RU2787552C1 - Powerful microwave field transistor - Google Patents

Abstract

FIELD: microwave field-effect transistors.

SUBSTANCE: powerful microwave field-effect transistor is claimed, containing a semi-insulating semiconductor substrate, on the front side of which a given structure of semiconductor layers based on gallium arsenide is made, on the front side of which there is at least one given topology of the passive and active regions of the field-effect transistor, the latter is a sequence of elements - single source, gate, drain electrodes, each with corresponding contact pads, a conductive channel with a groove between each pair of single source-drain electrodes for each single gate electrode, while the single electrodes of the same name - source, gate, drain are electrically connected. In which, on the surface of a given topology of the passive and active regions of the field-effect transistor or on the surface of a given topology of the passive region and on the surface of individual elements of a given topology of the active region, in their various combinations, a highly thermally conductive coating is made of a highly thermally conductive material with thermal conductivity k, thickness H, and the product of thermal conductivity k and thickness H is more than 10^-4 W/K.

EFFECT: increase in specific output power, output power, gain, durability, expansion of functionality.

8 cl, 3 dwg

Description

The invention relates to electronic engineering and can be used as active elements of microwave devices for various purposes and, above all, in a monolithic integrated design.

The output power and power gain (hereinafter referred to as the gain factor) are one of the main output parameters of high-power microwave field effect transistors (hereinafter referred to as the field effect transistor).

At present, possible ways to improve them:

- increasing the width of the gate electrode,

- reduction of thermal and parasitic electrical resistance,

- reduction of parasitic capacitances.

The most well-known are technical solutions in which, in order to increase the width of the gate electrode, a multi-gate design of a powerful microwave field effect transistor is used.

In this case, on the one hand, the greater the width of the common gate electrode, the higher the output power of the field-effect transistor.

However, on the other hand, there are a number of limitations, namely:

- with a sufficiently large width of a single gate electrode, the efficiency of the field-effect transistor decreases, that is, the specific output power per unit width of a single gate electrode due to a significant parasitic resistance of the common gate electrode,

- due to the imperfection of technological equipment and manufacturing technology, the design is characterized by inaccurate alignment of single gate electrodes and, accordingly, non-identity of its channels, the latter leads to a decrease in the efficiency of combining the power of the channels,

- for some sizes of the region of semi-insulating gallium arsenide (less than 4 μm), an increase in the leakage current between the single source-drain electrodes is observed, which leads to the appearance of a drain current gate that is not controlled by a single electrode,

- for some groove sizes (less than 0.5 μm) in pairs of single electrodes source - drain, in which single gate electrodes are located, there is a decrease in the breakdown voltage between the single electrodes gate - source and gate - drain.

And, as a consequence of this, there is a slight decrease in the output power and the gain of the microwave field effect transistor.

These shortcomings of the microwave field effect transistor with a multi-gate design have been successfully solved by the following technical solutions.

In order to reduce the parasitic resistance of the common gate electrode, the field-effect transistor is made in the form of a so-called comb of an alternating sequence of single source-gate-drain electrodes, while the single gate electrodes are located in the grooves of the channels made between the single source-drain electrodes. [“Field-effect transistors based on gallium arsenide. Operating principles and manufacturing technology, Ed. D.V. Di Lorenzo, D.D. Candeluola. Translation from English, ed. G.V. Petrova, M.: Radio and communication, 1988, p.118].

In order to eliminate the inaccuracy of matching the single gate electrodes of the field-effect transistor and, accordingly, the non-identity of its channels and, accordingly, the decrease in the efficiency of channel power addition, areas of semi-insulating gallium arsenide are located between pairs of single source-drain electrodes, the length of single gate electrodes located in pairs of single source-drain electrodes (not more than 0.7 μm), and at the same time, single gate electrodes are made in the grooves of the channels asymmetrically towards the single source electrodes. [“Powerful GaAs field-effect microwave transistors with a biased gate”, authors Lapin V.G., Krasnik V.A., Petrov K.I., Temnov A.M. Eleventh International Conference "Microwave Engineering and Telecommunication Technologies". Collection of materials of the conference September 10-14, 2001, Sevastopol, Crimea, Ukraine, p.135].

In order to reduce the leakage current between single electrodes source - drain and increase the breakdown voltage between single electrodes gate - source and drain - gate, the width of the semi-insulating gallium arsenide region, the width (0.9-1.3) μm and the depth (0. 2-0.3) µm grooves, the location of single gate electrodes in the grooves of the channels (at a distance equal to 0.1-0.3 and 0.5-0.7 µm, respectively. [Patent 2307424 of the Russian Federation. Powerful microwave field effect transistor with a Schottky barrier /Lapin VG and others// Bull. - 2007 - No. 3].

