A dry-wet combined superconducting thin film wafer etching residual image suppression method and system

Abstract

This invention relates to a method and system for suppressing etching residue on superconducting thin film wafers using a combined wet and dry etching process. The specific steps include: S1, acquiring wafer lithography rework information: reading the wafer's lithography rework record to obtain identification information indicating whether the wafer has undergone lithography rework and the number of rework cycles; S2, rotating wet source blocking treatment; S3, optical inspection and drying treatment before dry etching; S4, dry adaptive etching and cyclic cleaning; S5, wet purification treatment: after etching, the wafer is immersed in a buffer oxide etching tank unit for cleaning, and finally enters a drying tank unit for drying. This invention has the following advantages: while ensuring etching effect, it minimizes sputtering damage to the superconducting thin film by ions, avoids the generation of oxygen vacancy defects and lattice distortion, and effectively preserves the intrinsic superconducting properties of the superconducting thin film wafer.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor superconducting device manufacturing technology, specifically relating to a method and system for suppressing etching residues in superconducting thin film wafers using a combination of wet and dry etching techniques. It is applicable to the wet and dry etching processes of superconducting thin film wafers after photolithography rework. Background Technology

[0002] Superconducting thin-film wafers (such as yttrium barium copper oxide (YBCO) and bismuth strontium calcium copper oxide (BSCCO) have significant application value in quantum computing, superconducting electronic devices, and high-sensitivity detectors. In the fabrication of these devices, photolithography and dry etching are the core steps in the patterning process. Superconducting thin-film wafers (such as YBCO) are extremely sensitive to moisture; prolonged wet cleaning easily leads to hydrolysis and deterioration, generating non-superconducting impurity phases, resulting in surface roughness, reduced etching selectivity and uniformity, and severely deteriorating superconducting performance and pattern accuracy. Therefore, dry cleaning (mainly oxygen plasma cleaning) is generally used before etching. This utilizes the reaction of oxygen free radicals with organic contaminants to generate volatile products, thereby cleaning the wafer surface. Dry cleaning can be completed in situ within the etching chamber without removing the wafer from the vacuum environment.

[0003] However, traditional dry cleaning methods also have significant limitations in superconducting thin film applications. First, their ability to remove modified photoresist is limited. The photoresist remaining on the wafer surface after photolithography rework has undergone processes such as UV exposure and baking, resulting in irreversible changes in its chemical structure and the formation of a highly cross-linked modified layer. This modified photoresist has a dense carbon-carbon bond network, making it difficult for oxygen free radicals to penetrate, leading to an extremely low etching rate by oxygen plasma. To remove the modified photoresist, the dry cleaning time needs to be extended to several minutes or even tens of minutes, severely impacting process efficiency. Second, prolonged dry cleaning can damage the superconducting thin film. Prolonged exposure to oxygen plasma causes high-energy oxygen ions to continuously bombard the superconducting film surface, resulting in cumulative oxygen vacancy defects and increased surface roughness, leading to degradation of superconducting performance. Furthermore, oxygen plasma cannot remove inorganic byproducts such as metal fluorides generated during dry etching; these residues can become sources of particulate contamination in subsequent processes.

[0004] Traditional dry etching also has significant technical drawbacks. To achieve high etching rates and anisotropy, traditional dry etching typically employs high radio frequency bias power. High-energy ion bombardment causes oxygen atoms in the superconducting thin film lattice to be preferentially sputtered out, resulting in a decrease in the superconducting critical temperature and a widening of the superconducting transition edge. Simply reducing the etching power cannot effectively remove the trace amounts of altered photoresist remaining on the surface of the reworked wafer, as well as the non-volatile byproducts generated during the etching process. These residues form a silica grass-like micromasking structure, leading to image retention and increased pattern edge roughness. Although traditional dry cleaning can remove some organic contaminants before etching, prolonged oxygen plasma cleaning also causes cumulative oxygen vacancy defects and increased surface roughness in the superconducting thin film, and it cannot simultaneously remove newly generated byproducts during the etching process.

[0005] More importantly, while dry cleaning and dry etching can be performed within the same cavity in traditional processes, they are functionally separate and temporally disconnected—cleaning is only performed once before etching, and newly generated byproducts during etching cannot be removed simultaneously. Even with thorough pre-etching cleaning, new byproducts such as fluoropolymers and metal fluorides will continue to be generated during etching. Once these byproducts accumulate to a certain level, they form stable micromask structures that are difficult to remove with any subsequent cleaning. Furthermore, the surface residue state of rework wafers differs significantly from that of normal wafers, but traditional processes use fixed cleaning and etching parameters, which cannot be adjusted according to the actual rework state of the wafer, resulting in insufficient cleaning of rework wafers and over-processing of normal wafers.

[0006] Therefore, how to effectively remove the modified photoresist on the surface of the rework wafer without introducing moisture damage, while simultaneously removing newly generated byproducts during the dry etching process, avoiding damage to superconducting performance from high-energy ion bombardment, and achieving differentiated process adjustments based on the wafer rework status to suppress defects such as image retention, silica grass, and particle deposition has become a pressing technical challenge in this field. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method and system for suppressing etching residues in superconducting thin film wafers using a combined dry and wet method, effectively solving the above technical problems.

