Fine atomization resonant cavity structure and gluing method

Abstract

The invention relates to the technical field of photoresist coating of wafer level packaging, in particular to a fine atomization resonant cavity structure and a gluing method.The fine atomization resonant cavity structure comprises a resonant cavity, a spherical resonant cavity is arranged in the resonant cavity, and the diameter of the spherical resonant cavity is integer multiples of the half-wavelength of ultrasonic excitation; the top end of the resonant cavity is provided with an opening for ultrasonic excitation input, and the bottom end of the resonant cavity is provided with an acoustic resonance resonant cavity; and the liquid supply needle is inserted into the acoustic resonance cavity from the resonance cavity. According to the structure and the method, the uniformity of photoresist spraying and the quality of a film layer can be improved, accurate sound field regulation and control are utilized, a micro-channel is not needed to provide fluid flow, and the potential problem of spray hole blockage is avoided; the acoustic wave is focused in the resonant cavity, and liquid drops can be broken in an extremely short time, so that the atomization particle size is small, the concentration ratio is high, and the film thickness of the photoresist is uniform and controllable; and the film layer uniformity is high, the film layer defects are few, the conformal coating of the complex three-dimensional microstructure can be realized without being limited by the surface morphology of the wafer.

Description

Technical Field

[0001] The invention relates to the technical field of photoresist coating for wafer-level packaging, and in particular to a fine atomized resonant cavity structure and a coating method. Background Art

[0002] The rapid development of micro-electromechanical systems (MEMS) and three-dimensional integrated circuits (3D-IC) has brought new challenges to advanced semiconductor processes, especially nanoscale integrated circuits. Photolithography is the core link in chip manufacturing. In order to meet the growing demand for small-size and highly integrated devices, conformal coating must be achieved on structural surfaces such as grooves, V-grooves and through-silicon vias (TSVs), and the diameter and concentration of the atomized droplets directly affect the reliability of integrated circuits and the yield of devices.

[0003] Traditional photoresist coating mainly adopts spin coating process. Its principle is to use the centrifugal force of high-speed rotation to spread the photoresist on the surface of the wafer to form a film layer on the wafer substrate that is rotating at a high speed. The thickness and uniformity of the spin coating depend on factors such as the viscosity coefficient of the photoresist and the substrate, the rotation speed, the rotation time and the surface morphology characteristics. However, 1. Spin coating technology is usually only suitable for the coating of a single layer of thin film, and it is difficult to achieve precise control for spraying applications with specific thickness requirements; 2. For wafer substrates with complex microstructures, the radial flow of photoresist in the spin coating process causes the colloid to gather in the local area of ​​the microstructure, making it difficult to accurately control the thickness and uniformity of the photoresist coating; 3. For larger or non-circular wafers, spin coating technology will face operational difficulties or uneven coating problems, resulting in differences in film thickness in the edge and center areas of the wafer; 4. During the rotation process, excess photoresist will be thrown off, resulting in a large amount of photoresist being wasted, especially when the film thickness is small.

[0004] The main principle of conventional ultrasonic photoresist atomization spraying technology is to use high-frequency vibration to form photoresist droplets into fine droplets. The driving frequency of this type of atomization technology is usually 100-200kHz, and the atomization scale is 18μm. It is difficult to accurately control the size of the atomized droplets, and the particle size distribution of the atomized droplets is uneven, resulting in inconsistent photoresist film thickness, thereby affecting the exposure effect and the accuracy of pattern transfer. For silicon through-hole structures with large "aspect ratios" (≥5:1), smaller and more evenly distributed photoresist particles are required to achieve good conformal coverage. In addition, conventional ultrasonic atomization delivers the atomized solution to the atomization surface through microchannels, which can easily cause blockage problems and bring many hidden dangers to atomization spraying.

