GB2284096A

GB2284096A - Sealing processing chambers

Info

Publication number: GB2284096A
Application number: GB9422824A
Authority: GB
Inventors: Gordon Robert Green
Original assignee: Electrotech Ltd
Current assignee: Electrotech Ltd
Priority date: 1993-11-22
Filing date: 1994-10-11
Publication date: 1995-05-24
Also published as: GB9324002D0; GB9422824D0; JPH083745A

Abstract

This invention relates to a processing system in which a workpiece, such as a semi-conductor, is processed in a chamber 11 defined by a first enclosure part 10. The chamber 11 has a mouth 17 through which the workpieces are introduced and withdrawn along a path of movement. The mouth 17 can be closed by a second enclosure part 18 mounted on a suitable ram 19 for opening and closing movement in a direction which is inclined to the workpiece path of movement. This arrangement allows the mouth 17 to be relatively small. <IMAGE>

Description

PROCESSING SYSTEM The present invention relates to a processing system for processing workpieces. It is particularly, but not exclusively, concerned with processing systems in which the workpiece is a semiconductor wafer.

In our International Patent Application WO 93/08591 we discussed a processing system for processing semiconductor wafers and other similar workpieces, which was designed to subject a workpiece to elevated temperatures and/or pressures. In the processing of semiconductor wafers and other similar workpieces, it is sometime necessary to form layers which fill small holes (vias) in layers on the wafer.

It had been appreciated that it is possible to fill those holes by subjecting the wafer to elevated pressures, and possibly elevated temperatures, to cause the upper layer to deform to fill the hole.

In WO 93/08591, a pair of enclosure parts were forced together, with their opposed surfaces being shaped so as to define an enclosed void when the two enclosure parts are forced together. This enclosed void may then contain the workpiece to be processed. Pressurised gas can then be fed to the void, to increase the pressures therein.

The reason for using a pair of enclosure parts was to permit the wafer to be located between those enclosure parts before they are forced together. In general semiconductor wafers are moved generally parallel to their plane, so that the wafer could be inserted between the two enclosure parts and the enclosure parts brought together in the direction generally perpendicular to the plane of the wafer.

The present invention is concerned with developments and/or alternatives to the processing system disclosed in WO 93/08591. Note should also be taken of the disclosure of EP-A-0516344, which was concerned with the processing that may be carried out on the semiconductor wafer in order to fill vias and other holes therein by subjecting the wafer to elevated pressures.

A first aspect of the present invention is concerned with the structure of the enclosure in which the wafer is the subject of elevated temperatures and/or pressures. As discussed above, in WO 93/08591 the enclosure parts were moved generally perpendicular to the plane of the wafer.

In the first aspect of the present invention, a first enclosure part defines a cavity for receiving the workpiece, in which cavity the workpiece may be subjected to elevated temperatures and/or pressures, and the workpiece is movable into that cavity in the first enclosure part through a mouth thereof using suitable transport means. Then, a second enclosure part is provided for sealing that mouth. That second enclosure part is movable into or out of its sealing position in a direction which moves it clear of the path of the movement of the workpiece into the cavity.

Preferably, the second enclosure part moves in a direction which is inclined to the path of the workpiece.

In this way, the means for moving the second enclosure part may be moved clear of the path of the workpiece into the first enclosure part, but avoiding the perpendicular movement of WO 93/08591. Because of this, the mouth of the first enclosure part may be made relatively small, thereby reducing the size of the sealing surfaces between the first and second enclosure parts, which is desirable for minimising leakage and closure forces.

In one alternative, the second enclosure part is a plate which is forced into abutment with the periphery of the mouth of the first enclosure part, and sealed thereto by suitable seals. Alternatively, the second enclosure part may be a plug which is received within the mouth of the first enclosure part and is sealed thereto. The former is normally preferable, because there is then no sliding of the sealing surfaces, but the latter may lead to a more compact arrangement.

The second enclosure part may be moved by a suitable hydraulic, pneumatic or electric ram, and the first enclosure part may contain a heater for heating the workpiece. One or other of the enclosure parts will need an inlet/outlet for gas for pressurising the cavity within the first enclosure part, when it is sealed by the second enclosure part, so that the workpiece may be subjected to elevated pressures.

