High uniformity 12 inch silicon dioxide film and process method thereof

Abstract

The application discloses a kind of high uniformity 12 inch silicon dioxide film and process method thereof, belong to semiconductor integrated circuit manufacturing technical field.Process method includes: providing 12 inch silicon wafer substrate;Wafer is placed into process chamber one, and wafer surface is pre-cleaned using capacitive coupled plasma;Wafer is transmitted to process chamber two by vacuum conveying system, and silicon dioxide film is grown on wafer surface using in-situ water vapor generation process and in combination with step temperature control;In-situ film optical polarization analysis system, which is constituted by broadband light source and CCD detector integrated in process chamber one, is used to detect pre-cleaning effect, film thickness and uniformity in-situ;When detection result does not meet requirements, self-limiting cycle etch-back modification is carried out on film using capacitive coupled plasma, and detection and etch-back steps are repeated until film uniformity meets requirements.The 12 inch silicon dioxide film prepared by the application has a thickness of 10-12 nm and a uniformity of less than 0.3%.The process is completed in-line equipment, wafer does not contact atmospheric environment, particle contamination is avoided, film quality detection and uniformity control are integrated in the same process equipment, offline detection redundancy cost is saved, the uniformity and product yield stability of 12 inch silicon dioxide film are significantly improved, and the application is suitable for large-scale integrated circuit manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor integrated circuit manufacturing technology, specifically relating to a highly uniform 12-inch silicon dioxide thin film and its process method, particularly to a 12-inch silicon dioxide thin film preparation process based on in-situ water vapor generation (ISSG) technology, combined with in-situ optical monitoring and self-limiting cyclic etching to achieve online control of uniformity, and silicon dioxide thin film products prepared using this process. Background Technology

[0002] As integrated circuit manufacturing processes continue to evolve towards 14nm and below, 12-inch (300mm) silicon wafer technology has been fully established as the mainstream production platform for the integrated circuit industry. Silicon dioxide thin films, with their excellent insulation properties and process compatibility, play an indispensable role in the large-scale mass production of advanced memory chips and high-performance logic devices on 12-inch production lines. They are widely used in core process stages such as gate dielectric layers, shallow trench isolation (STI), interlayer dielectrics (ILD), and surface passivation protection. The uniformity, density, and interface state quality of silicon dioxide thin films directly determine the core electrical performance of devices, such as leakage current control capability, signal transmission delay, and breakdown voltage, thus affecting product yield and reliability.

[0003] Currently, in-situ steam generation (ISSG) technology can achieve the growth of high-quality silica films on 8-inch and smaller wafers, but there are few reports on the growth of highly uniform silica films on 12-inch wafers. Furthermore, existing technologies lack effective process control methods for the uniformity and density of silica films grown using ISSG. The industry generally adopts an offline inspection mode, where after completing the silica film process on the wafer, the wafer is moved to a separate inspection platform, and the uniformity and surface morphology of the wafer are characterized offline using equipment such as ellipsometry and scanning electron microscopy (SEM). When abnormal film thickness uniformity or particle contamination is detected, process parameter adjustments, contamination source tracing, and multiple rounds of trial and error verification are required to pinpoint an optimization solution. This adjustment process has a significant combined effect of time and economic costs, making it difficult to meet the stringent requirements of advanced processes for process convergence efficiency and production line yield stability. However, a breakthrough online real-time control technology or in-situ monitoring solution has not yet been developed.

[0004] Chinese patent document CN114068306A discloses a method for preparing a highly uniform silicon dioxide thin film. The method employs plasma-enhanced chemical vapor deposition (PECVD) to grow a silicon dioxide thin film on a wafer surface. A preheating process before deposition ensures sufficient contact between the substrate and the reactive gas. Adjustments to process conditions such as flow rate ratio, RF power, and deposition chamber pressure achieve highly uniform silicon dioxide film growth. This method can complete silicon dioxide deposition at low temperatures of 250~400℃, making it suitable for bonding layers at bonding interfaces. However, this patent document does not disclose the implementation effect of its PECVD process on 12-inch wafers for silicon dioxide growth. Furthermore, the silicon dioxide thin film grown by PECVD technology has low density and interface state quality, making it difficult to apply to the gate oxide layer process of advanced devices such as GAA.

[0005] Chinese patent document CN104465440A discloses a method for monitoring growth defects in in-situ water vapor-grown gate oxide films. This method involves locating areas on a silicon substrate where a gate oxide film (silicon dioxide thin film) has formed and areas where no gate oxide film has formed, and then performing scanning electron microscopy (SEM) analysis on cross-sections of both areas to obtain monitoring results on the presence of growth defects in the gate oxide film. This shortens the defect detection cycle and improves device yield. However, this method still uses offline detection to analyze film defects and cannot achieve in-situ monitoring of the film growth process or real-time processing of abnormal situations.

