TW202030777A - Composite substrate and manufacturing method thereof - Google Patents

Abstract

A composite substrate including a substrate and an aluminum nitride layer is provided. A top surface of the substrate includes a plurality of nano-patterned recesses which are separated from each other. The aluminum nitride is disposed on the top surface of the substrate. The film thickness of the aluminum nitride layer is less than 3.5 microns, and the defect density of the aluminum nitride layer is less than or equal to 5×10⁹ /cm² . A manufacturing method of a composite substrate is also provided.

Description

Composite substrate and manufacturing method thereof

The present invention relates to a substrate, and particularly relates to a composite substrate.

In the epitaxy process of light-emitting diodes, if you want to grow N-type and P-type III-V semiconductor layers and quantum well layers and other semiconductor layers on the substrate, you need to solve the problems of the substrate (such as sapphire substrate) and the above There is a difference in the lattice constant of the semiconductor layer. The difference in lattice constants will cause epitaxial defects, which in turn affects the luminous efficiency of the light-emitting diode. In order to solve the above-mentioned difference in lattice constants, a buffer layer with a smaller difference in lattice constants is generally formed before the semiconductor layer is grown.

On the other hand, in order to improve the quantum efficiency of the light-emitting diode, a patterned sapphire substrate (PSS) is layered out to increase the light extraction rate by light scattering of the convex pattern on the substrate. At this time, if the aluminum nitride layer is used as the buffer layer, the high activity of aluminum atoms and the low surface mobility result in high row density, high stitching thickness, and rough surface of the aluminum nitride layer. Problems such as cracks.

An embodiment of the present invention provides a composite substrate including a substrate and an aluminum nitride layer. The upper surface of the substrate includes a plurality of nano-patterned depressions, and these nano-patterned depressions are separated from each other. The aluminum nitride layer is disposed on the upper surface of the substrate, wherein the film thickness of the aluminum nitride layer is less than 3.5 microns, and the defect density of the aluminum nitride layer is less than or equal to 5×10 ⁹ /cm ² .

An embodiment of the present invention provides a method for manufacturing a composite substrate, including: preparing a substrate, the upper surface of the substrate includes a plurality of nano-patterned recesses, the nano-patterned recesses are separated from each other; forming on the upper surface of the substrate A first aluminum nitride layer; forming a planarization layer on the first aluminum nitride layer; gradually remove the material of the planarization layer, wherein when the material of the planarization layer is gradually removed to the bottom of the planarization layer, At the same time, part of the first aluminum nitride layer is gradually removed to planarize the first aluminum nitride layer; and a second aluminum nitride layer is formed on the planarized first aluminum nitride layer. The root mean square roughness of the upper surface of the aluminum nitride layer opposite to the substrate is less than 3 nm.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail in conjunction with the accompanying drawings.

1A and FIGS. 2 to 5 are schematic cross-sectional views of the manufacturing process of a composite substrate according to an embodiment of the present invention, and FIG. 1B is a schematic top view of the substrate in FIG. 1A. The manufacturing method of the composite substrate of this embodiment includes the following steps. First, referring to FIGS. 1A and 1B, a substrate 110 is prepared. The upper surface 112 of the substrate 110 includes a plurality of nano-patterned recesses 114, and the nano-patterned recesses 114 are separated from each other. In this embodiment, the substrate 110 is, for example, a sapphire substrate, and the depth H of the nano-patterned recesses 114 is in the range of 150 nanometers to 1.5 micrometers, preferably 100 nanometers to 1 micrometer, more preferably 200 nanometers. From nanometers to 500 nanometers. And the width W of these nano-patterned recesses falls within the range of 200 nanometers to 1.5 micrometers, preferably 300 nanometers to 800 nanometers, more preferably 400 nanometers to 600 nanometers. In this embodiment, the method for forming these nano-patterned recesses 114 is, for example, to wet-etch the upper surface of the unprocessed sapphire substrate to form these nano-patterned recesses 114, so the etching solution will follow multiple Different crystal planes etch the sapphire substrate, and a boundary line 113 of crystal planes is generated between two adjacent crystal planes. In this embodiment, a plurality of crystal faces of the nano-patterned recess 114 are in a chamfered cone shape (for example, three crystal faces are in an inverted triangular cone shape), and a plurality of crystal faces (for example, at least three, in this embodiment are three For example) The boundary line 113 meets at the bottom vertex of the inverted triangular pyramid. In this embodiment, the sidewalls of the nano-patterned recess 114 have a chamfered cone shape, and the bottom of the nano-patterned recess 114 has a pointed shape. However, in other embodiments, the method for forming these nano-patterned recesses 114 can also be dry etching, and the nano-patterned recesses 114 formed by this method do not have the aforementioned boundary line 113.

