Nano-Structural Control of Molecular-Pore Stacked (MPS) SiOCH Films Using Plasma Copolymerization Reaction
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0949-C07-10
Nano-Structural Control of Molecular-Pore Stacked (MPS) SiOCH Films using Plasma Copolymerization Reaction Hironori Yamamoto, Fuminori Ito, Munehiro Tada, Tsuneo Takeuchi, Naoya Furutake, and Yoshihiro Hayashi NEC Corporation, 1120, Shimokuzawa, Sagamihara, Kanagawa, 229-1198, Japan
ABSTRACT Nano-structure of porous SiOCH films was controlled by plasma copolymerization reaction using two types of precursors of 6-membered ring (ring-A) and 8-membered ring (ringB) organo-silica molecules, applicable for ULSI interconnect dielectrics toward 32nm-node and beyond. The 6-membered ring siloxane shows high plasma resistivity, while the 8-membered one becomes dissociated among PECVD process. The mechanical property of SiOCH films can be enhanced by adding 8-membered ring monomer which is reconstructed cross-linked Si-O-Si network structure at deposition process. INTRODUCTION To reduce power consumption and signal delay in scaled-down ASICs, introduction of low-k inter-metal-dielectric (IMD) film is crucial for the multilevel Cu interconnects [1]. In order to obtain a low k-value, a porogen removing technique has been developed. However porogen aggregation occurs with porogen volume increase, and film characteristics are not enough to realize highly reliable interconnects. Recently, it is reported that the copolymerization technique reinforces the mechanical property of low-k film [2,3]. We have developed molecularpore stacked (MPS) SiOCH films [4], which have small pore size (less than 1nm) and homogeneous pore distribution, and its copolymerization technology. In this study, the effect of molecule structure and copolymerization of organo-siloxane are investigated for high reliability.
EXPERIMENT We prepared two kinds of the ring-type organo-siloxane molecules (ring-A and -B) as the liquid source for the PECVD (Figure 1). Ring-A is a 6-member-ring siloxane, while the ring-B is an 8-member-ring siloxane. In the rings-A and –B, the molecular-pores involved at the ring centers were estimated as 0.45 nmφ and 0.35 nmφ, respectively. These molecules were vaporized in a liquid injection-type vaporizer with He carrier gas and were introduced into a PECVD reactor. The chemical composition of film was determined by Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopic analysis. Other film properties such as k-value, elastic modulus and pore size were measured by mercury-probe, nano-indenter, and small angle X-ray scattering (SAXS), respectively.
Ring-A Pore (0.35nm
Ring-B R2
φ）
Si O
R1 O
Si O
R1 Si
R2
Si O
O
Si
Si
O
R2
Pore (0.45nm
φ）
O Si
R1
R2
RF unit
copolymerization
Reactor
Figure 1. Schematic diagram of PE-CVD equipment for the SiOCH film deposition. Two monomer reservoirs are attached to the reactor.
RESULTS & DISCUSSION
Modulus(GPa)
Figure 2 shows the molar ratio of ring-A to ring-B dependences of k-value and elastic modulus. Molar ratio of 0 means the SiOCH film derived from only ring-A, while the molar ratio of 1.0 means one derived from only ring-B and intermediate v
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