Abstract:
The invention includes a number of methods and structures pertaining to semiconductor circuit technology, including: methods of forming DRAM memory cell constructions; methods of forming capacitor constructions; DRAM memory cell constructions; capacitor constructions; and monolithic integrated circuitry. The invention includes a method of forming a capacitor comprising the following steps: a) forming a mass of silicon material over a node location, the mass comprising exposed doped silicon and exposed undoped silicon; b) substantially selectively forming rugged polysilicon from the exposed undoped silicon and not from the exposed doped silicon; and c) forming a capacitor dielectric layer and a complementary capacitor plate proximate the rugged polysilicon and doped silicon. The invention also includes a capacitor comprising: a) a first capacitor plate; b) a second capacitor plate; c) a capacitor dielectric layer intermediate the first and second capacitor plates; and d) at least one of the first and second capacitor plates comprising a surface against the capacitor dielectric layer and wherein said surface comprises both doped rugged polysilicon and doped non-rugged polysilicon.

Description:
TECHNICAL FIELD  
         [0001]    The invention pertains to semiconductor capacitor constructions and to methods of forming semiconductor capacitor constructions. The invention is thought to have particular significance in application to methods of forming dynamic random access memory (DRAM) cell structures, to DRAM cell structures, and to integrated circuitry incorporating DRAM cell structures.  
         BACKGROUND OF THE INVENTION  
         [0002]    A commonly used semiconductor memory device is a DRAM cell. A DRAM cell generally consists of a capacitor coupled through a transistor to a bitline. A semiconductor wafer fragment  10  is illustrated in FIG. 1 showing a prior art DRAM array  83 . Wafer fragment  10  comprises a semiconductive material  12 , field oxide regions  14 , and wordlines  24  and  26 . Wordlines  24  and  26  comprise a gate oxide layer  16 , a polysilicon layer  18 , a silicide layer  20  and a silicon oxide layer  22 . Silicide layer  20  comprises a refractory metal silicide, such as tungsten silicide, and polysilicon layer  18  typically comprises polysilicon doped with a conductivity enhancing dopant. Nitride spacers  30  are laterally adjacent wordlines  24  and  26 .  
           [0003]    Electrical node locations  25 ,  27  and  29  are between wordlines  24  and  26  and are electrically connected by transistor gates comprised by wordlines  24  and  26 . Node locations  25 ,  27  and  29  are diffusion regions formed within semiconductive material  12 .  
           [0004]    A borophosphosilicate glass (BPSG) layer  34  is over semiconductive material  12  and wordlines  24  and  26 . An oxide layer  32  is provided between BPSG layer  34  and material  12 . Oxide layer  32  inhibits diffusion of phosphorus from BPSG layer  34  into underlying materials.  
           [0005]    Conductive pedestals  54 ,  55  and  56  extend through BPSG layer  34  to node locations  25 ,  27  and  29 , respectively. Capacitor constructions  62  and  64  contact upper surfaces of pedestals  54  and  56 , respectively. Capacitor constructions  62  and  64  comprise a storage node layer  66 , a dielectric layer  68 , and a cell plate layer  70 . Dielectric layer  68  comprises an electrically insulative layer, such as silicon nitride. Cell plate layer  70  comprises conductively doped polysilicon, and may alternatively be referred to as a cell layer  70 . Storage node layer  66  comprises conductively doped hemispherical grain (HSG) polysilicon.  
           [0006]    A conductive bitline plug  75  contacts an upper surface of pedestal  55 . Bitline plug  75  may comprise, for example, tungsten. Together, bitline plug  75  and pedestal  55  comprise a bitline contact  77 .  
           [0007]    A bitline  76  extends over capacitors  62  and  64  and in electrical connection with bitline contact  77 . Bitline  76  may comprise, for example, aluminum.  
