CN104953969A - Gallium nitride-based low current leakage fixed beam switch differential amplifier - Google Patents

Abstract

The GaN-based low-leakage current solid-supported beam switch differential amplifier of the present invention has significant advantages such as small size, easy integration, and fast switching speed; the traditional MESFET is replaced by a MESFET with a solid-supported beam switch, and the N-type used in the present invention The fixed-beam switch of the MESFET is suspended above the gate of the MESFET. A Schottky contact is formed between the gate of the MESFET and the substrate, and a depletion layer is formed in the substrate below the gate. The pull-down voltage of the switch is designed to be equal to the threshold voltage of the MESFET. When the voltage loaded between the switch and the pull-down electrode of the fixed beam is greater than the threshold voltage of the MESFET, the pull-down of the fixed beam is close to the gate. At this time, the MESFET trench The width of the depletion region in the channel region is reduced. When the voltage loaded between the fixed-supported beam switch and the pull-down electrode is less than the threshold voltage of the MESFET, the fixed-supported beam cannot be pulled down, and the MESFET cannot be turned on, so the gate leaks The current will not exist, reducing the power consumption of the differential amplifier.

Description

Gallium Nitride-based Low Leakage Current Fixed Beam Switching Differential Amplifier

technical field

The invention provides a gallium nitride-based low-leakage current solid-supported beam switch MESFET (metal-semiconductor field-effect transistor) differential amplifier, which belongs to the technical field of micro-electromechanical systems.

Background technique

With the rapid development of wireless communication technology, traditional silicon-based devices can no longer meet the requirements of high frequency, high efficiency and high temperature resistance, so various new devices and semiconductor materials are constantly being proposed. Transistors made of gallium nitride materials have high electron mobility, strong radiation resistance, and a large operating temperature range. GaN FETs can be used in high frequency and ultra high frequency amplifier circuits. Nowadays, the size of transistors has developed to the nanometer level, and the integration degree of the corresponding integrated circuit unit area is still continuously improving, and the functions of the chip are becoming more and more complex, showing a state of digital-analog hybrid, and the processing speed of the chip is getting higher and higher. ; Followed by the problem of power consumption of the integrated circuit, and excessive power consumption will make the chip overheat, and the operating characteristics of the transistor will be affected by the temperature and change, so the overheated chip temperature will not only reduce the life of the chip, And it will affect the stability of the chip. Since the development of battery technology has encountered an unprecedented technical bottleneck, it is very important to find a solution with low power consumption.

As an important part of the analog integrated circuit, the differential amplifier can amplify the differential mode signal while suppressing the common mode signal, thereby effectively suppressing the influence of temperature and other external factors on the circuit. The traditional MESFET has a large gate leakage current between the gate and the substrate in the working state. The development of MEMS technology has made the idea of manufacturing a new type of MESFET with a movable fixed beam switch a reality. The MESFET design amplifier can effectively reduce the gate leakage current of transistors in the differential amplifier and reduce the power consumption of the differential amplifier.

Contents of the invention

Technical problem: the purpose of this invention is to provide a kind of GaN-based low leakage current solid-supported beam switch MESFET differential amplifier, and the traditional MESFET differential pair adopted in the differential amplifier is replaced by a MESFET differential pair with a solid-supported beam switch structure. When the differential amplifier is in the working state, the gate leakage current of the transistor can be effectively reduced to reduce the power consumption of the differential amplifier.

Technical solution: The gallium nitride-based low-leakage current solid-supported beam switch differential amplifier of the present invention is composed of two first N-type MESFETs with solid-supported beam switches, a second N-type MESFET and a constant current source. The sources of the N-type MESFETs are connected together and connected to the constant current source, and the other end of the constant current source is grounded. The drains of the above two N-type MESFETs are respectively connected to the resistors. The resistors are used as loads. The two resistors are connected to the The power supply voltage is connected, the AC signal is input between the fixed beam switches of the two N-type MESFETs of the differential pair, and the amplified AC signal is output between the drains of the two N-type MESFETs and the load resistor; the leads are Made of metal, two N-type MESFET fixed-beam switches are suspended above the gate of the MESFET by the support of the anchor area. The fixed-beam switch is composed of titanium/gold/titanium, and the input AC signal is connected to the fixed-beam switch Above, the MESFET is composed of gate, source and drain, where the source and drain are composed of metal and heavily doped N regions to form ohmic contacts, the gate is composed of metal and channel regions to form Schottky contacts, and the anchor region Manufactured on the substrate, the N-type active region constitutes the source and drain, there is a pull-down electrode between the fixed beam switch and the substrate, the pull-down electrode is covered by silicon nitride, the pull-down electrode is grounded, and the circuit is made in P-type nitrogen on a gallium oxide substrate.

