JP4013664B2 - Manufacturing method of semiconductor light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor light emitting device formed on a wafer and separated by mesa grooves.
[0002]
[Prior art]
Many semiconductor light emitting devices are formed by laminating compound semiconductors on a wafer. If the semiconductor light-emitting device semi-finished products are separated and then tried to be inspected, it is difficult to handle and takes time. Therefore, a mesa groove is formed on the wafer, and the semiconductor light-emitting device half-processed by using the mesa groove. The product is energized and various inspections are performed.
[0003]
As a method for forming the mesa groove, there are a dry etching method, a dicing method, and a wet etching method.
[0004]
FIGS. 3A to 3I show a semiconductor light emitting device manufacturing process by dry etching, FIG. 4A is a sectional view of a semi-finished semiconductor light emitting device with a mesa groove formed, and FIG. The top view of the semi-finished product of the semiconductor light-emitting device arrange | positioned at the matrix form on the top is shown.
[0005]
As shown in FIG. 3A, the substrate 70 (wafer) is formed to a thickness of 240 μm, and the epitaxial layer 71 is formed to a thickness of 9 μm. As shown in FIG. 4A, the epitaxial layer 71 includes an N epitaxial layer 72, a PN junction layer 73, and a P epitaxial layer 74 from the bottom. More specifically, the N epitaxial layer 72 is composed of an n-GaAs buffer layer, an n-multilayer reflective film layer and an n-AlGaInP cladding layer, the PN junction layer 73 is composed of a u-AlGaInP active layer, and the P epitaxial layer 74 is composed of It is composed of a p-AlGaInP cladding layer and a p-AlGaAs window layer.
[0006]
As shown in FIG. 3B, an SiO ₂ film 75 is formed on the epitaxial layer 71 as an etching protective film. The thickness of the SiO ₂ film 75 is about 1 μm.
[0007]
As shown in (C), after forming a resist pattern 76 with a mesa street width of 60 μm, etching is performed using an HF-based etchant, and a part of the SiO ₂ film 75 is removed along the mesa street.
[0008]
Next, as shown in (D), after removing the resist pattern 76, dry etching is performed using SiCl ₄ gas to remove a part of the epitaxial layer 71 to form a mesa groove 77. The depth of the mesa groove 77 is formed to be about 10 to 15 μm, and the etching rate when etching the epitaxial layer 71 is about 0.5 μm / min. The upper surface of the SiO ₂ film 75 is also eroded at an etching rate of about 0.03 μm / min.
[0009]
In (E) and (F), the P electrode 78 shown in (F) is formed.
[0010]
As shown in (E), first, an Au / Zn + Au-sputtered film is formed, and a Ti + Au-EB deposited film is further laminated.
[0011]
As shown in (F), after forming a resist pattern 79, KCN (potassium cyanide) etching is performed to remove unnecessary portions of the sputtered film and the deposited film, thereby forming a P electrode 78.
[0012]
As shown in (G), a protective resist film 80 is formed on the entire front surface side, and the back surface side of the substrate 70 made of GaAs is etched with an H ₃ PO ₄ etching solution to a final thickness of 220 μm. After the adjustment, the protective resist film 80 is removed.
[0013]
As shown in (H), an Au / Ge / Ni + Au vapor deposition film is formed on the entire back surface, and this is used as the N electrode 81.
[0014]
Then, as shown in (I), it is left in a 460 ° C. atmosphere for 15 to 20 minutes to perform alloying heat treatment of the PN electrode, and an energization test is performed in this state.
[0015]
In dry etching, in the case of ion-assisted plasma etching, anisotropic etching in which etching is performed only in the depth direction is possible using the fact that the direction of etching progress is governed by the direction of ion movement, It is possible to form the mesa groove 77 having a shape substantially according to the resist pattern.
[0016]
FIG. 5A shows a cross-sectional view of a semi-finished product of a semiconductor light emitting element when a mesa groove is formed by wet etching. In the wet etching, since the etching progress is isotropic, the etching proceeds to the side as well as the depth direction. For this reason, the width of the mesa groove 82 is wider than the mesa street width.
[0017]
FIG. 6 shows a cross-sectional view of a semi-finished product of a semiconductor light emitting device when a mesa groove is formed using dicing.
[0018]
As shown in FIG. 6, when the mesa groove 84 is formed by dicing, it is mechanically processed. Therefore, even if the thickness of the epitaxial layer 83 is increased, it can be cut to a deep place, and the deep mesa groove is formed. 84 can be formed.
[0019]
FIG. 7 is a cross-sectional view of a semi-finished product of a semiconductor light emitting device when a mesa groove is formed by wet etching after dicing.
[0020]
As shown in FIG. 7, after the dicing process is performed on the portion indicated by the dotted line in the drawing, the crystal distortion on the dicing surface may be removed using wet etching.
[0021]
After forming a mesa groove by these methods and conducting a predetermined energization test, the semi-finished product of each semiconductor light emitting element is separated from the mesa groove and used as a completed semiconductor light emitting element.
