Patent Document

This application claims priority of provisional application 60/743,022 filed on Dec. 9, 2005. 

   FIELD OF THE INVENTION 
   The present invention relates to the field of semiconductor fabrication tooling; more specifically, it relates to a method of improving the performance of charged particle beam fabrication tooling and apparatus for improving the performance of charged particle beam fabrication tooling. 
   BACKGROUND OF THE INVENTION 
   Ion implantation tools and other charged particle beam tools, are used extensively in the semiconductor industry. An ongoing problem is the deposition of foreign material on the wafers being processed. Existing methods of mitigating foreign material require extensive manual cleaning of tools after the loss of product to foreign material becomes excessive. Therefore, there is an ongoing need in the industry for a method of mitigating foreign material related product loss on wafers processed in ion implantation tools and other charged particle beam tools. 
   SUMMARY OF THE INVENTION 
   A first aspect of the present invention is a method comprising: providing a chamber having an interior surface; providing a pump port for evacuating the chamber; providing a substrate holder within the chamber; forming a charged particle beam within the chamber, the charged beam generated by a source and the charged particle beam striking the substrate; and placing one or more liners in contact with one or more different regions of the interior surface of the chamber, the liners preventing material generated by interaction of the charged beam and the substrate from coating the one or more different regions of the interior surface of the chamber. 
   A second aspect of the present invention is the first aspect, wherein each of the one or more liners is removable from the chamber. 
   A third aspect of the present invention is the first aspect, further including one or more access ports in the chamber, the one or more access ports having corresponding access port covers and wherein each of the one or more liners is removable through at least one of the one or more access ports. 
   A fourth aspect of the present invention is the first aspect, further including one or more access ports in the chamber, the one or more access ports having corresponding access port covers and wherein each of the one or more liners is removeably attached to one of the access port covers. 
   A fifth aspect of the present invention is the first aspect, wherein each of the one or more liners has a first surface and a opposite second surface, the first surface in contact with a region of the interior surface of the chamber and the second surface facing the charged particle beam. 
   A sixth aspect of the present invention is the fifth aspect, wherein the second surface of at least one of the one or more liners is textured. 
   A seventh aspect of the present invention is the first aspect, wherein each of the one or more liners has a surface contour designed to mate with a corresponding contour of a region of the interior surface of the chamber. 
   An eighth aspect of the present invention is the first aspect, wherein at least one of the one or more liners is compression fitted to a corresponding region of the interior surface of the chamber. 
   A ninth aspect of the present invention is the first aspect, wherein at least one of the one or more liners is removeably fastened to a corresponding region of the interior surface of the chamber. 
   A tenth aspect of the present invention is the first aspect, wherein at least one of the liners has a thickness of between about 0.05 inches and about 0.20 inches. 
   An eleventh aspect of the present invention is the first aspect, wherein the liners comprise aluminum or graphite. 
