JP4915957B2 - Moisture removal method and apparatus in vacuum apparatus - Google Patents

Description

  The present invention relates to a vacuum apparatus and a water removal method for a vacuum apparatus mainly used as a semiconductor manufacturing apparatus, and more particularly to a water removal apparatus and a removal method for a plasma CVD apparatus.

  Conventionally, as a cleaning method inside a vacuum apparatus, as a method for easily removing particles deposited on a discharge electrode, there is a method for easily removing negatively charged particles using electrostatic force by charging an insulating wafer. It is publicly known (see Patent Document 1).

  In Patent Document 1, the size of the particle is not specified, but in this document, it is shown that the particle is removed by electrostatic force. Therefore, the particle here is a substance that can be charged. It is limited to.

  In general, since charging of a substance in such a vacuum occurs only when the size of the substance is from submicron to micron, particles that can be removed by the invention described in Patent Document 1 are at least larger than submicron. Limited to size.

On the other hand, a method for cleaning the inside of a vacuum apparatus by dry cleaning using high-frequency plasma is also known (see Patent Document 2).
JP-A-6-173041 JP-A-5-315098

  In the invention described in Patent Document 1, only a substance having a size larger than submicron can be removed. Moreover, in the invention described in Patent Document 2, it is not clear what substances are removed when dry cleaning is performed.

  In any of the above prior arts, there is no disclosure or suggestion about the removal of impurities (hereinafter referred to as “molecular impurities”) present as gas molecules having a size of angstrom order in the vacuum apparatus.

  By the way, in a vacuum apparatus in a plasma CVD apparatus or the like, if moisture exists in the apparatus, it adversely affects the quality of a semiconductor product or the like manufactured there, but it is usually difficult to remove the water component in the vacuum apparatus. Also in the prior arts shown in the above Patent Documents 1 and 2, there is no disclosure or suggestion about the point of removing the water component in the vacuum apparatus.

  The present invention realizes a means and a method for removing water components in a vacuum apparatus, which are usually considered difficult in view of the above-described conventional technical situation, and the cleanliness and base vacuum degree in the vacuum apparatus. It is an object of the present invention to realize means and methods for significantly improving the above.

  In order to solve the above-mentioned problems, the present invention provides a vacuum apparatus having an electrode capable of generating discharge and a heating device. For example, the present invention relates to a vacuum device comprising an openable / closable vacuum vessel, a plasma generator provided in the vacuum vessel, and an exhaust device, wherein the plasma generator comprises an anode electrode, a power input electrode, A high-frequency power source for applying a high-frequency voltage between the anode electrode and the power input electrode, and a heating device for heating the anode electrode. The heating device heats the anode electrode, thereby There is provided a vacuum device characterized in that a water component can be extracted and removed from the vacuum vessel by the exhaust device.

  The heating temperature of the anode electrode is 100 ° C. or higher.

The vacuum vessel is used as a plasma CVD apparatus for semiconductor fabrication.

The present invention is to solve the above problems, and an anode electrode that can generate discharge, possess an electrode and a heating device comprising a power input electrode, the vacuum device is used as a plasma CVD apparatus for semiconductor manufacturing A method for removing moisture,
The heating device heats the anode electrode to 100 ° C. or more simultaneously with the discharge between the anode electrode and the power input electrode , thereby extracting the water component in the vacuum vessel and removing it outside the vacuum vessel by the exhaust device The present invention provides a method for removing moisture from a vacuum apparatus.

  For example, the present invention relates to a moisture removal method for a vacuum apparatus including an openable / closable vacuum container, a plasma generator provided in the vacuum container, and an exhaust device, wherein the plasma generator includes an anode electrode, A power input electrode, a high frequency power source for applying a high frequency voltage between the anode electrode and the power input electrode, and a heating device for heating the anode electrode, wherein the heating device heats the anode electrode, A water removal method for a vacuum apparatus is provided, wherein a water component in the vacuum container, particularly in the vicinity of an anode electrode, is extracted and removed from the vacuum container by the exhaust device.

According to the present invention configured as described above, the following effects are produced.
(1) Since the heating device is attached in addition to the discharge generator inside the vacuum device, the water component in the vacuum device can be easily removed simply by heating at the same time as generating the discharge.

(2) The present invention can improve the cleanliness and the base vacuum degree of the vacuum apparatus very easily without providing any additional equipment in the existing vacuum apparatus having an apparatus such as an electrode required for discharging and a heating apparatus. .

