Preparation method of phosphosilicate glass bead probe

Abstract

The invention belongs to the technical field of semiconductors, and discloses a preparation method of a phosphosilicate glass bead probe. The method comprises the following steps: preparing a phosphosilicate glass film on a silicon wafer on an insulator through a low-pressure chemical vapor deposition method, wherein the silicon wafer on the insulator comprises a silicon substrate layer, an insulating silicon dioxide middle layer and a monocrystalline silicon top layer which are sequentially arranged from bottom to top; carrying out patterning treatment on the phosphosilicate glass film through photoetching and dry etching to form a phosphosilicate glass structure with a predetermined shape; performing deep silicon etching treatment on the monocrystalline silicon top layer to form a cantilever beam structure and a ball support structure; performing thermal oxidation treatment on the phosphosilicate glass structure to form a spherical needle tip; and processing the silicon substrate layer and the insulating silicon dioxide intermediate layer to form a needle holder structure so as to obtain the phosphosilicate glass bead probe. Based on the method, glue-free bonding preparation of the phosphosilicate glass bead probe can be realized, and the method has the advantages of high-precision positioning and avoidance of pollution and shedding.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a method for preparing a type of phosphosilicate glass microsphere probe. Background Technology

[0002] Atomic force microscopy (AFM), a high-resolution scanning and detection technique, is widely used in materials science, biomedicine, and nanotechnology. The core component of AFM is the probe, whose performance directly affects measurement accuracy and imaging quality. Traditional AFM probes typically use tapered silicon tips; however, when measuring soft materials (such as biological samples), these sharp probes can easily damage the sample surface, making it impossible to accurately obtain information about particle surface interactions.

[0003] To address this issue, microsphere probes have been proposed as an alternative. The tips of microsphere probes are spherical, offering advantages over traditional sharp probes, including load dispersion, high stability, and broad applicability. Currently, the fabrication of microsphere probes primarily relies on adhesive bonding methods, where micron-sized microspheres are fixed to the probe cantilever beam using glue. However, this method suffers from difficulties in positioning, risks of contamination, and microsphere detachment, severely impacting the probe's measurement accuracy and lifespan.

[0004] This section is intended to provide background or context for the embodiments of the invention set forth in the claims. It should not be construed as an admission that the description herein is prior art. Summary of the Invention

[0005] The method for preparing phosphosilicate glass microsphere probes provided in this invention at least solves the problems of positioning difficulties, contamination risks, and microsphere detachment in the preparation of microsphere probes in related technologies.

[0006] According to a first aspect of the present invention, a method for preparing a phosphosilicate glass microsphere probe is provided, comprising: Phosphosilicate glass films are prepared on silicon-on-insulator wafers by low-pressure chemical vapor deposition. The silicon-on-insulator wafers include a silicon substrate layer, an insulating silicon dioxide intermediate layer, and a monocrystalline silicon top layer arranged from bottom to top. The thickness of the monocrystalline silicon top layer is less than the thickness of the silicon substrate layer. The phosphosilicate glass film is located above the monocrystalline silicon top layer. The phosphosilicate glass film is patterned by photolithography and dry etching to form a phosphosilicate glass structure of a predetermined shape. Deep silicon etching is performed on the top layer of the monocrystalline silicon to form a cantilever beam structure and a ball support structure for supporting the phosphosilicate glass structure. The ball support structure is located on the cantilever beam structure. The phosphosilicate glass structure is subjected to thermal oxidation treatment, and the phosphosilicate glass structure is reflowed to form a spherical needle tip; The silicon substrate and the insulating silicon dioxide intermediate layer are processed to form a pin holder structure on the silicon substrate to obtain a phosphosilicate glass microsphere probe.

[0007] According to an embodiment of the present invention, the method further includes: A 300nm thick silicon dioxide layer was deposited on two 500μm thick silicon wafers by thermal oxidation to form an initial insulating silicon dioxide intermediate layer. After aligning the two silicon wafers with the initial insulating silicon dioxide intermediate layer, they are placed in a bonding machine and bonded at high temperature using a mold of the corresponding size to obtain silicon wafers on the initial insulator. One side of the initial silicon wafer on an insulator is mechanically thinned from 500 μm to 12 μm. The thinned silicon wafer serves as the top monocrystalline silicon layer, while the other side remains as the silicon substrate layer, thereby forming the silicon wafer on an insulator having the structure of the top monocrystalline silicon layer, the insulating silicon dioxide intermediate layer, and the silicon substrate layer.

