SiO2 is formed by the reaction below: Si (s) + O2 (g) -> SiO2 (s), occurring on

Question

SiO2 is formed by the reaction below: Si (s) + O2 (g) -> SiO2 (s), occurring on a flat surface (wafer) of Si. The molecular oxygen (O2), species (A) dissolve in SiO2 (s) and diffuses through the oxide film and then reacts with Si at the interface Si/SiO2. Develop an equation to calculate how the film thickness of SiO2 () varies over time, from the following considerations:
A) The oxidation process is controlled by the diffusion of O2 through the dioxide film. B) The process occurs in pseudo permanent regime C) ya=yas=cte. On the surface of the oxide film is exposed to oxygen (x=0) D) ya=0 on the surface Si/SiO2 (x=)
SiO2 is formed by the reaction below: Si (s) + O2 (g) -> SiO2 (s), occurring on a flat surface (wafer) of Si. The molecular oxygen (O2), species (A) dissolve in SiO2 (s) and diffuses through the oxide film and then reacts with Si at the interface Si/SiO2. Develop an equation to calculate how the film thickness of SiO2 () varies over time, from the following considerations:
A) The oxidation process is controlled by the diffusion of O2 through the dioxide film. B) The process occurs in pseudo permanent regime C) ya=yas=cte. On the surface of the oxide film is exposed to oxygen (x=0) D) ya=0 on the surface Si/SiO2 (x=)
SiO2 is formed by the reaction below: Si (s) + O2 (g) -> SiO2 (s), occurring on a flat surface (wafer) of Si. The molecular oxygen (O2), species (A) dissolve in SiO2 (s) and diffuses through the oxide film and then reacts with Si at the interface Si/SiO2. Develop an equation to calculate how the film thickness of SiO2 () varies over time, from the following considerations:
A) The oxidation process is controlled by the diffusion of O2 through the dioxide film. B) The process occurs in pseudo permanent regime C) ya=yas=cte. On the surface of the oxide film is exposed to oxygen (x=0) D) ya=0 on the surface Si/SiO2 (x=)

Explanation / Answer

The oxidation of silicon is a diffusion process as follows: Due to the relatively open structure of SiO2, oxygen molecules or water molecules will diffuse through the growing SiO2 layer and reach the silicon surface, whereupon these molecules will form SiO2. Under exposure to oxygen(1), a silicon surface oxidizes to form silicon dioxide (SiO2). Native silicon dioxide is a high-quality electrical insulator and can be used as a barrier material during impurity implants or diffusion, for electrical isolation of semiconductor devices, as a component in MOS transistors, or as an interlayer dielectric in multilevel metallization structures such as multichip modules. The ability to form a native oxide was one of the primary processing considerations which led to silicon becoming the dominant semiconductor material used in integrated circuits today. Thermal oxidation of silicon is easily achieved by heating the substrate to temperatures typically in the range of 900-1200 degrees C. The atmosphere in the furnace where oxidation takes place can either contain pure oxygen or water vapor. Both of these molecules diffuse easily through the growing SiO2 layer at these high temperatures. Oxygen arriving at the silicon surface can then combine with silicon to form silicon dioxide. The chemical reactions that take place are either

si + o_2 = sio_2

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