Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
1998-07-09
2001-07-10
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S135000, C257S136000
Reexamination Certificate
active
06259134
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to semiconductor devices, and is particularly concerned with trench devices, i.e., devices in which at least one electrode is set into the wall or bottom or forms part of a trench or recess below a major, usually planar, surface of a semiconductor device. The use of trenches is particularly advantageous for devices such as IGBT's (insulated gate bipolar transistors) which are capable of operating at high power and voltage levels. The limit on the upper value of voltage at which such devices can be used is determined by the breakdown voltage of a device. For a device which is capable of operating at high power and at high voltage levels, it is important that the device has a low on-state resistance and turns-off (i.e., current flow through the device ceases) promptly and reliably in response to a turn-off signal. It has proved difficult to produce such a device which reliably meets the conflicting requirements of high current, high voltage operation and a safe, reliable current control characteristic.
SUMMARY OF THE INVENTION
According to a first aspect of this invention, a MOS-controllable power semiconductor trench device having a trench gate extending into a first surface of a semiconductor body includes a thyristor structure located between said first surface and a second surface of the body; in which a gate signal is arranged to form an accumulation layer at a wall of the trench, said layer being part of a PIN diode created thereby, and the PIN diode being electrically in parallel with said thyristor, a base portion of which serves to protect the trench against high electric field breakdown when the device is in a non-conductive state; and wherein conduction of the PIN diode is arranged to trigger said thyristor into a conductive state which state persists while, and only while, said accumulation layer is present.
According to a second aspect of this invention, a MOS controllable power semiconductor trench device includes an active region having one or more trenches extending from a first surface of the device, with the trench penetrating first and second semiconductor regions of differing first and second conductivities so that current across the junction between said first and second regions is controllable by a field effect gate electrode at a wall region of the trench, and which electrode is operative to form a charge accumulation layer in said second region; localized regions of said first conductivity type being located within said second region and between said first region and a second surface of the device, said localized regions forming part of a thyristor structure, and the portion of said second region which is between adjacent said localized regions forming, in conjunction with said accumulation layer, part of a PIN diode, such that in operation forward conduction of said PIN diode initiates thyristor conduction in said localized regions for which said accumulation layer acts as the emitter thereof, said localized regions serving to protect said trench against high electric field breakdown while said device is in a non-conductive state.
According to a third aspect of this invention, a MOS-controllable power semiconductor trench device includes an active region having one or more trenches extending from a first surface of the device, with the trench penetrating an n+cathode region, a p region and an n base region so that a current between the n+cathode region and the n base region is controllable by a field effect gate electrode at a wall region of the trench formed in the p region and the n base region, and which electrode is operative to form an electron inversion layer in the p region and an electron accumulation layer in the n base region; the base region extending towards a p+ anode region; localized regions of p conductivity type being located within said n base region between the electron accumulation layer and the p+ anode region, said localized regions forming part of a thyristor structure with the electron accumulation layer as the electron emitter and the p+ anode region as the hole emitter thereof; the portion of the n base region which is between adjacent localized p regions being part of a PIN diode formed in conjunction with the electron accumulation layer and the p+ anode region such that in the on-state the PIN diode is in forward conduction and in parallel with the thyristor, and the PIN diode initiates thyristor conduction in said localized regions which serve to protect the said trench against high electric fields while said device is in its off-state.
Preferably, the n cathode region is shorted by a cathode electrode to the p region, and wherein a portion of the p region adjacent to the cathode electrode is p+ so as to ensure a good ohmic contact and reduced latch up.
An optional n+ layer is desirably present between the p+ anode region and the n base region. This reduces hole injection from the p+ region to speed up turn-off of the device. It also prevents depletion layer punch through to the p+ anode region.
Such a device can be turned-on rapidly, and is able to withstand high off-state potentials. With trench devices, the bottom of the trench and especially corners thereof are prone to voltage breakdown which limits the safe operating range of such devices. The localized regions act as a barrier to the high potential field and thus protect the trench.
REFERENCES:
patent: 4395723 (1983-07-01), Harari
patent: 4618781 (1986-10-01), Silber et al.
patent: 5086330 (1992-02-01), Minato
patent: 5202750 (1993-04-01), Gough
patent: 5324966 (1994-06-01), Muraoka et al.
patent: 5381026 (1995-01-01), Shinohe et al.
patent: 5569941 (1996-10-01), Takahashi
patent: 5637888 (1997-06-01), Iwamuro
patent: 5751024 (1998-05-01), Takahashi
patent: 5895939 (1999-04-01), Ueno
patent: 0 480 356 A2 (1992-04-01), None
Amaratunga Gehan A. J
Udrea Florin
Chaudhuri Olik
Ha Nathan W.
Kirschstein, et al
Mitel Semiconductor Limited
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