In recent years, in CCD image sensors and CMOS image sensors, sensitivity is reduced by a reduction in the number of photons incident on a unit pixel with a reduction in pixel size, thereby leading to a reduction in S/N. Moreover, in a currently widely used pixel arrangement where red, green, and blue pixels are arranged on a plane, green and blue light does not pass through a color filter in the red pixel and is not used in photoelectric conversion, thereby resulting in a loss of sensitivity. Further, an issue of a false color arises in association with generation of a color signal by interpolation processing between pixels.
As a method of solving these issues, there is known an image sensor configured by laminating three photoelectric conversion layers in a vertical direction to obtain photoelectric conversion signals of three colors by one pixel. As such a configuration in which photoelectric conversion layers of three colors are laminated in one pixel, for example, there is proposed a configuration in which a photoelectric conversion section configured to detect green light is provided above a silicon substrate and two PDs laminated in the silicon substrate are configured to detect blue light and red light (refer to PTL 1).
Moreover, there is proposed a backside illumination type configuration having a circuit formation surface formed on a side opposite to a light reception surface in a configuration in which one photoelectric conversion film is provided above a silicon substrate and photoelectric conversion sections of two colors are provided in the silicon substrate.
In addition, there is proposed specifically a backside illumination type configuration in which an organic photoelectric conversion section configured of an organic photoelectric conversion layer is formed above a silicon substrate (refer to PTL 2). In this configuration, a circuit, wiring, and the like are not formed between an inorganic photoelectric conversion section and the organic photoelectric conversion section; therefore, a distance between the inorganic photoelectric conversion section and the organic photoelectric conversion section in a same pixel is allowed to be reduced. Therefore, F-number dependence of each color is allowed to be suppressed, and variation in sensitivity among respective colors is allowed to be reduced.
In a case where the organic photoelectric conversion section is provided above the substrate, a level difference is formed by the organic photoelectric conversion section. Therefore, to form an on-chip lens on the organic photoelectric conversion section, it is necessary to eliminate the level difference for planarization.
The above-described PTL 2 describes a flow in which, after a laminate film of an organic photoelectric conversion layer and an upper electrode configuring the organic photoelectric conversion section is patterned, and processed by dry etching, a planarization film is embedded, and an on-chip lens is formed above the planarization film.
Moreover, as a planarization method of reducing a level difference, there is proposed a method in which formation of NSG by a coating film and etchback on an entire surface are performed (for example, refer to PTL 3). Further, there is proposed a technique in which a first passivation film is etched back to reduce a level difference and then a second passivation film is laminated (for example, refer to PTL 4).