Multi-Parameter Coupling Decoupling Control for High-Voltage Power Supply in Etching Equipment

In dry etching equipment, HVPS needs to simultaneously regulate four core parameters: output voltage (1-10kV), current (10-100mA), pulse width (1-100μs), and duty cycle (10%-90%). However, the strong coupling between parameters — such as a 15% current increase caused by voltage rise and 3% voltage fluctuation induced by duty cycle adjustment — makes it difficult for traditional single-parameter PID control to achieve multi-target stability, resulting in an etching rate fluctuation of over 7% and sidewall verticality below 85°.
The decoupling control scheme is built based on multi-variable Model Predictive Control (MPC): First, a parameter coupling mathematical model is established using the least square method to identify the voltage-current coupling coefficient (0.82A/kV) and duty cycle-etching rate correlation factor (0.5nm/min·%). Second, a feedforward compensation channel is introduced to collect the wafer surface resistance change in real time (sampling frequency 1kHz) and adjust the voltage output in advance to offset load disturbances. Finally, the MPC algorithm rolling optimizes the control variables and updates the parameter output every 10ms to achieve dynamic decoupling between parameters.
After applying this technology in the 3D NAND memory chip etching process, the etching rate fluctuation is reduced from 7.2% to 2.8%, and the sidewall verticality is increased from 84.3° to 89.1%. In the shallow trench isolation (STI) etching of logic chips, the critical dimension (CD) deviation is reduced from ±4nm to ±1.5nm, providing stable power control support for high-precision etching processes.