Abstract:
An integrated circuit plasma processing system, apparatus and method for reclaiming material, such as a plasma precursor and potentially useful components among their byproducts, from plasma-enhanced exhaust of a plasma process chamber for subsequent reuse in the chamber. The apparatus provides a recycle feedback loop for a plasma process chamber that provides the high purity materials necessary for microelectronic applications. Since the apparatus is in-situ, no byproducts that are not already present are possible. Accordingly, the apparatus guarantees purity of the recycled material. In addition to cost savings, the invention provides an environmentally friendly plasma process chamber and apparatus with very little production of waste.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Technical Field  
         [0002]     The present invention relates generally to material reclamation, and more particularly, to plasma processing material reclamation and reuse.  
         [0003]     2. Related Art  
         [0004]     Manufacture of integrated circuits (ICs) by means of plasma-enhanced processing such as deposition and etch processes often involves the use of expensive precursors such as tungsten hexafluoride or tetra ethyl orthosilicate. The percentage of precursor exhausted from plasma process chambers, either in original form or in the form of byproducts of plasma-induced reactions, can be very high. For example, for plasma-enhanced chemical vapor deposition (PECVD) of WF6 for tungsten deposition, approximately 82% of the tungsten is exhausted. Exhausting such high percentages of material poses environmental issues and economic issues.  
         [0005]     Relative to environmental issues, exhaust of such materials is generally to be avoided. Conventional approaches to addressing the environmental issues of this problem include implementing a scrubber to trap components of the exhaust for subsequent disposal or converting the exhaust into more environmentally friendly chemical species. Unfortunately, either approach generally results in a significant waste stream of non-recovered material.  
         [0006]     In terms of economics, materials such as a precursor are usually very expensive. Accordingly, exhausting a high percentage of a precursor from plasma process chambers is very inefficient. In some cases, attempts to recover exhaust for subsequent recycling have been implemented. However, these approaches introduce impurities into the reclamation process, which destroys precursor purity and the ability to reuse the reclaimed precursor.  
         [0007]     In view of the foregoing, there is a need in the art for a mechanism to reclaim material from plasma-enhanced exhaust for potential reuse.  
       SUMMARY OF INVENTION  
       [0008]     The invention includes an integrated circuit plasma processing system, apparatus and method for reclaiming material, such as a plasma precursor and potentially useful components among their byproducts, from plasma-enhanced exhaust of a plasma process chamber for subsequent reuse in the chamber. The apparatus provides a recycle feedback loop for a plasma process chamber that provides the high purity materials necessary for microelectronic applications. The apparatus is in-situ and does not introduce impurities into the reclaimed material. In addition to cost savings, the invention provides an environmentally friendly plasma process chamber and apparatus with very little production of waste.  
         [0009]     A first aspect of the invention is directed to an apparatus for reclamation of material used in an integrated circuit plasma process chamber, the apparatus comprising: a first separator receiving plasma-enhanced exhaust from a process chamber, the first separator including a plurality of temperature zones, each temperature zone including a temperature control device and a collection vessel for collecting material that condenses in the respective temperature zone.  
         [0010]     A second aspect of the invention is directed to an integrated circuit plasma processing system comprising: a process chamber for carrying out plasma-enhanced processing on a wafer; and a reclamation system including: a first separator receiving plasma-enhanced exhaust from the process chamber, the first separator including a plurality of temperature zones, each temperature zone including a collection vessel for collecting material that condenses in the respective temperature zone; a material processing unit coupled to an outlet of each collection vessel; and a material reuse unit coupled to each material processing unit.  
         [0011]     A third aspect of the invention is directed to a method of reclaiming material used in integrated circuit plasma processing, the method comprising the steps of: exposing plasma-enhanced exhaust from a process chamber to a plurality of temperature zones, each temperature zone having a lower temperature than a preceding temperature zone; and collecting material that condenses in each respective temperature zone.  
