JP2002070788A - Temperature control circuit for turbo-molecular pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature control circuit for a turbo-molecular pump, which is capable of warming under the right warm-up conditions against the different power supply voltage specification. SOLUTION: A temperature-detecting device 2 detects inside pump temperature warmed by heater 1 and the turning-on electricity calculation device 6 calculates the heater on time per unit time using the temperature difference between target temperature and detected temperature. At the same time, the electric current detecting device 3 detects the heater current, electric current square value device 4 integrates electric current square value, heater control device 5 compares electric current square limit value 7 with electric current square value, if electric current square value exceeds its limit value, even it is within the range of turn on electricity hour determined by turn on electricity calculation device 6, remaining time in the heater control unit time shields the heater current by the signal from the heater control device 5 to the switching element 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo-molecular pump, and more particularly to a turbo-molecular pump for preventing reaction products from adhering to the inside of a turbo-molecular pump used as an exhaust system in a semiconductor manufacturing apparatus or the like. It relates to a temperature control circuit.

[0002]

2. Description of the Related Art There is a turbo molecular pump as a vacuum pump for transporting a gas by mechanically giving a momentum in a certain direction to a gas molecule by a rotary wing or the like. A turbo-molecular pump has a rotating blade with an oblique slit in a disk and a shape almost the same as that of the rotating blade under low-pressure conditions where collisions between gas molecules can be ignored. The rotating blades are driven at an extremely high rotational speed, gas molecules pass through the gap between the two blades, and are evacuated to a vacuum to obtain an ultra-high vacuum. It is. In the vacuum evacuation system of the turbo molecular pump, an oil rotary pump, a dry vacuum pump, or the like is used as a back pressure pump. FIG. 3 shows a cross section of a turbo molecular pump provided with a magnetic bearing device. Turbo molecular pumps
The drive shaft 13 has a touch-down bearing 19a on the upper side and a touch-down bearing 19b on the lower side, has a magnetic levitation mechanism, and is rotated at a high speed by the high-frequency motor 11. And a stator blade 15 stacked with a spacer 16 is provided on the housing side facing the rotor blade 14 so that the rotor blade 1
4 rotates at a high speed, so that the inlet flange 21
The gas is sucked through the protection net 23 from the air inlet and the gas sucked from the outlet flange 22 at the lower part of the housing is exhausted, and is mounted on the caster 12. Since the rotor blades 14 rotate at a high speed, magnetic levitation control for supporting the rotating body of the drive shaft 13 in a non-contact manner is performed.
A thrust magnetic bearing 18 is provided as a set of axial direction control electromagnets for controlling the position of the drive shaft 13 in the direction,
On the other hand, as two sets of radial direction control electromagnets for performing position control in directions of two axes orthogonal to each other at two points of the drive shaft 13,
A radial magnetic bearing 17a is provided at an upper part, and a radial magnetic bearing 17b is provided at a lower part. As a sensor for detecting the displacement of the drive shaft 13, a gap sensor 20 is provided at the lowermost portion as a sensor for detecting an axial direction, and a gap sensor 20a is provided at an upper portion and a gap sensor 20b is provided below as a sensor for detecting a radial direction. Then, feedback control for magnetic levitation is performed.
The turbo molecular pump includes a pump main body and a power supply device, is connected to, for example, a process chamber of a semiconductor manufacturing apparatus, and is used for exhausting a process gas in a film forming process. Vacuum devices incorporating a turbo-molecular pump are not limited to vacuuming, but many devices have been evacuated and then introduced and reacted with various gases.
In apparatuses such as low-pressure CVD, plasma CVD, plasma etching, reactive ion etching, and ion implantation, flammable, explosive, toxic, corrosive, and odorous gases are used, which is extremely dangerous. In particular, countermeasures against these gases are taken for various devices for semiconductor manufacturing and the like.
The active gas corrodes various materials (vacuum vessel, gasket, pump oil, etc.) used in the equipment, and various ions and scattered electrons generated during the reaction are absorbed by various parts of the equipment and reflected. Be charged or charged. Therefore, a band heater 25 and a sheath heater 24 are provided on the outer periphery of the housing so that reaction products in the exhaust gas do not adhere to the inside of these components and the housing. And is controlled by the temperature control circuit of the power supply device. When it is desired to lower the temperature, it can be cooled by the cooling water pipe 26.

