GB2346953A - Removing water from articles - Google Patents

Abstract

Apparatus for and method of removing water from the surface of an article in a drying vessel containing a drying fluid, comprises heating and vaporising two fluids, causing the vaporised fluids to contact the article and condensing, collecting, separating said fluids and recycling at least one said fluid. The fluids may include (a) a solvent for water selected from aliphatic C<SB>1</SB> to C<SB>5</SB> alcohols, ketones, nitriles, and nitroalkanes, and (b) include a fire retardant which is a fluorinated organic compound. The fluids may be miscible or not.

Description

REMOVING WATER FROM ARTICLES This invention relates to the removal of water from articles.

There is an ever increasing demand for micro-circuitry and other patterned depositions formed on a substrate, and also for an increasing fineness of lines and shapes in such depositions. Typically, such a pattern may be printed as a pattern or over a resist which has been etched to expose the required pattern. For example a photo-resist may be laser-etched to expose the desired pattern on a substrate which is then overall coated with a deposit. The remaining resist material and overlying deposit is then removed to leave the desired pattern of deposit. The substrate may for example be a semi-conductor wafer or a glass or ceramic plate.

It will be appreciated that the finer the pattern which it is required to deposit, the cleaner must be the substrate, and there is presently a demand on an industrial scale for substrates which are free even from stains such as may be left by the evaporative drying of de-ionised water from such substrates. There is also a need in precision engineering for articles to be clean and stain free: an example is computer disk read heads.

There is thus a need, within industry, to clean components thoroughly, and rinse them, and thereafter completely to remove any water from the cleaned and rinsed components: the components must be stain free and dry upon completion of the process.

An ideal process for such a purpose would have at least the following properties: 1. The materials and methods used should not degrade, attack or modify the article in any way.

2. The process should be capable of processing components in less than five minutes.

3. The process should be able to dissolve and displace high purity water from microscopic complex geometric surfaces and deep trenches leaving zero residues detrimental to the components or subsequent operations.

4. During operation the process should completely remove high purity water without adding particles greater in size than 0.15 microns.

Ideally the process should act as an aid to the removal of any particles remaining on the surface of components after the cleaning and rinsing processes.

5. The process used should be essentially non-flammable during operation and the materials used within the process essentially non toxic, non-ozone depleting and thermally stable.

6. The equipment used should exhibit near zero solvent emissions during non-process operation and very low emissions during processing.

7. The process should be economical to operate.

For many years various drying processes have been used to remove water from semiconductor wafers, glass plates and other substrates. Centrifugal force, pure IPA (isopropanol) vapour and Marangoni effect drying have been the preferred methods used in a wide range of post operative drying processes. All of these methods satisfied some, but not all, of the above desiderata to varying degrees.

Centrifugal drying requires the articles to be dried to be subjected to considerable mechanical stress. This may be acceptable for small and/or robust articles. It is not acceptable for rather fragile articles. For example silicon wafers have been produced for some years in sizes of about 10cm. It has been the practice to place say 20 such wafers in a centrifuge boat and accept the fact that if one wafer breaks during centrifuging, the others will also shatter. But currently such wafers are being produced in sizes of about 30cm, and these are firstly more likely to fail during centrifuging, and secondly too expensive to risk breaking in that way. There is also the inconvenience of cleaning the centrifuge in order to remove any particles which might deposit onto an article which is subsequently dried in that centrifuge.

The principal known Marangoni effect drying method comprises forming a mist of IPA in a nitrogen atmosphere above a body of de-ionised water in a drying vessel. The IPA settles to form a meniscus layer of IPA on the water, and the articles to be dried are drawn through that IPA layer either by lifting them through it or by drawing the water down. The IPA film thus formed on the article and IPA condensing on it from the mist dissolve and carry off any residual water remaining on the article. This gives a satisfactory result, but it is time-consuming, there is a high capital investment cost, it involves a high nitrogen consumption, and uses considerable quantities of de-ionised water which becomes contaminated with IPA.

