Photoresist coating method

Abstract

The invention belongs to the technical field of semiconductor manufacturing, and provides a photoresist coating method which comprises the following steps: pretreating the surface of a substrate to reduce the surface contact angle and improve the surface energy, so that photoresist can be better coated; the substrate is placed in the working chamber, and the environment in the working chamber is adjusted to be in a microenvironment state, so that the influence of environmental factors on the photoresist coating quality is reduced; the substrate is driven to be in a first rotating state, a preset solvent and photoresist are sequentially sprayed to the surface of the substrate, low-speed pre-spreading can be conducted on colloid on the surface of the substrate, and initial edge accumulation is reduced; the substrate is driven to be in a second rotating state, so that a photoresist coating is formed on the surface of the substrate, air entrainment on the surface of the substrate can be inhibited, and spreading of photoresist is facilitated; and driving the substrate to be in a third rotating state, so that the photoresist coating reaches the preset thickness. According to the method, the film thickness uniformity of the formed photoresist coating can be improved, the defect rate of the photoresist coating is reduced, and the production cost is saved.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a photoresist coating method. Background Technology

[0002] Photolithography is one of the most frequently used and critical technologies in semiconductor manufacturing, used to achieve pattern transfer at the micron and even nanometer scale. The photolithography process mainly includes steps such as photoresist coating, soft baking, exposure, development, and hard baking. Currently, spin coating is the primary method for coating photoresist to form a photoresist film on the wafer surface. The basic principle of spin coating is as follows: a specific amount of photoresist is injected into the center of a rotating wafer. Under centrifugal force, the photoresist flows and spreads from the center to the edges, ultimately forming a photoresist film of a certain thickness.

[0003] However, with the continuous increase in wafer size, traditional spin coating processes often encounter abnormal thickness issues with photoresist at the wafer edges. For example, the photoresist may continuously be ejected outwards due to centrifugal force, resulting in excessively thin edges. Alternatively, the ejected photoresist may be subjected to reverse shear force at the junction of the wafer edge and the chuck, causing some of the resist to flow back and accumulate, resulting in excessively thick edges. Since there is a non-linear relationship between exposure dose and photoresist thickness, abnormal photoresist thickness can lead to uneven linewidth after exposure and development. Furthermore, factors such as the coating environment and solvent evaporation rate can cause radial thickness gradients and stripe defects after photoresist coating, potentially leading to wafer scrap in subsequent processes, reducing yield, and increasing production costs. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this application is to provide a photoresist coating method that can effectively improve the uniformity of the photoresist coating thickness and reduce the defect rate of the photoresist coating.

[0005] To achieve the above and other related objectives, this application provides a photoresist coating method, comprising the following steps: Pre-treat the substrate surface; The substrate is placed in the working chamber, and the environment inside the working chamber is adjusted to a microenvironment state; The substrate is driven into a first rotational state, and a preset solvent and photoresist are sequentially sprayed onto the surface of the substrate. The substrate is driven into a second rotational state to form a photoresist coating on the substrate surface; The substrate is driven to the third rotation state so that the photoresist coating reaches a preset thickness.

[0006] Optionally, the substrate surface is pretreated, including the following steps: The substrate is subjected to plasma surface treatment; A hydrophilic coating is formed on the surface of the substrate after surface treatment.

[0007] Optionally, in the step of performing plasma surface treatment on the substrate, the power source for the plasma surface treatment is a mixing power source, which includes a first radio frequency power source and a second radio frequency power source. The frequency of the first radio frequency power supply is 13.51MHz~13.61MHz, and the power density of the first radio frequency power supply is 0.5W / cm². 2 ~1.5W / cm 2 The power of the first radio frequency power supply accounts for 70% to 80% of the total power of the mixer power supply; The frequency of the second radio frequency power supply is 1MHz~5MHz, and the power density of the second radio frequency power supply is 0.2W / cm². 2 ~0.5W / cm 2 The power of the second radio frequency power supply accounts for 20% to 30% of the total power of the mixer power supply.

[0008] Optionally, the step of forming a hydrophilic coating on the surface of the substrate after surface treatment includes: A nanoparticle suspension is sprayed onto the surface of the substrate to form a hydrophilic coating on the substrate surface, wherein the thickness of the hydrophilic coating is less than 50 nm, and the nanoparticle suspension contains silica particles with a particle size of less than 5 nm.