In this embodiment, these nano-patterned recesses 114 are periodically arranged on the upper surface 112 of the substrate 110. However, in other embodiments, the nano-patterned recesses 114 may also be arranged irregularly.

Next, referring to FIG. 2, a first aluminum nitride layer 120 is formed on the upper surface 112 of the substrate 110. The method for forming the first aluminum nitride layer 120 may be metal organic chemical vapor deposition (MOCVD), sputtering, or hydride vapor phase epitaxy (HVPE) . In this embodiment, the film thickness T1 of the first aluminum nitride layer 120 is greater than the depth H of the nano-patterned recess 114.

Then, referring to FIG. 3 again, a planarization layer 130 is formed on the first aluminum nitride layer 120. After the planarization layer 130 covers the first aluminum nitride layer 120, the upper surface of the planarization layer 130 will be lower than the first nitride layer. The upper surface of the aluminum oxide layer 120 is flat. In this embodiment, the material of the planarization layer 130 is spin-on glass, for example. However, in other embodiments, the material of the planarization layer 130 may also be a polymer.

Afterwards, referring to FIG. 4, the material of the planarization layer 130 is gradually removed. When the material of the planarization layer 130 is gradually removed to the bottom of the planarization layer 130, part of the first aluminum nitride is also gradually removed. The first aluminum nitride layer 120 is flattened to form a first aluminum nitride layer 121 with a relatively flat upper surface. In this embodiment, the method of gradually removing the material of the planarization layer 130 is dry etching, for example, an inductively coupled plasma (ICP) etching method, and the etching conditions can be selected so that the planarization layer The etching rate of 130 is substantially the same as the etching rate of the first aluminum nitride layer 121, so when all the materials of the planarization layer 130 are etched, part of the first aluminum nitride layer 120 will be etched at this time Then, the top surface topography of the planarization layer 130 is transferred to the top surface of the first aluminum nitride layer 121 to form a relatively flat first aluminum nitride layer 121. However, in other embodiments, the method of gradually removing the material of the planarization layer 130 may also be mechanical polishing (mechanical polishing).

In addition, after the material of the planarization layer 130 is gradually removed, the planarized first aluminum nitride layer 121 may be annealed, for example, a high-temperature annealing process above 1500°C may be performed. The high temperature annealing treatment can initiate the recrystallization of the first aluminum nitride layer 121 and greatly reduce the displacement density in the film of the first aluminum nitride layer 121.

