A kind of structure and its system based on the low ohm contact resistance of gallium nitride power HEMT structure
Make method
Technical field
The invention belongs to microelectronics technology, specifically a kind of nitrogen based on Sn/Ti/Al/Ti/Au composite construction
Change the production method of gallium HEMT low resistance Ohmic contact, the device of preparation can be used for high-power application.
Background technique
Third generation semiconductor material, that is, broad stopband (Wide Band Gap Semiconductor, abbreviation WBGS) semiconductor
Material is grown up after first generation silicon, germanium and second generation GaAs, indium phosphide etc..In third generation semiconductor material,
Gallium nitride (GaN) have broad-band gap, direct band gap, high breakdown electric field, lower dielectric constant, high electronics saturation drift velocity,
Capability of resistance to radiation by force and the superior property such as good chemical stability, becomes and manufactures the micro- electricity of a new generation after germanium, silicon, GaAs
The key semiconductor material of sub- device and circuit.Especially high temperature, high-power, high frequency and Flouride-resistani acid phesphatase electronic device and all-wave
There is advantageous advantage in terms of long and short wavelength photoelectric device, be to realize high temperature and high-power, high frequency and anti-radiation, all-wave
The ideal material of long photoelectric device, be the new and high technologies such as microelectronics, power electronics, photoelectron and national defense industry, information industry,
The pillar industries such as mechanical and electrical industry and energy industry, which enter after 21 century to rely, continues the key basic material of development.
GaN base HEMT device is on the hetero-junctions that can form two-dimensional electron gas (2DEG) with metalloid semiconductcor field effect
The technique of transistor (MESFET) is answered to be fabricated to, the main conductance between source and drain is provided by 2DEG conducting channel, then by
Schottky gate in AlGaN potential barrier is biased to change the thickness of depletion region, to control the concentration and device of channel 2DEG
The working condition of part." the power GaN: extension, device, application and technology issued according to YoleD é veloppement company's last year
Trend -2017 editions " report, 2016, Global Power GaN market scale had reached 14,000,000 dollars.Power GaN technology with
It is estimated in a short time to show huge market potential by means of its high-performance and high frequency solution applicability.
Summary of the invention
It is an object of the invention to be directed to the difficult point of the high ohmic contact resistance of gallium nitride HEMT power device, from device technology
The optimization angle of preparation process proposes the gallium nitride HEMT low resistance Ohmic contact based on Sn/Ti/Al/Ti/Au composite construction
Production method improves the performance of HEMT device to reduce ohmic contact resistance.
To achieve the above object, each layer of device architecture of the invention is successively arranged from bottom to up, including substrate, low temperature nitride
Gallium nucleating layer, nitride buffer layer, gallium nitride channel layer, aln inserting layer, aluminum gallium nitride barrier layer, drain electrode, source electrode, grid
Electrode and dielectric layer, wherein the both ends of drain electrode and source electrode separation gate electrode, also set between gate electrode and aluminum gallium nitride barrier layer
There is dielectric layer, forms Two-dimensional electron gas channel between aln inserting layer and aluminum gallium nitride barrier layer.
Preferably, the substrate is all material that can be used to epitaxial nitride gallium film, including insulation or semi-insulated
The materials such as sapphire, silicon, silicon carbide, gallium nitride and diamond.
Preferably, low temperature nitride gallium nucleating layer, 400-700 DEG C of growth temperature, film thickness 10-50nm, for being subsequent
Nitride buffer layer growth provide nucleation node, improve gallium nitride film crystalline quality.
Preferably, the nitride buffer layer, to use metal organic source chemical vapor deposition (MOCVD) or other methods
The gallium nitride film layer that unintentional doped growing is formed, film thickness range are 100nm-10um.Its quality directly affects then
The quality of the hetero-junctions of growth, the various lattice defects in the region can also trapped electron, to influence the density of 2DEG.
Preferably, what is formed at the gallium nitride channel layer, aluminum gallium nitride insert layer and AlGaN barrier functions bed boundary is highly concentrated
Spend the channel of 2DEG.
Preferably, the drain electrode and source electrode are closed using tin/titanium/aluminium/titanium/gold (Sn/Ti/Al/Ti/Au) multilayer
Gold.Tin metal layer forms N-type heavy doping with a thickness of 1-20nm, reduces ohmic contact resistance.
Preferably, the gate electrode is conventional Schottky contacts or metal-dielertric-semiconductor structure.
