Monocrystalline silicon surface treatment method based on multi-stage etching

Abstract

The invention discloses a monocrystalline silicon surface treatment method based on multi-stage etching, and relates to the technical field of semiconductor material surface treatment.The monocrystalline silicon surface treatment method comprises the steps that the surface of a monocrystalline silicon substrate is coated with a photoresist layer, and a mask with a preset pattern is formed on the photoresist layer through the photoetching technology; carrying out primary etching on the monocrystalline silicon substrate by adopting a first etching solution; adding an isopropanol additive into the first etching solution, adjusting the concentration of the isopropanol additive to be 5-10 wt%, and continuing to etch the monocrystalline silicon substrate; the surface of the monocrystalline silicon substrate is cleaned with deionized water, and then fine etching is conducted on the monocrystalline silicon substrate with second etching liquid; and blow-drying the surface of the monocrystalline silicon substrate by using nitrogen to obtain the monocrystalline silicon substrate with the preset pattern structure. By accurately controlling photoetching and etching processes, a high-precision and high-stability monocrystalline silicon substrate pretreatment and pattern structure forming process is realized.

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 more and more attention from researchers for its precise control of surface microstructure and processing technology. Single crystal silicon surface treatment technology is widely used in the fields of micro-electromechanical systems (MEMS), integrated circuits (IC), optoelectronic devices, etc. Traditional single crystal silicon surface treatment methods mainly include dry etching and wet etching. Among them, wet etching is widely used in industrial production due to its advantages such as simple process, low cost, and suitability for large-scale production. However, the existing wet etching technology often has technical difficulties such as insufficient anisotropy control, uneven etching rate, and large surface roughness when processing deep micron or submicron fine structures, which seriously restricts the preparation and development of high-precision single crystal silicon devices.

[0003] At present, the industry generally adopts a single etching process to perform surface treatment on 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 fast etching process is used, although the processing efficiency can be improved, 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 the 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 the microstructure morphology, especially when preparing high aspect ratio structures, defects such as chamfers and rough side walls 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: 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: A photoresist layer is coated on the surface of the single crystal silicon substrate, and a mask of a preset pattern is formed on 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 5-10 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; The surface of the single crystal silicon substrate is dried by nitrogen to obtain a single crystal silicon substrate with a preset pattern structure.

[0007] As a preferred embodiment of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, 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 into the pre-mixed deionized water and stir with a PTFE-coated magnetic stirrer 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. The stirring speed was kept constant, and the pH value of the solution was monitored in real time using a pH meter to ensure that the final pH value was stable at 13.5±0.2, and 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.

[0008] As a preferred solution of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, 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 bottom of the groove 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.

[0009] As a preferred embodiment of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, wherein: adding isopropyl alcohol additive to the first etching solution comprises: The isopropanol additive is injected into the first etching solution at a constant drop rate of 0.5±0.1 ml / min, and the drop position is located 2-3 cm below the stirring paddle; during the drop process, a mechanical stirrer is used to stir at a uniform speed of 150 rpm, and a pause of 2 minutes is made after each drop of 50 ml of isopropanol. The mixed solution is sampled and tested by a digital density meter, and the density value change curve is recorded. When the mass fraction of the isopropanol additive reaches 7.5±2.5wt%, the drop addition is stopped.

[0010] As a preferred solution of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, wherein: continuing to etch the single crystal silicon substrate comprises: Slowly immersing the single crystal silicon substrate in the first etching solution modified by the isopropanol additive, continuously stirring with a stirrer at a speed of 120±5rpm, and monitoring the temperature of the etching solution in real time with an infrared thermometer so that the temperature fluctuation does not exceed ±2°C, and calculating the etching depth by the change of interference fringes; When it is observed that the change in the interference fringe spacing corresponds to an increase in etching depth of 4-5 μm, the automatic lifting device is started to lift the single crystal silicon substrate out of the etching solution at a uniform speed.

[0011] 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: in, for The cumulative etching depth at the moment, is the real-time etching rate, is the laser wavelength, is the etching depth, For temperature The refractive index under is the background light intensity, is the fringe visibility, is the concentration influence coefficient, is the comprehensive correction factor, is the isopropanol concentration, The midpoint of the interference pattern The light intensity at the place.

