CN103972069A - Method for manufacturing AlGaN-GaN heterojunction ohmic contact - Google Patents
Method for manufacturing AlGaN-GaN heterojunction ohmic contact Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 42
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 10
- 229910002704 AlGaN Inorganic materials 0.000 claims abstract description 66
- 239000000463 material Substances 0.000 claims abstract description 57
- 229910052751 metal Inorganic materials 0.000 claims abstract description 37
- 239000002184 metal Substances 0.000 claims abstract description 37
- 238000005530 etching Methods 0.000 claims abstract description 28
- 238000000137 annealing Methods 0.000 claims abstract description 20
- 230000008569 process Effects 0.000 claims abstract description 11
- 238000001259 photo etching Methods 0.000 claims abstract description 4
- 229920002120 photoresistant polymer Polymers 0.000 claims description 20
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 14
- 239000008367 deionised water Substances 0.000 claims description 7
- 229910021641 deionized water Inorganic materials 0.000 claims description 7
- 238000001312 dry etching Methods 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- 230000008020 evaporation Effects 0.000 claims description 6
- 238000001704 evaporation Methods 0.000 claims description 6
- 238000001020 plasma etching Methods 0.000 claims description 6
- 230000015572 biosynthetic process Effects 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 4
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- 230000008901 benefit Effects 0.000 abstract description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 abstract 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 abstract 1
- 229910052782 aluminium Inorganic materials 0.000 abstract 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 abstract 1
- 239000010931 gold Substances 0.000 abstract 1
- 229910052737 gold Inorganic materials 0.000 abstract 1
- 229910052759 nickel Inorganic materials 0.000 abstract 1
- 239000010936 titanium Substances 0.000 abstract 1
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- 238000005755 formation reaction Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000005468 ion implantation Methods 0.000 description 3
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/41—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions
- H01L29/417—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions carrying the current to be rectified, amplified or switched
- H01L29/41725—Source or drain electrodes for field effect devices
- H01L29/41766—Source or drain electrodes for field effect devices with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/28—Manufacture of electrodes on semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/268
- H01L21/283—Deposition of conductive or insulating materials for electrodes conducting electric current
- H01L21/285—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation
- H01L21/28506—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers
- H01L21/28575—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising AIIIBV compounds
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
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- H01L29/2003—Nitride compounds
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
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- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/778—Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface
- H01L29/7786—Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface with direct single heterostructure, i.e. with wide bandgap layer formed on top of active layer, e.g. direct single heterostructure MIS-like HEMT
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Abstract
The invention discloses a method for manufacturing AlGaN-GaN heterojunction ohmic contact. The problems that in the prior art, contact resistance is large, the process is complex, and cost is high are mainly solved. The method comprises the manufacturing steps that (1), photoetching is carried out on the surface of AlGaN-GaN heterojunction, an etching mask with a plurality of through holes on an ohmic electrode region is obtained, and the sum of the areas of the exposed parts of the through holes is 15 percent to 45 percent of the area of an ohmic electrode; (2), etching hole digging with the depth of 5 nm to 15 nm is carried out on AlGaN materials exposed out of the through holes of the mask; (3), titanium/aluminum/nickel/gold multilayer metal is deposited on the AlGaN-GaN materials of a source region and a drain region with holes dug; (4), annealing of 800 DEG C to 870 DEG C is carried out on deposited electrode metal, and a source and drain ohmic contact electrode is formed. The method has the advantages that the process is simple and easy to control, and the ohmic contact resistance is low, and the method can be used for manufacturing AlGaN-GaN heterojunction high-frequency high-power high-electronic devices high in work efficiency and high in grain.
Description
Technical field
The invention belongs to microelectronics technology, relate to semi-conducting material, element manufacturing, a kind of manufacturing process of semiconductor device ohmic contact specifically, can be used for making AlGaN/GaN heterojunction electronic device.
Background technology
Be with wide bandgap semiconductor with characteristics such as its large energy gap, high breakdown electric field, high heat conductance, high saturated electrons speed and heterojunction boundary two-dimensional electron gas height taking SiC and GaN as the 3rd of representative in recent years, make it be subject to extensive concern.In theory, utilize the devices such as high electron mobility transistor (HEMT) that these materials make, LED, laser diode LD to there is obvious advantageous characteristic than existing device, therefore researcher has carried out extensive and deep research to it both at home and abroad in the last few years, and has obtained the achievement in research attracting people's attention.
