JP4184846B2 - Ion generator for ion implanter - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ion generator in an implantation apparatus that efficiently implants ions of a target substance into an object to be processed such as a semiconductor or a liquid crystal device in a manufacturing process of a semiconductor or a liquid crystal device.
[0002]
[Prior art]
A flat panel display such as a liquid crystal display is often used for a mobile phone, a portable information terminal, a notebook PC, a monitor for a PC, or a large television. In the future, high precision, low power consumption, and low prices are strongly demanded in the liquid crystal display market, where significant demand growth is expected.
[0003]
As a high-current wide-beam ion implantation apparatus used to manufacture a small flat panel display used for such applications, an ion generation source that generates a large amount of ions and an ion beam extracted from the ion generation source are used. A mass separation magnet for expanding, deflecting, and converging, a resolving slit that blocks unwanted beams out of the converged beam, and a second that further deflects and parallelizes the beam that has passed through this resolving slit An apparatus for forming a highly uniform wide ribbon beam with a current of 1 mA or more and energy of several keV or more has been proposed (for example, see Patent Document 1).
[0004]
In addition, a gas containing a target substance in the arc chamber is ionized by plasma to generate ions, and deposition is performed in an ion source that moves the ions in the arc chamber to deposit the target substance. There has been proposed an apparatus for generating an ion beam containing a large amount of a target substance by disposing a member in an arc chamber and causing ions to collide with the member to precipitate the substance (see, for example, Patent Document 2).
[0005]
Further, the present applicant manufactures and sells an ion beam implantation apparatus applying the basic principle of the patent described in Patent Document 1 as “MD1-100”.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 6-342639 [Patent Document 2]
JP-A-8-17375 [0007]
[Problems to be solved by the invention]
A low-temperature polysilicon thin-film transistor liquid crystal display that has higher electron mobility than amorphous silicon and can be integrated with peripheral circuits to achieve the demands for high precision, high brightness, low power consumption, and low price. Attracted attention. In a conventional process (source / drain) for manufacturing a TFT on a low-temperature p-Si thin film, a method called ion shower is mainly used. However, in order to manufacture a higher performance thin film transistor (TFT) on a low-temperature p-Si thin film, as described in Patent Document 1, only ions are desired by mass separation as in the semiconductor process. Therefore, a high-precision ion implantation technique that can accurately control the dose is required.
[0008]
In order to increase the amount of ions, it is only necessary to increase the amount of plasma by increasing the implant current. To this end, the beam line is kept at a high vacuum and the target material supplied into the arc chamber is contained. It is necessary to increase the amount of gas (BF ₃ , PH ₃ ) such as boron fluoride.
[0009]
As shown in FIG. 2, the ion implantation apparatus 1 has an ion generation source 2 (a Bernas type ion generation apparatus) that generates ions by supplying a large amount of a gas containing impurities. x is extracted from the ion generation source 2 by the extraction electrode 3 and accelerated.
[0010]
The ion beam X extracted from the ion generation source 2 is bent by approximately 90 ° by the mass separation magnet of the mass separation unit 6, and only ions a having a predetermined mass are taken out. At this time, the selected ions c and d such as light ions and heavy ions are excluded.
[0011]
Thereafter, the intensity of the ion beam X is uniformly averaged by a uniform control mechanism 7 (multipole), and then a glass substrate (covered member) attached to a platen (support member) disposed in a process chamber (end station) 8 is used. It is injected into the processing body 9.
[0012]
In addition, the vacuum chamber 5 that communicates the ion source 2, the mass separator 6, and the path from the uniform control mechanism 7 to the process chamber 8 has a high displacement (not shown), particularly at a position subsequent to the uniform control mechanism 7. A pump is connected, and the entire vacuum chamber 5 system constitutes a high vacuum exhaust system 10.
[0013]
In order to increase the amount of ions by increasing the plasma amount, it is necessary to generate ions more efficiently than the ion generation source 2 (ion generator) as described above. As shown in FIG. 3, the ion generator includes an elongated box-shaped arc chamber 23 formed of a base plate 20, two side plates 21, and two end caps 22 and 22a. An insulator 24 (insulator) is interposed in the end cap 22 and the filament 25 and the cathode plate 26 are provided. On the other end cap 22a side, an insulator 24a is provided and a repeller plate 28 is provided. A source aperture 23 a (FIG. 2, a lid) having an elongated opening hole on the opening surface is provided.