The solid-supported beam switch of the first N-type MESFET or the second N-type MESFET 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 of the N-type MESFET. The pull-down voltage of the fixed-beam switch of the N-type MESFET is designed to be equal to the threshold voltage of the ESFET. When the voltage loaded between the fixed-beam switch and the pull-down electrode is greater than the threshold voltage of the MESFET At this time, the pull-down of the fixed beam switch is close to the gate, and the thickness of the depletion region of the N-type MESFET is reduced and turned on. On this basis, the amplification of the AC signal is realized; when the voltage applied between the fixed beam switch and the pull-down electrode When the threshold voltage of the MESFET is lower than the threshold voltage of the MESFET, the fixed beam switch 5 cannot be pulled down, and there is no voltage on the gate, the N-type MESFET cannot be turned on, and the gate leakage current does not exist, which reduces the power of the differential amplifier. consumption.

When the differential amplifier is in the working state, the pull-down electrodes of the two N-type MESFETs that make up the differential pair, that is, the first N-type MESFET and the second N-type MESFET, are grounded through the high-frequency choke coil to prevent the loss of the AC signal through the ground, and the The AC signal υin is loaded between the fixed-beam switches of the two N-type MESFETs through the anchor region 7, and this AC signal is large enough that when it is in the positive half cycle, the fixed-beam switch of the first N-type MESFET in the differential pair pulls down It is close to the gate of the MESFET, and the first N-type MESFET is turned on, and the second N-type MESFET is in the off state. When the AC signal υin is in the negative half cycle, the situation is opposite, so that the two in the differential amplifier An N-type MESFET is in a state of one on and one off alternately with the change of the AC signal. The off state of the MESFET means that its fixed beam switch is in a suspended state, that is, there is no voltage on the gate of the MESFET at this time, that is, There is no gate leakage current, so when an AC signal υin is input into the circuit, the differential amplifier can amplify the signal and output υout.

Beneficial effects: when the pull-down of the solid-supported beam switch MESFET in the gallium nitride-based low-leakage current solid-supported beam switch MESFET differential amplifier is in contact with the gate of the N-type MESFET, there will be voltage on the gate Existence, when the fixed beam switch is in the floating state, it cannot be effectively turned on, so the fixed beam switch MESFET can effectively reduce the gate leakage current and reduce the power consumption of the circuit; and the GaN-based MESFET has high electronic The mobility can meet the needs of the normal operation of the circuit under the radio frequency signal.

Description of drawings

Figure 1 is a top view of a GaN-based low-leakage current solid-supported beam switch MESFET differential amplifier

Figure 2 is the A-A' cross-sectional view of the GaN-based low-leakage current solid-supported beam switch MESFET differential amplifier

Figure 3 is a cross-sectional view of the GaN-based low-leakage current fixed-beam switch MESFET differential amplifier in the BB' direction

Figure 4 is a schematic diagram of a GaN-based low-leakage current solid-supported beam switch MESFET differential amplifier

The figure includes: a first N-type MESFET 1, a second N-type MESFET 2, a constant current source 3, a lead wire 4, a fixed beam switch 5, a gate 6, an anchor region 7, an N well 8, an N-type active region 9, Pull-down electrode 10, substrate 11.

