Sealed jig for removing silicon dioxide film on edge of silicon wafer and dry etching method

Abstract

The invention relates to the technical field of semiconductor manufacturing, and discloses a closed jig for removing a silicon dioxide film on the edge of a silicon wafer and a dry etching method. The fixture is composed of an upper cover body and a lower base which can be opened and closed, and an annular fluororubber ring is arranged in the fixture to form a sealed reaction chamber. A hydrofluoric acid solution is atomized to the particle size through an ultrasonic atomizer and mixed with nitrogen to form atomized gas-liquid two-phase flow with the volume concentration, and the atomized gas-liquid two-phase flow is introduced into the sealed cavity through a gas inlet hole. The mixed gas and the silicon dioxide film on the edge of the silicon wafer are subjected to gas-liquid-solid three-phase reaction in the wide annular reaction area, and the etching width is accurately controlled by adjusting the HF concentration and the reaction time. The hexafluorosilicic acid waste liquid generated by the reaction is discharged through an exhaust hole, and the HF-containing waste gas is subjected to two-stage treatment and is discharged after reaching the standard. The treated silicon wafer can directly enter the next process without being cleaned and dried, the single wafer treatment period is 150 seconds, and the yield and the electrical performance of the semiconductor device are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor manufacturing, and in particular relates to a dry etching method for removing silicon dioxide films at the edges of silicon wafers, and also relates to a sealed fixture for removing silicon dioxide films at the edges of silicon wafers. Background Art

[0002] In the high-temperature epitaxial growth process of wafer manufacturing, the volatilization of impurities in the substrate due to heat can easily cause unexpected self-doping, especially in heavily doped substrates. To solve this problem, the industry usually adopts the method of depositing a silicon dioxide film on the back of the substrate to form an effective barrier to the escape of impurities. However, this back-sealing process will cause silicon dioxide to remain in the chamfered area, front and back edges of the silicon wafer. These residual silicon dioxides can easily become the starting point for epitaxial growth, causing the edge of the silicon wafer to form a polycrystalline or amorphous structure. This will not only significantly affect the quality of the epitaxial layer and compress the effective epitaxial area, but also cause the lattice defects generated at the edge after epitaxy to lead to a decrease in the yield rate of the device edge in subsequent chip manufacturing.

[0003] Therefore, the edge removal process has become a key link in wafer manufacturing. This process can effectively avoid the amorphous silicon formed by edge effects during epitaxial growth by accurately removing the oxide film on the chamfers and edges of the silicon wafer, thereby laying an important foundation for the high-precision implementation of subsequent photolithography processes. In actual operation, hydrofluoric acid (HF) solution has become a commonly used processing medium for removing edge silicon dioxide films due to its specific etching properties for silicon dioxide. However, due to the strong corrosiveness of hydrofluoric acid, it will cause damage to other silicon dioxide films that need to be retained, so these areas must be protected.

[0004] At present, there are mainly two protective treatment processes in the industry: the first is to use a special acid-proof tape that is resistant to hydrofluoric acid (HF) corrosion, and precisely fit it to the area on the surface of the silicon wafer that needs to be protected. After the protection is completed, the silicon wafer is immersed in a hydrofluoric acid solution, and the unnecessary silicon dioxide film on the edge is directionally removed by etching. However, this process requires multiple steps such as tape attachment, etching and peeling, and has the problems of cumbersome operation, low efficiency and high cost. Another existing process uses a suction cup instead of tape, and uses the suction cup to mask the area of ​​the silicon dioxide film that needs to be retained. The process is completed by etching with a hydrofluoric acid (HF) solution, washing with clean water and drying. Although the loss of tape is avoided, the cleaning and drying steps extend the process cycle, and there is a risk of liquid residue.

