Low-stress chemical mechanical etching process suitable for brittle material

Abstract

The invention relates to a low-stress chemical mechanical etching process suitable for fragile materials, which belongs to the technical field of etching processing of fragile materials and comprises a precise chemical mechanical polishing machine, a polishing pad, a polishing solution conveying and managing system and end point detection equipment. The precise chemical mechanical polishing machine comprises a multi-zone pressure controllable polishing head, a high-precision rotating speed control system and a real-time thickness measuring system, a polishing pad is a polishing disc made of porous polyurethane materials, and the polishing liquid conveying and managing system comprises a multi-channel metering pump system and a stirring and temperature control unit. And the end point detection equipment comprises a surface profilometer, an atomic force microscope and a transmission electron microscope. According to the method, through fine cooperation of chemical reaction and mechanical grinding, microcrack initiation and propagation in the polishing process are effectively inhibited, surface and subsurface damage of the fragile material is remarkably reduced, the machined surface which is ultrahigh in smoothness and free of damage is obtained, and meanwhile the high material removal rate is kept.

Description

Technical Field

[0001] This invention relates to the field of etching processing technology for brittle materials, and in particular to a low-stress chemical mechanical etching process suitable for brittle materials. Background Technology

[0002] Chemical mechanical polishing is a finishing technique that combines chemical reactions and mechanical grinding to achieve global surface planarization. It uses a special chemical solution (polishing slurry) to soften the surface of the material to be removed, while a polishing head presses against the silicon wafer and rubs it on a rotating polishing pad, thus physically grinding away the softened material.

[0003] Chemical mechanical polishing (CMP) has become a key technology for achieving global planarization in semiconductor manufacturing. However, for brittle materials such as single-crystal silicon, silicon carbide, and sapphire, their tensile strength is much lower than their compressive strength. Under the mechanical stress of traditional CMP processes, they are prone to subsurface defects such as microcracks, scratches, and lattice damage. These defects can significantly reduce the mechanical strength, electrical performance, and reliability of devices.

[0004] Existing technologies typically reduce mechanical damage by lowering polishing pressure, using softer abrasives, or optimizing polishing pads, but this often comes at the cost of sacrificing material removal rate. On the other hand, while strong oxidants or corrosive chemicals can improve removal rate, they can exacerbate surface corrosion and create defects such as pits. Therefore, achieving a precise balance between chemical reaction and mechanical removal, while maintaining efficient material removal and minimizing stress and damage, is a pressing technical challenge in this field. To address this, a low-stress chemical mechanical etching process suitable for brittle materials is proposed. Through the precise synergy of chemical reaction and mechanical grinding, the initiation and propagation of microcracks during polishing are effectively suppressed, significantly reducing surface and subsurface damage to brittle materials. This results in an ultra-smooth, damage-free processed surface while maintaining a high material removal rate. Summary of the Invention

[0005] This invention provides a low-stress chemical mechanical etching process suitable for brittle materials, which solves the problem of unavoidable mechanical damage in the polishing of brittle materials, resolves the contradiction between high material removal rate and low surface damage, solves the problem of poor consistency and repeatability of polishing process, and solves the problem of global planarization uniformity of large-size wafers.

[0006] The present invention provides the following solution to the above-mentioned technical problems: a low-stress chemical mechanical etching process suitable for brittle materials, comprising a precision chemical mechanical polishing machine, a polishing pad, a polishing fluid delivery and management system, and an endpoint detection device. The precision chemical mechanical polishing machine includes a multi-zone pressure-controllable polishing head, a high-precision speed control system, and a real-time thickness measurement system. The polishing pad is a polishing disc made of porous polyurethane material. The polishing fluid delivery and management system includes a multi-channel metering pump system and a stirring and temperature control unit. The endpoint detection device includes a surface profilometer, an atomic force microscope, and a transmission electron microscope.

