JP5281535B2 - Manufacturing method of semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor light-emitting apparatus having a bonded structure of a supporting substrate and a semiconductor film, with higher yield compared with the conventional types. <P>SOLUTION: The semiconductor film is formed on a growing substrate by the vapor phase epitaxy method. An electrode layer is formed on the semiconductor film. A support substrate for supporting the semiconductor film is prepared. A recess part deeper than a height of a convex part is formed on a region, which is on a surface of the support substrate and which includes a part, corresponding to the convex part generated at an edge part of the semiconductor film, when the semiconductor film and a supporting substrate are jointed. A junction layer is formed on a surface on a side jointed to the semiconductor film of the supporting substrate. Positioning is carried out so that the edge part of the semiconductor film and the recess part mutually overlap to joint the semiconductor film and the supporting substrate via the junction layer and the electrode layer. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a semiconductor light emitting device, and in particular, a light emitting diode (LED) having a so-called bonded structure in which a semiconductor film is supported by a support substrate different from a growth substrate used for forming a semiconductor film. (Hereinafter referred to as LED).

Conventional technology

An LED is manufactured by epitaxially growing a GaN-based semiconductor film or the like on a growth substrate such as a sapphire substrate using a metal organic chemical vapor deposition (MOCVD) method or the like. The MOCVD method is a method for obtaining a semiconductor crystal by spraying an organic metal material vapor and a hydride gas onto a heated growth substrate and thermally decomposing the vapor. For example, in the case of forming a semiconductor film made of InGaN, a material vapor is taken out from liquid trimethylgallium (TMGa) and solid trimethylindium (TMIn), and this is mixed with ammonia (NH ₃ ) gas. Spray onto a heated sapphire substrate. Then, the material gas undergoes a thermal decomposition reaction on the sapphire substrate, and an InGaN crystal is generated while releasing methane gas and the like.

  However, when a semiconductor film is formed on the growth substrate by a vapor deposition method such as MOCVD, the flow of the source gas is disturbed near the edge of the growth substrate, and abnormal growth is likely to occur in this portion. As a result, a convex portion is formed in which the semiconductor film protrudes from other portions in the vicinity of the edge of the growth substrate. For example, when the thickness of the semiconductor film is 6 μm, the height of the convex portion may reach 12 to 18 μm. When such a convex portion is formed at the edge portion of the semiconductor film, the adhesion between the photomask and the non-processed substrate is deteriorated in the subsequent photolithography process, which leads to poor patterning of the semiconductor film.

  In Patent Document 1 and Patent Document 2, a convex portion is obtained by subjecting the edge portion of the sapphire substrate to curved surface processing or taper processing, and reducing the height of the surface of the edge portion of the sapphire substrate in which abnormal growth is likely to occur in advance. It is described that the surface of the semiconductor film can be flattened by preventing the occurrence of.

JP 2000-331940 A JP 2006-147891 A

  There is known an LED structure in which a semiconductor film is supported by a support substrate such as a silicon substrate or a metal substrate different from the sapphire substrate. In an LED having such a structure, after a semiconductor film is grown on a sapphire substrate, the support substrate and the semiconductor film are bonded through a bonding layer, and the sapphire substrate is removed by a laser lift-off method (LLO method) or the like. Can be obtained. According to this structure, it is possible to improve the thermal conductivity and light extraction efficiency of the LED by selecting the material of the support substrate, and it is also possible to use the support substrate as a conductive layer.

  In such an LED having a bonded structure, when the above-described convex portion occurs at the edge portion of the semiconductor film, the semiconductor film 1 and the support substrate 2 are formed at the edge portion of the semiconductor film 1 as shown in FIG. An unjoined region is generated. If the sapphire substrate 3 is peeled while having an unbonded region, the semiconductor film in the unbonded region falls off and cannot be used as an LED chip. The width A of the unbonded region between the semiconductor film 1 and the support substrate 2 sometimes reaches about 5 mm, which is a factor that significantly reduces the yield of LED chips.

  As in Patent Document 1 and Patent Document 2, it is possible to ensure the flatness of the semiconductor film by performing R processing or the like on the edge portion of the sapphire substrate, and this method is applied to an LED having a structure in which the semiconductor substrate is bonded to the support substrate. However, a certain effect can be expected. However, since the surface of the sapphire substrate subjected to R processing is separated from the crystal plane suitable for the growth of the semiconductor film, the film quality of the semiconductor film formed in this portion may change, which may change the light emission characteristics. There is. That is, the semiconductor film formed on the R-processed region of the sapphire substrate cannot usually be used as an LED. Since the R processing of the sapphire substrate is performed by mechanical polishing, the processing accuracy is limited, and the region that cannot be used as the LED chip extends to several hundred μm from the edge of the semiconductor film. As described above, the area that cannot be used as the LED chip even by the technique of performing the R processing on the edge portion of the sapphire substrate covers a wide range, and the yield improvement effect is limited.