After that, referring to FIG. 5, a second aluminum nitride layer 140 is formed on the planarized first aluminum nitride layer 121, for example, the second aluminum nitride layer 140 is formed by metal organic vapor deposition. Since the second aluminum nitride layer 140 is formed on the planarized first aluminum nitride layer 121, the root mean square roughness of the second aluminum nitride layer 140 opposite to the upper surface 142 of the substrate 110 ) Less than 3nm. Since the second aluminum nitride layer 140 is formed on the first aluminum nitride layer 121 with a relatively flat upper surface, the stitching thickness of the second aluminum nitride layer 140 can be smaller. In this embodiment, the film thickness T2 of the aluminum nitride layer 150 formed by the first aluminum nitride layer 121 and the second aluminum nitride layer 140 is less than 3.5 microns. In addition, since the second aluminum nitride layer 140 is formed on the first aluminum nitride layer 121 with a relatively flat upper surface, the aluminum nitride layer 150 may not have holes or smaller holes, and the aluminum nitride layer 150 The defect density is less than or equal to 5×10 ⁹ /cm ² , and it has good crystal quality. Smaller holes in the aluminum nitride layer 150 means that the aluminum nitride layer 150 has multiple holes inside, and the size of each hole in at least one direction parallel to the lateral direction of the substrate 110 and perpendicular to the longitudinal direction of the substrate 110 is less than 50 Nano.

In this embodiment, the aluminum nitride layer 150 formed after the step of FIG. 5 is disposed on the upper surface 112 of the substrate 110, and the aluminum nitride layer 150 faces the upper surface of the substrate 110 (that is, the second nitride layer). The root mean square roughness of the upper surface 142) of the aluminum layer 140 is less than 3 nanometers. In this way, the composite substrate 100 including the substrate 110 and the aluminum nitride layer 150 is formed. The composite substrate 100 can be formed on the N-type semiconductor layer, the quantum well layer and the P-type semiconductor layer of the light emitting diode, and helps to improve the crystal quality of the N-type semiconductor layer, the quantum well layer and the P-type semiconductor layer .

In this embodiment, when the second aluminum nitride layer 140 is formed on the first aluminum nitride layer 121, silicon may be doped in the second aluminum nitride layer 140 to control the residual stress. In this embodiment, the doping concentration of silicon in the second aluminum nitride layer 140 is greater than 2×10 ¹⁷ cm ⁻³ and less than 5×10 ¹⁹ cm ⁻³ .

In the composite substrate 100 and the manufacturing method thereof of the present embodiment, since a plurality of nano-patterned recesses 114 separated from each other are used on the upper surface 112 of the substrate 110, a nano-patterned recess 114 with a recessed nano-pattern is used. Rice patterned substrates replace the traditional patterned substrates with raised nano-patterns, which can greatly reduce the difficulty of innate grain stitching of aluminum nitride epitaxy. In addition, in this embodiment, the method of forming the nano-patterned recess 114 may be a wet etching method, which helps to improve the epitaxial quality of aluminum nitride directly on it. Furthermore, by forming the planarization layer 130 and then gradually removing the material of the planarization layer 130, the surface of the first aluminum nitride layer 121 is planarized, and the planarized first aluminum nitride Annealing the layer 121 can further improve the crystal quality of the aluminum nitride layer 150, reduce the difficulty of stitching, and expand the design space of the composite substrate 100.

