Characterization of oxygen and nitrogen rapid thermal annealing processes for ultra-low- k SiCOH films
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Jaeyoung Yang Advanced Nano-Tech Development Team, Semiconductor Business, Dongbu HiTek Co., Ltd., Eumseong-Gun, Chungbuk 369-852, Republic of Korea
Jin-hyo Boo Department of Chemistry, Sungkyunkwan University, Suwon 440-746, Republic of Korea
Hyoungsub Kim Department of Materials Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea
Jaewon Lee and Heeyeop Chaea) Department of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea (Received 1 November 2007; accepted 12 December 2007)
Rapid thermal annealing (RTA) processing under N2 and O2 ambient is suggested and characterized in this work for improvement of SiCOH ultra-low-k (k ⳱ 2.4) film properties. Low-k film was deposited by plasma-enhanced chemical vapor deposition (PECVD) with decamethylcyclopentasiloxane and cyclohexane precursors. The PECVD films were treated by RTA processing in N2 and O2 environments at 550 °C for 5 min, and k values of 1.85 and 2.15 were achieved in N2 and O2 environments, respectively. Changes in the k value were correlated with the chemical composition of C–Hx and Si–O related groups determined from the Fourier transform infrared (FTIR) analysis. As the treatment temperature was increased from 300 to 550 °C, the signal intensities of both the CHx and Si–CH3 peaks were markedly decreased. The hardness and modulus of the film processed by RTA have been determined as 0.44 and 3.95 GPa, respectively. Hardness and modulus of RTA-treated films were correlated with D-group [O2Si–(CH3)2] and T-group [O3Si–(CH3)] fractions determined from the FTIR Si–CH3 bending peak. The hardness and modulus improvement in this work is attributed to the increase of oxygen content in (O)x–Si–(CH3)y by rearrangement.
I. INTRODUCTION
As device features of integrated circuits (ICs) continue to shrink, the resistance × capacitance (RC) delay greatly limits their performance and reliability due to increased power dissipation and metal line cross-talk in multilevel interconnects.1 To solve this problem, it is necessary to replace the presently used interlayer dielectric SiO2 (relative dielectric constant, k ≈ 4.0) with low-dielectric constant materials (low-k: k 艋 3.0). Currently materials with k values of 2.7–3.0 are used in logic ICs at 90-nm node and below.2,3 The k values of the dielectric materials can be lowered (i) by replacing oxide films with hydrocarbon films, (ii) by incorporating hydrocarbon functional a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0106 856 J. Mater. Res., Vol. 23, No. 3, Mar 2008 http://journals.cambridge.org Downloaded: 10 Mar 2015
groups into oxide films (also called SiCOH films), or (iii) by forming porosity in the film. The SiCOH film is more popular because it is thermally more stable and mechanically stronger than hydrocarbon films at the typical backend processing conditions.4 Typically, the mechanical strength of the low-k film is significantly decreased as the k value is decreased, and the ultra-low-k films (k < 2.5) do not yet meet t
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