A kind of silica-based compound substrate
Technical field
The utility model relates to a kind of Semiconductor substrate, in particular to a kind of silica-based compound substrate that is used to prepare the nitride semiconductor epitaxial material.
Background technology
Nitride-based semiconductor, especially gallium nitride (GaN) are the key foundation materials that preparation is applied to the LED device in semiconductor lighting and display backlight field.Owing to lack the homoplasmon monocrystal material, the device application of GaN material is carried out in heterogeneous substrate usually, and that the most frequently used is sapphire (Al
2O
3) substrate, because sapphire substrates is non-conductive, hardness is big, price is higher, the GaN base LED device on it prepares difficulty and cost is difficult to reduce always.Sapphire and GaN are compared in carborundum (SiC) substrate better lattice match relation, but it costs an arm and a leg, and GaN base LED device technology is only grasped by indivedual major companies it on, so is not suitable for the widespread commercial popularization.One of approach that reduces GaN base LED device preparation cost is to adopt large-sized substrates, and present sapphire and SiC substrate more than 4 inches still is difficult to obtain and cost an arm and a leg.The existing large scale of silicon (Si) substrate is cheap again, and ripe application in microelectronics industry, does substrate with Si and can reduce GaN base LED preparation of devices cost significantly, and its economic benefit is considerable, and the marketing prospect also is expected most.But preparation GaN base LED epitaxial wafer material will face three aspect challenges in the Si substrate:
(1) Macrolattice mismatch problem.Between Si and the GaN because lattice constant is different, can in the GaN epitaxial loayer, gather very large lattice mismatch stress at early growth period, be not transferred and coordinate to discharge as lattice mismatch stress, will be after the GaN growth thickness surpasses a certain critical thickness to discharge in the form that causes high density dislocation and defective at the interface, the surface can be bred and extend to break-through dislocation wherein also.The crystalline quality that lattice mismatch stress causes worsens will greatly influence the photoelectric properties of GaN material;
(2) thermal mismatch problem.The thermal coefficient of expansion of Si is 2.6 * 10
-6The thermal coefficient of expansion that K, GaN are parallel to a axle is 5.6 * 10
-6K, thermal coefficient of expansion between Si and the GaN differs greatly, it is much thick to add that silicon base (thick hundreds of μ m) is compared GaN epitaxial loayer (thick a few μ m), drop to room temperature from 1050 ℃ of left and right sides growth temperatures and will produce very large thermal stress, and this thermal stress is very large tensile stress for the GaN material.So big hot tensile stress will cause GaN rete be full of cracks or crooked and can't carry out follow-up LED device architecture preparation as not being transferred and coordinating to discharge;
(3) surface chemistry problem.As direct growth GaN material in the Si substrate, 1050 ℃ of left and right sides growth temperatures can cause Si to spread to the GaN middle and high concentration; Simultaneously, the Ga of early growth period drips also can corrode the Si surface, Si and N reaction also easily formation amorphous silicon nitride (SiN
x) material.These surface chemistry problems have all greatly influenced GaN nucleation and continuous film forming, are unfavorable for GaN epitaxial loayer high-quality growth.
In order to overcome the above-mentioned big mismatch epitaxial problem of Si base GaN material, developed several different methods at present: as stress covariant layer (comprising resilient coating, flexible layer, insert layer etc.) and graph substrate.The mismatch stress coordination function of existing stress covariant layer is more single.Has better effects aspect transfer and the coordination release Macrolattice mismatch stress, but effect is limited aspect transfer and the big thermal mismatch stress of coordination release, as using aluminium nitride (AlN), the AlGaN of content gradually variational, scandium nitride (ScN), zirconium nitride (ZrN), zirconium boride (ZrB
2) wait and do lattice mismatch stress covariant layer and interface barrier, with aluminium oxide (γ-Al
2O
3) and hafnium nitride (HfN) do resilient coating and interface barrier etc.; Having preferably, thermal stress shifts and coordinates releasing effect, can prepare and have certain thickness flawless GaN epitaxial film materials, but the effect aspect coordination lattice mismatch stress is limited, even can reduce the crystalline quality of GaN epitaxial loayer, as doing resilient coating and interface barrier, do insert layer etc. with low temperature aluminium nitride (AlN) layer with titanium nitride (TiN).The graph substrate method then need be done mask and litho pattern (figure of nanometer or micro-meter scale) on silicon base or GaN epitaxial loayer, because of window place dislocation density is difficult to reduce repeatedly mask and litho pattern, complex process, not only greatly raised the material preparation cost, also be difficult to obtain the uniform large scale GaN epitaxial film materials of flawless and bending and crystalline quality simultaneously, as the GaN epitaxial film materials more than the 2 inches diameter.
