JP5424721B2 - Vacuum vessel simulation equipment - Google Patents

Description

  The present invention relates to a simulation apparatus that simulates the pressure in a vacuum vessel.

  Conventionally, in a manufacturing apparatus such as a semiconductor wafer or a liquid crystal substrate, no film is formed on the surface of the substrate, but the surface treatment is performed in a vacuum vessel. Then, for example, one end of an exhaust pipe provided with a vacuum valve is connected to the vacuum container, and a vacuum pump is connected to the other end of the exhaust pipe to discharge internal gas (gas). (For example, refer patent document 1).

  A pendulum-type gate valve called a pendulum valve is used as the vacuum valve. This vacuum valve is placed between the vacuum vessel and the vacuum pump to automatically control the pressure in the vacuum vessel. Has been.

JP 2007-278383 A

By the way, in the semiconductor manufacturing apparatus, the gas used according to the manufacturing process is nitrogen (N ₂ ), argon (Ar), perfluorocyclobutane (C ₄ F ₃ ), hydrogen (H ₂ ), etc. Many types of gas are used. In addition, the flow rate of gas flowing into the vacuum vessel and the pressure in the vacuum vessel are various, and in manufacturing apparatuses such as solar cells, the size of the vacuum vessel is increasing and a maximum of 600 L (liter) or more is beginning to appear.

  Exhaust characteristics in such a manufacturing apparatus vary greatly depending on the type of gas used, the gas flow rate, the pressure in the vacuum container, and the gas temperature, and the pressure response speed varies depending on the volume of the vacuum container.

In addition, there are problems that it is difficult to evaluate / verify the pressure control device in the environment where it is actually installed because many of the gases used require attention in handling.
SUMMARY OF THE INVENTION An object of the present invention is to provide a vacuum vessel simulation apparatus that simulates the dynamic characteristics of pressure in a vacuum vessel that varies depending on the gas type, gas flow rate, gas temperature, and the like.

In order to solve the above problems, a vacuum vessel simulation apparatus according to claim 1 of the present invention includes a vacuum vessel to which a gas supply line and a discharge line are connected, and the discharge line provided in the discharge line. A vacuum valve that can open and close the path, a pressure gauge that measures the pressure in the vacuum vessel, an opening detector that detects the valve opening of the vacuum valve, and a detection value from the pressure gauge and the opening detector A vacuum vessel simulation apparatus in a vacuum processing apparatus comprising a pressure control device for controlling the pressure in the vacuum vessel by inputting and controlling the opening degree of the vacuum valve at a predetermined processing time interval,
A conductance acquisition unit for obtaining the conductance of the vacuum valve based on the valve characteristic curve by inputting the valve opening detected by the opening detector;
An exhaust gas amount calculation unit that obtains an exhaust gas amount by multiplying the conductance obtained by this conductance acquisition unit by the pressure in the vacuum vessel at the time of the previous processing t (n-1);
Enter the inflow gas amount at the time t (n) of the current process obtained by the gas flow rate table that sets the inflow gas amount according to the processing elapsed time to the exhaust gas amount obtained by this exhaust gas amount calculation unit. A pressure change calculation unit for obtaining a pressure change in the vacuum vessel;
A container for obtaining the pressure in the vacuum container at the current processing time t (n) by adding the pressure change obtained by the pressure change calculation unit and the pressure in the vacuum container at the previous processing time t (n-1). And a pressure calculation unit.

  According to a second aspect of the present invention, the vacuum vessel simulation apparatus includes a valve characteristic curve indicating a relationship between the valve opening degree and the conductance according to the type of gas in the conductance acquisition unit of the simulation apparatus according to the first aspect. Is.

  According to a third aspect of the present invention, there is provided a simulation apparatus for a vacuum vessel, wherein the conductance acquisition unit in the simulation apparatus according to the first aspect has a conductance of a gas of a type different from the known gas based on a gas having a known conductance. The following equation (A) that can be estimated is provided.

上記式中、Ｃ（Ｍ，Ｔ）は分子量Ｍの気体で且つ温度Ｔにおけるコンダクタンスを表わし、Ｃａ（Ｍａ，Ｔａ）は分子量Ｍａの気体で且つ温度Ｔａにおけるコンダクタンスを表わす。

In the above formula, C (M, T) is a gas having a molecular weight M and represents conductance at a temperature T, and Ca (Ma, Ta) is a gas having a molecular weight Ma and represents conductance at a temperature Ta.

