CN102184842A

CN102184842A - Method for patterning sapphire by combining wet etching and dry etching

Info

Publication number: CN102184842A
Application number: CN 201110078480
Authority: CN
Inventors: 张建宝; 顾小云
Original assignee: HC Semitek Corp
Current assignee: HC Semitek Corp
Priority date: 2011-03-30
Filing date: 2011-03-30
Publication date: 2011-09-14
Anticipated expiration: 2031-03-30
Also published as: CN102184842B

Abstract

The invention discloses a method for patterning a sapphire substrate by combining wet etching and dry etching. The method comprises the following steps of: depositing a layer of silicon dioxide film on the sapphire substrate; preparing a photoresist masking film with a pattern on the silicon dioxide film through lithography; etching the lithography pattern onto the silicon dioxide film; etching the pattern onto the sapphire substrate by a method of combining wet etching and short-time dry etching, wherein the patterned silicon dioxide film serves as a masking film; and removing the silicon dioxide film through wet etching, cleaning the sapphire substrate and finishing the preparation of the patterned sapphire substrate. Because of the combination of wet etching and dry etching and the optimization of related technical parameters, the etching speed is guaranteed, the etching cost is reduced, better pattern precision can be achieved, and good etching effect can be achieved. The patterned sapphire substrate can be applied to the epitaxial growth of nitrides with low dislocation density and high crystal quality.

Description

Combine with the dry etching method of graphic sapphire of a kind of wet etching

Technical field

The present invention relates to technical field of semiconductors, relate in particular to combine with the dry etching method of graphic sapphire substrate of a kind of wet etching.

Background technology

In recent ten years, with III-V family gallium nitride (GaN) is that the nitride compound semiconductor material of representative has the extensive concern that characteristics such as wide direct band gap, high heat conductance, high rigidity, low-k, radioresistance have obtained people because of it, in fields such as solid-state illumination, solid state laser, optical information storage, ultraviolet detectors huge application potential is arranged all.At present, obtained important breakthrough in the GaN devices field in the world, high brightness blue, green light LED (LED) commercialization already, long-life ultraviolet light and blue laser are also succeeded in developing.Because lack suitable backing material, extension GaN carries out on foreign substrate.Sapphire (Al2O3) is the most general a kind of backing material of extension GaN film, owing to have very big lattice constant mismatch and thermal expansion coefficient difference between it and the GaN epitaxial loayer, can produce a large amount of crystal defects when epitaxial growth.In order to alleviate even to solve the problem that lattice and thermal mismatching are brought, foreign substrate GaN material growth field has formed a series of comparatively mature technique schemes.Wherein, adopt graphic sapphire substrate (Pattern Sapphire Substrate, abbreviation PSS) technology can be alleviated the stress in Sapphire Substrate and the GaN epitaxial growth preferably, reduces the defect concentration of the outer Yanzhong of GaN, improves the crystal mass of epitaxial material.In addition, in the LED application facet, adopt the graphic sapphire substrate technology not only can improve material quality, the light that active layer is sent, reduce because of the total reflection that refractive index difference caused by Sapphire Substrate, and then improve the luminous efficiency of LED integral body with periodic pattern structure.

At present, the method for preparing the graphic sapphire substrate mainly contains two kinds of dry etching and wet etchings.Wherein, dry etching has that etch rate can be regulated and control, figure transforms the precision height, fabulous advantages such as anisotropy, uniformity and good reproducibility, can prepare high-quality, highdensity figure.Yet, when utilizing the dry etching mode to prepare patterned substrate, have that etch rate is low, cost is high, to shortcomings such as material damage height.Comparatively speaking, wet etching is easy to operate, the etching cost is low, etch rate is fast, can be used for a large amount of productions, but its etching precision is not high, and the difficult control of etch rate easily forms lateral erosion, is difficult to prepare high-quality, high-precision figure.The more important thing is that wet etching can form a plurality of crystal faces, and nitride need be grown on specific crystal face, thereby wet etching can cause epitaxially grown difficulty.Because all there are defective in above-mentioned two kinds of methods, so development of new, the method for graphic sapphire substrate has great importance efficiently.

Summary of the invention

The objective of the invention is to overcome the defective that above-mentioned two kinds of methods exist, proposed a kind of new method for preparing the graphic sapphire substrate.This method combines wet etching with dry etching, and by optimizing relevant technological parameter, has reached etching effect preferably.

