Paper PS1-ThA1
Development of Atomic Radical Monitoring Probe for Spatial Distribution Measurements and its Application to Reactive Plasma Processes

Thursday, October 18, 2007, 2:00 pm, Room 606

Atomic radicals such as hydrogen(H), nitrogen(N), oxygen(O), and carbon(C) play important roles in the reactive plasma processes. In order to realize nano-scale etching processes and fabricate high functional nano-structure materials using the plasma processes, it is indispensable to clarify the mechanism of the etching or the deposition processes and control the process plasmas at the particle level. Moreover, it is necessary to develop the plasma processes based on not external parameters such as power, pressure, and gas mixture but the internal parameters such as radical densities, their energies, and so on. In our previous studies, we have developed the compact measurement system of the atomic radicals such as H, N, O, and C in the reactive process plasmas. The technique of the system is a vacuum ultraviolet absorption spectroscopy (VUVAS) using an atmospheric pressure microdishcarge hollow cathode lamp (MHCL). The MHCL was 9mm in diameter. So, the system for measuring the atomic radical densities can be easily handled. Using the system, we have carried out the measurements of the densities in various process plasmas and clarified the behaviors of the radicals. However, the two opposite ports are necessary to measure the densities using the system. Moreover, it is difficult to measure the spatial distribution of the atomic radical densities in reactive process plasmas. In this study, we have developed the monitoring probe for the atomic radical density measurements. The probe consisted of the MHCL, the optical part, the probe part, and the VUV monochromator. The size of the probe installed to the plasma was 2.7 mm in diameter. The necessary port for the measurements was only one. Moreover, we can measure the spatial distribution of atomic radical densities by moving the probe along the chamber radius. Using the probe, we carried out the spatial distribution of the H radical densities in the remote H₂ plasmas. The densities drastically decreased from 1.2 × 10¹² cm^-3 to 4.4 × 10¹¹ cm^-3 near the chamber wall at the pressure of 1.33 Pa, the RF power of 300 W. It was considered that the drastic decrease of the H atom density near the wall was due to the surface loss of the H radical on the chamber wall made of the stainless steel. The atomic radical monitoring probe was the ubiquitous measuring tool because using the probe, anyone can measure the atomic radical densities in any material process plasmas at any time.