Patterned composite substrate for stripping and preparation method and application thereof

Abstract

The invention provides a patterned composite substrate for stripping and a preparation method and application thereof. The patterned composite substrate comprises a sapphire substrate and a plurality of heterogeneous bulge structures arranged on the surface of one side of the sapphire substrate; the plurality of heterogeneous bulge structures form a periodic graphic array, graphic units of the periodic graphic array are similar to hexagonal pyramid structures, and the top view of each graphic unit is a regular hexagon; the pattern units in the periodic pattern array are connected in an angle-to-angle manner, the direction of linear connection of the pattern units in the angle-to-angle manner is recorded as a first direction, and the direction of linear connection of the pattern units in the central axis manner is recorded as a second direction; in the first direction, the bottoms of the adjacent pattern units are integrally connected; and in the second direction, gaps exist between the adjacent pattern units, and the C surface of the sapphire substrate is exposed. According to the patterned composite substrate provided by the invention, the stripping cost is reduced, and the stripping efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor manufacturing, and in particular relates to a patterned composite substrate for peeling, a preparation method and an application thereof. Background Art

[0002] Compared with Si and SiC, sapphire substrate has high light transmittance, strong hardness, stable chemical properties, and its (0001) plane has hexagonal symmetry. It is currently the most commonly used substrate material for manufacturing GaN-based LED chips. However, the thermal conductivity of sapphire material itself is only 0.41W / (cm·K), much smaller than Si (1.3W / (cm·K)) and SiC (1.3W / (cm·K)), which limits its use in high-power GaN-based LED chips or devices.

[0003] At present, there are laser stripping processes, mechanical stripping processes and composite stripping processes to separate GaN and sapphire to eliminate the adverse effects of sapphire's low thermal conductivity. However, the above traditional processes widely have problems such as low stripping efficiency, harsh process conditions and high scrap rate.

[0004] Therefore, there is an urgent need to design a sapphire substrate for stripping that has high stripping efficiency, low stripping cost and can reduce GaN wafer stress. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a patterned composite substrate for stripping, a preparation method and application thereof. The present invention arranges and designs the surface of the sapphire substrate in a pattern, obtains a heterogeneous protrusion structure connected by multiple sacrificial layers, sufficient sapphire C-face growth surface, multiple etching liquid channels and a pattern end auxiliary for GaN stress relaxation. The GaN epitaxial wafer based on the patterned composite substrate does not need to be stripped with complex equipment during the preparation process, which reduces the stripping cost and improves the stripping efficiency. The obtained GaN wafer has low stress, which is conducive to its use in high-power devices.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a patterned composite substrate for peeling, the patterned composite substrate comprising a sapphire substrate, and a plurality of heterogeneous protrusion structures arranged on a surface of one side of the sapphire substrate;

[0008] The plurality of heterogeneous protrusion structures form a periodic pattern array, the pattern units of the periodic pattern array are hexagonal pyramid-like structures, and the top view of the pattern units is a regular hexagon;

[0009] The graphic units in the periodic graphic array are connected in a diagonal manner, wherein the direction in which the graphic units are connected in a straight line in a diagonal manner is recorded as a first direction, and the direction in which the graphic units are connected in a straight line in a central axis manner is recorded as a second direction;

[0010] In the first direction, the bottoms of adjacent graphic units are integrally connected; in the second direction, there are gaps between adjacent graphic units, exposing the C-surface of the sapphire substrate.

[0011] The present invention arranges and designs patterns on the surface of a sapphire substrate to obtain a heterogeneous protrusion structure connected by multiple sacrificial layers, sufficient sapphire C-plane growth surfaces, multiple etching liquid channels, and pattern-end assistance for GaN stress relaxation. During the preparation process of a GaN epitaxial wafer based on the patterned composite substrate, there is no need to use complex equipment for stripping, which reduces the stripping cost and improves the stripping efficiency. In addition, the obtained GaN wafer has low stress, which is conducive to its use in high-power devices.

[0012] In the present invention, the graphic units in the periodic graphic array are connected in a diagonal form, and this arrangement has the following advantages: ① According to the above arrangement, the fastest way can be provided for the merging of adjacent graphic units; ② Each graphic unit forms 6 points connected with the surrounding graphic units, which can provide more abundant channels for the flow of etching liquid, which is conducive to improving the stripping efficiency; ③ Based on this arrangement, there is sufficient space between the three graphics, and the space has a large margin for change due to further expansion of the bottom width, which can provide sufficient sapphire C-plane for the epitaxial growth of GaN.

[0013] Preferably, the material of the heterogeneous protrusion structure includes any one of silicon dioxide, silicon nitride, phosphosilicate glass, gallium nitride or aluminum nitride, or a combination of at least two thereof.

[0014] In the present invention, the heterogeneous convex structure of the above material has the following properties: ① good stability at high temperature (800-1500°C); ② solubility in specific chemical etching agents, such as silicon dioxide (hydrofluoric acid), silicon nitride (phosphoric acid), phosphosilicate glass (nitric acid); ③ not conducive to the positioning and growth of GaN crystals; ④ easy chemical deposition and dry etching;

[0015] Preferably, the sapphire substrate includes a stacked sapphire base plate and a sapphire etching layer, and the sapphire etching layer is located below the graphic unit; the sapphire etching layer includes a plurality of etching units, adjacent etching units in the first direction are integrally connected, and there is a gap between adjacent etching units in the second direction.

