Semiconductor Etchants - Preparation of Electronic Materials

Preparation of Electronic Materials

The term, ‘microelectronic materials’ encompasses an extremely wide range of materials. This is due to the fact that most microelectronic devices are composites, containing any number of individual components. For example, present day microprocessor failure analysis might require the metallographer to precisely cross section through a silicon chip plated with multiple thin-film layers of oxides, polymers, ductile metals such as copper or aluminum, and refractory metals such as tungsten and/or titanium-tungsten. In addition, the packaging of such a device might contain materials of such varying mechanical properties as toughened aluminum oxide and solder. The solder materials may have compositions ranging up to 97 % lead. With such a vast number of materials incorporated into a single device, and with these materials having such highly disparate mechanical properties, it is virtually impossible to develop a general method for achieving perfect metallographic results. Instead, we must focus on a few individual materials, and develop a philosophy of preparation in which we give our attention specifically to the materials of interest.

First and foremost in the class of ‘microelectronic materials’ is silicon. Silicon is a relatively hard, brittle material, which does not respond well to grinding with large silicon carbide abrasives. Silicon carbide papers contain strongly bonded abrasive particles which, when they collide with the leading edge of a piece of silicon, create significant impact damage. In addition, they create tensile stresses on the trailing edge of silicon, which results in deep and destructive cracking. Cutting close to the target area is preferable to grinding, but to accurately approach the target area within a silicon device, fine grinding is still necessary.