           [0008]    The capacitors  62  and  64  are electrically connected to bitline contact  77  through transistor gates comprised by wordlines  26 . A first DRAM cell  79  comprises capacitor  62  electrically connected to bitline  76  through a wordline  26  and bitline contact  77 . A second DRAM cell  81  comprises capacitor  64  electrically connected to bitline  76  through wordline a  26  and bitline contact  77 . DRAM array  83  comprises first and second DRAM cells  79  and  81 .  
           [0009]    If capacitors  62  and  64  are inadvertently shorted together, a so-called “double bit failure” will occur. Such double bit failures can occur if a stray piece of polysilicon, or HSG polysilicon, breaks off during formation of DRAM array  83  and disadvantageously electrically connects capacitors  62  and  64 . Prior art capacitor fabrication methods employ chemical-mechanical polishing (CMP) of HSG polysilicon. HSG polysilicon pieces can break off during such CMP processes and cause double bit failures. It would be desirable to develop alternative DRAM constructions which could be formed by methods avoiding double bit failures.  
         SUMMARY OF THE INVENTION  
         [0010]    The invention includes a number of methods and structures pertaining to semiconductor circuit technology, including: methods of forming DRAM memory cell constructions; methods of forming capacitor constructions; DRAM memory cell constructions; capacitor constructions; and integrated circuitry. For instance, the invention encompasses a method of forming a capacitor wherein a mass of silicon material is formed over a node location, and wherein the mass comprises exposed doped silicon and exposed undoped silicon. The method can further include substantially selectively forming rugged polysilicon from the exposed undoped silicon and not from the exposed doped silicon. Also, the method can include forming a capacitor dielectric layer and a complementary capacitor plate proximate the rugged polysilicon and doped silicon.  
           [0011]    As another example, the invention encompasses a capacitor having a capacitor dielectric layer intermediate a first capacitor plate and a second capacitor plate, wherein at least one of the first and second capacitor plates has a surface against the capacitor dielectric layer and wherein said surface comprises both doped rugged polysilicon and doped non-rugged polysilicon.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    Preferred embodiments of the invention are described below with reference to the following accompanying drawings.  
         [0013]    [0013]FIG. 1 is a schematic cross-sectional view of a semiconductor wafer fragment comprising a prior art DRAM array.  
         [0014]    [0014]FIG. 2 is a schematic cross-sectional process view of a semiconductor wafer fragment at preliminary processing step of a processing method of the present invention.  
         [0015]    [0015]FIG. 3 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 2.  
         [0016]    [0016]FIG. 4 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 3.  
         [0017]    [0017]FIG. 5 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 4.  
         [0018]    [0018]FIG. 6 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 5.  
         [0019]    [0019]FIG. 7 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 6.  
         [0020]    [0020]FIG. 8 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 7.  
         [0021]    [0021]FIG. 9 is a top view of the FIG. 8 wafer fragment.  
         [0022]    [0022]FIG. 10 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 8.  
         [0023]    [0023]FIG. 11 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 10.  
         [0024]    [0024]FIG. 12 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 11.  
         [0025]    [0025]FIG. 13 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 12.  
         [0026]    [0026]FIG. 14 is a view of the FIG. 2 wafer fragment at a processing step subsequent to that of FIG. 6 processed according to a second embodiment of the present invention.  
         [0027]    [0027]FIG. 15 is a view of the FIG. 2 wafer fragment at a step subsequent to that of FIG. 14.  
         [0028]    [0028]FIG. 16 is a top view of the FIG. 15 wafer fragment.  
         [0029]    [0029]FIG. 17 is a view of the FIG. 2 wafer fragment at a step subsequent to that of FIG. 15.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    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).  
         [0031]    Methods of forming DRAM arrays of the present invention are described with reference to FIGS.  2 - 17 , with FIGS.  2 - 13  pertaining to a first embodiment of the invention, and FIGS.  14 - 17  pertaining to a second embodiment of the invention. In describing the first embodiment of the present invention, like numerals from the preceding discussion of the prior art are utilized where appropriate, with differences being indicated by the suffix “a” or with different numerals.  
