JPH08325720A - Production of thin compound oxide film - Google Patents

Abstract

PURPOSE: To produce a thin compound oxide film of large area by disposing plural sputtering cathodes in the same film formation chamber, supplying independent electric power to respective cathodes, and performing simultaneous sputtering. CONSTITUTION: Plural sputtering cathodes 7, 8, 9 are disposed on the same circumference in a sputtering chamber 16. Independent high frequency electric power sources 13, 14, 15 are connected to the cathodes 7, 8, 9, respectively. Targets 10, 11, 12, each containing a metallic element which is a part of a compound oxide, are fitted to the cathodes 7, 8, 9, respectively. A substrate 18 is fitted to a substrate holder 17 passing over the cathodes 7, 8, 9 while rotating, and sputtering is performed compensators 19 are provided on the targets 10, 11, 12, respectively, to correct a film composition so that the atomic substances emitted from the targets 10, 11, 12 can be made incident upon the substrate 18 uniformly. By this method, the thin film, having uniform composition, uniform film thickness, and large area, can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thin film of a composite oxide material such as lead zirconate titanate and bismuth titanate, which is applied to various electronic devices.

[0002]

2. Description of the Related Art Lead zirconate titanate (Pb (ZrT
i) O ₃ ), complex oxide thin films typified by bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ), etc. make full use of the characteristics of ferroelectric memory devices, pyroelectric infrared detection devices, piezoelectric devices,
It is applied to various electronic devices such as electro-optical elements.

As a method of forming such a complex oxide thin film, a general high frequency sputtering method is mainly used as a thin film forming means of a high melting point material.

In the sputtering method, plasma is generated in a sputtering chamber, positive ions in the plasma are made to collide with a target biased with a negative voltage, and the ion bombardment decomposes the substance constituting the target into atomic form. It is a thin film forming method in which the thin film is discharged outside the target and adhered to a predetermined substrate.

For example, in a sputtering chamber 1 as shown in FIG. 2, a sputtering cathode 2 provided with a complex oxide ceramics target 3 having a target composition is sputtered in an atmosphere of Ar gas or the like to bring it to a position opposed to the target. A complex oxide thin film having a target composition is formed on the surface of the thin film forming substrate 5 mounted on the placed substrate holder 4. In the figure, 6 is a high frequency power supply for supplying electric power to the cathode 2.

Further, Japanese Patent Publication No. 6-709920 discloses a method of forming a perovskite oxide thin film of a target composition by providing two targets and periodically moving a substrate on the targets.

[0007]

A conventional method for forming a complex oxide thin film using a sputtering method is that when a complex oxide thin film is formed on a substrate having a certain area or more, it is formed. In addition, the film thickness uniformity and film composition uniformity of the thin film were insufficient, and there was a problem in practical use.

When a thin film is formed by this sputtering method, the cause of the film thickness distribution is that the atomic angle substance emitted from the sputtering gate has an emission angle distribution. Therefore, from the geometrical positional relationship between the target and the substrate, It can be mentioned that position dependence occurs in the amount of released atomic substances that enter the substrate.

In particular, when a composite oxide thin film is formed, for example, when a ceramic target having the same composition as the target thin film is used, the emission angle distribution when released from the ceramic target differs for each constituent atom of the composite oxide. Therefore, a non-uniform distribution occurs in both the normal film thickness and the film composition.

A further problem is a composition non-uniformity phenomenon due to re-sputtering of the film composition after adhering to the substrate. This is a phenomenon that an element with a high vapor pressure in the thin film once attached to the substrate is impacted by the plasma in the sputtering chamber during the sputtering film formation, and selectively ejects again. Has a density distribution, resulting in a non-uniform composition distribution in the formed thin film. This non-uniform composition phenomenon due to re-sputtering becomes a serious problem when the substrate temperature during film formation is high.

As described above, it is theoretically difficult to form a complex oxide thin film with a uniform film thickness and a uniform composition by the sputtering method.

[0012]

The inventors of the present invention are, in principle, unavoidable in non-uniformity of film thickness and composition distribution when forming a complex oxide thin film by a sputtering method in a film forming technique using a sputtering phenomenon. In view of this, it proposes a method for improving these problems.

