AN ELECTROCHEMICAL INVESTIGATION ON Ti AND TiN

摘要

Most modern tungsten plug technologies use W/TiN/Ti stack where W is deposited by chemical vapor deposition using WF_6 gas at 350-450 C on Ti/TiN bilayer, which provides the necessary adhesion between the tungsten layer and the substrate. While there have been several studies reported on fundamental aspects of tungsten removal, there are very few studies reported on CMP of Ti and TiN. The purpose of this investigation is to examine the role of chemistry in controlling the removal in these systems. A detailed electrochemical analysis on these two materials is performed. Electrochemical tests include both potentiodynamic and potentiostatic polarization techniques. Electrochemical experiments were conducted using electrolytes, which were adjusted to the required pH values using suitable buffering agents. The oxidizing agents used were either 5% H_2O_2 or 0.25 M KIO_3. An addition of 0.1M KNO_3 was also made to the electrolyte to improve its conductivity. CMP studies were also carried out using alumina slurries. The slurry background chemistries were identical with the electrolytes used for electrochemical measurements. Electrochemical measurements provided very useful information such as corrosion currents, corrosion potential, passivation current and passivation current density, which give valuable clues regarding the behavior of the two materials during CMP.