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Researchers Submit Patent Application, "Pressure Control Device, Flow Rate Control Device and Recording Medium Having Programs Used for Pressure...

January 29, 2014



Researchers Submit Patent Application, "Pressure Control Device, Flow Rate Control Device and Recording Medium Having Programs Used for Pressure Control Device, Recording Medium Having Programs Used f

By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventor Takijiri, Kotaro (Kyoto-shi, JP), filed on July 3, 2013, was made available online on January 16, 2014.

No assignee for this patent application has been made.

News editors obtained the following quote from the background information supplied by the inventors: "For a semiconductor manufacturing process, a pressure control device is used for introducing a fluid such as a material gas at a predetermined constant pressure into a chamber that is maintained in vacuum.

"More specifically, the pressure control device is arranged in the upstream side of the chamber in the flow channel, and comprises a pressure sensor, a pressure control valve and a valve control part that controls the pressure control valve so as to make a measured pressure value measured by the pressure sensor at a set pressure value.

"Conventionally, only an accuracy of the pressure control in a steady state at a time when a predetermined period of time passes from an initial state is regarded as important for the pressure control of the fluid by the pressure control device, however, recently an accuracy of the pressure control or a responsiveness in a transition state which is a time period between an initial state and a steady state is also regarded as important.

"For example, in a semiconductor manufacturing process, it is required to further improve the accuracy or the responsiveness of the pressure control in the transition state while a response time which is a time period from the initial state to the steady state is shortened as much as possible. More concretely, if the set pressure value is large, the flow rate of the fluid required to be filled into the chamber also becomes large. As this result, there is a problem that the responsiveness is decreased because the response time becomes longer compared with a case that the set pressure value is small.

"One method to solve the problem represented improves the responsiveness of the pressure control by setting a large value as the PID coefficient (gain) in a case where the valve control part controls the open degree operated amount of the pressure control valve by means of the PID control.

"However, if a large value is simply set as the gain, such as the PID coefficient, in a case where the set pressure value is large, it is possible to shorten the response time because a large value of the open degree operated amount is input. However, in a case where the set pressure value is a target value that is small, the pressure control might be unstable because the pressure control valve is controlled at an excessive open degree operated amount although it is unnecessary to fill the fluid into the chamber so much. In other words, if the PID coefficient is determined to be large based on the large set pressure value as a reference, in a case where the set pressure value is small, the stability of the control is lost so that ringing might be generated or a big overshoot might be generated in the transition state as shown in FIG. 10. In order to make it possible to realize both the good responsiveness and the good stability at all of the set pressure values, the PID coefficient is changed according to the set pressure value. However, with this arrangement, since it is necessary to experimentally determine the PID coefficient for each of the set pressure values, it becomes very troublesome to adjust the parameter.

"Meanwhile, Patent Document 1 discloses a pressure control device wherein an upper limit value (a limit) is provided for the open degree operated amount of the pressure control valve in the transition state without changing the PID coefficient according to the set pressure value so as not to produce overshoot and to obtain the preferable responsiveness.

"This pressure control device comprises a PID control part that conducts a PID calculation on the deviation between the set pressure value and the measured pressure value and that outputs the open degree operated amount of the pressure control valve and a limiter part that sets an upper limit value to the open degree operated amount output by the PID control part during a transition response period from an initial state, which is a time of initiation of raising the pressure to a steady state.

"The limiter part is so configured that the upper limit value of the open degree operated amount is increased in proportion to the elapsed time from the time of the initiation of raising the pressure to the steady state. More specifically, in a case where the pressure control valve is continuously controlled at the open degree operated amount of the upper limit value from the time of the initiation of raising the pressure, the open degree gradually increases in accordance with the elapsed time.