The concrete steps of the technical solution used in the present invention are as follows: A, deposition layer of silicon dioxide film on Sapphire Substrate; B, utilize conventional photoetching technique on described silicon dioxide film, prepare the band figure the photoresist mask; C, litho pattern is etched on the silicon dioxide film; D, be mask, adopt behind the wet etching method in conjunction with the short time dry etching with patterned silicon dioxide film, with pattern etching on Sapphire Substrate; E, wet etching remove silicon dioxide film, and Sapphire Substrate is cleaned up, and finish the preparation of graphic sapphire substrate.The thickness of the silicon dioxide that wherein, deposits described in the steps A is 50nm to 5um.Wherein, litho pattern described in the step B is the periodic pattern array, and the unit of its litho pattern can be that one or more combination in circular, square, triangle or the irregular figure forms.The size of each unit and spacing are 1um to 5um in the litho pattern described in the step B.Litho pattern is etched on the silicon dioxide film described in the step C, used corrosive liquid are hydrofluoric acid+ammonium fluoride+H2O mixed liquor.The corrosive liquid that wet etching described in the step D adopts is the mixed liquor of sulfuric acid and phosphoric acid, and wherein the volume ratio of sulfuric acid and phosphoric acid is 3: 1 in the mixed liquor, and what described dry etching adopted is reactive ion etching RIE or inductively coupled plasma etching ICP equipment.Elder generation's employing wet etching etches 60%～80% etching depth among the step D, finishes the residue degree of depth with dry etching again.The corrosive liquid that wet etching described in the step e adopts is a diluted hydrofluoric acid.

The invention has the advantages that: the present invention combines dry etching and two kinds of methods of wet etching neatly, adopts behind the most of etching depth of first wet etching the method in conjunction with the short time dry etching, with pattern etching on Sapphire Substrate.Following advantage is arranged: (1) utilizes wet etching can obtain higher corrosion rate and lower batch process cost; (2) utilize dry etching can destroy a plurality of crystal faces that wet etching forms, help epitaxial growth (nitride epitaxial growth need be grown, and the nitride quality of growing on the different crystal faces differs greatly) on specific substrate crystal face; (3) dry etching behind the first wet etching of employing, can utilize the characteristics of dry etching rate stabilization, by at different etching depths different etch periods being set, it is inhomogeneous to overcome the degree of depth that early stage, wet etching speed instability was caused, thereby obtains consistent etching depth.

Description of drawings

Fig. 1 is combine with dry etching structural profile schematic diagram behind the graphic sapphire substrate deposition layer of silicon dioxide film of a kind of wet etching, and 1 is Sapphire Substrate among the figure, the 2nd, and silicon dioxide film;

Fig. 2 is for adopting the generalized section of conventional photoetching technique behind the photoresist mask of preparing the band figure on the described silicon dioxide film, and 1 is Sapphire Substrate among the figure, and the 2nd, silicon dioxide film, the 3rd, photoresist;

Fig. 3 is the generalized section after etching into litho pattern on the silicon dioxide film, and 1 is Sapphire Substrate among the figure, the 2nd, and silicon dioxide film;

Fig. 4 is mask for utilizing patterned silicon dioxide film, adopts behind the wet etching method in conjunction with the short time dry etching, and with the generalized section of figure transfer after the Sapphire Substrate, 1 is Sapphire Substrate among the figure, the 2nd, and silicon dioxide film;

Fig. 5 is that wet etching removes silicon dioxide film, and Sapphire Substrate is cleaned up, and is prepared into the generalized section behind the graphical sapphire substrate, and 1 is Sapphire Substrate among the figure.

Embodiment

See also Fig. 1-shown in Figure 5, combine with the dry etching method of graphic sapphire substrate of a kind of wet etching provided by the present invention comprises the steps:

Step 1: 1 deposition layer of silicon dioxide film 2 on Sapphire Substrate, the thickness of the silicon dioxide of wherein said deposition is 50nm to 5um;

Step 2: utilize conventional photoetching technique on described silicon dioxide film 2, to prepare the photoresist mask 3 of band figure, wherein litho pattern is the periodic pattern array, and the unit of its litho pattern can be that one or more combination in circular, square, triangle or the irregular figure forms.The size of each unit and spacing are 1um to 5um in this litho pattern;

Step 3: utilize hydrofluoric acid+ammonium fluoride+H2O mixed liquor, litho pattern is etched on the silicon dioxide film 2;

Step 4: with patterned silicon dioxide film 2 is mask, adopts behind the wet etching method in conjunction with the short time dry etching, with pattern etching on Sapphire Substrate 1.Wherein, the corrosive liquid that wet etching adopts is the mixed liquor of sulfuric acid and phosphoric acid, and the volume ratio of sulfuric acid and phosphoric acid is 3: 1.The wet etching degree of depth accounts for 60%～80% of total etching depth.Wet etching re-uses dry etching and finishes the residue degree of depth after finishing, and the equipment that is adopted is RIE or ICP equipment.

Step 5: utilize the dilute hydrofluoric acid solution wet etching to remove remaining silicon dioxide film 2, and Sapphire Substrate 1 is cleaned up, finish the preparation of graphic sapphire substrate 1.

