One kind mixes germanium carborundum Ohmic contact forming method
Technical field
Germanium carborundum Ohmic contact forming method is mixed the present invention relates to one kind, belongs to field of semiconductor device preparation.
Background technology
Carborundum (SiC) semi-conducting material is partly led from first generation elemental semiconductorses silicon (Si) and second generation compound
The third generation wide bandgap semiconductor materials grown up after body material GaAs, gallium phosphide, indium phosphide (GaAs, GaP, InP)
One of.Third generation wide bandgap semiconductor materials mainly include carborundum (SiC), cubic boron nitride (C-BN), gallium nitride (GaN),
Aluminium nitride (AlN), zinc selenide (ZnSe) and diamond thin etc..
Go deep into to carborundum crystals investigation of materials, it has been found that by adulterating, different elements can be to carborundum
Crystalline material causes different influences.Ge element is mixed in carbofrax material can change its band structure, reduce its forbidden band wide
Degree, this will expand application prospect of the carborundum crystals material in visible ray and infrared band.Because the presence of Ge element can
To reduce electronic device contact resistance, electron mobility and life-span are improved, therefore mix the heterojunction transistor of germanium silicon carbide substrate
(HBT) current gain in improves 50%, and initial voltage adds 33%.Therefore we can be by adjusting mixing for germanium
Miscellaneous amount adjusts the band structure and lattice constant of carborundum, can preferably carbofrax material be applied on device.
A key technology in silicon carbide device is the formation of Ohmic contact.The quality of Ohmic contact is directly connected to device
The size and long-term reliability of part conducting resistance.Ohmic contact as a kind of key process technology in semiconductor manufacturing, it
Purpose is so that the pressure drop of contact position when semi-conducting material applies voltage is sufficiently small so that not influenceing the performance of device.If Europe
The poor reliability of nurse contact resistance, can cause the ON resistance of device to raise, the performance of device can be influenceed when serious.Pass through deposition
Metal, such as nickel, and metal is annealed in high temperature had been known to form metal ohmic contact.CN105244266A is public
A kind of Ohmic contact forming method of SiC wafers, the process that this method is annealed in the SiC wafers that deposition has metal level are opened
In be passed through CO2Gas, so as to realize effective removal of carbon simple substance in annealing process, therefore removes carbon work without additionally increase
Skill, simplifies the handling process of SiC wafer ohmic contact crafts.But this can not effectively improve Ohmic contact effect.
CN106024597A discloses a kind of carborundum Ohmic contact forming method, and ion implanting is carried out forming ohmic contact regions,
One layer of carbon-coating is deposited in silicon carbide, the carbon-coating is removed after annealing again, deposit ohmic contacting metal retains ohmic contact regions
Metal in domain, last short annealing forms Ohmic contact.This method forms n-type and p-type Ohmic contact simultaneously, although reduce work
Skill step, but the actual effect of Ohmic contact can not be equally improved, form high-quality, low contact resistance high-performance ohm and connect
Touch.
The content of the invention
In view of the shortcomings of the prior art, the present invention provides a kind of forming method for mixing germanium carborundum Ohmic contact, it is intended to carry
High ohm contact performance, forms high-quality, low contact resistance high-performance ohm by changing the concentration for the Ge element that adulterates and connects
Touch.
Term explanation:
Mix germanium carborundum:Refer to the ternary alloy three-partalloy compound monocrystalline formed by incorporation Ge element in SiC growths.It is universal at present
Single-crystal silicon carbide is grown using physical vapor transport, dopant is germanium metal powder.
Electron beam evaporation:Electron beam evaporation is a kind of mode of vacuum evaporation, is to be entered under vacuum using electron beam
Row directly heats evaporation material, evaporation material is gasified and is transported to substrate, and the method for forming film is condensed in substrate.
Quick anneal oven (RTP):Quick anneal oven is that, using quartz-iodine lamp as heater element, programming rate is exceedingly fast, using S types
Thermocouple temperature measurement simultaneously uses fuzzy-adaptation PID control, with very high temperature-controlled precision < ± 5 DEG C >, and quick anneal oven has vacuum plant,
It can be worked under multiple atmosphere.Quick anneal oven is prior art.
Technical scheme is as follows:
One kind mixes germanium carborundum Ohmic contact forming method, including:
- provide and mix germanium silicon carbide wafer;
- metal electrode is formed by electron beam evaporation in described mix on germanium silicon carbide wafer;
- the temperature rise period:By after electrode formed above mix germanium silicon carbide wafer be put into Quick annealing device carry out it is quick
Annealing forms Ohmic contact, and the heating surface of the Quick annealing device is peripheric surface in furnace chamber, is led to while heating into furnace chamber
Enter argon gas;
The short annealing is divided into two temperature rise periods, and first stage temperature is increased to 300-500 DEG C, is persistently incubated 3-5
Minute, secondary stage annealing temperature is 600-800 DEG C, is persistently incubated 5-10 minutes;
- temperature-fall period:Cool the temperature to not higher than 60 DEG C.Take sample.
