Wafer jet printing glue coating device and process method

Abstract

The application provides a wafer jet printing glue coating device and a process method. The device comprises a host computer, a total controller, a motion control system, a stable ink supply system, an adsorption and heating device, and a jet printing control system. The host computer and the total controller communicate through an Ethernet interface. The total controller is connected to the motion control system, the stable ink supply system, the adsorption and heating device, and the jet printing control system. The total controller is directly connected to the motion control system through a parallel interface. The total controller is connected to the adsorption and heating device and the stable ink supply system through an Rs485 interface. The total controller is connected to the jet printing control system through a fiber serial interface. A multi-pore nozzle is used. The nozzles form an array according to a preset nozzle spacing. The nozzle array method can simultaneously perform multiple scanning movements. The nozzles and the nozzles directly do not generate boundaries, thereby fundamentally solving the problem of uneven film thickness at the connection.

Description

Technical Field

[0001] This invention belongs to the field of photoresist spraying film formation technology, specifically relating to a wafer spraying coating device and process method. Background Technology

[0002] The coating of the resist is a crucial step in the entire photolithography process. The thickness and uniformity of the coated resist layer determine the accuracy and resolution of the pattern generated by development, and affect key factors such as the performance quality, reliability, and yield of the manufactured integrated circuits.

[0003] Traditional photoresist coating primarily employs spin coating, the basic principle of which involves dispensing photoresist at the center of the wafer and using centrifugal force generated by high-speed rotation to uniformly coat the wafer surface. The thickness and uniformity of spin coating are mainly determined by factors such as the viscosity of the photoresist, substrate properties, rotation speed, rotation duration, and the complexity of the wafer's morphology. However, spin coating has several drawbacks: high-speed rotation disrupts the surrounding airflow, causing photoresist evaporation and resulting in poor uniformity of the photoresist film; high-speed centrifugation wastes approximately 90% of the photoresist; and for wafer substrates with complex microstructures, spin coating cannot control the uniformity of the photoresist coating. Therefore, spin coating is only suitable for wafers with flat surfaces and small areas, and it is difficult to achieve uniform photoresist coating on structures with large morphological variations and high aspect ratios.

[0004] With the development and maturation of nozzle atomization technology, atomized coating has also been applied to coating processes. The average droplet size of the atomized material is approximately 20μm, resulting in less photoresist waste and environmental friendliness. However, a large number of atomized droplets re-aggregate during their descent, causing changes in droplet size. Therefore, droplet uniformity can only reach 70%, which is not conducive to obtaining high-quality photoresist films on wafers with large aspect ratios, making it difficult to achieve ideal coating results. For 12-inch wafers, the coating time is also long. Atomized coating is not easy to atomize into particles when the viscosity is greater than 30 CP, making it unsuitable for coating high-viscosity photoresist solutions. This results in a narrow process window for subsequent optimization, failing to meet actual production needs. Taking AZ P4620 photoresist as an example, the mixing ratio of photoresist and acetone in atomized coating is generally only 1:10 or less, which easily flows on complex wafer surfaces, causing uneven thickness at the bottom and top.

[0005] With the rapid development of advanced 3D-IC packaging and MEMS devices, the application of photoresist on wafers with large aspect ratio structures is becoming increasingly widespread. Existing processes such as spin coating and atomization coating are difficult to achieve uniform photoresist film formation on such complex surfaces. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a wafer inkjet printing and coating apparatus and process, which effectively improves coating uniformity and spraying efficiency. It has a wide range of applications, and is particularly suitable for wafer surfaces with complex morphologies such as trenches, TSVs (through silicon vias), and MEMS (microelectromechanical systems) with large aspect ratios.

[0007] A wafer inkjet printing and coating device includes: a host computer, a main controller, a motion control system, a stable ink supply system, an adsorption and heating device, and an inkjet printing control system;

[0008] The host computer and the main controller communicate using an Ethernet interface. The main controller connects to four subsystems: motion control system, stable ink supply system, adsorption and heating device, and inkjet control system. The main controller is directly connected to the motion control system using a parallel interface, connected to the adsorption and heating device using an RS485 interface, connected to the stable ink supply system using an RS485 interface and terminal blocks, and connected to the inkjet control system using a fiber optic serial interface.

[0009] The host computer is used to receive feedback data and send execution commands to the main controller.

[0010] The main controller is used to receive and parse commands from the host computer, send them to each subsystem, integrate subsystem information, and feed it back to the host computer.

[0011] The motion control system is used to control the movement of the nozzle in the X and Y axis directions and the high-speed rotation of the wafer in the Z axis direction, receive grating displacement feedback, and realize the scanning motion of the nozzle on the entire wafer.

[0012] The stable ink supply system is used to store liquids and photoresist solutions for cleaning and pretreatment, ensuring that the printhead has a stable negative pressure to prevent ink seepage at the nozzle, while also achieving precise flow control during the spraying process.

[0013] The adsorption and heating device is used to fix and heat the wafer, realize vacuum adsorption of the wafer, and meet the temperature process requirements of the wafer processing.

