March 27, 2012

Joint Initiative To Develop Advanced Atomic Layer Deposition Technology For Next Generation Memories And Solar Cells

A*STAR Institute of Microelectronics (IME) and Picosun Oy, a Finland-based global manufacturer of Atomic Layer Deposition (ALD) equipment, have announced a partnership to develop advanced ALD techniques to enable continuing growth in the areas of next generation memories and solar cells.

With this collaboration, IME and Picosun will jointly develop innovative ALD and plasma-enhanced ALD (PEALD) processes for novel dielectrics and metals for applications in resistive switching non-volatile memories (NVM), multilayer metal-insulator-metal (MIM) capacitors, solar cells, and advanced complementary-metal-oxide-semiconductors (CMOS). Enabling integration of the processes with the devices for industrial applications will be the core objective of the joint research project.

Tufts University describes plasma-enhanced Atomic Layer Deposition

The key to Plasma Enhanced Atomic Layer Deposition (PEALD) is to remove passivating hydrogen atoms without the use of a thermal spike. Our approach is to break the remaining Si-H bonds using energy from Ar plasma, while decreasing the substrate temperature to within the thermal budget of front-end chip processing.
Schematic representation of one cycle of an atomic layer deposition (ALD) process. The cycle can be repeated until the film thickness projected is achieved.

Introduction to (plasma-enhanced) atomic layer deposition. Film growth by the atomic layer deposition (ALD) method relies on alternate pulsing of the precursor gases and vapors into a vacuum chamber and their subsequent chemisorption on the substrate surface. The different steps in the process are saturative such that ALD film growth is self-limiting yielding one submonolayer of film per deposition cycle. ALD has some unique characteristics making the method technologically very relevant:
(1) ultimate control of film thickness;
(2) excellent conformality on very high aspect ratio structures;
(3) good uniformity on large substrates; and
(4) straightforward to apply to produce multilayer structures.

In the last few years, research has provided several ALD processes of which some are currently implemented in industry. However, the materials that can be deposited by the strictly chemical method (thermal ALD) are limited by the availability of precursors and by (thermally-driven) surface reactions. By the introduction of a low-temperature plasma step in the ALD reaction cycle, it is possible to deliver additional reactivity to the surface in the form of plasma-produced species. This opens up a processing parameter space that is unattainable by the strictly thermally-driven process. Consequently, the plasma-enhanced ALD (PE-ALD) technique has a bright prospect for a large variety of applications also outside the typical use in semiconductor devices.

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