The method of the present invention by changing the concentration of doped germanium, prepare ohm contact performance it is more excellent mix germanium carbonization
Silicon.
According to currently preferred, the germania concentration for mixing germanium carborundum is 1017-1019Atoms/cm3.It is further excellent
Choosing, the germania concentration for mixing germanium carborundum is 1019Atoms/cm3。
It is described to mix the square that germanium silicon carbide whisker chip size is less than 10mm for the length of side for the ease of carrying out Hall test.
According to currently preferred, the metal electrode is that Ti, Pt, Au are grown in mix successively and formed on germanium silicon carbide wafer
Ti/Pt/Au three-deckers.Further preferably, the thickness of wherein Ti, Pt, Au metal level be respectively 60-80nm, 50-70nm and
600-700nm.The present invention forms Ohmic contact using Ti/Pt/Au structures, and Pt/Au layers can effectively be passivated in high temperature
Ti layers of oxidation tendency, and Au layers can penetrate Ti layers in high temperature and enter in SiC, reduce contact resistance, Pt layers also can be
The stabilization of ohm contact performance is maintained in annealing process.
According to currently preferred, the metal electrode is the square Ti/Pt/Au electrodes that the length of side is not more than 1mm.
According to currently preferred, the Quick annealing device is quick anneal oven (RTP).Prior art, it is commercially available.
According to currently preferred, the first stage heating rate is not more than 20 DEG C/sec, the second stage heating speed
Rate is not more than 10 DEG C/sec.It is further preferred that 11~20 DEG C/sec of the first stage heating rate, the second stage heating
Speed is 5~10 DEG C/sec.
According to currently preferred, the first stage temperature is increased to 300-500 DEG C, is persistently incubated 4-5 minutes, and second
Step annealing temperature is 600-800 DEG C, is persistently incubated 7-10 minutes.
According to currently preferred, the rate of temperature fall of the temperature-fall period is 10 DEG C -20 DEG C/sec.The method of the present invention is most
Latter step temperature-fall period, is that by highest annealing temperature sample is down into room temperature, rate of temperature fall is not more than 20 DEG C/sec.In this process
In, rate of temperature fall can influence annealing effect slowly excessively, cause Ohmic contact effect not good, and rate of temperature fall is too fast and can improve cooling
Cost, appropriate specific rate of temperature fall is an important technical in an annealing process.Cool drop described in temperature-fall period
It is that the temperature for instigating sample is down to not higher than 60 DEG C to not higher than 60 DEG C.
According to currently preferred, the temperature-fall period is that the temperature of annealing device is down into room temperature.The room temperature is this
Implication known to field, generally 20-26 DEG C.
Germanium carborundum of the present invention of mixing can be prepared by prior art.Present invention preferably provides following methods:
A kind of method that germanium single-crystal silicon carbide is mixed in use physical vapor transport growth, in the growth earthenware being positioned in furnace chamber
There is provided silicon carbide powder source and Germanium dopants in crucible, and it is in the silicon carbide seed of spaced relationship with source powder;Ge-doped amount is carbonization
The 3-7% mass percents of silicon source powder.Dopant is placed in growth crucible bottom, and mixed with silicon carbide powder source.Taken out in furnace chamber
Vacuum, growth crucible described in sensing heating sets up thermograde, and there is provided growing environment;To growth atmosphere in crystal growing process
Middle injection nitrogen, nitrogen flow is 15-30sccm, and growth temperature is 2100-2300 DEG C, and growth pressure is 50-80mbar.Growth
Cycle is 30-60 hours.
The obtained cutting for mixing germanium carborundum crystal ingot progress standard, grinding will be grown and obtain mixing germanium silicon carbide whisker after polishing
Piece.
The technical characterstic and excellent results of the present invention:
1st, the present invention passes through specific method for annealing shape to mix electrode of the germanium carborundum as substrate formation Ti/Pt/Au structures
Germanium silicon carbide device is mixed into good high-quality of ohm contact performance.The inventors discovered that, the germanium of mixing of different levels of doping is carbonized
Silicon sample, its ohm contact performance formed has obvious difference;, can be by changing doped germanium using the method for the present invention
Concentration, for preparing different ohm contact performances mixes germanium carborundum.Using when mixing germanium carborundum and preparing electronic device, Ke Yitong
The concentration for crossing change doped germanium realizes the ohm contact performance of control device Top electrode.On the other hand, by the present invention is made
The germanium silicon carbide electrode of mixing of formation Ohmic contact carry out Hall (Hall) test, to the silicon carbide electrodes of different germania concentrations
VA characteristic curve is analyzed, it is known that mix Ge-doped concentration in germanium carborundum by improving to prepare ohm contact performance good
Mix germanium silicon carbide device.