         [0012]     The foregoing and other features of the invention will be apparent from the following more particular description of embodiments of the invention. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0013]     The embodiments of this invention will be described in detail, with reference to the following figures, wherein like designations denote like elements, and wherein:  
         [0014]      FIG. 1  shows an integrated circuit plasma processing system including a reclamation system according to the invention.  
         [0015]      FIG. 2  shows a detail of a separator shown in  FIG. 1 .  
         [0016]      FIG. 3  shows a cross-sectional view of a temperature zone of the separator of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION  
       [0017]     With reference to the accompanying drawings,  FIG. 1  shows an integrated circuit (IC) plasma processing system  10  including a process chamber  12  and a reclamation (and reuse) system  14  according to the invention. Process chamber  12  may be any device for carrying out any now known or later developed plasma-enhanced processing. For example, plasma-enhanced chemical vapor deposition (PECVD) and/or reaction ion etching (RIE) on an IC wafer may be carried out in process chamber  12 . Plasma-enhanced processing generally involves use of a carrier gas or diluent (e.g., a relatively inert gas such as nitrogen (N 2 )) in combination with appropriate reactants. For example, one plasma-enhanced process for deposition of silicon dioxide (SiO 2 ) on a wafer can be accomplished by introduction of silane (SiH 4 ) and nitrous oxide (N 2 O) into a nitrogen plasma at relatively low temperatures (i.e., &lt;400 Å° C.). In another example, deposition of silicon dioxide (SiO 2 ) can be accomplished by introduction of tetra ethyl orthosilicate (TIOS) in an oxygen (O 2 ) plasma.  
         [0018]     Plasma-enhanced exhaust  16  is output by process chamber  14 . “Plasma-enhanced exhaust”  16  may include, in part, the carrier that is used to carry or react with a precursor, the precursor, any byproduct of a plasma-induced reactions and perhaps other byproduct(s). Since many plasma-enhanced precursors and byproducts are very expensive and in many cases environmentally unfriendly, it is advantageous to reclaim as much of them as possible. Reclamation system  14  provides an in-situ feedback loop to process chamber  12  that accomplishes this reclamation.  
         [0019]     Reclamation system  14  may include a first, primary separator  30  for receiving plasma-enhanced exhaust  16  from process chamber  12 , at least one material processing unit  32  coupled to primary separator  30 , and a material reuse unit  34  coupled to each material processing unit  32 . Reclamation system  14  may also optionally include at least one chemical reactive separator  36  and at least one priming device  38  (described below). Each chemical reactive separator  36  receives plasma-enhanced exhaust  16  prior to primary separator  30 , and separates chemically reactive material from plasma-enhanced exhaust  16  based on the material&#39;s chemical reactivity. For example, a chemical reactive separator  36  may include magnesium turnings to capture fluorine, zinc turnings to capture oxygen, or other mechanisms to capture chemically reactive materials.  
         [0020]     Primary separator  30  is provided to selectively separate out materials (not captured by chemical reactive separator  36  when provided) from plasma-enhanced exhaust  16 . Primary separator  30  may include a plurality of temperature zones TZ 1 , TZ 2 , TZ 3  â         TZn, where n is an integer, to condense materials out of plasma-enhanced exhaust  16  to accomplish this material separation. Referring to  FIGS. 1 and 2 , in one embodiment, primary separator  30  is provided as a separator chamber  50  including a series of temperature zones TZ, each separated by a baffle  52  to prevent remixing of materials. Each temperature zone TZ may include a temperature control device  54  and a collection vessel  56  for collecting material that condenses from plasma-enhanced exhaust  16  in the respective temperature zone TZ. Although separator chamber  50  is shown in a horizontal and straight orientation, it should be recognized that it can be, depending on space constraints, positioned horizontally, vertically and/or at some angle, and may be straight and/or curved. Alternatively, primary separator  30  may be implemented on already existing equipment, e.g., through the addition of temperature control devices  54  and collection vessels  56  to a pathway for plasma-enhanced exhaust  16 .  
