CN207038527U

CN207038527U - Ohmic contact structure

Info

Publication number: CN207038527U
Application number: CN201720867867.6U
Authority: CN
Inventors: 张艺蒙; 张玉明; 李彦良; 宋庆文; 汤晓燕
Original assignee: Xidian University
Current assignee: Xidian University
Priority date: 2017-07-18
Filing date: 2017-07-18
Publication date: 2018-02-23
Anticipated expiration: 2027-07-18

Abstract

A kind of ohmic contact structure is the utility model is related to, including：SiC substrate layer (10) and the SiC epitaxial layer (20) being sequentially located on the SiC substrate layer (10), the first Ni layers (30), Ti layers (40), Al layers (50), the 2nd Ni layers (60), TaSi₂Layer (70), Pt layers (80).The utility model ohmic contact structure has anti-aging, electrology characteristic stabilization and has superperformance under high temperature, air ambient.

Description

Ohmic contact structure

Technical field

The utility model belongs to silicon carbide device manufacturing technology field, and in particular to a kind of ohmic contact structure.

Background technology

Compared to traditional germanium, silicon materials, the advantage of third generation wide band gap semiconducter carborundum mainly includes：Electric field is born Ability is about ten times of silicon materials, and energy gap is about three times of silicon materials, and thermal conductivity factor is about silicon materials three times etc..Above material Characteristic causes it to show under the conditions of extreme temperature (especially high temperature) and big voltage, high-frequency and high power and intense radiation etc. The incomparable advantage of traditional silicon-based devices.

Ohmic contact is one of key influence factor that silicon carbide device is applied in the extreme environment such as high temperature, oxidizable, Its purpose, which is to realize when electrode is in and applies forward voltage, can carry pressure drop as small as possible, with this, to ensure device Performance.Assuming that ohm contact degradation or failure, certainly will influence the opening resistor of device, device performance can be influenceed when serious, Or even make component failure.So design good thermal stability, oxidation resistant ohmic contact structure seem particularly necessary.

At present, carborundum metal ohmic contact or alloy-layer Problems are weak including oxidation resistance, are in atmosphere It is oxidized；Heat endurance is poor, occurs degenerating under high temperature or fails；Hardness is low, easily by mechanical damage the shortcomings of, these shortcomings The reduction of ohmic contact structure reliability can be caused, seriously limit its application environment and scope, and then make the application of silicon carbide device Scope is with reliability by many influences and limitation.

Therefore, how to develop it is a kind of it is anti-oxidant, resistant to elevated temperatures carborundum ohmic contact structure is most important.

Utility model content

In order to solve the above-mentioned problems in the prior art, the utility model provides a kind of ohmic contact structure.

One embodiment of the present utility model provides a kind of ohmic contact structure, including：SiC substrate layer 10 and successively SiC epitaxial layer 20, the first Ni layers 30, Ti layers 40, Al layers 50, the 2nd Ni layers 60 on the SiC substrate layer 10, TaSi₂Layer 70, Pt layers 80.

In one embodiment of the present utility model, the material of the SiC substrate layer 10 is 4H-SiC.

In one embodiment of the present utility model, the thickness of the first Ni layers 30 is

In one embodiment of the present utility model, the thickness of the Ti layers 40 is

In one embodiment of the present utility model, the thickness of the Al layers 50 is

In one embodiment of the present utility model, the thickness of the 2nd Ni layers 60 is

In one embodiment of the present utility model, the TaSi₂Layer 70 thickness be

In one embodiment of the present utility model, the thickness of the Pt layers 80 is

Compared with prior art, the ohmic contact structure that prepared by the utility model have anti-aging, electrology characteristic stable and There is superperformance under high temperature, air ambient.

Brief description of the drawings

Fig. 1 is a kind of Pt/TaSi that the utility model embodiment provides₂/ Ni/Al/Ti/Ni/SiC ohmic contact structures Structural representation；

Fig. 2 a are a kind of ohmic contact structure CTLM structure domains that the utility model embodiment provides；

After Fig. 2 b peel off for a kind of ohmic contact structure metal level that the utility model embodiment provides under microscope Schematic diagram；

Fig. 3 is a kind of Pt/TaSi that the utility model embodiment provides₂/ Ni/Al/Ti/Ni/SiC structure specific contact resistivities It is worth the change curve with ageing time；

Fig. 4 a are a kind of Pt/TaSi that the utility model embodiment provides₂The annealed place of/Ni/Al/Ti/Ni/SiC structures Scanning electron microscope image (SEM) schematic diagram after reason；

Fig. 4 b are a kind of Pt/TaSi that the utility model embodiment provides₂/ Ni/Al/Ti/Ni/SiC structures through aging at Scanning electron microscope image (SEM) schematic diagram after reason.

