Benefits Of Dry Etching Using A Pulsed Power Supply？

What are the advantages of pulse mode over continuous wave power mode? What are pulsed vs. continuous wave power modes?

As shown in the figure above, the first one is CW, Continuous Wave. Continuous wave (CW) refers to a waveform that is continuous and constant in time, with constant power and intensity. It typically appears as a single-frequency signal with a narrow spectrum and a stable output. The average power of the CW is equal to the peak power, and the signal characteristics are simple and easy to control. The main advantage of CW is its high stability, which makes it ideal for applications where signal continuity is critical. At the same time, the CW signal has a low noise level, which facilitates accurate measurement and analysis. In addition, the CW system design is relatively simple, and control parameters such as power and frequency can be easily adjusted. In CW mode, the power output is a continuous waveform with no choppy pulses.

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The second is PW, Pulsed Power. A pulse wave is a waveform that is interrupted in time and consists of a series of signals with high intensity over a short period of time. The pulses are of limited duration and are repeated after a certain period of time. The pulse wave has the characteristics of instantaneous peak power much higher than the average power, and the output spectrum is wide and contains more frequency components. The biggest advantage of the pulse wave is its instantaneous high peak power, which can release extremely high energy in a short period of time. In addition, due to the intermittent output of the signal, the average power of the pulse wave is low, which effectively reduces the heat load pressure of the equipment. As a result, it is ideal for applications that require high temporal resolution or instantaneous high power. In PW mode, the output power of the power supply is off part of the time and on part of the time.

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Features of pulsed power supplies?
1,The interval work can dissipate the heat in time, so that the reactants can have time to transport to the surface of the wafer.

2,The output power can be increased to a very large extent, the duration is extremely short, and the pulse power, frequency, time, etc. can be controlled very precisely.
Benefits of using pulse mode?
1,Eliminate microload effects. In structural etching with high aspect ratios, such as deep holes or deep grooves. Smaller sized holes or slots have a smaller etching rate than larger sized holes or slots. If the CW mode is used, the microload effect can be improved by reducing the pressure and increasing the bias voltage, but the ability to improve is limited, while the microload effect can be greatly improved by using the pulse mode.

2,Reduces wafer surface damage. If pulses are used on a bias supply, the time it takes for the plasma to attack the wafer can be reduced, which in turn reduces surface damage.