[0006] In summary, existing technologies still have significant shortcomings in achieving high uniformity growth of silicon dioxide thin films on 12-inch wafers and in-situ monitoring and control. There is an urgent need for a process method that can achieve high uniformity growth of silicon dioxide thin films on 12-inch silicon substrates and has in-situ detection and online control capabilities.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention aims to provide a highly uniform 12-inch silicon dioxide thin film and its processing method. Through the process path of "plasma wafer pre-cleaning - ISSG silicon dioxide thin film growth - in-situ optical monitoring - plasma cyclic etching planarization", a silicon dioxide thin film is prepared on a 12-inch silicon substrate to improve the uniformity of the film and the stability of product yield, reduce process optimization costs, and is suitable for large-scale integrated circuit manufacturing.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a process for preparing a highly uniform 12-inch silicon dioxide thin film, the process comprising the following steps: (1) Provide 12-inch silicon wafer substrate; (2) The silicon wafer substrate is placed in process chamber one, and argon gas is ionized using capacitively coupled plasma (CCP) excitation to generate argon plasma (Ar). + The silicon wafer substrate surface is pre-cleaned with plasma; the capacitively coupled plasma provides high-density and energy-controllable vertical ion bombardment conditions, and by forming a stable DC self-bias on the wafer surface, Ar... + The ion energy is precisely adjusted by accelerating and guiding the physical sputtering in a direction perpendicular to the substrate without significantly changing the plasma density, thereby achieving atomic-level surface purification while ensuring high uniformity of the 12-inch wafer surface. This directional ion bombardment can efficiently remove stubborn particles and natural oxide layers from the surface while minimizing stress damage to the silicon crystal structure. (3) The pre-cleaned wafer is transferred from process chamber one to process chamber two through vacuum transfer system 3; process chamber one and process chamber two are respectively connected to independent transfer modules through vacuum transfer system 3. The two chambers are equipped with independent process control systems, which can realize synchronous independent operation without interference. (4) After the wafer enters the second process chamber, an optimized in-situ vapor generation (ISSG) process is performed to complete the growth of a silicon dioxide thin film. Specifically, the background vacuum of the second process chamber is maintained at 0.5-0.7 mTorr by a mechanical pump. During the ISSG process, the wafer tray adopts a magnetic levitation turntable, which achieves micron-level precision rotation by avoiding physical contact, thereby eliminating the risk of particulate contamination caused by mechanical friction and dynamic sealing.

[0010] Preferably, in step (2), plasma pre-cleaning of the 12-inch silicon wafer substrate includes: maintaining the background vacuum of the process chamber one at 10 using mechanical and molecular pumps. -4 The pressure is on the order of Pa; argon gas is introduced into the first process chamber, and the chamber pressure is controlled to be 0.8-5 Pa; the argon gas is ionized using capacitively coupled plasma, with a dual-frequency radio frequency source power of 800-1500 W and a working time of 20-120 s.

[0011] Preferably, in step (2), the wafer tray portion set in the process chamber 1 is filled with ethylene glycol to form a low-temperature tray for circulating cooling. The low-temperature tray is integrated with a zoned temperature control module, which can compensate for the temperature gradient between the edge and center of the wafer, ensure that the temperature fluctuation of the entire wafer is controlled within ±0.5℃, avoid wafer thermal damage, and ensure the uniformity of sputtering. During the pre-cleaning process, the overall temperature of the wafer is controlled at 40-60℃ by the wafer low-temperature tray.

[0012] After systematically modifying the surface of a 12-inch silicon wafer using the aforementioned plasma pre-cleaning process, the surface achieves deep activation and contaminant removal, with a wafer surface roughness Ra≤0.7 nm and uniformity ≤5%, meeting semiconductor process requirements and providing a highly reliable substrate foundation for subsequent silicon dioxide film deposition.

[0013] Preferably, in step (4), nitrogen gas is introduced into the second process chamber to raise the chamber pressure to 100 Torr, and the turntable is started with a rotation speed of 200-300 rpm; the nitrogen gas is 5N grade high-purity nitrogen gas, which is used to establish an inert protective atmosphere to prevent unintended thermal oxidation of the wafer surface when the temperature is below 1100℃.

