Thin Film Coating – Atomic Layer Deposition Method

High quality thin films with excellent chemical and structural purity, uniformity, and conformality can be manufactured using the ALD method, which involves gas-solid chemical adsorption reactions over the surface. These reactions are self-controlled and self-limiting, resulting in film growth by consecutive atomic layers.

A wide choice of materials can be deposited, including oxides, nitrides, fluorides, sulphides, pure metals (even noble ones), polymers, and graded, mixed or doped layers. Various multi-layered nanolaminates can be deposited with the option of customizing the properties of the individual layers on the molecular level.

The ALD technique not only coats silicon wafers but also 3D objects, powder, porous, and high aspect ratio (HAR) samples. Since the film grows by sequential atomic layers, chemical composition and thickness of the film can be precisely controlled. The ALD process is repeatable and various materials can be deposited at low temperatures, allowing use of also sensitive substrates such as plastics or papers.

High Purity Thin Films – Ion Beam Sputter Deposition

Ion beam sputter deposition is a process that is employed in a wide range of applications where high quality, high performance layer materials and precision film control are of great importance.

However, this process has certain difficulties – for instance, when an ion beam is used to sputter a target material, it is difficult to control the beam shape and collimation so as to prevent any energetic ions following trajectories whereby they could sputter other materials other than the intended target material, such as surrounding fixtures and furniture.

This may possibly contaminate the depositing film with impurities. The impact of this on the performance of the deposited film will depend on the levels of impurities, on the specific application targeted, and on the nature of the impurities.

Effective Thin Film Coating Basic Principles

There are two principal approaches to achieve this effect, namely Subtractive, or the Etch Back process; and Additive, or the Lift Off process.

Subtractive, or the Etch Back process involves the coating of the entire surface, followed by the removal of select portions to form the desired pattern.

Some sort of physical masking agent is normally used in the pattern generating step, followed by the removal of portions without damaging anything else by means of an appropriate type of etching system.

In the Additive, or Lift Off process, the pattern generating step involving some form of physical masking agent is followed by the coating process resembling the use of a stencil.

The openings in the mask allow only the desired pattern to get applied onto the actual substrate. The excess that ends up on the mask top is removed when the mask is lifted off. This article discusses this Lift Off Thin Film Deposition process.

Thin Film Deposition Vacuum Process

Thin Film Deposition is a vacuum process that involves the application of coatings of pure materials over the surface of many different objects. The coatings or films typically have a thickness range of microns and angstroms and can be of single material or multiple materials in a layered structure.

This article covers the basic principles involved in controlling the thickness and rate of Thin Film Deposition using quartz crystal monitoring.

Evaporation is a key class of deposition methods involving heating of a solid material within a high vacuum chamber to a temperature at which some vapor pressure is produced. Inside the vacuum chamber, even a relatively low vapor pressure is adequate to raise a vapor cloud, which is then condensed over surfaces in the chamber as a coating or film.

This process, including the common type of chamber designs generally used, is an ideal candidate for successfully controlling the thickness and rate by means of quartz crystals.