JPH0781183B2 - Method for producing oriented metal thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to electrodes for imaging devices, pyroelectric devices, piezoelectric devices, light-emitting devices, light-receiving devices, electrodes for various sensors, and orientation for application to the production of electronic circuits. The present invention relates to a method for manufacturing a metal thin film.

Structure of Conventional Example and Problems Thereof In recent years, thin-film electronic materials have been actively developed. In particular, the development of oriented thin films is urgently required in order to effectively utilize a specific property of a crystal such as a pyroelectric effect.
For example, a case where a thin film infrared detector is manufactured using a perovskite type ferroelectric such as lead titanate or barium titanate will be examined. Generally, the performance of a pyroelectric infrared detector is represented by (dpr / dT) (1 / ε). here,
pr represents the magnitude of spontaneous polarization of the sensor material, T represents temperature, and ε represents the dielectric constant of the sensor material. Therefore, a material with a large pyroelectric coefficient (dpr / dT) and a small dielectric constant ε has good performance. In the perovskite-type ferroelectric substance as described above, the polarization axis is the C-axis, and the permittivity in the C-axis direction is about half of the permittivity in the direction perpendicular to the C-axis, and its value is as small as about 100. C
If a perovskite type ferroelectric thin film oriented in the axial direction is produced, it can be an infrared detector with extremely good performance.

On the other hand, a metal thin film such as gold or platinum, which has been conventionally produced by a vapor deposition method or a sputtering method, has been used as a base electrode which becomes a substrate when producing such a pyroelectric infrared detector. However, since the gold thin film and the platinum thin film produced by the usual method are polycrystals, the ferroelectric thin film grown on them is not oriented and becomes polycrystal,
Its electrical characteristics also deteriorate. As described above, the polycrystalline electrode is disadvantageous for the preparation of the oriented ferroelectric thin film, which is a big drawback.

On the other hand, the case of using (100) -oriented platinum or gold is as follows.

The a-axis lattice constant of platinum or gold is very close to the a-axis lattice constant of perovskite compounds such as PbTiO ₃ . Therefore, it is possible to grow a perovskite compound such as PbTiO ₃ having a (100) plane parallel to the substrate by so-called epitaxial growth on a substrate on which a platinum or gold thin film with a-axis orientation or (100) orientation is grown. Become. PbTiO ₃ is a ferroelectric substance having a phase transition point at 490 ° C. and has an equiaxed crystal structure at a temperature above the phase transition point and a tetragonal system at a temperature below the phase transition point.

It is known that when cooling from this equiaxed system temperature range (high temperature) to the tetragonal system temperature range (low temperature), the a-axis of the crystal contracts and the c-axis rapidly expands.

Therefore, crystal growth of PbTiO ₃ on (100) -oriented platinum or gold (about 600 ° C) and subsequent cooling are performed so that the c-axis of the crystal is aligned perpendicular to the substrate when passing through the phase transition point. Is more energetically dominant, and as a result, a c-axis oriented PbTiO ₃ thin film is obtained.

In the present invention, the (100) -oriented platinum or gold thin film controls the orientation of the compound to be laminated on this thin film, so that the orientation of the compound to be laminated can be controlled regardless of the type of substrate.

OBJECT OF THE INVENTION The present invention eliminates the drawbacks of the above polycrystalline thin film electrode,
In particular, it is a novel (100-oriented) gold or platinum thin film electrode manufacturing method characterized in that a large-area oriented thin film can be easily produced, and an oriented gold or platinum thin film obtained thereby.

According to the present invention, when a gold thin film or a platinum thin film is formed by using a sputtering method, gold or platinum is sputtered on a metal oxide single crystal substrate in an argon gas atmosphere containing 5% or more oxygen by volume. And gold or platinum (10
It is characterized in that it is grown so that the (0) plane is parallel to the substrate, whereby a gold or platinum thin film oriented in the <100> direction is formed on the {100} plane of single crystal magnesium oxide. Easily obtained.