   A twelfth aspect of the present invention is the first aspect, wherein the liners are essentially free of iron, nickel, chrome, cobalt, molybdenum, beryllium, tungsten, titanium, tantalum, copper, magnesium, tin, indium, antimony, phosphorous, boron and arsenic. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The features of the invention are set forth in the appended claims. The invention itself, however, will be best understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
       FIG. 1  a schematic top view of an exemplary ion implantation system according to a embodiment of the present invention; 
       FIG. 2  is a schematic top view of the analyzer chamber of  FIG. 1  with removable liners in place; 
       FIG. 3  is a side view through line  2 B- 2 B of  FIG. 2  of the analyzer liner assembly of  FIG. 1 ; 
       FIG. 4  is an isometric view of the inner shield of  FIG. 1  and  FIG. 5  is an isometric view of the outer shield of  FIG. 1 ; 
       FIG. 6  is a schematic top view of the pumping chamber of  FIG. 1  with removable liners in place; 
       FIG. 7A  is a top view and  FIG. 7B  is a side view of pumping chamber liner  315  of  FIG. 6 ; 
       FIG. 8A  is a side view and  FIG. 8B  is a front view of the first aperture liner of  FIG. 6 ; 
       FIG. 9A  is a side view and  FIG. 9B  is a front view of the second aperture liner of  FIG. 6 ; 
       FIG. 10A  is a top view,  FIG. 10B  is a front view and  FIG. 10C  is a flat projection view of the access port liner of  FIG. 6 ; 
       FIG. 11A  is a top view,  FIG. 11B  is a front view and  FIG. 11C  is a flat projection view of the pump port liner of  FIG. 6 ; 
       FIG. 12  is a schematic top view of the resolving chamber of  FIG. 1  with removable liners in place; 
       FIG. 13A  is a side view and  FIG. 13B  is a front view of the third aperture liner of  FIG. 12   r  of  FIG. 12 ; 
       FIG. 14A  is a top view and  FIG. 14B  is a edge view of the first resolving chamber liner of  FIG. 12 ; 
       FIG. 15A  is a top view and  FIG. 15B  is a edge view of the second resolving chamber liner of  FIG. 12 ; and 
       FIG. 16  is a schematic top view of an exemplary charge particle beam tool according to a embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The term “charged particle beam tool or system” is defined to be any tool that generates a beam of charged atoms or molecules or other particles and is capable of directing that charged species to the surface of or into the body of a wafer or substrate. Examples of charged particle beam systems include but is not limited to ion implantation tools, ion milling tools and electron beam tools and other plasmas tools such as reactive ion etch (RIE) tools. A wafer is one type of semiconductor substrate. 
     FIG. 1  a schematic side view of an exemplary ion implantation system according to an embodiment of the present invention. In  FIG. 1 , an ion implantation system  100  includes a beam generation chamber  105 , an analyzer chamber  110 , a pumping chamber  115 , a resolving chamber  120  and a wafer chamber  125  connected to resolving chamber  120  by a flexible bellows  130 . The sidewalls of beam generation chamber  105 , analyzer chamber  110 , pumping chamber  115 , resolving chamber  120  and wafer chamber  125  are illustrated in sectional view, all other structures are illustrated in plan view. Beam generation chamber  105  includes an ion/plasma source  135 , an extractor  140  and a beam defining aperture  145 . Analyzer chamber  110  includes pole ends  150  of an electromagnet (not shown), an exit tube  155  an access port  160  and a access port cover  165 . Pumping chamber  115  includes a pumping port  170 , a deflector aperture  175 , an access port  180  and an access port cover  185 . Resolving chamber  120  includes a selectable aperture  190 , a beam sampler  195 , an electromagnetic aperture  200 , an electron shower aperture  205 , an electron shower tube  210 , a first access port  215 , a first access port cover  220 , a second access port  225 , a second access port cover  230 , a third access port  235  and a third access port cover  240 . Wafer chamber  125  includes a slideable and rotatable-stage  245 . 
   Beam generation chamber  105 , analyzer chamber  110 , pumping chamber  115 , resolving chamber  120  and a wafer chamber  125  are all connected together by vacuum tight seals and evacuated through pump port  170 . Additional pump ports may be provided, for example in beam generation chamber  105 . Wafer chamber  125  can be tilted relative to resolving chamber  120 . Beam generation chamber  105 , analyzer chamber  110 , pumping chamber  115 , resolving chamber  120  and a wafer chamber  125  are fabricated from solid or hollow cast blocks of aluminum that are bored out. Electromagnetic pole end  150  comprises iron. Electron shower tube  210  comprises graphite and is negatively charged. 
