Method for reducing reactive ion etch lag in low K dielectric etching

A method for processing a substrate, comprising:

• providing the substrate with a patterned first layer;
• providing a second layer underling the first layer;
• etching a first portion of the second layer with a non-atomic layer etch process while utilizing the patterned first layer as a mask;
• etching a second portion of the second layer with an atomic layer etch based process while utilizing the patterned first layer as the mask, the atomic layer etch based process comprising a cyclic process comprising at least a deposition process sub-step and an etch process sub-step;
• and
• controlling both the non-atomic layer etch process and the atomic layer etch based process so that the second layer is etched to achieve a desired etch lag effect,
• wherein the atomic layer etch based process comprising the deposition process sub-step, a purge sub-step and the etch process sub-step, the deposition process sub-step, the purge sub-step and the etch process sub-step being repeated a plurality of times, and
• the non-atomic layer etch process having etch lag and the atomic layer etch process having inverse etch lag.