Thin and Smooth Cu Seed Layer Deposition using the Reduction of Low Temperature Deposited Cu 2 O
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0914-F05-11
Thin and Smooth Cu Seed Layer Deposition using the Reduction of Low Temperature Deposited Cu2O Hoon Kim1, Yasuhiko Kojima2, Hiroshi Sato2, Naoki Yoshii2, Shigetoshi Hosaka2, and Yukihiro Shimogaki1 1 Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan 2 Technology Development Center, Tokyo Electron AT Limited, 650 Mitsuzawa, Hosaka-cho, Nirasaki-city, Yamanashi, 407-0291, Japan
ABSTRACT Thin and continuous CVD Cu seed layer is successfully deposited on Ru under-layer by Cu oxide deposition and its reduction at 100oC with novel chemistry. Cu oxide is formed with Cu(hface)TMVS and H2O2 at 100oC, and this film is reduced with formic acid at 100oC. Deposited Cu oxide films are Cu2O confirmed by XRD and XPS. The morphology of oxide films shows smooth and continuous on Ru and Ta substrate. The reduced Cu film on Ru maintains a good surface morphology. However, that on Ta has a poor morphology by agglomeration of Cu film during reduction. Oxidized Ru surface is easily reduced during reduction process thus it can maintain good Cu wettability, which results in less agglomeration of Cu. However, oxidized Ta having a poor Cu wettability is not reduced, which results in agglomeration of Cu film during reduction process. The readiness of reduction is very important merit of using Ru under-layer for this oxide deposition and reduction process. The Cu oxide deposition and reduction method on Ru under-layer can be a promising candidate for thin and continuous Cu seed layer deposition. INTRODUCTION Cu has been used as interconnect material for ultra large scale integration (ULSI) due to its low resistivity, excellent stress migration and electromigration resistances. Cu is filled up into narrow features to fabricate narrow line by electrochemical deposition (ECD), which has merits of low process temperature, high deposition rate, cost effective process, and good via filling capability. This ECD method requires seed layer as electrode. A seed layer has been deposited by sputtering with Ta and TaN barrier. However, beyond 45 nm generation, a sputtering cannot cover the side wall of via and trench due to the high aspect ratio of the features, which results in a void formation during ECD [1]. Such a void may cause high electric resistance or even an open circuit. Thus, conformal deposition method for Cu seed layer deposition is required. Chemical vapor deposition (CVD) and atomic layer deposition (ALD) are well known methods for conformal Cu seed layer deposition [2,3]. Considering producibility, CVD is the most promising candidate for seed layer deposition. However, Cu seed layers fabricated by CVD have shown poor morphology and problems of adhesion on diffusion barrier metals, such as Ta, TaN, and TiN. These poor adhesion properties of Ta and TaN have to Cu that may cause the reliability
problem [3,4]. Thus, the search for new barrier material has started to solve the problem, such as poor surface morphology and weak Cu adhesion property. Ruthenium (Ru) is an air
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