Thus, where the workpiece is a semiconductor wafer, it is moved into the interior of the first enclosure part by the transport means, and may be received on a suitable mounting therein, to enable the transport means to be removed. The interior of the first enclosure part needs to be large enough to receive the wafer, and its transport means, but wasted space can be minimised if the interior (and hence the mouth of the first enclosure part) is shaped to conform generally to the shape of the workpiece.

Once the workpiece is located within the first enclosure part, the transport means is removed and the second enclosure part is moved to seal the mouth of the first enclosure part. The wafer may then be subjected to elevated temperatures and pressures.

A second aspect of the present invention is concerned with the provision of high pressure gas to the enclosure in which the workpiece is to be processed.

In known high pressure processing systems, the high pressure gasses used are occasionally filtered in order to prevent blocking of valves and actuators in the processing apparatus. Generally, the object of such filtration is to extract particles which originate either on the workpieces being processed or from the gas pressurisation and delivery system; these particles might otherwise cause a system malfunction.

The filters used in such applications would typically be capable of retaining particles of one pm or larger in size. In such known high pressure processing systems, gas filtration is never used for the purpose of preventing contamination of the workpiece itself.

According to the second aspect of the present invention, a processing system for processing a workpiece comprises an enclosure in which the workpiece may be processed; means for introducing a gas into the enclosure so as to pressurise the enclosure; and filtering means for filtering the gas prior to its introduction into the enclosure. Using such a system, the high pressure gas may be filtered in order to protect the workpiece from chemical and/or particulate contamination during processing. This is of particular use where the workpiece to be processed is a semiconductor wafer, which is particularly susceptible to such contamination.

Accordingly, the processing system of the second aspect of the invention is preferably adapted for use in processing a semiconductor wafer. More particularly, the system may be of the type described in international patent application no. WO 93/08591, or a processing system in accordance with the first aspect of the present invention.

The filtering means preferably comprises two filters, a first being for the purpose of removing chemical contaminants from the gas and a second being for the purpose of removing particulate contaminants from the gas. The first filter may be activated charcoal filter - this would remove contaminants such as oil vapour from the gas. The second filter, which is ideally located as close as possible to the processing enclosure is preferably able to retain particles 0.02 pm or larger in size and may go as low as 0.01 ?m. Alternatively the filter may be sized to retain particles consistent with the critical dimensions of the workpiece being processed or larger in size. The critical dimensions relate to the minimum feature size intended to be formed on the workpiece. Thus depending on the process, the filter may retain particles of equivalent size or larger or may go down to l/1o or even 1/50 of these dimensions. Use of such high performance filtration is unique in the field of high pressure workpiece processing.

The system may be capable, for instance, of applying pressures in the processing enclosure of 100 bar or greater.

The system will also usually comprise means for heating the processing enclosure and/or a workpiece contained in it; thus, the system may additionally comprise heaters and other appropriate apparatus for generating the required processing conditions.

The present invention additionally provides a method of processing a workpiece, in particular a semiconductor wafer, which method comprises subjecting the workpiece to high pressure in a processing enclosure by introducing gas into the enclosure, wherein the gas is filtered prior to its introduction in to the enclosure. As described above, the gas is preferably passed through two filters, to remove both chemical and particulate contaminants.

Embodiments of the present invention will now be discussed in detail, by way of example, with reference to the accompanying drawings in which: Figure 1 is a sectional view through a first embodiment of the first aspect of the present invention.

Figure 2 is a side view of the embodiment of Figure 1; Figure 3 is a sectional view through part of a second embodiment of the first aspect of the present invention; Figure 4 is a sectional view through a third embodiment of the first aspect of the invention; Figure 5 is a side view of the embodiment of Figure 4; and Figure 6 is a sectional view through an embodiment of both the first and the second aspects of the invention.

Referring first to Figure 1, a first enclosure part 10 defines a chamber 11 for receiving a workpiece 12.

As illustrated in Figure 1, the first enclosure part 10 comprises two parts 13, 14 held together by bolts 15 sealed together by seals 16. One end of the chamber 11 is closed, but the other opens at a mouth 17, with the plane of that mouth being inclined to the direction of elongation of the chamber 11. A second enclosure part 18 is mounted to be movable by means of a suitable ram 19 towards, and away from, the mouth 17. A seal 20 is provided at the periphery of the mouth 17 for sealing the first enclosure part 10 to the second enclosure part 18.