[0014] Preferably, in step (4), the second process chamber starts the heating process to rapidly raise the temperature to the process temperature of 1100℃; the heating process adopts a stepped temperature control mode to prevent lattice thermal damage caused by rapid heating: the stepped temperature is 600℃, and when the wafer temperature reaches 600℃, oxygen is introduced into the second process chamber; during the heating process, the heating rate in the first stage (wafer temperature below 600℃) is 7.0-7.5℃ / s, and the heating rate in the second stage (wafer temperature 600℃-1100℃) is 18-26℃ / s; the heating rate and stepped design are set based on the thermal radiation performance and thermodynamic structure of the silicon wafer.

[0015] Preferably, during the ISSG process, the wafer is always rotating at a speed of 50-200 rpm.

[0016] Preferably, when the wafer temperature reaches 1100℃, hydrogen gas is introduced into process chamber two. By controlling the flow rates of hydrogen and oxygen, the molar ratio of hydrogen to oxygen is made to be 1:2-1:3, wherein the hydrogen flow rate is 5-15 slm and the oxygen flow rate is 15-60 slm. The hydrogen and oxygen directly synthesize highly reactive water vapor in the reaction chamber, which dissociates at high temperature to generate atomic oxygen. The atomic oxygen repairs the dangling bonds at the silicon / silicon dioxide interface and reduces the interface state density. The stepped temperature control process can effectively regulate the lattice stress release and impurity diffusion behavior. The silicon dioxide film thickness obtained by the above process is 100-110 Å.

[0017] After growth is complete, the vacuum pump is turned on and nitrogen is purged simultaneously to rapidly cool the wafer using thermal convection. The ISSG growth process, combined with stepped temperature control, significantly improves the density and reliability of 12-inch silicon dioxide films, breaking through the temperature and quality bottlenecks of traditional ISSG processes.

[0018] Secondly, the present invention provides a method for in-situ monitoring and uniformity control of a 12-inch silicon dioxide thin film, the steps of which are as follows: (a) The process chamber 1 is equipped with a broadband light source and a CCD detector. The broadband light source and the CCD detector form an in-situ thin film optical polarization analysis system, which uses polarized light to realize in-situ detection of the thickness and uniformity of 12-inch thin films. The principle of the optical detection is as follows: After the incident linearly polarized light is reflected by the thin film surface, it is transformed into elliptically polarized light due to the different amplitude attenuation and phase delay of the p-polarized component (parallel to the incident plane) and the s-polarized component (perpendicular to the incident plane). The film thickness data is obtained by analyzing the amplitude ratio and phase difference. (b) After the plasma pre-cleaning described in the first aspect is completed, in-situ optical thin film detection is performed to analyze whether the silicon native oxide layer on the 12-inch wafer surface has been removed; (c) After the growth of the silicon dioxide thin film described in the first aspect is completed, the wafer is transferred from process chamber two to process chamber one through a vacuum transfer system, and the silicon dioxide thin film is detected in situ using the optical polarization analysis system integrated in process chamber one to obtain film thickness and uniformity data.

[0019] S04: The second MCU receives data from the second CAN interface and forwards it to the first MCU for processing through the auxiliary communication link; at the same time, it receives status information sent by the first MCU and uploads it to the host computer through the second CAN interface.

[0020] Preferably, in the technical solution, if the first in-situ detection result does not meet the requirements, the optical system is turned off, the capacitively coupled plasma source is turned on, and the silicon dioxide thin film on the 12-inch wafer surface is subjected to self-limiting cyclic etching to achieve an atomic-level thin film surface modification effect. During the self-limiting cyclic etching process, trimethylaluminum (TMA), hydrogen, and sulfur hexafluoride (SF6) gas are introduced into process chamber one, with argon gas used as the TMA carrier gas. The cycle period is 0.3-0.8 seconds, the argon gas flow rate is 0.03-0.05 slm, and the hydrogen gas flow rate is 0.02-0.04 slm.

[0021] Preferably, in the technical solution, the TMA undergoes a ligand exchange reaction with Si-OH on the surface of silicon dioxide to generate a self-limiting aluminosilicate layer, and then the fluorine radicals generated by the dissociation of SF6 plasma react with the aluminosilicate layer to generate volatile fluorides; the hydrogen is used to reduce hydrocarbon byproducts (such as CH3F), suppress carbon residue, and avoid surface contamination leading to roughness rebound.

[0022] Preferably, in the technical solution, after the re-etching is completed, the optical polarization analysis system is turned on to detect the uniformity of the 12-inch silicon dioxide film after the re-etching in situ; the above detection and re-etching steps need to be repeated multiple times to achieve the film uniformity standard.

[0023] Thirdly, the present invention provides a highly uniform 12-inch silicon dioxide thin film product, which is grown on a 12-inch silicon substrate, with a film thickness controlled at 10-12 nm and a uniformity of less than 0.3%. The silicon dioxide thin film product is prepared according to the process methods described in the first and second aspects.

