JP2002359399A - Light emitting device manufacturing method and light emitting device - Google Patents

Abstract

(57) [Problem] To provide a method for manufacturing a light-emitting element and a light-emitting element capable of reducing complexity while increasing the luminance of the element. In a method of manufacturing a light emitting device according to the present invention, a mesa is provided on a first main surface of a semiconductor wafer having a first main surface of a first conductivity type and a second main surface of a second conductivity type. A mask forming step of forming an etching mask 20a ', a mesa etching step of forming a mesa portion 10 by mesa etching, an electrode forming step of patterning the mesa etching mask 20a' to form an electrode 20a, Semiconductor wafer 200 along part 10
A wafer cutting step of cutting the mesa 10
And a roughening process for roughening the side surface portion 11 are performed in this order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a light emitting device and a light emitting device.

[0002]

2. Description of the Related Art A pn junction is formed by laminating semiconductors of different conductivity types, and a semiconductor light emitting device utilizing a recombination of carriers occurring near the pn junction interface as a light emitting source has a high brightness. Lack is often a problem. In order to improve the luminous intensity of the device, the recombination of the carriers injected into the light emitting layer portion may be efficiently performed, and materials and structures for the purpose have been studied and improved. However, as a result of many years of progress, the photoelectric conversion efficiency based on the improvement of the material and structure of the light emitting layer is gradually approaching the theoretical limit. Therefore, when trying to obtain a device with a higher luminous intensity, the light extraction efficiency from the device becomes extremely important.

As a method of improving the light extraction efficiency, for example, Japanese Patent Application Laid-Open No. 2000-196141 discloses a technique of forming fine irregularities on the outer peripheral surface of an element. According to this technique, the phenomenon that light that is about to leak out from the light emitting layer portion returns to the inside due to total reflection on the surface of itself is reduced, and the light extraction efficiency can be improved.

[0004]

In the above-mentioned light emitting device, a semiconductor wafer to be separated into individual devices is used. After forming electrodes corresponding to the respective devices, a cutting blade such as a diamond cutter is used. By performing the half-die up to the pn junction, the electrical characteristics and the light emission characteristics of each element can be examined at the time of the wafer. This half-die method is not preferable because it is necessary to perform an etching process for removing the strain introduced into the semiconductor wafer by the half-die, and the dicing process is complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a method for manufacturing a light emitting device, which has a high luminous intensity while reducing the complexity of the process, and a light emitting device. Aim.

[0006]

Means for Solving the Problems and Functions / Effects The inventors of the present invention have studied a manufacturing method capable of reducing the complexity of the process while increasing the brightness of the element by rough surface processing. The inventors have invented a method for manufacturing the light emitting device shown. That is, the method for manufacturing a light emitting device of the present invention includes the first main surface of the first conductivity type, the second main surface of the second conductivity type, the side surface, and the first main surface and the side surface. In the method for manufacturing a light emitting device having the formed mesa portion, the first
Forming a mask for mesa etching on a first main surface of a semiconductor wafer having a first main surface of a conductivity type and a second main surface of a second conductivity type, and forming a mesa portion by a mesa etching process A mesa etching step, an electrode forming step of patterning a mesa etching mask into an electrode, a wafer cutting step of cutting a semiconductor wafer along the mesa section, and performing roughening at least on the mesa section and the side section. The rough surface processing step is performed in this order.

As shown in the method of manufacturing a light emitting device of the present invention, after an element isolation groove (hereinafter, referred to as a mesa groove) is formed by mesa etching, a power supply is performed by patterning the mesa etching mask. The electrode can be used as it is. Instead of doing a half die,
Since the mesa groove is formed to reach the pn junction by performing the mesa etching, the characteristics of the individual elements to be separated can be easily inspected just like the case of performing the half die. A complicated half dicing step is not required, and etching for removing processing distortion is not required. That is, the process is simplified and the processing cost can be reduced. When the wafer is cut along the mesa groove after the end of the characteristic inspection, a so-called mesa-type element having one electrode having a plateau shape is obtained.

