JP4639764B2 - Cylindrical target and film forming method - Google Patents

Description

  The present invention relates to a magnetron sputtering apparatus used for forming a thin film, and more particularly to a cylindrical target and a film forming method applied to an AC magnetron sputtering apparatus that can stably form a thin film with less arcing.

  Magnetron sputtering is known as one of the techniques for forming a thin film on a substrate such as glass or plastic. Patent Document 1 discloses a sputtering system that uses a rotating cylindrical target. This apparatus has a magnet inside a cylindrical target, and performs sputtering while rotating the target while cooling the target by flowing a cooling liquid inside the target. The cylindrical target has advantages in that the use efficiency is higher than that of a planar target called a planar type, and high-speed film formation is possible.

Further, the applicant of the present application disclosed in Patent Document 2 as a target material made of Si-impregnated SiC (silicon-impregnated silicon carbide), a backing tube made of SUS, and a compressive deformation as a joining material for joining the target material and the backing tube. A possible sheet-like cushioning member is proposed. According to this cylindrical target, cracking of the target material due to a difference in thermal expansion between the target material and the backing tube during use is prevented by interposing a buffer member such as carbon felt.
Japanese National Patent Publication No. 5-501586 JP 2002-155356 A

  However, the cylindrical target of Patent Document 2 using carbon felt as a bonding material cools the backing tube through which the cooling liquid flows, but effectively cools the target material due to the high thermal insulation of the carbon felt. However, there is a problem that the temperature of the target material rises excessively, and the O-ring made of fluoro rubber, which is a component of the film forming apparatus (coater), is damaged, or the aluminum protective plate is deformed. It was.

  This problem can be solved by replacing the carbon felt with a carbon sheet. That is, the carbon sheet has a thermal conductivity several times better than that of the carbon felt, and is thus effectively cooled by the coolant supplied to the backing tube.

  However, a cylindrical target using a carbon sheet and a SUS backing tube as a bonding material increases the power density of the power input to the target material in order to increase the sputtering rate (deposition rate). There was a problem that the target material of the sintered body was damaged due to thermal expansion.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a cylindrical target and a film forming method capable of increasing the film forming speed without damaging the target material.

In order to achieve the above object, the cylindrical target invention according to claim 1 is characterized in that a hollow cylindrical target material is disposed on the outer periphery of the cylindrical backing tube, and the backing tube and the target material are In a cylindrical target in which a backing tube and a target material are joined with a joining material interposed therebetween, the target material is Si-impregnated SiC, and the backing tube is at 20 to 600 ° C. according to JIS R1618. mean linear expansion coefficient (hereinafter simply referred to as the average linear expansion coefficient) higher than the target material is and fabricated of the following materials 12 × 10 -6 ^{/ K,} said bonding material is a Lee indium metal It is a feature.

According to the cylindrical target of the first aspect, first, Si-impregnated SiC having an average linear expansion coefficient of 3.5 to 5.5 × 10 ⁻⁶ / K is used as the target material. Here, the Si-impregnated SiC is a silicon carbide sintered body impregnated with silicon as described later.

Then, by using a backing tube having an average linear expansion coefficient higher than that of the target material and made of a material of 12 × 10 ⁻⁶ / K or less, an SUS having an average linear expansion coefficient of 17.3 × 10 ⁻⁶ / K. The amount of thermal expansion due to temperature rise is suppressed with respect to the made backing tube. In the present specification, the reason why the average linear expansion coefficient is defined in the range of 20 to 600 ° C. is that the temperature inside the target material and the backing tube is generally in the range of 20 to 600 ° C. Because it is considered.

And further, as a bonding material for bonding the backing tube and the target material, Lee indium metal was adopted to increase the thermal conductivity between the backing tube and the target material, at the time of charged power of the high power density on the target material Prevents excessive temperature rise of the target material and prevents damage to the internal parts of the coater.