[0007] The etching process includes the following steps: S1, prepare a special chemical mechanical polishing fluid; S2, Workpiece preparation and mounting: After cleaning the brittle material workpiece to be polished, it is clamped on the carrier of the multi-zone pressure controllable polishing head. S3, Equipment initialization and parameter setting, initialize the precision chemical mechanical polishing machine, load the process formula; S4, First step polishing: The polishing liquid is supplied to the rotating polishing pad at a first flow rate, the downward pressure of the polishing head on the workpiece is controlled to be 1-3 psi, and the speed ratio of the polishing head to the polishing pad is 0.8:1 to 1.2:1, to perform preliminary high-speed planarization; S5, Second polishing step: Adjust the polishing slurry supply so that the abrasive concentration is lower than in the first step, control the downward pressure of the polishing head on the workpiece to be 0.5-2 psi, and the speed ratio of the polishing head to the polishing pad to be 0.5:1 to 0.8:1 for fine low-stress polishing; S6, Process completion and post-processing: After fine low-stress polishing, the workpiece is separated from the polishing pad, the polishing fluid and abrasive are rinsed off, and the workpiece is removed and cleaned. Finally, it is tested and verified by the endpoint testing equipment.

[0008] Based on the above technical solution, the present invention can be further improved as follows.

[0009] Furthermore, the multi-zone pressure-controllable polishing head can apply independent, precise, and programmable downward pressure (typically controlled within the range of 0.1 psi to 5 psi) to different areas on the back of the wafer, ensuring uniform force on the wafer throughout the polishing process and preventing over-polishing at the edges or under-polishing at the center. The high-precision speed control system allows for independent stepless speed adjustment of the polishing head spindle and polishing pad spindle, with stable and precise speed control. The speed ratio (polishing head speed / polishing pad speed) is a key parameter for controlling the polishing mode (chemical-dominated or mechanical-dominated). The real-time thickness measurement system, integrated into the polishing head, uses an online thickness measurement module (such as optical interferometry or eddy current type) to monitor the material removal rate and remaining thickness in real time, providing data support for process endpoint detection. The multi-zone pressure-controllable polishing head can actively compensate for uneven pressure distribution caused by workpiece warping or the fixture system, fundamentally avoiding the "over-polishing at the edges" or "under-polishing at the center" phenomena that easily occur under traditional single pressure, ensuring a high degree of consistency in material removal across the entire processed surface, thereby achieving excellent global planarization. The high-precision speed control system... Precise control of the rotation speed ratio (e.g., close to 1:1 in the first step, less than 1 in the second step) allows for active adjustment of the polishing mode. At high rotation speed ratios, the mechanical action is enhanced, facilitating rapid planarization; at low rotation speed ratios, the shear force is reduced, and chemical action dominates, facilitating low-damage polishing. This controllability is the foundation for achieving different process objectives in the "two-step method." The real-time thickness measurement system elevates the process from traditional "time control" or "experience control" to "data-driven control." It not only provides real-time feedback on the material removal rate, offering data for process optimization, but also enables precise endpoint detection, automatically stopping polishing when the thickness reaches the target value, avoiding under-polishing or over-polishing, and greatly improving process repeatability and product yield.

[0010] Furthermore, the multi-channel metering pump system can store two or more polishing slurries with different formulations (such as high-concentration and low-concentration abrasive slurries) and can precisely switch and deliver them according to process instructions. Flow control must be precise and stable. The stirring and temperature control unit is a polishing slurry storage tank equipped with a continuous stirring device and temperature control function. This prevents abrasive sedimentation while stabilizing the polishing slurry temperature at a set value (such as 25±1°C) to maintain the stability of the chemical reaction rate. The multi-channel metering pump system can seamlessly connect two different chemical mechanical environments (high removal rate and low stress) in one process without removing the workpiece midway. This ensures process efficiency and avoids contamination or errors that may be introduced by secondary clamping. The stirring and temperature control unit can maintain the uniformity of the polishing slurry components and the stability of its chemical properties. Continuous stirring prevents the sedimentation and agglomeration of nano-abrasives, ensuring the consistency of polishing slurry performance and avoiding scratches. Precise temperature control stabilizes the chemical reaction rate within a predictable range, eliminating the problem of inconsistent polishing results caused by ambient temperature fluctuations, and significantly improving the stability and repeatability of the process.

[0011] Furthermore, the surface profilometer is used to measure the surface smoothness (TTV, BOW, WARP) after polishing; the atomic force microscope is used for precise measurement of nanoscale surface roughness; the transmission electron microscope is used for cross-sectional sampling to observe and evaluate subsurface damage; the surface profilometer is used to evaluate macroscale smoothness; the atomic force microscope is used to evaluate nanoscale surface roughness; and the transmission electron microscope is the ultimate means to observe and confirm the absence of lattice damage on the subsurface.