As a mask for mesa etching, Au is used.
Alternatively, an alloy mainly composed of Au can be suitably used. Au
Or, an alloy mainly composed of Au is hardly eroded by an etching solution for etching a wafer, and if this is used as a mask, the mask is peeled off when performing mesa etching, and a required portion is etched. Does not occur. That is, the mesa groove can be formed with higher precision than when masking with an organic resist (see FIGS. 7A and 7B). Since the mesa groove is formed with high precision, the inspection of the electrical characteristics and the light emission characteristics can be performed accurately, and the image recognition in the dicing device when cutting the individual devices is also performed accurately. Can be performed more smoothly. Then, if the surface is roughened after cutting the wafer, a rough surface is formed at least on the side surface and the mesa portion, and the light emitting device of the present invention with high luminous intensity can be obtained.

It is preferable that the surface of the element, other than the electrode portion, on the first main surface of the element, which is to be an electrode forming surface, be roughened. Further, the second main surface opposite to the first main surface is roughened. The surface is preferably a polished smooth surface. Light to be leaked from the inside of the device travels in all directions, but usually, the back surface of the device is not used as a light extraction surface. Is good.

The light emitting device of the present invention, which can be manufactured as described above, has a first main surface of a first conductivity type, a second main surface of a second conductivity type, a side surface, and a first main surface. And a mesa portion formed adjacent to the side surface portion, wherein at least the mesa portion and the side surface portion are roughened.

In the light emitting device according to the present invention, the surface and the mesa are roughened to form fine irregularities. By forming the mesa portion, light can be efficiently guided to the outside of the element. Further, since the mesa portion is also roughened, the probability that light is totally reflected on the surface is low.

A method for manufacturing a light emitting device using a mesa etching mask as an electrode as it is can also be as follows. The manufacturing method includes a first main surface of a first conductivity type, a second main surface of a second conductivity type, a side surface, and a mesa portion formed adjacent to the first main surface and the side surface. Forming a mesa-etching mask on a first main surface of a semiconductor wafer having a first main surface of a first conductivity type and a second main surface of a second conductivity type A mesa etching step of forming a mesa portion by a mesa etching process, a rough surface processing step of performing rough surface processing on the mesa portion, an electrode forming step of patterning a mesa etching mask into an electrode, and And a wafer cutting step of cutting the semiconductor wafer along the order.

According to the above-described manufacturing method, after the mesa groove is formed by mesa etching, the mesa etching mask is patterned so that the mesa groove can be used as it is as an electrode for power supply as well as the mesa groove is formed. Since the rough surface processing is performed in the process immediately after, the rough surface can be selectively formed only on the mesa portion. Since both main surfaces are not etched, it is effective when a light emitting element is manufactured using a semiconductor wafer that may have a possibility that the light intensity may be reduced if the rough surface processing is performed.

The light emitting device of the present invention, which can be manufactured as described above, has a first main surface of a first conductivity type, a second main surface of a second conductivity type, a side surface, and the first main surface. In a light-emitting element having a mesa portion formed adjacent to a surface and a side portion, a rough surface is applied to the mesa portion, and an outer peripheral surface excluding the mesa portion has a surface with less irregularities than the outer peripheral surface in the mesa portion. It is characterized by that.

