JP5665112B2 - Sputter deposition method - Google Patents

Description

The present invention relates to a sputter film forming method, and more particularly to a LaB ₆ film sputter film forming method.

In general, this type of LaB ₆ film has a low work function and a high electron emission efficiency, and is therefore used as an electrode material for the cathode body of various light sources.

Patent Document 1 describes a discharge cathode device for a plasma display using such a LaB ₆ film as a cathode body material. The discharge cathode device described in Patent Document 1 has an aluminum layer formed as a base electrode on a glass substrate and a LaB ₆ layer formed on the aluminum layer. In Patent Document 1, an aluminum layer is formed on a glass substrate kept at a predetermined temperature by a sputtering method, a vacuum deposition method, or an ion plating method, while a LaB ₆ layer is formed on the aluminum layer by a sputtering method or the like. doing.

Thus, Patent Document 1 discloses the formation by sputtering LaB ₆ layer, it is assumed that the formation by sputtering an aluminum layer and LaB ₆ layer on a flat glass substrate. For this reason, the technique of Patent Document 1 cannot be applied to a cold cathode body having a complicated shape, for example, an uneven cylindrical cup shape. Further, Patent Document 1, a material other than glass substrate, without using aluminum, does not disclose the adhesion good form LaB ₆ layers. Furthermore, patent document 1 does not point out improving the electron emission efficiency in the cold cathode body having a cylindrical cup shape.

JP-A-5-250994 WO / 2009/035074

  The present inventors have proposed in Patent Document 2 that a rare-earth element boride film is formed on an electrode member such as tungsten or molybdenum by sputtering using a rotating magnet type magnetron sputtering apparatus.

More specifically, Patent Document 2 uses a rotating magnet type magnetron sputtering apparatus to apply a rare earth element boride (particularly LaB ₄₎ to a cylindrical cup-shaped cathode member mainly composed of tungsten or molybdenum. A method for producing a cathode body for forming a LaB ₆ ) film is disclosed. In this case, the rotating magnet type magnetron sputtering apparatus uses a sintered body mainly composed of LaB ₆ as a target, and is a cathode body manufacturing jig equipped with a cylindrical cup-shaped cathode member facing the target. The tool is placed in the processing chamber, and the magnetic field pattern on the target is moved in the direction of the rotating magnet axis by rotating the rotating magnet group in this state. As a result, the plasma region on the target is continuously moved in the direction of the rotation axis with time, and the target is continuously sputtered by the plasma region to continuously form a LaB ₆ film on the cathode member in the processing chamber. it can. That is, in Patent Document 2, a LaB ₆ film can be formed on a cylindrical cup-shaped cathode member mounted on a cathode body manufacturing jig. The LaB ₆ film is formed by the rotating magnet type magnetron sputtering apparatus by sputtering a target containing LaB _{6 in} a state where argon plasma is generated in the processing chamber.

Further, Patent Document 2 measures the orientation (XRD measurement) and resistivity in order to verify the optimum conditions of the LaB ₆ film by sputtering. That is, as a film forming condition by sputtering of the LaB ₆ film, the surface of the electrode material is cleaned with argon (Ar) plasma of 90 mTorr (12 Pa) and RF 300 W before film formation, and then the pressure in the processing chamber is set to 20 mTorr (2.7 Pa) It is described that sputtering is performed in the vicinity (Ar plasma with an electron temperature of about 1.9 eV, ion irradiation energy of about 10 eV), and the specific resistance is minimized.

The deposited LaB ₆ film results of XRD measurement of, LaB ₆ film by sputtering by rotary magnet type magnetron sputtering apparatus, it is described that the film quality is excellent.

Further, the pressure dependence of the crystal plane (100) peak intensity and the sheet resistance in the LaB ₆ film has been studied. That is, when the normalized ion irradiation amount (Ar + / LaB ₆ ) is changed from about 1 to about 20, the change in the crystal plane (100) peak intensity and the sheet resistance is caused by the ion-irradiation energy by the RF-DC coupled discharge. It has been pointed out that when the normalized ion irradiation dose is increased to about 5 to 17 while being suppressed to about 10 eV or less, the resistance is lowered (specific resistance is 300 to 400 μΩcm) and the crystallinity is also improved.

However, according to the study by the present inventors, if the cathode member of cylindrical cup shape is formed by the tungsten, it is necessary to improve further the crystallinity of the LaB ₆ film, causing peeling of the LaB ₆ film There was found.

