CN1314081C

CN1314081C - Method for growing crackless III family nitride film on silicon substrate

Info

Publication number: CN1314081C
Application number: CNB2004100040289A
Authority: CN
Inventors: 陆沅; 刘祥林; 陆大成; 王晓晖; 王占国
Original assignee: Institute of Semiconductors of CAS
Current assignee: Institute of Semiconductors of CAS
Priority date: 2004-02-04
Filing date: 2004-02-04
Publication date: 2007-05-02
Anticipated expiration: 2024-02-04
Also published as: CN1652299A

Abstract

The present invention relates to a method for growing a crackless III family nitride film on a silicon substrate, which is characterized in that a buffer layer is grown by the following method which comprises the following steps: (A) a layer of thin liquid aluminum layer is firstly formed on the surface of the silicon substrate, and the liquid aluminum layer has a main function of preventing the formation of an amorphous silicon nitride layer; (B) a layer of aluminum nitride buffer layer with high temperature is then grown, and the aluminum content of the aluminum nitride buffer layer is larger than the nitrogen content.

Description

The method of growing flawless III-nitride film on silicon substrate

Technical field

The present invention relates to technical field of semiconductors, be meant the method for growing flawless III group-III nitride film on a kind of silicon (Si) substrate especially

Background technology

Therefore group iii nitride semiconductor is very promising material owing in fields such as demonstration, optical storage of data, high-speed high-power electronic device, ultraviolet detectors boundless application prospect is arranged all.

Yet owing to lack suitable substrate, people are difficult to obtain high-quality gallium nitride (GaN) film.Present most GaN film all obtains on sapphire (0001), but sapphire still has many shortcomings, such as insulation, seldom arrive large scale, very hard etc.Because silicon has cheapness, large scale, electrical conductance and thermal conductance are good and have the integrated potential prospect of opto-electronic device, people to carry out a large amount of effort not attempt using silicon to grow as substrate adding GaN, thereby overcome above-mentioned more sapphire shortcomings.

But, compare with sapphire, exist bigger lattice mismatch (20%) and thermal mismatching (56%) between silicon (Si) and the GaN, therefore growing GaN is very difficult on Si.In in the past 10 years, various resilient coatings such as 3C-SiC, AlN, GaAs, AlAs, Si ₃N ₄, γ-Al ₂O ₃Carried out trial in the intermediate layer that all is used as between GaN epitaxial loayer and the Si.Because AlN has wettability preferably on the Si substrate, experimental result shows with other resilient coating to be compared, and the AlN resilient coating can solve the difficulty of Si base GaN growth preferably.

By adopting AlN as resilient coating, the crystal mass of the GaN film of Si basal growth can be approaching with the crystal mass of Grown GaN film on Sapphire Substrate.At present, the light-emitting diode of Si base III-nitride, photo-detector, field effect transistor is all produced.But owing to the different thermal mismatchings that cause of the thermal coefficient of expansion of Si and GaN up to 56%, therefore in the temperature-fall period behind growth ending, have very big thermal stress in the GaN film, and owing to be tensile stress thereby cause the GaN film a lot of crackles to occur.These severe crack have influenced the performance of device and the rate of finished products of epitaxial wafer.

The crackle that draws among the basic GaN all making great efforts to study the stress that how to reduce among the Si base GaN, is eliminated by many in the world a few days ago groups.Mainly contain following several method, this several method all has different separately excellent pluses and minuses.

(1) selects regional epitaxy (SAG), this method utilizes photoetching technique to be formed with the medium masking film of figure on the Si substrate, utilize the selectivity of the growth of GaN on medium mask and substrate, the GaN outer layer growth is limited in the window area that does not have the medium mask.Because the area of the GaN film in each discrete window is very little at this moment, do not crack though there is stress to exist still.This method Grown GaN crystal mass and the characteristics of luminescence all improve a lot, but have improved production cost, and inhomogeneous easily at the thickness of the GaN film at the edge of each window region, thereby influence the performance of device.

(2) adopt low temperature AI N insert layer.Inserting one deck in the GaN epitaxial film has the thick low temperature AI N layer of tens nm approximately, can discharge a part because the stress that thermal mismatching causes is realized flawless GaN film by this one deck.But the shortcoming of this method is, there is the crystal mass of the GaN epitaxial film that inserts AlN always weaker than the crystal mass outline of the epitaxial film that does not insert AlN, this is owing to introduced the cause of new defective again between the GaN on low temperature AI N and upper strata layer, and these defectives will make the decreased performance of device.

(3) the AlGaN layer of employing gradient gradual change.Because the character constant (0.3113nm) of AlN is less than the lattice constant (0.3189nm) of GaN, therefore on the AlGaN layer, be compression in the Grown GaN, this compression will be offset the tensile stress that a part produces in the process that temperature descends, thereby will reduce the crackle in the GaN epitaxial film.But experiment finds to adopt AlGaN tonsure graded bedding will cause a large amount of dislocation densities, and these dislocations will further influence the crystal mass of upper strata GaN.