[0005] As the integrated circuit manufacturing process has entered the 10nm stage, its highly integrated microstructure devices have the characteristics of non-flat surfaces (channels, steps, V-grooves and deep holes). The current ultrasonic atomization spraying technology has many difficulties in uniformly coating complex microstructures, which restricts the further development of semiconductor device manufacturing processes. Therefore, a new fine atomization resonant cavity structure is urgently needed to achieve fine and uniform spraying of photoresist. The present invention optimizes a resonant cavity design, which can produce smaller and more uniform atomized droplets, and improve the film quality and film thickness consistency of the photoresist. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a fine atomization resonant cavity structure and a gluing method, which can improve the uniformity of photoresist spraying and the quality of the film layer, utilize precise acoustic field control, and do not require microchannels to provide fluid flow, thereby avoiding potential nozzle blockage problems; the sound waves are focused in the resonant cavity, and the droplets will break up in a very short time, resulting in a small atomization particle size and high concentration, thereby achieving uniform and controllable photoresist film thickness; the film layer has high uniformity and few film layer defects, is not limited by the surface morphology of the wafer, and can achieve conformal coating of complex three-dimensional microstructures.

[0007] The technical solution of the present invention is as follows: A resonant cavity structure for fine atomization includes a resonant cavity, a spherical resonant cavity is arranged inside the resonant cavity, the diameter of the spherical resonant cavity is an integer multiple of half the wavelength of ultrasonic excitation, an opening for ultrasonic excitation input is arranged at the top of the resonant cavity, and an acoustic resonance cavity is arranged at the bottom of the resonant cavity; a liquid supply needle is inserted from the resonant cavity into the acoustic resonance cavity.

[0008] The material of the resonant cavity structure is any one of metal, resin, plastic, quartz, glass, acrylic or nylon.

[0009] The excitation source of the ultrasonic excitation is any one of a piezoelectric ultrasonic transducer, a magnetostrictive transducer, an electrostatic transducer or a mechanical ultrasonic transducer.

[0010] The frequency range of ultrasonic excitation can be 0-2 MHz.

[0011] The top opening of the resonance cavity is circular or polygonal.

[0012] A fine atomization glue coating method, using a fine atomization glue coating device, the fine atomization glue coating device comprising an ultrasonic driving device, an ultrasonic excitation device, an acoustic wave focusing device, a liquid supply device and a motion device; The ultrasonic driving device is used to drive the ultrasonic excitation device to generate high-frequency ultrasonic vibration in the longitudinal direction; The ultrasonic excitation device includes a transducer, a horn and a tool head; The sound wave focusing device comprises a spherical resonant cavity and an acoustic resonant cavity, and is used to form a stable standing wave field in the acoustic resonant cavity through the reflection effect of the spherical resonant cavity on the sound wave; The liquid supply device is used to deliver the photoresist droplets to the position of the standing wave node in the acoustic resonance cavity; The motion device is used to drive the fine atomization glue coating device to complete scanning of the entire wafer; The use of the fine atomization glue coating device includes the following steps: Step 1: Fix the ultrasonic excitation device on the acoustic wave focusing device, with the two being coaxial in the vertical direction, and inserting the tool head of the ultrasonic excitation device into the spherical resonant cavity of the acoustic wave focusing device; Step 2: Adjust the distance from the tool head to the bottom of the spherical resonant cavity to an integer multiple of the ultrasonic half wavelength; Step 3: fix the needle of the liquid supply device at the position of the standing wave node of the acoustic resonance cavity, and the photoresist solution flows out of the needle to form droplets to the position of the standing wave node; Step 4: The ultrasonic driving device drives the ultrasonic excitation device, and the ultrasonic excitation device generates ultrasonic waves that propagate through the tool head into the spherical resonant cavity, forming a stable standing wave in the spherical resonant cavity; Step 5: Use a motion device to drive the scanning of the entire wafer in the X and Y axis directions.

[0013] The liquid supply device is provided with a flow control pump for controlling the flow rate of the photoresist.

[0014] The fine atomization glue coating method includes the following steps: Preparation stage: fix the acoustic wave focusing device on the motion device, adjust the relative positions of the ultrasonic excitation device, the spherical resonant cavity, the acoustic resonant cavity and the liquid supply needle, inject the photoresist into the acoustic resonant cavity, and preset the spraying parameters; Atomization stage: The ultrasonic excitation device is started, which generates high-frequency vibrations to generate stable standing waves in the spherical resonant cavity. The acoustic resonant cavity focuses and enhances the acoustic waves, and then atomizes the photoresist droplets at the nodes of the standing waves into tiny droplets. Spraying stage: The motion device adjusts the motion speed and step distance of the X and Y axes through the host computer to scan the entire wafer to ensure the uniformity of the coating and the consistency of the film thickness; Drying stage: After spraying, use ultraviolet light to quickly cure the photoresist, shorten the drying time and improve production efficiency; Maintenance phase: Clean the acoustic wave focusing device and ensure that there is no photoresist residue on the acoustic wave focusing device.

