JP5228182B2 - GAS CONTROL DEVICE, CONTROL METHOD FOR GAS CONTROL DEVICE, AND ION IMPLANTATION DEVICE USING THEM - Google Patents

Description

  The present invention relates to a gas control apparatus that controls the inflow of gas into a depressurizable chamber such as an ion source in a semiconductor manufacturing apparatus such as an ion implantation apparatus, and a control method therefor.

  In a foundry that manufactures semiconductors from a plurality of companies, one type of semiconductor is not continuously produced all day, but rather, many types of semiconductors are manufactured in small lots. In the manufacturing process of such a wide variety of semiconductors, when the characteristics of the semiconductor are modified by ion implantation, it is required that the ion implantation amount and the ion species to be implanted can be changed in a short time for each type of semiconductor. ing.

  The change of the ion species is performed by changing the type of gas flowing into the ion source which is a chamber capable of depressurization. In order to perform this gas switching and flow rate control, a gas control in which a primary side valve, a mass flow controller, and a secondary side valve are provided in this order on the gas line connecting the ion source and the gas supply means. A device is provided.

  The conventional gas change procedure in the gas control apparatus having such a configuration includes a closing process for stopping the gas flow into the chamber and exhausting the gas in the chamber, and a process for switching the type of gas in the gas supply means, And an opening process for starting the inflow of gas into the chamber.

  As a more specific procedure, in the closing process, as shown in FIG. 1, the primary side valve is fully closed (step OS1), and a decrease in the flow rate of the gas flowing through the gas line is confirmed by the mass flow controller (step OS2). Thereafter, the secondary side valve is fully closed (step OS3), and it is confirmed that the gas has been exhausted due to a decrease in the degree of vacuum in the chamber (step OS4). On the other hand, as shown in FIG. 2, the opening process opens the secondary side valve (step OS5), opens the primary side valve after a predetermined time has elapsed, and starts the flow control of the mass flow controller and ends. (Step OS6).

  By the way, in such a processing procedure, as described above, the opening degree of the flow variable valve in the mass flow controller is not particularly considered during the closing process. I don't know if it's time. For example, when the flow rate variable valve is fully opened at the end of the closing process and the state is maintained, when the primary side valve is opened after the secondary side valve is opened during the opening process, A rush in which a large amount of gas flows into the chamber suddenly occurs. Then, the pressure in the chamber causes a very large overshoot with respect to a predetermined pressure (degree of vacuum) appropriate for extracting the gas into plasma and extracting it as an ion beam, and the time taken to stabilize at the predetermined pressure. It will be long. In other words, every time the gas type is changed to switch the ion species, it is necessary to wait for the pressure in the chamber to stabilize, so the time for changing the setup becomes longer and the semiconductor manufacturing efficiency decreases. This problem occurs.

  A gas control device for preventing gas entry into the chamber at the start of gas supply is disclosed in a plasma processing apparatus as disclosed in Patent Document 1. This gas control device includes a control unit that instructs the mass flow controller to be fully closed during the opening process, and then instructs the primary side valve and the secondary side valve to be opened.

  However, although Patent Document 1 describes that the mass flow controller is fully closed prior to the opening process, the configuration described in Patent Document 1 does not always always fully close the mass flow controller. Specifically, in Patent Document 1, a full-close command is input to the mass flow controller to close the internal valve. However, the mass flow controller feeds back the measured flow rate of the fluid flowing through the flow path, and sets the set flow rate. For example, when there is almost no differential pressure before and after the mass flow controller and the flow rate is almost 0, a fully closed command, that is, a command to set the flow rate to 0 is controlled. Even if a value is input, since there is almost no difference, the opening degree of the variable flow valve is hardly controlled in the closing direction, and the opening degree at that time is maintained. Even if the full close command is compulsory not based on the feedback command, depending on the model and the structure of the variable flow valve, the valve will be fully closed unless there is a differential pressure before and after the mass flow controller. The present inventors have confirmed by experiments that this is not always the case.

