Abstract:
A pulsed-laser anneal technique includes performing an implant of a selected region of a semiconductor wafer. A co-constituent implant of the selected region is performed, and the pulsed-laser anneal of the selected region performed. A pre-amorphizing implant of the selected region can also be performed. In one embodiment, the implant of the selected region is performed as an insitu implant. In another embodiment, the co-constituent implant is performed as an insitu non-donor implant. In yet another embodiment, the implant and the co-constituent implant of the selected region are performed as an insitu donor and co-constituent implant.

Description:
TECHNICAL FIELD 
     Embodiments described herein are generally directed to the field of semiconductor fabrication. 
     BACKGROUND 
     High dopant activation in source/drain or tip regions of a semiconductor device can significantly improve device performance, i.e., by reducing Rext. Pulsed-laser anneal processes can produce highly active “superactive” regions in a device by melt and rapid regrowth of the doped region. These regions, however, are susceptible to deactivation by subsequent thermal processes. 
     While pulsed-laser “melt” anneal processes for source-drain formation are not common in high-volume manufacturing, available literature generally describes a pulsed-laser “melt” anneal process as including pre-amorphizing implant in source/drain (such as a silicon implant), a source-drain implant (such as a phosphorous implant), followed by the pulsed-laser anneal process. The pulsed-laser anneal process is targeted to melt the amorphous material without melting the underlying substrate in which the boundaries of the source and drain are defined by the amorphizing implant conditions. The melt process produces super-activated regions having abrupt, box-like dopant profiles. Another common, closely related technique omits the pre-amorphizing implanting step and relies on fine control of the laser energy to control the depth of the super-active region. Depending on species and precise process parameters, raw activation levels of up to 100% can be achieved. 
     One key challenge in integrating such processes is retaining high activation levels through the remainder of the manufacturing process. Deactivation from subsequent thermal processes reduces net activation back towards equilibrium levels in the final product, thereby reducing the overall benefit of the melt-and-anneal process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments disclosed herein are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements and in which: 
         FIGS. 1A-1H  respectively depict process flows for exemplary embodiments of a pulsed-laser anneal process according to the subject matter disclosed herein; 
         FIG. 2A  is a graph showing exemplary liquid-phase SIMS redistribution data for arsenic (As) concentration for an As-only system as a function of depth for different four laser anneal conditions; 
         FIG. 2B  is a graph showing exemplary liquid-phase SIMS redistribution data for arsenic (As) concentration for an As—C system as a function of depth for different four laser anneal conditions; and 
         FIG. 3  is a graph showing exemplary liquid-phase SIMS redistribution data for carbon concentration for the As—C system as a function of depth for four different laser anneal conditions. 
     
    
    
