JP4835409B2 - III-V group semiconductor device and manufacturing method thereof - Google Patents

Description

  In the present invention, an n layer and a p layer made of a group III-V semiconductor are grown on a growth substrate, and an electrode layer on the p layer is bonded to a support substrate using solder, and then the growth substrate is formed by laser lift-off. The present invention relates to a method for manufacturing a semiconductor element by removing the semiconductor element and the semiconductor element. In particular, the present invention relates to a method for protecting against an electrical short circuit on the side surfaces of a p layer and an n layer and a crack that may occur on an end face of a semiconductor element at the time of laser lift-off, and the semiconductor element structure.

  As a substrate for growing group III nitride semiconductors, a sapphire substrate that is chemically and thermally stable is generally used, but sapphire is not conductive and cannot pass current in the vertical direction. . Also, sapphire has no clear cleavage plane and is difficult to dice. In addition, sapphire has a low thermal conductivity and inhibits heat dissipation of the semiconductor element. Furthermore, there are total reflection at the bonding surface between the semiconductor layer and the sapphire substrate and light confinement at the semiconductor layer, and the external quantum efficiency is low. In order to improve the light extraction efficiency, it is conceivable to make the light extraction surface uneven, but sapphire is not easy to process.

  As a technique for solving this problem, a laser lift-off method is known. In this method, the sapphire substrate is separated and removed by laser irradiation.

  In Patent Document 1, after forming a group III nitride semiconductor element on a sapphire substrate, a groove is formed by etching to separate each element, and the group III nitride semiconductor element grown on the sapphire substrate is supported. A method of performing laser lift-off after bonding to a substrate is shown. The gas remaining inside the groove was thermally expanded by the laser and the group III nitride semiconductor element was cracked, but Patent Document 1 excludes the gas by filling the inside of the groove with a dielectric, There is a description that the occurrence of cracks due to this can be prevented.

  Further, in Patent Document 2, after filling a groove with a photoresist and joining a group III nitride semiconductor device and a support substrate, a metal layer is formed on top of the group III nitride semiconductor device, A method of performing laser lift-off is shown. It is described that the photoresist formed in the groove is for preventing metal from entering the groove when the metal layer is formed.

In Patent Document 3, a protective film such as SiO ₂ or Al ₂ O ₃ and a seed metal film are formed on the inclined end face of the semiconductor element, a metal layer is formed on the groove and the semiconductor element, and then laser lift-off is performed. How to do is shown.
JP-A-2005-333130 Special table 2005-522873 JP 2006-135321 A

  In the laser lift-off process, when the sapphire substrate is separated, a physical impact may be applied to the end face of the group III nitride semiconductor device, and the end face may be broken off. However, Patent Documents 1 to 3 do not disclose a method for preventing cracking of the end face of the semiconductor element caused by this physical impact.

  Further, in Patent Document 3, since the growth substrate and the protective film are firmly bonded, the protective film peels off when the sapphire substrate is separated, and a crack is generated in the semiconductor element. Another problem is that the metal layer formed on the semiconductor element must be cut during dicing. In addition, Patent Documents 2 and 3 are not based on bonding and bonding with a support substrate.

  In the case of bonding with a support substrate, there are the following problems. Because of the necessity of p-type activation, an n layer is first formed on the growth substrate, and then a p layer is formed. The n layer can be thick, but the p layer is thin and difficult to thicken. Therefore, in the structure in which the p layer and the support substrate are joined by solder, the distance between the support substrate and the n layer is short. Therefore, solder or metal adheres to the side surface of the semiconductor element during dicing or wafer bonding, and the p layer and the n layer are short-circuited.

  Accordingly, an object of the present invention is to separate a semiconductor layer in which an n layer is first formed on a substrate and then a p layer is separated into each semiconductor element, and is bonded to a support substrate via solder, and then laser When removing the substrate using lift-off, it is possible to prevent a short circuit between the n-layer and the p-layer at the end face of the semiconductor element, and the end face of the semiconductor element that may be caused by a physical impact in separating the substrate. It is to prevent cracking.