That is, according to the present invention, in the method for forming a composite oxide thin film by the sputtering method, at least a plurality of sputtering cathodes to which the sputtering power is independently supplied are provided in the same film forming chamber, and the substrate is moved on each cathode. Using a film forming device to form a thin film on top, each cathode is equipped with a target containing at least a part of the metal element of the target complex oxide, and each cathode is independently supplied with power to perform simultaneous sputtering. Provided is a method for producing a complex oxide thin film, characterized in that a film composition correction device having an opening having a specific shape is used for each cathode.

Here, the complex oxide thin film is, for example, a ferroelectric substance such as lead zirconate titanate (PZT), bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ), barium titanate (B).
aTiO ₃ ), lead germanate (Pb ₅ Ge ₃ O ₁₁ ), SB
Thin films such as tungsten bronze type ferroelectrics such as N, solid solutions of barium titanate and strontium titanate ((Ba, Sr) TiO ₃ ), which are high dielectric constant materials, lead lanthanum zirconate titanate (PLZT), etc. Examples include thin films.

The opening in the film composition correction apparatus used in the present invention has a specific shape experimentally determined by factors such as the geometrical configuration of the sputtering apparatus used, the target composition and manufacturing method, and the sputtering conditions. Have. For example, in a sputtering device in which a plurality of disk-shaped targets are arranged on the circumference, when forming a lead zirconate titanate thin film by a method of orbiting a substrate on each target, the film pressure distribution of the formed thin film, the composition distribution When the shape of the opening is selected so as to be uniform, the shape of the compound trapezoid having a wide outer peripheral portion is preferable. In addition to the complex trapezoidal shape, a film correction device having an opening such as a gourd shape is also used.

[0016]

According to the method for producing a complex oxide thin film by the sputtering method of the present invention, an element which is likely to cause a compositional non-uniform distribution in a target complex oxide is preliminarily treated as a target independent of a target having a main composition. Prepare and arrange in the same sputtering chamber so that simultaneous sputtering is possible. The substrate on which the thin film is formed is mounted on a substrate holder that periodically passes over the plurality of targets.

At this time, an opening is formed on the target of the element which is likely to cause the non-uniform composition distribution so as to cancel the position dependence of the amount of the atomic substance emitted from the target incident on the substrate holder and adhering to the substrate. A plate-shaped film composition correction device is installed.

Since the sputtered atomic substances are incident and deposited on the substrate mounted on the substrate holder so as not to generate a composition non-uniform distribution by the film composition correction device, there is no composition non-uniform distribution. A composite oxide thin film can be formed.

Further, by optimizing the openings of the composition compensating device so as not to cause non-uniform distribution of film thickness, the film thickness distribution,
A large-area complex oxide thin film having a uniform film composition distribution can be easily formed.

[0020]

The present invention will be described in detail below with reference to the drawings.

(Embodiment 1) FIG. 1 is a conceptual diagram of a sputtering apparatus used in the embodiment.

Inside the sputtering chamber 16, three sputtering cathodes 7, 8 and 9 are arranged on the same circumference, and independent high frequency power supplies 13, 14 and 15 are connected to the respective cathodes.

The substrate 18 is mounted on a substrate holder 17 which rotates concentrically with the circumference on which these cathodes are arranged and passes while rotating on each cathode.

A disk-shaped lead oxide target 10 having a diameter of 10 cm is attached to the first cathode 7, and a second cathode 8 is attached.
Similarly, a disk-shaped titanium oxide target 11 having a diameter of 10 cm is mounted on the third cathode 9, and a disk-shaped zirconium oxide target 12 having a diameter of 10 cm is mounted on the third cathode 9.

Immediately above each target is a film composition correction device 19 whose opening is adjusted so that the atomic substance emitted from the target is uniformly incident on the substrate. In order to avoid complexity of the drawing, FIG. 2 illustrates only the film composition correction device 19 arranged on the lead oxide target 10, and the film composition correction device arranged on the titanium oxide target 11 and the zirconium oxide target 12 is illustrated. The device is omitted.

FIG. 3 (a) is a conceptual view of the film composition correction apparatus as viewed from above the target, and FIG. 3 (b) is a conceptual view showing a cross section taken along the line AA 'in FIG. 3 (a). Is. In the figure, 31 and 33 are film composition correction devices, and 32 and 34, respectively.
Is a sputtering target, and 35 is a sputtering cathode. The opening of the film composition correction device arranged on each cathode is optimized according to each target composition and sputtering conditions. For example, FIG.
One having a complex trapezoidal opening as shown in (a), or one having a gourd-shaped opening depending on the target composition and sputtering conditions is used.

