Ionization gauge and cartridge

An ionization gauge includes an anode, a cathode, and an electromagnetic wave source. The cathode includes a first cathode plate having a through hole through which the anode passes, a storage portion configured to store the electromagnetic wave source, and a passage arranged between the storage portion and the through hole and configured to pass an electromagnetic wave generated by the electromagnetic wave source.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an ionization gauge and a cartridge.

Description of the Related Art

In an ionization gauge, a gas is ionized by applying a voltage between an anode and a cathode and thus causing discharge, and a current flowing between the cathode and the anode is measured to detect a pressure. The ionization gauge can be provided with an inducing unit configured to promote discharge between the anode and the cathode. In Japanese Patent No. 6177492, a cathode is irradiated with an electromagnetic wave, and electrons are emitted from the cathode by the photoelectric effect, thereby inducing discharge. However, in long-time use, substances may be deposited on the surface of the electrode, and discharge may be difficult to induce.

SUMMARY OF INVENTION

The present invention provides a technique advantageous in suppressing lowering of discharge inducing performance in an ionization gauge.

According to the first aspect of the present invention, there is provided an ionization gauge comprising an anode, a cathode, and an electromagnetic wave source, wherein the cathode comprises a first cathode plate including a through hole through which the anode passes, a storage portion configured to store the electromagnetic wave source, and a passage arranged between the storage portion and the through hole and configured to pass an electromagnetic wave generated by the electromagnetic wave source.

According to the second aspect of the present invention, there is provided a cartridge used in an ionization gauge including an anode, an electromagnetic wave source, and a container, the cartridge comprising a first cathode plate including a through hole through which the anode passes, a storage portion configured to store the electromagnetic wave source, and a passage arranged between the storage portion and the through hole and configured to pass an electromagnetic wave generated by the electromagnetic wave source.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments are not intended to limit the scope of the appended claims of the present invention. A plurality of features are described in the embodiments. However, not all of the plurality of features are necessarily essential to the present invention, and the plurality of features may arbitrarily be combined. Also, the same reference numerals denote the same or similar parts throughout the accompanying drawings, and a repetitive description thereof will be omitted.

FIG. 1shows a vacuum processing apparatus S according to an embodiment and an ionization gauge100attached to it. The vacuum processing apparatus S can be, for example, a deposition apparatus. Examples of the deposition apparatus are a sputtering apparatus, a PVD apparatus, and a CVD apparatus. The vacuum processing apparatus S may be a surface treatment processing such as an ashing apparatus or a dry etching apparatus.

The ionization gauge100can include a probe102, and a control unit13connected to the probe102. The vacuum processing apparatus S includes a vacuum container101, and can process a processing target object such as a substrate in the vacuum container101. The probe102is attached to an opening portion provided in the wall of the vacuum container101while holding airtightness. In an example, the probe102can be connected via a flange8of the vacuum container101. The control unit13and the probe102may be configured to be separable from each other or may be integrated.

FIG. 2shows the arrangement of an ionization gauge100according to the first embodiment. The ionization gauge100can be configured as, for example, a reverse magnetron type gauge, but is not limited to this. A probe102can include a container103that forms a cathode1, and an anode2. The container103that forms the cathode1can include a tubular portion TP having, for example, a tubular shape such as a cylindrical shape. The anode2can have a rod shape. The cathode1can be arranged to surround the rod-shaped anode2. A discharge space4can be defined by the anode2and the cathode1. The container103can be made of a conductor such as a metal (for example, stainless steel). The anode2can be made of a conductor such as a metal (for example, molybdenum, tungsten, nickel, or titanium). The probe102can further include a magnet3that forms a magnetic field. The magnet3can be arranged to surround the tubular portion TP, and can have a ring shape. The magnet3can be, for example, a permanent magnet such as a ferrite magnet. One end (the side of the vacuum container101) of the tubular portion TP of the container103can be opened, and the other end of the tubular portion TP can be sealed by an insulating sealing member6. In an example, the anode2can be arranged to extend through the sealing member6. The sealing member6can be made of, for example, alumina ceramic.

An exchangeable cartridge106may be arranged in the container103. The cartridge106can be a consumable component usable in the ionization gauge100. The cartridge106can be, for example, a cathode structure. The cartridge106can include pole pieces (cathode plates)104and105, and an inner tube110. The pole pieces104and105can have a function of adjusting a magnetic field, and a function of surrounding the discharge space4. The inner tube110can include an outer surface that is in contact with the inner surface of the container103, and an inner surface surrounding the discharge space4, and can support the pole pieces104and105. The pole pieces104and105and the inner tube110can be made of a conductor such as a metal. The conductor that can form the pole pieces104and105may be a magnetic material (for example, stainless steel having magnetism), or may be a nonmagnetic material (for example, stainless steel that has no magnetism).