[0014]
A magnet 29 is arranged on the two end caps 22 and 22a side, and a static magnetic field 30 directed from the cathode plate 26 side to the repeller plate 28 side is applied to the arc chamber 23.
[0015]
And when operating the said ion generator 1, while supplying the gas g of the substance which generate | occur | produces the substance for ion implantation from the gas supply source 31, holding the inside of the arc chamber 23 in a high vacuum with a vacuum pump, The filament 25 is energized from the filament power source 32 to generate heat to a high temperature (about 2000 ° C. or more), and an arc voltage V is applied between the filament 25 and the arc chamber 23 from the arc power source 33 to In the meantime, plasma P is generated by arc discharge, and the ion beam X is radiated to the beam line of the ion implantation apparatus 1 from the opening hole of the source aperture 23a.
[0016]
In the arc chamber 23, the thermoelectrons generated from the filament 25 and the ions in the plasma are affected by the static magnetic field 30 and spirally move (cyclotron motion), and the ions and electrons collide with the molecules of the source gas g. To maintain the plasma P easily (FIG. 4).
[0017]
For example, when the static magnetic field 30 is not applied in the ion generation source 2, ions and electrons move along a linear trajectory, and the opportunity for the ions and electrons to collide with the molecules of the source gas g is reduced. Therefore, by applying a static magnetic field 30, the ion and electrons are spirally moved to increase the chance of colliding with the molecules of the raw material gas g, and the plasma P is pushed out in a sausage shape toward the center of the arc chamber 23.
[0018]
(Problems with conventional devices)
The state when the ion generator is operated while supplying the gas g containing fluorine such as boron trifluoride to the ion source 2 of the ion implantation apparatus 1 will be described. The plasma P generated in 2 gradually decreased and an unstable state was generated in which a large amount of necessary ions x could not be generated.
[0019]
When this phenomenon was examined, when a gas containing fluorine such as boron trifluoride is supplied to the molybdenum arc chamber 23, the inner surface of the arc chamber 23 is corroded by the fluorine ionized and reactively activated. It was found that this caused the insulation failure.
[0020]
FIG. 5 is an explanatory diagram of the state of insulation failure. Metal atoms generated from the material of the arc chamber 23 are mixed and moved in the ionized gas. A cathode plate 26 is supported on the end cap 22 of the arc chamber 23 via two insulators 24 (insulators), and a filament 25 (a 1.5-turn pigtail shape) passes through the insulator 24. The metal atoms generated from the material of the arc chamber 23 as described above are deposited on the surface of the insulator 24 to form thin conductive films M1 and M2.
[0021]
The conductive films M1 and M2 are, for example, films formed by depositing metal atoms such as molybdenum and tungsten which are materials of the arc chamber. When this occurs, the cathode plate 26 and the filament 25 are passed through the surface of the insulator 24. And an arc chamber 22, an electric circuit is formed, and a leakage current R flows through this electric circuit.
[0022]
Thus, since the insulator 24 is electrically deteriorated by the conductive films M1 and M2, it becomes difficult to maintain the arc voltage V, and the sausage is stable over the entire length of the arc chamber 23 as shown in FIG. The generation of the plasma P becomes difficult.
[0023]
The behavior in which metal atoms are generated from the material of the arc chamber 23 will be described as follows.
[0024]
For example, when molybdenum is used as the material of the arc chamber 23 and the supply gas is trifluoride gas, a fluoride gas of “nF ⁺ + Mo → MoFn” is generated, and “MoFn → nF is generated by high heat and plasma. ^{+ +} Mo "reaction occurs of. The generated molybdenum atoms are deposited as conductive films M1 and M2 on the insulator 24 as shown in FIG.
[0025]
As the metal material constituting the arc chamber 23, heat-resistant molybdenum, tungsten, or the like is used. Since the inside of the arc chamber 23 becomes high temperature, this material can be easily changed to another material. I can't.
[0026]
An object of the present invention is to eliminate the disadvantage that the insulators 24, 24a supporting the cathode plate 26, the repeller plate 28, etc. in the prior art cause poor insulation due to poor insulation.
[0027]
[Means for Solving the Problems]
In order to achieve the above object, an ion generator for an ion implantation apparatus according to the present invention is configured as follows.
