CN104178807A - Method for obtaining self-supporting gallium nitride substrates by using thermal decomposition characteristics - Google Patents
Method for obtaining self-supporting gallium nitride substrates by using thermal decomposition characteristics Download PDFInfo
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- CN104178807A CN104178807A CN201410382392.2A CN201410382392A CN104178807A CN 104178807 A CN104178807 A CN 104178807A CN 201410382392 A CN201410382392 A CN 201410382392A CN 104178807 A CN104178807 A CN 104178807A
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- buffer layer
- gallium nitride
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Abstract
The invention discloses a method for obtaining self-supporting gallium nitride substrates by using thermal decomposition characteristics. The method comprises the following steps: sequentially growing a first buffer layer and a second buffer layer on a sapphire substrate; growing a gallium nitride thick film layer on the second buffer layer at high temperature; when the gallium nitride thick film layer grows, the first buffer layer is prepared into gallium and nitrogen by high-temperature thermal decomposition, so that a gap is produced between the gallium nitride thick film layer and the sapphire substrate; and after the buffer layers and the gallium nitride thick film layer completely grow, the gallium nitride thick film layer and the sapphire substrate are gradually separated in the process of cooling, so that a gallium nitride substrate is obtained. The method for obtaining self-supporting gallium nitride substrates provided by the invention is high in production efficiency, and can be used for producing gallium nitride substrates with a certain thickness, and cracks are not easily produced on the gallium nitride substrates, thereby improving the quality of production.
Description
Technical field
The present invention relates to a kind of between sapphire (Sapphire wafer) and the gan (GaN) that grows out above it, insert the good buffer layer of a kind of selective thermal resolution characteristic, then by thermolysis, gan is separated to obtain single Crystal gallium nitride base board from Sapphire Substrate.
Background technology
The nitride semi-conductor materials such as A1N, GaN, InN are the Direct Transfer N-type semiconductorN materials that band gap (Band gap) is 0.65eV～6.2eV, so these three kinds of materials can send infrared rays to ultraviolet all visible rays, also because like this, they are as LED (Light Emitting Diode), the material of the luminous element of LD (Laser Diode) and receiving much concern.In addition, because its material has advantages of that physical property is hard, (Electron mobility) is high for electron mobility, so it is also widely used as the electronic component of high temperature/high-capacity/high speed in the rugged environment such as high temperature, radiant.
In general green LED or White LED are made by growing gallium nitride on sapphire substrate (GaN) film, but in order to make ultra high power LED, the exigent gan element of this current density such as LD, just needs gallium nitride base board.Trace it to its cause is because the defect concentration of the gallium nitride film of growing on sapphire substrate is approximately 10
9～10
9/ cm
2, that is to say the problem that very high defect concentration can cause component life to reduce.
The defect concentration of the gallium nitride film of growing on single Crystal gallium nitride base board in contrast, is 10
7/ cm
2below, its advantage is exactly to make the life-span of element increase.In the method for making gallium nitride base board, hydrogen vapor phase epitaxial growth (Hydride Vapor Phase Epitaxy:HVPE) method is the method for commonly using the most, in addition, also has organometallic chemistry deposition (Metal-Organic Chemical Vapor Deposition:MOCVD) method, molecular beam epitaxial growth (Molecular Beam Epitaxy:MBE) method etc.HVPE is as one of method of vapor-phase growing, and its advantage is that the speed of growth is very fast and cost is lower, so be widely used in the growth of film and the growth of thick film crystallization.
Current gallium nitride base board manufacture craft is on sapphire substrate, to grow after gallium nitride single crystal thick film, utilize laser or chemical milling (Chemical etching) or working method physically that sapphire substrate is separated with gallium nitride single crystal thick film, then by gallium nitride single crystal thick film polishing.
For example, the method of utilizing separation by laser gallium nitride base board is to inject the little laser beam of Band gap wavelength than gan in sapphire substrate one side, can be gallium (Ga metal) and nitrogen (N by the gan thermolysis on this interface like this
2and separate sapphire substrate and GaN thick film gas).