[0005] Traditional edge removal processes use hydrofluoric acid (HF) wet etching, which relies on liquid etching media and requires protective, cleaning, and drying equipment. This process is cumbersome and expensive. Therefore, there is an urgent need to develop an efficient, low-cost, and clean-free edge removal technology to improve process economics and safety. Summary of the Invention

[0006] One purpose of the present invention is to provide a closed jig for removing silicon dioxide films from the edges of silicon wafers, which achieves directional etching through a mixture of hydrofluoric acid and nitrogen, replacing the traditional wet process, solving the problem of epitaxial defects while improving production efficiency and safety.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a closed fixture for removing silicon dioxide film at the edge of a silicon wafer, comprising:

[0009] An upper cover body and a lower base, wherein the upper cover body and the lower base are connected in an openable and closable manner.

[0010] The elastic rubber ring is arranged at the contact surface between the upper cover and / or the lower base and the silicon wafer, and is used for sealing and clamping the edge of the silicon wafer and buffering the pressure.

[0011] When the upper cover and the lower base are covered and the silicon wafer is placed between the upper cover and the lower base, the upper cover, the elastic rubber ring, the lower base and the silicon wafer together define a sealed reaction chamber around the edge of the silicon wafer.

[0012] An air inlet is provided on one side of the lower base, and the air inlet is connected to an atomized mixed gas supply device and is used to introduce a mixed gas containing hydrofluoric acid into the sealed chamber.

[0013] The exhaust hole is arranged on the other side of the lower base and is adapted to the air inlet for discharging waste gas after the reaction.

[0014] The air inlet and the air outlet are both communicated with the sealed reaction chamber.

[0015] In addition to the above technical features, the present invention has also made optimization and improvements in the following aspects:

[0016] As a preferred technical solution of the present invention, the air inlet is connected to an atomizer for converting the introduced mixed gas containing hydrofluoric acid into an atomized state.

[0017] As a preferred technical solution of the present invention, the elastic rubber ring is an annular fluororubber rubber ring, which forms a sealed space after compression and buffers the clamping pressure between the upper cover and the lower base.

[0018] As a preferred technical solution of the present invention, the inner diameter of the annular fluororubber rubber ring matches the diameter of the silicon wafer, and the distance between the inner edge of the closed annular fluororubber rubber ring and the edge of the silicon wafer forms a reaction zone with a width of 1 to 10 mm.

[0019] As a preferred technical solution of the present invention, the atomized mixed gas supply device includes a hydrofluoric acid storage tank, a nitrogen source and an ultrasonic atomizer. The hydrofluoric acid is atomized and mixed with nitrogen and transported to the air inlet.

[0020] Another object of the present invention is to provide a dry etching method for removing silicon dioxide film at the edge of a silicon wafer, comprising the following steps:

[0021] Wafer loading: Place the silicon wafer to be processed on the lower base of the sealed fixture, cover it with the upper cover and press it tightly to form a sealed reaction chamber;

[0022] Introducing reaction gas: A mixed gas containing hydrofluoric acid is introduced into the sealed reaction chamber inside the sealed fixture through the air inlet located on one side of the lower base;

[0023] Reactive film removal: The mixed gas reacts with the silicon dioxide film at the edge of the silicon wafer, etching away the silicon dioxide film at the edge; and the waste gas is discharged through the exhaust hole;

[0024] Take out the wafer: open the sealed fixture and take out the silicon wafer that has completed the edge removal process;

[0025] The mixed gas containing hydrofluoric acid introduced in the step of introducing the reaction gas is in a gaseous or atomized state, and after the wafer taking step, the taken-out silicon wafer is directly transferred to the next process.

[0026] As a preferred technical solution of the present invention, the mixed gas is a mixed gas of hydrofluoric acid gas and inert gas or a mixed gas-liquid two-phase flow of hydrofluoric acid droplets and nitrogen formed by atomization of atomizer.

[0027] As a preferred technical solution of the present invention, the mixed gas is an atomized mixed gas containing hydrofluoric acid formed by atomization treatment by an atomizer, and the mixed gas forms a bubble group in the sealed chamber to react with the silicon dioxide film.

