JP2018083971A - Magnetron sputtering device, and method for forming a transparent electrically conductive oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetron sputtering device capable of reducing the incident of an oxygen negative ion into a transparent electric conductive oxide film, when the transparent electric conductive oxide film is formed in a specimen.SOLUTION: A magnetron sputtering device 10 is equipped, over a specimen support 11 for mounting a specimen S, with a target 12 capable of forming a transparent conductive electric oxide film on a specimen S. The specimen S to be placed on the specimen support 11 is enclosed by a screening wall 13 capable of screening oxygen negative ions to be discharged from the target 12. The screening wall 13 is formed an opening A in a portion not opposing to the target 12, and is equipped at a portion opposing the opening A with a sample fixing plate for fixing the sample S. Over the sample fixing plate, an upper shielding plate is formed in conjunction with the sample fixing plate, and the two side portions of the sample fixing plate are formed with side shielding plates continuously with the side fixing plate. The length, in which the upper shielding plate is formed continuously with the sample fixing plate, is larger than the length, in which the side shielding plate is formed continuously from the sample fixing plate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetron sputtering apparatus and a method for forming a transparent conductive oxide film.

  Transparent conductive oxides are used in liquid crystal displays, plasma displays, transparent conductive oxide films for solar cells, heat ray reflective glass, and the like.

  As a method for forming a transparent conductive oxide film, sol-gel method, spray pyrolysis method, electroless plating, radio frequency (RF) magnetron sputtering method, direct current (DC) magnetron sputtering method, vacuum deposition method, ion plating method, pulse There are a laser deposition method (PLD), a CVD method, and the like.

  In the sputtering method using a metal target, since the metal target is conductive, a metal film can be formed by a DC magnetron sputtering method. In the case of sputtering using a metal target, when Ar is allowed to flow as a sputtering gas, a metal film can be easily formed by a DC magnetron sputtering method. At this time, a metal film can also be formed by RF magnetron sputtering.

  When forming a compound film using a metal target, there are several problems compared to the case where a metal film is formed using a metal target. As the compound, oxides and nitrides are common.

  The method of forming a compound film using a metal target is called a reactive sputtering method, and has technically difficult problems compared to normal RF sputtering, but the film formation speed is high and the target is a metal. There is an advantage that it is inexpensive.

  In the reactive sputtering method, it is technically difficult to adjust the supply amount of oxygen. When the supply amount of oxygen is small, the surface of the target becomes metal (metal mode), and when the supply amount of oxygen is large, the surface of the target is covered with oxide (oxide mode). For this reason, it is necessary to perform sputtering in an intermediate transition region between the two, and the oxygen supply amount must always be kept in a narrow transition region, and the operation is complicated.

  Moreover, when forming the compound film which consists of multiple elements using a metal target, a some target is required.

  There is an attempt to form an AZO film by a reactive sputtering method using a metal target. In this case, a Zn target and an Al target are used. It is technically difficult to add a small amount of Al into ZnO while simultaneously controlling two targets in parallel (see, for example, Non-Patent Document 1).

  Here, since the metal oxide is an insulator, conventionally, the metal oxide film is usually formed by RF sputtering using a metal oxide target having the same composition as the metal oxide film. . In recent years, it has become possible to artificially introduce oxygen defects into a metal oxide target, and a metal oxide film can be formed by a DC magnetron sputtering method (for example, Patent Documents 1 to 3). reference).

  There is also a problem when a metal oxide film is formed by a DC sputtering method using a metal oxide target.

Usually, Ar is used as the sputtering gas. Ar is ionized in the plasma, becomes Ar ⁺ ions, collides with the target, and strikes atoms constituting the target into the plasma as sputtered particles.

  The sputtered particles are knocked out into the plasma in a state having an energy of about 10 eV. For example, when the pressure of the sputtering gas is 1 Pa, the average free path of the sputtered particles is about 10 mm. If the distance between the substrate on which the metal oxide film is formed and the target is 100 mm, the sputtered particles repeatedly collide with the sputtering gas several times before reaching the substrate.

