Laser cleaning and repairing integrated equipment and process for OLED (Organic Light Emitting Diode) micro display

Abstract

The invention discloses laser cleaning and repairing integrated equipment and process for an OLED micro display, the equipment comprises a femtosecond laser, a mobile platform, a light path module, an image detection system and a control system, the light path module spreads laser emitted by the femtosecond laser to a bonding pad on the mobile platform, and meanwhile, the adjustment of the wavelength of a light beam and the size of a light spot can be realized; and the image detection system is used for acquiring an image and visual positioning of the bonding pad in the processing process. The equipment integrates laser material processing, the light path module and the high-precision moving platform, two laser processing functions of cleaning and repairing can be realized on the same equipment by adjusting laser through the light path module, and meanwhile, the accuracy of repairing and positioning can be effectively improved through mutual cooperation of the image detection system and the moving platform, so that the working efficiency is improved. And the machining precision and the production efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of pad cleaning technology for microdisplays, and particularly to an integrated cleaning and repair device and process for OLED microdisplays. Background Technology

[0002] OLED microdisplays integrate silicon-based driving circuits with organic light-emitting layers and are widely used in head-mounted displays, augmented reality / virtual reality, and targeting devices. During their manufacturing process, after forming metal leads and pads (PADs) on a silicon substrate, multiple photolithography, deposition, and etching processes are required. Following front-end processes such as oxidation, nitriding, and organic coating, aluminum oxide (Al2O3) coatings, silicon nitride (Si3N4) films, organic photoresists, and Parylene layers often remain on the PAD surface. These residues hinder metal bonding and must be thoroughly removed before evaporation and encapsulation.

[0003] Current cleaning technologies mostly employ excimer lasers in conjunction with homogenizing lenses and masks to process the PAD surface. This achieves patterned cleaning while avoiding the thermal damage caused by wet chemical or plasma cleaning. However, excimer lasers are nanosecond-level ultraviolet pulses with long energy deposition times and large heat-affected zones, making them only suitable for removing soft materials such as organic photoresists. They are difficult to selectively remove hard inorganic films such as aluminum oxide and silicon nitride. Furthermore, this type of light source lacks micron-level localized carbonization capabilities, making it impossible to accurately repair bright pixels generated during the evaporation and encapsulation processes of OLED microdisplays. Therefore, it is difficult to simultaneously integrate cleaning and repair processes. Typically, one excimer laser cleaning unit and one laser repair unit are needed to complete residual layer removal and bright spot carbonization repair, respectively. This results in high equipment investment, complex production lines, and problems with secondary alignment errors and low efficiency. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides an integrated laser cleaning and repair device and process for OLED microdisplays. The same device can clean and repair residual layers (aluminum oxide (Al2O3) coating, silicon nitride (Si3N4) film, organic photoresist, and Parylene, etc.) in OLED microdisplays, with accurate positioning and high processing precision.

[0005] An integrated laser cleaning and repair device for OLED microdisplays includes:

[0006] Femtosecond lasers, with output wavelengths in the ultraviolet or near-infrared range, pulse widths less than 1 picosecond, and adjustable average power and single-pulse energy, are used to provide the femtosecond laser beams required for cleaning and repair.

[0007] The moving platform is configured to move horizontally and is used to place the pads to be processed. The moving platform is driven by air bearings or linear motors and has micron-level positioning accuracy and high-speed movement capability.

[0008] The optical path module is used to propagate the laser emitted by the femtosecond laser to the pads on the moving platform, and is also used to adjust the beam wavelength and spot size. This optical path module can achieve different wavelengths and spot sizes in the same optical path, and can also work with the moving platform to achieve different scanning speeds, so as to meet the needs of non-destructive cleaning mode of various residual layers such as "aluminum oxide, silicon nitride, Parylene and photoresist" and local carbonization repair mode of bright pixels.

[0009] Image detection system, used to acquire images and visually locate pads during processing;

[0010] The control system is connected to the femtosecond laser, the moving platform, the optical path module, and the image detection system respectively. It is used to comprehensively control the output parameters of the femtosecond laser, the movement of the moving platform, the wavelength switching and spot adjustment of the optical path module, and the shooting and focusing of the image detection system. It is also used to generate and issue scanning path instructions based on preset process parameters and / or imported coordinate files to realize the configuration of processing parameters and spot positioning in cleaning mode and repair mode.

