CN1881626A - Method for making GaN-based blue light light-emitting diode with photon microstructure - Google Patents

Abstract

The invention relates to a method for preparing photon microstructure GaN base blue light emitting diode, which comprises: first, growing one layer of silicon dioxide layer on the upper surface of GaN sample, as the mask plate for etching GaN material; coating one layer of photo resist on the silicon dioxide mask plate that sensitive to used laser; using one short-wavelength laser as light source to be expanded via expanding lens; the expanded light is focused via the focus lens to radiate the photo microstructure mold plate; the photo microstructure mold plate is at the back of focus lens, while their distance is ZT; said mold plate is made by electron beam exposal technique whose pattern is photo microstructure; the laser, passing the photo microstructure mold plate, projects the photo microstructure mold plate on the GaN sample that distanced ZT, to form the image of mold plate on the photo resist mask plate, to be drying etched; therefore, the photo microstructure can be etched on the GaN material.

Description

The manufacture method of GaN-based blue light light-emitting diode with photon microstructure

Technical field

Present technique belongs to the development art of photon microstructure, particularly is used to improve the development technology of the photon microstructure of GaN base blue LED light extraction efficiency in the white-light illuminating engineering.

Background technology

The development semiconductor lighting is the development trend of following white-light illuminating, and the semiconductor lighting replacement traditional lighting that develops into of the development of semi-conducting material and technology and the research and production of semiconductor lighting has been showed bright prospects.Dropped into lot of manpower and material resources in field of semiconductor illumination both at home and abroad, in the hope of on the market of the white-light illuminating in future, strive one seat.The common popular way of based semiconductor material white-light illuminating is to adopt the blue-ray LED pumping fluorescent material based on GaN to obtain.But the light extraction efficiency of undressed GaN LED is all very low.Realize the white-light illuminating engineering, key is to improve the light extraction efficiency of gallium nitride based LED.And photonic crystal and photon microstructure are by one of method that is expected most.At present, there are many bibliographical informations (to see document [1] Shanhui Fan in the world about photon crystal structure, PierreR.Villeneuve, J.D.Joannopoulos, E.F.Schubert, High Extraction Efficiencyof Spontaneous Emission from Slabs of Photonic Crystals, Physycal Reviewletters, v.78, no.17,1997,3294-3297.[2] Alexei A.Erchak, Daniel J.Ripin, Shanhui Fan, Peter Rakich, John D.Joannopoulos, Erich P.Ippen, Gale S.Petrich and Leslie A.Kolodziejski, Enhanced coupling to vertical radiationusing a two-dimensional photonic crystal in a semiconductor light-emittingdiode, Applied Physics Letters, vol.78, no.5,2001,563-565.) aspect the experiment of photon crystal microstructure, Britain research group found that at the AlInGaP LED of the band DBR of slab construction surface etch 1-D photon crystal total light extraction efficiency reaches about 34%.Near infrared InGaAsP LED has studied in Korea S research group, add 2 D photon crystal thereon after, experiment and theoretical modeling are found all the have an appointment raising of 8-13 times of its light extraction efficiency.People such as Fan S.H. draw photon crystal structure by numerical simulation calculation and LED can be brought up to 94% to light extraction efficiency.Wherein, thus the main effect of photon crystal structure is to suppress the guided modes in the plate and guided modes extracted the outer raising that reaches light extraction efficiency of ejecting plate.This has proved that the photon microstructure of the structure of the photon crystal structure that utilizes the macrolattice constant or other large-sizes can improve the light extraction efficiency of LED significantly.Usually make photon crystal structure and use conventional electron beam exposure and dry etching method on led chip, complex process costs an arm and a leg, and the area of making is little, is unfavorable for the preparation of LED of the photon microstructure of practicability.And that the method that patent of the present invention proposes can be developed is various lattice constants, simple for production, method that can the large-area manufacturing photon crystal structure.

