Abstract: A “chained implant” technique forms a body region in a trench gated transistor. In one embodiment, a succession of “chained” implants can be performed at the same dose but different energies. In other embodiments different doses and energies can be used, and particularly, more than one dose can be used in a single device. This process produces a uniform body doping concentration and a steeper concentration gradient (at the body-drain junction), with a higher total body charge for a given threshold voltage, thereby reducing the vulnerability of the device to punchthrough breakdown. Additionally, the source-body junction does not, to a first order, affect the threshold voltage of the device, as it does in DMOS devices formed with conventional diffused body processes.

Abstract: The a trench semiconductor device such as a power MOSFET the high electric field at the corner of the trench is diminished by increasing the thickness of the gate oxide layer at the bottom of the trench. Several processes for manufacturing such devices are described. In one group of processes a directional deposition of silicon oxide is performed after the trench has been etched, yielding a thick oxide layer at the bottom of the trench. Any oxide which deposits on the walls of the trench is removed before a thin gate oxide layer is grown on the walls. The trench is then filled with polysilicon in or more stages. In a variation of the process a small amount of photoresist is deposited on the oxide at the bottom of the trench before the walls of the trench are etched. Alternatively, polysilicon can be deposited in the trench and etched back until only a portion remains at the bottom of the trench. The polysilicon is then oxidized and the trench is refilled with polysilicon.

Abstract: The a trench semiconductor device such as a power MOSFET the high electric field at the corner of the trench is diminished by increasing the thickness of the gate oxide layer at the bottom of the trench. Several processes for manufacturing such devices are described. In one group of processes a directional deposition of silicon oxide is performed after the trench has been etched, yielding a thick oxide layer at the bottom of the trench. Any oxide which deposits on the walls of the trench is removed before a thin gate oxide layer is grown on the walls. The trench is then filled with polysilicon in or more stages. In a variation of the process a small amount of photoresist is deposited on the oxide at the bottom of the trench before the walls of the trench are etched. Alternatively, polysilicon can be deposited in the trench and etched back until only a portion remains at the bottom of the trench. The polysilicon is then oxidized and the trench is refilled with polysilicon.

Abstract: The a trench semiconductor device such as a power MOSFET the high electric field at the corner of the trench is diminished by increasing the thickness of the gate oxide layer at the bottom of the trench. Several processes for manufacturing such devices are described. In one group of processes a directional deposition of silicon oxide is performed after the trench has been etched, yielding a thick oxide layer at the bottom of the trench. Any oxide which deposits on the walls of the trench is removed before a thin gate oxide layer is grown on the walls. The trench is then filled with polysilicon in or more stages. In a variation of the process a small amount of photoresist is deposited on the oxide at the bottom of the trench before the walls of the trench are etched. Alternatively, polysilicon can be deposited in the trench and etched back until only a portion remains at the bottom of the trench. The polysilicon is then oxidized and the trench is refilled with polysilicon.

Abstract: A trench-gated MOSFET formed using a super self aligned (SSA) process employs an insulating layer such as a glass layer and a contact mask to define contact openings for electrical connections to source regions of the MOSFET. Use a contact mask and an intervening glass in otherwise self-aligned process reduces the coupling capacitance between source metal and the top of the embedded trench gate. A metal layer deposited to make electrical contact to source regions can be planarized, for example, ground flat using chemical-mechanical polishing to provide a flat surface to avoid formation of conductive traces that extend over the steps that the glass layer forms.

Abstract: A lateral power metal-oxide-semiconductor field effect transistor (MOSFET) having a gate structure in which the insulated gate is coupled to the gate electrode through contacts at a plurality of locations. The source electrode includes first and second segments. The first segment is interposed between the drain electrode and the gate electrode and acts as a field plate.

Abstract: A “chained implant” technique forms a body region in a trench gated transistor. In one embodiment, a succession of “chained” implants can be performed at the same dose but different energies. In other embodiments different doses and energies can be used, and particularly, more than one dose can be used in a single device. This process produces a uniform body doping concentration and a steeper concentration gradient (at the body-drain junction), with a higher total body charge for a given threshold voltage, thereby reducing the vulnerability of the device to punchthrough breakdown. Additionally, the source-body junction does not, to a first order, affect the threshold voltage of the device, as it does in DMOS devices formed with conventional diffused body processes.