AlGaN/GaN heterojunction high electron mobility transistor (HEMT) is demonstrating advantageous advantage aspect high-temperature device and HIGH-POWERED MICROWAVES device, and pursuit device high-frequency, high pressure, high power have attracted numerous research.In recent years, the demand of AlGaN/GaN heterojunction High Electron Mobility Transistor aspect the high frequency power amplifier of radar application is more and more urgent, and how being optimized and improving from material structure and device structure design is mainly studying a question of facing now.Make device application under larger power and obtain higher efficiency, good source, to leak ohmic contact characteristic essential.At present, the energy gap that AlGaN/GaN heterojunction is larger because AlGaN has, is relatively difficult to search out suitable metal material and directly forms the ohmic contact that contact resistance is less.The method generally adopting is to form alloy effect with the metal Ti of low work function and material surface through annealing, increases tunnelling probability, utilizes tunnelling to reduce contact resistance, forms the ohmic contact of low additional impedance.The metal ingredient and the annealing temperature that are used to form alloy are known together at present substantially, for AlGaN/GaN heterojunction, adopt Ti/Al/Ni/Au multiple layer metal more, and Ti/Al ratio is 1:4～1:8; It is 800 DEG C～870 DEG C that annealing process condition adopts temperature conventionally, the rapid thermal annealing of 30～60s.Referring to Chaturvedi N, Zeimer U, Wurfl J, et al.Mechanismofohmic contact formation in AlGaN/GaN high electron mobility transistors[J] .Semicond SciTechnoi, 2006,21 (22): 175-179.
But along with the requirement of further raising device property, the technique of ohmic contact also needs to update on AlGaN/GaN heterojunction, constantly to reduce series resistance, reduces ghost effect, increase amplifying power and the efficiency of device.Current researcher improves ohmic contact method and mainly contains several below:
1. adopt the method for Implantation directly to carry out N-shaped dopant implant to source, drain regions, increase the doping content of contact layer, and then improve tunnelling probability and tunnelling current, reach the object that reduces ohmic contact resistance.Referring to Haijiang Yu, L.McCarthy, S.Rajan, et al, Ion Implanted AlGaN – GaN HEMTs With Nonalloyed Ohmic Contacts, IEEE Electron Device Letters, 2005,26 (5): 283-285.The method adopts ion implantation technology to increase the doping content of contact area, has increased charge carrier tunnelling probability, thereby has reduced contact resistance.But processing step relates to Implantation, technique is comparatively complicated, and cost is higher, and the injection of energetic ion also can be introduced new material surface damage.And the activation energy of impurity is very high in GaN based material, the N-shaped doping ion of injection needs 1000 DEG C of above annealing temperatures to activate, and this activated at technique may produce negative impact to other performances of material.
2. adopt source, leak Ohmic electrode district material etching reduction process, reduce source, drain contact resistance.Utilize dry plasma etch technology, the barrier layer of source, the side of leaking down is carried out to etching, reduce the distance of ohmic contact to two-dimensional electron gas, even metal directly touches 2DEG, thereby reduces ohmic contact resistance.Referring to W.S.Lau, J.B.H.Tan, B.P.Singh, at500 DEG C of by Ohmic contactrecess etching of Formation of Ohmic contacts in AlGaN/GaN HEMT structures, Microelectronics Reliability, 2009,49:558 – 561.The method can reduce ohmic contact resistance, even can adopt lower annealing temperature to form good ohmic contact, and this technique is simple compared with ion implantation technology.But because AlGaN layer in AlGaN/GaN heterojunction is generally less than 30nm, and dry etching speed is difficult to accurately control and etching poor repeatability, causes source-drain area AlGaN layer etching depth accurately to realize.If larger to source, drain region entirety etching depth, will damage all Two-dimensional electron gas-bearing formations in source-drain area below, device current is reduced, device property variation, therefore stability and repeatable poor.