[0011] The integrated laser cleaning and repair equipment for OLED microdisplays includes a cleaning mode and a repair mode.

[0012] In cleaning mode, the control system retrieves cleaning process parameters based on the residual layer material type and preset thickness parameters corresponding to the pads to be processed, as recorded in the process database. The image detection system acquires the surface state of the pads before and after cleaning and feeds the monitoring results back to the control system to confirm the cleaning effect or make necessary parameter adjustments. The control system then drives the femtosecond laser, optical path module, and moving platform to perform the cleaning process. The high peak power of the femtosecond laser causes the material layer to be cleaned to be directly ablated through nonlinear absorption, resulting in a small heat-affected zone. This effectively removes aluminum oxide (Al2O3) coatings, silicon nitride (Si3N4) films, and residues such as organic photoresists and Parylene without damaging the metal electrodes or silicon substrate.

[0013] In the repair mode, the image detection system completes the coordinate positioning of the bright pixel of the OLED microdisplay. The control system sets the pulse energy and scanning number of the femtosecond laser according to the color and transmittance threshold of the bright pixel, and controls the optical path module and moving platform according to the imported bright pixel coordinates to position the focused spot in the bright pixel area for spot repair. The repair mode uses the femtosecond laser to locally carbonize or evaporate the color filter or transparent conductive layer at the bright pixel to form a light-shielding layer, turning the bright spot into a dark spot.

[0014] Furthermore, the optical path module includes a harmonic generator, a beam expander, a beam shaper, a scanning galvanometer, and a focusing system arranged sequentially along the beam propagation direction;

[0015] The harmonic generator is used to perform frequency doubling or third harmonic conversion on the fundamental frequency light output by the femtosecond laser to generate lasers of various wavelengths suitable for cleaning or repairing bright spots of different residual layer materials.

[0016] The beam expander is used to expand or shrink the laser beam at a predetermined magnification, and to adjust the beam diameter and divergence angle so that it has a beam size and collimation characteristics suitable for subsequent shaping and focusing processes.

[0017] The beam shaper is used to homogenize the energy distribution and control the beam profile of the expanded laser beam, shaping the beam into a uniform beam, a Gaussian beam, or other preset beam shapes to meet the different requirements of cleaning mode and repair mode for beam energy distribution.

[0018] The scanning galvanometer is used to deflect the beam at high speed according to the instructions of the control system, so as to realize the rapid scanning of the preset processing path and the dynamic positioning of the target area.

[0019] The focusing system is used to precisely focus the laser beam, after being deflected by the scanning galvanometer, onto the area to be processed, forming large spot sizes of hundreds of micrometers or small spot sizes of micrometers according to the required processing mode, thereby meeting the different spot size and energy density requirements for residual layer cleaning or bright pixel repair.

[0020] Furthermore, the optical path module achieves adjustable output of wavelength and spot size through the synergistic action of a harmonic generator, beam expander, beam shaper, scanning galvanometer, and focusing system: the harmonic generator selects to output fundamental frequency light or its harmonics according to the control system command to obtain different wavelengths suitable for cleaning or repair; the beam expander adjusts the beam diameter and divergence angle to provide suitable incident conditions for spot formation required for different modes; the beam shaper generates a flat-topped uniform spot in cleaning mode and a local Gaussian spot in repair mode; the focusing system selects optical components with different focal lengths or numerical apertures to focus the above beams into large spots of hundreds of micrometers or small spots of micrometers, thereby completing wavelength switching and spot size switching within the same optical path.

[0021] Furthermore, the image detection system includes:

[0022] A microscope camera is used to acquire the surface condition of the pads before and after cleaning and to locate the coordinates with high precision.

[0023] Coaxial illumination and energy monitors are used to monitor the laser focus and energy.

