CN104935327A - Gallium Nitride-Based Low Leakage Current Dual Cantilever Beam Switching NOR Gate - Google Patents

Abstract

An NOR gate of a gallium nitride-based double-cantilever switch with low leakage current of the invention uses MESFET with double cantilever switches to replace traditional MESFET, wherein the two cantilever switches are suspended on the gate of the MESFET, and the positions of the two cantilever switches are symmetrical with each other in terms of the source-drain direction of the MESFET. Schottky contact is formed between the gate of the MESFET and a substrate. A depletion layer is formed in the substrate under the gate. The pull-down voltage of the cantilever switch is designed to be equal to the threshold voltage of the MESFET. When the voltage loaded between the cantilever switch and a pull-down electrode is more than the threshold voltage of the MESFET, the cantilever switch is pulled down to stick close to the gate to conduct the MESFET. When the voltage is less than the threshold voltage of the N type MESFET, the cantilever switch could not be pulled down and the MESFET is cut off. When the NOR gate works, the cantilever switch is in a suspending state when the NMOS transistor is closed. The NOR gate of the gallium nitride-based double-cantilever switch with low leakage current reduces the leakage current of the gate so as to reduce the power dissipation of a circuit.

Description

Gallium Nitride-Based Low Leakage Current Dual Cantilever Beam Switching NOR Gate

technical field

The invention provides a GaN (gallium nitride)-based low-leakage current double cantilever beam switch MESFET (metal-semiconductor field effect transistor) NOR gate, which belongs to the technical field of micro-electromechanical systems.

Background technique

With the development of wireless communication technology, the chips of radio frequency integrated circuits are also developing rapidly, the scale of integration continues to expand, and the operating frequency continues to increase. Traditional silicon-based materials can no longer meet the requirements. MESFET based on gallium nitride substrate is proposed and applied under this background. Due to the good characteristics of gallium nitride material, the transistor manufactured by it has high electron mobility, strong radiation resistance, and large range of working temperature. As the number of transistors in a chip increases, so does the power consumption of integrated circuits. With the development of integrated circuits, the scale of chips becomes larger, and people pay more and more attention to the power consumption of chips. Too high power consumption will impose higher requirements on the heat dissipation material of the chip, and will also affect the performance of the chip. Therefore, the design of low power consumption of devices is becoming more and more important in the design of integrated circuits.

The NOR gate circuit can realize the NOR logic function of the digital signal input by the two input terminals. As an important part of the digital circuit, the NOR gate has a huge application, so the power consumption and temperature control of the NOR gate circuit It is very important. The NOR gate composed of conventional MESFET, with the improvement of integration, the power consumption becomes more and more serious. The chip overheating problem caused by excessive power consumption will seriously affect the performance of integrated circuits. MEMS technology The development of the technology makes it possible to manufacture MESFETs with movable cantilever switches. MESFETs with movable cantilever switches can effectively reduce the gate leakage current, thereby reducing the power consumption of the NOR gate circuit.

Contents of the invention

Technical problem: the purpose of this invention is to provide a kind of GaN base low leakage current double cantilever beam switch MESFET NOR gate, two traditional MESFETs adopted in the NOR gate are changed into a MESFET with double cantilever beam switch structure, in this When the NOR gate is in the working state, the gate leakage current of the crystal can be effectively reduced, thereby reducing the power consumption of the NOR gate.

Technical solution: A gallium arsenide-based low-leakage current double cantilever switch NOR gate of the present invention is composed of a double cantilever switch N-type MESFET, a resistor and a power supply. The double cantilever switch MESFET is fabricated on a GaN substrate , the source and drain of the double cantilever beam switch MESFET are composed of metal and heavily doped N regions to form ohmic contacts, and the gate is composed of titanium/platinum/gold alloy and N-type active layer to form Schottky contacts. Two symmetrically designed cantilever beam switches made of titanium/gold/titanium are suspended above the gate of the beam switch N-type MESFET. A certain gap is left between the suspension ends of the two cantilever beam switches to ensure that the two cantilever beam switches The switches do not interfere with each other when they are pulled down. The positions of the two cantilever switches are symmetrical with respect to the source-drain direction of the MESFET. The anchor region of the cantilever switch is fabricated on a semi-insulating GaN substrate, and there is a pull-down electrode between the cantilever switch and the substrate. , the pull-down electrode is covered by silicon nitride material, the pull-down electrode of the cantilever beam switch N-type MESFET is grounded, the source of the double cantilever beam switch MESFET is grounded, the drain is connected to the power supply VCC through a resistor, and the source and drain are respectively connected to the leads , the leads are made of gold, the two input signals, signal A and signal B, are respectively input to the two cantilever switches of the double cantilever switch MESFET, and the output signal Y is output between the drain and the resistor of the double cantilever switch MESFET, The resistance value of the resistor is much larger than the turn-on impedance of the MESFET, so as to ensure that the output obtained by dividing the voltage by the resistor is a low level when the N-type MESFET of the cantilever beam switch is turned on.