[0008] The objective of this invention is achieved through the following technical solution: a dry-wet co-process method for suppressing etching residue on superconducting thin film wafers, the specific steps of which include,

[0009] S1. Obtain wafer lithography rework information: Read the wafer's lithography rework record to obtain the identification information of whether the current wafer has undergone lithography rework and the number of reworks;

[0010] S2, Rotary wet source blocking treatment: The wafer is transferred onto a self-rotating wafer chuck on a rotating platform. The rotating platform has multiple stations that rotate intermittently with its revolution axis. The multiple stations are a hydrofluoric acid tank unit, a combined cleaning tank unit, a drying tank unit, an optical inspection unit, a dry etching chamber unit, and a buffer oxide etching tank unit.

[0011] When a wafer has undergone at least one photolithography rework, it passes through a hydrofluoric acid bath unit to remove the natural oxide layer and photoresist residue from its surface, and then proceeds to a combined cleaning bath unit for combined cleaning. If the wafer has not undergone photolithography rework, it skips the combined cleaning bath unit and proceeds directly to the next station.

[0012] S3. Optical inspection and drying process before dry etching: The wafer is placed in the drying tank unit for drying. Then, the rotating platform drives the optical inspection unit to rotate to the bottom of the wafer chuck to monitor the photolithography residue state on the wafer surface and generate a residue detection signal.

[0013] S4. Dry Adaptive Etching and Cyclic Cleaning: The rotating platform moves the dry etching chamber unit to the bottom of the wafer chuck and selects the etching formula according to the photolithography rework mark: If the wafer has not undergone photolithography rework, a mixture of carbon tetrafluoride and oxygen is introduced to perform continuous etching; if the wafer has undergone at least one photolithography rework, a mixture of sulfur hexafluoride and oxygen is introduced and an alternating etching and cleaning cycle is performed.

[0014] S5. Wet cleaning process: After etching, the wafer is immersed in the buffer oxide etching tank unit for cleaning to selectively etch residual oxides and remove nanoscale particles. Finally, it enters the drying tank unit for drying to remove residual moisture from the wafer surface.

[0015] A further improvement of the present invention is that, in step S3, the cleaning time for dry adaptive etching in step S4 is determined based on the residual detection signal, specifically as follows:

[0016] When the residual detection signal indicates that the amount of photolithography residue on the wafer surface is lower than the first threshold, the cleaning time in step S4 is set to 5 to 8 seconds.

[0017] When the residual detection signal indicates that the amount of photoresist residue on the wafer surface is between the first threshold and the second threshold, the cleaning time in step S4 is set to 8 to 12 seconds.

[0018] When the residual detection signal indicates that the amount of photoresist residue on the wafer surface is higher than the second threshold, the cleaning time in step S4 is set to 12 to 20 seconds.

[0019] A further improvement of the present invention is that, in step S4, the cycle period of the alternating etching and cleaning process is synchronized with the dwell time of the rotary platform at each station, specifically:

[0020] When the wafer does not undergo photolithography rework, the dwell time at each station is equal to the cycle time;

[0021] When a wafer undergoes at least one photolithography rework, the dwell time at each station is an integer multiple of the cycle period;

[0022] The dwell time at each workstation is adjusted according to the number of times the wafer undergoes photolithography rework, specifically as follows:

[0023] When the number of lithography reworks is 0, the dwell time at each station is 10 to 20 seconds;

[0024] When the number of photolithography reworks is 1, the dwell time at each station is 20 to 30 seconds;

[0025] When the number of photolithography reworks is greater than or equal to 2, the dwell time at each station is 30 to 60 seconds.

[0026] A further improvement of the present invention is that: in step S4, an alternating etching and cleaning cycle is performed, specifically as follows:

[0027] Etching stage: A mixture of sulfur hexafluoride and oxygen is introduced with a volume flow ratio of 4:1 to 10:1, the radio frequency bias power is 20W to 40W, a pulse output mode is adopted, the pulse frequency is 1kHz to 10kHz, the duty cycle is 30% to 70%, the cavity pressure of the dry etching chamber unit is 15mTorr to 25mTorr, and the etching stage duration is 10 seconds to 20 seconds;

[0028] Cleaning stage: oxygen is introduced, the radio frequency bias power is 20W to 40W, the cavity pressure of the dry etching chamber unit is 15mTorr to 25mTorr, and the cleaning stage duration is 5 to 20 seconds according to the set value determined in step 3.

[0029] During the etching and cleaning stages, the wafer chuck drives the wafer to rotate at a speed of 5 rpm to 20 rpm.

[0030] A further improvement of the present invention is that, in step S4, continuous etching is performed, specifically as follows:

[0031] A mixture of carbon tetrafluoride and oxygen is introduced, with a volume flow rate ratio of 3:1 to 5:1, an RF bias power of 40W to 60W, and a cavity pressure of 10mTorr to 20mTorr for the dry etching cavity unit.

[0032] The wafer chuck drives the wafer to rotate at a speed of 5 rpm to 20 rpm.

