Showing papers on "Drain-induced barrier lowering published in 1980"

Design and characteristics of the lightly doped drain-source (LDD) insulated gate field-effect transistor

Abstract: The LDD structure, where narrow, self-aligned n-regions are introduced between the channel and the n+source-drain diffusions of an IGFET to spread the high field at the drain pinchoff region and thus reduce the maximum field intensity, is analyzed. The design is shown, including optimization of the n-dimensions and concentrations and the boron channel doping profile and an evaluation of the effect of the series resistance of the n-regions on device transconductance. Characteristics of experimental devices are presented and compared to those of conventional IGFET's. It is shown that significant improvements in breakdown voltages, hot-electron effects, and short-channel threshold effects can be achieved allowing operation at higher voltage, e.g., 8.5 versus 5 V, with shorter source-drain spacings, e.g., 1.2 versus 1.5 µm. Alternatively, a shorter channel length could be used for a given supply voltage. Performance projections are shown which predict 1.7 × basic device/circuit speed enhancement over conventional structures. Due to the higher voltages and higher frequency operation, the higher performance results in an increase in power which must be considered in a practical design.

MOS Power transistor with improved high-voltage capability

Abstract: Device means for reducing latch-back breakdown thus raising the reverse-biased power capability of a DMOS transistor or the like. A DMOS transistor is an MOS field effect transistor comprising a lightly-doped (usually diffused) body region formed in a drain region; a heavily-doped source region is located in the body region in proximity to the drain. Since such a device structure also exhibits substantial bipolar transistor action, it is prone to latch-back breakdown. Means for reducing latch-back breakdown include providing a distributed diode with a lower breakdown voltage than the DMOS transistor to non-destructively absorb reverse transients or by providing shunt conductance means for the diffused channel region to reduce both the voltage and the voltage gradient in the base of the parasitic bipolar device. These means may be used singly or in combination.

Power MOSFET with an anode region

Abstract: A vertical MOSFET device having source, body and drain regions, includes an anode region in series with the drain region. The source, body and drain regions have a first forward current gain and the anode, drain and body regions have a second forward current gain, such that the sum of the current gains is less than unity. The anode region provides minority carrier injection into the drain region, enhancing device performance in power applications.

Method of controlling MOSFET threshold voltage with self-aligned channel stop

Abstract: A process is provided for fabricating MOSFET devices having field source, gate and drain regions. The threshold voltage of both the channel and field regions of such devices is controlled by forming a comparatively thick oxide film on a semiconductor surface, defining enhancement mode transistor regions in the oxide film to expose portions of the semiconductor surface, implanting p-type ions under conditions such that the peak distribution of p-type atoms lies in the semi-conductor substrate just beneath the semiconductor/-oxide interface and counter-doping with n-type ions under conditions such that no implanted ions penetrate the oxide film. As a consequence, a desirably high threshold voltage is obtained in the field region, while a desirably low threshold voltage is obtained in the channel region. Depletion mode transistors are fabricated on the same wafer by masking the enhancement mode regions, defining depletion mode transistor regions in the oxide film to expose portions of the semiconductor surface and implanting n-type ions under conditions such that no ions penetrate the mask or oxide film. Metal gate or refractory gate technology is then employed to fabricate source, gate and drain regions and electrical contacts thereto. Parasitic conduction paths between neighboring transistors are substantially eliminated due to the peak distribution of p-type atoms in the field region.

Design and Characteristics of the Lightly Doped Drain-Source (LDD) Insulated Gate Field-Effect Transistor

Abstract: The LDD structure, where narrow, self-aligned n/sup -/ regions are introduced between the channel and the n/sup +/ source-drain diffusions of an IGFET to spread the high field at the drain pinchoff region and thus reduce the maximum field intensity, is analyzed. The design is shown, including optimization of then- dimensions and concentrations and the boron channel doping profile and an evaluation of the effect of the series resistance of the n- regions on device transconductance. Characteristics of experimental devices are presented and compared to those of conventional IGFET's. It is shown that significant improvements in breakdown voltages, hot-electron effects, and short-channel threshold effects can be achieved allowing operation at higher voltage, e.g., 8.5 versus 5 V, with shorter source-drain spacings, e.g., 1.2 versus 1.5 /spl mu/m. Alternatively, a shorter channel length could be used for a given supply voltage. Performance projections are shown which predict 1.7 X basic device/circuit speed enhancement over conventional structures. Due to the higher voltages and higher frequency operation, the higher performance results in an increase in power which must be considered in a practical design.

