Quantification of Interfacial Voids Using Positron Annihilation Spectroscopy for Mechanism Study on SiCN Bonding and SiN Bonding

Abstract

Hybrid bonding for 3D integration requires reliable direct bonding interface of dielectrics. Lately, the spotlight has focused on SiCN/SiCN bonding considering its superior bonding performance by the dangling bonds-facilitated nanovoid closure mechanisms, but it is reported to be sensitive to reactive species especially under the high temperatures. Recent work proposed SiN/SiO 2 asymmetric bonding showing a void-free bonding interface and bond energy higher than 2.5 J m −2 as a promising candidate for direct bonding applications. Interestingly, we observed opposite bonding behaviors between SiCN and SiN in corresponding symmetric bonding pair and asymmetric bonding pair (with SiO 2 ). Thus, a comprehensive fundamental understanding on the bonding of different dielectrics is needed to guide the specifications of the bonding layer for enabling a void-free and highly reliable bonding interface. In this study, we systematically quantified the nanovoids in the bonding interface of SiCN/SiCN, SiCN/SiO 2 , and SiN/SiO 2 through positron annihilation spectroscopy and simulation, dangling bond formation by electron spin resonance, and the film passivation property by quasi-steady-state photoconductance. By correlating the film properties and bonding performance, the model of SiCN bonding is extended towards its SiCN/SiO 2 asymmetric bonding, and a new model of the nanovoid closure mechanism in SiN bonding is first-time proposed.