Wafer regeneration method
By combining dry and wet etching methods to control the thickness of the silicon dioxide film on the wafer surface, and combining this with mechanical brushing, the challenges of film removal and substrate protection during wafer regeneration have been solved, achieving efficient regeneration and reducing material waste and costs in semiconductor manufacturing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- THING ELEMENT SEMICON TECH (QINGDAO) CO LTD
- Filing Date
- 2026-04-01
- Publication Date
- 2026-06-19
AI Technical Summary
Existing technologies struggle to protect the wafer substrate while thoroughly removing the thin film during wafer regeneration, leading to surface damage and material waste, which in turn affects the quality and cost of subsequent processes.
By combining dry etching and wet etching, and controlling the remaining film thickness after dry etching to 1000 Å~2000 Å, combined with mechanical brushing, efficient regeneration of the wafer surface is achieved.
It effectively removes the silicon dioxide film on the wafer surface, protects the integrity of the wafer substrate, improves wafer utilization, and reduces consumable costs.
Smart Images
Figure CN122249032A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor technology, and specifically relates to a wafer regeneration method. Background Technology
[0002] Semiconductor wafer regeneration technology is a crucial link in the semiconductor manufacturing supply chain. Wafers are the substrate for manufacturing chips and are typically made of high-purity silicon, making them expensive. During chip production, "test wafers," such as monitor wafers and dummy wafers, are often used to monitor process quality, simulate actual production conditions, test equipment status, or debug processes such as thin film deposition and etching. After use, these test wafers are covered with one or more thin films, such as silicon dioxide (SiO2) dielectric layers. Directly discarding them would result in significant material waste and increased production costs. Therefore, the core objective of wafer regeneration technology is to thoroughly remove the attached films and contaminants from these used wafers through surface treatment, restoring them to a surface state close to that of new wafers. This allows them to be reused in testing processes, significantly reducing consumable costs in semiconductor manufacturing.
[0003] However, the regeneration process is not a simple cleaning process. Its technical challenge lies in thoroughly removing the thin film without damaging the wafer itself. The wafer surface is extremely delicate; excessive etching or improper handling during the removal process can lead to abnormal surface morphology, such as micro-damage, increased roughness, or residual particles. Such surface defects can severely affect the uniformity of thin film deposition in subsequent processes and introduce additional particle contamination, causing chip reliability tests to fail and yields to decrease. Therefore, the regeneration process must achieve a precise balance between "removal" and "protection."
[0004] Currently, the commonly used thin film removal methods in the industry are mainly of two types: dry etching and wet etching, which have different principles and characteristics. Dry etching, also known as plasma etching, involves generating high-energy plasma to bombard the wafer surface, causing the thin film material to undergo physical or chemical reactions, generating volatile gases that are then removed. The advantages of this method are controllable etching direction, good uniformity, and it is particularly suitable for processing intricate patterns. It can also etch some chemically stable materials. However, its disadvantage is that if the high-energy ions in the plasma are not properly controlled, they can produce a strong physical sputtering effect, which can easily damage the underlying silicon material, leading to silicon loss (Si Loss), thereby thinning the wafer or destroying its crystal structure.
[0005] In contrast, wet etching utilizes chemical solutions for immersion cleaning. Hydrofluoric acid (HF) solutions are commonly used to remove silicon dioxide films. The principle is that HF reacts chemically with SiO2 to form soluble hexafluorosilicic acid, which is then washed away with water. The key advantage of wet etching lies in its selectivity: at appropriate concentrations and ratios (e.g., diluted HF solution), its reaction rate with SiO2 is much faster than its reaction with silicon. This means that it can relatively "gently" remove the surface silicon dioxide layer without causing significant corrosion to the silicon substrate. However, its disadvantage is its slow reaction rate. Summary of the Invention
[0006] In view of the problems existing in the prior art described above, this application provides a wafer regeneration method that can effectively improve wafer utilization and reduce production costs.
[0007] To achieve the above and other related objectives, the present invention provides a wafer regeneration method, comprising the following steps:
[0008] Provide a wafer to be regenerated with a silicon dioxide thin film deposited on its surface;
[0009] The wafer surface is treated using a dry etching process to remove part of the silicon dioxide film, and the thickness of the remaining silicon dioxide film after etching is controlled to be between 1000 Å and 2000 Å.