An object of the present invention is to provide a method for forming a LaB ₆ film that can further improve crystallinity and also has less peeling.

According to the knowledge of the present inventors, it has been found that when sputtering is performed in an atmosphere containing only argon (Ar), the LaB ₆ film is easily peeled off and the crystallinity of the LaB ₆ film is also deteriorated.

Based on the above findings, the present inventors have found that the crystallinity of the LaB ₆ film can be improved by adding nitrogen gas (N ₂ ) to the atmosphere.

That is, according to the first aspect of the present invention, a LaB ₆ target is prepared, and the LaB ₆ target is sputtered in an atmosphere to which nitrogen gas is added to form a LaB ₆ film on a substrate. A sputter film forming method is obtained.

  According to a second aspect of the present invention, there is provided a sputtering film forming method according to the first aspect, wherein the substrate is formed of a material containing tungsten or molybdenum and an oxide of a rare earth element. .

According to a third aspect of the present invention, in the second aspect, the rare earth element oxide is at least one oxide selected from the group consisting of La ₂ O ₃ , ThO ₂ , and Y ₂ O _3. Thus, a sputter film forming method characterized by being a product can be obtained.

According to the present invention, there can be obtained a production method capable of forming a LaB ₆ film containing nitrogen and having excellent crystallinity and little peeling with respect to a cylindrical cup-shaped substrate.

It is sectional drawing explaining the rotating magnet type magnetron sputtering device used for this invention. It is a cross-sectional view illustrating a cathode body having the formed LaB ₆ film using a magnetron sputtering apparatus shown in FIG. (A)-(D) are the schematic for demonstrating in order the process which concerns on one Example of this invention. Is a graph illustrating the analysis result of the obtained LaB ₆ film by sputtering method according to an embodiment of the present invention.

FIG. 1 is a diagram showing an example of a rotating magnet type magnetron sputtering apparatus used for LaB ₆ film sputtering film formation according to the present invention, and FIG. 2 shows a cathode body using the sputtering film formation method according to the present invention. It is a figure for demonstrating the case where it manufactures.

  The rotating magnet type magnetron sputtering apparatus shown in FIG. 1 includes a target 1, a polygonal shape (for example, a regular hexagonal shape) columnar rotating shaft 2, and a plurality of spirals attached spirally to the surface of the columnar rotating shaft 2. In contrast to the target 1 with respect to the fixed outer peripheral plate magnet 4 and the fixed outer peripheral plate magnet 4 arranged on the outer periphery of the rotating magnet group 3 so as to surround the rotating magnet group 3 and the rotating magnet group 3. An outer peripheral paramagnetic member 5 is provided on the side. Further, a backing plate 6 is bonded to the target 1, and portions other than the columnar rotating shaft 2 and the spiral plate magnet group 3 other than the target 1 side are covered with a paramagnetic material 15. Covered by.

  When viewed from the target 1, the fixed outer peripheral plate magnet 4 has a structure surrounding the rotating magnet group 3 constituted by a spiral plate magnet group, and is magnetized so that the side of the target 2 becomes an S pole. . The fixed outer peripheral plate magnet 4 and each plate magnet of the spiral plate magnet group are formed of Nd—Fe—B based sintered magnets.

  Further, a plasma shielding member 16 is provided in the space 11 in the illustrated processing chamber. Further, in the illustrated example, a cathode body manufacturing jig 19 is installed as a substrate to be processed so as to face the target 2. A plurality of cylindrical cup-shaped cathode members 30 are attached to the cathode body manufacturing jig 19.

  The plasma shielding member 16 extends in the axial direction of the columnar rotating shaft 2 and defines a slit 18 that opens the target 1 with respect to the cathode manufacturing jig 19. In a region that is not shielded by the plasma shielding member 16 (that is, a region that is opened with respect to the target 1 by the slit 18), a high-density, low-electron temperature plasma is generated with a strong magnetic field strength, and a cathode manufacturing jig 19 This is a region where no charge-up damage or ion irradiation damage is applied to the cathode member 30 provided at the same time, and at the same time a region where the film formation rate is fast. By shielding the region other than this region with the plasma shielding member 16, it is possible to perform film formation without damage without substantially reducing the film formation rate.