[0009] Optionally, the step of adjusting the environment within the working chamber to a microenvironmental state includes: The temperature inside the working chamber is controlled at 22.9℃~23.1℃ and the humidity at 44%~46%, and an inert gas is used to cover the surface of the substrate so that the environment inside the working chamber is in the microenvironment state.

[0010] Optionally, the step of driving the substrate into a first rotational state includes: During a first time period, the substrate is driven to rotate at a first rotation speed to put the substrate in a first rotation state, wherein the first rotation speed is 100rpm~300rpm and the duration of the first time period is 2s~5s.

[0011] Optionally, in the step of sequentially spraying a preset solvent and photoresist onto the substrate surface, the photoresist is sprayed onto the substrate surface using a target nozzle, wherein the target nozzle includes: The diffuser cavity has a horn-shaped structure to reduce the flow rate of the photoresist, and the inlet of the diffuser cavity is connected to the photoresist supply line; The defoaming sieve structure includes a porous filter membrane located at the outlet of the diffusion cavity to block air bubbles in the photoresist. The tapered end nozzle has a wide opening and a narrow opening. The wide opening of the end nozzle is connected to the inlet of the diffusion cavity, and the narrow opening of the end nozzle is used to spray the photoresist.

[0012] Optionally, in the step of driving the substrate to a second rotational state, the second rotational state is an accelerated rotational state, and during a second time period, the substrate is driven to gradually accelerate to a second rotational speed so that the substrate is in the second rotational state; Wherein, the second rotational speed is 1500rpm~2500rpm. During the process of driving the substrate to gradually accelerate to the second rotational speed, the acceleration of the substrate decreases nonlinearly from the first acceleration a1 to the second acceleration a2, and a2≤0.3a1, a2>0.

[0013] Optionally, the step of driving the substrate to the third rotational state includes: During the third time period, the substrate is driven to rotate at a third rotation speed so that the substrate is in a third rotation state; The third rotational speed is 1500 rpm to 3000 rpm, and the third rotational speed is greater than the second rotational speed.

[0014] Optionally, executing the third rotation state of the substrate further includes the following steps: The film thickness of the photoresist coating is obtained in real time; Calculate the fluctuation ratio between the film thickness and the preset thickness; When the fluctuation amplitude ratio is less than or equal to the preset amplitude ratio, the rotation speed of the substrate is adjusted in real time so that the film thickness of the photoresist coating is the preset thickness.

[0015] As described above, compared with the prior art, the photoresist coating method provided in this application has at least the following beneficial effects: In this method, pretreatment of the substrate surface reduces the surface contact angle, increases surface energy, and enhances the hydrophobicity of the substrate surface, allowing for better photoresist coating. Adjusting the environment within the working chamber to a microenvironment reduces fluctuations in solvent evaporation rates, mitigating the impact of environmental factors on photoresist coating quality. Placing the substrate in a first rotating state allows for low-speed pre-spreading of the photoresist on the substrate surface, reducing initial edge accumulation. Furthermore, rotating the substrate suppresses air entrainment on the substrate surface, facilitating photoresist spreading and improving the uniformity of the photoresist coating thickness. This method effectively improves the uniformity of the formed photoresist coating thickness, reduces defects such as bubbles or blank areas, lowers the defect rate of the photoresist coating, reduces photoresist usage and subsequent EBR processes, and saves production costs. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The diagram shown is a schematic flowchart of a photoresist coating method provided in Embodiment 1 of this application.

[0018] Figure 2 The diagram shows a specific process flow of a photoresist coating method provided in Embodiment 2 of this application, in which the substrate is driven into a third rotational state.

[0019] Figure 3 The diagram shown is a structural schematic of a target nozzle provided in Embodiment 3 of this application.

[0020] Figure 4 Displayed as Figure 3 The diagram shows a schematic of the diffusion cavity in a target nozzle.

[0021] Illustration of reference numerals in the attached diagram: 11. Target nozzle; 111. Diffusion chamber; 1111. Guide ridge; 112. Defoaming screen structure; 113. End nozzle; 21. Adhesive supply line. Detailed Implementation

[0022] To make the technical objectives, technical solutions, and technical effects of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of this application, it should be noted that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0025] In the description of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, for example, referring to both fixed connections and detachable connections. Furthermore, the descriptions using terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples" indicate that a specific feature, structure, material, or characteristic described in connection with an implementation or example is included in at least one implementation or example of this application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same implementation or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more implementations or examples.

