Bottom-up fill mechanisms of electroless copper plating with addition of mercapto alkyl carboxylic acid

Abstract

Copper electrodeposition is used in the damascene process for the fabrication of interconnections of ultralarge-scale integrated semiconductor devices. Copper electroless plating is one of the most promising processes for the formation of a seed layer for electroplating. In this article, the effect of additives of mercapto alkyl carboxylic acid (MACA) such as 3-mercaptopropionic acid, 11-mercaptoundecanoic acid, and 16-mercaptohexadecanoic acid on bottom-up filling of electroless copper in deep submicrometer via holes was investigated. The inhibition of copper plating deposition on the plane surface was observed with an addition of MACAs, and bottom-up fill was confirmed for MACAs with alkyl chain numbers of 3, 11, and 16. The bottom-up fill tendency was enhanced with increasing alkyl chain number. This result strongly suggests that the diffusion coefficient of inhibitor molecule plays an important role for bottom-up fill mechanisms, because MACA with longer alkyl chain has smaller diffusion coefficient than that with shorter alkyl chain.

Electroless Copper Bonding with Local Suppression for Void-Free Chip-to-Package Connections

“…Mercaptocarboxylic acids have a similar behavior to SPS in bottom-up ELD trench filling. 19 It is reasonable to conclude that the origin of the local suppression here, at high pH, is due to the adsorption of SPS via the mercapto group, not the sulfonate moiety.…”

“…The organic additives used to control the deposition rate include polyethylene glycol (PEG), 14, 15 bis-(3-sulfopropyl)-disulfide (SPS), 16, 17 similar mercapto or disulfide molecules, 18,19 or their combinations. [20][21][22][23][24][25] The most widely reported additive is PEG, which can be used to induce bottom-up filling in small trenches.…”

Preparation of luminescent ZnS:Cu nanoparticles for the functionalization of transparent acrylate polymers

“…The Zn 2 + and Cu 2 + ions are forming complexes [11,12] with the stabilizer b-mercaptopropionic acid having different stability constants. Due to the higher stability of complexes of Zn 2 + -ions with the b-mercaptopropionic acid, the ratio of Zn/Cu in the product is not the same as in the synthesis solution.…”

30 years of electroless plating for semiconductor and polymer micro-systems

“…Void-free filling of high aspect ratio via-holes was reported [44][45][46][47][48][49][50][51][52][53][54][55] with the proper choice of plating additives such as SPS and mercapto alkyl carboxylic acids as accelerator, and PEG-PPG triblock copolymers as inhibitors [48][49][50]. Void-free electroless copper deposition in sub-micrometer trenches was obtained in the presence of the single poly(ethylene glycol) (PEG) as inhibitor [44,51] as well as accelerating species such as SPS [52,53] and its derivatives, 3-N,N-dimethylamino-dithiocarbamoyl-1-propanesulfonic acid (DPS) [54] and 2-mercapto-5-benzimidazole-sulfonic acid (MBIS) [55].…”