Detailed ways

The GaN-based low-leakage current solid-supported beam switch MESFET differential amplifier of the present invention is mainly composed of two first N-type MESFET 1 with a solid-supported beam switch, a second N-type MESFET 2 and a constant current source 3, two The sources of the N-type MESFETs are connected together and connected to the constant current source 3, the other end of the constant current source 3 is grounded, the drains of the two N-type MESFETs are respectively connected to the resistors, and the resistors are used as loads. The two loads The resistors are connected to the power supply voltage together, the AC signal is input between the fixed beam switches of two N-type MESFETs, and output between the drains of the two N-type MESFETs and the load resistor; the lead wire 4 is made of metal, and the MEMS is fixedly supported The beam switch 5 is suspended on the gate 6 of the MESFET by the support of the anchor region 7. The fixed beam switch 5 is composed of titanium/gold/titanium. The input AC signal is connected to the fixed beam switch 5. The MESFET is connected by the gate 6. Composition of source and drain, wherein source and drain are composed of metal and heavily doped N region to form ohmic contact, gate is composed of metal and channel region to form Schottky contact, anchor region 7 is used to make substrate 11 On the top, the N-type active region 9 constitutes the source and drain, and there is a pull-down electrode 10 between the fixed beam switch 5 and the substrate 11. The pull-down electrode is covered by a silicon nitride material, and the pull-down electrode is grounded. The circuit is made in a P-type GaN substrate 11.

When the differential amplifier is in the working state, the pull-down electrodes 10 of the two N-type MESFETs are grounded through the high-frequency choke coil, and the AC signal is loaded to the fixed beam switch 5 of the two N-type MESFETs in the differential pair through the anchor region 7 Between, this AC signal is large enough, when it is in the positive half cycle, the fixed beam switch 5 of the first N-type MESFET on the left pulls down and sticks to its gate 6, and makes the left MESFET turn on, while the right The second N-type MESFET of the differential amplifier is in the off state, and the situation is reversed when the AC signal is in the negative half cycle, so that the two N-type MESFETs in the differential amplifier are in a state of one on and one off alternately with the change of the AC signal , the off state of the MESFET means that its fixed beam switch 5 is in a suspended state, that is to say, there is no voltage on the gate 6 of the MESFET at this time, so there is no gate leakage current. When an AC signal is input in the circuit In the future, the differential amplifier can amplify the signal and output υout, the formula used is as follows:

υout=Av×υin, where Av is the gain factor of the differential amplifier.

The preparation method of the GaN-based low-leakage current solid-supported beam switch MESFET differential amplifier includes the following steps:

1) Prepare a semi-insulating gallium nitride substrate 11;

2) Depositing a layer of silicon nitride, photolithography and etching the silicon nitride, and removing the silicon nitride in the channel region of the N-type MESFET;

3) N-type MESFET channel implantation, implanting phosphorus, and annealing in nitrogen environment; after annealing is completed, redistribute impurities at high temperature to form the channel region of N-type MESFET;

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

5) Photoetching the gate 6, removing the photoresist in the gate region;

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

7) remove the remaining 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 MESFET channel;

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

10) Carry out N-type light doping to the region, and perform rapid annealing on the N-type lightly doped active region 9 formed in the N-type MESFET source and drain regions;

11) photolithography source and drain, remove the photoresist of 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 source and drain;

15) Coating photoresist, removing the photoresist at the anchor region 7 of the power line, ground wire, lead wire 4, pull-down electrode 10 and fixed support beam switch;

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 to form the anchor region 7 of the power line, the ground wire, the lead wire 4, the pull-down electrode 10 and the fixed beam switch;

18) Deposit a layer thick silicon nitride;

19) photoetching and etching the silicon nitride dielectric layer, and retaining the silicon nitride on the pull-down electrode 10;

20) Depositing and photoetching a polyimide sacrificial layer: coating a 1.6 μm thick polyimide sacrificial layer on the gallium nitride substrate 11, which requires filling the pits; photoetching the polyimide sacrificial layer, Only keep the sacrificial layer under the fixed beam switch;

21) Evaporate titanium/gold/titanium with a thickness of 500/1500/

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-engraving titanium/gold/titanium, corroding the bottom gold to form a solid support beam switch 5;

26) Release the polyimide sacrificial layer: soak in developer solution, remove the polyimide sacrificial layer under the fixed beam switch 5, 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 the prior art is that

The solid-supported beam switch of the N-type solid-supported beam switch MESFET used in the mixer 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 fixed beam switch of the N-type MESFET is designed to be equal to the threshold voltage of the MESFET. When the voltage loaded between the fixed beam switch and the pull-down electrode is greater than that of the MESFET When the threshold voltage is lower than the threshold voltage, the pull-down of the fixed beam switch is close to the gate, and the thickness of the depletion region of the N-type MESFET is reduced and turned on. On this basis, the amplification of the AC signal is realized; when the fixed beam switch and the pull-down electrode When the applied voltage is lower than the threshold voltage of the MESFET, the fixed beam switch cannot be pulled down, and there is no voltage on the gate, so the N-type MESFET cannot be turned on, and the gate leakage current will not exist, thus reducing The power consumption of the differential amplifier is reduced.