The principal known isopropyl alcohol vapour drying method comprises forming a vapour of IPA in a drying vessel. The IPA condenses on the articles to be dried and takes the water into solution with the condensate, which then drains from the surface by gravity. As the articles reach an equilibrium temperature with the vapour and no further condensation takes place the articles are withdrawn to a cool area where any residual IPA vaporises. This gives a satisfactory result, but is time consuming, there is a need for continuous extraction of flammable IPA vapour to atmosphere, which results in a high consumption of IPA, and the system relies on fire suppression rather than prevention.

The semiconductor industry in particular demands a high degree of water removal and zero particulate addition which tends to preclude the use of conventional equipment and processes which would normally be acceptable within the general electronics and precision component industries. For this reason the industry has accepted one of the above methods for water removal despite non-compliance with one or more of the desiderata listed. Although the end products usually comply with most specifications and yield requirements, users tend to be less than satisfied with the equipment performance. The major criticisms are due to difficulties associated with the process management of the chosen removal method: for example, centrifugal dryers can damage wafers and are potential particle adders. IPA vapour drying is an inherently dangerous process, which uses large quantities of IPA due to atmospheric emissions and effluent waste stream. Marangoni effect dryers use large quantities of de-ionised water and nitrogen, are potential particles adders and waste effluent stream can be restricted in some locations due to IPA traces in the waste de-ionised water being above permitted water authority limits.

It is an object of the present invention to provide methods and apparatus for the removal of water from articles which go at least some way towards alleviating at least some of the disadvantages associated with previously known systems.

The present invention provides a method of removing water from the surface of an article in a drying vessel containing a drying fluid, characterised in that such method comprises heating and vaporising two fluids, causing the vaporised fluids to contact said article and condensing, collecting, separating said fluids and recycling at least one said fluid.

The invention extends to apparatus for removing water from the surface of an article comprising a drying vessel for containing a drying fluid, a support for conducting components into and out of said vessel and means for heating and vaporising two fluids, and means for condensing, collecting, separating and recycling at least one said fluid.

The invention provides certain improvements in techniques which may be married up with existing practices, but it also provides an alternative method which, at least in its most preferred embodiments is capable of completely removing relatively high quantities of water from a substrate using a dual solvent vapour process, which is capable of being operated in such a way that it complies with all the listed desiderata and whose process can be run more consistently and managed more easily.

The vapour may consist of two separate volatile fluids of for example similar boiling point. The first, being a flammable hydrophilic solvent, is used to dissolve the water into solution and the second being a fluorinated, organic, fire retardant compound is used primarily to suppress and inert the flammability of the first fluid and secondly to aid in the rinsing and removal of both the first fluid and any pre-operative remaining particulate matter.

The invention in its most preferred embodiments seeks to provide a means of removing relatively high quantities of water from a surface using a dual solvent vapour process to provide dissolution and displacement, wherein water laden components are slowly inserted, at a controlled rate, into the dual vapour which may contain varying percentages of solvent and fluorinated fluid vapours at or near to their respective boiling points. As the components enter the dual vapour zone, both types of vapour condense on the cooler surface of the articles being dried and hence return to their natural liquid state and drain off under gravity taking any water with them.

One preferred embodiment of the invention uses immiscible fluids, which immediately separate as they condense on the surface of the substrate.

Both liquids then flow in a downward motion due to gravity. The solvent fluid dissolves any water on the surface of the components whilst, simultaneously, the fluorinated fluid displaces the water and solvent solution from the surface.

A second preferred embodiment of the method of the invention uses a fluorinated compound with at least one hydrogen bond and a solvent which are either partially or fully miscible and which may condense as a single fluid or as separate fluids. The dual vapour may contain a percentage of an azeotrope formed by the two liquids. As the mixture condenses on the surface of the substrate the solvent is attracted to water present on the substrate surface, and combines with it. Upon contact with the water, any azeotrope present will be broken and the solvent will combine with the water forming an immiscible emulsion with the fluorinated fluid.

After a predetermined dwell time when all the water is dissolved and displaced the components are removed at a controlled rate to an area above the vapour which is cooled by either refrigeration or water-cooled coils and plates as described herein. The components remain in this area for a predetermined dwell period to enable all remaining vapours to evaporate and be collected in a controlled environment. The components are then removed from the process in a dry state.

The cool stage attracts the condensed vapours from the component surface, which are present in small quantities when the surface of the component is approximately the same temperature as the dual vapour.

