WO2024195439A1 - Vaporizer and method for supplying material gas to semiconductor manufacturing device - Google Patents

Abstract

This vaporizer is configured by: a tank that stores a precursor; a temperature sensor that measures the temperature of the precursor stored in the tank; a heater that heats the precursor stored in the tank to generate a material gas; an electric power control means that controls electric power supplied to the heater so that the temperature of the precursor measured by the temperature sensor becomes equal to a preset set temperature; a pipe that guides the material gas stored in the tank to the outside of the tank; an opening/closing valve that is interposed in the pipe for flowing or stopping the material gas; a valve control means that outputs an opening signal and a closing signal to the opening/closing valve; and a nozzle that is interposed in the pipe, and that is provided with a flow passage which communicates with an internal space of the pipe. The cross-sectional area at the narrowest position of the flow passage provided to the nozzle is smaller than the cross-sectional area of the internal space of the pipe. Due to this configuration, a vaporizer capable of supplying, with high accuracy, a material gas suitable for ALD can be realized with a simple device configuration and a simple operation.

Description

Vaporizer and method for supplying material gas to semiconductor manufacturing equipment

The present invention relates to a vaporizer used in the manufacturing process of semiconductor devices, and a method for supplying a material gas to a semiconductor manufacturing apparatus. Although not particularly limited, the present invention relates to a vaporizer suitable for manufacturing semiconductor devices by atomic layer deposition, and a method for supplying a material gas to a semiconductor manufacturing apparatus.

In the manufacturing process of semiconductor devices such as integrated circuits, various types of semiconductor material gases (hereinafter referred to as "material gases") are used depending on the purpose of the process. Material gases generated from precursors that are in a liquid or solid state at room temperature are supplied to the semiconductor manufacturing equipment via piping after vaporizing the precursors stored in a vaporizer. One method for generating material gas in a vaporizer is to heat a precursor stored in a tank to generate steam. Generally, vaporizers are equipped with a valve for starting and stopping the supply of the generated material gas and a mass flow controller for controlling the flow rate of the material gas.

With technological innovations in the manufacturing process of semiconductor devices, new specifications are required for vaporizers. For example, in a technology called atomic layer deposition (ALD), small amounts of multiple types of material gas are alternately supplied to the surface of a substrate to form a highly accurate and homogeneous thin film whose thickness and material are controlled at the atomic layer level. In semiconductor manufacturing using ALD, a flow-controlled material gas is supplied for a few seconds, and then the supply is stopped, and this cycle is repeated at regular intervals.

A vaporizer suitable for repeatedly turning on and off the supply of material gas in short cycles has been proposed. Patent documents 1 to 4 describe an invention for an apparatus that can repeatedly supply a constant volume of material gas to semiconductor manufacturing equipment for a short period of time by first filling a closed space consisting of a container or part of a pipe with the material gas and then opening a downstream valve. Patent document 5 describes an invention for an apparatus that can repeatedly supply a controlled flow rate of material gas to semiconductor manufacturing equipment for a short period of time by providing an orifice and a high-speed pulse valve in a flow control conduit provided downstream of a gas reservoir whose pressure is kept constant, and opening the high-speed pulse valve. The flow rate of the material gas in this apparatus is calibrated based on pressure changes in the gas reservoir.

US Patent Application Publication No. 2005/0223979 JP 2019-16096 A JP 2021-162906 A JP 2022-10150 A US Patent Application Publication No. 2019/0332129

In the devices described in Patent Documents 1 to 4 that employ a method of first filling a closed space consisting of a container or part of a pipe with a material gas, the device has a complex configuration, which causes problems such as high manufacturing costs and frequent breakdowns. In addition, there is a problem in that the amount of material gas that is filled into a small-volume container or part of a pipe is easily affected by changes in temperature and pressure, which causes fluctuations in the supply amount of material gas.

In the device described in Patent Document 5, which includes an orifice and a high-speed pulse valve, the flow rate of the material gas passing through the orifice is a function of the difference in pressure between the upstream and downstream sides of the orifice, so there is an issue that the supply amount of the material gas is easily affected by fluctuations in downstream pressure. In addition, there is an issue that the device configuration is complicated because a pressure controller is required to keep the pressure of the gas reservoir constant.

This disclosure was made in consideration of the above problems, and aims to realize a vaporizer that can supply material gas suitable for ALD with high precision using a simple device configuration and easy operation.

In one embodiment, the vaporizer according to the present disclosure is a vaporizer that generates a material gas from a precursor of the material gas and supplies it to the outside, and includes a tank for storing the precursor, a temperature sensor for measuring the temperature of the precursor stored in the tank, a heater for heating the precursor stored in the tank to generate a material gas, a power control means for controlling the power supplied to the heater so that the temperature of the precursor measured by the temperature sensor becomes equal to a preset temperature, a pipe for directing the material gas stored inside the tank to the outside of the tank, an opening/closing valve installed in the pipe for starting and stopping the flow of the material gas, a valve control means for outputting an open signal and a close signal to the opening/closing valve, and a nozzle installed in the pipe and provided with a flow path that communicates with the internal space of the pipe. In the vaporizer according to the present disclosure, the cross-sectional area of the flow path installed in the nozzle at the narrowest position is smaller than the cross-sectional area of the internal space of the pipe.

In a vaporizer having the above configuration, if the volume of material gas stored in the tank is sufficiently large compared to the flow rate of the material gas supplied to the outside, a pseudo-phase equilibrium is established between the reaction in which material gas is produced from the precursor in a solid or liquid state and the reverse reaction. Then, the pressure of the material gas in the tank is kept equal to the equilibrium vapor pressure at the set temperature, so the flow rate of the material gas when the opening and closing valve is opened is determined only by the temperature of the precursor. Also, because the nozzle acts to prevent the flow rate of the material gas from being affected by pressure fluctuations on the downstream side of the semiconductor manufacturing equipment, the supply amount of the material gas is stable.