Thereby, the crack at the time of using the target material manufactured with Si impregnation SiC by high-speed film-forming can be prevented. The reason why the average linear expansion coefficient of the backing tube is set larger than the average linear expansion coefficient of the target material will be described. If the average linear expansion coefficient of the backing tube is smaller than the average linear expansion coefficient of the target material, the temperature rises. This is because sometimes the gap between the backing tube and the target material becomes larger than the initial value, and as a result, heat conduction by the bonding material is difficult to occur, and the target material becomes hot and damages the coater. Further, since the bonding force of the bonding material is also reduced, there is a problem that the target material becomes non-rotatable. When the average linear expansion coefficient of the backing tube exceeds 12 × 10 ⁻⁶ / K, the backing tube thermally expands, and the backing tube presses the target material from the inside to the outside, causing stress in the target material. However, it is not preferable because the target material may be cracked.

  Note that the role of the bonding material is to thermally transfer the heat generated on the target by the discharge with the coolant flowing inside the backing tube, so that the target material and the backing tube are thermally transmitted. When the bonding material is indium metal, the thermal conductivity of indium is preferably 81.6 W / m · k, which is excellent in thermal conductivity. In addition, since the bonding is performed by liquefaction and solidification, the target material and the backing tube are used. Can be bonded with good adhesion. In addition, a carbon sheet is preferable because it can be bonded at room temperature and the backing tube can be easily reused.

  The invention according to claim 2 is the invention according to claim 1, wherein the backing tube is made of an alloy containing 60% by mass or more of titanium or molybdenum, or titanium or molybdenum.

According to the cylindrical target according to claim 2, for example, as a backing tube, titanium having an average linear expansion coefficient of 8.8 × 10 ⁻⁶ / K and an average linear expansion coefficient of 5.1 × 10 ⁻⁶ / K. Molybdenum can be adopted. When adopting molybdenum, an Si-impregnated SiC target material having an average coefficient of linear expansion smaller than that of molybdenum is used. Moreover, the additive element of the titanium alloy containing 60 mass% or more of titanium is Pd, Mo, Ni, Ta, Al, Sn, Zr, Nb, Si, Cu, V, Bi, Mn, Cr, Ru, and Fe. One or more elements selected from the group consisting of Further, the additive element of the molybdenum alloy containing 60 mass% or more of molybdenum is one or more elements selected from the group consisting of Ti, Zr, W, Nb, and C.

The invention of the film forming method according to claim 3 uses the cylindrical target according to any one of claims 1 and 2 to perform sputtering at a power density of 1 to 10 W / cm ^2. The method is characterized in that a film is formed on a substrate.

The cylindrical target of the present invention does not cause cracking or other damage even when high power density power is input to the target material, but when the power density exceeds 10 W / cm ² , the temperature of the target material increases. In addition, the cooling ability of the coolant flowing in the backing tube does not sufficiently cool the target material, causing damage to the coater. Thereby, the upper limit of the power density is set to 10 W / cm ² .

Here, the power density Q (W / cm ² ) is AC power supply power: P (W), the outer diameter of the cylindrical target material: D (cm), the length of the cylindrical target material: L (cm) Since the area of the outer surface to be sputtered per target material is πDL (cm ² ), the power density when one target material is installed in the coater is Q = P / πDL (W / Cm ² ), and the power density when two target materials are installed in the coater can be derived by the formula Q = P / 2πDL (W / cm ² ).

As described above, according to the cylindrical target and the film forming method according to the present invention, the target material is made of Si-impregnated SiC, the average linear expansion coefficient is higher than that of the target material, and 12 × 10 ⁻⁶ / K or less. Since the backing tube is made of the above material and the bonding material is a carbon sheet or indium metal, the deposition rate can be increased without damaging the target material. Moreover, since the upper limit of the power density of the electric power supplied to the cylindrical target is set to 10 W / cm ² , the device parts are not damaged.

  Preferred embodiments of a cylindrical target and a film forming method according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of a magnetron sputtering system 12 to which a cylindrical target according to an embodiment of the present invention is applied. The cylindrical target 10 shown in the figure is shown as a cutaway view to show the internal structure. A vacuum is maintained in the sealed reaction chamber 14 in which plasma is generated, and the base material 16 to be formed is placed below the two cylindrical targets 10 and 10.