[0010] A wet etching process is used to process the wafers that have undergone dry etching in order to remove the remaining silicon dioxide film.
[0011] The wafers after wet etching are cleaned to remove surface residues.
[0012] Optionally, in the dry etching step, the thickness of the remaining silicon dioxide film is controlled between 1000 Å and 2000 Å by controlling the etching time.
[0013] Optionally, the thickness of the remaining silicon dioxide film after dry etching can be monitored and confirmed by measuring the thickness at multiple points on the wafer surface.
[0014] Optionally, the wet etching process uses a hydrofluoric acid solution with a volume ratio of hydrofluoric acid to water of 1:50.
[0015] Optionally, the process temperature for wet etching is between 20°C and 25°C.
[0016] Optionally, mechanical brushing equipment can be used to clean the wafers after wet etching.
[0017] Optionally, the thickness of the regenerated wafer is between 12 Å and 14 Å.
[0018] Optionally, the number of surface particles on the regenerated wafer is less than 20.
[0019] Optionally, the wafer to be recycled is a test wafer used in semiconductor manufacturing, including a control wafer or a baffle.
[0020] Alternatively, the dry etching process can be performed using capacitively coupled plasma (CCP) equipment or inductively coupled plasma (ICP) equipment.
[0021] As described above, the wafer regeneration method provided by the present invention has at least the following beneficial technical effects:
[0022] The wafer regeneration method of this invention employs a three-step synergistic process of "dry etching—wet etching—mechanical brushing" to achieve efficient regeneration of test wafers. First, dry etching precisely removes most of the silicon dioxide film on the wafer surface, strictly controlling the remaining thickness within the range of 1000 Å to 2000 Å. This crucial buffer layer effectively blocks the physical sputtering of high-energy ions onto the silicon substrate, fundamentally avoiding silicon loss and crystal structure damage. Subsequently, wet etching is performed using hydrofluoric acid solution. Utilizing its extremely high etching selectivity between SiO2 and Si, the residual silicon dioxide film is gently and thoroughly removed at room temperature, precisely exposing a clean silicon surface without corroding the substrate. Finally, a single-wafer brushing machine, combined with deionized water and surfactants, performs precision cleaning. This combination of physical friction and fluid rinsing removes surface particles and chemical residues, ensuring that the number of surface particles on the wafer is less than 20. The wafer regeneration method of this embodiment thoroughly removes the silicon dioxide film on the wafer surface while maximizing the protection of the wafer substrate integrity, enabling the test wafer to be recycled and reused multiple times, significantly improving wafer utilization and greatly reducing the cost of consumables in the semiconductor manufacturing process. Attached Figure Description
[0023] Figure 1 The flowchart shown is a wafer regeneration method provided in an embodiment of the present invention.
[0024] Figure 2 The diagram shows the thickness of the wafer before etching, as provided in an embodiment of the present invention.
[0025] Figure 3 The diagram shows the thickness of the wafer after dry etching and wet etching, as provided in an embodiment of the present invention.
[0026] Figure 4 The diagram shows the number of surface particles on a wafer after cleaning, as provided in an embodiment of the present invention. Detailed Implementation
[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0028] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the actual number, shape and size of the components, the shape, quantity, positional relationship and proportion of each component can be arbitrarily changed under the premise of realizing the technical solution of this invention, and the layout of the components may also be more complex.
[0029] This embodiment provides a wafer regeneration method, referring to... Figure 1 This includes the following steps:
[0030] S100: Provides a wafer to be regenerated with a silicon dioxide thin film deposited on its surface;
[0031] S200: The wafer surface is processed using a dry etching process to remove part of the silicon dioxide film, and the thickness of the remaining silicon dioxide film after etching is controlled to be between 1000 Å and 2000 Å.
[0032] S300: The wafer that has undergone dry etching is processed using a wet etching process to remove the remaining silicon dioxide film;
[0033] S400: The wafer after wet etching is cleaned to remove surface residues.
[0034] First, a wafer to be regenerated is provided, with a silicon dioxide thin film deposited on its surface.
[0035] In this embodiment, the wafer to be recycled is a test wafer used in the semiconductor manufacturing process, such as a monitor wafer or a dummy wafer. These test wafers are mainly used in chip manufacturing to simulate actual production conditions, monitor process quality, detect equipment status, and debug processes such as thin film deposition and etching. Since wafers are usually made of high-purity silicon and are expensive, directly discarding them after use would result in a huge waste of materials. Therefore, these wafers, whose surfaces have been deposited with one or more layers of silicon dioxide (SiO2) film, need to be restored to a surface state close to that of a new wafer through recycling technology to achieve reuse.
