The vacuum plasma debonding machine efficiently peels off the photoresist on the wafer surface through high-energy plasma, and is widely used in semiconductor manufacturing, micro nano processing, and other fields. Its operation must strictly follow the following standardized procedures to ensure process stability and device yield:
1、 Preliminary preparation work
1. Sample pretreatment: The wafer to be processed needs to complete the exposure and development process in advance to form a complete patterned adhesive film. Use nitrogen to blow surface particles and avoid impurities interfering with plasma reactions. If there is a metal layer, it is necessary to confirm whether it is covered with a protective mask.
2. Equipment self-test: Before starting up, check the cooling water circulation system (water temperature ≤ 25 ℃), RF power supply connection wires, and vacuum pipeline sealing. Start the control software to execute the diagnostic program and confirm that all sensors (such as capacitive meters and mass flow meters) are working properly.
3. Process formula loading: Select preset process parameters based on the thickness of the adhesive layer (typical value 1-10 μ m): oxygen/argon mixture ratio (commonly O ₂: Ar=1:4), chamber background vacuum degree (<5 × 10 ⁻ ² mbar), RF power density (0.5-2W/cm ²), and processing time (60-180 seconds).
2、 Core operational steps
1. Stage positioning and fixation: Place the blue film or chuck carrying the wafer precisely in the center of the electrode stage, and pre pump it to a low vacuum (about 10 ³ Pa) through a mechanical pump to activate the electrostatic adsorption function to fix the sample. When processing multiple chips, it is necessary to maintain a spacing of ≥ 5mm between chips to prevent crosstalk.
2. Progressive vacuum pumping: Start the turbo molecular pump group and establish a high vacuum environment in two stages of "coarse pumping → fine pumping". Real time monitoring of vacuum curve, maintaining for 30 seconds after the pressure drops to the process threshold to remove residual water vapor.
3. Plasma excitation: Slowly increase the RF power to the set value and synchronously introduce the process gas. Observing the glow discharge color (normally light purple), abnormal whitening indicates that excessive power may cause damage to the silicon wafer. At this stage, continuous monitoring of the impedance matching network reflection coefficient (VSWR<1.5) is required.
4. Dynamic etching control: Adopting a segmented energy output strategy, the front-end high-power rapid film breaking, and the back-end power reduction fine control of lateral etching rate. When equipped with an endpoint detection module, the reaction can be automatically terminated by a sudden change in emission spectral intensity.
3、 Closing and post-processing
1. Safe pressure relief: After turning off the RF source, continue to introduce inert gas to replace residual active particles, and gradually fill dry nitrogen gas to restore normal pressure. Note that the exhaust rate should be less than 5mbar/s to prevent particle detachment caused by airflow impact.
2. Sampling and testing: Immediately after taking out the sample, perform CD-SEM scanning to confirm the integrity of the pattern, and use an ellipsometer to measure the residual adhesive thickness (required to be<5nm). If there is a phenomenon of floating glue, it is necessary to adjust the subsequent soft baking conditions (90-120 ℃, 30 seconds).
3. Equipment maintenance: Empty the reaction byproduct collection tank and replace the quartz lining of the processing chamber with a cycle of more than 50 times. Regularly calibrate the Mass Flow Controller (MFC) and clean the polymer deposits on the surface of the electrostatic suction cup.
4、 Key precautions
Safety protection: Operators must wear UV resistant face shields and direct visual inspection of the plasma is prohibited. The position of the emergency stop button should be prominently marked.
Process compatibility: For three-dimensional topological structures, it is recommended to use pulse modulation mode to reduce charge accumulation effects. Fluorinated rubber rings exposed to oxygen plasma will accelerate aging and need to be replaced regularly.
Pollution prevention and control: It is strictly prohibited for organic solvents to enter the vacuum chamber. Before and after each experiment, the inner wall of the chamber should be wiped with anhydrous ethanol. The waste liquid treatment system should be equipped with activated carbon filters to adsorb volatile organic compounds.
By standardizing the above process, it is possible to effectively control the uniformity of the glue removal rate (± 3%), ensure the fidelity of the pattern, and extend the equipment maintenance cycle. In practical operation, it is necessary to optimize parameter combinations based on specific process requirements and establish an SPC process control system to achieve batch consistency.