[0024] Compared with the prior art, the present invention has the following beneficial effects: The process described in this invention is completed entirely within the production line equipment, and the wafers do not come into contact with the atmospheric environment throughout the process, effectively avoiding particle contamination and improving process cleanliness.

[0025] This invention proposes for the first time a process method for growing highly uniform silicon dioxide thin films on 12-inch wafers. Within the process parameter range defined by this invention, 12-inch silicon dioxide thin films with a thickness of 100-110 Å and a uniformity of less than 0.3% can be stably produced, which is significantly better than the existing technology and can meet the stringent requirements of advanced processes for film quality.

[0026] The in-situ detection and back-etching modification method proposed in this invention integrates thin film quality detection and uniformity control into the same process equipment, eliminating the redundant time and economic costs caused by offline detection of thin film quality and repeated debugging of process parameters. It realizes in-situ, real-time growth of highly uniform silicon dioxide thin films, while effectively improving product yield and production line stability. Attached Figure Description

[0027] Figure 1 This is a flowchart of the high-uniformity 12-inch silicon dioxide thin film preparation process described in this invention; Figure 2 This is a schematic diagram of the reaction apparatus described in this invention; Figure 3 This is a schematic diagram illustrating the principle of 12-inch wafer plasma pre-cleaning as described in this invention; Figure 4 This is a schematic diagram illustrating the reaction principle of silicon dioxide thin film growth according to the present invention; Figure 5 This is a schematic diagram illustrating the principle of the in-situ thin film optical polarization analysis system for detecting thin film thickness and uniformity as described in this invention. Figure 6 This is a schematic diagram illustrating the principle of capacitively coupled plasma self-limiting cyclic etching modification of thin film uniformity as described in this invention. Figure 7 This is a graph showing the film thickness test results of the silicon dioxide thin film before uniformity modification in Example 1 of the present invention; Figure 8 The image shows the film thickness test results of the silicon dioxide film after uniformity modification in Example 1 of the present invention.

[0028] 1. Process Chamber One; 11. Upper Electrode; 12. Wafer Low Temperature Tray; 13. Zoned Temperature Control Module; 14. Ethylene Glycol Cooling Circulation Loop; 15. Air Inlet; 16. Vacuum Pump Unit; 17. Broadband Light Source; 18. CCD Detector; 19. Silicon Wafer; 2. Process Chamber Two; 21. Vacuum Pump Unit; 22. Magnetic Levitation Turntable; 23. Heating Module; 24. Air Inlet; 3. Vacuum Transfer System. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0030] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0031] like Figure 2 As shown, the reaction apparatus used in the fabrication process of the present invention includes a process chamber 1, a process chamber 2, and a vacuum transfer system 3 connecting the two. Process chamber 1 contains an upper electrode 11, a wafer cryogenic tray 12, an air inlet 15, a vacuum pump assembly 16, a broadband light source 17, and a CCD detector 18. The wafer cryogenic tray 12 integrates a zoned temperature control module 13 and is equipped with an ethylene glycol cooling circulation loop 14. The broadband light source 17 and the CCD detector 18 are symmetrically positioned on both sides above the silicon wafer 19, together forming an in-situ thin-film optical polarization analysis system. Process chamber 2 contains a magnetic levitation turntable 22, a heating module 23, an air inlet 24, and a vacuum pump assembly 21. During the process, the silicon wafer 19 is bidirectionally transferred between process chamber 1 and process chamber 2 via the vacuum transfer system 3. Example 1

[0032] like Figure 1-2 As shown, a process for preparing a highly uniform 12-inch silicon dioxide thin film includes the following steps: (1) Provide 12-inch silicon wafers with 19 substrates; (2) Place the silicon wafer 19 into the process chamber 1, and use the capacitively coupled plasma generated by the upper electrode 11 to excite argon gas to generate argon ions, and perform physical sputtering cleaning on the surface of the silicon wafer 19 (the principle is as follows). Figure 3 (As shown); During the pre-cleaning process, the background vacuum of process chamber 1 is maintained at 5 × 10⁻⁶ using vacuum pump unit 16. -4 Argon gas is introduced through inlet 15 to maintain the chamber pressure at 2Pa. The dual-frequency radio frequency source power is set to 1200W and the working time is 60s. The overall temperature of silicon wafer 19 is controlled at 50℃ through wafer low temperature tray 12 and zone temperature control module 13, and the temperature fluctuation of the whole wafer is controlled within ±0.5℃. After pre-cleaning, the surface of silicon wafer 19 is detected in situ using an in-situ thin-film optical polarization analysis system composed of broadband light source 17 and CCD detector 18 to confirm that the silicon natural oxide layer has been removed. At this time, the surface roughness of silicon wafer 19 Ra=0.5nm and the uniformity is 3.0%.

