대한전자공학회논문지SD (Journal of the Institute of Electronics Engineers of Korea SD)

대한전자공학회 (The Institute of Electronics and Information Engineers)
권호 표지

$BCl_3/Cl_2/Ar$ 고밀도 플라즈마에 의한 $(Ba, Sr)TiO_3$ 박막의 식각 메커니즘 연구

A Study on the Etching Mechanism of $(Ba, Sr)TiO_3$ thin Film by High Density $BCl_3/Cl_2/Ar$ Plasma

  • 발행 : 2000.11.01
PDF 다운로드
⟨ 이전 논문 다음 논문 ⟩

초록

(Ba,Sr)$TiO_3$ 박막은 ULSI-DRAM 즉 1-4 Gbit급 DRAM용 셀(cell) 커패시터의 새로운 유전물질로 각광받고 있다. 본 연구에서는 ICP 장비에서 $BCl_3/Cl_2/Ar$ 플라즈마로 (Ba,Sr)$TiO_3$ 박막을 식각하였다. 이때 RF power/dc bias voltage는 600W/-250V, 반응로의 압력은 10mTorr 이었다. $Cl_2/(Cl_2+Ar)$은 0.2로 고정하였고, $BCl_3$ 가스를 첨가하면서 (Ba,Sr)$TiO_3$ 박막을 식각하였다. $BCl_3$ 가스를 10% 첨가하였을 때, $480{\AA}/min$으로 (Ba,Sr)$TiO_3$ 박막은 가장 높은 식각 속도를 나타내었다. $Cl_2/Ar$가스에 $BCl_3$의 첨가 비에 따른 Cl, BCl 및 B의 라디칼 밀도를 optical emission spectroscopy(OES)에 의해 구하였다. $BCl_3$를 10% 첨가하였을 때 Cl의 라디칼 밀도가 가장 높았다. (Ba,Sr)$TiO_3$ 박막의 표면반응을 규명하기 위하여 XPS 분석을 수행한 결과 이온 bombardment 식각이 Ba-O 결합을 파괴하고 Ba와 Cl의 결합형태인 $BaCl_2$을 제거하기 위하여 필요하다. Sr과 Cl의 결합의 양은 많지 않고, Sr은 주로 물리적인 스퍼터링에 의하여 제거된다. Ti와 Cl은 화학적으로 반응하여 $TiCl_4$ 결합형태로 용이하게 제거된다. 식각후 단면사진을 SEM을 통해 본 결과 식각단면이 약 65~70$^{\circ}$ 정도였다.

(Ba,Sr)$TiO_3$ thin films have attracted great interest as new dielectric materials of capacitors for ultra-large-scale integrated dynamic random access memories (ULSI-DRAMs) such as 1 Gbit or 4 Gbit. In this study, inductively coupled $BCl_3/Cl_2/Ar$ plasmas was used to etch (Ba,Sr)$TiO_3$ thin films. RF power/dc bias voltage=600 W/-250 V and chamber pressure was 10 mTorr. The $Cl_2/(Cl_2+Ar)$ was fixed at 0.2 the (Ba,Sr)$TiO_3$ thin films were etched adding $BCl_3$. The highest (Ba,Sr)$TiO_3$ etch rate is $480{\AA}/min$ at 10 % $BCl_3$ to $Cl_2/Ar$. The change of Cl, B radical density measured by optical emission spectroscopy(OES) as a function of $BCl_3$ percentage in $Cl_2/Ar$. The highest Cl radical density was shown at the addition of 10% $BCl_3$ to $Cl_2/Ar$. To study on the surface reaction of (Ba, Sr)$TiO_3$ thin films was investigated by XPS analysis. Ion bombardment etching is necessary to break Ba-O bond and to remove $BaCl_2$. There is a little chemical reaction between Sr and Cl, but Sr is removed by physical sputtering. There is a chemical reaction between Ti and Cl, and $TiCl_4$ is removed with ease. The cross-sectional of (Ba,Sr)$TiO_3$ thin film was investigated by scanning electron microscopy (SEM), the etch slope is about 65~70$^{\circ}$.

키워드

참고문헌

  1. K. One, T. Horikawa, T. Shibano, N. Mikami, T. Kuroiwa, and T. Kawahara, $(Ba,Sr)TiO_3$ Capacitor Technology for Gbit-Scale DRAMs, IEDM Tech. Digest, pp. 803~806(l998) https://doi.org/10.1109/IEDM.1998.746477
  2. T. Kuroiwa, Y. Tsunemine, T. Horikawa, T. Makita, J. Tanimura, N. Mikami, and K. Sato, Dielectric Properties of $(Ba_xSr_{1-x})TiO_3$ Thin Films Prepared by RF Sputtering For Dynamic Random Access Memory Application, Jpn, J. Appl. Phys., Vol. 33, No. 3, Part 1, pp. 5187-5191(1994)
  3. T. Kawakubo, K. Abe, S. Komatsu, K. Sani, N. Tyanase, and H. Mochizuki, Novel Ferroelectric Epitaxial (Ba, Sr)$TiO_3$ Capacitor for Deep Sub-Micron Memory Applications, IEDM Tech. Digest, pp. 695-698(1996) https://doi.org/10.1109/IEDM.1996.554076
  4. Seung-Bum Kim, Chang-Il Kim, Eui-Goo Chang, and Guen-Young Yeom, Study on surface reaction of (Ba, Sr)$TiO_3$ thin Films by high density plasma etching, J. Vac. Sci. Tech. A 17(4), pp. 2156-2161(1999) https://doi.org/10.1116/1.581742
  5. Hand Book of X-ray Photoelectron Spectroscopy, edited by J. Chastain (Perkin Elmer, 1992), p. 72