In another embodiment, the method according to the present disclosure is a method for supplying a material gas to a semiconductor manufacturing apparatus, the method including the steps of storing a precursor of the material gas in a tank, heating the precursor while controlling the power supplied to the heater so that the temperature of the precursor stored in the tank is equal to a preset temperature to generate a material gas, outputting an open signal from a valve control means to an open/close valve disposed in a pipe that guides the material gas to the outside of the tank to open the open/close valve, supplying the material gas stored inside the tank to the semiconductor manufacturing apparatus via a nozzle disposed in the pipe and provided with a flow path that communicates with the internal space of the pipe, and outputting a close signal from the valve control means to the open/close valve to close the open/close valve and stop the supply of the material gas. In the method according to the present disclosure, the cross-sectional area at the narrowest position of the flow path disposed in the nozzle is smaller than the cross-sectional area of the internal space of the pipe.

By using the vaporizer or method disclosed herein, the number of vaporizer parts and manufacturing costs can be reduced, and vaporizer failures are reduced. In addition, the accuracy of the supply amount of material gas can be improved.

FIG. 1 is a schematic diagram showing an example of the configuration of a vaporizer according to a conventional technique. FIG. 2 is a schematic diagram showing an example of the configuration of a vaporizer according to the first embodiment of the present invention. FIG. 6 is a schematic diagram showing an example of the configuration of a vaporizer according to a second embodiment of the present invention. 5 is a flow chart illustrating a method according to a third embodiment of the present invention. 1 is a graph showing the relationship between equilibrium vapor pressure and collection amount in a reference example of the present invention.

<<Prior Art>>
In order to clarify the features of the vaporizer and method according to the present invention in comparison with the vaporizer and method, a vaporizer according to the prior art will first be described. Fig. 1 is a schematic diagram showing an example of the configuration of a vaporizer according to the prior art. Methods for vaporizing a precursor of a material gas in a vaporizer used in a manufacturing process of a semiconductor device include a baking method, a bubbling method, and a direct vaporization method. In the vaporizer 1' shown in Fig. 1, the baking method among these methods is adopted, and a precursor P in a liquid state is used.

Tank 2 is a sealable container capable of storing precursor P. Precursor replenishing means 11 is composed of, for example, piping and a valve. The tip of the piping reaches near the bottom inside tank 2. With the valve open, precursor P is replenished into tank 2 via the piping of precursor replenishing means 11. The valve is then closed, and precursor P is stored in a sealed state inside tank 2.

The temperature sensor 3 is a sensor that measures the temperature of the precursor P. The power supplied to the heater 4 is controlled by a power control means 5 (not shown) so that the temperature of the precursor P measured by the temperature sensor 3 becomes equal to a preset temperature. When the temperature of the heater 4 rises due to the passage of electricity, the precursor P inside the tank 2 that is in contact with the heater 4 is heated. The heated precursor P flows and is stirred inside the tank 2 by convection. This makes the temperature of the precursor P almost uniform.

Material gas G is generated by evaporation from the liquid surface of the heated precursor P. The generated material gas G is stored in the space above the liquid surface of the precursor P inside the tank 2 and inside the pipe 6 attached to the top surface of the tank 2. When material gas G is supplied from the vaporizer 1' to the semiconductor manufacturing equipment, a valve opening signal is output from the valve control means built into the flow sensor 8' to the flow control valve 7' to open the flow control valve 7'. The arrows in Figure 1 show the flow of this valve opening signal.

The material gas G flows from the upstream side of the pipe 6 through the flow control valve 7' and the flow sensor 8' to the downstream side and is supplied to a semiconductor manufacturing device (not shown). The flow sensor 8' measures the flow rate of the material gas G. The flow sensor 8' outputs a valve opening signal to the flow control valve 7' to perform feedback control so that the measured flow rate, which is the measured flow rate of the material gas G, is equal to a preset set flow rate. The flow control valve 7' and the flow sensor 8' may each be configured as independent components, or the two may be configured as an integrated mass flow controller.

The vaporizers according to the above-mentioned prior art are suitable for supplying material gas for a relatively long period of time, for example, several tens of seconds or more, but are not necessarily suitable for applications such as ALD, where the supply and stopping of material gas is repeated at short intervals of a few seconds. This is because, when the flow rate of the material gas is measured by the flow sensor 8' and a valve opening signal is output to the flow control valve 7' so that the measured flow rate is equal to the set flow rate, feedback control is performed, and it takes time to control the flow rate, so that the supply and stopping of the material gas cannot be quickly switched on and off.

One of the reasons why it takes time to control the flow rate in vaporizers according to conventional technology is the long response time of the flow sensor 8'. There are various types of flow sensors, such as thermal flow sensors and pressure flow sensors. Regardless of the type of flow sensor used, there is a time delay between when the flow rate of the material gas flowing through the flow sensor changes and when the flow sensor detects the change in flow rate and reflects it in the output signal. Another cause of delay is the time delay between when the valve opening signal output to the flow control valve 7' changes and when the change in the valve opening of the flow control valve 7' is completed.

Due to these causes of delay, the response time from when the value of the valve opening signal changes until the actual flow rate of the material gas approaches the set value in a mass flow controller that employs feedback control is usually not much less than 0.5 seconds. If it is desired to shorten the response time (for example, to 0.1 seconds or less) in order to realize a supply of material gas suitable for ALD, the response speed of the vaporizer 1' according to the conventional technology is insufficient.

First Embodiment
The present invention has been created with the objective of solving the problem of flow rate control delays that the vaporizers according to the above-mentioned prior art have, and providing a vaporizer suitable for use in ALD. The following describes in detail an embodiment of the present invention with reference to the drawings. Note that the following description is merely an example of an embodiment of the present invention, and the embodiment of the present invention is not limited to the embodiment described below.

