WO2002021230A2 - Method and device for regulating a vacuum in a chamber - Google Patents

Method and device for regulating a vacuum in a chamber Download PDF

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Publication number
WO2002021230A2
WO2002021230A2 PCT/EP2001/010057 EP0110057W WO0221230A2 WO 2002021230 A2 WO2002021230 A2 WO 2002021230A2 EP 0110057 W EP0110057 W EP 0110057W WO 0221230 A2 WO0221230 A2 WO 0221230A2
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WO
WIPO (PCT)
Prior art keywords
pressure
chamber
phv
vacuum
control
Prior art date
Application number
PCT/EP2001/010057
Other languages
German (de)
French (fr)
Inventor
Dirk Kalisch
Thomas Palten
Original Assignee
Leybold Vakuum Gmbh
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Filing date
Publication date
Application filed by Leybold Vakuum Gmbh filed Critical Leybold Vakuum Gmbh
Priority to AU2001287708A priority Critical patent/AU2001287708A1/en
Publication of WO2002021230A2 publication Critical patent/WO2002021230A2/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/02—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids specially adapted for several pumps connected in series or in parallel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C25/00—Adaptations of pumps for special use of pumps for elastic fluids
    • F04C25/02—Adaptations of pumps for special use of pumps for elastic fluids for producing high vacuum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/08—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by varying the rotational speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D19/00—Axial-flow pumps
    • F04D19/02—Multi-stage pumps
    • F04D19/04—Multi-stage pumps specially adapted to the production of a high vacuum, e.g. molecular pumps
    • F04D19/046—Combinations of two or more different types of pumps
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D16/00—Control of fluid pressure
    • G05D16/20—Control of fluid pressure characterised by the use of electric means
    • G05D16/2006—Control of fluid pressure characterised by the use of electric means with direct action of electric energy on controlling means
    • G05D16/2066—Control of fluid pressure characterised by the use of electric means with direct action of electric energy on controlling means using controlling means acting on the pressure source
    • G05D16/2073—Control of fluid pressure characterised by the use of electric means with direct action of electric energy on controlling means using controlling means acting on the pressure source with a plurality of pressure sources

Definitions

  • the invention relates to a method for regulating the vacuum in a chamber, in particular for regulating the vacuum pressure in a vacuum chamber in which process sequences are carried out, such as, for example, vapor deposition processes, etching processes in semiconductor technology and the like.
  • a multi-stage pump device is usually used, in which the first pump is often a turbomolecular pump and the downstream pumps are designed as roots pumps and / or backing pumps.
  • a pump device is described in WO 99/04325.
  • the pressure prevailing in the chamber is measured and kept constant by a controller at a setpoint value, which acts on the pressure on the fore-vacuum side of the first vacuum pump connected to the chamber.
  • the pressure control is carried out in such a way that if the pressure in the chamber deviates from a desired pressure, the fore-vacuum pressure is changed so that the pressure in the chamber assumes its setpoint.
  • a difficulty with pressure control in vacuum chambers is that the pumping speed of a friction vacuum pump, for example, depends on the gas flow and the type of gas and that this dependence influences the pressure control.
  • a friction vacuum pump as described in WO 99/04325, there is a strong dependence of the pumping speed on the prevailing fore-vacuum pressure, in the fore-vacuum pressure range of 2-4 mbar for N 2 . Regulation in a simple manner is therefore possible in this pressure range. However, this is different in the range below about 2 mbar.
  • the curve shows the chamber pressure on the ordinate as a function of the backing pressure. on the abscissa, almost horizontal. In the case of heavy gases, such as SF 6 , the horizontal course of this curve is even more pronounced, so that pressure control is extremely difficult here.
  • the problem is the very different gradients, not the absolute value.
  • WO 99/04325 describes a method for regulating the vacuum in a chamber using a regulator, which can be designed as a PID regulator and in which the regulating parameters are changed as a function of the respectively specified target pressure.
  • the control parameter consists of the coefficient or coefficients of the PID control, in particular the proportional coefficient and the integral coefficient. These control parameters can be changed according to the type of gas to be pumped. This makes it possible to carry out an acceptable pressure regulation in a very wide pressure range.
  • EP 0 857 876 A2 and EP 0 898 083 A2 each describe control methods for controlling the pressure of a vacuum chamber, whereby The first pump of the pump assembly is bridged via a control valve and the control valve is controlled by the chamber pressure.
  • the problem associated with controlling an extremely large pressure range and the problem resulting from the flat curve of the high vacuum pressure as a function of the fore vacuum pressure have not yet been solved.
  • the invention is based on the object of specifying a method and a device for regulating the vacuum in a chamber, with which a rapid and precise regulation of the chamber pressure is possible.
  • the chamber pressure is controlled with different control parameters, the current control parameter depending on the in the actual pressure prevailing in the chamber is determined. It has been found that the actual pressure prevailing in the chamber can be used better than the respective target pressure to determine the control parameter.
  • the determination of the control parameter on the basis of the actual pressure has the advantage that rapid regulation takes place and overshoot is largely avoided.