[0026] In traditional spin coating processes, the resulting photoresist films often suffer from numerous quality problems due to environmental factors, the properties of the photoresist, and the spin coating process itself. Specifically, for example, the photoresist at the wafer edge is prone to being too thick or too thin due to centrifugal force, leading to uneven linewidth after exposure and development; or, due to factors such as ambient temperature, humidity, and solvent evaporation, the coated photoresist is prone to radial thickness gradients and stripe defects; or, due to differences in wafer surface energy and contaminants, poor local wetting can lead to defects such as bubbles or blank areas; or, due to the viscosity of the photoresist, air bubbles can easily form during the spreading process.

[0027] In existing technologies, edge bead removal (EBR) can remove excessively thick photoresist at wafer edges, but this process only addresses post-processing issues and adds additional steps. Furthermore, the static spin-coating process used during photoresist coating cannot adapt to the influence of different photoresist types and environmental fluctuations. When HMDS (hexamethyldisilazane) is used for wafer surface pretreatment, the surface treatment effect is unstable. Therefore, improving the film quality of photoresist coatings has always been one of the key problems that those skilled in the art urgently need to solve.

[0028] In view of the above-mentioned shortcomings in the prior art, this application provides a photoresist coating method, which will now be described in detail with reference to the following embodiments.

[0029] Example 1 This embodiment provides a photoresist coating method to improve the quality of photoresist films on wafer surfaces and reduce defect rates. (Refer to...) Figure 1 The photoresist coating method includes steps S1 to S5, specifically including the following steps: Step S1: Pre-treat the substrate surface; Step S2: Place the substrate in the working chamber and adjust the environment inside the working chamber to a microenvironment state; Step S3: Drive the substrate to the first rotation state and spray the preset solvent and photoresist onto the substrate surface in sequence; Step S4: Drive the substrate to a second rotation state to form a photoresist coating on the substrate surface; Step S5: Drive the substrate to the third rotation state so that the photoresist coating reaches the preset thickness.

[0030] In this method, the substrate surface is pretreated to reduce the surface contact angle, increase surface energy, and enhance the hydrophobicity of the substrate surface, enabling better photoresist coating and improving coating uniformity. Maintaining a microenvironment within the working chamber reduces fluctuations in solvent evaporation rates, suppresses surface oxidation in the coating area, and minimizes the impact of environmental factors on photoresist coating quality, thus improving film quality and thickness uniformity. Placing the substrate in a first rotational state allows for low-speed pre-spreading of the photoresist on the substrate surface, eliminating uneven coverage in small areas caused by initial lubrication differences and reducing initial edge buildup. Placing the substrate in a second rotational state suppresses air entrainment on the substrate surface, facilitating photoresist spreading and improving thickness uniformity. Finally, placing the substrate in a third rotational state ensures the formed photoresist coating reaches a preset thickness, completing the photoresist coating process. This method can effectively improve the uniformity of the film thickness of the formed photoresist coating and reduce the occurrence of defects such as bubbles or blank areas, thereby reducing the defect rate of the photoresist coating. It can also reduce the amount of photoresist used and the subsequent EBR process, thus saving production costs.

[0031] In step S1, pre-treating the substrate surface may include the following steps: performing plasma surface treatment on the substrate; and forming a hydrophilic coating on the surface of the treated substrate. The substrate may be, for example, a wafer or other suitable semiconductor structure.

[0032] In an optional embodiment, in the step of performing plasma surface treatment on the substrate, the power supply for plasma surface treatment is a mixing power supply, which includes a first radio frequency power supply and a second radio frequency power supply. The first radio frequency power supply is used to generate a first plasma, and the second radio frequency power supply is used to generate a second plasma. The frequency of the first radio frequency power supply is greater than the frequency of the second radio frequency power supply.

[0033] Furthermore, in the step of performing plasma surface treatment on the substrate, the frequency of the first radio frequency power supply is 13.51MHz to 13.61MHz, specifically, it can be 13.51MHz, 13.56MHz, 13.61MHz or other suitable frequency values. Preferably, the frequency of the first radio frequency power supply is 13.56MHz. The power of the first radio frequency power supply accounts for 70% to 80% of the total power of the mixing power supply. This power percentage can be, for example, 70%, 72%, 75%, 78%, 80% or other suitable percentages, and the specific value can be set according to actual needs.

[0034] Furthermore, in the step of performing plasma surface treatment on the substrate, the power density of the first radio frequency power supply is 0.5 W / cm². 2 ~1.5W / cm 2 For example, it could be 0.5 W / cm2 0.8W / cm 2 1.2W / cm 2 1.5W / cm 2 Or other suitable values.