Summary of the invention

The object of the present invention is to provide a kind of on the Si substrate method of growing flawless III-nitride film, it is this that method is simple, can not increase cost, can effectively reduce the stress in the GaN film, thereby eliminate the crackle of GaN film, and can also improve the crystal mass of GaN epitaxial loayer greatly.

In order to realize purpose of the present invention, adopted following method to come grown buffer layer.

The present invention a kind of on silicon substrate the method for growing flawless III-nitride film, it is characterized in that, adopted following method to come grown buffer layer, comprise the steps:

(A) at first form the thin liquid aluminium lamination of one deck in surface of silicon, the main effect of this liquid state aluminium lamination is the formation that stops unbodied silicon nitride layer;

(B) one deck aluminum nitride buffer layer of growing then, the content of aluminium is greater than the content of nitrogen in this aluminum nitride buffer layer.

The temperature of the aluminum nitride buffer layer of wherein said growth is: between the 1050-1120 degree.

The content of aluminium is greater than the content of nitrogen in the wherein said aluminum nitride buffer layer, and its stoicheiometry is: 2-3: 1.

The thickness of wherein said aluminum nitride buffer layer is 20-50nm.

Wherein the kind of III-nitride film is a gallium nitride, aluminum gallium nitride, indium gallium nitrogen, the structural material that thin-film material such as aluminium indium gallium nitrogen or they are combined to form.

Description of drawings

For further specifying technology contents of the present invention, below in conjunction with embodiment and accompanying drawing describes in detail as after, wherein:

Fig. 1 is the structural representation of the present invention at the flawless GaN epitaxial film of Si basal growth;

Wherein: 1 is the Si substrate, and 2 is ultra-thin liquid Al layer, and 3 is the AlN resilient coating of rich Al, and 4 is the GaN epitaxial loayer;

Fig. 2 be with the surface of the GaN epitaxial film of common AlN buffer growth (figure a) with contrast with the surface (figure b) of the GaN epitaxial film of the AlN buffer growth of the rich Al of the inventive method, the thickness of the GaN epitaxial film of these two samples is 1 micron;

Fig. 3 is with the GaN epitaxial film of common AlN buffer growth and the comparison of GaN (0002) the X ray swing curve half-breadth of the GaN epitaxial film of the AlN buffer growth of the rich Al that uses the inventive method.

Embodiment

We are being example with the metal organic vapor phase epitaxy method.

(1) at first at 1080 ℃ of TMAl that feed big flow of high temperature,, therefore will form the very thin liquid Al layer 2 of one deck on Si substrate 1 surface because the fusing point of Al is 660 ℃;

(2) feed NH ₃, and keep the flow of temperature and TMAl constant.V/III when growing high temperature AlN resilient coating 3 usually is than between 3000～9000, and we are owing to adopted the TMAl of big flow, it is 450 that the V/III ratio significantly reduces, thereby the content of the aluminium in this layer AlN layer is greater than the content of nitrogen, its stoicheiometry is: 2.4: 1, this floor height temperature AlN layer thickness was about 30nm.

The process that does not have Alization when in general growing the ordinary buffer layer, perhaps the time very short, therefore the flow of TMAl is little in addition, can not well form thin liquid Al layer 2;

(3) epitaxial film 4 of the certain thickness III-nitride of growth.The kind of film can be a gallium nitride, aluminum gallium nitride, indium gallium nitrogen, the structural material that thin-film material such as aluminium indium gallium nitrogen or they are combined to form.

The present invention compares the significant effect that is had with background technology

Compare with other the technology of growing flawless GaN epitaxial film, it is simple and convenient to adopt the method for rich Al resilient coating to have, and does not increase the advantage of production cost.The crystal mass of finding the GaN epitaxial film of the rich Al buffer growth of employing simultaneously also has significantly raising.This be compare with other method the most estimable a bit, and other growing method realizes flawless to sacrifice certain crystal mass often.

Realize best way of the present invention

1. realize capital equipment of the present invention

Semiconductor film film preparation equipment mainly refers to the gas phase epitaxy of metal organic compound system, molecular beam epitaxy system ion sputtering, vacuum deposition etc.;

2. for different semiconductor film preparing systems, various growth parameter(s)s should be adjusted as the case may be.

Embodiment

We are being example with the metal organic vapor phase epitaxy method.

