摘要:
A process is provided for fabricating a transistor in which ion implantation of dopant into source/drain junctions is performed prior to defining the sidewall surfaces of a gate conductor. As such, the sidewall surfaces of the gate conductor are not subjected to damaging bombardment by ions. In one embodiment, a masking layer is patterned above a polysilicon layer dielectrically spaced above a semiconductor substrate. A S/D implant self-aligned to the sidewall surfaces of the masking layer is performed. Portions of the masking layer are removed to reduce the width of the masking layer and to form more closely spaced sidewalls. An LDD implant self-aligned to the new sidewalls of the masking layer is performed. Thereafter, the polysilicon layer is etched to define a gate conductor above and between LDD areas disposed within the substrate. In another embodiment, a sacrificial layer is patterned above a polysilicon layer dielectrically spaced above a semiconductor substrate. A S/D implant self-aligned to the sidewall surfaces of the sacrificial layer and an LDD implant self-aligned to exposed lateral edges of sidewall spacers arranged upon the sidewall surfaces of the sacrificial layer are performed. The polysilicon layer is then etched to define a gate conductor above and between LDD areas arranged within the substrate.
摘要:
A method is provided for forming a transistor in which the gate is coupled to a second substrate dielectrically spaced above a first substrate. According to an embodiment, a polysilicon layer is formed across an interposing dielectric layer which is disposed across a single crystalline silicon substrate. The polysilicon layer is doped, making it the second semiconductor substrate. Trench isolation structures may be formed within the second substrate between ensuing active areas. A gate oxide is formed across the second substrate, and an opening is etched through the gate oxide down to the second substrate. A conductive material is formed within the opening, and polysilicon is deposited across the gate oxide. The polysilicon may be etched to form a gate conductor above the gate oxide. LDD implant areas are formed within the second substrate between the gate conductor and adjacent isolation structures. Dielectric spacers are formed upon the opposed sidewall surfaces of the gate conductor, and S/D regions are formed within the second substrate. The S/D implant is self-aligned to the exposed lateral edges of the dielectric spacers. The resulting transistor may be switched on quickly and has reduced current leakage in the off state. Transistors formed within and upon the first substrate are isolated from noise which may be induced in the second substrate.
摘要:
A process is provided for forming a transistor gate conductor having an etch stop arranged at a depth below its upper surface such that the lateral width of the gate conductor above the etch stop may be exclusively narrowed to provide for reduction of transistor channel length. A masking layer, i.e., photoresist, patterned above the gate conductor is isotropically etched so as to minimize its lateral width prior to etching the gate conductor. Portions of the gate conductor not protected by the photoresist may be etched from above the etch stop to define a new pair of opposed sidewall surfaces for the upper portion of the gate conductor. The lateral width of the upper portion of the gate conductor thus may be reduced to a smaller dimension than that of conventional gate conductors. The gate conductor is subjected to an anisotropic etch in which portions of the gate conductor not protected by the narrowed photoresist are etched down to the etch stop. The presence of the etch stop ensures that substantial portions of the etch stop and underlying portions of the gate conductor are not removed before etching is completely terminated. As a result, a lower portion of the multi-layered gate conductor is wider than an upper portion of the gate conductor.
摘要:
A process is provided for forming a transistor gate conductor having an etch stop arranged at a depth below its upper surface such that the lateral width of the gate conductor above the etch stop may be exclusively narrowed to provide for reduction of transistor channel length. A masking layer, i.e., photoresist, patterned above the gate conductor is isotropically etched so as to minimize its lateral width prior to etching the gate conductor. Portions of the gate conductor not protected by the photoresist may be etched from above the etch stop to define a new pair of opposed sidewall surfaces for the upper portion of the gate conductor. The lateral width of the upper portion of the gate conductor thus may be reduced to a smaller dimension than that of conventional gate conductors. The gate conductor is subjected to an anisotropic etch in which portions of the gate conductor not protected by the narrowed photoresist are etched down to the etch stop. The presence of the etch stop ensures that substantial portions of the etch stop and underlying portions of the gate conductor are not removed before etching is completely terminated. As a result, a lower portion of the multi-layered gate conductor is wider than an upper portion of the gate conductor.
摘要:
An IGFET device isolation structure fabrication scheme includes the formation of electrically insulating isolation structures that extend into the substrate and extend above the surface of the substrate. The isolation structures are formed by providing a first mask to form trenches in the substrate. A layer of silicon dioxide is then deposited, filling the trenches and extending above the surface of the substrate. A second mask layer is formed. The second mask layer shadows the trench regions that were formed in the substrate. The silicon dioxide not shadowed by the second mask layer is removed, leaving isolation structures that extend both into the substrate and which rise above the substrate. A gate structure is formed in the region between two isolation structures, and, in the preferred embodiment, the gate structure extends above the substrate to the same height as the isolation structures. The isolation structures and the gate structure can be used to provide self-aligned doped source/drain regions. Spacers can be added to the isolation structure walls and the gate structure walls to provide heavily-doped self-aligned regions.