[0014] The printing control system is responsible for controlling the voltage and frequency parameters of the printhead and feeding this information back to the main controller. By controlling the magnitude, sign, duration, and spraying frequency of the printhead voltage, the printhead can achieve uniform spraying of photoresist.

[0015] The motion control system includes an X-axis motion platform, a Y-axis motion platform, a Z-axis rotary platform, and a motion controller. The X-axis motion platform includes an X-axis servo motor, an X-axis grating ruler, and an X-axis lead screw. The Y-axis motion platform includes a Y-axis servo motor, a Y-axis grating ruler, and a Y-axis lead screw. The X and Y axis servo motors drive the lead screws to convert rotational motion into linear motion. The grating ruler is mounted on the lead screw slide to perform closed-loop control of the nozzle displacement. The X-axis motion platform is fixed on the lead screw slide of the Y-axis motion platform and moves with the Y-axis lead screw. The Z-axis rotary platform includes a Z-axis servo motor and a turntable. The Z-axis servo motor drives the turntable to rotate. The main controller is connected to the motion controller, which is connected to the aforementioned servo motors and grating rulers. The motion controller receives and processes the displacement signals from the X and Y axis grating rulers and applies motion signals to the servo motors for control.

[0016] The stable ink supply system includes a negative pressure unit, a peristaltic pump, two-way valves, and ink cartridges, connected by ink tubes. Three ink cartridges store liquid M, liquid N, and photoresist solution respectively. In the process, liquid M used for cleaning is typically deionized water or an organic solvent, while liquid N used for pretreatment is typically pure water or a diluent. The photoresist solution is a mixture of photoresist and a diluent in a specific ratio. The negative pressure unit connects to the three ink cartridges, providing negative pressure. The peristaltic pump is connected to the ink cartridge storing the photoresist solution, and the main controller sets the flow rate via RS485 communication, controlling the spraying flow rate of the peristaltic pump. Three two-way valves are each connected between the three ink cartridges and the printhead assembly, controlling the on / off operation of the printhead assembly. Each two-way valve is controlled by a signal line from the main controller; a high voltage signal opens the two-way valve, and a low voltage signal closes it.

[0017] The adsorption and heating device includes a vacuum adsorption device and a heating device. The vacuum adsorption device is mounted on a turntable to generate a vacuum negative pressure to fix the wafer. The heating device is mounted below the turntable to heat the wafer on the turntable and includes a heating module, a temperature detection module, and a temperature controller. The heating module and the temperature detection module are respectively connected to the temperature controller, which is connected to the main controller. The temperature detection module uses a thermistor circuit to detect voltage and uses an AD conversion circuit to process the detected voltage to obtain the detected temperature. The temperature controller compares the detected temperature with the set temperature sent by the main controller and controls the switching of the heating module, thereby controlling the wafer temperature. The heating module heats the wafer; when the detected temperature is lower than the preset temperature, the switch is closed to continue heating; otherwise, the switch is opened to stop heating and allow the wafer to cool naturally.

[0018] The printing control system includes a printhead mounting plate, three printhead groups, and a printhead controller. The printhead mounting plate is fixed to the lead screw slide of the X-axis motion platform and is used to mount and fix each printhead group (divided into printhead groups A, B, and C). The printheads are piezoelectric ceramic multi-micro-pore structures. To achieve the various steps of the spraying process, multiple printheads are used to form three printhead groups. Printhead group A uses liquid M to clean the wafer; printhead group B uses liquid N to pre-treat the wafer to improve the uniformity of photoresist spraying; and printhead group C uses the photoresist solution to achieve uniform spraying of the wafer. All three printhead groups are installed according to the requirements of the printhead array method. The printhead controller is mounted on the printhead and controlled by the main controller. It applies a voltage signal for spraying to the printhead, controlling the spraying force, duration, and frequency. The printhead controller applies voltage to displace the piezoelectric ceramic; applying a positive voltage causes the nozzle to expand and accommodate droplets, while applying a negative voltage causes the nozzle to expel droplets. Due to the principle of pressure waves, when a fluid is squeezed and expanded by the piezoelectric ceramic in the nozzle chamber, a reaction force is generated. This force exhibits a sinusoidal waveform that gradually decays over time. This phenomenon can interfere with liquid flow and the photoresist spraying effect, requiring the application of voltage to the piezoelectric ceramic again at an appropriate time to counteract the influence of the pressure wave. Different parameters need to be set according to different photoresist concentrations, thicknesses, and uniformity requirements to effectively suppress the pressure wave problem.

[0019] The nozzle array requires multiple nozzles to be staggered in the Y-axis direction, meaning adjacent nozzles within a nozzle group are installed at certain intervals along both the X and Y axes. The installation intervals D1 and D2 between two adjacent nozzles in the Y-axis direction satisfy... Where δ represents the preset installation error value, and D represents the nozzle spacing of a single nozzle. The installation spacing is fine-tuned using adjusting screws. δ is set according to process requirements. For nozzle groups A and B, δ can take a relatively large range of values; however, due to the high uniformity requirements of photoresist spraying, nozzle group C requires δ to be smaller, generally below 0.05mm. To ensure the continuity of spraying, the installation spacing D3 between two adjacent nozzles in the X-axis direction within each nozzle group should be the minimum installation distance, that is, the minimum value taken within the allowable nozzle installation conditions.