Fig. 6A is a (002) X-ray rocking curve of three different samples of the composite substrate of Fig. 5 after the second aluminum nitride layer is grown, and Fig. 6B is a composite of Fig. 5 (102) X-ray swing curves of three different samples of the type substrate after the second aluminum nitride layer is grown. Please refer to FIG. 4, FIG. 5, FIG. 6A and FIG. 6B, where sample A, sample B, and sample C are used to verify the crystal quality of this embodiment. Sample A refers to a sample in which the first aluminum nitride layer 121 is formed on the substrate 110, but the first aluminum nitride layer 121 has not been annealed, and the film thickness T3 of the first aluminum nitride layer 121 is 300 nm. Sample B refers to a sample in which the first aluminum nitride layer 121 is formed on the substrate 110, the first aluminum nitride layer 121 has been annealed, and the film thickness T3 of the first aluminum nitride layer 121 is 300 nm. Sample C refers to a sample in which the first aluminum nitride layer 121 is formed on the substrate 110, the first aluminum nitride layer 121 has been annealed, and the film thickness T3 of the first aluminum nitride layer 121 is 600 nm. When the second aluminum nitride layer 140 has not been formed on Sample A, Sample B, and Sample C, the full width at half maximum of the (002) X-ray swing curve is 50 arcsec, 30 arcsec, and 70 arcsec. , And the FWHM of (102) X-ray swing curve is greater than 2000 arc seconds, 392 arc seconds and 371 arc seconds, respectively. The (002) X-ray swing curve and the (102) X-ray swing curve after forming the second aluminum nitride layer 140 on the sample A, the sample B and the sample C are respectively shown in FIG. 6A and FIG. 6B. After sample A, sample B, and sample C form the second aluminum nitride layer 140, the half-height widths of the (002) X-ray swing curve are 420 arcsec, 216 arcsec, and 144 arcsec, respectively. (102) The full width at half maximum of the X-ray swing curve is 560 arcsec, 400 arcsec and 280 arcsec. In this embodiment, the FWHM of the (002) X-ray swing curve of the aluminum nitride layer 150 is less than 150 arcsec, and the FWHM of the (102) X-ray swing curve of the aluminum nitride layer 150 is less than 350 Arc seconds. It can be verified from the above experimental data that the annealing treatment can effectively improve the crystal quality of the first aluminum nitride layer 121 before the second aluminum nitride layer 140 is grown, and a sufficient thickness of the first aluminum nitride layer 121 is helpful for further improvement. The crystal quality of the second aluminum nitride layer 140. In this embodiment, the final full width at half maximum of the (102) X-ray swing curve of the aluminum nitride layer 150 of the composite substrate 100 can reach 260 arcsec, and the converted row density is about 4×10 ⁸ cm ^-2 .

FIG. 7 is the Raman spectra of three different samples after the second aluminum nitride layer 140 is grown. Please refer to FIGS. 4, 5, and 7, the sample X in FIG. 7 refers to the formation of the first aluminum nitride layer 121 on the substrate 110, but the first aluminum nitride layer 121 has not undergone annealing treatment. A second aluminum nitride layer 140 that is not doped with silicon is grown on the aluminum layer 121. Sample Y means that the first aluminum nitride layer 121 is formed on the substrate 110. However, the first aluminum nitride layer 121 has been annealed. A second aluminum nitride layer 140 that is not doped with silicon is grown on an aluminum nitride layer 121. Sample Z means that the first aluminum nitride layer 121 is formed on the substrate 110, but the first aluminum nitride layer 121 has been annealed , A second silicon-doped aluminum nitride layer 140 is grown on the first aluminum nitride layer 121. The thickness of the aluminum nitride layer 150 of samples X, Y, and Z in Figure 7 are 2.11 microns, 2.12 microns, and 2.13 microns, respectively, and the warpages of samples X, Y, and Z in Figure 7 are 20.3 microns, respectively , 60.8 microns and 46.4 microns, and the E2 high mode (E2 high mode) frequency shifts of the Raman spectra of samples X, Y and Z in Fig. 7 are 658.9 cm ^-1 , 661.7 cm ^-1 and 659.6 cm ^{-respectively 1} . From the frequency shift of the Raman spectrum, it can be known from the literature that the stresses of the samples X, Y, and Z in Figure 7 are -1 GPa, -1.96 GPa, and -1.24 GPa, respectively. According to the degree of warpage, Shi Dong The Stoney equation calculates that the stresses of samples X, Y, and Z in Figure 7 are -0.54 GPa, -1.61 GPa, and -1.22 GPa, respectively.

FIG. 8 is a graph of (102) X-ray swing curve half-height versus warpage of three different samples X, Y, and Z of the composite substrate of FIG. 7 after the second aluminum nitride layer 140 is grown. The warpages of samples X, Y, and Z in Figure 8 are 20.3 microns, 60.8 microns, and 46.4 microns, respectively. After the sample X, the sample Y, and the sample Z form the second aluminum nitride layer 140, the full width at half maximum of the (102) X-ray swing curve is 521 arcsec, 259 arcsec, and 254 arcsec, respectively. It can be seen from the above experimental data that the high-temperature annealing treatment effectively improves the crystal quality, but the residual thermal compression strain causes large wafer warpage after the second aluminum nitride layer 140 is grown, and the second aluminum nitride layer 140 The method of doping silicon can counteract this strain while maintaining good crystalline quality.