Abstract: A trench-gated MOSFET formed using a super self aligned (SSA) process employs an insulating layer such as a glass layer and a contact mask to define contact openings for electrical connections to source regions of the MOSFET. Use a contact mask and an intervening glass in otherwise self-aligned process reduces the coupling capacitance between source metal and the top of the embedded trench gate. A metal layer deposited to make electrical contact to source regions can be planarized, for example, ground flat using chemical-mechanical polishing to provide a flat surface to avoid formation of conductive traces that extend over the steps that the glass layer forms.

Abstract: A super-self-aligned (SSA) structure and manufacturing process uses a single photomasking layer to define critical features and dimensions of a trench-gated vertical power DMOSFET. The single critical mask determines the trench surface dimension, the silicon source-body mesa width between trenches, and the dimensions and location of the silicon mesa contact. The contact is self-aligned to the trench, eliminating the limitation imposed by contact-to-trench mask alignment in conventional trench DMOS devices needed to avoid process-induced gate-to-source shorts. Oxide step height above the silicon surface is also reduced avoiding metal step coverage problems. Poly gate bus step height is also reduced. Other features described include polysilicon diode formation, controlling the location of drain-body diode breakdown, reducing gate-to-drain overlap capacitance, and utilizing low-thermal budget processing techniques.

Abstract: A super-self-aligned (SSA) structure and manufacturing process uses a single photomasking layer to define critical features and dimensions of a trench-gated vertical power DMOSFET. The single critical mask determines the trench surface dimension, the silicon source-body mesa width between trenches, and the dimensions and location of the silicon mesa contact. The contact is self-aligned to the trench, eliminating the limitation imposed by contact-to-trench mask alignment in conventional trench DMOS devices needed to avoid process-induced gate-to-source shorts. Oxide step height above the silicon surface is also reduced avoiding metal step coverage problems. Poly gate bus step height is also reduced. Other features described include polysilicon diode formation, controlling the location of drain-body diode breakdown, reducing gate-to-drain overlap capacitance, and utilizing low-thermal budget processing techniques.

Abstract: A super-self-aligned (SSA) structure and manufacturing process uses a single photomasking layer to define critical features and dimensions of a trench-gated vertical power DMOSFET. The single critical mask determines the trench surface dimension, the silicon source-body mesa width between trenches, and the dimensions and location of the silicon mesa contact. The contact is self-aligned to the trench, eliminating the limitation imposed by contact-to-trench mask alignment in conventional trench DMOS devices needed to avoid process-induced gate-to-source shorts. Oxide step height above the silicon surface is also reduced avoiding metal step coverage problems. Poly gate bus step height is also reduced. Other features described include polysilicon diode formation, controlling the location of drain-body diode breakdown, reducing gate-to-drain overlap capacitance, and utilizing low-thermal budget processing techniques.

Abstract: A super-self-aligned (SSA) structure and manufacturing process uses a single photomasking layer to define critical features and dimensions of a trench-gated vertical power DMOSFET. The single critical mask determines the trench surface dimension, the silicon source-body mesa width between trenches, and the dimensions and location of the silicon mesa contact. The contact is self-aligned to the trench, eliminating the limitation imposed by contact-to-trench mask alignment in conventional trench DMOS devices needed to avoid process-induced gate-to-source shorts. Oxide step height above the silicon surface is also reduced avoiding metal step coverage problems. Poly gate bus step height is also reduced. Other features described include polysilicon diode formation, controlling the location of drain-body diode breakdown, reducing gate-to-drain overlap capacitance, and utilizing low-thermal budget processing techniques.

Abstract: A novel super-self-aligned (SSA) structure and manufacturing process uses a single photomasking layer to define critical features and dimensions of a trench-gated vertical power DMOSFET. The single critical mask determines the trench surface dimension, the silicon source-body mesa width between trenches, and the dimensions and location of the silicon mesa contact. The contact is self-aligned to the trench, eliminating the limitation imposed by contact-to-trench mask alignment in conventional trench DMOS devices needed to avoid-process-induced gate-to-source shorts. Oxide step height above the silicon surface is also reduced avoiding metal step coverage problems. Poly gate bus step height is also reduced. Other features described include polysilicon diode formation, controlling the location of drain-body diode breakdown, reducing gate-to-drain overlap capacitance, and utilizing low-thermal budget processing techniques.