The two cantilever switches are suspended above the gate relying on the support of the anchor region, and a Schottky contact is formed between the gate and the substrate; the pull-down voltage of the two cantilever switches of the N-type MESFET is designed in accordance with The threshold voltages of the N-type MESFETs are equal, and only when the voltage applied to the cantilever switch of the N-type MESFET is greater than the threshold voltage of the N-type MESFET, the cantilever switch can be pulled down and contact the gate so that the double cantilever switch MESFET conducts When the applied voltage is less than the threshold voltage of the N-type MESFET, the cantilever switch cannot be pulled down, and the MESFET is turned off. When the NOR gate is working, when the N-type MESFET is turned off, the cantilever switch is in a suspended state, reducing the gate leakage current, thereby reducing power dissipation in the circuit.

When working, as long as one of the two digital signal input terminals A and B of the NOR gate is high level, the high level input signal is added to the cantilever switch of the double cantilever beam switch MESFET through the anchor area, which can Make the cantilever beam switch pull down and touch the gate to turn on the dual cantilever beam switch MESFET, so that the output Y is low, and only when both digital signal inputs are low, the two cantilever beams of the dual cantilever beam switch MESFET Beam switches cannot be pulled down, the MESFET is turned off, and the output Y is high level, so as to realize the function of NORing the input signal The double cantilever beam switch MESFET in the NOR gate is in the suspended state when the cantilever beam switch is in the off state, which reduces the gate leakage current, thereby reducing the power consumption of the circuit. The truth table of the NOR gate:

A B Y 0 0 1 1 0 0

0 1 0 1 1 0

Beneficial effects: when the two cantilever switches of the double cantilever switch MESFET in the GaN-based low leakage current MESFET NOR gate are pulled down and contact the gate of the N-type MESFET, the N-type MESFET is turned on. When the voltage applied between the cantilever switch and the pull-down electrode is less than the threshold voltage of the MESFET, the cantilever switch cannot be pulled down, and the N-type MESFET is turned off. At this time, the cantilever switch is in a floating state, which reduces the gate leakage current and thus reduces the The power consumption of the NOR gate.

Description of drawings

1 is a top view of a GaN-based low-leakage current double cantilever switch MESFET NOR gate of the present invention,

Figure 2 is a cross-sectional view of the P-P' direction of the GaN-based low-leakage current double cantilever switch MESFET NOR gate in Figure 1,

Figure 3 is a cross-sectional view of the A-A' direction of the GaN-based low-leakage current double cantilever switch MESFET NOR gate in Figure 1,

The figure includes: double cantilever switch N-type MESFET1, resistor 2, semi-insulating GaN substrate 3, lead 4, gate 5, cantilever switch 6, anchor region 7, pull-down electrode plate 8, silicon nitride layer 9, source Pole 10, N-type active layer 11, drain 12.

Detailed ways

The GaN-based low-leakage current double-cantilever switch MESFET NOR gate of the present invention is composed of a double-cantilever switch N-type MESFET and a resistor. The source of the GaN-based low-leakage current double-cantilever switch MESFET is grounded, and two input signals They are respectively connected to the two cantilever switches of the MESFET, the drain is connected to the resistor and connected to the power supply, the output signal is output between the drain and the resistor, the resistance is much larger than the on-resistance of the MESFET so that when the MESFET is turned output is low. The source and drain of the MESFET are composed of metal and heavily doped N regions to form ohmic contacts, and the gate is composed of titanium/platinum/gold alloys and N-type active layers to form Schottky contacts. In the cantilever beam switch N-type MESFET Two cantilever beam switches with symmetrical design made of titanium/gold/titanium are suspended above the grid. A certain gap is left at the suspension ends of the two cantilever beam switches to ensure that the two cantilever beam switches do not interfere with each other when they are pulled down. The positions of the two cantilever switches are symmetrical about the source-drain direction of the N-type MESFET. The AC signal is loaded on two cantilever beam switches. The anchor area of the cantilever beam switch is fabricated on a semi-insulating GaN substrate. There is a pull-down electrode between the cantilever beam switch and the substrate. The pull-down electrode is covered by silicon nitride material. The cantilever beam The pull-down electrode of the switching N-type MESFET is grounded.