  • the control parameter is determined based on the actual pressure of the chamber, but the setpoint pressure can also be taken into account, especially in situations in which the actual pressure is in the lower part of the pressure range relevant for pressure control or in the horizontal part of the curve, which shows the dependency of the chamber pressure from the backing pressure for the respective gas. If the actual pressure is in this lower part, it should be for the selection of the control parameter be significant whether the setpoint is more or less far above the actual value. If the control has left this extremely niad pressure state and the actual pressure has risen in the range of higher values, the control can be continued using the control parameter which is dependent solely on the actual pressure.
  • a parameter that is changed by the regulation can be the fore-vacuum pressure between two pumps of the pump device.
  • the change in the fore-vacuum pressure is possible in such a way that the suction line in question is connected to a pressure source or a vacuum source via a control valve or to the chamber whose pressure is to be regulated.
  • Another alternative is to change the running speed or the suction power of the subsequent pump of the pump device by the controller.
  • Fig. 1 is a schematic representation of a chamber in which a vacuum is maintained regulated
  • Fig. 2 is a diagram for explaining the selection of the control parameter as a function of the chamber pressure.
  • a chamber 10 which is hermetically sealed and in which a vacuum is to be generated.
  • the chamber 10 is, for example, a chamber in which workpieces or semiconductors are to be processed at a low pressure.
  • the chamber 10 has an inlet 11 on, which is connected to a process gas source PQ, through which at least one process gas is supplied to the chamber 10.
  • the pump device 13 is connected to a suction connection 12 of the chamber 10. This consists of several pumps connected in series in the suction line 14, the first pump 15 being a friction vacuum pump, for example a turbomolecular pump.
  • the second pump 16 is here a positive displacement pump, e.g. a roots pump.
  • the third pump 17 is a pump that compresses against atmospheric pressure.
  • the gas pressure in the chamber 10 is denoted by pHv (high vacuum) and the pressure behind the first pump 15, which represents the high vacuum pump, is denoted by pVv (fore-vacuum pressure),
  • a feed line 18 leads into the suction line 14 between the pumps 15 and 16, which contains a control valve 19 and is connected to a pressure source, which e.g. provides an inert gas with a defined pressure.
  • a pressure source which e.g. provides an inert gas with a defined pressure.
  • the forevacuum pressure pVv is changed as the first suction parameter by the control valve 19.
  • a second suction parameter is formed by the speed or frequency f of the pump 16.
  • This pump is driven by a voltage-to-frequency converter 20 via an asynchronous motor (not shown).
  • the control valve 19 and the pump 16 are controlled by a controller 21, the control being carried out in such a way that the opening of the valve 19 is at the same time associated with a reduction in the frequency f of the pump 16. Both measures cause an increase in the forevacuum pressure pVv.
  • the valve 19 closes with an increase in Frequency f of the pump 16 connected, which leads to a reduction in the backing pressure pVv.
  • An increase in the fore vacuum pressure results in an increase in the high vacuum pressure pHv and a decrease in the fore vacuum pressure results in a decrease in the high vacuum pressure.
  • the controller 21 receives the signal from a pressure sensor 22, which measures the high vacuum pressure pHv in the chamber 10. It also receives a setpoint via line 23, which can be specified manually or by a control device. This setpoint indicates the setpoint pressure that is to be generated in the chamber 10 and kept constant.
  • the controller 21 is a PID controller that changes the frequency f (t) of the pump 16 over time according to the following formula:
  • Kp is the proportional coefficient or proportional gain factor of the PID controller
  • Ki the integral coefficient Kd the derivative coefficient
  • P the actual pressure in the chamber and Ps the specified target pressure
  • x is the integration variable
  • t is the time.
  • control parameters K n The coefficients Kp, Ki and Kd are referred to in their entirety as control parameters K n , where n represents a sequential number that denotes a specific control parameter.
  • the current control parameter K1 to K8 is determined as a function of the high vacuum pressure pHv, which is measured by the pressure sensor 22.
  • the parameter is determined in accordance with Table 1 below. Table 1
  • the areas 1 to 6 indicate the pressure areas of the high vacuum pressure, in which the control parameter is exclusively dependent on the high vacuum pressure.
  • the forevacuum pressure pVv in mbar is plotted on the abscissa and the high vacuum pressure pHv in mTorr along the ordinate.
  • the display is logarithmic along the ordinate and non-linear along the abscissa.
  • Curve 25 shows the dependence of the high vacuum pressure pHv on the fore-vacuum pressure pVv for a certain gas (here: argon). It can be seen that below a fore-vacuum pressure of 2 mbar the curve 25 runs essentially horizontally, ie that in this area the high-vacuum pressure is largely independent of the fore-vacuum pressure. In contrast, curve 25 rises sharply above 2 mbar.
  • This area can be used for pressure control by influencing the backing pressure.
  • the limits of ranges 1 to 6 of high vacuum pressure are 5, 10, 15, 20, 35, 50 and 110 mTorr. If the target pressure for the high vacuum is less than 12 mTorr, the control parameter K is set solely on the basis of the high vacuum pressure. If, on the other hand, the setpoint pressure Ps is greater than 12 mTorr and pHv ⁇ 10 mTorr, the setpoint value is also included in the determination of the control parameter.
  • FIG. 2 shows the case where the actual pressure Pi measured by the pressure sensor 22 is 2 mTorr.
  • the set pressure Ps specified in line 23 is 100 mTorr.
  • the result of this is that the control parameter K8 takes effect, with the result that the high vacuum pressure and the fore vacuum pressure increase.