[0020] The spraying process of the nozzle array is as follows: the motor controls the movement of the nozzles, and the grating ruler provides feedback on the displacement information. The nozzle group first moves along the X-axis. After reaching the starting position on the X-axis, the first nozzle begins spraying. After moving D3 along the X-axis, the second nozzle begins spraying, and so on, until all nozzles have started spraying. Upon reaching the ending position on the X-axis, the first nozzle stops spraying. After moving D3 along the X-axis, the second nozzle stops spraying, and so on, until all nozzles have stopped spraying. Then, the nozzles move along the Y-axis to the uncoated area of ​​the wafer and repeat the above operation for the next spraying cycle. Through this control, all nozzles in the nozzle group start spraying at the designated starting position and stop spraying at the designated ending position. Using a nozzle array method to achieve simultaneous spraying by multiple nozzles reduces the number of scans and improves spraying efficiency.

[0021] A wafer inkjet printing and coating process includes:

[0022] Step 1: After placing the wafer on the Z-axis rotating platform, fix it using a vacuum adsorption device, and adjust the number, height, and installation spacing of the nozzles in nozzle groups A, B, and C. The number of nozzles in each nozzle group is generally determined according to process requirements. The distance between the bottom surface of the nozzle and the wafer surface is generally 1-3mm. To ensure high uniformity of photoresist spraying in the nozzle array, all nozzle holes in nozzle group C require high installation accuracy in the X-axis direction, while nozzle groups A and B have lower requirements.

[0023] Step 2: The coating process for each nozzle is controlled using an interdigitated spraying method to pre-treat the wafer, including cleaning, heating, and pre-treatment. Specifically:

[0024] Cleaning: Control the nozzle group A to spray high-speed, high-flow liquid M, scan the entire wafer according to the preset cleaning path, and at the same time start the turntable to drive the wafer to rotate at high speed to clean the dust.

[0025] Heating: Start heating to perform temperature treatment on the wafer and remove residual liquid M;

[0026] Pre-processing: Control the nozzle group B to spray liquid N, and scan the entire wafer according to the preset scanning path. The liquid N sprayed on the wafer surface can improve the uniformity of photoresist spraying.

[0027] Step 3: Set the peristaltic pump flow rate and turn on the peristaltic pump. Use nozzle group C to spray photoresist onto the wafer surface. Scan along the photoresist spraying path at the set speed and step size to form a uniform photoresist layer on the entire wafer surface.

[0028] Step 4: Heat the wafer to remove liquid nitrogen and photoresist diluent, while increasing the thickness of the adhesive layer at the top of the trench to make the coating more uniform.

[0029] The nozzle controller uses an interpolation spraying method for spraying individual nozzles along the X-axis. Each nozzle has a large number of staggered nozzles. The nozzles on each nozzle are encoded, with odd-numbered nozzles defined as odd-numbered nozzles and even-numbered nozzles as even-numbered nozzles. Specifically, the interpolation spraying method works as follows: Before spraying begins, the host computer sends the start position, end position, and spraying interval of the X-axis to the main controller. The main controller records a spraying position every spraying interval between the start and end positions, calculating all spraying positions along the X-axis. During spraying, the nozzle moves along the X-axis, and a grating ruler provides feedback on the position information. When an odd-numbered nozzle reaches a spraying position, the printhead controller applies voltage to perform one spraying operation. Similarly, when an even-numbered nozzle reaches the same spraying position on the X-axis, it also performs one spraying operation via voltage control. Because the odd and even nozzles are staggered on the Y-axis and have the same spraying position on the X-axis, the droplets sprayed from the even-numbered nozzles fall into the gaps between the droplets previously sprayed from the odd-numbered nozzles, causing the two sets of droplets to merge and achieve higher print density and reliability. As the printhead moves through each spraying position on the X-axis, the above voltage control is repeated to form a uniform photoresist film. The printhead has a staggered nozzle structure, but printheads without a staggered nozzle structure can use multiple printheads stacked together to form staggered nozzles, thus enabling interdigitated spraying.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention proposes a wafer inkjet printing coating apparatus and process method. It uses a nozzle with a multi-micro-hole structure for coating, where each nozzle has an identical structure. Therefore, the size and velocity of the sprayed droplets are highly uniform, with droplet size and velocity consistency exceeding 85%, and can be precisely controlled by adjusting the voltage. The nozzle employs an interdigital spraying method, resulting in excellent film uniformity and reliability. This method eliminates the need for the high-speed rotation process of spin coating, reducing material waste and power loss. Compared to atomized coating, the droplet concentration is higher, reaching over 90%, and the photoresist layer is more uniform.