[0012] As a preferred embodiment of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, wherein: 25wt% analytical 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 7.5wt%; 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 dropping dilute nitric acid.

[0013] As a preferred solution of the single crystal silicon surface treatment method based on multi-stage etching of the present invention, 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°, and the immersion speed was controlled at 1 cm / min; during the etching process, a magnetic stirrer was used to gently stir at a speed of 80 rpm, and the evolution of the etching morphology was observed in real time by a differential interference microscope, and a small amount of solution was taken out from the etching solution every 30 seconds, and the changes in the solution components were monitored by a conductivity meter, and fresh etching solution was dynamically added according to the measurement results to keep the etching solution concentration constant.

[0014] 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: 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, used for performing preliminary etching on the single crystal silicon substrate using a first etching solution; A modification module, used for 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; 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.

[0015] The beneficial effect of the present invention is that the invention realizes the high-precision and strong stability of the single crystal silicon substrate pretreatment and graphic structure formation process by accurately 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 the 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, the 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 the depth monitoring during the silicon wafer etching process. In addition, deionized water cleaning and fine etching are used to ensure the surface quality and the 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, accurate and reliable manufacturing process suitable for the manufacture of high-precision semiconductor devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order 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. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them: Figure 1The present invention is a flow chart of a single crystal silicon surface treatment method based on multi-stage etching. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0018] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and 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.

[0019] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0020] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0021] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0022] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] 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: 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 by a photolithography process; In a clean room environment, the 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; the positive photoresist AZ6270 is heated to 23-25° C., and the photoresist is evenly dripped onto the center of the surface of the single crystal silicon substrate at a flow rate of 2-3 ml / s using a syringe; 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, and the photoresist layer with a thickness of 2.0-2.2 μm is obtained; the layer coated with the photoresist layer is The single crystal silicon substrate is placed on a heating plate at a temperature of 95±2℃ for pre-baking 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 accurately aligned with the photoresist layer, the photoresist layer is exposed for 10 seconds using ultraviolet light with a wavelength of 365nm and a light intensity of 15mW / cm²; the exposed photoresist layer is developed using developer AZ300MIF, the development time is 45-50 seconds, the development temperature is 25℃, and then it is rinsed with deionized water for 60 seconds and gently blown dry with a nitrogen flow to form a mask with a preset pattern on the photoresist layer.

[0024] S2: using a first etching solution to preliminarily etch the single crystal silicon substrate; Analytical pure potassium hydroxide crystals (purity ≥ 99.99%, particle size 45-75 μm) were placed in a desiccator for pretreatment 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.

[0025] The mixed solution was placed in a fume hood and prepared using a 500 ml glass reaction bottle with four necks. The weighed potassium hydroxide crystals were slowly added to the pre-mixed deionized water and stirred at 200 rpm using a PTFE-coated magnetic stir bar until the potassium hydroxide was completely dissolved. Add the pre-prepared mixture of ethylene glycol and tetramethylammonium hydroxide (mixed in advance) dropwise into the solution, and control the addition rate at 2 ml / min while keeping the stirring speed unchanged; use a pH meter to monitor the pH value change of the solution in real time to ensure that the final pH value is stable at 13.5±0.2; use a programmable rotational viscometer to measure the viscosity of the prepared etching solution, and record the dynamic viscosity value at 25°C as 3.8-4.2 mPa·s; use a surface tension meter to measure the surface tension of the etching solution to ensure that the value is maintained in the range of 72-75 mN / m.

[0026] The prepared etching solution was filtered through a 0.1μm PTFE membrane filter to remove the insoluble particles. A quartz etching tank (volume 2000ml, wall thickness 5mm) with a PID temperature control system was used, and a sandwich circulation 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 through a multi-point temperature measurement system. The circulation 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 positions of the etching solution to ensure that the temperature field uniformity deviation did not exceed ±1℃.

[0027] The single crystal silicon substrate after the photolithography process is fixed on a polytetrafluoroethylene fixture and slowly immersed in the first etching solution at an angle of 30°. During the etching process, a PTFE-coated stirring paddle with variable frequency speed regulation is used to stir at a speed of 120±2rpm. The diameter of the stirring paddle is 1 / 3 of the groove diameter, and the height from the groove bottom is 1 / 4 of the groove depth.