  • the condition for maintaining K8 is no longer fulfilled. Consequently, the setpoint dependency is ended and the further regulation to the setpoint pressure Ps takes place successively with the control parameters K3, K4, K5 and K6.
  • the size of the control parameters is determined empirically by determining and minimizing the settling time to a setpoint step.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Control Of Fluid Pressure (AREA)

Abstract

The invention relates to a chamber (10) wherein a vacuum (pHv) is maintained in a regulated manner. Said chamber is connected to a suction line (14) comprising a plurality of pumps (15, 16, 17) arranged in a series. The regulation of the vacuum (pHv) is achieved by a regulator (21) which alters by a suction parameter, for example the pre-vacuum pressure (pVv) or the speed of a pump (16). As the control range is large, it is divided into sections wherein different regulating parameters are active. The sections are selected by means of the pressure of the vacuum (pHv) measured by a pressure sensor (22). The respectively active regulating parameter is, subsequently, determined according to the pressure of the vacuum, resulting in quicker and more reliable regulation.

Description

Verfahren und Vorrichtung zur Regelung des Vakuums in einer Kammer Method and device for regulating the vacuum in a chamber
Die Erfindung betrifft ein Verfahren zur Regelung des Vakuums in einer Kammer, insbesondere zur Regelung des Vakuumdruckes in einer Vakuumkammer, in der Prozessabläufe durchgeführt werden, wie beispielsweise Aufdampfprozesse, Ätzprozesse in der Halbleitertechnik und ähnliches.The invention relates to a method for regulating the vacuum in a chamber, in particular for regulating the vacuum pressure in a vacuum chamber in which process sequences are carried out, such as, for example, vapor deposition processes, etching processes in semiconductor technology and the like.
Zur Erzeugung eines Vakuums in einer Kammer wird üblicherweise eine mehrstufige Pumpvorrichtung eingesetzt, bei der häufig die erste Pumpe eine Turbomolekularpumpe ist und die nachgeordneten Pumpen als Roots-Pumpe und/oder Vorpumpen ausgebildet sind. Eine derartige Pumpvorrichtung ist in WO 99/04325 beschrieben. Bei dieser Pumpvorrichtung wird der in der Kammer herrschende Druck gemessen und durch einen Regler auf einem Sollwert konstantgehalten, welcher auf den Druck auf der Vorvakuumseite der mit der Kammer verbundenen ersten Vakuumpumpe einwirkt. Die Druckregelung erfolgt in der Weise, dass bei einem Abweichen des Drucks in der Kammer von einem Solldruck der Vorvakuumdruck derart verändert wird, dass der Druck in der Kammer seinen Sollwert einnimmt.To create a vacuum in a chamber, a multi-stage pump device is usually used, in which the first pump is often a turbomolecular pump and the downstream pumps are designed as roots pumps and / or backing pumps. Such a pump device is described in WO 99/04325. In this pump device, the pressure prevailing in the chamber is measured and kept constant by a controller at a setpoint value, which acts on the pressure on the fore-vacuum side of the first vacuum pump connected to the chamber. The pressure control is carried out in such a way that if the pressure in the chamber deviates from a desired pressure, the fore-vacuum pressure is changed so that the pressure in the chamber assumes its setpoint.
Eine Schwierigkeit bei der Druckregelung in Vakuumkammern besteht darin, dass das Saugvermögen z.B. einer Reibungsvakuumpumpe vom Gasfluss und von der Gasart abhängig ist und dass diese Abhängigkeit die Druckregelung beeinflusst. So besteht z.B. für eine Reibungsvakuumpumpe, wie in der WO 99/04325 beschrieben, eine starke Abhängigkeit des Saugvermögens vom anliegenden Vorvakuumdruck, im Vorvakuumdruck-Bereich von 2-4 mbar für N2. In diesem Druckbereich ist also eine Regelung in einfacher Weise möglich. Anders ist dies jedoch im Bereich unterhalb von etwa 2 mbar. Hierbei verläuft die Kurve, die den Kammerdruck auf der Ordinate als Funktion des Vorvakuumdrucks . auf der Abszisse wiedergibt, nahezu horizontal. Bei schweren Gasen, wie beispielsweise SF6 ist der horizontale Verlauf dieser Kurve noch ausgeprägter, so dass hier eine Druckregelung außerordentlich schwierig ist. Das Problem besteht in den stark unterschiedlichen Steigungen, nicht im absoluten Wert.A difficulty with pressure control in vacuum chambers is that the pumping speed of a friction vacuum pump, for example, depends on the gas flow and the type of gas and that this dependence influences the pressure control. For example, for a friction vacuum pump, as described in WO 99/04325, there is a strong dependence of the pumping speed on the prevailing fore-vacuum pressure, in the fore-vacuum pressure range of 2-4 mbar for N 2 . Regulation in a simple manner is therefore possible in this pressure range. However, this is different in the range below about 2 mbar. The curve shows the chamber pressure on the ordinate as a function of the backing pressure. on the abscissa, almost horizontal. In the case of heavy gases, such as SF 6 , the horizontal course of this curve is even more pronounced, so that pressure control is extremely difficult here. The problem is the very different gradients, not the absolute value.