         [0021]     Referring to  FIG. 3 , a cross-sectional view of one embodiment of a temperature zone TZ is shown. Each temperature zone TZ includes a temperature control device  54  to set and maintain the zone (including collection vessel  56 ) at a condensing temperature of a selected material to be collected from plasma-enhanced exhaust  16  ( FIG. 1 ). “Condensing temperature” may be any temperature that is below a boiling temperature of the selected material to be collected. A “selected material” may be any material, or combination of materials, that is/are to be reclaimed and is/are known to condense at the condensation temperature. In one embodiment, each temperature zone TZ(x) has a lower temperature than a preceding temperature zone TZ(x−1). That is, a warmest end of primary separator  30  receives plasma-enhanced exhaust  16  first. As a selected material condenses in a temperature zone TZ, the selected material collects in collection vessel  56 . Each collection vessel is coupled to a respective material processing unit  32  ( FIG. 1 ) for further processing, as described below. In one embodiment, each collection vessel  56  collects material by gravity feed. However, it should be recognized that other mechanisms are possible for material collection where necessary, e.g., vacuum feed, pumping, etc.  
         [0022]     Each temperature control device  54  may take any form necessary to generate as uniform temperature as possible within a temperature zone TZ, and to control the condensation process of a specific material occurring therein. Temperature control device  54  may be provided with a number of temperature adjustment mechanisms. For instance, cooling can be provided by flowing coolants such as liquid nitrogen through a coil(s) or finger(s)  60  in and/or around separator chamber  50 . Alternatively, heating may be provided by a heating element(s)  62  in and/or around separator chamber  50 . Each collection vessel  56  may also be maintained at the condensing temperature by coil(s)/finger(s)  60  and/or heating element(s)  62 .  
         [0023]     As one with skill in the art will recognize, a variety of alternative configurations can be provided to establish uniform temperature within a temperature zone TZ. For example, the density, shape, occupied internal volume, material of cooling coil(s)/finger(s)  60  and/or heating element(s)  62  can be adjusted. Additionally, coil(s)/finger(s)  60  may be designed to variably retard plasma-enhanced exhaust  16  ( FIG. 1 ) flow within separator chamber  50  in order to provide additional contact time to assure equilibrium. A uniform temperature within a temperature zone may also be enhanced by the use of a filler material  64 . In one embodiment, filler material  64  is provided as a steel wool-like material to maintain temperature uniformity within temperature zone. Other examples may include filler material shaped as spheres (or beads), pins/screws, saddles, etc. Filler material  64  also may increase an area for a selected material to condense on, and impede the flow of plasma-enhanced exhaust  16  so that the contact time may be increased to maximize the gas equilibrium within a respective temperature zone TZ. As a result, filler material  64  enhances condensation and collection efficiency. The condensation process may also be modified by altering flow parameters of plasma-enhanced exhaust  16  ( FIG. 1 ) such as volume, flow rate and/or introducing variations in filler material  64  makeup and/or density. Other modifications may also be provided such as gas flow restrictors (fixed or variable), a variation in baffle  52  design to increase surface area or retard flow, etc. Each temperature control device  54  may include a thermocouple sensor  66  and feedback system  68  to adjust the output of coil(s)/finger(s)  60  and/or heating element(s)  62 . Although each temperature zone TZ has been shown with an independent temperature control device  54 , it should be recognized that consolidation of all or part of temperature control devices may be possible.  
         [0024]     Primary separator  30  may also be provided with a regeneration device  70  for using heat generated by the primary separator. Regeneration device  70  is used to direct material used in other processes to primary separator  30  for preheating to decrease the energy required to heat the material. For example, liquid gas such as liquid nitrogen that requires heating by a vaporizing heater (not shown) in order to vaporize into a usable gaseous form may be exposed to regeneration device  70  prior to the vaporizing heater.  