  Examples of the substrate 16 include glass and plastic. Plastics include fluororesin, acrylic resin, polycarbonate resin (PC), triacetate (TAC), polyethersulfone (PES), polyethylene naphthalate film (PEN), polyimide (PI), polyethylene terephthalate (PET), polyether Examples include ether ketone. The base material 16 is preferably made of any material having a thickness of 15 mm or less, and in the case of glass, a material having a thickness of 0.5 to 15 mm is particularly preferable.

  In the cylindrical target 10, a hollow cylindrical target material 20 is disposed on the outer periphery of the backing tube 18, and a carbon sheet 22 shown in FIGS. 2 and 3 is inserted between the backing tube 18 and the target material 20. The backing tube 18 and the target material 20 are joined.

The target material 20 includes silicon carbide (SiC) and silicon (Si), the atomic ratio of C to Si is 0.5 to 0.95, and the density is 2.75 × 10 ^{3 to} 3.1 ×. The material is 10 ³ kg / m ³ .

  The manufacturing method of the target material 20 fills a metal mold | die and a rubber mold | die with a SiC powder raw material as a 1st process, and obtains a cylindrical molded object with a CIP (cold isostatic pressing) molding method. As a 2nd process, it finishes to a required dimension by a molded object process as needed. As a 3rd process, a molded object is baked at the temperature of 1450 to 2300 degreeC in vacuum or non-oxidizing atmosphere, such as argon and nitrogen, and a sintered compact is obtained. As a fourth step, the obtained molded body or sintered body is impregnated with molten silicon in a vacuum or a reduced pressure non-oxidizing atmosphere at a temperature of 1450 ° C. to 2200 ° C., and the pores of the molded body or sintered body are filled with silicon. To obtain a Si-impregnated SiC target material. As a fifth step, Si-impregnated SiC is finished to a necessary dimension by grinding as necessary to obtain a target material. The target material 20 is manufactured by the above process.

The carbon sheet 22 is a flexible graphite material obtained by rolling natural graphite as a main raw material and rolling expanded graphite particles obtained by applying a special chemical treatment thereto. The chemical treatment is an acid treatment for expanding the natural graphite, and an entangled cotton-like expanded graphite is obtained by increasing the temperature, and the carbon sheet 22 is produced by rolling this. . The carbon sheet 22 has excellent heat resistance, chemical resistance, lubricity and flexibility, a thickness of 0.2 to 2 mm, a density of 0.5 to 1.5 g / cm ³ , and a thickness direction thermal conductivity. 2 to 6 W / m · K, thickness resistivity in the thickness direction of 0.01 to 0.1 Ω · cm. Further, as shown in FIG. 1, the magnet unit 24 is accommodated in the backing tube 18. The backing tube 18 is cooled by passing water or other coolant through the interior, and the backing tube 18 is cooled, whereby the target material 20 is cooled to a predetermined temperature via the carbon sheet 22.

  The backing tube 18 holding the target material 20 is supported by a target driving device 26 so as to be rotatable about a longitudinal axis. In FIG. 1, the flat substrate 16 is held horizontally, and the longitudinal axis of the cylindrical target 10 is also held horizontally, but the positional relationship between the substrate 16 and the cylindrical target 10 is not limited to this. .

  The magnet unit 24 includes three rows of magnetic poles 28, 30, 32 parallel along the axis of the backing tube 18. The magnetic poles 28, 30 and 32 are each arranged to have a north pole, a south pole, and a north pole, and the magnetic field lines pass through the backing tube 18 and enter an adjacent pole having the opposite polarity. By this magnetic pole arrangement, a magnetic tunnel is generated, and a high sputtering speed is achieved.

  The cathode potential V necessary for causing sputtering is supplied from the AC power supply 34 to the one backing tube 18 via the power line 36 and is also supplied to the other backing tube 18 via the power line 38. Further, in order to obtain a low pressure required for sputtering, the sealed reaction chamber 14 is provided with an outlet tube 40 connected to a vacuum pump 39.

  The sealed reaction chamber 14 is provided with a gas supply means 42 for supplying a gas necessary for sputtering.

  2 is a perspective view of the cylindrical target shown in FIG. 1, FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2, and FIG. 4 is an exploded perspective view when the target is manufactured.

