Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from liquid or supercritical state – Liquid phase epitaxial growth
Reexamination Certificate
2001-06-14
2003-08-05
Hiteshew, Felisa (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from liquid or supercritical state
Liquid phase epitaxial growth
C427S252000, C438S680000, C438S681000, C438S683000, C438S685000
Reexamination Certificate
active
06602344
ABSTRACT:
Japanese Patent Application No. 2000-186529, filed on Jun. 21, 2000, and Japanese Patent Application No. 2001-178839, filed on Jun. 13, 2001, are hereby incorporated by reference in their entirety.
TECHNICAL FIELD
The present invention relates to a ceramic film and a method of manufacturing the ceramic film, a semiconductor device, and a piezoelectric device.
BACKGROUND OF THE INVENTION
As a ferroelectric film applied to semiconductor devices (ferroelectric memories (FeRAM), for example), ferroelectric films having a layered perovskite structure (BiLaTiO-based, BiTiO-based, and SrBiTaO-based ferroelectric films, for example) have been proposed. These ferroelectric films having a layered perovskite structure are generally formed by allowing crystals to grow from an amorphous state.
In the case of forming a ferroelectric film having a layered perovskite structure using this formation method, the crystal growth rate in the c-axis direction becomes lower than those in the a-axis direction and the b-axis direction due to the crystal structure of the ferroelectric film. Specifically, crystals tend to grow in the a-axis direction and the b-axis direction. Therefore, the ferroelectric film having a layered perovskite structure formed by using the above method has a rough surface morphology. Specifically, openings (holes or grooves, for example) are formed between crystals in the resulting ferroelectric film.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide a method of manufacturing a ceramic film capable of improving the surface morphology of the ceramic film.
Another objective of the present invention is to provide a ceramic film obtained by the method of manufacturing a ceramic film of the present invention.
Yet another objective of the present invention is to provide a semiconductor device and a piezoelectric device to which the ceramic film of the present invention is applied.
Method of Manufacturing Ceramic Film
(A) A first method of manufacturing a ceramic film of the present invention comprises:
a step of forming a ceramic film by crystallizing a raw material body,
wherein the raw material body includes different types of raw materials in a mixed state; and
wherein the different types of raw materials differ from one another in at least one of a crystal growth condition and a crystal growth mechanism in the crystallization of the raw materials.
The different types of raw materials differ from one another in at least one of the crystal growth condition and the crystal growth mechanism in the crystallization of the raw materials. Specifically, the raw materials are judged to be different depending on whether or not they differ from one another in at least one of the crystal growth condition and the crystal growth mechanism.
The crystal growth conditions and the crystal growth mechanism during crystallization of the raw materials include crystallization temperature, crystal nucleus formation temperature, crystal growth temperature, crystal growth rate, crystal nucleus formation rate, size of crystal nuclei, crystallization method, and the like.
In the present invention, the raw material body includes the different types of raw materials. Specifically, the raw material body includes at least two types of raw materials. The different types of raw materials differ from one another in at least one of the crystal growth condition and the crystal growth mechanism in the crystallization of the raw materials. Therefore, one of the raw materials can be crystallized prior to the other raw material, and then the other raw material can be crystallized in the openings between crystals which have been produced first by controlling various conditions, for example. Specifically, the openings between crystals produced from one of the raw materials can be filled with crystals produced from the other raw material. Therefore, the surface morphology of the ceramic film can be improved.
Moreover, the raw materials may be crystallized at the same time by controlling various conditions. For example, the crystallization temperature can be adjusted by allowing a metal element of the raw material to be replaced by other element. This enables the crystallization temperatures of the different types of raw materials to be approximately the same. The different types of raw materials can be crystallized at the same time by allowing the crystallization temperatures of the different types of raw materials to be approximately the same.
(B) A second method of manufacturing a ceramic film of the present invention comprises:
a step of forming a ceramic film by crystallizing a raw material body,
wherein the raw material body includes different types of raw materials in a mixed state; and
wherein the different types of raw materials differ from one another in crystal structures produced from the raw materials.
The different types of raw materials differ from one another in crystal structures produced from the raw materials. Specifically, the raw materials are judged to be different depending on whether or not they differ from one another in the crystal structures of the crystals obtained from the raw materials.
When the crystals obtained from the raw materials are expressed as (Bi
2
O
2
)
2+
(A
m−1
B
m
O
3m+1
)
2−
, the differences in the crystal structures of the crystals obtained from the raw materials include a difference in values for m, for example.
In the present invention, the different types of raw materials differ from one another in the crystal structure of the crystals produced from the raw materials. If they differ in the crystal structures of the crystals obtained from the raw materials, they also differ in the crystal growth conditions and the crystal growth mechanism of the raw materials. Therefore, the same effects as in the first method of manufacturing a ceramic film of the present invention can be obtained.
(C) A third method of manufacturing a ceramic film of the present invention comprises:
a step of forming a ceramic film by crystallizing a raw material body,
wherein the raw material body includes different types of raw materials in a mixed state; and
wherein the different types of raw materials are individually crystallized at least at an initial stage of crystallization.
The different types of raw materials are individually crystallized at least at an initial stage of crystallization.
In the third method of manufacturing a ceramic film of the present invention, the different types of raw materials are individually crystallized at least at an initial stage of crystallization. Therefore, crystals produced from one of the raw materials can be allowed to grow in the openings between crystals produced from the other raw material. As a result, formation of openings between the crystals can be prevented, whereby the surface morphology is improved.
The first to third methods of manufacturing a ceramic film of the present invention have at least any one of the following features.
(a) The ceramic film may be a ferroelectric film.
(b) The ceramic film may be a paraelectric film.
(c) The ceramic film may include ferroelectric and paraelectric materials in a mixed state.
(d) At least two of the different types of raw materials may differ from each other in a crystallization temperature in the crystallization of the raw materials.
(e) At least two of the different types of raw materials may differ from each other in a crystal nucleus formation temperature in the crystallization of the raw materials.
(f) At least two of the different types of raw materials may differ from each other in a crystal growth temperature in the crystallization of the raw materials.
(g) At least two of the different types of raw materials may differ from each other in a crystal growth rate in the crystallization of the raw materials.
(h) At least two of the different types of raw materials may differ from each other in a crystal nucleus formation rate in the crystallization of the raw materials.
(i) At least two of the different types of raw materials may differ from each other in the
Furuyama Koichi
Natori Eiji
Tasaki Yuzo
Hiteshew Felisa
Oliff & Berridge PLC.
Seiko Epson Corporation
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