The cantilever switch of the double cantilever switch N-type MESFET used in the NOR gate in the present invention is suspended above its gate, and a Schottky contact is formed between the gate of the N-type MESFET and the substrate. A depletion layer is formed in the substrate below the gate. The pull-down voltage of the cantilever switch of the N-type MESFET is designed to be equal to the threshold voltage of the MESFET. When the voltage loaded between the cantilever switch and the pull-down electrode is greater than the threshold voltage of the MESFET When the cantilever beam switch is pulled down and close to the gate, the N-type MESFET is turned on. When the voltage applied between the cantilever switch and the pull-down electrode is less than the threshold voltage of the MESFET, the cantilever switch cannot be pulled down, and the N-type MESFET is turned off. At this time, the cantilever switch is in a floating state, which reduces the gate leakage current and thus reduces the The power consumption of the NOR gate.

As long as one of the two digital signal input terminals of the NOR gate is high level, the high level input signal is added to the cantilever switch of the double cantilever beam switch N-type MESFET through the anchor area, which can make the cantilever beam switch pull down And conduction, so that the output is low. Only when the two digital signal input terminals are both low, the two cantilever switches of the double cantilever switch N-type MESFET cannot be pulled down, and the double cantilever switch N-type MESFET cannot be turned on, then the output is high level, thus Realize the function of NORing the input signal When the double cantilever switch N-type MESFET in the NOR gate is in the off state, the cantilever switch is in a suspended state, and there is no gate leakage current on the MESFET in the NOR gate at this time. Truth table for NOR gate:

A B Y 0 0 1 1 0 0 0 1 0 1 1 0

The preparation method of the GaN-based low-leakage current double cantilever switch MESFET NOR gate includes the following steps:

1) Prepare a semi-insulating GaN substrate;

2) Deposit silicon nitride, grow a layer of silicon nitride by plasma enhanced chemical vapor deposition (PECVD), and then photolithography and etch silicon nitride to remove silicon nitride in the active area of N-type MESFET ;

3) Ion implantation in the active area of N-type MESFET: after implanting phosphorus, anneal in nitrogen environment; after annealing, redistribute N ⁺ impurities at high temperature to form the N-type active layer in the active area of N-type MESFET;

4) Removing the silicon nitride layer: using dry etching technology to remove all the silicon nitride;

5) photolithography switch area, removing the photoresist in the switch area;

6) Electron beam evaporation of titanium/platinum/gold;

7) removing the photoresist and the titanium/platinum/gold on the photoresist;

8) heating to form a Schottky contact between the titanium/platinum/gold alloy and the N-type GaN active layer;

9) Coating photoresist, photolithography and etching the photoresist in the source and drain regions of the N-type MESFET;

10) Implanting heavily doped N-type impurities, forming N-type heavily doped regions in the N-type MESFET source and drain regions, and performing rapid annealing after implantation;

11) Photoetching the source and drain, removing the photoresist of the leads, source and drain;

12) Vacuum evaporation of gold germanium nickel/gold;

13) remove the photoresist and the gold germanium nickel/gold on the photoresist;

14) Alloying to form ohmic contact, forming leads, source and drain;

15) Coating photoresist, removing the photoresist at the anchor area position of the input lead, the electrode plate and the fixed support beam;

16) Evaporate the first layer of gold with a thickness of about 0.3 μm;

17) Remove the photoresist and the gold on the photoresist, and initially form the anchor area of the input lead, the electrode plate and the fixed support beam;

18) Deposition of silicon nitride: growth by plasma-enhanced chemical vapor deposition (PECVD) Thick silicon nitride dielectric layer;

19) Photolithography and etching the silicon nitride dielectric layer, and the silicon nitride on the electrode plate is retained;

20) Deposit and lithography polyimide sacrificial layer: Coat a 1.6 μm thick polyimide sacrificial layer on the gallium arsenide substrate, and it is required to fill the pits; photolithography polyimide sacrificial layer, only Retain the sacrificial layer under the fixed beam;

21) Evaporate titanium/gold/titanium to a thickness of Evaporation of base gold for electroplating;

22) Photolithography: remove the photoresist at the place to be electroplated;

23) Gold electroplating, the thickness of which is 2 μm;

24) Remove photoresist: remove photoresist where electroplating is not required;

25) Anti-etch titanium/gold/titanium, corrode the bottom gold, and form a solid support beam;

26) Release the polyimide sacrificial layer: soak in developer solution, remove the polyimide sacrificial layer under the fixed beam, soak in deionized water for a while, dehydrate with absolute ethanol, volatilize at room temperature, and dry in the air.