     It will be appreciated that for simplicity and/or clarity of illustration, elements depicted in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. The scaling of the figures does not represent precise dimensions and/or dimensional ratios of the various elements depicted herein. Further, if considered appropriate, reference numerals have been repeated among the figures to indicate corresponding and/or analogous elements. 
     DETAILED DESCRIPTION 
     Embodiments of techniques described herein relate to semiconductor fabrication and, more particularly, to fabricating superactive deactivation-resistant semiconductor junctions. In the following description, numerous specific details are set forth to provide a thorough understanding of embodiments disclosed herein. One skilled in the relevant art will recognize, however, that the embodiments disclosed herein can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the specification. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. Additionally, the word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not to be construed as necessarily preferred or advantageous over other embodiments. 
     Various operations may be described as multiple discrete operations in turn and in a manner that is most helpful in understanding the claimed subject matter. The order of description, however, should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation. Operations described may be performed in a different order than the described embodiment. Various additional operations may be performed and/or described operations may be omitted in additional embodiments. 
     The subject matter disclosed herein relates to semiconductor fabrication and; more particularly, to fabricating superactive deactivation-resistant semiconductor junctions. 
     The subject matter disclosed herein relates to a method to create a superactive junction that is resistant to deactivation from subsequent thermal processes. 
     The subject matter disclosed herein utilizes a liquid-phase redistribution of a multicomponent system that improves resilience against deactivation. An exemplary embodiment of the subject matter disclosed herein involves a pulsed-laser anneal process in which the melted region contains both the donor species and one or more co-constituents. 
     There are at least eight variations of the pulsed-laser anneal process disclosed herein, which are respectively depicted in  FIGS. 1A-1H . For the following exemplary embodiments, any or all implant processes may refer to a conventional beam line ion implantation, an angled implantation or a conformal-plasma implantation to address issues associated with nonplanar geometries. Additionally, one or more conventional annealing processes (e.g., furnace, RTP, or millisecond anneal) may be inserted into the flow. These particular anneals may serve purposes, such as defect reduction, partial regrowth, pre-activation, or dopant profile modification. 
     Because the subject matter disclosed herein is confined to a short and specific segment of an overall process flow, it expected that the techniques disclosed herein are be compatible with a wide variety of global process options. Implementation of the exemplary processes disclosed herein are be independent of the following parameters: (1) substrate type (e.g., compatible with BULK and SOI processes, and is independent of substrate orientation); (2) transistor architecture (e.g., compatible with planar and nonplanar architectures); (3) gate/gate oxide strategy (e.g. compatible with SiO 2 /poly and both gate-first/gate-last high-k/MG processes); and (4) pulsed-laser anneal integration scheme (e.g., compatible with ARC, absorber strategies). 
       FIG. 1A  is a flow diagram  110  depicting a first exemplary embodiment of a pulsed-laser anneal process according to the subject matter disclosed herein is an implant-only process. At  111  in  FIG. 1A , a pre-amorphizing implant is performed. The order of the implants is not critical. At  112 , a source/drain implant is performed. At  113 , a co-constituent, such as carbon, is implanted. Other exemplary co-constituents include antimony (Sb), tin (Sn) and fluorine (F), and selection of a particular co-constituent to form a superactive region that is deactivation resistant depends on the particular active dopant species as well as the particular semiconductor. At  114 , a pulsed-laser anneal process is performed. 
       FIG. 1B  is a flow diagram  120  depicting a second exemplary embodiment of a pulsed-laser anneal process according to the subject matter disclosed herein. The second exemplary embodiment is similar to the first exemplary embodiment, but omits the pre-amorphizing implant, in which case the boundaries of the melted region are defined by fine control of the laser energy applied during the pulsed-laser anneal process. At  121  in  FIG. 1B , a source/drain implant is performed. At  122 , a co-constituent, such as carbon, is implanted. At  123 , a pulsed-laser anneal process is performed. 
       FIG. 1C  is a flow diagram  130  depicting a third exemplary embodiment of a pulsed-laser anneal process according to the subject matter disclosed herein. The third exemplary embodiment utilizes an insitu-doped source-drain process in place of the source-drain implant process used in the first exemplary embodiment ( FIG. 1A ). In particular, at  131  in  FIG. 1C , a chemical vapor deposition (CVD) source/drain deposition, for example, is performed with insitu source-drain doping. The order of the insitu implants is not critical for the third exemplary embodiment. At  132 , a co-constituent, such as carbon, is implanted. At  133 , a pre-amorphizing implant is performed. At  134 , a pulsed-laser anneal process is performed. 
       FIG. 1D  is a flow diagram  140  depicting a fourth exemplary embodiment of a pulsed-laser anneal process according to the subject matter disclosed herein. The fourth exemplary embodiment is similar to the third exemplary embodiment, but omits the pre-amorphizing implant, in which case the boundaries of the melted region are defined by fine control of the laser energy applied during the pulsed-laser anneal process. At  141  in  FIG. 1D , a chemical vapor deposition (CVD) source/drain deposition, for example, is performed with insitu source-drain doping. The order of the insitu implants is not critical for the fourth exemplary embodiment. At  142 , a co-constituent, such as carbon, is implanted. At  143 , a pulsed-laser anneal process is performed. 
