JP2005072340A - Method of manufacturing optical semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical semiconductor device which obtains a high yield. <P>SOLUTION: The method comprises a step of forming a light emitting layer 3 having the first conductivity type clad layer 3c of an InGaAlP or AlGaAs compound semiconductor, an active layer 3b and a second conductivity type clad layer 3a on a first conductivity type compound semiconductor substrate 6, a step of forming a second conductivity type GaP buffer layer 2 on a second conductivity type GaP substrate 1, a step of bonding the second conductivity type clad layer 3a to the GaP buffer layer 2, a step of polishing the compound semiconductor substrate 6 to remove a specified thickness, and a step of removing the remaining semiconductor substrate 6' by dry etching. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing an optical semiconductor device used for forming an optical semiconductor device such as an LED.

  In recent years, high-intensity light-emitting diodes (LEDs) have attracted attention as light sources with high efficiency and low power consumption that can replace light bulbs.

  FIG. 13 shows an example of the structure of the LED. On the p-type GaP substrate 101, a p-type GaP buffer layer 102, a p-type cladding layer 103a made of an InGaAlP-based or AlGaAs-based compound semiconductor, an active layer 103b, and a light emitting layer 103 made of an n-type cladding layer 103c are formed. . Electrodes 104 and 105 are formed on the light emitting layer 103 and the p-type GaP substrate. And by applying a voltage to both electrodes, light is generated in the light emitting layer, and the light is taken out from the surface of the light emitting layer which becomes the light extraction surface.

  Such an LED is formed as follows. First, as shown in FIG. 14, an n-type cladding layer 103c, an active layer 103b, and a p-type cladding layer 103a made of an InGaAlP-based or AlGaAs-based compound semiconductor are sequentially epitaxially grown on an n-type GaAs substrate 106 to form a light emitting layer. 103 is formed. On the other hand, as shown in FIG. 15, a GaP buffer layer 102 is epitaxially grown on a p-type GaP substrate 101 that is transparent to the emission wavelength.

Next, as shown in FIG. 16, the surfaces of the p-type cladding layer 102 and the GaP buffer layer 103a are overlapped and thermocompression bonded. Then, as shown in FIG. 17, the n-type GaAs substrate 106 is removed by wet etching with a H ₂ O ₂ + H ₂ SO ₄ mixed solution. Further, the electrodes 104 and 105 are formed to form a high-intensity LED as shown in FIG.

  However, when the n-type GaAs substrate is removed, the adhesive substrate is exposed to the wet etching solution for a long time, usually 90 minutes, so that the light emitting layer is side-etched from the periphery of the wafer, and the adhesion surface of the substrate peels off to about 5 mm. There was a problem that occurred.

  On the other hand, as a technique for removing the substrate after the substrates are bonded together, there is a CMP (Chemical Mechanical Polish) method other than wet etching. (For example, refer to Patent Document 1).

  However, in the CMP method, it is difficult to detect and control the polishing end point, and the remaining film thickness varies by about 10 to 20 μm. There is a problem that it is difficult to apply as it is.

Accordingly, an object of the present invention is to provide a semiconductor manufacturing method capable of eliminating the conventional problems and obtaining a high yield.
JP 2000-216428 A

    According to one embodiment of the present invention, light emission having a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer made of an InGaAlP-based or AlGaAs-based compound semiconductor on a first conductivity-type compound semiconductor substrate. Forming a layer; forming a second conductivity type GaP buffer layer on a second conductivity type GaP substrate; adhering the second conductivity type cladding layer to the GaP buffer layer; There is provided a method for manufacturing an optical semiconductor device, comprising: removing the compound semiconductor substrate by a predetermined thickness by polishing; and removing the remaining compound semiconductor substrate by a dry etching method.

  According to one embodiment of the present invention, a step of forming an InGaP-based block layer on a first conductive type compound semiconductor substrate, and a direct or GaAs-based contact layer on the block layer. Forming a light emitting layer having a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer made of an InGaAlP-based or AlGaAs-based compound semiconductor; and a second conductivity type on a second conductivity type GaP substrate. A step of forming a GaP buffer layer, a step of adhering the second conductivity type cladding layer and the GaP buffer layer, a step of removing the compound semiconductor substrate by a predetermined thickness, and a step of removing the remaining compound semiconductor substrate. There is provided a method of manufacturing an optical semiconductor device comprising a step of removing and exposing a block layer, and a step of removing the block layer.