[0016] In the present invention, the presence of the sapphire etching layer can ensure that the heterogeneous layer of the entire wafer is etched through.

[0017] Preferably, the tip spacing between adjacent graphic units is denoted as P, and the value range of P is 1-5 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm or 5 μm.

[0018] Preferably, the length of the bottom diagonal of the graphic unit in the first direction is recorded as W1, and W1=P.

[0019] In the present invention, W1=P, which can ensure the connection of the graphic units in the first direction and provide a channel guarantee for the subsequent corrosion and flow of specific chemical corrosion reagents.

[0020] Preferably, the cross-sectional length of the etching unit in the second direction is denoted as W2, and W1>W2.

[0021] In the present invention, W1>W2 is defined to provide sufficient space for the crystallization and epitaxial growth of GaN.

[0022] Preferably, the width of the gap in the second direction is denoted as W3, and W3>100 nm, for example, may be 110 nm, 120 nm, 130 nm, 140 nm or 150 nm.

[0023] In the present invention, W3 is limited to 100 nm, which can provide sufficient space for the crystallization and epitaxial growth of GaN.

[0024] Preferably, the total height of the etching unit and the graphic unit above the etching unit is recorded as H1, and the value range of H1 is 0.8-3μm, for example, it can be 0.8μm, 1μm, 1μm, 1.5μm, 2μm, 2.5μm or 3μm.

[0025] In the present invention, the value range of H1 is limited to 0.8-3 μm, providing a template for controllable stress relaxation and release for the 3D growth and merging of GaN in each gap.

[0026] Preferably, the height of the etching unit is denoted as H2, 0.2H1>H2>50nm.

[0027] In the present invention, 0.2H1>H2>50nm is defined to ensure that the sapphire C-surfaces in the gaps between the graphic units are fully exposed in the process of obtaining the heterogeneous protruding structure, otherwise GaN cannot be epitaxially grown.

[0028] Preferably, the height of the joint where the bottoms of the graphic units are integrally connected is denoted as H3, and H1-H2>H3>0.1H1.

[0029] In the present invention, H1-H2>H3>0.1H1 is defined, which can ensure that the graphic units are connected in the first direction and have sufficient chemical etching reagent flow channels, thereby providing sufficient process windows for efficient stripping.

[0030] Preferably, the etching unit and the graphic unit located above the etching unit form a protruding microstructure; the side edge line of the protruding microstructure in the first direction is recorded as R1, and the height of the side edge surface of the protruding microstructure in the second direction is recorded as R2, R1>R2.

[0031] In the present invention, R1>R2 is defined, and the transition from R1 to R2 has a gradient decreasing slope distance and is centrally symmetrical, which is conducive to the release of stress during the GaN epitaxial growth process and obtains high-quality GaN crystals.

[0032] In a second aspect, the present invention provides a method for preparing a patterned composite substrate for peeling as described in the first aspect, the preparation method comprising the following steps:

[0033] (1) a heterogeneous layer and a mask layer are sequentially plated on one side surface of a sapphire substrate;

[0034] (2) patterning the mask layer to form a mask pattern, and then etching the mask layer using an etching process with a bottom width laterally expanded to form a plurality of heterogeneous protrusion structures, thereby obtaining the patterned composite substrate for stripping;

[0035] Wherein, the plurality of heterogeneous protrusion structures constitute a periodic pattern array, the pattern units of the periodic pattern array are hexagonal pyramid-like structures, and the top view of the pattern units is a regular hexagon;

[0036] The graphic units in the periodic graphic array are connected in a diagonal manner, wherein the direction of the diagonal straight line connection is recorded as a first direction, and the direction of the graphic units connected in a central axis straight line connection is recorded as a second direction;

[0037] In the first direction, the bottoms of adjacent graphic units are integrally connected; in the second direction, there are gaps between adjacent graphic units, exposing the C-surface of the sapphire substrate.

[0038] It should be noted that the etching process using the bottom width lateral expansion can make each graphic unit quickly connected in a corner-to-corner form to form a flow channel for the etching liquid. Exemplarily, the etching process can be ICP etching (inductively coupled plasma etching).

[0039] Preferably, the material of the mask layer in step (1) comprises photoresist;

[0040] Preferably, the top view of the mask pattern in step (2) is a regular hexagon.

[0041] Preferably, the etching process for lateral expansion of the bottom width in step (2) comprises the following steps:

[0042] The mask pattern is morphologically modified so that the front view of the mask pattern is a regular trapezoid, and then the bottom width of the dielectric layer is laterally expanded.

[0043] In the present invention, the mask pattern is modified in shape so that the front view of the mask pattern is a regular trapezoid. The mask pattern in this shape plays a positive auxiliary role in the lateral expansion of the bottom width of the heterogeneous protruding structure.

[0044] Preferably, during the morphology modification process, the etching gas includes a Cl-based gas and an auxiliary gas. Exemplarily, the Cl-based gas includes Cl2 or BCl3, etc., and the auxiliary gas includes N2 or O2, etc.

[0045] Preferably, the flow rate of the Cl-based gas is 30-90 sccm, for example, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm or 90 sccm, and the flow rate of the auxiliary gas is 5-25 sccm, for example, 5 sccm, 10 sccm, 15 sccm, 20 sccm or 25 sccm.

[0046] Preferably, the regular trapezoid satisfies the following relationship: the length of the lower base>2×the length of the upper base, and the degree of the base angle is 60-85°, for example, it can be 60°, 65°, 70°, 75°, 80° or 85°.