         [0025]     Returning to  FIG. 1 , each material processing unit  32  includes: a disposal unit  80  for disposing of reclaimed, but unwanted material; a reservoir  82  for holding reclaimed and wanted material; and a directing valve  84  for selectively directing material to one of disposal unit  80  and reservoir  82 . Directing valve  84  may be any now known or later developed mechanism for controlling the flow of a material, e.g., a computer controlled valve, which is received from a respective collection vessel  56 . Disposal unit  80  is any mechanism capable of disposing of a material reclaimed by a respective temperature zone TZ that is not reusable. Disposal unit may include, for example, mechanism(s) for containing a material (e.g., a tank, a barrel, dumpster, etc.), an incinerator for burning material, scrubber, an atmospheric exhaust (stack, drain, etc.) or any other mechanism(s) now known or later developed for disposing of a material. Reservoir  82  may be any device capable of holding a selected material directed thereto (e.g., a tank, a barrel, etc.).  
         [0026]     Optionally, each material processing unit  32  may also include a second separator  86  for further, higher stage separation of at least one selected material from material collected by a respective temperature zone TZ of primary separator  30 . Second separator  86  may be configured substantially similar to primary separator  30 , and may include at least one secondary temperature zone STZ 1  having a respective temperature control device (not shown) and collection vessel  88 . Each secondary temperature zone STZ has a temperature different than a respective preceding temperature zone TZ of primary separator  30  such that further separation of a material from plasma-enhanced exhaust  16  can be made. When second separator  86  is provided, directing valve  84  may direct material to one of disposal unit  80 , reservoir  82  and the second separator. Output of collection vessel(s)  88  may be to an additional reservoir(s) or disposal unit(s)  90 . Reservoir (s)/disposal unit(s)  90  are substantially similar to those described above.  
         [0027]     Plasma-enhanced exhaust  16  exiting from reclamation system  14  (e.g., from primary separator  30  or secondary separator  86 , if provided) may be sent to disposal unit  80  for appropriate disposal.  
         [0028]     Material reuse unit  34  includes: a mixing chamber  100  for receiving material from at least one reservoir  82 ,  90 , and an injector  102  coupled to each reservoir  82 ,  90 . Each injector  102  selectively communicates material from a respective reservoir  82 ,  90  to mixing chamber  100 . A non-reclaimed material supply  104  may also be coupled to mixing chamber  100  for supplying any number of fresh materials and/or modifying reagents thereto. Material supply  104  may include any number of supplies of fresh, unused material (e.g., a precursor and/or reactant material) used in process chamber  12  and/or any number of supplies of modifying reagents. A “modifying reagent” may be any material used to return a spent reactant to a chemical state similar to an original feedstock. One example modifying reagent is oxygen used to re-oxidize material to be injected in process chamber  12 . Each injector  102  may be computer controlled and linked to a recipe system (not shown) of process chamber  12  in a fashion identical to that employed for conventional fresh material feeds. Mixing chamber  100  is coupled to process chamber  12  for supplying reclaimed material, perhaps combined with non-reclaimed material, to process chamber  12 .  
         [0029]     A priming device  38  may be provided for each reservoir  82 ,  90 . Each priming device  38  is coupled to a respective reservoir  82  (and, although not shown for clarity, a respective reservoir  90 ) and to non-reclaimed material supply  104 . Each priming device  38  includes any mechanism (s) necessary to insert a non-reclaimed material from non-reclaimed material supply  104  to a respective reservoir  82 ,  90  in a desired form. The material that priming device  38  receives may be the same as or different than the material in a respective reservoir  82 ,  90 . For example, the material to be inserted may be the same as that in reservoir  82 ,  90 , but may require processing (e.g., breaking down, condensation and/or other modification) into a more desirable feedstock prior to insertion a respective reservoir  82 ,  90 . In another example, priming device  38  may insert any other material necessary such as a modifying reagent, reactant or additive to material in a respective reservoir  82 ,  90 . Priming device(s)  38  may also provide a mechanism for “priming” reclamation system  14  where reclaimed material in reservoir(s)  82 ,  90  is of insufficient quantity, or may require additives, in order to start the system.  
         [0030]     While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.