摘要:
A method of making N-channel and P-channel IGFETs is disclosed. The method includes providing a semiconductor substrate with N-type and P-type active regions, forming a gate material over the N-type and P-type active regions, forming a first masking layer over the gate material, wherein the first masking layer includes an opening above a first portion of the gate material over the P-type active region, and the first masking layer covers a second portion of the gate material over the N-type active region, introducing an N-type dopant into the first portion of the gate material without introducing the N-type dopant into the second portion of the gate material, applying a thermal cycle to drive-in and activate the N-type dopant in the first portion of the gate material before introducing any doping into the second portion of the gate material, before introducing any source/drain doping into the N-type active region, and before introducing any source/drain doping into the P-type active region, forming a second masking layer over the gate material, wherein the second masking layer covers portions of the first and second portions of the gate material, applying an etch to form first and second gates from unetched portions of the first and second portions of the gate material, respectively, and forming an N-type source and drain in the P-type active region and forming a P-type source and drain in the N-type active region. Advantageously, a dopant in the gate for the N-channel IGFET can be driven-in and activated at a relatively high temperature without subjecting any source/drain doping to this temperature.
摘要:
A composite gate electrode layer incorporates a diffusion-retarding barrier layer disposed at the bottom of the gate electrode layer to reduce the amount of dopant which diffuses into the gate dielectric layer from the gate electrode layer. A lower nitrogen-containing gate electrode layer provides a diffusion-retarding barrier layer against dopant diffusion into the gate dielectric layer disposed therebelow, and an upper gate electrode layer is formed upon the lower layer and is doped to form a highly conductive layer. Together the first and second gate electrode layers form a composite gate electrode layer which incorporates a diffusion-retarding barrier layer adjacent to the underlying gate dielectric layer. The barrier layer may be formed by annealing a first polysilicon layer in a nitrogen-containing ambient, such as N.sub.2, NO, N.sub.2 O, and NH.sub.3, by implanting a nitrogen-containing material, such as elemental or molecular nitrogen, into a first polysilicon layer, and by in-situ depositing a nitrogen-doped first polysilicon layer. Diffusion of dopants into the gate dielectric layer may be retarded, as most dopant atoms are prevented from diffusing from the composite gate electrode layer at all. In addition, the nitrogen concentration within the gate dielectric layer, particularly at or near the substrate interface, may be maintained at lower concentrations than otherwise necessary to prevent dopant diffusion into the underlying substrate. The present invention is particularly well suited to thin gate dielectrics, such as a those having a thickness less than approximately 60 .ANG. when using a p-type dopant, such as boron.
摘要:
A nitrogen implanted region formed substantially below and substantially adjacent to a source/drain region of an IGFET forms a liner to retard the diffusion of the source/drain dopant atoms during a subsequent heat treatment operation such as an annealing step. The nitrogen liner may be formed by implantation of nitrogen to a given depth before the implantation of source/drain dopant to a lesser depth. Nitrogen may also be introduced into regions of the IGFET channel region beneath the gate electrode for retarding subsequent lateral diffusion of the source/drain dopant. Such nitrogen introduction may be accomplished using one or more angled implantation steps, or may be accomplished by annealing an implanted nitrogen layer formed using a perpendicular implant aligned to the gate electrode. The liner may be formed on the drain side of the IGFET or on both source and drain side, and may be formed under a lightly-doped region or under a heavily-doped region of the drain and/or source. Such a liner is particularly advantageous for boron-doped source/drain regions, and may be combined with N-channel IGFETs formed without such liners.
摘要:
A photolithographic system including a light filter that varies light intensity according to measured dimensional data that characterizes a lens error is disclosed. The light filter compensates for the lens error by reducing the light intensity of the image pattern as the lens error increases. In this manner, when the lens error causes focusing variations that result in enlarged portions of the image pattern, the light filter reduces the light intensity transmitted to the enlarged portions of the image pattern. This, in turn, reduces the rate in which regions of the photoresist layer beneath the enlarged portions of the image pattern are rendered soluble to a subsequent developer. As a result, after the photoresist layer is developed, linewidth variations that otherwise result from the lens error are reduced due to the light filter. Preferably, the light filter includes a light-absorbing film such as a semi-transparent layer such as calcium fluoride on a light-transmitting base such as a quartz plate, and the thickness of the light-absorbing film varies in accordance with the measured dimensional data to provide the desired variations in light intensity. The invention is particularly well-suited for patterning a photoresist layer that defines polysilicon gates of an integrated circuit device.