WO 99/04325 beschreibt ein Verfahren zur Regelung des Vakuums in einer Kammer unter Benutzung eines Reglers, .der als PID-Regler ausgebildet sein kann und bei dem die Regelparameter in Abhängigkeit von dem jeweils vorgegebenen Solldruck verändert werden. Der Regelparameter besteht aus dem bzw. den Koeffizienten der PID-Regelung, insbesondere dem Proportional-Koef- fizienten und dem Integral-Koeffizienten. Diese Regelparameter können entsprechend der Art des zu pumpenden Gases verändert werden. Dadurch ist es möglich, in einem sehr weiten Druckbereich eine akzeptable Druckregelung vorzunehmen.WO 99/04325 describes a method for regulating the vacuum in a chamber using a regulator, which can be designed as a PID regulator and in which the regulating parameters are changed as a function of the respectively specified target pressure. The control parameter consists of the coefficient or coefficients of the PID control, in particular the proportional coefficient and the integral coefficient. These control parameters can be changed according to the type of gas to be pumped. This makes it possible to carry out an acceptable pressure regulation in a very wide pressure range.
EP 0 857 876 A2 und EP 0 898 083 A2 beschreiben jeweils Regelverfahren zur Regelung des Drucks einer Vakuumkammer, wobei über ein Regelventil die erste Pumpe der Pumpenbaugruppe überbrückt ist und das Regelventil von dem Kammerdruck gesteuert ist. Damit ist das Problem, das mit der Regelung eines extrem großen Druckbereichs verbunden ist, und das Problem, das sich durch die flache Kurve des Hochvakuumdrucks in Abhängigkeit vom Vorvakuumdruck ergibt, noch nicht gelöst.EP 0 857 876 A2 and EP 0 898 083 A2 each describe control methods for controlling the pressure of a vacuum chamber, whereby The first pump of the pump assembly is bridged via a control valve and the control valve is controlled by the chamber pressure. The problem associated with controlling an extremely large pressure range and the problem resulting from the flat curve of the high vacuum pressure as a function of the fore vacuum pressure have not yet been solved.
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren und eine Vorrichtung zur Regelung des Vakuums in einer Kammer anzugeben, mit denen eine schnelle und präzise Regelung des Kammerdrucks möglich ist.The invention is based on the object of specifying a method and a device for regulating the vacuum in a chamber, with which a rapid and precise regulation of the chamber pressure is possible.
Die Lösung dieser Aufgabe erfolgt erfindungsgemäß bei dem Verfahren mit den Merkmalen des Patentanspruchs 1 und bei der Vor-Errichtung mit den Merkmalen des Patentanspruchs 7. Nach der Erfindung erfolgt die Regelung des Kammerdrucks mit unterschiedlichen Regelparametern, wobei der jeweils aktuelle Regelparameter in Abhängigkeit von dem in der Kammer herrschenden Istdruck bestimmt wird. Es hat sich herausgestellt, dass zur Bestimmung des Regelparameters der in der Kammer herrschende Istdruck besser verwendbar ist als der jeweilige Solldruck. Die Bestimmung des Regelparameters anhand des Istdrucks hat den Vorteil, dass eine schnelle Ausregelung erfolgt und Überschwingen weitgehend vermieden wird.This object is achieved according to the invention in the method with the features of patent claim 1 and in the pre-erection with the features of patent claim 7. According to the invention, the chamber pressure is controlled with different control parameters, the current control parameter depending on the in the actual pressure prevailing in the chamber is determined. It has been found that the actual pressure prevailing in the chamber can be used better than the respective target pressure to determine the control parameter. The determination of the control parameter on the basis of the actual pressure has the advantage that rapid regulation takes place and overshoot is largely avoided.
Grundsätzlich erfolgt die Festlegung des Regelparameters anhand des Istdrucks der Kammer, jedoch kann zusätzlich auch der Solldruck Berücksichtigung finden, insbesondere in Situationen, in denen der Istdruck im unteren Teil des für die Druckregelung relevanten Druckbereichs liegt bzw. im horizontalen Teil der Kurve, die die Abhängigkeit des Kammerdrucks vom Vorvakuumdruck für das jeweilige Gas angibt. Wenn der Istdruck in diesem unteren Teil liegt, sollte es für die Wahl des Regelparameters bedeutsam sein, ob der Sollwert mehr oder weniger weit über dem Istwert liegt. Wenn die Regelung diesen extrem niadrigen Druckzustand verlassen hat und der Istdruck in dem Bereich höherer Werte angestiegen ist, kann die Regelung unter Verwendung des ausschließlich vom Istdruck abhängigen Regelparameters weitergeführt werden.Basically, the control parameter is determined based on the actual pressure of the chamber, but the setpoint pressure can also be taken into account, especially in situations in which the actual pressure is in the lower part of the pressure range relevant for pressure control or in the horizontal part of the curve, which shows the dependency of the chamber pressure from the backing pressure for the respective gas. If the actual pressure is in this lower part, it should be for the selection of the control parameter be significant whether the setpoint is more or less far above the actual value. If the control has left this extremely niad pressure state and the actual pressure has risen in the range of higher values, the control can be continued using the control parameter which is dependent solely on the actual pressure.
