| AVS 63rd International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS-WeA |
| Session: | Atomic Layer Etching and Low Damage Processing |
| Presenter: | Daisuke Ogawa, Chubu University, Japan |
| Authors: | D. Ogawa, Chubu University, Japan Y. Banno, Chubu University, Japan Y. Nakano, Chubu University, Japan K. Nakamura, Chubu University, Japan |
| Correspondent: | Click to Email |
Gallium nitride (GaN) is one of the candidate materials to realize miniaturized high power devices due to the wide band gap. The miniaturization of individual power devices, such as small inverters, are necessary to increase the electrical capacity, in particular, in upcoming electric vehicle era. In the last several decades, low-temperature plasma plays a role to speed computers up by fabrication. And now, the plasma is about to be applied to miniaturize high power devices. The advantage of the plasma processing is that a lot of semiconductor industries already have their own manufacture lines with the plenty of their processing experiences. However, it is also well known that plasma can create undesired change on the processing devices. This is called plasma induced damage (PID), which is created by ions, radicals, radiations, dusts etc. GaN cannot be the exception of the damage creation so that better understanding of damage developments is important to increase manufacture productivity.
We have been analyzing the evolution of GaN condition during plasma processing to clarify the damage creation mechanism. In-situ monitoring is a key diagnostic to understand the mechanism so that we have mainly utilized photoluminescence (PL) from the GaN that is exposed in processing plasma. The PL gives us the information of the volume-averaged damages from the surface to approximately 45 nm depth. The depth range is important because the change in the range affects the device performance when fabricated. The PL also gives us the indication of the optically-emissive intermediate states that are mostly caused by impurities and crystal defects in GaN. In particular, it is possible to know what kind of damage a specific plasma creates by observing a specific wavelength range of the PL, such as near-band-edge (NBE), blue (BL) and yellow luminescence (BL) range.
In this presentation, we will summarize our damage analysis on GaN that is exposed in processing (etching) plasma. Understanding of damage creation mechanism from the plasma is not trivial because plasma creates the surface damage in addition to the temperature increase due to the ion bombardments. The temperature can assist physical deformation of GaN and chemical reactions on the surface. This means that the isolation between the damage creation and the temperature rise by the plasma might be a good idea to understand the mechanism. Interestingly, our former PL measurements showed that cooling GaN kept PL better than non-cooling GaN even when exposing argon plasma.