(3) Since discharge and heating are both spatially and temporally selective if a structure and method are selected, it is possible to clean a specific place in the vacuum apparatus.

  The best mode for carrying out the vacuum apparatus and the moisture removing method in the vacuum apparatus according to the present invention will be described below with reference to the drawings based on the embodiments.

  The present invention, when performing discharge cleaning in a vacuum apparatus such as a plasma CVD apparatus, further heats the interior of the vacuum apparatus to 100 ° C. or higher, thereby removing water components that are usually difficult to remove, thereby providing a vacuum. An apparatus for improving the vacuum cleanliness of the apparatus is provided.

  Conventionally, as disclosed in the invention described in Patent Document 2, impurities in a vacuum apparatus have been removed by using discharge. However, sufficient cleanliness cannot be obtained only by discharge. In particular, the water component is difficult to remove because of its strong adsorption force to the inner wall of the apparatus.

  Therefore, in the course of advancing various research and development, the present inventors discharged water components, which had been difficult until now, into the gas phase when discharging inside the vacuum apparatus while heating it above a certain temperature. As a result, they have found that the degree of base vacuum in the vacuum apparatus is improved. This finding may be simple, but not known at all, and is a means of producing significant effects that can solve the very troublesome water component problem, as described below. .

  That is, the molecular impurities adsorbed on the inner wall of the vacuum device or permeating into the inner wall cannot be completely removed from the vacuum device simply by discharging from the wall surface. This is because molecular impurities once released from the wall cannot move further from the released wall unless sufficient energy is given, and eventually return to the original adsorption state or re-penetrate. is there.

  If more energy is given to the once released molecular impurities, the released molecular impurities are further excited, and the possibility of being released into the gas phase increases. Once released into the gas phase, molecular impurities can be easily removed from the vacuum apparatus by evacuation.

  Therefore, the inventors of the present invention, by simultaneously performing discharge and heating inside the vacuum apparatus, further releases molecular impurities released from the wall surface of the vacuum apparatus by discharge into the gas phase and removes them by vacuum exhaust, Invented the method. This makes it possible to remove mainly water components that were not removed only by discharge. As a result, the base vacuum degree of the vacuum apparatus was successfully improved.

  The apparatus shown in FIG. 1 is a diagram illustrating the overall configuration of a vacuum apparatus 1 according to the present invention. The vacuum apparatus 1 is provided with a plasma generator in a vacuum container 2 that can be opened and closed (the door is not shown), a gas introduction unit 3 for introducing a medium gas into the vacuum container 2, and a vacuum container 2 is provided with an exhaust device 5 having a pump 4 for removing gas, water components, and the like in 2.

  The plasma generator includes an anode electrode 6 (AE, discharge ground electrode), a power input electrode 7 (PE), and a high frequency power source 8 that applies a high frequency voltage between the anode electrode 6 and the power input electrode 7. A parallel plate electrode capable of generating a 13.56 MHz high-frequency glow discharge is formed. The anode electrode 6 includes a heating device that heats the anode electrode 6.

  The heating device is heated by a heater 9 provided in the vicinity of the anode electrode 6 to evaporate the water component in the vacuum vessel 2 desorbed by the discharge into the air, and is removed outside the vacuum vessel 2 by the exhaust device 5. The heating temperature is 100 ° C. or higher. As the heater 9 of the heating device, in this embodiment, an electric heater provided in contact with the anode electrode 6, for example, a sheath heater is used.

  The conditions for introducing the medium gas from the gas introduction unit 3 are 30 sccm of argon and 100 sccm of hydrogen, and the total pressure in the vacuum vessel 2 is 130 Pa.

  FIG. 2 shows the result of mass spectrometry of gas molecules existing in the vacuum apparatus 1 when the material gas is introduced into the vacuum apparatus 1 under the above conditions. Such measurement is called gas analysis, and this measurement is performed by introducing a part of the gas existing in the gas phase from the vacuum apparatus 1 through a thin tube (not shown) to the mass analyzer.

  Here, a quadrupole mass analyzer was used as the mass analyzer. This mass spectrometer is an instrument that performs mass spectrometry by ionizing sampled gas molecules and separating the generated ions for each mass by an electric field.

  FIG. 2 shows the result of gas analysis after introducing hydrogen and argon under the above conditions. The amount of molecules having the mass number shown on the horizontal axis indicates how much each molecule exists in the vacuum apparatus 1. At this time, no discharge is performed.