[0033] (3) The pre-cleaned silicon wafer 19 is transferred from process chamber 1 to process chamber 2 via vacuum transfer system 3.

[0034] (4) The silicon wafer 19 is placed on the magnetic levitation turntable 22, and the background vacuum of the process chamber 2 is maintained at 0.6 mTorr by the vacuum pump group 21; nitrogen gas is introduced through the gas inlet 24 to raise the chamber pressure to 100. Torr drives the magnetic levitation turntable 22 to rotate at a speed of 250 rpm; then the heating module 23 is activated, using a stepped temperature control mode to heat the silicon wafer 19 to 1100℃, with a heating rate of 7.2℃ / s below 600℃ and a heating rate of 22℃ / s from 600℃ to 1100℃. Oxygen is introduced through the air inlet 24 when the silicon wafer 19 reaches 600℃; the silicon wafer 19 is rotated continuously during ISSG growth at a speed of 150 rpm; after the silicon wafer 19 reaches 1100℃, hydrogen is introduced through the air inlet 24, controlling the molar ratio of hydrogen to oxygen to be 1:2.5 (hydrogen flow rate 10 slm, oxygen flow rate 25 slm). The two react in the cavity to generate highly reactive water vapor, which dissociates into atomic oxygen at high temperature (reaction principle as follows). Figure 4 As shown, a silicon dioxide thin film with a thickness of 105 Å was grown on the surface of silicon wafer 19. After growth, vacuum pump group 21 was turned on and nitrogen gas was introduced at the same time to purge, and the silicon wafer 19 was rapidly cooled by thermal convection.

[0035] (5) The grown silicon wafer 19 is transferred from process chamber 2 back to process chamber 1 via vacuum transfer system 3, and the in-situ thin film optical polarization analysis system is activated (the detection principle is as follows). Figure 5 As shown), in-situ detection of the silica thin film was performed: Figure 7 As shown, the film thickness is 105-107 Å, and the film thickness uniformity is about 0.6%, which does not meet the preset target of uniformity less than 0.3%.

[0036] (6) Turn off the optical polarization analysis system, turn on the capacitively coupled plasma source of process chamber 1, and introduce TMA (argon as carrier gas, flow rate 0.04 slm), hydrogen (flow rate 0.03 slm), and SF6 gas into process chamber 1. Perform 20 cycles with a cycle length of 0.5 seconds to perform a self-limiting cyclic etching of the silicon dioxide thin film surface (the etching reaction principle is as follows). Figure 6 As shown): TMA undergoes a ligand exchange reaction with the Si-OH groups on the film surface to generate a self-limiting aluminosilicate layer. Fluorine radicals generated by the dissociation of SF6 plasma react with the aluminosilicate layer to generate volatile fluorides, which are then removed by the vacuum system. Hydrogen gas simultaneously reduces hydrocarbon byproducts and inhibits carbon residue.

[0037] (7) Reactivate the optical polarization analysis system to perform in-situ detection of the film uniformity, such as... Figure 8 As shown, the thickness of the modified silicon dioxide film is 106±0.3Å, and the uniformity is 0.25%, which meets the preset standard, and the process is completed. According to statistics, the silicon wafer 19 in this embodiment did not come into contact with the atmospheric environment throughout the process, and the number of particles on the wafer surface was 0 per wafer. Example 2

[0038] The process steps in this embodiment are the same as in Embodiment 1, except that the process parameters are taken near the lower limit of the range defined by this invention: Pre-cleaning stage, process chamber 1 background vacuum 8×10⁻ 4 The argon pressure was 0.8 Pa, the dual-frequency RF source power was 800 W, the working time was 20 s, and the overall wafer temperature was 40 ℃. After pre-cleaning, the wafer surface roughness Ra = 0.65 nm and the uniformity was 4.8%. During the ISSG growth stage, the process chamber was under a background vacuum of 0.5 mTorr, the rotation speed was 200 rpm, the first stage heating rate was 7.0 ℃ / s, the second stage heating rate was 18 ℃ / s, the wafer rotation speed was 80 rpm during ISSG growth, the hydrogen to oxygen molar ratio was 1:2 (hydrogen flow rate 5 slm, oxygen flow rate 15 slm), and a silicon dioxide film thickness of 100 Å was obtained. In-situ testing showed that the film thickness uniformity before etching was approximately 0.5%, which did not meet the standard. Subsequently, a self-limiting cyclic etching process was initiated, with an argon carrier gas flow rate of 0.03 slm, a hydrogen flow rate of 0.02 slm, a cycle time of 0.3 seconds, and 15 cycles. After etching, in-situ testing again showed that the silicon dioxide film thickness was 100 ± 0.25 Å, and the uniformity was 0.28%, meeting the preset standard. In this embodiment, the wafer did not come into contact with the atmospheric environment throughout the entire process, and the particle count was 0 per wafer. Example 3