This made it possible to significantly increase the output power of the microwave field effect transistor.

The output power of these microwave field effect transistors is about (750, 1000) mW, the gain is about (10, 12) dB at a frequency of 10 GHz.

However, this field-effect transistor is distinguished by a rather large thickness of the semi-insulating gallium arsenide substrate under the active region (about 100 µm) and a rather small thickness (about 10 µm) in the region of maximum heat removal (metallized hole for grounding the electrodes).

This makes it difficult to ensure a dense packing of single electrodes source - gate - drain, which determines the high weight and size characteristics and makes it difficult to use a monolithic microwave integrated circuit in the crystal.

A powerful microwave field effect transistor is known, containing a semiconductor substrate with a given layer structure, on the front side of which there is at least one given topology of the elements of the active region of the field effect transistor, which is a sequence of single source, gate, drain electrodes, a conductive channel with a groove between each pair single electrodes source - drain for a single gate electrode, a protective coating of the elements of the active region of the field-effect transistor crystal, a metallized hole for grounding the common source electrode, an integral heat sink from a highly heat- and electrically conductive material on the reverse side of the semiconductor substrate, while the same-named single drain and gate electrodes , source connected electrically.

In which, in order to increase the output power and gain, reduce the weight and size characteristics, the semiconductor substrate is made in the form of a direct sequence of a semi-insulating layer, n ⁺ -type conductivity layer, stop layer, buffer layer, active layer, with a thickness of semi-insulating and buffer layers ( not less than 30.0) and (1.0-20.0) µm, respectively, a part of the metallized hole on the front side of the semiconductor substrate at a depth equal to the sum of the thicknesses of the active, buffer and stop layers is made with a metallized bottom, and the other part of the metallized hole from the reverse side of the semiconductor substrate to a depth equal to the sum of the thicknesses of the semi-insulating and n ⁺ -type conductivity layers, it is blind in the form of a continuous layer of highly thermally and electrically conductive material, while asymmetrically towards the common drain electrode relative to the vertical axis of the metallized hole, with the size cross section equal to the size of the cross section then the elements of the active region of the field-effect transistor, wherein the mentioned parts of the metallized hole overlap completely or partially in the horizontal plane of the place of their contact, and the integral heat sink is simultaneously a continuous layer of highly heat- and electrically conductive material of the other part of the metallized hole. [Patent 2463685 RF. Powerful microwave field effect transistor /Vorobiev A.A. et al. //Bul. - 2012 - No. 28] - prototype.

The presence in this powerful microwave field-effect transistor of an integral heat sink with a thickness of about 30 microns made it possible:

firstly, to reduce the thickness of the semiconductor substrate to 30 microns, and thereby reduce its thermal resistance and thereby increase heat removal and, as a result, increase the output power,

secondly, to increase the packing density of single electrodes of the source, gate, drain and thereby reduce the weight and size characteristics, and thereby the possibility of using this powerful microwave field effect transistor as part of a crystal of a monolithic microwave integrated circuit.

However, the output power of this powerful microwave field effect transistor is not high enough in some cases of its application.

The technical result of the claimed powerful microwave field effect transistor is to increase the specific output power, output power, gain, durability, and expand functionality.

The specified technical result is achieved by the claimed powerful microwave field effect transistor containing a semi-insulating semiconductor substrate, on the front side of which a given structure of semiconductor layers based on gallium arsenide is made, on the front side of the latter there are elements of at least one active area of the field effect transistor, while the active area contains single source, gate, drain electrodes, a channel with a groove between each pair of single source-drain electrodes for each single gate electrode.

Wherein

on the front side of the elements of the active region of the field-effect transistor or on the front side of individual elements of the active region in their various combinations, a heat-conducting coating is made, from a highly heat-conducting material, with thermal conductivity k, thickness H , and the product of thermal conductivity k and thickness H is more than 10 ^{- 4} W/K.

The specified structure of semiconductor layers based on gallium arsenide is made in the form of a homostructure or heterostructure.

Elements of at least one active area of the field-effect transistor are made according to its given topology.

A highly thermally conductive coating is provided between the single gate-drain electrodes and the single drain electrode itself.

A highly heat-conducting coating is made on the surface of the groove between the single electrodes source - gate, gate - drain and the single electrodes of the source, gate and drain.