  The collision between the sputtered particle and the sputter gas is elastic scattering, but the sputtered particle loses energy while repeating the collision with the sputter gas, and becomes the same energy as the sputter gas. Thereby, the direction of the movement of the sputtered particles is lost. This phenomenon is called thermalization. When the sputtered particles are heated, they reach the back side of the substrate on which the metal oxide film is formed.

  On the other hand, since the target is a metal oxide, oxygen negative ions are also generated. Oxygen negative ions are accelerated by the ion sheath and jump out of the target with energy of about 200 eV. Such oxygen negative ions having high energy have a strong straightness.

  As described above, sputtered particles and oxygen negative ions are released from the target during sputtering.

  For example, when a glass substrate is placed on a sample stage (anode) and Ar is flowed as a sputtering gas, a transparent conductive oxide film is formed on the substrate by a DC sputtering method using a metal oxide target. be able to. At the same time, oxygen negative ions also enter the transparent conductive oxide film.

  When oxygen negative ions are incident on the transparent conductive oxide film, the crystal structure is destroyed and oxygen defects are generated. At this time, the oxygen defect becomes the color center, the transparent conductive oxide film is colored yellow, electrons as carriers are captured by the oxygen defect, and the conductivity is lost.

  In order to avoid such a problem, there is a method called off-axis (see, for example, Non-Patent Documents 2 and 3). In this method, two targets (cathodes) are arranged so as to face each other, and a glass substrate (anode) is arranged so as to be perpendicular to a line connecting the two cathodes. By taking such an arrangement, it is possible to reduce the incidence of negative oxygen ions on the transparent conductive oxide film.

  Alternatively, when a sputtering apparatus capable of revolving the glass substrate relative to the target is used, oxygen negative ions are incident on the transparent conductive oxide film by revolving the glass substrate at an appropriate angle from directly above the target and removing the axis. Probability can be reduced.

JP 2012-72459 A JP-A-6-25838 JP-A-7-258836

Okuhara Y. et.al.Thin Solid Films, Vol.519, (2011) 2280. O. Michikami and M. Asahi, Japanese Journal of Applied Physics, Vol. 30, (1991) 939. J. Jia, A. Yoshimura, Y. Kagoya, N. Oka, Y. Shigesato, Thin Solid Films, Vol.559, (2014) 69.

  However, the above-described method cannot sufficiently reduce the incidence of negative oxygen ions on the transparent conductive oxide film.

  An object of one embodiment of the present invention is to provide a magnetron sputtering apparatus that can reduce the incidence of negative oxygen ions on a transparent conductive oxide film when the transparent conductive oxide film is formed on a sample. And

  One aspect of the present invention is a magnetron sputtering apparatus in which a target capable of forming a transparent conductive oxide film on a sample is installed on an upper part of a sample table on which the sample is placed. The sample placed on is surrounded by a shielding wall capable of shielding oxygen negative ions released from the target, and the shielding wall has an opening formed at a portion not facing the target, A sample fixing plate for fixing the sample at a portion facing the opening, and an upper shielding plate is formed on the upper portion of the sample fixing plate continuously with the sample fixing plate; The side shield plate is formed continuously on both sides with the sample fixing plate, and the length of the upper shield plate formed continuously with respect to the sample fixing plate is the side shield plate. Is against the sample fixing plate Greater than the length continuously formed.

  According to one aspect of the present invention, it is possible to provide a magnetron sputtering apparatus capable of reducing the incidence of oxygen negative ions on a transparent conductive oxide film when the transparent conductive oxide film is formed on a sample. Can do.

It is a figure which shows an example of the magnetron sputtering apparatus of this embodiment. It is a figure which shows the structure of the shielding wall of FIG. It is an X-ray diffraction spectrum of the AZO thin film of Examples 1 and 2 and Comparative Examples 1 and 2.