[0047] In the present invention, the mask pattern of this form plays a positive auxiliary role in the lateral expansion of the bottom width of the heterogeneous protrusion structure.

[0048] Preferably, in the process of lateral expansion of the bottom width of the dielectric layer, the etching gas includes a Cl-based gas and a F-based gas, the flow rate of the Cl-based gas is 50-150 sccm, for example, 50 sccm, 75 sccm, 100 sccm, 125 sccm or 150 sccm, etc., and the flow rate of the F-based gas is 0-20 sccm, for example, 5 sccm, 10 sccm, 15 sccm or 20 sccm, etc. Exemplarily, the Cl-based gas includes Cl2 or BCl3, etc., and the F-based gas includes CHF3, etc.

[0049] In the present invention, under the etching action of F-based gas, a large amount of by-product deposition will be generated between the inclination angles of the side walls of the mask pattern (the complementary outer angles of the bottom angles of the trapezoid), and the inclination angles of the side walls are relatively large, and the deposition direction is outward, forming a secondary mask for the heterogeneous layer. During the downward bombardment etching process of Cl-based gas, the lateral expansion rate is enhanced due to the action of the secondary mask. The entire etching process is carried out under low bias voltage, the bias effect of the wafer on the plasma is reduced, the plasma bombardment inclination angle is increased, and the lateral expansion rate is further enhanced, so that the bottoms of adjacent graphic units are connected, and a heterogeneous protruding structure can be obtained.

[0050] Preferably, the process of lateral expansion of the bottom width of the dielectric layer is performed under a low bias voltage.

[0051] It should be noted that the bias is controlled by the RF power supply. In order to allow the dielectric layer to perform bottom width lateral expansion under low bias, the RF power supply power is controlled in the range of 100-300W, for example, 100W, 150W, 200W, 250W or 300W.

[0052] Preferably, after the heterogeneous protrusion structure is formed in step (2), a post-modification step is further performed, specifically comprising:

[0053] The overall morphology of the obtained pattern substrate is modified, and the gap area between the pattern units is over-etched so that the sapphire C surface in the gap is exposed.

[0054] In the present invention, the functions of the post-modification step are: first, to modify the heterogeneous protrusion structure, improve the surface state of the pattern, and reduce the nucleation defects of the epitaxial growth film; second, to over-etch the gap area between the graphic units to ensure that the sapphire C surface is exposed to provide a nucleation area for the epitaxial growth of GaN.

[0055] Preferably, the post-modification step is performed using a Cl-based gas under a high bias pressure.

[0056] It should be noted that the bias voltage is controlled by the RF power supply. In order to enable the post-modification step to be carried out under high bias voltage using Cl-based gas, the RF power supply power is controlled in the range of 600-1000W, for example, 600W, 700W, 800W, 900W or 1000W.

[0057] In a third aspect, the present invention provides an application of the patterned composite substrate for peeling as described in the first aspect, wherein the patterned composite substrate for peeling is applied in the field of preparation of GaN epitaxial wafers.

[0058] Preferably, the method of applying the patterned composite substrate for stripping to a GaN epitaxial wafer comprises:

[0059] (1) depositing an epitaxial layer on one side of a patterned composite substrate having a plurality of heterogeneous protrusion structures, including a transition layer, a GaN buffer layer, an n-GaN layer, an Al-containing superlattice layer, an active layer, an electron blocking layer, a p-GaN layer, an In-containing superlattice layer and an ITO layer stacked in sequence to obtain an epitaxial wafer;

[0060] (2) using dry etching to remove the edge area of ​​the epitaxial wafer so as to expose the heterogeneous protrusion structure;

[0061] (3) placing the epitaxial wafer processed in step (2) in an etching solution, etching and removing the heterogeneous protrusion structure, and realizing the stripping of the sapphire substrate;

[0062] (4) The peeled surface of the epitaxial wafer is planarized.

[0063] It should be noted that the n-GaN layer is doped with Si, the Al-containing superlattice layer is a composite of an AlGaN layer and a GaN layer, the active layer is a GaN-based quantum well layer, the electron blocking layer is an AlGaN layer, the p-GaN layer is doped with Mg, and the In-containing superlattice layer is a composite of an InGaN layer and a GaN layer.

[0064] It should be noted that the epitaxial wafer after planarization can be further used to manufacture GaN devices.

[0065] It should be noted that the etching removal treatment can be carried out by an ultrasonic method. In the ultrasonic method, the ultrasonic horn and the epitaxial wafer are in a vertical position relationship, and the center of the ultrasonic horn is directly opposite the center of the epitaxial wafer. This is beneficial to the separation of GaN on the sapphire C-plane from the sapphire, and is also beneficial to accelerate corrosion, while balancing the surrounding corrosion rate and corresponding stress, and ensuring the integrity of the peeling.

[0066] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] The present invention arranges and designs patterns on the surface of a sapphire substrate to obtain a heterogeneous protrusion structure connected by multiple sacrificial layers, sufficient sapphire C-plane growth surfaces, multiple etching liquid channels, and pattern-end assistance for GaN stress relaxation. During the preparation process of a GaN epitaxial wafer based on the patterned composite substrate, there is no need to use complex equipment for stripping, which reduces the stripping cost and improves the stripping efficiency. In addition, the obtained GaN wafer has low stress, which is conducive to its use in high-power devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is a top view of the patterned composite substrate for peeling provided in Example 1 of the present invention.