[0028] As a preferred technical solution of the present invention, in the step of introducing the reaction gas, the width of the silicon dioxide film removed from the edge of the silicon wafer is controlled by adjusting the concentration of hydrofluoric acid in the mixed gas containing hydrofluoric acid and / or the time of introducing the gas.

[0029] As a preferred technical solution of the present invention, the volume concentration of hydrofluoric acid in the mixed gas is 5%-40%, and the introduction time is 10-300 seconds.

[0030] In combination with the description of the above technical content, the technical effects of the closed fixture for removing silicon dioxide film on the edge of silicon wafer and the dry etching method thereof of the present invention are mainly reflected in the following aspects:

[0031] 1. Process efficiency is significantly improved

[0032] Dry etching is achieved through a closed fixture with an integrated process of "loading-reaction-removal". The silicon dioxide film on the edge of the silicon wafer is directly removed by using a mixed gas containing hydrofluoric acid, avoiding the steps of applying acid-proof tape / suction cup protection, cleaning, and drying in traditional processes. After the silicon wafer is removed from the film, it is directly transferred to the next process, shortening the production process and significantly improving production efficiency.

[0033] Dry etching only targets the edge areas, without any contact damage to the functional areas on the front and back sides of the silicon wafer, eliminating the risk of film peeling in traditional wet processes.

[0034] 2. Enhanced etching accuracy and controllability

[0035] The elastic rubber ring accurately defines the etching area, which can prevent hydrofluoric acid from corroding the central functional area of ​​the silicon wafer. The elastic rubber ring can not only seal and clamp the edge of the silicon wafer, but also buffer the pressure to avoid crushing or damaging the silicon wafer.

[0036] Precise and controllable etching width: By adjusting the hydrofluoric acid concentration and injection time, the silicon dioxide film removal width can be precisely controlled to avoid over-etching or residue, meeting the requirements of different epitaxial processes.

[0037] 3. Etching uniformity and edge quality optimization

[0038] The atomized gas forms a uniform bubble group, which realizes uniform etching of the edge silicon dioxide film in the sealed chamber, helps to achieve a more uniform film removal effect, avoids the problem of uneven film layer caused by liquid immersion, eliminates the generation of polycrystalline / amorphous silicon, and reduces the defect rate of the epitaxial layer.

[0039] 4. Security and cost optimization

[0040] The atomized gas mixture (HF droplets / nitrogen) reacts in a sealed chamber, with exhaust gases discharged centrally, reducing the risk of hydrofluoric acid exposure. This eliminates the cost of acid-resistant tape and suction cups, reducing equipment maintenance costs.

[0041] The dry etching process leaves no liquid residue, eliminates water mark contamination, and ensures the integrity of the epitaxial layer lattice.

[0042] 5. Reduced resource consumption

[0043] The amount of hydrofluoric acid used is reduced, and inert gas (such as nitrogen) is used as a carrier to inhibit side reactions and ensure that the silicon dioxide film in the non-edge area of ​​the front / back side of the silicon wafer is retained intact.

[0044] Centralized waste gas treatment reduces the discharge of fluorine-containing waste liquid.

[0045] 6. Compatibility and scalability

[0046] The inner diameter of the elastic rubber ring can match silicon wafers of different diameters, and can be quickly switched by simply replacing the rubber ring.

[0047] In summary, the dry edge etching process of this application has achieved significant superiority over the traditional wet process in terms of efficiency, precision, uniformity, safety, cost, environmental protection and compatibility through closed fixture design, atomized gas application and elastic rubber ring innovation, providing a high-performance and high-reliability solution for silicon wafer manufacturing (especially epitaxial pre-processing). BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the structure of a closed fixture for removing silicon dioxide film at the edge of a silicon wafer according to the present invention;

[0049] Figure 2 The figure is a flow chart of a dry etching method for removing silicon dioxide film at the edge of a silicon wafer.

