Abstract:
A system for purging high purity interfaces connecting a high purity chemical container to process lines comprises a first purging manifold, connected at one end to a first adapter manifold extending from the high purity chemical container, and connected at the other end either to a process tool, to a second high purity container, to a source of gas, or to a source of vacuum on one side, or to a source of vent or to a source of vacuum on the other side; and a second purging manifold connecting the second adapter manifold either to a source of push gas, a source of purge gas, or a source of vacuum; or to a source of vent. A related method comprises blowing purge gas through both the first and the second purging manifolds, and, optionally, applying vacuum to both purging manifolds.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is a continuation-in-part of application Ser. No. 10/890,550 filed on Jul. 13, 2004 and titled “Purgeable Manifold System.” 
   STATEMENT REGARDING FEDERALLY SPONSORED REASEARCH AND DEVELOPMENT 
   Not applicable. 
   REFERENCE TO A COMPUTER LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention concerns a system and a method for purging high purity interfaces. More specifically, the present invention concerns a manifold system and a method for purging interfaces connected to containers of high purity, low vapor pressure chemicals, wherein potential areas of entrapment of the low vapor pressure chemical are eliminated. 
   2. Description of Related Art 
   Certain manufacturing processes require the use of low vapor pressure chemicals at high purity levels. One example is semiconductor manufacturing, which requires the distribution of highly reactive, low vapor pressure chemicals in high purity conditions, in order to avoid unwanted contamination during the fabrication process and to maintain competitive process yields. These low vapor pressure chemicals include, among others, organo-metallic precursors such as tetrakis(dimethylamido) titanium (TDMAT), tetrakis(diethylamino) titanium (TDEAT), tantalum pentaethoxide (TAETO), copper hexafluoroacetylacetonate-trimethylvinylsilane (Cu(hfac)TMVS), tetramethyltetracyclosiloxane (TMCTS), tetraethyl ortosilicate (TEOS), and trimethylphosphate (TMP). Typically, these low pressure chemicals are stored in containers having a capacity varying from 100 milliliters to 200 liters, which are known by a variety of common and trade names such as “canisters,” “ampoules,” or “hosts”, and are delivered to chemical vapor deposition (CVD) process tools, either by a direct liquid injection (DLI) process or by a “bubbler” process. 
   With DLI, the low vapor pressure chemical is delivered to a process tool by injecting a push gas (generally, an inert gas such as nitrogen or helium) through a first manifold into the container, in the headspace above the low vapor pressure chemical in liquid state. The increase in gas pressure inside the container causes the low vapor pressure chemical to be ejected from the container through a diptube immersed in the chemical and then through a second manifold connected to the container, and to be delivered eventually to the process tool, either directly, or by means of an intermediate, “refill” container. 
   With the “bubbler” process, a push gas (generally, an inert gas such as nitrogen or helium) is injected into the container through a first manifold connected to the container and through a diptube immersed in the low vapor pressure chemical in the container. Instead, the low vapor pressure chemical is supplied to the container as a liquid by means of pressurized gas delivery through a second manifold. The container is heated, in order to increase vapor pressure and to saturate the bubbling gas with vaporized chemical, and the bubbling mixture of gas and chemical is then ejected from the container through a third manifold and delivered to a process tool. The container needs to be refilled with the low vapor pressure chemical on a regular basis. A first container storing liquid low vapor pressure chemical may act as a “refill” container, providing a continuing supply of low vapor pressure chemical to the primary, “bubbler” container. 
   From time to time, it is necessary to replace and clean a container storing liquid low vapor pressure chemical, for instance, due to maintenance requirements, or due to decomposition of the low vapor chemical within the container, or for other reasons. Before detaching the container from the process chemical delivery lines, the low vapor pressure chemical must be completely removed from the points of connection between the manifold valves and the process lines. Typically, the low vapor pressure chemical is evacuated and purged through a multi-step procedure comprising sequences of blow cycles, which push the residual chemical into the container, and of vacuum cycles, which vaporize and remove the chemical particles trapped into the manifolds. Because of the high level of decontamination required, and because some liquid low vapor pressure chemical may remain trapped within the interstices, or dead spaces, of the system, this procedure is extremely time consuming and affects process yields significantly. Therefore, there is a need for a manifold system that can be purged with reduced cycle times. 
   Different invention have been disclosed in the prior art addressing the above needs to different degrees. U.S. Pat. No. 5,964,230 and U.S. Pat. No. 6,138,691, both to Voloshin et al., teach a solvent purging system that not only adds complexity to the purging procedure, but that also creates the additional requirement of expensive decontamination of highly toxic chemicals from the solvent. 
   U.S. Pat. No. 6,431,229 to Birtcher et al. discloses a solventless, purgeable, diaphragm valved manifold for low vapor pressure chemicals, comprising a block valve assembly that includes two diaphragm valves. There remains a dead space between the two valves in the valve block assembly, which complicates cleaning and which requires longer purge cycles in order to remove the chemical from that dead space. 
   U.S. Pat. No. 6,648,034 to Birtcher et al. teaches a purgeable manifold for low pressure chemical containers, with similar features and drawbacks as the invention taught in U.S. Pat. No. 6,431,229. 
   U.S. Patent Application 2003/0131885 to Birtcher et al. discloses a cabinet for chemical delivery with solvent purging, which includes some of the features and drawbacks of the inventions disclosed in U.S. Pat. Nos. 6,138,691 and 6,431,229. 
   Japanese Patent JP 2004-063833 A to Yoshitome Koichi teaches a low pressure chemical supply system for use in a CVD process, comprising a manifold block fed by entry and exit valves and containing a bypass route with two additional valves. While this invention appears to offer process improvements over the invention disclosed in U.S. Pat. No. 6,431,229, this supply system still contains dead spaces where the low pressure chemical may be trapped, requiring extended purge cycles. 
