Abstract:
A mask ROM stores information by selecting the work function of the gates of each FET in an array of FETs. The polysilicon gates of some of the FETs are doped N-type and the gates of the other FETs are doped P-type to form gates having different work functions, thereby forming FETs having different threshold voltages. The ROM consists of a parallel array of buried N+ bit lines formed in the substrate, a gate oxide layer deposited over the bit lines and a layer of polysilicon deposited on the gate oxide. The polysilicon is blanket doped P-type and then an encoding mask is formed, with openings in the encoding mask exposing regions of the polysilicon to be formed into gates of FETs with low threshold voltages. Either arsenic or phosphorus is doped into the polysilicon through the mask openings. The mask is removed, a layer of conductive material such as tungsten silicide is deposited and the polysilicon and the conductive material are formed into word lines for the ROM. The word lines of the ROM serve as gates for the FETs and the bit lines serve as sources and drains for the FETs.
Abstract:
A mask ROM stores information by selecting the work function of the gates of each FET in an array of FETs at a late stage in the manufacture of the ROM. The polysilicon gates of some of the FETs are doped N-type and the gates of the other FETs are doped P-type to form gates having different work functions, thereby forming FETs having different threshold voltages. The ROM consists of a parallel array of buried N.sup.+ bit lines formed in the substrate, a gate oxide layer deposited over the bit lines and a layer of polysilicon deposited on the gate oxide. The polysilicon is blanket doped N-type, gate electrodes are defined by photolithography, and then self-aligned silicide layers are formed on the gate electrodes. An insulating layer is then formed over the gate electrodes. Programming of the ROM is accomplished by forming a mask on the insulating layer and then implanting ions through openings in the mask, through the insulating layer and the silicide layer, and into the polysilicon layer. The implantation converts individual gate electrodes from N-type to P-type to alter the threshold voltage of the selected transistors. Relatively few additional processing steps are needed after the programming to complete the ROM.
Abstract:
A process for fabricating high-voltage MOSFET devices on a semiconductor substrate is disclosed. The substrate has heavily-doped impurities of a first conductivity type, and constitutes the drain region for the MOSFET. The process of fabrication comprises the steps of subsequently forming on the substrate a first doped layer, a second doped layer, a third doped layer and a shielding layer. All of these doped layers are of the first conductivity type. The second doped layer has an impurity concentration and a thickness smaller and larger than the impurity concentration and thickness respectively of the first doped layer, and larger and smaller than the impurity concentration and thickness respectively of the third doped layer. The impurity concentration of the first doped layer is smaller than the impurity concentration of the substrate. An opening in the shielding layer is formed, and then the source region of the MOSFET is formed in the area exposed by the opening. Afterwards, thermal oxidation is performed to form a field oxide layer over the surface of the source region. Next, an etching process is performed to remove the third doped layer, thereby revealing the surface of said second doped layer to form a source protruding body. Sidewalls of the source protruding body is then covered by an insulating layer. Finally, the field oxide layer and the insulating layer are then utilized as masking for implanting impurities of a second conductivity type into the second doped layer, thereby forming the gate region for the MOSFET.
Abstract:
An improved structure and process of fabricating a metal oxide field effect (MOSFET) which has a high resistance to electro-static discharge. The device has pre-gate heavily doped source and drain regions which overlap the gate electrode and the source and drain regions. This improved MOSFET device with overlapping pre-gate source and drain regions is incorporated into an electro-static discharge (ESD) circuit to form a memory device which has a high resistance to electro-static discharge (ESD).The MOSFET device with pre-gate heavily doped source and drain regions can be formed as follows. Spaced pre-gate source and drain regions of a second conductivity type are formed in the substrate with a background doping of a first conductivity type. A gate oxide and a gate is formed in the regions between the pre-gate source and drain regions. The gate at least partially overhangs the pre-gate source and drain regions. Subsequently, spacers are formed on the vertical sidewalls of the gate. Source and drain regions in the substrate are formed on either side of the spacers. Next, using conventional processes, insulating and metal layers are added to connect the circuit elements and form a memory device. The device is connected to form the input and input/output ESD circuits. The combination of the device of the invention and the ESD protection circuit forms an ESD resistant circuit using a minimum number of manufacturing steps.
