Preparation method of area thick film silicon nitride

Abstract

The invention provides a preparation method of area thick film silicon nitride, and the method comprises the following steps of sequentially forming a lower cladding layer and a sacrificial layer on asemiconductor substrate, wherein the height of the sacrificial layer is the same as the thickness of a preset waveguide device area; forming a plurality of core region grooves by taking the upper surface of the lower cladding layer as a stop layer; depositing a core layer material in the plurality of core region grooves and on the sacrificial layer to form a first core layer, wherein the thickness of the first core layer is smaller than that of the preset waveguide device area; removing the redundant first core layer by taking the upper surface of the sacrificial layer as the stop layer; repeating the above-mentioned steps until the thickness of the formed core layer reaches the thickness of the preset waveguide device area; removing the sacrificial layer to form a plurality of core regions by taking the upper surface of the lower cladding layer as the stop layer, and etching the core regions to form a preset waveguide device structure; and forming an upper cladding layer on the preset waveguide structure and the lower cladding layer. The preparation method of area thick film silicon nitride solves the problem of high stress caused by too thick film, is beneficial to realize highintegration of a chip, and simultaneously solves the problem that direct grooving is not beneficial to prepare a high-integration waveguide device.

Description

technical field [0001] The invention relates to the technical field of integrated optics, in particular to a preparation method of regional thick-film silicon nitride. Background technique [0002] At present, the silicon nitride film growth and preparation methods mainly include LPCVD (low pressure chemical vapor deposition) and PECVD (plasma chemical vapor deposition). Thick film deposition can be achieved by using PECVD, but there are many impurities in the film and the compactness is poor, so the waveguide prepared by it has high transmission loss. However, the silicon nitride film deposited by LPCVD has good quality and low waveguide loss, but there is a problem of high stress, especially when the film thickness is greater than 300 nanometers, it is difficult to achieve large-area growth, and a large number of cracks will appear in the film, which cannot realize high-performance devices. preparation. In the existing production process, a dry etching process is usually...

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Problems solved by technology

Using PECVD can achieve thicker film deposition, but there are many impurities in the film and the density is poor, so the waveguide prepared by it has high transmission loss

However, the silicon nitride film deposited by LPCVD has good quality and low waveguide loss, but there is a problem of high stress, especially when the film thickness is greater than 300 nanometers, it is difficult to achieve large-area growth, and a large number of cracks will appear in the film, which cannot realize high-performance devices. preparation of

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, but in the preparation of highly integrated nitrogen When siliconizing devices and chips, a lot of unequal width and high-density silicon dioxide grooves are required, which will cause unevenness of CMP and increase the difficulty of design and process. Problems such as poor straightness and high roughness

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