Paper PS2-ThA7
High Quality TEOS Oxide Film CVD by Microwave RLSA Plasma

Thursday, October 23, 2008, 4:00 pm, Room 306

A high-quality dielectric film CVD in low temperature is required in the processes of nano scale VLSI devices, FPDs, image sensors and flexible organic electronics. There have been many trials to form a high-quality low-temperature silicon dioxide using SiH4-O2 or TEOS-O2 PE-CVD methods. However, they have problems with not only their silicon oxide film qualities but also plasma-induced charging damages to underlying transistors during the plasma process. For example, with regard to the SiH4-O2 PE-CVD, it is hard to exclude Si-H and Si-OH bonds thoroughly to improve electrical properties such as leakage current and dielectric constant. For TEOS-O2 PE-CVD, unreacted TEOS precursor associated with carbon contaminations causes reliability problems and the Si-H and Si-OH contamination was reduced by controlling the plasma source power and Ar gas addition. We report a new low temperature (< 400C) PE-TEOS CVD technology using Microwave (2.45GHz) RLSA (Radial Line Slot Antenna) plasma.¹ It realizes high quality silicon dioxide film without causing charging damages. The film property is as good as a HTO (> 800C) with a good step-coverage performance. The 5%HF wet etch rate of the film is less than that of HTO. One of the unique characteristics of the Microwave RLSA plasma is its plasma generation and transportation system. A very high electron temperature region to produce high density plasma is located just beneath a quartz plate under a microwave antenna. The plasma diffuses to wafer region and the electron temperature in the wafer region becomes less than a half of it in the plasma production region. The electron temperature and density above the wafer in the RLSA plasma chamber can be controlled to produce desired proper precursors for an excellent CVD film by adjusting the pressure, material gas mixture ratio and position of the gas injections. To make the excellent silicon oxide film, the RLSA plasma produces specific precursors with plenty of sufficient oxygen radicals in the gas phase and supplies to the substrate surface. It also seems to provide ions with certain range of energy, that inhibits remaining C=C or C=O bond in the film but enough to proceed surface reaction. In the system, plasma charging damages were never observed even in a MOS capacitor TEG with an antenna-ratio of 1 M, because of the low electron temperature and uniform plasma potential above the wafer surface.

¹C. Tian, et al.: J. Vac. Sci. Technol. A24 (2006) 1421.