Abstract
Aimed at the problem of the small wet etching depth in sapphire microstructure processing technology, a multilayer composite mask layer is proposed. The thickness of the mask layer is studied, combined with the corrosion rate of different materials on sapphire in the sapphire etching solution, different mask layers are selected for the corrosion test on the sapphire sheet, and then the corrosion experiment is carried out. The results show that at 250 °C, the choice is relatively high when PECVD (Plasma Enhanced Chemical Vapor Deposition) is used to make a double-layer composite film of silicon dioxide and silicon nitride. When the temperature rises to 300 °C, the selection ratio of the silicon dioxide layer grown by PECVD is much greater than that of the silicon nitride layer. Therefore, under high temperature conditions, a certain thickness of silicon dioxide can be used as a mask layer for deep cavity corrosion.
Highlights
IntroductionThe traditional semiconductor pressure sensor can only be used in the low temperature range; even if silicon-on-insulator (SOI) is used, it can only work below 500 ◦ C [1–8]
The flatness of the sapphire etching cavity mask area is the key to the sapphire sensitive cavity bonding technology
To make sensitive cavities of different depths for different optical fiber signals, it is very important to choose the thickness of the mask layer according to the selection ratio of the wet corrosion of materials
Summary
The traditional semiconductor pressure sensor can only be used in the low temperature range; even if silicon-on-insulator (SOI) is used, it can only work below 500 ◦ C [1–8]. It was found that when the wavelength of the optical fiber signal needed to match the sensitive cavity with a depth of less than 10 μm, the size and depth error of the sensitive cavity were required to be less than 1 μm or even smaller, and when the SiO2 film made by PECVD was thin, the density was poor, which seriously affected the surface roughness of the substrate, resulting in a greatly reduced sapphire bond synthesis rate. It is proposed to make the mask layer by superposing SiO2 and the metal layer This method avoids the problem of a poor compactness of thin SiO2 and solves the problem of a poor bonding surface roughness after sapphire wet etching. While ensuring the integrity and roughness of the sapphire bonding surface, the depth of the sapphire sensitive cavity is increased, so as to realize the fabrication of the sapphire deep cavity structure
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