  As shown in these drawings, the cylindrical target 10 is formed by inserting a carbon sheet 22 as a bonding material between a backing tube 18 that is an inner cylinder and a cylindrical target material 20 that is an outer cylinder. Both are joined together. Instead of the carbon sheet 22, the melted indium metal can be poured into the gap between the target material 20 and the backing tube 18 to join them together. Similarly to the carbon sheet 22, the thickness of the indium metal is 0.2 to 2 mm.

The target material 20 is a hollow cylindrical body made of Si-impregnated SiC that forms a SiO ₂ (silicon oxide) film. For example, the length is 0.4 to 4 m, the outer diameter is φ70 to 180 mm, and the inner diameter is φ60. ˜140 mm, thickness: 5 to 20 mm are used.

The backing tube 18 that supports the target material 20 has an average coefficient of linear expansion higher than that of the target material, and is 12 × 10 ⁻⁶ / K or less, for example, an average coefficient of linear expansion of 8.8 × 10 ⁻⁶ / K. Made of titanium. In place of the titanium backing tube 18, a molybdenum backing tube having an average linear expansion coefficient of 5.1 × 10 ⁻⁶ / K can also be used. However, it is necessary to select a material for the backing tube 18 that has a larger average linear expansion coefficient than the target material 20. The average linear expansion coefficient of the Si-impregnated SiC sintered body is 3.5 to 5.5 × 10 ⁻⁶ / K at 20 to 600 ° C.

  On the other hand, the backing tube 18 having, for example, a length of 0.4 to 4 m, an outer diameter of 60 to 140 mm, an inner diameter of 50 to 136 mm, and a thickness of 2 to 5 mm corresponding to the dimensions of the target material 20 is used. It is done.

  As shown in FIG. 4, a carbon sheet 22 is provided on the inner surface of the target material 20, and this is inserted into the outside of the backing tube 18 using a dedicated jig (not shown). Thereby, the target material 20 and the backing tube 18 are joined via the carbon sheet 22.

  Further, when the inner peripheral surface of the target material 20 is unprocessed, the inner diameter accuracy is ± 0.5 mm. Therefore, the inner diameter accuracy is ± 0.1 mm (difference between the maximum value and the minimum value ≦ 0.2 mm by grinding) ) Is finished. Further, when the outer peripheral surface of the backing tube 18 is unprocessed, for example, in the case of a drawn material, the outer diameter accuracy is ± 0.3 mm, so that the outer diameter accuracy is ± 0.1 mm by cutting or the like (the maximum and minimum values are (Difference ≦ 0.2 mm). By disposing a carbon sheet 22 having a thickness substantially equal to the gap in the gap between the backing tube 18 and the target material 20, the backing tube 18 and the target material 20 are joined without gaps. That is, the degree of adhesion between the backing tube 18 and the target material 20 is improved.

  According to the cylindrical target of the embodiment configured as above, first, a carbon sheet 22 or indium metal was adopted as a bonding material for bonding the backing tube 18 and the target material 20.

  Thereby, since the thermal conductivity between the backing tube 18 and the target material 20 is enhanced, an excessive increase in temperature of the target material 20 when high-power density power is supplied to the target material 20 can be prevented. As a result, damage to the internal parts of the coater can be prevented.

Next, the average linear expansion coefficient is 17.3 × 10 ⁻⁶ by making the backing tube 18 with a material having an average linear expansion coefficient higher than that of the target material and 12 × 10 ⁻⁶ / K or less, for example, titanium. The thermal expansion of the backing tube 18 due to the temperature rise can be suppressed with respect to the / K SUS backing tube.

Thereby, the crack of the target material manufactured with Si impregnation SiC with an average linear expansion coefficient of 3.5-5.5 * 10 < ^-6 > / K can be prevented. Further, in a material in which the average linear expansion coefficient of the backing tube 18 exceeds 12 × 10 ⁻⁶ / K, the backing tube 18 presses the target material 20 from the inside to the outside due to thermal expansion of the backing tube 18. Since stress is generated in the target material 20 and the target material 20 may be cracked, it is not preferable.