3. the method for employing source, drain region etching regrowth N-shaped GaN reduces source-drain contact resistance, first source, drain region are carried out to etching, then in the source etching away, drain region growing n-type heavy doping GaN material, then on this n-GaN, carry out the metal deposit of ohmic contact.Referring to Liang Pang, Hui-Chan Seo, Patich Chapman, et al, Breakdown VoltageEnhancement of AlGaN/GaN High-Electron-Mobility Transistors via Selective-Area Growth forOhmic Contacts over Ion Implantation, Journal of ELECTRONIC MATERIALS, 2010,39 (5): 499-503.This method utilizes the high-dopant concentration of n-GaN to improve current tunnelling effect, though can obtain good ohmic contact characteristic, but adopt regrowth method complex process, should carry out etching, need again to regrow, also face the possibility of the material contamination in secondary material growth course, cost is very high.
4. adopt Ti/Al/Ti/Al/Ti/Al superlattice structure to make ohmic contact, i.e. the Ti/Al/Ti/Al/Ti/Al superlattice metal-layer structure of life cycle growth, replaces conventional Ti/Al double-layer metal structure, then deposit Ni/Au layer, realizes ohmic contact.Referring to Gong RM, Wang JY, Dong ZH, et al.Analysis On The New Mechanisms Of LowResistance Stacked Ti/al Ohmic Contact Structure On AlGaN/GaN Hemts[J] .Journal Of PhysicsD-applied Physics, 2010 (39).But this technique is ripe not enough, and the contact resistance of reporting improves effect and process mechanism need further checking.
5. adopt process of surface treatment to improve ohmic contact characteristic, before carrying out ohmic metal deposit, use acid, aqueous slkali and the semi-conductive contact-making surface of plasma treatment, remove oxide layer and the damage layer of contact interface, to make to obtain better ohmic contact effect after depositing metal.Referring to Selvanatiand D, Mohammed F M, Bae J O, et al, Investigation of surface treatment schemes on n-type GaN andAl0.2Ga0.8N[J] .JVST, 2005, B23 (6): 2538-2544.This technique is carried out surface treatment can remove oxide layer and damage layer, roughening contact surface, to reach better metal, semiconductor contact effect, and may introduce N room, the effect that similar alms giver can be played in N room in GaN or AlGaN material, therefore can improve ohmic contact effect.But this technique is limited to the improvement degree of ohmic contact, conventionally need to be used in conjunction with additive method.
Summary of the invention
The object of the invention is to the deficiency for above-mentioned prior art, a kind of improved AlGaN/GaN heterojunction Ohm contact production method is provided, to reduce contact resistance and process complexity, reduce costs, improve the stability of device and the repeatability of technique.
For achieving the above object, technical scheme of the present invention comprises the steps:
(1) AlGaN/GaN material is cleaned;
(2) source of the AlGaN/GaN material surface after cleaning, leakage Ohmic electrode district carry out photoetching, make the photoresist mask with a lot of through holes, and the area sum of these through holes is 15%～45% of the Ohm contact electrode gross area; In through hole, expose AlGaN material;
(3) utilize dry etching to carry out etching to the AlGaN material exposing in photoresist mask through hole, obtain source, leak Ohmic electrode district and dig the AlGaN material in a lot of holes, the borehole degree of depth is 5～15nm; Removal photoresist mask after etching completes;
(4) in the whole source of borehole, leak on the AlGaN material in Ohmic electrode region, deposit Ti/Al/Ni/Au multiple layer metal, and carry out 800～870 DEG C of annealing 30～60s, formation source, leaks Ohm contact electrode.
AlGaN/GaN material is cleaned in above-mentioned steps (1), carry out as follows:
First AlGaN/GaN heterojunction material is positioned in the HF solution of 1:5 and soaks 30s, remove surface oxide layer;
Again AlGaN/GaN heterojunction material is positioned over to acetone, ethanol organic solvent for ultrasonic and cleans, remove surface contamination, and with deionized water rinsing 5 minutes.
Dry etching in above-mentioned steps (3), its process conditions are as follows:
Adopt RIE reactive ion etching, reacting gas is Cl
2, its flow 40sccm,
Reative cell pressure is 10mT,
Electrode power is 50W,
Etch rate is 0.5nm/s.
