Plasma etching excites gas molecules with external energy to form active particles containing ions, electrons, and free radicals. Coupling refers to the interaction between the energy input method and the plasma state, which determines the efficiency and accuracy of etching. The mainstream coupling methods are divided into:
Capacitive coupling (CCP): Excitation of plasma through alternating electric fields between parallel plate electrodes.
Inductive coupling (ICP): Plasma is generated through the high-frequency magnetic field of an induction coil.
Principle and Characteristics of Capacitive Coupled Plasma (CCP)
Core components: Upper and lower parallel plate electrodes (upper electrode area>lower electrode), RF power supply (RF) applies high-frequency electric field.
Activation process: 1 The initial electrons accelerate in an electric field and collide with gas molecules to produce ionization. two Forming a low-temperature plasma in dynamic equilibrium (with electron temperature much higher than ion temperature).
Technical advantages: • Uniform plasma distribution (high uniformity of electrode electric field). Ion bombardment has strong energy (high sheath voltage), suitable for high aspect ratio etching.
Limitations: High pressure requirements (>50 mTorr) and significant ion divergence issues in high-order processes. The single frequency CCP process has a narrow window, while multi frequency CCP requires independent control of high and low frequency power supplies (27MHz/2MHz).
Core applications: Dielectric etching: DRAM capacitors, 3D NAND deep hole etching (aspect ratio>40:1).
Principle and Characteristics of Inductively Coupled Plasma (ICP)
Core components: Top spiral coil (3-5 turns), RF power supply excites alternating magnetic field.
Activation process: 1 Magnetic field changes generate induced electric fields, accelerating electron collisions and ionizing gases. two The plasma density is high (10-20 times that of CCP), and the pressure can be as low as 1-10 mTorr.
Technical advantages: • Independently control plasma density (source RF SRF) and ion energy (bias RF BRF). Under low pressure, ion directionality is better, suitable for advanced processes below 14nm.
Key design: Faraday shielding plate: eliminates parasitic capacitance interference between the coil and plasma. Coil optimization: Made of brass tube material and designed with 3-5 coils to improve coupling efficiency.
Core applications: Metal/FinFET etching: Copper interconnects, high-k metal gate (HKMG) structures.
Comparative Analysis of ICP and CCP

The essential difference between ICP and CCP lies in the energy coupling mode, and the two complement each other in advanced processes. With the increasing complexity of 3D storage and logic chips, composite etching technology and domestic equipment replacement will become key breakthrough directions.   

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