[0070] Figure 2 This is a cross-sectional view of the patterned composite substrate for peeling provided in Example 1 of the present invention in the first direction.

[0071] Figure 3 This is a cross-sectional view of the patterned composite substrate for peeling provided in Example 1 of the present invention in the second direction.

[0072] Figure 4 This is a process flow chart for preparing a patterned composite substrate for peeling provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0073] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0074] Example 1

[0075] This embodiment provides a patterned composite substrate for peeling, the patterned composite substrate comprising a sapphire substrate and a plurality of heterogeneous protrusion structures arranged on a surface of one side of the sapphire substrate; the material of the heterogeneous protrusion structures is silicon dioxide;

[0076] The plurality of heterogeneous protrusion structures form a periodic pattern array, the pattern units of the periodic pattern array are hexagonal pyramid-like structures, and the top view of the pattern units is a regular hexagon, such as Figure 1 As shown;

[0077] The graphic units in the periodic graphic array are connected in a diagonal manner, wherein the direction in which the graphic units are connected in a diagonal manner is recorded as a first direction, and the direction in which the graphic units are connected in a central axis manner is recorded as a second direction. Figure 2 and Figure 3 As shown;

[0078] In the first direction, the bottoms of adjacent graphic units are connected in an integrated manner; in the second direction, there are gaps between adjacent graphic units, exposing the C-surface of the sapphire substrate;

[0079] The sapphire substrate includes a stacked sapphire base plate and a sapphire etching layer, wherein the sapphire etching layer is located below the graphic unit; the sapphire etching layer includes a plurality of etching units, wherein adjacent etching units in the first direction are integrally connected, and there is a gap between adjacent etching units in the second direction.

[0080] The tip spacing between adjacent graphic units is recorded as P, and the value of P is 3μm; the bottom diagonal length of the graphic unit in the first direction is recorded as W1, W1=P; the cross-sectional length of the etching unit in the second direction is recorded as W2, W2=2.85μm, and W1>W2; the width of the gap in the second direction is recorded as W3, and W3=150nm; the total height of the etching unit and the graphic unit located above the etching unit is recorded as H1, and the value of H1 is 1.5μm; The height is recorded as H2, H2=200nm, 0.2H1>H2>50nm; the height of the joint where the bottom of the graphic unit is integrated is recorded as H3, H3=300nm, H1-H2>H3>0.1H1; the etching unit and the graphic unit located above the etching unit form a raised microstructure; the side edge line of the raised microstructure in the first direction is recorded as R1, R1=140nm, and the height of the side edge surface of the raised microstructure in the second direction is recorded as R2, R2=110nm, R1>R2.

[0081] This embodiment also provides a method for preparing the above-mentioned patterned composite substrate for peeling, and its preparation process flow chart is as follows: Figure 4 As shown, the preparation method comprises the following steps:

[0082] (1) using a CVD (chemical vapor deposition) method, a silicon dioxide heterogeneous layer with a thickness of 2 μm and a photoresist mask layer with a thickness of 2 μm are sequentially deposited on one surface of a sapphire substrate;

[0083] (2) The photoresist mask layer is patterned to form a mask pattern having a regular hexagonal top view, as shown in FIG. Figure 4 As shown in ①, an etching process with a bottom width laterally expanded is then used to perform etching treatment to form a plurality of heterogeneous protruding structures, and then a post-modification treatment is performed, that is, in a Cl2 atmosphere with a flow rate of 100 sccm, the bias is controlled by an RF power supply, and the RF power supply power is 800 W. The overall morphology of the obtained graphic substrate is modified, and at the same time, the gap area between the graphic units is over-etched to expose the sapphire C surface at the gap, and finally the graphic composite substrate for stripping is obtained, and its top view is shown in Figure 4 As shown in ② in the figure; the plurality of heterogeneous protrusion structures constitute a periodic graphic array, the graphic unit of the periodic graphic array is a hexagonal pyramid-like structure, and the top view of the graphic unit is a regular hexagon; the graphic units in the periodic graphic array are connected in a diagonal form, wherein the direction of the straight line connection in the diagonal form is recorded as the first direction, and the direction of the straight line connection in the form of the central axis is recorded as the second direction; in the first direction, the bottoms of adjacent graphic units are connected in an integrated manner; in the second direction, there are gaps between adjacent graphic units, exposing the C surface of the sapphire substrate;

[0084] The etching process for lateral expansion of the bottom width includes the following steps:

[0085] (a) using Cl2 as the main etching gas and N2 as the auxiliary etching gas, the flow rate of the main etching gas is 60 sccm, and the flow rate of the auxiliary etching gas is 15 sccm, and performing ICP dry etching to achieve morphological modification of the photoresist column, so that the photoresist column is a regular trapezoid in the front view, satisfying the length of the lower base>2×the length of the upper base, and the degree of the base angle is 75°;

[0086] (b) In an etching gas atmosphere composed of Cl2 and CHF3, the flow rate of Cl2 is 100 sccm, the flow rate of CHF3 is 10 ccm, the low bias voltage is controlled by an RF power supply, the power of the RF power supply is 200 W, and the bottom width of the dielectric layer is laterally expanded.