First, a 4-inch Si wafer is used as the substrate 18.
After mounting on the substrate holder 17, use an exhaust device to make 10 ^-4.
After exhausting to a vacuum degree of about Pa, oxygen is added to Ar gas to 20
% Mixed sputtering gas was introduced so that the pressure in the vacuum chamber was 0.5 Pa. Next, high-frequency power of 40 W is applied to the first cathode 7, 240 W to the second cathode 8, and 800 W to the third cathode 9, respectively.
A sputtering discharge was generated.

In this state, the substrate holder was rotated at a rotation speed of about 5 rpm, a shutter (not shown) was opened, and a lead zirconate titanate thin film was deposited on the substrate 18.

FIGS. 4 (a) and 4 (b) show the distribution of the adhesion weight and the film composition ratio of the lead zirconate titanate thin film formed at this time for each film constituent element. The horizontal axis of the graph indicates the distance from the substrate center of the Si substrate. As is clear from the graph, a thin film having a uniform film composition ratio and a deposited weight, that is, a uniform film thickness is formed in a radius of 40 mm or more.

FIG. 2 is a conceptual diagram of a sputtering apparatus used for forming a lead zirconate titanate thin film in order to compare the present invention with the prior art. In FIGS. 5A and 5B, the apparatus of FIG. 2 is used, a disc-shaped lead zirconate titanate sintered body having a diameter of 10 cm is mounted as a target, and a 4-inch S
The attached weight distribution and film composition ratio distribution according to the film constituent element of the formed thin film when the lead zirconate titanate thin film is formed on the i substrate are shown.

As is clear from FIGS. 5 (a) and 5 (b),
Both the adhesion weight and the film composition ratio show a remarkably non-uniform distribution, and the part that can be used as a uniform composition and a uniform film thickness is only a very small area in the center of the substrate. The lead film has problems in practical production yield and high cost.

FIG. 6 was also formed when the present invention was compared with the prior art, except that the film composition correction device was excluded from the sputtering device of FIG. 1 and the other conditions were the same as those of this embodiment. FIG. 2 shows the distribution of the weight of the attached lead zirconate titanate thin film and the distribution of the film composition ratio by film constituent element. Since the substrate holder is rotated at the time of film formation in this prior art example, the film composition ratio distribution is improved as compared with the prior art of FIG. 1, but it is not at all practically preferable. Further, the variation in the weight of the deposited film is extremely large, and the area that can be used as a thin film having a uniform thickness is about 1/4 of the substrate area.

As described above, the superiority of the method for producing a composite oxide thin film according to the present invention is clear from this embodiment.

(Embodiment 2) FIG. 7 is a conceptual diagram of a sputtering apparatus used in another embodiment of the present invention.

Inside the sputtering chamber 26, two sputtering cathodes 20 and 21 are arranged on the same circumference, and independent high frequency power supplies 24 and 25 are connected to the respective cathodes.

The substrate 28 is mounted on a substrate holder 27 that rotates concentrically with the circumference on which the cathodes are arranged and passes while rotating on each cathode.

A disk-shaped bismuth oxide target 22 having a diameter of 10 cm is mounted on the first cathode 20, and a disk-shaped titanium oxide target 23 also having a diameter of 10 cm is mounted on the second cathode 21.

Immediately above each target, there are arranged film composition correction devices 29 and 30 whose openings are adjusted so that atomic substances emitted from the target are uniformly incident on the substrate.

First, a 4-inch Si wafer is used as the substrate 28.
After mounting on the substrate holder 27, 10 ^{-4 with} an exhaust device
After exhausting to a vacuum degree of about Pa, oxygen is added to Ar gas at 50
% Mixed sputtering gas was introduced so that the pressure in the vacuum chamber was 0.3 Pa. Next, 80 W of high frequency power was applied to the first cathode 20 and 800 W of high frequency power to the second cathode 21, respectively, to generate sputtering discharge.