[0033] A system for a dry-wet co-processing method to suppress etching artifacts on superconducting thin film wafers, comprising:

[0034] Fixed foundation;

[0035] A rotating platform, comprising a platform base and a revolution drive mechanism, wherein the revolution drive mechanism is used to drive the platform base to rotate intermittently around the revolution axis;

[0036] Multiple workstations are fixedly set on a rotating platform and revolve with the rotating platform. The multiple workstations are sequentially arranged as follows: a hydrofluoric acid tank unit, a combined cleaning tank unit, an optical inspection unit, a drying tank unit, a dry etching chamber unit, and a buffer oxide etching tank unit. The hydrofluoric acid tank unit includes a hydrofluoric acid tank and a first rapid discharge rinsing tank. The buffer oxide etching tank unit includes a buffer oxide etching tank and a second rapid discharge rinsing tank.

[0037] The wafer chuck assembly is mounted on a fixed base and positioned above a rotating platform. The wafer chuck assembly includes a wafer chuck that carries the wafer and a lifting mechanism that drives the wafer chuck to move up and down, allowing the wafer to be immersed in various workstations or sealed and docked with a dry etching chamber unit. It also includes a rotation drive mechanism that drives the wafer chuck to rotate the wafer. The lifting mechanism and the rotation drive mechanism are independent of each other in motion.

[0038] A further improvement of the present invention is that the combined cleaning tank unit includes a cleaning chamber and an ultrasonic generator placed at the bottom of the cleaning chamber. The cleaning chamber is divided into an N-methylpyrrolidone chamber, an acetone chamber and an isopropanol chamber by a partition.

[0039] A further improvement of the present invention is that: the dry etching cavity unit includes

[0040] The main body of the chamber is fixedly mounted on the rotating platform. Its top has an opening and the edge of the opening has a sealing ring that fits against the lower surface of the wafer chuck.

[0041] The gas supply matrix includes carbon-containing gas channels and carbon-free gas channels. The carbon-containing gas channels are used to transport a mixture of carbon tetrafluoride and oxygen, while the carbon-free gas channels are used to transport a mixture of sulfur hexafluoride and oxygen or oxygen alone.

[0042] A further improvement of the present invention is that the wafer chuck assembly also includes:

[0043] The rotation shaft connects the rotation drive mechanism to the wafer chuck;

[0044] A sealing cover is installed between the lifting mechanism and the self-rotating drive mechanism. The sealing cover is sealed and connected to the top of the chamber body as the lifting mechanism drives it.

[0045] A further improvement of the present invention is that the lifting mechanism is an electric push rod or a servo electric cylinder, and the self-rotation drive mechanism is a servo motor or a stepper motor.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] 1. This invention abandons the water-based cleaning system and uses anhydrous solvents N-methylpyrrolidone, acetone, and isopropanol to construct a three-stage combined cleaning system. Utilizing the chemical properties of different solvents, it progressively swells, dissolves, and replaces the highly cross-linked modified photoresist, achieving gentle yet efficient residue removal. This process replaces the traditional oxygen plasma dry cleaning process, which takes several minutes or even tens of minutes. It fundamentally blocks the contact between water vapor and the superconducting thin film, completely avoiding hydrolytic degradation and the formation of non-superconducting impurities. It also significantly improves the removal efficiency of the modified photoresist, solving the problems of low etching rate and long processing time associated with traditional dry cleaning. Simultaneously, it lays a clean and intact surface foundation for subsequent etching processes, balancing cleaning effectiveness with the surface integrity of the superconducting thin film. Furthermore, this invention, through the initial anhydrous wet combined cleaning, efficiently removes most of the modified photoresist, significantly reducing the difficulty of subsequent dry etching and greatly shortening the wafer's exposure time in the plasma environment, thus reducing cumulative damage caused by plasma from the source. Meanwhile, the dry etching stage adopts a low-power pulse output mode, which effectively reduces the time-averaged ion energy and avoids continuous high-energy ion bombardment damage to the crystal lattice. For the cyclic etching process of rework wafers, low power parameters are also used to minimize ion sputtering damage to the superconducting thin film while ensuring the etching effect, avoid the generation of oxygen vacancy defects and crystal distortion, effectively preserve the intrinsic superconducting performance of the superconducting thin film wafer, and ensure the core performance indicators of subsequent superconducting devices.

[0048] 2. This invention addresses wafers undergoing photolithography rework by employing an alternating etching and cleaning process during the dry etching stage. An oxygen cleaning stage is initiated immediately after each etching cycle, before the etching byproducts have solidified or formed a stable structure. Low-power oxygen plasma can rapidly remove these byproducts, preventing their accumulation. Simultaneously, the etching and cleaning cycles are precisely synchronized with the dwell time of the rotating platform, ensuring timely and thorough removal of byproducts. This design not only effectively suppresses defects such as image retention and silica fume but also significantly reduces particulate contamination sources on the wafer surface, improving the edge smoothness and surface cleanliness of the etched patterns. This provides a precise patterning foundation for the high-performance fabrication of superconducting thin-film devices. Attached Figure Description

[0049] Figure 1 This is a schematic flowchart of a dry-wet co-processing method for suppressing etching residues on superconducting thin film wafers according to the present invention.

[0050] Figure 2This is a schematic diagram of the structure of a dry-wet co-processing superconducting thin film wafer etching retention suppression system according to the present invention.