[0012] Furthermore, in step S1, the special chemical mechanical polishing slurry comprises, by mass percentage: 0.1%-5% mild oxidant, 0.01%-2% complexing agent, 0.001%-0.5% surfactant / corrosion inhibitor, 0.1%-10% nano-scale soft abrasive, the balance being pH adjuster, and deionized water as solvent. The mild oxidant slowly softens the surface rather than causing severe corrosion; the complexing agent promptly removes reaction products to prevent secondary scratches; and the corrosion inhibitor preferentially protects protrusions, promoting self-leveling.

[0013] Further, by mass percentage, the mild oxidant is 0.1%-5%, and the mild oxidant is hydrogen peroxide, ammonium persulfate, or an organic peroxide; the complexing agent is 0.01%-2%, and the complexing agent is an organic acid, including oxalic acid, citric acid, tartaric acid, or glycine; the surfactant / corrosion inhibitor is 0.001%-0.5%, and the surfactant / corrosion inhibitor is benzotriazole or its derivatives; the nano-scale soft abrasive is 1%-10% in the first polishing step and 0.1%-2% in the second polishing step, and the nano-scale soft abrasive is silica, cerium oxide, or polymer microspheres with a particle size range of 20-80 nm; the pH adjuster is the balance, used to stabilize the pH of the polishing solution between 3 and 8; and the solvent is deionized water.

[0014] Furthermore, in step S2, the brittle material workpiece includes single-crystal silicon, silicon germanium, silicon carbide, gallium nitride, sapphire, glass, or quartz.

[0015] Furthermore, in step S3, a preset process formula is loaded into the high-precision speed control system. The formula should be clearly divided into two stages. Stage 1 parameters: downward pressure is set to 2 psi, polishing head speed is set to 60 rpm, polishing pad speed is set to 55 rpm, polishing fluid is selected as "high concentration formula", and flow rate is set to 150 mL / min. Stage 2 parameters: downward pressure is set to 0.8 psi, polishing head speed is set to 40 rpm, polishing pad speed is set to 70 rpm, polishing fluid is selected as "low concentration formula", and flow rate is set to 100 mL / min.

[0016] Furthermore, in step S4, the stirring and temperature control unit stabilizes the polishing liquid temperature at a set value (e.g., 25±1°C) to maintain the stability of the chemical reaction rate, and the multi-channel metering pump system begins to continuously and evenly spray the "high-concentration polishing liquid" onto the central area of ​​the rotating polishing pad.

[0017] Furthermore, in step S5, the endpoint of the second polishing stage can be controlled by time (e.g., 30 minutes) or by a real-time thickness measurement system. When the real-time thickness measurement system detects that the workpiece thickness has reached the preset target value, the equipment automatically sends an endpoint signal.

[0018] The beneficial effects of this invention are: This invention provides a low-stress chemical mechanical etching process suitable for brittle materials, which has the following advantages: 1. This invention solves the problem of unavoidable mechanical damage in the polishing of brittle materials. Traditional chemical mechanical polishing processes often use high downward pressure and sharp abrasives in pursuit of efficiency. This can generate huge mechanical stress on the surface of brittle materials such as silicon, silicon carbide, and sapphire, leading to subsurface defects such as microcracks, scratches, and lattice damage. These defects seriously affect the mechanical strength, electrical performance, and reliability of the final device. This invention fundamentally suppresses the generation of damage through the synergy of low pressure, soft abrasives, and optimized chemical action. By using nanoscale soft abrasives, a two-step method to reduce mechanical action, and the synergy of mild chemical reactions, an ultra-smooth surface can be obtained, which greatly improves the performance and lifespan of the product.

[0019] 2. This invention resolves the contradiction between high material removal rate and low surface damage. Existing technologies often face a trade-off between "high efficiency" and "high quality." Increasing the removal rate usually means increasing mechanical action, which exacerbates damage. However, to obtain a perfect surface, it is necessary to significantly reduce the removal rate, sacrificing production efficiency. The "two-step" process strategy of this invention cleverly resolves this contradiction. The first step rapidly removes most of the material under high pressure, achieving efficient planarization. The second step performs fine polishing under extremely low stress to eliminate damage, ultimately balancing efficiency and quality overall.

