CN102208338B - Sapphire-base compound substrate and manufacturing method thereof - Google Patents

Abstract

The invention provides a sapphire-base compound substrate and a manufacturing method thereof. The sapphire-base compound substrate is used for preparing a nitride semiconductor epitaxial material and is characterized by comprising a sapphire-base monocrystal substrate, a compound stress covariant layer which is covered on the sapphire-base monocrystal substrate and formed by alternatively stacking an aluminum nitride monocrystal thin film material and a multi-layer titanium nitride monocrystal thin film material, and a gallium nitride template layer which grows on the compound stress covariant layer and consists of a gallium nitride monocrystal thin film material.

Description

Sapphire-base compound substrate and manufacture method thereof

Technical field

The present invention relates to the substrate for epitaxial growth of semiconductor material growth, more specifically, relate to a kind of sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material.

Background technology

Nitride-based semiconductor, especially gallium nitride (GaN) are that Application and preparation is in the core material of light-emitting diode (LED) device in semiconductor lighting and display backlight field.Owing to lacking homoplasmon monocrystal material, the device application of GaN material is carried out conventionally in heterogeneous substrate, and that the most frequently used is sapphire (a-Al₂o₃) substrate.But because sapphire substrates and GaN material exist larger difference can run into the problem aspect two in lattice constant and thermal coefficient of expansion: (1) Macrolattice mismatch problem: because of lattice constant (a=0.3189nm, c=0.5185nm) and the a-Al of GaN₂o₃lattice constant (a=0.4758nm, c=1.299nm) difference causes at the GaN epitaxial loayer epitaxial growth initial stage and produces very large lattice mismatch stress, when the thickness of the GaN epitaxial loayer of growing exceedes a certain critical thickness, (several nm, tens nm or hundreds of nm are thick, specifically depending on the intermediate layer situation of introducing) after, this Macrolattice mismatch stress accumulating in GaN epitaxial loayer will discharge with the form that produces dislocation and defect in interface, and this is by the performance that causes the deterioration of GaN epitaxial loayer crystalline quality and then reduce follow-up LED device; (2) large thermal mismatch problem: because of thermal coefficient of expansion (a:5.59 × 10 of GaN^-6k, c:3.17 × 10^-6k) and a-Al₂o₃thermal coefficient of expansion (a:7.5 × 10^-6k, c:8.5 × 10^-6k) also exist big-difference to cause GaN epitaxial loayer or LED device architecture to gather very large thermal stress from very high growth temperature (as 800～1100 ℃) drops to the process of room temperature very much, this thermal stress is a kind of compression and then the bending that causes GaN epitaxial loayer for GaN epitaxial loayer.Larger thermal stress is gathered in employing and bending GaN epitaxial loayer is prepared LED device, certainly will affect the raising of LED device performance and yields.Shift at present and coordinate to discharge sapphire (a-Al₂o₃) common method of the large mismatch stress of GaN epitaxial loayer has in substrate: stress covariant layer (comprising resilient coating, flexible layer, insert layer etc.) and graph substrate.Existing stress covariant layer, as low temperature GaN resilient coating, AlGaN component-gradient buffer layer, thin AlN flexible layer, thin InAlGaN flexible layer etc., although have better effects aspect transfer and coordination release Macrolattice mismatch stress, aspect transfer and the large thermal mismatch stress of coordination release, effect is limited.And graph substrate method need to be done mask and litho pattern (figure of nanometer or micro-meter scale) on sapphire substrates or GaN epitaxial loayer, because being difficult to reduce, window place dislocation density needs repeatedly mask and litho pattern, complex process and further raised material preparation cost, also be difficult to obtain without bending and the uniform large scale GaN epitaxial film materials of crystalline quality, as GaN epitaxial film materials more than 2 inches diameter simultaneously.

Summary of the invention

The object of the invention is to for sapphire (a-Al₂o₃) prepare the Macrolattice mismatch in GaN-based LED epitaxial wafer material, large thermal mismatching and surface chemistry problem and the deficiencies in the prior art in substrate, a kind of sapphire-base compound substrate of preparing for GaN-based LED epitaxial wafer material is provided.

