Titanium Precursors for STO Deposition (18-Jan-2010)

Disclosed herein are non-limiting embodiments of methods, apparatus and compounds which may be used in the manufacture of semiconductor, photovoltaic, LCD-TFT, or flat panel type devices.

Summary of the Invention

One of the serious challenges the industry faces is developing new gate dielectric materials for DRAM and capacitors.  For decades, silicon dioxide (SiO₂) was a reliable dielectric, but as transistors have continued to shrink and the technology moved from “Full Si” transistor to “Metal Gate/High-k” transistors, the reliability of the SiO₂-based gate dielectric is reaching its physical limits.  The need for new high dielectric constant material and processes is increasing and it becomes more and more critical as the size for current technology is shrinking.  Novel dielectric materials like TiO₂ or new dielectric materials containing alkaline earth metals such as SrTiO₃ or Sr₂TiO₄ may provide a significant advantage in capacitance compared to conventional dielectric materials.

Nevertheless, deposition of titanium containing layers is difficult and new material and processes are more and more needed.  For instance, atomic layer deposition, ALD, has been identified as an important thin film growth technique for microelectronics manufacturing, relying on sequential and saturating surface reactions of alternatively applied precursors, separated by inert gas purging.  The surface-controlled nature of ALD enables the growth of thin films of high conformality, stoichiometric and uniformity with an accurate thickness control.  In case of STO deposition, available Sr precursors show excellent reactivity with O₃ and acceptable reactivity with water, whereas not many Ti precursors are available which are reactive with water and thermally stable at high process temperatures.  Examples; (a) Ti(NMe₂)₄/water ALD process has deposition rate of 0.6 Ǻ/cycle at 200 ˚C, (b) Ti(NMeEt)₄/water ALD process has deposition rate of 0.4 Ǻ/cycle at 200 ˚C, (c) Ti(NEt₂)₄/water ALD process has deposition rate of 0.27 Ǻ/cycle at 225 ˚C, (d) Ti(*Cp)(OMe)₃/water ALD process has no deposition.  Use of ozone as oxidant has very undesired results with underlying layer, such as TiN or SRO.  It either oxidizes TiN layer or etch Ru from SRO layer.  Therefore, there is an urgent need for developing new precursors suitable for titanium/H₂O ALD processes compatible with Sr ALD process, especially with higher thermal stability at higher process temperatures.  We propose titanium heteroleptic precursors derived from two classes of ligand systems, they are amidinates/foramidinates and amides.  Precursor design can help improving volatility, reducing the melting point (liquids or very low melting solids), high reactivity with water and increasing thermal stability for wider process window applications.

In some embodiments, the precursor may be a compound of the f...