  Next, the form for implementing this invention is demonstrated with drawing.

  FIG. 1 shows an example of a magnetron sputtering apparatus according to this embodiment.

  In the magnetron sputtering apparatus 10, a target 12 (cathode) capable of forming a transparent conductive oxide film on the surface of the sample S is installed above the sample table 11 (anode) on which the sample S is placed. . Here, the sample S placed on the sample stage 11 is surrounded by a shielding wall 13 capable of shielding oxygen negative ions released from the target 12. The shielding wall 13 is formed with an opening A at a portion that does not face the target 12. At this time, the sample S is placed on the sample table 11 in a state where it is fixed to a portion facing the opening A of the shielding wall 13. For this reason, when forming a transparent conductive oxide film on the surface of the sample S, the incidence of oxygen negative ions released from the surface of the target 12 on the transparent conductive oxide film can be reduced. As a result, the specific resistance of the transparent conductive oxide film decreases and the carrier concentration increases. Further, the sputtered particles P emitted from the surface of the target 12 can reach the sample S via the opening A.

  Note that the sample S need only be placed on the sample stage 11 in a state surrounded by the shielding wall 13 so as not to be exposed to the negative oxygen ions released from the target 12, and is not fixed to the shielding wall 13. May be.

  Further, the number of openings A may not be single, but may be plural.

  The sample S is not particularly limited as long as a transparent conductive oxide film can be formed, and examples thereof include a glass substrate.

  Examples of the material constituting the glass substrate include soda lime glass, Pyrex (registered trademark) glass, and quartz glass.

  The material constituting the sample stage 11 is not particularly limited as long as an anode can be formed, and examples thereof include stainless steel.

The material constituting the target 12 is not particularly limited as long as it can form a cathode and a transparent conductive oxide film on the surface of the sample S. However, Al-doped ZnO (AZO), Ga ZnO (GZO) doped with Nb, TiO ₂ (TNO) doped with Nb, In ₂ O ₃ (ITO) doped with Sn, and the like.

  The material constituting the shielding wall 13 is not particularly limited as long as the negative oxygen ions released from the target 12 can be shielded, and examples thereof include metals, quartz glass, and Pyrex glass.

  FIG. 2 shows the structure of the shielding wall 13. 2A, 2B, and 2C are a top view, a front view, and a side view, respectively.

  The sample S is fixed to a sample fixing plate 13a that is a portion facing the opening A of the shielding wall 13 with, for example, a double-sided tape. Here, an upper shielding plate 13b is formed continuously with the sample fixing plate 13a above the sample fixing plate 13a. Further, side shield plates 13c and 13d are formed on both sides of the sample fixing plate 13a so as to be continuous with the sample fixing plate 13a.

At this time, the length (L ₁ ) in which the upper shielding plate 13b is continuously formed with respect to the sample fixing plate 13a is such that the side shielding plates 13c and 13d are continuously formed with respect to the sample fixing plate 13a. Larger than the length (L ₂ ). Thereby, when forming a transparent conductive oxide film on the surface of the sample S, incidence of oxygen negative ions released from the surface of the target 12 to the transparent conductive oxide film can be reduced.

  When the shielding wall 13 is installed at a portion of the sample stage 11 that faces the target 12, it is possible to prevent the negative oxygen ions emitted from the surface of the target 12 from entering the transparent conductive oxide film. Specifically, oxygen negative ions incident from above can be shielded by the upper shielding plate 13b, and oxygen negative ions incident from the side can be shielded by the side shielding plates 13c and 13d.

  On the other hand, since the sputtered particles P emitted from the surface of the target 12 are heated, they reach the surface of the sample S via the opening A of the shielding wall 13 to form a transparent conductive oxide film. Can do.