         [0032]    Referring to FIG. 2, a semiconductor wafer fragment  10   a  is illustrated at a preliminary step of a process of the present invention. Wafer fragment  10   a  comprises a semiconductive material  12   a,  field oxide regions  14   a,  and a thin gate oxide layer  16   a.  Over gate oxide layer  16   a  is formed polysilicon layer  18   a,  silicide layer  20   a  and silicon oxide layer  22   a.  Silicide layer  20   a  comprises a refractory metal silicide, such as tungsten silicide, and polysilicon layer  18   a  typically comprises polysilicon doped with a conductivity enhancing dopant. Layers  16   a,    18   a,    20   a  and  22   a  can be formed by conventional methods.  
         [0033]    Referring next to FIG. 3, polysilicon layer  18   a.  suicide layer  20   a  and silicon oxide layer  22   a  are etched to form wordlines  24   a  and  26   a.  Such etching can be accomplished by conventional methods. Between wordlines  24   a  and  26   a  are defined electrical node locations  25   a,    27   a  and  29   a,  with wordlines  26   a  comprising transistor gages which electrically connect node locations  25   a,    27   a,  and  29   a.  Node locations  25   a,    27   a  and  29   a  are diffusion regions formed within semiconductive material  12   a.    
         [0034]    Referring to FIGS. 4 and 5, a nitride layer  28   a  is provided over wordlines  24   a  and  26   a  and subsequently etched to form nitride spacers  30   a  laterally adjacent wordlines  24   a  and  26   a.    
         [0035]    Referring to FIG. 6, an insulative material layer  34   a  is formed over material  12   a  and over wordlines  24   a  and  26   a.  Insulative layer  34   a  may comprise, for example, BPSG, and can be formed by conventional methods. Insulative layer  34   a  comprises an upper surface  35   a.  Openings  38   a,    39   a  and  40   a  are formed extending through insulative layer  34   a  to node locations  25   a,    27   a  and  29   a,  respectively.  
         [0036]    Referring to FIG. 7, an undoped silicon layer  100  is formed over insulative layer  34   a  and within openings  38   a,    39   a  and  40   a.  Undoped silicon layer  100  narrows openings  38   a,    39   a  and  40   a,  but does not fill such openings. Undoped silicon layer  100  preferably has a thickness of from about 50 Angstroms to about 1000 Angstroms, with a thickness of about 300 Angstroms being most preferred. Undoped silicon layer  100  preferably comprises substantially amorphous silicon. Such substantially amorphous layer can be 5-10% crystalline. Undoped silicon layer  100  can be formed by conventional methods, such as, for example, by deposition utilizing either silane or disilane. For purposes of the continuing discussion, and for interpreting the claims that follow, “undoped” silicon is defined as silicon having a dopant concentration of less than 5×10 18  atoms/cm 3 , and “doped” silicon is defined as silicon having a dopant concentration of at least 5×10 18  atoms/cm 3 . “Undoped” silicon preferably comprises less than or equal to 1×10 18  atoms/cm 3 , and “doped” silicon preferably comprises at least 1×10 19  atoms/cm 3 .  
         [0037]    A doped silicon layer  102  is formed over undoped silicon layer  100  and within openings  38   a,    39   a  and  40   a.  In the shown embodiment of the invention, doped layer  102  completely fills openings  38   a,    39   a  and  40   a.  However, in alternative embodiments of the invention, such as the embodiment discussed below with reference to FIGS.  14 - 17 , layer  102  can only partially fill openings  38   a,    39   a  and  40   a.  As will be appreciated by persons of ordinary skill in the art, the thickness of layer  102  will vary depending on whether layer  102  is chosen to completely fill openings  38   a,    39   a  and  40   a,  or to partially fill such openings. Doped silicon layer  102  preferably comprises doped polysilicon, and can be formed by conventional methods.  
