Single crystal silicon surface treatment method based on multi-stage etching

Abstract

The present invention discloses a single crystal silicon surface treatment method based on multi-stage etching, relating to the technical field of semiconductor material surface treatment, including coating a photoresist layer on the surface of a single crystal silicon substrate, forming a mask of a preset pattern in the photoresist layer by a photolithography process; using a first etching solution to preliminarily etch the single crystal silicon substrate; adding an isopropyl alcohol additive to the first etching solution, adjusting the concentration of the isopropyl alcohol additive to 5-10wt%, and continuing to etch the single crystal silicon substrate; cleaning the surface of the single crystal silicon substrate with deionized water, and then finely etching the single crystal silicon substrate using a second etching solution; drying the surface of the single crystal silicon substrate with nitrogen to obtain a single crystal silicon substrate with a preset pattern structure. The present invention achieves a high-precision, stable single crystal silicon substrate pretreatment and pattern structure formation process by accurately controlling photolithography and etching processes.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor material surface treatment, in particular to a single crystal silicon surface treatment method based on multi-stage etching. Background Art

[0002] With the rapid development of microelectronics technology and the semiconductor industry, single-crystal silicon, as an important semiconductor material, has attracted increasing attention from researchers for its precise control of surface microstructures and processing technology. Single-crystal silicon surface treatment technology has been widely used in the fields of micro-electromechanical systems (MEMS), integrated circuits (ICs), optoelectronic devices, etc. Traditional single-crystal silicon surface treatment methods mainly include dry etching and wet etching. Among them, wet etching has been widely used in industrial production due to its advantages such as simple process, low cost, and suitability for large-scale production. However, when performing deep micron or submicron fine structure processing, existing wet etching technology often has technical difficulties such as insufficient anisotropy control, uneven etching rate, and large surface roughness, which seriously restricts the preparation and development of high-precision single-crystal silicon devices.

[0003] Currently, the industry generally uses a single etching process to treat the surface of single-crystal silicon. This method is difficult to meet the dual requirements of etching depth and surface quality at the same time. In practical applications, if a rapid etching process is used, although it can improve processing efficiency, it is easy to cause problems such as uneven etching and irregular contours; if a mild etching process is used, although better surface quality can be obtained, the process cycle is long and production efficiency is low. In addition, the existing technology lacks effective means to control the surface tension during the etching process, which leads to low precision in the control of microstructure morphology. In particular, when preparing structures with high aspect ratios, defects such as chamfers and rough sidewalls often occur. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention proposes a single crystal silicon surface treatment method based on multi-stage etching.

[0005] Therefore, the present invention provides a single crystal silicon surface treatment method based on multi-stage etching, which can solve the problems mentioned in the background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides a single crystal silicon surface treatment method based on multi-stage etching, which comprises:

[0008] Coating a photoresist layer on the surface of a single crystal silicon substrate, and forming a mask of a preset pattern on the photoresist layer through a photolithography process;

[0009] Preliminarily etching the single crystal silicon substrate using a first etching solution;

[0010] adding an isopropyl alcohol additive to the first etching solution, adjusting the concentration of the isopropyl alcohol additive to 5-10 wt %, and continuing to etch the single crystal silicon substrate;

[0011] Cleaning the surface of the single crystal silicon substrate with deionized water, and then finely etching the single crystal silicon substrate with a second etching solution;

[0012] The surface of the single crystal silicon substrate is dried by nitrogen to obtain a single crystal silicon substrate with a preset pattern structure.

[0013] As a preferred embodiment of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, the first etching solution comprises potassium hydroxide crystals, ultrapure deionized water, high-purity ethylene glycol and electronic grade tetramethylammonium hydroxide;

[0014] Place the mixture in a fume hood and use a 500 ml glass reaction bottle with four necks to prepare the solution. Add the weighed potassium hydroxide crystals to the pre-mixed deionized water and stir with a PTFE-coated magnetic stir bar until the potassium hydroxide is completely dissolved.

[0015] A pre-prepared mixture of ethylene glycol and tetramethylammonium hydroxide was added dropwise to the solution at a rate of 2 ml / min while maintaining a constant stirring speed. A pH meter was used to monitor the pH value of the solution in real time to ensure that the final pH value was stable at 13.5±0.2, the dynamic viscosity at 25°C was 3.8-4.2 mPa·s, and the surface tension was maintained in the range of 72-75 mN / m.

