JPH06109409A - Electrostatic capacity-type film-thickness sensor - Google Patents

Abstract

PURPOSE:To expand the measuring range of a film thickness and to stably measure a laminated film thickness from an extremely thin state up to a comparatively thick state. CONSTITUTION:Stepped parts are formed at the tip part of a rod-shaped insulator 11 constituting a detection electrode part 10, metal films M are vapor- deposited respectively on opposite faces at every step, and three sets of measuring electrode pairs 12 to 14 provided with different distances between electrode plates are formed. For example, the distance between electrode plates for the narrowest electrode pair 12 is set at about 1mm, the distance between electrode plates for the intermediate electrode pair 13 is set at about 2mm and the distance between electrode plates for the widest electrode pair 14 is set at about 3 mm. Even a thinnest film thickness can be measured accurately for the electrode pair 12, and the film thickness of even an object, under test, which is thicker than the interval between the electrode pairs 12, 13 can be measured for the electrode pair 14 whose interval is widest. As a result, the film thickness can be measured in a wide range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type which detects the film thickness of a substance by utilizing the fact that the capacitance between the electrodes changes depending on the amount of the substance present between a pair of measuring electrodes. The present invention relates to a film thickness sensor.

[0002]

2. Description of the Related Art A capacitance type film thickness sensor applies a predetermined voltage between a pair of measuring electrodes arranged opposite to each other, and determines the electrode depending on the kind of substance existing between the electrodes, the presence or absence of the substance, the amount of the substance and the like. The thickness of the substance between the electrodes is measured by utilizing the change in the capacitance between the electrodes.

As an example of the use of this capacitance type film thickness sensor, for example, the measuring electrodes are arranged in the vertical direction of the liquid tank, and the change in the capacitance due to the vertical movement of the liquid level between the electrodes causes the liquid level to rise. A level gauge that detects the height of the paper or a measurement electrode that is placed across a paper transport path for bills, etc., and detects abnormalities in paper transport from changes in capacitance when feeding one sheet and when feeding two or more sheets. Things are known.

[0004]

However, the capacitance type film thickness sensor used for these conventional applications is effective only within a limited range.
It could only be used under certain conditions.

Therefore, the present invention can be used under a wide range of conditions, and in particular, it is possible to immediately detect the laminated film thickness of a substance that adheres to the surface of a measuring electrode to grow and laminate. It is an object of the present invention to provide a capacitance type film thickness sensor capable of stably detecting and measuring from a very thin state to a relatively thick state.

[0006]

In order to achieve the above-mentioned object, the electrostatic capacitance type film thickness sensor of the present invention applies a voltage between a pair of measurement electrodes formed in a detection electrode portion to apply a voltage between the electrode surfaces. A capacitance-type film thickness sensor for detecting the film thickness of the substance by a change in capacitance due to the substance present in the, wherein different electrode plate distances are provided in the detection electrode portion of the capacitance-type film thickness sensor. The present invention is characterized in that a plurality of measurement electrode pairs are provided, and further, the distance between the electrode plates of the measurement electrode pairs is adjustable.

[0007]

[Operation] By providing a plurality of measurement electrode pairs having different distances between electrode plates as described above, when the substance between the electrodes is thin, a signal from the measurement electrode with a small electrode plate distance causes The film thickness can be detected, and when the substance becomes thick, the film thickness of the substance can be detected by the signal from the measuring electrode having a wide distance between the electrode plates, and the range of the measured film thickness can be widened. Further, by forming the distance between the electrode plates of the measurement electrode pair so as to be adjustable, it is possible to obtain an optimal electrode plate distance according to the usage conditions.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below based on the embodiments shown in the drawings. 1 and 2 show a first embodiment of the present invention. FIG. 1 is a side view of a detection electrode portion in a capacitance type film thickness sensor, and FIG. 2 is a perspective view thereof.

The detection electrode section 10 has stepwise steps formed at the tip of a rod-shaped insulator 11 forming the electrode section.
A metal film M is vapor-deposited on the facing surface of each step, and three pairs of measuring electrodes 12, 13, 14 having different distances between electrode plates are provided.
For example, the distance between the electrode plates of the narrowest measuring electrode pair 12 is 1 mm, the distance between the electrode plates of the intermediate measuring electrode pair 13 is 2 mm, and the electrode plate distance of the widest measuring electrode pair 14 is 3 mm.
It is set to mm.

By providing the measuring electrode pairs 12, 13 and 14 having different distances between the electrode plates in this manner, the measuring electrode pair 12 having the narrowest distance enables accurate measurement even with a thin film thickness. Further, even if the distance between the measurement electrode pair 12 and the measurement electrode pair 13 is thicker, the film thickness can be measured by the measurement electrode pair 14 having the widest distance, so that the film thickness can be measured in a wide range.