Below introduce the preparation method's that will utilize principle, (Talbot is the Britain physicist to Talbot effect that Here it is, and this effect found by him, therefore with his naming.With the one dimension photon microstructure is the example explanation.When it is found that with the common amplitude grating of coherent light irradiation, at the picture that on some specific range of grating, can form grating, this be grating from imaging, this effect is called the Talbot effect).The Talbot effect approximately is before more than 100 year, finds that by Britain physicist H.F.Talbot this effect has important application (S.Nowak et al., Opt.Lett.22,1430-2 (1997) .) at optical measurement, optical array from aspects such as imagings.Below be the example explanation with the one dimension photon microstructure.Grating from imaging principle index path as shown in Figure 1, R is the radius of curvature of spherical wave.G (x among Fig. 1 ₁, y ₁) the expression grating, it is the sinusoidal grating that writes down on holographic dry plate with exposure technique.The cycle of supposing holographic grating is d, grating G (x ₁, y ₁) transmitance can be expressed as:

$G(x_1,y_1)=\underset{n}{\mathrm{\Σ}}{A}_n\exp \left[j2\mathrm{\π}\frac{n}{d_1}{x}_1\right]---\left(1\right)$

When the spherical wave illumination grating G that sends with point-source of light, the optical field distribution of grating G rear surface is:

$U(x,y,0)=\underset{n}{\mathrm{\Σ}}\mathrm{\Σ}{A}_n\exp \left(\mathrm{jR}\frac{x^2+y^2}{2R}\right)\exp \left[j2\mathrm{\π}\frac{n}{d}x\right]---\left(2\right)$

Utilize angular spectra theory to grating the light field U at z place (x, y z) carry out Fourier transform and obtain observing periodically at the z place at last the optical field distribution function is:

$U^{\′}(x,y,z)={\left(\frac{R}{R+Z}\right)}^2\exp \left(\mathrm{jkz}\right).---\left(3\right)$

$\exp \left(\mathrm{jk}\frac{x^2+y^2}{2(R+z)}\right)\·\underset{n}{\mathrm{\Σ}}{A}_n\exp (j2\mathrm{\π}\frac{R}{R+z}\·\frac{1}{d}\mathrm{nx})\exp (-\mathrm{j\π}\frac{\mathrm{\λRz}}{R+z}{\left(\frac{1}{d}\right)}^2{n}^2)$

Consider n=1,0 ,-1 situation, and establish A ₁=A _-1, then light distribution is:

$I(x,y,z)=A_0^2+2A_1^2+4A_0{A}_1\cos \left(\frac{\mathrm{R\λ}}{2d^2}\frac{z}{R+z}\right)\cos \left(\frac{2\mathrm{\π}}{d}\frac{R}{R+z}x\right)$

$+2A_1^2\cos \left[\frac{2\mathrm{\π}}{\mathrm{\λ}}\frac{2\mathrm{\λRx}}{(R+z)d}\right]---\left(4\right)$

When $\mathrm{\π}\frac{\mathrm{\λRz}}{R+z}\·\frac{1}{d^2}=\mathrm{m\π},m=\mathrm{1,2,3}\·\·\·\·\·\·---\left(5\right)$

$U^{\′}(x,y,z)=C\underset{n}{\mathrm{\Σ}}{A}_n^{\′}\exp \left[j2\mathrm{\π}\frac{n}{D}x\right]{(-1)}^{{\mathrm{mn}}^2}---\left(6\right)$

Make z=Z _T, in the formula $D=\frac{R+Z_T}{R}d$ For grating as the cycle.When writing light inlet is plane wave, R → ∞,

Then

$Z_T=\frac{{\mathrm{md}}^2}{\mathrm{\λ}},D=d---\left(7\right)$

$U^{\′}(x,y,z)=C\underset{n}{\mathrm{\Σ}}{A}_n^{\′}\exp \left(j2\mathrm{\π}\frac{n}{d}x\right)---\left(8\right)$

This be grating from imaging, as cycle be grating cycle d.

When incident light wave is a divergent spherical wave, R＞0, then:

$\frac{R{Z}_T}{R+Z_T}={\mathrm{md}}^2/\mathrm{\λ},D=\frac{R+Z_T}{Z_T}d>d---\left(9\right)$

This be amplify from imaging.