[0050] In the picture:

[0051] 1. Upper cover; 2. Lower base; 3. Elastic rubber ring; 4. Air inlet; 5. Exhaust hole. DETAILED DESCRIPTION

[0052] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0053] 1. Explanation of Descriptive Terms in the Present Invention

[0054] The embodiments of the present invention are provided in conjunction with the technical solutions to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art. It should be noted that unless otherwise specifically stated in the present invention, the relative arrangements of components described in these embodiments should be interpreted as merely exemplary and not as a limitation of the technical solutions of the present invention.

[0055] When used in this disclosure, directional terms such as "upper," "lower," "left," "right," "bottom," and "top" are defined relative to the directions in the accompanying drawings and are intended only to indicate relative positional relationships. These relative positional relationships may change accordingly if the absolute positions of the objects being described change. These and other directional terms should not be construed as restrictive.

[0056] In the present invention, words such as "a," "an," "an," and "the" do not limit the number and may refer to the singular or plural. The terms "include," "comprising," "having," and any variations thereof, as used in the present invention, are intended to cover non-exclusive inclusions. The terms "first," "second," and "third," etc., used in the present invention, are merely used to distinguish similar objects and do not indicate a specific ordering of the objects.

[0057] In the present invention, when a specific device is described as being located between a first device and a second device, an intervening device may or may not be present between the specific device and the first device or the second device. When a specific device is described as being connected to another device, the specific device may be directly connected to the other device without an intervening device, or may be directly connected to the other device but with an intervening device.

[0058] In addition, the present invention does not discuss in detail the technologies and equipment known to ordinary technicians in the relevant fields, but where appropriate, the technologies and equipment should be considered as part of the specification.

[0059] 2. Core technical issues to be solved by the technical solution of this application

[0060] Existing wafer edge stripping technologies face the following core challenges: First, the process is highly complex. Traditional wet etching requires multiple steps, including protective tape attachment / stripping or suction cup masking, hydrofluoric acid etching, cleaning, and drying, significantly increasing equipment investment and operating costs. Second, process efficiency is limited. The acid-resistant tape solution extends single-wafer processing time due to the multiple steps involved. While the suction cup solution reduces consumables, the cleaning and drying steps still take up a significant portion of the cycle time. Third, quality risks are significant. Liquid media easily remains on the silicon wafer surface, potentially causing subsequent epitaxial layer defects, and the highly corrosive nature of hydrofluoric acid always presents the risk of inadvertent etching of the silicon dioxide film in non-target areas. Finally, the wet process is not economically and safely feasible. The wet process requires continuous consumption of chemical reagents and ultrapure water, incurring hazardous waste disposal costs, and the safety risks of operators exposed to corrosive environments are difficult to completely eliminate. These shortcomings collectively limit the applicability of existing technologies in high-end semiconductor manufacturing.

[0061] 3. Based on the above problems, the present invention specifically provides a technical solution to the above problems. The following is combined with specific embodiments and reference to Figure 1 、 Figure 2 As shown, the technical solution, working principle and technical effects of the present invention are described in detail.

[0062] (1) Sealed fixture for removing silicon dioxide film from silicon wafer edges

[0063] 1. Sealing fixture structure

[0064] like Figure 1 As shown, the sealed fixture of this embodiment is composed of an upper cover 1, a lower base 2, an annular fluororubber elastic rubber ring 3, an air inlet 4 and an exhaust hole 5. The specific parameters and implementation methods are as follows:

[0065] 1.1 Upper cover and lower base

[0066] Material Selection: The upper cover 1 and lower base 2 are integrally molded from polytetrafluoroethylene (PTFE) with a surface roughness of ≤ Ra0.4μm, ensuring smooth contact with the silicon wafer. PTFE exhibits excellent hydrofluoric acid corrosion resistance (corrosion rate <0.1mm / year at HF ​​concentration ≤40%), ensuring long-term use.

[0067] Connection method: The upper cover 1 and the lower base 2 are connected by a 304 stainless steel hinge with an opening and closing angle of 0° to 180°. When closed, they are fixed by 4 sets of M5 stainless steel quick-lock bolts to ensure that the sealing pressure is ≥0.3MPa.

