Atomic Layer Deposition

Atomic Layer Deposition [ALD] is a self-limiting, sequential surface chemistry that deposits conformal thin-films of materials onto substrates of varying compositions.

ALD is similar in chemistry to chemical vapor deposition (CVD), except that the ALD reaction breaks the CVD reaction into two half-reactions, keeping the precursor materials separate during the reaction. Due to the characteristics of self-limiting and surface reactions, ALD film growth makes atomic scale deposition control possible. By keeping the precursors separate throughout the coating process, atomic layer control of film growth can be obtained as fine as ~0.1 Å per monolayer.
 

ALD is considered the deposition method that offers the greatest potential for producing very thin, conformal films, and the ability to control the thickness and composition of the films at the atomic level. A major driver behind the recent interest and acceptance of ALD in the IC industry are the prospects for ALD in the scaling down of microelectronic devices.

Recently scientific studies demonstrated that some types of ALD films have a good passivation potential, partially because of the negative charges that are present in some films. The potential of using ALD in solar applications to increase cell efficiency is high. However the cyclical nature of traditional ALD systems have relatively low growth rates, which makes it difficult to achieve the throughput numbers required by solar cell manufacturing environments.

In the Levitrack ALD system the solar wafers will travel at high throughput through repeating series of gas zones. This unique “space separation” technology closes the gap between the low deposition rates of traditional “time separation” ALD processes and the high throughput requirements in solar cell manufacturing.