[0028] 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 intensity of the reflected signal 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 drawn by computer to monitor the stability of the etching process.

[0029] S3: 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; High-purity isopropanol (purity ≥ 99.9%) is placed in a low-temperature constant temperature water bath and precooled to 15±1°C; a precision pipette system with a temperature sensor is used to inject the isopropanol additive into the first etching solution at a constant drop rate of 0.5±0.1ml / min, and the drop position is located 2-3cm below the stirring paddle; during the drop process, a mechanical stirrer is used to stir at a speed of 150rpm, and the stirring paddle is made of polytetrafluoroethylene, and the paddle diameter is 1 / 3 of the inner diameter of the etching tank; after each drop of 50ml of isopropanol, pause for 2 minutes, sample and test the mixed solution through a digital density meter, record the density value change curve, and stop dropping when the mass fraction of the isopropanol additive reaches 7.5±2.5wt% (corresponding to a density value of 1.18-1.22g / cm³).

[0030] 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 set to 40kHz, and the ultrasonic dispersion treatment was performed for 60±5 seconds at 65±5°C; 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 the tiny particles present.

[0031] The single crystal silicon substrate is slowly immersed in the filtered modified etching solution at an inclination angle of 30° through a special PTFE clamp, and the clamp lifting speed is adjusted to 2 cm / min; during the etching process, a stirrer is used to continuously stir at a speed of 120±5rpm, and the etching solution temperature is monitored in real time by an infrared thermometer to ensure that the temperature fluctuation does not exceed ±2°C; a laser interferometer is installed 30 cm above the etching tank, and a He-Ne laser beam with a wavelength of 632.8nm is used to scan the silicon surface in real time, and the etching depth is calculated by the change of interference fringes.

[0032] When the change in the interference fringe spacing is observed to correspond to an increase in 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 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 drawn by computer software.

[0033] 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: First, considering the effect of temperature on the refractive index, the temperature-corrected refractive index calculation formula is established: 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.

[0034] The influence factor of etching solution concentration on interference fringes is introduced as follows: in, is the phase difference, is the laser wavelength, is the etching depth, is the isopropanol concentration, is the concentration influence coefficient.

[0035] Further consider the nonlinear relationship between fringe intensity and depth: 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.

[0036] Introduce the modified equation for depth calculation: in, is the comprehensive correction factor: in, and is the dynamic correction coefficient, is the characteristic frequency of the etching process, is the system characteristic time constant.

[0037] The final real-time etching depth is obtained by time domain integration: in, for The cumulative etching depth at the moment, is the real-time etching rate, is the laser wavelength, is the etching depth, For temperature The refractive index under is the background light intensity, is the fringe visibility, is the concentration influence coefficient, is the comprehensive correction factor, is the isopropanol concentration, The midpoint of the interference pattern The light intensity at the place.

[0038] The better one is that by introducing temperature-corrected refractive index calculation, the comprehensive performance improvement is achieved, including 76% improvement in measurement accuracy, 70% reduction in response time, 2.8-3.5 times improvement in anti-interference ability, and expansion of the applicable depth range to 0.5-15μm, which significantly improves the accuracy and reliability of real-time depth monitoring during silicon wafer etching.

[0039] 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; The monocrystalline silicon substrate that has completed the first stage of etching is placed in a multi-stage cleaning device for cleaning; first, the substrate is sprayed and cleaned with deionized water (resistivity ≥ 18.2MΩ·cm) at 35±2°C, the spray pressure is controlled at 0.2-0.3MPa, and the spray time is 60±5 seconds; then the substrate is immersed in an ultrasonic cleaning tank, and ultrasonic cleaning is performed at 40kHz and a power density of 1.5W / cm² for 120±10 seconds; finally, a high-speed spin drying process (rotation speed 4000rpm, time 30 seconds) is used to remove residual surface moisture. The hydrophilicity of the silicon wafer surface is tested by a contact angle meter to ensure that the contact angle is less than 5°.

[0040] 25wt% 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 7.5wt%; 0.1wt% of a surfactant (polyoxyethylene ether) was added to the prepared solution to improve wettability, and 0.05wt% 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 dropping dilute nitric acid.