The field-effect transistor additionally contains an integrated heat sink made of a highly heat- and electrically conductive material, made on back side of the semi-insulating semiconductor substrate.

Between the elements of the active region or between any set of elements of the active region and a highly heat-conductive coating, a protective coating is made, with a thickness of less than 0.1 μm.

The field-effect transistor is made in the form of a single - discrete crystal, or as part of a crystal of a monolithic microwave integrated circuit.

The protective coating can be applied in any way outside the active region of the transistor

The thermally conductive coating can be applied in any way outside the active region of the transistor, both on the protective coating and on the surface of the semiconductor.

Disclosure of the essence of the invention.

The totality of the essential features of the claimed claims, both the restrictive part and the distinctive part, viz.

Execution on the front side of the elements of the active region of the field-effect transistor or on the front side of individual elements of the active region in their various combinations of a heat-conducting coating, from a highly heat-conducting material with thermal conductivity k, thickness H , and the product of thermal conductivity k and thickness H is more than 10 ^-4 W/K.

Implementation of a highly thermally conductive coating between the single gate-drain electrodes and the single drain electrode itself.

Implementation of a highly thermally conductive coating on a channel with a groove between the electrodes source - gate, gate - drain and the individual electrodes of the source, gate, drain.

It provides.

Firstly, the reduction of sharp temperature drops in the active region of the field-effect transistor and, thereby, uniform heat removal to the semi-insulating semiconductor substrate from all active elements of the active region of the field-effect transistor, and thus the maximum temperature decrease in the most heated parts of the active elements of the active region of the field-effect transistor, and thereby the maximum reduction in the total thermal resistance of the active elements of the active region of the field-effect transistor and, as a result, -

- increase in specific output power,

- output power,

- amplification factor,

- durability.

Secondly, the optimization of the structural and functional capabilities of a highly heat-conducting coating and, thereby, the possibility of implementing a dense packing of single source, gate, and drain electrodes, and thus the possibility of using this design of a field-effect transistor, both in the form of a single discrete crystal, and in the composition of the crystal of a monolithic microwave integrated circuit and, as a result, -

- reduction of weight and size characteristics,

- expansion of functionality.

The presence in a high-power microwave field-effect transistor of an additional integral heat sink made of a highly heat- and electrically conductive material, made on the reverse side of a semi-insulating semiconductor substrate, makes it possible to maximally thin the semiconductor substrate (up to a thickness of about 30 μm) and thereby increase heat removal, and thereby reduce thermal resistance of the semiconductor substrate and, as a result, an additional increase in the specific output power, output power, gain, durability.

The implementation between the elements of the active region of the field-effect transistor or between the single electrodes of the gate-drain and the very single electrode of the drain of the elements of the active region and the highly thermally conductive coating of the protective coating with a thickness of less than 0.1 μm ensures the durability of the transistor while maintaining low thermal resistance between the channel of the field-effect transistor and the substrate and, as a consequence, an additional increase in the specific output power, output power, gain, durability.

The presence of a heat-conducting coating outside the active region when applied inside the active region by any of the above methods leads to an additional decrease in the thermal resistance between the FET channel and the substrate, as a result, an additional increase in the specific output power, output power, gain, durability.

The possibility of using a given structure of semiconductor layers based on gallium arsenide both in the form of a homostructure and in the form of a heterostructure, as well as the given design of a powerful microwave field effect transistor, both in the form of a single discrete crystal, and as part of a crystal of a monolithic microwave integrated circuit, provides expansion functionality.

The possibility of using this powerful microwave field effect transistor as part of a monolithic microwave integrated circuit crystal is extremely relevant today.

The execution of a heat-conducting coating from a highly heat-conducting material, when the product of its thermal conductivity k and thickness H is less than 10 ^-4 W/K, is unacceptable, since this almost completely eliminates the specified technical result, and

The execution of a heat-conducting coating by several orders of magnitude more than 10 ^-4 W/K is limited only by technological capabilities.

The implementation of a protective coating with a thickness of more than 0.1 μm is not desirable, since it leads to a significant increase in the thermal resistance of the field-effect transistor.

So, the claimed powerful microwave field effect transistor fully provides the specified technical result - increasing the specific output power, output power, gain, durability, expanding functionality.

The invention is illustrated by drawings.

