AVS 46th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM1-ThM

Paper EM1-ThM4
Electrochemical Deposition Cu Films for ULSI Applications

Thursday, October 28, 1999, 9:20 am, Room 608

Session: Cu, Low-k Dielectrics and Interfaces
Presenter: J.C. Hu, National Tsing Hua University, Taiwan, R.O.C.
Authors: J.C. Hu, National Tsing Hua University, Taiwan, R.O.C.
T.C. Chang, National Nano Device Laboratory, Taiwan, R.O.C.
W.C. Gau, Chung-Yuan University, Taiwan, R.O.C.
C.L. Cheng, Chung-Yuan University, Taiwan, R.O.C.
M.S. Feng, National Chiao-Tong University, Taiwan, R.O.C.
Allen Yang, Merck-Kanto Advanced Chemical Ltd., Taiwan, R.O.C.
Kevin Lee, Merck-Kanto Advanced Chemical Ltd., Taiwan, R.O.C.
L.-J. Chen, National Tsing Hua University, Taiwan, R.O.C.
Correspondent: Click to Email
Cu is being considered to replace aluminium in ULSI circuit metallization for better conductivity, higher electromigration resistance and reliability. CVD and PVD used to deposit Cu layer have been well documented. Relatively little is known about electrochemical deposition method to deposit copper films despite successful applications in ULSI by a number of manufacturers. The additives play a very important role in super-filling behavior. However, most of additives in electoplating solution are not disclosed in the literatures. In the present work, the new additives of electroplating solution without brightening-agents were investigated. The texture of the electroplated Cu films was studied with various applied current densities. A kind of ester was investigated as a leveling-agent. The polyethers were used as surfactants. ECD Cu deposited on low dielectric constant material like hydrogen silsesquioxane (HSQ) was studied. The basic electroplating solution was composed of CuSO@sub 4@.5H@sub 2@O (50-100 g/l), H@sub 2@SO@sub 4@ (150-200 g/l), HCl (50-80 ppm). Patterned wafers were fabricated to examine the ability of gap filling of electroplated Cu. 30-nm-thick TaN films as barriers and 100-nm-thick Cu films as seed layers were deposited by ionized metal plasma (IMP) PVD, respectively. The opening width of trenches/vias was 0.18-0.8 µmm . Applied current densities were less than 1.0 A/dm@super 2@. Transmission electron microscopy and X-ray diffractometry were utilized to investigate the microstructures and crystal orientation. Auger electron spectrocopy was applied to determine the stoichiometry and uniformity along the depth direction. The morphology was studied by a scanning electron microscope. Low resistivity, low porosity, and highly uniform electroplated Cu films were obtained, even without brightening-agent. 0.2 µmm vias and trenches with an aspect ratio of 5 were filled completely without void or seam. The Cu films exhibit a good super-filling behavior. Super-filling behavior can be explained by a diffusion-controlled theory of leveling-agents. The resistivity of a 450-nm-thick Cu film is 1.84 µm@ohm@-cm. From XRD analysis, strong (111) texture was obtained in the electroplated Cu films. The concentration of oxygen in the sample was found to be rather low.