[0051] Figure 3 for Figure 2 A schematic diagram showing the positions of multiple workstations on the rotating platform.

[0052] Figure 4 for Figure 2 A schematic diagram of the structure of a modular cleaning tank unit.

[0053] Figure 5 This is a comparison of the effect of the method of the present invention and the traditional method on suppressing image retention on the surface of photolithographic rework wafers.

[0054] Numbering on the map:

[0055] 1-Fixed foundation, 2-Rotating platform, 3-Hydrofluoric acid tank, 4-First rapid discharge rinsing tank, 5-Combined cleaning tank unit, 6-Optical inspection unit, 7-Drying tank unit, 8-Dry etching chamber unit, 9-Buffer oxide etching tank, 10-Second rapid discharge rinsing tank, 11-Wafer chuck, 12-Lifting mechanism, 13-Rotation drive mechanism, 14-Rotation shaft, 15-Sealing cover, 16-Wafer;

[0056] 51-Cleaning chamber, 52-Ultrasonic generator, 53-N-Methylpyrrolidone chamber, 54-Acetone chamber, 55-Isopropanol chamber, 56-Separator;

[0057] 81-Cavity body, 82-Sealing ring, 83-Carbon-containing gas passage, 84-Carbon-free gas passage. Detailed Implementation

[0058] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and accompanying drawings. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0059] In the description of this invention, it should be understood that the terms indicating orientation or positional relationship, such as those based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the structure or unit referred to must have a specific orientation, and therefore should not be construed as a limitation of this invention.

[0060] In this invention, unless otherwise explicitly specified and limited, terms such as “connection,” “provided with,” and “have” should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can be described as a mechanical connection, a direct connection, or a connection through an intermediate medium. Those skilled in the art can understand the basic meaning of the above terms in this invention according to the specific circumstances.

[0061] A method for suppressing etching artifacts in superconducting thin film wafers using a combined wet and dry etching process, referring to... Figure 1 The specific steps include,

[0062] S1. Obtain wafer lithography rework information: Read the lithography rework record of wafer 15, and obtain the identification information of whether wafer 15 has undergone lithography rework and the number of reworks.

[0063] S2, Rotary wet source blocking treatment: Transfer wafer 15 onto the rotating platform 2 onto the self-rotating wafer chuck 11, as per [reference needed]. Figure 3 The rotating platform 2 has multiple workstations that rotate intermittently along its revolution axis. These workstations are a hydrofluoric acid tank unit, a combined cleaning tank unit 5, an optical inspection unit 6, a drying tank unit 7, a dry etching chamber unit 8, and a buffer oxide etching tank unit 9.

[0064] When wafer 15 has undergone at least one photolithography rework, after the natural oxide layer and photoresist residue on the surface of wafer 15 are removed by the hydrofluoric acid tank unit, wafer 15 is sent to the combined cleaning tank unit 5 for combined cleaning; if it has not undergone photolithography rework, the combined cleaning tank unit 5 is skipped and the wafer is directly transferred to the next station.

[0065] S3. Optical inspection and drying process before dry etching: Wafer 15 is placed in drying tank unit 7 for drying. Then, rotating platform 2 drives optical inspection unit 6 to rotate to the bottom of wafer chuck 11 to monitor the photolithography residue state on the surface of wafer 16 and generate residue detection signal.

[0066] S4. Dry Adaptive Etching and Cyclic Cleaning: The rotating platform 2 moves the dry etching chamber unit 8 to a position below the wafer chuck 11. The etching formula is selected according to the photolithography rework mark: If the wafer 15 has not undergone photolithography rework, a mixture of carbon tetrafluoride and oxygen is introduced to perform continuous etching; if the wafer 15 has undergone at least one photolithography rework, a mixture of sulfur hexafluoride and oxygen is introduced to perform an alternating etching and cleaning cycle.

[0067] S5. Wet cleaning process: After etching, wafer 15 is immersed in buffer oxide etching tank unit 9 for cleaning to selectively etch residual oxides and remove nanoscale particles. Finally, it enters drying tank unit 7 for drying to remove residual moisture on the surface of wafer 15.

[0068] This invention abandons water-based cleaning systems and employs a three-stage combined cleaning system using anhydrous solvents N-methylpyrrolidone, acetone, and isopropanol. Utilizing the chemical properties of different solvents, it progressively swells, dissolves, and replaces the highly cross-linked modified photoresist, achieving gentle yet efficient residue removal. This process replaces the traditional oxygen plasma dry cleaning method, which takes several minutes or even tens of minutes. It fundamentally blocks the contact between water vapor and the superconducting thin film, completely avoiding hydrolytic degradation and the formation of non-superconducting impurities. It also significantly improves the removal efficiency of the modified photoresist, solving the problems of low etching rates and long processing times associated with traditional dry cleaning. Furthermore, it lays a clean and intact surface foundation for subsequent etching processes, balancing cleaning effectiveness with the surface integrity of the superconducting thin film. Simultaneously, this invention, through the initial anhydrous wet combined cleaning, efficiently removes most of the modified photoresist, significantly reducing the difficulty of subsequent dry etching and drastically shortening the wafer's exposure time in the plasma environment, thus reducing cumulative damage caused by plasma from the source. Meanwhile, the dry etching stage adopts a low-power pulse output mode, which effectively reduces the time-averaged ion energy and avoids continuous high-energy ion bombardment damage to the crystal lattice. For the cyclic etching process of rework wafers, low power parameters are also used to minimize ion sputtering damage to the superconducting thin film while ensuring the etching effect, avoid the generation of oxygen vacancy defects and crystal distortion, effectively preserve the intrinsic superconducting performance of the superconducting thin film wafer, and ensure the core performance indicators of subsequent superconducting devices.

