摘要:
Semiconductor device with a semiconductor cathode having an emissive part (pn junction) separated from a contact part which has locations at which a controlled breakdown occurs on a contact part metallization at excessive voltages, so that, during manufacture and operation, the emissive part in an election tube is protected from damage.
摘要:
A semiconductor cathode (11) in a semiconductor structure, in which the sturdiness of the cathode is increased by covering the emitting surface (4) with a layer of a semiconductor material (7) having a larger bandgap than the semiconductor material of the semiconductor cathode. Various measures for increasing the electron-mission efficiency are indicated.
摘要:
A semiconductor device has a trench (42) adjacent to a cell (18). The cell includes source and drain contact regions (26, 28), and a central body (40) of opposite conductivity type. The device is bidirectional and controls current in either direction with a relatively low on-resistance. Preferred embodiments include potential plates (60) that act together with source and drain drift regions (30, 32) to create a RESURF effect.
摘要:
Consistent with an example embodiment, a reduced surface field effect type (RESURF) semiconductor device is manufactured having a drift region over a drain region. Trenches are formed through openings in mask. A trench insulating layer is deposited on the sidewalls and base of the trenches followed by an overetching step to remove the trench insulating layer from the base of the trenches as well as the top of the sidewalls of the trenches adjacent to the first major surface leaving exposed silicon at the top of the sidewalls of the trench and the base of the trenches. Silicon is selectively grown plugging the trenches with silicon plug (18) leaving void.
摘要:
A vertical power transistor trench-gate semiconductor device has an active area (100) accommodating transistor cells and an inactive area (200) accommodating a gate electrode (25) (FIG. 6). While an n-type layer (14) suitable for drain regions still extends to the semiconductor body surface (10a), gate material (11) is deposited in silicon dioxide insulated (17) trenches (20) and planarised to the top of the trenches (20) in the active (100) and inactive (200) areas. Implantation steps then provide p-type channel-accommodating body regions (15A) in the active area (100) and p-type regions (15B) in the inactive area (200), and then source regions (13) in the active area (100). Further gate material (111) is then provided extending from the gate material (11) in the inactive area (200) and onto a top surface insulating layer (17B) for contact with the gate electrode (25). The channel profiles of the device are optimised by providing the p-type regions (15A) after the trench insulation (17), and voltage breakdown at the bottom corners of the trenches (20) is suppressed by providing the p-type regions (15B) in the inactive area (200).
摘要:
A method of making a trench MOSFET includes forming a layer of porous silicon (26) at the bottom of a trench and then oxidizing the layer of porous silicon (26) to form a plug (30) at the bottom of the trench. This forms a thick oxide plug at the bottom of the trench thereby reducing capacitance between gate and drain.
摘要:
A RESURF trench gate MOSFET has a sufficiently small pitch (close spacing of neighbouring trenches) that intermediate areas of the drain drift region are depleted in the blocking condition of the MOSFET. However, premature breakdown can still occur in this known device structure at the perimeter/edge of the active device area and/or adjacent the gate bondpad. To counter premature breakdown, the invention adopts two principles: the gate bondpad is either connected to an underlying stripe trench network surrounded by active cells, or is directly on top of the active cells, and a compatible 2D edge termination scheme is provided around the RESURF active device area. These principles can be implemented in various cellular layouts e.g. a concentric annular device geometry, which may be circular or rectangular or ellipsoidal, in the active area and in the edge termination, or a device array of such concentric hexagonal or circular stripe cells, or a device array of square active cells with stripe edge cells, or a device array of hexagonal active cells with an edge termination of hexagonal edge cells.
摘要:
In a cellular power MOSFET or other semiconductor device, a wide connection across the perimeter of an active device area (120) is replaced with a plurality of narrower conducting fingers (111). The fingers (11) are used as follows in providing a doped edge region (15a) that is required below the connection (110). Dopant (150,151) is implanted at spaces (112) between and beside the fingers (111) and is diffused to form a single continuous region (15a) extending beneath the fingers (111) and at the spaces (112) therebetween. This doped edge region (15a) may be, for example, a deep guard ring in an edge termination of a power MOSFET, or an extension of its channel-accommodating region (15). A trench-gate network (11) of the MOSFET can be connected by the conducting fingers to a gate bond pad and/or field plate (114).
摘要:
The manufacture of a trench-gate semiconductor device, for example a power transistor or a memory device includes the steps of forming at a surface (10a) of a semiconductor body (10) a first mask (51) having a first window (51a), providing a thin layer of a second material (52) in the first window (51a), forming an intermediate mask (53A, 53B) of a third material having curved sidewalls and using the intermediate mask (53A, 53B) to form two L-shaped parts (52A, 52D and 52B, 52E) of the second material with a second window (52a) which is used to etch a trench-gate trench (20). The rectangular base portion (52D, 52E) of each L-shaped part ensures that the trench (20) is maintained narrow during etching. Narrow trenches are advantageous for low specific on-resistance and low RC delay in low voltage cellular trench-gate power transistors. Narrow deep trenches are also advantageous for cell density in DRAM devices where a memory cell has a switching transistor cell surrounded by a trench-gate and a storage capacitor in a lower part of the same trench.
摘要:
A cellular trench-gate field-effect transistor comprises a field plate (38) on dielectric material (28) in a perimeter trench (18). The dielectric material (28) forms a thicker dielectric layer than the gate dielectric layer (21) in the array trenches (11). The field plate (38) is connected to the source (3) or trench-gate (31) of the transistor and acts inwardly towards the cellular array rather than outwardly towards the body perimeter (15) because of its presence on the inside wall 18a of the trench (18) without acting on any outside wall (18b). The array and perimeter trenches (11,18) are sufficiently closely spaced, and the intermediate areas (4a, 4b) of the drain drift region (4) are sufficiently lowly doped, that the depletion layer (40) formed in the drain drift region (4) in the blocking state of the transistor depletes the whole of these intermediate areas between neighbouring trenches at a voltage less than the breakdown voltage. This arrangement reduces the risk of premature breakdown that can occur at high field points in the depletion layer (40), especially at the perimeter of the cellular array.