Method for processing silicon dioxide micro-nano structure on surface of polycrystalline silicon

Abstract

The invention provides a method for processing a silicon dioxide micro-nano structure on the surface of polycrystalline silicon, which is characterized in that the micro-nano structure is prepared by utilizing the difference of silicon dioxide growth rates on the surface of polycrystalline silicon with different doping concentrations; and the nano-scale micro-nano structure is directly prepared by controlling the oxidation growth time. Based on the principle that the surface oxidation rates of the n-type doped polycrystalline silicon and the p-type polycrystalline silicon are different, the nano structure with multiple functions can be prepared on the surface of the polycrystalline silicon by accurately controlling the oxidation process. The method is not only suitable for solar cells, grating devices and metasurface devices, but also can be used for preparing multilayer structure capacitors.

Description

Technical Field

[0001] The present invention relates to the field of novel micro-nano processing technology, and in particular to a method for processing silicon dioxide micro-nano structures on the surface of polysilicon. Background Art

[0002] Polycrystalline silicon is a key semiconductor material widely used in integrated circuits, solar cells, and optical devices. Polycrystalline silicon is a form of elemental silicon. When molten silicon solidifies under supercooled conditions, silicon atoms form a diamond lattice, forming numerous crystal nuclei. These nuclei then grow into grains with varying crystal plane orientations, ultimately crystallizing into polycrystalline silicon.

[0003] By doping polycrystalline silicon, its electrical properties can be manipulated, forming a pn junction structure and altering the flow characteristics of electrons and holes within the material. Polycrystalline silicon thin films are widely used in key structures of semiconductor devices such as MOS transistor gates, resistors, and bipolar circuits. In the field of solar cells, doping can create p-type and n-type regions within polycrystalline silicon, generating a potential difference under illumination and enabling photoelectric conversion. Due to their low cost and high photoelectric conversion efficiency, polycrystalline silicon solar cells have become a mainstream product in the photovoltaic power generation market.

[0004] In the actual process of polysilicon, the surface passivation process is an indispensable link. A layer of silicon dioxide needs to be grown on the surface of polysilicon to protect the device from oxidation and contamination, and serve as an insulating layer to reduce surface charge recombination, reduce device leakage current, and improve device performance and stability.

[0005] At present, the structuring process of polysilicon is mainly achieved through traditional micro-nano processing methods. In order to achieve the patterning of micro-nano structures, complex photolithography and etching processes are required. Photolithography technology is a technology that forms micro-nanoscale patterns on a substrate by using photoresist, mask and light source. The specific steps include: applying photoresist on the surface of the substrate, exposing it through the mask pattern, and then transferring the pattern to the photoresist through the development step. Next, etching technology is used to remove unnecessary materials to form micro-nano structures. Etching technology includes dry etching and wet etching. Dry etching often uses plasma etching, while wet etching uses chemical solutions to remove materials.

[0006] While traditional photolithography and etching processes offer the advantages of high resolution and precision, they also have limitations. For example, photolithography requires high-precision masks and complex exposure systems, resulting in high manufacturing costs and cumbersome process steps. Therefore, it is particularly important to develop a new method for fabricating silicon dioxide micro-nanostructures on polycrystalline silicon surfaces that can reduce the complexity of micro-nanofabrication processes and, through optimized process parameters and ingenious design, create micro-nanopatterned structures with diverse functions on polycrystalline silicon surfaces.

[0007] In response to the aforementioned background technology and existing challenges, we have proposed a novel method for fabricating silicon dioxide micro-nanostructures on polycrystalline silicon surfaces. This method, based on the principle that n-type and p-type doped polycrystalline silicon have different surface oxidation rates, enables the formation of nanostructures with diverse functions on the polycrystalline silicon surface by precisely controlling the oxidation process. This method is not only applicable to solar cells, grating devices, and metasurface devices, but can also be used to fabricate multilayer capacitors.

[0008] While traditional top-down micro-nanofabrication processes offer advantages in precision and resolution, they have limitations when fabricating complex three-dimensional structures and those with high aspect ratios. In contrast, bottom-up micro-nanofabrication processes, which autonomously assemble or deposit micro-nanostructures on a material's surface, offer advantages such as fewer processing steps, lower energy consumption, and wider applicability. Therefore, we propose a novel bottom-up micro-nanofabrication process to address the cumbersome and energy-intensive nature of existing polysilicon processing techniques. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for processing silicon dioxide micro-nano structures on the surface of polycrystalline silicon, so as to solve the problems of cumbersome and high energy consumption of existing polycrystalline silicon processing technology.

