Wafer surface particle deposition apparatus and method based on condensation growth

Abstract

The application discloses a wafer surface particle deposition device and method based on condensation growth. The device comprises a particle generator, a differential mobility analyzer, a condensation growth device, an optical particle counter and a wafer bearing assembly which are sequentially communicated along the direction of the air path. Monodisperse nanoparticles are condensed to form micron-sized particles with a condensate water film on the outer layer. The optical particle counter completes counting before the contraction acceleration. The micron-sized particles are inertially impacted on the heated wafer through the contraction type outlet. After the condensate water film evaporates, the monodisperse nanoparticles are deposited on the wafer surface. The wafer is moved by an XY moving table to realize uniform particle deposition. The application can solve the problems of difficult online counting of particles, low deposition efficiency of nanoparticles, uneven deposition distribution and easy agglomeration of particles.

Description

Technical Field

[0001] This invention relates to the field of semiconductor wafer surface particle standard material preparation technology, and in particular to a wafer surface particle deposition apparatus and method based on condensation growth. Background Technology

[0002] In semiconductor manufacturing, controlling particulate contaminants on the wafer surface is a key factor in ensuring device yield and performance. According to the international semiconductor technology roadmap, for advanced process nodes, the minimum particle size that needs to be detected and controlled has reached the tens of nanometers level. Particulate contaminants are one of the most common types of defects on wafer surfaces, having a highly destructive impact on wafer surface quality. In integrated circuit manufacturing, particulate contamination on the wafer surface can directly lead to short circuits, open circuits, or performance degradation, severely affecting device yield and reliability. Furthermore, as integrated circuit feature sizes continue to shrink to the nanometer level, with current advanced processes reaching 7 nanometer and even 3 nanometer nodes, even submicron-sized particles can cause fatal defects. Therefore, the requirements for the detection and control of particulate contaminants on wafer surfaces are becoming increasingly stringent.

[0003] Surface Scanning Inspection System (SSIS) is a crucial piece of equipment for ensuring that integrated circuit chip production lines can quickly enter the mass production stage and achieve stable high yields and economic benefits. SSIS uses laser scattering or optical imaging principles to perform high-speed scanning of the wafer surface, detecting and counting particulate contaminants of different sizes, providing quantitative data for particle control in the process. SSIS is an indispensable online inspection device in wafer fabrication companies; the accuracy of its results directly affects product yield and process adjustments. However, SSIS measurement is relative, determining particle presence and estimating particle size by comparing the detected scattering signal intensity or optical contrast with a preset threshold, rather than performing absolute physical size measurements. Therefore, differences in design, structure, and signal processing between different manufacturers, models, or levels of inspection equipment can be reflected in the test results. This inconsistency in measurement caused by differences in equipment principles and structures makes direct comparability of test results between different devices difficult.

[0004] To ensure measurement repeatability and relative accuracy, the verification and calibration of equipment using wafer surface particle standard materials with uniform and controllable particle size and quantity is a necessary foundation for the entry of domestically produced testing equipment into wafer fabrication enterprises. Wafer surface particle standard materials are reference samples with known particle size, known particle number density, and rigorously certified uniformity. Calibrating SSIS using standard materials verifies whether the testing equipment can correctly identify and count particles of the target size, confirming the equipment's detection sensitivity. Furthermore, it calibrates the correspondence between the scattering signal threshold of the testing equipment and particle size, ensuring the comparability and consistency of measurement results between different devices. Moreover, it monitors the performance drift of the testing equipment over time, promptly identifying and correcting measurement deviations, ensuring measurement repeatability throughout the equipment's entire service life. Only SSIS calibrated with standard materials can provide reliable particle detection data for wafer fabrication enterprises.

[0005] In the development of wafer surface particulate reference materials, the uniform and controllable deposition technology of wafer surface particles remains one of the main challenges. Preparing reference materials that meet calibration requirements places extremely stringent comprehensive requirements on the deposition process. According to particle counting standards such as ISO 15900 and SEMIF57, as well as the internal acceptance specifications of major domestic wafer foundries, particle size must be precisely controllable and highly monodisperse, with a particle size variation coefficient typically required to be less than 5%, obtained through sampling and statistical measurement of deposited particles using scanning electron microscopy (SEM). The particle number density on the wafer surface must be highly uniform; generally, SSIS is used to perform zoned scanning detection of the wafer surface, dividing the wafer into concentric ring regions, and calculating the deviation of particle density from the average density in each region, typically requiring less than 10%. Batch repeatability must be excellent; under the same testing conditions, the particle density deviation between different batches of reference materials must be less than 5%. Particles must exist in a monodisperse state, without agglomeration, determined by observing particle morphology using SEM. Existing particle deposition technologies are still unable to simultaneously meet all of the above requirements, which has become a core technological bottleneck restricting the independent development of wafer surface particulate reference materials in my country.

[0006] Imported wafer standard materials are expensive to procure, have long delivery cycles, and offer limited choices in terms of particle size and density, making it difficult to flexibly meet the diverse calibration needs of domestically produced testing equipment. Currently, international methods for depositing micro- and nano-particles on wafer surfaces are mainly based on DMA sieving and Brownian diffusion principles. Particle deposition methods based on condensation growth and inertial impaction principles have also been reported, but are relatively few.

[0007] (a) Aerosol spray deposition: This method sprays a suspension containing particles through an atomizing nozzle to form tiny droplets, which carry the particles and settle onto the wafer surface. The advantages of this method are simple equipment and low cost. The disadvantages are: (1) The droplet size distribution is wide, making it difficult to ensure the uniformity of particle deposition; (2) During the spreading and drying process of the sprayed droplets after landing on the wafer surface, the particles tend to gather at the edge of the droplet because the evaporation rate at the edge of the droplet is higher than that in the center area, resulting in severe particle agglomeration and uneven distribution; (3) It is difficult to accurately control the deposition density, and the number of particles in each spray fluctuates greatly, resulting in poor batch repeatability. These problems make it difficult for the spray deposition method to meet the high-quality requirements of the semiconductor industry for standard particle samples, especially the strict requirements of standard materials for particle number density uniformity and batch repeatability.

[0008] (ii) Electrostatic deposition: This method uses electrostatic force to accelerate charged particles toward the wafer surface and deposit them. Electrostatic deposition can achieve good directional control, with particles moving along the electric field lines to the wafer surface under the action of the electric field force. However, this method has the following shortcomings: (1) The equipment is complex, requiring a high-voltage power supply and a precision electrode structure; (2) Effective charging treatment of the particles is required, and the charging efficiency directly affects the deposition efficiency and uniformity; (3) For particle materials with different conductivity and dielectric properties, the deposition effect varies greatly, and the method has limited versatility; (4) Particles already deposited on the wafer surface will generate local charge accumulation, affecting the deposition behavior of subsequent particles, leading to a gradual deterioration of deposition uniformity over time. This characteristic makes it difficult to prepare large-area uniform standard material samples by electrostatic deposition.

[0009] (III) Deposition methods based on thermophoresis or diffusion principles: Thermophoretic deposition utilizes temperature gradients to drive particle migration from high-temperature regions to low-temperature regions; diffusion deposition relies on the Brownian motion of particles to randomly diffuse onto the wafer surface. Thermophoretic deposition has the advantage of good directionality, but its deposition rate is low, and it requires maintaining a stable temperature gradient field above the wafer, which is challenging in engineering implementation. Furthermore, the temperature gradient may affect existing device structures on the wafer. Diffusion deposition is mainly suitable for particles with extremely small diameters (typically less than 20 nanometers) because the intensity of Brownian motion is inversely proportional to particle size. For nanoparticles larger than 50 nanometers, diffusion deposition efficiency decreases significantly, and the deposition time is too long, making it difficult to meet practical application requirements. In addition, both thermophoresis and diffusion methods have difficulty precisely controlling particle deposition density, resulting in poor batch-to-batch repeatability and unsuitability for the mass production of standard materials.