But, current HVPE just cannot separate the GaN layer of growing on sapphire substrate as the growth of GaN, therefore must there is extra laser substrate separating technology, but on GaN single-crystal thick films, be easy to produce slight crack in laser substrate separating technology process, then can cause the low problem of GaN Substrate manufacture yield.
Problem sapphire substrate being separated from nitride-based semiconductor or remove improve the characteristic electron of element itself, final not only aspect the lifting of efficiency and reliability, also have in sapphire recycling and technologic manufacturing cost problem, be all the part that needs solution.
Summary of the invention
To be solved by this invention is in existing GaN single-crystal thick films making processes, and during by the GaN membrane sepn of sapphire substrate and growth, GaN film easily produces the problem of slight crack.
In order to address the above problem, the invention provides a kind of method of utilizing thermal decomposition characteristic to obtain self-standing gan substrate, it is characterized in that, comprise the following steps:
Step 1): on sapphire substrate, grow successively the first buffer layer, the second buffer layer;
Step 2): high growth temperature gallium nitride thick film layer on the second buffer layer;
Step 3): in the time of gallium nitride thick film layer growth, the first buffer layer high temperature thermolysis is gallium and nitrogen, makes to produce space between gallium nitride thick film layer and sapphire substrate;
Step 4): after gallium nitride thick film layer growth is complete, in process of cooling, gallium nitride thick film layer separates gradually with sapphire substrate, the gallium nitride base board obtaining.
Preferably, described step 1) in the first buffer layer be the gan growing out by HVPE, it grows in 600～800 DEG C of temperature, its growth thickness is 1～3 μ m, V/III ratio is 10～100.
Preferably, described step 1) in the second buffer layer after the first buffer growth completes, be warming up to 900 DEG C of growths, its thickness is 50～100 μ m, V/III ratio is 10～1000.
Preferably, described step 2) and step 1) between, the second buffer layer is also warming up to 1000 DEG C through thermal treatment.
Further, described step 2) in gallium nitride thick film layer after heat treatment continue to be warming up to 1200 DEG C of growths at the second buffer layer, its thickness is more than 300 μ m, V/III ratio is 10～50.
Preferably, the thermolysis in the time that temperature reaches more than 900 DEG C of described the first buffer layer is liquid-gallium and nitrogen.
Preferably, described gan can substitute with aluminium nitride or indium nitride, prepares aluminium nitride or indium nitride thick film layers.
The invention provides the good gan buffer layer of a kind of thermal decomposition characteristic and grow and the semi-conductive technology of separating nitrogen compound with this, buffer layer is as the method that semi-conductor is separated from growth substrate, can simplify technique and implementation is strong, is convenient to volume production.
There is chemical decomposition process because of thermal effectiveness in two buffer layers of growing on the heterogeneous substrates such as sapphire substrate.Particularly point out, the first buffer layer of low-temperature epitaxy is relatively unstable compared with other its structures of layer, so be easy to occur thermolysis, Just because of this, can on the first buffer layer, optionally accelerate thermal decomposition process.
For the first buffer layer being worked and thermolysis don't fail to have the second buffer layer, at this moment the effect of the second buffer layer is that the variation that prevents the first buffer layer in temperature rise process recrystallizes, and the high temperature nitrogen compound semi-conductor of growing above for the second buffer layer plays the effect of buffer layer.
Although, do not have the second buffer layer of the first buffer layer structurally can play the shock absorption of thick film growth, be difficult to produce self-supporting nitride semiconductor base plate.On the contrary, do not have the first buffer layer of the second buffer layer can recrystallize and cause the characteristic of gan to change in the process heating up, thermal decomposition characteristic can weaken so that finally be difficult to the separation of completing substrate like this.
To sum up, for the buffer layer that makes nitride-based semiconductor can play a role well by its thermal decomposition characteristic, must there is the first buffer layer and the second buffer layer simultaneously.
