Solid-state imaging device

A solid-state imaging device is provided and includes: a semiconductor substrate; a plurality of photoelectric conversion films stacked above the semiconductor layer and absorbing different wavelength regions of light; and a transmission-blocking film at least one between the plurality of photoelectric conversion films, the transmission-blocking film blocking a transmission of a particular region of light, the particular region of light having a wavelength in a region to be absorbed in a photoelectric conversion film located above and nearest to the transmission-blocking film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid-state imaging device having a plurality of photoelectric conversion films stacked above a semiconductor substrate and for absorbing different wavelength portions of light.

2. Description of Related Art

There is proposed a solid-state imaging device having a semiconductor substrate over which are stacked, in a plurality of levels, photoelectric converters each including a photoelectric conversion film that absorbs light and generates an electric charge in an amount commensurate therewith, a pixel electrode film where to move, of the charges generated at the photoelectric conversion film, the charge for use in producing image data, and a counter electrode film provided opposite to the pixel electrode film with respect to the photoelectric conversion film (see JP-A-2002-83946, for example). JP-A-2002-83946 discloses a structure stacking, as a photoelectric converter, an R photoelectric converter including a photoelectric conversion film to detect red (R), a G photoelectric converter including a photoelectric conversion film to detect green (G) and a B photoelectric converter including a photoelectric conversion film to detect blue (B), in this order.

However, in the structure photoelectric conversion films are stacked as in the solid-state imaging device described in JP-A-2002-83946, the unabsorbed portion of light in the upper photoelectric conversion film is to enter the another photoelectric conversion film, thus raising a concern that color separation is not fully done.

SUMMARY OF THE INVENTION

An object of an illustrative, non-limiting embodiment of the invention is to provide a solid-state imaging device capable of separating colors to a full extent.

According to an aspect of the invention, there is provided a solid-state imaging device including: a semiconductor substrate; a plurality of photoelectric conversion films stacked above the semiconductor layer and absorbing different wavelength regions of light; and at least one transmission-blocking film between the plurality of photoelectric conversion films, the transmission-blocking film blocking a transmission of a particular region of light, the particular region of light having a wavelength in a region to be absorbed in a photoelectric conversion film located above and nearest to the transmission-blocking film.

In the solid-state imaging device, the transmission-blocking film may absorb the particular region of light to block the transmission of the particular region of light.

In the solid-state imaging device according to claim1, the transmission-blocking film may transmit a wavelength region of light, the wavelength region being absorbed in a photoelectric conversion film located lower than the transmission-blocking film.

The solid-state imaging device may include a light-reflection film between the semiconductor substrate and a photoelectric conversion film located nearest to the semiconductor substrate.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Although the invention will be described below with reference to the exemplary embodiment thereof, the following exemplary embodiment and its modification do not restrict the invention.

According to an exemplary embodiment of the invention, a solid state imager capable of separating colors to full extent can be provided.

With reference to the drawings, explanation will be made on an exemplary embodiment according to the present invention.

FIG. 1is a plan view of a solid-state imaging device for explaining the embodiment of the invention.FIG. 2is a sectional view of theFIG. 1solid-state imaging device taken on line A-A.

As shown inFIG. 2, over an n-type semiconductor substrate1, there are stacked an R photoelectric conversion film15that absorbs a wavelength R of light (hereinafter, referred also to as “R-light”) and produces an R component of signal charge commensurate therewith, an G photoelectric conversion film19that absorbs a wavelength G of light (hereinafter, referred also to as “G-light”) and produces a G component of signal charge commensurate therewith, and a B photoelectric conversion film23that absorbs a wavelength B of light (hereinafter, referred also to as “B-light”) and produces a B component of signal charge commensurate therewith, in this order. Note that the stacking order of the photoelectric conversion films is not limited to that. Meanwhile, the photoelectric conversion films each preferably use an organic material. The number of the photoelectric conversion films stacked is not necessarily three but satisfactorily two or more.

As shown inFIG. 1, in a surface of the n-type semiconductor substrate1, there are formed are an n+region3that is a high-concentration n-type impurity region to store the signal charge caused at the R photoelectric conversion film15, an n+region4that is a high-concentration n-type impurity region to store the signal charge caused at the G photoelectric conversion film19, and an n+region5that is a high-concentration n-type impurity region to store the signal charge caused at the B photoelectric conversion film23. The n+regions3-5, arranged in a column direction (in a Y direction inFIG. 1), correspond to one pixel so that pixels are arranged in row (in an X direction inFIG. 1) and column directions in a square grid form. From one pixel, a signal is to be obtained that is commensurate with the R, G and B signal charges detected at the equal points on the respective photoelectric conversion films. Accordingly, based on that signal, one-pixel data can be produced.