Multiple layer metal deposit in above-mentioned steps (4), is undertaken by electron beam evaporation equipment, and process conditions are:
Evaporation initial vacuum degree reaches 10
-7below Tor, evaporation of metal speed is 0.3nm/s.
Deposit Ti/Al/Ni/Au multiple layer metal in above-mentioned steps (4), its thickness respectively: Ti is 20～30nm, and Al is 150～250nm, and Ni is 40～60nm, and Au is 60～100nm.
Annealing in above-mentioned steps (4), use equipment is RTP rapid thermal anneler, carries out as follows:
First, carry out deaeration to the N2 that passes into 10min in annealing furnace;
Then, the speed of 20 DEG C/s is warming up to the temperature setting;
Finally, in annealing furnace, pass into N2 with the speed of 3L/s, anneal by the time setting.
Tool of the present invention has the following advantages:
1) the present invention due in source, leak Ohm contact electrode district borehole, the lateral side regions in hole has increased the contact area of ohmic metal material and semiconductor surface, affect barrier shape, increased the possibility that forms tunnelling current, therefore can reduce ohmic contact resistance.
2) the present invention, because the hole that it digs has certain depth, makes after depositing metal, and in hole, metal reduces to the distance of two-dimensional electron gas, thereby has reduced ohmic contact resistance.
3) the present invention is only used on the basis of traditional handicraft increases a photoetching and etching technics, and therefore technique is relatively simple, and other compatible follow-up techniques, there is no stability problem.
4) the present invention subregion of AlGaN at source and drain that be etching, little on two-dimensional electron gas impact; Even and etching depth has deviation, can not destroy source, drain electrode below two-dimensional electron gas completely yet, ensure the stable of source that device forms, leakage current.
Brief description of the drawings
Fig. 1 is the fabrication processing schematic diagram of device of the present invention;
Fig. 2 adopts the ohmic contact that completes of technique of the present invention and the resistance data comparison diagram of traditional ohmic contact;
Fig. 3 adopts the ohmic contact that completes of technique of the present invention and the source-drain current comparison diagram of traditional ohmic contact.
Embodiment
The present invention provides following three kinds of embodiment:
Embodiment 1: making hole depth is 5nm, the ohmic contact that metal Ti/Al/Ni/Au thickness is 20nm/150nm/40nm/60nm.
With reference to Fig. 1, the performing step of this example is as follows:
Step 1. is cleaned AlGaN/GaN heterojunction material sample.
1.1) AlGaN/GaN heterojunction material sample is positioned in the HF solution of 1:5 and soaks 30s, remove surface oxide layer;
1.2) AlGaN/GaN heterojunction material sample is positioned over to acetone, ethanol organic solvent for ultrasonic and cleans, remove surface contamination, and with deionized water rinsing 5 minutes.
Step 2. Ohmic electrode district borehole.
2.1) with photoresist spinner, with the rotating speed of 5000 turn/min, the AlGaN/GaN heterojunction material sample surfaces after cleaning gets rid of the positive glue EPI621 of 0.6 μ m, the high temperature oven of the AlGaN/GaN heterojunction material that has got rid of glue being put into temperature again and be 110 DEG C is dried 1min, then adopt NSR1755I7A mask aligner to expose, finally develop, obtain the photoresist mask of Ohmic electrode region with some through holes, the area sum of these through holes is 45% of the Ohm contact electrode gross area;
2.2) adopt RIE plasma dry etching machine, at Cl
2under the plasma environment of gas, adopt the etching power of 50W, the AlGaN material exposing in the speed etching photoresist mask through hole with 0.5nm/s digs out the hole that some degree of depth are 5nm on the AlGaN material in source, leakage Ohmic electrode district;
2.3) AlGaN/GaN heterojunction material sample is placed on after completing etching, first use acetone soln ultrasonic cleaning 3 minutes, then use ethanolic solution ultrasonic cleaning 3 minutes, finally in deionized water, rinse 3 minutes, the photoresist mask that etching is used is removed completely.
Step 3. source, leakage Ohm contact electrode are made.