  In addition, the structure of the shielding wall 13 will not be specifically limited if it can shield the oxygen negative ion discharge | released from a target.

  Although it does not specifically limit as a magnetron sputtering apparatus, A direct current (DC) magnetron sputtering apparatus, a high frequency (RF) magnetron sputtering apparatus, etc. are mentioned.

As the transparent conductive oxide is not particularly limited, ZnO doped with Al (AZO), ZnO doped with _{Ga (GZO), TiO 2 (} TNO), In 2 O 3 doped with Sn doped with Nb ( ITO) and the like.

[Example 1]
An AZO thin film was formed on the sample S using a magnetron sputtering apparatus 10 (see FIG. 1) as a DC magnetron sputtering apparatus.

  As the sample S, a soda-lime glass substrate having a length of 20 mm, a width of 20 mm, and a thickness of 1 mm was used.

As the target 12, an AZO target (manufactured by Furuuchi Chemical) having a diameter of 4 inches (101.6 mm) was used. The target 12 contains 2% by mass of Al ₂ O _{3 in} zinc oxide. In addition, oxygen defects are introduced into the target 12 in advance so that DC magnetron sputtering can be performed.

After fixing the sample S to the sample fixing plate 13 a of the shielding wall 13, the shielding wall 13 was placed on the sample table 11. Here, the upper shielding plate 13b is 30 mm long and 60 mm wide, and the sample fixing plate 13a and the side shielding plates 13c and 13d are 20 mm long and 20 mm wide (see FIG. 2). At this time, the length (L ₁ ) in which the upper shielding plate 13b is continuously formed with respect to the sample fixing plate 13a is 30 mm, and the side shielding plates 13c and 13d are continuous with respect to the sample fixing plate 13a. The formed length (L ₂ ) is 20 mm. The sample stage 11 has a diameter of 90 mm, and the distance between the sample stage 11 and the target 12 is 65 mm.

The sputtering conditions are direct current (DC) and an output of 200 W. The flow rates of the sputtering gas are argon (Ar) 9 sccm and oxygen (O ₂ ) 1 sccm. The maximum ultimate vacuum is 1 × 10 ⁻⁵ Pa, and the pressure of the sputtering gas is 0.72 Pa. Sputtering time is 25 minutes. Moreover, sputtering was performed at room temperature and the sample S was not heated.

  At the end of sputtering, the AZO thin film formed on Sample S was colorless and transparent. From this, it is considered that oxygen negative ions are not incident on the AZO thin film.

  The thickness of the AZO thin film was 88 nm. The film thickness of the AZO thin film was measured using a step meter ET2000 (manufactured by Kosaka Manufacturing Co., Ltd.).

  Next, the X-ray diffraction spectrum by the CuKα ray of the AZO thin film was measured using a thin film X-ray diffractometer RAD-2X (manufactured by Rigaku Corporation).

  FIG. 3 shows an X-ray diffraction spectrum of the AZO thin film. In FIG. 3, the position and intensity of the diffraction peak of ZnO are also shown.

  From FIG. 3, it can be seen that there are a diffraction peak of (002) plane and a diffraction peak of (103) plane of ZnO.

  Next, the Hall effect of the AZO thin film was measured using a specific resistance / Hall measurement system Resi Test 8340 HT (manufactured by Toyo Technica Co., Ltd.).

As a result, the carrier concentration of the AZO thin film was 1.25 × 10 ²¹ cm ⁻³ . The carrier concentration of more than ^{10 21,} has reached approximately the highest level (e.g., "Technology of transparent conductive film" 168 pages, see Ohm Co. 2007). The specific resistance of the AZO thin film was 1.13 × 10 ⁻³ Ω · cm, and the hole mobility of the AZO thin film was 4.43 cm ² / V · s.

[Comparative Example 1]
An AZO thin film was formed on the sample S in the same manner as in Example 1 except that the side shielding plates 13c and 13d were omitted.