Over the n-type semiconductor substrate1, there are formed a vertical transferer50where the signal charges stored in the n+regions3-5are read out and transferred in the column direction, a horizontal transferer30where the signal charges transferred from the vertical transferers50are transferred in the row direction, and an output section40that externally outputs a signal commensurate with the signal charge transferred from the horizontal transferer30. In this manner, a solid-state imaging device100is constructed to read out a signal by means of a CCD signal read-out section including the vertical transferer50, the horizontal transferer30and the output section40. Note that the signal read-out section may be of the MOS type.

As shown inFIG. 2, the R photoelectric conversion film15is sandwiched between a pixel-electrode film14where to move the charge (generally electrons), for use in producing image data, of the charges generated in the R photoelectric conversion film15and a counter electrode film16arranged opposite to the pixel-electrode film14. From now on, the pixel-electrode film14, the R photoelectric conversion film15and the counter-electrode film16, included as a set in one pixel, are referred to as an R photoelectric converter.

The G photoelectric conversion film19is sandwiched between a pixel-electrode film18where to move the charge, for use in producing image data, of the charges generated in the G photoelectric conversion film19and a counter electrode film20arranged opposite to the pixel-electrode film18. From now on, the pixel-electrode film18, the G photoelectric conversion film19and the counter-electrode film20, included as a set in one pixel, are referred to as a G photoelectric converter.

The B photoelectric conversion film23is sandwiched between a pixel-electrode film22where to move the charge, for use in producing image data, of the charges generated in the B photoelectric conversion film23and a counter electrode film24arranged opposite to the pixel-electrode film22. From now on, the pixel-electrode film22, the B photoelectric conversion film23and the counter-electrode film24, included as a set in one pixel, are referred to as a B photoelectric converter.

The pixel-electrode films14,18,22are demarcated on a pixel-by-pixel basis. The counter electrode films16,20,24are usable commonly for all the pixels, and hence not separated on a pixel-by-pixel basis. Alternatively, those may be arranged with demarcation. Likewise, the photoelectric conversion films may be arranged with demarcation. The counter electrode films16,20,24each can be made of ITO (indium tin oxide) or SnO2, but the invention is not limited thereto.

Between the G photoelectric conversion film19and the R photoelectric conversion film15, there is provided a transmission-blocking film26sandwiched between a transparent insulation film17and a transparent insulation film27. The transmission-blocking film26is to block the transmission of the G portion of light to be absorbed in the G photoelectric conversion film19located above and nearest to the transmission-blocking film26.

Between the B photoelectric conversion film23and the G photoelectric conversion film19, there is provided a transmission-blocking film28sandwiched between a transparent insulation film21and a transparent insulation film29. The transmission-blocking film28is to block the transmission of the B portion of light to be absorbed in the B photoelectric conversion film23located above and nearest to the transmission-blocking film28.

The transparent insulation films17,21,27and29each can be made of SiO2, but the invention is not limited thereto.

The transmission-blocking film28serves to absorb B light to be absorbed in the B photoelectric conversion film23provided above the transmission-blocking film28but transmit R and G light other than B light. The film having such a property can be made of a sharp-cut filter, a yellow filter or the like to block B light.

The transmission-blocking film26serves to absorb G light to be absorbed in the G photoelectric conversion film19provided upper the transmission-blocking film26but transmit R and B light other than G. The film having such a property can be made of a sharp-cut filter, a magenta filter or the like to block G light.

Incidentally, the transmission-blocking film26can use an R color filter that blocks B light in addition to G light because the transmission of B light is not essentially. Namely, the transmission-blocking film26may serve to block the transmission of B light that is to be absorbed by the B photoelectric conversion film23. Where the transmission-blocking film26uses a sharp cut filter, a magenta filter or the like to block G light, an increased amount of light is to enter the R photoelectric conversion film15, leading to sensitivity improvement.

A p-well layer2is formed in a surface of the n-type semiconductor substrate1. An n+region3is formed in a surface of the p-well layer2. Connection is provided between the pixel electrode film14and the n+region3by a vertical line36. This provides an electric connection between the R photoelectric conversion film15and the n+region3. The vertical line36is arranged in electrical insulation from those except for the pixel electrode film14and n+region3in connection therewith. In the n+region3, the signal charge generated in the R photoelectric conversion film15is to flow through the pixel electrode film14and vertical line36and stored. The vertical line36can be made of conductive material such as tungsten, but the invention is not limited thereto.

Incidentally, although the n+ region3was illustrated in its section, the n+ regions4,5are similar in section toFIG. 2excepting that the n+ region shown inFIG. 2is changed as an n+ region4or5wherein the vertical line36is connected to the pixel electrode film18for the case with the n+ region4and to the pixel electrode film22for the case with the n+ region5. Accordingly, the n+ regions4,5is omitted to explain in their sections.

