GB2181366A - The extraction of particulate matter from vacuum processing apparatus - Google Patents

Abstract

Particulate contaminants are removed from a vacuum system, for example wherein ion implantation or vapour phase deposition is being performed, by locating trays 1 containing viscous, low vapour pressure oil or grease where contaminants are likely to occur. The effective surface area of the oil or grease is extended by needle like projections 2 or an open mesh structure. <IMAGE>

Description

SPECIFICATION The extraction of particulate matter from vacuum processing apparatus The present invention relates to the removal of contaminating particulate matter from vacuum processing systems.

A major problem in the manufacture of microelectronic devices by processes which employ vacuum based techniques such as ion implantation or the vapour phase deposition of coatings is the contamination of supposedly clean surfaces of substrates by particulate matter within the vacuum chamber in which the substrates are being processed. The particulate matter may enter the vacuum chamber during those stages of the processing of the substrate when the gas pressure in the chamber is allowed to rise, or it may be derived from the wear of substrate manipulating apparatus inside the chamber, or even substrates which might break during processing. However it arises, the problem is one of increasing severity as larger and larger scale integration is adopted and the individual circuit elements on a substrate become smaller and smaller.

According to the present invention there is provided a method of reducing the contamination by particulate matter of an exposed surface of a body undergoing processing in a vacuum chamber, comprising the operation of placing horizontal trapping surfaces adjacent expected sources of the said particulate matter in positions such that the expected trajectories of the particles comprising the particulate matter will cause them to impinge upon the trapping surfaces.

Also according to the invention there is provided a trapping device for particulate matter within a vacuum chamber comprising a tray for containing a viscous trapping medium and having therein means for substantially extending the surface area of the trapping medium.

The means for substantially extending the surface area of the trapping medium may comprise a plurality of needle-like projections over at least a proportion of the surface of which the viscous medium can migrate by capillary forces, or an open mesh structure.

Preferably the viscous medium is a vacuum oil or grease.

Also according to the invention there is provided a vacuum processing apparatus including a trapping device so positioned as to intercept the expected trajectories of the said particles of particulate matter.

The invention will now be described, by way of example, with reference to the accompanying drawing which is a cross-section of a particulate material trapping device embodying the invention.

Referring to the drawing, a device for trapping particulate matter generated within a vacuum processing chamber comprises a tray 1 in which there is a plurality of needles 2 projecting from the bottom of the tray 1. In use, the tray 1 is filled with a trapping medium 3 consisting of a high-viscosity, low vapour density oil such as a silicone-based vacuum pump oil. Capillary and surface tension forces cause the oil to rise between the needles 2, and also to migrate over their surfaces thus considerably increasing the effective surface area of the trapping medium 3.

It will be appreciated that under vacuum conditions even sub-micron particles will fall vertically with an acceleration equal to that of gravity. Therefore in use one or more of a trapping device such as that described is placed with its trapping surface horizontal under those regions where particulate matter may occur within a vacuum processing chamber. Such regions are:~ mechanisms which form part of ion implantation apparatus within the vacuum chamber, in particular substrate holders and manipulators for them; rotary seals for services into the vacuum chamber; and entry ports for bleed gases.

1. A method of reducing the contamination by particulate matter of an exposed surface of a body undergoing processing in a vacuum chamber, comprising the operation of placing horizontal trapping surfaces adjacent expected sources of the said particulate matter in positions such that the expected trajectories of the particules comprising the particulate matter will cause them to impinge upon the trapping surfaces.

2. A trapping device for particulate matter within a vacuum chamber comprising a tray for containing a viscous trapping medium and having therein means for substantially extending the surface area of the trapping medium.

3. A trapping device for particulate matter according to claim 2 wherein the means for substantially extending the surface area of the trapping medium comprises a plurality of needlelike projections.

4. A trapping medium for particulate matter according to claim 2 wherein the means for substantially extending the surface area of the trapping medium comprises an open mesh structure.

5. A trapping device for particulate matter according to any of claims 2 to 4 wherein the viscous medium is a vacuum oil or grease.

6. A vacuum processing apparatus including a trapping device according to any of claims 2 to 5 so positioned as to intercept the expect trajectories of the said particles of particulate matter.