The invention provides a kind of sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material, it is characterized in that, comprise: a sapphire single-crystal substrate; One combined stress covariant layer, covers in described sapphire single-crystal substrate, by nitride multilayer aluminium monocrystal thin films material and nitride multilayer ti single crystal thin-film material, is replaced and is stackingly formed; One gallium nitride template layer, is grown on described combined stress covariant layer, monocrystalline GaN film material, consists of.

In combined stress covariant layer, the thickness of aluminium nitride (AlN) layer is 15～90nm.

In combined stress covariant layer the thickness of every layer of titanium nitride monocrystal thin films material be not more than every layer of aluminum nitride single crystal film material thickness 1/3.

The layer contacting with sapphire substrates in combined stress covariant layer is aluminum nitride single crystal film material.

The layer contacting with gallium nitride template layer in combined stress covariant layer is aluminum nitride single crystal film material.

In combined stress covariant layer, the number of plies of aluminum nitride single crystal film material is 2～10 layers.

Aluminum nitride single crystal film material is to sapphire (a-Al₂o₃) suprabasil gallium nitride (GaN) material rise lattice mismatch stress shift with coordinate release action, to reduce the dislocation density of gallium nitride (GaN) epitaxial material and to improve crystalline growth quality.

Each titanium nitride (TiN) layer is inserted into respectively between each aluminium nitride (AlN) layer, and the rate of temperature fall that drops to room temperature from growth temperature by regulation and control gallium nitride (GaN) template layer is realized sapphire (a-Al₂o₃) base gallium nitride (GaN) material thermal stress shifts and coordination discharges, to eliminate stress and the bending of gallium nitride (GaN) template layer.

The thickness of gallium nitride (GaN) template layer is not less than 2 μ m, and the rate of temperature fall that drops to room temperature from the growth temperature of 1100 ℃ during growing gallium nitride template layer is 5～20 ℃/min.

For the preparation of the Material growth technique of the AlN in combined stress covariant layer and TiN monocrystal thin films material and GaN template layer, include 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).

Sapphire (a-Al₂o₃) base compound substrate can be 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 nitride semiconductor LED device architecture.

The present invention also provides a kind of method of manufacturing sapphire-base compound substrate, and this sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material, is characterized in that, comprises: get a sapphire single-crystal substrate; In described sapphire single-crystal substrate, form a combined stress covariant layer, described combined stress covariant layer is replaced and is stackingly formed by aluminum nitride single crystal film material and titanium nitride monocrystal thin films material; On described combined stress covariant layer, form a gallium nitride template layer, described gallium nitride template layer consists of monocrystalline GaN film material.

Accompanying drawing explanation

Fig. 1 is the sapphire (a-Al for the preparation of gallium nitride (GaN) LED epitaxial wafer material₂o₃) base composite substrate structure schematic diagram.

Embodiment

Below in conjunction with accompanying drawing, elaborate the preferred embodiment of the present invention.

Fig. 1 is the sapphire (a-Al for the preparation of gallium nitride (GaN) LED epitaxial wafer material₂o₃) base composite substrate structure schematic diagram.As shown in the figure, sapphire (a-Al₂o₃) base compound substrate 1 comprises a sapphire (a-Al₂o₃) single crystal substrates 11 and from sapphire (a-Al₂o₃) single crystal substrates 11 sides the combined stress covariant layer 12 and gallium nitride (GaN) the monocrystal thin films template layer 13 that set gradually.

Sapphire (a-Al₂o₃) single crystal substrates 11 plays a supportive role.