[0016] As a preferred embodiment of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, the preliminary etching comprises:

[0017] During the etching process, a PTFE-coated stirring paddle with variable frequency speed regulation was used for uniform stirring at a speed of 120±2rpm. The diameter of the stirring paddle was 1 / 3 of the groove diameter and the height from the groove bottom was 1 / 4 of the groove depth.

[0018] When the etching depth was detected to reach 8-10 μm, the etching was terminated and the sample was lifted out of the etching solution at a speed of 2 cm / min.

[0019] As a preferred embodiment of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, the step of adding isopropyl alcohol additive to the first etching solution comprises:

[0020] The isopropyl alcohol additive was injected into the first etching solution at a constant drop rate of 0.5±0.1 ml / min, and the drop position was located 2-3 cm below the stirring paddle. During the drop addition process, a mechanical stirrer was used to stir uniformly at a speed of 150 rpm. After each drop of 50 ml of isopropyl alcohol, a pause of 2 minutes was made. The mixed solution was sampled and tested using a digital density meter, and the density value change curve was recorded. When the mass fraction of the isopropyl alcohol additive reached 7.5±2.5 wt%, the drop addition was stopped.

[0021] As a preferred solution of the single crystal silicon surface treatment method based on multi-stage etching according to the present invention, further etching the single crystal silicon substrate comprises:

[0022] Slowly immersing the single crystal silicon substrate in the first etching solution modified with the isopropyl alcohol additive, continuously stirring with a stirrer at a speed of 120±5 rpm, while monitoring the etching solution temperature in real time with an infrared thermometer to ensure that the temperature fluctuation does not exceed ±2°C, and calculating the etching depth based on the change in interference fringes;

[0023] When the change in the interference fringe spacing is observed, which corresponds to an increase in the etching depth of 4-5 μm, the automatic pulling device is started to lift the single crystal silicon substrate out of the etching solution at a uniform speed.

[0024] As a preferred solution of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, the etching depth is calculated as shown in the following formula:

[0025]

[0026] in, for The cumulative etching depth at the moment, is the real-time etching rate, is the laser wavelength, is the etching depth, Temperature The refractive index under is the background light intensity, is the fringe visibility, is the concentration influence coefficient, is the comprehensive correction coefficient, is the isopropanol concentration, The midpoint of the interference pattern The light intensity at.

[0027] As a preferred embodiment of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, 25 wt % analytically pure tetramethylammonium hydroxide solution and deionized water are mixed in a volume ratio of 3:7 to prepare the second etching solution with a concentration of 7.5 wt %;

[0028] 0.1 wt % of a surfactant and 0.05 wt % of a complexing agent were added to the second etching solution, and the pH value was adjusted to 12.5±0.1 by dropwise adding dilute nitric acid.

[0029] As a preferred solution of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, the fine etching includes:

[0030] The prepared second etching solution was preheated to 80±1°C, and the cleaned single crystal silicon substrate was slowly immersed in the second etching solution at an inclination angle of 15°, with the immersion speed controlled at 1 cm / min. During the etching process, a magnetic stirrer was used for gentle stirring at a speed of 80 rpm. At the same time, the evolution of the etching morphology was observed in real time using a differential interference microscope. A small amount of solution was removed from the etching solution every 30 seconds, and the changes in the solution composition were monitored using a conductivity meter. Fresh etching solution was dynamically added based on the measurement results to maintain a constant etching solution concentration.

[0031] In a second aspect, an embodiment of the present invention provides a single crystal silicon surface treatment system based on multi-stage etching, which includes:

[0032] A mask generation module is used to coat a photoresist layer on the surface of a single crystal silicon substrate and form a mask of a preset pattern on the photoresist layer through a photolithography process;

[0033] A preliminary etching module, configured to perform preliminary etching on the single crystal silicon substrate using a first etching solution;

[0034] a modification module, configured to add an isopropyl alcohol additive to the first etching solution, adjust the concentration of the isopropyl alcohol additive to 5-10 wt %, and continue etching the single crystal silicon substrate;

[0035] The fine etching module is used to clean the surface of the single crystal silicon substrate with deionized water, and then finely etch the single crystal silicon substrate with a second etching solution.