According to the above light emitting element, even when the outer peripheral surface of the element except for the mesa portion is not intentionally roughened, at least the mesa portion has a rough surface. Higher luminous intensity can be obtained as compared with those without surface processing.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a light emitting device and a light emitting device according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view schematically showing a light emitting device of the present invention. First, the light emitting element 100 shown in FIG. 1 has a structure in which semiconductor single crystals of different conductivity types are stacked, and both ends in the stacking thickness direction have a first main surface (hereinafter, referred to as an upper surface) 12 of a first conductivity type and a second main surface. A second main surface (hereinafter referred to as a back surface) 13 of a conductivity type is provided, each of which has an electrode. For example, the back surface 13 indicating the second conductivity type is formed of the n-type semiconductor single crystal 1, and the p-type semiconductor single crystal 2 is stacked thereon to form the upper surface 12 indicating the first conductivity type. Then, pn is provided at the interface between the n-type semiconductor single crystal 1 and the p-type semiconductor single crystal 2.
A bond is formed. Electrodes 20a and 20b are formed on the upper surface 12 and the rear surface 13, respectively. The portion adjacent to the upper surface 12 is a mesa portion 10 in which the cross-sectional area in the direction perpendicular to the lamination thickness direction increases as approaching the rear surface 13. The mesa unit 10 has a concave curved outer peripheral surface. The side surface portion 11 of the light emitting element 100 is substantially perpendicular to the lamination thickness direction, and is adjacent to the back surface 13 and the mesa portion 10. Note that the mesa portion 10 is formed from the upper surface 12 to a region completely including the pn junction.

The outer peripheral surface excluding the back surface 13, that is, the upper surface 12 excluding the electrode portion, the mesa portion 10, and the side surface portion 11 are rough surfaces having fine irregularities which are roughened by wet etching. Thereby, at the interface between the light emitting element 100 and the periphery thereof, the probability that light emitted near the pn junction is totally reflected can be reduced, and the light extraction efficiency can be improved.

For example, Ga whose emission wavelength is around 600 nm
In an AsP-based light-emitting element, the refractive index n of GaP is about 3.3 and the refractive index n of GaAs is about 3.8. Therefore, the refractive index n of GaAsP, which is a mixed crystal thereof, is about 3.3.
It turns out that it is 3 to about 3.8. When light is incident from one medium having a different refractive index to another medium, the condition under which light is totally reflected at the interface between the media is determined according to the difference in the refractive indexes.

As shown in the schematic diagram of FIG. 6 (a), the critical angle theta _c when the light is just exit angle = 90 ° is totally reflected at the interface, the refractive index of the medium on the incident side n ₁ Θc = sin ⁻¹ (n ₂ / n ₁ )}, where n ₂ is the refractive index of the medium on the emission side. If the exit medium is air,
Since the refractive index can be considered to be approximately equal to the refractive index of vacuum (= 1), using this, it can be expressed as θc = sin ⁻¹ (1 / n ₁ ) ‥‥.

For example, in the case of a GaAsP mixed crystal having a refractive index n _{1 of} about 3.3 to about 3.8, the critical angle θc of total reflection is about 15
° to about 18 °. Only light that arrives at an angle smaller than θc, that is, an angle near perpendicular to the interface, is emitted into the air. Light that reaches the interface at an angle larger than θc is totally reflected inside the crystal and eventually absorbed.

On the other hand, if the light extraction surface is a rough surface having fine irregularities, even light that reaches the interface at an angle larger than θc as shown in FIG. 6B. In addition, since a convex surface having an angle smaller than θc exists locally, light can be transmitted into the air.

The degree of the unevenness is determined in consideration of the material, composition, structure, etc., of the light emitting device 100.
The light extraction efficiency can be optimized to be the best. That is, in consideration of the refractive index of the material constituting the element and the emission wavelength of the element, the etching conditions may be changed so that the unevenness is not too gentle and not too fine. For example, JP-A-2000-196141 The method described in the gazette can be applied.

On the other hand, the back surface 13 is preferably a smooth surface which has been subjected to polishing such as lapping and polishing. Normally, the back surface 13 is fixed to a frame or the like so that light cannot leak out. Therefore, it is better that the light reaching the back surface 13 be totally reflected and guided to another surface. That is, it is desirable that the back surface 13 be a smooth surface with as little unevenness as possible.