Ein Parameter, der durch die Regelung verändert wird, kann der Vorvakuumdruck zwischen zwei Pumpen der Pumpvorrichtung sein. Die Veränderung des Vorvakuumdrucks ist in der Weise möglich, dass die betreffende Saugleitung über ein Regelventil mit einer Druckquelle oder einer Vakuumquelle verbunden wird oder auch mit der Kammer, deren Druck geregelt werden soll. Eine andere Alternative besteht darin, die Laufgeschwindigkeit bzw. die Saugleistung der nachfolgenden Pumpe der Pumpvorrichtung durch den Regler zu verändern.A parameter that is changed by the regulation can be the fore-vacuum pressure between two pumps of the pump device. The change in the fore-vacuum pressure is possible in such a way that the suction line in question is connected to a pressure source or a vacuum source via a control valve or to the chamber whose pressure is to be regulated. Another alternative is to change the running speed or the suction power of the subsequent pump of the pump device by the controller.
Im folgenden wird unter Bezugnahme auf die Zeichnungen ein Ausführungsbeispiel der Erfindung näher erläutert.In the following an embodiment of the invention will be explained with reference to the drawings.
Es zeigen:Show it:
Fig. 1 eine schematische Darstellung einer Kammer, in der ein Vakuum geregelt aufrechterhalten wird, undFig. 1 is a schematic representation of a chamber in which a vacuum is maintained regulated, and
Fig. 2 ein Diagramm zur Erläuterung der Auswahl des Regelparameters in Abhängigkeit von dem Kammerdruck.Fig. 2 is a diagram for explaining the selection of the control parameter as a function of the chamber pressure.
Gemäß Fig. 1- ist eine Kammer 10 vorgesehen, die hermetisch abgeschlossen ist und in der ein Vakuum erzeugt werden soll. Die Kammer 10 ist beispielsweise eine Kammer, in der eine Bearbeitung von Werkstücken oder Halbleitern bei einem niedrigen Druck durchgeführt werden soll. Die Kammer 10 weist einen Einlass 11 auf, der an eine Prozessgasquelle PQ angeschlossen ist, durch die mindestens ein Prozessgas der Kammer 10 zugeführt wird.1- a chamber 10 is provided which is hermetically sealed and in which a vacuum is to be generated. The chamber 10 is, for example, a chamber in which workpieces or semiconductors are to be processed at a low pressure. The chamber 10 has an inlet 11 on, which is connected to a process gas source PQ, through which at least one process gas is supplied to the chamber 10.
An einen Sauganschluss 12 der Kammer 10 ist die Pumpvorrichtung 13 angeschlossen. Diese besteht aus mehreren hintereinander in die Saugleitung 14 geschalteten Pumpen, wobei die erste Pumpe 15 eine ReibungsVakuumpumpe, beispielsweise eine Turbomolekularpumpe ist. Die zweite Pumpe 16 ist hier eine Verdrängerpumpe, z.B. eine Roots-Pumpe. Die dritte Pumpe 17 ist eine Pumpe, die gegen den Atmosphärendruck komprimiert.The pump device 13 is connected to a suction connection 12 of the chamber 10. This consists of several pumps connected in series in the suction line 14, the first pump 15 being a friction vacuum pump, for example a turbomolecular pump. The second pump 16 is here a positive displacement pump, e.g. a roots pump. The third pump 17 is a pump that compresses against atmospheric pressure.
Der Gasdruck in der Kammer 10 ist mit pHv (Hochvakuum) bezeichnet und der Druck hinter der ersten Pumpe 15, die die Hochvakuumpumpe darstellt, ist mit pVv (Vorvakuumdruck) bezeichnet,The gas pressure in the chamber 10 is denoted by pHv (high vacuum) and the pressure behind the first pump 15, which represents the high vacuum pump, is denoted by pVv (fore-vacuum pressure),
In die Saugleitung 14 führt zwischen den Pumpen 15 und 16 eine Zuführleitung 18 hinein, die ein Regelventil 19 enthält und an eine Druckquelle angeschlossen ist, welche z.B. ein Inertgas mit einem definierten Druck liefert. Durch das Regelventil 19 wird bei diesem Ausführungsbeispiel der Vorvakuumdruck pVv als erster Saugparameter verändert.A feed line 18 leads into the suction line 14 between the pumps 15 and 16, which contains a control valve 19 and is connected to a pressure source, which e.g. provides an inert gas with a defined pressure. In this exemplary embodiment, the forevacuum pressure pVv is changed as the first suction parameter by the control valve 19.
Ein zweiter Saugparameter wird von der Drehzahl oder Frequenz f der Pumpe 16 gebildet. Diese Pumpe wird von einem Spannungs- Frequenz-Umsetzer 20 über einen (nicht dargestellten) Asynchron-Motor angetrieben.A second suction parameter is formed by the speed or frequency f of the pump 16. This pump is driven by a voltage-to-frequency converter 20 via an asynchronous motor (not shown).
Das Regelventil 19 und die Pumpe 16 werden von einem Regler 21 gesteuert, wobei die Steuerung in der Weise erfolgt, dass das Öffnen des Ventils 19 zugleich mit einer Verringerung der Frequenz f der Pumpe 16 verbunden ist. Durch beide Maßnahmen wird eine Erhöhung des Vorvakuumdrucks pVv verursacht. Andererseits ist das Schließen des Ventils 19 mit einer Erhöhung der Frequenz f der Pumpe 16 verbunden, was zu einer Verringerung des Vorvakuumdrucks pVv führt. Eine Erhöhung des Vorvakuumdrucks hat eine Erhöhung des Hochvakuumdrucks pHv zur Folge und eine Verringerung des Vorvakuumdrucks hat eine Verringerung des Hochvakuumdrucks zur Folge.The control valve 19 and the pump 16 are controlled by a controller 21, the control being carried out in such a way that the opening of the valve 19 is at the same time associated with a reduction in the frequency f of the pump 16. Both measures cause an increase in the forevacuum pressure pVv. On the other hand, the valve 19 closes with an increase in Frequency f of the pump 16 connected, which leads to a reduction in the backing pressure pVv. An increase in the fore vacuum pressure results in an increase in the high vacuum pressure pHv and a decrease in the fore vacuum pressure results in a decrease in the high vacuum pressure.