2nd, the present invention forms Ohmic contact using Ti/Pt/Au structures, and Pt/Au layers can effectively be passivated in high temperature
Ti layers of oxidation tendency, and Au layers can penetrate Ti layers in high temperature and enter in SiC, reduce contact resistance, Pt layers also can be
The stabilization of ohm contact performance is maintained in annealing process.
3rd, the present invention prepares the electrodes of Ti/Pt/Au structures using electron beam evaporation, it is to avoid metal film is with being deposited source material
The problem of directly contacting easily mutually mixed.
4th, the short annealing temperature rise period of the present invention is divided into two parts, and the annealing way can ensure peak value heat treatment temperature
Control accuracy under the premise of, improve heating rate.The heating process heating rate of first stage is not more than 20 DEG C/sec, Ran Houbao
Hold in described heating-up temperature, prevent there is the formation of oxide during short annealing, have impact on ohm contact performance.The
The heating process of two-stage, heating rate is not more than 10 DEG C/sec, is heated to carry out stabilization process during maximum temperature.Second stage
Temperature is set as no more than 800 DEG C, and the formation of Ohmic contact is influenceed to prevent from being formed other oxides.
5th, the present invention can use any thermal source, it is not necessary to the change in structure is carried out to short annealing equipment, simple easy
Operation, reduces cost.Whole electrode production process environmental protection of the invention, it is pollution-free.
Brief description of the drawings
Fig. 1 be the present invention prepare mix metal electrode schematic diagram on germanium carborundum.Wherein, 1 germanium silicon carbide wafer, is mixed, 2,
Ti metal levels, 3, Pt metal levels, 4, Au metal levels.
Fig. 2 is temperature and time schematic diagram of the sample of embodiment 1 in annealing process.
During Fig. 3 is embodiment 1, measure that to mix germanium silicon germanium carbide concentration of element be 10 by Hall test19Atoms/cm3Electrode
The VA characteristic curve schematic diagram of sample.
During Fig. 4 is embodiment 2, measure that to mix germanium silicon germanium carbide concentration of element be 10 by Hall test18Atoms/cm3Electrode
The VA characteristic curve schematic diagram of sample.
During Fig. 5 is embodiment 3, measure that to mix germanium silicon germanium carbide concentration of element be 10 by Hall test17Atoms/cm3Electrode
The VA characteristic curve schematic diagram of sample.
Embodiment
With reference to embodiment, the present invention will be further described, but not limited to this.
The preparation for mixing germanium single-crystal silicon carbide used, is grown, step is as follows using physical vapor transport in embodiment:
Sic powder 300g and dopant germanium powder 10-20g is placed in growth crucible in growth furnace room;By dopant
Crucible bottom is placed in, and is mixed with sic powder, silicon carbide seed is fixed on the seed crystal of crucible top seat.In crystal life
Nitrogen is injected in growth process into growth atmosphere, nitrogen flow is 20sccm, and growth temperature is 2100-2300 DEG C, growth pressure
For 50-80mbar.Growth cycle is 40-60 hours.
According to above method, feed according to the following ratio, obtain different Ge-doped concentration mixes germanium single-crystal silicon carbide:
Sic powder 300g and dopant germanium powder 20g, Ge-doped concentration is 1019Atoms/cm3, for embodiment 1;
Sic powder 300g and dopant germanium powder 15g, Ge-doped concentration is 1018Atoms/cm3, for embodiment 2;
Sic powder 300g and dopant germanium powder 10g, Ge-doped concentration is 1017Atoms/cm3, for embodiment 3.
10 × 10mm will be obtained after the cutting, grinding and the polishing that grow obtained crystal ingot progress standard2Mix germanium carborundum
Chip.
Embodiment 1, one kind mix germanium carborundum Ohmic contact forming method, including:
(1) it is 10 to provide Ge-doped concentration19Atoms/cm3Magnitude mixes germanium silicon carbide wafer, deposited by electron beam evaporation method
Prepare 1 × 1mm2Titanium platinum electrode, the thickness of wherein Ti, Pt, Au metal level is respectively 70nm, 60nm and 650nm.Mixed
Germanium silicon carbide electrode sample.Electrode structure schematic diagram is as shown in Figure 1.
(2) temperature rise period, sample is put into quick anneal oven (RTP), carries out rapid thermal annealing, be rapidly heated the stage point
For two stages, first stage:Temperature is increased to 400 DEG C by 16 DEG C/sec of heating rates, persistently 4 minutes are incubated.Second-order
Section:Temperature is increased to 700 DEG C by 8 DEG C/sec of heating rates, persistently 7.5 minutes are incubated.The heating surface of Quick annealing device is
Surrounding in cavity, is filled with protective gas argon gas while heating.
