CN104935327A

CN104935327A - NOR gate of gallium nitride-based double-cantilever switch with low leakage current

Info

Publication number: CN104935327A
Application number: CN201510379728.4A
Authority: CN
Inventors: 廖小平; 王小虎
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2015-07-01
Filing date: 2015-07-01
Publication date: 2015-09-23
Anticipated expiration: 2035-07-01
Also published as: CN104935327B

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 nitrate based low-leakage current double cantilever beam switch NOR gate

Technical field

The present invention proposes GaN (gallium nitride) base low-leakage current double cantilever beam switch MESFET (metal-semiconductor field effect transistor) NOR gate, belong to the technical field of microelectromechanical systems.

Background technology

Along with the development of wireless communication technology, the chip of radio frequency integrated circuit also develops rapidly, and integrated scale constantly expands, and operating frequency improves constantly, and traditional silica-base material can not meet the demands.MESFET based on gallium nitride substrate is suggested application under this background, because the characteristic that gallium nitride material is good makes the transistor manufactured by it have very high electron mobility, very strong capability of resistance to radiation, larger operating temperature range.Because in chip, the quantity of transistor gets more and more, the thing followed is exactly the power problems of integrated circuit.Along with the development of integrated circuit, the scale of chip becomes very large, and people more and more pay attention to for the power consumption of chip.Too high power consumption can propose higher requirement to the heat sink material of chip, and the performance of chip also can be made to be affected.So the design for the low-power consumption of device seems more and more important in the design of integrated circuit.

OR-NOT circuit can realize the NOR-logic function of the digital signal that two inputs input, NOR gate is as the important component part of digital circuit, there is huge application, so just seem very important to the power consumption of OR-NOT circuit and the control of temperature, the NOR gate be made up of conventional MESFET, along with the lifting of integrated level, power consumption becomes more and more serious, the excessive chip overheating problem brought of power consumption can have a strong impact on the performance of integrated circuit, the development of MEMS technology makes to manufacture the MESFET with movable cantilever switch becomes possibility, the MESFET with movable cantilever switch effectively can reduce grid leakage current, and then reduce the power consumption of OR-NOT circuit.

Summary of the invention

Technical problem: the object of this invention is to provide a kind of GaN base low-leakage current double cantilever beam switch MESFET NOR gate, adopt in NOR gate two traditional MESFET are changed to the MESFET that has double cantilever beam construction of switch, when this NOR gate is in running order, effectively can reduce the grid leakage current of crystal, thus reduce the power consumption of NOR gate.

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

Two described cantilever switch be rely on anchor district be supported and suspended on above grid, define Schottky contacts between grid and substrate, two cantilever switch of this N-type MESFET actuation voltage design equal with the threshold voltage of this N-type MESFET, when only having voltage added on the cantilever switch of N-type MESFET to be greater than the threshold voltage of N-type MESFET, its cantilever switch could be drop-down and contact grid thus make double cantilever beam switch MESFET conducting, when institute's making alive is less than the threshold voltage of N-type MESFET, cantilever switch just can not be drop-down, MESFET turns off, when NOR gate works, when N-type MESFET is in shutoff, its cantilever switch is just in suspended state, reduce grid leakage current, thus reduce the power consumption of circuit.

Operationally, two digital signal input end A and B of this NOR gate, as long as there is a road to be high level, this high level input signal is added in by anchor district on the cantilever switch of double cantilever beam switch MESFET, cantilever switch can be made drop-down and contact grid to make double cantilever beam switch MESFET conducting, thus make output Y be low level, only have when two digital signal input ends are all low level, two cantilever switch of double cantilever beam switch MESFET all can not be drop-down, this MESFET turns off, then exporting Y is high level, thus realize carrying out or non-function input signal when double cantilever beam switch MESFET in this NOR gate is in OFF state, its cantilever switch is in suspended state, reduces grid leakage current, thus reduces the power consumption of circuit, the truth table of NOR gate:

A	B	Y
			0	0	1
1	0	0

0	1	0
			1	1	0

Beneficial effect: the double cantilever beam switch MESFET in GaN base low-leakage current double cantilever beam switch MESFET NOR gate of the present invention two cantilever switch drop-down when contacting with N-type MESFET grid, N-type MESFET conducting.When between cantilever switch and pull-down electrode, institute's making alive is less than the threshold voltage of MESFET, cantilever switch can not be drop-down, and N-type MESFET turns off, and now cantilever switch is in suspended state, reduces grid leakage current thus reduce the power consumption of this NOR gate.