When incident light wave is the spherical wave of assembling, R＜0, the then picture that becomes to dwindle:

$\frac{R{Z}_T}{R+Z_T}={\mathrm{md}}^2/\mathrm{\λ}---\left(10\right)$

$D=\frac{R+Z_T}{Z_T}d>d---\left(11\right)$

In the scope for distance grating back distance c m magnitude, be that the grating of micron dimension is continuous from the position of imaging basically for grating constant, can be on the promptly basic optional position from imaging.Because the m numerical value in (7) formula is very big at this moment, on the m radix, increase by 1 integer value, Talbot is apart from Z _TChange micron dimension.Give like this and utilize Talbot effect inscription grating or photon microstructure to bring convenience.

Under proper condition, Fig. 1 experimental provision can be inscribed the minor cycle grating.If as being d,, must consider R＜0, be shown according to formula (9) Talbot distance and grating periodic table with assembling spherical wave in order to obtain the grating picture of minor cycle from the grating cycle of imaging:

$\left\{\begin{array}{c}{Z}_T=\frac{{\left|R\right|}^2\mathrm{\λ}}{\mathrm{mD}-\mathrm{\λ}\left|R\right|}\\ d=\frac{D{\left|R\right|}^2\mathrm{\λ}}{Z_T-\left|R\right|}\frac{1}{{\mathrm{mD}}^2-\mathrm{\λ}\left|R\right|}\end{array}\right.---\left(12\right)$

For the grating of determining the cycle,, can change by integer, so Talbot is apart from Z because m is very big integer in the formula _TBe transformable.In addition, by formula (9) and formula (11) as seen, the variation of the cycle D of etched diffraction grating or photon microstructure is regulated in the variation that can pass through.

Summary of the invention

The object of the present invention is to provide a kind of manufacture method of GaN-based blue light light-emitting diode with photon microstructure, the GaN LED of the photon microstructure that this method has is simple for production, can large-area manufacturing is to reach photon microstructure high efficiency, the power type white light LED purpose that realizes practicability.

The manufacture method of a kind of GaN-based blue light light-emitting diode with photon microstructure of the present invention is characterized in that, comprises the steps:

Step 1: at first at GaN sample upper surface growth layer of silicon dioxide layer, as the mask layer of etching GaN material; Spin coating last layer photoresist on silicon dioxide mask need be the photoresist to used laser sensitization;

Step 2: get a short wavelength laser as light source;

Step 3: get an extender lens, with the laser beam expanding of short wavelength laser, the light that expands after restrainting focuses on through convergent lens again;

Step 4: on the light beam irradiates photon microstructure template through lens and convergent lens, the photon microstructure template is behind convergent lens, and the two is apart from Z _T, the template that this template adopts electron beam lithography to make, figure is a photon microstructure on it;

Step 5: laser utilizes the Talbot effect by after the photon microstructure template, with photon microstructure template reflection with its distance be Z _TOn the GaN sample at place, the picture of photon microstructure template is become on the photoresist mask of GaN sample, promptly on photoresist, form the photon microstructure figure;

Step 6: utilize the photoresist that has formed the photon microstructure figure as mask,, photon microstructure is transferred to silicon dioxide layer by dry etching;

Step 7: utilize the silicon dioxide layer that has the photon microstructure figure to make mask, adopt dry etching method that photon microstructure is transferred on the GaN material.

Wherein used short wavelength laser is short wavelength's pulse or a continuous wave laser.

The wavelength 248nm of the excimer laser that the wavelength of wherein used short wavelength laser is, the wavelength 266nm of the wavelength 337nm of nitrogen molecular laser or Nd:YAG laser of quadruple pulse laser.

Wherein employed extender lens and convergent lens with laser beam by after reach and cover full template and treat imaging region, the focal length of convergent lens makes the photon microstructure template both can be placed in the focal length greater than 5cm, also can be placed on beyond times focal length.

Wherein the control translation precision of photon microstructure mask and GaN sample is less than 50nm, by regulate mask to assemble lens apart from Z _RWith regulate the GaN sample to the photon microstructure template apart from Z _T, reach the variation of regulating institute's etching photon microstructure lattice parameter on the material.