  The backing plate 6 is formed with a refrigerant passage 8 through which a refrigerant passes, and an insulating material 9 is provided between the housing 7 and the outer wall 14 forming the processing chamber. The feeder line 12 connected to the housing 7 is drawn to the outside through the cover 13. A DC power source, an RF power source, and a matching unit (not shown) are connected to the feeder line 12.

  In this configuration, plasma excitation power is supplied from the DC power source and the RF power source to the backing plate 6 and the target 1 through the matching unit, the feeder line 12 and the housing, and the plasma is excited on the surface of the target 1. Plasma excitation is possible only with DC power or RF power alone, but it is desirable to apply both from the viewpoint of film quality controllability and film formation rate controllability. The frequency of the RF power is usually selected from several hundred kHz to several hundred MHz. However, a high frequency is desirable from the viewpoint of high density and low electron temperature of the plasma. In this embodiment, a frequency of 13.56 MHz is used. ing.

  As shown in FIG. 1, a plurality of cylindrical cups 30 forming a cathode member are attached to a cathode body manufacturing jig 19 installed in a space 11 in a processing chamber as a base.

Referring also to FIG. 2, the cathode body manufacturing jig 19 has a plurality of support portions 32 that support the cylindrical cup 30. Here, the cylindrical cup 30 is formed of tungsten containing 4% to 6% lanthanum oxide (La ₂ O ₃ ) by volume ratio. As shown in FIG. 2, the cylindrical cup 30 includes a cylindrical electrode portion 301 and a lead portion 302 that is pulled out from the center of the bottom of the cylindrical electrode portion 301 in a direction opposite to the cylindrical electrode portion 301. In this example, it is assumed that the cylindrical electrode portion 301 and the lead portion 302 are integrally formed by, for example, MIM (Metal Injection Molding) or the like.

  The support part 32 of the cathode body manufacturing jig 19 includes a receiving part 321 that defines an opening having a size for receiving the cylindrical electrode part 301 of the cylindrical cup 30, and a flange part that defines a hole having a smaller diameter than the receiving part 321. 322 and an inclined portion 323 that connects the receiving portion 321 and the flange portion 322. As illustrated, the cylindrical electrode portion 301 is inserted into the support portion 32 of the cathode body manufacturing jig 19. That is, the lead portion 302 of the cylindrical electrode portion 301 passes through the flange portion 322 of the cathode body manufacturing jig 19, and the outer end portion of the cylindrical electrode portion 301 contacts the inclined portion 323 of the cathode body manufacturing jig 19. Yes.

  Here, the illustrated cylindrical cup 30 has a cylindrical electrode portion 301 having an inner diameter of 1.4 mm, an outer diameter of 1.7 mm, and a length of 4.2 mm. On the other hand, the length of the lead portion 302 of the cylindrical cup 30 may be shortened to about 1.0 mm, for example.

In this example, the cylindrical cup 30 is formed by mixing La ₂ O ₃ having a work function as small as 2.8 to 4.2 eV with tungsten, which is a refractory metal having good thermal conductivity. By using tungsten, heat generated in the cylindrical cup 30 can be efficiently discharged, and by mixing lanthanum oxide having a small work function, electrons can also be emitted from the cylindrical cup 30 itself. . Note that molybdenum (Mo) may be used in place of tungsten as a metal having high thermal conductivity for forming the cylindrical cup 30.

Here, the manufacturing method of the cylindrical cup 30 is demonstrated concretely. First, a tungsten alloy powder containing 3% La ₂ O ₃ by volume and a resin powder were mixed. Styrene was used as the resin powder, and the mixing ratio of the tungsten alloy powder and styrene was 0.5: 1 by volume. Next, a small amount of Ni was added as a sintering aid to obtain pellets. A cup-shaped molded product is produced by performing injection molding (MIM) on a cylindrical cup-shaped mold at a temperature of 150 ° C. using the pellets thus obtained. The produced molded product was degreased by heating in a hydrogen atmosphere to obtain a cylindrical cup 30.

The cylindrical cup 30 thus obtained is attached to the cathode manufacturing jig 19 shown in FIGS. 1 and 2, and is carried into the processing chamber 11 of the magnetron sputtering apparatus in which a LaB ₆ sintered body is set as the target 1. did.

A LaB ₆ sintered body was used as the target 1. As the LaB ₆ sintered body, one containing a slight amount of nitrogen may be used.