   None of the above inventions appears to disclose a system or method for purging high purity interfaces that eliminates dead spaces and also costly specialty valves. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention teaches a system and a method for purging high purity interfaces between the manifolds extending from a DLI container or a “refill” container and the process lines, and may be embodied in a variety of forms. 
   A first embodiment comprises a system including a first purging manifold, connected at one end by a low dead space fitting to a first adapter manifold extending from the high purity chemical container, and connected at the other end by low dead space fittings either to a process tool, to a second high purity container, to a source of gas, or to a source of vacuum on one side, or to a source of vent or to a source of vacuum on the other side. It further comprises a second purging manifold, connected at one end by a low dead space fitting to a second adapter manifold extending from the high purity chemical container, and at the other end by a low dead space fitting to a source of push gas, a source of purge gas, or a source of vacuum. 
   The embodiment of a first method for purging high purity interfaces comprises blowing purge gas through the first purging manifold in the first embodiment, and pressurizing the second purging manifold. Optionally, vacuum may also be applied to the both purging manifolds. 
   A second embodiment comprises a first purging manifold as in the first embodiment, and a second purging manifold connecting the second adapter manifold with low dead space fittings to a source of push gas, a source of purge gas, a source of vacuum; and to a source of vent. 
   The embodiment of a second method for purging high purity interfaces comprises blowing purge gas through both the first and the second purging manifolds in the second embodiment. Optionally, vacuum may also be applied to the both purging manifolds. 
   A primary advantage of the present invention is to teach a system for purging high purity interfaces system that is simple to construct and that does not require the use of costly specialty valves. 
   Another advantage of the present invention is to teach a method for purging high purity interfaces that is simple to perform and that is faster and more economical that the prior art. 
   A further advantage of the present invention is to teach a system for purging high purity interfaces wherein potential areas of entrapment of the low vapor pressure chemical within the system are eliminated. 
   Yet another advantage of the present invention is to teach a system for purging high purity interfaces that is compact, and that is compatible with existing CVD processes. 
   These and other advantages of the present invention will become apparent from a reading of the following description, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The drawings constitute a part of this specification and include exemplary embodiments of the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention. 
       FIG. 1  illustrates a schematic diagram of a first embodiment of the invention. 
       FIG. 2  illustrates a schematic diagram of a second embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Detailed descriptions of embodiments of the invention are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, the specific details disclosed herein are not to be interpreted as limiting, but rather as a representative basis for teaching one skilled in the art how to employ the present invention in virtually any detailed system, structure, or manner. 
   In accordance with the present invention, there is shown in  FIG. 1  a first embodiment  10  of the invention. A container  12 , suitable for the storage of a low vapor pressure chemical, is connected to the outside environment by a first adapter manifold  14 , comprising a first adapter valve  16 , and by a second adapter manifold  18 , comprising a second adapter valve  20 . 
   A first purging manifold  22  is connected to the first adapter manifold  14  by a first low dead space fitting  24 , preferably of low obstruction VCR design. First purging manifold  22  comprises a first diaphragm valve  26 , connected to first low dead space fitting  24  by a first conduit  28 , and a second diaphragm valve  30 , connected to first diaphragm valve  26  by a second conduit  32 , which extends from the same side of first diaphragm valve  26  as first conduit  28 . All conduits described in the present invention are preferably pressurization tubes. 
   A third conduit  34  extends from the side of second diaphragm valve  30  opposite to second conduit  32 , and is connected by a second low dead space fitting  36  to a first source, which comprises a source of vent or a source of vacuum. Second low dead space fitting  36 , which may be, among others, a low obstruction VCR fitting, a Fujikin UPG gasket fitting, or a Hy-Tech full Bore 002 fitting. 
   A fourth conduit  38  connects first diaphragm valve  26  to a third low dead space fitting  40 , which may also be, among others, a low obstruction VCR design, a Fujikin UPG gasket fitting, or a Hy-Tech full Bore 002. Fourth conduit  38  further connects first diaphragm valve  26  to a second source, which comprises a process tool, a second high purity chemical container, a source of purge gas, or a source of vacuum. 
   Instead, second adapter manifold  18  is connected to a second purging manifold  42  by a fourth low dead space fitting  44 , which is preferably of low obstruction VCR design. Second purging manifold comprises a fifth conduit  46 , connected at one end to fourth low dead space fitting  44 , and at the other end to a fifth low dead space fitting  48 , which in turn connects fifth conduit  46  with a third source, comprising a source of push gas, a source of purge gas, or a source of vacuum. 
   Each one of the diaphragm valves described herein may be actuated manually, pneumatically, or through a solenoid, and each will preferably have a medium or high CV. The seat side of first diaphragm valve  26  is preferably oriented in the direction of third dead space fitting  40 , and the seat of second diaphragm valve  30  is preferably oriented in the direction of first diaphragm valve  26 . 
   In a first variation of first embodiment  10 , second conduit  32  is not connected directly to first diaphragm valve  26 , but instead to first conduit  28 . In a second variation of first embodiment  10 , first diaphragm valve  26  and second diaphragm valve  30  may be combined in a dual valve block. 
   The purge method of high purity interfaces according to first embodiment  10  is summarized in Table I. 
   