(1) with Si (111) wafer as substrate;

(2) at first at 1080 ℃ of TMAl that feed flow of the people of high temperature, the time is 3 minutes, because the fusing point of Al is 660 ℃, therefore will form the very thin liquid Al layer of one deck at the Si substrate surface;

(2) feed NH ₃, and keeping the flow of temperature and TMAl constant, the time is 3 minutes.This moment, the V/III ratio was 450, and this floor height temperature AlN layer thickness is about 30nm;

(3) the GaN epitaxial film of continued growth 1 micron thickness on the basis of rich Al resilient coating.

Contrast can be seen (accompanying drawing 2) with the surface of the GaN epitaxial loayer of 1 micron thickness of these two kinds of buffer growth, just finds that with the GaN laminar surface of common buffer growth many crackles are arranged in 10 microns range of observation, and fine fisssure density can reach 1 * 10 ³Cm ^-1The fine fisssure line length of unit are (definition be fine fisssure density), and adopt the GaN epitaxial film surface of buffer growth of rich Al very smooth, in 100 microns range of observation, all seldom can find crackle.With the two product diffraction of X ray the crystal mass of GaN epitaxial film is tested, GaN (0002) diffraction maximum is carried out ω scanning, be significantly less than the half-breadth (accompanying drawing 3) of Grown GaN on common AlN resilient coating with the half-breadth of the swing curve of the GaN (0002) of the GaN of rich Al buffer growth, therefore much better than the crystal mass of the GaN of usefulness ordinary buffer layer growth with the crystal mass of the GaN of rich Al buffer growth.

The explanation of experiment mechanism

Experimental result find rich Al resilient coating crystal mass and not as the crystal mass of common AlN resilient coating good, but the content of Al is the twice of common AlN resilient coating in the resilient coating of rich Al, wherein a part forms the AlN crystal, and another part does not form crystal, but exists with the form of amorphous.In the process of growing GaN epitaxial loayer, this part Al atom that is not completed into compound will diffuse in the GaN epitaxial loayer, make the actual AlGaN layer that contains certain Al concentration and concentration gradient gradual change that becomes in bottom of GaN epitaxial loayer.Because the character constant of GaN is less than the character constant of AlN, therefore the AlGaN layer of bottom produces certain compression to the GaN epitaxial loayer on its top, and this compression under temperature with the time will offset a tensile stress that produces owing to thermal mismatching, thereby total stress in the minimizing epitaxial film, thereby reduce crackle.The resilient coating of rich Al contains the Al that depart from stoicheiometry because crystal mass is poorer than common AlN resilient coating more simultaneously, so the increase of the flexibility of resilient coating, and this also can discharge a part of stress to a certain extent.

This method is simple, does not increase cost, but from the mechanism that counter stress discharges, is not simply to change the V/III ratio, but a sudden change, the concentration of the TMAl that is adopted is 13 times of ordinary buffer layer.From the mechanism of Stress Release, not only rely on to have the slow of bigger flexibility; The middle level discharges stress, and utilize the characteristics of Al atom diffusion to the epitaxial loayer in the rich Al resilient coating, diffuse to form compression that the AlGaN layer produced by Al and alleviate the be unrealized growth of flawless GaN of the method for the tensile stress in a part of GaN epitaxial loayer, by the method, can obtain the flawless GaN epitaxial film of 1 micron thickness at least.

Being worth mentioning in addition is, the crystal mass of this method Grown GaN is better than the crystal mass of the Grown GaN of ordinary buffer layer greatly.At the GaN early growth period, GaN will nucleation form three-dimensional island on AlN crystal grain, the deviation in crystal orientation when these islands merge because between island and the island tend to produce various dislocations, so the dislocation density in the nucleation density of AlN and the GaN epitaxial loayer has very confidential relation.Experiment is found because the nucleation density of rich Al resilient coating is less than the cuclear density of defending of common resilient coating, and this probably is exactly the reason that the crystal mass of Grown GaN is better than the ordinary buffer layer on the resilient coating of rich AlN.

Claims

1. the method for a growing flawless III-nitride film on silicon substrate is characterized in that, has adopted following method to come grown buffer layer, comprises the steps:

2. according to claim 1 on silicon substrate the method for growing flawless III-nitride film, it is characterized in that the temperature of wherein said growing aluminum nitride resilient coating is: between the 1050-1120 degree.

3. according to claim 1 on silicon substrate the method for growing flawless III-nitride film, it is characterized in that the content of aluminium is greater than the content of nitrogen in the wherein said aluminum nitride buffer layer, its stoicheiometry is: 2-3: 1.

4. according to claim 1 on silica-based the method for growing flawless III-nitride film, it is characterized in that the thickness of wherein said aluminum nitride buffer layer is 20-50nm.

5. according to claim 1 on silicon substrate the method for growing flawless III-nitride film, it is characterized in that wherein the kind of III-nitride film is a gallium nitride, aluminum gallium nitride, indium gallium nitrogen, the structural material that thin-film material such as aluminium indium gallium nitrogen or they are combined to form.