[0036] In addition to the silicon dioxide film, the surface of the wafer to be regenerated may also contain other process residues or particulate contaminants. The type, distribution, and uniformity of the film thickness of these contaminants directly affect the effectiveness of subsequent regeneration processes. Therefore, it is preferable to pre-treat the wafer to be regenerated before regeneration. This pre-treatment step aims to remove soluble contaminants and some particles from the wafer surface and accurately assess the film condition, providing a basis for setting parameters for subsequent etching processes.
[0037] Specifically, it includes the following steps:
[0038] First, wet cleaning is performed. The wafer to be regenerated is immersed in SC-1 standard cleaning solution (a mixture of ammonia, hydrogen peroxide, and deionized water) and ultrasonically cleaned at a temperature of, for example, 40°C to 70°C to remove organic contaminants and some particles from the wafer surface. Then, SC-2 standard cleaning solution (a mixture of hydrochloric acid, hydrogen peroxide, and deionized water) is used to remove metal ion contaminants. Next, thickness measurement is performed. An optical thin film thickness gauge (e.g., an ellipsometer or reflectance spectrometer) is used to scan the silicon dioxide film thickness at multiple uniformly distributed points on the wafer surface. By obtaining the mean and uniformity data of the thickness, the initial state of the film can be determined, and the preset etching time for subsequent dry etching can be fine-tuned accordingly. In an optional embodiment of this example, refer to... Figure 2 The wafer thickness is 10897 Å. Finally, particle inspection is performed, using a laser surface scanner to count the number and size of particles on the wafer surface. This pretreatment effectively improves the stability and yield of the regeneration process, avoiding uneven etching or substrate damage caused by excessive differences in initial conditions.
[0039] Then, a dry etching process is used to treat the wafer surface to remove part of the silicon dioxide film, and the thickness of the remaining silicon dioxide film after etching is controlled to be between 1000 Å and 2000 Å.
[0040] In this embodiment, dry etching is performed using capacitively coupled plasma (CCP) or inductively coupled plasma (ICP) equipment. Both of these devices can generate a high-density plasma environment, achieving precise removal of the silicon dioxide film through the synergistic effect of physical bombardment and chemical reaction. The process gas for dry etching is a mixture of fluorine-containing gas (such as CF4, SF6, CHF3, etc.) and oxygen. The fluorine-containing gas decomposes in the plasma to generate fluorine free radicals, which react chemically with SiO2 to generate volatile SiF4 gas, which is then removed. The addition of oxygen helps to improve the etching rate and anisotropy.
[0041] In the dry etching step, precise control of the etching rate and wafer surface uniformity is achieved by adjusting key process parameters. Specifically, the RF power is set to approximately 100 W, the chamber pressure to 50 mTorr, the CHF3 flow rate to 70 sccm, and the O2 flow rate to 8 sccm. The RF power setting directly affects the plasma ionization degree and ion energy, thus determining the etching rate and physical sputtering intensity. The chamber pressure adjustment affects the mean free path of gas molecules and ion directionality, which are key factors in ensuring etching anisotropy and wafer surface uniformity. CHF3, as the main etching gas, decomposes in the plasma to generate CFx groups and fluorine radicals, which react chemically with SiO2 to generate volatile products. The addition of O2 helps to adjust the carbon-fluorine ratio, promote radical generation, increase the etching rate, and reduce polymer deposition, thereby improving surface cleanliness. Through the synergistic optimization of the above parameters, the remaining thickness of the SiO2 film can be precisely controlled while ensuring etching selectivity and uniformity, effectively avoiding physical damage to the silicon substrate and providing a uniform and reliable buffer layer foundation for subsequent wet etching.
[0042] By controlling the etching time to ensure that etching stops when the silicon dioxide film approaches the target remaining thickness of 1000 Å to 2000 Å, physical sputtering damage (Si Loss) to the silicon substrate by plasma is fundamentally avoided. If the remaining silicon dioxide film thickness is too small, hydrofluoric acid may penetrate the weak area and directly contact the silicon substrate during subsequent wet etching, causing pitting corrosion; if the remaining silicon dioxide film thickness is too large, it will prolong the wet etching time and increase the consumption of chemical reagents.