   In operation, an ion plasma is generated within ion source  135  and ions extracted from the ion source by extractor  140  to generate an ion beam that is projected along a beam path  250  by the electromagnet. After being passing through defining aperture  145 , the ion beam is passed through analyzer chamber  110  where only ions of a predetermined charge to mass ratio exit through exit aperture  155 . After passing through pumping chamber  135 , selectable aperture  190 , beam sampler  195 , electromagnetic aperture  200 , electron shower aperture  205 , and electron shower tube  210 , the ion beam strikes a substrate on stage  245 . 
   The exact locations and thicknesses of unwanted material layer formation is a function of the specific interior geometry and arrangement of components and the fabrication process being run, but in an example of one type of ion implantation tool these location occur in the analyzer, pumping and resolving chambers. These layers are formed by ions striking the walls and depositing there, materials (including photoresists) from the wafers vaporizing or being physically or chemically removed from the wafer as well as reaction of the ion/plasma beam with trace gases in the various chamber. When these layers become thick enough flakes break off and are swept down to the wafer chamber where they land on the wafers being processed. These flakes can have dimensions in the sub-micron regime. 
   There are several locations on the interior surfaces of analyzing chamber  110 , pumping chamber  115  and resolving chamber  120  that layers of material my build up on. These regions are discernable by buildup of layers of material after operation of implanter over extended periods of time. In analyzing chamber  110 , the top bottom and sidewalls in a region “A” partially defined by the dashed lines is a region of particularly heavy material deposition. In pumping chamber  115 , virtually all surfaces in a region “B” partially defined by the dashed lines is a region of particularly heavy material deposition. In resolving chamber  120 , lower surfaces in a region “C” partially defined by the dashed lines is a region of particularly heavy material deposition. 
     FIG. 2  is a schematic top view of the analyzer chamber  110  of  FIG. 1  with removable liners in place. The sidewalls of analyzer chamber  110  are illustrated in sectional view, all other structures are illustrated in plan view. In  FIG. 2 , an analyzer inner foreign material shield  260  and an analyzer outer foreign material shield  265  are removeably attached to the respective sidewalls  270  and  275  of analyzer chamber  110 . Removeably attached to access port cover  165  is an analyzer striker plate  280 . Removeably attached to outer foreign material shield  260  and striker plate  280  are an analyzer upper liner  285 A and an identical analyzer lower liner  285 B illustrated by heavy lines for clarity. 
   In one example, liners  2885 A and  285 B comprise aluminum. In one example liners  285 A and  285 B are between about 0.05 inches and about 0.20 inches thick. In one example, outer foreign material shield  260 , inner foreign material shield  265  and striker plate  280  are comprised of graphite or aluminum. Outer foreign material shield  260 , inner foreign material shield  265  and striker plate  280  roughened or textured by, for example, by machining, bead blasting, sand blasting, or etching. It is advantageous from a contamination point of view that outer foreign material shield  260 , inner foreign material shield  265 , striker plate  280  and liners  285 A and  285 B not contain significant amounts (are essentially free) of iron, nickel, chrome, cobalt, molybdenum, beryllium, tungsten, titanium, tantalum, copper, magnesium, tin, indium, antimony, phosphorous, boron or arsenic. A feature of shields  185 A and  285 B is that they do not overlap electromagnetic pole end  150  so as not to interfere with the magnetic flux lines of the electromagnet. 
     FIG. 3  is a side view through line  2 B- 2 B of  FIG. 2  of an  290  analyzer liner assembly of  FIG. 1 . Analyzing chamber  110  (see  FIG. 2 ) is rectangular in cross-section so analyzer assembly  290  comprising, striker plate  280  and liners  285 A and  285 B just fits in between a top wall  295 A and a bottom wall  295 B of analyzing chamber  110 . Striker plate  280  has a height “H 1 ” Inside surfaces  300 A and  300 B of respective liners  285 A and  285 B are advantageously roughened or textured by, for example, by machining, bead blasting, sand blasting, or etching. 