7. A method of reducing the contamination by particulate matter of a body undergoing processing in a vacuum chamber substantially as hereinbefore described with reference to the accompanying drawing.

8. A trapping device for particulate matter within a vacuum chamber substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION The extraction of particulate matter from vacuum processing apparatus The present invention relates to the removal of contaminating particulate matter from vacuum processing systems. A major problem in the manufacture of microelectronic devices by processes which employ vacuum based techniques such as ion implantation or the vapour phase deposition of coatings is the contamination of supposedly clean surfaces of substrates by particulate matter within the vacuum chamber in which the substrates are being processed. The particulate matter may enter the vacuum chamber during those stages of the processing of the substrate when the gas pressure in the chamber is allowed to rise, or it may be derived from the wear of substrate manipulating apparatus inside the chamber, or even substrates which might break during processing. However it arises, the problem is one of increasing severity as larger and larger scale integration is adopted and the individual circuit elements on a substrate become smaller and smaller. According to the present invention there is provided a method of reducing the contamination by particulate matter of an exposed surface of a body undergoing processing in a vacuum chamber, comprising the operation of placing horizontal trapping surfaces adjacent expected sources of the said particulate matter in positions such that the expected trajectories of the particles comprising the particulate matter will cause them to impinge upon the trapping surfaces. Also according to the invention there is provided a trapping device for particulate matter within a vacuum chamber comprising a tray for containing a viscous trapping medium and having therein means for substantially extending the surface area of the trapping medium. The means for substantially extending the surface area of the trapping medium may comprise a plurality of needle-like projections over at least a proportion of the surface of which the viscous medium can migrate by capillary forces, or an open mesh structure. Preferably the viscous medium is a vacuum oil or grease. Also according to the invention there is provided a vacuum processing apparatus including a trapping device so positioned as to intercept the expected trajectories of the said particles of particulate matter. The invention will now be described, by way of example, with reference to the accompanying drawing which is a cross-section of a particulate material trapping device embodying the invention. Referring to the drawing, a device for trapping particulate matter generated within a vacuum processing chamber comprises a tray 1 in which there is a plurality of needles 2 projecting from the bottom of the tray 1. In use, the tray 1 is filled with a trapping medium 3 consisting of a high-viscosity, low vapour density oil such as a silicone-based vacuum pump oil. Capillary and surface tension forces cause the oil to rise between the needles 2, and also to migrate over their surfaces thus considerably increasing the effective surface area of the trapping medium 3. It will be appreciated that under vacuum conditions even sub-micron particles will fall vertically with an acceleration equal to that of gravity. Therefore in use one or more of a trapping device such as that described is placed with its trapping surface horizontal under those regions where particulate matter may occur within a vacuum processing chamber. Such regions are:~ mechanisms which form part of ion implantation apparatus within the vacuum chamber, in particular substrate holders and manipulators for them; rotary seals for services into the vacuum chamber; and entry ports for bleed gases. CLAIMS

1. A method of reducing the contamination by particulate matter of an exposed surface of a body undergoing processing in a vacuum chamber, comprising the operation of placing horizontal trapping surfaces adjacent expected sources of the said particulate matter in positions such that the expected trajectories of the particules comprising the particulate matter will cause them to impinge upon the trapping surfaces.

2. A trapping device for particulate matter within a vacuum chamber comprising a tray for containing a viscous trapping medium and having therein means for substantially extending the surface area of the trapping medium.

3. A trapping device for particulate matter according to claim 2 wherein the means for substantially extending the surface area of the trapping medium comprises a plurality of needlelike projections.

4. A trapping medium for particulate matter according to claim 2 wherein the means for substantially extending the surface area of the trapping medium comprises an open mesh structure.

5. A trapping device for particulate matter according to any of claims 2 to 4 wherein the viscous medium is a vacuum oil or grease.

6. A vacuum processing apparatus including a trapping device according to any of claims 2 to 5 so positioned as to intercept the expect trajectories of the said particles of particulate matter.

7. A method of reducing the contamination by particulate matter of a body undergoing processing in a vacuum chamber substantially as hereinbefore described with reference to the accompanying drawing.

8. A trapping device for particulate matter within a vacuum chamber substantially as hereinbefore described with reference to the accompanying drawing.