[0020] 3. This invention solves the problems of poor consistency and repeatability in polishing processes. Traditional processes rely on operator experience, and uncertainties in the concentration, temperature, abrasive dispersion, and endpoint determination of the polishing slurry can lead to batch-to-batch fluctuations. This invention achieves precise control of key process parameters throughout the entire process by integrating systems such as real-time thickness monitoring, automatic switching of multi-channel liquid paths, and constant-temperature stirring of the polishing slurry. The first polishing step ensures a high average material removal rate, keeping the entire process highly efficient. The integrated real-time thickness measurement system enables accurate endpoint detection, avoiding defects caused by over-polishing or under-polishing, and significantly improving production yield and repeatability. The multi-channel metering pump and temperature-controlled stirring system ensure the high stability of the polishing slurry performance during long-term processes. All key process parameters can be precisely programmed and controlled, minimizing interference from human and environmental factors, and enabling consistent and predictable high-quality results for workpieces processed on different batches and different machines.

[0021] 4. This invention solves the problem of global planarization uniformity in large-size wafers. As wafer size increases, its inherent micro-warpage and imperfections in the fixture system lead to uneven polishing pressure distribution, resulting in inconsistent removal rates between the center and edges. The multi-zone pressure controllable polishing head of this invention can dynamically adjust the pressure in different areas and actively compensate for these differences, ensuring high-precision global planarization of the entire wafer. The multi-zone pressure control technology ensures uniform force distribution across the workpiece surface. Combined with a two-step polishing strategy, it can effectively eliminate surface undulations and achieve extremely high overall flatness, providing a perfect substrate for subsequent precision manufacturing steps such as photolithography.

[0022] 5. It has wide applicability to materials. By adjusting the type and concentration of chemical components in the polishing slurry (such as oxidants and complexing agents), this process can be applied to a variety of brittle materials, from single-crystal silicon and silicon germanium to third-generation semiconductors such as silicon carbide and gallium nitride, and then to sapphire, quartz glass and other materials. It has good universality and promotion value.

[0023] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 A process flow diagram of a low-stress chemical mechanical etching process suitable for brittle materials is provided in an embodiment of the present invention; Figure 2 A process flow diagram of the first polishing step in a low-stress chemical mechanical etching process suitable for brittle materials, provided as an embodiment of the present invention; Figure 3 A process flow diagram of the second polishing step in a low-stress chemical mechanical etching process suitable for brittle materials, provided as an embodiment of the present invention; Figure 4 This is a process flow diagram of the process termination and post-processing steps in a low-stress chemical mechanical etching process suitable for brittle materials, provided as an embodiment of the present invention. Detailed Implementation

[0025] The following is in conjunction with the appendix Figure 1-4 The principles and features of the present invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0026] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] like Figure 1-4 As shown, the present invention provides a low-stress chemical mechanical etching process suitable for brittle materials, including a precision chemical mechanical polishing machine, a polishing pad, a polishing slurry delivery and management system, and an endpoint detection device. The precision chemical mechanical polishing machine includes a multi-zone pressure-controllable polishing head, a high-precision speed control system, and a real-time thickness measurement system. The polishing pad is a polishing disc made of porous polyurethane material. The polishing slurry delivery and management system includes a multi-channel metering pump system, a stirring and temperature control unit, and the endpoint detection device includes a surface profilometer, an atomic force microscope, and a transmission electron microscope.

[0029] Preferably, the multi-zone pressure-controlled polishing head can apply independent, precise, and programmable downward pressure (typically within the range of 0.1 psi to 5 psi) to different areas on the back of the wafer, ensuring uniform force on the wafer throughout the polishing process and preventing over-polishing of the edges or under-polishing of the center; the high-precision speed control system allows for independent stepless speed adjustment of the polishing head spindle and polishing pad spindle, with stable and precise speed control, and a speed ratio (polishing head speed / ...) Polishing pad rotation speed is a key parameter for controlling the polishing mode (chemical-driven or mechanical-driven). The real-time thickness measurement system, integrated into the polishing head, uses an online thickness measurement module (such as optical interferometry or eddy current type) to monitor the material removal rate and remaining thickness in real time, providing data support for process endpoint detection. The high-precision rotation speed control system can actively adjust the polishing mode by precisely controlling the rotation speed ratio (e.g., close to 1:1 in the first step and less than 1 in the second step). At a high rotation speed ratio, the mechanical action is enhanced, which is conducive to rapid planarization; at a low rotation speed ratio, the shear force is reduced, and the chemical action is dominant, which is conducive to low-damage polishing. This controllability is the basis for achieving different process objectives of the "two-step method". The real-time thickness measurement system upgrades the process from traditional "time control" or "experience control" to "data-driven control". It can not only provide real-time feedback on the material removal rate to provide data for process optimization, but also achieve accurate endpoint detection, automatically stopping polishing when the thickness reaches the target value, avoiding under-polishing or over-polishing.

