A wet etching solution and etching method for InP-based disc microcavity
By optimizing the etching solution ratio and light-shielding treatment, the pitting defect problem in wet etching of InP-based ring and disk microcavities was solved, achieving efficient and smooth etching results and improving the performance and repeatability of the microcavity structure.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HAINAN NORMAL UNIV
- Filing Date
- 2026-02-28
- Publication Date
- 2026-06-05
Smart Images
Figure CN122146298A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor micro / nano manufacturing technology, specifically to a smooth, pit-free wet etching solution and etching method for InP-based circular rings and disk microcavities. Background Technology
[0002] InP and its related compounds are widely used in the fabrication of disk and ring-type microcavity lasers due to their excellent optoelectronic properties. For these microcavity structures, which require extremely high uniformity, the sidewall roughness and pit density directly determine the quality factor (Q value), mode purity, scattering loss, and lasing threshold.
[0003] Currently, most mainstream InP microcavity fabrication processes employ wet chemical etching with HBr / HCl / H2O2 / H2O as the primary solvent to form disk or ring structures. However, numerous studies have shown that this traditional etching solution suffers from unstable corrosion kinetics and an extremely narrow process window. In existing wet etching technologies, ambient light is generally not considered a critical process variable requiring strict control. Those skilled in the art typically believe that light shielding is merely a routine requirement for hydrogen peroxide storage, and that the impact of photodecomposition is negligible during the short etching process of tens of minutes. This perception leads process development to focus entirely on adjusting the chemical composition ratios, neglecting the decisive interference of environmental variables on reaction kinetics. Existing technologies lack in-depth discussion of oxidant photoinduced decomposition, nonlinear corrosion kinetics, and bubble masking and suppression mechanisms.
[0004] In summary, there is an urgent need in this field for a novel etching solution and etching method that can fundamentally solve the problem of pitting defects in the wet etching process of InP-based rings and disks to achieve a smooth etching surface. Summary of the Invention
[0005] In view of this, the present invention provides a wet etching solution and etching method for InP-based ring or disk microcavities. This method maintains the inherent advantages of wet etching, such as low cost, high throughput, and no lattice damage, while achieving a uniform, smooth, and pit-free etching morphology. It simultaneously achieves a highly repeatable technical solution for the ideal etching effect of pit-free formation and sidewall smoothing. This provides a reliable technical guarantee for the controllable fabrication of high-performance InP-based ring and disk microcavity lasers.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A wet etching solution for InP-based ring or disk microcavities, the etching solution being a mixture of hydrobromic acid, hydrochloric acid, hydrogen peroxide and deionized water, and the etching solution being allowed to stand for 4-8 hours under light-proof conditions after preparation.
[0008] This invention reveals that in etching solutions targeting high-precision microcavity structures, ambient light disrupts the established precise chemical equilibrium, making it impossible to reproduce the ideal morphology. This is one of the fundamental reasons for the poor repeatability and difficulty in locking the optimal window in existing processes. Allowing the etching solution to stand under light-shielding conditions after preparation aims to balance the microscopic mass transfer and initial reaction of the mixed solution system, eliminating fluctuations caused by temporary concentration gradients and ensuring consistent initial kinetic states for each etching operation. This is a crucial step in achieving high repeatability.
[0009] Preferably, the volume ratio of the corrosive liquid is HBr : HCl : H2O2 : H2O = (8~12) : (1.5~2.5) : (1~1.2) : 50; the mass fraction of H2O2 is 30%.
[0010] Currently, the commonly used classic etching solution ratio is HBr : HCl : H2O2 : H2O = 5 : 1 : 1 : 50. However, numerous studies have shown that under the traditional ratio, a large number of unevenly sized black pits appear on the edge and surrounding area of the disk (see the attached figures in this application specification). Figure 1 Through in-depth research and experiments, the inventors discovered that the root cause of the corrosion pitting problem resulting from the traditional formulation lies in the imbalance of the concentrations of each component, leading to uncontrolled corrosion kinetics. Specifically, the relatively insufficient concentrations of HBr and HCl result in a lower dissolution rate of oxidation byproducts compared to the oxidation rate of InP materials by H2O2. This kinetic imbalance triggers two main negative effects: (1) It causes H2O2 to decompose violently at material defects and generate stable attached bubbles. These bubbles cause local corrosion inhibition through the "masking effect" and form pits after the bubbles fall off. (2) This leads to the adhesion of insoluble or poorly soluble byproducts to the surface, forming a “local electrochemical corrosion cell”, which intensifies the preferential corrosion of specific areas (such as crystal defects).