  According to a fourth aspect of the present invention, there is provided a vacuum vessel simulation apparatus comprising the following equation (B) for calculating a pressure change in the pressure change calculation section of the simulation apparatus according to the first aspect.

上記式中、Ｔは温度、Ｔ_ＳＴＤは標準状態での温度、Ｐは圧力、Ｐ_ＳＴＤは標準状態での圧力、Ｆｓ１は流入ガス量、Ｆｓ２は排出ガス量を表わす。

In the above formula, T represents temperature, T _STD represents temperature in a standard state, P represents pressure, P _STD represents pressure in a standard state, Fs1 represents an inflow gas amount, and Fs2 represents an exhaust gas amount.

  According to the simulation apparatus of the first aspect, the pressure in the vacuum vessel changes depending on the gas type, the gas flow rate, the pressure in the vacuum vessel, the gas temperature, and the like by being used instead of the actual vacuum vessel in the vacuum processing apparatus. Evaluation (verification) of characteristics (dynamic behavior) and, in turn, evaluation (verification) of the vacuum processing apparatus can be performed easily and quickly.

It is a schematic diagram which shows schematic structure of the vacuum processing apparatus which concerns on embodiment of this invention. It is a principal part top view of the vacuum valve provided in the vacuum vessel of the vacuum processing apparatus. It is a graph which shows the relationship between the valve opening degree and pressure in the vacuum valve. It is a graph which shows the relationship between the valve opening degree and conductance in the same vacuum valve. It is a block diagram which shows schematic structure of the pressure control apparatus of the vacuum vessel. It is a block diagram which shows schematic structure of the inflow gas amount estimation part in the pressure control apparatus. It is a block diagram which shows schematic structure of the correction | amendment gas amount calculation part in the same pressure control apparatus. It is a block diagram which shows schematic structure of the valve opening calculation part in the pressure control apparatus. It is a control block diagram which shows schematic structure of the same pressure control apparatus. It is a block diagram which shows schematic structure of the simulation apparatus which concerns on embodiment of this invention.

Hereinafter, a vacuum vessel simulation apparatus according to an embodiment of the present invention will be described based on specific examples.
The vacuum container according to the present embodiment is provided, for example, in a vacuum processing apparatus as a semiconductor manufacturing apparatus and is used when manufacturing a semiconductor element or the like. Specifically, plasma is generated under a predetermined degree of vacuum. A simulation apparatus according to the present invention is used to supply a reaction gas (an example of a gas, hereinafter referred to as gas) in a state of being subjected to a predetermined surface treatment on a semiconductor wafer that is an object to be processed. Is for simulating the pressure in the vacuum vessel.

First, the basic concept of pressure control in a case where a simulation apparatus is not used, that is, in an actual vacuum vessel will be described.
The pressure in the vacuum chamber depends on the difference between the amount of gas flowing in (hereinafter referred to as the amount of inflowing gas and also the amount of supply gas) and the amount of gas flowing out (which can be referred to as the amount of outflowing gas but hereinafter referred to as the amount of exhaust gas). Therefore, in order to maintain the pressure at a constant value (which is also a predetermined value), the exhaust gas amount may be controlled to be equal to the inflow gas amount.

  That is, it is only necessary to measure the amount of inflow gas and discharge the gas by an amount equal to the measured amount of inflow gas. Since gas is generated, a large error occurs when the measured value is used. For this reason, on the calculation model using the gas amount based on the exhaust gas amount estimated from the valve opening (described later) of the vacuum valve (in other words, considering the exhaust gas amount) without using the measured value. The pressure in the vacuum vessel (hereinafter referred to as a virtual vacuum vessel) is calculated, and the pressure obtained by this calculation (hereinafter also referred to as the calculated pressure) and the measured pressure in the actual vacuum vessel (hereinafter also referred to as the actual vacuum vessel) The inflow gas amount as an estimated value obtained according to the difference is used.

