Patent ID: 8453318

Claim:
A method for making a planar coil, comprising the steps of: a) providing a substrate; b) covering a predetermined area of the substrate with a patterned photoresist layer; c) etching the substrate to form a trench at a place outside of the predetermined area; d) removing the photoresist layer; e) applying a barrier on the substrate; f) growing a seed layer on the barrier; g) covering the predetermined area with an isolative layer which extends slightly into the trench; h) filling up the trench with a conductive material by electroplating; and i) removing a portion of the isolative layer and the seed layer located above the predetermined area; wherein the isolative layer guides the conductive material to flow into a lower portion of the trench such that accumulation of the conductive material at opening of the trench is prevented before the lower portion of the trench is completely filled up, thereby avoiding gap formation in the trench.