Der Regler 21 empfängt das Signal eines Drucksensors 22, welcher den Hochvakuumdruck pHv in der Kammer 10 misst. Er empfängt außerdem über eine Leitung 23 einen Sollwert, der manuell oder von einer Steuervorrichtung vorgegeben werden kann. Dieser Sollwert gibt den Solldruck an, der in der Kammer 10 erzeugt und konstantgehalten werden soll.The controller 21 receives the signal from a pressure sensor 22, which measures the high vacuum pressure pHv in the chamber 10. It also receives a setpoint via line 23, which can be specified manually or by a control device. This setpoint indicates the setpoint pressure that is to be generated in the chamber 10 and kept constant.
Der Regler 21 ist ein PID-Regler, der die Frequenz f (t) der Pumpe 16 nach folgender Formel zeitlich verändert:The controller 21 is a PID controller that changes the frequency f (t) of the pump 16 over time according to the following formula:
f(t) = Kp(P(t) - Ps(t)) + Ki t(P(x) - Ps(x))dx + Kd(d(P(t)- Ps(t) )/dt)f (t) = Kp (P (t) - Ps (t)) + Ki t (P (x) - Ps (x)) dx + Kd (d (P (t) - Ps (t)) / dt)
Hierin ist Kp der Proportional-Koeffizient oder Proportionalverstärkungsfaktor des PID-Reglers, Ki der Integral-Koeffizient Kd der Ableitungs-Koeffizient, P der Istdruck in der Kammer und Ps der vorgegebene Solldruck, x ist die Integrationsvariable und t die Zeit.Herein, Kp is the proportional coefficient or proportional gain factor of the PID controller, Ki the integral coefficient Kd the derivative coefficient, P the actual pressure in the chamber and Ps the specified target pressure, x is the integration variable and t is the time.
Die Koeffizienten Kp, Ki und Kd werden in ihrer Gesamtheit als Regelparameter Kn bezeichnet, wobei n eine laufende Nummer darstellt, die einen bestimmten Regelparameter bezeichnet.The coefficients Kp, Ki and Kd are referred to in their entirety as control parameters K n , where n represents a sequential number that denotes a specific control parameter.
Der jeweils aktuelle Regelparameter- Kl bis K8 wird in Abhängigkeit von dem Hochvakuumdruck pHv bestimmt, der von dem Drucksensor 22 gemessen wird. Die Bestimmung des Parameters erfolgt nach der nachstehend aufgeführten Tabelle 1. Tabelle 1The current control parameter K1 to K8 is determined as a function of the high vacuum pressure pHv, which is measured by the pressure sensor 22. The parameter is determined in accordance with Table 1 below. Table 1
Bereich 1 OmTorr < pHv < 5mTorr - Kl Bereich 2 5mTorr < pHv < lO Torr - K2 Bereich 3 1OmTorr < pHv < 2OmTorr → K3 Bereich 4 2OmTorr < pHv < 35mTorr → K4 Bereich 5 35mTorr < pHv < 5OmTorr → K5 Bereich 6 5OmTorr < pHv < 11OmTorr → K6Area 1 OmTorr <pHv <5mTorr - Kl Area 2 5mTorr <pHv <lO Torr - K2 Area 3 1OmTorr <pHv <2OmTorr → K3 Area 4 2OmTorr <pHv <35mTorr → K4 Area 5 35mTorr <pHv <5OmTorr → K5 Area 6 5OmTorr < pHv <11OmTorr → K6
(OmTorr < pHv < lOmTorr) & (12mTorr<Ps) → Kl(OmTorr <pHv <lOmTorr) & (12mTorr <P s ) → Kl
(OmTorr < pHv < 1OmTorr) & (25mTorr<Ps) → K8(OmTorr <pHv <1OmTorr) & (25mTorr <P s ) → K8
Die Bereiche 1 bis 6 kennzeichnen die Druckbereiche des Hochvakuumdrucks, in denen der Regelparameter ausschließlich vom Hochvakuumdruck abhängig ist.The areas 1 to 6 indicate the pressure areas of the high vacuum pressure, in which the control parameter is exclusively dependent on the high vacuum pressure.