Combined stress covariant layer 12 covers sapphire (a-Al₂o₃) in single crystal substrates 11, by thick thin aluminium nitride (AlN) the monocrystal thin films material 121 of multilayer 15～90nm and thick ultra-thin titanium nitride (TiN) the monocrystal thin films material 122 of multilayer 5～30nm, replace stacking formation.As shown in Figure 1, in combined stress covariant layer 12 with sapphire (a-Al₂o₃) layer that contacts of single crystal substrates 11 is preferably AlN layer 121, this is because lattice constant and the sapphire (a-Al of AlN layer₂o₃) more approaching, can improve like this effect of the alleviation lattice mismatch power of combined stress covariant layer 12.But the present invention is not limited to the situation shown in Fig. 1, combined stress covariant layer and sapphire (a-Al₂o₃) substrate contact layer can be also TiN layer.The thickness of each TiN layer is not more than 1/3 of each AlN layer thickness.Thin AlN layer 121 is used for shifting and coordinates to discharge sapphire (a-Al₂o₃) substrate and on it growth gallium nitride single crystal film template layer 13 (will be described later) epitaxial process produce lattice mismatch stress.The GaN material that ultra-thin TiN layer 122 was used for shifting and coordinated to discharge process for sapphire-based Grown is in thermal stress that significantly temperature-fall period produces.The preparation method of AlN layer 121 and TiN layer 122 includes but not limited to metal-organic chemical vapor deposition equipment, ion beam epitaxy, molecular beam epitaxy, pulsed laser deposition, plasma auxiliary chemical vapor deposition and magnetron sputtering deposition.

Gallium nitride (GaN) monocrystal thin films template layer 13 covers on combined stress covariant layer 12, thickness is not less than 2 μ m, can reduce the dislocation density in GaN template layer 13 by thickness and the number of plies of the thin AlN layer 121 in regulation and control combined stress covariant layer 12, also can be by thickness and the number of plies of ultra-thin TiN layer 122 in regulation and control combined stress covariant layer 12 and the rate of temperature fall while controlling growing GaN template layer 13 eliminate thermal stress in GaN template layer 13 with bending.In addition, due to the lattice constant of AlN layer and the lattice constant of gallium nitride (GaN) monocrystal thin films template layer 13 more approaching, as shown in Figure 1, the layer contacting with gallium nitride (GaN) monocrystal thin films template layer 13 in combined stress covariant layer 12 is preferably AlN layer 122.The preparation method of gallium nitride (GaN) monocrystal thin films template layer 13 includes but not limited to metal-organic chemical vapor deposition equipment, ion beam epitaxy, molecular beam epitaxy, pulsed laser deposition, plasma auxiliary chemical vapor deposition and magnetron sputtering deposition.

Above-mentioned three combines the sapphire (a-Al of formation₂o₃) base compound substrate 1 can provide low-dislocation-density, unstressed and bending homogeneity single crystalline substrate template for the preparation of follow-up nitride semiconductor epitaxial sheet material.Although above-mentioned with sapphire (a-Al₂o₃) base compound substrate for the preparation of gallium nitride (GaN) for example is illustrated, but, will be appreciated that at sapphire (a-Al₂o₃) in base compound substrate, can also prepare lamination and the nitride semiconductor LED device architecture of the nitride semi-conductor materials such as growing aluminum nitride, indium nitride, aluminum gallium nitride, indium gallium nitrogen, aluminium gallium nitrogen monocrystal thin films material, above-mentioned various monocrystal thin films materials.

Combined stress covariant layer in the present invention is compared existing stress covariant layer technology (comprising resilient coating, flexible layer, insert layer etc.) and is had better stress transfer and coordinate releasing effect.Be embodied in following three aspects:

1) select and sapphire (a-Al₂o₃) and gallium nitride (GaN) multi-layer thin aluminium nitride (AlN) the monocrystal thin films material that has a fine Lattice Matching relation as the transfer of lattice mismatch stress with coordinate releasing layer.

Because thin AlN monocrystal thin films material is compared GaN monocrystal thin films material (thickness at least 2 micron thick) and sapphire (a-Al₂o₃) thickness of single crystal substrates (thickness at least 100 micron thick) is all thin a lot, based on compliant substrate (Compliantsubsrates) can covariant intermediate layer stress transfer thought, GaN and sapphire (a-Al₂o₃) between lattice mismatch stress can be first in the GaN of GaN template layer monocrystal thin films Material growth process shift to be assigned to and in each layer thin AlN monocrystal thin films material, coordinate release, thereby be reduced in the probability of introducing dislocation and defect in GaN template layer, even if introduce dislocation, be also first at sapphire (a-Al₂o₃) introduce with the interface of AlN monocrystal thin films material, and can not produce more bad impact to GaN template layer above.Particularly, multilayer Al N and the overlapping structure of TiN that the present invention adopts, the interface that introducing increases is played again and is stoped threading dislocation below upwards to breed the effect of extension, 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 lattice mismatch stress transfer and coordinate releasing layer, upwards breeding DeGrain aspect extension suppressing threading dislocation.