FIG. 4 shows a block diagram of a temperature control circuit in a power supply device. Depending on the film forming process, the reaction product may adhere to the inside of the pump, and the base of the pump is heated by the heater 1 to prevent the reaction product from adhering. The temperature control circuit includes a temperature detecting means 2 having a temperature detector 27 provided inside the pump body, a switching element 9 for switching and heating the heater 1, a target temperature 8.
And a heater control means 5 for turning on and off the switching element 9 based on the result of the calculation. Have been. FIG. 5 shows the relationship between the heating time and the pump temperature, FIG. 6 shows the relationship between the temperature difference from the target temperature and the energization time of the heater 1 within the unit time of the heater control, and FIG. 7 shows the elapsed time at 180 V and 264 V driving. 4 shows a relationship between heater temperatures. Here, the control unit time of the temperature control is set to 2.5 seconds, and the heater 1 is set during the temperature rise.
Is 100% energized during the control unit time. Then, as shown in FIG. 5, once the temperature is raised to near the target temperature, the heater 1 is turned on for a time corresponding to the difference from the target temperature in order to maintain the temperature thereafter. For example, if the temperature difference is 1 ° C., as shown in FIG. 6, the heater 1 is energized for 50% of the control unit time for 1.25 seconds.
Is controlled like the current waveform in (3) shown in FIG. If the temperature difference is 0.4 ° C, 20% of the heater control unit time
For 0.5 second.

[0004]

The temperature control circuit of a conventional turbo-molecular pump is constructed as described above.
The resistance value of the heater 1 is designed so that the pump consumes enough power (heat generation) for a certain period of time (for example, one hour) to sufficiently raise the temperature of the pump to the target temperature. That is, when the power supply voltage specification of the power supply device is 180 to 264 V, 1
The resistance value is designed so that the temperature rises sufficiently at 80V. However, when the heater 1 designed to supply a sufficient current for raising the temperature at a power supply voltage of 180 V is used at a power supply voltage of 264 V, the current flowing when the heater 1 is turned on is 264/180 =
The power becomes 1.47 times, and (264/180) ² = 2.15 times when considered in terms of the power consumed by the heater. If it is used as it is, the heating time will be shorter,
In the state where the current is supplied at 00%, there is a problem that the heater is overheated and the life is shortened. Therefore, conventionally, there has been a problem that the supply voltage to the heater must be made constant using a transformer, or a heater having a plurality of specifications must be prepared according to the power supply voltage.

The present invention has been made in view of such circumstances, and it is possible to heat a heater provided in a pump main body in an appropriate temperature rising state even with different power supply voltage specifications. It is an object of the present invention to provide a temperature control circuit of a turbo molecular pump that can be used.

[0006]

In order to achieve the above object, a temperature control circuit of a turbo-molecular pump according to the present invention has a rotating blade and a fixed blade alternately arranged and driven at a high rotation speed under a low pressure condition. A heater that controls the temperature by supplying an electric current to the turbo molecular pump that exhausts the gas molecules so that the reaction product does not adhere to the inside of the turbo molecular pump, a temperature detection unit thereof, and a difference between a target temperature and a pump temperature by the temperature detection unit. In a temperature control circuit of a turbo-molecular pump having a circuit for performing on / off control of a heater, a current detecting means for a heater current and a means for integrating a square of a current value of the heater are provided. The integrated value from the integrating means of
The current value is compared with the squared limit value, and when the limit value is exceeded during the unit time, the power supply to the heater is stopped for the remaining time of the unit time.