Here, the schematic overall configuration of the vacuum processing apparatus when the vacuum container is an actual container will be described with reference to FIGS. 1 and 2.
The vacuum processing apparatus includes a vacuum vessel 1 having a reaction gas supply port 2 and a gas discharge port 3 that can perform predetermined processing (for example, etching) by supplying a semiconductor wafer or the like to the inside, and the supply A gas supply pipe (an example of a gas supply pipe) 11 connected to the port 2 for supplying a reaction gas and a circular opening 5a connected to the discharge port 3 (in other words, a valve seat) And a valve body 6 that can open and close the opening 5a and a drive motor 7 that opens and closes the valve body 6 (specifically, a stepping motor is used as an example of a drive unit). A vacuum valve 4, a gas discharge pipe (one example of a gas discharge pipe) 12 having one end connected to the discharge port of the vacuum valve 4 and the other end connected to the vacuum pump 8, and the vacuum container And a pressure controller 9 Metropolitan for controlling the pressure of the inner. Although the vacuum valve 4 has been described as being directly provided in the discharge port 3, it is of course possible to provide it in the middle of the gas discharge pipe 12.

  The pressure control device 9 includes a pressure gauge 21 for measuring the degree of vacuum in the vacuum vessel 1, that is, a pressure (a plurality of pressure gauges are provided if necessary, but will be described here as one), and a valve body 6 of the vacuum valve 4. , Which is measured by an opening detector 22 (which specifically uses an encoder that detects the amount of rotation of the drive motor) 22 and the pressure gauge 21. The measured pressure and the valve opening detected by the opening detector 22 (hereinafter referred to as actual valve opening) are input so that the pressure in the vacuum vessel 1 becomes a target value (hereinafter referred to as set pressure). And a control device main body 23 for controlling the drive motor 7 of the vacuum valve 4.

Here, the operation of the valve body 6 of the vacuum valve 4 will be described.
As the vacuum valve 4, one having both functions of pressure control and vacuum sealing is used (however, it is not limited to one having both functions of pressure control and vacuum sealing). That is, when the valve body 6 of the vacuum valve 4 slides on the circular opening 5a, the flow rate of gas passing through the opening 5a can be controlled. And after the valve body 6 closes the opening 5a (here, it is not a sealed state, it means that the entire opening is covered with the valve body), and further around the opening 5a (so-called It is completely closed (sealed state) by moving to the valve seat side), that is, in the vertical direction. A general relationship between the valve opening degree of the vacuum valve 4 and the pressure on the controlled space side controlled by the vacuum valve 4 is shown in FIG.

  From this graph, it can be seen that the valve body 6 moves vertically to the closed position (20% in this case) and then moves vertically (so-called lifting operation), resulting in a completely sealed state. In other words, the pressure rises to some extent when moved to the closed position, but the pressure rises rapidly by the subsequent raising / lowering operation (of course, when applied to the pressure control of the vacuum vessel, the pressure suddenly increases). Will be reduced). That is, the relationship between the valve opening and the pressure in the vacuum valve 4 is non-linear.

  By the way, when calculating the estimated inflow gas amount, the calculated pressure in the virtual vacuum vessel is used. As described above, the gas amount based on the estimated exhaust gas amount is used to determine this calculated pressure. Strictly speaking, as the gas amount, an estimated exhaust gas amount that is an estimated value obtained from the valve opening, and an estimated inflow gas amount that is obtained based on the pressure difference between the calculated pressure in the virtual vacuum vessel and the measured pressure in the actual vacuum vessel, The difference in gas flow rate is used. Further, when obtaining the estimated exhaust gas amount, a characteristic curve of a vacuum valve (hereinafter referred to as a valve characteristic curve) is used. This valve characteristic curve is used to compensate for the non-linear relationship between the valve opening and the pressure.

  As shown in FIG. 4, this valve characteristic curve shows the relationship between the valve opening and the conductance. Specifically, the valve characteristic curve is held in a storage unit as a numerical table. For example, the conductance is calculated from the valve opening. An obtainable conductance acquisition unit (described later) is provided. The conductance indicates the ease of gas flow, and is a value obtained by dividing the gas flow rate by the pressure (gas flow rate / pressure).