  According to one embodiment of the present invention, a method for manufacturing an optical semiconductor device capable of obtaining a high yield can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a cross-sectional view of an optical semiconductor device formed according to an embodiment of the present invention. As shown in the figure, a p-GaP buffer layer 2 and a light emitting layer 3 are formed on a p-GaP substrate 1. The light emitting layer 3 is an InGaAlP system and has a laminated structure including a p-cladding layer 3a, an active layer 3b, and an n-cladding layer 3c each having a thickness of about 0.1 to 2.0 μm. The active layer is non-doped and has a composition with a smaller band gap energy than each cladding layer. A p-side electrode 4 and an n-side electrode 5 are formed on the p-GaP substrate 1 and the light emitting layer 3, respectively.

Such an optical semiconductor device is formed as follows. First, as shown in FIG. 2, an n-type GaAs substrate 6 having a thickness of 250 μm is placed in an MOCVD (metal organic chemical vapor deposition) apparatus, and trimethylgallium (TMG) and trimethylaluminum (TMA) are used as reaction gases. , Trimethylindium (TMI) and phosphine (PH ₃ ) are introduced together with SiH _{4 as} an n-type dopant gas and hydrogen (H ₂ ) as a carrier gas at a concentration of 500 to 900 ° C. while controlling the concentration by MFC (Mass Flow Controller). By epitaxially growing at a level of, for example, an n-cladding layer 3c made of In _0.49 (Ga _0.3 Al _0.7 ) _0.51 P with an n-carrier concentration of about 1.0 × E17 to 1.0 × E19 cm ⁻³ is 0.5 μm. Form. Next, TMA of the reactive gas is decreased to increase TMG, and the dopant gas is stopped. Similarly, after forming the active layer 3b made of non-doped In _0.49 (Ga _0.75 Al _0.25 ) _0.51 P to 0.5 μm, TMA, The TMG concentration was returned, and p-type dopant gas dimethylzinc (DMZ) was introduced. Similarly, In _0.49 (Ga _0.3 Al _0.7 ) _0.51 having a p-carrier concentration of about 1.0 × E16 to 1.0 × E19 cm ^−3. A p-cladding layer 3a made of P is formed to a thickness of 0.5 μm.

On the other hand, as shown in FIG. 3, a GaP buffer layer 2 having a p-carrier concentration of about 1.0 × E18 to 3.0 × E18 cm ⁻³ is formed on the p-type GaP substrate 1 by MOCVD. It is formed by epitaxial growth of about 1 to 5.0 μm.

Next, as shown in FIG. 4, the surface of the p-cladding layer 3a of the light-emitting layer shown in FIG. 2 is overlaid with the surface of the GaP buffer layer 2 shown in FIG. 3, and press-contacted at a pressure of about 0.1 to 10 kg / cm ^2. While heating to about 700 ° C. and pressure bonding, both substrates are joined to form an adhesive substrate.

Then, as shown in FIG. 5, the GaAs substrate 6 is removed by polishing to a predetermined thickness. As the polishing apparatus, a flat polishing apparatus as shown in FIG. 6 is used. The adhesive substrate 7 is held on the stage 8 and an abrasive is supplied to the surface. Then, the upper pad 9 is pressed at a predetermined pressure, and the stage 8 and the upper pad 9 are rotated at a predetermined number of revolutions to be mechanically polished. For example, the rotational speed of the stage holding the adhesive substrate 7 is 10 to 30 rpm, the rotational speed of the upper pad is 10 to 30 rpm, the pressure is 0.1 to 1.0 kg / cm ^2, and artificial diamond particles (˜ 100 μm) is used for mechanical polishing to make the GaAs substrate 100 μm thick.