     
       
             
           
         
             
               TABLE I 
             
             
                 
             
           
           
             
               (a) Close first diaphragm valve 26, and open second diaphragm valve 
             
             
               30. Blow purge gas from the second source into third low dead 
             
             
               space fitting 40, and vent into the first source through second 
             
             
               low dead space fitting 36. 
             
             
               (b) Close second adapter valve 20 and pressurize fifth conduit 46 
             
             
               by blowing purge gas from the third source into fifth low dead 
             
             
               space fitting 48. 
             
             
               (c) Repeat steps (a) and (b) to remove chemical from first 
             
             
               purging manifold 22 and second purging manifold 42 to a 
             
             
               predetermined level. 
             
             
               (d) Optionally, apply vacuum from the second source through 
             
             
               third low dead space fitting 40, and from the third source 
             
             
               through fifth low dead space fitting 48. 
             
             
                 
             
           
        
       
     
   
   One skilled in the art will appreciate that different variations in the cycles of Table I are possible, all falling within the scope of the present invention. For instance, different steps of the purge cycle in Table I may be individually repeated until a desired level of decontamination is achieved, or additional steps may be introduced, such as solvent cleaning. 
   Turning now to  FIG. 2 , there is shown a second embodiment  50  of the invention. A container  52 , suitable for the storage of a low vapor pressure chemical, is connected to the outside environment by a first adapter manifold  54 , which comprises a first adapter valve  56 , and by a second adapter manifold  58 , which comprises a second adapter valve  60 . 
   A first purging manifold  62  is connected to the first adapter manifold  54  by a first low dead space fitting  64 , preferably of low obstruction VCR design. First purging manifold  62  comprises a first diaphragm valve  66 , connected to first low dead space fitting  64  by a first conduit  68 , and a second diaphragm valve  70 , connected to first diaphragm valve  66  by a second conduit  72 , extending from the same side of first diaphragm valve  66  as first conduit  68 . 
   A third conduit  74  extends from the side of second diaphragm valve  70  opposite to second conduit  72 , and is connected by a second low dead space fitting  76  to a first source, which comprises a source of vent or a source of vacuum. Second low dead space fitting  76 , which may be, among others, a low obstruction VCR fitting, a Fujikin UPG gasket fitting, or a Hy-Tech full Bore 002 fitting. 
   A fourth conduit  78  connects first diaphragm valve  66  to a third low dead space fitting  80 , which may be, among others, a low obstruction VCR fitting, a Fujikin UPG gasket fitting, or a Hy-Tech full Bore 002, and which connects first diaphragm valve  66  to a second source, comprising a process tool, a second high purity chemical container, a source of purge gas, or a source of vacuum. 
   Instead, a second purging manifold  82  is connected to second adapter manifold  58  by a fourth low dead space fitting  84 , preferably of VCR design. Second purging manifold  82  comprises a third diaphragm valve  86  and a fourth diaphragm valve  88 , wherein one side of third diaphragm valve  86  is connected to fourth low dead space fitting  84  by a fifth conduit  90 , and wherein the other side of third diaphragm valve  86  is connected to one side a fourth diaphragm valve  88  by a sixth conduit  92 . The opposite side of fourth diaphragm valve  88  is instead connected to a fifth low dead space fitting  94  by a seventh conduit  96 . Fifth low dead space fitting  94  connects seventh conduit  96  to a third source, including a source of purge gas or a source of vent. Fifth low dead space fitting  94  and sixth low dead space fitting  100  are preferably of low obstruction VCR design, a Fujikin UPG gasket fitting, or a Hy-Tech full Bore 002 fitting. 
   An eight conduit  98  connects to one end of sixth low dead space fitting  100  the same side of third diaphragm valve  86  as that connected to sixth conduit  92 , while the other end of sixth low dead space fitting  100  is connected to a fourth source, which comprises a source of push gas, a source of purge gas, a source of vent, or a source of vacuum. 