[0032] 2. The inkjet printing coating process of this invention is not only applicable to smooth wafer surfaces, but also performs well on wafer surfaces with special morphologies such as trenches with large aspect ratios and MEMS. Spin coating can cause the colloid to aggregate locally in complex structures, while atomized coating has large particle size and low concentration at the boundaries, making it difficult to guarantee the thickness error and coverage of the colloid layer on complex morphologies. Compared with existing coating technologies, the droplet size of this invention is smaller, more stable, and has higher concentration. The inkjet printing coating process of this invention is applicable to photoresists of various viscosities (20CP-80CP), especially high-viscosity colloids. High-viscosity photoresists have shorter curing times and reduced fluidity, enabling uniform photoresist film formation on MEMS wafer surfaces with large aspect ratios.

[0033] 3. The thickness control of the adhesive spraying in this invention is more precise, mainly determined by three factors: photoresist concentration, inkjet frequency, and printhead scanning speed. All three factors are linearly related to the thickness of the adhesive layer, which is convenient for measurement and calculation.

[0034] 4. The inkjet printing and coating process of this invention has good potential for expansion and optimization. For example, this invention can achieve oblique spraying by rotating the printhead, reducing the spacing between adjacent nozzles and obtaining a higher droplet printing density. This invention can also use a printhead array with multiple printheads for coating. By configuring an appropriate number of printhead arrays for wafers of different sizes, the number of scans is reduced and the coating efficiency is improved. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the control principle of the wafer inkjet printing and coating device in this invention;

[0036] Figure 2 This is a circuit diagram of the wafer inkjet coating device in this invention;

[0037] Figure 3 This is a schematic diagram of the wafer inkjet printing and coating device in this invention;

[0038] Figure 4 This is a schematic diagram of the stable ink supply system in this invention;

[0039] Figure 5 (a) is a schematic diagram of the scanning motion of the nozzle assembly in this invention; (b) is a schematic diagram of the cleaning path; and (c) is a schematic diagram of the pretreatment and photoresist spraying path.

[0040] Figure 6 This is a schematic diagram of the defects of the low-viscosity colloid in the groove in this invention;

[0041] Figure 7 This is a schematic diagram of the interdigitated spraying principle in this invention;

[0042] Figure 8This is a schematic diagram of the droplet bounce type in this invention;

[0043] Figure 9 This is a schematic diagram of the oblique spraying method in this invention;

[0044] Figure 10 This is a schematic diagram of the nozzle array configuration in this invention;

[0045] Among them, 100 is the nozzle, 110 is the wafer, 120 is the photoresist film layer, 210 is the X-axis servo motor, 220 is the X-axis lead screw, 230 is the X-axis grating ruler, 240 is the Y-axis servo motor, 250 is the Y-axis lead screw, 260 is the Y-axis grating ruler, 270 is the Z-axis servo motor, 280 is the turntable, 310 is the nozzle group A, 320 is the nozzle group B, 330 is the nozzle group C, 340 is the nozzle mounting plate, 410 is the vacuum adsorption device, 420 is the heating device, 510 is the cleaning path, 520 is the pretreatment and photoresist spraying path, 530 is the odd number of droplets, 540 is the even number of droplets, 550 is the droplet bounce type P, and 560 is the droplet bounce type Q. Detailed Implementation

[0046] The invention will be further described below with reference to the accompanying drawings and specific embodiments. The present invention provides a wafer inkjet printing and coating apparatus and process method, which can greatly improve the uniformity of coating and the spraying efficiency. It has a wide range of applications, and is especially suitable for wafer surfaces with complex morphologies such as trenches, TSVs (through silicon vias), and MEMS (microelectromechanical systems) with large aspect ratios.

[0047] A schematic diagram of the control principle of a wafer inkjet printing and coating device is shown below. Figure 1 As shown, the system includes: a host computer, a main controller, a motion control system, a stable ink supply system, an adsorption and heating device, and a printing control system. The host computer and the main controller communicate via an Ethernet interface. The main controller connects to four subsystems: the motion control system, the stable ink supply system, the adsorption and heating device, and the printing control system. Specifically, the main controller is directly connected to the motion control system via a parallel interface, connected to the adsorption and heating device via an RS485 interface, connected to the stable ink supply system via an RS485 interface and terminal blocks, and connected to the printing control system via a fiber optic serial interface.

[0048] The circuit diagram of the wafer inkjet coating device is as follows: Figure 2 As shown, the host computer sends data and issues commands to the main controller. The main controller parses the data and commands and sends them to various systems to control various parameters of the servo motor, peristaltic pump, two-way valve, heating device and nozzle assembly, and feeds the information back to the host computer.

[0049] The host computer receives feedback data and sends execution commands to the main controller. The main controller receives and parses the host computer commands, sends them to various subsystems, integrates subsystem information, and feeds it back to the host computer. The motion control system controls the movement of the printhead in the X and Y axes and the high-speed rotation of the wafer in the Z axis, receives grating displacement feedback, and realizes the scanning motion of the printhead across the entire wafer. The stable ink supply system stores the cleaning and pretreatment liquids and photoresist solutions, ensuring a stable negative pressure on the printhead to prevent ink seepage at the nozzles, while also achieving precise flow control during the spraying process. The adsorption and heating device fixes and heats the wafer, achieving vacuum adsorption of the wafer and meeting the temperature process requirements of the wafer processing. The printing control system is responsible for controlling the voltage and frequency parameters of the printhead and feeding this information back to the main controller. By controlling the magnitude, sign, duration, and spraying frequency of the printhead voltage, uniform spraying of photoresist by the printhead is achieved.