[0010] (iv) Spin-coating deposition: A suspension containing nanoparticles is dropped onto the surface of a rotating wafer, and centrifugal force is used to spread the suspension evenly and then dry it. Spin-coating can achieve good uniformity under laboratory conditions, but it has the following problems: (1) The particle concentration and distribution are affected by multiple parameters such as spin-coating speed, acceleration time, and suspension concentration. Small fluctuations in these parameters can lead to significant changes in the deposition results; (2) Capillary forces during the drying process can easily cause particle agglomeration; (3) A large amount of suspension is thrown out during spin-coating, resulting in low material utilization; (4) It is not suitable for uniform deposition of large-size wafers. The above-mentioned defects of spin-coating make it difficult to meet the strict requirements for uniformity and repeatability in the preparation of standard materials.

[0011] (v) Deposition method based on condensation growth: Monodisperse nanoparticles are obtained by DMA sieving, and after condensation growth, they are enlarged into micron-sized droplets and then deposited onto the substrate surface by inertial impaction. However, the existing scheme has the following shortcomings: (1) It is only for particle deposition on half-inch wafers, and the applicability of particle deposition on large-size wafer surfaces needs to be explored. (2) Its inertial impaction nozzle is located at the growth unit outlet and is separated from the particle counting part, so it is impossible to realize online counting and real-time feedback control of the deposition process.

[0012] In summary, current wafer surface particle deposition technologies generally suffer from drawbacks such as poor deposition uniformity, insufficient particle size control precision, easy particle agglomeration, low deposition efficiency, poor batch-to-batch repeatability, or high equipment complexity. In particular, the condensation growth scheme, which is closest to this invention, while similar in basic principle, still has room for improvement. Therefore, developing a device and method capable of controllable and uniform deposition of nanoscale particles on wafer or substrate surfaces has significant industrial application value and scientific research significance. Summary of the Invention

[0013] The purpose of this invention is to provide a wafer surface particle deposition device and method based on condensation growth, which can solve the problems of difficulty in online particle counting, low inertial deposition efficiency of nanoparticles, uneven deposition on wafer surface and easy particle agglomeration in existing condensation growth deposition schemes, and achieve online counting, shrinkage acceleration, inertial impaction, rapid dehydration and uniform deposition of particles of target size.

[0014] To achieve the above objectives, the present invention provides the following solution: A wafer surface particle deposition apparatus based on condensation growth includes a particle generator, a differential electromobility analyzer, a condensation grower, and an optical particle counter arranged sequentially and interconnected along the gas path, as well as a wafer carrier assembly for supporting the wafer. The condenser grower is used to create a supersaturated steam environment, which allows water vapor to condense on the surface of monodisperse nanoparticles sieved by a differential electromobility analyzer, forming micron-sized particles with a condensate film on the outer layer. The optical particle counter includes a detection optical path, a shrinking section, and a shrinking outlet located at the end of the shrinking section. The detection optical path is located upstream of the shrinking section and is used to count micron-sized particles before they enter the shrinking section. The shrinking section is used to increase the airflow velocity carrying the micron-sized particles. The shrinking outlet is positioned opposite to the wafer surface so that the counted micron-sized particles are deposited onto the wafer surface by inertial impaction. The wafer carrier assembly includes a wafer carrier stage, a heating element disposed on the back of the wafer carrier stage, and an XY moving stage for driving the wafer carrier stage to move in a horizontal plane. The heating element is used to heat the wafer, so that when micron-sized particles impact the wafer surface, the condensate film evaporates and the monodisperse nanoparticles remain on the wafer surface.

[0015] Preferably, a diffusion dryer, a laminar flow meter, and a charge neutralizer are sequentially arranged between the particle generator and the differential electromobility analyzer along the gas path direction. The particle generator is used to atomize the particle suspension into droplets, the diffusion dryer is used to remove the solvent from the droplets to form a particle aerosol, the laminar flow meter is used to regulate the flow rate of the particle aerosol entering the differential electromobility analyzer, the charge neutralizer is used to make the particles in the particle aerosol reach the Boltzmann equilibrium charge distribution, and the differential electromobility analyzer is used to sieve the particles according to their electromobility to obtain monodisperse nanoparticles.

[0016] Preferably, the condenser includes a saturation chamber and a condensation chamber connected sequentially along the gas path, as well as a temperature control module; The saturation chamber uses deionized water as the working fluid. The temperature control module is used to control the temperature of the saturation chamber and the condensation chamber respectively, and to make the temperature of the saturation chamber higher than that of the condensation chamber. The saturation chamber is used to allow the carrier gas carrying monodisperse nanoparticles to absorb water vapor. The condensation chamber is used to make the carrier gas after absorbing water vapor form a supersaturated steam environment, so that the water vapor can form a condensate film with monodisperse nanoparticles as condensation nuclei.

[0017] Preferably, the flow cross-sectional area of ​​the contraction section gradually decreases along the air path direction, the contraction outlet has a conical nozzle structure, and the outlet diameter of the contraction outlet is 1.5 mm; The distance between the particle detection position of the detection optical path and the wafer surface is no more than 20 mm, and the distance between the shrink-type outlet and the wafer surface is 5 mm to 10 mm.

[0018] Preferably, the heating element is an aluminum block heated by electric heating, and a thermocouple is embedded in the aluminum block. The thermocouple is used to detect the temperature of the aluminum block, and the aluminum block is used to heat the wafer to 80°C to 120°C.

[0019] Preferably, the XY moving stage is used to drive the wafer carrier stage to move according to the bow-shaped scanning path, and the scanning speed and line spacing of the bow-shaped scanning path are set according to the count value of the optical particle counter and the target deposition surface density of the wafer surface. The wafer carrier assembly also includes a Z-stage, which is used to adjust the distance between the shrink-type exit and the wafer surface.

[0020] A method for depositing particles on a wafer surface based on condensation growth, comprising: The particles in the aerosol generated by the particle generator were screened by electromobility using a differential electromobility analyzer to obtain monodisperse nanoparticles of the target particle size. Monodisperse nanoparticles are introduced into a condenser with carrier gas, so that water vapor forms a condensate film in a supersaturated steam environment with the monodisperse nanoparticles as condensation nuclei, thus obtaining micron-sized particles with a condensate film on the outer layer. The detection optical path located upstream of the contraction section of the optical particle counter is used to count micron-sized particles and obtain the count value; The wafer surface is positioned opposite the shrinking outlet located at the end of the shrinking section. The scanning speed and scanning path spacing of the XY stage are set according to the count value and the target deposition areal density of the wafer surface. The wafer is then driven to move in the horizontal plane according to the preset scanning path by the XY stage. Heating the wafer; The airflow carrying the counted micron-sized particles is accelerated in the constriction section and then ejected towards the wafer surface from the constriction outlet; Micron-sized particles are deposited onto the wafer surface via inertial impaction during wafer movement, and the condensate film evaporates when the micron-sized particles impact the wafer surface, so that monodisperse nanoparticles are uniformly retained on the wafer surface.

