Formation method for double-shallow trench isolator

Abstract

A formation method for double-shallow trench isolator includes that an oxide layer and a hard mask layer are formed on the surface of a substrate, and the substrate is provided with a first area and a second area; the hard mask layer and the oxide layer on the first area are etched till the surface of the substrate is exposed, and the exposed surface of the substrate forms a first part area; the hard mask layer is taken as a mask to have the first part area further etched to form a first shallow trench; the first shallow trench is protected, the hard mask layer and the oxide layer on the second area are etched till the surface of the substrate is exposed, and the exposed surface of the substrate forms a second part area; the hard mask layer is taken as the mask to have the first shallow trench and the second part area further etched till the first shallow trench forms a third shallow trench and forms a second shallow trench of the second area. By the formation method, the double-shallow trench is stable in isolation shape, high in uniformity and good in feature.

Description

technical field [0001] The invention relates to the field of semiconductor manufacturing, in particular to a method for forming double shallow trench isolation. Background technique [0002] CMOS image sensors (CMOS image sensors, CIS) are used in applications including digital cameras. In semiconductor technology, CIS is used to sense light projected onto a semiconductor substrate. Generally, these devices utilize an array of active pixels (ie, image sensing elements or cells) that include photodiodes and other elements (eg, transistors) to convert images into digital data or electrical signals. [0003] CIS products usually include a pixel area and a logic (circuit) area. Shallow trench isolation (STI) is a characteristic feature of integrated circuits, used to prevent leakage current between adjacent semiconductor components. [0004] Dark current is the harmful current generated by the pixel when it is not illuminated. The signal corresponding to the dark current may...

AI Technical Summary

Problems solved by technology

Sources of dark current include impurities in the silicon wafer, which can damage the silicon crystal lattice due to manufacturing process technology and heat buildup in the pixel area

Excessive dark current can generate leakage current and cause image degradation and poor device performance

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