The utility model content
The purpose of this utility model is at Macrolattice mismatch, big thermal mismatching and surface chemistry problem and prior art deficiency in the preparation gallium nitride based LED epitaxial wafer material on the silicon base, and a kind of silica-based compound substrate that is used for gallium nitride, aluminium nitride, indium nitride, aluminum gallium nitride, indium gallium nitrogen, aluminium gallium nitrogen monocrystal thin films material and LED device architecture preparation growth thereof is provided.
The utility model provides a kind of silica-based compound substrate that is used to prepare the nitride semiconductor epitaxial material, comprises: a silicon (Si) single crystal substrates; One combined stress covariant layer is formed on silicon (Si) single crystal substrates, and repeatedly being overlapped each other by aluminium nitride (AlN) and titanium nitride (TiN) monocrystal thin films material constitutes; One gallium nitride (GaN) template layer is formed on the combined stress covariant layer, is made of gallium nitride (GaN) monocrystal thin films material.
The thickness of every layer on aluminium nitride (AlN) layer is 15~90nm in the described combined stress covariant layer, and 2~10 layers of the numbers of plies play the lattice mismatch stress to the basic gallium nitride of silicon (Si) (GaN) material and shift and coordinate to discharge and the interface barrier effect.
The thickness of every layer on titanium nitride (TiN) layer is not more than 1/3 of the every layer thickness of thin aluminium nitride (AlN) layer in the described combined stress covariant layer, and each titanium nitride (TiN) layer is inserted into respectively between each aluminium nitride (AlN) layer, realize that from the rate of temperature fall that growth temperature drops to room temperature the thermal stress of the basic gallium nitride of silicon (Si) (GaN) material shifts and coordinate release by regulation and control gallium nitride (GaN) template layer, to avoid gallium nitride (GaN) template layer to crack and bending.
The thickness of described gallium nitride (GaN) template layer is not less than 1 μ m, and the rate of temperature fall that drops to room temperature from 1100 ℃ of growth temperatures is 5~20 ℃/minute.
The material growth technique of gallium nitride (GaN) monocrystal thin films material includes but not limited to metal-organic chemical vapor deposition equipment (MOCVD), ion beam epitaxy (IBE), molecular beam epitaxy (MBE), pulsed laser deposition (PLD), plasma auxiliary chemical vapor deposition (PE-CVD) and magnetron sputtering deposition (MSD) in the described aluminium nitride (AlN) that is used for preparing combined stress covariant layer and titanium nitride (TiN) monocrystal thin films material and gallium nitride (GaN) template layer.
The basic compound substrate of described silicon (Si) can be used for the preparation growth of gallium nitride (GaN), aluminium nitride (AlN), indium nitride (InN), aluminum gallium nitride (AlGaN), indium gallium nitrogen (InGaN), aluminium gallium nitrogen (InAlGaN) monocrystal thin films material and LED device architecture thereof.