"However, with this arrangement, since the upper limit value of the open degree operated amount of the pressure control valve is fixed regardless of the elapsed time from the time of the initiation of raising the pressure, the time period to reach the steady state changes largely depending on the set pressure value. Concretely, even though the set pressure value is set at a large value such as 100% and it is required to raise the pressure to the set pressure value in a short period of time, since the limiter part sets the upper limit value of the open degree operated amount at a small value at a time of initiation of raising the pressure, the fluid does not flow into the downstream side so much so that the rising amount of the pressure also becomes small. As a result of this, in a case where the set pressure value is large, the response time to reach the steady state becomes longer as compared with a case in which the set pressure value is set at 50% or the like.

"On the other hand, as shown in the patent document 1, if the upper limit value of the open degree operated amount is changed according to the elapsed time, the response time from the initial state to the steady state varies depending on the set pressure value so that it is not possible to maintain the response time. As a result, in the semiconductor manufacturing process, the longest time period until reaching the steady state is set as a waiting period so as to make it possible to introduce the material gas stably into the chamber, however, especially in a case where the set pressure value is small, an unnecessary waiting time is generated so that a yield is lowered.

"In addition, the above-mentioned problems are also generated for a flow rate control device on a pressure basis that conducts a flow rate control based on a measured flow rate value output by the flow rate sensor of pressure type. More specifically, in a case of the flow rate sensor of pressure type, the flow rate is measured based on the pressure in the upstream side and the pressure in the downstream side of the fluid resistance where the pressure loss is generated, if the chamber is connected in the downstream side, the pressure in the downstream side is maintained generally in vacuum or at a constant value so that it becomes substantially equal to control the pressure value of the fluid in the upstream side of the fluid resistance. Accordingly, if the PID coefficient is set to be large in order to shorten the response time even though the set flow rate is large similar to the above-mentioned pressure control device, a problem of generating overshoot or ringing might be generated because the stability is lost in a case where the set flow rate is small."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventor's summary information for this patent application: "Problems to be Solved by the Invention

"The present claimed invention intends to solve all of the problems and a main object of this invention is to provide a pressure control device and a recording medium having programs used for the pressure control device that can prevent ringing or overshoot without changing gain even though the gain such as the PID coefficient is set large, that can change the pressure to the steady state in a short period of time even though the set pressure value is large and that can maintain the time period required from the initial state to the steady state regardless of the set pressure value. In addition, the object is to provide a flow rate control device and a recording medium having programs used for the flow rate control device that can solve technical problems corresponding to pressure control in controlling the flow rate.

"Means to Solve the Problems

"More specifically, the pressure control device of this invention comprises a pressure sensor that measures a pressure of a fluid flowing in a flow channel, a pressure control valve arranged in the flow channel, and a valve control part that controls the pressure control valve so as to make a measured pressure value measured by the pressure sensor at a set pressure value, and is characterized in that the valve control part comprises an open degree operated amount output part that outputs an open degree operated amount of the pressure control valve based on the measured pressure value and the set pressure value, and a limiter part that sets a tolerance of the open degree operated amount by setting a limit value of the open degree operated amount and that controls the pressure control valve at the open degree operated amount of the limit value in a case where the open degree operated amount output by the open degree operated amount output part is out of the tolerance, and the limiter part sets the limit value of the open degree operated amount according to the set pressure value.

"'The open degree operated amount' in this specification is an amount indicating an absolute open degree of the pressure control valve.

"In accordance with this arrangement, in a case of controlling a pressure increase, since the limiter parts sets the tolerance of the open degree operated amount by setting the limit value of the open degree operated amount according to the set pressure value, it is possible to shorten the time period until the steady state by setting the upper limit value large as the limit value of the open degree operated amount in a case where the set pressure value is large and there is a big margin until the overshoot is generated, or conversely, in a case where the set pressure value is small, it is possible to prioritize the stability by setting the upper limit value of the open degree operated amount small in an area where overshoot is generated immediately if the open degree operated amount is set too large.

"In addition, since the limiter part controls the pressure control valve at the open degree operated amount of the set upper limit value in a case where the open degree operated amount output by the open degree operated amount output part exceeds the upper limit value, it is possible to prevent overshoot even though the gain such as the PID coefficient is set large. Furthermore, if the gain such as the PID coefficient is set large, it is possible to improve a follow-up performance or responsiveness to a command value in the transition state and the steady state.