[0008] According to an embodiment of the present invention, the method further includes: The silicon wafer on the insulator is immersed in a mixed solution of ammonia, hydrogen peroxide and deionized water at a ratio of 1:1:5 at 75-80°C for 15 minutes. The silicon wafer on the insulator is rinsed with deionized water and dried with nitrogen gas to remove organic contaminants, oxide layer and ionic contaminants from the surface of the silicon wafer on the insulator.

[0009] According to an embodiment of the present invention, the preparation of a phosphosilicate glass thin film on an insulator-on-silicon wafer by low-pressure chemical vapor deposition includes: On the cleaned silicon wafer surface of the insulator, a phosphosilicate glass film is deposited using a low-pressure chemical vapor deposition method. The thickness of the phosphosilicate glass film is 1 μm. The deposition atmosphere of the low-pressure chemical vapor deposition is 20 sccm of silane, 50 sccm of oxygen, and 30 sccm of phosphine.

[0010] According to an embodiment of the present invention, the step of patterning the phosphosilicate glass film by photolithography and dry etching to form a phosphosilicate glass structure of a predetermined shape includes: A circular photoresist pattern is formed on the phosphosilicate glass film by photolithography, wherein the diameter of the circular photoresist pattern is less than or equal to 10 μm. The phosphosilicate glass film is etched using a dry etching process to remove the phosphosilicate glass in areas not protected by photoresist, thereby forming a phosphosilicate glass structure of a predetermined shape corresponding to the photoresist pattern.

[0011] According to an embodiment of the present invention, the deep silicon etching process performed on the top layer of the monocrystalline silicon to form a cantilever beam structure and a ball support structure for supporting the phosphosilicate glass structure includes: The top layer of the single-crystal silicon is etched using photolithography and etching processes to form the ball support structure, which is an 8μm high silicon pillar. The remaining 4μm of the single-crystal silicon top layer was then micro- and nano-fabricated using photolithography and etching processes to prepare the cantilever beam structure.

[0012] According to an embodiment of the present invention, the thermal oxidation treatment of the phosphosilicate glass structure to reflow the phosphosilicate glass structure to form a spherical needle tip includes: The phosphosilicate glass structure was subjected to thermal oxidation treatment at 1200℃ for 5 hours. During the thermal oxidation process, the low melting point of phosphosilicate glass is utilized to cause the phosphosilicate glass structure to reflux at high temperature, forming the spherical needle tip. The diameter of the spherical needle tip is determined by the patterned dimensions of the phosphosilicate glass structure before thermal oxidation.

[0013] According to an embodiment of the present invention, the step of processing the silicon substrate and the insulating silicon dioxide interlayer to form a pin holder structure on the silicon substrate to obtain a phosphosilicate glass microsphere probe includes: The back side of the silicon substrate, the cantilever beam structure, and the spherical tip are coated with a homogenate, and the front side of the silicon wafer on the insulator after homogenization is imprinted and bonded to the silicon carrier to protect the cantilever beam structure and the spherical tip. The needle holder structure for supporting the spherical needle tip is etched on the back side of the silicon substrate using photolithography and deep silicon etching processes. Remove the silicon substrate, the insulating silicon dioxide interlayer, and the photoresist used for bonding to obtain the phosphosilicate glass microsphere probe.

[0014] Beneficial effects of the embodiments of the present invention: The method for preparing the phosphosilicate glass microsphere probe provided in this invention involves preparing a phosphosilicate glass (PSG) thin film on the surface of a single-crystal silicon top layer of a silicon-on-insulator (SOI) using low-pressure chemical vapor deposition (LPCVD). Subsequently, the PSG is patterned using photolithography and dry etching processes to form a PSG structure of a predetermined shape. Then, a cantilever beam structure and a spherical support structure are formed by deep silicon etching of the single-crystal silicon top layer. Finally, the PSG is reflowed through thermal oxidation to form a spherical tip, and the silicon substrate is processed to form a support structure to support the spherical tip, thereby obtaining the phosphosilicate glass microsphere probe. This method fully utilizes the low melting point of PSG material to achieve PSG reflow and sphere formation at high temperatures, avoiding the problems of positioning difficulties, contamination, and microsphere detachment caused by traditional glue bonding methods. At the same time, it achieves precise control of the microsphere probe position through micro-nano fabrication technology, improving the stability and reliability of the probe. It can also prepare submicron-sized microsphere probes, expanding its applicability in high-precision applications such as in-situ measurement of biological samples. It has good process repeatability and scalability, making it suitable for large-scale production.

[0015] Details of one or more embodiments of the present invention are set forth in the following drawings and description, so that other features, objects and advantages of the invention will be more readily understood. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating a method for preparing a phosphosilicate glass microsphere probe, as provided in an embodiment of the present invention.