[0030] Preferably, the multi-channel metering pump system can store two or more polishing slurries with different formulations (such as high-concentration abrasive slurry and low-concentration abrasive slurry) and can precisely switch and deliver them according to process instructions. Flow control needs to be precise and stable. The stirring and temperature control unit is a polishing slurry storage tank equipped with a continuous stirring device and temperature control function. This prevents abrasive sedimentation while stabilizing the polishing slurry temperature at a set value (such as 25±1°C) to maintain the stability of the chemical reaction rate. The multi-channel metering pump system can seamlessly connect two different chemical mechanical environments (high removal rate and low stress) in one process without removing the workpiece midway. This ensures process efficiency and avoids contamination or errors that may be introduced by secondary clamping. The stirring and temperature control unit can maintain the uniformity of the polishing slurry components and the stability of its chemical properties. Continuous stirring prevents the sedimentation and agglomeration of nano-abrasives, ensuring the consistency of polishing slurry performance and avoiding scratches. Precise temperature control stabilizes the chemical reaction rate within a predictable range, eliminating the problem of inconsistent polishing results caused by ambient temperature fluctuations, and significantly improving the stability and repeatability of the process.

[0031] Preferably, a surface profilometer is used to measure the surface smoothness (TTV, BOW, WARP) after polishing; an atomic force microscope is used for precise measurement of nanoscale surface roughness; a transmission electron microscope is used for cross-sectional sampling to observe and evaluate subsurface damage; a surface profilometer is used to evaluate macroscale smoothness; an atomic force microscope is used to evaluate nanoscale surface roughness; and a transmission electron microscope is the ultimate means to observe and confirm the absence of lattice damage on the subsurface.