Embodiment

Further detailed description, but embodiment party of the present utility model are to the utility model with reference to specific embodiment Formula not limited to this.

Embodiment one

Fig. 1 is referred to, Fig. 1 is a kind of Pt/TaSi that the utility model embodiment provides₂/ Ni/Al/Ti/Ni/SiC Europe The structural representation of nurse contact structures；The ohmic contact structure includes：SiC substrate layer 10 and it is sequentially located at the SiC substrate layer SiC epitaxial layer 20, the first Ni layers 30 on 10, Ti layers 40, Al layers 50, the 2nd Ni layers 60, TaSi₂Layer 70, Pt layers 80.

Preferably, the material of the SiC substrate layer 10 is 4H-SiC.

Preferably, the thickness of the first Ni layers 30 is

Preferably, the thickness of the Ti layers 40 is

Preferably, the thickness of the Al layers 50 is

Preferably, the thickness of the 2nd Ni layers 60 is

Preferably, the TaSi₂Layer 70 thickness be

Preferably, the thickness of the Pt layers 80 is

Wherein, Pt/TaSi₂In/Ni/Al/Ti/Ni/SiC ohmic contact structures, Ni and SiC reacts.Ti layers 40 can be tied Close due to C caused by Ni and SiC reactions, in order to avoid the C atoms of free state gather on surface, and make rough surface or failure.

Embodiment two

A kind of Pt/TaSi is discussed in detail in the present embodiment₂/ Ni/Al/Ti/Ni/SiC ohmic contact structure preparation technologies, bag Include：

S01：4H-SiC substrate layers and SiC epitaxial layer are prepared, standard RCA is carried out to 4H-SiC substrate layers and SiC epitaxial layer Cleaning.

S02：In SiC epitaxial layer, vapour deposition process (the Plasma Enhanced of plasma enhanced chemical are utilized Chemical Vapor Deposition, PECVD) technique forms the thick SiO of ion implanting about 100nm₂Mask layer.

S03：The SiO2 mask layers are etched, P is carried out to SiC epitaxial layer⁺Ion implanting, highly doped P areas are formed, etched The remaining SiO2 mask layers simultaneously carry out high annealing.

Wherein, the doping concentration that highly doped P areas are formed by ion implanting is 1.3 × 10²⁰cm^-3, doping type P. The condition of high annealing is carried out to keep 1700 DEG C of temperature, is annealed 30 minutes.

S04：Deposit the first Ni layers, Ti layers, Al layers, the 2nd Ni layers, TaSi successively in SiC material₂Layer and Pt layers are formed Metal level.

Wherein, in used metal deposition methods, the first Ni layers, Ti layers, the 2nd Ni layers, Pt layers, Al layers use direct current Magnetron sputtering deposits；TaSi₂Layer is deposited using rf magnetron sputtering.

The power of Metal deposition is respectively that Al layers, Pt layers, Ti layers, the first Ni layers, the 2nd Ni layers are 100W, TaSi₂Layer be 60W。

The speed of Metal deposition is respectively Ti layers, Pt layers, TaSi₂Layer is 2.9nm/min, and the first Ni layers, the 2nd Ni layers are 9.8nm/min, Al layer are 10nm/min.

Metal deposition throughput Ni layers are 24Ar/sccm, and Ti layers, Pt layers, Al layers are 16Ar/sccm, TaSi₂Layer be 20Ar/sccm。

Metal deposition thickness is about the first Ni layers successivelyTi layersAl layers2nd Ni layersTaSi₂LayerPt layers

Deposit the first Ni layers, Ti layers, Al layers, the 2nd Ni layers, TaSi successively on SiC substrate layer₂The deposit of layer and Pt layers Intracavitary vacuum is≤5e^-6mTorr。

S05：The metal level is subjected to annealing and forms Ohmic contact.

Wherein, the method that performance test is carried out to the ohmic contact structure in the present embodiment is as follows：

Step 1：4H-SiC substrates and SiC epitaxial layer are prepared, it is clear to carry out standard RCA to 4H-SiC substrates and SiC epitaxial layer Wash.

Step 2：In SiC epitaxial layer, vapour deposition process (the Plasma Enhanced of plasma enhanced chemical are utilized Chemical Vapor Deposition, PECVD) technique forms the thick SiO of ion implanting about 100nm₂Mask.

Step 3：P is carried out to SiC epitaxial layer⁺Ion implanting, form highly doped P areas and carry out high annealing.

Step 4：Photoetching is carried out using mask plate, forms CTLM figures, primer is removed, removing natural oxidizing layer is removed using HF And other impurities.

Fig. 2 a are referred to, Fig. 2 a are a kind of ohmic contact structure CTLM structure domains provided in an embodiment of the present invention.Wherein, HF solution ratios are HF：H₂O=1：20.Go removing natural oxidizing layer to need first choice to be embathed in HF solution 2 minutes, use clear water afterwards Wash off HF solution, N₂Drying.