[0036] The beneficial effect of the present invention is that the invention realizes a high-precision and strong stability single crystal silicon substrate pretreatment and graphic structure formation process by precisely controlling the photolithography and etching processes. First, the photoresist is coated by vacuum adsorption and precise temperature control, and the mask pattern is formed by ultraviolet exposure and development process to ensure high resolution of the graphics. Then, by optimizing the etching solution preparation and temperature control system, combined with real-time process monitoring and data feedback, precise etching of the single crystal silicon substrate is achieved. In particular, the improved multi-parameter coupling calculation method improves the accuracy and anti-interference ability of the etching depth measurement, and significantly improves the accuracy and reliability of depth monitoring during silicon wafer etching. In addition, deionized water cleaning and fine etching are used to ensure the surface quality and accuracy of the graphics, and finally a high-quality single crystal silicon substrate with a preset graphic structure is obtained. The present invention provides an efficient, precise and reliable manufacturing process suitable for the manufacture of high-precision semiconductor devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0038] Figure 1 The present invention is a flow chart of a single crystal silicon surface treatment method based on multi-stage etching. DETAILED DESCRIPTION

[0039] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0040] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0042] The present invention is described in detail with reference to schematic diagrams. For ease of illustration, cross-sectional views of device structures may be partially enlarged and not to scale when describing embodiments of the present invention. Furthermore, the schematic diagrams are merely illustrative and should not limit the scope of the present invention. Furthermore, in actual production, the three-dimensional dimensions of length, width, and depth should be included.

[0043] In the description of the present invention, it should be noted that the terms "upper, lower, inner, and outer" and other references to orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first, second, or third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0044] In this disclosure, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they may refer to fixed, removable, or integral connections. They may also refer to mechanical, electrical, or direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this disclosure.

[0045] Reference Figure 1 , which is the first embodiment of the present invention, provides a single crystal silicon surface treatment method based on multi-stage etching, comprising:

[0046] S1: coating a photoresist layer on the surface of a single crystal silicon substrate, and forming a mask of a preset pattern on the photoresist layer through a photolithography process;

[0047] In a clean room environment, a pretreated single crystal silicon substrate is placed on a rotating platform of a coating machine, and the single crystal silicon substrate is fixed by vacuum adsorption; a positive photoresist AZ6270 is heated to 23-25° C., and a syringe is used to evenly drop the photoresist on the center of the surface of the single crystal silicon substrate at a flow rate of 2-3 ml / s; the coating machine is started, and the rotating platform is rotated at a speed of 500 rpm for 30 seconds to spread the photoresist, and then rotated at a speed of 3000 rpm for 60 seconds to complete the photoresist coating, to obtain the photoresist layer with a thickness of 2.0-2.2 μm; the substrate coated with the photoresist layer is placed on a plate The single crystal silicon substrate is placed on a heating plate at a temperature of 95±2°C and pre-baked for 5 minutes; the pre-baked single crystal silicon substrate is transferred to the alignment platform of the photolithography machine, and after the mask is precisely aligned with the photoresist layer, the photoresist layer is exposed to ultraviolet light with a wavelength of 365nm and an energy of a light intensity of 15mW / cm² for 10 seconds; the exposed photoresist layer is developed using developer AZ300MIF, with a development time of 45-50 seconds and a development temperature of 25°C, followed by rinsing with deionized water for 60 seconds and gently drying with a nitrogen flow to form a mask with a preset pattern on the photoresist layer.

[0048] S2: Preliminary etching of the single crystal silicon substrate using a first etching solution;

[0049] Analytical-grade potassium hydroxide crystals (purity ≥99.99%, particle size 45-75 μm) were pretreated in a desiccator for 24 hours to remove surface adsorbed moisture. Potassium hydroxide crystals, ultrapure deionized water (resistivity ≥18.2 MΩ·cm), high-purity ethylene glycol (purity ≥99.8%), and electronic-grade tetramethylammonium hydroxide (mass fraction 25%) were accurately weighed using an electronic balance in a mass ratio of 2:6:1:1.

[0050] Place the mixture in a fume hood and prepare the solution using a 500 ml glass reaction bottle with four necks. Slowly add the weighed potassium hydroxide crystals to the pre-mixed deionized water and stir at 200 rpm using a PTFE-coated magnetic stir bar until the potassium hydroxide is completely dissolved.

[0051] A pre-prepared mixture of ethylene glycol and tetramethylammonium hydroxide (mixed in advance) was added dropwise to the solution at a rate of 2 ml / min while maintaining a constant stirring speed. A pH meter was used to monitor the pH value of the solution in real time to ensure that the final pH value was stable at 13.5 ± 0.2. A programmable rotational viscometer was used to measure the viscosity of the prepared etching solution, and the dynamic viscosity value at 25°C was recorded as 3.8-4.2 mPa·s. A surface tension meter was used to measure the surface tension of the etching solution to ensure that the value was maintained within the range of 72-75 mN / m.