     FIG. 4  is an isometric view of the inner shield of  FIG. 1  and  FIG. 5  is an isometric view of the outer shield of  FIG. 1 . In  FIG. 4 , a region  305  of inner shield  260  has a height “H 1 ” and in  FIG. 5 , a region  310  of inner shield  260  also has a height “H 1 .” 
   Returning to  FIG. 2 , it can be seen that inner and outer shields  260  and  265  and striker plate  280  have a first function of collecting ionized species that do not have the required mass/charge ratio and as a consequence get coated with a layer of unwanted material. Thus inner and outer shields  260  and  265  and striker plate  280  serve a second function of preventing portions of the top and bottom walls of analyzer chamber from becoming coated with unwanted material. Liners  285 A and  285 B also become coated with unwanted layers of material. By removing access port cover  160 , liners  285 A and  285 B as well as outer foreign material shield  260 , inner foreign material shield  265 , striker plate  280  may be periodically removed for cleaning, clean and then reinstalled or a previously cleaned replacement set of liners, shields and striker plate installed in the machine while the removed liners and shields are cleaned. In either case tool down time is significantly less than cleaning the chamber surfaces themselves and the cleaning is more thorough. 
     FIG. 6  is a schematic top view of pumping chamber  115  of  FIG. 1  with removable liners in place. The sidewalls of pumping chamber  115  are illustrated in sectional view, all other structures are illustrated in plan view. In  FIG. 6 , a first aperture liner  315 , a second aperture liner  320 , a pump chamber liner  325 , a pump port liner  330  and an access port liner  335  (illustrated by heavy lines for clarity) are removeably positioned in contact with interior surfaces of pumping chamber  115 . L liners  315 ,  320 ,  325 ,  330  and  335  are removed and installed through access port  180 . By removing access port cover  185 , liners  315 ,  320 ,  325 ,  330  and  335  may be periodically removed for cleaning, clean and then reinstalled or a previously cleaned replacement set of liners installed in the machine while the removed liners are cleaned. In either case tool down time is significantly less than cleaning the chamber surfaces themselves and the cleaning is more thorough. 
   While gaps are illustrated between liners  315 ,  320 ,  325 ,  330  and  335 , these gaps are advantageously designed to be zero (liners touching) or as close to zero as practical without interfering with easy install and removal of the liners. 
   In one example, liners  315 ,  320 ,  325 ,  330  and  335  comprise aluminum. In one example liners  315 ,  320 ,  325 ,  330  and  335  are between about 0.05 inches and about 0.20 inches thick. Liners  315 ,  320 ,  325 ,  330  and  335  are roughened or textured by, for example, by machining, bead blasting, sand blasting, or etching blasting. It is advantageous from a contamination point of view that liners  315 ,  320 ,  325 ,  330  and  335  not contain significant amounts of iron, nickel, chrome, cobalt, molybdenum, beryllium, tungsten, titanium, tantalum, copper, magnesium, tin, indium, antimony, phosphorous, boron or arsenic. 
     FIG. 7A  is a top view and  FIG. 7B  is a side view of pumping chamber liner  315  of  FIG. 6 . Pumping chamber liner  315  is comprised of two identical liners, a lower liner  315 A and an upper liner  315 B, which are curved along beam path  250  to fit the main bore of pumping chamber  115  (see  FIG. 6 ) along the beam path direction. Notches  340 A and  340 B are curved to match the bore of an access port bore and a pump bore respectively. 
     FIG. 8A  is a side view and  FIG. 8B  is a front view of first aperture liner  320  of  FIG. 6 . First aperture liner  320  is comprised of two identical liners, a lower liner  320 A and an upper liner  320 B with corresponding bores  345 A and  345 B centered along beam path  250 . 
     FIG. 9A  is a side view and  FIG. 9B  is a front view of second aperture liner  325  of  FIG. 6 . Second aperture liner  325  includes a circular bore  350  centered along beam path  250 . 