[0015] The beneficial effects of the present invention are: 1. The present invention discloses a resonant cavity structure and a gluing method for fine atomization. The resonant cavity structure and the gluing method for fine atomization form a focusing standing wave field through the curved surface structure of the resonant cavity, thereby realizing the focusing enhancement of the sound wave energy. Compared with the traditional contact ultrasonic atomization method, a smaller particle size and a more concentrated particle size distribution can be achieved.

[0016] 2. The present invention discloses a fine atomization resonant cavity structure and a coating method, which significantly improves the uniformity of the film thickness of the photoresist by adjusting the process parameters of the spraying, and effectively improves the yield of the subsequent exposure process. Especially when dealing with MEMS wafers with a large aspect ratio structure, a smaller droplet size is a prerequisite for conformal coating in TSV holes.

[0017] 3. The present invention discloses a resonant cavity structure for fine atomization and a gluing method. The resonant cavity structure for fine atomization and the gluing method utilize the non-contact propagation characteristics of sound waves and optimize the resonant cavity structure for fine atomization to achieve regulation of the sound field. The photoresist droplets achieve non-contact atomization by absorbing ultrasonic energy. Compared with contact ultrasonic atomization, microchannels are not required to supply liquid to the atomization surface, which effectively avoids the problem of nozzle clogging.

[0018] 4. The present invention discloses a resonant cavity structure for fine atomization and a gluing method. The resonant cavity structure for fine atomization and the gluing method have a simple structure design, are easy to clean and maintain, and reduce the maintenance cost of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] By reading the detailed description of the preferred embodiment below, the scheme and advantages of the present application will become clear to those skilled in the art. The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present invention.

[0020] In the attached picture: Figure 1 A schematic diagram of a resonant cavity structure for fine atomization according to an embodiment of the present invention; Figure 2 The sound field distribution in the acoustic resonance cavity of a resonant cavity structure for fine atomization according to an embodiment of the present invention; Figure 3 The relationship between the diameter, length and sound pressure of the acoustic resonance cavity of a resonant cavity structure for fine atomization according to an embodiment of the present invention; Figure 4 The standing wave sound field particle velocity and sound pressure curve of a resonant cavity structure for fine atomization according to an embodiment of the present invention; The components represented by the reference numerals in the figure are: The present invention comprises: 1. an amplitude transformer, 2. a tool head, 3. a spherical resonance cavity, 4. a liquid supply needle, 5. an acoustic resonance cavity, and 6. a photoresist droplet. DETAILED DESCRIPTION

[0021] The fine atomization glue coating device includes: an ultrasonic driving device, an ultrasonic excitation device, an acoustic wave focusing device, a liquid supply device, and a motion device. The ultrasonic driving device mainly includes a signal generator and a power amplifier. The ultrasonic excitation device includes a transducer, a horn and a tool head. The acoustic wave focusing device includes an acoustic resonance cavity. The liquid supply device mainly includes a flow pump, a pipeline, a liquid supply needle, and a liquid circuit connector. The motion device includes a servo unit, a grating, a lead screw, a controller, etc.

[0022] like Figure 1 As shown, there is no requirement for the external shape of the acoustic wave focusing device (resonant cavity structure for fine atomization), the internal structure of the cavity is spherical, the spherical diameter is an integer multiple of the half wavelength of the ultrasonic excitation, an opening is left at the top of the resonant cavity structure for fine atomization for ultrasonic excitation input, and the acoustic resonance cavity is arranged at the bottom of the resonant cavity structure for fine atomization.

[0023] The materials of the resonant cavity structure of fine atomization include but are not limited to metal, resin, plastic, quartz, glass, acrylic, nylon and the like.

[0024] The excitation source for generating ultrasonic excitation includes, but is not limited to, a piezoelectric ultrasonic transducer, a magnetostrictive transducer, an electrostatic transducer or a mechanical ultrasonic transducer.

