Invited Paper PS-WeM3
Plasma Enhanced CVD processes: Dual Frequency PECVD with pulsing of liquid precursors and PEALD for Selective Deposition

Wednesday, November 9, 2016, 8:40 am, Room 104B

With this presentation we will address two topics concerning the development of specific Plasma Enhanced CVD processes for microelectronics applications: Dual Frequency (DF) with pulsed liquid injection of precursors and selective deposition.

First, we will talk about Dual Frequency processes for PECVD applications. Since the excitation frequency has extensive effects on the spatial distribution of species and their concentrations, the dissociation of the precursor can also be increased by crossing the discharge excitation frequency to the basic ion plasma frequency. This route is considered here with comparison and discussion over the improvements brought by Dual Frequency LF/RF plasmas in the case of thin metal gate (TiN) and Phase Change Material (GeSbTe) deposition. For this study we used 200 mm and 300 mm commercial PECVD tools from Altatech with a pulsed liquid injection of precursors. We will show that during TiN deposition the plasma enters a g-mode due to secondary electron heating. Then adding LF to RF modifies the sheath thickness of the plasma, increases the electron temperature of the gas and thus leads to strong modification of the carbon content, density and growth rate. For PCM applications, very different cycles (amorphous to crystalline) are obtained for GeTe materials elaborated in RF mode or DF mode. Moreover, we observe a very strong improvement of the gap filling capability of the process by using the DF mode.

The second part of this talk will be dedicated to the development of a selective deposition process by PEALD. One of the main challenges brought by the reduction of the transistor size below 10 nm is the development of selective deposition processes (for a self-forming Cu diffusion barrier for example). ALD is a suitable technique for selective deposition since it is a self-limited surface reaction process. The resulting selective process, called SeALD (Selective ALD) or AS-ALD (Area Selective ALD) is usually based on a specific surface treatment before deposition. Indeed, in ALD process, thin film nucleation depends strongly on the surface chemistry, so that by using a specific treatment one can transform a chemically reactive site into a nonreactive one. In this part, we propose a new selective ALD process, without surface treatment before deposition but using a Plasma assistance ALD process and by playing on the plasma chemistry. We will show for example that we are able to deposit selectively Ta₂O₅ oxide on top of metal (TiN) while no deposition is obtained on Si or SiO₂ surfaces. The process and its potential application will be described in more details during the talk.