Langmuir probe and OES diagnostic study of ECR plasma for amorphous silicon deposition process

• Main Authors: Guan-Min Juan, 阮冠閔
• Other Authors: Tomi Li
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/76298976637217918622

碩士 === 國立中央大學 === 光機電工程研究所 === 101 === Optical emission spectroscopy (OES) and homemade Langmuir probe are used for in-situ diagnosing the mixed H2-SiH4-Ar plasma characteristics in an electron cyclotron resonance chemical vapor deposition (ECR-CVD) system for hydrogenated amorphous silicon (a-Si:H) thin film process. The electron temperature (Te) and plasma density (Ne) are determined by Langmuir probe and the relative concentrations of plasma species are obtained from OES. By using a moveable Langmuir probe, the relation between distribution of plasma characteristics and a-Si:H film properties under various microwave power(700 - 1600W), working pressure(3 – 15mTorr), magnetic field and hydrogen dilution ratio are investigated in the scope of this research. Results indicate that high density H2-SiH4-Ar plasma can be obtained by increasing ECR microwave power even if the plasma density is near to the theoretical cut-off value. As the result of substrate heated by high concentration of electrons, the hydrogen precipitation occurs and hydrogen content is decreased by 46%. The result of Langmuir probe shows that electron temperature is rarely influenced by microwave power, and it also agrees well with OES measurement results. The R* and hydrogen concentration are measured using FTIR. The R* (2100 /2100+2000) shows the film’s property which is calculated with the strength of Si-H (2000cm-1) and Si-H2 (2100cm-1) peaks. The dominate factor about electron temperature is working pressure. The electron temperature decreases with increasing working pressure. In the same time, the R* increases with increasing pressure, but decreasing with hydrogen concentration. The best conductivity ratio can be received when electron temperature is 3eV. Since some standing waves could exist in the chamber, the position of ECR resonance zone would affect the plasma potential, R* and hydrogen concentration. When hydrogen dilution ratio (H2/SiH4) is adjusted from 0 to 24, hydrogen concentration can decrease thin film deposition rate effectively. When hydrogen concentration increases, the deposition rate becomes slower. Above all, this study demonstrates that the method for integrating in-situ Langmuir probe and OES can receive more reliable plasma characteristics in CVD process.