SGT-MOSFET semiconductor device
Technical Field
The invention relates to the technical field of power semiconductors, in particular to an SGT-MOSFET semiconductor device.
Background
The SGT-MOSFET is a novel power semiconductor device, has the advantages of low conduction loss of the traditional deep-groove MOSFET, and simultaneously has lower switching loss. The SGT-MOSFET is used as a switching device and applied to a motor driving system, an inverter system and a power management system in the fields of new energy electric vehicles, novel photovoltaic power generation, energy-saving household appliances and the like, and is a core power control component.
The SGT-MOSFET is an MOSFET with a deep groove longitudinal structure, an independent field plate between a drain end and a gate end is adopted, a shielding gate is connected with a source electrode potential, and source-drain parasitic capacitance formed between the shielding gate and a drain electrode does not obviously increase the switching time of a device. The SGT-MOSFET power device has smaller gate-drain parasitic capacitance, low switching loss, higher switching speed and better device performance.
The trench structure of a conventional SGT-MOSFET consists of two polysilicon portions: the upper half is the control gate and the lower half is the shield gate, which is located under the control gate, as shown in fig. 1. When the device is conducted, the drain current forms an inversion layer channel on the surface of the body region along the longitudinal side wall of the groove. When the source is forward biased, electrons travel from the source region to the drain region along the inversion layer channel. Electrons pass through the channel from the source region, enter the drift region at the bottom of the trench gate, and then the current spreads out over the entire cell cross-sectional width.
The electric field distribution structure of the traditional structure is single, the on-resistance is large, the voltage resistance of the device is poor, and the driving loss and the switching loss are too large.
Disclosure of Invention
The technical task of the invention is to solve the defects of the prior art and provide an SGT-MOSFET semiconductor device.
The technical scheme of the invention is realized in the following way, the SGT-MOSFET semiconductor device comprises an N-type heavily doped semiconductor substrate (1) and an N-type semiconductor drift region (2) positioned on the upper surface of the N-type heavily doped semiconductor substrate (1);
the upper surface of the N-type semiconductor drift region (2) is provided with a P-type region (3),
the upper surface of the P-type region (3) is provided with an N-type heavily doped semiconductor source region (4),
the N-type heavily doped semiconductor source region (4) is provided with a control gate (5) which penetrates through the P-type region (3) and extends into the N-type semiconductor drift region (2);
the N-type heavily doped semiconductor source region (4) is provided with a shielding grid (6) which penetrates through the P-type region (3) and extends into the N-type semiconductor drift region (2);
at least one control grid (5) is arranged, at least two shielding grids (6) are arranged,
the control grid (5) is arranged between two adjacent shielding grids (6);
the control grid (5) is provided with a control grid insulating medium (7) which is contacted with the N-type semiconductor drift region (2), the P-type region (3) and the N-type heavily doped semiconductor source region (4), and the control grid (5) is provided with a control grid conductive material (9) which is surrounded by the control grid insulating medium (7);
the shielding grid (6) is provided with a shielding grid insulating medium (77) which is in contact with the N-type semiconductor drift region (2), the P-type region (3) and the N-type heavily doped semiconductor source region (4) and a shielding grid conducting material (8) which is surrounded by the shielding grid insulating medium (77);
a source electrode (12) is led out from the upper surface of the N-type heavily doped semiconductor source region (4),
a shielding grid source electrode (13) is led out from the upper surface of the shielding grid conductive material (8);
a gate electrode (14) is led out from the upper surface of the control gate conductive material (9),
the drain electrode (15) is led out from the lower surface of the N-type heavily doped semiconductor substrate (1).
The device can be only provided with three polysilicon parts, wherein the three polysilicon parts are respectively a control gate and two shielding gates, and the control gate is arranged between the two shielding gates which are adjacent to each other at the left and the right.
The control gate (5) penetrates through the P-type region (3) layer from the surface of the N-type heavily doped semiconductor source region (4) layer downwards and extends into the N-type semiconductor drift region (2) layer;
the shielding grid (6) penetrates through the P-type region (3) layer from the surface of the N-type heavily doped semiconductor source region (4) layer downwards and extends into the N-type semiconductor drift region (2) layer.
The depth of the bottom end of the shielding grid (6) extending downwards into the N-type semiconductor drift region (2) is larger than the depth of the bottom end of the control grid (5) extending downwards into the N-type semiconductor drift region (2).
The adjacent control gate (5) and the shielding gate (6) are arranged with the separation distance of the N-type heavily doped semiconductor source region (4), the P-type region (3) and the N-type semiconductor drift region (2).