[0024] Furthermore, in repair mode, the identification and positioning of bright pixels are based on the bright pixel coordinates obtained from the microdisplay defect detection process. The specific process includes: in the OLED microdisplay defect detection process, optical inspection is performed on the display pixels by illuminating the product under inspection. The detection system identifies bright pixels with abnormal brightness and records the position of the bright pixels in the chip coordinate system using the motion platform of the inspection equipment. The bright pixel positions are then transformed to obtain bright pixel coordinate files in both the wafer coordinate system and the motion coordinate system of the inspection equipment. In repair mode, the control system of this equipment imports the bright pixel coordinate file and drives the moving platform and scanning galvanometer according to the bright pixel coordinates, causing the focused light spot to be sequentially positioned to the corresponding bright pixel position, performing localized carbonization repair on the bright pixel area.

[0025] Furthermore, in the cleaning mode, the pulse width of the femtosecond laser can be set to 50-400 fs, the repetition frequency can be 50kHz - 2MHz, the single pulse energy can be 0.2–10 µJ, and the spot diameter can be set to 50-600 µm as required.

[0026] In repair mode, the pulse width of the femtosecond laser can be set to 50-350 fs, the repetition frequency can be 1-50 kHz, the single pulse energy can be set to 0.1-3 µJ, and the spot diameter can be 1-5 µm as required.

[0027] The beneficial effects of this invention are:

[0028] (1) The present invention uses a femtosecond laser with adjustable parameters and an optical path module that adjusts the wavelength and spot size to meet the needs of non-destructive cleaning mode and local carbonization repair mode of various residual layers such as aluminum oxide, silicon nitride, Parylene and photoresist.

[0029] (2) The present invention achieves “cold ablation” processing through femtosecond pulses, resulting in a small heat-affected zone and avoiding damage to the metal electrodes and silicon-based driving circuits.

[0030] (3) The cooperation between the image detection system and the mobile platform can effectively improve the accuracy of positioning and increase production efficiency. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the integrated laser cleaning and repair equipment for OLED microdisplays in Example 1;

[0032] Figure 2 This is a schematic diagram of the optical path module in Example 1.

[0033] Figure label:

[0034] 9-Fundamental frequency light; 10-Femtosecond laser; 11-Harmonic generator; 12-Beam expander; 13-Beam shaper; 14-Scanning galvanometer; 15-Focusing system; 16-Moving platform; 17-Image detection system; 18-Control system. Detailed Implementation

[0035] The present invention will be further described in detail below through specific embodiments.

[0036] Example 1

[0037] like Figure 1 As shown in the figure, this embodiment discloses an integrated laser cleaning and repair device for OLED microdisplays. By combining a femtosecond laser with adjustable parameters and an optical path module that adjusts the wavelength and spot size, the cleaning mode and the local carbonization repair mode of bright pixels are integrated into the same device, thereby reducing equipment investment and improving production efficiency.

[0038] Specifically, the device includes: a femtosecond laser 10, a mobile platform 16, an optical path module, an image detection system 17, and a control system 18.

[0039] Among them, the femtosecond laser 10 has an output wavelength in the ultraviolet or near-infrared range, a pulse width of less than 1 picosecond, and adjustable average power and single pulse energy. The single pulse energy is 0.2–10 µJ in cleaning mode and 0.1–3 µJ in repair mode.

[0040] The optical path module includes a harmonic generator 11, a beam expander 12, a beam shaper 13, a scanning mirror 14, and a focusing system 15 arranged sequentially along the beam propagation direction. The coordinated action of these components enables adjustable output of wavelength and beam size. Specifically, the harmonic generator 11 performs frequency doubling or third harmonic conversion on the fundamental frequency light 9 output from the femtosecond laser according to control system commands to obtain different wavelengths suitable for cleaning or repair.

[0041] The beam expander 12 expands or shrinks the laser beam at a predetermined magnification and adjusts the beam diameter and divergence angle to give it a beam size and collimation characteristics suitable for subsequent shaping and focusing processes, thus providing suitable incident conditions for the formation of light spots required for different modes.

[0042] The beam shaper 13 homogenizes the energy distribution and modulates the beam profile of the expanded laser beam, shaping the beam into a uniform beam, a Gaussian beam, or other preset beam shapes. In cleaning mode, it generates a flat-top uniform beam, and in repair mode, it generates a local Gaussian beam.