Accompanying drawing explanation

Fig. 1 is the vertical view of GaN base low-leakage current double cantilever beam switch MESFET NOR gate of the present invention,

Fig. 2 be Fig. 1 GaN base low-leakage current double cantilever beam switch MESFET NOR gate P-P ' to profile,

Fig. 3 be Fig. 1 GaN base low-leakage current double cantilever beam switch MESFET NOR gate A-A ' to profile,

Figure comprises: double cantilever beam switch N-type MESFET1, resistance 2, semi-insulating GaN substrate 3, lead-in wire 4, grid 5, cantilever switch 6, anchor district 7, pull-down electrode plate 8, silicon nitride layer 9, source electrode 10, N-type active layer 11, drain electrode 12.

Embodiment

GaN base low-leakage current double cantilever beam switch MESFET NOR gate of the present invention is made up of a double cantilever beam switch N-type MESFET and resistance, the source ground of this GaN base low-leakage current double cantilever beam switch MESFET, two-way input signal is connected on two cantilever switch of this MESFET respectively, drain electrode is connected with resistance and is connected together with power supply, output signal and export between drain electrode and resistance, this resistance exports as low level much larger than MESFET conduction impedance thus when MESFET conducting.The source electrode of this MESFET and drain electrode form ohmic contact by metal and heavy doping N district and form, grid forms Schottky contacts by titanium/platinum/billon and N-type active layer and forms, the cantilever switch of the symmetric design that two are made with titanium/gold/titanium is left floating above the grid of cantilever switch N-type MESFET, the suspension end of two cantilever switch does not interfere with each other when leaving certain gap to ensure that two cantilever switch are drop-down, and the position of two cantilever switch is symmetrical about this N-type MESFET source-drain direction.AC signal is carried on two cantilever switch, the anchor district of cantilever switch is produced on semi-insulating GaN substrate, between cantilever switch and substrate, there is pull-down electrode, pull-down electrode is covered by silicon nitride material, the pull-down electrode ground connection of cantilever switch N-type MESFET.

The cantilever switch of the double cantilever beam switch N-type MESFET that the NOR gate in the present invention uses is suspended on its grid, Schottky contacts is defined between the grid of N-type MESFET and substrate, depletion layer is formed in substrate square under the gate, the actuation voltage of the cantilever switch of this N-type MESFET designs equal with the threshold voltage of MESFET, when being carried in the voltage between cantilever switch and pull-down electrode and being greater than the threshold voltage of MESFET, cantilever switch is drop-down to be close to grid, N-type MESFET conducting.When between cantilever switch and pull-down electrode, institute's making alive is less than the threshold voltage of MESFET, cantilever switch can not be drop-down, and N-type MESFET turns off, and now cantilever switch is in suspended state, reduces grid leakage current thus reduce the power consumption of this NOR gate.

As long as two of this NOR gate digital signal input ends have a road to be high level, this high level input signal is added in by anchor district on the cantilever switch of double cantilever beam switch N-type MESFET, this cantilever switch can be made drop-down and conducting, thus make output be low level.Only have when two digital signal input ends are all low level, two cantilever switch of double cantilever beam switch N-type MESFET all can not be drop-down, double cantilever beam switch N-type MESFET can not conducting, then export as high level, thus realizes carrying out or non-function input signal when double cantilever beam switch N-type MESFET in this NOR gate is in OFF state, its cantilever switch is in suspended state, and the MESFET now in this NOR gate does not exist grid leakage current.The truth table of NOR gate:

