Low Temperature Wafer Bonding Of Group Ⅳ Semiconductor By GeSn Interlayer

Semiconductor bonding technology is widely used in the field of wafer-level packaging,and has also attracted much attention in the preparation of 2D material heterojunction and thin film heterojunction.Lattice mismatches and thermal mismatches exist in traditional direct bonding methods,which deteriorates the bonding quality.Interlayer bonding is a new strategy to further reduce the bonding temperature as well as thermal stress.Decreasing the temperature,however,will lead to the deterioration of the bonding quality.Therefore,it is of great value to find materials with good bonding interface at low temperature.Amorphous Ge is compatible with semiconductor technology but has a high melting point,which recrystallization temperature can be significantly reduced by the addition of Sn.In this way,high strength wafer bonding can be achieved.In this paper,bonding wafer of Si/Si,Ge/Si and Ge/SiO2_Si by introducing the amorphous GeSn interlayer has been studied.The specific work is as follows:1.Si/Si homojunction was prepared by GeSn interlayer.In order to explore the bonding process of GeSn as the interlayer,the evolution mechanism of white spots at the interface of Si/Si bonding in ultrasonic test was studied at different Sn components,thickness of the interlayer,annealing temperature and annealing time,respectively.The crystallization of the intermediate amorphous GeSn was observed in different regions and in different degrees in the interlayer.Raman spectroscopy and SEM were used to analyze the relationship between the formation of bubbles at the interface and the crystallization of Si-based GeSn thin films.Si/Si bonding was achieved by using Ge0.86Sn0.14 interlayer with a thickness of 50 nm.2.GeSn interlayer realizes Ge/Si bonding.The effects of interlayer thickness and annealing temperature on the Ge/Si bonding were analyzed.The Ge/Ge0.95Sn0.05/Si bonded wafers were prepared and the quality of the bonded wafers was evaluated from the interface bubbles,mechanical strength and the properties of the GeSn interlayer.Ge/Si bonded wafer with high quality were achieved at low temperature of 300℃.Through contrast experiments,it is found that the a-GeSn film in the bonded wafer is easier to crystallize.Combined with ANSYS simulation,it is confirmed that the crystallization of the interlayer is due to the induction of the single crystal Ge substrate and the thermal stress introduced in the bond structure.Moreover,the crystallized interlayer is more beneficial to improve the bonding quality.This indicates that GeSn semiconductor interlayer bonding would be one of the potential technologies for bonding process.3.GOI was prepared by GeSn interlayer.The Ge0.86Sn0.14 interlayer with a thickness of 50 nm was used for Ge/SiO2_Si bonding,and the dendritic morphology of the GeSn film was observed.The thickness of the Ge0.86Sn0.14 interlayer is further reduced,and the quality of the GOI bonding wafer is improved after annealing.Due to the adsorption of SiO2 in GO I,even if annealed at low temperature,a near-bubble-free bonded interface is achieved.By further optimizing the thickness of the interlayer and the annealing process of the bonded wafer,the single crystallization of a-GeSn thin films was realized,and the interlayer crystalline GOI was prepared.