[0087] Example 2

[0088] This embodiment provides a patterned composite substrate for peeling, the patterned composite substrate comprising a sapphire substrate and a plurality of heterogeneous protrusion structures arranged on a surface of one side of the sapphire substrate; the material of the heterogeneous protrusion structures is silicon dioxide;

[0089] The plurality of heterogeneous protrusion structures form a periodic pattern array, the pattern units of the periodic pattern array are hexagonal pyramid-like structures, and the top view of the pattern units is a regular hexagon;

[0090] The graphic units in the periodic graphic array are connected in a diagonal manner, wherein the direction in which the graphic units are connected in a straight line in a diagonal manner is recorded as a first direction, and the direction in which the graphic units are connected in a straight line in a central axis manner is recorded as a second direction;

[0091] In the first direction, the bottoms of adjacent graphic units are connected in an integrated manner; in the second direction, there are gaps between adjacent graphic units, exposing the C-surface of the sapphire substrate;

[0092] The sapphire substrate includes a stacked sapphire base plate and a sapphire etching layer, wherein the sapphire etching layer is located below the graphic unit; the sapphire etching layer includes a plurality of etching units, wherein adjacent etching units in the first direction are integrally connected, and there is a gap between adjacent etching units in the second direction.

[0093] The tip spacing between adjacent graphic units is recorded as P, and the value of P is 1μm; the bottom diagonal length of the graphic unit in the first direction is recorded as W1, W1=P; the cross-sectional length of the etching unit in the second direction is recorded as W2, W2=850nm, and W1>W2; the width of the gap in the second direction is recorded as W3, and W3=200nm; the total height of the etching unit and the graphic unit located above the etching unit is recorded as H1, and the value of H1 is 1μm; The height is recorded as H2, H2=100nm, 0.2H1>H2>50nm; the height of the joint where the bottom of the graphic unit is integrated is recorded as H3, H3=50nm, H1-H2>H3>0.1H1; the etching unit and the graphic unit located above the etching unit form a raised microstructure; the side edge line of the raised microstructure in the first direction is recorded as R1, R1=90nm, and the height of the side edge surface of the raised microstructure in the second direction is recorded as R2, R2=70nm, R1>R2.

[0094] This embodiment also provides a method for preparing the above-mentioned patterned composite substrate for peeling, and the preparation method comprises the following steps:

[0095] (1) using a CVD (chemical vapor deposition) method, a silicon dioxide heterogeneous layer with a thickness of 900 nm and a photoresist mask layer with a thickness of 1.1 μm are sequentially deposited on one surface of a sapphire substrate;

[0096] (2) patterning the photoresist mask layer to form a mask pattern with a regular hexagon in top view, and then etching it using an etching process with a bottom width laterally expanded to form a plurality of heterogeneous protrusion structures, and then performing post-modification treatment, that is, in a BCl3 atmosphere with a flow rate of 100 sccm, the bias voltage is controlled by a radio frequency power supply, and the radio frequency power supply power is 800 W, the overall morphology of the obtained pattern substrate is modified, and at the same time, the gap area between the pattern units is over-etched to expose the sapphire C surface at the gap, and finally the patterned composite substrate for stripping is obtained; The plurality of heterogeneous protrusion structures constitute a periodic graphic array, the graphic units of the periodic graphic array are hexagonal pyramid-like structures, and the top view of the graphic units is a regular hexagon; the graphic units in the periodic graphic array are connected in a diagonal manner, wherein the direction of the straight line connection in the diagonal manner is recorded as a first direction, and the direction of the straight line connection in the form of a central axis is recorded as a second direction; in the first direction, the bottoms of adjacent graphic units are connected in an integrated manner; in the second direction, there are gaps between adjacent graphic units, exposing the C surface of the sapphire substrate;

[0097] The etching process for lateral expansion of the bottom width includes the following steps:

[0098] (a) using BCl3 as the main etching gas and N2 as the auxiliary etching gas, the flow rate of the main etching gas is 60 sccm, and the flow rate of the auxiliary etching gas is 10 sccm, and ICP dry etching is performed to achieve morphological modification of the photoresist column, so that the photoresist column is a regular trapezoid in the front view, and the length of the lower base is greater than 2×the length of the upper base, and the degree of the base angle is 75°;

[0099] (b) In an etching gas atmosphere consisting of BCl3 and CHF3, the flow rate of BCl3 is 100 sccm, the flow rate of CHF3 is 10 sccm, the low bias voltage is controlled by an RF power supply, the power of the RF power supply is 200 W, and the bottom width of the dielectric layer is laterally expanded.

[0100] Example 3

[0101] This embodiment provides a patterned composite substrate for peeling, the patterned composite substrate comprising a sapphire substrate and a plurality of heterogeneous protrusion structures arranged on a surface of one side of the sapphire substrate; the material of the heterogeneous protrusion structures is silicon dioxide;

[0102] The plurality of heterogeneous protrusion structures form a periodic pattern array, the pattern units of the periodic pattern array are hexagonal pyramid-like structures, and the top view of the pattern units is a regular hexagon;

[0103] The graphic units in the periodic graphic array are connected in a diagonal manner, wherein the direction in which the graphic units are connected in a straight line in a diagonal manner is recorded as a first direction, and the direction in which the graphic units are connected in a straight line in a central axis manner is recorded as a second direction;

[0104] In the first direction, the bottoms of adjacent graphic units are connected in an integrated manner; in the second direction, there are gaps between adjacent graphic units, exposing the C-surface of the sapphire substrate;

[0105] The sapphire substrate includes a stacked sapphire base plate and a sapphire etching layer, wherein the sapphire etching layer is located below the graphic unit; the sapphire etching layer includes a plurality of etching units, wherein adjacent etching units in the first direction are integrally connected, and there is a gap between adjacent etching units in the second direction.

