High-Temperature Reactor Cleaning Using Chlorine Trifluoride Gas for Silicon Carbide Chemical Vapor Deposition

Abstract

The high-temperature cleaning of a silicon carbide chemical vapor deposition reactor was developed using chlorine trifluoride gas and purified pyrolytic carbon (PyC) as the susceptor coating material. The purified PyC could be exposed to the chlorine trifluoride gas without causing serious damage at temperatures up to 570°C, which was in the range providing a sufficiently high silicon carbide etching rate. The spontaneous temperature increase at the susceptor surface due to the exothermic reaction heat was moderated by means of adding nitrogen gas. Thus, the particle-type silicon carbide layer could be cleaned while preventing peeling of the purified PyC surface and obtaining a practical etching rate. Additionally, the peeled surface of the purified PyC could be recovered by annealing at 900°C in ambient nitrogen containing oxygen.

Lowest Concentration of Chlorine Trifluoride Gas for Cleaning Silicon Carbide Chemical Vapor Deposition Reactor

“…The reason why the PPyC surface was not peeled while even having high R-values should be clarified. As reported in a previous study, 10,11 the PPyC surface peeling is considered to be caused by the diffusion of fluorine into the PPyC layer, as shown in Fig. 8a.…”

“…7 are those obtained by exposure of the bare PPyC surface to the chlorine trifluoride gas at 100% and 50 sccm for 10 min at temperatures of 300 °C-570 °C. 11 At temperatures higher than 570 °C, the R-value became higher than 1.5 along with causing a color change and thin layer peeling. Empirically, the peeled thin film had an R-value higher than 2.…”

“…The R-values obtained in this study were compared to those reported in previous studies. [10][11][12][13] The circles and triangles in Fig. 7 are those obtained by exposure of the bare PPyC surface to the chlorine trifluoride gas at 100% and 50 sccm for 10 min at temperatures of 300 °C-570 °C.…”

“…2a, the original surface of the PPyC coated carbon plate showed a gray-color with a pebble-like morphology which consisted of continuously-arranged shallow round-shaped hills. [9][10][11] The formed silicon carbide film had a gray-color, which was slightly different from the PPyC surface, based on a visual inspection. The silicon carbide film consisted of many small particles on the PPyC surface, as shown in Fig.…”

“…A cleaning process should be developed accounting for the etching of the deposited materials and the measure to protect the susceptor from the etching. The cleaning process for the silicon carbide CVD reactor has been developed [4][5][6][7][8][9][10][11][12][13] using chlorine trifluoride (ClF 3 ) gas and purified pyrolytic carbon (PPyC) as the cleaning gas and the anticorrosive coating film of the carbon susceptor, respectively. In a previous study, 12 the particle-type silicon carbide CVD film was found to be quickly detached from the PPyC surface during the early stage of the cleaning, such as within 2 min, using the 100% chlorine trifluoride gas.…”