[0032] The specific working principle and usage method of this invention are as follows: S1, Prepare a special chemical mechanical polishing slurry, which, by mass percentage, comprises: Mild oxidizing agent: 0.1%-5%, mild oxidizing agent is hydrogen peroxide, ammonium persulfate or organic peroxide; Complexing agent: 0.01%-2%, the complexing agent is an organic acid, including oxalic acid, citric acid, tartaric acid or glycine; Surfactant / corrosion inhibitor: 0.001%-0.5%, the surfactant / corrosion inhibitor is benzotriazole or its derivative; Nanoscale soft abrasive: The high-concentration formulation is 1%-10% during the first polishing step and the low-concentration formulation is 0.1%-2% during the second polishing step. The nanoscale soft abrasive is made of silica, cerium oxide or polymer microspheres with a particle size range of 20-80 nm. pH adjuster: Balance, used to stabilize the pH of the polishing solution between 3 and 8; Solvent: Deionized water; S2, Workpiece preparation and mounting; Cleaning: The brittle material workpiece to be polished (such as silicon carbide wafer) is cleaned using a standard RCA cleaning process to remove surface contaminants and particles; Clamping: Wet the surface of the workpiece with deionized water, place it face up and adsorb it onto the carrier of the multi-zone pressure controllable polishing head, and ensure that the workpiece is installed flat and firmly without any looseness or air bubbles to prevent vibration or breakage during polishing. S3, Device initialization and parameter settings; Equipment preparation: Start the precision chemical mechanical polishing machine, initialize the positions of the polishing head and polishing pad, install and clean the polishing pad, and pre-wet the polishing pad with deionized water; Process recipe loading: A preset process recipe is loaded into the high-precision speed control system. The recipe should be clearly divided into two stages: Stage 1 parameters: Downward pressure set to 2 psi, polishing head speed set to 60 rpm, polishing pad speed set to 55 rpm, polishing fluid selected as "high concentration formula", flow rate set to 150 mL / min; Phase 2 parameters: downward pressure set to 0.8 psi, polishing head speed set to 40 rpm, polishing pad speed set to 70 rpm, polishing fluid selected as "low concentration formula", flow rate set to 100 mL / min; S4, First step polishing - high-speed planarization; Start-up: During the execution of the first stage formula, the polishing pad and polishing head begin to rotate at the set speed; The polishing slurry is supplied, and the stirring and temperature control unit stabilizes the temperature of the polishing slurry at a set value (e.g., 25±1°C) to maintain the stability of the chemical reaction rate. The multi-channel metering pump system begins to continuously and evenly spray the "high-concentration polishing slurry" onto the central area of ​​the rotating polishing pad. Contact and polishing: The polishing head carries the workpiece and descends smoothly until it contacts the polishing pad and reaches the preset pressure of 2 psi. Polishing officially begins. The speed ratio of the polishing head to the polishing pad is 0.8:1 to 1.2:1 for initial high-speed planarization. Process monitoring: Operators can observe the material removal process in real time through a real-time thickness measurement system; Stage endpoint determination: The endpoint of this stage is controlled by time. Based on the removal rate determined in the preliminary experiment, the polishing time for this stage is set to 60 minutes. After the time is reached, the next stage begins. S5, Second Polishing Step - Fine Low-Stress Polishing; Parameter switching: The high-precision speed control system performs formula switching, and the polishing head pressure first drops to 0.8 psi; Polishing fluid switching: The multi-channel metering pump system stops delivering "high-concentration polishing fluid" and switches to delivering "low-concentration polishing fluid", with the flow rate adjusted to 100 mL / min; A high-precision speed control system adjusts the speed: the speed ratio between the polishing head and the polishing pad is adjusted to 0.5:1 to 0.8:1 for fine, low-stress polishing. Fine polishing: Polishing continues under these low-stress conditions. The purpose of this stage is no longer to quickly remove the material, but to repair any minor damage that may have occurred in the first step and achieve an atomically smooth surface. Final endpoint determination: The endpoint of this stage can be controlled by time (e.g., 30 minutes) or by a real-time thickness measurement system. When the real-time thickness measurement system detects that the workpiece thickness has reached the preset target value, the equipment will automatically send an endpoint signal. S6, Process completion and post-processing; Separation and Lifting: Upon reaching the endpoint, the polishing head automatically stops applying pressure and lifts up, separating the workpiece from the polishing pad; Rinsing: Use a large amount of deionized water to spray the polishing head and workpiece surface to rinse away residual polishing liquid and abrasive; Wafer removal and cleaning: Remove the workpiece from the polishing head, place it in the wafer cassette, and perform standard post-CMP cleaning to thoroughly remove all contaminants; Endpoint testing and verification: The workpiece is inspected using a surface profilometer, atomic force microscope, and transmission electron microscope to verify surface flatness, surface roughness, and subsurface damage.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Content not described in detail in this specification is prior art known to those skilled in the art.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A low-stress chemical mechanical etching process suitable for brittle materials, comprising a precision chemical mechanical polishing machine, a polishing pad, a polishing slurry delivery and management system, and an endpoint detection device, characterized in that, The precision chemical mechanical polishing machine includes a multi-zone pressure controllable polishing head, a high-precision speed control system, and a real-time thickness measurement system. The polishing pad is a polishing disc made of porous polyurethane material. The polishing fluid delivery and management system includes a multi-channel metering pump system and a stirring and temperature control unit. The endpoint detection equipment includes a surface profilometer, an atomic force microscope, and a transmission electron microscope. The etching process includes the following steps: S1, prepare a special chemical mechanical polishing fluid; S2, Workpiece preparation and mounting: After cleaning the brittle material workpiece to be polished, it is clamped on the carrier of the multi-zone pressure controllable polishing head. S3, Equipment initialization and parameter setting, initialize the precision chemical mechanical polishing machine, load the process formula; S4, First step polishing: The polishing liquid is supplied to the rotating polishing pad at a first flow rate, the downward pressure of the polishing head on the workpiece is controlled to be 1-3 psi, and the speed ratio of the polishing head to the polishing pad is 0.8:1 to 1.2:1, to perform preliminary high-speed planarization; S5, Second polishing step: Adjust the polishing slurry supply so that the abrasive concentration is lower than in the first step, control the downward pressure of the polishing head on the workpiece to be 0.5-2 psi, and the speed ratio of the polishing head to the polishing pad to be 0.5:1 to 0.8:1 for fine low-stress polishing; S6, Process completion and post-processing: After fine low-stress polishing, the workpiece is separated from the polishing pad, the polishing fluid and abrasive are rinsed off, and the workpiece is removed and cleaned. Finally, it is tested and verified by the endpoint testing equipment.