That is, FIG. 3 shows that the dielectric constant is 7.5 between the electrodes.
It shows the relationship between the number of glass thin plates in each electrode pair and the measured value when inserting the glass thin plate of, but as is clear from this result, it is necessary to arrange multiple electrode pairs with different electrode plate distances. This makes it possible to capture a wide range of changes in capacitance.

FIG. 4 shows a second embodiment of the present invention, in which a split groove 11a is formed at the tip of a rod-shaped insulator 11 which constitutes an electrode portion, and the split groove 11a is formed in the same manner as described above. The electrode holding member 11b on which the three measurement electrode pairs 12, 13, and 14 are formed is movably fitted in the insulator 11 in the radial direction.

As described above, by forming at least one of the electrode forming members movably so that the distance between the electrode plates can be adjusted, the distance between the electrode plates most suitable for the film thickness range to be measured can be obtained. The film thickness can be measured more accurately in a wide range.

FIG. 5 shows an example of use of the capacitance type film thickness sensor of the present invention. The present invention is applied to the intake port 21 and the exhaust port 22 of the dry shield type vacuum pump 20 having a non-contact seal structure. This is an example in which the electrostatic capacitance type film thickness sensor 23 is attached.

The dry shield type vacuum pump 20 having a non-contact seal structure has various advantages as a vacuum pump used in a semiconductor manufacturing apparatus as compared with a wet seal type vacuum pump using water or oil as a seal medium. However, the gas sucked from the semiconductor manufacturing apparatus contains powdery reaction products, gaseous reaction raw materials, and the like, which reduce the degree of vacuum. When the temperature drops, it deposits and accumulates in the pump, hindering the operation of the vacuum pump.

For this reason, it is necessary to disassemble the vacuum pump to clean the inside when the deposits are accumulated to some extent. Conventionally, however, the inspection and cleaning should be regularly performed at every predetermined operating time. It was However, the amount of reaction products and the like deposited inside the pump differs depending on the type of semiconductor manufacturing apparatus, the type of gas, the operating conditions of the vacuum pump, and the like, so it was difficult to set the cleaning cycle accurately.

Therefore, the capacitance type film thickness sensor 23 of the present invention is provided on at least one of the intake port 21 side and the exhaust port 22 side of the dry shield type vacuum pump 20.
By detecting and measuring the film thickness of the reaction product or the like deposited and laminated on the electrode surface of the sensor 23, it is possible to accurately predict the amount of the reaction product or the like deposited in the pump or the inlet pipe. Therefore, it is possible to prevent accidents such as the accumulation of the deposit inside the vacuum pump, or the deposit inside the inlet pipe falling into the pump and suddenly stopping the vacuum pump.

Particularly, in the capacitance type film thickness sensor of the present invention, since the film thickness can be measured in a wide range, from the thin film thickness at the initial stage of operation to the thick film thickness required to clean the inside of the pump. Can be immediately known, so that the maintenance and inspection time can be predicted from the increasing tendency, and the parts and the like can be arranged reliably.

As described above, the capacitance type film thickness sensor of the present invention is used for continuously monitoring the film thickness from a very thin state to a thick film in the process of growing the substance adhering to the electrode surface. It is particularly suitable for, and can be widely used for confirming the accumulation state of foreign matter in various fluid passages.

Since the electric circuit in the capacitance type film thickness sensor can have a conventionally known circuit configuration, its explanation is omitted. Also, the number and shape of the measurement electrode pairs can be arbitrarily set according to the state of the object to be measured.

[0021]

As described above, since the capacitance type film thickness sensor of the present invention is provided with a plurality of measurement electrode pairs having different distances between electrode plates, it is possible to reliably measure a wide film thickness range. Therefore, the tendency of the film thickness to increase from an extremely thin state can be reliably grasped.

[Brief description of drawings]

FIG. 1 is a side view of a detection electrode portion in a capacitance type film thickness sensor showing a first embodiment of the present invention.

FIG. 2 is a perspective view of the same.

FIG. 3 is a diagram showing a result of a detection experiment of a capacitance type film thickness sensor.

FIG. 4 is a perspective view of a detection electrode portion showing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a usage example of the capacitance type film thickness sensor of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Detection electrode part 11 ... Insulator 11a ... Split groove 11b ... Electrode holding member 12, 13, 14 ... Measurement electrode pair 20 ... Dry shield type vacuum pump 21 ... Suction port
22 ... Exhaust port

Claims (2)

[Claims] 1. A capacitance-type film for detecting a film thickness of a substance by applying a voltage between a pair of measurement electrodes formed on a detection electrode portion and changing a capacitance of the substance existing between the electrode surfaces. A capacitance type thickness sensor, wherein a plurality of measurement electrode pairs having different distances between electrode plates are provided in a detection electrode portion of the capacitance type thickness sensor. 2. The capacitance type film thickness sensor according to claim 1, wherein the distance between the electrode plates of the measurement electrode pair is adjustable.