[0022]
[Problems to be solved by the invention]
However, in the conventional method for manufacturing a semiconductor light emitting device, various methods are used for forming a mesa groove, but these have the following problems.
[0023]
As shown in FIG. 4A, in dry etching, etching can be performed only in the thickness direction by anisotropic etching. However, since the etching of the SiO ₂ film 75 proceeds simultaneously, the depth of the mesa groove 77 is reduced. When trying to form deeply, the thickness of the SiO ₂ film 75 must be increased. Recently, in order to improve the current spread and increase the emission intensity, the epitaxial layer is often formed thick. However, when dry etching is used, if the protective film is too thick, the protective film will crack. There is a problem that peeling occurs.
[0024]
As shown in FIG. 5B, when wet etching is used, side etching also proceeds according to the etching depth. Therefore, when the epitaxial layer 86 is thick, the groove width of the mesa groove 87 is necessary. There is a problem that the processing loss increases and the processing loss increases. In addition, since there is a difference in the etching rate due to the difference in the material composition of each layer constituting the epitaxial layer 86, there is also a problem that the side surface of each layer is formed uneven and the light emitting area is reduced.
[0025]
As shown in FIG. 6, when dicing is used, processing can be performed up to a deep position, but crystal distortion remains on the processed surface, and the processed surface becomes rough, resulting in poor light emission extraction efficiency. There is.
[0026]
As shown in FIG. 7, when wet etching is used after dicing to improve the method by dicing, crystal distortion can be removed and the side surface of the mesa groove 85 can be finished. The mesa groove 85 has a wider width due to the progress of the process, causing a processing loss and the problem that the side surface of the mesa groove 85 is not flat because of the difference in the etching rate described above, and the light emission efficiency is not improved. It remains.
[0027]
SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor light emitting device capable of forming a narrow mesa groove width, improving yield, and improving light emission characteristics and light output.
[0028]
[Means for Solving the Problems]
In the method for manufacturing a semiconductor light emitting device according to the present invention, the mesa groove is formed by performing dry etching processing after dicing processing.
[0029]
According to the present invention, a mesa groove can be formed narrowly by performing dry etching after dicing, and a method for manufacturing a semiconductor light emitting device that improves the yield and reliability, and improves the light emission characteristics and the light output can be obtained.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
According to a first aspect of the present invention, there is provided a method for manufacturing a semiconductor light emitting device comprising a step of laminating a compound semiconductor on a wafer and forming a mesa groove for inspection on the surface. The mesa groove is formed by dry etching after dicing. The semiconductor light emitting device manufacturing method is characterized in that a deep mesa groove can be formed by dicing and a side surface is formed in a flat shape by dry etching. Further, the groove width can be narrowed and the irregular reflection of light can be prevented, and the surface finish can be applied to increase the light extraction amount from the side.
[0031]
The second invention of the present application is characterized in that the dicing is performed to a depth reaching an N epitaxial layer formed immediately above the wafer, and the dry etching is performed to a depth reaching the wafer. The method of manufacturing a semiconductor light emitting device according to claim 1, wherein dicing is performed to a depth reaching the N epitaxial layer, and dry etching is performed to a depth reaching the wafer. The amount can be adjusted according to the thickness of the protective film of the epitaxial layer.
[0032]
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0033]
FIG. 1 is a front sectional view showing a state in which a mesa groove is formed in a semi-finished product of a semiconductor light emitting device of the present invention. In FIG. 1, a semi-finished product 1 of a semiconductor light emitting device is obtained by sequentially laminating an N epitaxial layer 3, a PN junction layer 4, and a P epitaxial layer 5, which are examples of a compound semiconductor, on a substrate 2 (wafer). An etching protective film 7 (SiO ₂ protective film) covering the layer 5 is provided. And it has the side wall part 10 isolate | separated by the mesa groove | channel 9 for a test | inspection formed in the surface of the board | substrate 2. As shown in FIG.
[0034]
When the semiconductor light emitting device is completed, the etching protective film 7 is removed, a P electrode (not shown) is provided on the P epitaxial layer 5, an N electrode is provided on the lower side of the substrate 2, and the mesa of the substrate 2 is further removed. The lower side of the groove 9 is cut and separated from other adjacent semiconductor light emitting elements.
[0035]
The N epitaxial layer 3 is formed to a thickness of 2 to 3 μm or less, and the PN junction layer 4 is formed to a thickness of 1 μm or less. The P epitaxial layer 5 is formed to a thickness of about 20 to 50 μm in order to improve current spreading and increase the emission intensity.
[0036]
The mesa groove 9 is formed by performing a dry etching process after the dicing process. With this configuration, the height of the side wall portion 10 is about 23 to 54 μm, which is a limit depth of formation of the mesa groove 9 by only dry etching of 10 to 15 μm or more.
[0037]
Further, the side wall 10 is formed in a planar shape and has a surface finish.