  The present invention has been made in view of the above points, and provides a method for manufacturing a semiconductor light-emitting device capable of manufacturing a semiconductor light-emitting device having a bonded structure of a support substrate and a semiconductor film at a higher yield than before. The purpose is to do.

  The method for manufacturing a semiconductor light emitting device according to the present invention includes a step of forming a semiconductor film on a growth substrate by a vapor deposition method, a step of forming an electrode layer on the semiconductor film, and supporting the semiconductor film. And a region including a portion corresponding to a convex portion generated at an edge portion of the semiconductor film when the semiconductor film and the support substrate are bonded to each other. A step of forming a concave portion deeper than the height of the convex portion, a step of forming a bonding layer on a surface of the support substrate to be bonded to the semiconductor film, and an edge portion of the semiconductor film and the concave portion so as to overlap each other. And a step of aligning and bonding the semiconductor film and the support substrate through the bonding layer and the electrode layer.

  According to the semiconductor light emitting device of the present invention, even when the convex portion is generated at the edge portion of the semiconductor film, when the support substrate and the semiconductor film are bonded to each other, the concave portion formed in the support substrate is formed. Since the convex portions of the semiconductor film are accommodated, it is possible to prevent the occurrence of an unjoined region that is not joined to the support substrate at the edge portion of the semiconductor film. Thereby, the yield of LED chips can be improved.

It is sectional drawing which shows a state when the semiconductor film in which the convex part was formed in the edge part, and a support substrate are bonded together (A)-(c) is sectional drawing which shows the manufacturing method of the semiconductor light-emitting device based on the Example of this invention. (D)-(g) is sectional drawing which shows the manufacturing method of the semiconductor light-emitting device based on the Example of this invention. (H)-(j) is sectional drawing which shows the manufacturing method of the semiconductor light-emitting device based on the Example of this invention. It is sectional drawing which shows the structure of the semiconductor light-emitting device which is an Example of this invention. It is sectional drawing which shows the structure of the semiconductor light-emitting device which is another Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings shown below, substantially the same or equivalent components and parts are denoted by the same reference numerals.

  2A to 2C, 3D to 3G, and 4H to 4J are cross-sectional views illustrating a method of manufacturing a semiconductor light emitting device according to an embodiment of the present invention. . The semiconductor light emitting device according to this example has a configuration in which a semiconductor film is supported by a support substrate prepared separately from a growth substrate used for growing a semiconductor film.

  First, a 2-inch sapphire substrate 20 used as a semiconductor film growth substrate is prepared. Note that the edge portion of the sapphire substrate 20 is not subjected to R processing or chamfering processing (FIG. 1A).

  Next, after the sapphire substrate 20 is thermally cleaned, a buffer layer, a base GaN layer, an n-GaN layer, an active layer, a p-type AlGaN cladding layer, and a p-GaN layer are sequentially formed on the sapphire substrate 20 by MOCVD. A semiconductor film 21 configured as a film is formed.

Specifically, the atmosphere temperature is set to 500 ° C., TMG (trimethyl gallium) (flow rate 10.4 μmol / min) and NH ₃ (flow rate 3.3 LM) are supplied for about 3 minutes to form a buffer layer made of a GaN layer. Thereafter, the temperature of the atmosphere is raised to 1000 ° C. and held for about 30 seconds to crystallize the buffer layer. Subsequently, TMG (flow rate: 45 μmol / min) and NH ₃ (flow rate: 4.4 LM) are supplied for about 20 minutes while maintaining the atmospheric temperature at 1000 ° C., and a base GaN layer having a thickness of about 1 μm is formed. Next, TMG (flow rate 45 μmol / min), NH ₃ (flow rate 4.4 LM) and SiH ₄ (flow rate 2.7 × 10 ⁻⁹ mol / min) as a dopant gas are supplied for about 40 minutes at an ambient temperature of 1000 ° C. An n-GaN layer of about 4 μm is formed. Subsequently, an active layer is formed on the n-GaN layer. In this example, a multiple quantum well structure made of InGaN / GaN was applied to the active layer. That is, five cycles of growth are performed with InGaN / GaN as one cycle. Specifically, TMG (flow rate 3.6 μmol / min), TMI (trimethylindium) (flow rate 10 μmol / min), NH ₃ (flow rate 4.4 LM) are supplied for about 33 seconds at an atmospheric temperature of 700 ° C., and the film thickness is about 2 A 2 nm InGaN well layer is formed, and then TMG (flow rate 3.6 μmol / min) and NH ₃ (flow rate 4.4 LM) are supplied for about 320 seconds to form a GaN barrier layer having a thickness of about 15 nm. An active layer is formed by repeating this process for five cycles. Next, the ambient temperature was raised to 870 ° C., TMG (flow rate 8.1 μmol / min), TMA (trimethylaluminum) (flow rate 7.5 μmol / min), NH ₃ (flow rate 4.4 LM) and CP2Mg (bis-cyclopentadienyl as a dopant). Mg) (flow rate: 2.9 × 10 ⁻⁷ μmol / min) is supplied for about 5 minutes to form a p-type AlGaN cladding layer having a thickness of about 40 nm. Subsequently, while maintaining the ambient temperature, TMG (flow rate 18 μmol / min), NH ₃ (flow rate 4.4 LM) and CP2Mg (flow rate 2.9 × 10 ⁻⁷ μmol / min) as a dopant were supplied for about 7 minutes, and the film thickness was about A 150 nm p-GaN layer is formed. On the sapphire substrate 20, a semiconductor film 21 having a film thickness of about 6 μm is formed. At the edge portion of the sapphire substrate 20, a convex portion 21a having a height of about 10 μm is generated due to the disturbance of the flow of the source gas during film formation (FIG. 2B).

