Iwao Sugiura

45 nm-node BEOL integration featuring porous-ultra-low-k/Cu multilevel interconnects

45 nm-node multilevel Cu interconnects with porous-ultra-low-k have successfully been integrated. Key features to realize 45 nm-node interconnects are as follows: 1) porous ultra-low-k material NCS (nano-clustering silica) has been applied to both wire-level and via-level dielectrics (what we call full-NCS structure), and its sufficient robustness has been demonstrated; 2) 70-nm vias have been formed by high-NA 193 nm lithography with fine-tuned model-based OPC and multi-hard-mask dual-damascene process - more than 90% yields of 1 M via chains have been obtained; 3) good TDDB (time-dependent dielectric breakdown) characteristics of 70 nm wire spacing filled with NCS has been achieved. Because it is considered that the applied-voltage (Vdd) of a 45 nm-node technology will be almost the same as that of the previous technology, the dielectrics have to endure the high electrical field. NCS in Cu wiring has excellent insulating properties without any pore sealing materials which cause either the k/sub eff/ value or actual wire width to be worse.

Thermal Expansion Coefficients of Nano-Clustering Silica (NCS) Films Measured by X-Ray Reflectivity and Substrate Curvature Methods

Two methods are applied to measure the coefficient of thermal expansion (CTE) of nano-clustering silica (NCS) films. A direct measurement of the film thickness using X-ray reflectivity yields an intrinsic CTE of 12±2 ppm/°C. From the analysis of the stress-temperature profile obtained by a substrate curvature method, the CTE of the NCS films is estimated to be approximately 9.7 ppm/°C, which almost agrees with the result of the X-ray reflectivity measurement. The advantage of each of these methods for CTE measurement of thin films is discussed.

A highly reliable nano-clustering silica with low dielectric constant (k<2.3) and high elastic modulus (E=10 GPa) for copper damascene process

A highly reliable nano-clustering silica (NCS) with low dielectric constant(k<2.3) and high elastic modulus (E=10 Gpa) for copper damascene process has been developed by controlling the size and distribution of pores in the NCS precursor. Using this material in a process compatible with the 90 nm technology node, we successfully demonstrated Cu wiring in NCS dielectrics.