This condensed vapour is collected and may be returned to the main process chamber as two separate liquid distillates, in the case of a perfluorinated fluid or a single fluid in the case of hydrogen containing fluorinated compound.

To avoid losses of both fluids it will be necessary to separate and to conserve the materials and remove the solution of water and alcohol from the fluorinated fluid by means of separation, cooling, distillation, condensation and recycling means known to the art. In some instances it is possible to re-use the separated solution without further processing. In all instances it is possible to recover the fluorinated fluid for re-use.

Thus, in a further aspect, the invention provides apparatus-for the dissolution and displacement drying of components, comprising of a reservoir containing both a solvent fluid and a highly fluorinated compound, means for heating and evaporating the solvent and the highly fluorinated compound from said reservoir, means for conducting a dual vapour, produced as a result of heating the fluids, to a process chamber and therefore fill said chamber with the same dual vapour, means for conducting components to be dried in and out of said chamber and means for condensing and recycling the fluids once condensed back into solvent and water solution and highly fluorinated compound, means for separating the said solution from the highly fluorinated compound. Preferably the heating means is via hot recirculated fluid heated indirectly by an electrical heating pad or immersed coil of low watt density.

The condensing means are suitably chilled coils which may be chilled by refrigeration, chilled water supply or town water depending on the acceptable losses and boiling point of the highly fluorinated compound.

The condensing means may be two stage wherein a row of condensing coils provide the primary cooling effect and are chilled to a particular temperature and the secondary cooling means may be a large surface area cooling plate above the cooling coils chilled to a lower temperature.

There may be a plurality of displacement process chambers to provide a further separation of fluids, and therefore a continuos supply of both fluids interconnected by means of weir division plates or air wall gaps as described herein.

Certain preferred features of the invention are as follows: said fluids are a solvent for water and a fire-retardant; said solvent is an organic solvent selected from the group consisting of aliphatic Cl to C5 alcohols, ketones, nitriles, and nitroalkanes; said fire retardant is a fluorinated organic compound; the fluorinated compound is chlorine and bromine free; said fire retardant liquid is denser than said solvent; said fluids are immiscible and of different densities so that together their liquids form a stratified body; heat transfer to said organic solvent is accomplished by bubbling a denser fire retardant liquid through it; the fluorinated compound is selected from the group consisting of perfluoroalkanes, perfluoro-alicyclic compounds, perfluoroamines, and perfluoroethers; the fluorinated compound is selected from the group consisting of perfluoroalkyls, perfluoro-polyalkylcyclohexanes and perfluoropolyethers ; the fluorinated compound is selected from the group consisting of perfluoro-1,3-dihydrocyclo-hexane, pefluoro-oxyalkylene, and perfluoromethylcyclohexane; said fluids are miscible; said miscible fluids form an azeotrope; said azeotrope is a mixture of methoxy-nonafluoro-butane and isopropanol; the fluorinated compound is selected from the group consisting of hydrofluoroethers, hydrofluorocarbons and hydrofluoropolyethers ; the fluorinated compound comprises dihydroperfluoropentane; the drying fluid comprises an organic solvent and a fluorinated compound which is present in a proportion less than that of the saturation solubility of that fluorinated compound in the organic solvent; the said fluid contacts the article while in the vapour phase and condenses thereon; during said drying an upper portion of the vessel is cooled to provide a cold trap and condense any such fluid vapour contained in the upper part of said vessel; said article is moved into and out of said vessel while carried by a support; the boiling points of said two fluids are within 15 C preferably 10 C of one another; the boiling point of said fluorinated compound is between 30 C and 250 C preferably between 30 C and 100 C and most preferably between 40 C and 90 C for example between 70 C and 90 C ; said drying fluid comprises an organic solvent which comprises water in a proportion less than that of the azeotropic composition of the water organic solvent system; the article being dried is a semiconductor wafer, glass or ceramic substrate; said drying vessel has an upper portion comprising a cold trap for condensing drying fluid vapour contained by said vessel; said drying vessel comprises liquid level sensing means adapted to sense the levels of the respective surfaces of at least two liquids; condensing means constituted as cooling coils and/or cooling plates; the fluid and vapour containment components are manufactured in stainless steel or quartz; the vessel contains means for collecting distillate condensed on articles being dried and for diverting that distillate out of the drying vessel; the support for said articles is constituted as said collecting and diverting means; means is provided for directing and diverting to the inner walls of the drying vessel any distillate condensed by cooling means within said drying vessel; heating means is provided for heating the walls of said drying vessel; means is provided for sealing said drying vessel during processing; said drying vessel contains means for monitoring the presence of a vapour; said vessel is provided with an offset boil sump for permitting rapid vaporisation of fluids and transfer thereof to the drying vessel; The invention will be further described, by way of example only, with reference to the accompanying drawing, which is a schematic view of an apparatus according to the invention.

