Abstract:
A method of fabricating integrated circuitry comprises forming a conductive line having opposing sidewalls over a semiconductor substrate. An insulating layer is then deposited and planarize polished using an outer etch stop cap of the line as an etch stop. The insulating layer is etched proximate the line along at least a portion of at least one sidewall of the line. An insulating spacer forming layer is then deposited over the substrate and the line. It is anisotropically etched to form an insulating sidewall spacer. Methods of forming conductive lines and methods of forming local interconnects, as well as other methods of forming integrated circuitry, are disclosed and claimed.

Description:
RELATED PATENT DATA 
     This patent application is a divisional application resulting from U.S. patent application Ser. No. 09/266,456 now U.S. Pat. No. 6,180,494, which was an application filed on Mar. 11, 1999. 
    
    
     TECHNICAL FIELD 
     This invention relates to integrated circuitry, to methods of fabricating integrated circuitry, to methods of forming local interconnects, and to methods of forming conductive lines. 
     BACKGROUND OF THE INVENTION 
     The reduction in memory cell and other circuit size implemented in high density dynamic random access memories (DRAMs) and other circuitry is a continuing goal in semiconductor fabrication. Implementing electric circuits involves connecting isolated devices through specific electric paths. When fabricating silicon and other semiconductive materials into integrated circuits, conductive devices built into semiconductive substrates need to be isolated from one another. Such isolation typically occurs in the form of either trench and refill field isolation regions or LOCOS grown field oxide. 
     Conductive lines, for example transistor gate lines, are formed over bulk semiconductor substrates. Some lines run globally over large areas of the semiconductor substrate. Others are much shorter and associated with very small portions of the integrated circuitry. This invention was principally motivated in making processing and structure improvements involving local interconnects, although the invention is not so limited. 
     SUMMARY OF THE INVENTION 
     The invention includes integrated circuitry, methods of fabricating integrated circuitry, methods of forming local interconnects, and methods of forming conductive lines. In one implementation, a method of fabricating integrated circuitry comprises forming a conductive line having opposing sidewalls over a semiconductor substrate. An insulating layer is deposited over the substrate and the line. The insulating layer is etched proximate the line along at least a portion of at least one sidewall of the line. After the etching, an insulating spacer forming layer is deposited over the substrate and the line, and it is anisotropically etched to form an insulating sidewall spacer along said portion of the at least one sidewall. 
     In one implementation, a method of forming a local interconnect comprises forming at least two transistor gates over a semiconductor substrate. A local interconnect layer is deposited to overlie at least one of the transistor gates and interconnect at least one source/drain region of one of the gates with semiconductor substrate material proximate another of the transistor gates. In one aspect, a conductivity enhancing impurity is implanted into the local interconnect layer in at least two implanting steps, with one of the two implantings providing a peak implant location which is deeper into the layer than the other. Conductivity enhancing impurity is diffused from the local interconnect layer into semiconductor substrate material therebeneath. In one aspect, a conductivity enhancing impurity is implanted through the local interconnect layer into semiconductor substrate material therebeneath. 
     In one implementation, field isolation material regions and active area regions are formed on a semiconductor substrate. A trench is etched into the field isolation material into a desired line configuration. A conductive material is deposited to at least partially fill the trench and form a conductive line therein. 
     In one implementation, integrated circuitry comprises a semiconductor substrate comprising field isolation material regions and active area regions. A conductive line is received within a trench formed within the field isolation material. 
     Other implementations are disclosed, contemplated and claimed in accordance with the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention are described below with reference to the following accompanying drawings. 
     FIG. 1 is a diagrammatic sectional view of a semiconductor wafer fragment at one processing step in accordance with the invention. 
     FIG. 2 is a view of the FIG. 1 wafer at a processing step subsequent to that shown by FIG.  1 . 
     FIG. 3 is a view of the FIG. 1 wafer at a processing step subsequent to that shown by FIG.  2 . 
     FIG. 4 is a view of the FIG. 1 wafer at a processing step subsequent to that shown by FIG.  3 . 
     FIG. 5 is a view of the FIG. 1 wafer at a processing step subsequent to that shown by FIG.  4 . 
