Studies On Plasma Enhanced Atomic Layer Deposition

Under the nanoscale miniaturization tend of integrated circuits, atomic layer deposition (ALD) has recently been widely studied for the precisely controlling the thickness and uniformity of ultra-thin film, especially for the high-k materials, as the semiconductor science and technology upgrading which suggests that ALD has the potential to become a new generation of nano-semiconductor field deposition technique. However, the normally applied thermal ALD system is restricted in industry applications for its low deposition rate of thin films and high deposition temperature. In order to overcome these two shortcomings of ALD technology, a lot of groups proposed different solutions, such as strong oxidants assisted atomic layer deposition, magnetron plasma assisted atomic layer deposition and so on. In this study we use the pulse modulated radio frequency(RF) plasma assisted ALD technique to decrease the high deposition temperature down to 100℃.Firstly, it describes the application and development of nano-thin film technology, also the principles, definitions, features, and applications of ALD and Plasma are outlined. By combining their advantages, the pulse modulated RF plasma enhanced ALD technique is proposed.In the experiment, we use the P-type 111 crystal orientation silicon wafer as the substrate, trimethyl aluminum (TMA) and H2O as the two precursors and the ALD pulse signal as the modulated signal for the RF power. The discharge curves are also recorded and analyzed during the deposition processes, which are very important for the regulation of substrate temperature and reducing of plasma power consumption. Plasma shows the improvement on the deposition situation, especially at the temperature of 90℃. It can successfully deposit Al2O3 films on the Si wafers, which is impossible for regular thermal ALD and proposes the deposition of the Al2O3 films on the polymer. We used ALD and pulse modulated RF enhanced ALD to make the comparative experiments under different deposition temperatures. With the thickness and dielectric constant of the Al2O3 films measured by the surface profilometer and ellipsometer, we got the regular ALD deposition rate of 0.16nm/cycle for Al2O3 film. By comparing the ALD and pulse modulated RF enhanced ALD, it is found that the applying of plasma can not increase the deposition rate during the low temperature (under the lowest regular deposition temperature of ALD). Because when below the lowest threshold temperature, ALD and plasma enhanced ALD can both get thicker films than the theoretical value, and the deposited film may not be the atomic layer structure. According to the experimental results, it is concluded that with the aid of plasmas, the minimum successful deposition temperature threshold value is reduced.