[0052] The prepared etching solution was filtered through a 0.1μm PTFE membrane filter to remove any insoluble particles. A quartz etching tank (2000ml capacity, 5mm wall thickness) with a PID temperature control system was used, and a sandwich circulating heating device was installed on the tank wall. Four thermocouple temperature sensors were installed around the etching tank, and the temperature distribution was monitored in real time by a multi-point temperature measurement system. The circulating heating system was started, the heating power was set to 800W, and the etching solution was heated to 65±5℃ at a heating rate of 2℃ / min. A digital thermometer was used to inspect different locations of the etching solution to ensure that the temperature field uniformity deviation did not exceed ±1℃.

[0053] The single crystal silicon substrate, having undergone the photolithography process, was secured to a polytetrafluoroethylene fixture and slowly immersed in the first etching solution at a 30° angle. During the etching process, a variable frequency PTFE-coated stirring paddle was used for uniform stirring at a speed of 120±2 rpm. The diameter of the stirring paddle was 1 / 3 of the groove diameter, and the height from the groove bottom was 1 / 4 of the groove depth.

[0054] The data acquisition system monitors and records process parameters such as temperature, pH value, and stirring speed in real time. When the etching depth is detected to reach 8-10μm (the corresponding change in the reflected signal intensity reaches the preset threshold), the system automatically sends a prompt signal. After confirming the etching depth, the sample is lifted out of the etching solution at a speed of 2cm / min. The entire etching process lasts 12-15 minutes, during which the etching rate-time curve is plotted by computer to monitor the stability of the etching process.

[0055] S3: adding isopropyl alcohol additive to the first etching solution, adjusting the concentration of the isopropyl alcohol additive to 5-10 wt %, and continuing to etch the single crystal silicon substrate;

[0056] High-purity isopropyl alcohol (purity ≥99.9%) was precooled to 15±1°C in a low-temperature constant-temperature water bath; the isopropyl alcohol additive was injected into the first etching solution at a constant drop rate of 0.5±0.1 ml / min using a precision pipette system equipped with a temperature sensor, with the drop addition position located 2-3 cm below the stirring paddle; during the drop addition process, a mechanical stirrer was used to stir uniformly at a speed of 150 rpm, with the stirring paddle made of polytetrafluoroethylene and having a blade diameter of 1 / 3 of the inner diameter of the etching tank; after each drop of 50 ml of isopropyl alcohol, a 2-minute pause was maintained, and the mixed solution was sampled and tested using a digital density meter, and the density change curve was recorded. Drop addition was stopped when the mass fraction of the isopropyl alcohol additive reached 7.5±2.5 wt% (corresponding to a density value of 1.18-1.22 g / cm³).

[0057] The modified etching solution was transferred to an ultrasonic processor equipped with an automatic temperature compensation system, the ultrasonic power was set to 200±10W, the frequency was 40kHz, and ultrasonic dispersion treatment was performed at 65±5°C for 60±5 seconds; a dynamic light scattering instrument was used to test the particle size distribution of the treated etching solution to ensure that the mixing uniformity reached more than 95%; the modified etching solution after ultrasonic treatment was filtered through a 0.22μm PTFE filter membrane to remove any small particles.

[0058] The single crystal silicon substrate was slowly immersed in the filtered modified etching solution at a 30° inclination angle using a special PTFE fixture, and the fixture lifting speed was adjusted to 2 cm / min. During the etching process, a stirrer was used to continuously stir at a speed of 120±5 rpm, and the etching solution temperature was monitored in real time using an infrared thermometer to ensure that the temperature fluctuation did not exceed ±2°C. A laser interferometer was installed 30 cm above the etching tank, and a He-Ne laser beam with a wavelength of 632.8 nm was used to scan the silicon surface in real time, and the etching depth was calculated based on the changes in the interference fringes.

[0059] When the change in the interference fringe spacing corresponding to an increase in etching depth of 4-5 μm is observed, the automatic pulling device is started to uniformly lift the single crystal silicon substrate out of the etching solution at a speed of 2 cm / min; during the entire etching process, the temperature, stirring speed, etching depth and other process parameters are recorded every 30 seconds by the data acquisition system, and the etching kinetics curve is plotted by computer software.

[0060] It should be noted that in the actual etching process, the local temperature fluctuation range can reach ±5°C. Experimental verification shows that every 1°C temperature fluctuation will result in a depth calculation error of about 0.12μm. The traditional method only considers the refractive index at a single temperature and ignores the impact of temperature fluctuations. Therefore, this embodiment uses an improved multi-parameter coupling calculation method to calculate the etching depth:

[0061] First, considering the effect of temperature on the refractive index, the temperature-corrected refractive index calculation formula is established:

[0062]

[0063] in, is the refractive index at temperature T, Standard temperature The refractive index under and are the first-order and second-order temperature coefficients, respectively.