In FIG. 1 shows a schematically declared powerful microwave field effect transistor, the section is when a highly heat-conducting coating is made on the front side of the elements of the active region, where

- semi-insulating semiconductor substrate - 1,

- on the front side, which made a given structure of semiconductor layers based on gallium arsenide - 2,

one given topology of the elements of the active region of the field-effect transistor, which are

- a sequence of single electrodes - source, gate, drain - 3, 4, 5, respectively,

- conductive channel - 6 with a groove - 7,

- protective coating - 8 elements of the active area of the field effect transistor,

- coating of highly heat-conducting material - 9,

- integral heat sink - 10 of highly heat and electrically conductive material on the reverse side of the semi-insulating semiconductor substrate.

And special cases of execution, when a highly thermally conductive coating is made:

between the single electrodes of the gate - drain and the single electrode of the drain of the elements of the active region (Fig. 1a);

on the channel with a groove between the single electrodes source - gate, gate - drain and the single electrodes of the source, gate, drain elements of the active region of the field effect transistor (Fig. 1 b).

A powerful microwave field effect transistor works as follows.

The required bias voltages from external sources are applied to the individual gate and drain electrodes of the microwave field effect transistor. At the same time, negative ones are applied to the individual gate electrodes, and positive ones to the individual drain electrodes relative to the individual source electrodes. A microwave signal is fed to single gate electrodes, which is amplified by a field-effect transistor and fed to its output - a drain electrode.

Examples of specific implementation.

Example 1

On the front side of the semi-insulating semiconductor substrate 1 made of GaAs AGChP-76.2-450-(100)2.5(110)-EJ-DSP TU 6365-01-52692510-2010, a given structure of semiconductor layers based on gallium arsenide 2 is made - a heterostructure as a direct sequence of the following semiconductor layers:

- buffer layer, 0.6 µm thick,

- unalloyed Al _0.3 Ga _0.7 As layer, 0.05 µm thick,

- doped GaAs layer, doped with silicon, with a dopant concentration of 10 ¹⁹ cm ^-3 , 0.001 μm thick,

- unalloyed Al _0.3 Ga _0.7 As layer, 0.002 µm thick,

- undoped GaAs layer, 0.002 µm thick,

- undoped In _0.17 Ga _0.83 As layer, 0.013 µm thick,

- undoped GaAs layer, 0.002 µm thick,

- unalloyed Al _0.3 Ga _0.7 As layer, 0.002 µm thick,

- doped GaAs layer, doped with silicon, with dopant concentration 2×10 ¹⁹ cm ^-3 , thickness 0.001 μm,

- unalloyed Al _0.3 Ga _0.7 As layer, 0.02 µm thick,

- undoped GaAs layer, 0.02 µm thick,

- doped layer GaAs, doped with silicon, with a dopant concentration of 5×10 ¹⁸ cm ^-3 , a thickness of 0.05 μm (contact layer).

On the front side of the heterostructure of semiconductor layers 2, one active region of the field-effect transistor is made according to its given topology, while the active region contains - single electrodes of source 3, gate 4, drain 5, channel 6 with a groove 7, single electrodes of source 3 - drain 5 under a single electrode shutter 5.

On the front side of the elements of the active region of the field-effect transistor, a heat-conducting coating 9 is made, from a highly heat-conducting material - polydiamond, with a specific thermal conductivityk equal to 1000 W/K/m, thicknessH equal to 5 µm, (while their product is equal tofive×10^-3 W/K, which is more than 10^-four) (Fig. 1).

Examples 2-3.

Similarly to example 1, samples of a powerful field-effect transistor were made, but with other design parameters of Fig.1.

Example 4

Similarly to example 1, samples of a powerful field-effect transistor (its special cases of its implementation) were made (Fig. 1 a, b).

The given structure is made in the form of a homostructure

the heat-conducting coating 13 is made.

Between the single electrodes gate 4 - drain 5 and the very single electrode drain 5 of the elements of the active region and on the elements outside the active region of the field-effect transistor (Fig. 1a).

On channel 6 with a groove 7 between single electrodes, source 5 - gate 6 and gate 6 - drain 7, and the single electrodes themselves of the source, gate, drain elements of the active region of the field-effect transistor (Fig. 1 b).

In this case, this sample of a powerful field-effect transistor contains:

- integral heat sink 10;

- between the said surface of the single electrodes gate 4 - drain 5 and the single drain electrode 5 of the elements of the active region of the field-effect transistor and the highly heat-conducting coating 9, a protective coating 8 is made, with a thickness of less than 0.1 microns.