[0035] The first radio frequency power supply can generate the first plasma. Utilizing the first plasma with high density and high energy, it can efficiently dissociate the reaction gases in the working chamber, such as oxygen, nitrogen, and hydrogen, to generate active free radicals, break the CH / CC bonds in organic matter, and thus modify the substrate surface. The modification depth can reach 5nm~10nm.

[0036] Furthermore, in the step of performing plasma surface treatment on the substrate, the frequency of the second radio frequency power supply is 1MHz to 5MHz, specifically, it can be 1MHz, 3MHz, 5MHz or other suitable frequency values. The frequency of the second radio frequency power supply is preferably 2MHz. The power of the second radio frequency power supply accounts for 20% to 30% of the total power of the mixing power supply. This power percentage can be specifically, for example, 20%, 22%, 25%, 28%, 30% or other suitable percentages. The specific value can be set according to actual needs.

[0037] Furthermore, in the step of performing plasma surface treatment on the substrate, the power density of the second radio frequency power supply is 0.2 W / cm². 2 ~0.5W / cm 2 For example, it could be 0.2 W / cm 2 0.3W / cm 2 0.4W / cm 2 0.5W / cm 2 Or other suitable values.

[0038] By utilizing a low-frequency second radio frequency power supply, a high DC bias can be established, accelerating ions to bombard the substrate surface vertically and generating a second plasma. The lower density and lower energy of the second plasma can sputter away contaminants on the substrate surface, activate surface dangling bonds, and effectively improve the surface energy of the substrate.

[0039] In an optional embodiment, in step S1, a mixer power supply consisting of a first radio frequency power supply with a frequency of 13.56MHz and a second radio frequency power supply with a frequency of 2MHz is used, and the total power density of the mixer power supply is controlled to be 1.2W / cm². 2The processing time is 5s to 10s to perform plasma surface treatment on the wafer surface, for example, the processing time can be controlled to 8s. By performing the above-mentioned plasma surface treatment on the wafer surface, the surface energy of the wafer can be increased from about 40mN / m to more than 72mN / m, and its surface contact angle can be reduced to below 5°, which effectively improves the subsequent photoresist spreading effect and helps to improve the uniformity of the photoresist coating thickness.

[0040] In an optional embodiment, the step of forming a hydrophilic coating on the substrate surface after surface treatment includes: spraying a nanoparticle suspension onto the substrate surface to form a hydrophilic coating, wherein the thickness of the hydrophilic coating is less than 50 nm, and the nanoparticle suspension contains silica particles with a particle size of less than 5 nm. Preferably, in the step of forming the hydrophilic coating, the thickness of the hydrophilic coating does not exceed 10 nm, so as to form a monomolecular coating on the substrate surface. By forming a hydrophilic coating on the substrate surface, the adsorption effect of the colloid on the substrate surface can be improved, which is beneficial for the photoresist to spread on the substrate surface to form a thin film structure.

[0041] In step S2, the working chamber is a cavity for performing the photoresist coating process. This cavity can be located in a photoresist spraying device or other suitable semiconductor process equipment. The substrate is adsorbed onto a base inside the working chamber to facilitate the rotation of the substrate. By adjusting the environmental parameters inside the working chamber, the environment inside the cavity is made suitable for photoresist coating, thereby reducing or avoiding the influence of environmental factors on the photoresist coating process.

[0042] In an optional embodiment, the step of adjusting the environment inside the working chamber to a microenvironment state includes: controlling the temperature inside the working chamber to 22.9°C~23.1°C and the humidity to 44%~46%, and covering the surface of the substrate with inert gas, so that the environment inside the working chamber is in a microenvironment state.

[0043] Preferably, in the step of adjusting the environment inside the working chamber to a microenvironment state, the temperature inside the working chamber is controlled at 23°C with a temperature error not exceeding 0.1°C, the humidity inside the working chamber is controlled at 45% with a humidity error not exceeding 1%, and nitrogen or other suitable inert gas is used to cover the photoresist coating area of ​​the substrate. This creates a microenvironment state inside the working chamber, which helps reduce fluctuations in the evaporation rate of the solvent on the substrate surface and inhibits surface oxidation, avoiding adverse effects on the photoresist coating process and improving film quality.

