Tin Fund Is A Gate Characteristics

As the CMOS device dramatically shrinks, the use of high-k material is unavoidable. However, due to various problems related with poly-Si gate such as poly-Si depletion effect, boron penetration and incompatibility with high-k (Fermi level pining and mobility degradation of channel carriers), the poly-Si gate should be replaced by metal gate. Titanium nitride (TiN) is considered as a promising metal gate material because of its good thermal stability, low resistivity, and its adjustable work function (WF). However, it's work function is as high as about 5.0 eV, which is only suitable for p-MOSFETs. It's necessary to modulate its work function to satisfy the requirement of n-MOSFETs. Hence, this thesis studies the deposition process of TiN thin film, the characteristic of the TiN metal gate, annealing effect on the metal gate effective WF modulation for the Al/TiN/SiO2/p-Si structure, TiN/Yb/TiN/SiO2/p-Si structure and TiN/Ta/TiN/SiO2/p-Si structure.The deposition process of the TiN thin film and the characteristics of the TiN metal gate:The dependence of the resistivity of TiN film on the PVD deposition process parameters is investigated. It reveals that comparing with RF sputtering DC sputtering is better for high quality TiN film fabrication. It also demonstrates that with a DC sputtering power of 200 W the resistivity of TiN film is lower when deposited with an annealing temperature between 600℃and 700℃. The WF of TiN metal gate is measured for TiN/SiO2/p-Si structure. It reveals that the WF of a pure TiN metal gate is as high as 5.0 eV and it is a little lowered as the thermal budget increases.Annealing effect on the metal gate effective WF modulation for the Al/TiN/SiO2/p-Si structure:Since the WF of TiN itself is so high that it is only suitable for p-MOSFETs. Due to the lower WF and resistivity of Al, it is employed to lower the WF of TiN metal gate. The study shows that the WF of the bi-layered Al/TiN metal gate increases a little after a short time high temperature annealing. However, as the annealing time increases, the WF can be lowered to 4.4 eV. The further material analysis reveals that the chemical status of Al in the TiN/SiO2 interface will determine the WF modulation results. When the interface dipole of Al-Si-O plays the main role, the gate effective WF will be modulated toward the valence band of Si. While when the direct contact of Al to SiO2 plays the main role, the gate effective WF will be modulated toward the conduction band of Si. It is further demonstrated that the introduction of Al does not increase the density of interface states.Annealing effect on the metal gate effective work-function modulation for the TiN/Yb/TiN/SiO2/p-Si and TiN/Ta/TiN/SiO2/p-Si structure:In order to further lower the WF of TiN metal gate, Yb and Ta both with a very lower WF are separately introduced as alloy element for TiN metal gate with a multi-layered structure of TiN/Yb/TiN/SiO2/p-Si and TiN/Ta/TiN/SiO2/p-Si structure. The experimental results show that the introduction of Ta or Yb can effectively lower the WF of TiN metal gate. The WF of TiN(Ta) metal gate is modulated to 4.4 eV. While a much lowerd WF of 4.1 eV is observed for TiN(Yb) metal gate, which is very close to the Si conduction band bottom. More experimental results demonstrate that the TiN(Yb) metal gate has a good thermal stability and the introduction of Yb to the interface does not affect the equivalent oxide thickness.