The utility model has adopted the combined stress covariant layer that is overlapped and constituted by nitride multilayer aluminium and titanium nitride monocrystal thin films material, wherein aluminium nitride and silicon (Si) and gallium nitride (GaN) all have fine lattice match relation and have good heat, chemical stability, thereby be reduced in the GaN template layer probability of introducing dislocation and defective, the thermal coefficient of expansion of titanium nitride is greater than silicon, the thermal coefficient of expansion of gallium nitride and aluminium nitride, hot tensile stress is transferred to earlier coordinated in each layer TiN monocrystal thin films material to discharge, multilayer Al N and TiN overlapping structure can be introduced more interfaces, and the break-through dislocation that play again below stoping at the interface of these increases is upwards bred progradation.Therefore, overlap the mutually combined stress covariant layer that constitutes of AlN and TiN has and compares existing stress covariant layer, resilient coating and the better lattice mismatch stress of low temperature insert layer and thermal stress shifts trade-off effect.
In addition, AlN and the TiN combined stress covariant layer that constitutes that overlaps mutually can adopt and the preparation successively on same equipment of GaN template layer identical materials growth technique, therefore compares existing graph substrate technology, and preparation technology is simpler also more practical.
In addition, the utility model only just can obtain low-dislocation-density flawless and crooked Si base compound substrate by the thickness and the rate of temperature fall behind the overlapping number of plies and the epitaxial growth GaN template layer of AlN in the regulation and control combined stress covariant layer and TiN monocrystal thin films material, therefore can obtain larger sized Si base compound substrate, with this kind large-sized substrate epitaxial growth GaN material and preparation LED device architecture, will certainly reduce the preparation cost of existing GaN base LED epitaxial wafer material significantly.
Description of drawings
Fig. 1 is the structural representation that is used for the basic compound substrate of silicon (Si) of gallium nitride (GaN) LED epitaxial wafer material preparation.
The main element symbol description
1: the basic compound substrate of silicon (Si);
11: silicon (Si) substrate;
12: combined stress covariant layer;
121: thin aluminium nitride (AlN) monocrystal thin films material;
122: ultra-thin titanium nitride (TiN) monocrystal thin films material;
13: gallium nitride (GaN) template layer.
Embodiment
Elaborate preferred implementation of the present utility model below in conjunction with accompanying drawing.
The utility model provides a kind of silicon (Si) basic compound substrate, and it can be used for gallium nitride, aluminium nitride, indium nitride, aluminum gallium nitride, indium gallium nitrogen, aluminium gallium nitrogen monocrystal thin films material and LED device architecture preparation growth thereof.
Fig. 1 is the structural representation that is used for the basic compound substrate 1 of silicon (Si) of gallium nitride (GaN) LED epitaxial wafer material preparation.This silica-based compound substrate comprises: a silicon (Si) single crystal substrates 11 plays a supportive role; One combined stress covariant layer 12; And gallium nitride (GaN) monocrystal thin films template layer 13.This combined stress covariant layer 12 is grown on the Si single crystal substrates 11, by thick thin aluminium nitride (AlN) monocrystal thin films material 121 of 15~90nm and thick ultra-thin titanium nitride (TiN) the monocrystal thin films material 122 of the 5~30nm formation that overlaps repeatedly.Wherein, the TiN layer thickness is not more than 1/3 of AlN layer thickness.Thin AlN layer 121 is used for shifting and coordinating to discharge the lattice mismatch stress that Si base GaN material produces in epitaxial process, and ultra-thin TiN layer 122 is used for shifting and coordinate to discharge the thermal stress that Si base GaN material produces at temperature-fall period significantly.
As shown in Figure 1, the layer that contacts with silicon single crystal substrate 11 in the combined stress covariant layer 12 is preferably AlN layer 121, and this is because the lattice constant and the silicon of AlN layer are more approaching, can improve the effect of the alleviation lattice mismatch power of combined stress covariant layer 12 like this.Yet the utility model is not limited to situation shown in Figure 1, and the layer that combined stress covariant layer contacts with silicon base also can be the TiN layer.In addition, because the lattice constant of AlN layer and the lattice constant of gallium nitride (GaN) monocrystal thin films template layer 13 are more approaching, as shown in Figure 1, the layer that contacts with gallium nitride (GaN) monocrystal thin films template layer 13 in the combined stress covariant layer 12 is preferably AlN layer 121, but is not limited thereto.