  At the end of sputtering, the AZO thin film formed on the sample S was yellow and transparent. From this, it is considered that oxygen negative ions are incident on the AZO thin film.

  The thickness of the AZO thin film was 199 nm. The film thickness of the AZO thin film was measured using a step meter ET2000 (manufactured by Kosaka Manufacturing Co., Ltd.).

  Next, the X-ray diffraction spectrum by the CuKα ray of the AZO thin film was measured using a thin film X-ray diffractometer RAD-2X (manufactured by Rigaku Corporation).

  FIG. 3 shows an X-ray diffraction spectrum of the AZO thin film.

  From FIG. 3, it can be seen that there are a diffraction peak of (002) plane and a diffraction peak of (103) plane of ZnO.

  Next, the Hall effect of the AZO thin film was measured using a specific resistance / Hall measurement system Resi Test 8340 HT (manufactured by Toyo Technica Co., Ltd.).

As a result, the carrier concentration of the AZO thin film was 6.92 × 10 ¹⁹ cm ⁻³ . The specific resistance of the AZO thin film was 1.15 × 10 ⁻² Ω · cm, and the hole mobility of the AZO thin film was 7.86 cm ² / V · s.

[Comparative Example 2]
The size of the upper shielding plate 13b is changed to 20 mm in length and 60 mm in width, that is, the length (L ₁ ) where the upper shielding plate 13b is continuously formed with respect to the sample fixing plate 13a is changed to 20 mm. In the same manner as in Example 1, an AZO thin film was formed on Sample S.

  At the end of sputtering, the AZO thin film formed on the sample S was yellow and transparent. From this, it is considered that oxygen negative ions are incident on the AZO thin film.

  The thickness of the AZO thin film was 200 nm. The film thickness of the AZO thin film was measured using a step meter ET2000 (manufactured by Kosaka Manufacturing Co., Ltd.).

  Next, the X-ray diffraction spectrum by the CuKα ray of the AZO thin film was measured using a thin film X-ray diffractometer RAD-2X (manufactured by Rigaku Corporation).

  FIG. 3 shows an X-ray diffraction spectrum of the AZO thin film.

  From FIG. 3, it can be seen that there are a diffraction peak of (002) plane and a diffraction peak of (103) plane of ZnO.

  Next, the Hall effect of the AZO thin film was measured using a specific resistance / Hall measurement system Resi Test 8340 HT (manufactured by Toyo Technica Co., Ltd.).

As a result, the carrier concentration of the AZO thin film was 9.41 × 10 ¹⁹ cm ⁻³ . The specific resistance of the AZO thin film was 5.10 × 10 ⁻² Ω · cm, and the hole mobility of the AZO thin film was 1.30 cm ² / V · s.

  Table 1 shows the measurement results of the film thickness and Hall effect of the AZO thin film.

非特許文献３の表５．５の特性比較表の透明導電特性によれば、種々元素をドープしたＺｎＯ系の膜の比抵抗［Ω・ｃｍ］は、１０^−４代が多いものの、１０^−３代の膜も少なくない。また、種々元素をドープしたＺｎＯ系の膜のホール移動度［ｃｍ^２／Ｖ・ｓ］は、２０から４０代が多いものの、一桁の例もある。さらに、種々元素をドープしたＺｎＯ系の膜のキャリア濃度［ｃｍ^−３］は、１０^２１代が多いものの、１０^２０代も少なくない。

According to the transparent conductive characteristics in the characteristic comparison table in Table 5.5 of Non-Patent Document 3, the specific resistance [Ω · cm] of ZnO-based films doped with various elements is large in the 10 ^{−4 range,} but 10 ^{− There are many 3rd} generation films. In addition, although the hole mobility [cm ² / V · s] of ZnO-based films doped with various elements is often in the 20s to 40s, there is a single digit example. Further, the carrier concentration of the film of ZnO-based doped with various elements ^{[cm -3],} although many ^{10 21} generations, not a few ^{10 20s.}