3.1) the first rotating speed with 2000 turn/min with photoresist spinner, whole AlGaN material surface get rid of thickness be 0.35 μ m peel off glue PMGI SF6, then with the rotating speed of 5000 turn/min, on peel off glue PMGI SF6, getting rid of thickness is the positive glue EPI621 of 0.6 μ m;
3.2) the AlGaN/GaN heterojunction material that has got rid of glue being put into temperature is that the high temperature oven of 110 DEG C is dried 1min, then adopts NSR1755I7A mask aligner to expose, and finally develops, and is only exposed the photoresist mask of AlGaN electrode zone with holes;
3.3) adopt the evaporation rate of Ohmiker-50 electron beam evaporation platform with 0.3nm/s, on AlGaN material with holes, carry out the deposit of source-drain electrode metal, source-drain electrode metal is selected Ti/Al/Ni/Au successively, wherein Ti thickness is 20nm, Al thickness is 150nm, Ni thickness is 40nm, and Au thickness is 60nm;
3.4) complete after the deposit of electrode metal, AlGaN/GaN heterojunction material is placed in stripper to heating water bath 5 minutes, use again acetone soln ultrasonic cleaning 3 minutes, then use ethanolic solution ultrasonic cleaning 3 minutes, finally in deionized water, rinse 3 minutes, the photoresist mask that depositing metal is used and unnecessary metal are removed completely.
Step 4. annealing forms ohmic contact.
The AlGaN/GaN heterojunction material of making source-drain electrode metal is put into RTP500 rapid thermal anneler, first pass into the N of 10min
2carry out deaeration, be then warming up to 800 DEG C with the speed of 20 DEG C/s, then in annealing furnace, pass into N with the speed of 3L/s
2, at the N of 800 DEG C
2the rapid thermal annealing that carries out 60s in atmosphere, carries out alloy to metal ohmic contact, completes the making of source, drain electrode, i.e. the making of S, D electrode.
Embodiment 2: making hole depth is 10nm, the ohmic contact that metal Ti/Al/Ni/Au thickness is 25nm/200nm/50nm/80nm.
With reference to Fig. 1, the performing step of this example is as follows:
Step 1. AlGaN/GaN heterojunction material is cleaned.
This step is identical with the step 1 in embodiment 1.
Step 2. Ohmic electrode district borehole.
(2a) the positive glue EPI621 of 0.6 μ m is got rid of on the AlGaN/GaN heterojunction material surface after cleaning, photoresist spinner rotating speed used is 5000 turn/min, with the high temperature oven that temperature is 110 DEG C, the AlGaN/GaN heterojunction material that has got rid of glue is dried to 1min again, then adopt NSR1755I7A mask aligner to expose, finally develop, obtaining Ohmic electrode area distribution has the photoresist mask of some through holes, and the area sum of these through holes is 30% of the Ohm contact electrode gross area;
(2b) with RIE plasma dry etching machine, the AlGaN material exposing in photoresist mask through hole is carried out to etching, etching gas is Cl
2, etching power is 50W, speed etching is 0.5nm/s, on the AlGaN material in source, leakage Ohmic electrode district, digs out the hole that some degree of depth are 10nm;
(2c) etching is successively placed on AlGaN/GaN heterojunction material in acetone soln, ethanolic solution and distinguishes ultrasonic cleaning 3 minutes after completing, and finally in deionized water, rinses 3 minutes, removes the photoresist mask using in etch step completely.
Step 3. making source, leakage Ohm contact electrode.
(3a) first whole AlGaN material surface get rid of thickness be 0.35 μ m peel off glue PMGI SF6, the rotating speed of photoresist spinner used is 2000 turn/min, then gets rid of the positive glue EPI621 of thickness as 0.6 μ m taking 5000 turn/min rotating speeds on peel off glue PMGI SF6;
(3b) with the high temperature oven that temperature is 110 DEG C, the AlGaN/GaN heterojunction material that has got rid of glue is dried to 1min, then adopt NSR1755I7A mask aligner to expose, finally develop, the photoresist mask obtaining only exposes AlGaN electrode zone with holes;
(3c) with Ohmiker-50 electron beam evaporation platform with 0.3nm/s evaporation rate, at Ni, the A of 80nm of Al, the 50nm of Ti, the 200nm on AlGaN surface with holes successively deposit 25nm
uas electrode;
(3d) after deposition of electrode metal, first with stripper soak deposit the AlGaN/GaN heterojunction material of metal, and heating water bath 5 minutes, then AlGaN/GaN heterojunction material is carried out to the ultrasonic cleaning of 3 minutes with acetone soln and ethanolic solution successively, finally use deionized water rinsing 3 minutes, remove the photoresist mask on AlGaN/GaN heterojunction material surface and unnecessary metal.
