JP4961513B1 - Split sputtering target and manufacturing method thereof - Google Patents

Abstract

Provided is a technique capable of effectively preventing a constituent material of a backing plate from being mixed into a thin film to be formed by sputtering in a divided sputtering target obtained by joining a plurality of target members. To do.
The present invention relates to a split sputtering target formed by bonding a plurality of target members on a backing plate with a low melting point solder, in a gap formed between the bonded target members. It is characterized by being filled with material. The ceramic material is preferably ceramic powder or ceramic fiber having the same composition as the target member, and the organic material is preferably a high resistance substance.
[Selection] Figure 3

Description

  The present invention relates to a split sputtering target obtained by joining a plurality of target members, and more particularly to a split sputtering target suitable when the target member is made of an oxide semiconductor.

  2. Description of the Related Art In recent years, a sputtering method has been widely used in manufacturing electronic parts such as information equipment, AV equipment, and home appliances. For example, a display device such as a liquid crystal display device has a semiconductor such as a thin film transistor (abbreviation: TFT). The element is formed by a sputtering method. This is because the sputtering method is extremely effective as a method for forming a thin film constituting a transparent electrode layer or the like with a large area and high accuracy.

  By the way, in recent semiconductor elements, an oxide semiconductor typified by IGZO (In—Ga—Zn—O) is attracting attention instead of amorphous silicon. And also about this oxide semiconductor, forming an oxide semiconductor thin film using a sputtering method is planned. However, in a sputtering target of an oxide semiconductor used for sputtering, since the material is ceramic, it is difficult to configure a large-area target with a single target member. Therefore, a large-area oxide semiconductor sputtering target is manufactured by preparing a plurality of oxide semiconductor target members having a certain size and bonding them onto a backing plate having a desired area (for example, Patent Documents). 1).

  As the backing plate of the sputtering target, a Cu backing plate is usually used, and a low-melting-point solder having good thermal conductivity, for example, an In-based metal is used for joining the backing plate and the target member. Yes. For example, when manufacturing a plate-shaped semiconductor oxide sputtering target with a large area, a large-area Cu backing plate is prepared, the backing plate surface is divided into a plurality of sections, and an oxide having an area suitable for the section A plurality of semiconductor target members are prepared. Then, a plurality of target members are arranged on the backing plate, and all target members are joined to the backing plate by using an In-based or Sn-based metal low melting point solder. In this bonding, in consideration of the difference in thermal expansion between Cu and the oxide semiconductor, adjustment is made so that a gap of 0.1 mm to 1.0 mm is formed between adjacent target members at room temperature. Has been.

  When forming a semiconductor element by forming a thin film by sputtering using a split sputtering target obtained by joining a plurality of such oxide semiconductor target members, a backing is formed from the gap between the target members during the sputtering process. There is a concern that Cu, which is a constituent material of the plate, is also sputtered and mixed into the oxide semiconductor thin film to be formed. Cu in the thin film has a mixing amount of several ppm level, but its influence is extremely large for the oxide semiconductor. For example, the field effect mobility in the TFT element characteristics corresponds to the gap between the target members. In the semiconductor element (thin film mixed with Cu) formed by the above, there is a tendency to be lower than the other semiconductor elements, and the ON / OFF ratio tends to be lowered. Such inconvenience has been pointed out as a major obstacle to the recent trend of increasing the area, and there is a demand for immediate technical improvement. Furthermore, the problem of such a split sputtering target may cause a similar problem even if the target member is made of a material other than an oxide semiconductor. In order to promote an increase in the area of the sputtering target, It is a problem to be solved.

JP 2005-232580 A

  The present invention has been made in the background as described above, and is a sputtering target having a large area, and a backing plate obtained by sputtering a split sputtering target obtained by joining a plurality of target members. An object of the present invention is to propose a split sputtering target capable of effectively preventing the constituent materials of the above from being mixed into a thin film to be formed.

  In order to solve the above-described problems, the present invention provides a split sputtering target formed by bonding a plurality of target members on a backing plate with a low melting point solder, and a ceramic formed in a gap formed between the bonded target members. The material or organic material was filled. In the present invention, the ceramic material or organic material filled in the gap is fixed to the bottom of the gap.

  In the present invention, the split sputtering target is a plate-like or cylindrical one. The plate-like sputtering target is a target in which a plurality of plate-like target members having a square surface are arranged on a plate-like backing plate and bonded together. In addition, the cylindrical sputtering target is a cylindrical backing plate having a plurality of cylindrical target members (hollow cylinders) penetrated and arranged in a multi-stage shape in the column axis direction of the cylindrical backing plate, or A target is obtained by joining a plurality of curved target members obtained by vertically dividing a hollow cylinder in the cylinder axis direction to the outer surface of the cylindrical backing plate in the circumferential direction. This plate-shaped or cylindrical divided sputtering target is frequently used in a large-area sputtering apparatus. Although the present invention is intended for plate-like and cylindrical shapes, it does not prevent application to other shapes of the split sputtering target, and the shape of the target member is not limited. The composition of the target member can also be applied to oxide semiconductors such as IGZO and ZTO, transparent electrodes (ITO), and the like, and the composition of the target member is not limited.