  In other words, Patent Document 1 does not consider at all whether or not there is a differential pressure before and after the mass flow controller, and simply inputs a command to fully close the mass flow controller. It is not possible to completely prevent the gas from entering, and it is not always possible to reduce the time required for the pressure in the chamber to stabilize to a predetermined pressure. Therefore, in such a gas control method, it is difficult to actually reduce the time required for the setup change such as ion species switching. In particular, the primary side valve and the secondary side valve are fully closed, there is residual gas in the volume formed by the flow path between the primary side valve and the secondary side valve, etc. In this case, even if the flow rate variable valve is closed, the gas remaining between the flow rate variable valve and the secondary side valve will enter the chamber, and it will take time for the pressure to stabilize. It will take. Also, if the flow rate variable valve of the mass flow controller is closed in the presence of residual gas, the internal pressure will increase by the amount that the valve has pushed the residual gas in the sealed space, and there will be a force in the direction of opening the variable flow rate valve. Because it works, it cannot be completely closed. Therefore, even if a fully closed signal is input to the mass flow controller, it cannot be fully closed during the opening process, and therefore, a residual gas intrusion that occurs in the space between the primary side valve and the mass flow controller also occurs. It takes time for the pressure to stabilize.

Japanese Patent Laid-Open No. 2002-85962

  The present invention has been made in view of the above-described problems, and includes a primary flow valve and a mass flow controller from upstream on a gas line that includes a variable flow valve and connects a depressurizable chamber and gas supply means. A gas control device in which secondary valves are provided in this order, the mass flow controller is surely fully closed during the opening process, and gas can be prevented from entering the chamber. It is an object of the present invention to provide a gas control device, a control method for the gas control device, and an ion implantation apparatus using them, which can shorten the time required for replacement.

  That is, the gas control device of the present invention is a gas control device provided in a gas line connecting a gas supply means and a depressurizable chamber, comprising a variable flow valve, and a flow rate of gas flowing into the chamber A mass flow controller for controlling the flow rate to a set flow rate, a primary side valve provided upstream of the mass flow controller, and a secondary side valve provided downstream of the mass flow controller. In the gas closing process for stopping the inflow of the gas, the mass flow controller, the primary side valve, and the secondary side valve are fully closed in this order, or the primary side valve is fully closed for a first predetermined time. A control unit that fully closes the mass flow controller and then fully closes the secondary valve. To.

  The control method of the gas control device of the present invention is a control method of a gas control device provided in a gas line connecting a gas supply means and a depressurizable chamber, wherein the gas control device includes the chamber A mass flow controller that controls the flow rate of the gas flowing into the gas flow rate to a set flow rate, a primary valve provided upstream of the mass flow controller, and a secondary valve provided downstream of the mass flow controller. In the gas closing process for stopping the gas flow into the chamber, the mass flow controller, the primary side valve, and the secondary side valve are fully closed in this order, or the primary side valve is fully closed. A step of fully closing the mass flow controller within a first predetermined time and then fully closing the secondary valve Characterized by comprising.

  Note that the phrase “the mass flow controller is fully closed within a first predetermined time after the primary side valve is fully closed” includes the case where the first predetermined time is zero before. And the concept of fully closing the mass flow controller at the same time. The first predetermined time is a concept including, for example, a time during which a differential pressure exists before and after the mass flow controller.

  If this is the case, the mass flow controller is fully closed before the primary side valve, or the mass flow controller is fully closed within a first predetermined time after the primary side valve is fully closed. Since it is closed, there can be a differential pressure before and after the mass flow controller, and the mass flow controller can be surely fully closed. In addition, since the secondary side valve is fully closed after the primary side valve and the mass flow controller are fully closed, the mass flow is higher than the pressure in the space between the primary side valve and the mass flow controller. After the pressure in the space between the controller and the secondary valve is reduced to a low pressure by the chamber, the secondary valve is fully closed. In other words, after the closing process is completed, the state where there is a differential pressure before and after the mass flow controller is maintained, so that the mass flow controller is also maintained in the fully closed state.

  Therefore, when the next opening process is performed, the mass flow controller is surely fully closed, so that the gas can be prevented from entering the chamber when the secondary valve is opened, and the desired amount in the chamber can be prevented. The amount of overshoot with respect to the pressure can be reduced, and the time to stabilize at the desired pressure can be shortened. That is, when changing the type of gas, etc., the pressure in the chamber can be stabilized in a short time, so that the time required for setup change can be shortened and the operating efficiency of the apparatus can be increased. become.