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device composed of a group III-V semiconductor, wherein a plurality of p-electrodes and a first low melting point metal diffusion prevention layer are provided on a substrate and separated from each other. The step of forming the semiconductor element, the step of forming an end face protective film made of a dielectric so as to cover the end face of the semiconductor element, and at least the upper surface of the end face protective film are made of a metal having good bonding property to the dielectric forming a metal film on the upper surface of the metal film, forming a second low melting point metal diffusion preventing layer, and the second support substrate conductive with a low melting point metal diffusion preventing layer of the semiconductor element A method for manufacturing a semiconductor device, comprising: a step of bonding through a low melting point metal layer; and a step of removing a substrate by laser lift-off.

  The end face protective film is desirably 100 nm to 500 nm. This end face protective film can be formed by, for example, a plasma CVD method. When there is a region where the p-electrode and the low melting point metal diffusion prevention layer are not formed on the upper surface of the semiconductor element, an end face protective film may be formed in the region.

  The metal film only needs to be formed on at least the upper surface of the end face protective film, and may be formed on the upper surfaces of the low melting point metal diffusion preventing layer and the end face protective film. Furthermore, the metal film may be formed on the end face of the semiconductor element by sandwiching the end face protective film by forming the low melting point metal diffusion preventing layer and the end face protective film.

  The p electrode is preferably made of a metal having high light reflectivity and low contact resistance, such as Ag, Rh, Pt, Ru, or an alloy containing these metals as a main component. In addition, Ni, Ni alloy, Au alloy, or the like can be used. Moreover, the composite layer which consists of transparent electrode films, such as ITO, and a highly reflective metal film may be sufficient. As the low melting point metal diffusion preventing layer, a multilayer film containing Ti / Ni such as Ti / Ni / Au, a multilayer film containing W / Pt such as W / Pt / Au, and the like can be used. The low melting point metal diffusion preventing layer is a layer that prevents the metal of the low melting point metal layer from diffusing beyond the low melting point metal diffusion preventing layer. The low melting point metal layer includes metal eutectic layers such as an Au—Sn layer, an Au—Si layer, an Ag—Sn—Cu layer, and a Sn—Bi layer, and is not a low melting point metal, but an Au layer, an Sn layer, Cu Layers and the like can be used.

  As the support substrate, a conductive substrate such as a Si substrate, a GaAs substrate, a Cu substrate, or a Cu—W substrate is used.

  According to a second aspect of the present invention, in the first aspect, the end face protective film is formed of any one of silicon dioxide, silicon nitride, zirconium oxide, niobium oxide, and aluminum oxide. is there.

  Examples of metals having good bondability with these dielectrics are Al, Ti, Ni, and V.

  A third invention is the method of manufacturing a semiconductor element according to the first invention, wherein the end face protective film is formed of silicon dioxide, and the metal film is an Al film.

  According to a fourth aspect, in the first to third aspects, the low melting point metal layer is formed of any one of Au-Sn, Au-Si, Ag-Sn-Cu, and Sn-Bi. This is a method for manufacturing a semiconductor device.

  A fifth invention is a method of manufacturing a semiconductor device according to any one of the first to fourth inventions, wherein the semiconductor device is made of a group III nitride semiconductor.

  A sixth invention is a method of manufacturing a semiconductor element, characterized in that, in the first to fifth inventions, the semiconductor element is a light emitting element.

  A seventh invention is the method of manufacturing a semiconductor element according to the sixth invention, wherein the metal film is also formed on the end face of the semiconductor element with the end face protective film interposed therebetween.

According to an eighth aspect of the present invention, there is provided a semiconductor element composed of a group III-V semiconductor and bonded to a conductive support substrate through a low-melting point metal layer, a p-electrode bonded to a p-type layer of the semiconductor element, The first low melting point metal diffusion prevention layer to be joined, the end face of the semiconductor element, and the junction surface of the p-type layer to the p electrode and the first low melting point metal diffusion prevention layer, the p electrode and the first low melting point Bonding between the end face protective film made of the dielectric formed in the region where the metal diffusion preventive layer is not formed and the dielectric formed on the top surfaces of the first low melting point metal diffusion preventive layer and the end face protective film A metal film made of an excellent metal, a second low melting point metal diffusion preventing layer bonded to the metal film, a support substrate supporting the semiconductor element, and a second low melting point metal diffusion preventing layer and the support substrate. A low melting point metal layer and n grown on the growth substrate prior to the p-type layer And a n-type layer from which the growth substrate has been removed .