In a first embodiment, the present invention is a vaporizer that generates a material gas from a precursor of the material gas and supplies it to the outside, and includes a tank for storing the precursor, a temperature sensor for measuring the temperature of the precursor stored in the tank, a heater for heating the precursor stored in the tank to generate a material gas, a power control means for controlling the power supplied to the heater so that the temperature of the precursor measured by the temperature sensor becomes equal to a preset temperature, a pipe for directing the material gas stored inside the tank to the outside of the tank, an opening/closing valve installed in the pipe for starting and stopping the flow of the material gas, a valve control means for outputting an open signal and a close signal to the opening/closing valve, and a nozzle installed in the pipe and provided with a flow path that communicates with the internal space of the pipe. In the vaporizer according to the present invention, the cross-sectional area of the flow path installed in the nozzle at the narrowest position is smaller than the cross-sectional area of the internal space of the pipe.

FIG. 2 is a schematic diagram showing an example of the configuration of a vaporizer according to a first embodiment of the present invention. The configuration of the vaporizer 1 shown in FIG. 2, except for the pipe 6 and its surrounding members, is common to the configuration of the vaporizer 1' according to the prior art shown in FIG. 1. The same symbols as those in FIG. 1 are used for these common parts, and explanations will be omitted unless particularly necessary.

The vaporizer 1 according to the present invention shown in FIG. 2 is significantly different from the vaporizer 1' according to the prior art shown in FIG. 1 in that, whereas in the prior art the flow rate of the material gas G flowing through the pipe 6 is feedback-controlled based on the measured flow rate measured by the flow rate sensor 8', in the present invention no flow rate control is performed during the supply of the material gas G.

As shown in FIG. 2, the pipe 6 of the vaporizer 1 according to the present invention is provided with an on-off valve 7 for starting and stopping the flow of the material gas G. The on-off valve 7 opens and closes according to an open signal and a close signal output from a valve control means 8 (not shown). The on-off valve 7 only switches between open and closed, and does not have the function of finely adjusting the valve opening. The on-off valve 7 can be configured, for example, by a pneumatic diaphragm valve and a drive mechanism for opening and closing it. As a drive mechanism for the pneumatic diaphragm valve, for example, an electromagnetic valve that applies or blocks compressed air pressure can be used. Alternatively, the on-off valve 7 can be a type of valve that can open and close the valve at high speed by the displacement of a piezoelectric element. Since the configuration of the vaporizer 1 according to the present invention lacks a flow sensor, there is no delay in response time due to the slow response of the flow sensor.

As shown in FIG. 2, a nozzle 9 having a flow path that communicates with the internal space of the pipe is interposed in the pipe 6. The cross-sectional area of the flow path in the nozzle 9 at its narrowest point is smaller than the cross-sectional area of the internal space of the pipe 6. The nozzle 9 may be of any shape as long as the cross-sectional area of the flow path through which the material gas flows at its narrowest point is smaller than the cross-sectional area of the internal space of the pipe. As a result, even if there is a change in pressure in the semiconductor manufacturing equipment (not shown) downstream of the pipe 6, changes in the flow rate of the material gas supplied from the vaporizer 1 are suppressed, and the supply amount of the material gas is stabilized.

The shape of the nozzle 9 does not have to be that of a critical nozzle or sonic nozzle in which the flow rate of the material gas passing through the nozzle 9 exceeds the speed of sound. If the nozzle 9 is to be configured as a critical nozzle or sonic nozzle, the shape of the narrowest part of the flow path, called the "throat," must be configured with a special curve called a Venturi shape, which increases manufacturing costs. The nozzle 9 of the present invention does not have to have such a special shape, and it is sufficient if the minimum cross-sectional area of the flow path provided in the nozzle is smaller than the cross-sectional area of the internal space of the pipe. However, configuring the nozzle 9 as a critical nozzle or sonic nozzle for a special purpose is permitted in the present invention.

On the other hand, it is preferable that the cross-sectional area of the internal space of the pipe 6 provided in the vaporizer 1 according to the present invention is as large as possible, and it is preferable that the conductance, which is a coefficient that indicates the ease with which the material gas flows in the piping that combines the pipe 6 and the on-off valve 7, is large. In such a case, the material gas flowing through the pipe 6 and the on-off valve 7 experiences less resistance from the piping, so the response time of the material gas flow rate can be shortened.

When applying the vaporizer 1 of the present invention to ALD, the lengths of the open and close signals output by the valve control means 8 to the opening and closing valve 7 can be set appropriately. As described above, the vaporizer 1 of the present invention has no response time due to a delay in the response of the flow sensor. Therefore, even if the time that the opening and closing valve 7 is kept open is very short (e.g., a few seconds), the proportion of the response time in that period can be made smaller than in the prior art, thereby improving the efficiency of semiconductor manufacturing.

Next, the portion of the configuration of the vaporizer 1 according to the first embodiment of the present invention shown in FIG. 2 that is related to temperature control of the precursor P will be described. The vaporizer 1 employs a baking method as a method for vaporizing the precursor P of the material gas, similar to the vaporizer 1' shown in FIG. 1. The power control means 5 (not shown) controls the power supplied to the heater 4 so that the temperature of the precursor P measured by the temperature sensor 3 becomes equal to a preset temperature. As a means for controlling the temperature of the precursor P by the power control means 5, a known control method such as PID control can be adopted.

The heater 4 may have any configuration as long as it can heat the precursor P stored in the tank 2. The heater 4 may be provided in a position in contact with the bottom of the tank 2 as shown in FIG. 2, or in a position in contact with the side or top of the tank 2. Alternatively, the heater 4 may be provided inside the tank 2, sealed in a container. The number of heaters 4 may be one or more.

As described above, when the precursor P is heated by the heater 4, the material gas G is generated by evaporation from the liquid surface of the heated precursor P. The generated material gas G is stored in the space above the liquid surface of the precursor P inside the tank 2 and in the space upstream of the opening and closing valve 7 inside the pipe 6 provided on the top surface of the tank 2.