  Due to the closing process, the variable flow valve is fully closed in a state where there is a differential pressure before and after the mass flow controller, and after a long time in that state, the variable flow valve is bitten, so the variable flow valve is opened again. To do that, you need a lot of power. If the secondary valve is first opened, the differential pressure before and after the mass flow controller is further increased. Therefore, when the flow control of the mass flow controller is started thereafter, the opening of the variable flow valve is increased. Control will be performed to make it even larger. When these things overlap, the opening of the variable flow valve does not change in the fully closed state for a certain period of time due to friction or the like. Gas will rush. In order to solve such a problem and allow gas to slowly flow into the chamber in a short time, the control unit performs the closing process during the gas opening process for starting the gas flow into the chamber. When the elapsed time from the time exceeds a predetermined time, the secondary valve may be opened after the mass flow controller starts the flow control.

  If not much time has passed after the closing process, the variable flow valve does not bite so much, so the opening can be changed immediately. In such a state, if the flow control of the mass flow controller is started first as described above, and then the secondary valve is opened, the opening of the variable flow valve becomes too large. The pressure greatly overshoots the desired pressure and takes time to stabilize. In order to prevent such a problem from occurring, the control unit, when the gas opening process for starting the inflow of gas into the chamber, when the elapsed time from the closing process is a predetermined time or less, After the secondary valve is opened, the mass flow controller may start flow control.

  In an ion implantation apparatus, in order to enable switching of ion species in a short time and to improve semiconductor manufacturing efficiency, an ion implantation apparatus having the gas control apparatus as described above is used. I just need it.

  Thus, according to the gas control device of the present invention, the control method thereof, and the ion implantation apparatus using them, the variable flow rate valve is configured to be fully closed in a state where there is a differential pressure before and after the mass flow controller. Therefore, the mass flow controller can be surely fully closed during the opening process. Therefore, even when the secondary valve is opened during the next opening process, gas can be prevented from entering the chamber, or the amount of the gas can be reduced, and the pressure in the chamber can be reduced. The time until the pressure becomes stable can be shortened. Therefore, the time required for the setup change such as changing the type of gas can be shortened, and the operating efficiency of the apparatus can be improved.

The flowchart which shows the operation | movement at the time of the closing process in the conventional gas control apparatus. The flowchart which shows the operation | movement at the time of the open process in the conventional gas control apparatus. The schematic diagram which shows the ion implantation apparatus which concerns on one Embodiment of this invention. The schematic diagram which shows the gas control apparatus in the embodiment. The typical sectional view showing the internal structure of the variable flow valve in the embodiment. The flowchart which shows the operation | movement at the time of the closing process in the embodiment. The graph which shows the change of the vacuum degree in an ion source when the closing process in the embodiment is performed. The flowchart which shows the operation | movement at the time of the open process in the embodiment. The graph which shows the change of the vacuum degree in an ion source when an opening process is performed after a long time passes after the closing process in the same embodiment. The graph which shows the change of the vacuum degree in an ion source when an opening process is performed after a short time passes after the closing process in the embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  The ion implantation apparatus 100 using the gas control apparatus 10 of the present invention changes its characteristics by implanting various types of ions at a predetermined angle, depth, and concentration, for example, on the surface of a silicon substrate or the like. It is used for reforming.

  The ion implantation apparatus 100 of the present embodiment selects only a desired type of ions from the ion beam IB extracted at a certain voltage from the ion source 1 as shown in FIG. By passing the ion beam IB after passing through the electrostatic accelerator tube 3, the ion beam IB is made to have desired energy and deflected so as to be incident on the target T at a predetermined incident angle.

  The ion source 1 is a depressurizable chamber having an exhaust mechanism and is connected to a gas cylinder as a gas supply means 5 by a gas line as shown in FIG. The beam IB is extracted.

  On the gas line, there is provided a gas control device 10 for controlling the flow rate of the gas flowing into the ion source 1 from the gas supply means 5 as shown in FIG. The gas control device 10 includes a variable flow valve 41, a mass flow controller 4 that controls the flow rate of the gas flowing through the gas line to a set flow rate, and a primary valve provided upstream of the mass flow controller 4. 6, a secondary side valve 7 provided downstream of the mass flow controller 4, and a control unit 8 that controls the opening degree of these valves.

  The mass flow controller 4 includes a flow meter 42 that measures the flow rate based on the differential pressure of the fluid flowing through the internal flow path, and a set flow rate in which the measured flow rate measured by the flow meter 42 is set. Thus, the opening degree of the variable flow valve 41 is controlled in such a direction that these deviations become smaller.