Compared with prior art, beneficial effect of the present invention is:
1., after growing in the early stage and inserting the first buffer layer and the second buffer layer between the nitride thick film semiconducting of substrate used and growth, can utilize the selective thermal destructive effect of the first buffer layer to separate in the situation that semi-conductive damage is minimum;
2. from the isolated sapphire substrate of gallium nitride layer because do not damage, so can be reused for the substrate of gan growth;
3. the first buffer layer and the second buffer layer are to insert in the process of growth of nitride-based semiconductor, so do not need additional other techniques and can complete growth under simple step, therefore in economy aspect, also show advantage;
4. the first buffer layer and the second buffer layer itself are nitride semiconductor layers, so can ensure the high-quality of the nitride-based semiconductor of growing in the above as buffer layer;
5. adopt method provided by the invention can utilize the first buffer layer and the second buffer layer can effectively make the self-supporting mono-crystal nitride semiconductor base plate of high-quality.
Brief description of the drawings
A kind of schematic diagram that utilizes thermal decomposition characteristic to obtain each step of the method for self-standing gan substrate that Fig. 1 a-c provides for embodiment;
Fig. 2 is the SEM photo comparison diagram in different gallium nitride layers cross section in sepn process.
Wherein: a is the cross section of the first buffer layer while starting to decompose; B is that the first buffer layer and the second buffer layer are from the isolated gallium nitride layer of sapphire substrate cross section; C is gallium nitride base board and the sapphire substrate separating after thermal treatment finishes.
embodiment
For the present invention is become apparent, hereby with preferred embodiment, and coordinate accompanying drawing to be described in detail below.
Embodiment 1
Utilize thermal decomposition characteristic to obtain a method for self-standing gan substrate, comprise the following steps:
Step 1): on sapphire substrate 1, grow successively the first buffer layer 3, the second buffer layer 4 (as shown in Figure 1a); The first buffer layer 3 is the gan that grow out by HVPE, and it grows in 700 DEG C of temperature, and its growth thickness is 2 μ m, and growth time is 10min, and V/III ratio is 10; The second buffer layer is warming up to 900 DEG C of growths after the first buffer layer 3 has been grown, and its thickness is 100 μ m, and growth time is 60min; Now, the thermolysis in the time that temperature reaches more than 900 DEG C of the first buffer layer 3 is liquid-gallium Ga and nitrogen N (as shown in Figure 1 b);
Step 2): the second buffer layer 4 is warming up to 1000 DEG C through thermal treatment 30min; Then high growth temperature gallium nitride thick film layer 2 on the second buffer layer 4, gallium nitride thick film layer 2 is warming up to 1200 DEG C of growths after the second buffer layer 4 thermal treatments, and its thickness is more than 300 um, and growth time is 4hr;
Step 3): in the time of gallium nitride thick film layer growth, the first buffer layer 3 high temperature thermolysiss are liquid-gallium Ga and nitrogen N, make to produce space between gallium nitride thick film layer 2 and sapphire substrate 1;
Step 4): after gallium nitride thick film layer 2 has been grown, in process of cooling, gallium nitride thick film layer 2 separates gradually with sapphire substrate 1, the gallium nitride base board (as shown in Fig. 1 c) obtaining.
In above-mentioned steps, gan can substitute with aluminium nitride or indium nitride, prepares aluminium nitride or indium nitride thick film layers.
The first buffer layer 3 is to grow at relative low temperature with the second buffer layer 4, so its physical property thermostability is poor.After Overheating Treatment, on the first buffer layer 3, can there is decomposition reaction, the nitrogen N easily gasifying can become gaseous volatilization to be fallen, and gallium Ga can be with liquid residue on the interface of sapphire substrate 1 and nitride substrate.That is to say, 3 li of the first buffer layers of decomposition comprise gallium Ga and space and undecomposed gan.
What show below is above-mentioned decomposition reaction formula.
2GaN(s)→2Ga(l)+N
2(g)
Then in the time period that, the liquid-gallium Ga on interface grows at gallium nitride thick film layer 2 part may with from the outside inject nitrogen ion recombine.
