Advances in Fabrication of Nanoscale Devices

GMR materials can be patterned to line widths of tens of nanometers.

Some advances have recently been made on several fronts in a continuing effort to develop of means of fabricating electronic and magnetic devices having dimensions of the order of tens to hundreds of nanometers. This effort is a collaboration of members, from three universities, whose interests, expertise, and facilities span synthesis of materials, nanoscale characterization, nanoscale lithography, and non-lithographic processing of nanostructures.

The most substantial body of work addressed the use of a novel inorganic resist material, hydrogen silsesquioxane (HSQ). This material was employed because of its potential utility as both a high-resolution resist and an etch mask. Of particular interest in this work was the use of HSQ in patterning giant-magnetoresistance (GMR) materials and their constituents (e.g., Ni, Fe, Co, and Cu). It is particularly difficult to pattern these materials at high resolution by means of dry etching because of a lack of volatile etch products. It was found that by use of either of two versions of a process involving the use of HSQ, the difficulty can be overcome sufficiently to enable the fabrication of structures in the size range of interest.

The process is summarized as follows:

1. The GMR material or other material of the device that one seeks to fabricate is coated with HSQ.
2. In one version of the process, the HSQ is patterned by electron-beam lithography, then etching in an argon plasma. In the other version of the process, the HSQ is patterned by use of a focused Ga⁺-ion beam, then etching in an argon plasma.
3. The GMR or other device material exposed by the opening(s) in the patterned HSQ is removed by direct argon-ion-beam sputtering, thereby transferring the desired pattern into the device material.