[0050] A schematic diagram of the wafer inkjet printing and coating device is shown below. Figure 3 As shown, the motion control system includes an X-axis motion platform, a Y-axis motion platform, a Z-axis rotary platform, and a motion controller. The X-axis motion platform includes an X-axis servo motor 210, an X-axis lead screw 220, and an X-axis grating ruler 230. The Y-axis motion platform includes a Y-axis servo motor 240, a Y-axis lead screw 250, and a Y-axis grating ruler 260. The X and Y axis servo motors drive the lead screws to move, converting rotational motion into linear motion. The grating ruler is mounted on the lead screw slide and performs closed-loop control of the nozzle displacement. The X-axis motion platform is fixed on the lead screw slide of the Y-axis motion platform and moves with the Y-axis lead screw 250. The Z-axis rotary platform includes a Z-axis servo motor 270 and a turntable 280. The Z-axis servo motor 270 drives the turntable 280 to rotate. The main controller is connected to the motion controller, which is connected to the aforementioned servo motors and grating rulers in the circuit. It receives and processes the displacement signals of the X and Y axis grating rulers and applies motion signals to the servo motors for control. The motion control system uses three servo motors to control the nozzle's movement along the X and Y axes and the wafer's rotation along the Z axis, achieving three degrees of freedom. A linear encoder is used on the X and Y axes for closed-loop control of the nozzle position. The X and Y axis motion platform enables the nozzle to scan the entire wafer, while the high-speed rotation along the Z axis is essential for wafer pretreatment and cleaning. During adhesive application, if the wafer has a simple surface structure, low-speed rotation can improve uniformity; however, rotation is not possible for wafers with complex surfaces.

[0051] The printing control system includes a printhead mounting plate 340, three printhead groups, and a printhead controller. The printhead mounting plate 340 is fixed to the lead screw slide of the X-axis motion platform. The printhead 100 is a piezoelectric ceramic multi-micro-orifice structure, mounted on the printhead mounting plate 340, and is divided into printhead group A 310, printhead group B 320, and printhead group C 330. Each group sprays different types of liquids and performs different processing steps. Printhead group A 310 uses liquid M to clean the wafer; printhead group B 320 uses liquid N to pre-treat the wafer to improve the uniformity of photoresist spraying; and printhead group C 330 uses a photoresist solution to achieve uniform spraying of wafer 110. All three printhead groups are installed according to the requirements of the printhead array method. The printhead controller connects to all printheads and controls the compression and expansion of the internal nozzles of the printheads by controlling factors such as the polarity, magnitude, frequency, and duration of the voltage. Due to the principle of pressure waves, when a fluid is squeezed and expanded by the piezoelectric ceramic nozzle, a reaction force is generated. This force exhibits a sinusoidal waveform that gradually decays over time. This phenomenon can interfere with liquid flow and the photoresist spraying effect, requiring the application of voltage to the piezoelectric ceramic again at an appropriate time to counteract the influence of the pressure wave. Different parameters need to be set according to different photoresist concentrations, thicknesses, and uniformity requirements to effectively suppress the pressure wave problem.

[0052] The stable ink supply system, such as Figure 4 As shown, the system includes a negative pressure unit, a peristaltic pump, two-way valves, and ink cartridges, all connected by ink tubes. Three ink cartridges store liquid M, liquid N, and photoresist solution, respectively. In the process, liquid M used for cleaning is typically deionized water or an organic solvent, while liquid N used for pretreatment is typically pure water or a diluent. The photoresist solution is a mixture of photoresist and a diluent in a specific ratio. The negative pressure unit connects to the three ink cartridges, providing negative pressure. Accurate thickness control is required during photoresist spraying; therefore, a peristaltic pump is used to precisely control the photoresist flow rate. The peristaltic pump is connected to the ink cartridge storing the photoresist solution, and the main controller sets the flow rate via RS485 communication, controlling the spraying flow of the peristaltic pump. Three two-way valves are each connected between the three ink cartridges and the printhead assembly, controlling the on / off operation of the printhead assembly. Each two-way valve is controlled by a signal line from the main controller. When the printhead is not working, close the two-way valve to prevent ink leakage. When working, open the required two-way valve and close the other two-way valves. Use a negative pressure machine to adjust the air pressure until the liquid gravity and negative pressure are balanced, so that the printhead is in good spraying condition.

[0053] The adsorption and heating device uses vacuum negative pressure to fix the wafer and meets the temperature process requirements of the wafer processing. The adsorption and heating device includes a vacuum adsorption device 410 and a heating device 420. The vacuum adsorption device 410 is mounted on a turntable 280 to generate vacuum negative pressure to fix the wafer. The heating device 420 is mounted below the turntable 280 to heat the wafer on the turntable 280. The heating device 420 includes a heating module, a temperature detection module, and a temperature controller. The heating module and the temperature detection module are respectively connected to the temperature controller, which is connected to the main controller. The temperature detection module uses a thermistor circuit to detect voltage and uses an AD conversion circuit to process the detected voltage to obtain the detected temperature. The temperature controller compares the detected temperature with the set temperature sent by the main controller and controls the switching of the heating module, thereby controlling the wafer temperature. The heating module heats the wafer; when the detected temperature is lower than the preset temperature, the switch is closed to heat; otherwise, the switch is opened to stop heating and allow the wafer to cool naturally.