[0043] The scanning galvanometer 14 deflects the beam at high speed according to the instructions of the control system 18, thereby realizing rapid scanning of the preset processing path and dynamic positioning of the target area.

[0044] The focusing system 15 precisely focuses the laser beam, after being deflected by the scanning galvanometer 14, onto the area to be processed, forming a large spot of hundreds of micrometers or a small spot of micrometers according to the required processing mode, thereby meeting the different spot size and energy density requirements for residual layer cleaning or bright pixel repair.

[0045] The mobile platform 16 is driven by an air bearing or a linear motor, and has micron-level positioning accuracy and high-speed movement capability. It is used to carry the substrate to be processed and to work with the scanning galvanometer to complete large-area processing.

[0046] The image inspection system 17 consists of a microscope camera, coaxial illumination, and an energy monitor. The microscope camera is used to acquire the surface condition of the pads before and after cleaning and to locate the coordinates with high precision. The coaxial illumination and energy monitor are used to monitor the laser focus and energy.

[0047] The control system 18 includes a graphics generation module, a process database, and a motion control module. The graphics generation module generates laser processing graphics and scanning paths based on process requirements. This includes: in cleaning mode, automatically generating corresponding surface scanning paths or line scanning trajectories based on parameters input from the control interface or program; and in repair mode, automatically generating point-by-point processing paths based on imported highlight coordinate files, and performing necessary rotation, offset, and scaling compensation on the coordinates to ensure the focused spot accurately falls on the target pixel. The processing graphics output by this module drive the scanning galvanometer 14 and the moving platform 16 to achieve precise beam positioning and scanning processing. The process database contains process parameters such as laser power, pulse width, scanning path, and moving speed for different processes and the conditions of the residue to be cleaned. The motion control module controls the moving platform 16 to move along the set path.

[0048] This device supports two operating modes:

[0049] Cleaning mode: The image detection system 17 is used to acquire the surface state of the pads before and after cleaning and to complete high-precision coordinate positioning. The control system 18 retrieves the cleaning parameters according to the residual layer material type and preset thickness parameters corresponding to the pads to be processed in the process database, selects the energy that matches the absorption rate of the residual layer material, and scans the PAD surface. The high peak power of the femtosecond laser enables the material to be directly ablated through nonlinear absorption. The heat-affected zone is small, which can effectively remove aluminum oxide (Al2O3) coating, silicon nitride (Si3N4) film, organic photoresist and Parylene residues without damaging the metal electrode or silicon substrate.

[0050] In repair mode, the identification and positioning of bright pixel is based on the bright pixel coordinates obtained from the microdisplay defect detection process. The specific process includes: In the OLED microdisplay defect detection process, optical inspection is performed on the display pixels by illuminating the product under inspection. The detection system identifies bright pixels with abnormal brightness and records the position of the bright pixel in the chip coordinate system using the motion platform of the inspection equipment. The bright pixel position is then processed by coordinate transformation to obtain a bright pixel coordinate file in both the wafer coordinate system and the motion coordinate system of the inspection equipment. In repair mode, the bright pixel coordinate file is imported into the control system of this equipment. The control system drives the moving platform 16 and the scanning galvanometer 14 according to the bright pixel coordinates, causing the focused light spot to be sequentially positioned to the corresponding bright pixel position. The image detection system 17 locates the bright pixel coordinates. The control system 18 sets the pulse energy and scanning number of the femtosecond laser 10 according to the input process parameters, and controls the optical path module and the moving platform 16 according to the imported bright pixel coordinates, causing the focused light spot to be positioned in the bright pixel area for bright pixel repair. The repair mode uses a femtosecond laser to locally carbonize or evaporate the color filter or transparent conductive layer at the bright pixel, forming a light-shielding layer and turning the bright spot into a dark spot.

[0051] The two modes can be selected through the control system software interface. The system automatically configures the optical path and scanning parameters, eliminating the need to replace hardware and enabling cleaning and repair to be completed in a single clamping operation.