2. The low-stress chemical mechanical etching process for brittle materials according to claim 1, characterized in that, The multi-zone pressure controllable polishing head can apply independent, precise, and programmable downward pressure to different areas on the back of the wafer; the high-precision speed control system allows for independent stepless speed adjustment of the spindle speed of the polishing head and the polishing pad spindle; the real-time thickness measurement system is integrated into the online thickness measurement module in the polishing head for real-time monitoring of material removal rate and remaining thickness.

3. The low-stress chemical mechanical etching process suitable for brittle materials according to claim 1, characterized in that, The multi-channel metering pump system can store two or more polishing slurries with different formulations and can switch and deliver them precisely according to process instructions. The flow control needs to be precise and stable. The stirring and temperature control unit is a polishing slurry storage tank equipped with a continuous stirring device and temperature control function.

4. The low-stress chemical mechanical etching process suitable for brittle materials according to claim 1, characterized in that, The surface profilometer is used to measure the surface smoothness after polishing; the atomic force microscope is used for precise measurement of nanoscale surface roughness; and the transmission electron microscope is used for cross-sectional sampling to observe and evaluate subsurface damage.

5. The low-stress chemical mechanical etching process for brittle materials according to claim 1, characterized in that, In step S1, the special chemical mechanical polishing fluid comprises, by mass percentage: 0.1%-5% mild oxidant, 0.01%-2% complexing agent, 0.001%-0.5% surfactant / corrosion inhibitor, 0.1%-10% nano-scale soft abrasive, the balance of pH adjuster, and deionized water as solvent.

6. The low-stress chemical mechanical etching process for brittle materials according to claim 5, characterized in that, By mass percentage, the mild oxidant is 0.1%-5%, and the mild oxidant is hydrogen peroxide, ammonium persulfate, or an organic peroxide; the complexing agent is 0.01%-2%, and the complexing agent is an organic acid, including oxalic acid, citric acid, tartaric acid, or glycine; the surfactant / corrosion inhibitor is 0.001%-0.5%, and the surfactant / corrosion inhibitor is benzotriazole or its derivatives; the nano-scale soft abrasive is 1%-10% in the first polishing step and 0.1%-2% in the second polishing step, and the nano-scale soft abrasive is silica, cerium oxide, or polymer microspheres with a particle size range of 20-80 nm; the pH adjuster is the balance, used to stabilize the pH of the polishing solution between 3 and 8; and the solvent is deionized water.

7. The low-stress chemical mechanical etching process for brittle materials according to claim 1, characterized in that, In step S2, the brittle material workpiece includes single-crystal silicon, silicon germanium, silicon carbide, gallium nitride, sapphire, glass, or quartz.

8. The low-stress chemical mechanical etching process for brittle materials according to claim 1, characterized in that, In step S3, a preset process formula is loaded into the high-precision speed control system. The formula should be clearly divided into two stages. Stage 1 parameters: downward pressure is set to 2 psi, polishing head speed is set to 60 rpm, polishing pad speed is set to 55 rpm, polishing fluid is selected with a high abrasive concentration formula, and the flow rate is set to 150 mL / min. Stage 2 parameters: downward pressure is set to 0.8 psi, polishing head speed is set to 40 rpm, polishing pad speed is set to 70 rpm, polishing fluid is selected with a low abrasive concentration formula, and the flow rate is set to 100 mL / min.

9. The low-stress chemical mechanical etching process for brittle materials according to claim 1, characterized in that, In step S4, the stirring and temperature control unit stabilizes the polishing liquid temperature at a set value to maintain the stability of the chemical reaction rate, and the multi-channel metering pump system begins to continuously and evenly spray the high-concentration polishing liquid onto the central area of ​​the rotating polishing pad.

10. The low-stress chemical mechanical etching process for brittle materials according to claim 1, characterized in that, In step S5, the endpoint of the second polishing stage is controlled by time control or real-time thickness measurement system. When the real-time thickness measurement system detects that the workpiece thickness has reached the preset target value, the equipment automatically sends an endpoint signal to complete the second stage of processing.

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