  The variable flow rate valve 41 is, for example, a solenoid type flow rate control valve as shown in the cross-sectional view of FIG. 5A, and is operated between the valve seat V2 by operating the valve body V1 by electromagnetic force. The flow rate of the fluid passing therethrough is controlled by adjusting the size of the gap formed. The valve seat V2 is coated so that the frictional resistance is increased, or the portion in contact with the valve body V1 is slightly softened. Such processing is performed so that the fully closed state is maintained even with a slight pressure fluctuation when the valve body V1 is completely in contact with the valve seat V2 as shown in FIG. 5 (b). It is to make it.

  The primary side valve 6 and the secondary side valve 7 are valves for on-off control configured to be in a fully open state or a fully closed state.

  The control unit 8 is a so-called computer having a CPU, a memory, an I / O channel, an output device such as a display, an input device such as a keyboard, an AD converter, and the like, and the CPU and its peripherals according to a program stored in the memory. When the device operates, at least functions as the closing time measuring unit 81 and the opening setting unit 82 are exhibited. In addition, the control part 8 may be provided in the said massflow controller 4, and the computer etc. which were provided in another place may be sufficient as it.

  The closing time measuring unit 81 measures and stores the elapsed time since the closing process is performed, and the measured elapsed time determines the order in which the valves are opened during the opening process. Therefore, the opening setting unit 82 is used.

  In the closing process for stopping the gas inflow to the ion source 1 and the opening process for restarting the gas inflow to the ion source 1, the opening degree setting unit 82 includes the mass flow controller 4 and the primary valve 6. The secondary valve 7 is opened and closed according to a predetermined order or condition.

More specifically, the opening setting unit 82 fully closes the set flow rate of the mass flow controller 4 at 0 cc and closes the primary side valve 6 substantially simultaneously in the closing process, and then closes the secondary side. The valve 7 is fully closed. Further, at the time of the opening process, when a long time has passed since the end of the closing process, for example, when the elapsed time measured by the time measuring unit 81 exceeds the second predetermined time of 20 minutes, After the mass flow controller 4 changes the set flow rate from 0 cc to another value and starts flow rate control, the secondary valve 7 is opened. On the other hand, when only a short time has passed since the end of the closing process, for example, when the elapsed time measured by the time measuring unit 81 is within 20 minutes, the second valve is opened, The mass flow controller 4 starts flow control.
In addition, as another aspect of the opening degree setting part 82, instead of setting the set flow rate of the mass flow controller to 0 cc, a fully closed signal may be input. In this case, in order to start the flow control again, first, the full-close command is canceled, and then the flow control is started.

  In the ion implantation apparatus 100 configured as described above, the gas control apparatus 10 in the case of switching the gas supplied from the gas supply means 5 to the ion source 1 in order to change the ion implantation conditions by switching the ion species. The operation will be described.

  Switching of the gas supplied from the gas supply means 5 is performed by performing a closing process for stopping the gas from flowing into the ion source 1 while performing vacuum evacuation, and after switching or replacing the gas supply means 5, And an opening process for starting a new gas flow into the ion source 1 again. Hereinafter, the operation of each device in the closing process and the opening process will be described in detail with reference to the flowcharts shown in FIGS.

  As shown in FIG. 6, in the closing process, first, the opening setting unit 82 has the primary side valve 6 and the secondary side valve 7 opened, gas flows into the gas line, and the mass flow controller In the state where the differential pressure exists before and after 4, the set flow rate is changed to 0 cc with respect to the mass flow controller 4 (step S1). Then, the mass flow controller 4 is operated in a direction to fully open the variable flow valve 41 by feedback control.

  Next, the opening setting unit 82 sets the opening of the primary valve 6 to be fully closed (step S2). Here, since the mass flow controller 4 approaches the fully closed state by feedback control, the mass flow controller 4 and the primary side valve 6 are almost all at the same time because there is a slight time delay until the mass flow controller 4 is fully closed. It is closed (step S3).

