Liquid Si-Induced 4H-SiC Surface Structuring Using a Sandwich Configuration

Abstract

In view of obtaining a step bunched morphology on large 4H-SiC surfaces, a sandwich configuration is investigated. A piece of silicon is melted between two 4H-SiC 4° off wafers, allowing a better spreading of the liquid than a Si drop approach. This successfully leads to highly step-bunched surfaces, though with irregular steps. The most regular step and terrace stuctures were found to be the result of epitaxial growth via a dissolution-precipitation process occuring from the edges to the center of the wafers. This is probably caused by radio-frequency induced electromagnetic convection within liquid Si. This process is quenched when using smaller liquid thickness.

Controlled Macrostepping of Si-Face 4°off 4H-SiC over a Large Area via Liquid Si-Induced Reconstruction

“…Regarding the latter technique, the entire reconstructed areas were characterized using Multiple Images Alignment (MIA) which involved the assembling of 20 to 40 images in each case. The amount (mass) of Si inside the sandwich was chosen as to form a film of ̴ 30 µm thickness since this was found to be the best condition for controlling the mass transport inside the liquid and thus the homogeneity of the process (see ref [6,7] for calculation details). In these conditions, the natural vertical thermal gradient present within the stack generates a continuous carbon transport from the hotter bottom SiC wafer to the cooler top one: the bottom SiC is thus dissolved while the top SiC receives epitaxial deposition.…”

“…However, the sessile drop configuration used in these works does not allow the processing of surfaces > ̴ 0.5 cm 2 , hence this approach cannot be seriously considered as a device processing step. To solve this problem, a sandwich configuration allowing the processing of larger 4H-SiC areas is being investigated by the authors [5]. The preliminary results have shown a difficulty in obtaining regular and parallel macrosteps without uncontrolled mass transport inside the liquid.…”

From dissolution to controlled macrostepping of 4H-SiC during liquid Si-induced structuring in a sandwich configuration

“…Such approach does not allow the processing of surfaces > ̴ 0.5 cm 2 so that it cannot be seriously considered as a device processing step. To solve this problem, a SiC/Si/SiC sandwich configuration, virtually allowing the possible processing of larger 4H-SiC areas, is being investigated by the authors [11,12]. The preliminary experiments were successful in terms of uniform spreading of the liquid Si and formation of highly step-bunched surfaces.…”

Transport Phenomena during Liquid Si-Induced 4H-SiC Surface Structuring in a Sandwich Configuration

“…A simple way for fabricating such 4H-SiC macrostepped surface is to put it in contact with a liquid Si. Toward this end, we recently explored a sandwich configuration where a bulk piece of silicon is melted between two 4H-SiC (0001) 4°off Si-face wafers [4]. It was successful for spreading uniformly the liquid Si and forming highly step-bunched surfaces.…”