[0044] In step S3, during the first time period, the substrate is driven to rotate at a first rotational speed, so that the substrate is in the first rotational state. Specifically, after adjusting the environment in the working chamber to a microenvironment state, the substrate is driven to start rotating, increasing the substrate's rotational speed from 0 to the first rotational speed, and rotating at the first rotational speed. Optionally, the first rotational speed is 100rpm~300rpm, for example, 100rpm, 150rpm, 200rpm, 250rpm, 300rpm or other suitable rotational speeds, and the duration of the first time period is 2s~5s, for example, 2s, 3s, 4s, 5s or other suitable times. The specific value can be set according to the spreading of the solvent on the substrate surface.

[0045] In step S3, when the substrate is driven to rotate, a preset solvent is sprayed onto the substrate surface. The preset solvent spreads on the substrate surface, making the substrate surface more wetted, improving surface lubrication, reducing the diffusion resistance of the photoresist on the substrate surface, facilitating photoresist coating, and reducing the amount of photoresist used. The preset solvent can be, for example, OK73 solvent or other suitable organic solvents; please refer to existing technologies for details, which will not be elaborated further in this embodiment.

[0046] After the preset solvent is spread, photoresist is sprayed onto the spread surface of the preset solvent. The photoresist spreads naturally on the substrate surface. Since the substrate is in the first rotational state at a low speed, the photoresist on the substrate surface can be pre-spread at a low speed to effectively eliminate the uneven coverage of micro-areas caused by the initial lubrication difference, reduce the initial edge accumulation, and help improve the thickness uniformity of the film.

[0047] In step S4, the substrate is driven to the second rotation state, which is an accelerated rotation state. During the second time period, the substrate is driven to gradually accelerate to the second rotation speed so that the substrate is in the second rotation state. The photoresist on the substrate surface spreads outward under the action of centrifugal force, thereby forming a photoresist coating on the substrate surface.

[0048] In this embodiment, the second rotation speed is greater than the first rotation speed when the substrate is in the first rotation state. The second time period and the first time period form a continuous time period, that is, the end time of the first time period is the start time of the second time period. The duration of the second time period is related to factors such as photoresist type, preset film thickness, first rotation speed, and second rotation speed. Its specific value can be set according to the actual production requirements, which will not be elaborated in this embodiment.

[0049] In an optional embodiment, the second rotational speed is 1500 rpm to 2500 rpm, specifically, for example, 1500 rpm, 1800 rpm, 2200 rpm, 2500 rpm, or other suitable rotational speeds. During the process of gradually accelerating the substrate to the second rotational speed, the substrate's acceleration non-linearly decays from the first acceleration a1 to the second acceleration a2, further wherein a2 ≤ 0.3a1, and a2 > 0. The first acceleration can non-linearly decay to the second acceleration using a polynomial curve, an exponential curve, or other suitable types of curves. The specific decay curve of the substrate's acceleration can be set according to actual needs.

[0050] Furthermore, in the step of gradually accelerating the substrate to the second rotational speed, the first acceleration decays non-linearly to the second acceleration with an exponential curve. The acceleration of the substrate is denoted as a(t). During the second time interval, the acceleration a(t) of the substrate has the following relationship with time t: a(t) = a0e^(-t / t). -kt Where a0 is the preset acceleration amplitude, the specific value of which can be set according to the specific values ​​of the first rotation speed, the second rotation speed, and the preset film thickness, and k is the rheological characteristic parameter of the photoresist, the specific value of which can be set according to the rheological characteristics of the photoresist. Further, a0 can be, for example, 300 rpm / s, and k can be, for example, set to 0.05 CP, where CP is the viscosity of the photoresist. The value of k can be updated in real time by measuring the temperature-viscosity change of the photoresist using an online viscometer.

[0051] In this embodiment, by controlling the substrate to accelerate from the first rotational speed to the second rotational speed with a decaying nonlinear acceleration, a low-pressure environment is easily formed during the spreading of photoresist on the substrate surface, which can effectively suppress air entrainment, thereby facilitating the spreading of photoresist on the substrate surface and helping to improve the uniformity of the photoresist coating thickness.

[0052] Step S5, the step of driving the substrate to the third rotation state, includes: driving the substrate to rotate at a third rotation speed during a third time period to bring the substrate to the third rotation state. Specifically, the third rotation speed is greater than the second rotation speed when the substrate is in the second rotation state. After the substrate reaches the second rotation speed, the substrate is accelerated to the third rotation speed and rotates at the third rotation speed to bring the substrate to the third rotation state, so that the adhesive force of the photoresist and the centrifugal force are balanced, thereby bringing the thickness of the photoresist coating to a preset thickness. The preset thickness can be set according to actual needs. The first time period, the second time period, and the third time period form a continuous time period, that is, the end time of the second time period is the start time of the third time period.