[0028]
1) In an ion generator in which an electrode portion is disposed facing the inner surface of an end cap that forms both ends of an arc chamber, the electrode portion is supported inside the arc chamber via an insulator and oxidized to the electrode portion. A conductive film suppressing member made of aluminum, aluminum nitride, or boron nitride is applied to improve insulation between the electrode portion and the arc chamber.
[0029]
2) In an ion generator in which electrode portions are arranged facing the inner surface of an end cap that forms both ends of an arc chamber, the one electrode portion includes at least a filament, and the other electrode portion is a repeller plate, The conductive film restraining member is provided on the side facing the end cap that is closest to and adjacent to the surface to improve the insulation between the electrode portion and the arc chamber.
[0030]
3) In an ion generator in which electrode portions are arranged facing the inner surfaces of end caps that form both ends of an arc chamber, the one electrode portion includes at least a filament, and the other electrode portion is a repeller plate, one or both An inner surface of the end cap is formed of a conductive film suppressing member.
[0031]
4) In the ion generator in which the electrode portions are arranged facing the inner surfaces of the end caps that form both ends of the arc chamber, the one electrode portion is a filament and a cathode plate, and the other electrode portion is formed by a repeller plate. In addition, a conductive film suppression member is provided on one side of the cathode plate and the repeller plate that faces the end cap that is closest to and adjacent to the cathode plate and the repeller plate to improve insulation between the electrode portion and the arc chamber. It is characterized by.
[0033]
6) The ion implantation apparatus generates an ion to be transmitted to the beam line and selects an ion transmitted from the ion generation source by a mass separation magnet to generate ions having a predetermined mass. It is characterized by having a beam line leading to.
[0034]
In the present invention, a layer made of a conductive film suppressing material is formed on the electrode portion, specifically on both the cathode plate and the repeller plate made of a metal plate, or on the surface facing the end cap of the member on which the conductive film is easily deposited. As a result, the conductive film is prevented from growing from the cathode plate and the repeller plate as a starting point. As a result, the arc chamber 23 and the cathode plate 26 or the arc chamber 23 and the repeller plate 28 shown in FIG. This prevents or suppresses leakage R due to the formation of a conduction circuit.
[0035]
In some cases, the same effect can be obtained even when the inner surface of the end cap is formed of a layer made of the conductive film inhibiting material.
[0036]
As a conductive film inhibiting material, a compound of an element that does not produce a conductive film in an atmosphere of 1000 to 2500 ° C. after being thermally decomposed with a heat resistant material such as aluminum oxide, aluminum nitride, boron nitride, etc. it can. For example, aluminum oxide may precipitate at a high temperature, but since the boiling point is low, a metal film is not deposited on the surface of the insulator.
[0037]
The present invention relates to an electrode portion such as a cathode plate or a repeller plate, which is disposed on the surface of an insulator that supports the electrode portion during operation of the ion generator, for example, at the base portion of a filament that is one of the electrodes. It is intended to prevent the metal atoms forming the arc chamber from precipitating and accumulating on the surface of the insulator by extending the back side of the material with a conductive film suppressing material. is there.
[0038]
In that sense, the conductive film inhibiting material is preferably a compound composed of an element such as aluminum oxide or aluminum nitride that does not form a conductive thin film in an atmosphere of 1000 to 2500 ° C. after decomposition. A highly efficient ion generation source can be configured by selecting a material that does not have a conductive effect even if it is deposited on the surface of the insulator forming the electrode portion.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to FIG.
[0040]
The configuration of the arc chamber 23 itself is the same as that of the apparatus shown in FIG. 3 and the like, but in the present invention, the surface layer F made of a material conventionally used for the cathode plate 26a and the conductive film suppression on the back side thereof. It is characterized in that a two-layer structure or a composite plate structure composed of a back layer B made of a material (heat-resistant insulating material) is formed.
[0041]
This composite plate structure is formed not only on the cathode plate 26a but also on the opposite repeller plate 28a side, and has the same effect.
[0042]
The thickness of the back surface layer B does not have to be as thick as that of the surface layer F, that is, the conventional cathode plate, and the conductive films M1 and M2 are formed on the insulator 24 as shown in FIG. For example, when boron nitride is used for the back surface layer B, it may be about 0.2 to 2 mm, and the processing method for the back surface layer B is after coating or laminating. Various methods such as laminating and pasting without gaps such as baking can be adopted.