[0064] The influence factor of etching solution concentration on interference fringes is introduced:

[0065]

[0066] in, is the phase difference, is the laser wavelength, is the etching depth, is the isopropanol concentration, is the concentration influence coefficient.

[0067] Further consider the nonlinear relationship between fringe intensity and depth:

[0068]

[0069] in, The midpoint of the interference pattern The light intensity at is the background light intensity, is the fringe visibility, is the initial phase distribution.

[0070] Introduce the modified equation for depth calculation:

[0071]

[0072] in, is the comprehensive correction factor:

[0073]

[0074] in, and is the dynamic correction coefficient, is the characteristic frequency of the etching process, is the system characteristic time constant.

[0075] The final real-time etching depth is obtained by time domain integration:

[0076]

[0077] in, for The cumulative etching depth at the moment, is the real-time etching rate, is the laser wavelength, is the etching depth, Temperature The refractive index under is the background light intensity, is the fringe visibility, is the concentration influence coefficient, is the comprehensive correction coefficient, is the isopropanol concentration, The midpoint of the interference pattern The light intensity at.

[0078] The best solution is to introduce temperature-corrected refractive index calculation to achieve a 76% improvement in measurement accuracy, a 70% reduction in response time, a 2.8-3.5-fold increase in anti-interference capability, and an extension of the applicable depth range to 0.5-15μm. This significantly improves the accuracy and reliability of real-time depth monitoring during silicon wafer etching.

[0079] S4: cleaning the surface of the single crystal silicon substrate with deionized water, and then finely etching the single crystal silicon substrate with a second etching solution, wherein the second etching solution is a tetramethylammonium hydroxide solution;

[0080] After the first stage of etching, the single-crystal silicon substrate was placed in a multi-stage cleaning apparatus for cleaning. First, the substrate was spray-cleaned with deionized water (resistivity ≥18.2 MΩ·cm) at 35±2°C, with a spray pressure of 0.2-0.3 MPa and a spray time of 60±5 seconds. The substrate was then immersed in an ultrasonic cleaning tank and ultrasonically cleaned at 40 kHz and a power density of 1.5 W / cm² for 120±10 seconds. Finally, a high-speed spin drying process (4000 rpm for 30 seconds) was used to remove any residual surface moisture. The hydrophilicity of the silicon wafer surface was tested using a contact angle meter to ensure the contact angle was less than 5°.

[0081] A 25 wt% analytically pure tetramethylammonium hydroxide solution and deionized water were mixed in a volume ratio of 3:7 to prepare a second etching solution with a concentration of 7.5 wt%; 0.1 wt% of a surfactant (polyoxyethylene ether) was added to the prepared solution to improve wettability, and 0.05 wt% of a complexing agent (ethylenediaminetetraacetic acid) was added to chelate metal ions; the pH value of the solution was measured using a precision pH meter, and the pH value was adjusted to 12.5±0.1 by dropwise addition of dilute nitric acid.

[0082] The prepared second etching solution was preheated to 80±1°C, and a high-precision temperature control system was used to maintain temperature stability. The cleaned single crystal silicon substrate was slowly immersed in the second etching solution at an inclination angle of 15°, and the immersion speed was controlled at 1 cm / min. During the etching process, a magnetic stirrer was used for gentle stirring at a speed of 80 rpm, and the evolution of the etching morphology was observed in real time using a differential interference microscope. A small amount of solution was removed from the etching solution every 30 seconds, and the changes in the solution components were monitored using a conductivity meter. Fresh etching solution was dynamically added based on the measurement results to maintain a constant etching solution concentration.

[0083] S5: using nitrogen to blow dry the surface of the single crystal silicon substrate to obtain a single crystal silicon substrate having a preset pattern structure.

[0084] Furthermore, this embodiment also provides a single crystal silicon surface treatment system based on multi-stage etching, comprising:

[0085] A mask generation module is used to coat a photoresist layer on the surface of a single crystal silicon substrate and form a mask of a preset pattern on the photoresist layer through a photolithography process;

[0086] A preliminary etching module, configured to perform preliminary etching on the single crystal silicon substrate using a first etching solution;

[0087] a modification module, configured to add an isopropyl alcohol additive to the first etching solution, adjust the concentration of the isopropyl alcohol additive to 5-10 wt %, and continue etching the single crystal silicon substrate;

[0088] The fine etching module is used to clean the surface of the single crystal silicon substrate with deionized water, and then finely etch the single crystal silicon substrate with a second etching solution.