Below in conjunction with accompanying drawing and specific embodiment combine with the dry etching method of graphic sapphire substrate of a kind of wet etching provided by the present invention is described in further detail.

Embodiment 1

At first, using plasma strengthens the silicon dioxide film 2 of chemical vapour deposition (CVD) (PECVD) deposition techniques 0.5um on 2 inches C surface sapphire substrate 1, and post-depositional structural profile as shown in Figure 1;

Then, on silicon dioxide film 2, utilize conventional photoetching technique resist coating layer 3, by the circular array of exposure imaging.The size of this circular array cellular construction and spacing are 2um, and the structural profile after the photoetching as shown in Figure 2;

Then, utilize hydrofluoric acid+ammonium fluoride+H ₂The O mixed liquor etches into litho pattern on the silicon dioxide film 2, and its structural profile as shown in Figure 3;

Subsequently, with silicon dioxide film 2 is the figure mask, and at first to utilize volume ratio be 3: 1 sulfuric acid and phosphoric acid mixed liquor 260 ℃ of corrosion C surface sapphire substrate 1 down, and corrosion depth is 1.6um, then use the residue degree of depth of ICP etching 0.4um, its structural profile as shown in Figure 4;

At last, utilize the dilute hydrofluoric acid solution wet etching to remove remaining silicon dioxide film 2, and Sapphire Substrate 1 is cleaned up, promptly finish the preparation of graphic sapphire substrate 1, its structural profile as shown in Figure 5.The Sapphire Substrate of gained has periodic pattern.Because in preparation process, the mode that has adopted wet etching to combine with dry etching, shortcomings such as the etch rate that single employing dry etching brings is low, etching cost height had both been improved, also avoided the caused etching precision of single employing wet etching not high, easily form problems such as lateral erosion, thereby reach good etching effect, prepare high-quality, high-precision graphic sapphire substrate.The Sapphire Substrate of gained is used for the epitaxial growth of nitride, can reduce the crystal defect in the epitaxial growth, improves crystal mass, thereby improves the performance of device.Simultaneously, in the LED application facet, epitaxial growth GaN on this Sapphire Substrate can not only obtain superior crystal quality, can also promote the light extraction yield of LED by the periodic patterns on the substrate effectively, thereby make LED possess better photoelectric characteristic.

Claims

1. the wet etching method of graphic sapphire that combines with dry etching, this method may further comprise the steps: A, deposition layer of silicon dioxide film on Sapphire Substrate; B, utilize photoetching technique on described silicon dioxide film, prepare the band figure the photoresist mask; C, litho pattern is etched on the silicon dioxide film; D, be mask, adopt behind the wet etching method in conjunction with dry etching with patterned silicon dioxide film, with pattern etching on Sapphire Substrate; E, wet etching remove silicon dioxide film, and Sapphire Substrate is cleaned up, and finish the preparation of graphic sapphire substrate.

2. according to combine with the dry etching method of graphic sapphire of the described a kind of wet etching of claim 1, it is characterized in that: the thickness of the deposition of silica film described in the steps A is 50nm to 5um.

3. combine with the dry etching method of graphic sapphire substrate of a kind of wet etching according to claim 1, it is characterized in that: the litho pattern described in the step B is the periodic pattern array, and the unit of its litho pattern can be that one or more combination in circular, square, triangle or the irregular figure forms.

4. combine with the dry etching method of graphic sapphire substrate of a kind of wet etching according to claim 1, it is characterized in that: the size of each unit and spacing are 1um to 5um in the litho pattern described in the step B.

5. combine with the dry etching method of graphic sapphire substrate of a kind of wet etching according to claim 1, it is characterized in that: litho pattern is etched on the silicon dioxide film described in the step C, used corrosive liquid are hydrofluoric acid+ammonium fluoride+H2O mixed liquor.

6. combine with the dry etching method of graphic sapphire substrate of a kind of wet etching according to claim 1, it is characterized in that: the corrosive liquid that the wet etching described in the step D adopts is the mixed liquor of sulfuric acid and phosphoric acid, wherein the volume ratio of sulfuric acid and phosphoric acid is 3: 1 in the mixed liquor, and what described dry etching adopted is reactive ion etching machine or inductively coupled plasma etching machine.

7. combine with the dry etching method of graphic sapphire substrate of a kind of wet etching according to claim 1 is characterized in that: adopt wet etching to etch 60%～80% etching depth among the step D earlier, finish the residue degree of depth with dry etching again.

8. combine with the dry etching method of graphic sapphire substrate of a kind of wet etching according to claim 1, it is characterized in that: the corrosive liquid that wet etching described in the step e adopts is a diluted hydrofluoric acid.