     FIG. 10A  is a top view,  FIG. 10B  is a front view and  FIG. 10C  is a flat projection view of pump port liner  330  of  FIG. 6 . In  FIG. 10C , an outside edge  355 A will face pump port  170  (see  FIG. 6 ) and an inside edge  355 B will face the interior of pumping chamber  115  (see  FIG. 6 ). In  FIG. 10B , the curves of inside edge  355 B are shaped to match intersection of the pump port bore and the main bore of pumping chamber  115  (see  FIG. 6 ) when rolled to form a ring having a gap  360  where edges  365 A and  365 B are proximate to each other. Gap  360  allows access port liner to “spring” or compression fit inside pumping chamber  115  (see  FIG. 6 ). 
     FIG. 11A  is a top view,  FIG. 11B  is a front view and  FIG. 11C  is a flat projection view of access port liner  335  of  FIG. 6 . In  FIG. 11C , an outside edge  370 A will face access port  170  (see  FIG. 6 ) and an inside edge  370 B will face the interior of pumping chamber  115  (see  FIG. 6 ). In  FIG. 11B , the curves of inside edge  370 B are shaped to match intersection of the access port bore and the main bore of pumping chamber  115  (see  FIG. 6 ) when rolled to form a ring having a gap  375  where edges  380 A and  380 B are proximate to each other. Gap  375  allows pump port liner to “spring” fit inside pumping chamber  115  (see  FIG. 6 ). 
   Returning to  FIG. 6 , liners  320  and  325  are held in place by liner  315  which in turn is held in place by liners  330  and  335 . Thus liners  315 ,  320 ,  325 ,  330  and  335  are can be easily removed for cleaning and clean liners easily installed. 
     FIG. 12  is a schematic top view of resolving chamber  120  of  FIG. 1  with removable liners in place. The sidewalls of resolving chamber  120  are illustrated in sectional view, all other structures are illustrated in plan view. In  FIG. 12 , a third aperture liner  385 , a first lower pump chamber liner  390 , and a second lower pump chamber liner  395  are removeably positioned in contact with interior surfaces of resolving chamber  120 . Liners  385 ,  390  and  395  are installed and removed through access port  215 . By removing access port cover  220 , liners  385 ,  390  and  395  may be periodically removed for cleaning, clean and then reinstalled or a previously cleaned replacement set of liners installed in the machine while the removed liners are cleaned. In either case tool down time is significantly less than cleaning the chamber surfaces themselves and the cleaning is more thorough. 
   While gaps are illustrated between liners  385 ,  390  and  395 , these gaps are advantageously designed to be zero (liners just touching) or as close to zero as practical without interfering with easy install and removal of the liners. 
   In one example, liners  385 ,  390  and  395  comprise aluminum. In one example liners  385 ,  390  and  395  are between about 0.05 inches and about 0.20 inches thick. Liners  385 ,  390  and  395  are roughened or textured by, for example, by machining, bead blasting, sand blasting, or etching. It is advantageous from a contamination point of view that liners  385 ,  390  and  395   5  not contain significant amounts of iron, nickel, chrome, cobalt, molybdenum, beryllium, tungsten, titanium, tantalum, copper, magnesium, tin, indium, antimony, phosphorous, boron or arsenic. 
     FIG. 13A  is a side view and  FIG. 13B  is a front view of third aperture liner  385  of  FIG. 12 . Third aperture liner  385  includes a circular bore  400  centered along beam path  250 . Also illustrated in  FIG. 13A , (in cross-section) is second aperture liner  325  and a portion of resolving chamber  120 . It can be seen that second aperture liner  325  fits into bore  400  to prevent foreign material from being trapped between third aperture liner  385  and walls of resolving chamber  120 . 
     FIG. 14A  is a top view and  FIG. 14B  is a edge view of first resolving chamber liner  390  of  FIG. 12 . Liner  390  is curved along beam path  250  to fit the main bore of resolving chamber  120  (see  FIG. 12 ) along the beam path direction. A key  405  is provided on one side of liner  390 . Liner  390  is positioned on the bottom surfaces of resolving chamber  120  under selectable aperture  190 , and beam sampler  195  (see  FIG. 12 ). 