[0021] Preferably, monodisperse nanoparticles are introduced into a condenser with a carrier gas, allowing water vapor to condense in a supersaturated steam environment using the monodisperse nanoparticles as condensation nuclei to form a condensate film, thereby obtaining micron-sized particles with an outer condensate film, including: The carrier gas carrying monodisperse nanoparticles flows sequentially through the saturation chamber and the condensation chamber of the condenser growth chamber; Deionized water was used as the working fluid in the saturation chamber, and the temperature of the saturation chamber was set to 50°C, so that the carrier gas could absorb water vapor in the saturation chamber. The temperature of the condenser is set to 10℃, so that the carrier gas after absorbing water vapor forms a supersaturated steam environment in the condenser. The flow rate of the carrier gas is set to 1 to 2 liters per minute, so that water vapor forms a condensate film with monodisperse nanoparticles as condensation nuclei, and the monodisperse nanoparticles grow into micron-sized particles with a particle size of 1 to 4 micrometers.

[0022] Preferably, the flow cross-sectional area of ​​the contraction section gradually decreases along the airflow direction, and the contraction outlet is a conical nozzle with an outlet diameter of 1.5 mm; The distance between the particle detection position of the detection optical path and the wafer surface is no more than 20 mm, and the distance between the shrink-type outlet and the wafer surface is 5 mm to 10 mm.

[0023] Preferably, the wafer heating temperature is 80°C to 120°C, the preset scanning path is a bow-shaped scanning path, and the scanning path spacing is the row spacing between adjacent scanning rows in the bow-shaped scanning path; The scanning speed and row spacing are set according to the count value and the target deposition areal density, and the wafer is driven to move along the bow-shaped scanning path by the XY stage.

[0024] The present invention discloses the following beneficial effects: (1) This invention uses a differential electromobility analyzer to sieve the aerosol generated by the particle generator, so that the particles entering the condenser growth unit have the target particle size and monodisperse characteristics. Compared with the wide-distribution particle aerosol without particle size sieving, the above structure can reduce the differences in condensation growth rate and inertial motion capability of particles of different sizes, avoid the particle size distribution shift caused by the preferential deposition of large-size particles and the difficulty in deposition of small-size particles, and provide conditions for forming particle deposition results with high particle size consistency on the wafer surface.

[0025] (2) This invention utilizes a condenser to create a supersaturated steam environment, causing water vapor to condense on the surface of monodisperse nanoparticles and form a condensate film, thereby transforming the monodisperse nanoparticles into micron-sized particles with a condensate film on the outer layer. After the particles grow from the nanoscale to the micron scale, the particle inertia increases accordingly, which can reduce the tendency of the particles to deflect near the wafer surface with the airflow, solving the problem of low deposition efficiency when nanoparticles are directly deposited by inertial impaction, and enabling nanoparticles to achieve inertial impaction deposition by means of the temporary increase in particle size after condensation growth.

[0026] (3) In this invention, the detection optical path of the optical particle counter is set upstream of the shrinking section, so that the micron-sized particles are counted before entering the shrinking section and being accelerated. The shrinking section further increases the airflow velocity carrying the micron-sized particles, and guides the counted micron-sized particles to the wafer surface through a shrinking outlet set opposite to the wafer surface. Detection and accelerated deposition are continuously completed by the same optical particle counter, which can reduce particle transport loss and counting object deviation caused by the separation of the detection position and the deposition nozzle, making the counting result closer to the actual number of particles participating in deposition. At the same time, the shrinking airflow is used to increase the impact velocity of the particles, ensuring that the micron-sized particles are deposited on the wafer surface by inertial impact.

[0027] (4) In this invention, a heating element is provided on the back of the wafer carrier stage. When micron-sized particles impact the wafer surface, the condensate film covering the monodisperse nanoparticles evaporates due to the heat. The water after particle size amplification is removed in time, and the monodisperse nanoparticles remain directly on the wafer surface. This treatment method avoids the continuous spread and slow drying of the condensate film on the wafer surface, which can reduce particle aggregation and edge enrichment caused by liquid phase migration, and reduce the probability of particle agglomeration and coffee ring distribution.

[0028] (5) In this invention, the wafer carrier stage is driven to move in a horizontal plane by an XY moving stage, so that different areas of the wafer surface pass sequentially through the particle impact area corresponding to the shrinking outlet. Compared with the concentration of particles in a localized location when the wafer is stationary, the movement of the wafer in a horizontal plane can change the particle impact position, distributing the counted and accelerated particles to a larger area of ​​the wafer surface, reducing the problem of excessively high local particle density or insufficient deposition in edge areas, thereby improving the uniformity of particle deposition distribution on the wafer surface. The above effects are all produced by the sieving, condensation growth, pre-deposition counting, shrinking acceleration, wafer heating, and horizontal movement structure described in the independent claims, without depending on specific temperature, flow rate, distance, or scanning path parameters. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the device structure provided in an embodiment of the present invention; Figure 2 This is a flowchart of a method provided in an embodiment of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The terminology used in the implementation section of this application is only used to explain specific embodiments of this application and is not intended to limit this application. The described embodiments are only a part of the embodiments of this application, not all of them. Other implementation methods that can be obtained by those skilled in the art based on the disclosure of this application without creative effort are all within the scope of the technical concept disclosed in this application.

[0032] The terms "first," "second," etc., used in the embodiments of this application are only for distinguishing different technical objects and do not indicate a fixed order, quantitative relationship, or degree of importance among the corresponding technical objects. Unless otherwise expressly stated, expressions such as "including," "having," "equipped with," and "connected" are open-ended and do not exclude the existence of other components or processes not explicitly listed. The connection between two components can be a direct connection or a connection through an intermediate component capable of realizing the corresponding gas delivery, signal transmission, or structural support functions.

[0033] The wafer surface particle deposition apparatus and method based on condensation growth provided in this application can be used to prepare wafer surface particle standard materials. The prepared wafer surface particle standard materials can be used to verify and calibrate surface scanning monitoring systems, including verifying whether the surface scanning monitoring system can identify and count target-size particles, determining the correspondence between scattering signal thresholds or optical contrast and particle size, and monitoring performance drift of the surface scanning monitoring system over time. The above application scenarios are only illustrative of this embodiment and are not intended to limit the scope of this application.

[0034] In this embodiment, the surface scanning monitoring system can be abbreviated as SSIS. SSIS scans the wafer surface using laser scattering or optical imaging, determines the presence of particles on the wafer surface based on the intensity of the detected scattering signal or optical contrast, and measures the number and size of the particles. The wafer surface particle standard material used to calibrate SSIS needs to have known particle size, number, or areal density, and meet the requirements for particle distribution uniformity and batch repeatability.

[0035] In this embodiment, the gas path direction refers to the direction in which the particulate aerosol moves from the particle generator, through particle drying, charge neutralization, and particle size sieving, into the condenser growth unit, then through the optical particle counter, and finally towards the wafer surface via a shrinking outlet. The aerosol includes a carrier gas and particles dispersed within it. Monodisperse nanoparticles refer to nanoparticles whose particle size is concentrated within the target particle size range after being sieved by a differential electromobility analyzer according to electromobility. Micron-sized particles refer to particles formed by the condensation of water vapor on the surface of monodisperse nanoparticles, with an outer layer of condensate film. The condensate film temporarily increases the overall aerodynamic particle size without changing the solid core particle size of the particles to be deposited.

[0036] Target areal density refers to the number of particles that need to be deposited per unit wafer surface area. Aerosol particle number concentration refers to the number of particles contained in a unit volume of carrier gas. The unit for aerosol particle number concentration can be... The unit of the target sedimentary surface density should be . These two are different physical quantities and cannot be represented by the same name. In this embodiment, approximately... This refers to the aerosol particle number concentration, not the target deposition areal density on the wafer surface.

