Daniel Kropman

Effect of Ultrasonic Treatment on the Defect Structure of the Si-SiO2 System

The effect of ultrasonic treatment (UST) on the defect structure of the Si–SiO2 system is characterised by means of electron spin resonance (ESR), metallography, MOS capacitance measurements and secondary ion mass spectroscopy (SIMS). A non-monotonous dependence of the defect densities on the ultrasonic wave intensity has been observed. The influence of the UST frequency on the ESR signal intensity of the defect centres depended on the defect’s type and structure and may be caused by vibrational energy dissipation which is a function of the defect centre’s type. The influence of the UST on the Si–SiO2 interface properties depends on the oxide thickness and crystallographic orientation. The density of point defects and absorbed impurities at the Si–SiO2 interface can be reduced and its electrical parameters improved by an appropriate choice of UST and oxidation conditions.

Interaction of Point Defects with Impurities in the Si-SiO2 System and its Influence on the Properties of the Interface

The results of investigation of the point defect generation and interaction with impurities in the Si-SiO2 system during the process of its formation by means of electron paramagnetic resonance (EPR) and nucleous magnetic resonance (NMR) technique are presented. It has been shown that the diference in point defects interaction with hydrogen at the Si-SO2 interface with n- and p-type conductivity are connected with the sign of hydrogen ions incorporation dependence on the Fermi level position in accordance with the proposed model. The interface properties may be improved by laser irradiation.

Hydrogen Interaction with Point Defects in the Si-SiO2 Structures and its Influence on the Interface Properties

The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation condition: temperature, cooling rate, oxidation time, impurity content. Interaction between the point defects with extended defects and impurities affects the SiO2 structure and Si-SiO2 interface properties. Hydrogen adsorption on n- and p- type wafers is different. One possible reason for that can be the strength of the magnetic interaction between the hydrogen and paramagnetic impurities of the adsorbent. The influence of point defects and impurities may be diminished and the interface properties improved by an appropriate choice of the oxidation conditions and postoxidation laser irradiation.

Stress Relaxation Mechanism by Strain in the Si-SiO2 System and its Influence on the Interface Properties

The results of the investigation of stresses relaxation by strain by means of EPR spectra, IR absorption spectra, SEM and samples deflection are presented. It has been shown that stresses relaxation mechanism depended on the oxidation conditions: temperature, cooling rate, oxide thickness. In the Si-SiO2-Si3N4 system the stresses relaxation by the strain occur due to the opposite sign of the thermal expansion coefficient of Si-SiO2 and Si3N4 on Si. Laser irradiation allows to modify the system stresses.

Interaction of Point Defects with Impurities in the Si-SiO2 System and its Influence on the Interface Properties

The results of an investigation of the point defects (PD) generation, redistribution and interaction with impurities in the Si-SiO2 system during the process of its formation in use of of electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectra are presented. The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation conditions: temperature, cooling rate, oxidation time and impurity content. The difference between interface properties of n- and p-type wafers could be related to different Fermi level position at the interface and to different PD densities in volume.

Stress relaxation mechanism by strain in the Si-SiO2 system and its influence on the interface properties

The results of the investigation of stresses relaxation by strain by means of EPR spectra, IR absorption spectra, scanning electron microscopy and samples deflection are presented. It is shown that stresses relaxation mechanism depend on the oxidation condition: temperature, cooling rate and oxide thickness. In the Si-SiO2-Si3N4 system the stresses relaxation by the strain occurs due to the opposite sign of the thermal expansion coefficient of Si-SiO2 and Si3N4 on Si. Laser irradiation allows modifying the system stresses.

Point Defects Generation Kinetics in the Si-SiO2 System and its Influence on the Interface Properties

It has been shown by means of EPR and NMR technique that at the Si-SiO2 interface at appropriate oxidation temperature (time) local dynamical equilibrium may be achieved. At oxidation temperature 1130oC the dencity of point defects is less than at lower and higher temperature (1100oC and 1200°C) and the content of absorbed impurities (hydrogen, oxygen) diminishes.

Point Defects Interaction with Extended Defects and Impurities and Its Influence on the Si-SiO2 System Properties

The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation condition: temperature, cooling rate, oxidation time, impurity content. The interaction between point defects with extended defects and impurities affect the Si-SiO2 interface properties. The influence of point defects may be diminished and the interface properties improved by an appropriate choice of oxidation conditions.