반도체 배선용 알루미늄 박막에서 티타늄(Titanium) 또는 루테늄(Ruthenium) 도핑이 hillock 형성에 미치는 영향

Aluminum interconnect;Aluminum;thin film stress;stress induced hillock;grain boundary diffusion;Al-Ti;Al-Ru;620.11

공과대학 재료공학부(하이브리드 재료) ;

University:서울대학교 대학원

关键词: Aluminum interconnect;    Aluminum;    thin film stress;    stress induced hillock;    grain boundary diffusion;    Al-Ti;    Al-Ru;    620.11;   

Others  :  http://s-space.snu.ac.kr/bitstream/10371/161048/1/000000157237.pdf

美国|英语

来源: Seoul National University Open Repository

【 摘 要 】

Aluminum has been used as global interconnects for D-RAM products due to relatively low resistivity(2.7㎛•㎝) and compatibility with Si process. However, the difference in the thermal expansion coefficient (CTE) between Al and Si is very large, which can cause hillocks due to the stress applied to the Al interconnects during repeated heat treatment. These hillocks can lead to reliability problems, such as electrical circuit shorts between interconnects. Therefore, it is very important to find and control the factors that can suppress the hillocks in order to produce highly reliable products. In this study, we will discuss the effect of doping other materials on Al thin films. Ti and Ru are selected as doping materials because the differences in the CTE with Si are smaller than Al and the melting point is high. Therefore, it is expected that the hillocks formation will be suppressed by the reduction of diffusion during repeated heat treatment.Pure Al and Al alloy films were fabricated using DC magnetron sputter on SiO2/Si substrate. By the wafer curvature method, the abrupt compressive stress relaxation in both the Al-Ti and the Al-Ru alloy film was observed at a certain temperature range. It was found by XRD measurement that the alloy precipitated at this temperature range. By transmission electron microscopy and ASTAR analysis, compared with the Al-14at.%Ti alloy film, the amount of alloy 석출 in the Al-14at.%Ru alloy film is more than four times that of the Al-14at.%Ti alloy film. The surface roughness (RMS) using AFM analysis of the pure Al, the Al-14at.%Ti alloy and the Al-14at.%Ru alloy were 14.7nm, 19.4nm and 4nm, respectively. It was confirmed that hillock of the Al-14at.%Ru alloy was mostly suppressed.Both the Al-Ti alloy film and the Al-Ru alloy film have smaller grain size than the pure Al film. As the grain size decreased, grain growth during annealing reduce the compressive stress and suppress the hillocks. In addition, more alloy 석출 was found in Al-Ru alloy film than in Al-Ti alloy film, which helps hillocks further suppressed due to densification. Hence, Ruthenium is interesting candidates with potential as dopant for Al interconnects.