Content of the present invention provides a kind of GaN LED structure and manufacture method with photon microstructure, particularly has GaN based light-emitting diode than the photon crystal structure of macrolattice constant and preparation method thereof.Adopt the Talbot effect from the photoetching technique of imaging principle and the method for dry etching, go out periodic photon microstructure, increase substantially with the light extraction efficiency that reaches LED in the LED surface etch.

Description of drawings

For further specifying concrete technology contents of the present invention, carry out below that embodiment and accompanying drawing describe in detail as after, wherein:

Fig. 1 utilizes the Talbot effect to inscribe the grating schematic diagram;

Fig. 2 Talbot effect etching photon microstructure experimental provision schematic diagram;

Fig. 3 Talbot effect is inscribed the photon microstructure flow chart on semi-conducting material.

Embodiment

See also Fig. 2 also in conjunction with consulting Fig. 3, the manufacture method of a kind of GaN-based blue light light-emitting diode with photon microstructure of the present invention comprises the steps:

Step 1: at first at GaN sample 8 upper surfaces growth layer of silicon dioxide layer 11, as the mask layer of etching GaN material; Spin coating last layer photoresist 12 on silicon dioxide mask need be the photoresist (among Fig. 3) to used laser sensitization;

Step 2: get a short wavelength laser 1 as light source; Wherein used short wavelength laser 1 is the common excimer laser or the pulse or the continuous wave laser of nitrogen molecular laser or Nd:YAG laser of quadruple pulse laser or other wavelength; The wavelength of used short wavelength laser 1 is 248nm; The wavelength of nitrogen molecular laser is that the wavelength of 337nm or Nd:YAG laser of quadruple pulse laser is 266nm;

Step 3: get an extender lens 2, with the laser beam expanding of short wavelength laser, the light that expands after restrainting focuses on through convergent lens 4 again; Wherein employed extender lens 2 and convergent lens 4 with laser beam by after reach and cover full template and treat imaging region, the focal length of convergent lens 4 is greater than 5cm, make photon microstructure template 6 both can be placed in the focal length, also can be placed on beyond 2 times of focal lengths;

Step 4: on the light beam irradiates photon microstructure template 6 through extender lens 2 and convergent lens 4, photon microstructure template 6 is behind convergent lens 4, and the two is apart from Z _T, the template that this template adopts electron beam lithography to make, figure is a photon microstructure on it; Wherein the control translation precision of photon microstructure mask 6 and GaN sample 8 is less than 50nm, by regulate mask to assemble lens 4 apart from Z _RWith regulate GaN sample 8 to photon microstructure template 6 apart from Z _T, reach the variation that is adjusted in institute's etching photon microstructure lattice parameter on the material;

Step 5: laser is by after the photon microstructure template 6, with photon microstructure template 6 reflections with its distance be Z _TOn the GaN sample 8 at place, the picture of photon microstructure template 6 is become on photoresist 12 masks of GaN sample 8, promptly on photoresist 12, form photon microstructure figure 13;

Step 6: utilize the photoresist 12 that has formed photon microstructure figure 13 as mask,, photon microstructure is transferred to silicon dioxide layer 11 by dry etching;

Step 7: utilize the silicon dioxide layer 11 that has the photon microstructure figure to make mask, adopt dry etching method that photon microstructure is transferred on the GaN material 10.

Embodiment

In order to utilize the GaN LED of Talbot effect development photon microstructure, Fig. 3 is consulted in the experimental provision schematic diagram and the combination of at first building as shown in Figure 2, comprising:

Short wavelength laser 1, at extender lens 2 thereafter, convergent lens 4,, back apart from Z apart from convergent lens 4 in photon microstructure template 6 apart from the photon microstructure template 6 that is placed on for the L place on the accurate electronic control translation stage 7 _TThe place is placed on GaN sample 8 or other semiconductor samples on the accurate electronic control translation stage 9.