  As can be seen from FIG. 2, in addition to hydrogen (mass number 2) and argon (40), which are intentionally introduced as material gases, it is considered that there are some gas molecules, although these are very small compared to these. A mass peak appears. The peak of mass number 20 is a signal due to argon divalent ions. The result of FIG. 2 shows that some unintended gas molecules, that is, molecular impurities are present in the gas phase of the vacuum apparatus 1.

  These are considered to originate mainly from various members existing in the inner wall of the vacuum vessel 2 and the inside of the vacuum apparatus 1. Since only the medium gas and molecular impurities are present in the gas phase, the cleanliness and vacuum of the vacuum apparatus 1 can be improved by removing these molecular impurities.

  For this purpose, it is necessary to first release these molecular impurities from the member including the inner wall surface of the vacuum vessel 2. This is because the molecular impurities seen in FIG. 2 are mainly released from the members including the inner wall of the vacuum chamber 2, and many molecular impurities are adsorbed and permeated into these members.

  FIG. 3 shows the result of further starting discharge in the situation as shown in FIG. 2 and comparing the conventional discharge cleaning method with the present invention.

  3 (a) and 3 (b), the time is taken on the horizontal axis, and when discharge is started and stopped at an input power of 100 W, the results of the same gas analysis as described above are shown as the power input electrode 7. The measurement was carried out by changing the temperature of the anode electrode 6 (AE) which is the opposite electrode.

  As described above, all gases other than hydrogen and argon are molecular impurities present in the gas phase. Among these molecular impurities, those having typical mass numbers of 18 and 28 are discharged for each molecular impurity having a different mass. The change with time is shown. Here, the substance having a mass number of 18 is water, and the mass number is considered to be carbon monoxide.

  In FIG. 3A, when a discharge is generated at a temperature near the discharge, the amount of detected molecular impurities such as carbon monoxide is increased, and these molecular impurities are released. There is almost no change in water.

  On the other hand, in the case of FIG. 3B in which the discharge was performed by raising the temperature to 200 ° C., an increase in the water peak due to the discharge was observed in addition to the carbon monoxide. This result is presumed that the moisture desorbed by the discharge is released into the gas phase by heating, and the moisture peak is increased by taking it into the mass spectrometer.

  As described above, it was confirmed by mass spectrometry that the discharge of the water component was accelerated when members such as the inner wall of the vacuum vessel 2 and the anode electrode 6 in the vacuum apparatus 1 were heated in discharge cleaning using hydrogen or a rare gas. It was. Therefore, it was shown that the removal of moisture, which has been difficult to remove by heating, is accelerated by heating.

  In order to clarify the details of the heating effect, other conditions are left as they are, and the result of performing a similar experiment while changing only the set temperature (anode electrode temperature) of the anode electrode 6 is shown in FIG. In addition, since the discharge amount changes with time, the average value of the amount increased during discharge was used. When the anode electrode temperature is room temperature, almost no moisture is released, but it can be seen that the amount of moisture released increases as the anode electrode temperature rises.

  Regarding specific discharge conditions, since there are a wide variety of discharge conditions, there is no general rule for optimization, and the discharge conditions vary depending on individual apparatuses. However, it can be optimized by adjusting each discharge condition so as to maximize the moisture peak during heating discharge while using the mass spectrometry as shown here.

  The individual discharge conditions include the type of material gas, the introduction flow rate, the gas pressure in the vacuum device, the input power, the potential in the electrode and the space in the vacuum device 1, and the like.

  On the other hand, the heating conditions are estimated from the result of the temperature dependence of the anode electrode 6 shown in FIG. 4, at least 100 ° C. or more and about 150 ° C. are necessary for removing water. The result that the required temperature is 100 ° C. or higher is considered to correlate with the boiling point of water being 100 ° C., and the required temperature in the present invention is limited to 100 ° C. or higher.

  The upper limit temperature is not limited from the viewpoint of moisture release, but in reality, the temperature that can be withstood by the vacuum apparatus and its internal members, and at the highest, the melting point of these materials is the limit temperature. For example, stainless steel often used as a vacuum device has a limit temperature (melting point) of 1500 ° C., 3500 ° C. for noble metals such as tungsten used as a member in the vacuum device, 1820 ° C. for titanium, 1750 ° C. for zirconium, and 1750 ° C. for carbon. 3800 ° C.