The cartridge106is electrically connected to the tubular portion TP, and the pole pieces104and105and the inner tube110can form a part of the cathode1. If the cartridge106has degraded due to collision of ions or the like against the cartridge106, the degraded cartridge106is exchanged with a new cartridge106, thereby recovering the function of the ionization gauge100. In this example, the cartridge106is exchangeable. However, the cartridge106may be inseparably coupled with the tubular portion TP.

The pole piece (first cathode plate)105can include a through hole11through which the anode2extends, and a storage portion22that stores an electromagnetic wave source15. The through hole11is provided not to electrically connect the pole piece105and the anode2, that is, to form a gap between the pole piece105and the anode2. The electromagnetic wave source15can be, for example, a light source. The pole piece105is provided with a cover25that covers the electromagnetic wave source15. When the cartridge106is detached from the tubular portion TP, the cover25can be detached from the tubular portion TP together with the pole piece105. In this case, the cover25can be exchanged by exchanging the cartridge106. The cover25can be made of a material (for example, silica) that passes an electromagnetic wave radiated from the electromagnetic wave source15. The cover25prevents particles generated by sputtering the cathode1(mainly the cartridge106) facing the discharge space4from being deposited on the electromagnetic wave source15. The cover25can have, for example, a cylindrical shape.

The pole piece (second cathode plate)104is arranged apart from the pole piece105, and the discharge space4can be defined between the pole piece105and the pole piece104. The pole piece105can be arranged between the pole piece104and the sealing member6. The pole piece105can be arranged at an end of the inner tube110(an end on the side of the sealing member6). The pole piece104can be arranged at the other end of the inner tube110(an end on the open end of the tubular portion TP). The pole piece104includes one or a plurality of through holes10, and the vacuum container101and the discharge space4communicate via the one or the plurality of through holes10.

The cartridge106or the cathode1can further include a cathode plate (third cathode plate)20between the pole piece105(first cathode plate) and the pole piece104(second cathode plate). The cathode plate20can be arranged to be in contact with the pole piece105. The cathode plate20includes a through hole to pass the anode2. The cathode plate20can be configured to transmit the electromagnetic wave generated by the electromagnetic wave source15to the discharge space4surrounded by the pole piece104, the cathode plate20, and the inner tube110(tubular portion TP). For example, the cathode plate20can be configured to form a gap21between the cathode plate20and the inner tube110and transmit, via the gap21, the electromagnetic wave generated by the electromagnetic wave source15to the discharge space4. Not only the electromagnetic wave generated by the electromagnetic wave source15but also electrons generated by the photoelectric effect upon irradiating a portion between the cathode plate20and the pole piece105in the inner tube110with the electromagnetic wave can be supplied to the discharge space4via the gap21. The inner tube110can be made of the same material as the pole pieces105and104.

The anode2is electrically connected to the control unit13. The control unit13can include a power supply18configured to apply a voltage to the anode2, and a current detection unit19configured to measure a discharge current flowing between the anode2and the cathode1. The discharge current detected by the current detection unit19has a correlation with the pressure in the discharge space4, and the pressure can be calculated by a processor (not shown) based on the correlation. The pressure in the vacuum container101can thus be detected.

FIG. 3Ais a plan view of the pole piece105shown inFIG. 2, which is viewed from the + direction of the z-axis inFIG. 2. Note that inFIG. 3A, the cathode plate20is not illustrated.FIG. 3Bis a sectional view of the pole piece105taken along a line A-A′ inFIG. 3A. As shown inFIGS. 2, 3A, and 3B, the pole piece (first cathode plate)105can include, between the storage portion22and the through hole11, a passage50configured to pass the electromagnetic wave generated by the electromagnetic wave source15. The passage50can be provided to form a linear path between the electromagnetic wave source15and the through hole11. The passage50can extend in a radial direction to connect the storage portion22and the through hole11. The passage50can be provided to face a space5surrounded by the pole piece105, the sealing member6, and the tubular portion TP. When the passage50is provided in the pole piece105, the electromagnetic wave generated by the electromagnetic wave source15irradiates the surface of the through hole11via the passage50, and generates electrons on the surface of the through hole11by the photoelectric effect. The electromagnetic wave generated by the electromagnetic wave source15can directly irradiate the surface of the through hole11, and can also be reflected by the surface of the passage50and/or the anode2and then irradiate the surface of the through hole11. A part of the electromagnetic wave generated by the electromagnetic wave source15can generate electrons on the surface of the passage50by the photoelectric effect. The electrons generated on the surface of the through hole11and the surface of the passage50can be supplied to the discharge space4. In addition, the inter-electrode distance (the distance between the pole piece105and the anode2) in the through hole11is relatively shorter than the inter-electrode distance in another space in the ionization gauge100. Hence, the electric field in the through hole11is relatively large. For this reason, the electric field efficiently concentrates in a bending portion (projection)60formed at the boundary between the passage50and the through hole11, and electrons can be generated by field emission from the bending portion (projection)60. From the above, when the passage50is provided, the amount of electrons emitted to the discharge space4can be increased, and as a result, discharge inducing performance can be improved.