The invention provides a kind of manufacture method of GaN-based blue light light-emitting diode with photon microstructure, main implementation process is: at first at GaN sample 8 upper surfaces growth layer of silicon dioxide mask 11, as the mask layer of etching GaN material 10; Spin coating last layer photoresist 12 on silicon dioxide mask need be the photoresist to used laser sensitization.Get a short wavelength laser 1 as light source; Utilize extender lens 2 to expand bundle the laser of short wavelength laser, the light that expands after restrainting focuses on through convergent lens 4 again; The light beam irradiates of passing through extender lens 2 and convergent lens 4 is back apart from Z at convergent lens 4 _TPhoton microstructure template 6 on, the template that this mould substrate adopts electron beam lithography to make, figure is the about micron dimension photon microstructure of lattice constant on it.Laser is Z with photon microstructure template 6 reflections in distance photon microstructure template 6 back distances by after the photon microstructure template 6 _TOn the GaN sample 8 at place, the picture of photon microstructure template 6 is become on the mask of GaN sample 8.That is to say, utilize the Talbot effect, short wavelength laser forms the picture of photon microstructure template 6 by illumination photons micro-structural template 6 on photoresist, promptly forms photon microstructure figure 13 on photoresist.Utilize the photoresist 12 that has formed photon microstructure figure 13 as mask,, photon microstructure is transferred to silicon dioxide layer 11 by dry etching.Utilization has the silicon dioxide layer 11 of photon microstructure figure and makes mask, adopts dry etching method that photon microstructure is transferred on the GaN material 10.

Put it briefly, on the GaN material 10 making step of photon microstructure as shown in Figure 3, as follows:

The first step is made mask, and the silicon dioxide mask 11 about the upper surface growth 200nm of GaN material 10 is as the mask layer of etching GaN material 10; The photoresist 12 of 100 to hundreds of nm thickness in spin coating on the silicon dioxide mask is to the photoresist of used laser sensitization;

In second step, utilize the Talbot effect directly to write photon microstructure.Laser by illumination photons micro-structural template 6, forms the picture of photon microstructure template 6 through extender lens 2 and convergent lens 4 expansion bundles with after focusing on photoresist, promptly form photon microstructure figure 13 on photoresist;

In the 3rd step, the etching photon microstructure utilizes the photoresist layer that has formed photon microstructure figure 13 as mask, by dry etching, photon microstructure is transferred to silicon dioxide layer 11.Utilization has the silicon dioxide layer of photon microstructure figure and makes mask, utilizes dry etching that photon microstructure is transferred on the GaN material.Thus, can on the GaN material, prepare photon microstructure in the correct position place.

The manufacture method of described a kind of GaN-based blue light light-emitting diode with photon microstructure, used light source is a short wavelength laser 1, can adopt common excimer laser (wavelength 248nm), nitrogen molecular laser (wavelength 337nm) or Nd:YAG laser of quadruple pulse laser (wavelength 266nm), also can adopt the pulse or the continuous wave laser of other wavelength, so long as get final product as the light activated wavelength laser of the photoresist of mask as GaN.Certainly, the photon microstructure precision of using short wavelength laser to obtain is higher.Employed extender lens 2 and convergent lens 4 with laser beam by after reach and cover full template and treat imaging region, the focal length long enough of convergent lens 4 makes photon microstructure template 6 both can be placed in the focus, also can be placed on beyond 2 times of focal lengths.

Used GaN material 10 can be prepared like this: utilize the N type GaN of the about 1 μ m of metal vapor deposition method (MOCVD) technology growth on saphire substrate material, about four pairs of GaN quantum well of growing then, the P type GaN of the about 200nm of growth thereon.