[0037] Figure 1 This is a schematic diagram of a wafer surface particle deposition system provided in an embodiment of this application. Figure 1 As shown, the wafer surface particle deposition system is divided into four parts according to the particle processing process: particle generation, particle sieving, particle growth and counting, and particle deposition. Figure 1 The dashed boxes in the diagram represent the corresponding processing stages, and the arrows between the dashed boxes indicate that the particulate aerosol is passed sequentially along the gas path. Figure 1 This is only used to illustrate the compositional relationship between the components and the order of particle processing. The spatial position and scale of each component in the drawing do not constitute a limitation on the actual installation position and structural dimensions.

[0038] Figure 1 The particle generating section includes an air compressor, a particle generator containing a polystyrene latex suspension, a diffusion dryer, a laminar flow meter, and a neutralizer. The air compressor is connected to the particle generator to supply compressed air. The outlet of the particle generator is connected to the inlet of the diffusion dryer, and the outlet of the diffusion dryer is connected to the neutralizer via the laminar flow meter. The outlet of the neutralizer is connected to the particle screening section. Figure 1 The arrows indicate that compressed air drives the polystyrene latex suspension to form droplets containing particles. After the solvent is removed by the diffusion dryer, the droplets form particulate aerosols. The particulate aerosols are then fed into the differential electromobility analyzer after flow regulation and charge neutralization.

[0039] Figure 1 The particle sieving section includes a DMA controller, a differential electromobility analyzer (DMA), and a condensed particle counter (CPC). The DMA controller is connected to the differential electromobility analyzer and is used to set or adjust the applied voltage and related operating parameters of the analyzer. The neutralized particulate aerosol enters the differential electromobility analyzer and is separated according to electromobility under the influence of an electric field and sheath gas. The condensed particle counter is located on the outlet side of the differential electromobility analyzer and is used to measure the particle number concentration after sieving, and to confirm whether the differential electromobility analyzer stably forms monodisperse nanoparticles of the target particle size.

[0040] Figure 1The particle growth and counting section includes a saturation tube, a condenser tube, a grower, and an optical particle counter (OPC). The saturation tube and condenser tube form the saturation chamber and condensation chamber of the condensation grower, respectively, and together they constitute the growth pipeline for the particle aerosol to pass through. The grower also includes temperature control modules for controlling the temperatures of the saturation tube and condenser tube. Monodisperse nanoparticles, sieved by a differential electromobility analyzer, enter the saturation tube with a carrier gas. After the carrier gas absorbs water vapor, it enters the condenser tube, where the water vapor condenses on the surface of the monodisperse nanoparticles, causing them to grow into micron-sized particles with a condensate film on the outer layer. The optical particle counter is located at the end of the gas path of the condensation grower and is used for online counting of the micron-sized particles after condensation growth. Valves can also be installed in the illustrated gas path to control the opening and closing of the corresponding gas paths or to regulate the gas flow rate.

[0041] Figure 1 The particle deposition section is housed within a glove box. The glove box contains the particle deposition area and includes an aerosol inlet and an aerosol outlet. The aerosol inlet connects to the gas path of the contracted outlet of the optical particle counter, while the aerosol outlet discharges undeposited carrier gas and remaining particles. The particle deposition section also includes nozzles, a wafer, a heated aluminum block, a heat shield, an XY stage, and a Z stage. The nozzle is located above the wafer and opposite to its surface. The nozzle is formed from the contracted outlet at the end of the optical particle counter and is not considered a separate nozzle component independent of the optical particle counter.

[0042] The wafer is placed on a wafer carrier stage, and a heating aluminum block is positioned behind the wafer carrier stage to heat the wafer. A heat shield is placed between the heating aluminum block and the XY moving stage to reduce the heat transferred from the heating aluminum block to the XY moving stage. The XY moving stage drives the wafer carrier stage and the wafer to move in the horizontal plane, while the Z moving stage adjusts the distance between the wafer surface and the nozzle. Figure 1 The aerosol shown is sprayed from the nozzle toward the wafer surface, and the carrier gas is discharged through the aerosol outlet of the glove box after the particles impact the wafer surface.

[0043] In this embodiment, the particle generator can be a Topas GmbH ATM220 spray-type nanoparticle generator. A polystyrene latex suspension is added to the particle generator, and the mass concentration of the polystyrene latex suspension can be [missing information]. The air compressor supplies pressure to the particle generator. The compressed air is used by the particle generator to atomize the polystyrene latex suspension into fine droplets containing polystyrene latex particles.

[0044] The particle generator can be equipped with an independent pressure regulating valve. By fine-tuning the compressed air pressure or the outlet flow rate of the particle generator through the pressure regulating valve, the amount of particulate aerosol generated can be changed. After the particulate droplets generated by the particle generator enter the diffusion dryer, the solvent in the droplets is removed, forming dried polystyrene latex nanoparticle aerosols.

[0045] The laminar flow meter can be the AF-02 type. The laminar flow meter is used to regulate the flow rate of particulate aerosols entering the differential electromobility analyzer; the typical flow range is [missing information]. By adjusting the aerosol flow rate, the airflow velocity at the subsequent contraction outlet can be altered, thereby affecting the impact velocity and deposition efficiency of the micron-sized particles after condensation growth.

[0046] The neutralizer can be an XRC-05 type neutralizer. The neutralizer can use a Kr-85 radioactive source or a corona discharge method. The neutralizer is used to bring the particles to a Boltzmann equilibrium charge distribution, thereby enabling the differential electromobility analyzer to perform stable sieving based on particle electromobility.

[0047] The original particle size of the polystyrene latex suspension can be The particle size distribution of the particulate aerosol generated by the particle generator depends on the original particle size of the particles in the polystyrene latex suspension. The particle number concentration of the particulate aerosol can be approximately... The carrier gas can be clean and dry compressed air, which delivers the particulate aerosol to the differential electromobility analyzer.

[0048] The differential mobility analyzer can be a Model 5710. The differential mobility analyzer connects to the particle generator via a gas pipeline and uses an electric field to sieve particles according to their electromobility. The main operating parameters of the differential mobility analyzer include sheath gas flow rate, sample gas flow rate, applied voltage, and the ratio of sheath gas flow rate to sample gas flow rate.

[0049] Sheath gas flow rate can be The sample gas flow rate can be The ratio of sheath gas flow rate to sample gas flow rate can be In another process setup, the particulate aerosol delivery flow rate into the differential electromobility analyzer can be... The applied voltage is set according to the target particle size of the particles to be deposited. The correspondence between the applied voltage and the target particle size can be determined according to the particle mobility relationship used by the differential electromobility analyzer. Particles that meet the target electromobility range enter the subsequent gas path from the outlet of the differential electromobility analyzer, thereby obtaining monodisperse nanoparticles of the target particle size.

[0050] The condensed particle counter can be a CPC-C003 type. It is typically connected after the differential mobility analyzer for preliminary measurement of the aerosol particle number concentration at the analyzer's outlet. During particle generator commissioning or aerosol generation status checks, the condensed particle counter can also be selectively connected to the particle generator outlet to measure the aerosol particle number concentration generated by the generator. These two locations are selective connection points for different detection conditions; it is not required that the same condensed particle counter be set in both locations simultaneously.

[0051] A condensed particle counter or an optical detection device suitable for particle size determination can be connected to the outlet of the differential electromobility analyzer to confirm the formation state of monodisperse particles. In one testing example, the coefficient of variation of particle size after sieving can be less than [value missing]. This was to verify whether the particles formed by the differential electromobility analyzer had monodispersity that met the requirements for subsequent deposition.