  A ninth invention is the semiconductor element according to the eighth invention, wherein the end face protective film is formed of any one of silicon dioxide, silicon nitride, zirconium oxide, niobium oxide, and aluminum oxide.

  A tenth invention is the semiconductor device according to the eighth invention, wherein the end face protective film is formed of silicon dioxide, and the metal film is an Al film.

  In an eleventh aspect based on the eighth aspect to the tenth aspect, the low melting point metal layer is formed of any one of Au—Sn, Au—Si, Ag—Sn—Cu, and Sn—Bi. This is a featured semiconductor element.

  A twelfth invention is a semiconductor device characterized in that, in the eighth invention to the eleventh invention, the semiconductor element is made of a group III nitride semiconductor.

  A thirteenth aspect of the invention is a semiconductor element according to the eighth aspect to the twelfth aspect of the invention, wherein the semiconductor element is a light emitting element.

  A fourteenth invention is the semiconductor element according to the thirteenth invention, wherein the metal film is also formed on the end face of the semiconductor element with the end face protective film interposed therebetween.

  In the first invention, the end face of the semiconductor element is covered with an end face protective film made of a dielectric, and a metal film having good bondability with the end face protective film is formed between the end face protective film and the low melting point metal layer. ing. The end face protective film can prevent a short circuit with a low melting point metal at the end face of the semiconductor element. In addition, it is possible to prevent cracking of the end face of the semiconductor element that may occur due to physical impact due to substrate removal at the time of laser lift-off after bonding to the support substrate.

  The metal film is provided for the following reason. When only the end face protective film is formed, the bondability between the end face protective film and the low-melting point metal layer is poor and may be separated, and voids may be generated between the end face protective film and the low-melting point metal layer. . The holes may cause the end face protective film to peel off when the substrate is removed, causing cracks on the end face of the semiconductor element, which may be broken off. Therefore, by forming a metal film having good bonding properties with the end face protective film between the end face protective film and the low melting point metal layer, it is possible to prevent pores due to separation of the end face protective film and the low melting point metal layer, It is possible to prevent the end face protective film from being peeled off from the end face of the semiconductor element. Therefore, the end face protection film does not impair the end face protection function, and the effect of preventing cracking of the end face of the semiconductor element is greater than when only the end face protection film is formed.

  Further, as in the sixth invention, when the metal film is also formed on the end face of the light emitting element with the end face protective film interposed therebetween, emitted light from the end face can be prevented.

  In the semiconductor elements of the seventh to twelfth inventions, an end face protective film is formed on the end face of the semiconductor element, and the bonding property of the end face protective film is between the end face protective film and the low melting point metal layer. Since a good metal film is formed, the semiconductor element has no cracks on the end face of the semiconductor element.

  Hereinafter, specific examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the examples.

  FIG. 1 is a diagram illustrating a manufacturing process of a light-emitting element by laser lift-off according to the first embodiment.

  First, a group III nitride semiconductor layer 11 is formed on a sapphire substrate 10 by epitaxial growth, and a p-electrode 13 and a low-melting point metal diffusion prevention layer 14 are formed on the upper surface of a region where each light emitting element 12 is formed (FIG. 1A). ). For the p electrode, Ag, Rh, Pt, Ru, a metal having a high light reflectivity and a low contact resistance such as an alloy containing these metals as a main component, Ni, a Ni alloy, an Au alloy, or the like can be used. Moreover, the composite layer which consists of transparent electrode films, such as ITO, and a highly reflective metal film may be sufficient. For the low melting point metal diffusion preventing layer 14, a multilayer film containing Ti / Ni such as Ti / Ni / Au, a multilayer film containing W / Pt such as W / Pt / Au, or the like is used. The group III nitride semiconductor layer 11 includes an n-type layer 100, an MQW layer 101, and a p-type layer 102, as shown in FIG.

  Next, a predetermined place of the group III nitride semiconductor layer 11 is etched until the sapphire substrate 10 is exposed, thereby separating the light emitting elements 12 (FIG. 1B). Etching was performed so that the end face of the light emitting element 12 was vertical.