[0011] Therefore, pit formation is an inevitable phenomenon under the aforementioned imbalanced ratio, with bubbles and byproducts acting as key mediators. Based on this understanding, this invention optimizes the ratio to HBr:HCl:H2O2:H2O = (8-12):(1.5-2.5):(1-1.2):50, significantly improving solubility and restoring the dynamic balance between oxidation and dissolution, thereby eliminating the conditions for pit formation at its root. Preferably, the volume ratio of the corrosive liquid is HBr : HCl : H2O2 : H2O = (10~12) : (2~2.5) : (1~1.2) : 50; and the mass fraction of H2O2 is 30%.
[0012] Preferably, the volume ratio of the corrosive liquid is: HBr : HCl : H2O2 : H2O = 10 : 2 : 1 : 50; the mass fraction of H2O2 is 30%.
[0013] A wet etching method for InP-based annular or disk microcavities, wherein etching is performed under light-shielding conditions using the etching solution described in any one of claims 1 to 3.
[0014] This invention is the first to explicitly propose an inseparable synergistic relationship between optimized formulation and light-shielding environment. Specifically, within the optimized formulation range, "full-process light shading" is a necessary condition for triggering and stabilizing the "critical transition." Under exposure conditions, even with the precise formulation of this invention and the same process conditions and operating environment, H2O2 decomposes rapidly due to photocatalysis, leading to a rapid decrease in the oxidant concentration in the etching solution. Experiments demonstrate that, under the same optimized formulation (10:2:1:50), light shading not only eliminates pitting but also achieves a synergistic optimization of over 20% increase in corrosion rate and a significant reduction in surface roughness. This overturns the traditional understanding that "increasing the corrosion rate inevitably sacrifices surface quality." The mechanism lies in the fact that light shading fundamentally inhibits the photo-induced ineffective decomposition of H2O2, avoiding secondary interference from oxygen microbubbles, thereby firmly "locking" the corrosion kinetics into a diffusion-controlled stable state. Therefore, the "specific formulation" and the "light-shielding environment" together constitute an inseparable, predictable, and highly repeatable process system—a core finding not previously disclosed in existing technologies.
[0015] Preferably, the corrosion is carried out under static conditions at room temperature with complete light shielding, and the corrosion time is 8-12 minutes.
[0016] Preferably, no mechanical shaking or stirring is performed during the corrosion process to avoid localized electrochemical disturbances.
[0017] Preferably, after the corrosion is completed, the InP-based ring or disk is removed and immediately quenched with deionized water, then cleaned and dried.
[0018] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: First, the effect is counterintuitive: in the exact same chemical system, shading does not reduce the reaction rate, but instead significantly improves the corrosion efficiency while enhancing the morphology quality, breaking the traditional technical understanding.
[0019] Second, the mechanism of action is substantial: the key role of light shielding is not only to prevent reagent deterioration, but also to fundamentally avoid the generation of oxygen microbubbles and their secondary masking interference on the surface by inhibiting the photocatalytic decomposition of H2O2 at the corrosion interface, thereby keeping the corrosion kinetics stable in a diffusion-controlled state.
[0020] Third, the technical elements are synergistic: the significant optimization effect of light shading on morphology and rate is only fully realized within the specific ratio range. This indicates that "optimized ratio" and "light-shading environment" constitute an inseparable organic whole, jointly defining a new process window for achieving stable, repeatable, and high-performance corrosion. Without either condition, a smooth, pit-free microcavity structure cannot be reliably obtained.
[0021] This invention breaks through the traditional technical bias that "wet etching does not require strict light avoidance." For the first time, it explicitly establishes "full-process light protection" as a key process variable for achieving and locking the ideal corrosion morphology of InP-based microcavities, and, in conjunction with specific formulations, constitutes a complete, stable, and predictable process system. This discovery provides a new control dimension and theoretical basis for wet etching processes. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0023] Figure 1 : Schematic diagram of microcavity pits in a disk caused by traditional corrosive solutions; Figure 2 Example 1 of this invention: A circular diagram of a disk with a corrosion solution HBr:HCl:H2O2:H2O=10:2:1:50; Figure 3 Example 1 of this invention: A diagram showing the evolution of the corrosion morphology of the disk-ring as a function of acid ratio; Figure 4 Example 2 of the present invention: Comparison of the corrosion effects of light-shielding / non-light-shielding. Figure 5 : Process flow diagram of the corrosion method of the present invention. Detailed Implementation
[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0025] Example 1: (1) Under light-shielding conditions, deionized water, HBr, HCl and H2O2 (30%) were slowly added to the flask in the order of proportions in Table 1 and mixed.