  The reason why the average linear expansion coefficient of the backing tube 18 is set larger than the average linear expansion coefficient of the target material 20 will be described. The average linear expansion coefficient of the backing tube 18 is smaller than the average linear expansion coefficient of the target material 20. When the temperature rises, the gap between the backing tube 18 and the target material 20 becomes larger than the initial value. As a result, the thermal conductivity is lowered, the temperature of the target material 20 is increased, and the coater is damaged. This is because. Further, since the bonding force between the target material 20 and the backing tube 18 is also reduced, there is a problem that the target material 20 cannot be rotated.

Further, the average linear expansion coefficient of the backing tube 18 is particularly preferably in the range of 8 to 10 × 10 ⁻⁶ / K. Thereby, it is possible to perform stable film formation while maintaining good adhesion between the backing tube 18 and the target material 20 without being affected by other variable factors (cooling liquid amount, input power, bonding adhesion, etc.). .

For the above reasons, it is important that the backing tube 18 is made of a material having an average linear expansion coefficient higher than that of the target material and not more than 12 × 10 ⁻⁶ / K. Therefore, according to the cylindrical target of the present invention, the deposition rate can be increased without damaging the Si-impregnated SiC target material 20.

On the other hand, molybdenum having an average linear expansion coefficient of 5.1 × 10 ⁻⁶ / K can be adopted as the backing tube 18, but the backing tube 18 has an average line higher than that of the target material 20 depending on the type of the target material 20. It is necessary to select a material with a large expansion coefficient.

Further, according to the film formation method using the sealed reaction chamber 14, a silicon oxide thin film is formed on the substrate 16 by performing sputtering with a power having a power density of 1 to 10 W / cm ² using a cylindrical target. Form. A particularly preferable power density range is 3 to 10 W / cm ² .

Although the cylindrical target of the embodiment does not cause damage such as cracking even when high-power-density power is input to the target material, the temperature of the target material 20 becomes excessive when the power density exceeds 10 W / cm ^2. The target material 20 is not sufficiently cooled by the cooling ability of the coolant that rises and flows in the backing tube 18, causing damage to the coater. Thereby, in the film forming method of the embodiment, the upper limit of the power density is set to 10 W / cm ² .

Further, even a titanium alloy satisfying an average linear expansion coefficient of 12 × 10 ⁻⁶ / K or less can be applied to the cylindrical target of the present invention. The additive element of the titanium alloy is one or more selected from the group consisting of Pd, Mo, Ni, Ta, Al, Sn, Zr, Nb, Si, Cu, V, Bi, Mn, Cr, Ru, and Fe. It is an element. Even a molybdenum alloy having an average linear expansion coefficient of 12 × 10 ⁻⁶ / K or less can be applied to the cylindrical target of the present invention. The additive element of the molybdenum alloy is one or more elements selected from the group consisting of Ti, Zr, W, Nb, and C.

Example 1
Using a sputtering apparatus, a continuous discharge experiment was performed under the following conditions. In the sputtering apparatus, two cylindrical rotating cathodes and an AC power source for applying an AC voltage thereto were installed.

Backing tube material: Titanium Backing tube outer diameter (difference between maximum value and minimum value ≦ 0.2 mm): φ134.6 mm, inner diameter: φ125 mm
Target material:
Cylindrical target material containing silicon carbide (SiC) and silicon (Si) (silicon carbide (SiC) 70% by volume, silicon (Si) 30% by volume; atomic ratio C / Si≈0.7)
This target material was obtained by firing and sintering a cylindrical molded body of silicon carbide powder raw material at a temperature of 1800 ° C. and then impregnating with molten silicon at a temperature of 1700 ° C.

Target material outer diameter: φ156 mm, inner diameter (difference between maximum value and minimum value ≦ 0.1 mm): φ136.5 mm
・ Density 3.0 × 10 ³ kg / m ³ (relative density about 100%)
・ Specific resistance 1.2 × 10 ^-3 Ω ・ m
・ Thermal conductivity measured by laser flash method 150W / m ・ K
-Only the crystal phase of SiC and Si was observed by X-ray diffraction analysis, and Si existed to fill the gaps between the SiC particles and was a continuum.

