Dry etching of 6H silicon carbide(6H-SiC)wafers in a C_4Fs/Ar dual-frequency capacitively coupled plasma(DF-CCP)was investigated.Atomic force microscopy(AFM)and X-ray photoelectron spectroscopy(XPS)were used to measure the SiC surface structure and compositions,respectively.Optical emission spectroscopy(OES)was used to measure the relative concentration of F radicals in the plasma.It was found that the roughness of the etched SiC surface and the etching rate are directly related to the power of low-frequency(LF)source.At lower LF power,a smaller surface roughness and a lower etching rate are obtained due to weak bombardment of low energy ions on the SiC wafers.At higher LF power the etching rate can be efficiently increased,but the surface roughness increases too.Compared with other plasma dry etching methods,the DF-CCP can effectively inhibit C_xF_y films'deposition,and reduce surface residues.
A novel technique to generate high-density plasma-called inductively coupled plasma(ICP),enhanced capacitively coupled plasma(CCP)- is successfully developed.The plasma can be generated using different frequency configurations,such as ICP-enhanced single-frequency capacitively coupled plasma(SFCCP) and dual-frequency capacitively coupled plasma(DFCCP).The characteristics of the plasma in the following frequency combinations are mainly investigated using a Langmuir probe,SFCCP(60 MHz),DFCCP(60 MHz,13.56 MHz),SFCCP(60 MHz) and inductively coupled plasma(13.56 MHz),DFCCP(60 MHz,13.56 MHz) and inductively coupled plasma(13.56 MHz).In this letter,the nitrogen and hydrogen mixture gas discharge characteristics of different configurations are studied.After the analysis,we can acquire the electron temperature and ion density.Then,the effect of inductively coupled discharge on SFCCP and DFCCP can be summarized.In our preliminary investigations,the main results can be given as follows.ICP can make the density of SFCCP increase and the distribution of the electron temperature in a radial direction more uniform.In addition,ICP not only can make the ion density of DFCCP increase,but also can improve the radial uniformity.Further experiments may be needed to clarify the mechanism.
