High-sensitivity image sensor and fabrication method thereof

Abstract

A method of fabricating a high-sensitivity image sensor is disclosed. The disclosed method comprises: etching a predetermined region of active silicon and a buried oxide layer by using a mask over an SOI substrate to expose an N-type silicon substrate; implanting P-type ions into the exposed N-type silicon substrate to form a P-type region; forming crossed active silicon by patterning the rest of the active silicon not etched while the active silicon is etched to expose the N-type silicon substrate; implanting P-type ions into first two predetermined regions facing each other of the crossed active silicon to form P-type regions; implanting N-type ions into second two predetermined regions facing each other except for the P-type regions of the crossed active silicon to form N-type regions; forming a gate oxide layer and a gate electrode on the crossed active silicon; and forming a connection part to connect the P-type region of the crossed active silicon to the P-type region of the silicon substrate.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an image sensor and, more particularly, to a high-sensitivity image sensor embodied on a silicon-on-insulator (hereinafter referred to as “SOI”), achieving a high sensitivity and a high degree of integration. [0003] 2. Background of the Related Art [0004] Referring to FIG. 1a, an image sensor generally has stacked structure comprising a P-type silicon substrate 1 and an N-type silicon substrate 2 formed by epitaxial growth. The stacked structure also includes a photodiode 3 and a bipolar transistor 4 that functions as a circuit for processing a signal produced from the photodiode 3. The N-type silicon substrate is divided into plural regions by P-type buried diffusion layers 5. The photodiode 3 and the bipolar transistor 4 are provided in or on the plural regions of the N-type silicon substrate. [0005] The photodiode 3 is constructed by using a PN junction that is an interface betwee...

AI Technical Summary

Benefits of technology

[0013] An object of the present invention is to provide a method of fabricating a high-sensitivity image sensor embodied on a SOI, achieving a high sensitivity and a high degree of integration.

[0014] Another object of the present invention is to provide a high-sensitivity image sensor embodied on a SOI, achieving a high sensitivity and a high degree of integration.

Problems solved by technology

A conventional CMOS image sensor using a bulk-silicon substrate has a technical limitation in terms of the improvement of sensitivity and a noise characteristic, and the possibility that light-excited carriers can be created in undesirable region by light irradiation always remains.

Furthermore, a presence of parasitic stray capacitance causes an increment of a noise and the degradation of operation speed, so that a characteristic of the sensor is deteriorated.

Moreover, for a CMOS image sensor using a conventional SOI substrate, an epitaxial silicon layer placed on a buried oxide layer is so thin that an operation of a high voltage transistor is difficult.

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