Referring back toFIG. 2, an n region6is formed on the right of the n+ region3with a somewhat spacing, as an n-type impurity region lower in concentration than the n+ region3extending in the Y direction. Over the n region6, a transfer electrode11is formed of polysilicon extending up to the above of the n+ region3and serving also as a read-out electrode. A shielding film12is formed over the transfer electrode11. The shielding film12can be made of silicide film including refractory metal such as tungsten, but the invention is not limited thereto. The n region6and the transfer electrode11constitute a vertical transferer50. By applying a read out pulse of a high voltage to the transfer electrode11, the overlap region g of the p-well region2with the transfer electrode11, between the n+ region3and the n region6, turns into a signal read-out region from which the signal charge stored in the n+region3is to be read out. The signal charge, stored in the n+ region3, is to be read out to the n region6by way of the signal read-out region.

An element isolation region7is provided in a region left adjacent the n+ region3, by a p+region higher in concentration than the p-well layer2, or of silicon oxide or the like. This provides an isolation from the adjacent vertical transferer50. On the extreme surface of the n-type silicon substrate1, a silicon oxide film10is formed on which the transfer electrode11is formed.

The shielding film12and the transfer electrode11are buried in a transparent insulation layer13.

In case the light of from a subject enters the solid-state imaging device thus structured, B component of the incident light is absorbed in the B photoelectric conversion film23, to cause hole-electron pairs in an amount commensurate with the absorption amount of light. In this state, in case voltage is applied to the B photoelectric conversion film23by applying a predetermined voltage to between the pixel electrode film22and the counter electrode film24, the electrons generated at the B photoelectric conversion film23flow from the pixel electrode film22through the vertical line36to the n+region5, thus being stored therein.

The light passed through the B photoelectric conversion film23enters the transmission-blocking film28where the unabsorbed portion of B light in the B photoelectric conversion film23is absorbed therein thus blocking the transmission of B light. Thus, only the R and B components of light are allowed to transmit through the transmission-blocking film28and enter the G photoelectric conversion film19.

Of the incident light entered the G photoelectric conversion film19, G light is absorbed in the G photoelectric conversion film19and hole-electron pairs occur commensurate with the absorption amount of light. In this state, in case voltage is applied to the G photoelectric conversion film19by applying a predetermined voltage to between the pixel electrode film18and the counter electrode film20, the electrons generated at the G photoelectric conversion film19flow from the pixel electrode film18through the vertical line36to the n+region4, thus being stored therein.

The light passed through the G photoelectric conversion film19enters the transmission-blocking film26where the unabsorbed portion of G light in the G photoelectric conversion film19is absorbed therein thus blocking the transmission of G light. Thus, only the R component of light is allowed to transmit through the transmission-blocking film26and enter the R photoelectric conversion film15.

Of the incident light entered the R photoelectric conversion film15, R light is absorbed in the R photoelectric conversion film15and hole-electron pairs occur commensurate with the absorption amount of light. In this state, in case voltage is applied to the R photoelectric conversion film15by applying a predetermined voltage to between the pixel electrode film14and the counter electrode film16, the electrons generated at the R photoelectric conversion film15flow from the pixel electrode film14through the vertical line36to the n+region3, thus being stored therein.

The electrons stored in the n+region3,4,5are transferred through the vertical and horizontal transferers50,30and then converted into a signal by the output section40, thus being outputted.

As described above, according to the solid-state imaging device100, the unabsorbed portion of B light in the B photoelectric conversion film23can be prevented from entering the G photoelectric conversion film19or the R photoelectric conversion film15. In addition, the unabsorbed portion of G light in the G photoelectric conversion film19can be prevented from entering the R photoelectric conversion film15. Therefore, color separation is to be done to full extent, thus enabling to take an image with quality.

Explanation was made so far on the example having the three levels of photoelectric conversion films. However, with photoelectric conversion films in two or four or more levels, color separation is made possible to full extent by providing transmission-blocking films between the photoelectric conversion films in a manner to block particular wavelengths of light. In such a case, the particular wavelength of light satisfactorily includes at least a wavelength region of light to be absorbed in the photoelectric conversion film provided upper and nearest to the relevant transmission-blocking film.

Meanwhile, the light, entered the R photoelectric conversion film15located in the lowest level, is reduced in light amount by the absorption in the films stacked above the R photoelectric conversion film15, thus possibly making the sensitivity-to-R lower than that of another color. In order to prevent the lowering of sensitivity, a light-reflection film31is preferably provided between the R photoelectric conversion film31and the semiconductor substrate1, as shown inFIG. 3. The reflection film31is formed on the insulation film13. On the reflection film31, a transparent film32is formed on which the pixel electrode film14is formed.

With the structure as shown inFIG. 3, the unabsorbed portion of R light through the R photoelectric conversion film15is reflected by the reflection film31into the R photoelectric conversion film15and absorbed therein. This improves the sensitivity to R light.

This application claims foreign priority from Japanese Patent Application No. 2006-113644, filed Apr. 17, 2006, the entire disclosure of which is herein incorporated by reference.