This gallium nitride (GaN) monocrystal thin films template layer 13 is grown on the combined stress covariant layer 12, thickness is not less than 1 μ m, can be by the thickness of the thin AlN layer 121 in the regulation and control combined stress covariant layer 12 and the dislocation density that the number of plies reduces GaN monocrystal thin films in the GaN template layer 13, the thickness that also can be by ultra-thin TiN layer 122 in the regulation and control combined stress covariant layer 12 and the rate of temperature fall of the number of plies and cooling are significantly eliminated crackle and the bending in the GaN template layer 13.
Silicon (Si) single crystal substrates 11, combined stress covariant layer 12 and gallium nitride (GaN) monocrystal thin films template layer 13 threes combine and constitute the basic compound substrate 1 of silicon (Si), for the material preparation of follow-up gallium nitride (GaN) LED epitaxial wafer provides low-dislocation-density, flawless and crooked gallium nitride (GaN) homogeneity single crystalline substrate template.
Introduce the preparation method of the above-mentioned silica-based GaN compound substrate of preparation below.Should be appreciated that preparation method described below is only for preparing an instantiation of silica-based GaN compound substrate of the present utility model.Those skilled in the art can make change according to design needs and other factors under instruction of the present utility model.
Embodiment 1:
It is as follows to adopt metal-organic chemical vapor deposition equipment (MOCVD) prepared to be used for the technological process of the basic compound substrate of silicon (Si) of gallium nitride (GaN) LED epitaxial wafer material preparation.
Step 1: get one and have 4 inches Si single crystal substrates 11 of Si (111) face;
Step 2: the Si that will clean (111) single crystal substrates 11 is put into the MOCVD equipment reaction chamber;
Step 3: on Si (111) single crystal substrates 11, prepare the thin AlN monocrystal thin films material 121 of growth 1 bed thickness 50nm earlier as barrier layer and lattice mismatch stress covariant layer with MOCVD technology;
Step 4: grow the ultra-thin TiN monocrystal thin films of 1 bed thickness 10nm material 122 as thermal stress covariant layer with the preparation on the thin AlN layer 121 of thick 50nm of MOCVD technology again.
Step 5: repeating step 3 and step 4 obtain the combined stress covariant layer material 12 that is overlapped and constituted by thin AlN layer 121 of 5 bed thickness 50nm and the ultra-thin TiN layer 122 of 4 bed thickness 10nm with the MOCVD prepared.
Step 6: use the MOCVD technology GaN monocrystal thin films material that 1 layer of 2 μ m of regrowth is thick on combined stress covariant layer material 12 as GaN template layer 13.
Step 7: the rate of temperature fall of regulation and control GaN template layer 13, drop to 750 ℃ with 10 ℃/minute rate of temperature fall from 1050 ℃ earlier, drop to 250 ℃ with 20 ℃/minute rate of temperature fall from 750 ℃ again, drop to room temperature at last naturally.
Step 8: the Si base compound substrate 1 of taking out the GaN template layer 13 that comprises Si single crystal substrates 11, combined stress covariant layer 12, low-dislocation-density flawless and bending from the MOCVD equipment reaction chamber.
After finishing 4 inches Si base compound substrate 1 as mentioned above, can do GaN homogeneity single crystalline substrate template with this Si base compound substrate 1, adopt the efficient luminous basic blue-ray LED epitaxial wafer of gallium nitride (GaN) material of MOCVD prepared.
Realized beneficial effect as described below according to silica-based compound substrate of the present utility model.
