US 4,721,986 A · Bidirectional output semiconductor field effect transistor and method for its maufacture

Abstract

A high voltage bidirectional output semiconductor field effect transistor (BOSFET) is disclosed which is turned on from the electrical output of a photovoltaic stack which is energized from an LED. The process for manufacture of the device is also disclosed. The BOSFET device consists of two lateral field effect transistors formed in an implanted N(-) region in a P(-) substrate. Two spaced drain regions feed inwardly toward a common N(+) source region separated from the drains by respective P type diffusions. The surface of these diffusions can be inverted by application of voltage to the suitably disposed gate electrode. The depletion field between channel and drain regions is well controlled over the surface of the device. The source contact remains close to the potential of the gate contact at all times so that the device can be used for high voltage switching of either polarity. A diode, PNP transistor and resistor are integrated into the same chip containing the lateral BOSFET device to form a solid state relay circuit having characteristics similar to a reed relay. The diode defines a forward conduction path from a photovoltaic pile voltage source directly to the BOSFET gate so that the BOSFET gate capacitance can be quickly charged during turn-on. The PNP transistor is a high gain transistor coupled to the diode and to the input resistance of the circuit. The input impedance of the circuit is reduced by the gain of the transistor when the photovoltaic output voltage is turned off and its voltage drops to below the gate voltage by about 0.6 volt to turn on the transistor. This allows the BOSFET to quickly turn off as though the circuit had a relatively low input impedance. Another control circuit is disclosed which employs a dV/dt suppression clamp circuit and a regenerative turn-off circuit.

Claims28

Dependent claims

A bidirectional conduction insulated gate field effect transistor;

said transistor comprising a high resistivity body of one of the conduction types;
a shallow high resistivity implanted region of the other of the conductivity types formed by implantation and drive into one surface of said body;
first and second laterally displaced drain regions of said other conductivity type formed in said implanted region;
a central region of said one of the conductivity types formed in said implanted region and located centrally between and spaced from said drain regions, and extending completely through said implanted region;
a source region means of said other conductivity type formed in the surface of said central region and defining two opposed channel means in said central region which can be inverted from said one conductivity type to said other conductivity type;
insulated gate means disposed above the surface of said central region and aligned with said two opposed channel means, and a gate insulation layer disposed between said two opposed channel means and said gate means;
first and second drain electrode means connected to said first and second drain regions, respectively;
and source electrode means connected to said source region means, to provide a biasing reference for said gate means, and to said central region, said source electrode means being disposed adjacent said gate means and insulated therefrom, whereby current can flow bidirectionally between said drain electrode means and through said source electrode when said channel means is inverted by a voltage on said gate means.

5 more elements

A bidirectional conduction insulated gate field effect transistor comprising:

a high resistivity body of one of the conductivity types;
a shallow high resistivity layer of the other of the conductivity types on the top of said body;
first and second colinear elongated drain regions of said other conductivity type formed in the surface of said high resistivity layer, with their adjacent ends spaced from one another;
an elongated central region of said one conductivity type formed in the surface of said high resistivity layer and extending parallel to and laterally spaced from said first and second drain regions and dividing one from the other;
a source region means of said one conductivity type formed in the surface of said central region and extending coextensively therewith;
the edges of said source region being spaced from the edges of said central region to define two opposed elongated channel means which can be inverted from said other conductivity type to said one conductivity type;
a gate insulation layer on the surface of said body and overlying said two opposed elongated channel means, and a gate electrode disposed atop said gate insulation layer;
an elongated source electrode connected to said source region means to provide a biasing reference for said gate electrode;
said source electrode being disposed adjacent to but insulated from said gate electrode;
and first and second drain electrodes connected to said first and second drain regions, whereby current can flow bidirectionally between said first and second drain electrodes when said channel means is inverted.

7 more elements

A bidirectional conduction insulated gate field effect transistor having a pair of main current electrodes, comprising, in a single chip:

a substrate of one conductivity type with a high resistivity surface layer of the opposite conductivity type;
first P-N junctions defining a first lateral conduction field effect transistor;
second P-N junctions defining a second lateral conduction field effect transistor;
a semiconductor region of one conductivity type formed in said surface layer containing a common source or drain region of an opposite conductivity type for the first and second field effect transistors;
said semiconductor region having respective channel regions for the first and second transistors;
and respective gate portions dielectrically spaced from the respective channel regions and being connected together so as to be at the same electric potential and to serve as a single gate for the first and second field effect transistors;
and
an electrode connected to said source or drain region and to said semiconductor region and providing a reference potential for biasing said gate.

5 more elements

Dependencies are inferred from the claim text.

Bidirectional output semiconductor field effect transistor and method for its maufacture

Life of this patent

Bidirectional output semiconductor field effect transistor and method for its maufacture

Life of this patent

Abstract

Claims28