Abstract:
A ROM device includes cells with buried bit lines in a semiconductor substrate. A thin insulating layer covers the substrate has closely spaced, parallel, word lines formed thereon arranged orthogonally relative to the bit lines. The word lines are covered with reflowed glass insulating layers about 2500.ANG. thick. The glass insulating layers comprise a sublayer of undoped glass and an overlayer of doped glass, the underlayer about 500.ANG.-1500.ANG. thick and the overlayer about 1000.ANG.-1500.ANG. thick. An etched, patterned metal layer is formed on the glass insulating layer. The overlayer has been substantially removed by etching where the metal layer has been etched. An ion implantation pattern has been implanted into the substrate adjacent to the conductive lines. The device has been passivated. The implanted impurity ions having been activated by annealing the device.
Abstract:
A test system provides defect information rapidly and systematically. The test system includes a plurality of test units arranged in a matrix, a plurality of bit lines and a plurality of word lines. Each test unit has a first terminal and a second terminal. Each second terminal of the test unit is electrically connected to a ground point. The first terminals of the test units are electrically connected to the bit lines. The word lines are coupled to the test units. Defects in the each test unit can be identified by providing voltages to the bit lines and the word lines. Accordingly, defects in various devices of an integrated circuit can be detected rapidly and systematically by applying signals to the test system.
Abstract:
A method of fabricating an anti-fuse includes firstly forming a dielectric layer on a substrate having a first conductive type. Next, a conductive layer is formed on the dielectric layer. A first ion implantation process is then performed, such that the conductive layer has the first conductive type. Thereafter, the conductive layer and the dielectric layer are patterned to form a gate and a gate dielectric layer. The gate and the gate dielectric layer together construct a gate structure. Finally, two source/drain regions having a second conductive type are formed in the substrate at respective sides of the gate. Besides, a method of programming an anti-fuse includes firstly applying a voltage to a gate to break down a gate dielectric layer. The gate and a substrate are then electrically conducted or a P/N forward bias is then formed in a P/N junction after the breakdown of the gate dielectric layer.
Abstract:
A parasitic capacitance-preventing dummy solder bump structure on a substrate has at least one conductive layer formed on the substrate, a dielectric layer employed to cover the conductive layer, an under bump metallurgy layer (UBM layer) formed on the dielectric layer, and a solder bump formed on the UBM layer.
Abstract:
A method for eliminating plasma-induced charging damage during manufacture of an integrated circuit is described. A semiconductor substrate having a first conductivity type is provided. An oxide layer is formed on the semiconductor substrate. An opening is formed in the oxide layer. A polysilicon layer is formed over the oxide layer and in the opening. A diffusion region is formed in the semiconductor substrate, connected to the polysilicon layer through the opening, having a second conductivity type opposite to the first conductivity type, whereby a buried contact is formed. The buried contact is connected, through the substrate, to a ground reference. Further processing in a plasma environment is performed that would normally produce charging damage to the integrated circuit, but whereby the buried contact prevents the charging damage.
Abstract:
A ROM device with an array of cells and a method of manufacturing comprises: forming closely spaced conductors in the surface of a semiconductor substrate having a second type of background impurity. Insulation is formed on the substrate. Closely spaced, parallel, conductors on the insulation are arranged orthogonally to the line regions. Glass insulation is formed over the conductors. Reflowing the glass insulation, forming contacts and forming a metal layer on the glass insulation follow. A resist is formed, exposed forming a resist metal pattern, then etching through the resist to pattern metal and removing the resist. Depositing a resist onto the patterned metal, and exposing the second resist with a custom code pattern, developing the resist into a mask follow. Impurity ions are implanted into the substrate adjacent to the conductors through the openings in a second resist layer. The device is passivated followed by activating the implanted impurity ions by annealing the device at a temperature less than or equal to about 520.degree. C. in a forming gas or N.sub.2 atmosphere.