Next, an end face protective film 15 made of SiO ₂ is formed by plasma CVD on the end face of the light emitting element 12 and the upper surface 121 of the light emitting element 12 where the p-electrode 13 and the low melting point metal diffusion preventing layer 14 are not formed ( FIG. 1C). The film thickness is preferably about 100 nm to 500 nm. The thickness of 100 nm or less is not preferable because the adhesion between the end face of the light emitting element 12 and the end face protective film 15 is low, and the thickness of 500 nm or more is not desirable because a long etching time is required for subsequent patterning. In addition to SiO ₂ , Si ₃ N ₄ (silicon nitride), ZrO ₂ (zirconium oxide), NbO (niobium oxide), Al ₂ O ₃ (aluminum oxide), or the like can be used.

  Next, a metal film 16 made of Al is formed on the upper surfaces of the low melting point metal diffusion preventing layer 14 and the end face protective film 15 (FIG. 1D). As the metal film 16, any material other than Al may be used as long as it has good bondability with the end face protective film 15. For example, Ni, Ti, V, etc.

  A low melting point metal diffusion preventing layer 17 is formed again on the upper surface of the metal film 16, and a low melting point metal layer 18 is formed on the upper surface of the low melting point metal diffusion preventing layer 17 (FIG. 1E). The low melting point metal layer 18 includes a metal eutectic layer such as an Au—Sn layer, an Au—Si layer, an Ag—Sn—Cu layer, and a Sn—Bi layer, an Au layer, a Sn layer, A Cu layer or the like can be used. The end face protective film 15, the metal film 16, and the low melting point metal diffusion preventing layer 17 are formed in a predetermined pattern by photolithography.

  Next, the support substrate 19 and the low melting point metal layer 20 are joined via the low melting point metal layer 20 formed on the upper surface of the support substrate 19 made of Si (FIG. 1F). As the support substrate 19, GaAs, Cu, or Cu—W can be used in addition to Si. The low melting point metal diffusion preventing layers 14 and 17 are layers for preventing the metal of the low melting point metal layers 18 and 20 from diffusing beyond the low melting point metal diffusion preventing layers 14 and 17.

Then, the sapphire substrate 10 is separated and removed by laser lift-off (FIG. 1G). Laser irradiation is performed by irradiating the wafer with a KrF laser having a wavelength of 248 nm under a condition of 0.7 J / cm ² or more.

  When the metal film 16 is not present at the time of laser lift-off, since the bonding property between the end face protective film 15 and the low melting point metal layer 18 is poor, the low melting point metal layer 18 is peeled off from the upper end face of the end face protective film 15, There will be voids in between. Due to the holes, the end face protective film 15 may be peeled off when the sapphire substrate 10 is removed, or the end face of the light emitting element 12 may be broken off. Therefore, as in the first embodiment, by providing the metal film 16 made of a metal having good bonding property to the end face protective film between the upper end face of the end face protective film 15 and the low melting point metal layer 18, voids are generated. Can be prevented, and peeling of the end face protective film 15 and cracking of the end face of the light emitting element 12 can be prevented.

  Thereafter, the n-electrode is formed and diced, whereby the individual light-emitting elements 12 formed on the support substrate 19 are manufactured.

  As shown in FIG. 3, the second embodiment is different from the first embodiment in that the metal film 16 is also formed on the end face of the light emitting element 12 with the end face protective film 15 interposed therebetween. All other steps are the same as in Example 1. Since Al is a highly reflective metal, emitted light from the end face of the light emitting element 12 can be suppressed by the metal film 16. In particular, when the end face of the light emitting element 12 is inclined, it is desirable to form the metal film 16 on the end face as described above.

  Examples 1 and 2 are light emitting element manufacturing methods, but the present invention is not limited to light emitting elements, but can be applied to any semiconductor element manufactured by laser lift-off. Further, the present invention can be applied not only to a semiconductor element composed of a group III nitride semiconductor but also to a semiconductor element composed of a group III-V semiconductor such as GaAs or GaP.

  In Examples 1 and 2, the p-electrode 13 and the low-melting-point metal diffusion prevention layer 14 are formed and then separated into the light-emitting elements 12 by etching. Alternatively, the low melting point metal diffusion preventing layer 14 may be formed.

  According to the present invention, the yield of semiconductor device manufacturing by laser lift-off can be improved.