[0068] 1.2 Elastic rubber ring

[0069] Ring specifications: The annular fluororubber ring 3 has an inner diameter of 200mm (compatible with 200mm diameter silicon wafers), a cross-sectional diameter of 8mm, and a Shore A hardness of 75. The ring surface is sprayed with a polyimide coating (50μm thick) to enhance hydrofluoric acid resistance.

[0070] Sealing Design: The rubber ring is installed in a 6mm deep annular groove on the lower base 2. When the fixture is closed, the rubber ring is compressed by 20% to 30% (i.e., a compressed height of 5.6 to 4.9mm), creating a sealing pressure while preventing damage to the silicon wafer. After closing, the inner edge of the rubber ring forms a 5mm-wide annular reaction zone with the edge of the silicon wafer, ensuring that the hydrofluoric acid gas is only applied to the edge.

[0071] 1.3 Gas supply system

[0072] Air inlet 4: Located on the side wall of the lower base 2, with an inner diameter of 6mm, connected to the ultrasonic atomization mixing device. The device consists of the following parts:

[0073] Hydrofluoric acid storage tank: 500 mL, made of PFA, equipped with a PTFE magnetic stirrer (speed adjustable from 0 to 500 rpm) to prevent precipitation of the HF solution.

[0074] Nitrogen source: Provide nitrogen with a purity of 99.999%, with a pressure adjustment range of 0.1 to 0.5 MPa, and the flow rate is controlled by a mass flow meter.

[0075] Ultrasonic atomizer: operating frequency 1.7 MHz, atomizes 40% hydrofluoric acid solution to a particle size of 1-5 μm, and the atomization volume is adjustable from 0 to 10 mL / h.

[0076] Exhaust hole 5: located on the opposite side of the lower base 2, with an inner diameter of 8 mm, connected to the corrosion-resistant pipe to the exhaust gas treatment device (containing a NaOH neutralization tank) to ensure that the HF concentration of the exhaust gas is <5ppm.

[0077] 2. Operation process

[0078] 2.1 Jig assembly

[0079] The silicon wafer to be processed (with the photoresist edge exposed) is placed horizontally on the rubber ring 3 of the lower base 2, with the edge of the silicon wafer aligned with the inner edge of the rubber ring.

[0080] Close the upper cover 1, tighten the quick-lock bolts, and monitor the sealing pressure using a pressure gauge (target value 0.25 MPa).

[0081] 2.2 Process parameter setting

[0082] Hydrofluoric acid atomization volume: 5mL / h

[0083] Nitrogen flow rate: 300 sccm

[0084] Response time: 120s

[0085] Reaction temperature: room temperature (25±2℃)

[0086] 2.3 Reaction process

[0087] The ultrasonic atomizer was started, and the HF solution was atomized and mixed with nitrogen to form a mixed gas with a hydrofluoric acid mass fraction of 2%.

[0088] The mixed gas enters the sealed chamber through the air inlet 4 and reacts with the silicon dioxide film (thickness 1μm) on the edge of the silicon wafer in the 5mm wide reaction zone. The hexafluorosilicic acid gas and unreacted HF generated by the reaction are discharged through the exhaust hole 5 and neutralized by the exhaust gas treatment device.

[0089] 3. Implementation Effect

[0090] Silicon dioxide film removal width: 4.8±0.2mm (meets the design requirement of 5mm reaction area)

[0091] Surface roughness: After treatment, the edge of the silicon wafer Ra is less than 0.2μm, and there is no over-corrosion.

[0092] Sealing verification: Chamber pressure test (0.3MPa nitrogen) leakage rate <0.5% / h.

[0093] This embodiment achieves efficient and accurate removal of the silicon dioxide film at the edge of the silicon wafer through precise sealing structure design and atomization process control, while avoiding corrosion of the effective area of ​​the silicon wafer, meeting the requirements of semiconductor manufacturing processes.

