Controlled Lateral Etching of Titanium Nitride in a CMOS Gate Structure using DSP+

摘要

The metal gate electrode is used in advanced CMOS semiconductor devices to address new requirements including high conductivity to minimize delays due to interconnections between devices and tunable work function to allow n and p-type devices to operate in surface channel mode with minimal gate depletion effects. The introduction of metal elements to the CMOS gate, such as titanium nitride can impose significant changes to the device fabrication process. This includes process chemistry to pattern metallic structures and to remove metallic-containing residues. In this paper we will report the results of titanium nitride recession in the metal gate stack using a dilute mixture of sulfuric acid, hydrogen peroxide and hydrofluoric acid known by the trade name DSP+. This paper demonstrates that DSP+ can recess the TiN into the gate stack more efficiently than oxidation/etch solutions allowing tuning of the gate length and ensuring complete sidewall encapsulation of the gate.