[0039] The process steps in this embodiment are the same as in Embodiment 1, except that the process parameters are taken near the upper limit of the range defined by this invention: Pre-cleaning stage, process chamber 1 background vacuum 2×10⁻ 4 The argon pressure was 5 Pa, the dual-frequency RF source power was 1500 W, the working time was 120 s, and the overall wafer temperature was 60 ℃. After pre-cleaning, the wafer surface roughness Ra = 0.68 nm and the uniformity was 4.5%. During the ISSG growth stage, the process chamber II had a background vacuum of 0.7 mTorr, a rotation speed of 300 rpm, a first-stage heating rate of 7.5 ℃ / s, a second-stage heating rate of 26 ℃ / s, a wafer rotation speed of 200 rpm during ISSG growth, and a hydrogen to oxygen molar ratio of 1:3 (hydrogen flow rate 15 slm, oxygen flow rate 60 slm). The resulting silicon dioxide film had a thickness of 110 Å. In-situ testing showed that the film thickness uniformity before etching was approximately 0.55%, which did not meet the standard. Subsequently, a self-limiting cyclic etching process was initiated, with an argon carrier gas flow rate of 0.05 slm, a hydrogen flow rate of 0.04 slm, a cycle period of 0.8 seconds, and 25 cycles. After etching, in-situ testing again showed that the silicon dioxide film thickness was 110 ± 0.3 Å, and the uniformity was 0.22%, meeting the preset standard. In this embodiment, the wafer did not come into contact with the atmospheric environment throughout the entire process, and the particle count was 0 per wafer.

[0040] Comparative Example 1 used the exact same plasma pre-cleaning and ISSG growth process parameters as Example 1, but the in-situ thin-film optical polarization analysis system was not integrated into process chamber 1. After the silicon dioxide thin film growth was completed, the wafer was directly removed from the production line and transferred to an independent inspection platform for offline inspection using an ellipsometry and SEM: the film thickness was 106 Å, and the uniformity was 0.6%, failing to meet the target of less than 0.3% uniformity. Furthermore, because the wafer had to undergo atmospheric handling and multiple loading and unloading processes during the offline inspection, the number of particles on the wafer surface was detected to be approximately 3 per wafer. Since offline inspection cannot perform online modification of the thin film, if uniformity needs to be improved, reloading and rework are required. Statistically, the cumulative process debugging cycle increased by more than 48 hours compared to the method of this invention.

[0041] Comparative Example 2, referring to the process conditions disclosed in Chinese Patent Document CN114068306A, uses plasma-enhanced chemical vapor deposition (PECVD) on the same 12-inch silicon substrate to deposit a silicon dioxide thin film at 300°C. The film thickness uniformity is optimized by adjusting the reactive gas flow rate ratio, RF power, and cavity pressure, and the film thickness is controlled at around 106 Å. Offline testing shows that the uniformity is about 1.2%, and the film density and silicon / silicon dioxide interface state density are significantly lower than those of the film obtained by the ISSG process of this invention. Therefore, it is difficult to meet the film quality requirements of advanced device gate oxide processes such as GAA.

[0042] For ease of comparison, the main process parameters and test results of Examples 1 to 3 and Comparative Examples 1 and 2 are summarized in Table 1.

[0043] Table 1 Summary of main process parameters and test results for the examples and comparative examples Pre-cleaning power (W) / time (s) 1200 / 60 800 / 20 1500 / 120 1200 / 60 — ISSG growth film thickness (Å) 105 100 110 106 106 In-situ inspection + re-engraving modification yes yes yes no no Final film thickness (Å) 106±0.3 100±0.25 110±0.3 106 (Unedited) 106 (Unedited) Final uniformity (%) 0.25 0.28 0.22 0.6 1.2 Number of particles (per tablet) 0 0 0 Approximately 3 Unassessed As shown in Table 1, in Examples 1 to 3, when the plasma pre-cleaning and ISSG growth process parameters varied within the range defined by this invention (corresponding to combinations of the middle value, near the lower limit, and near the upper limit, respectively), the thickness of the silicon dioxide film could be stably controlled within the range of 100-110 Å after in-situ optical detection and self-limiting cyclic etching modification, and the uniformity was less than 0.3%. Furthermore, the wafer did not come into contact with the atmospheric environment throughout the process, and the particle count was 0 per wafer. This indicates that the process method of this invention has good stability, repeatability, and scalability within the defined parameter window.