"Conversely, in a case of controlling a pressure decrease from a state maintained at a certain pressure value to the set pressure value, since the limiter part sets the tolerance of the open degree operated amount by setting the lower limit value as a limit value of the open degree operated amount according to the set pressure value, it is possible to shorten the response time regardless of the set pressure value and to prevent overshoot or ringing even though the pressure drop amount is small.

"In a case where the open degree operated amount output by the open degree operated amount output part is less than or equal to the upper limit value of the open degree operated amount set by the limiter part, in order to make it possible to control the pressure in a state wherein both the responsiveness and the stability are secured, the limiter part may be so configured that an upper limit value is set as the limit value of the open degree operated amount, and in a case where the open degree operated amount that is output by the open degree operated amount output part is equal to or less than the upper limit value, the limiter part controls the pressure control valve at the open degree operated amount output by the open degree operated amount output part.

"In order to generally maintain the time period from the initial state to the steady state regardless of the set pressure value, the limiter part may be so configured that the larger the set pressure value is, the larger the upper limit value of the open degree operated amount is set. In accordance with this arrangement, the larger the set pressure value is, the larger the upper limit value of the open degree operated amount is set. As a result of this, the larger the set pressure value is, the more the amount of the fluid passing the pressure control valve can be, so that the larger the set pressure value is, the larger the pressure change amount per unit time can be. As a result of this, it is possible to generally maintain the time from the initial state to the steady state in each of the set pressure values.

"In order to generally maintain the time period from the initial state to the steady state regardless of the set pressure value by making a relationship between the set pressure value and the pressure change amount per unit time from the initial state to the steady state generally proportional, the limiter part may be so configured that the upper limit value of the open degree operated amount changes non-linearly to the set pressure value in the elapsed time. In accordance with this arrangement, even though the relationship between the open degree of the pressure control vale and the flow rate of the fluid passing the pressure control valve is non-linear, it is possible to determine the upper limit value of the open degree operated amount by accounting for the non-linearity of the relationship. As a result of this, it is possible to maintain the response time from the initial state to the steady state.

"For example, in order to make it possible to keep the time period constant from the initial state to the steady state regardless of the set pressure value and irrespective of a volume of a chamber, which is an object whose pressure is to be controlled, the limiter part may be so configured to set the upper limit value of the open degree operated value according to the volume of the downstream side of the pressure control valve in the transition state.

"In particular, in order to make it possible change the pressure from the initial state to the steady state in a short period of time while maintaining the responsiveness and the stability even though the volume of the downstream side of the pressure control valve is variable, the limiter part may be so configured such that the larger the volume of the downstream side of the pressure control valve is, the larger the upper limit value of the open degree operated amount is set.

"A concrete example of a method for setting the upper limit value of the open degree operated amount in order to equalize the time period from the initial state to the steady state regardless of the set pressure value includes the limiter part so configured to set the open degree operated amount that corresponds to a flow rate value necessary to achieve a pressure in a volume in the downstream side of the pressure control valve to be the set pressure value at a time when a target time period passes after a time when the pressure control is initiated as the upper limit value.

"In order to make it possible to realize a function as the pressure control device of this invention by rewriting programs of a conventional pressure control device, a recording media may use a recording medium having programs used for a pressure control device comprising a pressure sensor that measures a pressure of a fluid flowing in a flow channel and a pressure control valve arranged in the flow channel, and is characterized by comprising a valve control part that controls the pressure control valve so as to make a measured pressure value measured by the pressure sensor at a set pressure value, wherein the valve control part comprises an open degree operated amount output part that outputs an open degree operated amount of the pressure control valve based on the measured pressure value and the set pressure value, and a limiter part that sets a tolerance of the open degree operated amount by setting a limit value of the open degree operated amount and that controls the pressure control valve at the open degree operated amount of the limit value in a case where the open degree operated amount output by the open degree operated amount output part is out of the tolerance, and the limiter part sets the limit value of the open degree operated amount according to the set pressure value.