  Furthermore, as a result, the improvement of the cleanliness / vacuum degree of the vacuum apparatus 1 was recognized. In FIG. 5, the moisture content obtained by the above-described mass spectrometry is used as an index of the cleanliness / vacuum degree of the vacuum apparatus 1, and the relative value of this value is plotted against the elapsed days. As shown in FIG. 5, the amount of released water decreased with the elapsed days, and the cleanliness / vacuum degree of the vacuum apparatus 1 increased.

  The basic principle of the present invention is to perform discharging and heating simultaneously in the vacuum apparatus 1. As for the specific configuration and method of these discharges and heating, it is possible to use various techniques and forms accumulated so far depending on the internal shape and use form of the vacuum apparatus 1.

  As described above, since there are a wide variety of discharge conditions, there is no general rule for optimizing the conditions for removing moisture in the high-frequency discharge here, so it is appropriate to optimize by monitoring the mass peak. However, the heating temperature needs to be kept at 100 ° C. or higher as described above.

  Further, in this case, since the range of the bright portion of the discharge is limited to between the discharge electrodes (between AE and PE), it is presumed that the desorption of molecular impurities by the discharge is almost limited to the surface of the discharge electrode.

  As for the type of discharge, in addition to the above forms, gases such as direct current glow discharge, microwave discharge, magnetron discharge, ECR electron cycletron resonance, surface wave excitation discharge, atmospheric pressure discharge, thermal plasma, arc plasma, hollow cathode discharge, etc. Any discharge that uses as a medium can be used.

  Here, in FIG. 3, since the water peak increases rapidly immediately after the start of discharge, the water discharge may be due to a transient state immediately after the start of discharge. As this transient state, a state where the electron temperature or the electron density is high is conceivable. In order to efficiently use a transient state immediately after the start of the discharge, a high repetition pulse discharge in which a short time discharge is repeated is effective.

  As a heating method, in addition to using a sheath heater (electric heater), means using light such as lamp heating or laser irradiation can be applied. Of the above, for surface wave excitation discharge, atmospheric pressure discharge, thermal plasma, and some other discharges of arc plasma, the temperature of the part where the discharge exists is inevitably high, so an additional heating device must be installed. The present invention can be realized without.

  The best mode for carrying out the present invention has been described based on the embodiments. However, the present invention is not limited to such embodiments, and within the scope of the technical matters described in the claims. Needless to say, there are various embodiments.

  Since the vacuum apparatus and the water removal method for the vacuum apparatus according to the present invention have the above-described configuration, they are optimal as means for use in a plasma CVD apparatus.

It is a figure explaining the whole structure of the vacuum device which concerns on this invention. In the vacuum apparatus which concerns on this invention, it is a figure which shows the result of having measured the distribution state of content according to the mass number of the impurity contained in the vacuum apparatus before discharge and a heating. In the vacuum apparatus which concerns on this invention, it is a figure which shows the change of content of the impurity by heating time, (a) is heating at room temperature, (b) has shown the measurement result at the time of heating at 200 degreeC, respectively. . In the vacuum apparatus which concerns on this invention, it is a figure which shows the measurement result of the discharge | release water relative intensity | strength to the gaseous phase with respect to the change of an anode electrode (ground electrode) temperature. It is a figure which shows the measurement result of the discharge | release water relative intensity | strength to the gaseous phase with respect to the change of the days in the vacuum apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum apparatus 2 Vacuum container 3 Gas introduction part 4 Pump 5 Exhaust apparatus 6 Anode electrode 7 Power supply electrode 8 High frequency power supply 9 Heater (heating apparatus)

Claims (2)

An anode electrode to produce discharge, have a exhaust device with an electrode composed of a power-on electrode, a vacuum device is used as a plasma CVD apparatus for semiconductor manufacturing,
Wherein simultaneously with the discharge between the electrodes, by providing a heating device for heating the anode electrode than 100 ° C., vacuum apparatus characterized by having a function to exclude moisture that occurs in the vacuum apparatus. An anode electrode to produce discharge, possess an electrode and a heating device comprising a power-on electrode, a water removal method of a vacuum device used as a plasma CVD apparatus for semiconductor manufacturing,
The heating device heats the anode electrode to 100 ° C. or more simultaneously with the discharge between the anode electrode and the power input electrode , thereby extracting the water component in the vacuum vessel and removing it outside the vacuum vessel by the exhaust device A method for removing moisture from a vacuum apparatus.

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