Growth of Micropipe-Free Single Crystal Silicon Carbide (SiC) Ingots Via Physical Vapor Transport (PVT)

Abstract

The move towards commercialization of SiC based devices places increasing demands on the quality of the substrate material. While the industry has steadily decreased the micropipe (MP) levels in commercial SiC substrates over the past years, the achievement of wafers that are entirely free of MPs marks an important milestone in commercialization of SiC based devices. We present the results of a study for controlling the nucleation and propagation of MP defects in SiC ingots grown via PVT. Our studies confirm that during bulk growth of SiC, foreign polytype nucleation such as 3C-polytype occurs at the initial stages of growth (nucleation period) and/or during subsequent growth in the presence of facets. Results in this investigation suggest that polytype instability during crystal growth adversely impacts the MP density. Based on this key concept, growth conditions for nucleation and growth stages were optimized. These conditions were subsequently implemented in an innovative PVT growth environment to achieve a growth technique with highly effective polytype control. Under continuously modulated growth conditions, MPs induced by seed material and/or formed during the growth were eliminated. 2-inch and 3-inch diameter MP-free (zero MP density) conducting 4H-SiC ingots were obtained.

Structure and Morphology of Inclusions in 4° Offcut 4H-SiC Epitaxial Layers

“…1 Significant work has been performed to grow low-dislocation-density (<10 4 cm À2 ) and micropipe-free SiC substrates and epilayers. [2][3][4] However, extended defects in SiC epitaxy continue to play a critical role in degrading the performance and reliability of SiC power devices. [5][6][7] Until recently, 4H-SiC epitaxy was grown on SiC substrates cut 8°off-axis from the h11 " 20i direction, in order to maintain the 4H-SiC polytype by stepflow growth.…”

Evaluation of the quality of commercial silicon carbide wafers by an optical non-destructive inspection technique

“…However, since the sensational announcement of ZMP (Zero Micro Pipe) technology by Intrinsic Semiconductor Corporation [4], purchase of ZMP wafers has become much easier due to the abundant supply of cost-effective ZMP wafers from Intrinsic. Now, ZMP features in a device-grade SiC wafer are available from a few SiC wafer vendors.…”

“…Measurements by optical profiler, ellipsometry, scatterometry and reflectometry give a topographic image, a scattering image, an abs-phase image and a specular image of an inspected wafer [4]. Spot size of the laser beam is 5 mm.…”

Initial stages of SiC crystal growth by PVT method

“…The controlling of nucleation and propagation of defects is effective if special attention is paid to parasitic polytype nucleation at the initial stages of growth and during subsequent growth in the presence of facets [5,6]. The highly effective polytype control was used by leading manufacturers to successful elimination of micropipes induced by seed material and formed during growth [6]. However, there is lack of analysis of the evolution of crystallization front morphology in the initial stage of the growth.…”

“…The growth conditions reducing the growth-induced defects are close to equilibrium [2,3] with slow growth rate and carefully prepared source material [4]. The controlling of nucleation and propagation of defects is effective if special attention is paid to parasitic polytype nucleation at the initial stages of growth and during subsequent growth in the presence of facets [5,6]. The highly effective polytype control was used by leading manufacturers to successful elimination of micropipes induced by seed material and formed during growth [6].…”