At the same time, this structure of semiconductor layers based on gallium arsenide 2 is made in the form of a homostructure, a direct sequence:

- semi-insulating layer,

- n ⁺ -type conductivity layer, 30.0 µm thick,

- stop layer,

- buffer layer, 10 microns thick,

- active layer, (Fig.1 a, 1 b).

Example 5 corresponds to the prototype.

On the manufactured samples of a powerful microwave field effect transistor, the electrical parameters were measured by the method of matching transformers, namely, specific output power (W/mm), output power W, gain (dB) at a frequency of 10 GHz.

The durability was determined when operating in continuous mode with the maximum output power output experimentally and by calculation .

The data are presented in the table.

As can be seen from the table, the indicated parameters of the declared powerful field-effect transistor are approximately:

- specific output power 1.0 W/mm,

- output power 0.8 W,

- gain 10.5 dB,

- durability (5-10)×10 ⁶ hours (examples 2-4).

In contrast to the prototype sample, which has approximately a specific output power of 0.8 W/mm, an output power of 0.65 W, a gain of 9.5 dB, a durability of 10 ⁶ hours.

Thus, the claimed powerful microwave field effect transistor, in comparison with the prototype, will provide an increase in:

- specific output power by 10-15 percent,

- output power by 10-15 percent,

- gain by 10-15 percent,

- durability in 2-3 times.

POWERFUL MICROWAVE FIELD TRANSISTOR

Table No. Structural parameters of a powerful field-effect transistor Measurement results High thermal conductivity coating Protective covering Material Specific thermal conductivity
k (W/m/K) Thickness H (µm) H×k Material Thickness (µm) Output power (W) Specific power (W/mm) Coef. gain (dB) Durability (h) 1 Corresponds to note 1 and figure 1, paragraph 1 polydiamond 1000 5.0 5×10 ^-3 W/K Si ₃ N ₄ 0.005 0.8 1.0 10.5 9⋅10 ⁶ 2 Corresponds to figure 1 a polydiamond 1000 1.0 10 ^-3 W/K Si ₃ N ₄ 0.005 0.76 0.95 10.4 5⋅10 ⁶ 3 Corresponds to Fig.1 b polydiamond 1000 50.0 5×10 ^-2 W/K _SiO2 0.005 0.81 1.01 10.51 10⋅10 ⁶ four polydiamond 1000 0.1 10 ^-4 W/K Si ₃ N ₄ 0.01 0.661 0.826 10.0 1.5⋅10 ⁶ 5 Prototype No high thermal conductivity coating Si ₃ N ₄ 0.005 0.66 0.825 10.0 10 ⁶

Claims (8)

1. A powerful microwave field effect transistor containing a semi-insulating semiconductor substrate, on the front side of which a given structure of semiconductor layers based on gallium arsenide is made, on the front side of the latter there are elements of at least one active region of the field effect transistor, while the active region contains single source electrodes, gate, drain, channel with a groove between each pair of single electrodes, source - drain for each single gate electrode, characterized in that on the front side of the elements of the active region of the field-effect transistor or on the front side of the individual elements of the active region in their various combinations, a heat-conducting coating of highly thermally conductive material with thermal conductivity k, thickness H, and the product of thermal conductivity k and thickness H is more than 10 ^-4 W/K. 2. Powerful microwave field effect transistor according to claim 1, characterized in that the given structure of semiconductor layers based on gallium arsenide is made in the form of a homostructure or heterostructure. 3. A powerful microwave field effect transistor according to claim 1, characterized in that a highly thermally conductive coating is made between the single gate-drain electrodes and the single drain electrode itself. 4. Powerful microwave field effect transistor according to claim 1, characterized in that the highly thermally conductive coating is made on the channel with a groove between the single electrodes source - gate, gate - drain and the single electrodes of the source, gate, drain. 5. A powerful microwave field-effect transistor according to claim 1, characterized in that the field-effect transistor additionally contains an integrated heat sink made of a highly heat- and electrically conductive material, made on back side of the semi-insulating semiconductor substrate. 6. A powerful microwave field effect transistor according to claim 1, characterized in that a protective coating less than 0.1 µm thick is made between the elements of the active region and the highly thermally conductive coating. 7. A powerful microwave field-effect transistor according to claim 1, characterized in that the field-effect transistor is made in the form of a single discrete crystal or as part of a crystal of a monolithic microwave integrated circuit. 8. Powerful microwave field effect transistor according to paragraphs. 1-7, characterized in that the heat-conducting coating is applied in any way outside the active area.

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