[0018] Figure 2 A flowchart illustrating another method for preparing a phosphosilicate glass microsphere probe provided in an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of a silicon-on-insulator structure provided in an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of a silicon wafer on an insulator after deposition of a PSG thin film, provided as an embodiment of the present invention.

[0021] Figure 5 This is a schematic diagram of a patterned PSG-backed silicon-on-insulator structure provided in an embodiment of the present invention.

[0022] Figure 6 This is a schematic diagram of a silicon wafer on an insulator after forming a ball support structure, provided as an embodiment of the present invention.

[0023] Figure 7 This is a schematic diagram of a silicon wafer on an insulator after forming a cantilever beam structure, provided as an embodiment of the present invention.

[0024] Figure 8 This is a schematic diagram of a silicon wafer on an insulator after forming a spherical needle tip, provided as an embodiment of the present invention.

[0025] Figure 9 This is a schematic diagram of a silicon wafer on an insulator after back-side exposure and front-side spin coating of photoresist, provided as an embodiment of the present invention.

[0026] Figure 10 This is a schematic diagram of the structure of a silicon wafer on an insulator bonded to a silicon carrier after an embodiment of the present invention.

[0027] Figure 11 This is a schematic diagram of a silicon wafer on an insulator after forming a pin holder structure, provided as an embodiment of the present invention.

[0028] Figure 12 This is a schematic diagram of the structure of a phosphosilicate glass microsphere probe provided in an embodiment of the present invention. Detailed Implementation

[0029] Embodiments of this embodiment will now be described in more detail with reference to the accompanying drawings. While some embodiments of this embodiment are shown in the drawings, it should be understood that this embodiment can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this embodiment. It should be understood that the accompanying drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this embodiment.

[0030] Atomic force microscopy (AFM) is a high-precision surface probing technique widely used in materials, biology, and nanotechnology. Its probe is a key component affecting measurement accuracy. Traditional sharp silicon probes are prone to damage when examining soft samples, making it difficult to accurately characterize surface interactions. Therefore, spherical probes have been proposed, which can disperse pressure, improve stability, and are suitable for in-situ observation of biological samples. However, current methods often use glue to bond micron-sized spheres, leading to problems such as inaccurate positioning, contamination, and detachment, affecting probe performance and lifespan.

[0031] To address the above problems, this invention provides a method for preparing phosphosilicate glass microsphere probes. Figure 1 This is a flowchart illustrating a method for preparing a phosphosilicate glass microsphere probe according to an embodiment of the present invention. Figure 1As shown, the method includes the following steps.

[0032] Step S101: A phosphosilicate glass film is prepared on a silicon-on-insulator wafer by low-pressure chemical vapor deposition. The silicon-on-insulator wafer includes a silicon substrate layer, an insulating silicon dioxide intermediate layer, and a monocrystalline silicon top layer arranged from bottom to top. The thickness of the monocrystalline silicon top layer is less than the thickness of the silicon substrate layer. The phosphosilicate glass film is located above the monocrystalline silicon top layer.

[0033] Step S102: The phosphosilicate glass film is patterned by photolithography and dry etching to form a phosphosilicate glass structure of a predetermined shape.

[0034] Step S103: Deep silicon etching is performed on the top layer of the monocrystalline silicon to form a cantilever beam structure and a ball support structure for supporting the phosphosilicate glass structure. The ball support structure is located on the cantilever beam structure.

[0035] Step S104: The phosphosilicate glass structure is subjected to thermal oxidation treatment, so that the phosphosilicate glass structure is reflowed to form a spherical needle tip.

[0036] Step S105: The silicon substrate and the insulating silicon dioxide intermediate layer are processed to form a pin holder structure on the silicon substrate to obtain a phosphosilicate glass microsphere probe.

[0037] First, a phosphosilicate glass film is prepared on a silicon-on-insulator (SOI) wafer using a low-pressure chemical vapor deposition method. In this embodiment, the SOI wafer comprises, from bottom to top, a silicon substrate layer, an insulating silicon dioxide intermediate layer, and a monocrystalline silicon top layer. The thickness of the monocrystalline silicon top layer is less than the thickness of the silicon substrate layer, and the phosphosilicate glass film is located above the monocrystalline silicon top layer.

[0038] In this embodiment, after the pretreatment of the silicon-on-insulator (SOI) wafer is completed, a phosphosilicate glass (PSG) thin film is deposited on the top surface of the monocrystalline silicon using low-pressure chemical vapor deposition (LPCVD). This process can be performed under relatively low pressure conditions, and in practical applications, it can be operated at or near atmospheric pressure to reduce the non-uniformity caused by gas diffusion.