       FIG. 1E  is a flow diagram  150  depicting a fifth exemplary embodiment of a pulsed-laser anneal process according to the subject matter disclosed herein. The fifth exemplary embodiment utilizes an insitu-doped source-drain process in place of the source-drain implant process that is used in the third exemplary embodiment ( FIG. 1C ). At  151  in  FIG. 1E , a chemical vapor deposition (CVD) source/drain deposition, for example, is performed with insitu (non-donor) source-drain doping. The order of the insitu implants is not critical for the fifth exemplary embodiment. At  152 , a source/drain implant is performed. At  153 , a pre-amorphizing implant is performed. At  154 , a pulsed-laser anneal process is performed. 
       FIG. 1F  is a flow diagram  160  depicting a sixth exemplary embodiment of a pulsed-laser anneal process according to the subject matter disclosed herein. The sixth exemplary embodiment is similar to the fifth exemplary embodiment, but omits the pre-amorphizing implant, in which case the boundaries of the melted region are defined by fine control of the laser energy applied during the pulsed-laser anneal process. At  161 , a chemical vapor deposition (CVD) source/drain deposition, for example, is performed with insitu (non-donor) source-drain doping. The order of the insitu implants is not critical for the sixth exemplary embodiment. At  162 , a source/drain implant is performed. At  163 , a pulsed-laser anneal process is performed. 
       FIG. 1G  is a flow diagram  170  depicting a seventh exemplary embodiment of a pulsed-laser anneal process according to the subject matter disclosed herein. The seventh exemplary embodiment is similar to the third exemplary embodiment ( FIG. 1C ), but differs by having all implants replaced by insitu doping. At  171 , a chemical vapor deposition (CVD) source/drain deposition, for example, is performed with insitu implant of donor and co-constituent source-drain doping. The order of the insitu implants is not critical for the seventh exemplary embodiment. At  172 , a pre-amorphizing implant is performed. It should be understood that in an alternative exemplary embodiment, the pre-amorphizing implant could be performed prior to the insitu implant of donor and co-constituent source-drain doping. At  173 , a pulsed-laser anneal process is performed. 
       FIG. 1H  is a flow diagram  180  depicting an eighth exemplary embodiment of a pulsed-laser anneal process according to the subject matter disclosed herein. The eighth exemplary embodiment is similar to the seventh exemplary embodiment ( FIG. 1G ), but omits the pre-amorphizing implant, in which case the boundaries of the melted region are defined by fine control of the laser energy applied during the pulsed-laser anneal process. At  181 , a chemical vapor deposition (CVD) source/drain deposition, for example, is performed with insitu of donor and co-constituent source-drain doping. The order of the insitu implants is not critical for the eighth exemplary embodiment. At  182 , a pulsed-laser anneal process is performed. The effectiveness of the subject matter disclosed herein has been demonstrated on As-implanted blanket wafers with and without carbon as a co-constituent. The process flow for the As-only system included deep p-well implants and activation followed by a 12 keV 7×10 14  silicon pre-amorphizing implant, and a 10 keV 4.8×10 15  As implant. Process flow for the As—C system was the same and carbon was added by two successive implants at 4 keV 2 keV to achieve ˜1% total C concentration. 
       FIG. 2A  is a graph showing exemplary liquid-phase SIMS redistribution data for arsenic (As) concentration for the As-only system as a function of depth for different four laser anneal conditions. The ordinate of  FIG. 2A  is As concentration measured as As atoms/cm 3 , and the abscissa of  FIG. 2A  is depth in Ångstroms. The four laser anneal conditions are (1) no anneal shown at  201 , pulsed-laser anneal using 500 mJ/cm 2  shown at  202 ; pulsed-laser anneal using 550 mJ/cm 2  shown at  203 ; and pulsed-laser anneal using 600 ml/cm 2  shown at  204 .  FIG. 2B  is a graph showing exemplary liquid-phase SIMS redistribution data for arsenic (As) concentration for the As—C system as a function of depth for different four laser anneal conditions. The ordinate of  FIG. 2B  is As concentration measured as As atoms/cm 3 , and the abscissa of  FIG. 2B  is depth in Ångstroms. The four laser anneal conditions are no anneal shown at  211 , pulsed-laser anneal using 500 mJ/cm 2  shown at  212 ; pulsed-laser anneal using 550 mJ/cm 2  shown at  213 ; and pulsed-laser anneal using 600 mJ/cm 2  shown at  214 . 
       FIG. 3  is a graph showing exemplary liquid-phase SIMS redistribution data for carbon (C) concentration for the A-C system as a function of depth for four different laser anneal conditions. The ordinate of  FIG. 3  is As concentration measured as C atoms/cm 3 , and the abscissa of  FIG. 3  is depth in Ångstroms. Again, the four laser anneal conditions are no anneal shown at  301 , pulsed-laser anneal using 500 mJ/cm 2  shown at  302 ; pulsed-laser anneal using 550 mJ/cm 2  shown at  303 ; and pulsed-laser anneal 600 mJ/cm 2  shown at  304 . 
     Table 1 shows the sheet resistance (Rs) and absolute active-carrier concentration after pulsed-laser anneal and a series of subsequent deactivating anneals (i.e., 700 C spike anneal plus 300 C one-hour furnace anneal). 
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Rs 
                 [Active 
                   
               
               
                   
                 (Ω/cm 2 ) 
                 Carrier]/cm 2   
                 Enhancement 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 As 
                 223.38 
                 2.17 × 10 20   
                 N/A 
               
               
                   
                 As + C 
                 194.55 
                 2.93 × 10 20   
                 35% 
               
               
                   
                   
               
             
          
         
       
     
     Both the As-only system and the As+C system have a concentration of As of approximately 1.6×10 21  atoms/cm 3  and junction depth Xj (i.e., the depth at which the concentration of As drops below 1×10 19  atoms/cm 3 ) of approximately 30 nm. After annealing, the liquid-phase redistribution of As+C system according to the subject matter disclosed herein exhibits activation enhanced of about 35% over the As-only system. 
     These modifications can be made in light of the above detailed description. The terms used in the following claims should not be construed to limit the scope to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the embodiments disclosed herein is to be determined by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.