Such a light emitting device of the present invention can be manufactured as follows. For example, GaP on a GaP single crystal substrate
Since the light emitting device 100 of the present invention having a mesa shape can be obtained by processing an epitaxial wafer on which an AsP single crystal layer is epitaxially grown, this will be described below as an embodiment.

Hereinafter, description will be made with reference to the process explanatory diagram of FIG.
Is described. First, the plane orientation of the main surface is (100)
On an n-type GaP single crystal substrate 30, n-type GaP epitaxy
Layer 31, n-type GaAs having a variable mixed crystal ratio x_1-xP
_xMixed crystal ratio changing layer 32, n-type GaAs doped with nitrogen
_1-xP_xAfter sequentially stacking the constant mixed crystal ratio layers 33, n
Type GaAs_1-xP_xFrom the surface of the constant mixed crystal ratio layer 33, Zn
Is diffused into n-type GaAs_1-xP_xMixed crystal ratio constant layer 3
3 is inverted to p-type to form p-type GaAs_1-xP _xMixed
A constant crystallinity layer 34 is formed, and the mixed crystal ratio constant layers 33 and 34 are formed.
GaAsP epitaxy with pn junction at boundary
A wafer 200 is obtained (wafer manufacturing process). n-type
GaAs_1-xP_xThe mixed crystal ratio changing layer 32 is made of n-type GaP
From the epitaxial layer 31 to n-type GaAs_1-xP_xMixed crystal ratio
The composition of the mixed crystal gradually changes over the constant layer 33,
The strain due to lattice mismatch is reduced.

Next, after the back surface 13 of the wafer 200 is subjected to polishing such as lapping and polishing, Au, Au—Ge—Ni alloy, Au
A metal coating is formed with a -Si alloy, an Au-Si-Ni alloy, or the like. This metal film is coated with, for example, an etching solution KI-
After processed into a desired shape by photo-etching using an I ₂ aqueous solution, in an inert atmosphere of Ar gas or the like in order to obtain ohmic contact with the wafer 200, approximately 400 ° C. ~
Heat treatment is performed at a temperature of 600 ° C. to obtain a back electrode 20b (back electrode forming step). Since the heat treatment conditions vary depending on the types of the semiconductor and the metal, it is preferable to optimize them according to the situation.

Light emitting device 100 of the present invention in the form of a mesa
Can be obtained by forming a mesa groove to be the mesa portion 10 shown in FIG. 1 at the time of the wafer 200 and cutting the wafer along the inner peripheral surface of the mesa groove. When an etching is attempted by masking with an organic resist in order to form a mesa groove, as shown in the schematic diagram of FIG. 7B, as the mesa etching progresses, the mask 20r is gradually removed. It is difficult to form the mesa groove accurately. If the mesa groove 50 is not sharply formed, not only the electrical characteristics and the light emission characteristics cannot be accurately inspected, but also the image recognition for determining the dicing position when the dicing is finally performed to separate the elements is not accurate. Troubles, such as the inability to perform the measurement and reduction of the luminous intensity.

In the method for manufacturing a light emitting device of the present invention, Au or an alloy mainly composed of Au is used as a mask for mesa etching. The frequency of peeling is very low. Therefore, as shown in FIG. 7A, a mesa groove etched with high accuracy can be formed.

The mesa etching mask 20a 'for forming the mesa groove can be obtained by the same method as when the back electrode 20b is formed (mask forming step). After forming the mesa etching mask 20a ', for example, 85 V
When the upper surface 12 is etched using an etching solution in which an ol% phosphoric acid aqueous solution and a 30 vol% hydrogen peroxide solution are mixed at a volume ratio of 1: 1, a concave mesa groove 50 is formed (a mesa etching step). Note that the wafer 200 may be previously adhered to an adhesive tape for a semiconductor such that the back surface 13 is a contact surface, or an acid-resistant wax is applied to the back surface 13 to protect the back surface 13 of the wafer 200 from an etchant.