When sufficient time has passed since the heater 4 started to heat the precursor P, the temperature of the precursor P in the tank 2 stabilizes and phase equilibrium is established between the precursor P and the material gas G. Phase equilibrium refers to a state in which different phases of the same substance coexist in a system and their composition ratio does not appear to change. The precursor P and material gas G in the above state meet the conditions for phase equilibrium to be established in the closed system consisting of the tank 2 and pipe 6, since there is no apparent flow of heat or material in or out. When phase equilibrium is established, the pressure of the material gas G becomes equal to the equilibrium vapor pressure at that temperature. The value of the equilibrium vapor pressure is determined only by the temperature at phase equilibrium.

After the temperature of the precursor P and the pressure of the material gas G have stabilized, the on-off valve 7 is opened to start supplying the material gas G to the semiconductor manufacturing equipment (not shown), and strictly speaking, phase equilibrium is no longer established because the system is no longer closed. However, if the amount of precursor P stored in the tank 2 and the amount of material gas G remaining in the vaporizer 1 are sufficiently large compared to the amount of material gas G released from the on-off valve 7, the flow of heat and material can be ignored, and the state of phase equilibrium is maintained in a pseudo manner. Then, as long as the temperature of the precursor P in the tank 2 is managed to be constant by the power control means 5, the pressure of the material gas G in the tank 2 is also maintained at a pressure equal to the equilibrium vapor pressure at that temperature.

The present invention utilizes the above-described laws of nature. As a result, even though the vaporizer 1 according to the first embodiment of the present invention has a simpler configuration than the vaporizer 1' according to the prior art, it can supply a constant amount of pulsed material gas G to the semiconductor manufacturing equipment by opening the opening/closing valve 7 at a predetermined interval for a predetermined holding time while the pressure of the material gas G in the tank 2 is maintained at the equilibrium vapor pressure of the material gas G at the controlled temperature of the precursor P.

The vaporizer 1 according to the present invention does not require a structure for feedback control of flow rate, such as a mass flow controller, and therefore has the following advantages over the vaporizer 1' according to the prior art. First, it is small and low-cost, with a low risk of failure. Also, since there are no precision parts that require special attention regarding the heat resistance temperature, the precursor can be heated to a higher temperature. Secondly, in principle, it can be operated even if the pressure of the material gas is extremely low. Furthermore, there is little individual difference between devices in the change in flow rate over time when the material gas starts to flow.

In the first embodiment, it is permitted to use not only precursors in a liquid state but also precursors in a solid state as precursors. To generate a material gas using a precursor in a solid state, for example, the precursor in a solid state is charged into the tank through an openable and closable insertion port provided in the tank. In addition, a temperature sensor for measuring the temperature of the precursor can be provided, for example, on the surface of the precursor in a solid state or in a hole provided in the precursor so that the temperature measuring part is in direct contact with the precursor. Regarding phase equilibrium, the phase equilibrium when the precursor is in a liquid state is a phase equilibrium involving evaporation and condensation between the liquid and the gas, whereas the phase equilibrium when the precursor is in a solid state is a phase equilibrium involving sublimation between the solid and the gas. The law of nature utilized in the present invention, in which the pressure of the material gas inside the tank is kept equal to the equilibrium vapor pressure at that temperature by maintaining the temperature of the precursor constant, does not change even when the precursor is in a solid state.

Next, a modified example of the first embodiment will be described. In a preferred embodiment, the nozzle provided in the vaporizer according to the present invention is an orifice comprising a plate with holes. The nozzle 9 provided in the vaporizer 1 shown in Figure 2 is composed of such an orifice, and Figure 2 shows a cross section of the orifice. The nozzle 9 of this configuration can be manufactured by drilling one or more through holes in a plate-shaped member using a drilling process, so that the manufacturing costs can be reduced compared to nozzles with a more complicated configuration. The number and diameter of the through holes and the thickness of the plate can be set appropriately depending on the flow rate of the target material gas G.

As a method for inserting the nozzle 9 consisting of an orifice into the pipe 6, a known method can be used, such as fixing the nozzle 9 with a fixing jig that does not interfere with the flow of the material gas G flowing through the pipe 6. It is preferable to fix the nozzle 9 in a manner that allows the nozzle 9 to be easily replaced. In this case, the nozzle 9 can be easily replaced when the nozzle 9 is damaged and/or when it is desired to change the diameter of the nozzle hole.

In a preferred embodiment, the nozzle provided in the vaporizer according to the present invention is located downstream of the on-off valve. The nozzle 9 provided in the vaporizer 1 shown in FIG. 2 is configured as such a nozzle, and the nozzle 9 is disposed downstream of the on-off valve 7, i.e., on the opposite side to the tank 2. As described above, the material gas G stored in the tank 2 exists in the space above the liquid level of the tank 2 and inside the pipe 6. In a preferred embodiment, when the on-off valve 7 is closed, the material gas G in the pipe 6 is stored upstream of the on-off valve 7. Normally, the pipe 6 downstream of the on-off valve 7 is connected to a semiconductor manufacturing device, and the internal pressure is maintained in a vacuum state similar to that of the processing chamber of the semiconductor manufacturing device.

When the on-off valve 7 is opened by an open signal output from the valve control means 8 and the material gas G is released, the space from the outlet of the on-off valve 7 to the nozzle 9 is immediately filled with the material gas G at equilibrium vapor pressure, and the action of the nozzle 9 starts a fixed supply of the material gas G from the material gas G to the semiconductor manufacturing equipment with almost no delay. If the positional relationship between the on-off valve 7 and the nozzle 9 is reversed from that described above, the material gas G stored between the nozzle 9 and the on-off valve 7 is first released all at once toward the semiconductor manufacturing equipment the moment the on-off valve 7 opens, and then the fixed supply of the material gas G starts due to the action of the nozzle 9, so the flow of the material gas G is likely to be irregular.

In the above preferred embodiment, from the viewpoint of shortening the response delay, it is more preferable to make the volume of the space from the outlet of the on-off valve 7 to the nozzle 9 as small as possible. Specifically, for example, the nozzle 9 can be provided inside the joint that connects the outlet of the on-off valve 7 to the pipe 6.

