Analysis of the Basal Plane Dislocation Density and Thermomechanical Stress during 100 mm PVT Growth of 4H-SiC.

Johannes Steiner,Andreas Danilewsky,Stefan Sandfeld,Binh Duong Nguyen,Peter J Wellmann,Melissa Roder

doi:10.3390/ma12132207

Abstract

Basal plane dislocations (BPDs) in 4H silicon carbide (SiC) crystals grown using the physical vapor transport (PVT) method are diminishing the performance of SiC-based power electronic devices such as pn-junction diodes or MOSFETs. Therefore, understanding the generation and movement of BPDs is crucial to grow SiC suitable for device manufacturing. In this paper, the impact of the cooldown step in PVT-growth on the defect distribution is investigated utilizing two similar SiC seeds and identical growth parameters except for a cooldown duration of 40 h and 70 h, respectively. The two resulting crystals were cut into wafers, which were characterized by birefringence imaging and KOH etching. The initial defect distribution of the seed wafer was characterized by synchrotron white beam X-ray topography (SWXRT) mapping. It was found that the BPD density increases with a prolonged cooldown time. Furthermore, small angle grain boundaries based on threading edge dislocation (TED) arrays, which are normally only inherited by the seed, were also generated in the case of the crystal cooled down in 70 h. The role of temperature gradients inside the crystal during growth and post-growth concerning the generation of shear stress is discussed and supported by numerical calculations.

Highlights

Bulk silicon carbide (SiC) grown using the physical vapor transport (PVT) growth method has been established as a new material for high performance power electronic devices [1,2]
The distance between camera and sample amounted to about 100 mm
For crystals B and C, identical growth parameters were utilized except for a Figure 4c depicts the evolution of the Basal plane dislocations (BPDs) density of crystals B and C

Summary

Introduction

Bulk silicon carbide (SiC) grown using the physical vapor transport (PVT) growth method has been established as a new material for high performance power electronic devices [1,2]. To achieve high device performance it is essential to understand defect generation during crystal growth. Since BPDs lie perpendicular to the c-axis, i.e., the growth direction employed in PVT-growth, they cannot propagate into the grown crystal from the seed. Instead, they have to be generated either during the growth itself or after finishing the growth while the crystal is cooling down. Contrary to BPDs, threading edge dislocations (TEDs), threading screw dislocations (TSDs) and micropipes (MPs) will be inherited from the seed crystal due to their direction

Methods

Results

Conclusion