Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Reexamination Certificate
2002-05-01
2004-06-08
Williams, Alexander Oscar (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S758000, C257S759000, C257S700000, C257S701000, C257S015000, C257S018000, C257S020000, C257S022000, C257S027000, C257S750000, C257S753000
Reexamination Certificate
active
06747357
ABSTRACT:
This application claims priority under 35 U.S.C. §§ 119 and/or 365 to Application No 2002-9767 filed in Korea on Feb. 23, 2002; the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dielectric device having a multi-layer oxide artificial lattice and a method for fabricating the same, and more particularly to a dielectric device having a multi-layer oxide artificial lattice formed by depositing atomic unit layers or unit lattice layers having a specific alignment so as to improve tunability of a microwave voltage tunable device and dielectric constant of a capacitor for memory and a gate oxide for MOS devices, and a method for fabricating the same.
2. Description of the Related Art
Recently, semiconductor technologies, which are representative technology of late twenty century, make great stride so that the semiconductor technologies become a symbolic meaning of a development of scientific technique. The high speed and large capacitance of semiconductor devices with regard to a CPU and a memory thereof are rapidly achieved. The semiconductor memory is highly integrated above 1 Giga byte (GB) and a high-speed DRAM capable of inputting/outputting data at a high speed of few nano seconds is suggested (Hitachi, Ltd., (TSE:6501) and Elpida Memory, Inc., Japan, Sep., 26, 2001/Kang, tae won, physics and high technology 9 (7/8), 33 (2000)). In order to achieve the high speed and large capacitance of the semiconductor device required for recent information telecommunication society in which large amount of information is communicated, studies regarding to new semiconductor processes and material have been carried out. The studying object is metal oxide. Metal oxide has various crystal structures, so it has various physical features. Accordingly, metal oxide can provide various functions, which cannot be achieved from conventional semiconductor materials and insulation materials. That is, due to its high dielectric constant, metal oxide is widely utilized in a large scaled integration memory, a non-volatile memory, a microwave dielectric for mobile telecommunication part, a high-temperature superconductor, a sensor using a magnetoresistance effect, and an electrode of semiconductor/electronic devices using the conductivity, so it is recently called as “oxide electronic engineering” (P. A. Cox, Transition Metal Oxide (Clarendon, Oxford, 1992)).
The development of oxide materials having the high dielectric constant is a main point for the large scaled integration, so the study thereof has been actively carried out. In the future capacitor industry, the next-generation materials having an effective equivalent thickness below 1 nm is required, and a gate insulation film of CMOS (gate size 70 nm grade) also requires the effective equivalent thickness below 1 nm. Among oxide dielectrics, ferroelectric oxide has relatively high dielectric constant, so it is spotlighted and studied in the world as materials for achieving the large scaled integration above Giga grade in DRAM (R. A. Mckee et al., Phys. Rev. Lett. 81, 3014 (1998)/D. E. Kotech, Integr. Ferroelectrics, 16, 1 (1997)). In addition, in order to achieve the large scaled integration and high-speed of CMOS, which is a base structure of a semiconductor, the thickness of a gate insulation film is required to be set below 2 nm. However, as the thickness of the insulation film becomes thin, the quantum effect, such as tunneling effect of electrons, occurs. In order to solve the above problem, ferroelectric materials having the high dielectric constant was recently used as the gate insulation film. Among oxides having the high dielectric constant, oxide having peroveskite structure has been spotlighted. Peroveskite oxide has various physical properties, such as the high dielectric constant, ferroelectric, piezoelectric, and electro-optical properties, so it is widely utilized in non-volatile semiconductor memories, piezoelectric devices, optical telecommunication devices, and superconductive devices, and studies utilizing the peroveskite oxide in the devices has been widely carried out (M. Hong et al., Science, 1897 (1999)). The peroveskite oxide has a simple structure of ABO
3
and mainly forms a cubic structure, so the physical properties thereof are easily understood so that it is utilized in various applications. For example, BaTiO
3
, SrTiO
3
, (Ba, Sr)TiO
3
, and (Pb, Zr)TiO
3
are used as the peroveskite oxide. However, various electronic and optical devices using the ferroelectrics adopt the above materials existing in nature. Accordingly, the critical phenomenon, which is a basic limit of the ferroelectrics, cannot be overcome. That is, the high-integration and large scaled integration of devices and the nano-scale of materials are limited so that a highly-functional nano device cannot be obtained. To achieve the nano device, besides a conventional material to be used, a dielectric artificial material is required (K. Ueda, H. Tabata and T. Kawai, Science 280, 1064 (1998)). The manufacturing of an oxide artificial lattice is recently studied for obtaining a new superconductive material or a ferromagnetic spin alignment, which cannot be obtained from nature. Accordingly, the oxide artificial lattice becomes a new advanced material allowing the nano-scaled thin film growing technology and materials design (H. Tabata, Tanaka and T. Kawai, Appl. Phys. Lett. 65, 1970 (1994)/E. D. Specht et al., Phys. Rev. Lett. 80, 4317 (1998)).
On the other hand, the recently used telecommunication device, that is a microwave voltage tunable device such as a phase shifter, a tunable filter, and a steerable antenna, requires a high tunability. In case of a conventional microwave voltage tunable device, (Ba, Sr)TiO
3
is used as an insulation film formed between metal electrodes, so that a metal-insulator-metal structure is achieved. Then, an electric field of 1 MV/cm is applied to the metal electrodes, and about 74% of the tunability is obtained therefrom (“Composition-control of magnetron-sputter-deposited (BaxSr1-x)Ti1+yO
3
+Z thin films for voltage tunable device”, J. Im et al. Appl. Phys. Lett. 76. 625). In addition, when a meta-insulator-metal structure is formed by using SrTiO
3
thin films, which is an insulation film formed between metal electrodes, about 55% of the tunability is obtained from the electric filed of 1 MV/cm applied to the metal electrodes (“Effects of strain on the dielectric properties of tunable dielectric. SrTiO
3
thin films”, S. Hyun and K. Char, Appl. Phys. Lett. 79, 254).
SUMMARY OF THE INVENTION
It is an object of the present invention to manufacture a nano-scaled dielectric (may be semi-stable phase), which does not exist in nature, by forming a dielectric in nano-scale through performing deposition process of an oxide artificial lattice consisting of various atomic stacking sequence with layer-by-layer growth process to overcome the limit of materials existing in nature by growing the artificial material, thereby providing high dielectric constant to a capacitor of tera-level semiconductor memory and a gate oxide of MOS based devices, and also providing high voltage tunability to microwave tunable (or frequency agile) devices.
To achieve the above object, the present invention provides dielectric devices including a multi-layer oxide artificial lattice having a high tunability and dielectric constant and a method for manufacturing the same, wherein an oxide thin film used ma microwave voltage tunable device, dynamic random-access memory (DRAM) OR metal-oxide-semiconductor (MOS) based devices is replaced with the artificial lattice, in which dielectric materials such as BaTiO
3
(abbreviated herein as BTO) or SrTiO
3
(abbreviated herein as STO) are periodically deposited and grown, thereby compacting the size of the microwave voltage tunable device or memory, and matching with the high speed and high-frequency requirements. When the artificial lattice is formed by forcibly growing the BTO or SSTO atomic layer with l
Kim Ju-ho
Kim Leejun
Kim Young Sung
Lee Jaichan
Burns Doane Swecker & Mathis L.L.P.
Sungkyunkwan University
Williams Alexander Oscar
LandOfFree
Dielectric device having multi-layer oxide artificial... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dielectric device having multi-layer oxide artificial..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dielectric device having multi-layer oxide artificial... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3343161