  The ceramic material in the present invention is preferably a ceramic powder having the same composition as the target member. When the gap is filled with ceramic powder having the same composition as the target member, it is possible to effectively prevent the constituent material of the backing plate from being sputtered, and even if a sputtering phenomenon occurs in the gap, the thin film is formed. This is because there is little influence.

  The organic material in the present invention is preferably a high resistance substance. When the gap formed between the bonded target members is filled with an organic material that is a high-resistance substance, the sputtering phenomenon inside the gap during sputtering can be suppressed, and adverse effects on the thin film to be deposited can be prevented. Because it can. For example, it is preferable to use a substance having a larger volume resistance than the target member, that is, an organic material of a high resistance substance. It is preferable that the organic material of such a high-resistance substance has a volume resistivity (Ω · cm) of the high-resistance substance that is 10 times or more the volume resistivity of the target member.

  In the present invention, as a method of filling the gap between the bonded target members with an organic material, a liquid or gel-like organic material is injected into the gap, and then the solvent is vaporized, for example. By solidifying, the gap can be filled with an organic material. The volume resistance of the organic material described above is the volume resistance of the organic material in a solidified state.

  In addition, as the organic material in the present invention, synthetic resin materials such as phenol resin, melamine resin, epoxy resin, urea resin, vinyl chloride resin, polyethylene and polypropylene, and general-purpose plastic materials such as polyethylene, polyvinyl chloride, polypropylene and polystyrene And semi-general plastic materials such as polyvinyl acetate, ABS resin, AS resin, and acrylic resin. Furthermore, engineering plastics such as polyacetal, polycarbonate, modified polyphenylene ether (PPE), and polybutylene terephthalate, and super engineering plastics such as polyarylate, polysulfone, polyphenylene sulfide, polyether ether ketone, polyimide resin, and fluororesin can also be used. In particular, a polyimide resin or the like is suitable for the present invention because of its high heat resistance and insulation. The filling thickness of the organic material is preferably 0.0001 mm to 1.0 mm.

  When ceramic powder having the same composition as the target member is employed as the ceramic material in the present invention, the filling thickness of the ceramic powder is preferably 10% to 70% of the depth of the gap formed between the target members. . If it is less than 10% of the gap depth, the effect of suppressing the sputtering of the constituent material of the backing plate tends to decrease, and if it exceeds 70%, the filled ceramic powder falls off and particles are generated during sputtering. Cause. This gap depth is determined by the thickness of the end portion of the target member or the end portion thickness of the entire sputtering target manufactured, and the initial gap in which the divided sputtering target was manufactured before being used for sputtering. Say depth.

As the ceramic material in the present invention, when employing a ceramic powder of the target member and the same composition, packing density of the ceramic powder is 40% to 70%, an average particle diameter _{D 50} of the ceramic powder 0.5μm~8.0μm It is preferable that Ceramic powder filled in the gap, for example, when it is to be filled with slurry, which was the average particle diameter D ₅₀ of the ceramic powder is less than 0.5 [mu] m, dried by filling the slurry, solidification The cracked ceramic powder is likely to be cracked and easily fall off from the gap. On the other hand, when the average particle diameter D ₅₀ is larger than 8.0 μm, when the gap is filled as a slurry and then dried, the filling density of the ceramic powder tends to be less than 40%, and the gap is easily dropped from the gap. Therefore, when the average particle diameter _{D 50} of the ceramic powder is 0.5Myuemu～8.0Myuemu, it is possible to suppress the dropping of the ceramic powder filled in the gap. The packing density of the ceramic powder is the same as that for manufacturing the split sputtering target, and the slurry of the ceramic powder is poured into a container of a predetermined shape, for example, a cylindrical container, and the slurry is completely dried. Then, the input capacity and weight can be measured and specified. The ceramic powder filling density is such that the density of the target member is 100%.

  The ceramic material in the present invention may be a ceramic fiber. In recent years, alumina and silica yarns have been supplied as ceramic fibers, and the fiber diameters are very thin. Therefore, an effect similar to that of the ceramic powder described above can be realized by filling the gaps with such ceramic fibers. When filling this gap with a ceramic fiber, the ceramic fiber having a fiber diameter that matches the width of the gap (single wire or a twisted strand of a plurality of fine wires) is pushed into the gap to cover the surface of the backing plate. can do. Further, a small amount of low melting point solder such as In used for joining the backing plate and the target member is left in the gap, and the ceramic fiber can be fixed to the gap bottom using the low melting point solder. Furthermore, the ceramic material in the present invention can be applied to a ceramic (filler) dispersed in a resin.