[0052] The condenser grower is connected to the differential electromobility analyzer. The condenser grower includes a saturation chamber, a condensation chamber, and a temperature control module; deionized water can be used as the working fluid. The saturation chamber can be composed of… Figure 1 The saturated tube shown is formed, and the condensation chamber can be formed by... Figure 1 The condenser tube shown is formed.

[0053] The saturation chamber temperature can be set to This allows the carrier gas entering the saturation chamber to absorb water vapor and reach or nearly reach saturation. The condensation chamber temperature can be set to... The temperature in the condenser chamber is lower than that in the saturation chamber. When the carrier gas, after absorbing water vapor, enters the condenser chamber from the saturation chamber, a supersaturated steam environment is formed.

[0054] Monodisperse nanoparticles, sieved by a differential electromobility analyzer, enter the condensation chamber with the carrier gas and serve as condensation nuclei. Water vapor condenses on the surface of the monodisperse nanoparticles, forming a condensate film. As the water vapor continues to condense, the overall aerodynamic particle size of the monodisperse nanoparticles increases, forming micron-sized particles with an outer layer of condensate film.

[0055] The flow rate of the carrier gas entering the condenser grower can be By controlling the saturation chamber temperature, condensation chamber temperature, the temperature difference between the saturation and condensation chambers, and the carrier gas flow rate, a stable particle size can be obtained. Micron-sized particles. The condensation growth process increases the overall aerodynamic particle size only through the condensate film, while the solid particle size of the polystyrene latex particles remains at the target particle size sieved by the differential electromobility analyzer.

[0056] An optical particle counter is located at the end outlet of the condenser growth unit. The optical particle counter includes a detection optical path, a contraction section, and a contraction-type outlet, and combines online detection of micron-level particles with inertial impaction-accelerated deposition capabilities.

[0057] The detection optical path is located upstream of the contraction section. Micron-sized particles with an outer condensation film enter the optical particle counter along with the carrier gas and first pass through the detection optical path. The detection optical path counts the micron-sized particles based on the scattered light signals generated by the particles, ensuring that the particles are detected before entering the contraction section and being accelerated.

[0058] The flow cross-sectional area of ​​the contraction section gradually decreases along the airflow direction. After the airflow carrying micron-sized particles enters the contraction section, the airflow velocity increases as the flow cross-sectional area decreases. A contraction-type outlet is located at the end of the contraction section, forming a conical nozzle structure. The outlet diameter of the contraction-type outlet can be... .

[0059] The particle size of the micron-sized particles after condensation growth is After entering the contraction section, micron-sized particles acquire high velocities under the acceleration of the airflow. Under the given particle size, airflow velocity, and outlet size conditions in this embodiment, the Stokes number of the micron-sized particles is... Much larger The particles have a large inertia and are difficult to deflect in front of the wafer surface with the airflow, so they can impact the wafer surface in an almost perpendicular direction.

[0060] The distance from the shrink-type outlet to the wafer surface is If the distance is too small, the airflow will not diffuse sufficiently before reaching the wafer surface, leading to an overly concentrated particle deposition area. If the distance is too large, some particles may be deflected by the airflow, resulting in decreased deposition efficiency or reduced particle distribution uniformity. The distance from the shrinkage outlet to the wafer surface should be set to... This allows for a suitable balance between particle impact capability and deposition zone width.

[0061] The gas path distance between the particle detection position (located in the detection optical path) and the particle deposition position on the wafer surface can be controlled within... Within this range. Shortening the gas path distance from when the particles finish counting to when they impact the wafer surface can reduce the loss of particles within the gas path wall, making the number of particles measured by the optical particle counter closer to the actual number of particles involved in deposition.

[0062] The gas path distance between the detection location and the deposition location does not exceed Furthermore, under conditions of clean gas path inner walls and stable flow, particle wall losses can be approximated as negligible, and deposition efficiency can be assumed to be close to... Process estimation is performed. The actual deposition efficiency and the actual number of particles remaining on the wafer surface are still determined by subsequent SSIS testing results, and will not be approximated. As an absolute value that can be confirmed without testing.

[0063] The wafer carrier assembly includes a wafer stage, heating elements, an XY stage, and a Z stage. The wafer stage is used to hold the wafer, and the wafer surface is positioned opposite the shrink-type exit of the optical particle counter.

[0064] The heating element is located on the back of the wafer carrier. The heating element can be an aluminum block, which is electrically heated. A thermocouple is embedded inside the aluminum block to detect the temperature of the aluminum block or the wafer carrier and provide temperature feedback. By adjusting the heating power based on the thermocouple readings, temperature control accuracy can be maintained. .

[0065] The adjustable temperature range of the heating element can be: During particle deposition, the wafer temperature can be controlled at... In a preferred embodiment, the temperature of the wafer surface and the near-field space between the wafer surface and the OPC shrink-type outlet is controlled at... Typical wafer temperature setpoint is .

[0066] The glass transition temperature of polystyrene is approximately In this embodiment, by controlling the wafer temperature, the heating time after particle impact, and the evaporation time of the condensate film, the condensate film can be rapidly evaporated, while the morphological changes of the polystyrene latex particles caused by heating are controlled within an acceptable range, avoiding undesirable changes in the physical state of the wafer surface or the solid core of the particles.

[0067] Upon impact with the wafer surface, the condensate film encasing the polystyrene latex particles rapidly evaporates due to the wafer surface temperature. This condensate film can be submicron thick and evaporates instantaneously. After evaporation, the polystyrene latex nanoparticles, sieved by a differential electromobility analyzer, remain directly on the wafer surface.

[0068] The rapid evaporation of the condensate film after particle impact reduces droplet spreading on the wafer surface and the slow drying process, minimizing particle migration and aggregation driven by capillary forces during liquid-phase drying, and reducing the distribution of coffee rings caused by droplet edge evaporation. When using high-purity deionized water as the working fluid, no dissolved residue or obvious watermarks are left after the condensate film evaporates.

[0069] By controlling the distance from the shrinking outlet to the wafer surface and the airflow velocity, micron-sized particles can be made to have appropriate impact kinetic energy. This particle impact kinetic energy is used to ensure stable contact between polystyrene latex particles and the wafer surface, while preventing significant particle bounce or secondary migration on the wafer surface.

[0070] The XY stage is positioned at the bottom of the wafer carrier and is used to drive the wafer to move horizontally along a preset path during the deposition process. The preset path can be a bow-shaped scan path, also known as a serpentine scan path. A bow-shaped scan path consists of multiple parallel scan lines, with adjacent scan lines connected by turning segments.

[0071] The row spacing of the scan path is set based on the wafer size, the effective deposition width corresponding to the shrinkage exit, and the target deposition areal density. The scan speed is set based on the required target deposition areal density on the wafer surface and the number of particles measured by the optical particle counter. When the particle number concentration is high or the target deposition areal density is low, the scan speed can be increased; when the particle number concentration is low or the target deposition areal density is high, the scan speed can be decreased.

[0072] The Z-stage is used to adjust the distance between the wafer surface and the shrinkage exit. The XY stage is used to perform two-dimensional scanning of the wafer surface, and the Z-stage is used to adjust the impact distance to... The range of heat transfer is limited. A heat insulation plate is installed between the heated aluminum block and the XY moving stage to reduce the impact of heat transfer on the positioning accuracy and operating status of the XY moving stage.