In order to insert a workpiece, such as a semiconductor wafer, into the first enclosure part 10, the second enclosure part 18 is withdrawn from the mouth 17 by the ram 19. A suitable transport means 30 transports the workpiece 12 from the exterior of the first enclosure part 10 through the mouth 17 and into the cavity 11 to the position shown in Figure 1. At that position, the workpiece 12 is received on supports 31, and the transport means 30 can then be withdrawn clear of the first enclosure part 10. The ram 19 then moves the second enclosure part 18 so that it abuts the seal 20, thereby sealing the mouth 17.

Heaters 32 may be provided in the first enclosure part 10, with suitable power connections 33 to enable the cavity 11, and hence the workpiece 12, to be heated. An inlet/outlet 34 for gas is provided to enable the cavity 11 to be pressurised, thereby subjecting the workpiece 12 to elevated pressures. A seal 35 is preferably provided at the inlet/outlet 34.

As can be seen from Figure 1, the direction of movement of the second enclosure part 18 is inclined to the direction of movement of the transport means 30 (that direction being shown by arrow 36), so that the ram can withdraw the second enclosure part 18 clear of the mouth 17 to enable the workpiece 12 to be inserted into the first enclosure part 10. The exact inclination of that movement is not critical.

In general, the smaller the inclination, the smaller the size of the mouth 17. In general, it is advantageous for the mouth to be as small as possible, to minimise the sealing area. On the other hand, the smaller the angle of inclination, the greater the movement of the second enclosure part 18 needed to move it clear of the path of the transport means 30. Thus, a balancing of these conflicting requirements is required in any particular embodiment. In practice, angles of the order of 30C to 60O are suitable.

In the embodiment of Figure 1, the second enclosure part 18 is wider than the mouth 17, and therefore the seals to the periphery thereof. In the second embodiment of the invention, shown in Figure 3, the second enclosure part 18 is shaped so as to fit within a region 40 defining the mouth of the first enclosure part 10, and seals 41 are provided on the second enclosure part 18 for sealing that second enclosure part to the walls of region 40. Other parts of this embodiment may be identical to that of Figures 1 and 2, and are indicated by the same reference numerals.

The embodiment of Figure 3 has the disadvantage that the seals 41 slide along the walls of the region 40 when the second enclosure part 18 is inserted into the first enclosure part 10, and this is not always desirable. In particular, where the workpiece is a semiconductor wafer, such sliding of the seals may cause particles to be generated which could contaminate the wafer. On the other hand, for other situations, the arrangements shown in Figure 3 may be satisfactory.

Figures 4 and 5 show a processing system similar to that of Figure 1, with like parts designated by the same reference numerals. The system of Figures 4 and 5 has an alternative type of second enclosure part 18 for sealing the mouth 17 of the first enclosure part 10. In this case, the second enclosure part comprises a sealing plate 18, located inside the cavity 11, and arranged to overlap and abut, when in its closed position, the seal 20 and the surrounding edges of the cavity mouth 17. The sealing plate is opened and closed relative to the mouth 17 by the action of a number of rams 19. In its open position, the sealing plate 18 occupies the space labelled 50, provided in the cavity 11.

A key difference between the second enclosure member of Figure 4 and that of Figure 1 is that, in the embodiment shown in Figure 4, the rams 19 do not have to withstand the force due to gas pressure inside cavity 11. The sealing plate 18 against the inner walls of cavity 11 is actually energised by forces due to pressurised gas entering the cavity.

On the other hand, the embodiment of Figures 4 and 5 suffers from the disadvantage, relative to that of Figures 1 and 2, that the space 50 into which the sealing plate 18 must be moved to allow clearance for the workpiece 12 to enter and leave the cavity, increases the volume of the overall cavity.

In the embodiment of Figure 4, as in the other illustrated embodiments, other types of actuating mechanism may be used for the second enclosure part rather than the ram(s) 19. This is particularly the case in the Figure 4 embodiment where, because the actuating mechanism does not need to withstand high gas pressures, other types of mechanism such as a magnetic actuator, or ram(s) entering the top of the chamber 11 via high pressure seals, may be of use.

Figure 5, which is a side view of the system shown in Figure 4, illustrates the two rams 19 which cause movement of the sealing plate 18 into and out of its closed position.