[0052] The specific processes for different working modes are as follows:

[0053] PAD residue cleaning

[0054] 1) Equipment preparation: Mount the silicon substrate to be processed on the moving platform 16 and select the cleaning mode. Set the laser pulse width to 200 fs, repetition frequency to 200 kHz, single pulse energy to 2–5 µJ, and spot diameter to approximately 200 µm.

[0055] 2) Parameter settings: Select the scanning speed and line spacing according to the material and thickness of the residual layer. For example, when cleaning 80 nm thick silicon nitride, the scanning speed is 100 mm / s, the line spacing is 5 µm, and the pulse energy is 3 µJ; when cleaning the composite coating of aluminum oxide and silicon nitride, the energy is appropriately increased to 4 µJ to achieve direct ablation.

[0056] 3) Perform cleaning: Drive the scanning galvanometer 14 and the moving platform 16 to scan all PAD areas along a preset path. The image detection system 17 monitors the cleaning effect in real time, adjusting the energy or repeating the scan if necessary until the residual layer is completely removed.

[0057] Highlight Defect Repair

[0058] 1) Defect detection: Identify the location of bright pixel and record its coordinates using a microscope camera or an external automatic inspection system.

[0059] 2) Switching modes: Select the repair mode, reduce the focused spot size to about 2 µm, adjust the single pulse energy to 1-2 µJ, set the repetition frequency to 10kHz, and set the duration to 10ms.

[0060] 3) Carbonization Repair: Set an appropriate energy threshold based on the color of the bright sub-pixel, such as approximately 8% transmittance for green sub-pixels and approximately 24% for blue. Control the galvanometer and platform to position the light spot and scan the bright area once or multiple times, causing localized carbonization or evaporation of the color filter or transparent conductive layer, forming a light-blocking layer, thereby turning the bright spot into a dark spot. After repair, re-inspect; if residual light leakage is found, the process can be repeated or the carbonized area expanded.

[0061] Integrated process

[0062] 1) The OLED microdisplay wafer to be processed is clamped onto the moving platform and positioned;

[0063] 2) In cleaning mode, femtosecond laser scanning is performed on all pad areas to remove residual layers such as aluminum oxide, silicon nitride, Parylene, and photoresist;

[0064] 3) After cleaning, the wafer is transferred to the probe station for testing; the probe station uses an automated defect detection system to identify all bright pixels under full-card illumination conditions, records their coordinates in the array, and then converts the coordinates to the wafer coordinate system to generate the corresponding coordinate file.

[0065] 4) Chips with detected bright spot defects will be marked and transferred to the repair process;

[0066] 5) Import the bright spot coordinate file into the femtosecond laser cleaning and repair integrated equipment, and the equipment will use the wafer coordinate system to schedule the motion platform to locate the defect point by point;

[0067] 6) Switch to repair mode and perform femtosecond laser carbonization repair point by point according to the imported coordinate list;

[0068] 7) After the repair is completed, the chip is sent back to the probe station for a re-inspection. The automated inspection system confirms that all bright spots have been eliminated and no new defects have been generated.

[0069] 8) After passing the re-inspection, remove the chip and proceed to the next process.

[0070] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. An integrated laser cleaning and repair device for OLED microdisplays, characterized in that, include: Femtosecond laser; The mobile platform is configured to move horizontally and is used to place the pads to be processed. The optical path module is used to propagate the laser emitted by the femtosecond laser to the pads on the moving platform, and is also used to adjust the beam wavelength and spot size. Image detection system, used to acquire images and visually locate pads during processing; The control system is connected to the femtosecond laser, the moving platform, the optical path module, and the image detection system respectively. It is used to comprehensively control the output parameters of the femtosecond laser, the movement of the moving platform, the wavelength switching and spot adjustment of the optical path module, and the shooting and focusing of the image detection system. It is also used to generate and issue scanning path instructions based on preset process parameters and / or imported coordinate files to realize the configuration of processing parameters and spot positioning in cleaning mode and repair mode. The integrated laser cleaning and repair equipment for OLED microdisplays includes a cleaning mode and a repair mode. In cleaning mode, the control system retrieves cleaning parameters based on the residual layer material type and preset thickness parameters corresponding to the pads to be processed in the process database. The image detection system acquires the surface state information of the pads before and after cleaning and feeds it back to the control system. At the same time, it also completes high-precision visual coordinate positioning. Based on this, the control system controls the femtosecond laser, optical path module and moving platform to perform cleaning processing. In the repair mode, the image detection system completes the coordinate positioning of the bright pixel of the OLED microdisplay through visual positioning. The control system sets the femtosecond laser pulse energy and scanning number according to the input process parameters, and controls the optical path module and moving platform according to the imported bright pixel coordinates to position the focused spot in the bright pixel area for spot repair.