Next, Pt (1 nm) / Ag (300 nm) / Ti (100 nm) / Pt (200 nm) / Au (200 nm) are sequentially deposited on the semiconductor film 21 by a sputtering method or the like to form the p electrode layer 22 (see FIG. FIG. 2 (c))
On the other hand, a 3-inch silicon substrate 10 having a thickness of 525 μm made of a silicon single crystal or the like used as a support substrate is prepared. Then, this silicon substrate 10 is put into a thermal oxidation furnace and subjected to thermal oxidation treatment in an oxygen and water vapor atmosphere to form an oxide film 11 made of silicon dioxide (SiO ₂ ) having a thickness of about 1 μm on the surface of the silicon substrate 10. (FIG. 3 (d)).

  Next, a resist mask 12 is formed on the oxide film 11. The resist mask 12 has an opening 12a in a region including a portion facing the convex portion 21a formed on the edge portion of the semiconductor film 21 when the semiconductor film 21 and the silicon substrate 10 as a supporting substrate are bonded to each other. Specifically, the opening 12a has an annular shape with an opening width L of about 30 μm around a circle whose inner diameter R is about 15 μm smaller than the 2-inch sapphire substrate 20. Since the opening 21a can be formed using a fine processing technique such as photolithography, a highly accurate resist mask can be formed (FIG. 3E). In addition, it is preferable that the diameter of the silicon substrate 10 used as the support substrate is larger than that of the sapphire substrate 20 in consideration of handling properties in each process after the semiconductor film and the support substrate are bonded together.

  Next, the silicon substrate 10 is immersed in BHF (buffered hydrofluoric acid), and the oxide film 11 exposed from the opening 12a of the resist mask 12 is etched. As a result, an opening 11 a having the same pattern as the opening pattern of the resist mask 12 is formed in the oxide film 11. Thereafter, the resist mask 12 is removed. Next, the silicon substrate 10 is immersed in a potassium hydroxide aqueous solution (KOH) having a concentration of 40 weight percent. As a result, the silicon substrate 10 exposed in the opening 11a of the oxide film 11 is etched, and a recess 10a constituted by an annular groove having a width of about 30 μm and a depth of about 20 μm is formed on the surface of the silicon substrate 10. The depth of the concave portion 10 a only needs to be deeper than the height of the convex portion 21 a of the semiconductor film 21 formed on the sapphire substrate 20. The depth of the recess 10 a can be adjusted by changing the width of the opening 11 a of the oxide film 11. That is, in order to increase the depth of the recess 10a, the width of the opening 11a of the oxide film may be increased. However, if the depth of the recess 10a is made too deep, the yield of the LED chip will be reduced. Therefore, the depth of the recess 10a is preferably 50 μm or less. When Si is etched using KOH, anisotropic etching appears where a predetermined crystal plane appears, and the cross-sectional shape of the recess 10a becomes trapezoidal (inverted triangular shape as etching progresses) (FIG. 3 (f)).

  Next, the silicon substrate 10 is again immersed in BHF (buffered hydrofluoric acid), and the oxide film 11 is removed (FIG. 3G).

  Next, Pt, Ti, Ni, Au, Pt, and AuSu are sequentially formed on the surface of the silicon substrate 10 on which the concave portion 10a is formed by vapor deposition or the like, whereby the electrode layer 13 containing a eutectic material is formed. Is formed (FIG. 4H). The electrode layer 13 functions as a bonding layer when the semiconductor film 21 and the silicon substrate 10 are bonded together.