     FIG. 6 is a view of the FIG. 1 wafer at a processing step subsequent to that shown by FIG.  5 . 
     FIG. 7 is a view of the FIG. 1 wafer at a processing step subsequent to that shown by FIG.  6 . 
     FIG. 8 is a view of the FIG. 1 wafer at a processing step subsequent to that shown by FIG.  7 . 
     FIG. 9 is a view of the FIG. 1 wafer at a processing step subsequent to that shown by FIG.  8 . 
     FIG. 10 is a diagrammatic sectional view of an alternate embodiment semiconductor wafer fragment at one processing step in accordance with the invention. 
     FIG. 11 is a view of the FIG. 10 wafer at a processing step subsequent to that shown by FIG.  10 . 
     FIG. 12 is a view of FIG. 11 taken through line  12 — 12  in FIG.  11 . 
     FIG. 13 is a view of the FIG. 10 wafer at a processing step subsequent to that shown by FIG.  11 . 
     FIG. 14 is a view of FIG. 13 taken through line  14 — 14  in FIG.  13 . 
     FIG. 15 is a view of the FIG. 10 wafer at a processing step subsequent to that shown by FIG.  13 . 
     FIG. 16 is a view of FIG. 15 taken through line  16 — 16  in FIG.  15 . 
     FIG. 17 is a diagrammatic sectional view of another alternate embodiment semiconductor wafer fragment at one processing step in accordance with the invention, and corresponds in sequence to that of FIG.  16 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8). 
     Referring to FIG. 1, a semiconductor wafer in process is indicated generally with reference numeral  10 . Such comprises a bulk monocrystalline silicon substrate  12 . In the context of this document, the term “semiconductor substrate” is defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductor substrates described above. 
     A gate dielectric layer  14 , such as silicon dioxide, is formed over semiconductor substrate  12 . A conductively doped semiconductive layer  16  is formed over gate dielectric layer  14 . Conductively doped polysilicon is one example. An insulative capping layer  18  is formed over semiconductive layer  16 . An example material is again silicon dioxide. Intervening conductive layers, such as refractory metal silicides, might of course also be interposed between layers  16  and  18 . An etch stop layer  20  is formed over insulative capping layer  18 . An example preferred material is polysilicon. 
     Referring to FIG. 2, the above-described layers over substrate  12  are patterned and etched into a plurality of exemplary transistor gate lines  22 ,  24  and  26 . Lines  22 ,  24  and  26  have respective opposing sidewalls  27  and  28 ,  29  and  30 , and  31  and  32 . Lines  22 ,  24  and  26  are shown in the form of field effect transistor gates, although other conductive lines are contemplated. LDD implant doping is preferably conducted to provide illustrated implant regions  33  for the transistors. One example implant dose for regions  33  would be 2×10 13  ions/cm 2 . Alternately, the LDD implant doping can implanted after source/drain regions have been formed (or a combination of both). Forming LDD regions later in the process reduces the D t  seen by such implants. 
     Referring to FIG. 3, an insulating layer  34  is deposited over substrate  12  and lines  22 ,  24  and  26 . The thickness of layer  34  is preferably chosen to be greater than that of the combined etch stop layer, capping layer and semiconductor layer, and to be received between the transistor gate lines to fill the illustrated cross-sectional area extending between adjacent gate lines. Example and preferred materials include undoped silicon dioxide deposited by decomposition of tetraethylorthosilicate, and borophosphosilicate glass. 
     Referring to FIG. 4, insulative material layer  34  has been planarized. Such is preferably accomplished by chemical-mechanical polishing using etch stop layer  20  of gates  22 ,  24  and  26  as an etch stop for such polishing. 
     Referring to FIG. 5, a layer of photoresist  36  has been deposited and patterned. Insulative material  34  is etched to effectively form contact openings  38 ,  39  and  40  therein to proximate substrate  12 , and preferably effective to outwardly expose material of semiconductor substrate  12 . For purposes of the continuing discussion, the exposed portions of semiconductor substrate  12  are designated as locations  42 ,  43  and  44 . The depicted etching constitutes but one example of etching insulating layer  34  proximate lines  22  and  24  along at least a portion of facing sidewalls  28  and  29 . Such portion preferably comprises a majority of the depicted sidewalls, and as shown constitutes the entirety of said sidewalls to semiconductor substrate  12 . 
