Evaluation of PECVD deposited Boron Nitride as Copper Diffusion Barrier on Porous Low-k Materials
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Evaluation of PECVD deposited Boron Nitride as Copper Diffusion Barrier on Porous Low-k Materials J. Liu1, 2, W. D. Wang1, L. Wang1, and D. Z. Chi1,*, and K. P. Loh2, # 1
Institute of Material Research and Engineering, 3 Research Link, Singapore 117602
2
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
* e-mail: [email protected]
Abstract Ultra low dielectric constant (k) material is needed as the inter-metal dielectrics to reduce RC delay when device dimension is scaled to sub-100nm. Porous dielectric films have been considered as good candidates for the application as inter-metal dielectrics due to their ultra low-k properties. Identifying proper dielectric copper diffusion barrier on the porous low-k films is critical for the low-k/Cu damascene fabrication process. In this study, we have evaluated the compatibility of plasma-deposited amorphous Boron Nitride film as a dielectrics copper diffusion barrier on a MSQ-based porous low-k LKD5109 film (from JSR). Both microwave plasma enhanced CVD (2.45 GHz) and radio-frequency plasma enhanced CVD (13.56 MHz) were applied for the BN deposition in order to evaluate the compatibility of the two plasma processes with the porous film. Growth parameters were optimized to minimize the boron diffusion and carbon depletion in the porous low-k films, which were found to have deleterious effects on the dielectric properties of the low-k films. FTIR and micro-Raman were employed for analyzing the changes in chemical structure of the low-k films after BN growth. Capacitance-voltage measurement was used to characterize the dielectric constants of BN film on Si and the BN-deposited porous low-k film. SIMS characterization was carried out to evaluate the performance of the BN film against copper diffusion. Introduction Ultra low dielectric constant (k) material is needed as the inter-metal dielectrics to reduce RC delay when device dimension is scaled to sub-100 nm. Porous dielectric films have been considered as good candidates for the application as inter-metal dielectrics (IMD) due to their ultra low-k properties. Identifying suitable dielectric copper diffusion barrier on the porous low-k films is critical for the successful integration of the porous low-k films into the low-k/Cu damascene interconnect scheme. SiN and a-SiC have been two most extensively studied dielectrics as dielectric diffusion barriers or etch stop layers in the back-end process [1-4]. However, the k values of these films are about 4.0 or even higher and therefore the use of these materials as dielectric barriers will certainly increase the effective k value of dielectric stack when integrated with porous low-k material. As known to have a low dielectric constant (≈2.2), boron nitride (BN) or boron carbon nitride (BCN) thin films have been studied previously on silicon substrates for their potential applications as inter-metal dielectrics [5, 6], but not for dielectric barriers on the porous low-k films. Although low-dielectric-constant BN can
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