[0106] The tip spacing between adjacent graphic units is recorded as P, and the value of P is 5μm; the bottom diagonal length of the graphic unit in the first direction is recorded as W1, W1=P; the cross-sectional length of the etching unit in the second direction is recorded as W2, W2=4.2μm, and W1>W2; the width of the gap in the second direction is recorded as W3, and W3=200nm; the total height of the etching unit and the graphic unit located above the etching unit is recorded as H1, and the value of H1 is 3μm; the height of the etching unit The height of the bottom integrated connection of the graphic unit is recorded as H3, H3=200nm, H1-H2>H3>0.1H1; the etching unit and the graphic unit located above the etching unit form a raised microstructure; the side edge line of the raised microstructure in the first direction is recorded as R1, R1=180nm, and the height of the side edge surface of the raised microstructure in the second direction is recorded as R2, R2=120nm, R1>R2.

[0107] This embodiment also provides a method for preparing the above-mentioned patterned composite substrate for peeling, and the preparation method comprises the following steps:

[0108] (1) using a CVD (chemical vapor deposition) method, a silicon dioxide heterogeneous layer with a thickness of 3.5 μm and a photoresist mask layer with a thickness of 2.5 μm are sequentially deposited on one surface of a sapphire substrate;

[0109] (2) patterning the photoresist mask layer to form a mask pattern that is a regular hexagon in top view, and then etching it using an etching process with a bottom width that is laterally expanded to form a plurality of heterogeneous protrusion structures, and then performing post-modification treatment, that is, in a Cl2 atmosphere with a flow rate of 100 sccm, the bias voltage is controlled by a radio frequency power supply, and the radio frequency power supply power is 800 W, the overall morphology of the obtained pattern substrate is modified, and at the same time, the gap area between the pattern units is over-etched to expose the sapphire C surface at the gap, and finally the patterned composite substrate for stripping is obtained; The plurality of heterogeneous protrusion structures constitute a periodic graphic array, the graphic units of the periodic graphic array are hexagonal pyramid-like structures, and the top view of the graphic units is a regular hexagon; the graphic units in the periodic graphic array are connected in a diagonal manner, wherein the direction of the straight line connection in the diagonal manner is recorded as a first direction, and the direction of the straight line connection in the form of a central axis is recorded as a second direction; in the first direction, the bottoms of adjacent graphic units are connected in an integrated manner; in the second direction, there are gaps between adjacent graphic units, exposing the C surface of the sapphire substrate;

[0110] The etching process for lateral expansion of the bottom width includes the following steps:

[0111] (a) using Cl2 as the main etching gas and O2 as the auxiliary etching gas, the flow rate of the main etching gas is 60 sccm, and the flow rate of the auxiliary etching gas is 25 sccm, and performing ICP dry etching to achieve morphological modification of the photoresist column, so that the photoresist column is a regular trapezoid in the front view, satisfying the length of the lower base>2×the length of the upper base, and the degree of the base angle is 70°;

[0112] (b) In an etching gas atmosphere composed of Cl2 and CHF3, the flow rate of Cl2 is 100 sccm, the flow rate of CHF3 is 10 sccm, the low bias voltage is controlled by an RF power supply, the power of the RF power supply is 200 W, and the bottom width of the dielectric layer is laterally expanded.

[0113] Example 4

[0114] The difference between this embodiment and Embodiment 1 is that the bottom diagonal length W1 of the graphic unit in the first direction is 2 μm, and W1≠P.

[0115] The rest of the preparation methods and parameters were the same as those in Example 1.

[0116] Example 5

[0117] The difference between this embodiment and embodiment 1 is that W1=W2.

[0118] The rest of the preparation methods and parameters were the same as those in Example 1.

[0119] Example 6

[0120] The difference between this embodiment and embodiment 1 is that W3=80nm.

[0121] The rest of the preparation methods and parameters were the same as those in Example 1.

[0122] Example 7

[0123] The difference between this embodiment and embodiment 1 is that the value of H1 is 0.5 μm.

[0124] The rest of the preparation methods and parameters were the same as those in Example 1.

[0125] Example 8

[0126] The difference between this embodiment and embodiment 1 is that the value of H1 is 4 μm.

[0127] The rest of the preparation methods and parameters were the same as those in Example 1.

[0128] Example 9

[0129] The difference between this embodiment and the first embodiment is that the height H2 of the etching unit is 0.5 μm, so that 0.2H1<H2.

[0130] The rest of the preparation methods and parameters were the same as those in Example 1.

[0131] Example 10

[0132] The difference between this embodiment and embodiment 1 is that the height H2 of the etching unit is 50 nm.

[0133] The rest of the preparation methods and parameters were the same as those in Example 1.

[0134] Embodiment 11

[0135] The difference between this embodiment and embodiment 1 is that H3=200 nm, so that H1-H2<H3.

[0136] The rest of the preparation methods and parameters were the same as those in Example 1.

[0137] Example 12

[0138] The difference between this embodiment and embodiment 1 is that H3=0.15 μm, so that H3=0.1H1.

[0139] The rest of the preparation methods and parameters were the same as those in Example 1.

[0140] Embodiment 13

[0141] The difference between this embodiment and embodiment 1 is that R1=R2.

[0142] The rest of the preparation methods and parameters were the same as those in Example 1.