After moving the above-described target 1 and the cathode manufacturing jig 19 on which the cylindrical cup 30 is mounted, nitrogen gas (N ₂ ) is introduced into the processing chamber 11 in addition to argon (Ar). Then, the pressure was set to about 20 mTorr (2.7 Pa) and the temperature of the cathode manufacturing jig 19 was heated to 300 ° C. to perform sputtering.

  A cylindrical cup 30 obtained as a result of sputtering is shown in FIG.

In FIG. 2, a thick LaB ₆ film 341 is formed in a region having an aspect ratio of 1 which is a ratio between the depth and the inner diameter of the cylindrical electrode portion 302, and is a lower portion of the cathode manufacturing jig 19. A thin LaB ₆ film 342 is formed. Furthermore, a very thin LaB ₆ film (bottom LaB ₆ film) 343 is formed on the inner bottom surface of the cylindrical electrode portion 302.

In the illustrated example, the thick LaB ₆ film 341, the thin LaB ₆ film 342, and the bottom LaB ₆ film 343 were 300 nm, 60 nm, and 10 nm, respectively.

The LaB ₆ film formed on the cylindrical cup 30 containing tungsten as a main component in a nitrogen-containing atmosphere is superior in crystallinity compared to the LaB ₆ film formed in an atmosphere not containing nitrogen gas. confirmed.

  The process according to one embodiment of the present invention will now be described with reference to FIG. Here, the process when the rotating magnet type magnetron sputtering apparatus shown in FIG. 1 is used will be described.

  First, a substrate (here, a cylindrical cup 30 attached to a cathode manufacturing jig 19) is introduced into the processing chamber 11 of the rotating magnet type magnetron sputtering apparatus schematically shown in FIG. 3 (FIG. 3). (A)) The surface of the cylindrical cup 30 is cleaned before film formation. In this case, as shown in FIG. 3B, the substrate is moved to a position facing the target, for example, 90 mTorr (12 Pa) with Ar plasma and plasma cleaning with RF 300 W are performed, and the inside of the processing chamber 11 is switched to an Ar atmosphere. Then, the cleaning is finished (FIG. 3C).

Next, as shown in FIG. 3D, a LaB ₆ target is used with argon (Ar) added with nitrogen gas (N 2) introduced into the processing chamber 11 of the rotating magnet type magnetron sputtering apparatus. Sputtering is performed to form a LaB ₆ film. As a result, a LaB6 film containing nitrogen was formed on the surface of the substrate (here, a cathode manufacturing jig with a cylindrical cup attached) 19. Note that the pressure in the processing chamber 11 at this time is about 50 mTorr, and the crystallinity of the LaB ₆ film was improved as the pressure was increased. Further, during sputtering, 99.95% by volume of argon gas and 0.05% by volume of nitrogen gas were supplied, and the total flow rate was 2000 sccm. The flow rate of nitrogen gas may be 1% by volume, and is preferably in the range of 0.01-5% by volume. 0.05-1 volume% is especially preferable. The RF power for sputtering was 800 W, and DC 300 V was applied to the target.

It is preferable to anneal after forming the LaB ₆ film by sputtering. The annealing temperature is preferably 400 ° C to 1000 ° C. The annealing time may be 30 minutes or more and 3 hours or less. The atmosphere of annealing is preferably an inert gas.

Referring to FIG. 4, the result of analyzing the LaB ₆ film formed in the nitrogen gas-containing atmosphere by XRD is shown. As is clear from FIG. 4, the LaB ₆ film formed in the nitrogen gas-containing atmosphere is extremely good in terms of crystallinity in the (100) crystal plane compared to the LaB ₆ film formed in the atmosphere not containing nitrogen gas. I understand.

Further, also in adhesion to tungsten, LaB ₆ film formed by a nitrogen gas-containing atmosphere has been found to be superior LaB ₆ film formed in an atmosphere containing no nitrogen gas.

In the embodiment described above, the case where a LaB ₆ film is formed on a tungsten material containing 4 to 6% by volume of La ₂ O ₃ as a base formed by a cylindrical cup has been described. Without being limited to this, various modifications are possible.

  For example, even when tungsten, molybdenum, silicon, resin, glass, or silicon oxide is used as the substrate, a rare earth element boride can be formed in the same manner. The shape of the substrate is not limited to the cup shape, and a flat shape or any other shape can be used.