  The opening setting unit 82 confirms that the flow rate is lower than a predetermined value by the flow meter 42 in the mass flow controller 4 (step S4). This operation is performed to confirm that the mass flow controller is fully closed. After the confirmation is completed, the secondary side valve 7 is fully closed (step S5). Finally, a decrease in the degree of vacuum is confirmed by an IG meter (not shown) for measuring the degree of vacuum provided in the ion source 1, and the closing process is terminated. From this time point, the time measuring unit 81 starts measuring the elapsed time from the end of the closing process (step S6).

  Here, the effect by performing such a closing process will be described. As described above, since the set flow rate of the mass flow controller 4 is initially set to 0 cc, there is a differential pressure before and after the mass flow controller 4, so that the variable flow valve 41 is reliably fully closed. . Further, after the primary side valve 6 and the mass flow controller 4 are fully closed substantially simultaneously, the secondary side valve 7 is fully closed after the downstream of the mass flow controller 4 is made low pressure by evacuation. Even at the end time, since the differential pressure exists before and after the mass flow controller 4, the fully closed state is maintained. Therefore, in the initial state of the opening process described later, the mass flow controller 4 can be surely kept in the fully closed state.

  Furthermore, the degree of vacuum of the ion source 1 becomes substantially zero, and the time required for stabilization can be shortened. FIG. 7 shows the change in the degree of vacuum when the secondary valve 7 is fully closed after the primary valve 6 is fully closed without setting the flow rate to the mass flow controller 4 as in the prior art. The change in the degree of vacuum by the closing method is shown. Conventionally, since the opening degree of the mass flow controller 4 is not known at the time of the opening process, the entry of gas at the time of the opening process is prevented by eliminating the residual gas at the time of the closing process. For this reason, since all the volumes of gas downstream from the primary side valve 6 are evacuated, it takes time to stabilize since a large amount of gas needs to be evacuated. On the other hand, according to the closing processing method of the present embodiment, the mass flow controller 4 is surely fully closed at the time of performing the opening processing, so that the residual gas is between the primary side valve 6 and the flow rate variable valve 41. Even if there is, gas can be prevented from entering the ion source 1. That is, the primary valve 6 is fully closed with the mass flow controller 4 fully closed or close to it, and the residual gas existing in the volume between the primary valve 6 and the flow rate variable valve 41 is evacuated. There is no problem even if it is not performed. Accordingly, the amount of gas to be evacuated by the volume between the primary side valve 6 and the flow rate variable valve 41 can be greatly reduced as compared with the prior art, so that it can be stabilized to approximately 0 cc in a short time.

  Next, the operation during the opening process will be described with reference to FIG.

  The order in which the valves are opened during the opening process is selected according to the elapsed time from the end of the closing process described above. This is because when the variable flow valve 41 is fully closed for a long time with a differential pressure, the valve body V1 is drawn to the downstream side, which is the low pressure side, with respect to the valve seat V2 due to the differential pressure. The valve body V1 bites into the valve seat V2, making it difficult to remove. Then, since a larger force than usual is required to separate the valve body V1 from the valve seat V2 at the time of initial movement, even if the set flow rate is not 0 cc, the fully closed state is maintained and opened. If this happens, the frictional resistance disappears all at once, so that it opens too much, and gas may enter. In view of such problems, in the opening process, the opening order of the valves is determined in consideration of the amount of biting of the variable flow valve 41.

  As a specific method for opening each valve, when the elapsed time measured by the time measuring unit 81 exceeds 20 minutes (step S7), the opening setting unit 82 first sets the mass flow controller. 4 is set to a set flow rate other than 0 cc (step S8), the variable flow valve 41 is gradually opened with respect to bite, and then the secondary valve 7 is opened (step S9). Finally, the primary valve 6 is opened (step S10), and the opening process is terminated.

  When the elapsed time measured by the time measuring unit 81 is within 20 minutes (step S7), the opening setting unit 82 first opens the secondary valve 7 (step S10), and then A set flow rate other than 0 cc is set in the mass flow controller 4 (step S11). Finally, the primary valve 6 is opened and the opening process is finished (step S12).

  Here, on the premise of the above-described closing process, the effect of performing such an opening process will be described.

  FIG. 9 shows a change in the degree of vacuum in the ion source 1 when the opening process is performed after a long time has elapsed after the closing process.