Since the mask 20a 'completely covers the upper surface 12, light cannot leak out as it is.
Therefore, after patterning the mask 20a 'in such a manner that the peripheral portion is removed so that the upper surface 12 of the wafer is exposed, the peripheral portion is removed by etching to obtain the upper surface electrode 20a having an optimal size and shape. (Electrode formation step). Thereafter, in order to obtain ohmic contact with the wafer, a heat treatment similar to that for forming the back electrode 20b is performed.

Then, the wafer 200 is cut along the concave mesa groove 50 for use as an actual element, that is, with the cutting blade in contact with the deepest position of the groove (wafer cutting step).

The outer peripheral surface of the cut individual elements with respect to, for example, the _{I 2} to 1 parts, 40 parts and 80 parts of nitric acid, 40 parts to 300 parts of hydrogen fluoride, 400 parts to 2000 parts of acetic acid Rough surface processing is performed using an etching solution contained in an aqueous solution at a molar composition ratio (rough surface processing step). By the rough surface processing, fine irregularities (rough surfaces) are formed on the upper surface 12 excluding the upper electrode 20a of the element 100, the mesa portion 10 and the side surface portion 11. Since the back surface 13 is protected by the adhesive tape, no rough surface is formed. By performing each step in the order described above, the light-emitting element 100 of the present invention can be obtained.

By the way, as described above, according to the method of manufacturing a light emitting device of the present invention in which a mask and an electrode for mesa etching are used, only the mesa portion 10 as shown in FIG. It is also possible to obtain a light emitting element 100 ′ which is roughened and has an outer peripheral surface other than the mesa portion 10 with less irregularities than the outer peripheral surface of the mesa portion 10. Usually, rough surface processing to improve light extraction efficiency
As described above, it is desirable that the processing be performed on all the light extraction surfaces. On the other hand, in order to improve the light extraction efficiency, the p-type single crystal 2 itself may be formed of a very thin layer of several μm, and a pn junction may be formed in a region very close to the main surface of the device. In such a case, if the upper surface 12 is roughened, much of the p-type layer is scraped off, and conversely, the luminous efficiency may be reduced. Therefore, the light emitting device 1 in which only the mesa portion 10 is roughened
00 'can be exemplified. Hereinafter, a method for manufacturing the light emitting device 100 ′ shown in FIG. 4 will be described with reference to the process explanatory diagram of FIG.

The steps from the manufacturing process of the wafer 200 shown in FIG. 5 to the mesa etching process for forming the mesa unit 50 are the same as those described in the process explanatory diagram of FIG. The difference is that before the mask 20a 'for mesa etching is
This is a point that rough surface processing (rough surface processing step) is performed on the main surface of No. 0. Wafer 2 obtained by such a process sequence
No. 00 ′ has fine unevenness (rough surface) only in the mesa groove 50. Thereafter, photoetching is performed, and the surface electrode 20a is formed.
Is formed (electrode forming step). After that, the wafer 20
By cutting the 0 'along the mesa groove 50 (wafer cutting step), the light emitting device 100' shown in FIG. 4 is obtained.

For example, as shown in FIG. 3, the obtained light emitting device 100 or 100 ′ is
0, and wire-bonded, and the periphery is coated with epoxy to form a single lamp LE.
D101 is obtained.

[0036]

EXPERIMENTAL EXAMPLE A GaAsP epitaxial wafer having a GaAsP single crystal layer laminated on a GaP single crystal substrate was produced by a known vapor phase epitaxial growth method by adjusting the mixed crystal ratio so that the emission wavelength became 618 nm. Using this GaAsP epitaxial wafer, the outer peripheral surface of the element other than the electrodes 20a, 20b and the back surface 13 is roughened by the method for manufacturing a light emitting device of the present invention.
Mesa-type light-emitting device 100 of the present invention in which the surface is polished.
I got The size of the element was 0.29 × 0.29 mm □, which was measured by projecting in the direction of crystal stacking. The obtained light emitting device is fixed on a lead frame 70 with silver paste, bonded with a gold wire, and molded around a transparent epoxy resin to form a single lamp LED.
(Light emitting diode) was produced. When a direct current of 20 mA was applied to the manufactured light emitting diode and the luminous intensity was measured, a luminous intensity of 5.669 mcd was obtained.