[0073] A particle generator atomizes the particle suspension into particle-containing droplets, and a diffusion dryer removes the solvent from the droplets, forming a nanoparticle aerosol. A neutralizer brings the nanoparticles to Boltzmann equilibrium charge distribution, and a differential electromobility analyzer sieves monodisperse nanoparticles of the target particle size according to their electromobility. The monodisperse nanoparticles enter the condenser growth chamber with the carrier gas. Under the temperature difference between the saturation chamber and the condensation chamber, the water vapor in the carrier gas becomes supersaturated. The water vapor condenses around the monodisperse nanoparticles as nuclei, forming a condensate film that temporarily grows the nanoparticles into micron-sized particles.

[0074] Micron-sized particles are counted online as they pass through the detection optical path of an optical particle counter, and then enter the contraction section. The contraction section increases the airflow velocity, and the contraction-type outlet ejects the micron-sized particles toward the wafer surface. The micron-sized particles impact the wafer surface due to their increased aerodynamic diameter and inertia. Heating components on the back of the wafer maintain a preset temperature. When the micron-sized particles impact the wafer surface, the condensate film surrounding the monodisperse nanoparticles evaporates rapidly, leaving the monodisperse nanoparticles on the wafer surface. An XY stage drives the wafer along a preset scanning path, ensuring that the particle impact points cover different areas of the wafer surface.

[0075] Figure 2 A flowchart of a wafer surface particle deposition method based on condensation growth provided in an embodiment of this application. Figure 2 This section, placed after the description of the device's composition and working principle, serves to summarize the subsequent implementation process. For example... Figure 2 As shown, the method flow unfolds in the following sequence: particle sieving, condensation growth, online counting, scanning parameter setting and wafer movement, wafer heating, shrinkage acceleration ejection, and inertial impaction deposition. The arrows between steps 100 and 700 indicate that the particle state, count value, or motion state formed in the previous step is transferred to the next step. Figure 2 There is no requirement that each step must be performed by an independent device.

[0076] Step 100: Use a differential electromobility analyzer to perform electromobility sieving on the particles in the aerosol generated by the particle generator to obtain monodisperse nanoparticles of the target particle size. Step 200: Monodisperse nanoparticles are introduced into the condenser with carrier gas, so that water vapor forms a condensate film in a supersaturated steam environment with monodisperse nanoparticles as condensation nuclei, and micron-sized particles with a condensate film on the outer layer are obtained. Step 300: Count the micron-sized particles using the detection optical path located upstream of the contraction section of the optical particle counter to obtain the count value; Step 400: Position the wafer surface opposite the shrinking outlet located at the end of the shrinking section, set the scanning speed and scanning path spacing of the XY stage according to the count value and the target deposition areal density of the wafer surface, and drive the wafer to move in the horizontal plane according to the preset scanning path through the XY stage. Step 500: Heat the wafer; Step 600: The airflow carrying the counted micron-sized particles is accelerated through the contraction section and then ejected towards the wafer surface from the contraction outlet; Step 700: Deposit micron-sized particles onto the wafer surface via inertial impact during wafer movement, and evaporate the condensate film when the micron-sized particles impact the wafer surface, so that monodisperse nanoparticles are uniformly retained on the wafer surface.

[0077] Before performing step 100, the target particle size, target areal density of the wafer surface, and wafer size can be determined according to the specifications of the SSIS to be calibrated. The particles can be of a particle size of... Polystyrene latex particles. Wafer size can be... , , , or The sheath gas flow rate, applied voltage, and sample gas flow rate of the differential electromobility analyzer are set according to the target particle size; the saturation chamber temperature, condensation chamber temperature, and supersaturation are set according to the target particle size after condensation growth; the height from the OPC shrink outlet to the wafer surface, gas flow rate, and wafer temperature are set according to the inertial impaction conditions; and the scan path type, scan speed, and line spacing are set according to the wafer size and target deposition areal density.

[0078] In step 100, the mass concentration is... A polystyrene latex suspension was added to an ATM220 spray-type nanoparticle generator, utilizing a pressure of... Compressed air atomizes the polystyrene latex suspension. The resulting droplets containing particles enter a diffusion dryer to remove the solvent, and then pass through an XRC-05 neutralizer to achieve a Boltzmann equilibrium charge distribution for the polystyrene latex nanoparticles. An AF-02 laminar flow meter regulates the aerosol flow rate, and clean, dry air is used as the carrier gas to deliver the aerosol to a differential electromobility analyzer. The number concentration of the aerosol particles generated by the particle generator can be approximately [missing information]. .

[0079] Set the applied voltage, sheath gas flow rate, and sample gas flow rate of the Model 5710 differential electromobility analyzer according to the target particle size. The sheath gas flow rate can be set to... The sample gas flow rate can be set to The ratio of sheath gas flow rate to sample gas flow rate can be set to... The particles are separated according to their electromobility within the electric field of the differential electromobility analyzer, allowing only monodisperse nanoparticles within the target electromobility range to enter the analyzer's outlet. A CPC or an OPC suitable for detecting sieved particles can be connected to the analyzer's outlet to confirm the monodisperse particles and verify whether the particle size variation coefficient of the sieved particles is less than [value missing]. .

[0080] In step 200, the sieved monodisperse nanoparticles are introduced into the condenser growth chamber along with the carrier gas. The saturation chamber temperature is set to... This allows the carrier gas to fully absorb water vapor; the condenser temperature is set to... This allows the carrier gas, after absorbing water vapor, to form a supersaturated vapor environment in the condenser chamber. The carrier gas flow rate is controlled at... This process utilizes monodisperse nanoparticles as condensation nuclei, causing water vapor to condense on the surface of the nanoparticles to form a condensate film, thereby growing the monodisperse nanoparticles to a particle size of [missing information]. Micron-sized particles.

[0081] In step 300, micron-sized particles are passed through the detection optical path of the OPC. The detection optical path performs optical counting before the micron-sized particles enter the contraction section, generating a count value corresponding to the number of micron-sized particles passing through the detection optical path. The detection optical path is located upstream of the contraction section, ensuring that the micron-sized particles are detected before the airflow velocity increases, thus reducing the impact of airflow acceleration on the stability of scattered light detection.

[0082] In step 400, the wafer surface is positioned opposite the OPC shrink-type exit, and the scanning speed and scan path spacing are set according to the count value, wafer size, and target deposition areal density on the wafer surface. The preset scan path can be a bow-shaped scan path. The bow-shaped scan path includes multiple sequentially connected scan rows. After the wafer completes its movement along one scan row, the XY stage drives the wafer to move laterally by one row spacing, and then moves in the opposite direction to the next scan row. By continuously executing the above movement process, the particle impact area corresponding to the shrink-type exit covers the wafer surface.

[0083] In step 500, the wafer is heated using a heating aluminum block disposed on the back of the wafer carrier stage. The adjustable temperature range of the heating element can be [missing information]. The wafer temperature during the deposition process can be set to... Preferred setting is Typical settings are Thermocouples detect the temperature of the heated aluminum block or wafer carrier stage, and adjust the heating power based on the detection results to achieve precise temperature control. .

[0084] In step 600, the counted micron-sized particles are carried by the airflow into the contraction section. The airflow is accelerated within the contraction section, where the cross-sectional area gradually decreases, and exits through an outlet with a diameter of [missing information]. The shrink-type outlet ejects the OPC towards the wafer surface. The impact distance from the OPC shrink-type outlet to the wafer surface is set to... And ensure that the gas path distance between the OPC detection location and the wafer deposition location does not exceed Micron-sized particles are ejected through a shrinking outlet and move in a direction approximately perpendicular to the wafer surface.