[0043] To ensure that dry etching stops precisely when the remaining silicon dioxide film thickness reaches 1000 Å to 2000 Å, in addition to precisely controlling the etching time, it is preferable to use optical or spectroscopic methods for real-time endpoint monitoring. Common endpoint detection methods include, but are not limited to, laser interferometry, optical emission spectroscopy (OES), and voltage bias monitoring.
[0044] Laser interferometry involves perpendicularly irradiating the wafer surface with a laser beam of a specific wavelength (e.g., 670 nm). As the film thickness decreases, the interference fringes of the reflected light undergo periodic changes. By monitoring the oscillation frequency and amplitude changes of the interference signal in real time, the current film thickness can be calculated. When the signal indicates that the film is close to the preset remaining thickness (i.e., 1000 Å~2000 Å), the system issues a command to stop etching. This method is particularly effective for monitoring the thickness of transparent films. Optical emission spectroscopy (OES) detects the reaction byproducts (e.g., SiF4) and reactive gases (e.g., CF4) during plasma etching. xThe SiO2 layer emits a spectrum at specific wavelengths. The etching process can be determined by monitoring the intensity changes of characteristic spectral lines associated with SiO2 etching (e.g., the SiF4 line at 440 nm). When the SiO2 layer is almost completely etched away, exposing the underlying silicon substrate, the SiF4 signal generated by the reaction of silicon with fluorine radicals rapidly weakens or disappears, causing a sudden change in the intensity of the characteristic spectrum. This point of change marks the etching endpoint. The voltage bias monitoring method works by observing the slight change in the DC self-bias voltage applied to the cathode as the etching interface moves from the SiO2 layer into the silicon substrate. This change in material conductivity and dielectric constant causes a slight change in the voltage. By monitoring this voltage change in real time using a high-precision sensor, the endpoint can also be accurately determined.
[0045] To ensure process consistency and reliability, thickness measurements should be performed at multiple locations on the wafer surface after etching to verify whether its uniformity meets the requirements. In an optional embodiment of this example, thickness measurements should be performed at 25 locations on the wafer surface after etching to verify whether its uniformity meets the requirements.
[0046] Next, a wet etching process is used to process the wafer that has undergone dry etching to remove the remaining silicon dioxide film.
[0047] The dry-etched wafer is immersed in a prepared hydrofluoric acid (HF) solution, preferably with a HF to deionized water volume ratio of 1:50. This dilution ratio is precisely optimized to ensure a sufficient etching rate to efficiently remove residual 1000 Å–2000 Å silicon dioxide film while ensuring an extremely low corrosion rate on the silicon substrate. Under these concentration conditions, HF reacts chemically with SiO2 to generate soluble hexafluorosilicic acid (H2SiF6) and water. This reaction rate is significantly higher than that between HF and single-crystal silicon, resulting in excellent selective etching with minimal corrosion damage to the silicon substrate. The process temperature is typically controlled at room temperature (20°C–25°C) or slightly higher. Within this temperature range, the reaction rate is stable and easily controlled, eliminating the need for additional heating or cooling devices, thus reducing process complexity and energy consumption. In practice, operators should record the time the wafer is immersed in the HF solution and supplement this with visual observation (when the wafer surface changes from hydrophilic (with an oxide layer) to hydrophobic (bare silicon), it indicates that the oxide layer has been completely removed). Once it is confirmed that the thin film has been completely removed, the wafer should be immediately removed from the HF solution. In an optional embodiment of this example, refer to... Figure 3 A wafer with a thickness of 10897 Å has a thickness of 14 Å after dry etching and wet etching.
[0048] Finally, the wafers after wet etching are cleaned to remove surface residues.
[0049] After the wafer is removed from the solution, it must be quickly transferred to a deionized water rinsing tank to rapidly dilute and remove residual HF, completely terminate the chemical reaction, and prevent any form of over-etching or lateral drilling.
