标题: 钛酸锶钡薄膜之温度电特性探讨
Study of the Temperature Effects on the Electrical Properties of (Ba,Sr)TiO3 Thin Films
作者: 郭孟维
Mng-Wei Kuo
郑晃忠
Huang-Chung Cheng
电子研究所
关键字: 钛酸锶钡;薄膜;温度;(Ba,Sr)TiO3;thin film;temperature
公开日期: 2002
摘要: 铁电材料由于具有高介电常数以及压电性,热电性等特点,近来广泛应用在动态随机存取记忆体的电容器以及各种感测元件上面。
一般来说,铁电材料具有两种状态:顺电相与铁电相。当温度高于居礼温度时,呈现顺电相,反之,则呈现铁电相。动态随机存取记忆体便是利用在顺电相时具有高介电常数的特点,而温度感测器则是利用在相变时,介电常数或电阻发生巨大变化,侦测电容或电流变化以得知温度的变化。因此,我们可以知道,温度对于铁电材料的电性影响是很大的,所以本论文着重在温度对于钛酸锶钡薄膜电性上的影响,特别是在电流机制以及温度电阻效应方面。
首先,我们将钛酸锶钡薄膜溅镀在Pt/TiN/Ti/Ox的基板上面,接着溅镀Pt为上电极,形成金属/绝缘层/金属(MIM)的结构,再经过不同温度的快速热退火处理之后,进行电性量测。我们改变量测时的基板温度,以得知温度对于钛酸锶钡薄膜电性上的影响。
接下来,同样在Pt/TiN/Ti/Ox的基板上,我们溅镀了钛酸锶钡/铬/钛酸锶钡(BST/Cr/BST)多层薄膜的结构,接着溅镀Pt为上电极,在经过高温长时间的炉管退火处理,利用热扩散的方式,使铬进入上下两层的钛酸锶钡薄膜之中,然后再进行电性量测。同样地,我们改变量测时的基板温度,以得知温度对于添加铬的钛酸锶钡薄膜电性上的影响。
我们发现钛酸锶钡薄膜具有不错的正温度电阻效应,并可以Heywang model来加以解释;此外,当添加了铬之后,有效地降低了钛酸锶钡薄膜的漏电流,而且大幅提升了正电阻效应,对于不管是在动态随机存取记忆体或是热敏电阻的运用上,都是很有利的。
Ferroelectric materials with high dielectric constant, pyroelectricity and piezoelectricity have recently been extensively applied on DRAM capacitors and sensors.
For ferroelectric materials, when temperature is higher than Curie temperature (Tc), they are paraelectric, while they are ferroelectric if temperature is lower than Tc. For DRAM applications, paraelectric (Ba,Sr)TiO3 (BST) is applied because of its high dielectric constant. For applications on sensors, large variations of dielectric constant and resistivity of BST thin films with temperature during phase transition are used to improve sensitivity. Thus the temperature effects on the electrical properties are important, especially on conduction mechanism and temperature coefficient of resistivity (TCR) effect.
The BST thin films with low crystallization temperature were deposited onto the Pt/TiN/Ti/Ox/Si substrate by rf magnetron sputter at 300oC substrate temperature. The BST thin films were then post annealed by rapid thermal annealing (RTA). Finally, physical and electrical properties of the BST thin films were investigated.
In order to investigate the properties of the Cr-incorporated BST thin films, the BST/Cr/BST multi-films structure was deposited on Pt/TiN/Ti/Ox/Si substrate by rf magnetron sputter at 300oC substrate temperature. High temperature and long period furnance annealing was adopted as post treatment method to implement thermal diffusion of Cr into BST thin films. The effects of Cr incorporation were investigated by means of different annealing temperature, Cr film thickness, and measurement temperature.
In our experiments, BST thin films revealed positive TCR (PTCR) effect. For Cr-incorporated BST films, advantages of leakage suppression and PTCR enhancement can be applied on DRAM capacitors and thermal sensors.
URI: http://140.113.39.130/cdrfb3/record/nctu/#NT910428058
http://hdl.handle.net/11536/70389
显示于类别:Thesis