TSD Reduction by RAF (Repeated <i>a</i>-Face) Growth Method

Abstract

A reduction in threading screw dislocation (TSD) density in 4H-SiC (silicon carbide) crystal is required for SiC power devices. In this study, TSD’s transformation by the RAF (repeated a-face) growth method [1] is observed by transmission X-ray topography (g=0004) of the cross-section of the crystal. Increasing the number of repetitions of a-face growth and offsetting c-face growth to an angle of several degrees reduce TSDs. TSD density is reduced to 1.3 TSD/cm2. The RAF growth method is very effective towards growing high quality SiC crystals.

Development of RAF Quality 150mm 4H-SiC Wafer

“…Next, 4H-SiC crystal is grown to the a-axis <1-100> direction that is perpendicular to the <11-20> direction, on the {1-100} seed that is prepared from the a-face growth described previously. By repeating these process several times, higher quality SiC crystal can be obtained [6]. We have to eliminate stacking fault in the seed crystal due to the repeated a-face growth.…”

Conversion Behavior of Threading Screw Dislocations on C Face with Different Surface Morphology During 4H-SiC Solution Growth

“…Remarkable progress has been made in reducing defect density of SiC crystal wafers. However, the densities of TSD and TED are still on the order of 10 2 –10 3 and 10 3 –10 4 cm –2 , respectively. − …”

Open Issues in SiC Bulk Growth

“…Strongly supported by the development of numerical process modeling (see for instance [5][6][7]), SiC crystal growth has benefited from significant achievements. After solving the long standing problem of micropipes, the recent most striking achievement is probably the demonstration of a threading screw dislocations (TSD) density of about 1-2 /cm², by using the repeated a-face (RAF) method [8]. In parallel to the vapor phase processes and after being tried in the sixties and put aside, the growth of SiC from high temperature solution [9,10] is back in force because of its inherent strengths, especially for the reduction of extended defect density.…”