TiN Metallization Barriers: From 1.2μ to 0.35μ Technology

Abstract

ABSTRACTThe evolution of modern integrated circuit technology to sub micron dimensions has brought about a number of challenges, specially in the field of metallization. Decreasing junction depths have imposed stringent demands on the materials used for the electrical contacts. This is due to the potential interactions between the contact metal and silicon (or suicide in the case of salicide processes) causing junction leakage and/or shorting. The solution most commonly applied to this problem is that in which a barrier material is interposed between the metallization and the contact. The material most often selected for this purpose has been TiN. TiN can be deposited via the reactive sputtering of Ti in a N2 atmosphere or it can be also obtained by sputtering Ti and then reacting it with either N2 or NH3. Shrinking VLSI dimensions have brought about the need for improved planarization for the purposes of metal definition. It has also prevented the tapering of contacts for space saving reasons. Both of these issues resulted in deep, straight wall contacts with aspect ratios greater than 1 that cannot be metallized appropriately with conventional sputtering techniques. These requirements have driven the development of a conformai CVD TiN barrier process. This paper describes the evolution of the TiN metallization barrier from the requirements of 1.2μ to 0.35μ technologies.