The tungsten or molybdenum used as the substrate may contain lanthanum oxide, or at least one selected from the group consisting of La ₂ O ₃ , ThO ₂ , and Y ₂ O _3. It may be.

Furthermore, as the boride of a rare earth element to be formed, addition of _{LaB 6, LaB 4, YbB 6} , GaB 6, and may be at least one boride selected from the group consisting of CeB _6.

  Further, the atmosphere in which the nitrogen gas is added may be another rare gas such as Kr or Xe, or a mixed gas thereof, instead of the Ar gas.

  Examples of the present invention are listed below.

In one embodiment of the present invention, a LaB ₆ target is prepared, and the LaB ₆ target is sputtered in an atmosphere to which nitrogen gas is added to form a LaB ₆ film on a substrate. Is obtained.

In another embodiment of the present invention, the LaB ₆ film formed on the substrate in the nitrogen gas addition atmosphere is compared with the LaB ₆ film formed in an atmosphere without addition of the nitrogen gas, A sputter deposition method characterized by high crystallinity is obtained.

In another embodiment of the present invention, there is obtained a sputtering film forming method characterized in that the LaB ₆ film is formed after the substrate is plasma-cleaned.

  In another embodiment of the present invention, there is obtained a sputtering film forming method characterized in that the atmosphere is made of a rare gas to which nitrogen gas is added.

  In another embodiment of the present invention, there is obtained a sputter deposition method characterized in that the amount of nitrogen gas added is 0.01 to 5% by volume, preferably 0.05 to 1% by volume.

  In another embodiment of the present invention, there is obtained a sputter deposition method characterized in that the substrate is formed of any one of tungsten, molybdenum, silicon, resin, glass, and silicon oxide.

  In still another embodiment of the present invention, there is obtained a sputter deposition method characterized in that the tungsten or molybdenum contains an oxide of a rare earth element.

In another embodiment of the present invention, the oxide of the rare earth element is at least one oxide selected from the group consisting of La ₂ O ₃ , ThO ₂ , and Y ₂ O _3. A sputter deposition method is obtained.

  Still another embodiment of the present invention is characterized by having a cylindrical cup-shaped cathode member and a rare earth element boride film containing nitrogen formed in the cylindrical cup portion of the cathode member. A cathode body is obtained.

In another embodiment of the present invention, the rare earth element boride film is at least one boride selected from the group consisting of LaB ₄ , LaB ₆ , YbB ₆ , GaB ₆ , and CeB _6. A characteristic cathode body is obtained.

  In still another embodiment of the present invention, a fluorescent tube including the above-described cathode body is obtained.

  The present invention can be used as a cold cathode body of a cold cathode fluorescent tube used as a backlight light source of a liquid crystal display device.

DESCRIPTION OF SYMBOLS 1 Target 2 Columnar rotating shaft 3 Rotating magnet group 4 Fixed outer periphery magnet 5 Outer periphery paramagnetic body 6 Backing plate 7 Housing 8 Refrigerant passage 9 Insulating material 11 Space in processing chamber 12 Feeder wire 13 Cover 14 Outer wall 15 Paramagnetic body 16 Plasma shielding member 18 Slit 19 Cathode body manufacturing jig 30 Cylindrical cup 301 Cylindrical electrode part 302 Lead part 321 Receiving part 322 Gutter part 323 Inclined part 341 Thick LaB ₆ film 342 Thin LaB ₆ film 343 Bottom LaB ₆ film

Claims (5)

Compared with the case where a LaB ₆ target is prepared, the LaB ₆ target is sputtered in a rare gas atmosphere to which nitrogen gas is added in an amount of 0.01 to 5% by volume, and is sputtered in a rare gas atmosphere to which no nitrogen gas is added. A sputter film forming method characterized by forming a LaB ₆ film excellent in the above on a substrate.   2. The sputter deposition method according to claim 1, wherein the substrate is formed of a material containing tungsten or molybdenum and an oxide of a rare earth element. _{3. The} sputter deposition method according to claim 2, wherein the rare earth element oxide is at least one oxide selected from the group consisting of La ₂ O ₃ , ThO ₂ , and Y ₂ O _3. . 4. The sputter deposition method according to claim 1, wherein the rare gas atmosphere is made of Ar gas, Kr gas, Xe gas, or a mixed gas thereof to which nitrogen gas is added. In one of claims 1-3, sputtering method, characterized in that the rare gas added to the nitrogen gas is argon.

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