The lattice constant and the lattice constant on the photon microstructure template 6 of the photon microstructure that forms are proportional, utilize the Talbot effect, use a photon microstructure template 6 both can make the photon microstructure littler, also can make than the big photon microstructure of photon microstructure lattice in the photon microstructure template 6 than the lattice in the photon microstructure template 6.The convergent lens 4 general convex lens that use, focal length is longer, and more than the 5cm, focal length is determined, also promptly assembles the radius of curvature R of spherical wave and also just determines.If we place photon microstructure template 6 in the focus of convergent lens 4, so just can be so that the picture that photon microstructure template 6 becomes to dwindle on GaN sample 8 so just can be made the little photon microstructure of lattice constant; If photon microstructure template 6 is placed on beyond the focus of convergent lens 4 position greater than two focus length, the picture of photon microstructure template 6 through becoming to amplify on GaN sample 8 after the laser radiation so just can be produced the bigger photon microstructure of lattice constant on material so.Simultaneously photon microstructure lattice constant can also by regulate photon microstructure template 6 to extender lens 2 apart from Z _RAnd with GaN sample 8 apart from Z _TRegulate.Therefore use a photon microstructure template 6, utilize as shown in Figure 2 experimental provision and Talbot effect principle, we can develop to be of a size of benchmark on the photon microstructure template 6, with the photon microstructure of the proportional multiple lattice constant of its size.Photon microstructure mask 6 and GaN sample 8 are placed on the accurate automatically controlled adjustment rack, and control translation precision reaches 50nm, by regulate mask 6 to assemble lens 4 apart from Z _RReach adjusting to institute's etching photon microstructure area size, by regulate GaN sample 8 to photon microstructure template 6 apart from Z _T, reach the isoparametric variation of etching photon microstructure lattice constant on GaN sample 8.

After photon microstructure prepares on the GaN sample 8, further on GaN sample 8, prepare electrode etc., finish the making of the complete chip of GaN LED of band photon microstructure.Detailed process is as follows: utilize mask plate photoetching and etching table top, etch the table top in N type district; Deposit P type transparency electrode and N type electrode.Electrode adopts the method for electron beam evaporation that metal is deposited to material surface, and then adopts stress relief annealed method to make.Deposit pad material forms P type pad and N type pad.Finish the making of entire chip.

Preparing electrode process in addition also can utilize before above-mentioned Talbot effect prepares photon microstructure.

Claims (5)

1, a kind of manufacture method of GaN-based blue light light-emitting diode with photon microstructure is characterized in that, comprises the steps:

Step 1: at first at GaN sample upper surface growth layer of silicon dioxide layer, as the mask layer of etching GaN material; Spin coating last layer photoresist on silicon dioxide mask need be the photoresist to used laser sensitization;

Step 2: get a short wavelength laser as light source;

Step 3: get an extender lens, with the laser beam expanding of short wavelength laser, the light that expands after restrainting focuses on through convergent lens again;

Step 4: on the light beam irradiates photon microstructure template through lens and convergent lens, the photon microstructure template is behind convergent lens, and the two is apart from Z _T, the template that this template adopts electron beam lithography to make, figure is a photon microstructure on it;

Step 5: laser utilizes the Talbot effect by after the photon microstructure template, with photon microstructure template reflection with its distance be Z _TOn the GaN sample at place, the picture of photon microstructure template is become on the photoresist mask of GaN sample, promptly on photoresist, form the photon microstructure figure;

Step 6: utilize the photoresist that has formed the photon microstructure figure as mask,, photon microstructure is transferred to silicon dioxide layer by dry etching;

Step 7: utilize the silicon dioxide layer that has the photon microstructure figure to make mask, adopt dry etching method that photon microstructure is transferred on the GaN material.

2, the manufacture method of GaN-based blue light light-emitting diode with photon microstructure according to claim 1 is characterized in that, wherein used short wavelength laser is short wavelength's pulse or a continuous wave laser.

3, the manufacture method of GaN-based blue light light-emitting diode with photon microstructure according to claim 1 and 2, it is characterized in that, the wavelength 248nm of the excimer laser that the wavelength of wherein used short wavelength laser is, the wavelength 266nm of the wavelength 337nm of nitrogen molecular laser or Nd:YAG laser of quadruple pulse laser.

4, the manufacture method of GaN-based blue light light-emitting diode with photon microstructure according to claim 1, it is characterized in that, wherein employed extender lens and convergent lens with laser beam by after reach and cover full template and treat imaging region, the focal length of convergent lens is greater than 5cm, make the photon microstructure template both can be placed in the focal length, also can be placed on beyond times focal length.

5, the manufacture method of GaN-based blue light light-emitting diode with photon microstructure according to claim 1 is characterized in that, wherein the control translation precision of photon microstructure mask and GaN sample is less than 50nm, by regulate mask to assemble lens apart from Z _RWith regulate the GaN sample to the photon microstructure template apart from Z _T, reach the variation of regulating institute's etching photon microstructure lattice parameter on the material.