(3) temperature-fall period, by rate of temperature fall, 15 DEG C/sec are cooled, and make to mix germanium carborundum Ohmic contact sample by highest
Temperature is down to room temperature.Take out sample.
The temperature and time schematic diagram such as Fig. 2 of the sample of embodiment 1 in annealing process.Prepared under the conditions of the embodiment
Germanium silicon carbide electrode sample of mixing tested by Hall, the VA characteristic curve figure measured is as shown in Figure 3.VA characteristic curve is
Linearly, illustrate to have formed Ohmic contact under this preparation condition.The slope of VA characteristic curve is approximately equal to 1, illustrates that what is prepared mixes
Germanium silicon carbide electrode sample Ohmic contact effect is very good.
Embodiment 2
One kind mixes germanium carborundum Ohmic contact forming method, including:
It is 10 to provide Ge-doped concentration18Atoms/cm3Magnitude mixes germanium silicon carbide wafer, prepared by deposited by electron beam evaporation method
1×1mm2Titanium platinum electrode, the thickness of wherein Ti, Pt, Au metal level is respectively 80nm, 70nm and 700nm.Obtain mixing germanium carbon
SiClx electrode sample.Electrode structure schematic diagram is as shown in Figure 1.
Temperature rise period, sample is put into quick anneal oven (RTP), carries out rapid thermal annealing, the stage of being rapidly heated is divided into
Two stages.Temperature is increased to 500 DEG C by the first stage by 18 DEG C/sec of heating rate, is persistently incubated 5 minutes.Second stage:
Temperature is upgraded to 800 DEG C by 9 DEG C/sec of heating rates, persistently 10 minutes are incubated.The heating surface of quick anneal oven is four in cavity
Week, heating is filled with protective gas argon gas simultaneously.
Temperature-fall period:By rate of temperature fall, 20 DEG C/sec are cooled, and are made to mix germanium carborundum Ohmic contact sample and are annealed by highest
Temperature is down to room temperature.Take out sample.
The germanium silicon carbide electrode sample of mixing prepared under the conditions of the embodiment is tested by Hall, and the C-V characteristic measured is bent
Line chart is as shown in Figure 4.VA characteristic curve is linear, illustrates to have formed Ohmic contact under this preparation condition.C-V characteristic is bent
The slope of line is approximately equal to 0.8.
Embodiment 3
One kind mixes germanium carborundum Ohmic contact forming method, including:
(1) it is 10 to provide Ge-doped concentration17Atoms/cm3Magnitude mixes germanium silicon carbide wafer, deposited by electron beam evaporation method
Prepare 1 × 1mm2Titanium platinum electrode, the thickness of wherein Ti, Pt, Au metal level is respectively 60nm, 50nm and 600nm.Mixed
Germanium silicon carbide electrode sample.Electrode structure schematic diagram is as shown in Figure 1.
(2) temperature rise period, sample is put into quick anneal oven (RTP), carries out rapid thermal annealing, be rapidly heated the stage point
For two stages.Temperature is increased to 300 DEG C by the first stage by 14 DEG C/sec of heating rate, is persistently incubated 3 minutes.Second-order
Temperature is upgraded to 600 DEG C by section by 6 DEG C/sec of heating rate, is persistently incubated 5 minutes.The heating surface of quick anneal oven is cavity four
Week, heating is filled with protective gas argon gas simultaneously.
(3) temperature-fall period, by rate of temperature fall, 10 DEG C/sec are cooled, and make to mix germanium carborundum Ohmic contact sample by highest
Temperature is down to room temperature.Take out sample.
The germanium silicon carbide electrode sample of mixing prepared under the conditions of the embodiment is tested by Hall, and the C-V characteristic measured is bent
Line chart is as shown in Figure 5.VA characteristic curve is linear, illustrates to have formed Ohmic contact under this preparation condition.C-V characteristic is bent
The slope of line is approximately equal to 0.5.
Preparation described in above example mixes germanium silicon carbide electrode as shown in Figure 1,3 kinds of metals of titanium platinum in order according to
Secondary be grown in by electron-beam vapor deposition method is mixed on germanium silicon carbide wafer.Accompanying drawing 2 is temperature of the sample of embodiment 1 in annealing process
Degree and time diagram, this annealing process be all embodiments in formation Ohmic contact best results annealing conditions.Germanium is dense
Degree often raises the electrode sample of a magnitude, and the Ohmic contact slope of a curve of formation can be increased, and Ohmic contact effect has
It is significant to improve.Therefore, high germania concentration can be successfully prepared out using the inventive method and Ohmic contact effect is preferable
Silicon carbide electrode sample.The sample of the different Ohmic contact effects of different germania concentrations can also be prepared, different answer can be met
With needs.