[0053] In an optional embodiment, the third speed is 1500rpm~3000rpm. Since the third speed is greater than the second speed, the above range can be understood as the third speed being greater than 1500rpm and not exceeding 3000rpm. Specifically, the third speed can be, for example, a value slightly greater than 1500rpm, or it can be 2000rpm, 2500rpm, 3000rpm or other suitable values.

[0054] In this embodiment, a first plasma with high density and high energy and a second plasma with low density and low energy are generated using a frequency mixer to pre-treat the substrate surface. This effectively improves the hydrophobicity of the substrate surface, reduces the surface contact angle, and increases the surface energy, allowing the photoresist to be better coated onto the substrate surface. By controlling the substrate environment to a microenvironment, fluctuations in the solvent evaporation rate during coating are reduced, surface oxidation in the coated area is suppressed, and the impact of environmental factors on the quality of the photoresist coating is reduced. By placing the substrate in a first rotational state to pre-spread the colloid on the substrate surface at a low speed, uneven coverage of small areas caused by initial lubrication differences can be eliminated, initial edge buildup is reduced, and the uniformity of film thickness is improved. By accelerating the substrate to a second rotational speed with a nonlinear decaying acceleration, a low-pressure environment is easily formed during the photoresist spreading process, which effectively suppresses air entrainment, facilitates photoresist spreading, and improves the uniformity of the photoresist coating thickness.

[0055] Therefore, using this method for photoresist coating can effectively improve the uniformity of the formed photoresist coating thickness, reduce the standard deviation of the photoresist coating thickness on the substrate surface to below 1%, reduce the subsequent EBR process requirements, reduce the amount of photoresist used, save production costs, and reduce the occurrence of defects such as bubbles, reducing the defect rate from above 1% to below 0.1%.

[0056] Example 2 This embodiment provides another photoresist coating method, which also includes steps S1 to S5 of Embodiment 1. The similarities with Embodiment 1 will not be repeated. The difference lies in the following: Referring to... Figure 2 In this embodiment, the step of driving the substrate to the third rotation state in step S5 includes S51 to S54, as described below.

[0057] Step S51: During the third time period, drive the substrate to rotate at a third rotation speed so that the substrate is in the third rotation state.

[0058] Step S52: Obtain the film thickness of the photoresist coating in real time.

[0059] Specifically, the thickness of the photoresist coating on the substrate surface can be measured in real time using a film thickness gauge, spectrometer, or other suitable semiconductor equipment to obtain the film thickness. Optionally, step S52 may further include: acquiring the rheological properties parameters of the photoresist coating in real time. The rheological properties parameters of the photoresist are parameters describing the flow characteristics of the photoresist, including the viscosity parameters of the photoresist and other suitable parameters. For example, the temperature-viscosity change of the photoresist can be monitored in real time using an online viscometer to acquire the viscosity parameters of the photoresist coating in real time.

[0060] Step S53: Calculate the fluctuation ratio between the film thickness and the preset thickness. The preset thickness of the photoresist coating can be set according to actual needs. Calculate the difference between the measured film thickness and the preset thickness, and record the ratio of this difference to the preset thickness as the fluctuation ratio.

[0061] Step S54: When the fluctuation amplitude ratio is less than or equal to the preset amplitude ratio, adjust the rotation speed of the substrate in real time so that the film thickness of the photoresist coating is the preset thickness.

[0062] In this embodiment, the third rotation state can be understood as an approximately uniform rotation state. When the substrate is in the third rotation state, the rotation speed of the substrate can be the third rotation speed, or slightly less or slightly greater than the third rotation speed. When the fluctuation amplitude ratio does not exceed the preset amplitude ratio, the rotation speed of the substrate can be finely adjusted in real time when the substrate is in the third rotation state so that the film thickness of the photoresist coating on the substrate surface reaches the preset thickness. When the film thickness is less than the preset thickness, the rotation speed of the substrate is appropriately reduced; when the film thickness is greater than the preset thickness, the rotation speed of the substrate is appropriately increased.

[0063] In an optional embodiment, the step of performing step S54 may further include: when the fluctuation amplitude ratio is less than or equal to the preset amplitude ratio, calculating the rotational speed deviation value according to the rheological characteristics and the preset film thickness-rotational speed relationship, and adjusting the rotational speed of the substrate according to the rotational speed deviation value so that the film thickness of the photoresist coating is the preset thickness.