  In FIG. 9, the mass flow controller 4 is not fully closed in the closing process, and the primary valve 6 and the mass flow controller 4 are simultaneously opened after the secondary valve 7 is opened in the opening process. The measurement result B when the conventional open processing method described above is performed after performing the conventional measurement result A when the process is started and the closing process of the present embodiment, and the opening process and the closing process of the present embodiment are performed. The measurement result C when performed is shown.

  In measurement result A, a gas rush occurs, so a large overshoot occurs with respect to the target degree of vacuum, and it takes time to stabilize, whereas in measurement result B, no overshoot occurs, It can be seen that although the time required to stabilize the target vacuum degree is shortened, it takes time to rise. In the measurement result B, since the second valve and the first valve are opened with the variable flow valve 41 biting in, the differential pressure before and after the mass flow controller 4 becomes larger, and the variable flow valve 41 is The force to bite in the opposite direction becomes larger than the force to open. In other words, the reason why it takes time to start up is considered to be because it takes time until the variable flow rate valve 41 is opened because the magnitude of the force that is actually opened is reduced.

  In the measurement result C, since the variable flow valve 41 is opened before the differential pressure increases, a larger force can be applied to the variable flow valve 41 than in the measurement result B. For this reason, compared with the overshoot in the case of the measurement result A, it suppresses the bite of the variable flow valve 41 in a shorter time than the case of the measurement result B, and shortens the rise time while suppressing the overshoot to a level that can be ignored in practice. Have been able to.

  FIG. 10 shows a change in the degree of vacuum in the ion source 1 when the opening process is performed when only a short time has passed after the closing process. FIG. 10 shows a conventional measurement result A as a comparison with the measurement result D of the degree of vacuum in the ion source 1 when the closing process of the present embodiment and the opening process when the elapsed time from the closing process is short are performed. It is shown. Since the measurement result D can be reduced to a practically negligible amount with respect to the conventional measurement result A, the measurement result D can be handled in substantially the same manner as the measurement result C described above, and can be used for a short time. It can be seen that the target value is stable.

  Further, if the opening process is performed in the same manner as the measurement result C with the amount of biting of the variable flow valve 41 being small, the mass flow controller 4 is substantially fully opened before the secondary valve 7 is opened, It becomes almost the same as the conventional measurement result A. Therefore, when only a short time has elapsed since the closing process, it is effective to start the flow control of the mass flow controller 4 after opening the secondary side valve 7 as in this embodiment. .

  As described above, according to the ion implantation apparatus 100 and the gas control apparatus 10 of the present embodiment, in the closing process, the mass flow controller 4 is fully closed while the differential pressure exists. It is possible to ensure that the mass flow controller 4 is fully closed in the initial state. Therefore, the amount of gas that enters the ion source 1 in the opening process can be eliminated or made extremely small, and the time taken to stabilize to a predetermined degree of vacuum can be shortened.

  In addition, since the mass flow controller 4 is first fully closed in the closing process, fluctuations in the degree of vacuum due to the primary side valve 6 being fully closed can be prevented, and the primary side valve 6 and the flow rate can be reduced as compared with the prior art. Since it is not necessary to perform evacuation by the amount of gas corresponding to the volume between the variable valves 41, the time required until the degree of vacuum is stabilized and the closing process is completed can be shortened.

  Furthermore, in the opening process, the order in which the valves are opened is changed according to the elapsed time from the closing process, so that the opening process in consideration of the amount of biting of the variable flow valve 41 can be performed as described above. It is possible to shorten the time required to stabilize at a desired degree of vacuum.

  As described above, the time required for the work in the closing process and the opening process can be greatly shortened. Therefore, even when ion implantation is performed on a small lot and a variety of semiconductors, the setup can be changed in a short time. And the production efficiency of semiconductors can be improved. Moreover, since the degree of vacuum suitable for extracting the ion beam IB can be achieved in a short time, the amount of gas flowing unnecessarily can be reduced, the gas consumption can be reduced, and the operation cost can be reduced. it can.

  Other embodiments will be described.

  In the embodiment, the mass flow controller and the primary side valve are fully closed at the same time during the closing process. However, the mass flow controller is fully closed first, and the primary side valve is then fully closed. You may comprise. Alternatively, the primary valve may be fully closed first, and then the mass flow controller may be fully closed. In this case, the mass flow controller may be fully closed after the primary side valve is fully closed and before the differential pressure is lost before and after the mass flow controller due to evacuation. That is, the mass flow controller may be fully closed within a first predetermined time after the primary side valve is fully closed. Even in such a case, the mass flow controller can be fully closed reliably in a state where there is a differential pressure before and after.