[0069] Based on this embodiment, in step S3, the cleaning time for dry adaptive etching in step S4 is determined according to the residual detection signal, specifically as follows:

[0070] When the residual detection signal indicates that the amount of photolithography residue on the surface of wafer 15 is lower than the first threshold, the cleaning time in step S4 is set to 5 to 8 seconds.

[0071] When the residual detection signal indicates that the amount of photoresist residue on the surface of wafer 15 is between the first threshold and the second threshold, the cleaning time in step S4 is set to 8 to 12 seconds.

[0072] When the residual detection signal indicates that the amount of photoresist residue on the surface of wafer 15 is higher than the second threshold, the cleaning time in step S4 is set to 12 to 20 seconds.

[0073] Based on this embodiment, in step S4, the cycle period of the alternating etching and cleaning process is synchronized with the dwell time of the rotating platform 2 at each station, specifically as follows:

[0074] When wafer 15 does not undergo photolithography rework, the dwell time at each station is equal to the cycle time;

[0075] When wafer 15 has undergone at least one photolithography rework, the dwell time at each station is an integer multiple of the cycle period;

[0076] The dwell time at each workstation is adjusted according to the number of lithography rework cycles for wafer 15, specifically as follows:

[0077] When the number of lithography reworks is 0, the dwell time at each station is 10 to 20 seconds;

[0078] When the number of photolithography reworks is 1, the dwell time at each station is 20 to 30 seconds;

[0079] When the number of photolithography reworks is greater than or equal to 2, the dwell time at each station is 30 to 60 seconds.

[0080] This invention achieves precise and differentiated adjustment of multi-dimensional parameters by reading wafer lithography rework information in the early stage and optically detecting the amount of lithography residue on the surface: different etching formulas are selected according to whether rework is required; non-reworked wafers are continuously etched with a mixture of carbon tetrafluoride and oxygen, while reworked wafers are cyclically etched with a mixture of sulfur hexafluoride and oxygen; the cleaning time is set according to the residual amount threshold, and the station dwell time is adjusted according to the number of reworks. The all-dimensional adaptive adjustment makes the process parameters highly consistent with the actual state of the wafer, which avoids damage to the superconducting thin film caused by over-processing and eliminates residues and defects caused by under-processing, greatly improving the stability and yield of the process.

[0081] Based on this embodiment, in step S4, an alternating etching and cleaning cycle is performed, specifically as follows:

[0082] Etching stage: A mixture of sulfur hexafluoride and oxygen is introduced with a volume flow ratio of 4:1 to 10:1, the radio frequency bias power is 20W to 40W, a pulse output mode is adopted, the pulse frequency is 1kHz to 10kHz, the duty cycle is 30% to 70%, the cavity pressure of the dry etching cavity unit 8 is 15mTorr to 25mTorr, and the etching stage duration is 10 seconds to 20 seconds;

[0083] Cleaning stage: oxygen is introduced, the radio frequency bias power is 20W to 40W, the cavity pressure of dry etching chamber unit 8 is 15mTorr to 25mTorr, and the cleaning stage duration is executed according to the set value determined in step three, which is 5 seconds to 20 seconds.

[0084] During the etching and cleaning stages, the wafer chuck 11 drives the wafer 15 to rotate at a speed of 5 rpm to 20 rpm.

[0085] This invention targets wafers undergoing photolithography rework. During the dry etching stage, it employs an alternating etching and cleaning process. An oxygen cleaning stage is initiated immediately after each etching cycle. At this point, etching byproducts have not yet solidified or formed a stable structure, allowing low-power oxygen plasma to rapidly remove them, preventing byproduct accumulation. Simultaneously, the etching and cleaning cycle is precisely synchronized with the rotary platform's dwell time, ensuring timely and thorough byproduct removal. This design not only effectively suppresses defects such as image retention and silica fume, but also significantly reduces particulate contamination sources on the wafer surface, improving the edge smoothness and surface cleanliness of the etched patterns. This provides a precise patterning foundation for the high-performance fabrication of superconducting thin-film devices.

[0086] Based on this embodiment, in step S4, continuous etching is performed, specifically as follows:

[0087] A mixture of carbon tetrafluoride and oxygen is introduced, with a volume flow rate ratio of 3:1 to 5:1, an RF bias power of 40W to 60W, and a cavity pressure of 10mTorr to 20mTorr for the dry etching cavity unit 8.

[0088] The wafer chuck 11 drives the wafer 15 to rotate at a speed of 5 rpm to 20 rpm.

