gauge provided in the vaporization unit 12 or the amount of gas supplied.

[0078] In addition, in the above, an example of configuring a gas supply system using two or three vaporization supply devices connected in parallel has been explained, but of course, a gas supply system may be configured using four or more vaporization supply devices.

Industrial Applicability

[0079] The gas supply system and gas supply method according to the embodiments of the present invention are suitably used, for example, for generating a gas used in a semiconductor manufacturing process by vaporization and continuously supplying this to a process chamber.

Explanation of Reference Numerals

[0080] 2 Liquid raw material source 4 Process chamber 6 Vacuum pump 8 Common flow path 10 Vaporization supply device 10A First vaporization supply device 10B Second vaporization supply device 12 Vaporization unit 12A First vaporization unit 12B Second vaporization unit 14 Control valve 14A First control valve 14B Second control valve 16 Supply pressure sensor 16A First supply pressure sensor 16B Second supply pressure sensor 18 Liquid replenishment valve 18A First liquid replenishment valve 18B Second liquid replenishment valve 20 Pressure-type flow control device 20A First pressure-type flow control device 20B Second pressure-type flow control device 24 Throttle section 24A First throttle section 24B Second throttle section 26 Pressure sensor 26A First pressure sensor 26B Second pressure sensor 30 Control circuit 100 Gas supply system

Claims

1. A first vaporization supply device including a first vaporization section having a heater for storing a raw material, a first control valve provided in a downstream flow path of the first vaporization section, a first throttle section provided in a downstream flow path of the first control valve, and a first pressure sensor for measuring a gas pressure between the first control valve and the first throttle section, and supplying a gas with controlled flow rate; A second vaporization supply device including a second vaporization section having a heater for storing a raw material, a second control valve provided in a downstream flow path of the second vaporization section, a second throttle section provided in a downstream flow path of the second control valve, and a second pressure sensor for measuring a gas pressure between the second control valve and the second throttle section, and supplying a gas with controlled flow rate; Control equipment connected to the first vaporization supply device and the second vaporization supply device; A common flow path that communicates with a downstream flow path of the first vaporization supply device and a downstream flow path of the second vaporization supply device respectively; A gas supply system comprising: The first vaporization supply device alternately supplies a gas controlled to a first flow rate and a second flow rate including zero, which is smaller than the first flow rate, to the common flow path by changing an opening degree of the first control valve. The second vaporization supply device alternately supplies a gas controlled to a third flow rate and a fourth flow rate including zero, which is smaller than the third flow rate, to the common flow path by changing an opening degree of the second control valve. The gas supply system is configured to flow a gas through the common flow path at a constant control flow rate.

2. The gas supply system according to claim 1, wherein the second flow rate and the fourth flow rate are non-zero flow rates, and the first control valve and the second control valve are maintained in an open state so as not to be completely closed.

3. The gas supply system according to claim 1 or 2, wherein when the first vaporization supply device supplies gas to the common flow path at the first flow rate, the second vaporization supply device supplies gas to the common flow path at the fourth flow rate, and when the second vaporization supply device supplies gas to the common flow path at the third flow rate, the first vaporization supply device supplies gas to the common flow path at the second flow rate.

4. The gas supply system according to any one of claims 1 to 3, wherein a total flow rate of the first flow rate and the fourth flow rate is the same as a total flow rate of the second flow rate and the third flow rate.

5. The first flow rate and the third flow rate are the same flow rate, the second flow rate and the fourth flow rate are the same flow rate, and a period in which the first vaporization supply device supplies gas to the common flow path at the first flow rate and a period in which the second vaporization supply device supplies gas to the common flow path at the third flow rate are alternately repeated a plurality of times. The gas supply system according to claim 4.

6. The gas supply system according to claim 3, wherein an overlapping period between a period in which the first vaporization supply device supplies gas to the common flow path at the first flow rate and a period in which the second vaporization supply device supplies gas to the common flow path at the third flow rate is provided.

7. The first vaporization section and the second vaporization section have the same shape and the same volume, and the length of a period in which the first vaporization supply device supplies gas to the common flow path at the first flow rate and the length of a period in which the second vaporization supply device supplies gas to the common flow path at the third flow rate are the same. The gas supply system according to claim 5.

8. The first vaporization supply device includes a first supply pressure sensor that measures the gas pressure upstream of the first control valve, and the second vaporization supply device includes a second supply pressure sensor that measures the gas pressure upstream of the second control valve. The gas supply system according to any one of claims 1 to 7, wherein gas flows at the first flow rate through the first control valve only when the output of the first supply pressure sensor is equal to or higher than a predetermined value, and gas flows at the third flow rate through the second control valve only when the output of the second supply pressure sensor is equal to or higher than a predetermined value.

9. A third vaporization section having a heater in which a raw material is stored, a third control valve provided in a downstream flow path of the third vaporization section, a third throttle section provided in a downstream flow path of the third control valve, and a third pressure sensor that measures a gas pressure between the third control valve and the third throttle section, and further includes a third vaporization supply device that supplies gas with its flow rate controlled. The third vaporization supply device is connected to the control device, and its downstream flow path communicates with the common flow path. The third vaporization supply device is configured to alternately supply a gas controlled to a fifth flow rate and a sixth flow rate including zero, which is smaller than the fifth flow rate, to the common flow path by changing the opening degree of the third control valve, and to flow the gas through the common flow path at a constant control flow rate. The gas supply system according to any one of claims 1 to 8.

10. A first vaporization supply device including a first vaporization unit having a heater for storing a raw material, a first control valve provided in a downstream flow path of the first vaporization unit, a first throttle portion provided in a downstream flow path of the first control valve, and a first pressure sensor for measuring a gas pressure between the first control valve and the first throttle portion; A second vaporization supply device including a second vaporization unit having a heater for storing a raw material, a second control valve provided in a downstream flow path of the second vaporization unit, a second throttle portion provided in a downstream flow path of the second control valve, and a second pressure sensor for measuring a gas pressure between the second control valve and the second throttle portion; Control equipment connected to the first vaporization supply device and the second vaporization supply device; A common flow path in which a downstream flow path of the first vaporization supply device and a downstream flow path of the second vaporization supply device communicate with each other A gas supply method for flowing a gas through the common flow path at a constant control flow rate, which is executed in a gas supply system including: Step (a) of flowing a gas from the first vaporization supply device to the common flow path at a first flow rate while flowing a gas from the second vaporization supply device to the common flow path at a fourth flow rate smaller than the first flow rate; After step (a), by changing the opening degree of the first control valve, while flowing a gas from the first vaporization supply device to the common flow path at a second flow rate smaller than the first flow rate and corresponding to the fourth flow rate, by changing the opening degree of the second control valve, flowing a gas from the second vaporization supply device to the common flow path at a third flow rate corresponding to the first flow rate (step (b)); Including, the gas supply method in which step (a) and step (b) are repeatedly executed a plurality of times.

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