Extended drain self-aligned silicon gate MOSFET

Abstract: A Metal-Oxide-Semiconductor-Field Effect Transistor (MOSFET) is described wherein a body of semiconductor material is provided with source, drain and channel regions. A gate structure is provided over the interstitial channel region of the semiconductor body between the drain and source regions, one edge of which is aligned with the source region. The remainder of the channel region, between the other edge of the gate structure and the adjacent edge of the drain region is provided with a drift region of a conductivity type that is the same as the source and drain.

Method of forming non-volatile EPROM and EEPROM with increased efficiency

Abstract: The floating gate in an N channel EPROM cell extends over the drain diffusion and over a portion of the channel thereby to form a "drain" capacitance between the drain and the floating gate and a "channel" capacitance between the channel and the floating gate. A control gate overlaps the floating gate and extends over the remainder of the channel near the source diffusion thereby to form a "control" capacitance between the channel and the control gate. These three capacitances form the coupling for driving each cell. The inversion region in the channel directly under the control gate is established directly by a "write or read access" voltage applied to the control gate. The inversion region in the channel directly under the floating gate is established indirectly through the drain and control capacitances and the channel capacitance by the control gate voltage and by another write access voltage applied to the drain. In effect, the drain voltage is coupled to the portion of the channel adjacent to the drain through the series driving circuit formed by the drain capacitance and the channel capacitance. During write, hot electrons from the write channel current are directed toward and injected into the floating gate by the transverse electric field between the floating gate and the underlying channel. Stored injection charge on the floating gate raises the conduction threshold of the programmed cell, causing the cell to remain nonconductive during read when standard ("low") access voltages are applied to the control gate. An unprogrammed cell conducts in response to the low read voltages applied to its control gate and drain drive circuit. A cell is erased either by ultraviolet illumination or by electrons from the floating gate tunneling through a region of thinned oxide. The non-symmetrical arrangement of the control gate and floating gate with respect to source and drain allows a very dense array implementation.

Non-volatile eprom with increased efficiency

Abstract: The floating gate in an N channel EPROM cell extends over the drain diffusion and over a portion of the channel thereby to form a "drain" capacitance between the drain and the floating gate and a "channel" capacitance between the channel and the floating gate. A control gate overlaps the floating gate and extends over the remainder of the channel near the source diffusion thereby to form a "control" capacitance between the channel and the control gate. These three capacitances form the coupling for driving each cell. The inversion region in the channel directly under the control gate is established directly by a "write or read access" voltage applied to the control gate. The inversion region in the channel directly under the floating gate is established indirectly through the drain and control capacitances and the channel capacitance by the control gate voltage and by another write access voltage applied to the drain. A cell is erased either by ultraviolet illumination or by electrons from the floating gate tunneling through a region of thinned oxide. The non-symmetrical arrangement of the control gate and floating gate with respect to source and drain allows a very dense array implementation.

A simple model of the threshold voltage of short and narrow channel MOSFETs

Abstract: Simple but reasonably accurate equations are proposed which describe the behavior of threshold voltage for short and narrow-channel MOSFETs, for low drain-source voltages. It will be shown that good agreement is obtained between the model, experiment and two dimensional calculations, for channel lengths and widths as small as 1 ∼ 2 μm. Moreover, by careful analysis of the model results, some new properties of the threshold voltage of small size devices can be derived.

A 600-volt MOSFET designed for low on-resistance

Abstract: A 600-V vertical power MOSFET with low on-resistance is described. The low resistance is achieved by means of achieving near-ideal drain junction breakdown voltage and reduced drain spreading resistance from the use of an extended channel design. The various tradeoffs inherent in the design are discussed. Both calculated and experimental data are presented. The remote source configuration of the experimental device is also discussed.

Method of making contact electrodes to silicon gate, and source and drain regions, of a semiconductor device

Abstract: In the fabrication of a metal oxide semiconductor field effect transistor (MOSFET) or of a metal gate field effect transistor (MESFET), characterized by a polycrystalline silicon gate (13) and a short channel of about a micron or less, a sequence of steps is used involving the simultaneous formation of source, drain, and gate electrode contacts by a bombardment with a transition metal, such as platinum, which forms metal-silicide layers (19, 21, 18) on the source and drain regions (10.1, 10.2) as well as the silicon gate electrode (13).