[0089] A system for suppressing etching artifacts in superconducting thin film wafers using a combined wet and dry etching approach, referring to... Figure 2 ,include

[0090] Fixed foundation 1;

[0091] Rotating platform 2 includes a platform base and a revolution drive mechanism, which drives the platform base to rotate intermittently around the revolution axis.

[0092] Multiple workstations are fixedly set on the rotating platform 2 and revolve with the rotating platform 2. The multiple workstations are sequentially arranged as follows: a hydrofluoric acid tank unit, a combined cleaning tank unit 5, an optical inspection unit 6, a drying tank unit 7, a dry etching chamber unit 8, and a buffer oxide etching tank unit 9. The hydrofluoric acid tank unit includes a hydrofluoric acid tank 3 and a first rapid discharge rinsing tank 4. The buffer oxide etching tank unit includes a buffer oxide etching tank 9 and a second rapid discharge rinsing tank 10.

[0093] The wafer chuck assembly is mounted on a fixed base 1 and positioned above a rotating platform 2. The wafer chuck assembly includes a wafer chuck 11 that carries a wafer 15 and a lifting mechanism 12 that drives the wafer chuck 11 to move up and down, so that the wafer 15 is immersed in various workstations or sealed and docked with the dry etching chamber unit 8. It also includes a rotation drive mechanism 13 that drives the wafer chuck 11 to rotate the wafer 15. The lifting mechanism 12 and the rotation drive mechanism 13 are independent of each other in motion.

[0094] Furthermore, the combined cleaning tank unit 5 includes a cleaning chamber 51 and an ultrasonic generator 52 placed at the bottom of the cleaning chamber 51. The cleaning chamber 51 is divided into an N-methylpyrrolidone chamber 53, an acetone chamber 54 and an isopropanol chamber 55 by a partition 56.

[0095] Furthermore, the dry etching cavity unit 8 includes

[0096] The chamber body 81 is fixedly mounted on the rotating platform 2. Its top has an opening and the edge of the opening has a sealing ring 82 that fits against the lower surface of the wafer chuck 11.

[0097] The gas supply matrix includes a carbon-containing gas passage 83 and a carbon-free gas passage 84. The carbon-containing gas passage 83 is used to transport a mixture of carbon tetrafluoride and oxygen, while the carbon-free gas passage 84 is used to transport a mixture of sulfur hexafluoride and oxygen or to transport oxygen alone.

[0098] Furthermore, the wafer chuck assembly also includes

[0099] The rotation axis 14 is connected to the rotation drive mechanism 13 and the wafer chuck 11;

[0100] The sealing cover 15 is located between the lifting mechanism 12 and the self-rotating drive mechanism 13. The sealing cover 15 is sealed and connected to the top of the chamber body 81 as the lifting mechanism 12 is driven.

[0101] The lifting mechanism 12 is an electric push rod or a servo cylinder, and the self-rotation drive mechanism 13 is a servo motor or a stepper motor.

[0102] In this invention, the wafer chuck 11 drives the wafer to rotate, achieving the following technical effects:

[0103] During wet cleaning, the rotation speed of 5-20 rpm creates a dynamic solvent flow field through centrifugal force, continuously refreshing the cleaning solvent on the wafer surface. This eliminates the solvent concentration gradient between the center and the edge, allowing the swelling and dissolution effects of solvents such as N-methylpyrrolidone and the ultrasonic cavitation effect to uniformly cover the entire area, avoiding local photoresist residue or over-cleaning. The rotation speed also ensures uniform transmission of ultrasonic vibrations without dead zones, preventing micro-damage to the thin film caused by local superposition of ultrasonic waves under static conditions. At the same time, centrifugal force quickly removes residual solvent, reducing prolonged local contact between solvent and the thin film. It can quickly peel off photoresist residue and nano-sized particles after solvent dissolution, while centrifugation removes cleaning solvent adhering to the surface, avoiding local solvent accumulation and laying the foundation for subsequent anhydrous drying, reducing etching defects caused by solvent residue.

[0104] During the dry etching / cleaning cycle, the rotation of the plasma ions and oxygen radicals uniformly bombard / contact all areas of the wafer, overcoming the density gradient problem in the plasma chamber. This ensures consistent etching rate and by-product removal throughout the entire process, preventing local etching deviations and by-product accumulation that could form micromasks. Low-power pulse etching reduces the average ion energy, and the rotation further prevents ions from continuously bombarding the same location, avoiding repeated impacts on the local lattice that could lead to oxygen vacancy defects and lattice distortion. It also reduces the increase in local surface roughness, effectively protecting the intrinsic superconducting properties of the superconducting thin film wafer. Under the sealed chamber environment, centrifugal force can quickly desorb and remove metal fluorides and fluorocarbons generated during etching, as well as volatile organic products generated during cleaning, from the wafer surface and out of the chamber. This prevents by-products from solidifying after a brief adhesion, improving wafer surface cleanliness and reducing secondary contamination by by-products, resulting in superior by-product removal efficiency in the etching-cleaning cycle.

[0105] To further verify the practical effect of the dry-wet synergistic superconducting thin film wafer etching retention suppression method provided by this invention, this embodiment uses a superconducting thin film wafer (YBCO) that has undergone one photolithography rework as the test object. The conventional process (single oxygen plasma dry cleaning + continuous dry etching) and the method of this invention are compared. After etching, the wafer surface morphology is observed using a scanning electron microscope. The results are as follows: Figure 5 As shown.