[0089] This embodiment also provides a computer device, which is suitable for the case of a single crystal silicon surface treatment method based on multi-stage etching, including a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute computer-executable instructions to implement the single crystal silicon surface treatment method based on multi-stage etching proposed in the above embodiment.

[0090] The computer device may be a terminal, comprising a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device comprises a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner may be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a button, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse.

[0091] This embodiment further provides a storage medium storing a computer program, which, when executed by a processor, implements the single crystal silicon surface treatment method based on multi-stage etching as proposed in the above embodiment.

[0092] The storage medium proposed in this embodiment and the data storage method proposed in the above embodiment belong to the same inventive concept. Technical details not fully described in this embodiment can be found in the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0093] This is the second embodiment of the present invention, which provides a single crystal silicon surface treatment method based on multi-stage etching. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0094] In a clean room with a cleanliness level of Class 1000, 8 pieces were selected. <100> 4-inch P-type monocrystalline silicon wafers with a resistivity of 1-10 Ω·cm and a thickness of 500±10 μm were used as experimental samples. First, the wafer surface was pretreated using a standard cleaning process, SC1 (NH₄OH:H₂O₂:H₂O = 1:4:20) and SC2 (HCl:H₂O₂:H₂O = 1:1:6), to remove organic and metallic contaminants. The pretreated wafer was placed on the rotating platform of a spin coater and secured using vacuum suction. The AZ6270 photoresist temperature was precisely controlled at 24.0°C, and an automated dispensing system was used to apply the photoresist to the center of the wafer at a steady flow rate of 2.5 ml / s. The programmable spin coater operated in a dual-speed rotation mode: initially at 500 rpm for 30 seconds to achieve initial photoresist spreading, followed by 3000 rpm for 60 seconds to complete uniform film formation. The photoresist thickness was measured at 9 points on the silicon wafer surface using an ellipsometer. The average thickness was 2.15μm and the uniformity reached 98.5%.

[0095] The coated silicon wafer was pre-baked on a hot plate precisely controlled at 94.8°C for 5 minutes. Exposure was performed using a KarlSuss MA6 double-sided photolithography machine, using a chrome mask with a resolution of 0.5μm. The pattern contained lines, squares, and circular patterns of varying widths (2-50μm). Under a 365nm UV light source, precise exposure was performed for 10 seconds at an energy density of 15mW / cm². The development process used an automatic development system, using AZ300MIF developer at a temperature of 25.0°C for 48 seconds, followed by rinsing with 18.2MΩ·cm ultrapure water for 60 seconds and gentle drying with nitrogen. The development quality was checked using an optical microscope to confirm that the pattern integrity and edge sharpness met the requirements.

[0096] The developed silicon wafer is placed in the first etching solution prepared above for preliminary etching. The etching solution temperature is stabilized at 65.0°C, and the process parameters are recorded by a real-time monitoring system. When the etching depth reaches 9.2μm, isopropyl alcohol pre-cooled to 15.0°C is added to the etching solution at a rate of 0.5ml / min until its mass fraction reaches 7.5wt%. The modified etching solution is ultrasonically treated at 40kHz for 60 seconds, and the dynamic light scattering test shows that the mixing uniformity reaches 96.8%. After etching for another 15 minutes, the sample is washed with deionized water, ultrasonically cleaned, and spin-dried. Finally, fine etching is performed in the second etching solution at 80.0°C for 10 minutes to obtain the final sample.

[0097] The following is the comparative experimental data of this method and the existing method:

[0098] Table 1 Comparison of multi-stage etching process parameters and test results

[0099] Sample number Initial etching depth (μm) Etching depth after modification with isopropyl alcohol (μm) Final etching depth (μm) Surface roughness Ra (nm) Sidewall inclination (°) Aspect ratio Uniformity deviation (%) Sample-A 9.2 13.8 15.2 3.2 89.5 7.6 2.1 Sample-B 8.9 13.5 14.9 3.5 89.3 7.4 2.3 Sample-C 9.4 14.1 15.5 3.1 89.6 7.7 2.0 Control group 1 8.5 12.2 13.8 8.9 86.2 5.8 5.6 Control group 2 8.7 12.5 14.1 8.5 86.5 5.9 5.4 Control group 3 7.9 11.8 13.2 9.2 85.8 5.5 5.8

[0100] The following conclusions can be drawn from the analysis of the table data:

[0101] First, the multi-stage etching method of the present invention (Sample-A / B / C) demonstrated significant advantages in controlling etching depth. The first-stage etching depth reached 8.9-9.4 μm, and the cumulative second-stage depth after isopropyl alcohol modification reached 13.5-14.1 μm, with a final depth of 14.9-15.5 μm. In comparison, the traditional single-stage etching method (control group) achieved a final depth of only 13.2-14.1 μm, with depths at each stage significantly lower than those in the experimental group. This demonstrates that the present method not only achieves greater etching depths but also provides a more controllable etching process.