[0054] A wafer inkjet printing and photoresist coating process, comprising the following steps, using the aforementioned wafer inkjet printing and photoresist coating apparatus for photoresist coating:

[0055] Step 1: Place the wafer and fix it using the vacuum adsorption device 410 to ensure that the wafer will not slip during rotation. Adjust the number, height, and spacing of the three nozzle groups according to the wafer size and process requirements. Nozzle groups A 310 and B 320, used for cleaning and pretreatment, have no requirements for coating uniformity and lower requirements for nozzle spacing accuracy. However, nozzle group C 330 requires high uniformity of the adhesive layer and necessitates ensuring high nozzle installation accuracy.

[0056] Step 2: Perform pre-processing on the wafer, including cleaning, heating, and pretreatment, as detailed below:

[0057] Cleaning: Use nozzle assembly A 310 to spray high-speed, high-flow-rate liquid M to clean the wafer, following the instructions... Figure 5 (a) The cleaning path 510 shown is scanned, and the dust is cleaned in conjunction with the high-speed rotation of the wafer 110.

[0058] Heating: The wafer is heated using heating device 420 to remove residual liquid M;

[0059] Pre-treatment: Using nozzle assembly B 320, spray liquid N, scanning the entire wafer according to pre-treatment path 520 to facilitate the subsequent application of photoresist into trenches and deep holes; according to... Figure 5 (b) The pretreatment and photoresist spraying path 520 shown in the figure are scanned;

[0060] Step 3: Set the peristaltic pump flow rate and turn on the peristaltic pump. Use the nozzle group C 330 to spray photoresist on the wafer surface. Scan along the photoresist spraying path 520 at the set speed and step size to form a uniform photoresist film layer 120 on the entire wafer surface.

[0061] Step 4: Use heating device 420 to heat the wafer to remove liquid N and diluent solvent from the photoresist solution, increase the thickness of the adhesive layer at the top of the trench, and make the coating more uniform.

[0062] Depending on the actual working conditions, the mixing ratio of photoresist and diluent, as well as the required thickness and uniformity of the photoresist layer, will vary. Therefore, the spraying platform is designed with a wide range of adjustable parameters, including voltage, waveform, frequency, motion speed, temperature, and ink pressure, which can be adjusted in real time according to process requirements. It is suitable for spraying photoresist with viscosities ranging from 20 CP to 80 CP. Taking AZP4620 photoresist as an example, it is sufficient to ensure the spraying effect of photoresist and diluent mixtures with ratios between 1:10 and 1:2.

[0063] Traditional spin coating uses a center-tipping method, leveraging the centrifugal force generated by the high-speed rotation of the wafer to obtain a relatively uniform photoresist layer. Atomized coating, on the other hand, uses air pressure to spray photoresist in a conical atomized state, coordinating with the scanning motion of the nozzle to complete the coating across the entire wafer. However, on complex wafer surfaces, the radial flow of photoresist in spin coating can cause localized aggregation of the photoresist in complex structures, making it difficult to control the thickness and uniformity of the photoresist coating. Atomized coating exhibits significant particle size variations, which are generally normally distributed, especially at the boundaries where the particle diameter is large and the number is small, resulting in low concentration and instability. Atomized coating is only suitable for low-viscosity photoresists, but low-viscosity photoresist layers can flow on complex surfaces, causing issues such as… Figure 6 The bottom aggregation and top corner disconnection phenomena shown make it difficult to ensure the uniform conformal morphology of the photoresist layer 120 and the wafer 110. Therefore, as the wafer morphology becomes increasingly complex, existing spraying methods cannot achieve good process results.

[0064] This method uses a nozzle with multiple nozzles, each of which can be configured to spray adhesive according to the requirements of the coating platform. Furthermore, the number of sprayed droplets can be adjusted through grayscale control, enabling on-demand coating on the wafer surface. The nozzle uses piezoelectric ceramic extrusion to spray droplets. This coating method is suitable for photoresists of various viscosities. Under the parameter control of the coating platform, it can achieve the coating of high-viscosity adhesives, reducing adhesive flow problems and achieving conformal and uniform coverage with the substrate surface.

[0065] Because of its staggered nozzle structure, the nozzle can be used for interlocking spraying. The droplets sprayed by the nozzle 100 are divided into odd-numbered droplets 530 and even-numbered droplets 540. During the spraying process, one group of droplets fills the gap between another group of droplets, which can achieve high precision and high reliability spraying. Even if a few nozzles are blocked, it will not affect the coating.