         [0038]    After formation of layers  100  and  102 , an upper surface of wafer fragment  10   a  is planarized to remove layers  100  and  102  from over insulative layer  34   a.  Such planarization can be accomplished by, for example, chemical-mechanical polishing (CMP).  
         [0039]    Referring to FIG. 8, after the above-discussed planarization, pedestals  104 ,  106  and  108  remain in openings  38   a,    39   a  and  40   a  (shown in FIG. 7), respectively. Pedestals  104 ,  106  and  108  comprise undoped silicon layer  100  and doped silicon layer  102 , and are over node locations  25   a,    27   a  and  29   a,  respectively. Pedestals  104 ,  106  and  108  also comprise exposed upper surfaces  116 ,  118  and  120 , respectively.  
         [0040]    [0040]FIG. 9 illustrates a top view of the FIG. 8 wafer fragment, and shows that pedestals  104 .  106  and  108  actually comprise a core of doped silicon layer  102  surrounded by undoped silicon layer  100 .  
         [0041]    Referring again to FIG. 8, insulative layer  34   a  is selectively removed relative to the silicon of pedestals  104 ,  106  and  108  to form a new upper surface  37   a  lower than previous upper surface  35   a  (shown in FIG. 7). The preferred BPSG insulative layer  34   a  can be selectively removed relative to pedestals  104 ,  106  and  108  using a conventional oxide etch. The selective removal of insulative layer  34   a  exposes a sidewall surface  110  of pedestal  104 , a sidewall surface  112  of pedestal  106 , and a sidewall surface  114  of pedestal  108 . Sidewall surfaces  110 ,  112  and  114  comprise undoped silicon layer  100 . Additionally, in the shown embodiment a portion of undoped silicon layer  100  is below upper surface  37   a  of BPSG layer  34   a,  and remains unexposed. The depth of removal of insulative layer  34   a  can be controlled by a number of methods. For example, layer  34   a  could be removed via a timed etch. As another example, an etch stop layer could be formed within layer  34   a  at a desired depth of surface  37   a.  An example of a layer  34   a  comprising an etch stop layer is a layer comprising BPSG and having a silicon nitride etch stop layer formed within the BPSG at a level of upper surface  37   a.    
         [0042]    As exposed sidewall surfaces  110 ,  112  and  114  of pedestals  104 ,  106  and  108  comprise undoped silicon layer  100 , and as exposed upper surfaces  116 ,  118  and  120  of the pedestals comprise exposed doped silicon layer  102 , as well as exposed undoped silicon layer  100 , the pedestals comprise exposed doped silicon and exposed undoped silicon at the processing step of FIG. 8.  
         [0043]    Referring to FIG. 10, a rugged polysilicon layer  122  is substantially selectively formed from the exposed undoped silicon of surfaces  110 ,  112   114 ,  116 ,  118 , and  120  (shown in FIG. 8), and not from the exposed doped silicon of surfaces  116 ,  118  and  120 . Rugged polysilicon layer  122  comprises materials selected from the group consisting of HSG and cylindrical grain polysilicon. The substantially selective formation of a preferred HSG polysilicon layer  122  from undoped silicon surfaces but not from doped silicon surfaces can be accomplished by the following process.  
         [0044]    First, wafer fragment  10   a  is loaded into a conventional chemical vapor deposition (CVD) furnace and is subjected to an in situ hydrofluoric acid (HF) clean to remove native oxide. The in situ HF clean preferably comprises a flow rate of 85 standard cubic centimeters per minute (sccm) of HF gas and 8500 sccm of H 2 O gas, at a pressure of 15 Torr, for a time of about 20 seconds. Wafer fragment  10   a  is then exposed to silane to form amorphous silicon seeds on the undoped silicon. Wafer fragment  10   a  is then annealed for approximately 20 minutes at about 560° C. The seeding and anneal steps convert undoped amorphous silicon into rugged polysilicon (such as hemispherical grain polysilicon), while leaving exposed doped silicon layers not converted to rugged polysilicon. It is noted that the above-described process for forming HSG polysilicon does not require disilane, and hence is different than the “pure” selective hemispherical grain deposition utilized in high vacuum tools with disilane.  
