1
Memory Effect of Sol-Gel Derived V-doped SrZrO
3Thin Films
Chih-Yi Liu, Chun-Chieh Chuang, Jian-Shian Chen, Arthur Wang*, Wen-Yueh Jang*,
Jien-Chen Young*, Kuang-Yi Chiu*, and Tseung-Yuen Tseng
Department of Electronics Engineering and Institute of Electronics, National Chiao-Tung
University, Hsinchu 300, Taiwan
*Winbond Electronics Corp., Hsinchu 300, Taiwan
Tel: (+886)-3-5731879; Fax: (+886)-3-5724361; E-mail: [email protected]
Abstract
V-doped SrZrO3 (SZO) thin films on LaNiO3/SiO2/Si substrate are synthesized by sol-gel
method to form metal-insulator-metal (MIM) sandwich structure. The physical and electrical
properties of the MIM device are studied. The structure and surface morphology of the SZO
films are also characterized by X-ray diffraction and scanning electron microscopy. Such a
device has the bistable switching properties of current-voltage characteristics. The resistive
switching between the high-state and low-states can also be operated with voltage pulses. The
device with the properties of long retention time and non-destructive readout is expected to be
suitable for nonvolatile memory application.
2
1. Introduction
Following the popularity of portable equipments, such as mobile phone, digital camera, and
notebook computer, nonvolatile memory becomes one of the mainstreams of semiconductor
industry. The nonvolatile memory device should keep the stored information for a long time
without requiring power supply. The criteria for a perfect nonvolatile memory device includes
low operation voltage, low power consumption, long retention time, small cell size, high
operation speed, low cost, high endurance, non-destructive readout, and simple structure [1].
However, so far there is no nonvolatile memory device that satisfies all these requirements.
Although flash memory is the mainstream among the nonvolatile memory devices nowadays, it
has many drawbacks including high operation voltage, low operation speed, and poor endurance.
In addition, as the device is continuously scaled down in size, the flash memory faces the
challenge of gate oxide thinning that causes the unsatisfactory retention time. Therefore, many
nonvolatile memories are eagerly investigated to replace flash memory. Resistance random
access memory (RRAM) is one of the promising candidates for the next generation nonvolatile
memory application. Perovskite materials are investigated for many applications, such as gate
dielectrics [2], dynamic random access memory (DRAM) [3], and tunable microwave device [4].
Recently, A. Beck et al. proposed that Cr-doped SrZrO3 (SZO) film had reversible bistable
switching properties and was suitable for nonvolatile memory application [5]. We adopted the
oriented LaNiO3 film as the bottom electrode for the considerations of low cost and low process
3
investigate the electrical and physical properties. Sol-gel method has the advantages that include
low cost, easy stoichiometric control, and high uniformity. The influence of process conditions of
thermal treatment on the physical properties of the films was also investigated. The V-doped
SZO film was found to have the reversible switching behavior and the memory effect.
2. Experimental Procedures
The 4-inch boron-doped p-type (100) silicon wafer was adopted as substrate for device
fabrication. After the standard Radio Company of America (RCA) cleaning, the 200 thick nm
SiO2 film was thermally grown by a furnace to insulate the leakage current density from Si
substrate. Then the 100 nm thick LaNiO3 (LNO) film was deposited at 300oC by a
radio-frequency (rf) magnetron sputter as the bottom electrode. The base pressure of the vacuum
chamber was 1.3x10-3 Pa. The power density was fixed at 23.3 W/cm2 and constant working
pressure of 5.3 Pa which was maintained by a mixture of Ar and O2 at a mixing ratio of 3:2 with
a total flow of 40 sccm. The deposited LNO film with (100) and (200) preferred orientation was
verified by XRD, which is suitable to be a template [6]. After that, the 0.2% V-doped SrZrO3
films with 50 nm thickness were prepared by an acetate precursor sol-gel route on the bottom
electrode as the resistive layer. Stoichiometric amounts of the starting materials including
Strontium acetate, zirconium n-propoxide, and V2O5, were dissolved in acetic acid and
Acetylacetone. The above prepared 0.1M precursor solution was spin-coated on the
9
References
[1] W.W. Zhuang, W. Pan, B.D. Ulrich, J.J. Lee, L. Stecker, A. Burmaster, D.R. Evans, S.T. Hsu, M. Tajiri, A. Shimaoka, K. Inoue, T. Naka, N. Awaya, K. Sakiyama, Y. Wang, S. Q. Liu, N. J. Wu, and A. Ignatiev,” in IEDM Tech. Dig., 2002, p.193
[2] C. Y. Liu, H. T. Lue, and T. Y. Tseng, Appl. Phys. Lett., 81 (2002) 4416
[3] M. S. Tsai, S. C. Sun, and T. Y. Tseng, IEEE Trans. on Electron Device, 46 (1999) 1829 [4] H. T. Lue, and T. Y. Tseng, IEEE Trans on UFFC, 48 (2001) 1640
[5] A. Beck, J.G. Bednorz, Ch. Gerber. C. Rosseel, and D.Widmer, Appl. Phys. Lett., 77 (2000) 139
[6] C. Y. Liu, J. S. Chen, C. C. Chuang, A. Wang, W. Y. Jang, J. C. Young, K. Y. Chiu, and T. Y.
Tseng, Appl. Phys. Lett. (submitted)
[7] C. Y. Liu, P. H. Wu, A. Wang, W. Y. Jang , J. C. Young, K. Y. Chiu, and T. Y. Tseng, IEEE Device Lett. (revised).
