Paper PS1-ThA4
Measurement of the Gas Temperature Distribution in UHF-ECR Dielectric Etching System

Thursday, October 18, 2007, 3:00 pm, Room 606

Plasma etching is widely used for the fabrication of semiconductor devices. In this process, particle contamination continue to be an issue. Recently, for the purpose of controlling the particle transport, use of the thermophoretic force, that move the particles toward lower gas temperature region, has been investigated. We measured the particle behavior in plasmas by using UHF-ECR etching apparatus having a laser particle monitor. The laser particle monitor consist of 532nm-YAG laser, lenses to form the laser sheet light passing above the wafer, and CCD camera to detect the laser light scatted by particles. We injected particles into plasmas by gas puffing and we found that particles gathered above the wafer center, when plasma density was decreased at the wafer center. Though, particles moved away from the region above the wafer, when plasma density was increased at the wafer center. We simulated particle transport by considering gas viscous force and thermophoretic force. And, it was predicted that there existed gas temperature gradient of 1000 K/m. In this study, the gas temperature distribution across the wafer was investigated. The gas temperature can be assumed to be equal to the rotational temperature of the nitrogen molecules. Thus, we measured the emission spectra of the second positive system of nitrogen molecules. The rotational temperature was determined by comparison of the measured spectral profiles and theoretical spectral profiles calculated by assuming rotational temperatures. The emission from the plasmas was measured through the top plate. Nitrogen and CHF₃ gases were used for plasma discharge by considering the SiOC damascene etching. When plasma density was increased at the wafer center, the gas temperature at the wafer center and the wafer edge were 450 K and 460 K, respectively. On the contrary, when plasma density was decreased at the wafer center, the gas temperatures at the wafer center and the wafer edge were 410 K and 510 K, respectively. Consequently, we confirmed that the gas temperature distribution across the wafer can be controlled by changing plasma distribution and the gas temperature gradient of 1000 K/m can be made.