Abstract:
Fixtures and methods for clamping workpieces in a workplace to enable the optimized exposure thereof to a stream or flow of a supercritical fluid. Provided is a rotatably indexable chuck or locator mounting the workpiece and enabling orientating the latter in specific static pitch position within a high pressure vessel in order to subject the workpiece to a full frontal exposure to the supercritical fluid stream within the vessel. This mounting arrangement facilitates an optimum positioning of the workpiece being processed in the flow path of the supercritical fluid stream while oriented in selectively indexed rotational positions.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to fixtures for the processing of workpieces in a supercritical fluid, and more particularly relates to fixture and methods for clamping workpieces in a workplace to enable the optimized exposure thereof to a stream or flow of a supercritical fluid. 
     2. Discussion of the Prior Art 
     In the technology of producing articles or workpieces, such as semiconductor devices which may have film layers applied thereto, is frequently necessary to process these in a workplace incorporating an environment constituted of supercritical fluids, wherein a surface or surfaces of the workpiece is or are exposed to a flow or stream of the supercritical fluid, and in which it is vital that the film and/or the workpiece is suitably protected from any possible damage or destruction. 
     Concerning the foregoing, the workpiece may be arranged in a suitable pressure vessel under a high-pressure condition, wherein the workpiece is then exposed to the stream or flow of the supercritical fluid. However, difficulties have been encountered in being able to arrange the workpieces in an optimized orientation relative to the fluid flow or stream of the supercritical fluid to which they are exposed in the pressure vessel. 
     SUMMARY OF THE INVENTION 
     Accordingly, in order to be able to take full advantage of the streams or flow directions of the supercritical fluids within the pressure vessel which impinge against the surface (or surfaces) of the workpiece, pursuant to the present invention there are provided novel and unique workplace fixtures employing in processing a workpiece in the supercritical fluid medium which affords the greatest degree of efficiency and efficacy in the treatment of the workpiece. 
     On the one hand, pursuant to a first embodiment of the invention, there may be provided a rotatably indexable chuck or locator mounting the workpiece and enabling orientating the latter in specific static pitch position within a high pressure vessel in order to subject the workpiece to a full frontal exposure to the supercritical fluid stream within the vessel. This mounting arrangement facilitates a film-protective treatment of the workpiece being processed in the flow path of the supercritical fluid stream while oriented in selectively indexed rotational positions. 
     Pursuant to another embodiment of the invention, a mounting fixture in the chamber of the pressure vessel may comprise a cup-shaped holder for receiving the workpiece, which facilitates the latter to be loaded thereon and immersed in the supercritical fluid or liquid. Suitable orifices in the chamber are provided to be enable excess liquid to drain off the workpiece down to a point whereby any forces are equalized, such as the surface tension, which will maintain the workpiece in an immersed condition while minimizing the amount of liquid which is to be processed through the pressure vessel. 
     Accordingly, it is a primary object of the present invention to provide a workplace incorporating a workpiece mounting fixture which will facilitate the processing of the workpiece in a supercritical fluid. 
     Another object of the present invention is to provide a novel workpiece mounting fixture which will facilitate the rotatably adjustable indexed positioning of the workpiece within the chamber of a high-pressure vessel while being subjected to a flow of a supercritical fluid enabling the processing or treatment thereof. 
     Yet another object of the present invention is to provide a workplace including a fixture in a high-pressure vessel in which a workpiece is adapted to be contained in a holder enabling excess amounts of a supercritical liquid to be drained to impart a balancing of surface tensions so as to maintain the workpiece in a immersed condition while minimizing the quantity of the liquid to be processed. 
     A still further object of the invention resides in the provision of methods of implementing the utilization of the above-mentioned fixtures processing workpieces in a supercritical fluid or liquid in a pressurized environment so as to facilitate the efficacious and efficient processing thereof. 
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
     Reference may now be made to the following detailed description of preferred embodiments of the invention, taken in conjunction with the accompanying drawings in which: 
     FIG. 1 illustrates a longitudinal sectional view of a high pressure vessel incorporating an inventive fixture for mounting workpieces for optimized exposure to a stream or flow of a supercritical fluid; 
     FIG. 2 illustrates an enlarged detail view of the workpiece mounting portion of the fixture of FIG. 1; and 
     FIG. 3 illustrates a modified embodiment of a cup-shaped holder for workpieces adapted to be utilized in the fixture for processing the workpieces in a supercritical fluid. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now in specific detail to the drawings, and particularly the embodiments shown in FIGS. 1 and 2 thereof, FIG. 1 illustrates a vessel  10  having an elongated cylindrical wall portion  12  and constituting a high-pressure container which possesses a hollow cylindrical interior or chamber  14  and a closed bottom  16 . The vessel  10  is preferably constructed from a high-strength metallic material which is able to resist extremely high internal operating pressures. 