     FIG. 15A  is a top view and  FIG. 15B  is a edge view of second resolving chamber liner  395  of  FIG. 12 . Liner  395  is curved along beam path  250  to fit the main bore of resolving chamber  120  (see  FIG. 12 ) along the beam path direction. A keyhole  410  is provided on one side of liner  395 . Liner  395  is positioned on the bottom surfaces of resolving chamber  120  under selectable aperture  190 , and beam sampler  195  (see  FIG. 12 ). Key  405  of liner  390  (see  FIG. 14A ) engages keyhole  410  of liner  395  when the liners are in place. 
   Returning to  FIG. 12 , there is no liner under electromagnetic aperture  200  and electron shower aperture  205  or on the upper surfaces of resolving chamber  120 , because buildup of material in these locations is not significant. There are two options designing liners. The first option is to place liners over as many interior surfaces of the charged particle beam tools as possible without interfering with the operation of the tool. The second option is to place liners over only those interior surfaces of the charged particle beam tools where significant material buildup is expected (for example, cooler surfaces) or has been found to occur. 
     FIG. 16  is a schematic top view of an exemplary charged particle beam tool  420  according to a embodiment of the present invention. In  FIG. 16 , charged particle beam system  420  comprises a source chamber  425 , a pumping chamber  430 , a beam alignment/defection chamber  435  and a target chamber  440 . The arrangement of chambers can vary from tool to tool and some chambers may be combined into a single chamber. Pumping chamber  430  includes replaceable aperture liners  445 A and  445 B and replaceable pump chamber liners  450 A,  450 B and  450 C which may be installed and removed through an access port  455 . Beam alignment/defection chamber  435  includes replaceable aperture liners  460 A and  460 B and replaceable pump chamber liners  465 A,  465 B,  465 C and  465 D which may be installed and removed through an access ports  470 A and  470 B. 
   A charged particle beam  475  is generated in source chamber  420  by a beam source  480 , passes through pump chamber  430 , beam alignment/defection  435  and strikes a target  485  in target chamber  440 . In one example, beam  475  comprises a species selected from the group consisting of phosphorus containing species ions, boron containing species ions, arsenic containing species ions, germanium containing species ions, carbon containing species ions, nitrogen containing species ions, helium ions, electrons, protons, or combinations thereof. 
   All liners  445 A,  445 B,  450 A,  450 B.  450 C,  460 A,  460 B,  465 A,  465 B,  465 C and  465 D are formed of material selected to not contain chemical elements detrimental to the operation of or process being performed by tool  420 . Liners  445 A,  445 B,  450 A,  450 B.  450 C,  460 A,  460 B,  465 A,  465 B,  465 C and  465 D may be held in place by compression, fasteners or gravity. There may be more or less liners than the number shown in  FIG. 16 . The surfaces of liners  445 A,  445 B,  450 A,  450 B.  450 C,  460 A,  460 B,  465 A,  465 B,  465 C and  465 D away from the inside surfaces of the various chambers may be advantageously roughened or textured by machining, bead blasting, sand blasting, or etching. Liners  445 A,  445 B,  450 A,  450 B.  450 C,  460 A,  460 B,  465 A,  465 B,  465 C and  465 D may be cleanable or disposable. 
   Thus, the embodiments of the present invention provide an apparatus and a method of mitigating foreign material related product loss on wafers processed in ion implantation tools and other charged particle beam tools. 
   The description of the embodiments of the present invention is given above for the understanding of the present invention. It will be understood that the invention is not limited to the particular embodiments described herein, but is capable of various modifications, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, it is intended that the following claims cover all such modifications and changes as fall within the true spirit and scope of the invention.

Technology Category: h