2) select Multilayer ultrathin titanium nitride (TiN) monocrystal thin films material that thermal coefficient of expansion is large as the transfer of thermal stress and coordinate releasing layer.The thermal coefficient of expansion of TiN is 9.35 × 10^-6k, not only compares 5.59 × 10 of GaN^-64.15 × 10 of K and AlN^-6k is much larger, also than sapphire (a-Al₂o₃) 7.5 × 10^-6k is large, adds that ultra-thin TiN monocrystal thin films material compares GaN monocrystal thin films material and the sapphire (a-Al of thin AlN monocrystal thin films material, GaN template layer₂o₃) single crystal substrates is all thin a lot, based on compliant substrate can covariant intermediate layer stress transfer thought, at GaN monocrystal thin films template layer, from the growth temperature of 800～1100 ℃, drop to room temperature process because of sapphire (a-Al₂o₃) and GaN between thermal expansion coefficient difference can produce the large thermal stress gathering, by regulation and control rate of temperature fall, can make thermal stress first transfer to the form with tensile stress in each layer of ultra-thin TiN monocrystal thin films material and coordinate to discharge, and then it is unstressed and bending to realize GaN template layer.In addition, the TiN material that the present invention selects and AlN material have good Lattice Matching relation, 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 TiN material is very thin, ultra-thin TiN layer is clipped between each thin AlN layer and AlN coherent growth, thereby compares existing low temperature insert layer technology and can not affect the crystalline growth quality of GaN template layer above.

3) the combined stress covariant layer that thin AlN and ultra-thin TiN replace stacking formation had both had to be compared existing stress covariant layer (comprising resilient coating, flexible layer and low temperature insert layer) better lattice mismatch stress and thermal stress shifts trade-off effect, also can adopt the growth technique identical with GaN template layer preparation successively on same equipment, therefore compare existing graph substrate technology, preparation technology is more simply also more practical.

The only thickness by the thin AlN in regulation and control combined stress covariant layer and ultra-thin TiN layer and replace rate of temperature fall after the stacking number of plies and epitaxial growth GaN template layer and just can obtain low-dislocation-density and unstressed and bending sapphire (a-Al of the present invention₂o₃) base GaN compound substrate, with this kind of large-sized substrate epitaxial growth GaN material and preparation LED device architecture, will certainly increase substantially performance and the yields of the gallium nitride based LED epitaxial wafer material of preparing in existing sapphire substrates.Therefore, be applicable to very much application and marketing.

Introduce the above-mentioned sapphire (a-Al of preparation below₂o₃) preparation method of base GaN compound substrate.Should be appreciated that, preparation method described below is only preparation sapphire (a-Al of the present invention₂o₃) instantiation of base GaN compound substrate.Those skilled in the art can under instruction of the present invention, according to design, need and other factors are made change.

Adopt the sapphire (a-Al of metal-organic chemical vapor deposition equipment (MOCVD) technique for the preparation of nitride semiconductor epitaxial sheet material₂o₃) technological process of base compound substrate is as follows:

Step 1: the sapphire (a-Al that gets a 2 inches diameter₂o₃) single crystal substrates 11;

Step 2: the sapphire single-crystal substrate 11 of cleaning is put into MOCVD equipment reaction chamber;

Step 3: the thin AlN monocrystal thin films material 121 of first preparing growth 1 bed thickness 50nm by MOCVD technique in sapphire single-crystal substrate 11 is as lattice mismatch stress covariant layer;

Step 4: prepare the ultra-thin TiN monocrystal thin films of growth 1 bed thickness 10nm material 122 as thermal stress covariant layer on the thin AlN layer 121 of thick 50nm by MOCVD technique again;

Step 5: repeating step 3 and step 4, prepare by 5 layers of thick thick ultra-thin TiN layer 122 of 121 and 4 layers of 10nm of thin AlN layer of 50nm and replace the stacking combined stress covariant layer material 12 forming by MOCVD technique;