Preferably, the insulating medium layer is SiNxOr SiO2Thin-film material is straight with gate electrode for completely cutting off AlGaN
Contact reduces grid leak electricity, improves device electric breakdown strength.
Preferably, Ohmic contact refers to contact of the Sn/Ti/Al/Ti/Au alloy with AlGaN/GaN, the resistance of contact surface
Value is much smaller than the resistance of semiconductor itself, will not generate apparent additional impedance, will not make inside AlGaN/GaN hetero-junctions
Significant change occurs for equilibrium carrier concentration.When device works, most voltage drop is at behaviour area (Active region)
Without the C-V characteristic in contact surface, during will not influence.In high frequency and high power device, Ohmic contact is to design and manufacture
One of critical issue.
The Ohmic contact is prepared on the principle AlGaN/GaN hetero-junctions using tunnel-effect.Metal and
When semiconductor contact, if doping content of semiconductor is very high, potential barrier sector width can be thinning, and ohmic contact resistance becomes smaller, and electronics is very
It is easy to generate tunnel current by tunnel-effect.Its contact resistance size is defined by formula 1:
Wherein, mn *Indicate that electron effective mass, ε indicate dielectric constant, NDIndicate doping concentration.It can be seen from formula 1
Doping concentration is higher, contact resistance RcSmaller, present invention introduces Sn metal, the first purpose is to improve AlGaN/GaN hetero-junctions
The electron adulterated concentration of the N-type on surface.
The ohmic contact resistance generally uses transmission line model (Transmission Line Model:TLM) to carry out
Measurement.Table top is formed by etachable material surface, is fabricated to a series of a length of W linearly arranged, the rectangular metal electricity that width is d
Pole.A different spacing is all corresponding between every two adjacent electrode, all-in resistance R consists of two parts:
Wherein, Rc is contact resistance size, RSHFor the square resistance of material, L is the spacing of adjacent two electrode.
Preferably, the Schottky contacts refer to contact of the alloys such as Ni/Au with AlGaN/GaN, since the two combines
Contact berrier is higher afterwards, forms Schottky contacts.
Preferably, the Sn/Ti/Al/Ti/Au alloy is prepared using electron beam evaporation method, successively sputter Sn,
Five kinds of materials of Ti, Al, Ti, Au form multiple layer metal, finally form alloy by high annealing.
Preferably, the Ti/Al/Ti/Au is as traditional alloying metal, and wherein Al is natural Ohmic contact material
Material, basic work function is low, using affected for main material;First layer Ti can form TiN, while shape with bottom AlGaN/GaN
At a large amount of vacancy N for playing n-type doping, contact resistance is reduced;Protective layer of the Au as top layer, protects alloy not by air oxygen
Change;Second layer Ti prevents Au from permeating downwards as barrier layer.
Preferably, the Sn is formed with bottom AlGaN/GaN phase separation as the film layer deposited at first and is largely played n
The vacancy N of type doping, reduces contact berrier.
Preferably, the high-temperature annealing process, temperature range are 300 DEG C -1000 DEG C, annealing time 5-300s.
Preferably, the ohmic contact resistance is capable of mutual conductance and the saturation current of effective influence HEMT device.Ohm
Contact resistance is lower, and the mutual conductance of device is higher, and saturation current is bigger, and the electrical characteristics of device are better.
Preferably, the Sn metal layer with a thickness of 3nm, 5nm or 8nm.
Compared with prior art, the invention has the advantages that and technical effect:
The device is a kind of HEMT devices of GaN base, the Ohmic contact formed using this method,
For contact resistance lower than the state of the art (reducing by 0.2 Ω .cm or so), the conducting resistance of device can decline 10%-20%, mutual conductance
Increase 5%-15%, and manufacturing process is simple, reproducible feature.In combination with the original high threshold electricity of device HEMT
Pressure, high-breakdown-voltage, high current density and excellent pinch-off behavior are suitable for high-power electronic device applications.
Detailed description of the invention
Fig. 1 is the structural diagram of the present invention.
Wherein: 101- substrate, 102- nucleating layer, 103- buffer layer, 104- channel layer, 105- insert layer, 106- aluminum gallium nitride
Barrier layer, 107- drain electrode, 108- source electrode, 109- gate electrode, 110- Two-dimensional electron gas channel, 111- dielectric layer.
Specific embodiment
To be easy to understand the technical means, the creative features, the aims and the efficiencies achieved by the present invention, below with reference to
Specific embodiment, the present invention is further explained.