In the following descriptions references to perfluorocarbon are to be taken to include references to highly fluorinated organic compounds and vice versa.

In the following descriptions references to IPA are to be taken to include references to flammable hydrophilic based fluids with a closed cup flash point below 55 C and vice versa.

A first method and a relatively simple form of apparatus according to the invention will now be described with reference to the accompanying drawing.

Example 1 The drawing shows a drying vessel 2 containing a dense perfluorocarbon fluid 40 and IPA 41. These remain separate layers because the two liquids 40 and 41 are mostly immiscible. A heater 27 is fixed to the outside or inside wall of the base of the drying vessel, and further heaters 10 are placed on the outside or inside side walls of the drying vessel these being of a low watts/density. The temperature of each heater is controlled by separate thermocouples 42 and control circuitry pertinent to the application. Cooling coils 7 and plates 3 are located inside the upper part of the drying vessel. The plates 3 are arranged to form a cold trap forcing condensation of any vapour which reaches the upper portion of the drying vessel and are arranged to cause condensate forming thereon to trickle onto the side walls of the drying vessel and thus to flow back down to its base. A coolant fluid, for example at-20 C is arranged to flow through those cooling plates to maintain them at low temperature. When the heater 27 is activated perfluorocarbon fluid 40 is heated to boiling point and vapour bubbles are produced such that IPA fluid 41 is heated to boiling point and vapour of both types of fluid 40 and 41 rise to create a dense vapour 8 in the mid part of the drying vessel eventually covering all space above the fluid up to approximately the mid point of the cooling coils 2 which are suitably maintained at about 0 C to 5 C. The upper level of vapour 8 is controlled by the cooling coils 7 which condense both vapours and the resultant liquid condensate is diverted via troughs 23 below the coils down the side walls of drying vessel 2 and returns by gravity to the base of drying vessel 2 to be re-heated by heater 27. Loss of the perfluorocarbon and IPA fluid from the drying vessel is greatly reduced due to the design of the component carrier 12, and the presence of the sealed lid 1 and of the cooling coils 7 and the cold trap constituted by the cooling plates 3. When the fluid levels 41 and 40 at the base of drying vessel 2 fall to levels insufficient to operate the process effectively and to prevent this situation from affecting the repeatability and efficiency of the process, low level sensors 19 and 20 are used at two different height levels to firstly call for additional fluids at the higher level which are presented automatically and secondly to switch off the heaters 27 and 10 and alert the operator at the lower level. Both level devices 19 and 20 are able to distinguish between the two different fluids.

Any perfluorocarbon may be used provided that it is compatible and its boiling point will not affect the components.

The flash-point of the flammable organic fluid may be below the temperature of the process chamber and the perfluorocarbon vapour temperature. The use of perfluorocarbon and most other HFOC materials in the vapour phase will provide a non-flammable inert vapour blanket. As vapour 8 is created in drying vessel 2 it will eventually fill the entire space above the fluids 40 and 41 and below the coils 7. In order to operate the process safely the vapour 8 must be present before components are introduced into the apparatus, a vapour present temperature probe 9 is provided in the drying vessel to monitor the vapour temperature and is coupled to a thermostatic control which requires a vapour 8 to be present before allowing the top sealed door 1 to be opened.

In the event of a failure of the cooling coils 7 to contain the vapour at the correct level the vapour 8 will rise above the coils 7 and into freeboard space 4. This could lead to unacceptable and dangerous losses of both fluid vapours from the apparatus. A temperature probe 6 is provided to sense such a rise in temperature and switch off the heater circuit to prevent the creation of additional vapour.