[0085] In step 700, micron-sized particles impact the wafer surface via inertial impaction during wafer movement. The outer condensate film evaporates rapidly under the influence of the wafer surface temperature, leaving the polystyrene latex nanoparticles directly on the wafer surface. The condensate film can be submicron thick and can evaporate within milliseconds. Due to the rapid evaporation of the condensate film, it does not spread on the wafer surface for an extended period, reducing the risk of particle migration, agglomeration, or edge enrichment caused by capillary forces during liquid-phase drying. When high-purity deionized water is used as the working fluid, no dissolved residue or obvious watermarks are produced after evaporation.

[0086] Assuming negligible particle loss in the short gas path between the OPC detection location and the wafer surface, the total number of particles participating in deposition is determined by the aerosol particle number concentration, aerosol flow rate, and deposition time. The original calculation relationship was: When aerosol flow rate is pre-calculated Deposition time adopted At that time, it can make This represents the theoretical total number of particles. This indicates the aerosol particle number concentration at the OPC detection location. Indicates aerosol flow rate, The deposition time is expressed by the following formula: In the formula, The unit is , The unit is , The unit is , The unit is .

[0087] When aerosol flow rate Still using Deposition time use When converting the flow rate unit, the calculation formula is as follows: In the formula, This is the conversion factor between liters and cubic centimeters. This is the conversion factor between minutes and seconds. The theoretical total number of particles is used for the initial setting of scanning speed, scanning path spacing, and deposition time. The actual number of particles remaining on the wafer surface is determined by SSIS detection results.

[0088] After particle deposition, SSIS is used to perform a full-surface scan of the wafer to detect the particle size, number, and spatial distribution of the deposited particles. The wafer can be divided into multiple concentric ring regions, and the number of particles in each region can be counted, the particle areal density of each region can be calculated, and the deviation between the particle areal density of each region and the average particle areal density of the wafer surface can be calculated.

[0089] When the total number of deposited particles or the uniformity of particle distribution exceeds the target range, the scanning speed of the XY stage, the row spacing of the zigzag scanning path, or the aerosol flow rate can be adjusted based on the SSIS detection results, and particle deposition can be repeated. As a detection and judgment method, when the deviation between the regional particle surface density and the average particle surface density is greater than... If necessary, the above deposition parameters can be adjusted and the material prepared again.

[0090] When the total number of deposited particles exceeds the target particle count, the scanning speed can be increased, the line spacing increased, or the aerosol flow rate decreased. When the total number of deposited particles is less than the target particle count, the scanning speed can be decreased, the line spacing decreased, or the aerosol flow rate increased. When the particle distribution is uneven, the local scanning speed or scanning path can be adjusted according to the location of areas with lower or higher particle areal density.

[0091] Scanning electron microscopy (SEM) can also be used to observe the particle morphology and measure the particle size of sampled areas on the wafer surface to confirm whether the particles remain monodisperse and whether agglomeration exists. When preparing wafer surface particle standard materials, testing can be performed in accordance with ISO 15900, SEMI F57, and the internal acceptance specifications of wafer processing companies.

[0092] In a standard material preparation example, the deposited particles were sampled and statistically analyzed using SEM, ensuring that the particle size variation coefficient was less than [value missing]. The wafer is divided into concentric ring regions using SSIS, and the deviation between the particle areal density of each region and the average particle areal density is less than [value missing]. Under the same testing conditions, the particle areal density deviation between different batches of wafers should be less than [a certain value]. SEM observation of particle morphology confirmed that the particles existed in a monodisperse state and showed no obvious agglomeration. The above values ​​are used to illustrate the quality judgment indicators that can be used in the preparation of standard substances, and do not limit the use of the same indicators in other application scenarios.

[0093] In an alternative embodiment, in addition to clean, dry air, high-purity nitrogen can be used as the carrier gas. When using high-purity nitrogen, the gas flow rate of the differential electromobility analyzer and the airflow parameters at the constricted outlet can be adjusted according to the flow characteristics of high-purity nitrogen.

[0094] In an alternative embodiment, the working fluid of the condenser growth chamber, in addition to deionized water, can also be n-butanol, butanol, or isopropanol. When using n-butanol, butanol, or isopropanol, the saturation chamber temperature, condensation chamber temperature, and wafer heating temperature are adjusted according to the saturated vapor pressure, boiling point, and volatility characteristics of the corresponding working fluid. Deionized water, with its low residue after evaporation and high safety, can be considered a preferred working fluid.

[0095] In an alternative embodiment, in addition to polystyrene latex particles, standard silica particles can also be used as the particles to be deposited. The density of silica particles is approximately... The density of polystyrene latex particles is approximately When using silica particles, the sieving voltage of the differential electromobility analyzer and the supersaturation parameter of the condenser can be adjusted according to the differences in particle density and electromobility to enable the silica particles to complete the target particle size sieving and condensation growth.

[0096] In an alternative implementation, the XY moving stage may employ a spiral scanning path, a concentric circle scanning path, or a bow-shaped scanning path. When using a spiral scanning path, the scanning path spacing can represent the radial distance between adjacent spiral trajectories; when using a concentric circle scanning path, the scanning path spacing can represent the radial distance between adjacent circular trajectories.

[0097] In an alternative implementation, a combination of CPC and OPC can be used for detection. CPC is used for measuring the particle number concentration of nanoscale particles and confirming the DMA sieving status, while OPC is used for online detection and deposition control of micron-sized particles after condensation growth. CPC and OPC are applied to different particle size stages, respectively.

[0098] In an alternative embodiment, in addition to heating the aluminum block, the heating element can also be a ceramic heating plate or an infrared radiation heating element. When using different heating elements, temperature detection and feedback control are used to ensure that the wafer surface reaches a temperature that allows the condensate film to evaporate rapidly without causing undesirable changes to the particles to be deposited or the wafer surface.

[0099] In this embodiment, monodisperse nanoparticles of the target particle size are formed using a differential electromobility analyzer (DMA), and then temporarily grown into micron-sized particles using a condensation film. The micron-sized particles are counted by an OPC before entering the shrinkage section and, after being accelerated through a shrinkage outlet, impact the heated wafer surface. The condensation film evaporates upon impact, leaving the monodisperse nanoparticles on the wafer surface. An XY stage drives the wafer movement, distributing the particle impact points across different areas of the wafer, while a Z stage adjusts the impact distance between the shrinkage outlet and the wafer surface. This process utilizes the particle size sieving effect of DMA, the condensation growth effect, the online counting and shrinkage acceleration effect of OPC, the wafer heating effect, and the two-dimensional movement effect to complete the particle deposition on the wafer surface.

[0100] Using the wafer surface particle deposition apparatus and method provided in this embodiment, the detection optical path of the optical particle counter completes the counting of micron-sized particles before they enter the shrinking section. The shrinking section and shrinking outlet then increase the airflow velocity carrying the micron-sized particles, causing the counted micron-sized particles to be deposited onto the wafer surface by inertial impaction. The scanning speed and scanning path spacing of the XY stage are set according to the count value obtained from the optical particle counter, the target deposition areal density of the wafer surface, and the wafer size. This ensures that the particle impact position covers the area to be deposited on the wafer, reducing distribution differences caused by excessively high or low particle counts in certain areas. The heating element on the back of the wafer stage heats the wafer to a preset temperature, causing the condensate film surrounding the particles to be deposited to evaporate rapidly when the particles impact the wafer surface. The particles to be deposited remain directly on the wafer surface, thereby reducing particle migration, agglomeration, and edge enrichment caused by the spread of condensate on the wafer surface and slow drying. The sieving parameters of the differential electromobility analyzer, the temperature and carrier gas flow rate of the condenser grower, the structural parameters and impact distance of the shrinkage outlet, the wafer heating temperature, and the scanning parameters of the XY stage can be set separately, so that the same device can be used to prepare standard materials of wafer surface particles with particle sizes from 60 nanometers to 500 nanometers and different target deposition areal densities; under the same detection conditions and process parameter control conditions, the particle areal density deviation between different batches of wafers can be controlled within 5%.