The electromagnetic wave source15can generate an electromagnetic wave, for example, soft x-rays. The storage portion22that stores the electromagnetic wave source15can be, for example, a through hole or a concave portion provided in the pole piece105. The storage portion22may be in contact with the electromagnetic wave source15or not. The storage portion22may hold the electromagnetic wave source15or not. In an example, the distance between the storage portion22and the inner tube110may be shorter than the distance between the storage portion22and the anode2. In another viewpoint, the distance between the electromagnetic wave source15and the inner tube110may be shorter than the distance between the electromagnetic wave source15and the anode2. This arrangement can reduce the attenuation of the electromagnetic wave that is generated by the electromagnetic wave source15and enters the inner tube110. This is advantageous in increasing the electrons emitted from the inner tube110to the discharge space4by the photoelectric effect.

The cathode plate20can be arranged between the electromagnetic wave source15and the discharge space4. The cathode plate20can prevent particles generated by sputtering the cathode1(mainly the cartridge106) facing the discharge space4from being deposited on the electromagnetic wave source15. In an example, a surface of the pole piece105on the side of the discharge space4can include a portion that tilts to provide the electromagnetic wave radiated from the electromagnetic wave source15to the inner tube110and/or the gap21. Power supply to the electromagnetic wave source15can be done by a power cable27. The power cable27can be extracted to the outside of the container103via the sealing member6. The arrangement for extracting the power cable27and the anode2to the outside via the sealing member6common to these is advantageous in simplifying the structure of the ionization gauge100.

At least one of the electromagnetic wave source15and the cover25may be coated with a film made of a material of a low work function, for example, a metal. If the electromagnetic wave enters the material of the low work function, electrons are efficiently generated. Hence, when at least one of the electromagnetic wave source15and the cover25is coated with the film made of the material of the low work function, electrons can efficiently be generated. In addition, the inner surface of the inner tube110may be coated with a material whose work function is lower than that of the base material of the inner tube110.

FIGS. 4A, 5A, and 5Bshow the arrangement of an ionization gauge100according to the second embodiment. Here,FIG. 5Ais a plan view of a pole piece105shown inFIG. 4A, which is viewed from the + direction of the z-axis inFIG. 4A. Note that inFIG. 5A, a cathode plate20is not illustrated.FIG. 5Bis a sectional view of the pole piece105taken along a line B-B′ inFIG. 5A. Matters that are not mentioned as the second embodiment can comply with the first embodiment.

As shown inFIGS. 4A, 5A, and 5B, the pole piece (first cathode plate)105can include, between a storage portion22and a through hole11, a passage70configured to pass an electromagnetic wave generated by an electromagnetic wave source15. The passage70can be a through hole that makes the storage portion22and the through hole11communicate. The passage70can be provided to form a linear path between the electromagnetic wave source15and the through hole11. The passage70can extend in a radial direction to connect the storage portion22and the through hole11. When the passage70is formed as a through hole, the electromagnetic wave radiated from the electromagnetic wave source15can be confined in the passage70, and the electromagnetic wave can therefore more efficiently reach the surface of the through hole11. The passage70may include a portion extending between the storage portion22and an inner tube110.

FIGS. 4B, 5C, and 5Dshow the arrangement of a modification of the ionization gauge100according to the second embodiment. Here,FIG. 5Cis a plan view of the pole piece105shown inFIG. 4B, which is viewed from the + direction of the z-axis inFIG. 4B. Note that inFIG. 5C, the cathode plate20is not illustrated.FIG. 5Dis a sectional view of the pole piece105taken along a line B-B′ inFIG. 5C. In the modification, the passage70is formed as a groove or a slit exposed to a space5. This arrangement is excellent because machining is easy. The passage70may include a portion extending between the storage portion22and the inner tube110.

FIGS. 6, 7A, and 7Bshow the arrangement of an ionization gauge100according to the third embodiment. Here,FIG. 7Ais a plan view of a pole piece105shown inFIG. 6, which is viewed from the + direction of the z-axis inFIG. 6.FIG. 7Bis a sectional view of the pole piece105taken along a line C-C′ inFIG. 7A. Matters that are not mentioned as the third embodiment can comply with the first or second embodiment.

As shown inFIGS. 6, 7A, and 7B, the pole piece (first cathode plate)105can include, between a storage portion22and a through hole11, a passage80configured to pass an electromagnetic wave generated by an electromagnetic wave source15. The passage80can be provided to face a space5surrounded by the pole piece105, a sealing member6, and a tubular portion TP. The passage80may be a through hole that makes the storage portion22and the through hole11communicate. The passage80can be provided to form a linear path between the electromagnetic wave source15and the through hole11. The passage80can extend in a radial direction to connect the storage portion22and the through hole11. The electromagnetic wave radiated from the electromagnetic wave source15can move in the passage80while being reflected and reach the surface of the through hole11. A surface of the pole piece105on the side of the space5can include a portion that tilts to provide the electromagnetic wave radiated from the electromagnetic wave source15to an inner tube110and/or a gap21.