[0066] The specific process of finger spraying is as follows: Figure 7 As shown: the spray nozzles are divided into odd-numbered nozzles and odd-numbered nozzles. First, the odd-numbered nozzles spray out an odd number of droplets 530, which fall onto the wafer to form a spray adhesive layer L1. Then, the odd-numbered nozzles also spray adhesive, and the even-numbered droplets 540 fall into the gaps between the odd-numbered droplets 530, forming a spray adhesive layer L2. Spray adhesive layers L1 and L2 merge and complement each other, ultimately forming a uniform adhesive layer. Compared with traditional spin and atomization coating processes, using interdigitated spraying can achieve higher coating uniformity and reliability.

[0067] In photoresist spraying, droplets were observed to bounce off the substrate, mainly due to... Figure 8 The droplet bounce types shown are P550 and Q560. Droplet bounce type P550 is broken up, its diameter decreases, and it becomes more disordered, forming a large number of uniform droplets that eventually disperse and fall onto the substrate. Droplet bounce type Q560, on the other hand, sticks to the bottom surface of the nozzle, which is detrimental to subsequent spraying. Therefore, adjusting the height difference between the bottom surface of the nozzle and the wafer to 1-3mm, increasing droplet bounce type P550 and decreasing droplet bounce type Q560, is more conducive to continuous spraying and uniform film thickness.

[0068] Multi-micro-orifice printheads can achieve smaller orifice spacing and higher print density through rotation. For example... Figure 9 As shown, spraying is performed by rotating the nozzle by 100 degrees at an angle θ (typically 0°-60°), allowing the nozzle spacing to be adjusted within a certain range, which significantly enhances the droplet density. Although the coating width is reduced, the spraying quality is improved, and the spraying effect is greatly enhanced, making it more suitable for wafer surfaces with complex structures.

[0069] A nozzle array is a system that arranges several nozzles in order to... Figure 10 Install and control the nozzle spacing as shown, ensuring that the nozzle installation spacing D1 and D2 in the Y-axis direction satisfy the following relationship with the nozzle orifice spacing D: To ensure high uniformity of photoresist spraying, the spacing error of all nozzles in the nozzle array must be less than the maximum error value δ in the Y-axis direction. δ is set according to process requirements. For nozzle group A 310 and nozzle group B 320, δ can take a relatively large range; while for nozzle group C 330, the higher the uniformity requirement, the smaller δ should be. The installation spacing D3 between adjacent nozzles in the X-axis direction should be minimized within the allowable nozzle installation range to improve spraying continuity.

[0070] Compared to spin coating and atomized coating, which require multiple reciprocating motions, nozzle arrays can complete the overall coating of large-size wafers with fewer or even single motions. Furthermore, nozzles can be installed or removed at any time according to wafer size and process requirements, significantly saving time and improving coating efficiency. Nozzle arrays also effectively reduce stacking defects at junctions. In all coating processes, photoresist diffuses freely on the wafer, forming uneven boundaries. This is especially true for atomized coating, where the concentration is relatively low at the conical boundary, resulting in the most severe defects. During multiple scans with a single nozzle, overlaps or gaps are easily generated at the coating boundaries. The nozzle array method allows for simultaneous scanning motions, eliminating boundaries between nozzles and fundamentally solving the problem of uneven film thickness at junctions.

Claims

1. A wafer inkjet printing and coating process method, implemented based on a wafer inkjet printing and coating apparatus, wherein the wafer inkjet printing and coating apparatus comprises: Host computer, main controller, motion control system, stable ink supply system, adsorption and heating device, printing control system; The host computer and the main controller communicate using an Ethernet interface. The main controller connects to four subsystems: motion control system, stable ink supply system, adsorption and heating device, and inkjet control system. The main controller is directly connected to the motion control system using a parallel interface, connected to the adsorption and heating device using an RS485 interface, connected to the stable ink supply system using an RS485 interface, and connected to the inkjet control system using a fiber optic serial interface. The printing control system is responsible for controlling the voltage and frequency parameters of the printhead and feeding this information back to the main controller. By controlling the magnitude, sign, duration, and spraying frequency of the printhead voltage, the printhead can achieve uniform spraying of photoresist. Its characteristic is that it includes the following steps: Step 1: After placing the wafer on the Z-axis rotating platform, fix it using a vacuum adsorption device, and adjust the number, height, and installation spacing of the nozzles in nozzle groups A, B, and C. Step 2: Use interdigitated spraying to control the spraying of each nozzle and perform pretreatment on the wafer, including cleaning, heating and pretreatment; Before spraying begins, the host computer sends the start position, end position, and spraying interval of the X-axis to the main controller. The main controller records a spraying position every spraying interval between the start and end positions, calculating all spraying positions along the X-axis. During spraying, the nozzle moves along the X-axis, and the grating ruler provides feedback on the position information. When an odd-numbered nozzle reaches a spraying position, the nozzle controller applies voltage to perform one spraying operation. When an even-numbered nozzle reaches the same spraying position on the X-axis, it also performs one spraying operation through voltage control. Since odd and even nozzles are staggered on the Y-axis and have the same spraying position on the X-axis, the droplets sprayed by the even-numbered nozzles will fall into the gap between the droplets sprayed by the previous odd-numbered nozzles, and the two sets of droplets merge together, resulting in higher printing density and reliability. As the nozzle moves through each spraying position on the X-axis, the above voltage control is repeated to form a uniform photoresist film. Step 3: Set the peristaltic pump flow rate and turn on the peristaltic pump. Use nozzle group C to spray photoresist onto the wafer surface. Scan along the photoresist spraying path at the set speed and step size to form a uniform photoresist layer on the entire wafer surface. Step 4: Heat the wafer to remove liquid nitrogen and photoresist diluent, while increasing the thickness of the adhesive layer at the top of the trench to make the coating more uniform.

