Mechanism of ultimate recording density in nano-scale phase-change memories

纳米级相变存储器的极限记录密度机制

• 批准号: 18560001
• 负责人: TANAKA Keiji
• 金额: $ 2.39万
• 依托单位: Hokkaido University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2006
• 资助国家: 日本
• 起止时间: 2006 至 2007
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18560001/
• 关键词: DVD; phase change; optical recording; ultimate recording; amorphous; Ge-Sb-Te; PRAM; 記録密度

Performance of rewritable digital-versatile-disk (DVD) memories is steady progressing. Then, a main object of the present study is to give an answer to a question "How high can we increase the recording density? ", which can be paraphrased to "How small can we reduce the mark size in phase change memories? ", since a smaller mark can give a higher recording density. It is known that, in the devices presently commercialized, the minimal mark size is 150 nm. However, this size is governed by the wavelength of the recording light, and we expect that a recording film Ge_2Sb_2Te_5 may be capable to produce much smaller marks.To produce the smallest mark, I have adopted two notions. One is that, instead of the optical phase change, the electrical phase change should be used, since smaller marks will be written using small electrodes. The other is, as the electrode, to employ the scanning probes in a scanning tunneling microscope (STM) and an atomic force microscope (AFM). These machines will produce the ultimately small mark even in a common laboratory room without dust controlling.The present study has demonstrated that the minimal size can be reduced to 〜10 nm. Interestingly, both of the minimal marks, i.e. a crystallized mark in an amorphous film and an amorphous mark in a crystalline film, the latter being the method presently used in DVDs, are around 10 nm. Consequently, it can be assumed that the recording density can surpass 1 TB / layer in a near future.The origins of the ultimate mark size of 〜10 nm have been investigated. The minimal size of crystallized marks can be understood thermodynamically. On the other hand, that of the amorphous mark is governed by the size of crystallites in crystalline recording films.In addition, un-stability of Ge_2Sb_2Te_5 films has been pointed out through studies on the electrical phase change. For electrical phase-change random access memories (PRAM), newer materials will be needed.

数字多功能光盘（DVD）存储器的性能正在稳步发展。然后，本研究的一个主要目的是回答一个问题“我们可以增加多高的记录密度？“，这可以解释为“我们可以把相变存储器中的标记尺寸减小到多小？“，因为较小的标记可以给出较高的记录密度。已知在目前商业化的器件中，最小标记尺寸为150 nm。然而，这个尺寸是由记录光的波长决定的，我们期望记录膜Ge_2Sb_2Te_5能够产生更小的标记。一个是，代替光学相变，应该使用电相变，因为使用小电极将写入较小的标记。另一种是将扫描探针作为电极应用于扫描隧道显微镜（STM）和原子力显微镜（AFM）中。这些机器将产生最终的小标记，即使在一个普通的实验室，没有灰尘控制。本研究表明，最小尺寸可以减少到10纳米。有趣的是，两个最小标记，即非晶膜中的结晶标记和结晶膜中的非晶标记，后者是目前在DVD中使用的方法，都是大约10 nm。因此，可以假设在不久的将来，记录密度可以超过1 TB /层。结晶标记的最小尺寸可以从化学上理解。另一方面，非晶标记的稳定性受晶体记录膜中微晶尺寸的影响，另外，通过对Ge_2Sb_2Te_5薄膜电相变的研究，指出了Ge_2Sb_2Te_5薄膜的不稳定性。对于电相变随机存取存储器（PRAM），将需要更新的材料。

项目成果

Smallest(〜10 nm)phase-change marks in amorphous and crystalline Ge_2Sb_2Te_5

非晶态和晶态 Ge_2Sb_2Te_5 中最小（~10 nm）的相变标记

• 发表时间: 2007
• 期刊: J. Non-Cryst. Solids 353
• 作者: M. Suzuki;Y. Yamada;E. Tajitsu;S. Kojima;and K. Anagawa;K. Tanaka
• 通讯作者: K. Tanaka

Ultimate features phase-change memories(Invited)

终极特性相变存储器（特邀）

• 发表时间: 2007
• 作者: K.Anagawa;T.Watanabe;M.Suzuki;K. Tanaka
• 通讯作者: K. Tanaka

Un-stability of Ge_2Sb_2Te_5 films in electrical phase change

Ge_2Sb_2Te_5薄膜电相变的不稳定性

• 发表时间: 2008
• 作者: K. Anagawa;T. Watanabe;and M. Suzuki;A. Saitoh and K. Tanaka
• 通讯作者: A. Saitoh and K. Tanaka

Smallest phase-changes marks in amorphous and crystalline Ge_2Sb_2Te_5 films

非晶态和晶态Ge_2Sb_2Te_5薄膜中的最小相变标记

• 发表时间: 2006
• 作者: Y.Yamada;M.Suzuki;K. Tanaka;K. Tanaka;K. Tanaka
• 通讯作者: K. Tanaka

Comment on "Investigation of the optical and electronic properties of Ge_2Sb_2Te_5 phase change material in its amorphous, cubic, and hexagonal phases"

对“Ge_2Sb_2Te_5相变材料非晶相、立方相和六方相的光学和电子特性的研究”的评论

• 发表时间: 2007
• 期刊: J. Appl. Phys. 101
• 作者: R. Takemura;T. Kumano;M. Ohmaki;T. Watanabe;and M. Suzuki;K. Tanaka
• 通讯作者: K. Tanaka