Epitaxial layer structure for electrochemical corrosion of GaN nanopore and electrochemical corrosion method

Abstract

The invention relates to the technical field of semiconductor manufacturing, in particular to an epitaxial layer structure for GaN nanopore electrochemical corrosion and an electrochemical corrosion method. A bottom uGaN layer which is not doped with GaN and has a thickness of 1-2 [mu] m; the Si doping concentration of the current diffusion layer is 1 * 10 < 19 > / cm < 3 >, and the thickness of the current diffusion layer is 0.1-0.5 mu m; the Si doping concentration of the gradient cut-off layer is gradually increased from 1 * 10 < 18 > / cm < 3 > to 5 * 10 < 18 > / cm < 3 > in a gradient manner, and the thickness of the gradient cut-off layer is 0.5-1 The Si doping concentration of the nanopore structure layer is 5 * 10 < 18 > / cm < 3 >, and the thickness is 1-10 [mu] m; and the Si doping concentration of the surface protection layer is 4 * 10 < 18 > / cm < 3 >, and the thickness is 0.3-0.5 mu m. The invention provides an optimized epitaxial layer structure design aiming at the problem of poor consistency of pore morphology (pore diameter, pore depth and pore density) caused by non-uniform current distribution in the process of preparing a nano-porous structure through GaN electrochemical corrosion in the prior art. According to the design, a surface protection layer with specific doping concentration, a doping concentration gradient transition region between a functional layer and a diffusion layer and a bottom current diffusion layer are introduced in the GaN epitaxial growth process.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a method and structural design for improving the uniformity of GaN electrochemical corrosion by optimizing the doping structure of an epitaxial layer. Background Art

[0002] GaN electrochemical etching is a conventional electrochemical etching process, typically using acidic substances such as hydrochloric acid, nitric acid, and oxalic acid. Electrochemical etching creates cavities by conducting an electric current. In Si-doped n-type GaN structures, the etching size, rate, and aspect ratio can be controlled. This structure is commonly used for in-situ LED chip-level packaging or surface treatment of some optical devices. Conventional etching processes often result in significant inconsistencies in etching rate, pore uniformity, and depth due to current diffusion within the nGaN epitaxial layer. Excessive current can also cause surface structure loss, preventing the formation of uniform, nanoporous cavities. Electrochemical etching of GaN materials (typically using acidic electrolytes such as hydrochloric acid, nitric acid, or oxalic acid) is a common method for fabricating nanoporous structures. By applying an electric current to n-type (usually Si-doped) GaN, nanopores can be controllably formed, with their size, etching rate, and aspect ratio being regulated. This structure has potential applications in areas such as in-situ LED chip packaging and surface treatment of optical devices.

[0003] A key challenge facing existing technologies is that, when performing large-scale electrochemical etching on conventional n-type GaN epitaxial layers, the uneven diffusion of current within the GaN material leads to significant variations in the etching rate, resulting in nanopore diameter, pore depth, and pore density across different regions. This unevenness not only affects the uniformity of the nanopore structure but can also lead to excessive corrosion and flaking of the GaN surface in localized areas with excessively high current density, making it difficult to achieve a uniform, nanoporous structure over a large area. Summary of the Invention

[0004] The object of the present invention is to provide an epitaxial layer structure and an electrochemical etching method for GaN nanopore electrochemical etching, so as to solve the problems raised in the above background technology.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an epitaxial layer structure for electrochemical etching of GaN nanopores, comprising, from bottom to top:

[0006] Sapphire substrate;

[0007] Bottom uGaN layer, undoped GaN, 1-2 μm thick;

[0008] Current diffusion layer, Si doping concentration 1×10 19 / cm 3, thickness 0.1-0.5μm;

[0009] Gradual cut-off layer, Si doping concentration from 1×10 18 / cm 3 , the gradient increases to 5×10 18 / cm 3 , thickness 0.5-1μm;

[0010] Nanoporous structure layer, Si doping concentration 5×10 18 / cm 3 , thickness 1-10 μm;

[0011] Surface protection layer, Si doping concentration 4×10 18 / cm 3 , thickness 0.3-0.5μm.

[0012] Preferably, the doping concentration gradient of the graded cutoff layer increases linearly or exponentially.

[0013] Preferably, the electron mobility of the current diffusion layer is greater than 50 cm 2 / V·s.

[0014] A GaN nanopore electrochemical etching method, characterized by comprising:

[0015] epitaxially growing a bottom uGaN layer, a current diffusion layer, a gradient cutoff layer, a nanopore structure layer and a surface protection layer on a sapphire substrate in sequence;

[0016] The surface protective layer is electrochemically corroded using an acidic electrolyte, and the following is achieved through a doping concentration gradient:

[0017] a) The surface protective layer limits the initial current density and prevents excessive corrosion of the orifice;

[0018] b) The nanopore structure layer guides the current to penetrate longitudinally to form the target nanopore;

[0019] c) Gradient cutoff layer dynamically adjusts the corrosion depth consistency;

[0020] d) The current spreading layer provides laterally uniform current distribution.

[0021] Preferably, the acidic electrolyte is hydrochloric acid, nitric acid or oxalic acid solution.

[0022] Preferably, the current density during the corrosion process is controlled at 1-100 mA / cm 2 .

