ALD Reactors

This article discusses the science and technology behind ALD deposition reactors. A deposition reactor is a macroscopic object that enables atomic growth processes to be carried out in a reproducible and controlled manner. The choice of reactor and its configuration are often the most important steps in setting up an ALD project, whether on a laboratory or plant scale.

The development and marketing of ALD equipment takes place within the vacuum thin-film deposition equipment industry. On a global scale, this industry dedicated to the world market was born and has developed over the last 35 years to produce and market machines using techniques such as PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition)...

There is a general trend in the thin-film equipment industry to increase the technological content, and therefore the added value, of its offering. All equipment manufacturers now have engineering and process demonstration laboratories where they develop and demonstrate new deposition processes. It is common practice to demonstrate deposition as part of an equipment purchase project, and to provide the necessary know-how for proper operation and maintenance of the equipment, including standard operating parameters and recipes, recommended suppliers of consumables such as chemicals and spare parts. Most users will then focus their development efforts on integrating the OEM-developed deposition process into the particular manufacturing sequence of their device. This route to commercializing advances in nanotechnology has proved extremely efficient, so that the equipment supplier's substantial R&D costs can be spread over a large number of component manufacturers, without limiting the equipment users' ability to differentiate themselves from their competitors in their market.

The ALD equipment market has grown steadily over the past two decades. The industry's average annual growth rate has been in excess of 20%, and the total market now exceeds 1 billion euros per year. This market is served by a variety of suppliers, based mainly in North America, Europe and increasingly in Asia.

In this article, we will review the basic conditions that are necessary for the realization of an ALD process.

We will then formulate performance criteria that allow us to evaluate and compare how well a certain piece of equipment is suited to a particular use. Some ALD reactor architectures that have been developed to date are presented. Finally, some practical applications will be described.