When comparing Example 1 and Comparative Example 1 using the upper shielding plate 13b having a length of 30 mm and a width of 60 mm, the thickness of the AZO thin film is more than twice that of Comparative Example 1, and the specific resistance of the AZO thin film is comparative example. 1 is one digit larger, and the carrier concentration of the AZO thin film is two orders of magnitude less in Comparative Example 1. Here, the difference in hole mobility of the AZO thin film is considered to be within an error range. On the other hand, since the specific resistance and carrier concentration of the AZO thin film differ by digits, it is considered that there is a significant difference. Specifically, the specific resistance of the AZO thin film of Example 1 is 10 ⁻³ generation, and the specific resistance of the AZO thin film of Comparative Example 1 is 10 ⁻² generation. The carrier concentration of the AZO thin film of Example 1 is ^{10 21} generations, the carrier concentration of the AZO thin film of Comparative Example 1 is ^{10 19} generations.

  As described above, when Example 1 is compared with Comparative Example 1, Example 1 is superior in specific resistance and carrier concentration of the AZO thin film. From this fact, it can be said that the side shielding plates 13c and 13d are effective in preventing the incidence of negative oxygen ions on the AZO thin film.

  The shielding wall 13 is installed on the sample stage 11 and is surrounded by plasma. Therefore, when the side shielding plates 13c and 13d are removed, the sputtered particles P come around from both sides. Therefore, as is clear from Table 1, in Comparative Example 1 in which the side shielding plates 13c and 13d are omitted, even if the area of the upper shielding plate 13b is the same, the film of the AZO thin film is greater than in Example 1. The thickness is increasing.

Further, when Example 1 is compared with Comparative Example 2, Example 1 is superior in specific resistance and carrier concentration of the AZO thin film. From this fact, the length (L ₁ ) in which the upper shielding plate 13b is continuously formed with respect to the sample fixing plate 13a is formed so that the side shielding plates 13c and 13d are continuously formed with respect to the sample fixing plate 13a. It can be said that it is effective to prevent the incidence of negative oxygen ions on the AZO thin film to be larger than the length (L ₂ ).

DESCRIPTION OF SYMBOLS 10 Magnetron sputtering apparatus 11 Sample stand 12 Target 13 Shielding wall 13a Sample fixing plate 13b Upper shielding plate 13c, 13d Side shielding plate A Aperture P Sputtered particle S Sample

Claims (4)

A magnetron sputtering apparatus in which a target capable of forming a transparent conductive oxide film on the sample is installed on an upper part of a sample stage on which the sample is placed,
The sample placed on the sample stage is surrounded by a shielding wall capable of shielding oxygen negative ions released from the target,
The shielding wall has an opening formed at a portion not facing the target, and has a sample fixing plate for fixing the sample at a portion facing the opening, and an upper shielding is provided above the sample fixing plate. A plate is formed continuously with the sample fixing plate, and a side shielding plate is formed continuously with the sample fixing plate on both sides of the sample fixing plate,
The magnetron sputtering apparatus in which the length of the upper shielding plate formed continuously with respect to the sample fixing plate is larger than the length of the side shielding plate formed continuously with respect to the sample fixing plate. .   The magnetron sputtering apparatus according to claim 1, which is a direct current magnetron sputtering apparatus or a high frequency magnetron sputtering apparatus. The transparent conductive oxide is made of AlO-doped ZnO (AZO), Ga-doped ZnO (GZO), Nb-doped TiO ₂ (TNO), and Sn-doped In ₂ O ₃ (ITO). The magnetron sputtering apparatus according to claim 1 or 2, wherein the magnetron sputtering apparatus is selected.   The formation method of the transparent conductive oxide film which forms a transparent conductive oxide thin film in the said sample using the magnetron sputtering apparatus as described in any one of Claims 1 thru | or 3.

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