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention addresses the problem of uneven current distribution in the existing GaN electrochemical corrosion process for preparing nanoporous structures, which leads to poor consistency in pore morphology (pore diameter, pore depth, and pore density). By doing so, the present invention provides an optimized epitaxial layer structure design. This design introduces a surface protection layer with a specific doping concentration, a doping concentration gradient transition zone between the functional layer and the diffusion layer, and a bottom current diffusion layer during the GaN epitaxial growth process. This structure can effectively guide and homogenize the current path during the electrochemical corrosion process, enabling highly uniform current diffusion across the entire wafer surface. This significantly improves the pore diameter consistency, pore depth consistency, and pore density uniformity of the formed nanopores, while avoiding surface structural damage caused by excessive local current. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 is a table of epitaxial growth parameters of the present invention;

[0027] Figure 2 This is a flow chart of a GaN nanopore electrochemical corrosion method of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] See also Figures 1 to 2 , the present invention provides a technical solution:

[0030] An epitaxial layer structure for electrochemical etching of GaN nanopores, comprising, from bottom to top:

[0031] Sapphire substrate;

[0032] Bottom uGaN layer, undoped GaN, 1-2 μm thick;

[0033] Current diffusion layer, Si doping concentration 1×10 19 / cm 3 , thickness 0.1-0.5μm;

[0034] Gradual cut-off layer, Si doping concentration from 1×10 18 / cm 3 , the gradient increases to 5×10 18 / cm 3 , thickness 0.5-1μm;

[0035] Nanoporous structure layer, Si doping concentration 5×10 18 / cm 3 , thickness 1-10 μm;

[0036] Surface protection layer, Si doping concentration 4×10 18 / cm 3 , thickness 0.3-0.5μm.

[0037] Specifically, the doping concentration gradient of the graded cut-off layer increases linearly or exponentially.

[0038] Specifically, the electron mobility of the current diffusion layer is greater than 50 cm 2 / V·s.

[0039] A GaN nanopore electrochemical etching method, characterized by comprising:

[0040] epitaxially growing a bottom uGaN layer, a current diffusion layer, a gradient cutoff layer, a nanopore structure layer and a surface protection layer on a sapphire substrate in sequence;

[0041] The surface protective layer is electrochemically corroded using an acidic electrolyte, and the following is achieved through a doping concentration gradient:

[0042] a) The surface protective layer limits the initial current density and prevents excessive corrosion of the orifice;

[0043] b) The nanopore structure layer guides the current to penetrate longitudinally to form the target nanopore;

[0044] c) Gradient cutoff layer dynamically adjusts the corrosion depth consistency;

[0045] d) The current spreading layer provides laterally uniform current distribution.

[0046] Specifically, the acidic electrolyte is hydrochloric acid, nitric acid or oxalic acid solution.

[0047] Specifically, the current density during the corrosion process is controlled at 1-100 mA / cm 2 .

[0048] The current dynamic regulation system is constructed through a four-layer collaborative structure of surface protection layer (low doping) - nanopore structure layer (medium doping) - gradual cutoff layer (gradient doping) - current diffusion layer (high doping):

[0049] Surface protection layer (low Si doping 4×1018 / cm 3 ):

[0050] Limit the initial corrosion current and avoid hole collapse;

[0051] After the hole is opened, the current automatically flows to the bottom of the hole because the resistance of the lower layer is lower.

[0052] Nanoporous structure layer (Si doped 5×10 18 / cm 3 ):

[0053] As the main corrosion zone, high doping ensures corrosion efficiency.

[0054] Gradient cutoff layer (1×10 18 ~5×10 18 / cm 3 gradient):

[0055] Compensation for local corrosion rate differences through resistance gradients;

[0056] The faster corrosion area is limited by the high resistance, while the slower corrosion area is accelerated by the low resistance.

[0057] Current diffusion layer (ultra-high doping 1×10 19 / cm 3 ):

[0058] Achieve uniform lateral current distribution and eliminate the difference between edge and center

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An epitaxial layer structure for electrochemical corrosion of GaN nanopores, characterized by: From bottom to top, they include: Sapphire substrate; Bottom uGaN layer, undoped GaN, 1-2 μm thick; Current diffusion layer, Si doping concentration 1×10 19 / cm 3 , thickness 0.1-0.5μm; Gradual cut-off layer, Si doping concentration from 1×10 18 / cm 3 , the gradient increases to 5×10 18 / cm 3 , thickness 0.5-1μm; Nanoporous structure layer, Si doping concentration 5×10 18 / cm 3 , thickness 1-10 μm; Surface protection layer, Si doping concentration 4×10 18 / cm 3 , thickness 0.3-0.5μm.

2. The epitaxial layer structure for GaN nanopore electrochemical corrosion according to claim 1, characterized in that: The doping concentration gradient of the graded cut-off layer increases linearly or exponentially.

3. The epitaxial layer structure for GaN nanopore electrochemical corrosion according to claim 1, characterized in that: The electron mobility of the current diffusion layer is >50cm 2 / V·s.

4. A GaN nanopore electrochemical corrosion method, characterized in that: include: epitaxially growing a bottom uGaN layer, a current diffusion layer, a gradient cutoff layer, a nanopore structure layer and a surface protection layer on a sapphire substrate in sequence; The surface protective layer is electrochemically corroded using an acidic electrolyte, and the following is achieved through a doping concentration gradient: a) The surface protective layer limits the initial current density and prevents excessive corrosion of the orifice; b) The nanopore structure layer guides the current to penetrate longitudinally to form the target nanopore; c) Gradient cutoff layer dynamically adjusts the corrosion depth consistency; d) The current spreading layer provides laterally uniform current distribution.

5. The GaN nanopore electrochemical etching method according to claim 4, characterized in that: The acidic electrolyte is hydrochloric acid, nitric acid or oxalic acid solution.

6. The GaN nanopore electrochemical etching method according to claim 4, characterized in that: The current density during the corrosion process is controlled at 1-100mA / cm 2 .

Images