The difference between the present invention and prior art is:

Two cantilever switches of the double cantilever switch MESFET used in the NOR gate in the present invention are suspended above its gate, and a Schottky contact is formed between the gate of the N-type MESFET and the substrate, and the A depletion layer is formed in the substrate below the gate. The pull-down voltage of the cantilever switch of the N-type MESFET is designed to be equal to the threshold voltage of the MESFET. When the voltage loaded between the cantilever switch and the pull-down electrode is greater than the threshold voltage of the MESFET When the cantilever beam switch is pulled down and close to the gate, the N-type MESFET is turned on. When the voltage applied between the cantilever beam switch and the pull-down electrode is less than the threshold voltage of the MESFET, the cantilever beam switch cannot be pulled down, and the MESFET is turned off. At this time, the cantilever beam switch is in a floating state, which reduces the gate leakage current and thus reduces the or The power consumption of the NOT gate.

A structure satisfying the above conditions is regarded as the GaN-based low-leakage current double cantilever switch MESFET NOR gate of the present invention.

Claims (2)

1. a GaAs based low-leakage current double cantilever beam switch NOR gate, it is characterized in that this NOR gate is by having double cantilever beam switch N-type MESFET (1), resistance (2) and power supply composition, this double cantilever beam switch MESFET (1) is produced on semi-insulating GaN substrate (3), the source electrode (10) of this double cantilever beam switch MESFET (1) and drain electrode (12) form ohmic contact by metal and heavy doping N district and form, grid (5) forms Schottky contacts by titanium/platinum/billon and N-type active layer (11) and forms, grid (5) top in cantilever switch N-type MESFET (1) left floating the cantilever switch (6) of the symmetric design that two are made with titanium/gold/titanium, do not interfere with each other when leaving certain gap between the suspension end of two cantilever switch (6) to ensure that two cantilever switch (6) are drop-down, the position of two cantilever switch (6) is symmetrical about this MESFET source-drain direction, the anchor district (7) of cantilever switch (6) is produced on semi-insulating GaN substrate (3), pull-down electrode (8) is there is between cantilever switch (6) and substrate, pull-down electrode (8) is covered by silicon nitride material (9), pull-down electrode (8) ground connection of cantilever switch N-type MESFET (1), source electrode (10) ground connection of this double cantilever beam switch MESFET (1), drain electrode (12) is connected with power supply VCC by resistance (2), source electrode (10) is connected with lead-in wire (4) respectively with drain electrode (12), lead-in wire (4) gold makes, two-way input signal and signal A and signal B are respectively in two cantilever switch (6) inputs of double cantilever beam switch MESFET (1), output signal Y exports between the drain electrode (12) and resistance (2) of this double cantilever beam switch MESFET (1), the resistance of resistance (2) is much larger than the impedance of this MESFET conducting, thus ensure that obtaining output when cantilever switch N-type MESFET (1) conducting by electric resistance partial pressure is low level.

2. GaAs based low-leakage current double cantilever beam switch NOR gate according to claim 1, it is characterized in that two described cantilever switch (6) are being supported and suspended on above grid (5) of dependence anchor district (7), between grid (5) and substrate (3), define Schottky contacts, two cantilever switch (6) of this N-type MESFET actuation voltage design equal with the threshold voltage of this N-type MESFET, only have when the upper added voltage of cantilever switch (6) of N-type MESFET is greater than the threshold voltage of N-type MESFET, its cantilever switch (6) could be drop-down and contact grid (5) thus make double cantilever beam switch MESFET (1) conducting, when institute's making alive is less than the threshold voltage of N-type MESFET, cantilever switch (6) just can not be drop-down, MESFET turns off, when NOR gate works, when N-type MESFET is in shutoff, its cantilever switch (6) is just in suspended state, reduce grid leakage current, thus reduce the power consumption of circuit.