Dies ist in dem Diagramm von Fig. 2 verdeutlicht. Dort ist auf der Abszisse der Vorvakuumdruck pVv in mbar aufgezeichnet und längs der Ordinate der Hochvakuumdruck pHv in mTorr. Die Darstellung ist entlang der Ordinate logarithmisch und entlang der Abszisse nichtlinear. Die Kurve 25 gibt für ein bestimmtes Gas (hier: Argon) die Abhängigkeit des Hochvakuumdrucks pHv von dem Vorvakuumdruck pVv wieder. Man erkennt, dass unterhalb eines Vorvakuu druckes von 2 mbar die Kurve 25 im wesentlichen horizontal verläuft, d.h. dass in diesem Bereich der Hochvakuumdruck weitgehend unabhängig ist vom Vorvakuumdruck. Oberhalb von 2 mbar steigt dagegen die Kurve 25 stark an. Dieser Bereich kann für eine Druckregelung durch Beeinflussung des Vorvakuumdrucks benutzt werden. Die Grenzwerte der Bereiche 1 bis 6 des Hochvakuumdrucks sind 5,10,15,20,35,50 und 110 mTorr. Wenn der Solldruck für das Hochvakuum kleiner ist als 12 mTorr, erfolgt die Festsetzung des Regelparameters K allein aufgrund des Hochvakuumdrucks . Ist der Solldruck Ps dagegen größer als 12 mTorr und pHv < 10 mTorr, geht auch die Sollwerthöhe in die Bestimmung des Regelparameters ein.This is illustrated in the diagram in FIG. 2. The forevacuum pressure pVv in mbar is plotted on the abscissa and the high vacuum pressure pHv in mTorr along the ordinate. The display is logarithmic along the ordinate and non-linear along the abscissa. Curve 25 shows the dependence of the high vacuum pressure pHv on the fore-vacuum pressure pVv for a certain gas (here: argon). It can be seen that below a fore-vacuum pressure of 2 mbar the curve 25 runs essentially horizontally, ie that in this area the high-vacuum pressure is largely independent of the fore-vacuum pressure. In contrast, curve 25 rises sharply above 2 mbar. This area can be used for pressure control by influencing the backing pressure. The limits of ranges 1 to 6 of high vacuum pressure are 5, 10, 15, 20, 35, 50 and 110 mTorr. If the target pressure for the high vacuum is less than 12 mTorr, the control parameter K is set solely on the basis of the high vacuum pressure. If, on the other hand, the setpoint pressure Ps is greater than 12 mTorr and pHv <10 mTorr, the setpoint value is also included in the determination of the control parameter.
In Fig. 2 ist der Fall dargestellt, dass der Istdruck Pi der vom Drucksensor 22 gemessen wird, 2 mTorr beträgt. Der in der Leitung 23 vorgegebene Solldruck Ps betrage 100 mTorr. Hieraus ergibt sich, dass der Regelparameter K8 wirksam wird, was zur Folge hat, dass der Hochvakuumdruck und der Vorvakuumdruck- ansteigen. Sobald der Hochvakuumdruck den Grenzwert 10 mTorr erreicht hat, ist die Bedingung zur Beibehaltung von K8 nicht mehr erfüllt. Folglich wird die Sollwertabhängigkeit beendet und die weitere Regelung auf den Solldruck Ps erfolgt aufeinanderfolgend mit den Regelparametern K3,K4,K5 und K6.FIG. 2 shows the case where the actual pressure Pi measured by the pressure sensor 22 is 2 mTorr. The set pressure Ps specified in line 23 is 100 mTorr. The result of this is that the control parameter K8 takes effect, with the result that the high vacuum pressure and the fore vacuum pressure increase. As soon as the high vacuum pressure has reached the limit value of 10 mTorr, the condition for maintaining K8 is no longer fulfilled. Consequently, the setpoint dependency is ended and the further regulation to the setpoint pressure Ps takes place successively with the control parameters K3, K4, K5 and K6.
Die Größe der Regelparameter wird jeweils empirisch bestimmt, indem die Ausregelzeit auf einen Sollwertsprung ermittelt und minimiert wird.The size of the control parameters is determined empirically by determining and minimizing the settling time to a setpoint step.
Abweichend von dem vorstehenden Ausführungsbeispiel ist es auch möglich, den Regelparameter nicht in Schritten zu verändern, sondern kontinuierlich, wobei zwischen - den festgelegten Regelparametern eine Interpolation erfolgen kann. Wenn der Regelparameter in Schritten verändert wird, ist in einem Rechner eine Liste der einzelnen Bereiche und der zugehörigen Regelparameter gemäß Tabelle 1 hinterlegt. Aus dieser Liste wird der jeweils aktuelle Regelparameter ausgelesen. Deviating from the above exemplary embodiment, it is also possible not to change the control parameter in steps, but continuously, it being possible for interpolation to take place between the defined control parameters. If the control parameter is changed in steps, a list of the individual areas and the associated control parameters according to Table 1 is stored in a computer. The current control parameter is read from this list.

Claims

PATENTANSPRÜCHE
1. Verfahren zur Regelung des Vakuums in einer Kammer (10), welche mit einer mehrere Pumpen (15,16,17) in Serie enthaltenden Pumpvorrichtung (13) verbunden ist, bei welchen mindestens ein Saugparameter in Abhängigkeit von dem in der Kammer herrschenden Hochvakuumdruck (pHv) und einem vorgegebenen Solldruck (Ps) verändert wird, wobei die Veränderung des Saugparameters unter Verwendung mindestens eines Regelparametes (Kn) erfolgt, d a d u r c h g e k e n n z e i c h n e t , dass der Regelparameter (Kπ) in Abhängigkeit von dem in der1. A method for regulating the vacuum in a chamber (10) which is connected to a pump device (13) containing several pumps (15, 16, 17) in series, in which at least one suction parameter is dependent on the high vacuum pressure prevailing in the chamber (pHv) and a predetermined target pressure (Ps) is changed, the change in the suction parameter using at least one control parameter (K n ), characterized in that the control parameter (K π ) as a function of that in the
Kammer (10) herrschenden Hochvakuumdruck (pHv) bestimmt wird.Chamber (10) prevailing high vacuum pressure (pHv) is determined.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass der Regelparameter (Kn) zusätzlich in Abhängigkeit von dem Solldruck (Ps) bestimmt wird.2. The method according to claim 1, characterized in that the control parameter (K n ) is additionally determined as a function of the target pressure (Ps).