Still with reference to the drawing, an article to be dried 11 is lowered into the dual vapour 8 for an appropriate time using the carrier 12, following which the dual vapour 8 cools and condenses on the surface of the component immediately separating and returning to the two fluid states 41 and 40. The IPA portion of the vapour 8 dissolves any water on the surface of the component 11 whilst the perfluorocarbon portion of the vapour 8 displaces the solution of IPA and water. The two fluids travel in a downward direction due to gravity and fall into the collection zone built into the carrier 12. The flow of fluid formed is restricted by means of a baffle built into carrier 12 until such time as the carrier 12 meets with outlet pipe 14. When carrier 12 is coupled to tube 14 valve 15 is operated automatically and both fluids flow into separation chamber 16.

The fluids remain as separate and distinct layers within separation chamber 16 and continue to rise in level as further cycles are operated until reaching level device 17 when pump 24 is automatically activated and the fluids are transferred via tube 18, check valve 25, tube 26, filter 35 and tube 33 into further separation chamber 32. The pipe arrangement 33 and position of level devices 30 and 31 within chamber 32 are such as to ensure that only perfluorocarbon fluid entering vessel 32 is allowed to flow back into drying vessel 2 and water contaminated IPA is removed from the vessel 32 via U tube 34 and outlet tube 43 for external recycling as required. Both level devices 30 and 31 operate only in the presence of perfluorocarbon. As the fluids continue to flow into vessel 32 the level will rise to and past level device 30 until perfluorocarbon reaches level device 31 at which point valve 28 will open and perfluorocarbon will flow back into drying vessel 2 via filter 37 until such time as perfluorocarbon reaches level 30 in vessel 32 or the correct operating level of perfluorocarbon in drying vessel 2 is reached at which point valve 28 will close. Tubes 5 and 36 are pressure balancing tubes, which prevent overpressurisation of the system. Perfluorocarbon 40 is introduced into the system as and when required via suitable external source feed line 39 check valve 38 and filter 35 the outflow side of which can be connected as shown in the drawing. Drying fluid (IPA) 41 may be introduced via a separate source feed line or in any way deemed appropriate.

After the appropriate time the component 11 is automatically withdrawn to the area 4 above the vapour 8 and cooled by the air in the space 4 above the vapour 8, the air is cooled by the plates 3. Any remaining fluids on the component 11 or carrier 12 will vaporise and be attracted to the cool plates 3 where it will condense and drip down into the base of the drying vessel 2 via troughs 23 and side wall heaters 10 before returning to the process fluids 40 & 41. Following a suitable time in the cool area the component 11 is withdrawn from the drying vessel 2 to a position above the door 1 or may be returned to the vapour 8 for secondary vapour drying. During the operation of the process the emission of fluids is minimised by a sealed lid 1 which compresses suitable sealing material underneath the lid.

The component 11 thus finishes the process in a dry state with no residual contaminants thereby providing a clean dry component.

Example 2 A second embodiment of the method using a slightly modified but still simple form of apparatus according to the invention will now be described with reference to the same accompanying drawing.

The drawing shows a drying vessel 2 containing a heavily fluorinated fluid containing at least one hydrogen bond 40 and IPA 41. As soon as any form of agitation takes place the two fluids partially or fully mix. A heater 27 is fixed to the base of the drying vessel and further heaters 10 fixed to the side walls of the drying vessel and are again of a low watts/density. The temperature of each heater is controlled by separate thermocouples 42 and control circuitry pertinent to the application.

Cooling coils 7 and plates 3 are located inside the upper part of the drying vessel. When the heater 27 is activated the mixed fluids 40 and 41 are heated to their boiling points and vapour bubbles are produced such that vapour of both types of fluid 40 and 41 and possibly an azeotropic blend of both rise to create a dense vapour 8 in the mid part of the drying vessel eventually covering all space above the fluid up to approximately the mid point of the cooling coils. The vapour level of 8 is controlled by the cooling coils 7 which condense the vapours and the resultant liquid condensate is diverted via troughs 23 below the coils down the side walls of drying vessel 2 and returns by gravity to the base of drying vessel 2 to be re-heated by heater 27. Loss of the fluorocarbon and solvent fluid from the drying vessel is greatly reduced using the same methods described Example 1. When the density of the fluid 41 at the base of drying vessel 2 falls to a level insufficient to operate the process effectively, in order to prevent this situation from affecting the repeatability and efficiency of the process density monitors 19 and 22 are used firstly to call for additional IPA or fluorinated fluid (which are presented automatically) and secondly to switch off the heaters 27 and 10 and alert the operator at the lower level.