     With respect to line  26 , the illustrated insulating layer  34  etching is conducted along at least a portion of each of opposing line sidewalls  31  and  32 . Further with respect to lines  22  and  24 , such etching of insulating layer  34  is conducted along portions of sidewalls  28  and  29 , and not along the respective opposing sidewalls  27  and  30 . Further, such insulating layer  34  etching exposes conductive material of at least one of the transistor gates, with such etching in the illustrated example exposing conductive material  16  of sidewalls  28 ,  29 ,  31  and  32  of the illustrated transistor gates. Further with respect to gate lines  22  and  24 , the insulative material is etched to remain/be received over the one sidewalls  27  and  30 , and not sidewalls  28  and  29 . 
     After etching of layer  34 , at least one of the exposed sidewalls is covered with insulating material. Such preferably comprises deposition of an insulating layer  46  over substrate  12 ; lines  22 ,  24  and  26 ; and planarized and etched insulative material  34  to a thickness which less than completely fills at least some of the contact openings. Such layer preferably comprises a spacer forming layer, with silicon dioxide and silicon nitride being but two examples. 
     Referring to FIG. 7, spacer forming layer  46  is anisotropically etched to form insulative sidewall spacers  47 ,  48 ,  49 ,  50  and  52 . Such constitutes but one example of forming the illustrated insulative sidewall spacers. In one implementation, insulating layer  34  is received between at least one of the sidewalls and one of the sidewall spacers, for example as shown with respect to line  24  between sidewall  30  and spacer  49 . Further with respect to this example line  24 , insulative material  34  is received between the one sidewall  30  and the one insulative spacer  49  formed thereover, and is not received between the opposing sidewall  29  and the other spacer  48  formed thereover. Yet, in the depicted section, insulative sidewall spacers  48  and  49 , and  50  and  52  are formed over each of the respective opposing line sidewalls of lines  24  and  26 , wherein in the depicted section only one insulative spacer  47  is formed over one sidewall of line  22 . Further, insulative material  34  received between sidewall  30  and insulative spacer  49  of line  24  has a maximum lateral thickness which is greater than or equal (greater as shown) to a maximum lateral thickness of sidewall spacer  49 . Source/drain implanting may occur at this point in the process, if desired. 
     Referring to FIG. 8, a local interconnect layer  56  is deposited to overlie at least one of the transistor gates, and ultimately interconnect locations  42 ,  43  and  44  of substrate  12 , and is thus provided in electrical connection therewith. An example preferred material for layer  56  is polysilicon. Due to the spacing constraints between the insulative spacers of lines  22  and  24  versus that of lines  24  and  26 , layer  56  completely fills contact opening area  38  and less than completely fills contact opening areas  39  and  40 . 
     Depending on the circuitry being fabricated and the desires of the processor, layer  56  might be in situ conductively doped as deposited and/or separately implanted with conductivity enhancing impurity subsequent to deposition. Further, any such subsequent implantings might be masked to only be provided within portions of layer  56  where, for example, both n-type and p-type substrate regions are being conductively connected by an ultimately conductive interconnect formed from layer  56 . Most preferably, interconnect layer  56  will ultimately comprise suitably conductively doped semiconductive material. Where such will comprise both n-type and p-type doping material, another conductive strapping layer, such as a refractory metal silicide, will ideally be formed atop layer  56  to avoid or overcome an inherent parasitic diode that forms where p-type and n-type materials join. Further with respect to combined n-type and p-type processing, multiple local interconnect layers might be provided and patterned, and perhaps utilize intervening insulative layers, spacers or etch stops. Further prior to deposition of layer  56 , a conductive dopant diffusion barrier layer might also be provided. 