(1) the combined stress covariant layer in the utility model is compared existing intermediate layer technology (comprising crystal lattice stress covariant layer and resilient coating) and insert layer technology and is had better stress transfer and coordinate releasing effect.Be embodied in following three aspects:
1) select for use multi-layer thin aluminium nitride (AlN) the monocrystal thin films material that with silicon (Si) and gallium nitride (GaN) fine lattice match relation is arranged all and have good heat, a chemical stability to do the transfer and the coordination releasing layer of lattice mismatch stress.The lattice mismatch of AlN and Si is 2.76%, the lattice mismatch of GaN and AlN is-2.47%, because the thickness that thin AlN monocrystal thin films material is compared GaN monocrystal thin films material and Si single crystalline substrate all approaches a lot, but based on covariant substrate (Compliantsubsrates) but the stress transfer thought in covariant intermediate layer, lattice mismatch stress between GaN and the Si can shift earlier to be assigned in the thin AlN monocrystal thin films material of each layer in the GaN of GaN template layer monocrystal thin films material growth course and coordinate to discharge, thereby be reduced in the GaN template layer probability of introducing dislocation and defective, even introduce dislocation also is the at the interface introducing of elder generation at Si and AlN monocrystal thin films material, and can not produce more bad influence to top GaN template layer.Particularly, multilayer Al N and TiN overlapping structure that the utility model adopts can be introduced more interfaces, and the break-through dislocation that play again below stoping at the interface of these increases is upwards bred progradation, thereby has further reduced dislocation density.In more existing research work and technology, mostly adopt single thin layer AlN material or other materials to do that crystal lattice stress shifts and coordinate releasing layer, upwards breed DeGrain aspect the extension suppressing the break-through dislocation.
2) select transfer and the coordination releasing layer of the ultra-thin titanium nitride of the big multilayer of thermal coefficient of expansion (TiN) monocrystal thin films material for use as thermal stress.The thermal coefficient of expansion of TiN is 9.35 * 10
-6K compares 5.59 * 10 of GaN
-64.15 * 10 of K, AlN
-62.6 * 10 of K and Si
-6K is big a lot, the GaN monocrystal thin films material that adds ultra-thin TiN monocrystal thin films material thin in comparison AlN monocrystal thin films material and GaN template layer all approaches a lot, but but based on the stress transfer thought in the covariant intermediate layer of covariant substrate, thermal expansion coefficient difference can produce and gather very large hot tensile stress GaN monocrystal thin films template layer drops to the room temperature process because of Si and GaN from the growth temperature up to 1100 ℃ between, by the regulation and control rate of temperature fall hot tensile stress is transferred to earlier and be coordinated in the ultra-thin TiN monocrystal thin films of each layer material to discharge, and then realize GaN template layer flawless and bending.Can in the TiN material, produce earlier even crack also, and can top GaN template layer not exerted an influence.In addition, TiN material that the utility model is selected for use and AlN material have lattice match relation preferably, the lattice mismatch of cube TiN (111) face and six side AlN (0002) faces is 3.45%, although with the lattice mismatch of six side GaN (0002) faces be-6.14%, because the TiN material is very thin, ultra-thin TiN layer is clipped between each thin AlN layer grows with the AlN coherence, thereby compares existing low temperature insert layer technology, also can not influence top GaN template layer crystalline growth quality.
3) overlap the mutually combined stress covariant layer that constitutes of thin AlN and ultra-thin TiN had both had and had compared existing stress covariant layer, resilient coating and the better lattice mismatch stress of low temperature insert layer and thermal stress shifts trade-off effect, also can adopt and the preparation successively on same equipment of GaN template layer identical materials growth technique, therefore compare existing graph substrate technology, preparation technology is simpler also more practical.
(2) the utility model only just can obtain low-dislocation-density flawless and crooked Si base compound substrate by the thickness and the rate of temperature fall behind the overlapping number of plies and the epitaxial growth GaN template layer of thin AlN in the regulation and control combined stress covariant layer and ultra-thin TiN monocrystal thin films material, as increase the size of Si substrate, can obtain diameter and be not less than 4 inches GaN homogeneity monocrystalline template, with this kind large-sized substrate epitaxial growth GaN material and preparation LED device architecture, will certainly reduce the preparation cost of existing GaN base LED epitaxial wafer material significantly.Therefore, have appreciable economic benefit and extraordinary marketing prospect.
Above execution mode does not just limit its protection range to exemplary illustration of the present utility model.Those skilled in the art can carry out the part to it and change, and not breaking away under the utility model spirit prerequisite, all belong to the utility model is equal to replacement, therefore all within the utility model protection range.