  In the above embodiment, in order to fully close the mass flow controller, the set flow rate is set to 0 cc, and the mass flow controller is fully closed by feedback control. However, the mass flow controller is forced to fully close regardless of feedback control. You can do it. Even if it can be forcibly fully closed, depending on the mechanism and structure, if there is no differential pressure before and after the mass flow controller, it cannot be fully closed, and gas entry cannot be prevented. For example, in the forced fully closed mode, in the pivot type valve that is configured so that the supporting force to the valve body is lost and the valve seat is fitted by the flow of fluid, the valve body is fully closed when there is no differential pressure. I can't. Further, even a valve that is fully closed by fitting the valve body into the valve seat by an external force is usually pressed only by a force that does not break the valve seat. Therefore, even if the valve can be fully closed in the absence of differential pressure, the valve body will come off the valve seat when the secondary valve is fully closed and the gas that has been pushed away becomes counter pressure. It is also conceivable that the fully closed state cannot be maintained. Therefore, even if the mass flow controller can be forcibly fully closed, it is important that the mass flow controller be fully closed with a differential pressure before and after. It is possible to prevent the gas from entering the ion source.

  For example, when the flow rate that can be flowed by the mass flow controller is 5 cc in full scale, and the flow rate that is actually flowed is about 1 cc in normal use, the gas control of the present invention is always used in a state close to full closure. The method is particularly effective.

  The mass flow controller of the above embodiment may be a thermal type that measures the flow rate by differential pressure. Further, the gas control device of the present invention is not necessarily applied only to the ion implantation device. You may use for a plasma processing apparatus etc.

  In addition, various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Ion implantation apparatus 10 ... Gas control apparatus 1 ... Ion source (chamber)
4 ... Mass flow controller 41 ... Variable flow valve 5 ... Gas supply means 6 ... Primary side valve 7 ... Secondary side valve 8 ... Control part

Claims (7)

A gas control device provided in a gas line connecting a gas supply means and a depressurizable chamber,
A mass flow controller comprising a variable flow valve and controlling the flow rate of the gas flowing into the chamber to be a set flow rate;
A primary valve provided upstream of the mass flow controller;
A secondary valve provided downstream of the mass flow controller,
In the gas closing process for stopping the gas flow into the chamber, the mass flow controller, the primary side valve, and the secondary side valve are fully closed in this order, or the primary side valve is fully closed. A gas control apparatus comprising: a control unit that fully closes the mass flow controller within a first predetermined time and then fully closes the secondary valve.   The control unit starts flow control for the mass flow controller when an elapsed time from the closing process exceeds a second predetermined time during the gas opening process for starting the gas flow into the chamber. The gas control device according to claim 1, wherein the secondary valve is opened after the operation.   When the elapsed time from the closing process is less than or equal to a second predetermined time during the gas opening process for starting gas inflow into the chamber, the control unit opens the secondary valve. The gas control device according to claim 1, wherein the mass flow controller starts flow control.   An ion implantation apparatus using the gas control device according to claim 1. A control method of a gas control device provided in a gas line connecting a gas supply means and a depressurizable chamber,
The gas control device includes a variable flow valve, a mass flow controller that controls a flow rate of gas flowing into the chamber to be a set flow rate, a primary valve provided upstream of the mass flow controller, and the mass flow controller A secondary side valve provided downstream of the
In the gas closing process for stopping the gas flow into the chamber, the mass flow controller, the primary side valve, and the secondary side valve are fully closed in this order, or the primary side valve is fully closed. A method for controlling a gas control device comprising the steps of: fully closing the mass flow controller within a first predetermined time and then fully closing the secondary valve.   In the gas opening process for starting the inflow of gas into the chamber, if the elapsed time from the closing process exceeds a second predetermined time, after the step of causing the mass flow controller to start the flow control, The control method of the gas control apparatus according to claim 5, further comprising a step of opening the secondary side valve.   In the gas opening process for starting gas inflow into the chamber, if the elapsed time from the closing process is equal to or shorter than a second predetermined time, the mass flow controller is opened after the step of opening the secondary valve. The control method of the gas control apparatus of Claim 5 or 6 provided with the step which starts flow control.