Patent ID: 7473597

Claim:
A method of forming a plug structure, comprising: forming an insulating layer; forming an opening through the insulating layer, the opening having an aspect ratio, a longitudinal opening axis, a sidewall surface and a bottom surface; forming a first filling layer on an upper surface of the insulating layer and the sidewall surface and the bottom surface of the opening; removing an upper portion of the first filling layer while retaining a lower portion of the first filling layer within the opening, the lower portion of the first filling layer forming a partial plug covering the original bottom surface and a lower region of the sidewall surface to form a modified opening having a modified aspect ratio, wherein removing the upper portion of the first filling layer while retaining a lower portion of the first filling layer within the opening includes etching the upper portion of the first filling layer using ion beam etching (IBE), the ion beam having a first incident angle that is offset from the longitudinal opening axis so the ion beam does not directly strike the bottom surface of the opening; forming a subsequent filling layer on the upper surface of the insulating layer, an upper portion of the sidewall surface and the partial plug; removing an upper portion of the subsequent filling layer while retaining a lower portion of the subsequent filling layer within the modified opening, the lower portion of the subsequent filling layer forming an extension of the partial plug and covering an intermediate region of the sidewall surface, wherein removing the upper portion of the subsequent filling layer while retaining a lower portion of the subsequent filling layer within the opening includes etching the upper portion of the subsequent filling layer using ion beam etching (IBE), the ion beam having a second incident angle that is offset from the longitudinal opening axis; and repeating the forming of the subsequent filling layer and the removing of an upper portion of the subsequent filling layer processes as necessary to fill the opening with portions of a plurality of filling layers to form the plug structure.