In-situ Observation of the Formation and Growth of Twin in the Copper Electrodeposits for Ultra Large Scale Integration
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0914-F06-04
In-situ Observation of the Formation and Growth of Twin in the Copper Electrodeposits for Ultra Large Scale Integration Heung Nam Han1, Hyo-Jong Lee1, Do Hyun Kim1, Ui-hyoung Lee1, Pil-Ryung Cha2, and Kyu Hwan Oh1 1 Material Science and Engineering, Seoul National University, San 56-1, Shinrim-dong, Kwanak-gu, Seoul, 151-744, Korea, Republic of 2 School of Advanced Materials Engineering, Kookmin University, 861-1, Chongnung-dong, Songbuk-gu, Seoul, 136-702, Korea, Republic of
ABSTRACT During the self-annealing in the copper electrodeposits for the copper metallization, an in-situ observation of grain growth of the copper at room temperature was performed by using EBSD (electron backscatter diffraction). The thin film structure of the copper electrodeposits after annealing was columnar. New twin was initiated at the front surface of growing twin and grew along the normal direction of the twin boundary between the new and parent twins. It was confirmed that the annealing twin in the copper electrodeposits during the self-annealing have an {111} growth front surface. INTRODUCTION Since copper was adopted for the interconnection material in 1997, many researches have been performed on the copper texture. The copper texture had the correlation with the interconnection reliabilities of electromigration and stress-migration. It was reported that {111} textured copper had good resistance of electromigration and {100} textured copper had good resistance of stress-migration [1-3]. Therefore, it was important to understand the texture evolution in copper interconnects. The copper electrodeposits show the grain growth at room temperature, so-called self-annealing because the electrodeposits are composed of the nano-sized grains with high purity [4,5]. This self-annealing phenomenon enabled us to investigate the grain growth by using the EBSD (electron backscattered diffraction) system without any heating stage [6]. In addition, as the thin film has columnar structure, the investigation at the surface of the thin film is representative of the overall grain growth of the copper electrodeposits. Fig. 1(a) shows a planar EBSD measurement of copper electrodeposits after annealing. Fig. 1(b) shows the crosssectional EBSD measurement for the white region in Fig. 1(a). The thin film in the copper electrodeposits after the annealing is columnar. In this study, the authors observed the planar grain growth during the self-annealing of copper electrodeposits by an in-situ experiment using EBSD. We discussed the mechanism of twin formation and growth during the self-annealing.
EXPERIMENT
Figure 1. Crystalline orientation map. (a) Planar EBSD measurement of a copper electrodeposit and (b) cross sectional EBSD measurement of the white region in Fig. 1(a).
Figure 2. Thin film structure of the sample.
Figure 3. Two models for twin formation. (a) The growth direction is normal to the coherent twin boundary, and (b) the growth direction is parallel to the coherent twin boundary [7].
Fig. 2 shows thin film structure of the sam
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