Naturally, the mechanism by which the sealing plate 18 is moved must be of an appropriate shape to allow insertion and removal of the workpiece 12, through the mouth 17, into the chamber 11.

The processing system illustrated in Figure 6 is in accordance with both the first and second aspect of the present invention. In most respects it is the same as the apparatus illustrated in Figure 1, with like parts being designated by the same reference numerals. However, the system of Figure 6 additionally incorporates a filter assembly 53, positioned in the gas inlet/outlet 34 immediately before the entrance to the cavity 11. The filter assembly comprises two filters 53a,b: the first, 53a, being for the purpose of removing chemical contaminants from gas entering the cavity 11, and the second, 53b, being for the purpose of removing particulate contaminants. Thus, the workpiece 12 is protected from contamination which might otherwise have entered the cavity 11.

The filters themselves are of conventional design; it is their position relative to cavity 11, and the particular purpose for which they are used in the processing system of the present invention, which is an essential feature of the system shown in Figure 6. The particular filter is also unusually fine, trapping particles of a size 0.0lem or 0.02m or larger. The actual operating characteristics of this filter will be selected to be consistent with the critical dimensions of the workpiece as previously mentioned.

Claims

1. A processing system for a workpiece, having: a first enclosure part defining a cavity for receiving a workpiece, and a mouth for the cavity through which the workpiece can be inserted and withdrawn along a path of movement; a second enclosure part for sealing the mouth of the cavity, and means for moving the second enclosure part into a first sealing position in which closes and seals the mouth and out of the first position into a second position in which it is clear of the workpiece path of movement.

2. A system as claimed in Claim 1 wherein the moving means moves the second enclosure part in a direction which is inclined to the path of movement of the workpiece.

3. A system as claimed in Claim 1 or Claim 2 wherein: - the second enclosure part is a plate; the first enclosure part defines an abutment around the periphery of the mouth and includes sealing means extending around the mouth; and the means for moving forces the plate against the abutment and seals in the first part on.

4. A system as claimed in Claim 1 or Claim 2 wherein the second enclosure part is in the form of a plug which can be inserted in the mouth to seal it.

5. A system as claimed in any one of the preceding claims wherein the first and second positions lie within the cavity.

6. A system as claimed in any one of the preceding claims wherein the means for moving include ram.

7. A system as claimed in any one of the preceding claims further comprising a heater for heating the workpiece.

8. A system as claimed in any of the preceding claims further including an inlet for gas for pressuring the cavity when it is sealed by the second enclosure part, so that the workpiece may be subjected to elevated pressure.

9. A system as claimed in any of the preceding claims including transport means for transporting the workpiece along the path of movement into and out of the cavity.

10. A system as claimed in any one of the preceding claims further including a support for the workpiece within the cavity.

11. A processing system for processing a workpiece comprises an enclosure in which: a workpiece can be processed; means for introducing a gas into the enclosure so as to pressurise the enclosure; and filtering means for filtering the gas prior to its introduction into the enclosure.

12. A system as claimed in Claim 11 wherein the filtering means comprises two filters; a first for removing chemical contaminants from the gas and second for removing particulate contaminants.

13. A system as claimed in Claim 12 wherein the filter retains particles consistent with the intended critical dimensions of the workpiece size.

14. A system as claimed in Claim 12 or Claim 13 wherein the second filter is able to retain particles of 0.01 m or larger in size.

15. A system as claimed in any one of Claims 11 to 13 including a system as claimed in any one of Claims 1 to 10 or as claimed in International Patent No. WO 93/08591.

16. A processing system substantially as hereinbefore described with reference to any one of the accompanying drawings or combinations thereof.

17. A method of processing a workpiece, comprising subjecting a workpiece to high pressures in a processing enclosure by introducing gas into the enclosure, wherein the gas is filtered prior to its introduction into the enclosure.

18. A method of processing a workpiece as claimed in Claim 17 wherein gas is filtered for both chemical and particulate contaminants.

19. A method of processing a workpiece including introducing a workpiece along a path of movement into a caviuty through a mouth thereof and sealing the mouth by moving a sealing part along a path of movement which is inclined to the workpiece path of movement.

20. A method of processing a workpiece substantially as hereinbefore described with reference to any one of the accompanying drawings or combinations thereof.