Any fluorinated solvent may be used for this method provided it contains at least one hydrogen bond and that it is compatible and it's boiling point will not affect the components.

As vapour 8 is created in drying vessel 2 it will eventually fill the entire space above the fluid 41 up to approximately the mid point of the cooling coils. In order to operate the process safely the vapour 8 must be present before articles to be dried are introduced into the apparatus; accordingly a vapour present temperature probe 9 is provided in the drying vessel to monitor the vapour temperature and is coupled to a thermostatic control which requires a vapour 8 to be present before allowing the top sealed door 1 to be opened.

Still with reference to the drawing an article to be dried 11 is lowered into the vapour 8 for an appropriate time using the carrier 12, following which the dual vapour 8 cools and condenses on the surface of the component. As the IPA portion of the vapour mixture or azeotrope 8 is hydrophilic it dissolves any water on the surface of the component 11 whilst separating from the hydrogen containing fluorocarbon portion of the vapour 8 which displaces the solution of IPA and water. The two fluids travel in a downward direction due to gravity and fall into the collection zone built into the carrier 12. The flow of fluid formed is restricted by means of a baffle built into carrier 12 until such time as the carrier 12 meets with outlet pipe 14. When the carrier 12 is coupled to tube 14 valve 15 is operated automatically and both fluids flow into separation chamber 16.

The fluids, excluding the displaced water, may recombine within separation chamber 16 as one fluid and continue to rise in level as further cycles are operated until reaching level device 17 when pump 24 is automatically activated and the fluids are transferred via tube 18, check valve 25, tube 26, filter 35, which may include a coalescer, and tube 33 into a further heated separation chamber 32. The pipe arrangement 33 and position of level devices 30 and 31 within chamber 32 are such as to ensure that only fluorocarbon fluid entering vessel 32 is allowed to flow back into drying vessel 2 and any separated remaining water contaminated IPA is removed from the vessel 32 via U tube 34 and outlet tube 43. Both level devices 30 and 31 operate only in the presence of excess fluorinated fluid and solvent mixture or azeotrope. As the fluids continue to flow into vessel 32 the level will rise to and past level device 30 until fluorocarbon reaches level device 31 at which point valve 28 will open and outflow side of which can be connected as shown in the drawing or any other way deemed appropriate.

Claims (39)