[0041] 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 to gently stir at a speed of 80 rpm, and the evolution of the etching morphology was observed in real time by a differential interference microscope; a small amount of solution was taken out from the etching solution every 30 seconds, and the changes in the solution components were monitored by a conductivity meter, and fresh etching solution was dynamically added according to the measurement results to keep the etching solution concentration constant.

[0042] S5: using nitrogen to blow dry the surface of the single crystal silicon substrate to obtain a single crystal silicon substrate with a preset pattern structure.

[0043] Furthermore, this embodiment also provides a single crystal silicon surface treatment system based on multi-stage etching, comprising: 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, used for performing preliminary etching on the single crystal silicon substrate using a first etching solution; A modification module, used for 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; 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.

[0044] 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 as proposed in the above embodiment.

[0045] The computer device may be a terminal, and the computer device includes 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 includes 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 can 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 screen 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 key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0046] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, the single crystal silicon surface treatment method based on multi-stage etching as proposed in the above embodiment is implemented.

[0047] The storage medium proposed in this embodiment and the data storage method proposed in the above embodiment belong to the same inventive concept. The 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.

[0048] This is the second embodiment of the present invention. This embodiment 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.

[0049] In a clean room with a cleanliness level of Class 1000, 8 pieces were selected. <100> A 4-inch P-type single crystal silicon wafer with a crystal orientation, a resistivity of 1-10Ω·cm, and a thickness of 500±10μm was used as the experimental sample. First, the surface of the silicon wafer was pretreated using the SC1 (NH4OH:H2O2:H2O=1:4:20) and SC2 (HCl:H2O2:H2O=1:1:6) standard cleaning processes to remove surface organic and metal pollutants. The pretreated silicon wafer was placed on the rotating platform of the coating machine and fixed by vacuum adsorption. The temperature of AZ6270 photoresist was precisely controlled to 24.0℃, and the photoresist was dripped onto the center of the silicon wafer at a stable flow rate of 2.5ml / s using an automatic glue injection system. The programmable coating machine operated in a dual-speed rotation mode: first, it rotated at 500rpm for 30 seconds to achieve initial spreading of the photoresist, and then rotated at 3000rpm 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%.

[0050] The coated silicon wafer was pre-baked on a heating plate precisely controlled at 94.8°C for 5 minutes. A KarlSuss MA6 double-sided photolithography machine was used for exposure, using a chrome mask with a resolution of 0.5μm. The pattern contained lines, squares and circular patterns of different 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 by optical microscopy to confirm that the pattern integrity and edge sharpness met the requirements.

[0051] The developed silicon wafer is placed in the first etching solution prepared above for preliminary etching. The temperature of the etching solution is stabilized at 65.0℃, and the process parameters are recorded by a real-time monitoring system. When the etching depth reaches 9.2μm, isopropanol precooled to 15.0℃ 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 treated with 40kHz ultrasound for 60 seconds, and the dynamic light scattering test shows that the mixing uniformity reaches 96.8%. After etching for 15 minutes, the sample is washed with deionized water, ultrasonically cleaned and spin-dried in turn. Finally, fine etching is carried out in the second etching solution at 80.0℃ for 10 minutes to obtain the final sample.

[0052] The following is the comparative experimental data of this method and the existing method: Table 1 Comparison of multi-stage etching process parameters and test results Sample No. Initial etching depth (μm) Etching depth after modification with isopropyl alcohol (μm) Final etching depth (μm) Surface roughness Ra(nm) Sidewall inclination angle (°) 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 The following conclusions can be drawn from the analysis of the table data: First, in terms of etching depth control, the multi-stage etching method of the present invention (Sample-A / B / C group) shows significant advantages. The etching depth of the first stage reaches 8.9-9.4μm, the cumulative depth of the second stage after isopropanol modification reaches 13.5-14.1μm, and the final depth reaches 14.9-15.5μm. In contrast, the final depth of the traditional single-stage etching method (control group) is only 13.2-14.1μm, and the depth of each stage is significantly lower than that of the experimental group. This shows that the method of the present invention can not only obtain a greater etching depth, but also the etching process is more controllable.

[0053] 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 isopropanol 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.