  When the target member in the present invention is an oxide semiconductor, the oxide semiconductor is preferably made of an oxide containing at least one of In, Zn, and Ga. Specifically, IGZO (In—Ga—Zn—O), GZO (Ga—Zn—O), IZO (In—Zn—O), and ZnO can be given.

  In addition, when the target member in the present invention is an oxide semiconductor, the oxide semiconductor includes at least one of Sn, Ti, Ba, Ca, Zn, Mg, Ge, Y, La, Al, Si, and Ga. It is preferable to consist of the oxide which contains. Specifically, Sn-Ba-O, Sn-Zn-O, Sn-Ti-O, Sn-Ca-O, Sn-Mg-O, Zn-Mg-O, Zn-Ge-O, Zn-Ca. -O, Zn-Sn-Ge-O, or the oxide which changed Ge of these oxides to Mg, Y, La, Al, Si, Ga is mentioned.

And when the target member in this invention is an oxide semiconductor, it is preferable that the oxide semiconductor consists of an oxide containing any 1 or more types of Cu, Al, Ga, and In. Specific examples include Cu ₂ O, CuAlO ₂ , CuGaO ₂ , and CuInO ₂ .

  In the split sputtering target according to the present invention, a gap formed between bonded target members is filled with a fluid containing ceramic powder having the same composition as the target member, dried, and then irradiated with laser or infrared rays. It can be realized by sintering the ceramic powder.

The fluid containing ceramic powder in the present invention can be prepared by mixing a predetermined amount of ceramic powder having the same composition as the target member using an appropriate solvent. For example, when the target member is made of an IGZO oxide semiconductor, a predetermined amount of each of In ₂ O ₃ , Ga ₂ O ₃ , and ZnO powder raw materials is put into a 5 L polypot, and water and a dispersant (carboxylic acid) are added. Ammonia) is added, a predetermined amount of φ10 mmZr ball media is put into a polypot, and a fluid is prepared by ball mill stirring and mixing at a peripheral speed of 50 rpm for 10 hours. It is desirable that the water and the dispersant are 16% by mass: 0.25% by mass or 17% by mass: 0.5% by mass with respect to the total amount of powder to be added. Also, the powder raw material is preferably adjusted to ^{3m 2} / ^g~20m 2 / g approximately powder with BET value. In addition, although a powder raw material can also be used as it is, what performed the calcination process of 700 to 1300 degreeC can also be used. When using the powder raw material which performed the calcination process, water and a dispersing agent mix water at 10 mass%-15 mass% and a dispersing agent at 0.25 mass%-0.5 mass%. It is preferable.

In the present invention, after filling and drying a fluid containing ceramic powder, the filled portion is irradiated with laser, for example, a wavelength of 308 nm, a frequency of 100 Hz, a pulse width of 30 ns, and an energy density of 100 mJ / cm ^{2 to} 1000 mJ / cm ^2. When the laser irradiation is performed, the outermost surface side of the ceramic powder filled in the gap is sintered. Moreover, it is also possible to heat-treat the filled ceramic powder by converging infrared rays into the gap portion.

  According to the present invention, in the split sputtering target obtained by joining a plurality of target members, sputtering prevents the constituent material of the backing plate from being mixed into the thin film to be formed. be able to.

The division | segmentation sputtering target schematic perspective view. The cross-sectional schematic of this embodiment. The cross-sectional schematic of this embodiment.

  Hereinafter, embodiments of the present invention will be described.

  In the present embodiment, a case where a plate-like divided sputtering target as shown in FIG. 1 is manufactured will be described as an example. As shown in FIG. 1, the split sputtering target in this embodiment includes an oxygen-free copper backing plate 10 (thickness 10 mm, length 630 mm, width 710 mm) and six IGZO target members 20 (thickness 6 mm, length 210 mm, 355 mm in width). In was used as the low melting point solder for bonding. The gap 30 between the target members was 0.5 mm.

The target member made from IGZO weighed each raw material powder of In ₂ O ₃ , Ga ₂ O ₃ , and ZnO at a ratio of 1 mol: 1 mol: 2 mol, and mixed with a ball mill for 20 hours. And after adding and mixing 8 mass% of polyvinyl alcohol aqueous solution diluted to 4 mass% as a binder with respect to the powder total amount, it shape | molded by the pressure of 500 kgf / cm < ² >. Then, a plate-like sintered body was obtained by firing at 1450 ° C. for 8 hours in the atmosphere. Then, both surfaces of this sintered body were polished by a surface grinding machine to produce an IGZO target member having a thickness of 6 mm, a length of 210 mm, and a width of 355 mm.