Design one with floating P-well (10):
the bottom end of the control gate (5) extending into the N-type semiconductor drift region (2) is provided with a floating P well (10) in the N-type semiconductor drift region (2), and the floating P well (10) at the bottom end of the control gate (5) and the N-type semiconductor drift region (2) form a PN junction.
Design scheme two with floating P well (10):
the bottom end of the shielding grid (6) extending into the N-type semiconductor drift region (2) layer is provided with a floating P well (10) in the N-type semiconductor drift region (2), and the floating P well (10) at the bottom end of the shielding grid (6) and the N-type semiconductor drift region (2) form a PN junction.
Design three with floating P well (10):
floating P wells (10) in the N-type semiconductor drift region (2) are arranged at the bottom ends of the control grid (5) and the shielding grid (6) which extend into the N-type semiconductor drift region (2);
a floating P trap (10) at the bottom end of the control grid (5) and the N-type semiconductor drift region (2) form a PN junction;
the floating P trap (10) at the bottom end of the shielding grid (6) and the N-type semiconductor drift region (2) form a PN junction.
Expanding the design scheme:
an N-drift region (11) layer is arranged between the bottom edge of the N-type semiconductor drift region (2) and the N-type heavily doped semiconductor substrate (1).
The optimization design scheme is as follows:
an N-drift region (11) layer is arranged between the bottom edge of the N-type semiconductor drift region (2) and the N-type heavily doped semiconductor substrate (1), and a floating P well (10) at the bottom end of the shielding grid (6) is arranged in the N-drift region (11) layer.
Compared with the prior art, the invention has the following beneficial effects:
the SGT-MOSFET semiconductor device provided by the invention has the advantages that the split gate and floating P well technology is utilized to obviously reduce the on resistance, the withstand voltage of the device is improved, and the performance of the trench gate device is greatly improved.
The floating P well configuration of the N-type semiconductor drift region and the configuration of the N-drift region have an optimized electric field distribution structure, the voltage resistance of the device is improved, and the on-resistance is reduced, so that the driving loss and the switching loss are reduced.
The SGT-MOSFET semiconductor device has the advantages of reasonable design, simple structure, safety, reliability, convenience in use, easiness in maintenance and good popularization and use values.
Drawings
FIG. 1 is a schematic diagram of a conventional SGT-MOSFET in the prior art;
FIG. 2 is a schematic structural diagram of a first embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a second embodiment of the present invention;
fig. 4 is a schematic structural diagram of a third embodiment of the present invention.
The reference numerals in the drawings denote:
1. n-type heavily doped semiconductor substrate, 2N-type semiconductor drift region, 3P-type region, 4N-type heavily doped semiconductor source region,
5. a control gate, 6, a shield gate,
7. a control gate insulating dielectric, 77, a shield gate insulating dielectric,
8. a shield gate conductive material, 9, a control gate conductive material,
10. the P-well is floated and the P-well,
11. an N-drift region is formed in the substrate,
12. source electrode, 13, shield gate source electrode, 14, gate electrode, 15, drain electrode.
Detailed Description
An SGT MOSFET semiconductor device according to the present invention will be described in detail with reference to the accompanying drawings.
The SGT-MOSFET semiconductor device adopts a split gate structure and consists of three polysilicon parts: the device comprises an N-type heavily doped semiconductor substrate 1 and an N-type semiconductor drift region 2 positioned on the upper surface of the N-type heavily doped semiconductor substrate 1; the upper surface of the N-type semiconductor drift region 2 is provided with a P-type region 3; the upper surface of the P-type region 3 is provided with an N-type heavily doped semiconductor source region 4; the middle part of the N-type heavily doped semiconductor source region 4 is provided with a control gate 5 which penetrates through the P-type region 3 and extends into the N-type semiconductor drift region 2; the two sides of the N-type heavily doped semiconductor source region 4 are provided with shielding gates 6 which penetrate through the P-type region 3 and extend into the N-type semiconductor drift region 2; the shielding grid 6 is provided with a shielding grid insulating medium 77 which is contacted with the N-type semiconductor drift region 2, the P-type region 3 and the N-type heavily doped semiconductor source region 4 and a shielding grid conducting material 8 which is surrounded by the shielding grid insulating medium 77; the control gate 5 is provided with a control gate insulating medium 7 which is contacted with the N-type semiconductor drift region 2, the P-type region 3 and the N-type heavily doped semiconductor source region 4 and a control gate conductive material 9 which is surrounded by the control gate insulating medium 7; the bottom of the control gate 5 is provided with a floating P well 10 in an N-type semiconductor drift region 2; a source electrode 12 is led out from the upper surface of the N-type heavily doped semiconductor source region 4, a drain electrode 15 is led out from the lower surface of the N-type heavily doped semiconductor substrate 1, a gate electrode 14 is led out from the upper surface of the control gate conductive material 9, and a shielding gate source electrode 13 is led out from the upper surface of the shielding gate conductive material 8.
