Method for preparing thick film silicon nitride waveguide

Abstract

The invention discloses a method for preparing a thick film silicon nitride waveguide, comprising the steps of: sequentially forming a lower cladding layer and a sacrificial layer on a semiconductor substrate, wherein the height of the sacrificial layer is the same as the thickness of a preset waveguide; photoetching and etching the sacrificial layer to form a core layer groove by using an upper surface of the lower cladding layer as a termination layer, wherein the width of the core layer groove is greater than the width of the preset waveguide; depositing a core layer material in the core layer groove and on the sacrificial layer to form a first core layer; removing the excess first core layer by using a surface planarization process and by using the upper surface of the sacrificial layer as the termination layer; repeating the above step until the thickness of the core layer formed in the core layer groove reaches the thickness of the preset waveguide; removing the sacrificial layerand etching the core layer to form a preset waveguide structure by using the upper surface of the lower cladding layer as the termination layer; and forming an upper cladding layer on the preset waveguide structure on the lower cladding layer. By adopting the scheme, the high stress problem caused by the excess thickness of the thin film is solved, and the shape of the waveguide is optimized to reduce the sidewall roughness.

Description

technical field [0001] The invention relates to the technical field of integrated optics, in particular to a method for preparing a thick-film silicon nitride waveguide. Background technique [0002] At present, the silicon nitride film growth and preparation methods mainly include LPCVD (low pressure chemical vapor deposition) and so on. The silicon nitride film deposited by LPCVD has good quality and low waveguide loss. However, when the thickness of the film is greater than 300 nanometers, due to the difference in thermal expansion coefficient between the film and the substrate, when the film grows in a large area, there will be a large stress and cracks will easily occur, thereby affecting the performance of the device. In the existing production process, a dry etching process is usually used to open a groove in the silicon dioxide cladding layer, and then fill the groove with silicon nitride to obtain a thick-film silicon nitride optical waveguide. However, the proble...

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Problems solved by technology

However, the problem of high stress in the growth of thick film silicon nitride has not been well solved. In addition, in the traditional trenching method, there will be many cavities, the shape of the waveguide is not good enough, and the sidewall is rough.

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