An chucking of electrostatic chucks (ESC) involves several electrical characteristics. The following is an introduction to three types of chucking principles, but not necessarily only one force is working, but a combination of several forces that combine to chuck an object. At Creative Technology, we divide the types of ESCs in terms of “which force is dominant?” The ESC, which has different chucking principles depending on the material and design, is one of the ongoing research themes for our company, which specializes in ESCs.

Three Types of Chucking Principles

①Coulomb Force

An ESC, which is dominated by the Coulomb force, can reliably chuck materials by applying a high voltage. It is a standard chucking principle that is excellent in chucking conductive materials and is often used in semiconductor manufacturing equipment. On the other hand, this type is difficult to adapt to non-conductive materials that are difficult to polarize.

【Image of Coulomb Force】

②Johonson-Rabeck Force

An ESC, which is dominated by the Johnson-Rabeck force, is a type that chucks an object by adjusting the insulating properties of the dielectric layer to create a state in which a small amount of current flows. When a voltage is applied to the internal electrode, the charge gradually moves to near the top surface of the dielectric layer, creating a virtual electrode. Since the generated virtual electrode is close to the object, high chucking power can be obtained at low voltage.

【Image of Johonson-Rabeck Force】

③Gradient Force

An ESC, which is dominated by Gradient force, is a type that uses the “electric field” generated between the two electrodes to chuck by finely alternating electrodes of the positive and negative electrodes, and is mainly suitable for the chucking of non-conductive materials. Non-conductive materials that are less likely to be polarized make it difficult to obtain enough chucking force with Coulomb force or Johnson-Rabeck force, so it is necessary to use an electric field to forcibly attract the object. The narrower the space between the electrodes, the higher the chucking force tends to be, but on the other hand, the durability between the electrodes decreases, so a design that considers the balance between the two is required.

【Image of Gradient Force】