摘要:
A method of making NMOS and PMOS devices with reduced masking steps is disclosed. The method includes providing a semiconductor substrate with a first active region of first conductivity type and a second active region of second conductivity type, forming a gate material over the first and second active regions, forming a first masking layer over the gate material, etching the gate material using the first masking layer as an etch mask to form a first gate over the first active region and a second gate over the second active region, implanting a dopant of second conductivity type into the first and second active regions using the first masking layer as an implant mask, forming a second masking layer that covers the first active region and includes an opening above the second active region, and implanting a dopant of first conductivity type into the second active region using the first and second masking layers as an implant mask. Advantageously, the dopant of first conductivity type counterdopes the dopant of second conductivity type in the second active region, thereby providing source and drain regions of second conductivity type in the first active region and source and drain regions of first conductivity type in the second active region with a single masking step and without subjecting either gate to dopants of first and second conductivity type.
摘要:
An IGFET with a gate electrode and metal spacers in a trench is disclosed. The IGFET includes a trench with opposing sidewalls and a bottom surface in a semiconductor substrate, metal spacers adjacent to the sidewalls and the bottom surface, a gate insulator on the bottom surface between the metal spacers, protective insulators on the metal spacers, a gate electrode on the gate insulator and protective insulators, and a source and drain adjacent to the bottom surface. A method of forming the IGFET includes implanting a doped layer into the substrate, etching completely through the doped layer and partially through the substrate to form the trench and split the doped layer into source and drain regions, applying a high-temperature anneal to diffuse the source and drain regions beneath the bottom surface, depositing a blanket layer of conductive metal over the substrate and applying an anisotropic etch to form the metal spacers, depositing a continuous insulative layer over the substrate to provide the gate insulator and the protective insulators, depositing a blanket layer of gate electrode material over the substrate, and polishing the gate electrode material so that the gate electrode is substantially aligned with a top surface of the substrate. Advantageously, the channel length is significantly smaller than the trench length, and the metal spacers reduce the parasitic resistance of lightly doped source and drain regions.
摘要:
A method of making an IGFET with a multilevel gate that includes upper and lower gate levels is disclosed. The method includes providing a semiconductor substrate with an active region, forming a gate insulator on the active region, forming a first gate material with a thickness of at most 1000 angstroms on the gate inslator and over the active region, forming a first photoresist layer over the first gate material, irradiating the first photoresist layer with a first image pattern and removing irradiated portions of the first photoresist layer to provide openings above the active region, etching the first gate material through the openings in the first photoresist layer using the first photoresist layer as an etch mask for a portion of the first gate material that forms a lower gate level, removing the first photoresist layer, forming an upper gate level on the lower gate level after removing the first photoresist layer, and forming a source and drain in the active region. Advantageously, the first photoresist layer can be ultra-thin to enhance the accuracy in which the image pattern is replicated, thereby reducing variations in channel length and device performance.
摘要:
An IGFET with metal spacers is disclosed. The IGFET includes a gate electrode on a gate insulator on a semiconductor substrate. Sidewall insulators are adjacent to opposing vertical edges of the gate electrode, and metal spacers are formed on the substrate and adjacent to the sidewall insulators. The metal spacers are electrically isolated from the gate electrode but contact portions of the drain and the source. Preferably, the metal spacers are adjacent to edges of the gate insulator beneath the sidewall insulators. The metal spacers are formed by depositing a metal layer over the substrate then applying an anisotropic etch. In one embodiment, the metal spacers contact lightly and heavily doped drain and source regions, thereby increasing the conductivity between the heavily doped drain and source regions and the channel underlying the gate electrode. The metal spacers can also provide low resistance drain and source contacts.
摘要:
A method of forming a shallow junction in an IGFET is disclosed. The method includes forming a gate insulator on a semiconductor substrate of first conductivity type, forming a gate electrode on the gate insulator, forming a sidewall insulator on an edge of the gate electrode, forming a silicon-based spacer over the substrate such that the sidewall insulator separates and electrically isolates the spacer and the gate electrode, and diffusing a dopant of second conductivity type from the spacer into the substrate. The diffused dopant forms a shallow region of second conductivity type in the substrate, and a shallow junction is substantially laterally aligned with the edge of the gate electrode.
摘要:
An IGFET with metal spacers is disclosed. The IGFET includes a gate electrode on a gate insulator on a semiconductor substrate. Sidewall insulators are adjacent to opposing vertical edges of the gate electrode, and metal spacers are formed on the substrate and adjacent to the sidewall insulators. The metal spacers are electrically isolated from the gate electrode but contact portions of the drain and the source. Preferably, the metal spacers are adjacent to edges of the gate insulator beneath the sidewall insulators. The metal spacers are formed by depositing a metal layer over the substrate then applying an anisotropic etch. In one embodiment, the metal spacers contact lightly and heavily doped drain and source regions, thereby increasing the conductivity between the heavily doped drain and source regions and the channel underlying the gate electrode. The metal spacers can also provide low resistance drain and source contacts.