[0050] During cleaning, mechanical brushing equipment (such as a single-wafer scrubber) is used. This equipment is usually equipped with polyvinyl alcohol (PVA) sponge brushes or nylon brushes. By precisely controlling the brush head rotation speed (usually several hundred to several thousand revolutions per minute), the applied pressure (controlled within a small range of Newtons), and the wafer rotation speed, and using deionized water or a special cleaning solution containing surfactants, the trace amounts of hydrofluoric acid, fluorosilicates, and other chemical residues, as well as particulate contaminants attached or generated in previous processes, are thoroughly removed from the wafer surface through the synergistic effect of physical friction and fluid flushing.
[0051] During the brushing process, the brushing time and pressure must be strictly controlled to avoid mechanical damage to the silicon surface. After brushing, the wafer needs to undergo further high-speed rotational rinsing, using a large amount of deionized water to centrifuge and rinse the surface, followed by rotary drying or isopropyl alcohol (IPA) vapor drying to remove surface moisture, ensuring that the surface is absolutely clean and free of watermarks.
[0052] The final control of the regenerated wafer should meet the following requirements: fewer than 20 surface particles and a thickness between 12 Å and 14 Å. This ensures that the surface morphology and electrical properties of the regenerated wafer are close to those of the virgin wafer, allowing it to be directly reused in the production line. In an optional embodiment of this example, refer to... Figure 4 The regenerated wafer should have a surface particle count of 8.
[0053] This embodiment of the wafer regeneration method employs a three-step synergistic process of "dry etching—wet etching—mechanical brushing" to achieve efficient regeneration of test wafers. First, dry etching precisely removes most of the silicon dioxide film on the wafer surface, strictly controlling the remaining thickness within the range of 1000 Å to 2000 Å. This crucial buffer layer effectively blocks the physical sputtering of high-energy ions onto the silicon substrate, fundamentally avoiding silicon loss and crystal structure damage. Subsequently, wet etching is performed using a 1:50 volume ratio of hydrofluoric acid to deionized water. Utilizing its extremely high etching selectivity between SiO2 and Si, the residual silicon dioxide film is gently and thoroughly removed within seconds to tens of seconds at room temperature, precisely exposing a clean silicon surface without corroding the substrate. Finally, a single-wafer brushing machine, combined with deionized water and surfactants, performs precision cleaning. This combination of physical friction and fluid rinsing removes surface particles and chemical residues, ensuring that the number of surface particles on the wafer is less than 20. The wafer regeneration method of this embodiment thoroughly removes the silicon dioxide film on the wafer surface while maximizing the protection of the wafer substrate integrity, enabling the test wafer to be recycled and reused multiple times, significantly improving wafer utilization and greatly reducing the cost of consumables in the semiconductor manufacturing process.
[0054] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A wafer regeneration method, characterized in that, Includes the following steps: Provide a wafer to be regenerated with a silicon dioxide thin film deposited on its surface; The wafer surface is treated using a dry etching process to remove part of the silicon dioxide film, and the thickness of the remaining silicon dioxide film after etching is controlled to be between 1000 Å and 2000 Å. The wafer that has undergone dry etching is processed using a wet etching process to remove the remaining silicon dioxide film; The wafer after wet etching is cleaned to remove surface residues.
2. The wafer regeneration method according to claim 1, characterized in that, In the dry etching step, the remaining silicon dioxide film thickness is controlled between 1000 Å and 2000 Å by controlling the etching time.
3. The wafer regeneration method according to claim 2, characterized in that, The thickness of the remaining silicon dioxide film after dry etching is monitored and confirmed by measuring the thickness at multiple points on the wafer surface.
4. The wafer regeneration method according to claim 1, characterized in that, The wet etching process uses a hydrofluoric acid solution, and the volume ratio of hydrofluoric acid to water is 1:
50.
5. The wafer regeneration method according to claim 5, characterized in that, The process temperature of the wet etching process is between 20°C and 25°C.
6. The wafer regeneration method according to claim 1, characterized in that, The wafer after wet etching is cleaned using mechanical brushing equipment.
7. The wafer regeneration method according to claim 1, characterized in that, The thickness of the regenerated wafer is between 12 Å and 14 Å.
8. The wafer regeneration method according to claim 1, characterized in that, The number of surface particles on the regenerated wafer is less than 20.
9. The wafer regeneration method according to claim 1, characterized in that, The wafer to be recycled is a test wafer used in semiconductor manufacturing, including a control wafer or a baffle.
10. The wafer regeneration method according to claim 1, characterized in that, The dry etching process is performed using either capacitively coupled plasma (CCP) or inductively coupled plasma (ICP) equipment.