  The amount of metal impurities by ICP (inductively coupled plasma emission spectroscopy) method was 1% by mass or less with respect to the total amount of the target.

Carbon sheet thickness: 1 mm, density: 1.0 g / cm ³
Joining method of backing tube and target material: A 0.95 mm gap between the backing tube and the target material was filled with a 1 mm thick carbon sheet to join the backing tube and the target material.

Target area: 3580cm ²
Atmosphere: Ar gas 210sccm, O ₂ gas 190sccm
Pressure during film formation: 4.1 × 10 ⁻³ hPa
AC frequency: 31 kHz
AC power supply power: 30kW
Power density: 4.2 W / cm ²
Rotation speed of cylindrical target: 15rpm
Even after 24 hours from the start of discharge, no abnormalities such as cracks were observed in the target material, and normal discharge could be continued.

(Example 2)
A continuous discharge experiment is performed in the same manner as in Example 1 except that the bonding method between the backing tube and the target material is changed to In (indium) bonding. Even after 24 hours from the start of discharge, no abnormalities such as cracks are observed on the target, and normal discharge can be continued. Note that the thickness of In bonding is 0.5 mm.

(Comparative Example 1)
A continuous discharge experiment was performed in the same manner as in Example 1 except that the material of the backing tube was changed to SUS304. Five hours after the start of discharge, the target material was cracked, and the discharge could not be continued any further. This was because the thermal expansion amount of SUS304 was larger than the thermal expansion amount of titanium.

(Comparative Example 2)
A continuous discharge experiment is performed in the same manner as in Example 2 except that the material of the backing tube is changed to SUS304. Three hours after the start of the discharge, the target material is cracked and the discharge cannot be continued any further. Similarly, it is considered that the thermal expansion amount of SUS304 is larger than the thermal expansion amount of titanium.

(Comparative Example 3)
A continuous discharge experiment is performed in the same manner as in Comparative Example 1 except that the bonding method between the backing tube and the target material is changed to a 2 mm thick carbon felt sandwich. Two hours after the start of discharge, it is predicted that the fluororubber O-ring of the coater burns out and the aluminum protective plate is deformed. This is probably because the temperature of the target material was excessively increased due to the heat insulating effect of the carbon felt. Carbon felt is a product processed into a felt shape using carbon fiber as a raw material, and has a low bulk density and excellent compressibility and heat insulation. The initial density of carbon felt is 0.12 g / cm ³ , and the volume resistivity in the thickness direction in the initial state is 8 Ω · cm. Further, since the average gap between the backing tube and the target material is 1 mm, the compression ratio of the carbon felt at this time is 50%.

Configuration diagram of a cylindrical magnetron sputtering system to which the cylindrical target of the present invention is applied The perspective view of the cylindrical target which concerns on embodiment of this invention Sectional view along line 3-3 in FIG. The exploded perspective view at the time of manufacture of the cylindrical target of this example

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Cylindrical target, 12 ... Cylindrical magnetron sputtering system, 14 ... Sealed reaction chamber, 16 ... Base material, 18 ... Backing tube, 20 ... Target material, 22 ... Carbon sheet, 24 ... Magnet unit, 26 ... Target drive device , 28, 30, 32 ... magnetic poles, 34 ... alternating current power source, 36, 38 ... power line, 39 ... vacuum pump, 40 ... outlet tube, 42 ... gas supply means

Claims (3)

A cylindrical shape in which a hollow cylindrical target material is disposed on the outer periphery of a cylindrical backing tube, and the backing tube and the target material are joined with a joining material interposed between the backing tube and the target material. In the target,
The target material is Si-impregnated SiC,
The backing tube is a material having an average coefficient of linear expansion at 20 to 600 ° C. according to JIS R1618 higher than that of the target material and 12 × 10 ⁻⁶ / K or less.
Cylindrical target, wherein the bonding material is a Lee indium metal.   2. The cylindrical target according to claim 1, wherein the backing tube is made of an alloy containing 60 mass% or more of titanium or molybdenum, or titanium or molybdenum. Using the cylindrical target according to any one of claims 1 and 2 , a film is formed on a substrate by performing sputtering at a power density of 1 to 10 W / cm ^2. Membrane method.

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