[0054] In terms of aspect ratio, the experimental group achieved an excellent level of 7.4-7.7, which is about 30% higher than the control group's 5.5-5.9. This result fully demonstrates the unique advantages of the multi-stage etching strategy in the preparation of high aspect ratio microstructures. It is particularly noteworthy that the uniformity deviation of the experimental group is only 2.0-2.3%, while the control group is as high as 5.4-5.8%, an improvement of more than 60%. This significant improvement in uniformity is due to precise process parameter control and the optimized formula of the modified etching solution.

[0055] In summary, the multi-stage etching method proposed in the present invention has achieved significant improvements in key technical indicators such as etching depth, surface roughness, sidewall inclination, aspect ratio and uniformity, providing a new technical approach for the preparation of high-quality single-crystal silicon microstructures. In particular, through the synergistic effect of isopropyl alcohol modification and fine etching, the technical problem of the difficulty in balancing depth control and surface quality in traditional processes has been successfully solved.

[0056] 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 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: A photoresist layer is coated on the surface of the single crystal silicon substrate, and a mask of a preset pattern is formed on 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 5-10 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; The surface of the single crystal silicon substrate is dried by nitrogen to obtain a single crystal silicon substrate with a preset pattern structure.

2. The method for treating the surface of single crystal silicon based on multi-stage etching according to claim 1, characterized in that: The first etching solution includes 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 into the pre-mixed deionized water and stir with a PTFE-coated magnetic stirrer 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. The stirring speed was kept constant, and the pH value of the solution was monitored in real time using a pH meter to ensure that the final pH value was stable at 13.5±0.2, and 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 the surface of single crystal silicon based on multi-stage etching according to claim 2, characterized in that: 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 bottom of the groove 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.

4. The method for treating the surface of single crystal silicon based on multi-stage etching according to claim 3, characterized in that: Adding the isopropyl alcohol additive to the first etching solution comprises: The isopropanol additive is injected into the first etching solution at a constant drop rate of 0.5±0.1 ml / min, and the drop position is located 2-3 cm below the stirring paddle; during the drop process, a mechanical stirrer is used to stir at a uniform speed of 150 rpm, and a pause of 2 minutes is made after each drop of 50 ml of isopropanol. The mixed solution is sampled and tested by a digital density meter, and the density value change curve is recorded. When the mass fraction of the isopropanol additive reaches 7.5±2.5wt%, the drop addition is stopped.

5. The method for treating the surface of single crystal silicon based on multi-stage etching according to claim 4, characterized in that: Continuing to etch the single crystal silicon substrate comprises: Slowly immersing the single crystal silicon substrate in the first etching solution modified by the isopropanol additive, continuously stirring with a stirrer at a speed of 120±5rpm, and monitoring the temperature of the etching solution in real time with an infrared thermometer so that the temperature fluctuation does not exceed ±2°C, and calculating the etching depth by the change of interference fringes; When it is observed that the change in the interference fringe spacing corresponds to an increase in etching depth of 4-5 μm, the automatic lifting device is started to lift the single crystal silicon substrate out of the etching solution at a uniform speed.

6. The method for treating the surface of single crystal silicon based on multi-stage etching according to claim 5, characterized in that: The etching depth is calculated as follows: in, for The cumulative etching depth at the moment, is the real-time etching rate, is the laser wavelength, is the etching depth, For temperature The refractive index under is the background light intensity, is the fringe visibility, is the concentration influence coefficient, is the comprehensive correction factor, is the isopropanol concentration, The midpoint of the interference pattern The light intensity at the place.

7. The method for treating the surface of single crystal silicon based on multi-stage etching according to claim 6, characterized in that: 25 wt % of 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 %; 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 dropping dilute nitric acid.

8. The method for treating the surface of single crystal silicon based on multi-stage etching according to claim 7, characterized in that: 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°, and the immersion speed was controlled at 1 cm / min; during the etching process, a magnetic stirrer was used to gently stir at a speed of 80 rpm, and the evolution of the etching morphology was observed in real time by a differential interference microscope, and a small amount of solution was taken out from the etching solution every 30 seconds, and the changes in the solution components were monitored by a conductivity meter, and fresh etching solution was dynamically added according to the measurement results to keep the etching solution concentration constant.

9. 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 8, 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, used for performing preliminary etching on the single crystal silicon substrate using a first etching solution; A modification module, used for 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; 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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