[0094] How it works

[0095] This enclosed fixture achieves efficient and accurate removal of silicon dioxide film from the edge of silicon wafers through precise sealing structure and atomization process control. Its working principle can be divided into the following four stages:

[0096] 1. Sealed chamber construction stage

[0097] When the fixture is closed, the upper cover 1 and lower base 2 exert a clamping force of 0.25 MPa via the quick-lock bolts, forcing the annular fluororubber rubber ring 3 to undergo a 20% to 30% compression deformation. The polyimide coating on the ring forms a chemically inert interface with the PTFE fixture body, preventing hydrofluoric acid penetration.

[0098] The compressed rubber ring has a dual function: first, it forms a dynamic seal with the edge of the silicon wafer. The pressure test shows that the leakage rate is <0.5% / h under a nitrogen pressure of 0.3MPa; second, it buffers the clamping stress through elastic deformation to prevent micro cracks in the silicon wafer.

[0099] 2. Atomized gas generation stage

[0100] A 40% HF solution in a hydrofluoric acid tank was stirred at 300 rpm using a PTFE magnetic stirrer to prevent stratification. The solution was then transported through a PFA line to an ultrasonic atomizer, where it was broken into micron-sized droplets of 1 to 5 μm at a high-frequency vibration of 1.7 MHz.

[0101] The droplets are thoroughly mixed with 99.999% high-purity nitrogen in the mixing chamber to form a gas mixture with a 2% hydrofluoric acid mass fraction. The nitrogen acts as both an atomizing medium and a carrier gas to transport the reactants to the reaction zone, while also diluting the reactants to prevent localized excessive concentrations that could lead to excessive corrosion of the silicon wafer.

[0102] 3. Directed corrosion reaction stage

[0103] The mixed gas enters the sealed chamber through inlet 4 at a flow rate of 300 sccm. Within the 5mm-wide annular reaction zone, it undergoes a vapor-phase etching reaction with the silicon dioxide film at the edge of the silicon wafer. The resulting hexafluorosilicic acid aqueous solution flows down the edge of the silicon wafer under the action of gravity and is discharged through exhaust 5. The width of the reaction zone is precisely controlled to 5mm by the difference between the inner diameter of the rubber ring and the diameter of the silicon wafer. The actual removal width reaches 4.8±0.2mm, with an edge roughness Ra of less than 0.2μm.

[0104] 4. Waste gas treatment stage

[0105] HF-containing waste gas is transported to the waste gas treatment unit via corrosion-resistant piping. It first passes through a neutralization tank filled with 2 mol / L NaOH solution, where it undergoes a neutralization reaction. After two stages of wet scrubbing, the HF concentration is reduced to <5 ppm, meeting semiconductor industry emission standards. The treated wastewater then enters the wastewater treatment system for further processing.

[0106] Key points of process control

[0107] Temperature control: The low thermal conductivity of the PTFE material of the fixture (thermal conductivity 0.25W / m·K) achieves natural thermal buffering, and the reaction temperature is maintained at 25±2℃ throughout the process.

[0108] Time control: A reaction time of 120 seconds can completely remove a 1μm thick silicon dioxide film. Prolonging the reaction time will increase the edge roughness.

[0109] Pressure monitoring: Chamber pressure is controlled by the nitrogen flow rate and exhaust valve opening to ensure uniform distribution of reaction gases.

[0110] The fixture optimizes the gas flow field through fluid dynamics simulation and combines it with precision mechanical design to achieve nanoscale control of silicon wafer edge corrosion, significantly improving the yield rate of semiconductor devices.

[0111] (2) Dry etching method for removing silicon dioxide film on the edge of silicon wafer

[0112] like Figure 2 As shown, the present application also describes a dry etching method for removing silicon dioxide film at the edge of a silicon wafer, comprising the following steps:

[0113] 1. Film loading steps

[0114] 1.1 Place a 200mm (8-inch) silicon wafer with photoresist edge exposure (exposure area width 5mm) horizontally on the lower base 2 of the sealing fixture, ensuring that the center of the silicon wafer is concentric with the positioning pin of the lower base, and the edge of the silicon wafer is aligned with the inner edge of the annular fluororubber rubber ring 3.