         [0045]    After the formation of rugged polysilicon layer  122 , a short polysilicon etch is performed to remove any monolayers of silicon deposited on insulative layer  34   a  during the above-described seeding step. Such polysilicon etch can be accomplished with conventional conditions, and may comprise either a wet etch or a dry etch.  
         [0046]    The above-described process for forming rugged polysilicon layer  122  advantageously avoids formation of polysilicon on a back side (not shown) of wafer fragment  10   a.  The method can also avoid double bit failures by removing monolayers of silicon after formation of HSG.  
         [0047]    Subsequent thermal processing of pedestals  104 ,  106  and  108  can out-diffuse dopant from doped polysilicon layer  102  into undoped silicon layer  100  (shown in FIG. 8), to convert unexposed portions of undoped silicon layer  100  into a doped polysilicon layer  119 . Subsequent thermal processing can also out-diffuse dopant from doped polysilicon layer  102  into rugged polysilicon layer  122 . Thermal processing to out-diffuse dopant from doped polysilicon layer  102  into adjacent undoped layers will typically comprise temperatures of 800° C. or greater.  
         [0048]    Referring to FIG. 11, a dielectric layer  124  is provided over insulative layer  34   a  and over pedestals  104 ,  106  and  108 . Dielectric layer  124  will typically comprise silicon nitride and or silicon oxide, although other suitable materials are known to persons of skill in the art. A capacitor cell plate layer  126  is provided over dielectric layer  124 . Capacitor cell plate layer  126  will typically comprise doped polysilicon, but other suitable materials are known to persons of skill in the art.  
         [0049]    Referring to FIG. 12, a patterned masking layer  128  is formed over pedestals  104  and  108 , leaving pedestal  106  exposed. Subsequently, wafer fragment  10   a  is subjected to etching conditions which remove cell plate layer  126  and dielectric layer  124  from proximate pedestal  106 . After such etching, pedestal  106  is electrically isolated from pedestals  104  and  108 , with the only remaining electrical connection between pedestal  106  and pedestals  104  and  108  being through wordlines  26   a.  Methods for removing cell plate layer  126  and dielectric layer  124  from proximate pedestal  106  are known to persons of ordinary skill in the art.  
         [0050]    Referring to FIG. 13, masking layer  128  is removed and an insulative layer  130  is formed over pedestals  104 ,  106  and  108 , and over insulative layer  34   a.  Insulative layer  130  may comprise, for example, BPSG, and can be formed by conventional methods. A conductive bitline plug  75   a  is formed extending through insulative layer  130  and in electrical contact with pedestal  106 . Pedestal  106  comprises rugged lateral surfaces  136  and an upper surface  118  which has a predominant portion not comprising rugged-polysilicon. As shown, the non-rugged polysilicon of upper surface advantageously provides a smooth landing region for bitline plug  75   a.    
         [0051]    Pedestal  106  and bitline plug  75   a  together form a bitline contact  77   a.  A bitline  76   a  is formed over bitline plug  75   a  and in an electrical connection with pedestal  106  through bitline plug  75   a.  Bitline  76   a  and bitline plug  75   a  may be formed by conventional methods.  
         [0052]    The above-describe method can be used to avoid chemical-mechanical polishing of a rugged polysilicon layer, thus avoiding a potential source of double bit failures.  
