Solid-state imaging device and method of producing solid-state imaging device

Abstract

A solid-state imaging device includes a sensor including an impurity diffusion layer provided in a surface layer of a semiconductor substrate; and an oxide insulating film containing carbon, the oxide insulating film being provided on the sensor.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a solid-state imaging device and a method of producing a solid-state imaging device. In particular, the present invention relates to a solid-state imaging device in which an interface state of a surface of a semiconductor substrate having a sensor that performs photoelectric conversion can be compensated for.[0003]2. Description of the Related Art[0004]It is known that, in a solid-state imaging device such as a CCD or CMOS image sensor, crystal defects in the sensor composed of a photodiode and an interface state at an interface between a surface of the sensor and a film disposed thereon become causes of generation of dark current. A hole accumulated diode (HAD) structure is known as a technology for suppressing the generation of dark current due to the interface state, which is one of the above causes.[0005]FIG. 8A shows a structure to which the HAD structure is not applied. In the stru...

AI Technical Summary

Benefits of technology

[0009]However, there is a trade-off relationship between the depth of the hole accumulation layer 207 and dark current due to the interface state at the surface of the HAD structure. Accordingly, decreasing the thickness of the hole accumulation layer 207 is a factor of increasing the dark current. In addition, as the depth of the hole accumulation layer 207 decreases, variations increase and thus an effect on an increase in the dark current increases.

[0010]Accordingly, it is desirable to provide a solid-state imaging device in which dark current due to an interface state can be decreased without providing a hole accumulation layer composed of an impurity diffusion layer, thereby providing a sensor at a shallow position within a semiconductor substrate to improve a charge transfer efficiency, and a method of producing the same.

[0013]In the solid-state imaging device having the above structure, the oxide insulating film containing carbon is provided on the sensor. The oxide insulating film containing carbon functions as a negative-charge accumulation layer having a negative fixed charge. Consequently, by providing the oxide insulating film on the sensor, positive charges can be efficiently attracted to the surface side of the semiconductor substrate by a negative band-bending effect in the oxide insulating film. Consequently, a hole accumulation layer is formed in this portion, thus compensate for the interface state. Furthermore, the amount of negative fixed charge in the oxide insulating film is controlled by the carbon concentration. Accordingly, the hole accumulation layer can be reliably formed on the surface side of the semiconductor substrate by a sufficient band-bending effect.

[0014]As described above, according to the solid-state imaging device according to an embodiment of the present invention, by providing an oxide insulating film having a sufficient negative band-bending effect obtained by controlling the carbon concentration, a hole accumulation layer can be reliably formed in a surface layer of a semiconductor substrate having a sensor, and thus an interface state can be compensated for. Accordingly, generation of dark current and white spots can be prevented by constituting an HAD structure without providing on a surface of a sensor a hole accumulation layer being composed of an impurity diffusion layer which is formed by performing a heat treatment at a high temperature. As a result, the sensor can be provided at a shallow position in a surface of a semiconductor substrate, thereby increasing a transfer efficiency of charges to a floating diffusion portion which is disposed on a side of the sensor with a gate electrode provided between the sensor and the floating diffusion portion.

Problems solved by technology

It is known that, in a solid-state imaging device such as a CCD or CMOS image sensor, crystal defects in the sensor composed of a photodiode and an interface state at an interface between a surface of the sensor and a film disposed thereon become causes of generation of dark current.

Images