In the film formation by the sputtering method, the raw material particles pass through the plasma and fly onto the substrate. At this time, when plasma is generated in an atmosphere containing oxygen, activated oxygen atoms or molecules are generated and react with the raw material elements to form an oxidation precursor, which reaches the substrate.

Here, as the substrate, for example, (100) MgO or (100) S
When a single crystal substrate such as rTiO ₃ is used, the oxides have a high chemical affinity, so that the precursors of this oxide are arranged according to the atomic arrangement of the substrate.

On the other hand, noble metal oxides such as platinum or gold do not exist stably, so they decompose into oxygen and platinum atoms or gold atoms on the substrate, and the (100) plane becomes parallel to the substrate plane, reflecting the atomic arrangement of the substrate. The arrayed platinum or gold thin film grows epitaxially.

However, when oxygen-free plasma is used, such oxide precursors are not formed and reach the substrate as platinum or gold atoms. In this case, even if the substrate is an oxide single crystal, there is no chemical affinity between the platinum atom or gold atom and the oxide of the substrate, and the close-packed surface of platinum or gold is (111). Arranged parallel to the board surface,
A platinum or gold thin film arranged on the (100) plane cannot be obtained.

Description of Examples The thin film was produced by a high frequency magnetron sputtering method. A magnesium oxide single crystal plate cleaved along the {100} plane was fixed on a heater to form a substrate. Board temperature is 70
It is 0 ° C. The atmosphere gas used was a mixture of argon gas and oxygen. The mixing ratio is 0% by volume of oxygen.
It was changed within the range of 50%. In all cases, the total pressure is 0.5p
It was a. The sputtered film deposition rate is 15 to 50Å / min. The obtained thin film was subjected to X-ray diffraction and electron diffraction to identify crystals and determine the orientation. X-ray diffraction patterns of gold and platinum are shown in FIGS. FIG. 2 shows the relationship between the ratio of the (200) X-ray diffraction intensity to the other platinum diffraction intensity and the oxygen mixing ratio in the case of platinum. As is clear from these figures, by mixing oxygen into the atmospheric gas, a <100> -oriented thin film of gold and platinum can be obtained. Further, in the electron beam diffraction images of the <100> -oriented thin films of gold and platinum, each diffraction point was separated and appeared as spots, which confirmed that epitaxial growth was performed on MgO. In addition, the substrate temperature is 400 ℃
From 700 to 700 ° C, by sputtering in an argon atmosphere containing 5% or more of oxygen,
It was possible to reproducibly obtain a 100> oriented thin film of gold or platinum.

On the gold and platinum thin films produced as described above, PbTiO ₃ thin films, which are perovskite type ferroelectrics and are promising as an infrared detector, were prepared. As a result, gold,
In each case of platinum, a very thin film of PbTiO ₃ oriented in the C-axis direction was obtained. This was first obtained by using a gold or platinum thin film oriented in the <100> direction.

EFFECTS OF THE INVENTION As is clear from the above results, according to the method for producing a gold or platinum thin film of the present invention, a <100> -oriented thin film can be produced stably and with good reproducibility. In addition, these oriented thin films are extremely effective for producing single crystal thin films and C-axis oriented films.

[Brief description of drawings]

1 (a) and 1 (b) are X-ray diffraction patterns of gold and platinum thin films prepared by the method of the present invention, respectively. FIG. 2 is a graph showing oxygen mixing ratio in argon gas and platinum (200). ) A diagram showing a relationship between a ratio of diffraction intensity to another diffraction intensity.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H01L 41/22 (72) Inventor Ichiro Ueda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Hiroshi Ouchi 1006, Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-46-5213 (JP, A) JP-A-52-131727 (JP, A) JP-B Sho-49 -1134 (JP, B1) JP-B-49-45464 (JP, B1)

Claims (1)

[Claims] 1. Gold or platinum is sputtered on a metal oxide single crystal substrate in an argon gas atmosphere containing 5% or more by volume of oxygen so that the (100) plane of gold or platinum is parallel to the substrate. 1. A method for producing an oriented metal thin film, which comprises growing the film to a thin film.