   All valves may be actuated manually, pneumatically, or through a solenoid, and have preferably a medium or high CV. As in first embodiment  10 , different variations are possible within second embodiment  50 . For instance, second conduit  72  may be connected to first conduit  68  and not to first diaphragm valve  66 ; and sixth conduit  92  may be connected to fifth conduit  90  and not to third diaphragm valve  86 . Further, first diaphragm valve  66  and second diaphragm valve  70  may be combined in a dual valve block, or third diaphragm valve  86  and fourth diaphragm valve  88  may be combined in a dual valve block. 
   The seat side of first diaphragm valve  66  is preferably oriented in the direction of third dead space fitting  80 , and the seat of second diaphragm valve  70  is preferably oriented in the direction of first diaphragm valve  66 . Conversely, the seat side of third diaphragm valve  86  is preferably in the direction of the sixth low dead space fitting  100 , and the seat side of fourth diaphragm valve  88  is preferably in the direction of sixth conduit  92 . Moreover, sixth conduit  92  may be connected to the same side of third diaphragm valve  86  as fifth conduit  90 , instead of the same side as seventh conduit  98 ; and also, sixth conduit  92  may consist of a plurality of segments connected by low dead space fittings, such as low obstruction VCR fittings, a Fujikin UPG gasket fittings, or a Hy-Tech full Bore 002 fittings. 
   The purge method of high purity interfaces according to first embodiment  50  is summarized in Table II. 
   
     
       
             
             
           
         
             
                 
               TABLE II 
             
             
                 
                 
             
           
           
             
                 
               (a) Close first diaphragm valve 26, and open second diaphragm 
             
             
                 
               valve 30. Blow purge gas from the second source into third 
             
             
                 
               low dead space fitting 40, and vent into the first source 
             
             
                 
               through second low dead space fitting 36. 
             
             
                 
               (b) Close third diaphragm valve 86, and open fourth diaphragm 
             
             
                 
               valve 88. Blow purge gas from the fourth source into sixth 
             
             
                 
               low dead space fitting 100, and vent into the third source 
             
             
                 
               through fifth low dead space fitting 94. 
             
             
                 
               (c) Repeat steps (a) and (b) to remove chemical from first 
             
             
                 
               purging manifold 62 and second purging manifold 82 to a 
             
             
                 
               predetermined level. 
             
             
                 
               (d) Optionally, apply vacuum from the second source through 
             
             
                 
               third low dead space fitting 80, and from the fourth source 
             
             
                 
               through sixth low dead space fitting 100. 
             
             
                 
                 
             
           
        
       
     
   
   One skilled in the art will appreciate that different variations in the cycles of Table II are possible, all falling within the scope of the present invention. For instance, individual steps of the purge cycle in Table II may be repeated until a desired level of decontamination is achieved, or additional steps may be introduced, such as solvent cleaning. Further, sixth low dead space fitting  100  may be connected to third low dead space fitting  80 , and purge gas may be blown into second purging manifold  82  through fifth low dead space fitting  94 , exiting through sixth low dead space fitting  100 , entering then first purging manifold  62  through third low dead space fitting  80  and exiting through second low dead space fitting  76 . 
   While the invention has been described in connection with a number of embodiments, it is not intended to limit the scope of the invention to the particular forms set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the scope of the invention.