The first embodiment is as follows:
as shown in fig. 2, which is a schematic structural diagram of this example, compared with a conventional split gate structure, in the present invention, the floating P-well 10 is arranged at the bottom of the control gate 5 to adjust the electric field distribution at the upper part of the N-type drift region, the floating P-well 10 and the N-type semiconductor drift region form a PN junction and are mutually depleted, and meanwhile, a thick gate oxide layer is present at the bottom of the control gate, so that a large electric field cannot be concentrated, the withstand voltage of the device can be improved, and the on-resistance can be reduced; the shielding grid and the control grid are arranged in different grooves, the conducting channel density is increased, and a deep groove structure is adopted, so that the on-resistance of the device is obviously reduced, the increase of the resistivity of the adjacent N-type drift region caused by the floating P well is inhibited to a certain extent, and the device has smaller on-resistance.
Example two:
as shown in fig. 3, which is a schematic structural diagram of this example, compared with a conventional split gate structure, in the present invention, floating P-wells 10 are arranged at the bottoms of the shielding gates 6 on both sides to adjust the electric field distribution at the lower part of the N-type drift region, and the floating P-wells and the N-type semiconductor drift region form two PN junctions and are mutually depleted, so that the electric field at the bottom of the shielding gate in the N-type semiconductor drift region is weakened, thereby improving the withstand voltage of the device; the shielding grid and the control grid are arranged in different grooves, and the conducting resistance of the device is obviously reduced by increasing the density of the conducting channel and adopting a deep groove structure.
As shown in fig. 3, the difference between this example and embodiment 1 is that the floating P-well is disposed at the bottom of the shielding gates on both sides, so as to optimize the electric field distribution structure at the lower part of the N-type drift region and improve the withstand voltage of the device.
Example three:
expanding the optimized design, as shown in fig. 4, the difference between this example and embodiment 1 is that floating P-wells are respectively disposed at the bottom of a control gate and a shield gate, and two floating P-wells at the bottom of the shield gate are located in an N-drift region 11, so that the electric field distribution structures of an upper N-type drift region and a lower N-drift region are optimized, the withstand voltage of the device is improved, and the on-resistance is reduced.
As shown in fig. 4, which is a schematic structural diagram of this example, compared with a conventional split gate structure, floating P-wells are respectively disposed at the bottom of a control gate 5 and at the bottoms of shielding gates 6 on two sides at the same time to adjust electric field distribution of an N-type drift region at the upper portion and an N-drift region at the lower portion, the floating P-wells at the bottom of the control gate and the N-drift region form PN junctions and are mutually depleted, the floating P-wells at the bottom of the shielding gates and the N-drift region form two PN junctions and are mutually depleted, electric field distribution structures of the drift regions at the bottom of the control gate and the bottom of the shielding gates are optimized, voltage resistance of a device can be improved, and on; the shielding grid and the control grid are arranged in different grooves, and the conducting resistance of the device is obviously reduced by increasing the density of the conducting channel and adopting a deep groove structure.
Example four:
on the basis of the body structure of the above embodiment, the floating P-well is connected to the bottom of the control gate.
Example five:
on the basis of the body structure of the above embodiment, the floating P-well is connected to the bottom of the shield gate.
Embodiments one to three employ a floating P-well unconnected configuration. The fourth and fifth embodiments adopt the configuration that the floating P well is connected with the bottom of the control gate/shielding gate.
In the SGT-MOSFET structure existing in the prior art, a control gate and a shield gate are located in the same trench. The invention adopts the shielding grid and the control grid arranged in different grooves, and is an increased MOSFET structure.
In the prior art, a P-type floating layer is arranged at the bottom of each trench in a configuration structure, the discontinuity is illustrated by the distance between adjacent trenches, and the breakdown voltage is improved and the Rsp is reduced by changing the spike change of the electric field at the bottom of the trench. The invention utilizes the characteristic that the shielding grid and the control grid are positioned in different grooves and the difference of the depth of the grooves to optimize the electric field distribution of different parts in the drift region, thereby raising the withstand voltage of the device and reducing the on-resistance.