"In order to make it possible to generally equalize the response time from the initial state to the steady state regardless of the size of the set flow rate value and to prevent overshoot or ringing, the flow rate control device may be a flow rate control device comprising a pressure sensor that measures a pressure of a fluid flowing in a flow channel, a flow rate control valve arranged in the flow channel, and a valve control part that controls the flow rate control valve so as to make a measured flow rate value calculated based on a measured pressure value measured by the pressure sensor at a set flow rate value, and is characterized in that the valve control part comprises an open degree operated amount output part that outputs an open degree operated amount of the flow rate control valve based on the measured flow rate value and the set flow rate value, and a limiter part that sets a tolerance of the open degree operated amount by setting a limit value of the open degree operated amount and that controls the flow rate control valve at the open degree operated amount of the limit value in a case where the open degree operated amount output by the open degree operated amount output part is out of the tolerance, and the limiter part sets the limit value of the open degree operated amount according to the set flow rate value.

"In order to keep the response time constant regardless of the set flow rate value and to add a function of preventing overshoot or ringing by changing programs of a conventional flow rate control device, a recording media may use a recording medium having programs used for a flow rate control device comprising a pressure sensor that measures a pressure of a fluid flowing in a flow channel and a flow rate control valve arranged in the flow channel, and is characterized by comprising a valve control part that controls the flow rate control valve so as to make a measured flow rate value calculated based on a measured pressure value measured by the pressure sensor at a set flow rate value, wherein the valve control part comprises an open degree operated amount output part that outputs an open degree operated amount of the flow rate control valve based on the measured flow rate value and the set flow rate value, and a limiter part that sets a tolerance of the open degree operated amount by setting a limit value of the open degree operated amount and that controls the flow rate control valve at the open degree operated amount of the limit value in a case where the open degree operated amount output by the open degree operated amount output part is out of the tolerance, and the limiter part sets the limit value of the open degree operated amount according to the set flow rate value.

"Effect of the Invention

"In accordance with the pressure control device of this invention, since the upper limit value of the open degree operated amount of the pressure control valve is not changed according to the elapsed time from the initial state but determined according to the set pressure value by the limiter part, it is possible to equalize the time period from the initial state to the steady state even though the set pressure value varies. In addition, in a case where the open degree operated amount output by the open degree operated amount output part exceeds the upper limit value of the open degree operated amount set by the limiter part, the pressure control valve is controlled at the upper limit value. As a result of this, even though a case that the gain, such as the PID coefficient, is set large, it is possible not to generate overshoot.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a schematic showing a pressure control device in accordance with a first embodiment of this invention.

"FIG. 2 is a block diagram showing a control system of the pressure control device in the first embodiment.

"FIG. 3 is a graph showing a valve characteristic of a pressure control valve in the first embodiment.

"FIG. 4 is a graph showing a relationship between a set pressure value and a flow rate of a fluid to be required in the first embodiment.

"FIG. 5 is a graph showing a relationship between the set pressure value and an upper limit value of an open degree operated amount in the first embodiment.

"FIG. 6 is a flow chart showing an operation of the pressure control device in the first embodiment.

"FIG. 7 is a graph showing one example of a pressure control result by the pressure control device in the first embodiment.

"FIG. 8 is a graph showing a relationship between a set pressure value and an open degree operated amount in a modified embodiment of the pressure control device in the first embodiment.

"FIG. 9 is a schematic showing a flow rate control device in a second embodiment.

"FIG. 10 is a graph showing a problem that is generated in a case that a PID coefficient is made large in a conventional pressure control device."

For additional information on this patent application, see: Takijiri, Kotaro. Pressure Control Device, Flow Rate Control Device and Recording Medium Having Programs Used for Pressure Control Device, Recording Medium Having Programs Used for Flow Rate Control Device. Filed July 3, 2013 and posted January 16, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5527&p=111&f=G&l=50&d=PG01&S1=20140109.PD.&OS=PD/20140109&RS=PD/20140109

Keywords for this news article include: Patents, Electronics, Semiconductor.

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Source: Electronics Newsweekly


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