Theory of the fully depleted SOS/MOS transistor

Abstract: The subject of full film depletion of the SOS/MOS transistor and its impact on threshold voltage and the weak inversion slope factor is addressed. A rigorous one dimensional field analysis of the SOS transistor is performed. The silicon/sapphire interface is treated in the analysis as a discrete interface. The depletion approximation is invoked in order to obtain relatively simple expressions for threshold voltage and the weak inversion slope factor. Experimental data is then compared with data generated by the mathematical models. Both the experimental and model data indicate increase in both absolute threshold voltage and weak inversion slope factor with decreasing epitaxial film thickness.

Self-aligned Schottky metal semi-conductor field effect transistor with buried source and drain

Abstract: A semi-conductor structure and particularly a high speed VLSI Self-Aligned Schottky Metal Semi-Conductor Field Effect Transistor with buried source and drain, fabricated by the ion implantation of source and drain areas at a predetermined range of depths followed by very localized laser annealing to electrically reactivate the amorphous buried source and drain areas thereby providing effective vertical separation of the channel from the buried source and drain respectively. Accordingly, spatial separations between the self-aligned gate-to-drain, and gate-to-source can be relatively very closely controlled by varying the doping intensity and duration of the implantation thereby reducing the series resistance and increasing the operating speed.

Power FET short circuit protection

Abstract: A protection circuit for a semiconductor device such as a field effect transistor is disclosed having an oscillator which is connected to both the gate turn on circuitry and to the drain-source circuit of the field effect transistor for sensing the voltage of the drain-source circuit and for turning off cyclically the field effect transistor upon the simultaneous occurrence of a gate turn on signal to the gate of the transistor and high drain-source voltage.

Non-volatile EPROM with enhanced drain overlap for increased efficiency

Abstract: The floating gate in an N channel EPROM cell extends over the drain diffusion and over a portion of the channel thereby to form a "drain" capacitance between the drain and the floating gate and a "channel" capacitance between the channel and the floating gate. A control gate overlaps the floating gate and extends over the remainder of the channel near the source diffusion thereby to form a "control" capacitance between the channel and the control gate. These three capacitances form the coupling for driving each cell. The inversion region in the channel directly under the control gate is established directly by a "write or read access" voltage applied to the control gate. The inversion region in the channel directly under the floating gate is established indirectly through the drain and control capacitances and the channel capacitance by the control gate voltage and by another write access voltage applied to the drain. In effect, the drain voltage is coupled to the portion of the channel adjacent to the drain through the series driving circuit formed by the drain capacitance and the channel capacitance. During write, hot electrons from the write channel current are directed toward and injected into the floating gate by the transverse electric field between the floating gate and the underlying channel. Stored injection charge on the floating gate raises the conduction threshold of the programmed cell, causing the cell to remain non-conductive during read when standard ("low") access voltages are applied to the control gate. An unprogrammed cell conducts in response to the low read voltages applied to its control gate and drain drive circuit. A cell is erased either by ultraviolet illumination or by electrons from the floating gate tunneling through a region of thinned oxide. The non-symmetrical arrangement of the control gate and floating gate with respect to source and drain allows a very dense array implementation.

Low power CMOS crystal oscillator

Abstract: A two transistor CMOS inverter has the two transistor gates coupled together by a coupling capacitor. D-C gate bias is supplied to each transistor through high value resistors. The P-channel transistor is biased one threshold below V DD and the N-channel transistor is biased one threshold above ground. The biasing voltages are developed through the use of a current mirror so that the biasing is independent of processing variables and temperature. This form of biasing renders the circuit class B regardless of the source to drain voltage and ensures low current operation. A crystal oscillator created using such an inverter and biasing will operate at voltages substantially below sum of P and N thresholds and at a current level about one-fifth of that of a conventional CMOS oscillator.

Field effect transistor with combination Schottky-junction gate

Abstract: A field effect transistor device is constituted by a semiinsulating substrate consisting of a compound semiconductor, an N type semiconductor layer formed on the substrate, a plurality of P type semiconductor gate regions aligned along a straight line and extending through the semiconductor layer to reach the substrate, source and drain electrodes disposed on the semiconductor layer on the opposite sides of the drain regions, a gate electrode having an ohmic contact with the gate regions and having a Schottky contact with the semiconductor layer interposed between the gate regions. Two gate regions on the opposite ends of the array are in contact with the boundary region of the transistor. The field effect transistor device is useful for fabricating an integrated circuit and consumes less electric power. Further it reduces dispersion in the gate pinch off voltage and can be prepared at a high yield.