[0010] The technical solution of the present invention is to provide a method for processing silicon dioxide micro-nano structures on the surface of polycrystalline silicon, utilizing the difference in silicon dioxide growth rate on the surface of polycrystalline silicon with different doping concentrations to achieve the preparation of micro-nano structures; by controlling the oxidation growth time, nanometer-level micro-nano structures are directly prepared.

[0011] Further, the following steps are included:

[0012] S1. Preparation of doped polysilicon;

[0013] S2, thermal oxidation reaction;

[0014] S3, oxidation rate control;

[0015] S4, diffusion and reconstruction of dopant atoms;

[0016] S5. Stage changes in reaction rate.

[0017] Furthermore, the step S1 specifically includes:

[0018] Doping ions of different concentrations are implanted into polysilicon; the doping elements include phosphorus and boron. For highly doped polysilicon substrates, before the thermal oxidation reaction, the concentration distribution of the doping atoms conforms to the Gaussian distribution, that is, as the depth of the substrate increases, the concentration of the doping atoms gradually decreases, and the doping concentration is adjusted according to specific needs.

[0019] Furthermore, the step S2 specifically includes:

[0020] The doped polysilicon is subjected to a thermal oxidation reaction at an appropriate temperature; dry oxidation is suitable for producing a high-quality thin passivation layer, and wet oxidation is suitable for growing a relatively thick passivation layer.

[0021] Furthermore, the thin passivation layer is a MOS process gate oxide dielectric layer; the relatively thick passivation layer is a mask, local oxidation isolation or capacitor structure.

[0022] Furthermore, in step S3, the high doping concentration on the surface increases the crystal defects at the reaction interface, providing a large number of reaction sites and promoting the oxidation reaction rate; the doping atoms diffused into the silicon dioxide also increase the defectivity of the silicon dioxide, making it easier for the oxidant to diffuse to the reaction interface, thereby accelerating the oxidation reaction rate.

[0023] Furthermore, in step S4, depending on the type of dopant atoms, the diffusion and reconstruction of the dopant atoms during the oxidation process depends on the difference in their solubility in silicon and silicon dioxide.

[0024] Furthermore, in step S5, from the initial stage of the oxidation reaction to the thin layer oxidation stage, the reaction rate mainly depends on the interface reaction rate; the high concentration of phosphorus doping at the interface provides a large number of electrons, which accelerates the charge transfer process and thus increases the reaction rate; as the oxide layer thickens, the reaction rate dominated by the diffusion of the oxidant changes more significantly, and the grown silicon dioxide layer has a higher thickness.

[0025] The beneficial effects achieved by the method for processing silicon dioxide micro-nanostructures on the surface of polycrystalline silicon provided by the present invention are:

[0026] This method, based on the principle that n-type and p-type doped polysilicon have different surface oxidation rates, can precisely control the oxidation process to create nanostructures with various functions on the polysilicon surface. This method is not only applicable to solar cells, grating devices, and metasurface devices, but can also be used to fabricate multilayer capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention will be further described below with reference to the accompanying drawings:

[0028] Figure 1 Schematic diagram of the mechanism of the influence of dopant atom segregation effect on the growth rate during the oxidation process of heavily doped polysilicon;

[0029] Figure 2 High-resolution cross-sectional images of polysilicon substrates with different doping conditions under the same process conditions;

[0030] Figure 3 In order to realize the fabrication of micro-nano grating structures by controlling the growth rate of doped polysilicon. DETAILED DESCRIPTION

[0031] The following is a detailed description of the method for fabricating silicon dioxide micro-nanostructures on the surface of polycrystalline silicon, in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are highly simplified and not accurately scaled, and are intended solely to facilitate and clarify the purpose of illustrating the embodiments of the present invention.

[0032] This paper proposes a novel bottom-up micro-nanofabrication process that exploits the differences in silicon dioxide growth rates on the surface of polysilicon with varying doping concentrations to fabricate micro-nanostructures. By controlling the oxidation growth time, this method effectively avoids the tedious and complex photolithography and etching steps, enabling the direct fabrication of nanoscale micro-nanostructures.

