摘要:
A field-effect transistor having cells (18) each having a source region (22), source body region (26), drift region (20), drain body region (28) and drain region (24) arranged longitudinally, laterally alternating with structures to achieve a reduced surface field. In embodiments, the structures can include longitudinally spaced insulated gate trenches (35) defining a gate region (31) adjacent the source or drain region (22, 24) and a longitudinally extending potential plate region (33) adjacent the drift region (20). Alternatively, a separate potential plate region (33) or a longitudinally extending semi-insulating field plate (50) may be provided adjacent the drift region (20). The transistor is suitable for bi-directional switching.
摘要:
A method of manufacturing a trench-gate semiconductor device (1), the method including forming trenches (20) in a semiconductor body (10) in an active transistor cell area of the device, the trenches (20) each having a trench bottom and trench sidewalls, and providing silicon oxide gate insulation (21) in the trenches such that the gate insulation (33) at the trench bottoms is thicker than the gate insulation (21) at the trench sidewalls in order to reduce the gate-drain capacitance of the device. The method includes, after forming the trenches (20), the steps of: (a) forming a silicon oxide layer (21) at the trench bottoms and trench sidewalls; (b) depositing a layer of doped polysilicon (31) adjacent the trench bottoms and trench side walls; (c) forming silicon nitride spacers (32) on the doped polysilicon (21) adjacent the trench sidewalls leaving the doped polysilicon exposed at the trench bottoms; (d) thermally oxidising the exposed doped polysilicon to grow said thicker gate insulation (33) at the trench bottoms; (e) removing the silicon nitride spacers (32); and (f) depositing gate conductive material (34) within the trenches to form a gate electrode for the device. The final thickness of the thicker gate insulation (33) at the trench bottoms is well controlled by the thickness of the layer of doped polysilicon (31) deposited in step (b). Also the doped (preferably greater than 5 e 19 cm-3) polysilicon oxidises fast at low temperatures (preferably 700-800° C.), reducing the risk of diffusing (e.g. p body) implantations present in the device at that stage.
摘要:
A method of making a trench MOSFET includes forming a nitride liner 50 on the sidewalls 28 of a trench and a plug of doped polysilicon 26 at the bottom of a trench. The plug of polysilicon 26 may then be oxidised to form a thick oxide plug 30 at the bottom of the trench whilst the nitride liner 50 protects the sidewalls 28 from oxidation. This forms a thick oxide plug at the bottom of the trench thereby reducing capacitance between gate and drain.
摘要:
In semiconductor devices which include an insulated trench electrode (11) in a trench (20), for example, trench-gate field effect power transistors and trenched Schottky diodes, a cavity (23) is provided between the bottom (25) of the trench electrode (11) and the bottom (27) of the trench (20) to reduce the dielectric coupling between the trench electrode (11) and the body portion at the bottom (27) of the trench in a compact manner. In power transistors, the reduction in dielectric coupling reduces switching power losses, and in Schottky diodes, it enables the trench width to be reduced.
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:
A field-effect semiconductor device, for example a MOSFET of the trench-gate type, comprises side-by-side device cells at a surface (10a) of a semiconductor body (10), and at least one drain connection (41) that extends in a drain trench (40) from the body surface (10a) to an underlying drain region (14a). A channel-accommodating region (15) of the device extends laterally to the drain trench (40). The drain trench (40) extends through the thickness of the channel-accommodating region (15) to the underlying drain region (14a), and the drain connection (41) is separated from the channel-accommodating region (15) by an intermediate insulating layer (24) on side-walls of the drain trench (40). A compact cellular layout can be achieved, with a significant proportion of the total cellular layout area accommodating conduction channels (12). The configuration in a discrete device avoids a need to use a substrate conduction path and so advantageously reduces the ON resistance of the device.
摘要:
Inner trenches (11) of a trenched Schottky rectifier (1a; 1b; 1c; 1d) bound a plurality of rectifier areas (43a) where the Schottky electrode (3) forms a Schottky barrier 43 with a drift region (4). A perimeter trench (18) extends around the outer perimeter of the plurality of rectifier areas (43a). These trenches (11, 18) accommodate respective inner field-electrodes (31) and a perimeter field-electrode (38) that are connected to the Schottky electrode (3). The inner field-electrodes (11) are capacitively coupled to the drift region (4) via dielectric material (21) that lines the inner trenches (11). The perimeter field-electrode (38) is capacitively coupled across dielectric material (28) on the inside wall (18a) of the perimeter trench 18, without acting on any outside wall (18b). Furthermore, the inner and perimeter trenches (11, 18) are closely spaced and the intermediate areas (4a, 4b) of the drift region (4) are lowly doped. The spacing is so close and the doping is so low that the depletion layer (40) formed in the drift region (4), from the Schottky barrier (43) and from the field-relief regions (31,21; 38,28) in the blocking state of the rectifier, may deplete the whole of the intermediate areas (4a, 4b) between the trenches (11, 18) at a blocking voltage just below 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 array of rectifier areas (43a).
摘要:
A trench MOSFET with drain (8), drift region (10) body (12) and source (14). In order to improve the figure of merit for use of the MOSFET as control and sync FETs, the trench (20) is partially filled with dielectric (24) adjacent to the drift region (10) and a graded doping profile is used in the drift region (10).
摘要:
A field-effect transistor having cells (18) each having a source region (22), source body region (26), drift region (20), drain body region (28) and drain region (24) arranged longitudinally, laterally alternating with structures to achieve a reduced surface field. In embodiments, the structures can include longitudinally spaced insulated gate trenches (35) defining a gate region (31) adjacent the source or drain region (22, 24) and a longitudinally extending potential plate region (33) adjacent the drift region (20). Alternatively, a separate potential plate region (33) or a longitudinally extending semi-insulating field plate (50) may be provided adjacent the drift region (20). The transistor is suitable for bi-directional switching.
摘要:
Semiconductor devices may be fabricated using nanowires. In an example embodiment, a conductive gate may be used to control conduction along the nanowires, in which case one of the contacts is a drain and the other a source. The nanowires may be grown in a trench or through-hole in a substrate or in particular in an epitaxial layer on substrate. In another example embodiment, the gate may be provided only at one end of the nanowires. The nanowires can be of the same material along their length; alternatively different materials can be used, especially different materials adjacent to the gate and between the gate and the base of the trench.