JPH0417659A - Production of thin oxide film - Google Patents

Abstract

PURPOSE:To produce a thin oxide film having excellent crystallinity and orientational property with superior reproducibility by applying etching to the surface of a substrate in an oxygen-containing atmosphere and then forming a thin oxide film. CONSTITUTION:A substrate of MgO, etc., is etched by means of sputtering in an atmospheric gas, such as oxygen-containing Ar gas. Subsequently, a thin oxide film, such as thin high dielectric film, is grown by a magnetron sputtering method, etc. By this method, the adhesive strength of the thin film can be increased and the occurrence of peeling can be perfectly prevented, and the high- efficiency thin oxide film can be attained in superior yield.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing an oxide thin film used in pyroelectric infrared detection elements, piezoelectric elements, electro-optical elements, nonvolatile memories, and the like.

BACKGROUND ART In order to produce an oriented thin film or an epitaxial thin film of an oxide, it is required that the thin film and the substrate material be similar in terms of crystal structure, symmetry, interatomic distance, etc.

In particular, epitaxial films and alignment films of oxide ferroelectrics having a perovskite structure are made of sapphire, M g O,
It is often produced using an oxide crystal such as S r TiOa as a substrate.

For example, a thin film element that uses pyroelectric current generated in the direction of the orientation axis by providing an electrode on a plane perpendicular to the orientation axis of a lead titanate thin film oriented in the <001> direction has a pyroelectric coefficient larger than that of a non-oriented one. reported at the 30th Spring Applied Physics Society (Proceedings 7p-Z-2) that the dielectric constant is low and the figure of merit of pyroelectric materials (pyroelectric coefficient/permittivity) is large.

The <001> oriented lead titanate thin film is grown on a (100) separated MgO single crystal substrate.

The characteristics of a thin film device formed on a substrate are largely influenced by the characteristics of the substrate itself and the interaction between the thin film and the substrate. Therefore, configurations have been proposed for pyroelectric infrared sensors and piezoelectric vibrators in which the main part of the substrate is removed. Furthermore, an integrated device has been proposed in which an epitaxial thin film is formed after growing an intermediate layer on a semiconductor substrate.

Problems to be Solved by the Invention Oxide single-crystal substrates are cut out from single-crystal blocks as thin pieces, and their surfaces are polished to be used as substrates for various devices. After polishing, the crystallinity of the surface of the substrate was poor, and the crystallinity and orientation of the thin film formed on the substrate were not good. Furthermore, the adhesion of the thin film was weak, and peeling of the thin film also occurred.

Means for Solving the Problems Production of an oxide thin film, which comprises etching the surface of the substrate in an oxygen-containing atmosphere before forming the oxide thin film on a substrate. Method.

Effect: By the production method as described above, an oxide thin film with good crystallinity and orientation can be produced with good reproducibility. In addition, the adhesion of the thin film is enhanced, there is no peeling of the thin film, and a high-performance oxide thin film with good yield can be realized.

Example An embodiment of the present invention will be described in detail below.

(100) mirror-polished MgO single crystal, A
Sputter etching was performed for 40 minutes in an atmospheric gas in which 02 was mixed with r gas and the total pressure was 2 Pa.

Using this MgO single crystal as a substrate, a ferroelectric thin film P ba
, q L ao, + T Ia, qqs 03 (P
LT) was grown to a thickness of about 3 μm by high-frequency magnetron sputtering. A mixed gas of Ar (90%) and 02 (10%) was used, the gas pressure was IPa, the substrate temperature was 600 °C, and the sputtering target was (0,8P bo, qLao, 1T1o, q, so8+
0.2P bo) powder.

The crystal orientation of the obtained thin film was determined by X-ray diffraction.

FIG. 1 shows an X-ray diffraction pattern of a PLT thin film formed on a sputter-etched MgO substrate.

Only the (001) and (100) reflections of the perovskite structure and their higher-order reflections are observed. Also, since the intensity of the (001) reflection is significantly larger than that of (100), C
It can be seen that this is an axially oriented film.