As described above, the present invention is not limited to the embodiments, and it goes without saying that the present invention can be implemented in various modes without departing from the scope of the invention. In addition, it is to be noted that the drawings are schematic diagrams for understanding.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a light-emitting element of the present invention.

FIG. 2 is a process explanatory view illustrating a method for manufacturing a light emitting device of the present invention.

FIG. 3 is a schematic sectional view of a single lamp LED.

FIG. 4 is a cross-sectional view illustrating a modification of the light-emitting element of the present invention.

FIG. 5 is a process explanatory view illustrating a method for manufacturing the light-emitting element shown in FIG.

FIG. 6 is an explanatory diagram illustrating total reflection conditions of light.

FIG. 7 is a schematic cross-sectional view showing a mesa groove formation mode on a wafer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Mesa part 11 Side part 12 Top surface (1st main surface) 13 Back surface (2nd main surface) 20a Top surface electrode 20b Back surface electrode 20a 'Mesa etching mask 50 Mesa groove 100, 100' Light emitting element 200 Semiconductor wafer

Continuing from the front page (72) Inventor Yasunori Kaneko 2-1-1 Isobe, Annaka-shi, Gunma Shin-Etsu Semiconductor Co., Ltd. Isobe Plant F-term (reference) 5F041 AA03 CA02 CA37 CA38 CA74 CA75 CA77 CA85 DA18 DA44

Claims (7)

[Claims] 1. A first main surface of a first conductivity type, a second main surface of a second conductivity type, a side portion, and a mesa portion formed adjacent to the first main surface and the side portion. A mask for forming a mesa etching mask on the first main surface of a semiconductor wafer having a first main surface of a first conductivity type and a second main surface of a second conductivity type. A forming step, a mesa etching step of forming a mesa portion by a mesa etching process, an electrode forming step of patterning the mask for mesa etching into an electrode, and a wafer cutting for cutting the semiconductor wafer along the mesa portion A method of manufacturing a light-emitting element, comprising: performing a roughening process for roughening at least the mesa portion and the side surface portion in this order. 2. A first main surface of a first conductivity type, a second main surface of a second conductivity type, a side surface, and a mesa portion formed adjacent to the first main surface and the side surface. A mask for forming a mesa etching mask on the first main surface of a semiconductor wafer having a first main surface of a first conductivity type and a second main surface of a second conductivity type. A forming step, a mesa etching step of forming a mesa portion by a mesa etching process, a rough surface processing step of performing rough surface processing on the mesa portion, and an electrode forming step of patterning the mesa etching mask to form an electrode. And a wafer cutting step of cutting the semiconductor wafer along the mesa portion in this order. 3. The method according to claim 1, wherein the mask for the mesa etching is Au.
3. The method according to claim 1, wherein the light emitting device is made of an alloy mainly composed of Au. 4. A first main surface of a first conductivity type, a second main surface of a second conductivity type, a side portion, and a mesa portion formed adjacent to the first main surface and the side portion. The light emitting device according to claim 1, wherein at least the mesa portion and the side surface portion are roughened. 5. A first main surface of a first conductivity type, a second main surface of a second conductivity type, a side surface, and a mesa portion formed adjacent to the first main surface and the side surface. Wherein the mesa portion is roughened, and the outer peripheral surface excluding the mesa portion is a surface having smaller irregularities than the outer peripheral surface of the mesa portion. 6. The light emitting device according to claim 4, wherein an electrode is formed on the first main surface, and the first main surface except for the electrode portion is roughened. 7. The light emitting device according to claim 4, wherein the second main surface is polished.