2. The wafer inkjet printing and coating process method according to claim 1, characterized in that, The motion control system includes an X-axis motion platform, a Y-axis motion platform, a Z-axis rotary platform, and a motion controller. The X-axis motion platform includes an X-axis servo motor, an X-axis grating ruler, and an X-axis lead screw. The Y-axis motion platform includes a Y-axis servo motor, a Y-axis grating ruler, and a Y-axis lead screw. The X and Y axis servo motors drive the lead screws to convert rotational motion into linear motion. The grating ruler is mounted on the lead screw slide to provide closed-loop control of the nozzle displacement. The X-axis motion platform is bolted to the lead screw slide of the Y-axis motion platform and moves with the Y-axis lead screw. The Z-axis rotary platform includes a Z-axis servo motor and a turntable. The Z-axis servo motor drives the turntable to rotate. The servo motors and grating rulers are connected to the motion controller, which receives and processes the displacement signals from the X and Y axis grating rulers, applies motion signals to the servo motors for control, and the motion controller is connected to the main controller.

3. The wafer inkjet printing and coating process method according to claim 1, characterized in that, The stable ink supply system includes a negative pressure unit, a peristaltic pump, three two-way valves, and three ink cartridges. The three ink cartridges store different liquids M, N, and photoresist solutions respectively. The negative pressure unit is connected to the three ink cartridges to provide negative pressure. The peristaltic pump is connected to the ink cartridge storing the photoresist solution, and the main controller controls the spraying flow rate of the peristaltic pump. Each of the three two-way valves is connected between the three ink cartridges and the printhead assembly, controlling the on / off operation of the printhead assembly. Each two-way valve is controlled by a signal line from the main controller; a high voltage signal opens the two-way valve, and a low voltage signal closes it.

4. The wafer inkjet printing and coating process method according to claim 1, characterized in that, The adsorption and heating device includes a vacuum adsorption device and a heating device; The vacuum adsorption device is installed on the turntable to generate a vacuum negative pressure to fix the wafer; The heating device is installed under the turntable to heat the wafer on the turntable. It includes a heating module, a temperature detection module, and a temperature controller. The heating module and the temperature detection module are respectively connected to the temperature controller, which is connected to the main controller. The temperature controller compares the detected temperature with the set temperature sent by the main controller and controls the switch of the heating module to control the wafer temperature. The heating module heats the wafer. When the detected temperature is lower than the preset temperature, the switch is closed to heat the wafer. Otherwise, the switch is opened to stop heating and allow the wafer to cool naturally.

5. The wafer inkjet printing and coating process method according to claim 1, characterized in that, The nozzle array requires multiple nozzles to be installed in a staggered manner along the Y-axis, meaning that adjacent nozzles within a nozzle group are installed at certain intervals along both the X and Y axes; the installation spacing between two adjacent nozzles along the Y-axis... , satisfy ,in This indicates the preset installation error value. D represents the nozzle spacing of a single nozzle. The installation spacing D3 between two adjacent nozzles in the X-axis direction within each nozzle group should be the minimum installation distance, that is, the minimum value should be taken under the condition that nozzle installation is allowed.

6. The wafer inkjet printing and coating process method according to claim 5, characterized in that, The spraying process of the nozzle array is as follows: the motor controls the movement of the nozzles, and the grating ruler provides feedback on the displacement information; the nozzle group first moves along the X-axis. After the nozzle group reaches the starting position on the X-axis, the first nozzle begins spraying. After the nozzle group moves D3 along the X-axis, the second nozzle begins spraying, and after moving D3 again, the third nozzle begins spraying. This process is repeated until all nozzles begin spraying. After reaching the ending position on the X-axis, the first nozzle stops spraying. After the nozzle moves D3 along the X-axis, the second nozzle stops spraying, and after moving D3 again, the third nozzle stops spraying. This process is repeated until all nozzles stop spraying. Then the nozzles move along the Y-axis to the uncoated area of ​​the wafer, and the above operation is repeated for the next spraying.

7. The wafer inkjet printing and coating process method according to claim 1, characterized in that, Step 2 involves pre-processing the wafer, specifically described as follows: Cleaning: Control the nozzle group A to spray high-speed, high-flow liquid M, scan the entire wafer according to the preset cleaning path, and at the same time start the turntable to drive the wafer to rotate at high speed to clean the dust. Heating: Start heating to perform temperature treatment on the wafer and remove residual liquid M; Pre-processing: Control the nozzle group B to spray liquid N, and scan the entire wafer according to the preset scanning path. The liquid N sprayed on the wafer surface can improve the uniformity of photoresist spraying.

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