Field effect transistor having an extremely short channel length

Abstract: A field effect transistor having an extremely short channel length in which a doped semiconductor layer of one conductivity type has oppositely doped source and drain zones in a surface side thereof. A first gate electrode is separated from the semiconductor layer surface by an insulating layer. The first gate electrode covers the region between the source and drain zones with the exception of a strip-like semiconductor region directly adjoining the source zone. A second gate electrode is provided above the strip-like semiconductor region and is insulated from the first gate electrode by a second insulating layer. The first gate electrode is connected to a bias voltage source and the second gate electrode is arranged to be connected to a control voltage.

Dynamic monolithic memory

Abstract: In a dynamic monolithic memory including a plurality of memory cells each of which comprises a capacitance and a switching field-effect transistor, the source and drain electrodes of the transistor are connected to a data line and the capacitance, respectively. Upon reading a memory cell, the transistor is switched on when difference between the data line voltage and the word line voltage applied to a gate electrode of the transistor exceeds a threshold voltage of the transistor.

N-Channel JFET device compatible with existing bipolar integrated circuit processing techniques

Abstract: A buried n-channel junction field-effect transistor (JFET) fabricated in standard bipolar integrated circuit starting material. The transistor has a deep p-well as the bottom gate formed in an n-type body. The source is surrounded by the p-well while the drain is the epitaxial layer near the surface of the body outside the p-well. A buried channel connects the source and drain. A p-layer above the buried channel forms the top gate. Gate leakage current and noise are very low.

Insulated gate field effect transistor

Abstract: An Insulated Gate Field Effect Transistor (IG FET) comprises two depletion mode gate portions formed along the surface of a V-shaped recess in a semiconductor layer, an enhancement mode gate portion disposed between the two depletion mode gate portions, and a source region and a drain region disposed on respective sides of, and adjacent to, the depletion mode gate portion at the surface of the semiconductor layer. The V-shaped recess extends downwardly from the surface of, and through, a first semiconductor layer having comparatively low impurity concentration into an underlying second semiconductor layer having comparatively high impurity concentration. The first semiconductor layer provides, in the recess, the depletion mode gate portion, and the second semiconductor layer provides, in the recess, the enhancement mode gate portion of the IG FET. The source region and drain region are disposed on respective sides of, and adjacent to, the V-shaped recess, and are spaced apart from each other at the uppermost surface of the substrate. The IG FET, as thus described, has a very short effective channel length, but also allows easy formation of electrodes on the source and drain regions. Moreover, the described IG FET is characterized by a high punch-through voltage regardless of the polarity of the voltage applied thereto, and precludes occurrence of the short-channel effect by virtue of the provision of the two depletion mode channels adjacent to the source region and drain region, respectively. A further embodiment employing dual recesses is also disclosed.

Method of making a circular high voltage field effect transistor

Abstract: A circular high voltage field effect transistor suitable for inclusion in LSI circuits, and the process for making said transistor, are described. The transistor comprises a central drain and concentric circular field plate, gate and source. Alternate embodiments include an intermediate gate and resistive gate. Implantation and diffusion techniques are described for producing the source and channel regions, and various device dimensions may be varied to improve either current or voltage handling capability or speed capability.

The effect of field dependent mobility on the threshold voltage of a small geometry MOSFET

Abstract: Threshold voltage calculations for small geometry MOSFET's typically assume a constant mobility. Calculations are performed with a two-dimensional computer model to determine the effect of field dependent mobility on the threshold voltage. The field dependent mobility is seen to decrease the threshold voltage as compared with the constant mobility case as the drain voltage is increased. For low to moderate drain voltages, this effect is not of significant magnitude to be of concern.

Power MOSFET protection circuit - has potentiometer controlled diode preceding auxiliary transistor applying voltage proportional to residual source and drain voltage

Abstract: The protecting circuit for a power MOSFET (1) uses an auxiliary transistor (2) preceded by a diode (6) which conducts when MOSFET operates. The auxiliary transistor applies a voltage which is proportional to the residual voltage between the source (S) and drain (D) connections of the MOSFET. The diode is connected to a potentiometer (5) so as to control this proportionality. The diode is connected on one side with the drain connected and on the other side by a resistance (7) to a switch (16) at the positive side of a voltage source (8). Thepolarityof the diode is selected so that it conducts when the MOSFET conducts. Also between the gate and source is a Zener diode (12). The auxiliary transistor is controlled by a parallel capacitor (10). The MOSFET control voltage is alternatively supplied by a converter secondary winding (13) in series with a rectifier (14) and smoothing capacitor (15).