Each layer of device architecture of the invention is successively arranged from bottom to up, comprising: substrate 101, low temperature nitride gallium nucleating layer
102, nitride buffer layer 103, gallium nitride channel layer 104, aln inserting layer 105, aluminum gallium nitride barrier layer 106, drain electrode
107, source electrode 108, gate electrode 109 and dielectric layer 111, wherein drain electrode 107 and source electrode 108 are lived apart the two of gate electrode 109
End, is additionally provided with dielectric layer 111, in aln inserting layer 105 and aluminum gallium nitride gesture between gate electrode 109 and aluminum gallium nitride barrier layer 106
Two-dimensional electron gas channel 110 is formed between barrier layer 106.Device architecture of the invention is prepared by the following method:
Embodiment 1
(1) use MOCVD technology and equipment in the substrate insulation or semi-insulated sapphire, silicon, carbonization of 6inch size
The materials such as silicon, gallium nitride, zinc oxide and diamond carry out AlGaN/GaN heterogenous junction epitaxy.The technology is general traditional technology,
AlGaN/GaN heterojunction structure successively includes GaN buffer layer 102, low temperature GaN nucleating layer 103, GaN channel layer 104, AlGaN gesture
Build the Two-dimensional electron gas channel 110 of the high concentration 2DEG of functional layer 105 and interface formation.
(2) it is deposited using plasma-reinforced chemical deposition method (PECVD) on above-mentioned AlGaN/GaN heterojunction material surface
Layer of sin x film layer is as dielectric layer, with a thickness of 100nm.
(3) above-mentioned material for obtaining step (2) carries out organic washing, will using lithography and etching technology after cleaning
The thin film dielectric layer at hetero-junctions both ends is dispelled, remaining place retains photoresist coating, forms source-drain electrode groove.
(4) by step (3) obtain above-mentioned material carry out organic washing, after cleaning using electron beam evaporation technique into
Row metal deposition.Tin (Sn), titanium (Ti), aluminium (Al), titanium (Ti) and golden (Au) five kinds of metals are sequentially depositing, wherein x value is
10%, the thickness of five layers of metal layer is respectively 3nm, 20nm, 1500nm, 30nm and 100nm.Metal-stripping is used after vapor deposition
Equipment dispels the multiple layer metal above photoresist, forms the figure for only having above-mentioned hetero-junctions both ends just to there is the multiple layer metal
Case.
(5) above-mentioned material for obtaining step (4) carries out organic washing, carries out at annealing after cleaning to above-mentioned material
Reason, annealing temperature are 830 DEG C, annealing time 30s.
(6) above-mentioned material for obtaining step (5) carries out organic washing, will using lithography and etching technology after cleaning
Thin film dielectric layer among hetero-junctions is dispelled, remaining place retains photoresist coating, forms gate electrode groove.
(7) by step (6) obtain above-mentioned material carry out organic washing, after cleaning using electron beam evaporation technique into
Row metal deposition.It is sequentially depositing nickel (Ni), platinum (Pt), golden (Au) and four kinds of metals of titanium (Ti), thickness difference 15nm, 20nm,
5000nm and 5nm.The multiple layer metal above photoresist is dispelled using metal-stripping equipment after vapor deposition, formation only has
Among above-mentioned hetero-junctions just there is the pattern of the multiple layer metal in gate electrode position.
Embodiment 2
(1) use MOCVD technology and equipment in the substrate insulation or semi-insulated sapphire, silicon, carbonization of 6inch size
The materials such as silicon, gallium nitride, zinc oxide and diamond carry out AlGaN/GaN heterogenous junction epitaxy.The technology is general traditional technology,
AlGaN/GaN heterojunction structure successively includes GaN buffer layer 102, low temperature GaN nucleating layer 103, GaN channel layer 104, AlGaN gesture
Build the channel 110 of the high concentration 2DEG of functional layer 105 and interface formation.
(2) it is deposited using plasma-reinforced chemical deposition method (PECVD) on above-mentioned AlGaN/GaN heterojunction material surface
Layer of sin x film layer is as dielectric layer, with a thickness of 150nm.
(3) above-mentioned material for obtaining step (2) carries out organic washing, will using lithography and etching technology after cleaning
The thin film dielectric layer at hetero-junctions both ends is dispelled, remaining place retains photoresist coating, forms source-drain electrode groove.