Next, the configuration of the pressure control device 9 will be described with reference to FIG.
The pressure control device 9 is broadly divided into a pressure setting unit 31 that sets a target set pressure (also referred to as a target pressure) of the vacuum vessel 1, an actual valve opening detected by the opening detector 22, and While calculating the pressure in the virtual vacuum vessel based on the gas flow rate difference that is the difference between the estimated exhaust gas amount measured from the pressure measured by the pressure gauge 21 and the estimated inflow gas amount described later, An inflow gas amount estimation unit 32 for obtaining an estimated inflow gas amount based on a pressure difference that is a difference between the calculated pressure and the measurement pressure obtained in this manner, the set pressure from the pressure setting unit 31 and the measurement pressure from the pressure gauge 21 are input. Then, the correction gas amount calculation unit 33 for calculating the correction gas amount based on the pressure deviation and the estimated inflow gas amount obtained by the inflow gas amount estimation unit 32 are added to the correction gas amount meter. The correction gas amount obtained by the unit 33 is added to obtain a correction gas amount and the correction gas amount is output as a set exhaust gas amount, and the set exhaust gas amount output from the adder 34 and The valve opening calculation unit 35 is configured to calculate a target valve opening (hereinafter referred to as a set valve opening) in the vacuum valve 4 based on the set pressure from the pressure setting unit 31.

As shown in FIG. 6, the inflow gas amount estimation unit 32 includes a conductance acquisition unit 41 that obtains the conductance of the vacuum valve 4 based on the valve characteristic curve of the vacuum valve 4 from the actual valve opening, and the conductance acquisition unit 41. And the multiplier 42 for obtaining an estimated value of the gas flow rate discharged by inputting the conductance obtained in step 1 and the measured pressure from the pressure gauge 21 and multiplying the conductance by the measured pressure, and the multiplier 42 for obtaining the estimated value. A pressure calculator that calculates the pressure in the virtual vacuum vessel by inputting a gas flow rate difference that is the difference between the estimated exhaust gas amount and the estimated inflow gas amount (details will be described later) [specifically integration The transfer function on the calculation model is 1 / (β _n s), and β _n is the pressure gain (nominal value) of the container] 43. The pressure subtractor 44 for obtaining the pressure difference, which is the difference between the calculated pressure and the pressure measured from the pressure gauge 21, and a predetermined gain (K _obs ) for the pressure difference obtained by the pressure subtractor 44. And an amplifier 45 for obtaining an estimated inflow gas amount by multiplying by the above, and further, the amplifier 45 is disposed between the multiplier 42 and the pressure calculation unit 43 and is calculated from the estimated inflow gas amount obtained by the amplifier 45. A gas amount subtractor 46 for obtaining a gas flow rate difference obtained by subtracting the estimated exhaust gas amount is provided.

  The function of the inflow gas amount estimation unit 32 will be described. A gas flow rate difference obtained by subtracting the estimated exhaust gas amount estimated from the actual valve opening from the estimated inflow gas amount obtained by the inflow gas amount estimation unit 32. Estimated inflow gas volume according to the pressure difference between the calculated pressure in the virtual vacuum vessel on the calculation model obtained by integrating (the pressure in the vessel is obtained by accumulating the gas flow rate difference) and the actual measured pressure Is what you want. In other words, when the calculated pressure deviates from the measured pressure, correction is performed according to the pressure difference, that is, the gas flow rate difference is obtained so that the calculated pressure approaches the measured pressure [calculated pressure Is configured to follow the measured pressure (a calculation processing loop including a gas amount subtractor 46, a pressure calculation unit 43, a pressure subtractor 44, and an amplifier 45)]. Therefore, the estimated inflow gas amount obtained in a certain calculation loop (a certain period) is used when obtaining the gas flow rate difference used in the next calculation loop (the next period). Note that the calculation loop (including acquisition of the actual valve opening) is repeatedly performed at a predetermined cycle (a calculation cycle or a control cycle, for example, 10 msec).

As shown in FIG. 7, the correction gas amount calculation unit 33 includes a subtractor (subtraction unit) 51 that inputs a set pressure from the pressure setting unit 31 and a measured pressure from the pressure gauge 21 to obtain a pressure deviation. The pressure deviation obtained by the subtractor 51 is inputted to obtain a gas amount proportional to the pressure deviation, and at the same time, a proportional controller (proportional control unit; proportional gain _Kp) that outputs the gas amount as a corrected gas amount is multiplied. ) 52.