2. The integrated laser cleaning and repair equipment for OLED microdisplays as described in claim 1, characterized in that, The optical path module includes a harmonic generator, a beam expander, a beam shaper, a scanning galvanometer, and a focusing system arranged sequentially along the beam propagation direction. The harmonic generator is used to perform frequency doubling or third harmonic conversion on the fundamental frequency light output by the femtosecond laser to generate laser beams of different wavelengths. The beam expander is used to expand or shrink the laser beam generated by the harmonic generator at a predetermined magnification, and to adjust the beam diameter and divergence angle. The beam shaper is used to homogenize the energy distribution and control the beam profile of a laser beam that has been expanded or contracted. The scanning galvanometer is used to deflect the beam at high speed according to the instructions of the control system, so as to realize the rapid scanning of the preset processing path and the dynamic positioning of the target area. The focusing system is used to precisely focus the laser beam, after being deflected by the scanning galvanometer, onto the area to be processed on the pad, to form the desired large spot size of hundreds of micrometers or small spot size of micrometers.

3. The integrated laser cleaning and repair equipment for OLED microdisplays as described in claim 2, characterized in that, In repair mode, the control system reads the bright spot coordinate file detected in the OLED microdisplay defect detection process, drives the moving platform and scanning galvanometer according to the bright spot coordinates, and positions the focused spot sequentially to the corresponding bright spot position to perform local carbonization repair on the bright spot pixel area.

4. The integrated laser cleaning and repair equipment for OLED microdisplays as described in claim 1, characterized in that, The image detection system includes: The microscope camera is used to monitor the state of residual material on the pads before and after cleaning and to perform high-precision visual positioning. It is also used for high-precision positioning of bright pixel coordinates in the bright pixel repair process. Coaxial illumination and energy monitors are used to monitor laser focus and energy.

5. The integrated laser cleaning and repair equipment for OLED microdisplays as described in claim 1, characterized in that, In cleaning mode, the femtosecond laser has a pulse width of 50-400 fs, a repetition frequency of 50 kHz - 2 MHz, a single pulse energy of 0.2–10 µJ, and a spot diameter of 50-600 µm.

6. The integrated laser cleaning and repair equipment for OLED microdisplays as described in claim 1, characterized in that, In repair mode, the femtosecond laser has a pulse width of 50-350 fs, a repetition frequency of 1-50 kHz, a single pulse energy of 0.1-3 µJ, and a spot diameter of 1-5 µm.

7. An integrated process for an integrated laser cleaning and repair device for OLED microdisplays as described in any one of claims 1-6, characterized in that, include: 1) The OLED microdisplay wafer to be processed is clamped onto the moving platform and positioned; 2) In cleaning mode, femtosecond laser scanning is performed on all pad areas to remove residual layers such as aluminum oxide, silicon nitride, Parylene, and photoresist; 3) After cleaning, the wafer is transferred to the probe station for testing; the probe station uses an automated defect detection system to identify all bright pixels under full-card illumination conditions, records their coordinates in the array, and then converts the coordinates to the wafer coordinate system to generate the corresponding coordinate file. 4) Chips with detected bright spot defects will be marked and transferred to the repair process; 5) Import the bright spot coordinate file into the femtosecond laser cleaning and repair integrated equipment, and the equipment will use the wafer coordinate system to schedule the motion platform to locate the defect point by point; 6) Switch to repair mode and perform femtosecond laser carbonization repair point by point according to the imported coordinate list; 7) After the repair is completed, the chip is sent back to the probe station for a re-inspection. The automated inspection system confirms that all bright spots have been eliminated and no new defects have been generated. 8) After passing the re-inspection, remove the chip and proceed to the next process.

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