Mirror Etching of Single Crystalline C-Face 4H-Silicon Carbide Wafer by Chlorine Trifluoride Gas

Abstract

In order to evaluate the potential of a non-plasma dry etcher for silicon carbide, a 50-mm-diameter C-face 4H-silicon carbide wafer was etched using chlorine trifluoride gas at 500 • C. The wafer deformation was sufficiently small after the repetitive etching, even though the wafer was very thin, that is, about 160-μm thick. When the wafer surface was significantly etched, concentric-circleshaped valleys were formed at the radii corresponding to the circular-shaped arrays of pinholes at the gas distributor. Because the local pattern of the 4H-silicon carbide wafer etching rate corresponded to that of the chlorine trifluoride gas supply, the etching rate distribution was determined to be mainly governed by the chlorine trifluoride gas flow. Because the surface morphology and roughness after the etching was comparable to that of the mirror-polished wafer surface, the etcher evaluated in this study was expected to have a significant potential for mirror etching. In order to reduce the electric energy loss, power electronics 1-3 is currently playing major roles and making enormous contributions over the world. The power devices have various key positions to govern and improve the overall power consumption efficiency. They will have more functions and capabilities achieved by advancing the technologies of material production and device designs.The power devices are made of semiconductor materials, 2,3 such as silicon (Si), silicon carbide (SiC) and gallium nitride (GaN). The silicon carbide power devices have been developed by many researchers and engineers due to their fascinating nature, such as a high dielectric breakdown voltage, for high voltage use. The silicon carbide power devices are actually installed and currently working in trains and vehicles.2,3 Because the power device demand will further increase in the future, the process of silicon carbide material production should be improved.The significantly hard and nonreactive properties of the silicon carbide very often make the device fabrication processes long and complex. When the wafer back side is thinned by mechanical or chemical mechanical polishing after the device fabrication, the thinning processes require several hours or more. The removal rate is still about 0.2 μm/min when the plasma and Pt catalyst are used for the polishing.4-10 For developing a high speed process, an alternative high speed process, such as chemical etching, is expected.For improving the removal rate by the chemical approach, chlorine trifluoride (ClF 3 ) gas 11-17 is expected to be useful. The chlorine trifluoride gas has been reported to quickly etch the Si-and C-faces single-crystalline 4H-silicon carbide (SiC) material at a high rate, such as 5 μm/min.11 The C-face 4H-silicon carbide could be etched while maintaining the mirror-polished surface. 11,17In order to realize an industrial-scale wafer etching process, the SiC single-wafer dry etcher has been designed, fabricated and evaluated. [13][14][15][16] In this reactor, the entire etching rate profile over the 50 mm-diamet...

Chlorine Trifluoride Gas Etching Design for Quickly and Uniformly Removing a Thick C-Face 4H-Silicon Carbide Layer

“…The etching rate profile was significantly uniform in contrast to those reported in previous studies. 9,12 In this study, the wafer rotation rate was fixed at 10 rpm. Because the wafer rotation at around 10 rpm takes the average of the etching rate along the concentric circle, 10,15 the window of the allowable and effective wafer rotation rate is very wide, probably those between 1 and several tens rpm.…”

“…In previous studies [9][10][11][12] for developing the dry etcher using the chlorine trifluoride gas, the local etching rate was shown to depend on the local chlorine trifluoride gas supply, similar to the chemical vapor deposition rate. 13 The gas distributor design [9][10][11][12] have been studied based on the theoretical calculations and experiments, in order to show the concept that the etching rate profile might be the average between different wavy etching rate profiles.…”

Anticorrosive Behavior of Aluminum Nitride Surface Exposed to Chlorine Trifluoride Gas at High Temperatures

“…The aluminum nitride was used as the susceptor in the silicon carbide etching reactor using the chlorine trifluoride gas at atmospheric pressure. 24,25 As shown in Fig. 10, the 50-mm-diameter and 300 μmthick aluminum nitride wafer was placed between the 50-mmdiameter silicon carbide wafer and the quartz susceptor.…”

4H-Silicon Carbide Wafer Surface after Chlorine Trifluoride Gas Etching

“…The relationship between the etching rate distribution and the chlorine trifluoride gas concentration has been analyzed and clarified by means of the numerical calculations accounting for the transport phenomena [4,5] in the reactor. Next, for applying this technique to the power device fabrication process, the 4H-silicon carbide should be evaluated [7].…”