  The six target members thus fabricated were arranged and bonded as shown in FIG. 1 using In low melting point solder. In this bonding, both the backing plate and the target member are heated to 200 ° C., the molten low melting point solder (In) is applied to the surface of the backing plate, the target member is placed on the low melting point solder, and the room temperature is reached. This was done by cooling. In this joining, a spacer of a heat-resistant material was interposed at a position corresponding to the gap formed between the target members so as to prevent the low melting point solder from entering the gap portion.

Next, a fluid of IGZO ceramic powder was prepared. Each powder raw material of In ₂ O ₃ (138.8 g), Ga ₂ O ₃ (93.7 g), ZnO (81.4 g) is put into a 5 L polypot, and water and a dispersant (ammonium carboxylate) are added. A fluid was prepared by putting a predetermined amount of φ10 mmZr ball media into a polypot and performing ball mill stirring and mixing for 10 hours. Water and dispersant were 16%: 0.25% of water: dispersant with respect to the total amount of powder to be charged. Then, as shown in FIG. 2, the prepared ceramic powder fluid 100 was injected into the gap 30 between the target members using a syringe. The injection amount at this time was 50% of the target member thickness. Then, the drying process was performed at 70 to 120 degreeC in air | atmosphere, and the inject | poured fluid was dried.

Thereafter, as shown in FIG. 3, the dried fluid 100 in the gap 30 between the target members was irradiated with laser. The laser irradiation conditions were a wavelength of 308 nm, a frequency of 100 Hz, a pulse width of 30 ns, an energy density of 500 mJ / cm ^2, and the outermost surface side of the ceramic powder filled in the gap was sintered. After this laser treatment, no falling off of the ceramic powder filled from the split sputtering target was confirmed.

  Further, the packing density of the ceramic powder was calculated by pouring the above-mentioned ceramic powder fluid into a cylindrical container of φ20 mm, completely drying the fluid, and measuring its input capacity and weight. 60%. The average particle size of the ceramic powder was 0.6 μm.

As described above, the sputtering evaluation test was performed on the divided sputtering target in which the gap between the target members was filled with the ceramic powder. In this sputtering evaluation test, a sputtering apparatus (SMD-450B, manufactured by ULVAC) was used to form an IGZO thin film having a thickness of 14 μm on a non-alkali glass substrate (370 mm × 470 mm × 0.7 mm thickness: manufactured by Nippon Electric Glass Co., Ltd.). . The sputtering conditions were Ar 100 cc, O ₂ 10 cc, sputtering pressure 0.7 Pa, and power 4.3 kW.

  And about this board | substrate formed into a film, the board | substrate of the just upper part corresponding to the gap | interval part of a division | segmentation sputtering target and board | substrates other than a gap | interval part were cut out. The cut substrate was subjected to sputter evaluation by measuring the amount of Cu mixed in the IGZO thin film by atomic absorption analysis. For comparison, a sputter evaluation test was similarly performed on a split sputtering target in which the gap portion was not filled with ceramic powder.

  As a result, when the ceramic powder was filled, the amount of Cu mixed into the IGZO thin film was less than 2 ppm (below the detection limit of atomic absorption analysis). On the other hand, in the case where the ceramic powder was not filled, the amount of Cu mixed into the IGZO thin film was 19 ppm.

  According to the present invention, when forming a thin film using a large-area divided sputtering target, it is possible to effectively prevent impurities from being mixed during sputtering.

10 backing plate 20 target member 30 gap 50 low melting point solder 100 ceramic powder (fluid)

Claims (3)

In the split sputtering target formed on the backing plate by bonding a plurality of target members with low melting point solder,
The gap formed between the joined target members is filled with a ceramic material made of ceramic powder containing a metal element constituting the target member ,
The division sputtering target characterized in that the filling thickness of the ceramic powder is 10% to 70% of the depth of the gap formed between the target members . 2. The split sputtering target according to claim 1 , wherein a packing density of the ceramic powder is 40% to 70%, and an average particle diameter D ₅₀ of the ceramic powder is 0.5 μm to 8.0 μm. In the manufacturing method of the division | segmentation sputtering target of Claim 1 or Claim 2 formed by joining a several target member on a backing plate with a low melting-point solder.
After filling the gap formed between the joined target members with a fluid containing ceramic powder of the same composition as the target member and drying,
A method of manufacturing a split sputtering target, wherein a ceramic powder is sintered by irradiating a filled portion with laser or infrared rays.

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