No abstract

A new process of applying molecular resists to block HfO2 and Pt atomic layer deposition has been investigated. Monolayer films are formed from octadecyltrichlorosilane (ODTS) or tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS) and water vapor on native silicon oxide surfaces and from 1-octadecene on hydrogen-passivated silicon surfaces through a low-pressure chemical vapor deposition process. X-ray photoelectron spectroscopy data indicates that surfaces blocked by these monolayer resists can prevent atomic layer deposition of both HfO2 and Pt successfully. Time-dependent studies show that the ODTS monolayers continue to improve in blocking ability for as long as 48 h of formation time, and infrared spectroscopy measurements confirm an evolution of packing order over these time scales.

In this letter, we demonstrate that negative bias temperature instability of high-k (HfO 2 /SiO 2 ) gate dielectric stacks can be greatly improved by incorporating fluorine and engineering its concentration depth profile with respect to HfO 2 /SiO 2 interface. It was found that fluorine is easily incorporated in HfO 2 /SiO 2 at low temperatures (≤ 400 • C) by F 2 anneal in the presence of UV radiation. Fluorine tends to segregate at the HfO 2 /SiO 2 interface and, to a lesser extent, diffuses into the underlying SiO 2 /Si interface. The HfO 2 /SiO 2 stacks with F addition show significantly reduced (<50%) positive charge trapping and interface states generation compared to control samples without F.Index Terms-Fluorine, HfO 2 /SiO 2 , high-k, interface states, negative bias temperature instability (NBTI), positive charges.

Hf O 2 films were grown by atomic layer deposition using two different precursor chemistries—HfCl4 and tetrakis(diethylamido)hafnium (TDEAH) with H2O as the oxidant. Electrical measurements on capacitor structures fabricated using the films showed a 0.4V positive shift in the flatband voltage for the chloride-HfO2 with respect to the amide-derived HfO2, indicating a considerable negative fixed charge in the dielectric. Secondary ion mass spectrometry depth profiles of the gate stack showed that Cl segregated preferentially at the HfO2∕SiO2 interface for chloride-derived HfO2. In situ vacuum anneals of the HfCl4-derived films at 500°C did not affect the profile, indicating that Cl is stably bonded at that interface. A similar analysis of the TDEAH-derived HfO2 showed very low concentrations of C, N, and H impurities. A positive fixed charge of +4.5×1011∕cm2 was extracted for the amide-HfO2 whereas a negative fixed charge of −1.86×1012∕cm2 was estimated for the chloride-HfO2. Thus, Cl incorporation can significantly alter both the magnitude and sign of the fixed charge in the HfO2∕SiO2∕Si gate stacks.

The electrical properties of metal-oxide-semiconductor (MOS) capacitors composed of atomic-layer-deposited (ALD) hafnium-dioxide (HfO2) dielectrics and plasma-synthesized interface layers were investigated. MOS capacitor with oxynitride interface layer shows negative flatband voltage (Vfb) shift from the ideal value. Hafnium-alkylamide ALD process performed on a plasma nitrided silicon surface causes negative Vfb shift. Germanium MOS capacitors show additional negative Vfb shift (−0.5V). X-ray photoelectron spectroscopy shows evidence of germanium diffusion into the HfO2 layer. Germanium MOS capacitor with tantalum-oxynitride (TaON) interface layer shows superior electrical properties. These results indicate that the selection of the interface layer strongly influences germanium MOS capacitor electrical properties.