摘要:
A method is provided for forming a transistor in which capacitive coupling between the gate conductors and adjacent structures employed by the integrated circuit is reduced. According to an embodiment, a gate conductor is dielectrically spaced above a semiconductor substrate, and a masking structure is arranged upon an upper surface of the gate conductor. A source/drain implant self-aligned to opposed lateral sidewalls of the masking structure is performed to form source/drain implant areas within the substrate. Select portions of the gate conductor are removed such that opposed ends of the masking structure extend beyond opposed sidewall surfaces of the gate conductor. A lightly doped drain implant self-aligned to the opposed sidewall surfaces of the narrowed gate conductor is performed to form lightly doped drain implant areas within the substrate. An interlevel dielectric is deposited to a level above the gate conductor across the semiconductor topography such that air gaps are formed laterally adjacent the opposed sidewall surfaces of the gate conductor, and the interlevel dielectric is planarized to a level substantially coplanar with an upper surface of the masking structure. In an alternative embodiment, a refractory metal is deposited across an upper surface of the masking structure and across the source/drain implant areas subsequent to forming said source/drain implant areas. The refractory metal is heated to form a metal silicide overlying the source/drain implant areas and residual refractory metal is removed from above the masking structure. In yet another alternative embodiment, a single high-energy ion implant is used to simultaneously form the source/drain implant area and the lightly doped drain implant area following removal of select portions of the gate conductors.
摘要:
A method is provided for forming a transistor in which capacitive coupling between the gate conductors and adjacent structures employed by the integrated circuit is reduced. According to an embodiment, a gate conductor is dielectrically spaced above a semiconductor substrate, and a masking structure is arranged upon an upper surface of the gate conductor. A source/drain implant self-aligned to opposed lateral sidewalls of the masking structure is performed to form source/drain implant areas within the substrate. Select portions of the gate conductor are removed such that opposed ends of the masking structure extend beyond opposed sidewall surfaces of the gate conductor. A lightly doped drain implant self-aligned to the opposed sidewall surfaces of the narrowed gate conductor is performed to form lightly doped drain implant areas within the substrate. An interlevel dielectric is deposited to a level above the gate conductor across the semiconductor topography such that air gaps are formed laterally adjacent the opposed sidewall surfaces of the gate conductor, and the interlevel dielectric is planarized to a level substantially coplanar with an upper surface of the masking structure. In an alternative embodiment, a refractory metal is deposited across an upper surface of the masking structure and across the source/drain implant areas subsequent to forming said source/drain implant areas. The refractory metal is heated to form a metal silicide overlying the source/drain implant areas and residual refractory metal is removed from above the masking structure. In yet another alternative embodiment, a single high-energy ion implant is used to simultaneously form the source/drain implant area and the lightly doped drain implant area following removal of select portions of the gate conductors.
摘要:
An integrated circuit fabrication process is provided for forming, a mutual implant region within a well which is shared by a source region of a transistor residing within the well and a well-tie region coupled to the well, thereby providing a single electrical link to the well and the source region. Contacts may be coupled to the mutual implant region, and a conductor may be connected to the contacts. In the instance that the well is a p-type well in which NMOS transistors are formed, a ground voltage may be applied to the conductor to bias both the source region and the well. On the other hand, if the well is an n-type well in which PMOS transistors are formed, a power voltage, VCC, may be applied to the conductor to bias both the source region and the well. Absent the need to form contacts to both the source region and the well-tie region and conductors to such contacts, less space is required to bias the well and the source region. Also, merging a portion of the well-tie region with a portion of the source region affords increased packing density of an integrated circuit. The higher packing density is achieved without resorting to decreasing the dimensions of the well-tie region, and thus without detrimentally increasing the resistance of the well-tie region.
摘要:
An asymmetrical transistor, and a gate conductor used in forming that transistor, are provided. The gate conductor is formed by removing upper portions of the gate conductor along an elongated axis which the gate conductor extends. The removed portions presents a partially retained region of lesser thickness than the fully retained region immediately adjacent thereto. An implant is then forwarded to the substrate adjacent and partially below the gate conductor. Only the partially retained portions allow a subset of the originally forwarded ions to pass into the substrate to form a lightly doped drain (LDD) between the channel and the drain. The partially retained region occurs only near the drain and not adjacent the source so that the LDD area is self-aligned between the edge of the conductor and a line of demarcation separating the fully retained portion and the partially retained portion. There may be numerous lines of demarcation and corresponding numerous thicknesses across the gate conductor length to provide a graded LDD area if desired.
摘要:
A wafer includes levels elevated above the wafer substrate or base substrate which includes separated substrates suitable for circuit device element formation. In one embodiment, a first level dielectric is formed over circuit devices having elements formed in the wafer substrate. Contacts from the circuit elements may extend to the surface of the first level dielectric. A second dielectric is formed on the first level dielectric and etched to create separated openings with some openings exposing contacts. The openings are filled with substrate material, thus forming elevated substrates and local interconnects where exposed contact top surfaces are present. The substrate material is suitable for circuit device fabrication. Additional levels of elevated substrates and concurrently formed local interconnects may be subsequently fabricated.