Broadband circuit with rapidly variable resistor

Abstract: To provide for essentially inertia-free amplitude adjustment of video signals, an electrical circuit is provided with a field effect transistor having variable source-drain resistance. The circuit includes two junction transistors which are connected to the gate electrode of the field effect transistor and either to the source electrode or the drain electrode. One such transistor is connected as an impedance converter, and the other in grounded base configuration. By means of a variable voltage applied to a resistor is connected to the gate electrode of the field effect transistor, source-drain resistance of the field effect transistor can be varied essentially linearly.

Method of manufacturing short channel MOS devices

Abstract: A short channel MOS transistor and the method for fabricating same is described wherein the dopant concentrations of the source and drain regions are maintained at different levels of conductivity modifiers. The method described teaches first doping the source region while maintaining the drain region masked and then doping both the source and drain regions.

Active refresh circuit for dynamic MOS circuits

Abstract: Circuitry for automatically and selectively refreshing a dynamic node to a desired logic level. Nodes at ground potential are left at ground while nodes at an intermediate level are brought up to a supply voltage level. In a preferred use the dynamic node is a digit line in a random access memory. The circuitry includes a first transistor connected between the drain supply and a digit line having a gate connected to the source of a second transistor. The drain of the second transistor is connected to a clocked source of potential at least one threshold above the drain supply. The gate of the second transistor is precharged to a potential near the drain supply voltage preferrably concurrent with precharging of digit lines in the memory proper. A third transistor is connected between the gate of the second transistor and the digit line and has a gate connected to a clocked source of a reference potential between a digit line precharge level and the level of one threshold above ground. After the state of a memory cell is read out by a sense amplifier, the reference potential is applied to the gate of the third transistor to discharge the gate of the second transistor in the event that the digit line is at a low voltage. If the cell read out on the digit line was at a high potential the gate of the second transistor remains charged so that when a potential exceeding the drain voltage by at least one threshold is applied to the drain of the second transistor it is coupled through to the gate of the first transistor which in turn pulls the digit line potential to the drain supply voltage.

Mosfet logic inverter buffer circuit for integrated circuits

Abstract: The inverter buffer circuit disclosed includes two transistorized circuits each coupled to an input circuit and an output circuit capable of carrying high current and providing full output swing between a high voltage or binary "1" and a low voltage or binary "0". Each of the two circuits include a first enhancement field effect transistor having its drain electrode connected to a drain voltage and operating as a source follower, a first depletion field effect transistor having its drain electrode and source electrode connected to back bias acting as a load for the first enhancement transistor, second and third enhancement field effect transistors having their source electrodes coupled to the back bias and interconnected to form a flip-flop controlled by the first enhancement transistor and a second depletion field effect transistor having its drain electrode coupled to the drain voltage and acting as the load for the flip-flop. The output circuit includes two depletion field effect transistors connected in series between the drain voltage and source voltage with the gate electrodes thereof connected to a different one of the two flip-flops and an output terminal coupled to the series connection between the two depletion transistors. Three embodiments of the input circuit are disclosed.

A sample and hold circuit

Abstract: In a sample-and-hold circuit having a first MOS transistor (5) for sampling an input voltage and a holding capacitor (C o ) for holding the sampled voltage, a second MOS transistor (10) has its source and its drain both connected to the output terminal (4) of the circuit. The capacitance between the gate and output electrode (S) of the first MOS transistor (5) is substantially equal to the sum of the capacitances between the gate and the drain, and between the gate and the source, of the second MOS transistor (10). When a voltage is applied to the gate of the first MOS transistor to turn it on or off, the gate of the second MOS transistor receives the same voltage after inversion (8), so that the charge accumulated in the channel region of the first transistor, can be absorbed in the channel region of the second transistor when the first transistor is turned off. In this way, the sampled voltage can be held constant after turning off the first MOS transistor.

Normally-on enhancement mode MOSFET with negative threshold gating

Abstract: A VLSI enhancement mode metal oxide semiconductor field effect transistor operative to be Normally-On except during those periods when a negative threshold voltage is applied to the gate electrode. A submicron MOSFET channel having relatively high resistivity substrate allows for source and drain PN junction with overlapping depletion regions to create an electric field that promotes a surface inversion layer in the channel for conduction between the source and drain in a Normally-On mode except upon application of a negative gate threshold that acts to invert the channel surface to a non-conducting mode.