Step 6: use the MOCVD technique GaN monocrystal thin films material that 1 layer of 2 μ m of preparation growth is thick again 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, first with the rate of temperature fall of 10 ℃/min, drop to 750 ℃ from 1050 ℃, then drop to 250 ℃ with the rate of temperature fall of 20 ℃/min from 750 ℃, finally naturally drop to room temperature;

Step 8: take out and comprise sapphire (a-Al from MOCVD equipment reaction chamber₂o₃) sapphire (a-Al of single crystal substrates 11, combined stress covariant layer 12, low-dislocation-density and unstressed and bending GaN template layer 13₂o₃) base compound substrate 1;

Step 9: with 2 inches of sapphire (a-Al₂o₃) base compound substrate 1 does GaN homogeneity single crystalline substrate template, adopts MOCVD technique to prepare gallium nitride (GaN) the base blue-ray LED epitaxial wafer material of High Efficiency Luminescence.

Finally it should be noted that above example is only in order to technical scheme of the present invention to be described but not be limited.Although the present invention is had been described in detail with reference to given example, those of ordinary skill in the art can modify to technical scheme of the present invention as required or be equal to replacement, and does not depart from the spirit and scope of technical solution of the present invention.

Claims (11)

1. for the preparation of a sapphire-base compound substrate for nitride semiconductor epitaxial material, it is characterized in that, comprise:

One sapphire single-crystal substrate;

One combined stress covariant layer, covers in described sapphire single-crystal substrate, by nitride multilayer aluminium monocrystal thin films material and nitride multilayer ti single crystal thin-film material, is replaced and is stackingly formed;

One gallium nitride template layer, is grown on described combined stress covariant layer, monocrystalline GaN film material, consists of.

2. the sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material according to claim 1, is characterized in that, in wherein said combined stress covariant layer, the thickness of every layer of described aluminum nitride single crystal film material is 15～90nm.

3. the sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material according to claim 1, it is characterized in that, in described combined stress covariant layer the thickness of every layer of described titanium nitride monocrystal thin films material be not more than every layer of described aluminum nitride single crystal film material thickness 1/3.

4. the sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material according to claim 1, is characterized in that, the layer contacting with described sapphire substrates in described combined stress covariant layer is described aluminum nitride single crystal film material.

5. the sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material according to claim 1, is characterized in that, the layer contacting with described gallium nitride template layer in described combined stress covariant layer is described aluminum nitride single crystal film material.

6. the sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material according to claim 1, is characterized in that, the number of plies of described aluminum nitride single crystal film material is 2～10 layers.

7. the sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material according to claim 1, is characterized in that, the thickness of described gallium nitride template layer is not less than 2 μ m.

8. the sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material according to claim 1, is characterized in that, the rate of temperature fall that drops to room temperature from the growth temperature of 1100 ℃ during described gallium nitride template layer in growth is 5～20 ℃/min.

9. the sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material according to claim 1, it is characterized in that, for the preparation of the Material growth technique of the aluminum nitride single crystal film material in described combined stress covariant layer and titanium nitride monocrystal thin films material and gallium nitride template layer, comprise metal-organic chemical vapor deposition equipment, ion beam epitaxy, molecular beam epitaxy, pulsed laser deposition, plasma auxiliary chemical vapor deposition and magnetron sputtering deposition.

10. the sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material according to claim 1, it is characterized in that, described sapphire-base compound substrate can be for the preparation growth of gallium nitride, aluminium nitride, indium nitride, aluminum gallium nitride, indium gallium nitrogen, aluminium gallium nitrogen monocrystal thin films material and nitride semiconductor LED device architecture.

The manufacture method of 11. 1 kinds of sapphire-base compound substrates, this sapphire-base compound substrate for the preparation of nitride semiconductor epitaxial material, is characterized in that, comprises:

Get a sapphire single-crystal substrate;

In described sapphire single-crystal substrate, form a combined stress covariant layer, described combined stress covariant layer is replaced and is stackingly formed by aluminum nitride single crystal film material and titanium nitride monocrystal thin films material;

On described combined stress covariant layer, form a gallium nitride template layer, described gallium nitride template layer consists of monocrystalline GaN film material.