[0102] Secondly, in terms of surface quality, the method of the present invention shows outstanding advantages. The surface roughness Ra value of the experimental group samples is stable in the range of 3.1-3.5nm, while the Ra value of the control group is between 8.5-9.2nm, a difference of nearly 3 times. This significant difference is mainly attributed to the surface tension regulation effect brought about by isopropyl alcohol modification and the mild process conditions in the fine etching stage. At the same time, the side wall inclination angle of the experimental group samples reached 89.3-89.6°, close to the ideal verticality, while the control group was only 85.8-86.5°, indicating that the method of the present invention can effectively inhibit lateral etching.

[0103] In terms of aspect ratio, the experimental group achieved an excellent level of 7.4-7.7, an approximately 30% improvement over the control group's 5.5-5.9. This result fully demonstrates the unique advantages of the multi-stage etching strategy in fabricating high-aspect-ratio microstructures. Of particular note, the uniformity deviation in the experimental group was only 2.0-2.3%, while the control group was as high as 5.4-5.8%, an improvement of over 60%. This significant improvement in uniformity is due to precise process parameter control and the optimized formulation of the modified etching solution.

[0104] In summary, the multi-stage etching method proposed in this paper achieves significant improvements in key technical indicators such as etch depth, surface roughness, sidewall tilt angle, aspect ratio, and uniformity, providing a new technical approach for the preparation of high-quality single-crystal silicon microstructures. In particular, the synergistic effect of isopropyl alcohol modification and fine etching successfully solves the technical difficulties of balancing depth control and surface quality in traditional processes.

[0105] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for treating a single crystal silicon surface based on multi-stage etching, characterized in that: include: Coating a photoresist layer on the surface of a single crystal silicon substrate, and forming a mask of a preset pattern on the photoresist layer through a photolithography process; Preliminarily etching the single crystal silicon substrate using a first etching solution; adding an isopropyl alcohol additive to the first etching solution, adjusting the concentration of the isopropyl alcohol additive to 5-10 wt %, and continuing to etch the single crystal silicon substrate; Cleaning the surface of the single crystal silicon substrate with deionized water, and then finely etching the single crystal silicon substrate with a second etching solution; Blowing dry the surface of the single crystal silicon substrate with nitrogen to obtain a single crystal silicon substrate with a preset pattern structure; The preliminary etching comprises: During the etching process, a PTFE-coated stirring paddle with variable frequency speed regulation was used for uniform stirring at a speed of 120±2rpm. The diameter of the stirring paddle was 1 / 3 of the groove diameter and the height from the groove bottom was 1 / 4 of the groove depth. When the etching depth reaches 8-10 μm, the etching is terminated and the sample is lifted out of the etching solution at a speed of 2 cm / min. Adding the isopropyl alcohol additive to the first etching solution comprises: The isopropyl alcohol additive is injected into the first etching solution at a constant drop rate of 0.5±0.1 ml / min, with the drop position being 2-3 cm below the stirring paddle; during the drop addition process, a mechanical stirrer is used to uniformly stir at a speed of 150 rpm, and a 2-minute pause is performed after each 50 ml of isopropyl alcohol is added. The mixed solution is sampled and tested using a digital density meter, and a density value change curve is recorded. When the mass fraction of the isopropyl alcohol additive reaches 7.5±2.5 wt%, the drop addition is stopped; Continuing to etch the single crystal silicon substrate includes: Slowly immersing the single crystal silicon substrate in the first etching solution modified with the isopropyl alcohol additive, continuously stirring with a stirrer at a speed of 120±5 rpm, while monitoring the etching solution temperature in real time with an infrared thermometer to ensure that the temperature fluctuation does not exceed ±2°C, and calculating the etching depth based on the change in interference fringes; When the change in the interference fringe spacing is observed, which corresponds to an increase in the etching depth of 4-5 μm, the automatic pulling device is started to lift the single crystal silicon substrate out of the etching solution at a uniform speed; The improved multi-parameter coupling calculation method is used to calculate the etching depth: First, considering the effect of temperature on the refractive index, the temperature-corrected refractive index calculation formula is established: n(T)=n0[1+α(T-T0)+β(T-T0) 2 ] Where n(T) is the refractive index at temperature T, n0 is the refractive index at standard temperature T0, α and β are the first-order and second-order temperature coefficients respectively; The influence factor of etching solution concentration on interference fringes is introduced: Where Δφ is the phase difference, λ is the laser wavelength, h is the etching depth, C IPA is the isopropanol concentration, γ is the concentration influence coefficient; Further consider the nonlinear relationship between fringe intensity and depth: I(x,y)=I0[1+V cos(Δφ+θ(x,y))] Where I(x,y) is the light intensity at the midpoint (x,y) of the interference pattern, I0 is the background light intensity, V is the fringe visibility, and θ(x,y) is the initial phase distribution. Introduce the modified equation for depth calculation: Among them, K c is the comprehensive correction factor: Among them, η1 and η2 are dynamic correction coefficients, ω is the characteristic frequency of the etching process, and τ is the characteristic time constant of the system; The final real-time etching depth is obtained by time domain integration: Where H(t) is the cumulative etching depth at time t, is the real-time etching rate, λ is the laser wavelength, h is the etching depth, n(T) is the refractive index at temperature T, I0 is the background light intensity, V is the fringe visibility, γ is the concentration influence coefficient, K c is the comprehensive correction coefficient, C IPA is the isopropyl alcohol concentration, and I(x,y) is the light intensity at the midpoint (x,y) of the interference pattern.