[0101] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the apparatus disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the apparatus description.

[0102] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A wafer surface particle deposition apparatus based on condensation growth, characterized in that, It includes a particle generator, a differential electromobility analyzer, a condenser grower, and an optical particle counter arranged sequentially and interconnected along the gas path, as well as a wafer carrier assembly for carrying the wafer. The condenser is used to create a supersaturated steam environment, which allows water vapor to condense on the surface of monodisperse nanoparticles sieved by the differential electromobility analyzer, forming micron-sized particles with a condensate film on the outer layer. The optical particle counter includes a detection optical path, a shrinking section, and a shrinking outlet located at the end of the shrinking section. The detection optical path is located upstream of the shrinking section and is used to count the micron-sized particles before they enter the shrinking section. The shrinking section is used to increase the airflow velocity carrying the micron-sized particles. The shrinking outlet is disposed opposite to the wafer surface, so that the counted micron-sized particles are deposited on the wafer surface by inertial impaction. The wafer carrier assembly includes a wafer carrier stage, a heating component disposed on the back of the wafer carrier stage, and an XY moving stage for driving the wafer carrier stage to move in a horizontal plane. The heating component is used to heat the wafer, so that when the micron-sized particles impact the wafer surface, the condensate film evaporates and the monodisperse nanoparticles remain on the wafer surface.

2. The wafer surface particle deposition apparatus based on condensation growth according to claim 1, characterized in that, A diffusion dryer, a laminar flow meter, and a charge neutralizer are sequentially arranged between the particle generator and the differential electromobility analyzer along the gas path. The particle generator is used to atomize the particle suspension into droplets, the diffusion dryer is used to remove the solvent from the droplets to form a particle aerosol, the laminar flow meter is used to regulate the flow rate of the particle aerosol entering the differential electromobility analyzer, the charge neutralizer is used to make the particles in the particle aerosol reach the Boltzmann equilibrium charge distribution, and the differential electromobility analyzer is used to sieve the particles according to their electromobility to obtain the monodisperse nanoparticles.

3. The wafer surface particle deposition apparatus based on condensation growth according to claim 1, characterized in that, The condenser grower includes a saturation chamber and a condensation chamber connected sequentially along the gas path, as well as a temperature control module. The saturation chamber uses deionized water as the working fluid. The temperature control module is used to control the temperature of the saturation chamber and the condensation chamber respectively, and to make the temperature of the saturation chamber higher than that of the condensation chamber. The saturation chamber is used to allow the carrier gas carrying the monodisperse nanoparticles to absorb water vapor. The condensation chamber is used to allow the carrier gas after absorbing water vapor to form a supersaturated steam environment, so that the water vapor forms the condensate film with the monodisperse nanoparticles as condensation nuclei.

4. The wafer surface particle deposition apparatus based on condensation growth according to claim 1, characterized in that, The flow cross-sectional area of ​​the contraction section gradually decreases along the air passage direction, the contraction outlet is a conical nozzle structure, and the outlet diameter of the contraction outlet is 1.5 mm. The distance between the particle detection position of the detection optical path and the wafer surface is no more than 20 mm, and the distance between the shrink-type outlet and the wafer surface is 5 mm to 10 mm.

5. The wafer surface particle deposition apparatus based on condensation growth according to claim 1, characterized in that, The heating component is an aluminum block heated by electric heating. The heating aluminum block has a thermocouple embedded in it. The thermocouple is used to detect the temperature of the heating aluminum block. The heating aluminum block is used to heat the wafer to 80°C to 120°C.

6. The wafer surface particle deposition apparatus based on condensation growth according to claim 1, characterized in that, The XY moving stage is used to drive the wafer carrier stage to move according to the bow-shaped scanning path. The scanning speed and line spacing of the bow-shaped scanning path are set according to the count value of the optical particle counter and the target deposition surface density of the wafer surface. The wafer carrier assembly also includes a Z-stage, which is used to adjust the distance between the shrink-type outlet and the wafer surface.

7. A method for depositing particles on a wafer surface based on condensation growth, characterized in that, include: The particles in the aerosol generated by the particle generator were screened by electromobility using a differential electromobility analyzer to obtain monodisperse nanoparticles of the target particle size. The monodisperse nanoparticles are introduced into a condenser with a carrier gas, so that water vapor forms a condensate film in a supersaturated steam environment with the monodisperse nanoparticles as condensation nuclei, and micron-sized particles with the condensate film on the outer layer are obtained. The micron-sized particles are counted using a detection optical path located upstream of the contraction section of an optical particle counter to obtain a count value; The wafer surface is positioned opposite the shrinking outlet located at the end of the shrinking section. The scanning speed and scanning path spacing of the XY moving stage are set according to the count value and the target deposition areal density of the wafer surface. The wafer is then driven to move in the horizontal plane along a preset scanning path by the XY moving stage. Heating the wafer; After the airflow carrying the counted micron-sized particles is accelerated through the contraction section, it is ejected toward the wafer surface from the contraction outlet. The micron-sized particles are deposited onto the wafer surface via inertial impact during the wafer's movement, and the condensate film evaporates when the micron-sized particles impact the wafer surface, so that the monodisperse nanoparticles are uniformly retained on the wafer surface.

8. The wafer surface particle deposition method based on condensation growth according to claim 7, characterized in that, The monodisperse nanoparticles are introduced into a condenser with a carrier gas, allowing water vapor to condense in a supersaturated steam environment using the monodisperse nanoparticles as condensation nuclei to form a condensate film, thereby obtaining micron-sized particles with the condensate film on the outer layer, including: The carrier gas carrying the monodisperse nanoparticles is sequentially passed through the saturation chamber and the condensation chamber of the condensation grower; Deionized water is used as the working fluid in the saturation chamber, and the temperature of the saturation chamber is set to 50°C, so that the carrier gas absorbs water vapor in the saturation chamber. The temperature of the condensation chamber is set to 10°C, so that the carrier gas after absorbing water vapor forms a supersaturated steam environment in the condensation chamber. The flow rate of the carrier gas is set to 1 liter / minute to 2 liters / minute, so that the water vapor forms the condensate film with the monodisperse nanoparticles as condensation nuclei, and the monodisperse nanoparticles grow into micron-sized particles with a particle size of 1 micrometer to 4 micrometers.

9. The wafer surface particle deposition method based on condensation growth according to claim 7, characterized in that, The flow cross-sectional area of ​​the contraction section gradually decreases along the airflow direction, and the contraction outlet is a conical nozzle with an outlet diameter of 1.5 mm. The distance between the particle detection position of the detection optical path and the wafer surface is no more than 20 mm, and the distance between the shrink-type outlet and the wafer surface is 5 mm to 10 mm.

10. The wafer surface particle deposition method based on condensation growth according to claim 7, characterized in that, The heating temperature of the wafer is 80°C to 120°C, the preset scanning path is a bow-shaped scanning path, and the scanning path spacing is the row spacing between adjacent scanning rows in the bow-shaped scanning path. The scanning speed and the row spacing are set according to the count value and the target deposition areal density, and the wafer is driven to move along the bow-shaped scanning path by the XY stage.

Images