The temperature control circuit of the turbo-molecular pump according to the present invention is constructed as described above, and includes a current detecting means for detecting a heater current and a square (in proportion to the electric power) of the heater current during energization of the heater. A heater current value integration means for providing a squared integration of the heater current value to a specified value (current value) even when the heater control means is within an energization time range determined by a temperature difference from a target temperature. When the value exceeds the limit value (square value), the heater is turned off for the remaining time within the heater control unit time. for that reason,
Since the power supplied to the heater per unit time is constant, even if a heater designed for a power supply voltage of 180 V is used at a power supply voltage of 264 V, for example, an excessive temperature rise of the heater can be prevented. Accordingly, one heater can support a plurality of power supply voltage specifications.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a temperature control circuit for a turbo molecular pump according to the present invention will be described with reference to FIG. FIG. 1 shows a block diagram of a temperature control circuit of a turbo molecular pump according to the present invention. The temperature control circuit of the turbo-molecular pump includes a heater 1 for controlling the temperature so that the reaction product does not adhere to the inside of the pump, a temperature detecting means 2 having a temperature detector 27 for detecting the internal temperature, and a heater 1. The on-time of the heater 1 per unit time is calculated from the current detection means 3 for detecting the flowing current, the integration means 4 for squaring the current value of the heater 1, and the difference between the target temperature 8 and the pump temperature by the temperature detection means 2. Of the current value of the heater 1, the current value of the heater 1, and the limit value 7 of the current value squared. And a switching element 9 for turning on and off a current flowing through the heater 1 by the heater control means 5. The temperature control circuit of the turbo molecular pump includes a current detection means 3 for detecting a current flowing through the heater 1 in a conventional temperature control circuit, and a current value square integration means 4 having a circuit for squaring and integrating the current value. , A current value squared limit value 7 is added. Thus, when a current is flowing through the heater 1, the integrated value of the square of the current value (proportional to the electric power) from the integrating means 4 is compared with the limit value 7 of the square of the current value (proportional to the electric power). , The limit value of the square of the current value (proportional to the power) during the unit time 7
Is exceeded, the switching element 9 is turned off from the heater control means 5, and the power supply to the heater 1 is stopped for the remaining time of the unit time.

Next, when the design values of the power supply voltage and the power value are 1
The heater 1 of 80 V and 400 W will be described with a digital circuit using a microcomputer. The resistance value of the heater 1 at 180 V and 400 W is 81 Ω.
The current value when used at 0 V is 2.22 A. Therefore, if the current value of the heater 1 is 2.22 A, the design is such that there is no problem in the life even if the current is continuously supplied.
Without 2A flow, the pump cannot be heated in the specified time. Therefore, with respect to the limit value 7 of the square of the current value, the power supply voltage is set to 100 V during the heater control unit time at 180 V.
Set so that the% heater 1 can be turned on. When the heater control unit time is 2.5 seconds and the square of the current value is calculated 50 times (= 2.5 s) every 50 ms, the limit value 7 of the square of the current value is 2.22 × 2 .22 × 50 = 2
46.4. Then, a case where the temperature of the pump is controlled at a power supply voltage of 180 V will be described. When the temperature rise is started from the room temperature state, the energization time calculation means 6 sets the temperature detection means 2
From the temperature difference between the pump temperature and the target temperature 8, 100% of the heater control unit time
(= 2.5 s). Then, the heater control unit 5 turns on the heater 1 and monitors the integrated value of the square of the current value, which is calculated every 50 ms, by the integrating unit 4. FIG. 2A shows the time on the horizontal axis, the squared integrated value of the current value of the heater 1 on the vertical axis, and FIG. 2B shows the heater current on the vertical axis. 1. When the power supply voltage is 180 V,
Since the integrated value of the square of the current value does not reach the limit value 7 of the square of the current value (= 246.4) within 5 s,
As shown in (b), the pump continues to heat at 100% current (2.22 A). At this time, the power consumed by the heater during 2.5 s is 2.22 A × 180 V × 2.5 s =
1000 W · s. When the difference from the target temperature 8 is within 2 ° C., the energizing time calculating means 6 is used in accordance with the straight line shown in FIG.
The heater control means 5 accordingly sequentially reduces the time to be turned on in the heater control unit time (2.5 s). Next, consider a case where the heater 1 is used at a power supply voltage of 264V. As in the case of 180 V, when the temperature rise is started from the room temperature, the energization time calculation means 6 gives the heater control means 5 100% of the heater control unit time (=
2.5%). The heater control means 5 turns on the heater 1 and monitors the integrated value of the square of the current value, which is calculated every 50 ms, by the integrating means 4. When the power supply voltage is 264 V, the current flowing when the heater is on is
264 V / 81Ω = 3.26 A, and the integrated value of the square of the current value is 246.4 / (3.26 × 3.26) = 2
3.2, and after the 24th 1.2 s, as shown in (a), the limit value 7 of the square of the current value (246.
Go over 4). If the integrated value of the square of the current value exceeds the limit value 7 of the square of the current, the heater control means 5 will continue to operate as shown in FIG. Next, the heater current flowing through the heater 1 is turned off so that no more power is supplied to the heater 1. When the next heater control unit time starts,
As shown in (b), the heater control means 5 again controls the heater 1
Is turned on and the above operation is repeated. At this time, the power consumed by the heater 1 in 2.5 seconds is 3.26 A × 264 V ×
1.2 s = 1033 W · s, which is almost the same as 1000 W · s when the power supply voltage is 180 V. When the difference from the target temperature 8 is within 2 ° C., the indicated value from the energization time calculation means 6 is sequentially reduced from 100% by the determination of the energization time in the temperature control method of FIG. If the time is 1.2 s or longer, the squared limit value 7 of the current value is effective, and the heater 1 is not turned on for a longer time. When the instruction value from the power-on time calculating means 6 becomes 1.2 s or less, the heater control means 5 firstly turns on the power-on time calculating means 6.
The heater 1 is turned on for the time as instructed. Thus, even when the power supply voltage is 264 V, it is possible to prevent the temperature of the heater from excessively rising.