[0033] Principle description:

[0034] 1. Thermal oxidation reaction of doped polysilicon:

[0035] After different concentrations of dopant ions are implanted into polysilicon, a Gaussian distribution of doping concentrations is formed. When the thermal oxidation reaction of silicon is carried out at an appropriate temperature, the high doping concentration increases the crystal defects at the reaction interface and promotes the oxidation reaction rate. The different solubility and diffusion characteristics of dopant atoms (such as phosphorus and boron) in silicon and silicon dioxide lead to different oxidation rates, such as Figure 1 shown.

[0036] 2. Five-Stream Dunham Model:

[0037] According to this model, phosphorus atoms concentrate at the interface during oxidation, while boron atoms primarily enter the oxide layer. High phosphorus concentrations at the interface increase the electron supply, promoting charge transfer and the oxidation reaction rate. As the oxide layer thickness increases, oxidant diffusion gradually becomes the dominant factor, affecting the oxidation rate.

[0038] 3. Control of reaction rate:

[0039] By controlling the doping concentration and oxidation time, the thickness of the silicon dioxide layer can be precisely controlled. The doping area can be controlled graphically to achieve the fabrication of nanoscale micro-nanostructures.

[0040] Application areas:

[0041] This micro-nano processing method is not only suitable for the preparation of solar cells, grating devices and super surface devices, but also can be used for the preparation of multilayer capacitors. By graphically controlling the doping area, similar Figure 2 The structure in the module can realize various functional applications.

[0042] The specific scheme adopted in the present invention is as follows:

[0043] 1. Preparation of doped polysilicon:

[0044] Dopant ion implantation at varying concentrations is performed in polysilicon. The doping elements include phosphorus and boron. For highly doped polysilicon substrates, before thermal oxidation, the concentration of dopant atoms follows a Gaussian distribution. This means that the concentration of dopant atoms decreases with increasing depth in the substrate. The doping concentration is adjusted based on specific needs.

[0045] 2. Thermal oxidation reaction:

[0046] Thermal oxidation of doped polysilicon is performed at an appropriate temperature. Dry oxidation is suitable for producing high-quality thin passivation layers, such as the gate oxide dielectric layer of the MOS process. Wet oxidation is more suitable for growing relatively thick passivation layers, such as those used for masks, local oxidation isolation, and capacitor structures, such as Figure 1 As shown in the picture above.

[0047] 3. Oxidation rate control:

[0048] The high doping concentration on the surface increases the crystal defects at the reaction interface, providing a large number of reaction sites and promoting the oxidation reaction rate. The doping atoms diffused into the silicon dioxide also increase the defectivity of the silicon dioxide, making it easier for the oxidant to diffuse to the reaction interface, thereby accelerating the oxidation reaction rate.

[0049] 4. Diffusion and reconstruction of dopant atoms:

[0050] Depending on the type of dopant atoms, the diffusion and reconstruction of dopant atoms during oxidation depends on the difference in their solubility in silicon and silicon dioxide. The segregation coefficient of phosphorus at the interface of silicon and silicon dioxide is 10, while the segregation coefficient of boron is between 0.1 and 0.3. During the oxidation reaction, the concentration of phosphorus atoms at the reaction interface increases significantly, while a small amount of phosphorus atoms penetrates into the silicon dioxide. In contrast, boron atoms mainly enter the oxide layer, resulting in a decrease in the concentration of dopant atoms at the interface, such as Figure 1 As shown in the figure below.

[0051] 5. Stage changes in reaction rate:

[0052] From the initial oxidation stage to the thin-layer oxidation stage, the reaction rate is primarily determined by the interface reaction rate. High phosphorus doping at the interface provides a large number of electrons, accelerating the charge transfer process and thus increasing the reaction rate. As the oxide layer thickens, the reaction rate, driven by oxidant diffusion, changes more significantly, resulting in a thicker silicon dioxide layer.

[0053] Example 1: Doping polysilicon with phosphorus at a concentration of 9.5×10 19 atoms / cm 3 , the boron doping concentration is 4.8×10 19 atoms / cm 3 . A silicon wet growth process was adopted, with the following specific process parameters: temperature 800°C, wet oxygen atmosphere (flow rate O2=7SLM, H2=10SLM), and process time 4.5 minutes. The results showed that the thickness of the phosphorus-doped silicon dioxide layer was 46.85nm, while the thickness of the boron-doped silicon dioxide layer was 12.34nm. The surface morphology of the grown silicon dioxide layer was smooth and the nanostructure was clear. By controlling the doping concentration, the bottom-up growth preparation of micro-nanostructures of different thicknesses can be achieved. The results are shown in the figure. Figure 2 shown.