[0143] Embodiment 14

[0144] The difference between this embodiment and embodiment 1 is that the sapphire substrate does not have a sapphire etching layer, that is, in step (2), the overall morphology of the graphic substrate is not modified, and the gap area between the graphic units is not over-etched.

[0145] The rest of the preparation methods and parameters were the same as those in Example 1.

[0146] Comparative Example 1

[0147] The difference between this comparative example and Example 1 is that the graphic unit of the periodic graphic array is a quadrangular pyramid-like structure, and the top view of the graphic unit is a regular quadrilateral, that is, the top view of the mask graphic in the adjustment step (2) is a regular quadrilateral.

[0148] The rest of the preparation methods and parameters were the same as those in Example 1.

[0149] Comparative Example 2

[0150] The difference between this comparative example and Example 1 is that, in the second direction, there is no gap between adjacent graphic units.

[0151] The rest of the preparation methods and parameters were the same as those in Example 1.

[0152] Application Example 1

[0153] This application example provides a method for stripping an epitaxial wafer, and the specific steps include:

[0154] (1) depositing an epitaxial layer on the surface of the patterned composite substrate having a plurality of heterogeneous protrusion structures described in Example 1, including a GaN buffer layer, an n-GaN layer, an Al-containing superlattice layer, a GaN-based quantum well layer, an electron blocking layer, a p-GaN layer, an In-containing superlattice layer and an ITO layer stacked in sequence to obtain an epitaxial wafer;

[0155] (2) using dry etching to longitudinally etch and remove 200 μm of the edge of the epitaxial wafer, so that the heterogeneous protrusion structure in the epitaxial wafer is exposed;

[0156] (3) placing the epitaxial wafer treated in step (2) into a 70±5° C. BOE solution (buffered oxide solution, prepared by mixing a hydrofluoric acid (49 wt %) aqueous solution and an ammonium fluoride aqueous solution (40 wt %) in a volume ratio of 1:6), and performing ultrasonic treatment using an ultrasonic horn (100 W, 50 kHz), wherein the ultrasonic horn is perpendicular to the epitaxial wafer and the center of the ultrasonic horn is directly opposite to the center of the epitaxial wafer, and the heterogeneous protrusion structure is corroded and removed to achieve stripping of the sapphire substrate;

[0157] (3) The peeling surface of the epitaxial wafer is planarized.

[0158] Application Example 2-15

[0159] The difference between Application Example 2-15 and Application Example 1 is that the patterned composite substrate in step (1) is provided by Examples 2-15, respectively.

[0160] The remaining stripping methods and parameters are consistent with those in Application Example 1.

[0161] Application Comparative Example 1-2

[0162] The difference between Application Comparative Examples 1-2 and Application Example 1 is that the patterned composite substrate in step (1) is provided by Comparative Examples 1-2 respectively.

[0163] The remaining stripping methods and parameters are consistent with those in Application Example 1.

[0164] In summary, the present invention obtains a heterogeneous protrusion structure connected by multiple sacrificial layers, sufficient sapphire C-face growth surface, multiple etching liquid channels and graphic end assistance for GaN stress relaxation by patterning and designing the surface of the sapphire substrate. The GaN epitaxial wafer based on this patterned composite substrate does not need to be peeled off with complex equipment during the preparation process, which reduces the peeling cost and improves the peeling efficiency. The obtained GaN wafer has low stress, which is conducive to its use in high-power devices.

[0165] It can be seen from Application Example 1 and Application Example 4 that if the bottom diagonal length W1≠P of the pattern unit in the first direction in the patterned composite substrate, the patterns are not connected.

[0166] It can be seen from Application Examples 1 and 5 that if W1=W2 in the patterned composite substrate, the C-plane disappears and GaN cannot be grown.

[0167] It can be seen from Application Examples 1 and 6 that if W3=80nm in the patterned composite substrate, which is less than 100nm, the GaN growth surface is too small and is not conducive to epitaxy.

[0168] It can be seen from Application Example 1 and Application Examples 7-8 that if the value of H1 in the patterned composite substrate is too small, the GaN layer growth coverage time is too short; if the value of H1 in the patterned composite substrate is too large, the GaN layer growth coverage time is too long.

[0169] It can be seen from Application Examples 1 and 9 that if 0.2H1<H2 in the patterned composite substrate, there is a high risk that the heterogeneous layer at the edge of the wafer will not be etched through.

[0170] It can be seen from Application Examples 1 and 10 that if H2=50nm in the patterned composite substrate, which does not meet the requirement of H2>50nm, there is a high risk that the heterogeneous layer at the edge of the wafer will not be etched through.

[0171] It can be seen from Application Examples 1 and 11 that if H1-H2<H3 in the patterned composite substrate, the etching solution channel is insufficient.

[0172] It can be seen from Application Examples 1 and 12 that if H3=0.1H1 in the patterned composite substrate, the etching solution channel is insufficient.

[0173] It can be seen from Application Example 1 and Application Example 13 that if R1=R2 in the patterned composite substrate, the cross section of the pattern is a circle.

[0174] It can be seen from Application Example 1 and Application Example 14 that if the sapphire substrate does not have a sapphire etching layer, there is a high risk that the heterogeneous layer at the edge of the wafer will not be etched through.

[0175] It can be seen from Application Example 1 and Application Comparative Example 1 that if the graphic unit of the periodic graphic array is a quadrangular pyramid-like structure and the top view of the graphic unit is a regular quadrilateral, the C-surface area is too large and is not easy to peel off.