[0039] During deposition, the gas mixture used includes silane (SiH4), oxygen (O2), and phosphine (PH3). Silane provides the silicon source, oxygen acts as an oxidant to promote the oxidation reaction, and phosphine introduces phosphorus, resulting in a PSG film with good fluidity and a low melting point. The deposition atmosphere parameters can be adjusted according to actual process requirements. For example, the silane flow rate is controlled at 20 sccm, the oxygen flow rate at 50 sccm, and the phosphine flow rate at 30 sccm to ensure a balance between deposition rate and film quality. After deposition, the obtained PSG film is approximately 1 micrometer thick and uniformly covers the surface of the single-crystal silicon top layer, providing a good foundation for subsequent patterning processing.

[0040] The phosphosilicate glass film prepared in this embodiment not only possesses high density and uniformity, but also exhibits unique physicochemical properties, such as low melting point and high fluidity, enabling it to undergo reflow during subsequent thermal oxidation treatment, thereby forming the desired spherical needle tip structure. Furthermore, since the PSG film is directly deposited on the top layer of single-crystal silicon, rather than through adhesive bonding, problems such as positioning deviation, contamination, and detachment inherent in traditional methods can be avoided, further enhancing the stability and reliability of the probe.

[0041] In the implementation of this invention, before preparing the phosphosilicate glass thin film, it is first necessary to prepare an insulator-on-silicon substrate material with a specific structure. This substrate material consists of three layers: a silicon substrate layer, an insulating silicon dioxide intermediate layer, and a single-crystal silicon top layer, from bottom to top. The silicon substrate layer typically uses a relatively thick single-crystal silicon wafer as the support structure, with a thickness of approximately 500 micrometers, to ensure the overall mechanical strength and stability of the structure. The insulating silicon dioxide intermediate layer is formed on the surface of the silicon substrate layer through a thermal oxidation process, with a thickness of approximately 300 nanometers, serving as an insulator. The single-crystal silicon top layer is the main target for subsequent micro / nano processing; its thickness should be less than that of the silicon substrate layer, and can be reduced to approximately 12 micrometers to meet the requirements of subsequent microstructure processing. After completing the preparation of the above structure, the insulator-on-silicon wafer is cleaned to remove any organic contaminants, oxide layers, and ionic impurities that may be present on the surface, ensuring the smooth progress of subsequent deposition processes.

[0042] Specifically, in the fabrication of silicon-on-insulator (SOI) wafers, a 300 nm thick silicon dioxide layer is first deposited on two 500 μm thick silicon wafers using a thermal oxidation method to form an initial insulating silicon dioxide intermediate layer. Then, the two silicon wafers with the initial insulating silicon dioxide intermediate layer are aligned, placed in a bonding machine, and bonded at high temperature using a mold of the corresponding size to obtain the initial SOI wafer. Finally, one side of the initial SOI wafer is mechanically thinned from 500 μm to 12 μm. The thinned wafer serves as the top monocrystalline silicon layer, while the other side remains as the silicon substrate layer, thus forming an SOI wafer with a structure of a top monocrystalline silicon layer, an insulating silicon dioxide intermediate layer, and a silicon substrate layer.

[0043] After obtaining the silicon-on-insulator (SiI) wafer, it can be immersed in a mixed solution of ammonia, hydrogen peroxide, and deionized water at a ratio of 1:1:5 at 75-80°C for 15 minutes; then rinsed with deionized water and dried with nitrogen gas to remove organic contaminants, oxide layer, and ionic contaminants from the surface of the SiI wafer.

[0044] After the deposition of the phosphosilicate glass film is completed, the phosphosilicate glass film is patterned by photolithography and dry etching to form a phosphosilicate glass structure of a predetermined shape.

[0045] In this embodiment, the cleaned and dried silicon-on-insulator wafer is first placed in a photolithography apparatus, and a standard photolithography process is used to pattern the phosphosilicate glass film. During the photolithography process, photoresist is applied to the surface of the phosphosilicate glass, and specific areas are exposed using a mask. This causes a chemical change in the photoresist within the exposed area, thereby forming a photoresist pattern with a specific geometric shape. The size of the photoresist pattern can be adjusted according to actual needs. In this embodiment, its diameter can be controlled to be less than or equal to 10 micrometers to ensure that a precise spherical needle-like structure can be formed during the subsequent thermal oxidation process.

[0046] Subsequently, the areas of phosphosilicate glass not covered by photoresist are selectively removed using dry etching equipment. Dry etching employs plasma or chemical gas reactions to perform high-precision, low-damage etching of the phosphosilicate glass. During this process, the etching rate can be controlled between 0.5 and 2 micrometers per minute to ensure the uniformity and stability of the etching process and avoid sidewall roughness or pattern distortion caused by excessively rapid etching. By precisely controlling the etching time and parameters, a predetermined phosphosilicate glass structure corresponding to the photoresist pattern is finally formed on the phosphosilicate glass film. This structure serves as the basis for subsequent thermal oxidation reflow to form spherical tips, and its shape and size directly affect the performance and quality of the final probe tip. The entire patterning process is carried out in a clean environment to prevent external contaminants from affecting the phosphosilicate glass surface, ensuring that the final spherical probe has good surface quality and structural consistency.