[0064] In this embodiment, the mathematical relationship between parameters such as film thickness, viscosity, and rotation speed of the photoresist coating can be denoted as the film thickness-rotation speed relationship formula. Different types of photoresists have their specific film thickness-rotation speed relationship formulas. These formulas can be provided by the manufacturer or obtained in advance through experimental measurement and data fitting. By substituting the rheological characteristics of the photoresist coating acquired in real time and the preset thickness into the film thickness-rotation speed relationship formula, the theoretical preset rotation speed corresponding to the set thickness can be calculated, and the difference between the preset rotation speed and the current rotation speed can be calculated to obtain the rotation speed deviation value. The preset amplitude ratio can be set according to actual needs. Optionally, the preset amplitude ratio can be set to, for example, 5% or other suitable values.

[0065] In an optional embodiment, the step of driving the substrate to the third rotation state further includes: S55, when the fluctuation amplitude ratio is greater than the preset amplitude ratio, resetting the value of the third rotation speed in the third rotation state and recording it as the fourth rotation speed, driving the substrate to rotate at the fourth rotation speed so that the film thickness of the photoresist coating is the preset thickness.

[0066] Specifically, when the fluctuation amplitude ratio exceeds the preset amplitude ratio, step S54 is less effective or it is difficult to make the film thickness of the photoresist coating reach the preset thickness. Therefore, when the fluctuation amplitude ratio is greater than the preset amplitude ratio, the value of the third rotation speed in step S5 is reset and recorded as the fourth rotation speed. The substrate is driven to rotate at the fourth rotation speed. The operation process from step S51 to step S55 is referred to until the film thickness of the photoresist coating reaches the preset thickness.

[0067] In this embodiment, by real-time monitoring of the photoresist coating film thickness and providing real-time feedback on the film thickness, the substrate rotation speed can be adjusted in real time. This allows the photoresist coating film thickness to quickly reach the preset thickness. By real-time monitoring of the rheological properties of the photoresist coating and adjusting the substrate rotation speed accordingly, this method can adapt to various photoresist types and environmental fluctuations, effectively broadening the process window and expanding the applicable viscosity range of the photoresist to 5 cP~50 cP.

[0068] Example 3 This embodiment provides another photoresist coating method, which also includes steps S1 to S5 in Embodiment 1. The similarities with Embodiment 1 will not be repeated. The difference is that in this embodiment, in the step of spraying photoresist onto the substrate surface in step S3, the photoresist is sprayed onto the substrate surface using the target nozzle 11.

[0069] In this embodiment, refer to Figure 3 and Figure 4 The target nozzle 11 includes a diffusion cavity 111, an anti-foaming screen structure 112, and an end nozzle 113. The diffusion cavity 111 has a trumpet-shaped structure to reduce the flow rate of the photoresist. The inlet of the diffusion cavity 111 is connected to the photoresist supply line 21 to supply photoresist to the target nozzle 11 through the photoresist supply line 21. Optionally, the trumpet-shaped diffusion cavity 111 has a diffusion angle of 135°, which can be understood as the angle between the straight side and the inclined side in the cross-sectional view of the diffusion cavity 111 along its axis. The diffusion cavity 111 is provided with flow guiding ridges 1111, which have a spiral structure and are distributed on the inner wall of the diffusion cavity 111. After the photoresist enters the diffusion cavity 111 through the photoresist supply line 21, the flow rate of the photoresist can be reduced to below 0.1 m / s.

[0070] The defoaming sieve structure 112 includes a porous filter membrane located at the outlet of the diffusion cavity 111 to block air bubbles. Optionally, the porous filter membrane is a porous ceramic filter membrane with a number of pores. The pore size of the pores in the porous ceramic filter membrane does not exceed 10 μm, which can effectively block air bubbles in the photoresist.

[0071] The end nozzle 113 has a conical structure with a wide opening and a narrow opening. The wide opening of the end nozzle 113 is connected to the outlet of the diffuser cavity 111, and the narrow opening of the end nozzle 113 is used to spray photoresist. Optionally, the conical end nozzle 113 has a cone angle of 15°. In use, the distance between the target nozzle 11 and the substrate is adjustable from 1 mm to 5 mm.

[0072] In this embodiment, the target nozzle 11 with a multi-stage microchannel structure can effectively reduce the flow rate of photoresist through the diffusion cavity 111 with a spiral flow guide ridge 1111. The defoaming sieve structure 112 can ensure the separation effect of photoresist and air bubbles. The conical end nozzle 113 can effectively spray photoresist onto the substrate surface while ensuring the photoresist delivery efficiency.