In a preferred embodiment, the vaporizer 1 according to the present invention includes multiple pipes, each of which includes an on-off valve and a nozzle. The multiple pipes may be individually connected to a tank, or a pipe connected to the tank may branch into multiple pipes along the way. By providing multiple flow paths for supplying the material gas G to the semiconductor manufacturing equipment in this way, the flow rate of the material gas G can be increased compared to a single pipe. In addition, by providing multiple pipes with multiple nozzles having different cross-sectional areas of the flow paths and changing the selection of the pipe through which the material gas G flows by operating the on-off valve, the supply amount of the material gas G can be changed or adjusted within a certain range without changing the temperature of the precursor P.

In a preferred embodiment, the pipe 6, on-off valve 7, and nozzle 9 constituting the vaporizer 1 according to the present invention are equipped with a heating means. The heating means heats these components to a temperature approximately equal to that of the precursor P. This prevents a drop in the temperature of the material gas G flowing through the flow path of the pipe 6, making it possible to more stabilize the supply amount of the material gas G. Furthermore, in cases where the material gas G is a material that is easily liquefied by a drop in temperature, the liquefaction of the material gas G can be prevented by heating these components.

Second Embodiment
In the second embodiment, the present invention is an invention of a vaporizer including, in addition to the configuration of the first embodiment described above, a liquid level sensor that detects the liquid level of the precursor stored in the tank, and a precursor replenishing means that replenishes the precursor inside the tank when the liquid level of the precursor drops. Unlike the first embodiment, the precursor used in the vaporizer according to the second embodiment is limited to a precursor in a liquid state.

FIG. 3 is a schematic diagram showing an example of the configuration of a vaporizer according to a second embodiment of the present invention. Here, the configuration unique to the second embodiment will be described, and the description of the configuration common to the first embodiment will be omitted unless specifically necessary.

As described above, the vaporizer of the present invention maintains the pressure of the material gas at a pressure equal to the equilibrium vapor pressure by creating a pseudo-phase equilibrium state inside the tank. However, as a result of continuing to supply the material gas to the semiconductor manufacturing equipment via a pipe, the amount of precursor stored in the tank decreases, and when the precursor is finally consumed, phase equilibrium is no longer maintained. Furthermore, even if the precursor is not completely depleted, if the position of the precursor liquid level drops significantly compared to the initial state, the balance between the amount of precursor and the amount of material gas is lost, making it difficult to maintain thermal equilibrium within the system.

The vaporizer according to the second embodiment of the present invention detects a decrease in the remaining amount of precursor P by including a liquid level sensor 10 that detects the liquid level of precursor P stored in tank 2. The liquid level sensor 10 may be any sensor that can detect a change in the liquid level of precursor P. For example, as shown in FIG. 3, the liquid level sensor 10 may be a sensor that includes a float that moves up and down along a rod-shaped member in accordance with the rise and fall of the liquid level.

The vaporizer according to the second embodiment of the present invention includes a precursor replenishing means for replenishing the precursor inside the tank when the liquid level of the precursor drops. The precursor replenishing means 11 illustrated in FIG. 3 includes a reservoir 11a for storing precursor P for replenishing the tank 2. The reservoir 11a preferably has a volume larger than the volume of the tank 2 and is a sealable container similar to the tank 2.

The precursor replenishing means 11 further includes a gas cylinder 11b for replenishing the precursor P from the reservoir 11a to the tank 2 by the pressure of the high-pressure gas. The gas cylinder 11b stores a high-pressure gas that is an inert gas such as nitrogen gas or argon gas and does not chemically react with the precursor P. The gas cylinder 11b and the reservoir 11a are connected by a pressurized pipe 11d. A valve 11e is provided midway through the pressurized pipe 11d. A pressure reducing valve (not shown) may be provided in the pressurized pipe 11d.

The reservoir 11a and the vaporizer tank 2 are joined by a single liquid supply pipe 11c. Both ends of the liquid supply pipe 11c are provided at positions close to the bottom of the reservoir 11a and the tank 2. As a result, both ends of the liquid supply pipe 11c are always located below the liquid level of the precursor P. However, as long as the tip of the liquid supply pipe 11c on the reservoir 11a side is located below the liquid level of the precursor P, a configuration in which the tip of the liquid supply pipe 11c on the tank 2 side is positioned above the liquid level of the precursor P is also permitted in the second embodiment.

To replenish the precursor P into the tank 2 using the precursor replenishing means 11 having the above-mentioned configuration, the valve 11e installed in the pressurized pipe 11d connecting the gas cylinder 11b and the reservoir 11a is opened to apply high-pressure gas pressure to the liquid surface of the precursor P stored in the reservoir 11a. This pressure is set to be higher than the pressure of the material gas G stored in the tank 2 of the vaporizer 1. As a result, the precursor P inside the reservoir 11a is replenished into the tank 2 via the liquid delivery pipe 11c. When the liquid level of the precursor P refilled into the tank 2 reaches a preset liquid level, the valve 11e is closed to stop the liquid delivery.

According to the second embodiment, the liquid level of the precursor P inside the tank 2 can be kept constant at all times. This makes the phase equilibrium between the precursor P in a liquid state inside the tank 2 and the material gas G more stable, and the change in the supply amount of the material gas G supplied from the vaporizer 1 to the semiconductor manufacturing equipment becomes smaller.

In the second embodiment, the liquid level of the precursor P inside the tank 2 is always kept constant. For this reason, for example, as shown in FIG. 3, the temperature sensor 3 can be installed horizontally instead of vertically to more accurately measure the temperature at a position close to the liquid surface of the precursor P. This allows the supply amount of the material gas G to be more accurately controlled.