[0106] from Figure 5 The comparison chart clearly shows:

[0107] The wafer surface processed by traditional processes exhibits obvious image retention, which manifests as irregular micro-masking structures at the edges of the pattern, residual modified photoresist and etching byproducts in some areas, significantly increased roughness at the edges of the pattern, and visible silicon grass-like defects in some areas.

[0108] The wafer surface pattern processed by the method of the present invention has clear and flat edges, no afterimages or micro-masking structures, good overall surface cleanliness, high pattern transfer accuracy, and significantly reduced edge roughness.

[0109] The comparison results fully demonstrate that the present invention achieves a significant image retention suppression effect through the following technical means:

[0110] 1. Anhydrous wet combination cleaning: Using a three-stage solvent system of N-methylpyrrolidone, acetone and isopropanol, it efficiently removes highly cross-linked modified photoresist from the surface of photolithography rework wafers, avoiding the problems of long cleaning time and incomplete removal in traditional dry cleaning.

[0111] 2. Alternating etching and cleaning cycle process: For reworked wafers, a mixture of sulfur hexafluoride and oxygen gas is used for low-power pulse etching, and oxygen cleaning is performed immediately after each etching cycle to remove non-volatile byproducts such as fluoropolymers and metal fluorides generated during the etching process in a timely manner, so as to prevent them from solidifying into micro-mask structures.

[0112] 3. Low-power pulse output and wafer rotation synergy: The RF bias power is controlled at 20W to 40W, combined with pulse output mode (duty cycle 30%-70%) and wafer rotation (5rpm-20rpm), which effectively reduces the continuous bombardment energy of ions on the superconducting thin film, avoids local oxygen vacancy defects and lattice damage, and ensures uniform desorption of by-products.

[0113] 4. Adaptive matching of process parameters and wafer status: The cleaning time and station dwell time are adjusted according to the number of lithography reworks and residual detection signals to achieve differentiated process control and avoid over-processing or under-processing.

[0114] In summary, the method of this invention achieves efficient and non-destructive image retention suppression on the surface of photolithographic rework wafers, significantly improving the edge smoothness and surface cleanliness of etched patterns, and providing a reliable patterning process guarantee for the high-performance fabrication of superconducting thin film devices.

[0115] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing etching artifacts in superconducting thin film wafers using a combined wet and dry etching process, characterized in that: The specific steps include, S1. Obtain wafer lithography rework information: Read the wafer's lithography rework record to obtain the identification information of whether the current wafer has undergone lithography rework and the number of reworks; S2. Rotary wet source blocking treatment: The wafer is transferred onto a self-rotating wafer chuck on a rotating platform. The rotating platform has multiple stations that rotate intermittently with its revolution axis. The multiple stations are a hydrofluoric acid tank unit, a combined cleaning tank unit, a drying tank unit, an optical inspection unit, a dry etching chamber unit, and a buffer oxide etching tank unit. When a wafer has undergone at least one photolithography rework, it passes through a hydrofluoric acid bath unit to remove the natural oxide layer and photoresist residue from its surface, and then proceeds to a combined cleaning bath unit for combined cleaning. If the wafer has not undergone photolithography rework, it skips the combined cleaning bath unit and proceeds directly to the next station. S3. Optical inspection and drying process before dry etching: The wafer is placed in the drying tank unit for drying, and then the rotating platform drives the optical inspection unit to rotate to the bottom of the wafer chuck to monitor the photolithography residue state on the wafer surface and generate a residue detection signal. S4. Dry adaptive etching and cyclic cleaning: The rotating platform drives the dry etching cavity unit to be placed below the wafer chuck. The etching formula is selected according to the photolithography rework mark. If the wafer has not undergone photolithography rework, a mixture of carbon tetrafluoride and oxygen is introduced to perform continuous etching. If the wafer has undergone at least one photolithography rework, a mixture of sulfur hexafluoride and oxygen is introduced, and an alternating etching and cleaning cycle is performed. S5. Wet cleaning process: After etching, the wafer is immersed in the buffer oxide etching tank unit for cleaning to selectively etch residual oxides and remove nanoscale particles. Finally, it enters the drying tank unit for drying to remove residual moisture from the wafer surface.

2. The method for suppressing etching residue in superconducting thin film wafers using a combined wet and dry etching process according to claim 1, characterized in that, In step S3, the cleaning time for dry adaptive etching in step S4 is determined based on the residual detection signal, specifically as follows: When the residual detection signal indicates that the amount of photolithography residue on the wafer surface is lower than the first threshold, the cleaning time in step S4 is set to 5 to 8 seconds. When the residual detection signal indicates that the amount of photoresist residue on the wafer surface is between the first threshold and the second threshold, the cleaning time in step S4 is set to 8 to 12 seconds. When the residual detection signal indicates that the amount of photoresist residue on the wafer surface is higher than the second threshold, the cleaning time in step S4 is set to 12 to 20 seconds.