  Next, the silicon substrate 10 manufactured by performing each of the above processes and the semiconductor film 21 formed on the sapphire substrate 20 in the previous step are bonded together. At this time, alignment is performed so that the edge portion of the semiconductor film 21 and the concave portion 10a formed in the silicon substrate 10 overlap. That is, the alignment is performed so that the convex portion 21 a of the semiconductor film is accommodated in the concave portion 10 a of the silicon substrate 10. Then, the semiconductor film 21 and the silicon substrate 10 are brought into close contact with the p electrode layer 22 and the electrode layer 13 containing a eutectic material facing each other, and thermocompression-bonded in a nitrogen atmosphere. The semiconductor film 21 and the silicon substrate 10 are joined by melting and solidifying the eutectic material contained in the electrode layer 13 on the silicon substrate 10 (FIG. 4I). As described above, the surface of the silicon substrate 10 is formed with the concave portion 10a that can accommodate the convex portion 21a formed on the edge portion of the semiconductor film 21 when the semiconductor film 21 abuts. Also, the adhesion between the semiconductor film 21 and the silicon substrate 10 is ensured, and the occurrence of an unbonded region at the edge portion as shown in FIG. 1 can be prevented.

Next, the sapphire substrate 20 is peeled from the semiconductor film 21. For peeling off the sapphire substrate 20, a known method such as an LLO (laser lift-off) method can be used. In the LLO method, the irradiated laser decomposes the GaN layer formed on the sapphire substrate 20 into metal Ga and N ₂ gas. For this reason, the decomposition occurs in the n-GaN layer or the underlying GaN layer in the semiconductor film, and the n-GaN layer or the underlying GaN layer appears on the surface from which the sapphire substrate 20 is peeled off (FIG. 4J). ).

  Next, the surface of the semiconductor film 21 exposed by peeling the sapphire substrate 20 is etched to flatten the surface, and then an n-electrode made of TiAl or the like is formed by a lift-off method or the like. Thereafter, the LED chips are separated into individual pieces in the dicing process. The semiconductor light emitting device is completed through the above steps.

  As is clear from the above description, according to the method for manufacturing a semiconductor light emitting device according to the present invention, even when the convex portion 21 a is generated at the edge portion of the semiconductor film 21, the support substrate 10 and the semiconductor film 21. When the substrate is bonded, the convex portion 21a of the semiconductor film is accommodated in the concave portion 10a formed in the support substrate 10, so that an unbonded region that is not bonded to the support substrate 10 is generated at the edge portion of the semiconductor film 21. Can be prevented. Thereby, as shown in FIG. 5, it becomes possible to use from the edge of the semiconductor film 21 to the inner side of 20 to 30 μm, and the yield of the LED chip can be improved. Since the concave portion 10a provided in the support substrate 10 can be formed by applying an existing micromachining technique such as photolithography, the semiconductor film is formed in comparison with a method of performing chamfering such as curved surface processing or taper processing on the sapphire substrate. The usable area can be further expanded, and the yield can be further improved.

  In the above-described embodiment, the concave portion is formed by etching the silicon substrate using KOH. However, the present invention is not limited to this, and the concave portion may be formed by dry etching such as RIE. .

  In addition, the shape of the recess formed in the support substrate is not limited to the groove shape as described above, and can be obtained by etching all regions outside the portion corresponding to the edge portion of the semiconductor film as shown in FIG. It may be a notch shape.

  The support substrate is not limited to a silicon substrate, but may be a Ge substrate, a GaAs substrate, a metal substrate made of Cu, or the like. Further, the growth substrate is not limited to the sapphire substrate, but may be a GaN substrate or a SiC substrate.

DESCRIPTION OF SYMBOLS 10 Silicon substrate 10a Concave part 11 Oxide film 20 Sapphire substrate 21 Semiconductor film 21a Convex part

Claims (3)

Forming a semiconductor film on the growth substrate by vapor deposition;
Forming an electrode layer on the semiconductor film;
Preparing a support substrate for supporting the semiconductor film;
A concave portion deeper than the height of the convex portion is formed on a surface of the support substrate, including a portion corresponding to the convex portion generated at the edge portion of the semiconductor film when the semiconductor film and the support substrate are bonded. Forming, and
Forming a bonding layer on the surface of the support substrate to be bonded to the semiconductor film;
Aligning the edge portion of the semiconductor film with the concave portion and joining the semiconductor film and the support substrate through the bonding layer and the electrode layer. Device manufacturing method.   The method of manufacturing a semiconductor light emitting device according to claim 1, further comprising a step of removing the growth substrate.   The method for manufacturing a semiconductor light emitting device according to claim 1, wherein the concave portion is formed of an annular groove.

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