As a modification of the second embodiment, in a preferred embodiment, the vaporizer according to the present invention further includes an exhaust means for degassing the gas dissolved in the precursor stored in the tank. When the pressure of the high-pressure gas from the gas cylinder is applied to the precursor P stored in the reservoir 11a, the gas dissolves in the precursor P in a liquid state according to the pressure of the high-pressure gas. According to Henry's law, the amount of gas dissolved in the liquid is proportional to the pressure of the gas. When the precursor P containing dissolved gas from the gas cylinder 11b is replenished to the tank 2 by the precursor replenishment means 11 and then heated by the heater 4, the gas dissolved in the precursor P becomes gas again, emerges from the liquid surface, and is mixed into the material gas G. Then, a mixed gas of the material gas G and the dissolved gas is stored in the space above the liquid surface in the tank 2.

Even if the material gas G is mixed with a dissolved gas, the partial pressure of the material gas G will be equal to the equilibrium vapor pressure at that temperature. However, since the flow rate of the gas passing through the nozzle 9 depends on the total pressure of the mixed gas, the presence of the mixed gas causes fluctuations in the supply amount of the material gas G.

In a preferred embodiment, the vaporizer 1 is equipped with an exhaust means for degassing the gas dissolved in the precursor P. As exemplified in FIG. 3, the exhaust means 12 can be configured with a pipe and a valve installed on the upper surface of the tank 2. The dissolved gas can be degassed by connecting a vacuum pump (not shown) to the pipe and reducing the pressure in the space above the liquid level in the tank 2. The time required to degas the dissolved gas using the vacuum pump depends on the type and temperature of the precursor P. Typically, a time of, for example, several tens of seconds to several tens of minutes is required. This makes it possible to suppress fluctuations in the supply amount of the material gas due to the influence of the dissolved gas.

Third Embodiment
In the third embodiment, the present invention is a method for supplying a material gas to a semiconductor manufacturing apparatus, the method including the steps of storing a precursor of the material gas in a tank, heating the precursor while controlling the power supplied to the heater so that the temperature of the precursor stored in the tank is equal to a preset temperature, generating a material gas, outputting an open signal from a valve control means to an open/close valve interposed in a pipe that leads the material gas to the outside of the tank to open the open/close valve, supplying the material gas stored in the tank to the semiconductor manufacturing apparatus via a nozzle interposed in the pipe and provided with a flow path communicating with the internal space of the pipe, and outputting a close signal from the valve control means to the open/close valve to close the open/close valve and stop the supply of the material gas. In the method according to the present invention, the cross-sectional area at the narrowest position of the flow path provided in the nozzle is smaller than the cross-sectional area of the internal space of the pipe. In the following description, the same symbols are used for terms common to the inventions according to the first and second embodiments, and explanations will be omitted unless otherwise necessary.

FIG. 4 is a flow chart showing a method according to a third embodiment of the present invention. The method according to the present invention is a method for supplying a material gas to a semiconductor manufacturing apparatus, and the first step is step S1, in which a precursor P of the material gas G is stored in a tank 2. The precursor P stored in the tank 2 may be liquid or solid.

The next step is step S2, in which the precursor P stored in the tank 2 is heated while controlling the power supplied to the heater 4 so that the temperature of the precursor P becomes equal to a preset temperature, thereby generating a material gas G. The temperature of the precursor P can be measured, for example, using a temperature sensor 3. The temperature control of the precursor P can be performed by a power control means 5 equipped with a known temperature control function.

The next step is step S3, in which an open signal is output from the valve control means 8 to the on-off valve 7 provided in the pipe 6 that guides the material gas G to the outside of the tank 2, thereby opening the on-off valve 7. The inlet of the pipe 6 can be provided on the top surface of the tank 2. The open signal output by the valve control means 8 is a signal for fully opening the on-off valve 7, and is not a signal for adjusting the valve opening of the on-off valve 7 to control the flow rate of the material gas G.

The next step is step S4, in which the material gas G stored inside the tank 2 is supplied to the semiconductor manufacturing equipment via a nozzle 9 that is installed in the pipe 6 and has a flow path that communicates with the internal space of the pipe. As described above, the cross-sectional area of the flow path installed in the nozzle 9 at its narrowest position is smaller than the cross-sectional area of the internal space of the pipe 6. The nozzle 9 may be installed in the pipe 6 either upstream or downstream of the opening/closing valve 7.

The next step is step S5, in which a close signal is output from the valve control means 8 to the on-off valve 7 to close the on-off valve 7 and stop the supply of the material gas G. The close signal output by the valve control means 8 is a signal for fully closing the on-off valve 7.

By executing steps S1 to S5 above, the material gas G can be rapidly supplied to the semiconductor manufacturing equipment without delays associated with flow rate control. In the case of ALD, steps S3 to S5 can be repeatedly executed after step S5 is completed.

Next, a modified example of the third embodiment will be described. In a preferred embodiment, the method according to the present invention includes, in addition to the method according to the third embodiment, a step of measuring in advance the flow rate of the material gas G supplied to the semiconductor manufacturing equipment between the time when the opening/closing valve 7 is opened and the time when it is closed. In this embodiment, the flow rate of the material gas G is not measured while the material gas G is actually being supplied to the semiconductor manufacturing equipment.

The step of measuring the flow rate of the material gas G in advance (hereinafter referred to as "step 0 (zero)") is completed before executing steps S3 to S5 in which the material gas G is actually supplied to the semiconductor manufacturing equipment. In the method according to the present invention, the flow rate of the material gas G is not monitored while the material gas G is actually being supplied to the semiconductor manufacturing equipment, so there is no means of directly knowing the flow rate of the material gas G while the method according to the present invention is being performed. In this preferred embodiment, after manufacturing the vaporizer 1 and before operation, step 0 is performed to measure the flow rate of the material gas G in advance, so that the flow rate of the material gas G when steps S3 to S5 are being performed can be estimated.