[0073] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify, alter, or combine the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A photoresist coating method, characterized in that, Includes the following steps: Pre-treat the substrate surface; The substrate is placed in the working chamber, and the environment inside the working chamber is adjusted to a microenvironment state; The substrate is driven into a first rotational state, and a preset solvent and photoresist are sequentially sprayed onto the surface of the substrate. The substrate is driven into a second rotational state to form a photoresist coating on the substrate surface; The substrate is driven into a third rotational state so that the photoresist coating reaches a preset thickness.

2. The photoresist coating method according to claim 1, characterized in that, Pre-treatment of the substrate surface includes the following steps: The substrate is subjected to plasma surface treatment; A hydrophilic coating is formed on the surface of the substrate after surface treatment.

3. The photoresist coating method according to claim 2, characterized in that, In the step of performing plasma surface treatment on the substrate, the power source for the plasma surface treatment is a mixing power source, which includes a first radio frequency power source and a second radio frequency power source. The frequency of the first radio frequency power supply is 13.51MHz~13.61MHz, and the power density of the first radio frequency power supply is 0.5W / cm². 2 ~1.5W / cm 2 The power of the first radio frequency power supply accounts for 70% to 80% of the total power of the mixer power supply; The frequency of the second radio frequency power supply is 1MHz~5MHz, and the power density of the second radio frequency power supply is 0.2W / cm². 2 ~0.5W / cm 2 The power of the second radio frequency power supply accounts for 20% to 30% of the total power of the mixer power supply.

4. The photoresist coating method according to claim 2, characterized in that, The step of forming a hydrophilic coating on the surface of the substrate after surface treatment includes: A nanoparticle suspension is sprayed onto the surface of the substrate to form a hydrophilic coating on the substrate surface, wherein the thickness of the hydrophilic coating is less than 50 nm, and the nanoparticle suspension contains silica particles with a particle size of less than 5 nm.

5. The photoresist coating method according to claim 1, characterized in that, The steps of adjusting the environment within the working chamber to a microenvironment state include: The temperature inside the working chamber is controlled at 22.9℃~23.1℃ and the humidity at 44%~46%, and an inert gas is used to cover the surface of the substrate so that the environment inside the working chamber is in the microenvironment state.

6. The photoresist coating method according to claim 1, characterized in that, The steps of driving the substrate into a first rotational state include: During a first time period, the substrate is driven to rotate at a first rotation speed to put the substrate in a first rotation state, wherein the first rotation speed is 100rpm~300rpm and the duration of the first time period is 2s~5s.

7. The photoresist coating method according to claim 1, characterized in that, In the step of sequentially spraying a preset solvent and photoresist onto the substrate surface, the photoresist is sprayed onto the substrate surface using a target nozzle, wherein the target nozzle includes: The diffuser cavity has a horn-shaped structure to reduce the flow rate of the photoresist, and the inlet of the diffuser cavity is connected to the photoresist supply line; The defoaming sieve structure includes a porous filter membrane located at the outlet of the diffusion cavity to block air bubbles in the photoresist. The tapered end nozzle has a wide opening and a narrow opening. The wide opening of the end nozzle is connected to the inlet of the diffusion cavity, and the narrow opening of the end nozzle is used to spray the photoresist.

8. The photoresist coating method according to claim 1, characterized in that, In the step of driving the substrate to a second rotational state, the second rotational state is an accelerated rotational state. During a second time period, the substrate is driven to gradually accelerate to a second rotational speed so that the substrate is in the second rotational state. Wherein, the second rotational speed is 1500rpm~2500rpm. During the process of driving the substrate to gradually accelerate to the second rotational speed, the acceleration of the substrate decreases nonlinearly from the first acceleration a1 to the second acceleration a2, and a2≤0.3a1, a2>0.

9. The photoresist coating method according to claim 8, characterized in that, The steps of driving the substrate to the third rotation state include: During the third time period, the substrate is driven to rotate at a third rotation speed so that the substrate is in a third rotation state; The third rotational speed is 1500 rpm to 3000 rpm, and the third rotational speed is greater than the second rotational speed.

10. The photoresist coating method according to claim 9, characterized in that, The process of driving the substrate to a third rotational state further includes the following steps: The film thickness of the photoresist coating is obtained in real time; Calculate the fluctuation ratio between the film thickness and the preset thickness; When the fluctuation amplitude ratio is less than or equal to the preset amplitude ratio, the rotation speed of the substrate is adjusted in real time so that the film thickness of the photoresist coating is the preset thickness.

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