FIG. 6 shows a manufacturing process of the light-emitting element of Example 1; FIG. 6 shows a manufacturing process of the light-emitting element of Example 1; FIG. 6 shows a manufacturing process of the light-emitting element of Example 1; FIG. 6 shows a manufacturing process of the light-emitting element of Example 1; FIG. 6 shows a manufacturing process of the light-emitting element of Example 1; FIG. 6 shows a manufacturing process of the light-emitting element of Example 1; FIG. 6 shows a manufacturing process of the light-emitting element of Example 1; The figure which shows the structure of a group III nitride semiconductor layer. FIG. 6 shows part of a manufacturing process of the light-emitting element of Example 2.

10: Sapphire substrate 11: Group III nitride semiconductor layer 12: Light emitting element 13: P electrode 14, 17: Low melting point metal diffusion prevention layer 15: End face protective film 16: Metal film 18, 20: Low melting point metal layer 19: Support Substrate 100: n-type layer 101: MQW layer 102: p-type layer

Claims (14)

In a method for manufacturing a semiconductor device composed of a group III-V semiconductor,
Forming a plurality of the semiconductor elements having a p-electrode and a first low-melting-point metal diffusion preventing layer on an upper surface and separated from each other on a substrate;
Forming an end face protective film made of a dielectric so as to cover the end face of the semiconductor element;
Forming a metal film made of a metal having good bondability with the dielectric on at least the upper surface of the end face protective film;
Forming a second low melting point metal diffusion preventing layer on the upper surface of the metal film;
A step of bonding the second supporting substrate conductive with a low melting point metal diffusion preventing layer of the semiconductor element via the low melting point metal layer,
Removing the substrate by laser lift-off;
A method for manufacturing a semiconductor device, comprising:   2. The method of manufacturing a semiconductor device according to claim 1, wherein the end face protective film is formed of any one of silicon dioxide, silicon nitride, zirconium oxide, niobium oxide, and aluminum oxide. The end face protective film is formed of silicon dioxide,
The method of manufacturing a semiconductor device according to claim 1, wherein the metal film is an Al film.   The low-melting-point metal layer is formed of any one of Au-Sn, Au-Si, Ag-Sn-Cu, and Sn-Bi. The manufacturing method of the semiconductor element of description.   5. The method of manufacturing a semiconductor element according to claim 1, wherein the semiconductor element is made of a group III nitride semiconductor. 6.   The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is a light emitting device.   The method of manufacturing a semiconductor element according to claim 6, wherein the metal film is also formed on an end face of the semiconductor element with the end face protective film interposed therebetween. In a semiconductor element composed of a group III-V semiconductor and bonded to a conductive support substrate via a low melting point metal layer,
A p-electrode joined to the p-type layer of the semiconductor element;
A first low melting point metal diffusion preventing layer bonded to the p electrode;
An end surface of the semiconductor element, and a junction surface of the p-type layer with respect to the p-electrode and the first low-melting-point metal diffusion prevention layer, wherein the p-electrode and the first low-melting-point metal diffusion prevention layer are formed. An end face protective film made of a dielectric formed in a region that is not ,
A metal film made of a metal having good bondability to the dielectric , formed on the top surfaces of the first low melting point metal diffusion preventing layer and the end face protective film ;
A second low-melting point metal diffusion preventing layer bonded to the metal film;
A support substrate for supporting the semiconductor element;
A low melting point metal layer that joins the second low melting point metal diffusion preventing layer and the support substrate;
An n-type layer grown on the growth substrate prior to the p-type layer, wherein the n-type layer is removed from the growth substrate;
Semiconductor device characterized by having.   9. The semiconductor element according to claim 8, wherein the end face protective film is formed of any one of silicon dioxide, silicon nitride, zirconium oxide, niobium oxide, and aluminum oxide. The end face protective film is formed of silicon dioxide,
The semiconductor element according to claim 8, wherein the metal film is an Al film.   The low-melting-point metal layer is formed of any one of Au-Sn, Au-Si, Ag-Sn-Cu, and Sn-Bi. The semiconductor element as described.   12. The semiconductor element according to claim 8, wherein the semiconductor element is made of a group III nitride semiconductor.   The semiconductor device according to claim 8, wherein the semiconductor device is a light emitting device.   The semiconductor element according to claim 13, wherein the metal film is also formed on an end face of the semiconductor element with the end face protective film interposed therebetween.

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