1998 Fiscal Year Final Research Report Summary
Fabrication of Ferroelectric Thin Films on Large Size Wafers at High Growth Rate by Metal Organic Chemical Vapor Deposition and Their Application to Memory
| Project/Area Number |
09555099
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 展開研究 |
|---|
| Research Field |
Electronic materials/Electric materials
|
|---|
| Research Institution | NARA INSTITUTE OF SCIENCE AND TECHNOLOGY (1998)
Kyoto University (1997) |
|---|
Principal Investigator |
SHIOSAKI Tadashi Nara Institute of Science and Technology, Material Science, Professor, 物質創成科学研究科, 教授 (80026153)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
ONISHI Shigeo SHARP Corporation, VLSI Development Laboratories, Development Department II,Seni, 超LSI開発研究所, 主任研究員
NAKATANI Kenichi Corporation of Amaya seisakusyo, 技術第一部, 開発係長
SHIMIZU Masaru Himeji Institute of Technology, Department of Electronics, Associate Professor, 工学部, 助教授 (30154305)
OKAMURA Soichirou Nara Institute of Science and Technology, Material Science, Associate Professor, 物質創成科学研究科, 助教授 (60224060)
|
|---|
| Project Period (FY) |
1997 – 1998
|
| Keywords | ferroelectric thin film / FeRAM / Pb (Zr_2Ti) O_3 / MOCVD / Ir electrode / source purity / size effect / space charge |
|---|
| Research Abstract |
Pb-based ferroelectric thin films such as Pb(Zr, Ti)O3 (PZT) were fabricated on large size silicon wafers at high growth rate by metalorganic chemical vapor deposition (MOCVD) and their properties were evaluated for the applications to memory devices such as FeRAM.Homogeneous PZT thin films with a composition distribution of +- 1.1% and a thickness distribution of +-1.2% were formed on 6-8 inch wafers. However growth rate was 4-15 nm/min. It is not enough for mass production and improvement of source delivery system. We have found that thin Ir bottom electrodes (23 nm) had little effect on improvement of ferroelectric properties of PZT thin films although relatively thick Ir bottom electrodes significantly improved the properties. It seems that Pb-Ir amorphous layer formed at the interface between the PZT films and the Ir electrodes suppress the diffusion of Pb atoms into the electrodes. IrO_2/Ir/PZT/Ir/IrO_2 capacitor exhibited fatigue-free properties. We have also found that purity of metalorganic sources using in MOCVD had some effect on the electrical properties of PZT thin films. PZT thin films fabricated by using high purity sources (99.9999%) were better in fatigue properties, leakage current and breakdown voltage than those fabricated by using low purity ones (99.995%). We have succeeded in the control of grain size of PZT thin films with same thickness by changing the grain size of bottom Ir electrodes. It is found that remanent polarization of the PZT thin films begin to decrease with decreasing of grain size from about 150 nm. Some defects in the films and their entrapment at the interface or boundary generate space charge distribution. We have concluded that this space charge distribution cause the shift of hysteresis loops and domain pinning.
|