3. The method for suppressing etching residue in superconducting thin film wafers using a combined dry and wet etching process according to claim 2, characterized in that, In step S4, the cycle period of the alternating etching and cleaning process is synchronized with the dwell time of the rotary platform at each station. Specifically: When the wafer does not undergo photolithography rework, the dwell time at each station is equal to the cycle time; When a wafer undergoes at least one photolithography rework, the dwell time at each station is an integer multiple of the cycle period; The dwell time at each workstation is adjusted according to the number of times the wafer undergoes photolithography rework, specifically as follows: When the number of lithography reworks is 0, the dwell time at each station is 10 to 20 seconds; When the number of photolithography reworks is 1, the dwell time at each station is 20 to 30 seconds; When the number of photolithography reworks is greater than or equal to 2, the dwell time at each station is 30 to 60 seconds.

4. The method for suppressing etching residue in superconducting thin film wafers using a combined dry and wet etching process according to claim 3, characterized in that, In step S4, an alternating etching and cleaning cycle is performed, specifically as follows: Etching stage: A mixture of sulfur hexafluoride and oxygen is introduced with a volume flow ratio of 4:1 to 10:1, the radio frequency bias power is 20W to 40W, a pulse output mode is adopted, the pulse frequency is 1kHz to 10kHz, the duty cycle is 30% to 70%, the cavity pressure of the dry etching chamber unit is 15mTorr to 25mTorr, and the etching stage duration is 10 seconds to 20 seconds; Cleaning stage: oxygen is introduced, the radio frequency bias power is 20W to 40W, the cavity pressure of the dry etching chamber unit is 15mTorr to 25mTorr, and the cleaning stage duration is 5 to 20 seconds according to the set value determined in step 3. During the etching and cleaning stages, the wafer chuck drives the wafer to rotate at a speed of 5 rpm to 20 rpm.

5. The method for suppressing etching residue in superconducting thin film wafers using a combined wet and dry etching process according to claim 4, characterized in that, In step S4, continuous etching is performed, specifically as follows: A mixture of carbon tetrafluoride and oxygen is introduced, with a volume flow rate ratio of 3:1 to 5:1, an RF bias power of 40W to 60W, and a cavity pressure of 10mTorr to 20mTorr for the dry etching cavity unit. The wafer chuck drives the wafer to rotate at a speed of 5 rpm to 20 rpm.

6. A system for implementing the dry-wet co-processing superconducting thin film wafer etching retention suppression method according to any one of claims 1 to 5, characterized in that, include Fixed foundation; A rotating platform, comprising a platform base and a revolution drive mechanism, wherein the revolution drive mechanism is used to drive the platform base to rotate intermittently around a revolution axis; Multiple workstations are fixedly installed on a rotating platform and revolve with the platform. The multiple workstations are sequentially arranged as follows: a hydrofluoric acid tank unit, a combined cleaning tank unit, an optical inspection unit, a drying tank unit, a dry etching chamber unit, and a buffer oxide etching tank unit. The hydrofluoric acid tank unit includes a hydrofluoric acid tank and a first rapid discharge rinsing tank. The buffer oxide etching tank unit includes a buffer oxide etching tank and a second rapid discharge rinsing tank. A wafer chuck assembly is mounted on a fixed base and positioned above a rotating platform. The wafer chuck assembly includes a wafer chuck that carries the wafer and a lifting mechanism that drives the wafer chuck to move up and down, allowing the wafer to be immersed in various workstations or sealed and docked with a dry etching chamber unit. It also includes a rotation drive mechanism that drives the wafer chuck to rotate the wafer. The lifting mechanism and the rotation drive mechanism are independent of each other in motion.

7. The dry-wet co-processing superconducting thin-film wafer etching ghosting suppression system according to claim 6, characterized in that, The combined cleaning tank unit includes a cleaning chamber and an ultrasonic generator placed at the bottom of the cleaning chamber. The cleaning chamber is divided into an N-methylpyrrolidone chamber, an acetone chamber, and an isopropanol chamber by a partition.

8. The dry-wet co-processing superconducting thin-film wafer etching ghosting suppression system according to claim 7, characterized in that, The dry etching cavity unit includes The chamber body is fixedly mounted on a rotating platform, and its top has an opening with a sealing ring at the edge of the opening that fits against the lower surface of the wafer chuck. A gas supply matrix, comprising a carbon-containing gas passage and a carbon-free gas passage, wherein the carbon-containing gas passage is used to transport a mixture of carbon tetrafluoride and oxygen, and the carbon-free gas passage is used to transport a mixture of sulfur hexafluoride and oxygen or to transport oxygen alone.

9. The dry-wet co-processing superconducting thin-film wafer etching ghosting suppression system according to claim 8, characterized in that, The wafer chuck assembly also includes A rotating shaft, wherein the rotating shaft connects the rotating drive mechanism to the wafer chuck; A sealing cover is disposed between the lifting mechanism and the self-rotating drive mechanism. The sealing cover is sealed and connected to the top of the chamber body as the lifting mechanism drives it.

10. The dry-wet co-processing superconducting thin-film wafer etching ghosting suppression system according to claim 9, characterized in that, The lifting mechanism is an electric push rod or a servo electric cylinder, and the self-rotation drive mechanism is a servo motor or a stepper motor.

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