[0026] (2) The purpose of 6 hours of light-shielding and standing is to allow the microscopic mass transfer of the mixed solution system to reach equilibrium with the initial reaction, eliminate fluctuations caused by temporary concentration gradients, and ensure that the initial kinetic state of each corrosion is consistent. This is a key step to achieve high repeatability.
[0027] (3) Under exposure conditions, the patterned InP substrate is completely immersed in the etching solution and etched at 25°C for 10 minutes.
[0028] (4) Immediately quench the reaction with a large amount of deionized water, then remove the glue, wash and dry.
[0029] Table 1 Corrosion results of corrosive solutions with different ratios
[0030] This experiment clearly demonstrates that, as the experimental data of this invention explicitly reveals, the pitting continuously decreases with increasing acid ratio, completely disappearing at a ratio of 10:2:1:50; while the roughness Ra value exhibits a non-monotonic change, first increasing and then suddenly decreasing, dropping sharply to its lowest point at the same ratio and remaining stable. This trend is visually illustrated in the accompanying drawings. Figure 3 This phenomenon indicates that corrosion kinetics undergo a sudden shift from imbalance to uniformity within a specific window, with pit elimination and surface smoothing occurring simultaneously. This exhibits significant unpredictability and high creativity, providing a stable and reliable process basis for the controllable fabrication of high-performance InP microcavities.
[0031] The traditional system has a low acid content, resulting in insufficient ability to dissolve oxidation byproducts. This leads to localized autocatalytic corrosion and severe anisotropic corrosion at grain boundaries and defect regions. Experiments show that increasing the acid concentration based on the traditional formulation results in a non-monotonic change in the surface roughness Ra value, which first increases and then decreases, rather than the expected monotonic improvement. This unpredictable morphological fluctuation reflects a severe imbalance between oxidation and dissolution rates in the traditional process system, making it impossible to achieve synergistic optimization of pit elimination and surface smoothing, further limiting a reliable and repeatable process window.
[0032] In traditional corrosion systems, increasing the acid ratio is generally expected to linearly enhance the corrosion rate. However, this invention reveals for the first time the key window that triggers a nonlinear abrupt change in corrosion kinetics. The corrosion morphology exhibits a unique nonlinear law as the acid ratio evolves (see the accompanying drawings in this application specification). Figure 3Experiments show that as the HBr / HCl ratio gradually increases from the traditional 5:1 ratio, the pitting phenomenon continuously weakens with increasing acid concentration; simultaneously, the surface roughness Ra value exhibits a non-monotonic response, first increasing and then suddenly decreasing. This seemingly contradictory evolution pattern undergoes a synergistic transformation when the ratio enters the range of (8-12):(1.5-2.5):(1-1.2):50—the pits completely disappear, and the Ra value also drops sharply from its peak to a low point and enters a stable plateau. This phenomenon indicates that the corrosion mechanism undergoes a fundamental leap from reaction control to diffusion control within this window, achieving a dynamic balance reconstruction between oxidation and dissolution rates, thereby simultaneously eliminating local masking effects and electrochemical cell effects. This effect of dual-parameter synergistic optimization and synchronous mutation cannot be obtained by linear extrapolation from existing ratios, demonstrating the significant creativity and foresight of this process in corrosion kinetics control.
[0033] The reason for this is that during the roughness-increasing stage, when the acid ratio is increased from the traditional ratio but before reaching the optimization window of this invention, the increase in HBr and HCl concentrations, while improving the solubility, has not yet established an optimal match with the oxidation rate of H2O2. At this point, the increase in the dissolution rate does not completely inhibit selective surface corrosion; instead, it may temporarily exacerbate the uneven etching of surface micro-regions due to differences in local reaction rates, manifested as a gradual increase in the roughness Ra value. This is essentially a kinetic characteristic of the corrosion system transitioning from an unbalanced state to a new equilibrium.