[0115] 1.2 Close the upper cover 1 and apply a clamping force of 0.25 MPa using four sets of M5 stainless steel quick-lock bolts, compressing the fluororubber rubber ring by 25% (from an 8 mm cross-sectional diameter to 6 mm), creating a sealing pressure. The inner edge of the rubber ring and the edge of the silicon wafer now form a 5 mm wide annular reaction zone, and the sealed chamber volume is 50 mL.

[0116] 2. Reaction gas configuration

[0117] 2.1 The gas supply system was started, and the 40% HF solution in the hydrofluoric acid tank (PFA material) was delivered to the ultrasonic atomizer (operating frequency 1.7 MHz) at a flow rate of 5 mL / h to generate atomized droplets with a particle size of 1 to 5 μm.

[0118] 2.2 The atomized droplets are mixed with 99.999% high purity nitrogen in the mixing chamber. The nitrogen flow rate is controlled at 300 sccm by a mass flow meter to form an atomized mixed gas with a hydrofluoric acid volume concentration of 2% (HF:N 2＝ 1:49 volume ratio).

[0119] 3. Reaction membrane removal control

[0120] 3.1 The mixed gas enters the sealed chamber through the air inlet 4 of the lower base 2 with an air inlet pressure of 0.15 MPa. The gas forms a bubble group in the reaction zone and undergoes a gas-liquid-solid three-phase reaction with the silicon dioxide film on the edge of the silicon wafer.

[0121] 3.2 The reaction time is precisely set to 120 seconds by the PLC control system. During this time, the chamber temperature is naturally controlled by the nitrogen flow at 25±2°C. The hexafluorosilicic acid solution generated by the reaction flows down the edge of the silicon wafer and is discharged through the exhaust hole 5.

[0122] 4. Etching width control

[0123] 4.1 Etching width control by adjusting HF concentration and reaction time:

[0124] Experimental data show that under the conditions of HF concentration of 2% and reaction time of 120 seconds, the etching width is 4.8±0.2mm;

[0125] If the etching width needs to be increased to 6 mm, the HF concentration can be increased to 5% and the reaction time can be extended to 180 seconds.

[0126] 5. Waste gas treatment and film collection

[0127] 5.1 HF-containing waste gas is transported to the waste gas treatment device through corrosion-resistant pipelines. It is first treated in a neutralization tank filled with 2 mol / L NaOH solution, and then treated in an activated carbon adsorption tower. The final HF concentration in the discharge is <5 ppm.

[0128] 5.2 After the reaction is completed, open the quick-lock bolts and remove the silicon wafer. The residual droplets on the edge of the silicon wafer will evaporate naturally under nitrogen protection (ambient humidity <30% RH). No additional cleaning or drying is required and the wafer can be directly put into the next process (such as diffusion or ion implantation).

[0129] Process validation data

[0130] Edge roughness: Ra<0.2μm (AFM test)

[0131] Residual film thickness: <5nm (ellipsometry test)

[0132] Particle contamination: ≥0.3μm particles <10 (KLA-Tencor SP5 test)

[0133] Production capacity: Single wafer processing cycle 150 seconds (including loading / unloading time)

[0134] This embodiment achieves highly selective and low-damage removal of silicon dioxide films at the edges of silicon wafers through atomized gas-liquid two-phase flow technology and precision fixture design, avoiding the edge drilling and cleaning residue problems of traditional wet etching, and significantly improving the electrical performance and production yield of semiconductor devices.

