Device for carrying out a plasma-assisted process

Abstract

A device for carrying out a plasma enhanced process includes, within a vacuum chamber, at least one magnetron electrode (32) constituting an unbalanced magnetron having a flat magnetron face (20) with peripheral and central magnetic poles of opposite polarities connected to a source (34) of alternating voltage. The device further includes a device for positioning a substrate (25), the substrate having a surface to be treated facing the magnetron face (20), and a gas supply device for supplying a process gas or process gas mixture to the space between the magnetron face (20) and the treated surface. The distance between the magnetron face (20) and the treated surface is adapted to the magnetic field created by the magnetron electrode (32) such that there is a visible plasma band running between darker tunnels formed by magnetic field lines extending between peripheral and central magnetic poles of the magnetron face (20) and the treated surface, the plasma band having a minimum width but having homogeneous brightness towards the treated surface.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The invention relates to a device for carrying out a plasma enhanced process, in particular a plasma enhanced chemical vapour deposition. The device serves e.g. for coating one side of a web of film or sheet material, in particular for coating a web of polymer film with silicon oxide in order to improve its barrier properties. [0003] 2. Description of Related Art [0004] It is known e.g. from the publication EP-299754 (BOC) to deposit a thin film of silicon oxide on a substrate in a plasma enhanced chemical vapour deposition process. According to this publication a vacuum chamber is provided in which the electrically isolated substrate is positioned to face a magnetron being powered with an alternating voltage. A stream of a process gas mixture consisting of an organosilicon compound, oxygen and an inert gas (e.g. argon or helium) is flown into the space between the face of the magnetron and the substrate and the pla...

AI Technical Summary

Benefits of technology

[0007] The object of the invention is to improve the above named devices applicable for plasma enhanced processes, in particular for plasma enhanced chemical vapour deposition but also for e.g. plasma etching or plasma processes for changing the wetability or adhesion characteristics of a surface and belonging to the type being based on a magnetron. The improvement is to regard in particular process efficiency. For a deposition process deposition rate and deposition quality are to be improved.

[0010] Visual observation of a plasma maintained between an unbalanced magnetron with a flat rectangular face (observation parallel to the longer side of the magnetron face) and a surface to be treated and arranged substantially parallel to the magnetron face shows the named tunnels as quite clearly distinguishable darker areas within the plasma, which outside of the tunnels appears brighter. The above discussed setting of the distance between the magnetron face and the substrate to be dependent on the characteristics of the magnetic field can easily be based on such observation. The surface to be coated is positioned beyond the tunnels such that there is a bright plasma band extending between the tunnels and the surface to be treated, the band having a minimum width but having towards the surface to be coated a homogeneous brightness, i.e. the same brightness at positions above tunnels as at a position above the gap between tunnels.

Problems solved by technology

The unbalanced magnetron is known to not fully confine electrons and ions of the plasma such that there is a limited amount of electron and ion bombardment of the substrate which is said to improve the deposition quality.

The magnetron face of the unbalanced magnetron according to EP-0299754 comprises peripheral north poles and a central core of soft iron, resulting in an only small portion of the field lines extending from the north poles to the core (highly unbalanced magnetron).

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