2. The method for treating a single crystal silicon surface by multi-stage etching according to claim 1, wherein: The first etching solution comprises potassium hydroxide crystals, ultrapure deionized water, high-purity ethylene glycol and electronic grade tetramethylammonium hydroxide; Place the mixture in a fume hood and use a 500 ml glass reaction bottle with four necks to prepare the solution. Add the weighed potassium hydroxide crystals to the pre-mixed deionized water and stir with a PTFE-coated magnetic stir bar until the potassium hydroxide is completely dissolved. A pre-prepared mixture of ethylene glycol and tetramethylammonium hydroxide was added dropwise to the solution at a rate of 2 ml / min while maintaining a constant stirring speed. A pH meter was used to monitor the pH value of the solution in real time to ensure that the final pH value was stable at 13.5±0.2, the dynamic viscosity at 25°C was 3.8-4.2 mPa·s, and the surface tension was maintained in the range of 72-75 mN / m.

3. The method for treating a single crystal silicon surface based on multi-stage etching according to claim 2, wherein: 25 wt % analytically pure tetramethylammonium hydroxide solution and deionized water were mixed in a volume ratio of 3:7 to prepare the second etching solution with a concentration of 7.5 wt %; 0.1 wt % of a surfactant and 0.05 wt % of a complexing agent were added to the second etching solution, and the pH value was adjusted to 12.5±0.1 by dropwise adding dilute nitric acid.

4. The method for treating the surface of single crystal silicon based on multi-stage etching according to claim 3, wherein: The fine etching comprises: The prepared second etching solution was preheated to 80±1°C, and the cleaned single crystal silicon substrate was slowly immersed in the second etching solution at an inclination angle of 15°, with the immersion speed controlled at 1 cm / min. During the etching process, a magnetic stirrer was used for gentle stirring at a speed of 80 rpm. At the same time, the evolution of the etching morphology was observed in real time using a differential interference microscope. A small amount of solution was removed from the etching solution every 30 seconds, and the changes in the solution composition were monitored using a conductivity meter. Fresh etching solution was dynamically added based on the measurement results to maintain a constant etching solution concentration.

5. A single crystal silicon surface treatment system based on multi-stage etching, based on the single crystal silicon surface treatment method based on multi-stage etching according to any one of claims 1 to 4, characterized in that: include: A mask generation module is used to coat a photoresist layer on the surface of a single crystal silicon substrate and form a mask of a preset pattern on the photoresist layer through a photolithography process; A preliminary etching module, configured to perform preliminary etching on the single crystal silicon substrate using a first etching solution; a modification module, configured to add an isopropyl alcohol additive to the first etching solution, adjust the concentration of the isopropyl alcohol additive to 5-10 wt %, and continue etching the single crystal silicon substrate; The fine etching module is used to clean the surface of the single crystal silicon substrate with deionized water, and then finely etch the single crystal silicon substrate with a second etching solution.

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