         [0053]    [0053]FIG. 13 illustrates a DRAM array  83   a  of the present invention. DRAM array  83   a  comprises capacitors  62   a  and  64   a.  Capacitors  62   a  and  64   a  comprise capacitor storage nodes  132  and  134 , respectively, which comprise doped polysilicon layer  102 , doped polysilicon layer  119  and rugged-polysilicon layer  122 . As the doped polysilicon layer  119  is formed from the undoped silicon layer  100  (shown in FIG. 8), the undoped silicon layer  100  and doped silicon layer  102  of pedestals  104  and  108  in FIG. 8 together define capacitor storage nodes  132  and  134 . Storage nodes  132  and  134  have rugged-polysilicon-comprising lateral surfaces  138  and  140 , respectively. Storage nodes  132  and  134  further comprise top surfaces  116  and  120 , respectively, which have predominant portions which do not comprise rugged-polysilicon.  
         [0054]    Cell plate layer  126  and dielectric layer  124  are operatively proximate to storage nodes  132  and  134  so that the storage nodes, together with cell plate layer  126  and dielectric layer  124 , form operative capacitors  62   a  and  64   a.  Dielectric layer  124  contacts rugged surfaces  138  and  140 , as well as top surfaces  116  and  120  of storage nodes  132  and  134 .  
         [0055]    Capacitors  62   a  and  64   a  are connected to pedestal  106  through wordlines  26   a.  Capacitor  62   a,  together with bitline contact  77   a  and an interconnecting wordline  26   a,  comprises a first DRAM cell  79   a.  Capacitor  64   a,  together with bitline contact  77   a  and an interconnecting wordline  26   a,  comprises a second DRAM cell  81   a.    
         [0056]    A second embodiment of the invention is described with reference to FIGS.  14 - 17 . In describing the embodiment of FIGS.  14 - 17 , numbering similar to that utilized above for describing the embodiment of FIGS.  2 - 13  is utilized, with differences being indicated by the suffix “b”, or by different numbers.  
         [0057]    Referring to FIG. 14, a wafer fragment  10   b  is shown at a processing step subsequent to that of the above-discussed FIG. 6. Wafer fragment  10   b  comprises wordlines  24   b  and  26   b  having constructions identical to that discussed above with regard to the prior art. Wafer fragment  10   b  further comprises node locations  25   b,    27   b  and  29   b  between wordlines  24   b  and  26   b.  Wafer fragment  10   b  also comprises a semiconductor substrate  12   b  and field oxide regions  14   b  formed over substrate  12   b.    
         [0058]    An insulative material layer  34   b  is formed over wordlines  24   b  and  26   b,  and over semiconductive material  12   b.  Insulative layer  34   b  may comprise a number of materials known to persons of ordinary skill in the art, including BPSG. Openings  38   b,    39   b  and  40   b  extend through insulative layer  34   b  to node locations  25   b,    27   b  and  29   b,  respectively.  
         [0059]    A first undoped silicon layer  146  extends over insulative layer  34   b  and within openings  38   b,    39   b  and  40   b.  Undoped silicon layer  146  preferably comprises amorphous silicon, and preferably has a thickness of from about 50 Angstroms to about 500 Angstroms. Undoped silicon layer  146  can be formed by conventional methods, such as CVD. Undoped silicon layer  146  narrows openings  38   b,    39   b  and  40   b.    
         [0060]    A doped silicon layer  148  is formed over undoped silicon layer  146  and within narrowed openings  38   b,    39   b  and  40   b.  Doped silicon layer  148  preferably comprises polysilicon, and can be formed by conventional methods, such as CVD. Doped silicon layer  148  preferably has a thickness of from about 50 Angstroms to about 500 Angstroms, and preferably does not fill openings  38   b,    39   b  and  40   b.  Rather, doped silicon layer  148  preferably further narrows openings  38   b,    39   b  and  40   b  beyond where openings  38   b,    39   b  and  40   b  were narrowed by undoped silicon layer  146 .  
         [0061]    A second undoped silicon layer  150  is formed over doped silicon layer  148  and within openings  38   b,    39   b  and  40   b.  Undoped silicon layer  150  preferably comprises the same preferable materials of first undoped silicon layer  146 . Accordingly, second undoped silicon layer  150  preferably comprises substantially amorphous silicon. Second undoped silicon layer  150  preferably has a thickness of from 50 to 500 Angstroms, and in the shown preferred embodiment does not fill openings  38   b,    39   b  and  40   b.    