[0047] In practical applications, a circular photoresist pattern can be formed on a phosphosilicate glass film using photolithography. The diameter of the circular photoresist pattern is less than or equal to 10 μm. Then, a dry etching process is used to etch the phosphosilicate glass film to remove the phosphosilicate glass in areas not protected by the photoresist, so that the phosphosilicate glass film forms a phosphosilicate glass structure of a predetermined shape corresponding to the photoresist pattern.

[0048] After patterning the phosphosilicate glass film, the next step is to perform deep silicon etching on the top layer of monocrystalline silicon to form a cantilever beam structure and a ball support structure to support the phosphosilicate glass structure. The ball support structure is located on the cantilever beam structure.

[0049] In this embodiment, a photolithography process is first performed on the top layer of monocrystalline silicon to form a protective layer in a specific area using photoresist, thereby defining the area to be etched. Subsequently, deep silicon etching techniques, such as dry etching or wet etching, are used to precisely process the top layer of monocrystalline silicon according to the designed pattern. During this process, the etching depth must be strictly controlled to ensure that sufficient structural strength and stability are retained while removing some of the monocrystalline silicon material. Through this step, the top layer of monocrystalline silicon is processed into a section with a cantilever beam structure. This structure is a thin sheet-like structure with a certain length and width, providing good mechanical properties and sensitivity. Simultaneously, a ball-shaped support structure is formed at an appropriate location on the cantilever beam structure to support the phosphosilicate glass structure. The ball-shaped support structure is a tiny silicon pillar or platform, whose height and size ensure that the phosphosilicate glass structure can be stably attached to it during subsequent thermal oxidation processing, and that it undergoes reflow at high temperatures to form a spherical tip. This step achieves high-precision processing of the single-crystal silicon top layer through precise photolithography and etching processes, thus laying a solid foundation for the subsequent positioning and fixation of the phosphosilicate glass structure and the final formation of the spherical tip.

[0050] In practical applications, photolithography and etching processes can be used to perform deep silicon etching on the top layer of single-crystal silicon to form a ball support structure, which is an 8μm high silicon pillar; then, photolithography and etching processes can be used again to perform micro-nano processing on the remaining 4μm of the top layer of single-crystal silicon to prepare a cantilever beam structure.

[0051] After patterning the glass phosphosilicate film, a glass phosphosilicate structure with a specific shape and size is formed on the top layer of single-crystal silicon using photolithography and dry etching processes. This structure is typically a small, circular or near-circular region. At this point, the glass phosphosilicate structure is in a state without high-temperature treatment, and its surface is relatively flat and possesses a certain degree of mechanical strength. To achieve the spherical design of the probe tip, the glass phosphosilicate structure needs to undergo thermal oxidation. Specifically, thermal oxidation of the glass phosphosilicate structure can be performed to reflow the glass phosphosilicate structure and form a spherical tip.

[0052] In this embodiment, the thermal oxidation treatment is carried out in a high-temperature environment, and a high-temperature oxidation furnace can be used as the main equipment. In this embodiment, the temperature of the thermal oxidation treatment is set to about 1200°C; this temperature can effectively activate the melting characteristics of phosphosilicate glass, causing it to flow and gradually reflow to form a spherical structure after being heated. During the heating process, phosphosilicate glass material exhibits good thermal responsiveness due to its lower melting point (about 500°C lower than that of traditional silica materials), and can complete the transformation from a planar structure to a spherical structure in a short time. At the same time, the thermal oxidation process can also improve the surface quality of phosphosilicate glass, reduce surface defects, and thus improve the smoothness and stability of the needle tip.

[0053] During the thermal oxidation process, under high temperature, the molecular chains inside the phosphosilicate glass begin to loosen, and the material gradually softens. Subsequently, under the combined action of gravity and surface tension, the softened material begins to flow and redistribute, ultimately forming an approximately spherical structure. This process depends not only on temperature control, but also on the diameter of the spherical tip, which is determined by the patterned dimensions of the phosphosilicate glass structure before thermal oxidation. For example, if the initial pattern is a circular structure with a diameter less than or equal to 10 μm, the thermally oxidized spherical tip will have a corresponding size to meet the needs of different application scenarios. Furthermore, the thermal oxidation time also affects the final shape of the spherical tip; typically, the holding time can be set to around 5 hours to ensure sufficient material reflow and stable molding.