Step 5：Deposit Ni, Ti, Al, Ni, TaSi successively in SiC material₂With Pt metal levels.

Step 6：Metal-stripping forms ohmic contact structure with short annealing and carries out performance to the ohmic contact structure Test.

Fig. 2 b are referred to, Fig. 2 b are after a kind of ohmic contact structure metal level that the utility model embodiment provides is peeled off Schematic diagram under microscope.Wherein, step 6 is specially that (wherein, SiC substrate layer 10 and metal level are whole by the slice, thin piece of deposit completion Body turns into slice, thin piece) it is placed in acetone to soak about 10 hours and tilts to metal level on photoresist layer, carry out ultrasound about 3min extremely afterwards Metal level is tilted to completely fall off.Observation metal level does not have adhesion under the microscope.The condition of annealing is 800 DEG C of temperature, indifferent gas In the protection atmosphere of body, annealing time 2 minutes.

Fig. 3 is referred to, Fig. 3 is the Pt/TaSi that the utility model embodiment provides₂/ Ni/Al/Ti/Ni/SiC structures Specific contact resistivity value with ageing time change curve.TaSi2 layers 70 be prevent ohmic contact structure aoxidize key, its energy Effectively stop that O spreads downwards, TaSi₂Decomposition index of coincidence form enable this structure for a long time effectively, TaSi₂It is slow Decompose therefore each metal-layer structure is remained unchanged substantially, this structure can be made to expose and carry out burn-in test in atmosphere. The Ni metal-layer structures of metal level 5 have not only acted as the effect of adhesive, and can reduce annealing temperature by introducing Ni, To reach the anti-aging effect of enhancing metal structure.Pt/TaSi₂The Ohmic contact of the p-type of/Ni/Al/Ti/Ni/SiC structures, than Contact resistance value has reached the magnitude of -5 powers, has reached international level.

Please referring also to Fig. 4 a and Fig. 4 b, Fig. 4 a are a kind of Pt/TaSi that the utility model embodiment provides₂/Ni/Al/ Scanning electron microscope image (SEM) schematic diagram after the annealed processing of Ti/Ni/SiC structures；Fig. 4 b are implemented for the utility model A kind of Pt/TaSi that example provides₂Scanning electron microscope image (SEM) of/Ni/Al/Ti/Ni/SiC structures after burin-in process Schematic diagram.Wherein Fig. 4 a are the Pt/TaSi₂After/Ni/Al/Ti/Ni/SiC structures complete annealing, the scanning electron on surface shows Micro mirror image (SEM), Fig. 4 b are the Pt/TaSi₂/ Ni/Al/Ti/Ni/SiC structures carry out 400h at 600 DEG C in air After aging condition, the scanning electron microscope image (SEM) on surface.To Pt/TaSi₂The p-type of/Ni/Al/Ti/Ni/SiC structures Ohmic contact structure carry out high temperature, burn-in test in atmosphere, electrology characteristic does not change substantially at 400 hours.Illustrate The stable electrology characteristic of the ohmic contact structure of the p-type of the present embodiment.The surface of the ohmic contact structure of p-type in the present embodiment Suppress to keep smooth in annealing, ageing process.

Finally it should be noted that：Above example is only to illustrate the technical solution of the utility model, rather than its limitations； Although the utility model is described in detail with reference to the foregoing embodiments, it will be understood by those within the art that： It can still modify to the technical scheme described in foregoing embodiments, or which part technical characteristic is carried out etc. With replacement；And these modifications or replacement, the essence of appropriate technical solution is departed from various embodiments of the utility model technology The spirit and scope of scheme.

Claims

A kind of 1. ohmic contact structure, it is characterised in that including：SiC substrate layer (10) and it is sequentially located at the SiC substrate layer (10) SiC epitaxial layer (20), the first Ni layers (30) on, Ti layers (40), Al layers (50), the 2nd Ni layers (60), TaSi₂Layer (70), Pt layers (80).
2. ohmic contact structure according to claim 1, it is characterised in that the material of the SiC substrate layer (10) is 4H- SiC。
3. ohmic contact structure according to claim 1, it is characterised in that the thickness of the first Ni layers (30) is
4. ohmic contact structure according to claim 1, it is characterised in that the thickness of the Ti layers (40) is
5. ohmic contact structure according to claim 1, it is characterised in that the thickness of the Al layers (50) is
6. ohmic contact structure according to claim 1, it is characterised in that the thickness of the 2nd Ni layers (60) is
7. ohmic contact structure according to claim 1, it is characterised in that the TaSi₂Layer (70) thickness be
8. ohmic contact structure according to claim 1, it is characterised in that the thickness of the Pt layers (80) is