[0025] The frequency range of ultrasonic excitation can be 0-2 MHz.

[0026] The opening at the top of the resonant cavity structure for fine atomization includes, but is not limited to, polygons such as circle, triangle, quadrilateral, pentagon, hexagon, etc.

[0027] The acoustic resonance cavity includes, but is not limited to, a spherical, ellipsoidal, cylindrical, prismatic, and the like.

[0028] A photoresist spraying method for a finely atomized resonant cavity structure comprises the following steps: Preparation stage: Fix the fine atomization resonant cavity device on the motion mechanism, adjust the relative positions of the acoustic wave excitation device, the resonant cavity structure, the acoustic resonant cavity and the liquid supply needle, inject the photoresist into a specific position in the acoustic resonant cavity, and preset the spraying parameters (such as pressure, substrate temperature, flow rate, spraying speed, step distance, spraying height, photoresist ratio, etc.).

[0029] Atomization stage: Start the ultrasonic excitation device, which generates high-frequency vibrations to produce stable standing waves in the resonant cavity structure of fine atomization. The acoustic resonant cavity focuses and enhances the sound waves, and then atomizes the photoresist droplets at the standing wave nodes into tiny droplets.

[0030] Spraying stage: The motion device adjusts the movement speed and step distance of the X and Y axes through the host computer to scan the entire wafer to ensure the uniformity of the coating and the consistency of the film thickness.

[0031] Drying stage: After spraying is completed, ultraviolet light is used to quickly cure the photoresist, shortening the drying time and improving production efficiency.

[0032] Maintenance stage: Clean the fine atomization resonant cavity structure and nozzle to ensure that there is no photoresist residue in the fine atomization resonant cavity structure and the acoustic resonant cavity.

[0033] Driven by the ultrasonic drive device, the ultrasonic excitation device generates high-frequency ultrasonic vibrations in the longitudinal direction, and through the reflection of the spherical resonant cavity on the sound wave, a stable standing wave field is formed in the acoustic spherical resonant cavity. This patent innovatively introduces the resonance effect of the sound wave into non-contact atomization, and uses the coupling effect between the diffraction wave and the waveguide mode in the subwavelength resonator to generate a precisely controlled and highly localized standing wave acoustic field. That is, the ultrasonic energy is focused in the acoustic resonant cavity. Kinetic energy and potential energy are continuously converted between the wave node and the anti-node. The edge of the droplet located at the standing node will produce stronger instability. Under high ultrasonic energy, the droplet will be broken and atomized in a very short time, resulting in a smaller particle size and a more concentrated particle size concentration. By optimizing the spraying process (pressure, substrate temperature, flow rate, spraying speed, step distance, spraying height, photoresist ratio, etc.), the controllability of the film thickness and the uniformity of the film layer are improved to achieve conformal coating of the structural wafer.

[0034] The specific implementation steps are as follows: Step 1: Fix the ultrasonic excitation device on the spherical resonant cavity, ensuring that the two are coaxial in the vertical direction. The tool head of the ultrasonic excitation device extends into the spherical resonant cavity, and the longitudinal height of the tool head can be adjusted.

[0035] Step 2: Adjust the distance from the tool head to the bottom of the spherical resonant cavity to an integer multiple of the ultrasonic half wavelength.

[0036] Step 3: Fix the liquid supply needle at the position of the standing wave node of the acoustic resonance cavity. The photoresist solution flows out of the needle to form droplets to the position of the standing wave node. The liquid supply needle is connected to an external flow control pump to control the flow rate of the photoresist.

[0037] Step 4: The driving device drives the ultrasonic excitation device by adjusting the frequency, phase, waveform and power of the output signal. The ultrasonic excitation generates ultrasonic waves which propagate through the tool head to the spherical resonant cavity, forming a stable standing wave in the spherical resonant cavity.

[0038] Step 5: Fix the atomization device on the motion device, and use the host computer to adjust the movement speed and step distance of the X and Y axes of the motion device to scan the entire wafer.

[0039] The ultrasonic driving device provides ultrasonic energy input for the ultrasonic excitation device, mainly includes a signal generator and a power amplifier, and drives the ultrasonic excitation device by adjusting the frequency, phase, waveform and power of the output signal.