[0176] It can be seen from Application Example 1 and Application Comparative Example 2 that if there is no gap between adjacent graphic units in the second direction, there is no GaN growth surface.

[0177] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A patterned composite substrate for peeling, characterized in that: The patterned composite substrate includes a sapphire substrate and a plurality of heterogeneous protrusion structures arranged on a surface of one side of the sapphire substrate; The plurality of heterogeneous protrusion structures form a periodic pattern array, the pattern units of the periodic pattern array are hexagonal pyramid-like structures, and the top view of the pattern units is a regular hexagon; The graphic units in the periodic graphic array are connected in a diagonal manner, wherein the direction in which the graphic units are connected in a straight line in a diagonal manner is recorded as a first direction, and the direction in which the graphic units are connected in a straight line in a central axis manner is recorded as a second direction; In the first direction, the bottoms of adjacent graphic units are integrally connected; in the second direction, there are gaps between adjacent graphic units, exposing the C-surface of the sapphire substrate.

2. The patterned composite substrate for peeling according to claim 1, characterized in that: The material of the heterogeneous protrusion structure includes any one of silicon dioxide, silicon nitride, phosphosilicate glass, gallium nitride or aluminum nitride, or a combination of at least two thereof; Preferably, the sapphire substrate comprises a stacked sapphire base plate and a sapphire etching layer, and the sapphire etching layer is located below the graphic unit; The sapphire etching layer includes a plurality of etching units, the adjacent etching units are integrally connected in the first direction, and the gap exists between the adjacent etching units in the second direction.

3. The patterned composite substrate for peeling according to claim 2, characterized in that: The tip spacing between adjacent graphic units is recorded as P, and the value range of P is 1-5 μm; Preferably, the bottom diagonal length of the graphic unit in the first direction is recorded as W1, and W1=P; Preferably, the cross-sectional length of the etching unit in the second direction is recorded as W2, and W1>W2; Preferably, the width of the gap in the second direction is denoted as W3, and W3>100 nm, preferably 100-200 nm.

4. The patterned composite substrate for peeling according to claim 2 or 3, characterized in that: The total height of the etching unit and the graphic unit located above the etching unit is recorded as H1, and the value range of H1 is 0.8-3 μm; Preferably, the height of the etching unit is denoted as H2, 0.2H1>H2>50nm; Preferably, the height of the joint where the bottoms of the graphic units are integrally connected is denoted as H3, and H1-H2>H3>0.1H1.

5. The patterned composite substrate for peeling according to any one of claims 2 to 4, characterized in that: The etching unit and the pattern unit located above the etching unit form a protruding microstructure; The side edge line of the raised microstructure in the first direction is marked as R1, and the height of the side edge surface of the raised microstructure in the second direction is marked as R2, R1>R2.

6. A method for preparing a patterned composite substrate for peeling according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) a heterogeneous layer and a mask layer are sequentially plated on one side surface of a sapphire substrate; (2) patterning the mask layer to form a mask pattern, and then etching the mask layer using an etching process with a bottom width laterally expanded to form a plurality of heterogeneous protrusion structures, thereby obtaining the patterned composite substrate for stripping; Wherein, the plurality of heterogeneous protrusion structures constitute a periodic pattern array, the pattern units of the periodic pattern array are hexagonal pyramid-like structures, and the top view of the pattern units is a regular hexagon; The graphic units in the periodic graphic array are connected in a diagonal manner, wherein the direction of the diagonal straight line connection is recorded as a first direction, and the direction of the graphic units connected in a central axis straight line connection is recorded as a second direction; In the first direction, the bottoms of adjacent graphic units are integrally connected; in the second direction, there are gaps between adjacent graphic units, exposing the C-surface of the sapphire substrate.

7. The preparation method according to claim 6, characterized in that: The material of the mask layer in step (1) includes photoresist; Preferably, the top view of the mask pattern in step (2) is a regular hexagon; Preferably, the etching process for lateral expansion of the bottom width in step (2) comprises the following steps: The mask pattern is morphologically modified so that the front view of the mask pattern is a regular trapezoid, and then the bottom width of the dielectric layer is laterally expanded.

8. The preparation method according to claim 7, characterized in that: During the morphology modification process, the etching gas includes a Cl-based gas and an auxiliary gas; Preferably, the flow rate of the Cl-based gas is 30-90 sccm, and the flow rate of the auxiliary gas is 5-25 sccm; Preferably, the regular trapezoid satisfies the following relationship: the length of the lower base>2×the length of the upper base, and the degree of the base angle is 60-85°; Preferably, in the process of lateral expansion of the bottom width of the dielectric layer, the etching gas includes a Cl-based gas and a F-based gas, the flow rate of the Cl-based gas is 50-150 sccm, and the flow rate of the F-based gas is 0-20 sccm; Preferably, the process of lateral expansion of the bottom width of the dielectric layer is performed under a low bias voltage.

9. The preparation method according to claim 7 or 8, characterized in that: After the heterogeneous protrusion structure is formed in step (2), a post-modification step is further performed, specifically comprising: The overall morphology of the obtained pattern substrate is modified, and the gap area between the pattern units is over-etched so that the sapphire C surface in the gap is exposed; Preferably, the post-modification step is performed using a Cl-based gas under a high bias pressure.

10. An application of the patterned composite substrate for peeling as claimed in any one of claims 1 to 5, characterized in that: The patterned composite substrate for peeling is applied in the field of preparing GaN epitaxial wafers.

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