A method for precise measurements of absolute electron density in the plasma using plasma frequency is developed. A microwave perturbation of a frequency is introduced to plasma from a network analyzer and transmits in the plasma. The transmitting wave at a distance from a radiating antenna is monitored using a spectrum analyzer to scan the perturbing frequency. The transmitting wave rapidly decays by a cutoff at the plasma frequency, which gives the absolute electron density. The transmitting waves of some frequency including plasma frequency are characterized. The measured plasma frequency by this method is coincident with that obtained by the plasma oscillation method.

The characteristics of HfO 2 films grown on Si substrates using a tetrakis-diethyl-amino-hafnium precursor by the remote plasma atomic layer deposition ͑RPALD͒ and direct plasma ALD ͑DPALD͒ methods were investigated by physical and electrical measurement techniques. The as-deposited HfO 2 layer from RPALD exhibits an amorphous structure, while the HfO 2 layer from DPALD exhibits a clearly visible polycrystalline structure. Medium energy ion scattering measurement results indicate that the interfacial layer consists of the interfacial SiO 2−x and silicate layers. These results suggested that the stoichiometric change in the depth direction could be related to the energetic reactant in a state of plasma used in the plasma ALD process, resulting in damage to the Si surface and interactions between Hf and SiO 2−x . The as-deposited HfO 2 films using RPALD have the better interfacial layer characteristics than those using DPALD. A metal-oxide-semiconductor capacitor fabricated using the RPALD method exhibits electrical characteristics such as equivalent oxide thickness ͑EOT͒ of 1.8 nm with an effective fixed oxide charge density ͑Q f,eff ͒ of ϳ4.2 ϫ 10 11 q/cm 2 and that for DPALD has a EOT ͑2.0 nm͒, and Q f,eff ͑ϳ−1.2ϫ 10 13 q/cm 2 ͒.

A method for precise measurements of absolute electron density in plasma using wave cutoff is described. This method of measurement uses a network analyzer with radiating and detecting antenna A microwave signal of 10 kHZ–3 GHz frequency is introduced into the plasma from a radiating port of the network analyzer and propagates in the plasma. The transmitted wave is monitored at a distance from a radiating antenna using an antenna connected to the receiving port of the network analyzer. The transmitted wave decays rapidly at a cutoff plasma frequency, which is a direct measure of the absolute electron density. This cutoff method is free of many difficulties often encountered with a Langmuir probe, such as thin film deposition and plasma potential fluctuation. The cutoff probe can also measure the spatial distribution of the electron density. The measurement technique is analyzed theoretically and experimentally, demonstrated in density measurements of an inductively coupled radio-frequency plasma, and is compared with the double probe and a plasma oscillation methods.

The characteristics of nitrided HfO2 films suggest that the diffusion of Si from the Si substrate to the film surface is induced by annealing in an NH3 ambient and that the incorporation of N is closely related to the diffusion of Si. Changes in the core-level energy state of the N 1s peaks of nitrided HfO2 films indicate that the quantity of N incorporated into the film drastically increases with increasing annealing temperature, especially at temperatures over 900°C. The incorporated N is mostly bonded to Si that diffused from the Si substrate into the film, while some N is incorporated to HfO2 at high annealing temperature. Some molecular N2 is generated in the film, which is easily diffused out after additional annealing. Moreover, the chemisorbed N in the film is not completely stable, compared to that at the interfacial region: i.e., the N in the film predominantly out diffuses from the film after additional annealing in a N2 ambient.

Articles you may be interested inDependence of optimized annealing temperature for tetragonal phase formation on the Si concentration of atomic-layer-deposited Hf-silicate film Change in phase separation and electronic structure of nitrided Hf-silicate films as a function of composition and post-nitridation anneal Thermal stability and electronic structure of xHfO 2 · ͑100− x͒SiO 2 ͑HfSiO͒ ͑x = 25%, 50%, and 75%͒ grown by atomic layer deposition were investigated by various measurement tools. The quantity of incorporated SiO 2 content changes the binding energy of HfO 2 as the charging effect in the silicate is enhanced with the quantity SiO 2 . When the annealing temperature is increased over 800°C, phase separation between SiO 2 and HfO 2 is observed in the films with 50% and 75% HfO 2 , while it does not occur in a Hf-silicate film with a high mole fraction of SiO 2 . The phase separation begins in the surface region via the segregation of SiO 2 . After the annealing treatment, the quantity of SiO 2 supplied to the film surface due to interfacial interactions influences the phase separation process, resulting in no phase separation being observed, even at a high annealing treatment of 900°C.