Next, as shown in FIG. 7, the remaining GaAs substrate 6 ′ is removed by dry etching. An ICP apparatus as shown in FIG. 8 is used for the dry etching process. The adhesive substrate 7 is placed on the stage 11 in the chamber 10 and a reaction gas is introduced. Then, a high frequency is applied by the high frequency applying means 12, and etching proceeds by the generated plasma. For example, the reaction gas is Cl ₂ gas: 50 to 200 sccm, Ar gas: 10 to 100 sccm, pressure is 10 to 100 mTorr, source power is 300 to 500 W, bias power is 50 to 100 W, and the remaining 100 μm thick GaAs substrate. Is subjected to dry etching for 40 minutes. Under such conditions, a high etching rate of 3.0 μm / min or more can be obtained even in dry etching.

  Further, by forming the p-side electrode 4 and the n-side electrode 5 into a chip, an optical semiconductor device as shown in FIG. 1 is formed. For example, a metal film such as an Au—Ti alloy or an Au—Zn—Ni alloy is formed on the entire surface of the GaP substrate side by vacuum vapor deposition or the like to form a p-side electrode. Further, a metal film such as an Au-Ge-Ni alloy is formed on the surface of the light emitting layer from which the GaAs substrate has been removed, and this is patterned to form an n-side electrode, and then dicing is performed to form a chip.

  According to the present embodiment, the amount of side etching in the light emitting layer in the periphery of the substrate can be suppressed to a level that is not recognized on the visual level (0.1 mm or less). Chips can be obtained even from a 5 mm region, and the yield can be dramatically improved. Furthermore, the processing time can be shortened to about 2/3 as compared with the conventional case (90 min).

(Embodiment 2)
In the present embodiment, an optical semiconductor device similar to that of the first embodiment is formed, but is different in that a block layer is used when removing the GaAs substrate.

  That is, as shown in FIG. 9, on the same GaAs substrate 6 as in the first embodiment, a block layer 13 made of, for example, InGaP containing In, which is in a lattice matching allowable range, is formed, and a contact layer 14 made of GaAs. After forming about 0.1 to 1.0 μm, the light emitting layer 3 is formed in the same manner as in the first embodiment.

  Then, similarly to the first embodiment, after bonding to the GaP buffer layer 2 formed on the GaP substrate 1, the GaAs substrate 6 is removed by mechanical polishing leaving a thickness of 100 μm. The remaining GaAs substrate 6 'is wet-etched for a short time with a mixed solution of ammonia and hydrogen peroxide, and stops when reaching the InGaP block layer 13 as shown in FIG.

  Next, as shown in FIG. 11, the InGaP block layer 13 is wet-etched for a short time with hydrochloric acid, and is etched when reaching the GaAs contact layer 14.

Then, as shown in FIG. 12, the n-side electrode 5 is formed by patterning, and this electrode is used as a mask to form an electrode with an SH liquid (H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 8: 1: 64). The GaAs contact layer 14 in the other region is removed by etching. In addition, it becomes possible by this SH liquid to obtain a favorable etching rate of 0.1-0.5 micrometer / min, and to suppress side etching.

  According to the present embodiment, the time for exposure to wet etching can be significantly shortened, yield can be improved by suppressing side etching, and the etching state can be easily and accurately controlled by the block layer. Become.

(Embodiment 3)
In the present embodiment, an optical semiconductor device similar to that of the second embodiment is formed, but is different in that dry etching is used when removing the GaAs substrate.

  That is, as in the second embodiment, a block layer made of, for example, InGaP is formed on a GaAs substrate, a contact layer made of GaAs is formed, and then a light emitting layer is formed. Then, after bonding with the GaP buffer layer formed on the GaP substrate, the GaAs substrate is removed by mechanical polishing leaving a thickness of 100 μm.

  Next, the remaining GaAs substrate is removed by dry etching. Etching is stopped at the In detection point (when reaching the block layer) by the light emission monitor.

  Then, as in the second embodiment, the InGaP block layer is wet-etched with hydrochloric acid for a short time and is stopped when reaching the GaAs contact layer. Further, similarly, an n-side electrode is formed by patterning, and using this electrode as a mask, the GaAs contact layer in a region other than the electrode is removed by etching with SH liquid.

  According to this embodiment, it is possible to further reduce the time for exposure to wet etching, improve the yield by suppressing side etching, and easily and accurately control the etching state by the block layer. .