9 is a schematic cross-sectional view of a composite substrate according to another embodiment of the present invention. Please refer to FIG. 9, the composite substrate 100 a of this embodiment is similar to the composite substrate 100 of FIG. 5, but the main differences between the two are as follows. The upper surface 112a of the substrate 110a of the composite substrate 100a of this embodiment is a flat surface without the nano-patterned recess 114 as shown in FIG. 5. In addition, the method for manufacturing the composite substrate 100a of this embodiment is to directly form an aluminum nitride layer 150 on the upper surface 112a of the substrate 110a, and the aluminum nitride layer 150 is doped with silicon to effectively control the residual stress. The material of the substrate 110a of this embodiment is the same as that of the substrate 110 of FIG. 5, and the method of forming the aluminum nitride layer 150 of this embodiment may be a metal organic chemical vapor deposition method.

In summary, in the composite substrate and the manufacturing method of the embodiment of the present invention, since a plurality of nano-patterned recesses separated from each other are used on the upper surface of the substrate, that is, a recessed nano-patterned recess is used. Patterned nano-patterned substrates replace the traditional patterned substrates with raised nano-patterns, which can greatly reduce the difficulty of innate grain stitching of aluminum nitride epitaxy. In addition, in the embodiment of the present invention, the method for forming the nano-patterned recesses may be a wet etching method, which helps to improve the epitaxial quality of aluminum nitride directly on it. Furthermore, in the embodiment of the present invention, the surface of the first aluminum nitride layer is planarized by a method of gradually removing the material of the planarization layer after the planarization layer is formed, and Annealing the first aluminum nitride layer can further improve the crystal quality of the aluminum nitride layer, reduce the difficulty of stitching, and expand the design space of the composite substrate.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be determined by the scope of the attached patent application.

100, 100a: composite substrate 110, 110a: substrate 112, 112a, 142: upper surface 113: Borderline 114: Nano patterned depression 120, 121: the first aluminum nitride layer 130: Planarization layer 140: The second aluminum nitride layer 150: aluminum nitride layer H: depth T1, T2, T3: film thickness W: width

1A and FIGS. 2 to 5 are cross-sectional schematic diagrams of the manufacturing process of a composite substrate according to an embodiment of the present invention. FIG. 1B is a schematic top view of the substrate in FIG. 1A. 6A is a (002) X-ray swing curve diagram of three different samples of the composite substrate of FIG. 5 after the second aluminum nitride layer has grown. 6B is a (102) X-ray swing curve diagram of three different samples of the composite substrate of FIG. 5 after the second aluminum nitride layer has grown. FIG. 7 is the Raman spectra of three different samples of the composite substrate after the second aluminum nitride layer is grown. Fig. 8 is a graph of (102) X-ray swing curve half-height versus warpage of three different samples of the composite substrate of Fig. 7 after the second aluminum nitride layer is grown. 9 is a schematic cross-sectional view of a composite substrate according to another embodiment of the present invention.

