What Gases Are Needed to Produce SiO2 by PECVD?

In this paper, the principle and influencing factors of the preparation of silicon oxide by PECVD are introduced.

Reaction equation for the preparation of silicon oxide by PECVD

To prepare SiO2, a silicon source and an oxygen source are required. Silicon source: We are using silane as an example, and the oxygen source can be O₂, N₂O, NO, or CO₂. The reaction equation is：

SiH₄ + 4N₂O → SiO₂ + 2H₂ + 4 N₂

SiH₄ + O₂ → SiO₂ + 2H₂

Note: With oxygen as the oxygen source, the reaction is very fast and can occur at room temperature, which will lead to the formation of particles, and direct contact between the two needs to be avoided. Therefore, N₂O is often used instead of O₂.

Factors influencing deposition rate and film quality

Silane concentration: Directly affects the deposition rate.

Ratio of SiH₄ and N₂O determines the refractive index and stress of the film.

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Effect of the ratio of silane to oxygen on thin films

1,Excess oxygen: SiO₂ and moisture (H₂O) containing hydroxyl groups (OH) are generated, which can lead to a decrease in film quality or stress. The equation is：

SiH₄ + oxygen source ⟶ SiO₂:(OH) + nH₂O

2,Oxygen Balance: Produces high-purity SiO₂ for the best quality of deposited films. The equation is：

SiH₄ +oxygen source ⟶ SiO₂ + 2H₂

3,Insufficient oxygen: SiO₂ hydrogenous compounds are generated, and more hydrogen content is present in the film, resulting in changes in refractive index and stress. The equation is：

SiH₄ + oxygen source ⟶ SiO₂:H + nH₂

END