Preliminary flow rate measurements can be performed by various methods. For example, the flow rate of material gas G per supply can be estimated by measuring the weight loss of tank 2 resulting from supplying material gas G a specified number of times. Alternatively, the flow rate of material gas G per supply can be estimated by measuring the thickness of a semiconductor film formed by performing ALD using a known method. Another method is to use a flow rate measurement function provided in the semiconductor manufacturing equipment that supplies material gas G by the method of the present invention. The flow rate measurement function in this case is, for example, a function that automatically measures pressure changes and temperature changes in the process chamber of the semiconductor manufacturing equipment and estimates the flow rate of material gas G from the measured values.

No matter which of the above methods is adopted, the flow rate measurement in step 0 must be performed in advance, and step 0 must not be performed simultaneously with steps S3 to S5.

If the flow rate of the material gas G obtained by executing step 0 does not match the target flow rate of the method of the present invention, the flow rate of the material gas G may be adjusted in advance by changing the conditions. For example, to adjust the flow rate of the material gas G to be larger, the temperature of the precursor P heated by the heater 4 may be increased to increase the equilibrium vapor pressure. Alternatively, the number of times the material gas G is flowed or the duration of each flow may be increased. Conversely, to adjust the flow rate of the material gas G to be smaller, the equilibrium vapor pressure may be lowered or the number of times or duration the material gas G is flowed may be reduced.

The measurement of the flow rate of the material gas using step 0 can be performed not only immediately after manufacturing the vaporizer, but also when it is desired to change the type and/or flow rate of the material gas, and when it is desired to check for any changes over time after using the vaporizer for a certain period of time.

In a preferred embodiment, the method according to the present invention is a method for supplying material gas G to a semiconductor manufacturing apparatus using precursor P in a liquid state, and in addition to the method according to the third embodiment, further includes a step of refilling the interior of tank 2 with precursor P when the liquid level of precursor P stored in tank 2 drops. By using precursor refilling means 11 to keep the liquid level of precursor P inside tank 2 at a constant height, the phase equilibrium between precursor P in a liquid state inside tank 2 and material gas G becomes more stable, and the change in the supply amount of material gas G supplied from vaporizer 1 to the semiconductor manufacturing apparatus becomes smaller.

In this preferred embodiment, if the method further includes a step of degassing the gas dissolved in the precursor P stored in the tank 2, this is even more preferable, since, as described above, this can suppress fluctuations in the supply amount of the material gas due to the influence of the dissolved gas.

In a preferred embodiment, the method according to the present invention is a method for supplying material gas G to a semiconductor manufacturing apparatus using precursor P in a liquid state, and in addition to the method according to the third embodiment, further includes a step of adjusting the value of pressure P1 inside the tank 2 to a value equal to or greater than the value of pressure P2 downstream of the nozzle 9. The adjustment of pressure P1 can be performed by adjusting the temperature of the precursor P. The adjustment of pressure P2 can be performed by adjusting the pressure of the processing chamber of the semiconductor manufacturing apparatus. This can prevent backflow of material gas G from the downstream side of the nozzle 9 to the upstream side, so that even if the pressure of the processing chamber of the semiconductor manufacturing apparatus changes, the change in the flow rate of material gas G supplied from the vaporizer 1 is suppressed, and the supply amount of material gas G becomes more stable. It is more preferable to adjust the value of pressure P1 to twice the value of pressure P2 or more, since the speed of material gas G flowing through the nozzle 9 is more likely to exceed the speed of sound, and the supply amount of material gas G becomes more stable.

<<Example>>
The vaporizer according to the present invention is designed based on the hypothesis (hereinafter referred to as the "vaporizer hypothesis") that "the flow rate of the material gas can be controlled by controlling only the temperature of the precursor in a vaporizer placed in a pseudo-phase equilibrium state." Here, experimental data suggesting that the vaporizer hypothesis is correct will be presented in place of an embodiment of the present invention.

A vaporizer 1 having the structure shown in FIG. 2 was prepared. The volume of the tank 2 included in the vaporizer 1 was 2.0 liters. The nozzle 9 included in the vaporizer 1 was an orifice with a hole of 0.5 mm in diameter drilled in the center of a gasket with a thickness of 0.8 mm. Only 0.8 liters of ion-exchanged water was stored inside the tank 2 via the precursor replenishing means 11. After that, the exhaust means 12 (not shown) provided on the upper surface of the tank 2 was operated for 10 minutes to degas the gas dissolved in the ion-exchanged water stored in the tank 2.

Next, a collection vessel for collecting water vapor was prepared. The weight of the empty collection vessel was 954.05 grams. The outlet of the pipe 6 was connected to the collection vessel downstream of the nozzle 9 using a stainless steel flexible tube. Next, while the temperature of the ion-exchanged water in the tank 2 was measured by the temperature sensor 3, the power supplied to the heater 4 was controlled using the power control means 5 (not shown) to adjust the water temperature to 50°C. After waiting for the water temperature to be sufficiently stabilized, the opening and closing valve 7 was opened using the valve control means 8 (not shown), and the water vapor stored in the space above the liquid level in the tank 2 was sent to the collection vessel via the nozzle 9. After 10 minutes had passed since the opening and closing valve 7 was opened, the opening and closing valve 7 was closed using the valve control means 8. Then, the power supplied to the heater 4 was set to zero.

After stopping the heating and waiting for the collection vessel to cool, the collection vessel was detached from pipe 6 and the combined weight of the collection vessel and its contents was measured. The amount of water vapor captured in the collection vessel was calculated by subtracting the weight of the empty collection vessel from this. This series of measurements was carried out while changing the water temperature in 5°C increments in the range from 50°C to 65°C, and this cycle was repeated three times. These measurement data are referred to as Group A. The relationship between water temperature and the amount of water vapor captured in Group A is shown in Table 1. Table 1 also lists the equilibrium vapor pressure of water vapor at each water temperature, calculated based on the literature.

Next, on a different day from the day when the Group A measurements were carried out, the above series of measurements was carried out, this time changing the water temperature in 5°C increments within the range of 65°C to 80°C, and this cycle was repeated three times. These measurement data are referred to as Group B. The relationship between water temperature and the amount of water vapor collected in Group B is shown in Table 2.