1. CLAIMS 1. A method of removing water from the surface of an article in a drying vessel containing a drying fluid, characterised in that such method comprises heating and vaporising two fluids, causing the vaporised fluids to contact said article and condensing, collecting, separating said fluids and recycling at least one said fluid.
2. 2. A method according to Claim 1, wherein said fluids are a solvent for water and a fire-retardant.
3. 3. A method according to Claim 2, wherein said solvent is an organic solvent selected from the group consisting of aliphatic Cl to C5 alcohols, ketones, nitriles, and nitroalkanes.
4. 4. A method according to Claim 2 or 3, wherein said fire retardant is a fluorinated organic compound.
5. 5. A method according to Claim 4 wherein the fluorinated compound is chlorine and bromine free.
6. 6. A method according to any of claims 2 to 5, wherein said fire retardant liquid is denser than said solvent.
7. 7. A method according to any preceding claim, wherein said fluids are immiscible and of different densities so that together their liquids form a stratified body.
8. 8. A method according to Claims 6 and 7, wherein heat transfer to said organic solvent is accomplished by bubbling a denser fire retardant liquid through it.
9. 9. A method according to Claim 4 or 5 and Claim 6 wherein the fluorinated compound is selected from the group consisting of perfluoroalkanes, perfluoro-alicyclic compounds, perfluoroamines, and perfluoroethers.
10. 10. A method according to Claim 9 wherein the fluorinated compound is selected from the group consisting of perfluoroalkyls, perfluoro polyalkylcyclohexanes and perfluoropolyethers.
11. 11. A method according to Claim 10 wherein the fluorinated compound is selected from the group consisting of perfluoro-1, 3-dihydrocyclohexane, perfluoro-oxyalkylene, and perfluoromethylcyclohexane.
12. 12. A method according to any of Claims 2 to 7 wherein said fluids are miscible.
13. 13. A method according to Claim 12, wherein said miscible fluids form an azeotrope.
14. 14. A method according to claim 13, wherein said azeotrope is a mixture of methoxy-nonafluoro-butane and isopropanol.
15. 15. A method according to Claim 12 or 13 wherein the fluorinated compound is selected from the group consisting of hydrofluoroethers, hydrofluorocarbons and hydrofluoropolyethers.
16. 16. A method according to Claim 15 wherein the fluorinated compound comprises dihydroperfluoropentane.
17. 17. A method according to any of Claims 12 to 16 wherein the drying fluid comprises an organic solvent and a fluorinated compound which is present in a proportion less than that of the saturation solubility of that fluorinated compound in the organic solvent.
18. 18. A method according to any preceding claim wherein the said fluid contacts the article while in the vapour phase and condenses thereon.
19. 19. A method according to any preceding claim wherein during said drying an upper portion of the vessel is cooled to provide a cold trap and condense any such fluid vapour contained in the upper part of said vessel.
20. 20. A method according to any preceding claim wherein said article is moved into and out of said vessel while carried by a support.
21. 21. A method according to any preceding claim wherein the boiling points of said two fluids are within 15 C preferably 10 C of one another.
22. 22. A method according to Claim 5 wherein the boiling point of said fluorinated compound is between 30 C and 250 C preferably between 30 C and 100 C and most preferably between 40 C and 90 C, for example between 70 C and 90 C.
23. 23. A method according to any preceding claim wherein said drying fluid comprises an organic solvent which comprises water in a proportion less than that of the azeotropic composition of the water organic solvent system.
24. 24. A method according to any preceding claim wherein the article being dried is a semiconductor wafer, glass or ceramic substrate.
25. 25. Apparatus for removing water from the surface of an article comprising a drying vessel for containing a drying fluid, a support for conducting components into and out of said vessel and means for heating and vaporising two fluids, and means for condensing, collecting, separating and recycling at least one said fluid.
26. 26. Apparatus according to Claim 25 wherein said drying vessel has an upper portion comprising a cold trap for condensing drying fluid vapour contained by said vessel.
27. 27. Apparatus according to Claim 25 or 26 wherein said drying vessel comprises liquid level sensing means adapted to sense the levels of the respective surfaces of at least two liquids.
28. 28. Apparatus according to any of claims 25 to 27 which comprises condensing means constituted as cooling coils and/or cooling plates.
29. 29. Apparatus according to any of Claims 25 to 28 wherein the fluid and vapour containment components are manufactured in stainless steel or quartz.
30. 30. Apparatus according to any of Claims 25 to 29 wherein the vessel contains means for collecting distillate condensed on articles being dried and for diverting that distillate out of the drying vessel.
31. 31. Apparatus according to Claim 30 wherein the support for said articles is constituted as said collecting and diverting means.
32. 32. Apparatus according to any of Claims 25 to 31 wherein means is provided for directing and diverting to the inner walls of the drying vessel any distillate condensed by cooling means within said drying vessel.
33. 33. Apparatus according to any of Claims 25 to 32 wherein heating means is provided for heating the walls of said drying vessel.
34. 34. Apparatus according to any of Claims 25 to 33 wherein means is provided for sealing said drying vessel during processing.
35. 35. Apparatus according to any of Claims 25 to 34 wherein said drying vessel contains means for monitoring the presence of a vapour.
36. 36. Apparatus according to any of Claims 25 to 35 wherein said vessel is provided with an offset boil sump for permitting rapid vaporisation of fluids and transfer thereof to the drying vessel.
37. 37. A method of drying articles substantially as herein described with reference to the accompanying drawing.
38. 38. Apparatus for displacing a liquid and drying articles, substantially as herein described with reference to, and as shown in, the accompanying drawing.
39. 39. A method for the drying of semiconductor wafers substantially as herein described with reference to the accompanying drawing.