         [0062]    After formation of layers  146 ,  148  and  150 , wafer fragment  10   b  is planarized to remove layers  146 ,  148  and  150  from over insulative layer  34   b.  Such planarizing may be accomplished by, for example, chemical-mechanical polishing. After the planarization of wafer fragment  10   b,  pedestals  104   b,    106   b  and  108   b  (shown in FIG. 15) having upper surfaces  116   b,    118   b  and  120   b  (shown in FIG. 15), respectively, remain within openings  38   b,    39   b  and  40   b.    
         [0063]    Referring to FIG. 15, the material of insulative layer  34   b  is selectively removed relative to the silicon of pedestals  104   b,    106   b  and  108   b  to form an upper surface  37   b  of insulative layer  34   b  which is below upper surfaces  116   b,    118   b  and  120   b  of pedestals  104   b,    106   b  and  108   b.  The removal of insulative layer  34   b  exposes sidewalls  110   b,    112   b  and  114   b  of pedestals  104   b,    106   b  and  108   b,  respectively. The exposed sidewalls  110   b,    112   b  and  114   b  comprise first undoped silicon layer  146 . Additionally, in the shown embodiment a portion of undoped silicon layer  146  is below upper surface  37   b  of BPSG layer  34   b,  and remains unexposed. In the shown preferred embodiment, pedestals  104   b,    106   b  and  108   b  comprise hollow interiors corresponding to openings  38   b,    39   b  and  40   b  (shown in FIG. 14). The depth of removal of insulative layer  34   b  can be controlled by methods such as those discussed above with reference to FIG. 8 for controlling the depth of removal of insulative layer  34   a.    
         [0064]    Referring to FIG. 16, which is a top view of the FIG. 15 wafer fragment, second undoped silicon layer  150  lines the hollow interiors corresponding to openings  38   b,    39   b  and  40   b.    
         [0065]    Referring to FIG. 17, wafer fragment  10   b  is subjected to processing identical to that discussed above regarding FIG. 10 to convert exposed undoped silicon surfaces to rugged-polysilicon surfaces, while not roughening exposed doped silicon surfaces. Such treatment forms a rugged-polysilicon layer  122   b  from exposed portions of first undoped silicon layer  146  (shown in FIG. 15) and forms a rugged-polysilicon layer  160  from second undoped silicon layer  150  within the interiors of pedestals  104   b,    106   b  and  108   b.  Such processing also out-diffuses dopant from doped silicon layer  148  into adjacent undoped layers and thus converts unexposed portions of undoped layer  146  (shown in FIG. 15) into doped regions  119   b.    
         [0066]    Subsequent processing, similar to the processing discussed above with reference to FIGS.  11 - 13 , may be conducted to form a DRAM array from pedestals  104   b,    106   b  and  108   b.  In such DRAM array, pedestals  104   b  and  108   b  would be storage nodes for first and second capacitors, respectively, and pedestal  106   b  would form a conductive contact to a bitline. Such subsequent processing is not illustrated as the description above regarding FIGS.  11 - 13  is sufficient to enable a person of skill in the art to form a DRAM array from the structure of FIG. 17. It is noted, however, that the storage nodes formed from pedestals  104   b  and  108   b  would differ from the storage nodes of FIG. 13 in that the storage nodes formed from pedestals  104   b  and  108   b  would have the shape of upwardly open containers, with the interiors of such containers being lined by rugged-polysilicon layer  160 .  
         [0067]    The above-described DRAMs and capacitors of the present invention can be implemented into monolithic integrated circuitry, including microprocessors.  
         [0068]    To aid in interpretation of the claims that follow, the term “semiconductive 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 semiconductive substrates described above.  
         [0069]    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.