Lattice Defects and Exfoliation Efficiency of 6H-SiC via H2+ Implantation at Elevated Temperature.

Tao Wang,Tongmin Zhang,Zhen Yang,Shuai Xu,Jun Li,Bingsheng Li,Qing Liao,Fangfang Ge

doi:10.3390/ma13245723

Abstract

Silicon carbide (SiC) is an important material used in semiconductor industries and nuclear power plants. SiC wafer implanted with H ions can be cleaved inside the damaged layer after annealing, in order to facilitate the transfer of a thin SiC slice to a handling wafer. This process is known as “ion-cut” or “Smart-Cut”. It is worth investigating the exfoliation efficiency and residual lattice defects in H-implanted SiC before and after annealing. In the present paper, lattice damage in the 6H-SiC implanted by H2+ to a fluence of 5 × 1016 H2+/cm2 at 450 and 900 °C was investigated by a combination of Raman spectroscopy and transmission electron microscopy. Different levels of damage caused by dynamic annealing were observed by Raman spectroscopy and transmission electron microscopy in the as-implanted sample. Atomic force microscopy and scanning white-light interferometry were used to observe the sample surface morphology. Surface blisters and exfoliations were observed in the sample implanted at 450 °C and then annealed at 1100 °C for 15 min, whereas surface blisters and exfoliation occurred in the sample implanted at 900 °C without further thermal treatment. This finding can be attributed to the increase in the internal pressure of platelets during high temperature implantation. The exfoliation efficiency, location, and roughness after exfoliation were investigated and possible reasons were discussed. This work provides a basis for further understanding and improving the high-efficiency “ion-cut” technology.

Highlights

Silicon carbide (SiC) is regarded as one of the most important wide-band gap semiconductors due to its excellent physical, electronic, and optical performances, i.e., a high melting temperature, a high strength, a high thermal conductivity, a large breakdown voltage, and a high electron mobility [1,2].Much effort has been made to develop the potential applications of SiC devices, such as Schottky barrier diodes in next-generation, large-scale integrated circuits
A lattice swelling of 5% was observed in the H2 + -implanted 6H-SiC at 450 ◦ C
A microcrack was observed in the front of the damage band in the sample implanted with H2 + ions at 450 ◦ C and subsequently annealed at 1100 ◦ C for 15 min

Summary

Introduction

Silicon carbide (SiC) is regarded as one of the most important wide-band gap semiconductors due to its excellent physical, electronic, and optical performances, i.e., a high melting temperature, a high strength, a high thermal conductivity, a large breakdown voltage, and a high electron mobility [1,2]. The “Smart-Cut” technology contains three main processes, initially hydrogen or helium ion implantation with a fluence of the order of 1016 to 1017 cm−2 at room temperature, wafer bonding to another rigid substrate (handling wafer) before thermal annealing, and fracture to achieve thin layer transfer at elevated temperatures [5,6,7]. It is critical to investigate the formation and growth of platelets in SiC implanted with H ions under different experimental conditions, such as the implantation fluence, temperature, and annealing treatment. It is well known that the growth of micro-cracks inside the SiC wafer can induce surface blisters when the SiC wafer is not bonded to a substrate, and the same activation energy between blister formation and layer splitting is argued by Tong et al [8]; it is a convenient way to evaluate the smart-cut threshold condition via observation of surface blisters and exfoliation. We studied the exfoliation efficiency of 6H-SiC implanted at 450 ◦ C and subsequently annealed at 1100 ◦ C for 15 min, compared with 6H-SiC implanted at 900 ◦ C without annealing

Experimental Process

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Discussion

Findings

Conclusions

Methods