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

The preparation method of GaN base low-leakage current double cantilever beam switch MESFET NOR gate comprises following step:

1) semi-insulating GaN substrate is prepared;

2) deposit silicon nitride, grows one deck silicon nitride by plasma-enhanced chemical vapour deposition technique (PECVD), then photoetching and etch silicon nitride, removes the silicon nitride of N-type MESFET active area;

3) N-type MESFET active area ion implantation: after injecting phosphorus, anneal in a nitrogen environment; After having annealed, at high temperature carry out N ⁺dopant redistribution, forms the N-type active layer of N-type MESFET active area;

4) silicon nitride layer is removed: adopt dry etching technology all to be removed by silicon nitride;

5) photoetching switch region, removes the photoresist of switch region;

6) electron beam evaporation titanium/platinum/gold;

7) titanium/platinum/gold on photoresist and photoresist is removed;

8) heat, make titanium/platinum/billon and N-type GaN active layer form Schottky contacts;

9) photoresist is applied, photoetching the photoresist of etching N type MESFET source electrode and drain region;

10) inject heavily doped N-type impurity, in the N-type heavily doped region that N-type MESFET source electrode and drain region are formed, after injection, carry out short annealing process;

11) photoetching source electrode and drain electrode, removes the photoresist of lead-in wire, source electrode and drain electrode;

12) vacuum evaporation gold germanium nickel/gold;

13) gold germanium nickel/gold on photoresist and photoresist is removed;

14) alloying forms ohmic contact, forms lead-in wire, source electrode and drain electrode;

15) apply photoresist, remove the photoresist of the anchor zone position of input lead, battery lead plate and clamped beam;

16) evaporate ground floor gold, its thickness is about 0.3 μm;

17) remove the gold on photoresist and photoresist, begin to take shape the anchor district of input lead, battery lead plate and clamped beam;

18) deposit silicon nitride: with plasma-enhanced chemical vapour deposition technique (PECVD) growth thick silicon nitride medium layer;

19) photoetching etch nitride silicon dielectric layer, is retained in the silicon nitride on battery lead plate;

20) deposit photoetching polyimide sacrificial layer: apply 1.6 μm of thick polyimide sacrificial layer in gallium arsenide substrate, require to fill up pit; Photoetching polyimide sacrificial layer, only retains the sacrifice layer below clamped beam;

21) evaporate titanium/gold/titanium, its thickness is the down payment of evaporation for electroplating;

22) photoetching: remove and will electroplate local photoresist;

23) electrogilding, its thickness is 2 μm;

24) photoresist is removed: remove and do not need to electroplate local photoresist;

25) anti-carve titanium/gold/titanium, corrosion down payment, forms clamped beam;

26) discharge polyimide sacrificial layer: developer solution soaks, remove the polyimide sacrificial layer under clamped beam, deionized water soaks slightly, and absolute ethyl alcohol dewaters, and volatilizees, dry under normal temperature.

Difference with the prior art of the present invention is:

Two cantilever switch of the double cantilever beam switch MESFET that the NOR gate in the present invention uses are suspended on its grid, Schottky contacts is defined between the grid of N-type MESFET and substrate, depletion layer is formed in substrate square under the gate, the actuation voltage of the cantilever switch of this N-type MESFET designs equal with the threshold voltage of MESFET, when being carried in the voltage between cantilever switch and pull-down electrode and being greater than the threshold voltage of MESFET, cantilever switch is drop-down to be close to grid, N-type MESFET conducting.When between cantilever switch and pull-down electrode, institute's making alive is less than the threshold voltage of MESFET, cantilever switch can not be drop-down, and its MESFET turns off, and now cantilever switch is in suspended state, reduces grid leakage current thus reduce the power consumption of this NOR gate.

Namely the structure meeting above condition is considered as GaN base low-leakage current double cantilever beam switch MESFET NOR gate of the present invention.

Claims

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.