[0054] Through the aforementioned thermal oxidation process, the phosphosilicate glass structure was successfully reflowed and formed into a spherical tip. This spherical tip possesses excellent geometry and surface quality, making it suitable for use in high-precision inspection equipment such as atomic force microscopes. This step not only achieves precise control over the tip shape but also avoids problems such as inaccurate positioning, contamination, and detachment caused by the use of adhesives in traditional methods, further improving the reliability and lifespan of the probe.

[0055] After completing the thermal oxidation reflow of the phosphosilicate glass structure and forming the spherical needle tip, the silicon substrate layer of the silicon wafer on the insulator needs to be further processed to form a needle holder structure to support the entire probe structure.

[0056] First, before processing the silicon substrate and insulating silicon dioxide interlayer, the front structure of the probe is typically protected to prevent damage to the formed cantilever structure and spherical tip during subsequent processes such as etching or cleaning. To achieve this, a layer of photoresist is coated onto the front of the probe using a spin coating process, and then patterned using photolithography to cover only the cantilever structure and spherical tip area, thus protecting it during subsequent back-side processing. Next, the protected silicon-on-insulator (SOS) wafer is imprinted and bonded to another clean silicon substrate. Nanoimprint lithography is used to ensure a tight fit between the probe front and the substrate, preventing damage to the front structure during subsequent deep silicon etching. After the protection and bonding operations, the back of the silicon substrate is subjected to photolithography and deep silicon etching. By precisely controlling etching parameters such as etching gas, etching time, and etching rate, a portion of the silicon substrate material is gradually removed, forming a support structure on the back of the silicon substrate to support the spherical tip. This probe holder structure not only provides stable mechanical support for the probe, but also ensures the positioning accuracy and stability of the probe during use.

[0057] After the probe holder structure is formed, the probe needs to undergo a photoresist removal process. This involves using a suitable solvent to remove the previously coated photoresist, as well as other auxiliary materials used in the bonding process, such as the silicon substrate used for bonding and some residues of the insulating silicon dioxide interlayer. This process can use hydrofluoric acid (HF) solution to remove a portion of the insulating silicon dioxide interlayer to facilitate subsequent separation operations. Finally, after completing all necessary etching and cleaning steps, the probe can be peeled off from the silicon substrate to obtain a complete phosphosilicate glass microsphere probe. The probe prepared in this embodiment possesses good mechanical strength and structural stability, enabling it to operate reliably in various environments. It is suitable for high-precision detection equipment such as atomic force microscopes, and exhibits excellent performance, especially when measuring soft materials.

[0058] The preparation method of a phosphosilicate glass microsphere probe provided by the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0059] Figure 2 A flowchart illustrating another method for preparing a phosphosilicate glass microsphere probe provided in an embodiment of the present invention. Figure 2 As shown, the preparation method of the phosphosilicate glass microsphere probe in this embodiment includes the following steps: S201: Preparation of SOI substrate.

[0060] In this embodiment, a 300nm thick silicon dioxide layer is deposited on two 500μm thick monocrystalline silicon wafers using a thermal oxidation method. The two silicon wafers with SiO2 layers are aligned and placed in a bonding machine, where they are bonded at high temperature using a mold of corresponding size. After bonding, one of the silicon wafers is mechanically thinned from 500μm to 12μm, serving as the "front side" in subsequent processes. The other wafer remains as the "back side," thus forming a silicon-on-insulator (SiO2) wafer with a monocrystalline silicon top layer, an insulating silicon dioxide intermediate layer, and a silicon substrate layer. A schematic diagram of the SiO2 wafer structure is shown below. Figure 3 As shown.

[0061] S202: Perform RCA cleaning on the SOI substrate.

[0062] In this embodiment, the prepared SOI sheet was subjected to RCA cleaning by immersing it in a mixed solution of ammonia, hydrogen peroxide, and deionized water at a ratio of 1:1:5 at 75-80°C for 15 minutes to remove surface organic contaminants, oxide layers, and ionic contaminants. It was then rinsed with deionized water and dried with nitrogen gas.

[0063] S203: Deposit a PSG thin film on an SOI substrate.

[0064] In this embodiment, a 1 μm thick layer of phosphosilicate glass (PSG) was deposited on the surface of an SOI wafer using low-pressure chemical vapor deposition (LPCVD). The deposition atmosphere was: silane (SiH4) 20 sccm, oxygen (O2) 50 sccm, and phosphine (PH3) 30 sccm. The deposited PSG exhibited good fluidity, and its melting point was reduced by approximately 500°C compared to conventional SiO2. A schematic diagram of the silicon wafer structure on the insulator after PSG film deposition is shown below. Figure 4 As shown.