100: Composite substrate

110: substrate

112, 142: upper surface

114: Nano patterned depression

121: The first aluminum nitride layer

140: The second aluminum nitride layer

150: aluminum nitride layer

T2: Film thickness

Claims (20)

A composite substrate includes: a substrate, the upper surface of which includes a plurality of nano-patterned recesses, the nano-patterned recesses are separated from each other; and an aluminum nitride layer is disposed on the upper surface of the substrate, wherein The film thickness of the aluminum nitride layer is less than 3.5 microns, and the defect density of the aluminum nitride layer is less than or equal to 5×10 ⁹ /cm ² . According to the composite substrate described in item 1 of the scope of patent application, the root-mean-square roughness of the upper surface of the aluminum nitride layer behind the substrate is less than 3 nanometers. The composite substrate described in the first item of the scope of patent application, wherein the half-height width of the (002) X-ray swing curve of the aluminum nitride layer is less than 150 arcsec. The composite substrate as described in item 1 of the scope of patent application, wherein the full width at half maximum of the (102) X-ray swing curve of the aluminum nitride layer is less than 350 arcsec. According to the composite substrate described in item 1 of the scope of patent application, the depth of the nano-patterned recesses falls within the range of 150 nanometers to 1.5 micrometers. According to the composite substrate described in item 1 of the scope of patent application, the width of the nano-patterned recesses falls within the range of 200 nanometers to 1.5 micrometers. According to the composite substrate described in claim 1, wherein the nano patterned recesses are periodically arranged on the upper surface of the substrate. The composite substrate according to claim 1, wherein the aluminum nitride layer has a plurality of holes, and the size of each hole in at least one direction parallel to the substrate and perpendicular to the longitudinal direction of the substrate is smaller than 50nm. According to the composite substrate described in claim 1, wherein the aluminum nitride layer includes a first aluminum nitride layer and a second aluminum nitride layer on the first aluminum nitride layer, and the first aluminum nitride layer The aluminum nitride layer is doped with silicon. According to the composite substrate described in item 9 of the scope of patent application, the doping concentration of silicon in the second aluminum nitride layer is greater than 2×10 ¹⁷ cm ⁻³ and less than 5×10 ¹⁹ cm ⁻³ . According to the composite substrate described in claim 1, wherein the sidewalls of the nano-patterned recesses are chamfered cones. As for the composite substrate described in item 11 of the scope of patent application, at least three boundary lines intersect at the bottom apex of the chamfered cone. A method for manufacturing a composite substrate includes: Preparing a substrate, the upper surface of the substrate includes a plurality of nano-patterned recesses, and the nano-patterned recesses are separated from each other; Forming a first aluminum nitride layer on the upper surface of the substrate; Forming a planarization layer on the first aluminum nitride layer; The material of the planarization layer is gradually removed. When the material of the planarization layer is gradually removed to the bottom of the planarization layer, part of the first aluminum nitride layer is gradually removed at the same time, so that the Planarization of the first aluminum nitride layer; and A second aluminum nitride layer is formed on the planarized first aluminum nitride layer, wherein the root mean square roughness of the upper surface of the second aluminum nitride layer opposite to the substrate is less than 3 nm. The manufacturing method of the composite substrate as described in item 13 of the scope of patent application further includes: After gradually removing the material of the planarization layer, annealing is performed on the planarized first aluminum nitride layer. According to the method for manufacturing a composite substrate described in item 13 of the scope of patent application, the material of the planarization layer includes polymer or spin-on glass. According to the method for manufacturing a composite substrate as described in claim 13, wherein the method of gradually removing the material of the planarization layer is dry etching or mechanical polishing. According to the manufacturing method of the composite substrate described in claim 13, wherein the second aluminum nitride layer is doped with silicon, and the doping concentration of silicon in the second aluminum nitride layer is greater than 2×10 ¹⁷ cm ^-3 and less than 5×10 ¹⁹ cm ^-3 . According to the manufacturing method of the composite substrate described in the scope of the patent application, the nano-patterned recesses are formed by wet etching. According to the manufacturing method of the composite substrate described in the scope of patent application, the film thickness of the first aluminum nitride layer plus the second aluminum nitride layer is less than 3.5 microns. The method for manufacturing a composite substrate as described in claim 13, wherein the depth of the nano-patterned recesses is in the range of 150 nanometers to 1.5 microns, and the width of the nano-patterned recesses It falls within the range of 200 nanometers to 1.5 microns.

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