[0040] The ultrasonic excitation device converts the alternating electrical signal into an acoustic signal within the ultrasonic frequency range, mainly providing ultrasonic energy input for the fine atomization resonance cavity. The ultrasonic excitation device includes but is not limited to a piezoelectric transducer, a magnetostrictive transducer, an electrostatic transducer or a mechanical ultrasonic transducer. In order to improve the acoustic wave transmission efficiency of the piezoelectric ceramic sheet, the transducer is connected to the horn below by a thread. The structure of the horn can be a stepped, exponential or composite structure, and the length of the horn is usually an integer multiple of the half wavelength of the ultrasonic excitation source. The end of the horn is equipped with a metal block as a tool head, and the ultrasonic wave is transmitted to the acoustic wave focusing device through the tool head. The ultrasonic frequency in the present invention can be 0-2MHz.

[0041] The spherical resonant cavity structure uses the radiation end of the ultrasonic excitation device to generate high-frequency vibrations to form a sound field in the medium, and places a reflection end on the sound wave transmission path to make the sound wave reflected back and superimposed on the incident sound wave. The distance between the radiation end face and the reflection end face is adjusted to an integer multiple of the half wavelength of the ultrasonic wave. The incident wave and the reflected wave are repeatedly superimposed in the sound field space to form a high-intensity spherical standing wave sound field. The particle velocity and sound pressure curves of the standing wave sound field are shown in Figure 1. Figure 2 As shown, the droplets placed in the standing wave acoustic field are subjected to the effect of the radiated acoustic pressure, thereby achieving non-contact atomization of the photoresist droplets.

[0042] Compared with the conventional contact atomization method, the material of the atomizing nozzle in the present invention is not necessarily metal, and the spherical resonant cavity includes but is not limited to metal, resin, plastic, quartz, glass, acrylic, and nylon. In order to form a higher sound pressure gradient in the spherical resonant cavity, the diameter of the spherical resonant cavity is an integer multiple of half the wavelength.

[0043] The acoustic field distribution of the acoustic resonance cavity is as follows: Figure 3 As shown. The acoustic resonant cavity is fixed at the bottom of the spherical resonant cavity, that is, the antinode of the standing wave in the spherical resonant cavity. The material of the acoustic resonant cavity can be metal, resin, plastic, quartz, glass, acrylic, nylon. The shape of the acoustic resonant cavity can be spherical, ellipsoidal, cylindrical, prism or other polygonal shapes. The relationship between the diameter and length of the acoustic resonant cavity and the sound pressure is shown in Figure 4 shown.

[0044] The liquid supply device mainly provides flow supply for photoresist atomization. The liquid supply device can be a flow pump. The liquid supply device is connected to the liquid supply needle in the middle of the acoustic resonance cavity through a pipeline. The photoresist liquid flows out from the liquid supply needle tip, aiming to match the relationship between the atomized droplet flow and the ultrasonic energy of the acoustic cavity. It is worth noting that in the present invention, the needle thickness is only used as a liquid supply mechanism under a specific sound field intensity. As the sound field energy input increases, the nozzle diameter can be enlarged to increase the liquid supply flow.

[0045] The liquid supply needle is fixed at the position of the standing wave node of the acoustic resonance cavity, and the photoresist solution flows out from the needle to form droplets to the position of the standing wave node. The liquid supply needle is connected to an external flow control pump to control the photoresist flow.

[0046] The motion device described above: The fine atomization resonant cavity is vertically fixed on the motion mechanism. The motion device scans the wafer in an "S" shape by controlling the motion speed and splicing width of the motor in the X and Y axes to ensure that the entire wafer is completely covered. During this process, the solvent in the photoresist evaporates and leaves a uniform photoresist film layer.

[0047] Through the above-mentioned specific implementation methods, the fine atomization resonant cavity structure can be effectively utilized to achieve efficient and uniform photoresist spraying, providing reliable technical support for semiconductor manufacturing.