A structure that satisfies the above conditions can be regarded as the GaN-based low-leakage current solid-supported beam switch MESFET differential amplifier of the present invention.

Claims (3)

1. A gallium nitride-based low-leakage current solid-supported beam switch differential amplifier, characterized in that the differential amplifier consists of two first N-type MESFETs (1) and second N-type MESFETs (2) with solid-supported beam switches Composed of a constant current source (3), the sources of the above two N-type MESFETs are connected together and connected to the constant current source (3), the other end of the constant current source is grounded, and the drains of the above two N-type MESFETs The poles are respectively connected to the resistors, and the resistors are used as loads. The two resistors are connected to the power supply voltage. The AC signal is input between the fixed beam switches (5) of the two N-type MESFETs of the differential pair, and the amplified AC The signal is output between the drains of the two N-type MESFETs and the load resistor; the leads (4) are made of metal, and the fixed beam switches (5) of the two N-type MESFETs are suspended on the MESFETs by the support of the anchor area (7). On the gate (6), the fixed beam switch (5) is composed of titanium/gold/titanium, the input AC signal is connected to the fixed beam switch (5), and the MESFET is composed of the gate (6), source and drain, wherein the source and drain are composed of metal and heavily doped N regions to form ohmic contacts, the gate (6) is composed of metal and channel regions to form Schottky contacts, and the anchor region (7) is made on the substrate On the bottom (11), the N-type active region (9) constitutes the source and drain, and there is a pull-down electrode (10) between the fixed beam switch (5) and the substrate (11), and the pull-down electrode (10) consists of Covered with silicon nitride, the pull-down electrode (10) is grounded, and the circuit is fabricated on a P-type gallium nitride substrate (11). 2. The gallium nitride-based low-leakage current solid-supported beam switch differential amplifier according to claim 1, characterized in that the solid-supported beam switch of the first N-type MESFET (1) or the second N-type MESFET (2) (5) is suspended above its gate (6), and a Schottky contact is formed between the gate (6) of the N-type MESFET and the substrate (11), and the substrate below the gate (6) The depletion layer is formed in (11), and the pull-down voltage of the fixed-beam switch (5) of the N-type MESFET is designed to be equal to the threshold voltage of the ESFET. When loaded on the fixed-beam switch (5) and the pull-down electrode (10) When the voltage between them is greater than the threshold voltage of the MESFET, the fixed beam switch (5) is pulled down and close to the gate (6), and the thickness of the depletion region of the N-type MESFET is reduced and turned on. On this basis, the AC signal is realized Amplify; when the voltage applied between the fixed beam switch (5) and the pull-down electrode (10) is less than the threshold voltage of the MESFET, the fixed beam switch 5 cannot be pulled down, and there is no voltage on its grid (6), the The N-type MESFET cannot be turned on, and the gate leakage current does not exist, which reduces the power consumption of the differential amplifier. 3. The GaN-based low-leakage current solid-supported beam switch differential amplifier according to claim 1, wherein when the differential amplifier is in the working state, the two N-type MESFETs forming the differential pair are the first N-type MESFET ( 1) and the pull-down electrode (10) of the second N-type MESFET (2) are both grounded through a high-frequency choke coil to prevent the AC signal from being lost through the ground, and the AC signal υin is loaded to the two N-type MESFETs through the anchor region 7 Between the fixed beam switch (5), this AC signal is large enough that when it is in the positive half cycle, the fixed beam switch (5) of the first N-type MESFET (1) in the differential pair is pulled down to the gate of the MESFET ( 6) Closely attached, and the first N-type MESFET (1) is turned on, and the second N-type MESFET (2) is in the off state. When the AC signal υin is in the negative half cycle, the situation is opposite, so that the differential amplifier The two N-type MESFETs are in a state of one on and one off alternately with the change of the AC signal. The off state of the MESFET means that the fixed beam switch (5) is in a floating state, that is, the gate of the MESFET (6 ) There is no voltage, and there is no gate leakage current, so when the AC signal υin is input in the circuit, the differential amplifier can amplify the signal and output υout.