[0038]
Next, a method for manufacturing a semiconductor light emitting element will be described.
[0039]
2A to 2E are explanatory views showing a manufacturing procedure of the semiconductor light emitting element.
[0040]
As shown to (A), the board | substrate 2 (wafer) is formed in the thickness of 240 micrometers, and the epitaxial layer 11 is formed in the thickness of about 23-54 micrometers. The epitaxial layer 11 is composed of an N epitaxial layer 3, a PN junction layer 4, and a P epitaxial layer 5 from the bottom, and each layer is further composed of a plurality of layers.
[0041]
As shown in (B), an etching protective film 7 made of SiO ₂ is formed on the epitaxial layer 11. The thickness of the etching protective film 7 is about 1 μm.
[0042]
As shown in (C), after forming a resist pattern 14 with a mesa street width of 60 μm, etching is performed using an HF-based etchant to remove a part of the protective protective film 7.
[0043]
Next, as shown in (D), after removing the resist pattern 14, the N epitaxial layer is formed with the blade 13 having a thickness of 40 to 50 μm so that the kerf width (cutting groove width) is within the mesa street width. Dicing is performed to a depth reaching 3.
[0044]
As shown in (E), anisotropic etching is performed using a chlorine-based gas such as SiCl ₄ or BCl ₃ using a dry etching apparatus such as RIE (Reactive Ion Etching) to remove part of the epitaxial layer 11. Thus, the mesa groove 9 is formed. The depth of etching is set to about 10 to 15 μm, and the deepest part of the mesa groove 9 reaches the inside of the substrate 2. By performing dry etching, crystal distortion and processing waste generated on the dicing surface are removed and the semiconductor semi-finished product 1 of the adjacent semiconductor light emitting element is electrically separated.
[0045]
The etching rate when etching the epitaxial layer 11 at this time is about 0.5 μm / min. The upper portion 8 of the etching protective film 7 is also eroded at an etching rate of about 0.03 μm / min.
[0046]
After the mesa groove is formed, the P electrode and the N electrode are formed in the same procedure as in the prior art, and each semiconductor light emitting element is separated after the energization test.
[0047]
In this way, a semiconductor light emitting device can be manufactured.
[0048]
【The invention's effect】
As described above, according to the method for manufacturing a semiconductor light emitting device of the present invention, the mesa groove is formed by performing a dry etching process after the dicing process. Therefore, the mesa groove having the same shape as the mesa mask pattern even if the epitaxial layer thickness is large. This makes it possible to form a mesa groove with a narrow mesa groove width and to improve the wafer yield.
[0049]
In addition, a deep mesa groove can be formed to increase the amount of light extracted from the side, and the side surface can be formed flat to prevent irregular reflection of light, thereby improving the light emission output.
[0050]
Furthermore, the surface finish can be applied by dry etching to improve the light emission characteristics.
[0051]
Also, if the dicing process is performed to a depth that reaches the N epitaxial layer, and the dry etching process is performed to a depth that reaches the wafer, the processing amount of the dry etching can be adjusted according to the thickness of the protective film of the epitaxial layer, Manufacturing time can be shortened while ensuring the reliability of the apparatus.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing a state of a semi-finished product of a semiconductor light emitting device of the present invention when a mesa groove is formed. FIGS. 2A to 2E are explanatory views showing a manufacturing procedure of the semiconductor light emitting device. 3 (A) to (I) are explanatory views showing a process for manufacturing a semiconductor light emitting device by dry etching. FIG. 4 (A) is a front sectional view of a semi-finished semiconductor light emitting device showing a state in which a mesa groove is formed. FIG. 5B is a plan view of a semi-finished product of a semiconductor light emitting device arranged in a matrix on the wafer. FIG. 5A is a plan view of a semi-finished product of the semiconductor light emitting device when a mesa groove is formed by wet etching Sectional view (B) is a sectional view showing a state where a semi-finished product of a semiconductor light emitting device with a thick epitaxial layer is subjected to wet etching. FIG. 6 shows the semiconductor light emitting device when a mesa groove is formed using dicing. Cross section of semi-finished product [Fig. 7] Dicing [EXPLANATION OF SYMBOLS] sectional view of a semi-finished product of the semiconductor light emitting element when forming the mesa groove by wet etching
1 Semi-finished product of semiconductor light emitting device 2 Substrate (wafer)
3 N epitaxial layer 4 PN junction layer 5 P epitaxial layer 7 Protective film 8 for etching Upper part 9 Mesa groove 10 Side wall part 11 Epitaxial layer 13 Blade 14 Resist pattern

Claims (1)

In a method for manufacturing a semiconductor light emitting device comprising a step of laminating a compound semiconductor on a wafer and forming a mesa groove for inspection on this surface,
The mesa groove is diced to a depth reaching an N epitaxial layer formed immediately above the wafer, and then dry-etched to a depth reaching the wafer . Production method.

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