Crystalline and Electrical Properties of Mictamict TiSiN Gate Metal–Oxcide–Semiconductor Capacitors

Abstract

The crystal structures and electrical characteristics of Ti–Si–N metal–oxide–semiconductor (MOS) gate electrodes in the mictamict state, which is a comprehensive term referring to amorphous structures both with and without nanocrystals, were investigated. By increasing the N2 concentration of the sputtering ambient, the nitrogen (N) content of the Ti–Si–N films increased and consequently the Ti–Si–N films did not crystallize. At a N2 concentration of more than 3.0%, the N content of the films was almost constant at about 53%, which indicates that all Ti and Si atoms deposited in the form of TiN and Si3N4, respectively. In such Ti–Si–N films with a saturated N content, only 2–3-nm-grain-size nanocrystallites formed, which were embedded in amorphous layers even after post-deposition annealing (PDA) above 900 °C. At the same time, with increasing N2 concentration of the sputtering ambient, the change in the film resistivity after the PDA became smaller and the capacitance equivalent thickness (CET) fluctuation gradually ceased to occur. The work function of the mictamict Ti–Si–N gate electrodes, which were deposited in 5.0% N2 ambient and annealed at 500 °C, was determined to be 4.6 eV.

Thermal Stability and Scalability of Mictamict Ti-Si-N MOS Gate Electrodes

“…The Rutherford back scattering (RBS) results indicated that N contents in Ti-Si-N films increased as the N 2 /Ar mixture ratio increased. The Ti-Si-N films deposited in the sputtering ambient with the N 2 /Ar ratio more than 3.0% have N contents larger than 53%, while those in the case of the N 2 /Ar ratio below 3.0% is less than 40% [9]. Hereinafter, the former is called "high-N-content" films and the later "low-N-content" ones.…”

“…Hereinafter, the former is called "high-N-content" films and the later "low-N-content" ones. According to the transmission electron microscopy (TEM) observations, the high-N-content Ti-Si-N films have near-amorphous structures in which nanocrystallites and amorphous layers are mixed [9]. these X-ray diffraction peaks.…”

“…We have been reported nanocrystalline structures and electrical properties of the Ti-Si-N alloys in a previous paper [9]. As well as most of amorphous alloys, Ti-Si-N alloys tend to crystallize during the high temperature annealing in ULSI processes and, however, nanocrystallites in the high-nitrogen (N)-content Ti-Si-N hardly grow during the annealing below 900°C and keeps a near-amorphous structure with nanocrystallites in amorphous matrixes.…”

Crystalline Structures and Electrical Properties of High Nitrogen-content Hf-Si-N Films

“…Transition metal (TM) -silicon (Si) -nitrogen (N) alloys often have amorphous states, so they have been investigated as boundary-less barrier metals in multilayer Cu interconnects and metal gate materials with very small workfunction variations in recent years [1][2][3][4][5]. Although nanocrystallites often segregate in those films after post-deposition annealing (PDA) treatments at high temperatures, such a mixed structure of amorphous layer and nanocrystallites can be regarded as a uniform material if nanocrystallites are sufficiently dense and small compared to sizes of gates or interconnects.…”

“…In previous papers, we have reported crystalline structures and electrical properties of the Ti-Si-N and Hf-Si-N MOS metal gates [5][6][7]. At low N contents, their resistivity increases with increasing the N content due to increase of Si3N4 component and development of amorphization.…”