In the above embodiment, a case where a digital circuit is used has been described. However, a similar function can be implemented by a configuration using an analog circuit.

[0011]

The temperature control circuit of the turbo-molecular pump according to the present invention is constructed as described above, detects the current of the heater for heating the pump, and squares the detected heater current (in proportion to the electric power). A circuit is provided for integrating the heater current squared value within the range of the energizing time determined by the temperature difference between the temperature detection value in the pump and the target temperature. (Limit value), the heater is turned off for the remaining time within the heater control unit time, so that the power supplied to the heater per unit time is constant, preventing the heater from overheating. be able to. Therefore, one type of heater can be made compatible with a plurality of power supply voltages without impairing the life of the heater. Further, there is no need to prepare various heaters, and no transformer for voltage conversion is required.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a temperature control circuit of a turbo molecular pump of the present invention.

FIG. 2 is a diagram illustrating a relationship between heater control currents of a temperature control circuit of a turbo-molecular pump according to the present invention.

FIG. 3 is a diagram showing a cross-sectional structure of a turbo-molecular pump.

FIG. 4 is a diagram showing a temperature control circuit of a conventional turbo-molecular pump.

FIG. 5 is a diagram showing a temperature rising state of a conventional turbo-molecular pump.

FIG. 6 is a diagram showing a method of controlling the temperature of a conventional turbo-molecular pump.

FIG. 7 is a diagram showing a current-carrying state of the conventional turbo-molecular pump at each temperature rise.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Heater 2 ... Temperature detection means 3 ... Current detection means 4 ... Current value square integration means 5 ... Heater control means 6 ... Electrification time calculation means 7 ... Current value square limit value 8 ... Target temperature 9 ... Switching element

Claims (1)

[Claims] An electric current is supplied to a turbo-molecular pump, which has rotating blades and fixed blades alternately arranged and is driven at a high rotational speed under a low pressure condition to exhaust gas molecules, so that reaction products do not adhere to the inside. In a temperature control circuit of a turbo-molecular pump having a heater for controlling the temperature by flowing, a temperature detection means thereof, and a circuit for performing on / off control of the heater based on a difference between a target temperature and a pump temperature by the temperature detection means, current detection of a heater current is performed. Means and means for integrating the square of the current value of the heater, and when the heater is ON, the integrated value from the means for integrating the square of the current value is compared with the limit value of the square of the current value, and the unit time is calculated. A temperature control circuit for a turbo-molecular pump, wherein when a limit value is exceeded, power supply to the heater is stopped for the remaining time of the unit time.