(3-Aminopropyl)trimethoxysilane Self-Assembled Monolayer as Barrier of Porous SiOCH for Electroless Cu Metallization: Optimizations of SiOCH Hydroxylation and Monolayer Functionalization

Abstract

Self-assembled monolayers (SAMs) are potential diffusion barriers of nanoporous carbon-doped organosilica (p-SiOCH) for Cu metallization. A concern regarding silanization of the p-SiOCH using a wet chemical process is that its dielectric properties and bonding structures could be damaged by the chemical solution used, which is rarely addressed. In this study, the capacity of various (3-aminopropyl)trimethoxysilane self-assembled monolayers (APTMS-SAMs) as a barrier of p-SiOCH for electroless Cu metallization is evaluated. The processing of hydroxylation of the p-SiOCH (for silanization) and functionalization of APTMS-SAMs (for seeding of electroless metallization) was controlled through examining dielectric properties and bond structures of the hydroxylated p-SiOCH and functionalized APTMS-SAMs. Through tailoring the wet chemical treatments, the dielectric constant, insulating capacity, and bonding structure of post-treated p-SiOCH could be preserved at the pristine states, and the APTMS-SAM fabricated turns out to be a reliable barrier thermally stable up to 500 °C, 100 °C greater than that of the p-SiOCH without an SAM barrier. The integration of electroless Cu metallization reliably with p-SiOCH using a near-zero-thickness monolayer (free of a conventional metallic barrier) in an all-wet manner will be demonstrated. However, to make this approach working, both the hydroxylation of p-SiOCH and functionalization of APTMS-SAM have to be optimized.

Strengthening the Electromigration Resistance of Nanoscaled Copper Lines by (3-aminopropyl)trimethoxysilane Self-Assembled Monolayer

“…The patterned SiO 2 /Si substrate was then subjected to a succession of wet chemical treatments, as detailed elsewhere before, 12,19 from sonication clean, hydroxylation, APTMS silanization, functionalization, Ni seeding, finally to Cu electroless deposition, as schematically shown in Fig. 1.…”

“…Notably, our previous studies have shown that the APTMS-SAM synthesized here was about 1.5 nm thick and is terminated by highly oriented −NH 2 groups. 12,18,19 After the silanization, the sample was ultrasonically cleaned by anhydrous toluene for 5 min, followed by 5 min of deionized water rinsing three times to remove the APTMS residues. Finally, the sample was heated at 100 °C for 15 min to remove residual toluene and water.…”

“…1d). This treatment created surfaceactive sites for Ni seeding, generating seed-trapping Si-OH hydrophilic bonds, 19 which was performed in a 25 °C, 0.40 M Ni(NO 3 ) 2 aqueous solution for 30 min, followed by a reduction treatment in a 0.015 M (pH = 10) NaBH 4 solution for 30 min (Fig. 1e).…”

“…18 The well-aligned APTMS-SAM has been studied as an underlayer providing Ni seeding-adsorbing functional groups for a succeeding electroless deposition of Cu. 19 The APTMS-SAM interposed between SiO 2 and Cu has also been confirmed as an effective barrier. 12,[19][20][21][22][23] However, the role that an APTMS-SAM barrier plays in maintaining the electromigration resistance of a trench-filled Cu interconnect is rarely addressed.…”

“…19 The APTMS-SAM interposed between SiO 2 and Cu has also been confirmed as an effective barrier. 12,[19][20][21][22][23] However, the role that an APTMS-SAM barrier plays in maintaining the electromigration resistance of a trench-filled Cu interconnect is rarely addressed. Therefore, this study presents the results of APTMS-SAM as an electromigration retarder for the Cu interconnect through a mean time to failure (MTTF) measurements under an electrical stressing.…”