New Process Creates 3-D Nanostructures With Magnetic Materials

Tag : alloy materials

The NIST team also demonstrated that key process variables arelinked to relatively quick and inexpensive electrochemicalmeasurements, pointing the way to a fast and efficient way tooptimize the process for new materials.
The NIST process is a variation of a technique called"Damascene metallization" that often is used to createcomplicated three-dimensional copper interconnections, the"wiring" that links circuit elements across multiplelayers in advanced, large-scale integrated circuits. Named afterthe ancient art of creating designs with metal-in-metal inlays, theprocess involves etching complex patterns of horizontal trenchesand vertical "vias" in the surface of the wafer and thenuses an electroplating process to fill them with copper. The highaspect ratio features may range from tens of nanometers to hundredsof microns in width. Once filled, the surface of the disk is groundand polished down to remove the excess copper, leaving behind thetrench and via pattern.
The big trick in Damascene metallization is ensuring that thedeposited metal completely fills in the deep, narrow trencheswithout leaving voids. This can be done by adding a chemical to theelectrodeposition solution to prevent the metal from building uptoo quickly on the sides of the trenches and by careful control ofthe deposition process, but both the chemistry and the processvariables turn out to be significantly different for activeferromagnetic materials than for passive materials like copper.
In addition to devising a working combination of electrolytes andadditives to do Damascene metallization with nickel and anickel-iron alloy, the NIST team demonstrated straightforwardmeasurements for identifying and optimizing the feature-fillingprocess thereby providing an efficient path for the creation ofquality nanoscale ferromagnet structures.
The new process makes it feasible to create complexthree-dimensional MEMS devices such as inductors and actuators thatcombine magnetic alloys with non-magnetic metallizations such ascopper interconnects using existing production systems.
Journal reference : C.H. Lee, J.E. Bonevich, J.E. Davies and T.P. Moffat. Magnetic materials for three-dimensional Damascene metallization:void-free electrodeposition of Ni and Ni70Fe30 using2-mercapto-5-benzimidazolesulfonic acid . Journal of The Electrochemical Society , 155 (7) D499-D507 (2008)