The composition was analyzed using an X-ray microanalyzer and was found to be almost the same as the target.

FIG. 2 shows the influence of the sputter etching treatment of the MgO substrate on the half-width Δθ of the (001) reflection of the PLT thin film and the C-axis orientation rate α. The atmospheric gas was Ar (97%
) and 02 (3%). Here, the C-axis orientation rate α is 6α-1(001)/+1(00
1)+I(100)+1(001) and 1(100) are
tl, the reflection intensity of the (001) plane and the (100) plane, respectively.

By performing the sputter etching process in a mixed gas of Ar and 02, the half-width Δθ becomes smaller, that is, the crystallinity improves, the C-axis orientation rate increases, and their variations are greatly reduced. It became clear that

In order to clarify the cause of this, the crystalline state of the surface of MgO was investigated. The as-polished MgO and the sputter-etched MgO under these conditions were observed by electron beam diffraction (RHEED).

As a result, it was found that the as-polished specimen was in an amorphous state, and the sputter-etched specimen had a bathoturn on a clean spot, indicating that crystal planes were exposed.

Note that the sample subjected to the sputtering niche treatment in an atmospheric gas containing only Ar was not only inferior in crystallinity and orientation compared to the sample treated under these conditions, but also had peeling of the PLTI film. This effect was produced when 02 was about 3%.

Next, the sample sputter-etched in the Ar and 02 atmosphere gases was left in the bell jar without being taken out to the outside air, and the direction of the sputtering power source was reversed.
A film was formed. The sputtering conditions are as described above.

In these samples, the adhesion of the PLT thin film to the MgO substrate was increased, and there was no peeling of the thin film.

Furthermore, when extracting electrical signals from the PLT thin film, the PLT
An electrode thin film is required between the ¥S film and the MgO substrate. After patterning this electrode thin film using photolithography, when a PLT thin film is grown on this electrode thin film, carbonate groups etc. are generated on the exposed surface of the MgO substrate.
Crystallinity and orientation deteriorate, and peeling of the PLTI film occurs. At this time, the substrate temperature is temporarily maintained at 600°C or higher,
By removing carbonate groups etc. from the surface of the substrate,
Crystallinity and orientation have been improved, and peeling of the PLT thin film has been drastically reduced.

Effects of the Invention According to the production method of the present invention, an oxide thin film with good crystallinity and orientation can be produced with good reproducibility. In addition, the adhesion of the thin film is enhanced, there is no peeling of the thin film, and a high-performance oxide thin film with good yield can be realized.

[Brief explanation of the drawing]

FIG. 1 is an X-ray diffraction pattern diagram of an oxide thin film according to an embodiment of the present invention, and FIG. 2 is a diagram showing the half-width Δθ of (001) reflection and the C-axis orientation rate α of an oxide thin film according to an embodiment of the present invention. FIG. 3 is an explanatory diagram showing the influence of sputter etching treatment in FIG. Name of agent: Patent attorney Shigetaka Awano Figure 2 θ <de>)

Claims (4)

[Claims] (1) A method for producing an oxide thin film, which comprises etching the surface of a substrate in an oxygen-containing atmosphere before forming the oxide thin film. (2) When producing an oxide thin film having a perovskite structure by sputtering on a MgO (100) plane substrate, the surface of the MgO substrate is etched by sputtering in a mixed gas of Ar and O_2. The method for producing an oxide thin film according to claim 1, characterized in that: (3) Before forming the oxide thin film, the surface of the substrate is etched by sputtering in a mixed atmosphere of Ar and O_2, and then the film is formed without taking out the substrate into the air. Method for manufacturing thin films. (4) Before forming the oxide thin film, lower the substrate temperature to 60°C.
A method for producing an oxide thin film, which comprises maintaining the temperature at 0° C. or higher to remove carbonate groups and the like from the surface of the substrate.