As shown in Tables 1 and 2, in both Group A and Group B, the amount of water vapor collected in three measurements was nearly the same when the water temperature was the same. From this, it can be considered that the amount of water vapor collected in Group A and Group B is highly reproducible.

Next, Figure 5 shows a graph in which the equilibrium vapor pressure of water vapor shown in Tables 1 and 2 is plotted on the horizontal axis, and the amount of water vapor collected on the vertical axis. In Figure 5, the circle plots represent the data for Group A, and the triangle plots represent the data for Group B. The dotted line is an approximation line obtained by the least squares method based on all the plots. As is clear from the graph in Figure 5, both the plots for Group A and Group B match well with the approximation line shown by the dotted line. This shows that in vaporizer 1, the amount of water vapor collected in the collection vessel is represented by a linear function of the equilibrium vapor pressure of water vapor, which is determined only by the temperature inside tank 2. This experimental fact suggests that the vaporizer hypothesis described above is correct.

In addition, the dotted line extending the plot in the graph of Figure 5 does not pass through the origin. This is thought to be because the weight of the water remaining inside the stainless steel flexible tube connecting the outlet of pipe 6 to the collection vessel is not included in the measured amount of collection. However, according to the above reference example, it is clear that the amount of water vapor collected, that is, the flow rate of water vapor passing through nozzle 9 within a specified time, can be controlled by controlling only the temperature of the ion-exchanged water, which is regarded as a precursor of the material gas. Furthermore, as mentioned above, if the flow rate of the material gas is measured in advance and adjusted, the desired amount of material gas can be supplied by opening and closing the opening and closing valve 7 once.

REFERENCE SIGNS LIST 1 Vaporizer 2 Tank 3 Temperature sensor 4 Heater 5 Power control means 6 Pipe 7 Opening/closing valve 8 Valve control means 9 Nozzle 10 Liquid level sensor 11 Precursor refilling means 11a Reservoir 11b Gas cylinder 11c Liquid delivery pipe 11d Pressurized pipe 11e Valve 12 Exhaust means P Precursor G Material gas 1' Vaporizer (prior art)
7' Flow Control Valve (Prior Art)
8' Flow sensor (prior art)

Claims (12)

A vaporizer that generates a material gas from a precursor of the material gas and supplies it to the outside, comprising: a tank that stores the precursor; a temperature sensor that measures the temperature of the precursor stored in the tank; a heater that heats the precursor stored in the tank to generate the material gas; power control means that controls the power supplied to the heater so that the temperature of the precursor measured by the temperature sensor becomes equal to a preset temperature; a pipe that guides the material gas stored inside the tank to the outside of the tank; an opening/closing valve that is interposed in the pipe and that allows the material gas to flow or stop; valve control means that outputs an open signal and a close signal to the opening/closing valve; and a nozzle that is interposed in the pipe and has a flow path that communicates with the internal space of the pipe, the vaporizer having a cross-sectional area at the narrowest position of the flow path provided in the nozzle that is smaller than the cross-sectional area of the internal space of the pipe. 2. The vaporizer of claim 1,
the nozzle is an orifice comprising a plate with holes;
Carburetor. 2. The vaporizer of claim 1,
The nozzle is located downstream of the opening and closing valve.
Carburetor. 2. The vaporizer of claim 1,
a plurality of the pipes, each of the plurality of pipes including one of the on-off valves and one of the nozzles;
Carburetor. 2. The vaporizer of claim 1,
The pipe, the on-off valve and the nozzle are equipped with a heating means.
Carburetor. 2. The vaporizer of claim 1,
the precursor is in a liquid state;
a liquid level sensor that detects a liquid level of the precursor stored in the tank, and a precursor replenishing means that replenishes the precursor into the tank when the liquid level of the precursor drops.
Carburetor. 7. The carburetor of claim 6,
The present invention further includes an exhaust means for degassing a gas dissolved in the precursor stored in the tank.
Carburetor. A method for supplying a material gas to a semiconductor manufacturing apparatus, comprising the steps of:
storing the precursor of the material gas in a tank;
a step of heating the precursor while controlling power supplied to a heater so that the temperature of the precursor stored in the tank becomes equal to a preset temperature to generate the material gas;
a step of outputting an open signal from a valve control means to an on-off valve disposed in a pipe for leading the material gas to the outside of the tank, thereby opening the on-off valve;
supplying the material gas stored in the tank to the semiconductor manufacturing equipment through a nozzle that is disposed in the pipe and has a flow path that communicates with an internal space of the pipe;
a step of outputting a close signal from the valve control means to the on-off valve to close the on-off valve and stop the supply of the material gas,
A cross-sectional area at the narrowest position of the flow passage provided in the nozzle is smaller than a cross-sectional area of an internal space of the pipe.
A method for supplying a material gas to a semiconductor manufacturing device. 9. A method for supplying a material gas to a semiconductor manufacturing apparatus according to claim 8, comprising the steps of:
a step of measuring in advance a flow rate of the material gas supplied to the semiconductor manufacturing equipment during a period from when the on-off valve is opened to when it is closed,
A method for supplying a material gas to a semiconductor manufacturing device. 9. A method for supplying a material gas to a semiconductor manufacturing apparatus according to claim 8, comprising the steps of:
the precursor is in a liquid state;
The method further includes replenishing the precursor inside the tank when the liquid level of the precursor stored in the tank drops.
A method for supplying a material gas to a semiconductor manufacturing device. 11. A method for supplying a material gas to a semiconductor manufacturing apparatus according to claim 10, comprising the steps of:
The method further includes a step of degassing the precursor stored in the tank to remove any dissolved gas.
A method for supplying a material gas to a semiconductor manufacturing device. 9. A method for supplying a material gas to a semiconductor manufacturing apparatus according to claim 8, comprising the steps of:
The pressure value inside the tank is adjusted to a value equal to or greater than a pressure value downstream of the nozzle.
A method for supplying a material gas to a semiconductor manufacturing device.

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