3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, dass Bereiche (1-6) des Hochvakuumdrucks (pHv) vorbestimmt werden, in denen der Regelparameter (Kn) ausschließlich durch den Hochvakuumdruck (pHv) bestimmt wird, und ein Bereich, in dem der Regelparameter zusätzlich durch den Solldruck (Ps) bestimmt wird, wenn dieser Solldruck einen Schwellwert übersteig .3. The method according to claim 2, characterized in that areas (1-6) of the high vacuum pressure (pHv) are predetermined, in which the control parameter (K n ) is determined exclusively by the high vacuum pressure (pHv), and a range in which the Control parameters are additionally determined by the target pressure (Ps) if this target pressure exceeds a threshold value.
4. Verfahren nach einem der Ansprüche 1-3, dadurch gekennzeichnet, dass ein Saugparameter, der durch die Regelung verändert wird, der Vorvakuumdruck (pVv) zwischen zwei Pumpen (15,16) der Pumpvorrichtung ist. 4. The method according to any one of claims 1-3, characterized in that a suction parameter, which is changed by the control, is the backing pressure (pVv) between two pumps (15, 16) of the pump device.
5. Verfahren nach einem der Ansprüche 1-4, dadurch gekennzeichnet, dass ein Saugparameter, der durch .die Regelung verändert wird, die Drehzahl einer der Pumpen (16) der Pumpvorrichtung (13) ist.5. The method according to any one of claims 1-4, characterized in that a suction parameter that is changed by the control, the speed of one of the pumps (16) of the pumping device (13).
6. Verfahren nach einem der Ansprüche 1-5, dadurch gekennzeichnet, dass ein Regelparameter (K) mit einem Propor- tional-Koeffizienten (Kp) und einem Integral-Koeffizienten (Ki) verwendet wird.6. The method according to any one of claims 1-5, characterized in that a control parameter (K) with a proportional coefficient (Kp) and an integral coefficient (Ki) is used.
7. Vorrichtung zur Regelung des Vakuums in einer Kammer (10), welche mit einer mehrere Pumpen (15,16,17) in Serie enthaltenden Pumpvorrichtung (13) verbunden ist, mit einem Regler (21), der den Wert des in der Kammer. (10) herrschenden Hochvakuumdrucks (pHv) und einen Sollwert empfängt, dadurch gekennzeichnet, dass der Regler (21) mindestens einen Regelparameter (Kn) benutzt, der in Abhängigkeit von dem Hochvakuumdruck (pHv) veränderbar ist.7. Device for regulating the vacuum in a chamber (10), which is connected to a pump device (13) containing a plurality of pumps (15, 16, 17) in series, with a regulator (21) which determines the value of the in the chamber , (10) prevailing high vacuum pressure (pHv) and receives a target value, characterized in that the controller (21) uses at least one control parameter (K n ) which can be changed as a function of the high vacuum pressure (pHv).
8. Vorrichtung nach Anspruch 7, dadurch gekennzeichnet, dass der Regelparameter (Kn) ein Regelkoeffizient ist.8. The device according to claim 7, characterized in that the control parameter (K n ) is a control coefficient.
9. Vorrichtung nach Anspruch 7 oder 8, dadurch gekennzeichnet, dass der Regler (21) ein mit einer Saugleitung (14) verbundenes Regelventil (19) steuert.9. The device according to claim 7 or 8, characterized in that the controller (21) controls a control valve (19) connected to a suction line (14).
10. Vorrichtung nach einem der Ansprüche 7-9, dadurch gekennzeichnet, dass der Regler (21) die Drehzahl einer der Pumpen (16) der Pumpvorrichtung (13) steuert. 10. Device according to one of claims 7-9, characterized in that the controller (21) controls the speed of one of the pumps (16) of the pumping device (13).
PCT/EP2001/010057 2000-09-06 2001-08-31 Method and device for regulating a vacuum in a chamber WO2002021230A2 (en)

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FR2854667B1 (en) * 2003-05-09 2006-07-28 Cit Alcatel PRESSURE CONTROL IN THE CHAMBER OF PROCESSES BY VARIATION OF PUMPS SPEED, CONTROL VALVE AND INJECTION OF NEUTRAL GAS
DE10354205A1 (en) * 2003-11-20 2005-06-23 Leybold Vakuum Gmbh Method for controlling a drive motor of a vacuum displacement pump
FR2878913B1 (en) * 2004-12-03 2007-01-19 Cit Alcatel CONTROL OF PARTIAL GAS PRESSURES FOR PROCESS OPTIMIZATION
DE102011103748A1 (en) 2011-05-31 2012-12-06 Ipsen International Gmbh Method for controlling vacuum pumps in an industrial furnace plant
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