[0034] During the roughness reduction and stabilization phase, when the acid ratio is further increased and enters the optimization window established in this invention, the oxidation and dissolution rates reach a precise dynamic equilibrium. At this point, reaction homogenization is achieved, meaning that sufficient HBr and HCl can instantly remove oxidation byproducts, avoiding any local masking or electrochemical cell formation, allowing the corrosion reaction to proceed synchronously and uniformly across the entire surface; surface passivation layer suppression, meaning that the optimized high-acid environment is conducive to the formation of an extremely thin and uniform passivation intermediate layer on the InP surface, which is rapidly dissolved, and its formation and removal cycles are highly uniform at the microscale, thereby significantly smoothing the surface morphology.
[0035] Therefore, for the critical transition phenomenon, the turning point where roughness increases and then decreases sharply marks a key shift in the corrosion mechanism from reaction-controlled to diffusion-controlled. Under this mechanism, the diffusion advantage at the surface micro-protrusions is eliminated, and corrosion proceeds isotropically, resulting in a precipitous drop in Ra value and the entry into a stable plateau period.
[0036] Example 2: Experiment on the effects of shading / non-shading Following the corrosion method of Example 1, experiments were conducted with and without light shading (indoor light) at the same ratio of 10:2:1:50.
[0037] Table 2 Experimental Results of the Effect of Shading / Non-Shading
[0038] Comparison of corrosion effects under light-shielding and non-light-shielding conditions, as shown in the attached diagram of the instruction manual. Figure 4 As shown, this comparison strongly demonstrates that, under the stated formulation, the shading condition is not merely an auxiliary step, but rather the key to achieving the synergistic optimization of "high rate and high smoothness." Under non-shading conditions, even with the optimal formulation, the effective oxidant will decay due to H2O2 photolysis, and bubble interference will be introduced, causing the system to deviate from steady state and recurring the roughening problem. Under the same optimized formulation, the shading treatment yielded a significantly smoother surface morphology and a higher corrosion rate. This proves that shading is a necessary condition for achieving stable kinetics and an indispensable synergistic element for realizing the "critical transition window" described in this invention. This indicates that shading effectively suppresses the photodecomposition of H2O2, maintains the steady state of oxidation-dissolution kinetics, improves process efficiency, and ensures the consistency and controllability of the morphology. This embodiment confirms that the integrated "formulation-shading" technical solution is indispensable for obtaining stable, repeatable, and excellent corrosion results.
[0039] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.
[0040] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A wet etching solution for InP-based annular or disk microcavities, characterized in that, The etching solution is a mixture of hydrobromic acid, hydrochloric acid, hydrogen peroxide and deionized water. After preparation, the etching solution is left to stand for 4 to 8 hours under light-proof conditions.
2. The wet etching solution for InP-based annular or disk microcavities according to claim 1, characterized in that, The volume ratio of the corrosive liquid is HBr : HCl : H2O2 : H2O = (8~12) : (1.5~2.5) : (1~1.2) : 50; the mass fraction of H2O2 is 30%.
3. The wet etching solution for InP-based annular or disk microcavities according to claim 1, characterized in that, The volume ratio of the corrosive liquid is HBr : HCl : H2O2 : H2O = (10~12) : (2~2.5) : (1~1.2) : 50; the mass fraction of H2O2 is 30%.
4. The wet etching solution for InP-based annular or disk microcavities according to claim 1, characterized in that, The volume ratio of the corrosive liquid is HBr : HCl : H2O2 : H2O = 10 : 2 : 1 : 50; the mass fraction of H2O2 is 30%.
5. A wet etching method for InP-based annular or disk microcavities, characterized in that, The etching is performed under light-shielding conditions using the etching solution described in any one of claims 1 to 4.
6. The wet etching method for InP-based annular or disk microcavities according to claim 5, characterized in that, The corrosion process was carried out under static conditions at room temperature with complete shading, and the corrosion time was 8-12 minutes.
7. The wet etching method for InP-based annular or disk microcavities according to claim 6, characterized in that, No mechanical shaking or stirring is performed during the corrosion process.
8. A wet etching method for InP-based annular or disk microcavities according to claim 6, characterized in that, After etching is complete, remove the InP-based ring or disk and immediately quench the reaction with deionized water, then clean and dry it.