[0135] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0136] In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that ordinary technicians in this field can implement them; when the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A closed fixture for removing silicon dioxide film from the edge of a silicon wafer, characterized in that: include An upper cover (1) and a lower base (2), wherein the upper cover (1) and the lower base (2) are connected in an openable and closable manner; An elastic rubber ring (3) is arranged at the contact surface between the upper cover (1) and / or the lower base (2) and the silicon wafer, and is used for sealing and clamping the edge of the silicon wafer and buffering pressure; When the upper cover (1) and the lower base (2) are covered and the silicon wafer is placed between the upper cover (1) and the lower base (2), the upper cover (1), the elastic rubber ring (3), the lower base (2) and the silicon wafer together define a sealed reaction chamber surrounding the edge of the silicon wafer; An air inlet (4) is provided on one side of the lower base (2), the air inlet being connected to an atomized mixed gas supply device for introducing a mixed gas containing hydrofluoric acid into the sealed chamber; An exhaust hole (5) is provided on the other side of the lower base, adapted to the air inlet, and used to discharge waste gas after the reaction; Wherein, the air inlet (4) and the air outlet (5) are both communicated with the sealed reaction chamber.

2. The enclosed fixture for removing silicon dioxide film from the edge of a silicon wafer according to claim 1, characterized in that: The air inlet (4) is connected to an atomizer for converting the mixed gas containing hydrofluoric acid into an atomized state.

3. The enclosed fixture for removing silicon dioxide film from the edge of a silicon wafer according to claim 1, characterized in that: The elastic rubber ring (3) is an annular fluororubber rubber ring, which forms a sealed space after compression and buffers the clamping pressure between the upper cover (1) and the lower base (2).

4. The enclosed jig for removing silicon dioxide film from the edge of a silicon wafer according to claim 3, characterized in that: The inner diameter of the annular fluororubber rubber ring matches the diameter of the silicon wafer; after closing, the inner edge of the annular fluororubber rubber ring and the edge of the silicon wafer form a reaction zone with a width of 1 to 10 mm.

5. The enclosed fixture for removing silicon dioxide film from the edge of a silicon wafer according to claim 1, characterized in that: The atomized mixed gas supply device includes a hydrofluoric acid storage tank, a nitrogen source and an ultrasonic atomizer. The hydrofluoric acid is atomized and mixed with nitrogen and transported to the air inlet.

6. A dry etching method for removing silicon dioxide film from the edge of a silicon wafer, using the sealed fixture according to any one of claims 1 to 5, characterized in that: The following steps are involved: Wafer loading: Place the silicon wafer to be processed on the lower base of the sealed fixture, cover it with the upper cover and press it tightly to form a sealed reaction chamber; Introducing reaction gas: A mixed gas containing hydrofluoric acid is introduced into the sealed reaction chamber inside the sealed fixture through the air inlet located on one side of the lower base; Reactive film removal: The mixed gas reacts with the silicon dioxide film at the edge of the silicon wafer, etching away the silicon dioxide film at the edge; and the waste gas is discharged through the exhaust hole; Take out the wafer: open the sealed fixture and take out the silicon wafer that has completed the edge removal process; The mixed gas containing hydrofluoric acid introduced in the step of introducing the reaction gas is in a gaseous or atomized state, and after the wafer taking step, the taken-out silicon wafer is directly transferred to the next process.

7. The dry etching method for removing silicon dioxide film at the edge of a silicon wafer according to claim 6, characterized in that: The mixed gas is a mixed gas of hydrofluoric acid gas and inert gas or a mixed gas-liquid two-phase flow of hydrofluoric acid droplets and nitrogen formed by atomization of an atomizer.

8. The dry etching method for removing silicon dioxide film at the edge of a silicon wafer according to claim 6, characterized in that: The mixed gas is an atomized mixed gas containing hydrofluoric acid formed by atomization treatment by an atomizer. The mixed gas forms a bubble group in the sealed chamber to react with the silicon dioxide film.

9. The dry etching method for removing silicon dioxide film at the edge of a silicon wafer according to claim 6, characterized in that: In the step of introducing the reaction gas, the width of the silicon dioxide film removed from the edge of the silicon wafer is controlled by adjusting the concentration of the hydrofluoric acid in the mixed gas containing hydrofluoric acid and / or the time of introducing the gas.

10. The dry etching method for removing silicon dioxide film at the edge of silicon wafer according to claim 9, characterized in that: The volume concentration of hydrofluoric acid in the mixed gas is 5%-40%, and the introduction time is 10-300 seconds.

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