In this state, the substrate holder was rotated at a rotation speed of about 5 rpm, a shutter (not shown) was opened, and a bismuth titanate thin film was deposited on the substrate 28.

FIGS. 8 (a) and 8 (b) show the weight distribution and the film composition ratio of the bismuth titanate thin film formed at this time for each film constituent element. As is clear from the graph, a thin film having a uniform film composition ratio and a deposited weight, that is, a uniform film thickness, is formed in a radius of 40 mm or more by the manufacturing method of the present invention.

In order to compare the present invention with the prior art, FIG. 9 shows the bismuth titanate when all the film composition correction devices are excluded from the sputtering device of FIG. 7 and the other conditions are the same as those of this embodiment. The distribution of the deposition weight of each thin film constituent element and the film composition ratio are shown. The bismuth titanate thin film formed in this example of the prior art exhibits a remarkably non-uniform film composition distribution and a film adhesion weight distribution, and is significantly less practical than the bismuth titanate thin film according to the method of the present invention.

The superiority of the method for producing a composite oxide thin film according to the present invention is apparent from the above-mentioned embodiment.

[0044]

By using the method for producing a composite oxide thin film of the present invention, it becomes possible to produce a complex oxide thin film having a uniform composition and a uniform film thickness, which has been difficult in the past, in a large area. Therefore, if the manufacturing method of the present invention is used, the manufacturing cost of the electric device using the composite oxide thin film is reduced and the manufacturing yield is improved,
Further, it becomes possible to make the characteristics of the manufactured electric device uniform.

[0045]

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a sputtering apparatus used in Example 1 of the present invention.

FIG. 2 is a conceptual diagram of a high-frequency sputtering device according to a conventional technique.

3A and 3B are conceptual diagrams of a film composition correction apparatus used in Example 1 of the present invention.

FIG. 4 (a) is a deposition weight distribution by constituent element of the lead zirconate titanate thin film formed in Example 1 of the present invention and (b).
Film composition ratio distribution

FIG. 5: (a) Adhesion weight distribution by constituent element and (b) film composition ratio distribution of a lead zirconate titanate thin film formed by a conventional technique.

FIG. 6 is (a) an attachment weight distribution by constituent element and (b) a film composition ratio distribution of a lead zirconate titanate thin film formed by a conventional technique.

FIG. 7 is a conceptual diagram of a sputtering apparatus used in Example 2 of the present invention.

FIG. 8 (a) Adhesion weight distribution by constituent element and (b) film composition ratio distribution of the bismuth titanate thin film formed in Example 2 of the present invention.

9A and 9B are distribution diagrams of the deposition weights of the bismuth titanate thin films formed by the prior art by constituent element and FIG.

[Explanation of symbols]

 1. Sputtering chamber 2. Sputtering cathode 3. 3. Lead zirconate titanate sintered compact target 4. Substrate holder 5. Si substrate 6. High frequency power supply 7. First sputtering cathode 8. Second sputtering cathode 9. Third sputtering cathode 10. Lead oxide target 11. Titanium oxide target 12. Zirconium oxide target 13. High frequency power supply 14. High frequency power supply 15. High frequency power supply 16. Sputtering chamber 17. Substrate holder 18. Si substrate 19. Film composition correction device 20. First sputtering cathode 21. Second sputtering cathode 22. Bismuth oxide target 23. Titanium oxide target 24. High frequency power supply 25. High frequency power supply 26. Sputtering chamber 27. Substrate holder 28. Si substrate 29. Device for correcting film composition used for bismuth oxide target 30. Film composition correction device used for titanium oxide target 31. Film composition correction device 32. Sputtering target 33. Film composition correction device 34. Sputtering target 35. Sputtering cathode

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 21/316 H01L 21/316 Y 41/24 H05B 33/10 // H05B 33/10 33/22 33/22 H01L 41/22 A

Claims (1)

[Claims] 1. A sputtering apparatus in which a plurality of sputtering cathodes are provided in the same film forming chamber, and a target containing at least a part of a metal element of a target complex oxide is attached to each cathode, and each sputtering cathode is used. In a method for producing a complex oxide thin film, in which electric power is independently supplied to each of the substrates and simultaneous sputtering is performed to form a thin film on a substrate moving on each cathode, each cathode has a film composition correction device having an opening. A method for producing a composite oxide thin film, which is characterized.