  In these embodiments, the InGaAlP system is used for the light emitting layer, but the same effects can be obtained even with the GaAlP system. The light emitting layer has a double heterostructure in which the active layer is sandwiched between p and n cladding layers. However, a pn junction structure without an active layer or an MQW (Multi Quantum Well) structure is used for the active layer. A thing may be sufficient and it does not specifically limit. The p and n cladding layers may be a two-stage cladding layer as a countermeasure against deterioration. In order to improve the light extraction efficiency, a current diffusion layer or the like may be provided. Further, the substrate is not limited to the n-type, and the conductivity type of each layer may be reversed using a p-type substrate.

The present invention is not limited to the above-described embodiment, and can be implemented with various modifications without departing from the scope of the invention.

The figure which shows the optical semiconductor device formed by one embodiment of this invention. The figure which shows the manufacturing process of the optical semiconductor device by one embodiment of this invention. The figure which shows the manufacturing process of the optical semiconductor device by one embodiment of this invention. The figure which shows the manufacturing process of the optical semiconductor device by one embodiment of this invention. The figure which shows the manufacturing process of the optical semiconductor device by one embodiment of this invention. The figure which shows the manufacturing apparatus of the optical semiconductor device in one embodiment of this invention. The figure which shows the manufacturing process of the optical semiconductor device by one embodiment of this invention. The figure which shows the manufacturing apparatus of the optical semiconductor device in one embodiment of this invention. The figure which shows the manufacturing process of the optical semiconductor device by one embodiment of this invention. The figure which shows the manufacturing process of the optical semiconductor device by one embodiment of this invention. The figure which shows the manufacturing process of the optical semiconductor device by one embodiment of this invention. The figure which shows the manufacturing process of the optical semiconductor device by one embodiment of this invention. The figure which shows an example of the structure of LED. The figure which shows the manufacturing process of the conventional optical semiconductor device. The figure which shows the manufacturing process of the conventional optical semiconductor device. The figure which shows the manufacturing process of the conventional optical semiconductor device. The figure which shows the manufacturing process of the conventional optical semiconductor device.

Explanation of symbols

11, 101 p-GaP substrate 2, 102 p-GaP buffer layer 3, 103 light-emitting layer 4, 104 p-side electrode 5, 105 n-side electrode 6, 6 ', 106 n-type GaAs substrate 7 adhesive substrate 8, 11 stage 9 Upper pad 10 Chamber 12 High frequency applying means 13 Block layer 14 Contact layer

Claims (6)

Forming a light emitting layer having a first conductive cladding layer, an active layer, and a second conductive cladding layer made of an InGaAlP-based or AlGaAs-based compound semiconductor on a first conductive type compound semiconductor substrate;
Forming a second conductivity type GaP buffer layer on the second conductivity type GaP substrate;
Adhering the second conductivity type cladding layer and the GaP buffer layer;
Removing the predetermined thickness by polishing the compound semiconductor substrate;
A method of manufacturing an optical semiconductor device, comprising a step of removing the remaining compound semiconductor substrate by a dry etching method.   2. The method of manufacturing an optical semiconductor device according to claim 1, wherein the compound semiconductor substrate is a GaAs substrate. Forming an InGaP-based block layer on the first conductivity type compound semiconductor substrate;
A step of forming a light emitting layer having a first conductive type cladding layer, an active layer, and a second conductive type cladding layer made of an InGaAlP-based or AlGaAs-based compound semiconductor on the block layer directly or via a GaAs-based contact layer. When,
Forming a second conductivity type GaP buffer layer on the second conductivity type GaP substrate;
Adhering the second conductivity type cladding layer and the GaP buffer layer;
Removing the predetermined thickness by polishing the compound semiconductor substrate;
Removing the remaining compound semiconductor substrate and exposing the block layer;
A method of manufacturing an optical semiconductor device, comprising a step of removing the block layer.   4. The method of manufacturing an optical semiconductor device according to claim 3, wherein the compound semiconductor substrate is a GaAs substrate.   5. The method of manufacturing an optical semiconductor device according to claim 3, wherein the step of exposing the block layer is performed by dry etching.   6. The method of manufacturing an optical semiconductor device according to claim 3, wherein the step of exposing the block layer and / or the step of removing the block layer is performed by wet etching.

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