Because recombine now mainly occurs in the surface of dissimilar substrate (being sapphire substrate 1) and the back side of nitride substrate (facing to the side of dissimilar substrate), so the bonding force of dissimilar substrate and the first buffer layer 3 nitride substrate above obviously weakens, and exists with a kind of space form.Fig. 2 is visible, in a figure, only in the first buffer layer 3, selective separation has occurred.Under the state separating with sapphire substrate 1 at nitride substrate, can see at the recrystallize of the back side of nitride substrate gan more, at this moment because of the sapphire compared with dissimilar substrate, on the nitride surface of material of the same race, be easier to the process of the recombine that liquid-gallium occurs.What b figure showed is utilizes the first buffer layer and the second buffer layer SEM photo from the cross section of the isolated nitride substrate of sapphire substrate.C figure separates the SEM surface picture recording after nitride substrate and sapphire substrate after thermal treatment finishes.
Claims (7)
1. utilize thermal decomposition characteristic to obtain a method for self-standing gan substrate, it is characterized in that, comprise the following steps:
Step 1): the first buffer layer (3) of growing successively on sapphire substrate (1), the second buffer layer (4);
Step 2): at the upper high growth temperature gallium nitride thick film layer (2) of the second buffer layer (4);
Step 3): in the time that gallium nitride thick film layer (2) is grown, the first buffer layer (3) high temperature thermolysis is gallium (Ga) and nitrogen (N), makes to produce space between gallium nitride thick film layer (2) and sapphire substrate (1);
Step 4): after gallium nitride thick film layer (2) has been grown, in process of cooling, gallium nitride thick film layer (2) separates gradually with sapphire substrate (1), the gallium nitride base board obtaining.
2. the method for utilizing thermal decomposition characteristic to obtain self-standing gan substrate as claimed in claim 1, it is characterized in that, described step 1) in the first buffer layer (3) be the gan growing out by HVPE, it grows in 600～800 DEG C of temperature, its growth thickness is 1～3 μ m, and V/III ratio is 10～100.
3. the method for utilizing thermal decomposition characteristic to obtain self-standing gan substrate as claimed in claim 1, it is characterized in that, described step 1) in the second buffer layer (4) after the first buffer layer (3) has been grown, be warming up to 900 DEG C of growths, its thickness is 50～100 μ m, and V/III ratio is 10～1000.
4. the method for utilizing thermal decomposition characteristic to obtain self-standing gan substrate as claimed in claim 1, is characterized in that described step 2) and step 1) between, the second buffer layer (4) is also warming up to 1000 DEG C through thermal treatment.
5. the method for utilizing thermal decomposition characteristic to obtain self-standing gan substrate as claimed in claim 4, it is characterized in that, described step 2) in gallium nitride thick film layer (2) after heat treatment continue to be warming up to 1200 DEG C of growths at the second buffer layer (4), its thickness is more than 300 μ m, and V/III ratio is 10～50.
6. the method for utilizing thermal decomposition characteristic to obtain self-standing gan substrate as claimed in claim 1, is characterized in that, the thermolysis in the time that temperature reaches more than 900 DEG C of described the first buffer layer is liquid-gallium (Ga) and nitrogen (N).
7. the method for utilizing thermal decomposition characteristic to obtain self-standing gan substrate as claimed in claim 1, is characterized in that, described gan can substitute with aluminium nitride or indium nitride, prepares aluminium nitride or indium nitride thick film layers.
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| CN107275188A (en) * | 2017-06-26 | 2017-10-20 | 镓特半导体科技（上海）有限公司 | Semiconductor structure, self-standing gan layer and preparation method thereof |
| CN107316801A (en) * | 2017-06-26 | 2017-11-03 | 镓特半导体科技（上海）有限公司 | Semiconductor structure, self-standing gan layer and preparation method thereof |
| CN107316803A (en) * | 2017-06-26 | 2017-11-03 | 镓特半导体科技（上海）有限公司 | Semiconductor structure, self-standing gan layer and preparation method thereof |
| CN107316800A (en) * | 2017-06-26 | 2017-11-03 | 镓特半导体科技（上海）有限公司 | Self-standing gan layer and preparation method thereof |
| CN111430220A (en) * | 2020-03-26 | 2020-07-17 | 江苏南大光电材料股份有限公司 | Preparation method of GaN self-supporting substrate |
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Application publication date: 20141203 |