  Further, as shown in FIG. 8, the valve opening calculation unit 35 includes a conductance calculation unit 61 for obtaining conductance by inputting the set exhaust gas amount output from the adder 34 and the set pressure from the pressure setting unit 21. Then, the conductance calculated by the conductance calculation unit 61 is input, and the valve opening degree obtaining unit 62 for obtaining the valve opening degree from the valve characteristic curve (the curve is opposite to the valve characteristic curve in the conductance obtaining unit 41). It consists of and.

  By the way, the calculation pressure of the virtual vacuum vessel obtained by the inflowing gas amount estimation unit 32 has been described as being obtained by integrating the gas flow rate difference obtained by subtracting from the estimated inflowing gas amount, but more specifically described. Then, the calculated pressure obtained in the current calculation loop is obtained by adding the gas flow difference obtained this time as a pressure to the calculated pressure obtained in the previous calculation loop. Note that since the previous calculation loop does not exist at the start of the calculation loop, the pressure value in the actual vacuum vessel measured at the start is used as the initial value.

Next, the pressure control method in the vacuum vessel described above will be described.
It is assumed that the pressure state in the vacuum vessel 1 is stable at a certain value, and a new set pressure is set by the pressure setting unit 31.

  In this state, when the actual valve opening is input from the opening detector 22 to the inflow gas amount estimation unit 32, conductance is obtained by the conductance acquisition unit 41 and a measured pressure is applied to the conductance by the multiplier 42. The estimated exhaust gas amount is obtained by multiplication. Then, the gas amount subtractor 46 subtracts the estimated exhaust gas amount obtained this time from the estimated inflow gas amount obtained in the previous calculation cycle to obtain a gas flow rate difference, and this gas flow rate difference is calculated by pressure calculation. The pressure in the virtual vacuum vessel in the calculation model, that is, the calculated pressure is obtained by being input to the unit 43.

  Next, a pressure difference that is the difference between the calculated pressure and the pressure measured from the pressure gauge 21 is obtained, and the amplifier 45 multiplies a predetermined gain to obtain a new estimated inflow gas amount. This new estimated inflow gas amount is used to determine the gas flow rate difference in the next calculation loop, that is, the next calculation cycle, and the calculated pressure is controlled to approach the measured pressure.

  On the other hand, the set pressure set in the pressure setting unit 31 is input to the correction gas amount calculation unit 33, and the subtractor 51 obtains a pressure deviation that is the difference between the set pressure and the measured pressure from the pressure gauge 21. At the same time, this pressure deviation is input to the proportional controller 52, and the pressure deviation is multiplied by the proportional gain to obtain the correction gas amount.

Then, the correction gas amount and the estimated inflow gas amount newly obtained by the inflow gas amount estimation unit 32 are input to the adder 34, and the set exhaust gas amount is obtained.
Next, the set exhaust gas amount and the set pressure from the pressure setting unit 31 are input to the valve opening calculation unit 35, and a set valve opening degree that matches the set exhaust gas amount is obtained. Specifically, the set exhaust gas amount and the set pressure are input to the conductance calculating unit 61 to obtain conductance, and this conductance is input to the valve opening obtaining unit 62 to obtain the valve opening from the valve characteristic curve. It is done. The valve opening command is output to the drive motor 7 and the valve body 6 is driven so as to achieve a predetermined valve opening.

  Then, when the above-described operation is repeatedly performed and the calculated pressure becomes equal to the measured pressure or the calculated pressure follows the measured pressure with a certain deviation, the inflow gas amount estimating unit 32 obtains the calculated pressure. It can be considered that the estimated inflow gas amount is equal to the actual inflow gas amount.

In this way, the pressure in the vacuum vessel is controlled to be constant, that is, the set pressure.
A control block diagram (using a transfer function) of the pressure control system described above is shown in FIG.

  In FIG. 9, (a) is a part representing a vacuum vessel. Although not described in the above embodiment, as shown in FIG. 9, a set pressure filter and a noise removal filter are provided in the middle of outputting the set pressure and the measured pressure to the correction gas amount calculation unit. It has been.

