Reproducible defect etching of SiC single crystals

Optimization of KOH etching parameters for quantitative defect recognition in n- and p-type doped SiC

“…The samples were weighed before and after etching using a Mettler AT250 balance and the etching rate (in mol/s) was determined by the change in mass over etching time (Dm/Dt) with an accuracy of better than 3.3%. It should be pointed out, that most authors determine the etching rate by measuring the thickness of the sample before and after etching [11], some use the increase in the etch pit sizes [5]. We preferred to measure the weight of the samples (a) to rule out errors from wafer thickness inhomogeneities and (b) because the method is relatively, in a wafer-to-wafer characterization run, more accurate.…”

“…In literature etchings at 570 1C for 10 min [4], 530 1C for 10 min [7], 500 1C for 20 min [5] and at 480 1C for 6 min [8] have been reported for 6H-SiC with good results. It should be noted, however, that the KOH temperature was not measured directly in the melt.…”

“…Defect etching of SiC wafers is usually carried out using molten KOH; it has been shown by various authors (see e.g. [4][5][6][7]) that distinct etch pit patterns may be related to distinct dislocation types, i.e. screw dislocations, micro-pipes, threading edge and basal-plane dislocations.…”

“…In the past there has been considerable variations in SiC etching parameters, i.e. temperature and time [4,5,7,8], of different research groups due to different approaches made in temperature measurements. In Ref.…”

“…In Ref. [5], for instance, the temperature of the melt has been measured indirectly with a temperature sensor placed outside the melt on the outer walls of the crucible in the etching furnace. Different temperature measuring methods result in varying etching conditions for varying setup designs.…”