source power

Source power refers to the RF (radio frequency) power applied to generate and sustain the plasma in semiconductor etch and deposition equipment, as distinct from bias power which controls ion bombardment energy at the wafer surface. In inductively coupled plasma (ICP) etch systems, source power is delivered through a coil antenna (typically at 13.56 MHz or 2 MHz) positioned above or around the plasma chamber, creating a time-varying magnetic field that induces an electric field to accelerate electrons and sustain ionization. In transformer-coupled plasma (TCP) and helicon sources, similar principles apply with different antenna geometries. The source power primarily controls the plasma density — higher source power produces more electron-ion pairs through increased ionization, generating greater concentrations of reactive radicals and ions. This directly increases etch rate and can improve etch uniformity. In modern dual-frequency etch tools, source power and bias power are independently adjustable, enabling decoupled control of radical/ion flux (via source power) and ion bombardment energy (via bias power). This decoupling is essential for advanced process optimization where high etch rates with low damage, or high selectivity with adequate profile control, are required simultaneously. Typical source power ranges from 200W to 3,000W or more depending on the tool platform and application. Increasing source power increases dissociation of feed gas molecules, which can change the dominant etch species — for example, higher source power in fluorocarbon plasmas produces more fluorine atoms relative to CFx radicals, shifting the process from polymer-forming (passivating) toward more aggressive etching. Source power also affects gas-phase reactions, residence time effects, and the electron energy distribution function (EEDF). Process engineers optimize source power to balance etch rate, selectivity, profile control, and damage budget for each specific application layer.