[0044] Comparative Example 1 used the exact same growth parameters as Example 1, but without the in-situ detection and self-limiting etch-back modification steps described in this invention. Its uniformity was only 0.6%, failing to reach the target of less than 0.3%. Furthermore, the atmospheric exposure caused by offline detection and multiple wafer loading and unloading significantly increased particulate contamination (approximately 3 particles / wafer) and greatly prolonged the process debugging cycle. This indicates that the in-situ detection and self-limiting cyclic etch-back steps play a crucial role in improving film uniformity, reducing particulate contamination, and shortening the process debugging cycle.

[0045] Comparative Example 2 shows that the silica film prepared by the existing PECVD low-temperature process has significantly lower uniformity (about 1.2%) and film density than the film prepared by the ISSG process of this invention. This further verifies the significant technical advantages of this invention over the prior art in terms of uniformity and film quality of 12-inch silica films.

[0046] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A process for preparing a highly uniform 12-inch silicon dioxide thin film, characterized in that, Includes the following steps: (1) Provide 12-inch silicon wafer substrate; (2) The silicon wafer substrate is placed in process chamber one, and argon ions are generated by capacitively coupled plasma ionization of argon gas to perform plasma pre-cleaning treatment on the surface of the silicon wafer substrate. (3) The pre-cleaned silicon wafer substrate is transferred from process chamber one to process chamber two via a vacuum transfer system; (4) In the second process chamber, an in-situ water vapor generation process is used to grow a silicon dioxide thin film on the surface of the silicon wafer substrate.

2. The fabrication process of the highly uniform 12-inch silicon dioxide thin film according to claim 1, characterized in that, The plasma pre-cleaning process includes maintaining the background vacuum of process chamber one at 10°C using mechanical and molecular pumps. - 4 The pressure is on the order of Pa; argon gas is introduced into the first process chamber, and the chamber pressure is controlled to be 0.8-5 Pa; the argon gas is ionized using capacitively coupled plasma, with a dual-frequency radio frequency source power of 800-1500 W and a working time of 20-120 s.

3. The fabrication process of the highly uniform 12-inch silicon dioxide thin film according to claim 2, characterized in that: The process chamber is equipped with a wafer cryogenic tray. Ethylene glycol is added to the wafer cryogenic tray to form a circulating cooling loop. A zoned temperature control module is integrated below the wafer cryogenic tray to compensate for the temperature gradient between the wafer edge and the center, so that the temperature fluctuation of the entire wafer is controlled within ±0.5℃. During the plasma pre-cleaning process, the overall temperature of the wafer is controlled at 40-60℃ by the wafer cryogenic tray.

4. The preparation process of the highly uniform 12-inch silicon dioxide thin film according to claim 3, characterized in that: After the plasma pre-cleaning treatment, the surface roughness Ra of the silicon wafer substrate is ≤0.7 nm and the uniformity is ≤5%.

5. The fabrication process of the highly uniform 12-inch silicon dioxide thin film according to claim 1, characterized in that: The first process chamber and the second process chamber are respectively connected to an independent transmission module through the vacuum transmission system, and the first process chamber and the second process chamber are respectively equipped with independent process control systems, which can operate synchronously and independently without interference.

6. The fabrication process of the highly uniform 12-inch silicon dioxide thin film according to claim 1, characterized in that: The process of growing a silicon dioxide thin film on the surface of a silicon wafer substrate using in-situ water vapor generation includes: maintaining the background vacuum of the second process chamber at 0.5-0.7 mTorr using a mechanical pump; introducing nitrogen into the second process chamber to raise the chamber pressure to 100 Torr and driving the wafer tray to rotate at a speed of 200-300 rpm; heating the second process chamber to a process temperature of 1100°C; and after the wafer temperature reaches 1100°C, introducing hydrogen and oxygen into the second process chamber to react the hydrogen and oxygen to generate water vapor, thereby growing a silicon dioxide thin film on the surface of the silicon wafer substrate.

7. The fabrication process of the highly uniform 12-inch silicon dioxide thin film according to claim 6, characterized in that: The wafer tray in the second process chamber is a magnetically levitated turntable, which achieves wafer rotation by avoiding physical contact; the nitrogen gas is 5N grade high-purity nitrogen gas, which is used to establish an inert protective atmosphere at temperatures below 1100°C to prevent unintended thermal oxidation of the wafer surface.