Step 4. annealing forms ohmic contact.
The AlGaN/GaN heterojunction material of making electrode metal is annealed by RTP500 rapid thermal anneler, first deaeration, passes into the N of 10min
2, being then warming up to 840 DEG C, speed is 20 DEG C/s, then in annealing furnace, passes into N
2, speed is 3L/s, the AlGaN/GaN heterojunction material that makes to make source-drain electrode metal is at the N of 840 DEG C
2rapid thermal annealing 45s in atmosphere, after annealing, metal ohmic contact forms alloy, completes the making of source, drain electrode, i.e. the making of S, D electrode.
Embodiment 3: making hole depth is 15nm, metal Ti/Al/Ni/Au thickness is 30nm/250nm/60nm/100nm, ohmic contact.
With reference to Fig. 1, the performing step of this example is as follows:
Steps A. AlGaN/GaN heterojunction material is cleaned.
This step is identical with the step 1 in embodiment 1.
Step B. Ohmic electrode district borehole.
(B1) the AlGaN/GaN heterojunction material after cleaning is put into photoresist spinner, adjusting photoresist spinner rotating speed is 5000 turn/min, AlGaN/GaN heterojunction material surface positive-glue removing EPI621 after cleaning, glue is thick is 0.6 μ m, again in high temperature oven, with the temperature of 110 DEG C, the AlGaN/GaN heterojunction material that has got rid of glue is dried to 1min, then adopt NSR1755I7A mask aligner to expose, finally develop, obtain the photoresist mask of Ohmic electrode region with some through holes, the area sum of these through holes is 15% of the Ohm contact electrode gross area;
(B2) the AlGaN/GaN heterojunction material with photoresist mask is put into RIE plasma dry etching machine, adopt the etching power of 50W, pass into Cl
2gas, the AlGaN material exposing in the speed etching photoresist mask through hole with 0.5nm/s digs out the hole that some degree of depth are 15nm on the AlGaN material in source, leakage Ohmic electrode district;
(B3) complete after etching, AlGaN/GaN heterojunction material after etching is placed in to ultrasonic environment, with acetone soln cleaning 3 minutes, then clean 3 minutes with ethanolic solution, finally leave ultrasonic environment, with deionized water rinsing 3 minutes, remove photoresist mask on AlGaN/GaN heterojunction material.
Step C. source, leakage Ohm contact electrode are made.
(C1) the AlGaN/GaN heterojunction material that digs via hole is put into photoresist spinner, the rotating speed of adjusting photoresist spinner is 2000 turn/min, get rid of and peel off glue PMGI SF6 at whole AlGaN material surface, thickness is 0.35 μ m, the rotating speed of adjusting again photoresist spinner is 5000 turn/min, positive-glue removing EPI621 on peel off glue PMGI SF6, thickness is 0.6 μ m;
(C2) in high temperature oven, the AlGaN/GaN heterojunction material that has got rid of glue is dried 1min by the temperature with 110 DEG C, then uses NSR1755I7A mask aligner to expose, and finally develops, and only exposed the photoresist mask of AlGaN electrode zone with holes;
(C3) by the Al with mask
gan/GaN heterojunction material is put into Ohmik
er-50 electron beam evaporation platforms, with the evaporation rate of 0.3nm/s, carry out the deposit of Ti/Al/Ni/Au source-drain electrode metal at AlGaN material surface with holes, metal thickness is 30nm/250nm/60nm/100nm;
(C4) after deposition of electrode metal completes, AlGaN/GaN heterojunction material is placed in stripper to heating water bath 5 minutes, then be positioned in ultrasonic environment, first clean 3 minutes with acetone soln, clean 3 minutes with ethanolic solution again, finally leave ultrasonic environment, use deionized water rinsing 3 minutes, the photoresist mask of making at AlGaN/GaN heterojunction material while removing depositing metal, peels off unnecessary metal.
