GB2073942A

GB2073942A - Vacuum treatment apparatus

Info

Publication number: GB2073942A
Application number: GB8009519A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-03-21
Filing date: 1980-03-21
Publication date: 1981-10-21

Abstract

Vacuum treatment apparatus comprising a chamber (10) connected at (11) to an evacuating pump and including a platen (12) within the chamber for supporting a number of silicon wafers (17) or other articles to be treated, the chamber also including a rotary drive shaft (13) for rotating the platen. A gas inlet duct (14) provides for admission of a selected gas such as CHF3 or SF6 to the chamber. The chamber also includes a high voltage electrode (15) connected to a high voltage conductor (16), the platen being connected to the other pole of the supply. Both the electrode (15) and the platen table (12) are formed of aluminium or titanium with internal cooling passages and their surfaces are coated with a thin layer of a protective non-metallic material such as polytetrafluoroethylene. <IMAGE>

Description

SPECIFICATION Vacuum treatment apparatus This invention relates to vacuum treatment apparatus of the type designed for treatment of workpieces under high vacuum conditions, often in the presence of a gas plasma. For example, such apparatus may be used for applying coatings to, or etching or removing surface materials from workpieces such as silicon wafers.

The vacuum treatment apparatus normally includes means for connecting the interior of a vacuum chamber to an evacuating pump, means for supporting a workpiece to be treated within the chamber, and at least one high voltage electrode within the chamber, connected or connectable to an external high voltage source to generate the required electric field.

The electrodes and work supports in such apparatus are conventionally formed of a material such as aluminium or titanium, and it has been found that in use under the high vacuum gas plasma conditions, very small microscopic particles of the metals break away from the metal surfaces and can cause damage to the silicon wafers or other workpieces being treated. It is accordingly an object of the present invention to reduce or eliminate this cause of possible damage.

Broadly stated, the invention consists in vacuum treatment apparatus comprising a chamber connected or connectable to an evacuating pump, at least one electrode in the chamber connected or connectable to a high voltage electric source, and means for supporting a workpiece to be treated within the chamber, and in which at least part of the internal surfaces or components within the chamber are coated with a layer of a nonmetallic protective material.

According to a preferred feature of the invention the protective material is a synthetic plastics, and the third plastic materials are halogenated ethylene polymers. A particular preferred material is polytetrafluoroethylene (P.T. F. E.).

The protective material is preferably applied to the surfaces of the electrode and/or the support for the workpiece and from another aspect the invention consists in an electrode or work support for use in such vacuum treatment apparatus, having at least part of its surface coated with a protective non-metallic surface layer.

The invention may be performed in various ways and one specific embodiment will now be described by way of example with reference to the accompanying drawing which is a diagrammatic sectional side elevation illustrating vacuum treatment apparatus according to the invention.

In this example the apparatus comprises a vacuum chamber 10 having an opening door (not shown) which can be closed to form a hermetically sealed internal volume the chamber being provided with a duct 11 for connection to a high vacuum evacuating pump. The chamber also contains a work supporting table or platen 12, means 1 3 for rotating or otherwise moving the work support as required, controlled gas inlet supply means 14 for admitting a selected gas to the chamber when required, and a high voltage electrode 1 5 connected via conductor 1 6 which is installed from the wall of the chamber to an external high voltage source (not shown).In use, under the high vacuum conditions established within the chamber, with the high voltage electric field applied between the electrode 1 5 and the work supporting table 1 2 (which is itself connected to the opposite pole of the high voltage source) there is a tendency for small particles of the metal forming the electrode and work support to break free from the metal surfaces and become embedded in or otherwise damage the silicon wafers 1 7 or other workpieces to be treated, resting on the table 12.

Now in accordance with the present invention both the electrode 1 5 and the work supporting table 12, which are normally formed of a metal such as aluminium or titanium, and may also be formed with internal cooling passages, have their surfaces coated with a thin layer of a protective nonmetallic material, in this case preferably P.T.F.E. or P.V.C.

It is found surprisingly that the use of this protective synthetic plastics material inhibits or at least reduces the potential damage to the workpieces under the high vacuum conditions. For certain particular gases such as CHF3, C2CIF5, CF4, SF6 or CCl4. the risk of damage to the workpieces in the gas plasma is particularly high. It is not fully understood why or how the synthetic plastics coating reduces or eliminates this risk of damage but it is believed that it operates partly as a mechanical barrier preventing breakaway of particles from the metal surface, and also partly as a protective layer preventing erosion or attack by the gas plasma on the surface.

One of the great advantages of the invention is that the coating on the electrode or other surfaces reduces or eliminates sputtering of the metal. This is particularly important when the invention is applied to a plasma etching treatment in which the gas plasma is used to etch away a pattern through a thick oxide surface layer on a silicon wafer for the purpose of forming a semi-conductor microcircuit. It will be appreciated that any small metal particles might become embedded and would so produce short circuits, thus destroying the whole component.

The protective layer may be applied not only to electrodes within the chamber but also to any work supporting device or platen, and also to other parts such as the shielding normally located within the chamber.

In addition to the materials mentioned above, the protective coating may, in general, be formed of any organic or inorganic polymer, and particularly polyvinylchloride.

The voltage source will normally be an alternating voltage supply either at high frequency (R.F. or micro-wave) or down to the range of normal AC main supply.

Claims

1. Vaccum treatment apparatus, comprising a chamber connected or connectable to an evacuating pump, at least one electrode in the chamber connected or connectable to a high voltage electric source, and means for supporting a workpiece to be treated within the chamber, and in which at least part of the internal surfaces or components within the chamber are coated with a layer of a nonmetallic protective material.

2. Apparatus according to claim 1, in which the protective material is a synthetic plastics.

3. Apparatus according to claim 2, in which the plastics material is a halogenated ethylene polymer.

4. Apparatus according to claim 3, in which the plastics material is polytetraflyoroethylene (P.T.F.E.).

5. Apparatus according to any of the preceding claims, in which the protective material is applied to the surfaces of the electrode and/or the support for the workpiece.

6. An electrode, or work support, for use in vacuum treatment apparatus according to any of the preceding claims, the electrode or work support being at least partly coated with a protective non-metallic surface layer.

7. Vacuum treatment apparatus substantially as described with reference to the accompanying drawings.