Claims

1. A resonant cavity structure for fine atomization, characterized in that: The invention comprises a resonant cavity, wherein a spherical resonant cavity (3) is arranged inside the resonant cavity, the diameter of the spherical resonant cavity (3) is an integral multiple of half the wavelength of ultrasonic excitation, an opening for ultrasonic excitation input is arranged at the top end of the resonant cavity, and an acoustic resonance cavity (5) is arranged at the bottom end of the resonant cavity; a liquid supply needle (4) is inserted from the resonant cavity into the acoustic resonance cavity (5).

2. A resonant cavity structure for fine atomization according to claim 1, characterized in that: The resonant cavity structure is made of any one of metal, resin, plastic, quartz, glass, acrylic or nylon.

3. The resonant cavity structure for fine atomization according to claim 1, characterized in that: The excitation source of the ultrasonic excitation is any one of a piezoelectric ultrasonic transducer, a magnetostrictive transducer, an electrostatic transducer or a mechanical ultrasonic transducer.

4. The resonant cavity structure for fine atomization according to claim 3, characterized in that: The frequency range of the ultrasonic excitation may be 0-2 MHz.

5. The resonant cavity structure for fine atomization according to claim 1, characterized in that: The top opening of the resonance cavity is circular or polygonal.

6. A fine atomization gluing method, characterized in that: Using a fine atomization glue coating device, the fine atomization glue coating device includes an ultrasonic driving device, an ultrasonic excitation device, an acoustic wave focusing device, a liquid supply device and a motion device; The ultrasonic driving device is used to drive the ultrasonic excitation device to generate high-frequency ultrasonic vibration in the longitudinal direction; The ultrasonic excitation device comprises a transducer, a horn (1) and a tool head (2); The sound wave focusing device comprises a spherical resonant cavity (3) and an acoustic resonant cavity (5), and is used to form a stable standing wave field in the acoustic resonant cavity (5) through the reflection effect of the spherical resonant cavity (3) on the sound waves; The liquid supply device is used to deliver the photoresist droplets (6) to the position of the standing wave node in the acoustic resonance cavity (5); The motion device is used to drive the fine atomization glue coating device to complete scanning of the entire wafer; The use of the fine atomization glue coating device comprises the following steps: Step 1: fix the ultrasonic excitation device on the acoustic wave focusing device, with the two being coaxial in the vertical direction, and the tool head (2) of the ultrasonic excitation device extending into the spherical resonance cavity (3) of the acoustic wave focusing device; Step 2: adjusting the distance between the tool head (2) and the bottom of the spherical resonant cavity (3) to an integer multiple of a half wavelength of ultrasound; Step 3: fix the needle of the liquid supply device at the position of the standing wave node of the acoustic resonance cavity (5), and the photoresist solution flows out of the needle to form droplets at the position of the standing wave node; Step 4: The ultrasonic driving device drives the ultrasonic excitation device, and the ultrasonic excitation device generates ultrasonic waves which are propagated through the tool head (2) to the spherical resonant cavity (3), thereby forming a stable standing wave in the spherical resonant cavity (3); Step 5: Use a motion device to drive the scanning of the entire wafer in the X and Y axis directions.

7. A fine atomization gluing method according to claim 6, characterized in that: The liquid supply device is provided with a flow control pump for controlling the flow rate of the photoresist.

8. A fine atomization gluing method according to claim 6, characterized in that: The following steps are involved: Preparation stage: fix the acoustic wave focusing device on the moving device, adjust the relative positions of the ultrasonic excitation device, the spherical resonant cavity (3), the acoustic resonant cavity (5) and the liquid supply needle (4), inject the photoresist into the acoustic resonant cavity (5), and preset the spraying parameters; Atomization stage: the ultrasonic excitation device is started, the ultrasonic excitation device generates high-frequency vibration to generate a stable standing wave in the spherical resonant cavity (3), and the acoustic resonant cavity (5) focuses and enhances the acoustic wave to atomize the photoresist droplets (6) located at the nodes of the standing wave into tiny droplets; Spraying stage: The motion device adjusts the motion speed and step distance of the X and Y axes through the host computer to scan the entire wafer to ensure the uniformity of the coating and the consistency of the film thickness; Drying stage: After spraying, use ultraviolet light to quickly cure the photoresist, shorten the drying time and improve production efficiency; Maintenance phase: Clean the acoustic wave focusing device and ensure that there is no photoresist residue on the acoustic wave focusing device.

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