[0065] S204: Graphical PSG.

[0066] In this embodiment, a circular photoresist pattern is formed on the PSG thin film using photolithography. The diameter of the photoresist pattern is less than or equal to 10 μm. Subsequently, a dry etching process is used to remove the PSG in areas not protected by the photoresist, with an etching rate of 0.5~2 μm / min to ensure patterning accuracy and avoid lateral etching. A schematic diagram of the silicon wafer on insulator structure after patterning the PSG is shown below. Figure 5 As shown.

[0067] S205: Deep silicon etching forms a ball support structure.

[0068] In this embodiment, a 12μm thick single-crystal silicon layer on the front side of the SOI wafer is processed using photolithography and deep silicon etching to etch an 8μm high silicon pillar, which serves as a support structure for the spherical tip. This silicon pillar prevents excessive flow of PSG during thermal oxidation, ensuring the shape stability of the spherical tip. A schematic diagram of the silicon wafer structure on the insulator after forming the spherical support structure is shown below. Figure 6 As shown.

[0069] S206: Micro-nano fabrication forms a cantilever beam structure.

[0070] In this embodiment, after etching the spherical support structure, the remaining 4μm thick single-crystal silicon is further micro- and nano-fabricated to form a cantilever beam structure to support the spherical needle tip. A schematic diagram of the silicon wafer on the insulator after forming the cantilever beam structure is shown below. Figure 7 As shown.

[0071] S207: Thermal oxidation forms a spherical needle tip.

[0072] In this embodiment, the patterned PSG structure is placed in an oxidation furnace and subjected to thermal oxidation at 1200°C for 5 hours. Due to the low melting point of PSG, it reflows at high temperatures, forming spherical tips. The final size of the spherical tips is determined by the patterned size of the PSG before thermal oxidation. A schematic diagram of the silicon-on-insulator structure after forming the spherical tips is shown below. Figure 8 As shown.

[0073] S208: Backside protection treatment.

[0074] In this embodiment, the back side of the SOI wafer undergoes homogenization and photolithography, while the front side is spin-coated with photoresist to protect the front structure from subsequent back-side processes. A schematic diagram of the silicon-on-insulator (SOI) wafer structure after back-side exposure and front-side photoresist spin-coating is shown below. Figure 9 As shown.

[0075] S209: Imprint bonding.

[0076] In this embodiment, the front side of the SOI wafer after photoresist coating is imprinted and bonded to another clean silicon carrier wafer to facilitate subsequent etching processes on the back side. A schematic diagram of the structure after bonding the front side of the silicon wafer to the silicon carrier wafer on the insulator is shown below. Figure 10 As shown.

[0077] S210: Etching to form a pin holder structure.

[0078] In this embodiment, photolithography and deep silicon etching processes are used to etch a needle holder structure for supporting the spherical needle tip onto a 500μm thick silicon wafer on the back side of the SOI wafer. A schematic diagram of the silicon wafer structure on the insulator after the needle holder structure is formed is shown below. Figure 11 As shown.

[0079] S211: Remove the bonding layer and photoresist to obtain a complete probe.

[0080] In this embodiment, HF acid is used to remove the intermediate SiO2 layer, and then acetone solution is used to remove the silicon carrier and photoresist used for bonding, finally obtaining a complete phosphosilicate glass microsphere probe. A schematic diagram of the phosphosilicate glass microsphere probe structure is shown below. Figure 12 As shown.

[0081] It should be noted that the term "comprising" and its variations used in the embodiments of the present invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "multiple" mentioned in the embodiments of the present invention are illustrative and not restrictive. Those skilled in the art should understand that, unless explicitly indicated otherwise in the context, they should be understood as "one or more".

[0082] The steps described in the method embodiments provided by this invention can be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of protection of this invention is not limited in this respect.

[0083] The term "embodiment" in this specification refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply independence or alternativeity from other embodiments. The various embodiments in this specification are described in a related manner, with reference to each other for similar or identical parts. In particular, for apparatus, device, and system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, and relevant details are referred to in the description of the method embodiments.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for preparing a phosphosilicate glass microsphere probe, characterized in that, include: Phosphosilicate glass films are prepared on silicon-on-insulator wafers by low-pressure chemical vapor deposition. The silicon-on-insulator wafers include a silicon substrate layer, an insulating silicon dioxide intermediate layer, and a monocrystalline silicon top layer arranged from bottom to top. The thickness of the monocrystalline silicon top layer is less than the thickness of the silicon substrate layer. The phosphosilicate glass film is located above the monocrystalline silicon top layer. The phosphosilicate glass film is patterned by photolithography and dry etching to form a phosphosilicate glass structure of a predetermined shape. Deep silicon etching is performed on the top layer of the monocrystalline silicon to form a cantilever beam structure and a ball support structure for supporting the phosphosilicate glass structure. The ball support structure is located on the cantilever beam structure. The phosphosilicate glass structure is subjected to thermal oxidation treatment, and the phosphosilicate glass structure is reflowed to form a spherical needle tip; The silicon substrate and the insulating silicon dioxide intermediate layer are processed to form a pin holder structure on the silicon substrate to obtain a phosphosilicate glass microsphere probe.