     Example preferred implantings, whether p-type, n-type, or a combination of the same, is next described still with reference to FIG.  8 . Such depicts two preferred implantings represented by peak implant locations or depths  58  and  60 . Such are preferably accomplished by two discrete implantings which provide peak implant location  60  deeper relative to layer  56  than implant  58 . For example within layer  56  in contact openings  38  and  39 , regions of layer  56  are shown where peak implant  60  is deeper within layer  56  than is peak implant  58 . Yet, the peak implant location or depth for implant  60  is preferably not chosen to be so deep to be within conductively doped material  16  of lines  22 ,  24  and  26 . Further in contact opening locations  39  and  40 , the implanting to produce depicted implant  60  is conducted through local interconnect layer  56  and into semiconductor substrate material  12  therebeneath. Diffusing of the conductivity enhancing impurity provided within layer  56  might ultimately occur from local interconnect layer  56  into semiconductor substrate material  12  therebeneath within locations  42 ,  43  and  44  to provide the majority of the conductivity enhancing impurity doping for the source/drain regions of the illustrated transistor lines. Depending on the processor&#39;s desire and the degree of diffusion, such source/drain regions might principally reside within semiconductor substrate material  12 , or reside as elevated source/drain regions within layer  56 . 
     Further and as shown, layer  56  in certain locations acts as a spacer for the deeper implant. Further, such may actually reduce junction capacitance by counter doping halo implants that are further away from gate polysilicon. This can provide flexibility in the settings of the halo implants. 
     Referring to FIG. 9, local interconnect layer  56  is formed (i.e., by photopatterning and etching) into a local interconnect line  57  which overlies at least portions of illustrated conductive lines  24 ,  26  and  28 , and electrically interconnects substrate material locations  42 ,  43  and  44 . 
     Further considered aspects of the invention are next described with reference to FIGS. 10-16. FIG. 10 illustrates a semiconductor wafer fragment  10   a  comprising a bulk monocrystalline silicon substrate  12 . Semiconductor substrate  12  has been patterned to form field isolation region  64  and active area region  62 . In the illustrated example, material  66  of field isolation region  64  comprises silicon dioxide fabricated by LOCOS processing. Such might constitute other material and other isolation techniques, for example trench and refill resulting from etching trenches into substrate  12  and depositing oxide such as by CVD, including PECVD. 
     Fragment  10   a  in a preferred and exemplary embodiment comprises an extension of fragment  10  of the first described embodiment, such as an extension in FIG. 10 starting from the far right portion of FIG. 4 of the first described embodiment. Accordingly, insulating layer  34  is shown as having been deposited and planarized. 
     Referring to FIGS. 11 and 12, a trench  68  is etched into field isolation material  66  and is received within insulating layer  34 . Such includes opposing insulative sidewalls  77  and a base  79 . Trench  68  in this illustrated example extends to an edge  70  of isolation material  66  proximate, and here extending to, active area substrate material  12  of region  62 . An example preferred depth for trench opening  68  is 10% to 20% greater than the combined thickness of the conductive and insulating materials of gate stacks  22 ,  24  and  26 . 
     Referring to FIGS. 13 and 14, a conductive material  72  is deposited to at least partially fill trench  68 , and electrically connects with substrate material  12  of active area region  62 . As shown, material  72  is preferably deposited to overfill trench  68 . The width of trench  68  is preferably chosen to be more narrow than double the thickness of layer of material  72 . Such preferred narrow nature of trench  68  facilitates complete filling thereof with conductive material  72  in spite of its depth potentially being greater than the globally deposited thickness of layer  72 . 
     Referring to FIGS. 15 and 16, conductive layer  72  has been etched to produce the illustrated local interconnect line  75  which includes a line segment  76  received within trench  68  over isolation material  66 . A small degree of overetch preferably occurs as shown to assure complete removal material  72  from over the outer surface of insulating layer  34 . Ideally, the shape of trench  68  is chosen and utilized to define the entire outline and shape of the conductive line being formed relative to isolation material  66 . Further, conductive material of line  75  preferably contacts material  66  of trench sidewalls  77  and base  79 . 
     FIG. 17 illustrates an exemplary alternate wafer fragment  10   b  embodiment corresponding to FIG. 16, but using a trench isolation oxide  66   b  as opposed to LOCOS oxide  66 . An exemplary preferred trench filled line  68   b  is shown. 
     In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.