What is PECVD?

PECVD is Plasma Enhanced Chemical Vapor Deposition or Plasma Assisted Chemical Vapor Deposition. PECVD mainly ionises the process gas by RF power supply, and then the ionised gas reaches the substrate surface by diffusion, and then a chemical reaction takes place to complete the thin film growth.

What is the relationship between RF power supply and PECVD?

The RF power supply is the core component of PECVD thin film deposition equipment, providing a stable RF source to generate glow discharge plasma.

Compared to traditional CVD equipment, PECVD equipment forms high-density, high-performance films at relatively low reaction temperatures without destroying the existing film or the underlying circuitry, achieving faster film deposition speeds, and is the most widely used type of equipment in the chip fabrication thin film deposition process. The technology uses low-temperature plasma to generate a glow discharge at the cathode of the process chamber under low gas pressure, and the glow discharge is used to warm the wafer to a predetermined temperature.

The appropriate amount of process gas is then passed through, and these gases undergo a series of chemical and plasma reactions, eventually forming a solid film on the surface of the wafer. In the reaction process, the reaction gas enters the furnace chamber from the air inlet, gradually diffuses to the wafer surface, and decomposes into electrons, ions and reactive groups under the action of the electric field excited by the RF power supply. Specifically: PECVD is generally carried out in a vacuum chamber with parallel trays spaced several inches apart. Silicon wafers are placed on the trays and RF power is applied to the upper electrodes. A plasma is generated as the raw gas flows through the gas host and the middle of the deposition, and excess gas is vented through the periphery of the lower electrode. Sometimes, reactive gases are introduced from the perimeter of the lower electrode and expelled from the middle of the electrode.

The higher the RF power the greater the ion bombardment energy, which is conducive to the improvement of the quality of the deposited film. Increased power can enhance the concentration of free radicals in the gas, improve the deposition rate, when the power is increased to a certain extent, the reaction gas is completely ionised, the free radicals are saturated, and the deposition rate tends to stabilise.