8. The fabrication process of the highly uniform 12-inch silicon dioxide thin film according to claim 6, characterized in that: The process of heating the second process chamber to the process temperature of 1100°C adopts a stepped temperature control mode: when the wafer temperature is below 600°C, the first stage heating rate is 7.0-7.5°C / s; when the wafer temperature reaches 600°C, oxygen is introduced into the second process chamber, and the second stage heating rate is 18-26°C / s, until the wafer temperature rises to 1100°C.

9. The fabrication process of the highly uniform 12-inch silicon dioxide thin film according to claim 8, characterized in that: During the growth of the silicon dioxide thin film, the wafer is always rotating at a speed of 50-200 rpm.

10. The fabrication process of the highly uniform 12-inch silicon dioxide thin film according to claim 6, characterized in that: The molar ratio of hydrogen to oxygen is controlled to be 1:2-1:3, with the hydrogen flow rate being 5-15 slm and the oxygen flow rate being 15-60 slm; the thickness of the grown silicon dioxide film is 100-110 Å.

11. The fabrication process of a highly uniform 12-inch silicon dioxide thin film according to claim 6, characterized in that: After the silicon dioxide thin film is grown, the vacuum pump is turned on and nitrogen is purged at the same time to cool the wafer using thermal convection.

12. The process for preparing a highly uniform 12-inch silica thin film according to any one of claims 1 to 11, characterized in that, It also includes the following in-situ monitoring and uniformity control steps: (a) The process chamber is equipped with a broadband light source and a CCD detector, which together constitute an in-situ thin-film optical polarization analysis system. (b) After the plasma pre-cleaning treatment is completed, the surface of the silicon wafer substrate is optically inspected using the in-situ thin-film optical polarization analysis system to determine whether the natural oxide layer on the surface of the silicon wafer substrate has been removed. (c) After the silicon dioxide thin film is grown, the wafer is transferred from the second process chamber back to the first process chamber through the vacuum transfer system. The silicon dioxide thin film is then subjected to in-situ detection using the in-situ thin film optical polarization analysis system to obtain film thickness and uniformity data.

13. The fabrication process of a highly uniform 12-inch silicon dioxide thin film according to claim 12, characterized in that: The detection principle of the in-situ thin film optical polarization analysis system is as follows: After the incident linearly polarized light is reflected by the surface of the silicon dioxide thin film, its p-polarized component and s-polarized component are transformed into elliptically polarized light due to different amplitude attenuation and phase delay. The film thickness data of the silicon dioxide thin film is obtained by analyzing the amplitude ratio and phase difference of the reflected light.

14. The fabrication process of a highly uniform 12-inch silicon dioxide thin film according to claim 12, characterized in that: When the in-situ detection results do not meet the preset uniformity requirements, the in-situ thin film optical polarization analysis system is turned off, the capacitively coupled plasma source of the first process chamber is turned on, and the silicon dioxide thin film is subjected to self-limiting cyclic etching.

15. The fabrication process of a highly uniform 12-inch silicon dioxide thin film according to claim 14, characterized in that: During the self-limiting cyclic etching process, trimethylaluminum, hydrogen, and sulfur hexafluoride gas are introduced into the process chamber 1, with argon gas used as the carrier gas for trimethylaluminum. The cycle period is 0.3-0.8 seconds, the argon gas flow rate is 0.03-0.05 slm, and the hydrogen gas flow rate is 0.02-0.04 slm.

16. The fabrication process of a highly uniform 12-inch silicon dioxide thin film according to claim 15, characterized in that: The trimethylaluminum undergoes a ligand exchange reaction with the Si-OH groups on the surface of the silica film to generate a self-limiting aluminosilicate layer; the fluorine radicals generated by the plasma dissociation of sulfur hexafluoride react with the aluminosilicate layer to generate volatile fluorides; the hydrogen is used to reduce hydrocarbon byproducts and suppress carbon residue.

17. The fabrication process of a highly uniform 12-inch silicon dioxide thin film according to claim 14, characterized in that: After completing the self-limiting cyclic etching, the in-situ thin film optical polarization analysis system is activated to perform in-situ detection on the uniformity of the etched silicon dioxide film. If the detection result does not meet the preset uniformity requirements, the in-situ detection and self-limiting cyclic etching steps are repeated until the uniformity of the silicon dioxide film meets the preset requirements.

18. A highly uniform 12-inch silica thin film product, characterized in that: The silicon dioxide film is prepared using the preparation process described in any one of claims 1-11 and 13-17; the silicon dioxide film is grown on a 12-inch silicon substrate, the film thickness is 10-12 nm, and the uniformity is less than 0.3%.

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