[0054] Example 2: Doping different elements on a polycrystalline silicon substrate, forming a doped substrate with pn junction characteristics by precisely controlling the doping concentration and doping area. First, a polycrystalline silicon substrate is selected, and phosphorus (P) and boron (B) are doped in different areas, with the doping concentrations set to 1×10 19 atoms / cm 3 and 5×10 18 atoms / cm 3 The doped substrate is heat treated to cause the P and B elements to diffuse to the required depth, forming a pn junction doping structure.

[0055] The doped substrate is then oxidized to grow a thin layer of silicon dioxide. The process conditions are: 900°C, a wet oxygen atmosphere (5 SLM of O2 flow, 8 SLM of H2 flow), and a 30-minute process. During the oxidation process, the doping elements (P and B) diffuse into the substrate, forming micro-nano pillar structures of controlled height. For P-doped regions, the resulting silicon dioxide micro-nano pillars are approximately 200 nm in height; for B-doped regions, the height is approximately 100 nm.

[0056] Due to the excellent optical properties of polysilicon and silicon dioxide, this deep micro-nanostructure is suitable for multifunctional transmission gratings, especially for use in solar panels to enhance light absorption and improve photoelectric conversion efficiency, such as Figure 3 shown.

[0057] Anything not described in detail in this specification belongs to the prior art known to those skilled in the art. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of equivalents of the claims be encompassed within the present invention.

Claims

1. A method for processing silicon dioxide micro-nanostructures on the surface of polycrystalline silicon, characterized in that: The difference in the growth rate of silicon dioxide on the surface of polysilicon with different doping concentrations is used to prepare micro-nano structures; by controlling the oxidation growth time, nano-scale micro-nano structures can be directly prepared.

2. The method for processing silicon dioxide micro-nanostructures on the surface of polycrystalline silicon according to claim 1, characterized in that: The steps include: S1. Preparation of doped polysilicon; S2, thermal oxidation reaction; S3, oxidation rate control; S4, diffusion and reconstruction of dopant atoms; S5. Stage changes in reaction rate.

3. The method for processing silicon dioxide micro-nano structures on the surface of polycrystalline silicon according to claim 2, characterized in that: The step S1 specifically includes: Doping ions of different concentrations are implanted into polysilicon; the doping elements include phosphorus and boron. For highly doped polysilicon substrates, before the thermal oxidation reaction, the concentration distribution of the doping atoms conforms to the Gaussian distribution, that is, as the depth of the substrate increases, the concentration of the doping atoms gradually decreases, and the doping concentration is adjusted according to specific needs.

4. The method for processing silicon dioxide micro-nanostructures on the surface of polycrystalline silicon according to claim 2, characterized in that: The step S2 specifically includes: The doped polysilicon is subjected to a thermal oxidation reaction at an appropriate temperature; dry oxidation is suitable for producing a high-quality thin passivation layer, and wet oxidation is suitable for growing a relatively thick passivation layer.

5. The method for processing silicon dioxide micro-nano structures on the surface of polycrystalline silicon according to claim 2, characterized in that: The thin passivation layer is a MOS process gate oxide dielectric layer; the relatively thick passivation layer is a mask, local oxidation isolation or capacitor structure.

6. The method for processing silicon dioxide micro-nano structures on the surface of polycrystalline silicon according to claim 2, characterized in that: In step S3, the high doping concentration on the surface increases the crystal defects at the reaction interface, providing a large number of reaction sites and promoting the oxidation reaction rate; the doping atoms diffused into the silicon dioxide also increase the defectivity of the silicon dioxide, making it easier for the oxidant to diffuse into the reaction interface, thereby accelerating the oxidation reaction rate.

7. The method for processing silicon dioxide micro-nanostructures on the surface of polycrystalline silicon according to claim 2, characterized in that: In step S4, depending on the type of dopant atoms, the diffusion and reconstruction of the dopant atoms during the oxidation process depends on the difference in their solubility in silicon and silicon dioxide.

8. The method for processing silicon dioxide micro-nanostructures on the surface of polycrystalline silicon according to claim 7, characterized in that: In step S5, from the initial stage of the oxidation reaction to the thin layer oxidation stage, the reaction rate mainly depends on the interface reaction rate; the high concentration of phosphorus doping at the interface provides a large number of electrons, accelerating the charge transfer process, thereby increasing the reaction rate; as the oxide layer thickens, the reaction rate dominated by the diffusion of the oxidant changes more significantly, and the grown silicon dioxide layer has a higher thickness.

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