[0043]
Further, the cathode plate 26a and the repeller plate 28a are not of a structure in which two plate materials are combined as shown in FIG. 1, but the metal plate is inserted into a dish-shaped case made of an insulating material. It may have a structure in which an insulating material is disposed on the collar portion.
[0044]
In the present invention, an electrode composed of a cathode plate 26a and a repeller plate 28a supported via an insulator in the arc chamber 23 is formed in a two-layer structure composed of a metal layer and an insulating layer, and the cathode plate 26a and the like are supported. Since the surface on the side in contact with the insulator is formed of an insulating conductive film suppressing material, metal atoms generated from the material of the arc chamber 23 are deposited on the insulators 24 and 24a when forming a plasma. Thus, a conductive film is not formed.
[0045]
Accordingly, the arc can be generated in the arc chamber 23 with high accuracy under high temperature and high vacuum, so that ions can be generated stably. As a result, high performance ion implantation can be achieved. An apparatus can be provided.
[0046]
【The invention's effect】
An ion generator for an ion implantation apparatus according to the present invention is an ion generator in which an electrode portion is disposed on an inner surface of an end cap that forms both ends of an arc chamber, and the electrode portion is connected to an arc chamber through an insulator. In addition to being supported inside, a conductive film suppressing member is applied to the electrode portion to improve insulation between the electrode portion and the arc chamber.
[0047]
Accordingly, since it is possible to suppress the formation of a conductive film that forms a short circuit between one or both of the cathode plate and the repeller plate and the arc chamber, a high-performance ion implantation apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a Bernas type ion generation source according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of an ion implantation apparatus.
FIG. 3 is a cross-sectional view of a conventional ion generation source.
FIG. 4 is an explanatory diagram of plasma generated inside an ion generation source.
FIG. 5 is an explanatory diagram of a state of forming a conductive film generated by a conventional ion generation source.
[Brief description of symbols]
DESCRIPTION OF SYMBOLS 1 Ion implantation apparatus 2, 2a Ion generation source 3 Extraction electrode 4 Gas interruption | blocking plate 5 Vacuum bar 6 Mass separation part 7 Uniform control mechanism 8 Process chamber 9 Glass substrate 20 Base plate 21 Side plate 24 Insulation 22, 22a End cap 23 Arc chamber 25 Filament 26, 26a Cathode plate 28, 28a Repeller plate 29 Magnet 30 Static magnetic field 31 Gas supply source F Surface layer (metal layer) B Back surface layer (layer of conductive film inhibiting material)
R Leakage current

Claims (5)

In an ion generating apparatus in which an electrode part is disposed facing an inner surface of an end cap that forms both ends of an arc chamber, the electrode part is supported inside the arc chamber via an insulator, and aluminum oxide or An ion generator for an ion implantation apparatus, wherein a conductive film suppressing member made of aluminum nitride or boron nitride is applied to improve insulation between the electrode portion and the arc chamber.   In the ion generator in which the electrode portions are arranged facing the inner surfaces of the end caps that form both ends of the arc chamber, the one electrode portion includes at least a filament, and the other electrode portion is a repeller plate. 2. The ion implantation apparatus according to claim 1, wherein the conductive film suppressing member is provided on a side facing the nearest adjacent end cap to improve insulation between the electrode portion and the arc chamber. Ion generator.   In the ion generator in which the electrode portions are arranged facing the inner surfaces of the end caps that form both ends of the arc chamber, the one electrode portion includes at least a filament, the other electrode portion is a repeller plate, and one or both of the above 2. The ion generator for an ion implantation apparatus according to claim 1, wherein an inner surface of the end cap is formed of the conductive film suppressing member. In the ion generator in which the electrode portions are arranged facing the inner surfaces of the end caps that form both ends of the arc chamber, the one electrode portion is a filament and a cathode plate, and the other electrode portion is formed by a repeller plate. , said a one surface of the cathode plate and Riperapureto, said providing a conductive film restraining member on the side facing the nearest adjacent end caps to each enhanced insulation between the electrode portion and the arc chamber The ion generator for an ion implantation apparatus according to claim 1, wherein:   The ion generation device generates ions and sends them to a beam line, and selects ions sent from the ion generation source by a mass separation magnet to guide ions of a predetermined mass to an ion processing station. The ion generator for an ion implantation apparatus according to claim 1, further comprising a beam line.

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