  Next, based on the configuration of the pressure control device 9 of the vacuum vessel 1, a simulation device according to the present invention, that is, a simulation device for simulating the pressure of the vacuum vessel will be described.

  In the above description, the vacuum vessel 1 has been described as an actual vessel. However, the simulation apparatus represents the vacuum vessel 1 with a mathematical model, and this mathematical model will be described below. In addition, when representing the internal state of the vacuum vessel, naturally, the above-described valve characteristic curve is used, and the pressure which is the internal state is obtained by calculation instead of the pressure gauge. The simulation is continuously performed at a predetermined processing time interval (which is also a step interval, for example, 10 msec which is the same as the control period).

  As shown in FIG. 10, in this simulation device 71, a conductance acquisition unit 72 (conductance acquisition unit) that inputs the valve opening detected by the opening detector 22 and obtains the conductance of the vacuum valve 4 based on the valve characteristic curve. 41, and therefore the conductance acquisition unit 41 may be used), and the conductance obtained by the conductance acquisition unit 72 is added to the inside of the vacuum vessel at the time t (n-1) of the previous processing. An exhaust gas amount calculation unit 73 that obtains an exhaust gas amount by multiplying the pressure, and a gas flow rate table (also referred to as a time-gas flow rate table) for setting an inflow gas amount corresponding to each processing, that is, the processing elapsed time. From the exhaust gas amount and gas flow rate table obtained by the exhaust gas amount calculating unit 73 The pressure change calculation unit 75 for obtaining the pressure change in the vacuum vessel per time by inputting the inflow gas amount at the present (current) processing time t (n), and the pressure obtained by the pressure change calculation unit 75 A container pressure calculation unit 76 is provided for adding the change and the pressure in the vacuum container at the previous processing time t (n-1) to obtain the pressure in the vacuum container at the current processing time t (n). .

Of course, the pressure in the vacuum vessel at the current processing time t (n) obtained by the vessel pressure calculation unit 76 is input to the pressure controller 9 as a simulated calculated pressure.
As described in the section of the conductance acquisition unit 41, the conductance acquisition unit 72 is provided with a valve characteristic curve indicating the relationship between the valve opening and the conductance, and is held as a numerical table. This valve characteristic curve is obtained by measuring the conductance by flowing the gas actually used. For example, the valve characteristic curve is prepared according to the size of the valve, the type of gas to be flowed, and the like.

  By the way, although it has been described that the measured value actually measured is used as the valve characteristic curve, a different type and a predetermined temperature are used using a known valve characteristic curve measured for a certain kind of gas and at a certain temperature. The conductance for the gas at may be determined based on the following equation (1).

ここで、Ｃ（Ｍ，Ｔ）は分子量Ｍの或るガスについて温度Ｔにおけるコンダクタンスを示し、Ｃａ（Ｍａ，Ｔａ）は分子量Ｍａの或るガスについて且つ温度Ｔａにおけるコンダクタンスを示す。

Here, C (M, T) represents the conductance at a temperature T for a certain gas having a molecular weight M, and Ca (Ma, Ta) represents the conductance for a certain gas having a molecular weight Ma and at a temperature Ta.

  As described above, the gas flow rate setting unit 74 includes a gas flow rate table for setting the inflow gas amount. For example, the inflow gas amount is set stepwise at intervals of 10 seconds. For example, 100 sccm is set for less than 0-10 seconds, 200 sccm is set for less than 10-20 seconds, and 300 sccm is set for less than 20-30 seconds. Therefore, the inflow gas amount is determined according to the processing elapsed time.

  In the pressure change calculation unit 75, the pressure change is obtained based on the following equation (2).

この圧力変化計算部７５では、処理時間間隔当たりの真空容器内の圧力変化をリアルタイムで計算している。

The pressure change calculation unit 75 calculates the pressure change in the vacuum container per processing time interval in real time.

Here, how to derive the above equation (2) will be described.
If the gas flow rate at the inlet of the vacuum vessel is G1 (Kg / s) and the gas flow rate of the exhaust system is G2 (Kg / s), the gas flow rate m (Kg) staying in the vacuum vessel is expressed by the following equation (3). It is.

