Improved etching characteristics of silicon-dioxide by enhanced inductively coupled plasma

Among various types of plasma sources, such as electron cyclotron resonance (ECR), planar inductively coupled plasma (ICP) (or TCP), helical resonator, or surface wave plasma, the ICP type plasma source has been well known as a promising source of uniform high density plasma with the ability of expansion and economical merit. We have proposed and developed a novel plasma process technique, named ‘Enhanced-ICP’, which uses periodic control of weak axial magnetic field to provide better uniformity and a higher etch rate with higher plasma density than normal continuous wave mode (cw)-ICP. The E-ICP process, so far, is considered as a damage-free technique with much improved characteristics. It has already shown better spatial uniformity than 1% and much improved etch rate within a diameter of 10 cm for a photo-resist etch process. The adoption of E-ICP operation for SiO2 etch with CF4 gas also provides better etch profile and higher etch rate than cw-ICP process. The optimum frequency of axial magnetic field for CF4 gas is ∼80 Hz, which is approximately two times that of oxygen plasma. The etch rate of E-ICP operation in the vertical direction is approximately 1.5 times larger than that of a cw-ICP, while side etch rate does not vary noticeably, to provide more vertical etch profile than normal.