Step D. annealing forms ohmic contact.
Put into make source-drain electrode metal after, to the N that passes into 10min in RTP500 rapid thermal anneler
2carry out deaeration, be then warming up to 870 DEG C with the speed of 20 DEG C/s, then in annealing furnace, pass into N with the speed of 3L/s
2, at the N of 870 DEG C
2the rapid thermal annealing carrying out in atmosphere, the time is 30s, makes the metal ohmic contact on AlGaN/GaN heterojunction material form alloy, completes the making of source, drain electrode, i.e. the making of S, D electrode.
Effect of the present invention can further illustrate by following test result:
Test 1, the source after the embodiment of the present invention 1 is completed, the contact resistance that leakage Ohm contact electrode carries out transmission line model are tested, and obtain the comparative result of ohmic contact resistance and conventional ohmic contact resistance, as shown in Figure 2.
As seen from Figure 2, source, leakage Ohm contact electrode that the present invention makes, its ohmic contact resistance has dropped to 0.21 Ω mm from 0.43 Ω mm of routine.
Test 2, source after the embodiment of the present invention 1 is completed, leaks Ohm contact electrode and has carried out saturation current test between electrode, obtains between electrode the comparative result of saturation current between saturation current and conventional electrodes, as shown in Figure 3.
As seen from Figure 3, source, leakage Ohm contact electrode that the present invention makes, between its electrode, saturation current has risen to 950mA/mm from conventional 800mA/mm.
Claims (6)
1. an Ohm contact production method on AlGaN-GaN heterojunction, comprises the steps:
(1) AlGaN/GaN material is cleaned;
(2) source of the AlGaN/GaN material surface after cleaning, leakage Ohmic electrode district carry out photoetching, make the photoresist mask with a lot of through holes, and the area sum of these through holes is 15%～45% of the Ohm contact electrode gross area; In through hole, expose AlGaN material;
(3) utilize dry etching to carry out etching to the AlGaN material exposing in photoresist mask through hole, obtain source, leak Ohmic electrode district and dig the AlGaN material in a lot of holes, the borehole degree of depth is 5～15nm; Removal photoresist mask after etching completes;
(4) in the whole source of borehole, leak on the AlGaN material in Ohmic electrode region, deposit Ti/Al/Ni/Au multiple layer metal, and carry out 800～870 DEG C of annealing 30～60s, formation source, leaks Ohm contact electrode.
2. according to the method described in claims 1, AlGaN/GaN material is cleaned in wherein said step (1), carry out as follows:
First AlGaN/GaN heterojunction material is positioned in the HF solution of 1:5 and soaks 30s, remove surface oxide layer;
Again AlGaN/GaN heterojunction material is positioned over to acetone, ethanol organic solvent for ultrasonic and cleans, remove surface contamination, and with deionized water rinsing 5 minutes.
3. according to the method described in claims 1, the dry etching in wherein said step (3), process conditions are as follows:
Adopt RIE reactive ion etching, reacting gas is Cl
2, its flow 40sccm,
Reative cell pressure is 10mT,
Electrode power is 50W,
Etch rate is 0.5nm/s.
4. according to the method described in claims 1, the multiple layer metal deposit in wherein said step (4), is undertaken by electron beam evaporation equipment, and process conditions are as follows:
Evaporation initial vacuum degree reaches 10
-7below Tor, evaporation of metal speed is 0.3nm/s.
5. according to the method described in claims 1, deposit Ti/Al/Ni/Au multiple layer metal in wherein said step (4), its thickness respectively: Ti is 20～30nm, and Al is 150～250nm, and Ni is 40～60nm, and Au is 60～100nm.
6. according to method described in claims 1, the annealing in wherein said step (4), use equipment is RTP rapid thermal anneler, carries out as follows:
First, to the N that passes into 10min in annealing furnace
2carry out deaeration;
Then, the speed of 20 DEG C/s is warming up to the temperature setting;
Finally, in annealing furnace, pass into N with the speed of 3L/s
2, anneal by the annealing time setting.
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