真空容器内の圧力をＰ（Pa）、真空容器内のガス温度をＴ（K）、真空容器の容積をＶ（m³）、真空容器内に滞留するガスの分子量をｍ（Kg）とすると、下記（４）式に示す理想気体の状態方程式が成立する。

When the pressure in the vacuum vessel is P (Pa), the gas temperature in the vacuum vessel is T (K), the volume of the vacuum vessel is V (m ³ ), and the molecular weight of the gas staying in the vacuum vessel is m (Kg). The equation of state of the ideal gas shown in the following equation (4) is established.

温度を一定として、（４）式の両辺を時間で微分して整理すると、下記（５）式が得られる。

When the temperature is constant and both sides of the equation (4) are differentiated by time and arranged, the following equation (5) is obtained.

ここで、真空容器内での化学反応を無視し、真空容器入口のガス流量をＦｓ１（sccm）、排気系のガス流量をＦｓ２（sccm）とすると、標準状態（０℃、１気圧で、記号Ｐ_ＳＴＤ，Ｔ_ＳＴＤで表わす）でのガス密度ρ（Kg/m³）は、下記（６）式で表わされる。

Here, ignoring the chemical reaction in the vacuum vessel, assuming that the gas flow rate at the inlet of the vacuum vessel is Fs1 (sccm) and the gas flow rate in the exhaust system is Fs2 (sccm), the symbol is The gas density ρ (Kg / m ³ ) at P _STD and T _STD is expressed by the following equation (6).

したがって、Ｇ１（Kg/s）およびＧ２（Kg/s）は下記（７）式にて表わされる。

Therefore, G1 (Kg / s) and G2 (Kg / s) are expressed by the following equation (7).

上記（７）式を（５）式に代入して整理すると、下記（８）式が得られる。すなわち、圧力変化を示す（２）式が得られる。

Substituting the above equation (7) into the equation (5) and rearranging the following equation (8) results. That is, the expression (2) indicating the pressure change is obtained.

ここで、圧力変化計算部７５での計算について説明しておく。

Here, the calculation in the pressure change calculation unit 75 will be described.

First time;
a1. Time t = t (0)
Pressure P (0) = P0 is set as an initial value at time t = t (0).

b1. The inflow gas amount (Fs1) at t = t (0) is acquired from the gas flow rate table, and the exhaust gas amount (Fs2) at t = t (0) is calculated.
c1. The pressure change per hour (dP / dt) at t = t (0) is calculated using Fs1 and Fs2 obtained in b1.

Second time;
a2. Calculate the pressure P (1) at time t = t (1).
b2. The inflow gas amount (Fs1) at t = t (1) is acquired from the gas flow rate table, and the exhaust gas amount (Fs2) at t = t (0) is calculated.

c2. Using Fs1 and Fs2 obtained in b2, the pressure change per time (dP / dt) at t = t (1) is calculated.
The pressure change is sequentially calculated by the procedure described above.

Next, calculation for obtaining the pressure in the vacuum vessel in the vessel pressure calculation unit 76 will be described.
First time;
Time t = t (0)
Pressure P (0) = P0 (initial value)
Second time;
Time t = t (1)
Pressure P (1) = P0− [dP / dt × t (1) −t (0)} at t = t (0)]
3rd time;
Time t = t (2)
Pressure P (2) = P1 + [dP / dt at t = t (1) × {t (2) −t (1)}]
4th;
Time t = t (3)
Pressure P (3) = P2 + [dP / dt × t (3) −t (2)} at t = t (2)]
nth;
Time t = t (n)
Pressure P (n) = P (n−1) + [dP / dt × t (n) −t (n−1)} at t = t (n−1)]
Note that {t (1) −t (0)} = {t (2) −t (1)} = {t (n) −t (n−1)} = Δt (for example, 10 msec)
Here, the pressure simulation in the vacuum vessel will be specifically described.

  First, the detected opening value detected by the opening detector 22 of the vacuum valve 4 is input to the conductance acquisition unit 72 to acquire the conductance. This conductance is input to the exhaust gas amount calculation unit 73, and the exhaust gas amount (Fs2) is obtained by multiplying the conductance by the pressure obtained at the previous processing time t (n-1).