     The upper end  18  of the cylindrical wall portion  12  of the vessel  10  is provided with an external screwthread  20  so as to be able to engagingly receive a screwthreaded cover structure  22  which has a narrow orifice  24  drilled therethrough communicating with chamber  14 , and forms a connection to an infeed source (not shown) for a supercritical fluid. The entire vessel  10  and the cover structure  22 , when mounted thereon in a sealed relationship through the interposition of an annular gasket seal or O-ring  26 , may be attached to a support plate  28  of an apparatus (not shown) and fastened thereto by means of suitable screws or threaded bolts  30 . 
     Extending downwardly within the interior chamber  14  of the high-pressure vessel  10  in coaxial relationship with the longitudinal center axis of internal cylindrical chamber  14  is an elongated rod-like rib member  32  extending downwardly into a position which is somewhat centrally located within the cylindrical chamber  14 , and which includes a shaft element  34  rotatable about a transverse axis proximate the lower free end of member  32 . Rotatably journaled on the shaft element  34  about a transverse axis in the direction of double-headed arrow A, as also shown in more extensive detail in FIG. 2, is a workpiece mounting member  36 . This member  36  may be a plate like locator or chuck structure, having a clamping device  38  pivotably fastened to one end  40  thereof so as to be able to firmly clamp a workpiece W against a surface  42  thereof. 
     The workpiece W is retained in position by the clamping device  38  which also clamps the workpiece positioning plate or locator structure  36  in position. 
     As illustrated in FIGS. 1 and 2 of the drawings, the workpiece mounting member  36 , together with the workpiece W and the clamping device  38  by means of which they are fastened, may be rotated conjointly in either direction of arrow A until the surface  42  of the member  36  mounting the workpiece W, the surface of the latter of which may have a film for processing located thereon, is indexed into a suitable angular position for processing thereof to a desired exposure angle or orientation relative to the stream or flow of a supercritical fluid being introduced into the chamber  14  through the orifice  24  under a high superatmospheric pressure. 
     After the rotatably indexable fixture which comprises the mounting member  36 , shaft element  34  and clamping device  38 , has been oriented in its desired angular alignment relative to the longitudinal axis of the chamber  14  of the high-pressure vessel  10 , suitable latching means (not shown) operatively associated with the shaft element  34 , may lock it to the mounting member  36  in a predetermined fixed angular position. Thereafter, the vessel cover structure  22  may be sealingly secured to the vessel body, and a stream of supercritical fluid injected into chamber  14  through the inlet orifice  24  at the upper or head end of the pressure vessel  10 , in a manner well known in the technology. 
     Referring to FIG. 3 of the drawings, illustrating a second embodiment of the invention, wherein there may be utilized a pressure vessel  50  analogous with or similar to that employed in connection with the embodiment of FIGS. 1 and 2, and wherein components which are similar thereto or identical therewith are identified by the same reference numerals. In this instance, rather than having the rotatable workpiece the mounting fixture as shown in FIG. 1, mounting member or the fixture  52  which is rotatably connected to free or the bottom end of the vertical rib member  32  extending downwardly within the chamber  14  of the pressure vessel  50 , is comprised of a cup-shaped holder  54  for receiving a workpiece W. The cup-shaped holder  54  may be provided with suitable apertures  56  selectively extending through, respectively, the bottom  58  and side walls  60  thereof, and in which the processing with the supercritical fluid is effected in, essentially the same mode as referred to hereinabove. 
     However, in this instance wherein the workpiece holder  54  is cup-shaped, in contrast with the embodiment of FIGS. 1 and 2, in which the workpiece W is typically immersed in a supercritical fluid and co-solvent mixtures in effecting process steps, it is desirable to utilize the transfer to the supercritical fluid processing by maintaining a limited amount of fluid coating. This basically enables the continuation of fluid coating through the intermediary of surface tension effects. The limiting control is provided by means of the apertures  56  or so-called weep holes which are formed in respectively, the bottom and side wall  58 ,  60  of the cup-shaped workpiece holder  54  and enabling excess supercritical fluid to be stream out therethrough. In essence, once the workpiece W is loaded in the cup-shaped holder  54  and the fixture is inserted and retained in the pressure vessel  50 , in that the entire assembly including its mounting and being rotatably oriented on the vertical rib member  32 , with the vessel then being sealed and secured as described in connection with FIGS. 1 and 2, the flow of the supercritical fluid under high pressure into the high pressure vessel  50  can them commence through the orifice  24  provided in the vessel cover structure  22 , as is known in the technology and the processing of the workpiece W can be initiated as required. 
     From the foregoing it thus becomes readily apparent that the embodiments of present invention provide for unique and highly advantageous fixtures for processing workpieces under high pressure in a supercritical or pressurized fluid and possible co-solvent mixture flow or stream which will be protective of any film located on the workpiece W and resultingly inhibit any damage thereto during processing. 
     While the invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.