Abstract: A novel super-self-aligned (SSA) structure and manufacturing process uses a single photomasking layer to define critical features and dimensions of a trench-gated vertical power DMOSFET. The single critical mask determines the trench surface dimension, the silicon source-body mesa width between trenches, and the dimensions and location of the silicon mesa contact. The contact is self-aligned to the trench, eliminating the limitation imposed by contact-to-trench mask alignment in conventional trench DMOS devices needed to avoid process-induced gate-to-source shorts. Oxide step height above the silicon surface is also reduced avoiding metal step coverage problems. Poly gate bus step height is also reduced. Other features described include polysilicon diode formation, controlling the location of drain-body diode breakdown, reducing gate-to-drain overlap capacitance, and utilizing low-thermal budget processing techniques.

Abstract: A power MOSFET or other semiconductor device contains a layer of silicon combined with germanium to reduce the on-resistance of the device. The proportion of germanium in the layer is typically in the range of 1-40%. To achieve desired characteristics the concentration of germanium in the Si-Ge layer can be uniform, stepped or graded. In many embodiments it is desirable to keep the germanium below the surface of the semiconductor material to prevent germanium atoms from being incorporated into a gate oxide layer. This technique can be used in vertical DMOS and trench-gated MOSFETs, quasi-vertical MOSFETs and lateral MOSFETs, as well as insulated gate bipolar transistors, thyristors, Schottky diodes and conventional bipolar transistors.

Abstract: A vertical DMOSFET includes a buried layer which is of the same conductivity type as the drain and which extends into the heavily doped substrate and approaches or extends to the surface of the epitaxial layer at a central location in the MOSFET cell that is defined by the body regions of the MOSFET. In some embodiments the upper boundary of the buried layer generally conforms to the shape of the body region, forming a dish shaped structure under the body region. A significant portion of the current flowing through the channel is drawn into the buried layer and since the buried layer represents a relatively low-resistance path, the total resistance of the MOSFET is lowered without any significant effect on the breakdown voltage. The conformal buried layer can be formed by implanting dopant into the epitaxial layer at a high energy (0.5 to 3 MeV). Before the implant, a thick oxide layer is formed in a central region of the MOSFET cell.

Abstract: The gate of a MOSFET is located in a lattice of trenches which define a plurality of cells. Most of the cells contain a MOSFET, but a selected number of the cells at predetermined locations in the lattice contain either a PN diode or a Schottky diode. The PN and Schottky diodes are connected in parallel with the channels in the MOSFET cells, with their anodes tied to the anode of the parasitic diodes in the MOSFET cells and their cathodes tied to the cathode of the parasitic diodes. When the MOSFET is biased in the normal direction (with the parasitic diode reverse-biased), the PN diodes provide a predictable breakdown voltage for the device and ensure that avalanche breakdown occurs at a location away from the trench gate where the hot carriers generated by the breakdown cannot damage the oxide layer which lines the walls of the trench. When the device is biased in the opposite direction, the Schottky diodes conduct and thereby limit charge storage at the PN junctions in the diode and MOSFET cells.

Abstract: A vertical N-channel trenched-gate power MOSFET includes an integral temperature detection diode. The diode includes an N+ region which serves as the cathode and which is formed within a tub of P-type material, which serves as the anode. The N+ region is separated from the trench. The anode of the temperature detection diode may be shorted to the source or may be separately biased. The temperature of the MOSFET is monitored by supplying a current through the diode in the forward direction and measuring the voltage across the forward-biased diode. In an alternative embodiment, a pair of N+ regions are formed within the P-tub, constituting a diode pair, and the temperature is detected by monitoring the difference in the voltages across the diodes. An overtemperature detection unit compares the voltage across the diode or diodes with a reference voltage and provides an output which can be used to turn the MOSFET off when the temperature reaches a predetermined level.

Abstract: A trenched-gate power MOSFET includes a body region that is formed within a mesa between adjacent gate trenches. The doping concentration of the body region is established such that the body region does not fully deplete at normal drain voltages. The MOSFET also includes a gate which is doped with material of a conductivity type opposite to that of the body. The width of the mesa and the doping concentration of the body region and gate are established such that the body region is fully depleted by the combined effects of the source-body and drain body junctions and the gate. As a result, the conventional source-body short can be eliminated, providing a greater cell packing density and lower on-resistance while maintaining acceptable levels of leakage current when the MOSFET is in the off-state.