(4) by step (3) obtain above-mentioned material carry out organic washing, after cleaning using electron beam evaporation technique into
Row metal deposition.Tin (Sn), titanium (Ti), aluminium (Al), titanium (Ti) and golden (Au) five kinds of metals are sequentially depositing, wherein x value is
10%, the thickness of five layers of metal layer is respectively 5nm, 20nm, 1500nm, 30nm and 100nm.Metal-stripping is used after vapor deposition
Equipment dispels the multiple layer metal above photoresist, forms the figure for only having above-mentioned hetero-junctions both ends just to there is the multiple layer metal
Case.
(5) above-mentioned material for obtaining step (4) carries out organic washing, carries out at annealing after cleaning to above-mentioned material
Reason, annealing temperature are 830 DEG C, annealing time 30s.
(6) above-mentioned material for obtaining step (5) carries out organic washing, will using lithography and etching technology after cleaning
Thin film dielectric layer among hetero-junctions is removed, remaining place retains photoresist coating, forms gate electrode groove.
(7) by step (6) obtain above-mentioned material carry out organic washing, after cleaning using electron beam evaporation technique into
Row metal deposition.It is sequentially depositing nickel (Ni), platinum (Pt), golden (Au) and four kinds of metals of titanium (Ti), thickness difference 15nm, 20nm,
5000nm and 5nm.The multiple layer metal above photoresist is dispelled using metal-stripping equipment after vapor deposition, formation only has
Among above-mentioned hetero-junctions just there is the pattern of the multiple layer metal in gate electrode position.
Embodiment 3
(1) use MOCVD technology and equipment in the substrate insulation or semi-insulated sapphire, silicon, carbonization of 6inch size
The materials such as silicon, gallium nitride, zinc oxide and diamond carry out AlGaN/GaN heterogenous junction epitaxy.The technology is general traditional technology,
AlGaN/GaN heterojunction structure successively includes GaN buffer layer 102, low temperature GaN nucleating layer 103, GaN channel layer 104, AlGaN gesture
Build the Two-dimensional electron gas channel 110 of the high concentration 2DEG of functional layer 105 and interface formation.
(2) it is deposited using plasma-reinforced chemical deposition method (PECVD) on above-mentioned AlGaN/GaN heterojunction material surface
Layer of sin x film layer is as dielectric layer, with a thickness of 150nm.
(3) above-mentioned material for obtaining step (2) carries out organic washing, will using lithography and etching technology after cleaning
The thin film dielectric layer at hetero-junctions both ends is dispelled, remaining place retains photoresist coating, forms source-drain electrode groove.
(4) by step (3) obtain above-mentioned material carry out organic washing, after cleaning using electron beam evaporation technique into
Row metal deposition.Tin (Sn), titanium (Ti), aluminium (Al), titanium (Ti) and golden (Au) five kinds of metals are sequentially depositing, wherein x value is
10%, the thickness of five layers of metal layer is respectively 8nm, 20nm, 1500nm, 30nm and 100nm.Metal-stripping is used after vapor deposition
Equipment dispels the multiple layer metal above photoresist, forms the figure for only having above-mentioned hetero-junctions both ends just to there is the multiple layer metal
Case.
(5) above-mentioned material for obtaining step (4) carries out organic washing, carries out at annealing after cleaning to above-mentioned material
Reason, annealing temperature are 830 DEG C, annealing time 30s.
(6) above-mentioned material for obtaining step (5) carries out organic washing, will using lithography and etching technology after cleaning
Thin film dielectric layer among hetero-junctions is dispelled, remaining place retains photoresist coating, forms gate electrode groove.
(7) by step (6) obtain above-mentioned material carry out organic washing, after cleaning using electron beam evaporation technique into
Row metal deposition.It is sequentially depositing nickel (Ni), platinum (Pt), golden (Au) and four kinds of metals of titanium (Ti), thickness difference 15nm, 20nm,
5000nm and 5nm.The multiple layer metal above photoresist is dispelled using metal-stripping equipment after vapor deposition, formation only has
Among above-mentioned hetero-junctions just there is the pattern of the multiple layer metal in gate electrode position.
As known by the technical knowledge, the present invention can pass through the embodiment party of other essence without departing from its spirit or essential feature
Case is realized.Therefore, embodiment disclosed above, in all respects are merely illustrative, not the only.Institute
Have within the scope of the present invention or is included in the invention in the change being equal in the scope of the present invention.