Anisotropic deformation of 4H-SiC wafers: insights from nanoindentation tests
Xiaoshuang Liu, Rong Wang, Junran Zhang, Yunhao Lu, Yiqiang Zhang, Deren Yang, Xiaodong Pi
Abstract
Abstract In this work, the anisotropic deformation and anisotropic mechanical properties of 4H silicon carbide (4H-SiC) single crystal wafers are proposed by using nanoindentation. The C face of a 4H-SiC wafer has higher hardness and lower fracture toughness than those of the Si face. Because the deformation of 4H-SiC is assisted by the nucleation and slip of basal plane dislocations (BPDs), especially the slip of Si-core partial dislocations (PDs) of the BPDs, the nucleation and slip of the Si-core PDs in the Si face of 4H-SiC is easier than those in the C face, which releases the nanoindentation-induced stress and results in the decrease of the hardness and increase of the fracture toughness of the Si face of 4H-SiC wafers. Due to the hexagonal lattice of 4H-SiC, the hardness along <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo><</mml:mo> <mml:mn>1</mml:mn> <mml:mover> <mml:mn>1</mml:mn> <mml:mo>ˉ</mml:mo> </mml:mover> <mml:mn>00</mml:mn> <mml:mo>></mml:mo> </mml:math> of 4H-SiC is higher than that along <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo><</mml:mo> <mml:mn>11</mml:mn> <mml:mover> <mml:mn>2</mml:mn> <mml:mo>ˉ</mml:mo> </mml:mover> <mml:mn>0</mml:mn> <mml:mo>></mml:mo> </mml:math> , but the fracture toughness along the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo><</mml:mo> <mml:mn>1</mml:mn> <mml:mover> <mml:mn>1</mml:mn> <mml:mo>ˉ</mml:mo> </mml:mover> <mml:mn>00</mml:mn> <mml:mo>></mml:mo> </mml:math> is lower than that along the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo><</mml:mo> <mml:mn>11</mml:mn> <mml:mover> <mml:mn>2</mml:mn> <mml:mo>ˉ</mml:mo> </mml:mover> <mml:mn>0</mml:mn> <mml:mo>></mml:mo> </mml:math> , as a result of the enhanced glide of dislocations along the most closely-packed direction. The insights gained in this work are expected to shed light on the optimization of the mechanical processing of 4H-SiC wafers.