2. The method according to claim 1, characterized in that, The method further includes: A 300nm thick silicon dioxide layer was deposited on two 500μm thick silicon wafers by thermal oxidation to form an initial insulating silicon dioxide intermediate layer. After aligning the two silicon wafers with the initial insulating silicon dioxide intermediate layer, they are placed in a bonding machine and bonded at high temperature using a mold of the corresponding size to obtain silicon wafers on the initial insulator. One side of the initial silicon wafer on an insulator is mechanically thinned from 500 μm to 12 μm. The thinned silicon wafer serves as the top monocrystalline silicon layer, while the other side remains as the silicon substrate layer, thereby forming the silicon wafer on an insulator having the structure of the top monocrystalline silicon layer, the insulating silicon dioxide intermediate layer, and the silicon substrate layer.

3. The method according to claim 2, characterized in that, The method further includes: The silicon wafer on the insulator is immersed in a mixed solution of ammonia, hydrogen peroxide and deionized water at a ratio of 1:1:5 at 75-80°C for 15 minutes. The silicon wafer on the insulator is rinsed with deionized water and dried with nitrogen gas to remove organic contaminants, oxide layer and ionic contaminants from the surface of the silicon wafer on the insulator.

4. The method according to claim 2, characterized in that, The preparation of a phosphosilicate glass thin film on an insulator-on-silicon wafer by low-pressure chemical vapor deposition includes: On the cleaned silicon wafer surface of the insulator, a phosphosilicate glass film is deposited using a low-pressure chemical vapor deposition method. The thickness of the phosphosilicate glass film is 1 μm. The deposition atmosphere of the low-pressure chemical vapor deposition is 20 sccm of silane, 50 sccm of oxygen, and 30 sccm of phosphine.

5. The method according to claim 2, characterized in that, The step of patterning the phosphosilicate glass film using photolithography and dry etching to form a phosphosilicate glass structure of a predetermined shape includes: A circular photoresist pattern is formed on the phosphosilicate glass film by photolithography, wherein the diameter of the circular photoresist pattern is less than or equal to 10 μm. The phosphosilicate glass film is etched using a dry etching process to remove the phosphosilicate glass in areas not protected by photoresist, thereby forming a phosphosilicate glass structure of a predetermined shape corresponding to the photoresist pattern.

6. The method according to claim 2, characterized in that, The deep silicon etching process performed on the top layer of the monocrystalline silicon to form a cantilever beam structure and a ball support structure for supporting the phosphosilicate glass structure includes: The top layer of the single-crystal silicon is etched using photolithography and etching processes to form the ball support structure, which is an 8μm high silicon pillar. The remaining 4μm of the single-crystal silicon top layer was then micro- and nano-fabricated using photolithography and etching processes to prepare the cantilever beam structure.

7. The method according to claim 2, characterized in that, The thermal oxidation treatment of the phosphosilicate glass structure, causing it to reflow and form a spherical needle tip, includes: The phosphosilicate glass structure was subjected to thermal oxidation treatment at 1200℃ for 5 hours. During the thermal oxidation process, the low melting point of phosphosilicate glass is utilized to cause the phosphosilicate glass structure to reflux at high temperature, forming the spherical needle tip. The diameter of the spherical needle tip is determined by the patterned dimensions of the phosphosilicate glass structure before thermal oxidation.

8. The method according to claim 2, characterized in that, The process of treating the silicon substrate and the insulating silicon dioxide interlayer to form a pin holder structure on the silicon substrate to obtain a phosphosilicate glass microsphere probe includes: The back side of the silicon substrate, the cantilever beam structure, and the spherical tip are coated with a homogenate, and the front side of the silicon wafer on the insulator after homogenization is imprinted and bonded to the silicon carrier to protect the cantilever beam structure and the spherical tip. The needle holder structure for supporting the spherical needle tip is etched on the back side of the silicon substrate using photolithography and deep silicon etching processes. Remove the silicon substrate, the insulating silicon dioxide interlayer, and the photoresist used for bonding to obtain the phosphosilicate glass microsphere probe.

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