The Effect of Contamination Solutions and Substrate Conditions on Copper Particle Growth Behavior
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Geun-Min CHOI*, Katsuyuki SEKIjNE**, Hiroshi MORITA*~*, and Tadahiro OHMI** *Memory R&D Division, Hyundai Electronics Industries Co., LTD, San 136-1, Ami-Ri, Bubal-Eub, Ichon-Si, Kyoungki-Do, 467-701 Korea **Department of Electronics, Tohoku University, Aza-Aoba, Aramaki, Sendai 980, Japan
ABSTRACT
Cu particle growth behavior on two silicon substrates, amorphous and single crystal silicon, has been investigated using two contamination solutions. This study reveals that the growth behavior of Cu particle depends on substrate conditions and copper contamination solutions. Contamination level is independent of split conditions. From the SEM images of an amorphous silicon shows a big difference in the number of particles depending on copper contamination solution. The amorphous silicon has similar native oxide thickness in ultrapure water spiked with CuF2 and CuClz, whereas the single crystal silicon is different from the native oxide thickness depending on copper contamination solution. When 1 ppm of Cu in ultrapure water was spiked as a function of time, the amount of Cu impurity on amorphous silicon in the early dipping stage was measured 10 times higher than that on single crystal silicon for both of copper contamination solutions.
IiNTRODUCTION As semiconductor devices are scaled down, ultra-clean Si surface is essential for device integrity. It is well known that metallic contamination on the Si surface is fatal to semiconductor devices [1]. The metallic contamination increases leakage current at P-N junction, decreases oxide breakdown voltage, and reduces minority-carrier lifetime. Therefore, effective removal of metallic impurities is further required to reduce the metallic contamination below detection limit. It was reported in previous study that the Cu impurities contaminated on a-Si (amorphous silicon), compared to that on c-Si (single crystal silicon), remain in Si wafer with a direct bond to Si atoms as well as being embedded inside of native oxide [2]. For Cu impurities both in native oxide and direct bond to Si atoms, the sulfuric acid and hydrogen peroxide mixture (SPM) cleaning is not effective although it has high redox potential value as shown in Fig. 1. An a-Si is widely used in forming channel silicon of thin film transistor liquid crystal display (TFT-LCD) and interconnects in ultra large scale integrated (ULSI) circuits. In order to remove metallic impurities from an a-Si film surface, the understanding of metallic particle growth behavior is important. Therefore, we have investigated the effect of copper contamination solutions to substrate conditions in the growth of Cu particle.
275 Mat. Res. Soc. Symp. Proc. Vol. 477 o 1997 Materials Research Society
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