  Next, the inflow gas amount setting unit 74 obtains the inflow gas amount Fs1 corresponding to the processing time based on the gas flow rate table, and the inflow gas amount Fs1 and the exhaust gas amount obtained by the exhaust gas amount calculation unit 73 ( Fs2) is input to the pressure change calculator 75, and the pressure change (dP / dt) in the vacuum vessel is obtained based on the equation (10).

  Next, the pressure change obtained by the pressure change calculation unit 75 is input to the container pressure calculation unit 76 and added to the pressure at the previous processing to obtain the current (current) pressure in the vacuum vessel. .

And the pressure calculated | required by the container pressure calculation part 76 is input into the pressure control apparatus 9, and the opening degree of the vacuum valve 4 is controlled.
According to the simulation apparatus 71 described above, the evaluation of the vacuum vessel, that is, the vacuum processing apparatus, can be performed easily and quickly.

  Specifically, for example, there are many (several tens of) gases used in the semiconductor process. When evaluating (verifying) the pressure control device in such an environment, the gas inflow system (each gas cylinder, mass flow) It is necessary to install a controller, piping, etc.), but considering the handling of process gas and the manufacturing cost of the inflow system, it is difficult to actually install it. Therefore, in such a case, by using the above-described simulation apparatus, it is possible to easily and quickly evaluate the vacuum processing apparatus, particularly the pressure control apparatus, according to various gas types and different conditions. it can.

DESCRIPTION OF SYMBOLS 1 Vacuum container 4 Vacuum valve 7 Drive motor 8 Vacuum pump 9 Pressure control apparatus 11 Gas supply pipe 12 Gas discharge pipe 21 Pressure gauge 22 Opening detector 41 Conductance acquisition part 71 Simulation apparatus 72 Conductance acquisition part 73 Exhaust gas amount calculation part 74 Gas flow rate setting unit 75 Pressure change calculating unit 76 Container pressure calculating unit

Claims (4)

A vacuum vessel to which a gas supply line and a discharge line are connected; a vacuum valve that is provided in the discharge line and that can open and close the discharge line; and a pressure gauge that measures the pressure in the vacuum container; An opening detector for detecting the valve opening of the vacuum valve, and the detected values from the pressure gauge and the opening detector are input to control the opening of the vacuum valve at a predetermined processing time interval. A simulation apparatus for the vacuum vessel in a vacuum processing apparatus comprising a pressure control device for controlling the pressure of
A conductance acquisition unit for obtaining the conductance of the vacuum valve based on the valve characteristic curve by inputting the valve opening detected by the opening detector;
An exhaust gas amount calculation unit that obtains an exhaust gas amount by multiplying the conductance obtained by this conductance acquisition unit by the pressure in the vacuum vessel at the time of the previous processing,
Enter the inflow gas amount at the time of the current process obtained by the gas flow rate table that sets the inflow gas amount according to the processing elapsed time to the exhaust gas amount obtained by this exhaust gas amount calculation unit. A pressure change calculation unit for obtaining a pressure change;
And a vessel pressure calculation unit for adding the pressure change obtained by the pressure change calculation unit and the pressure in the vacuum vessel during the previous process to obtain the pressure in the vacuum vessel during the current process. A vacuum vessel simulation device.   2. The vacuum vessel simulation apparatus according to claim 1, wherein the conductance acquisition unit includes a valve characteristic curve indicating a relationship between a valve opening degree and conductance according to a gas type. 2. The vacuum according to claim 1, wherein the conductance acquisition unit includes the following equation (A) that can estimate the conductance of a gas of a type different from the known gas based on a gas having a known conductance. Container simulation device.

In the above formula, C (M, T) is a gas having a molecular weight M and represents conductance at a temperature T, and Ca (Ma, Ta) is a gas having a molecular weight Ma and represents conductance at a temperature Ta. The vacuum vessel simulation apparatus according to claim 1, wherein the pressure change calculation unit includes the following equation (B) for calculating the pressure change (dP / dt).

In the above formula, T represents temperature, T _STD represents temperature in a standard state, P represents pressure, P _STD represents pressure in a standard state, Fs1 represents an inflow gas amount, and Fs2 represents an exhaust gas amount.

Images