WO2010134063A2

WO2010134063A2 - Image sensor and method of producing the same

Info

Publication number: WO2010134063A2
Application number: PCT/IL2010/000334
Authority: WO
Inventors: Damian Goldring
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-05-18
Filing date: 2010-04-25
Publication date: 2010-11-25
Anticipated expiration: 2011-11-18
Also published as: WO2010134063A3

Abstract

An active pixel image sensor that comprises a semiconducting layer having a plurality of photon absorbing regions (89) each separately converting radiation into electrical signal, a plurality of nanoparticles (407), each placed to scatter photons in an adjacent photon absorbing region of the plurality of photon absorbing regions, and a plurality of transistors each connected to receive and amplify the electrical signal from at least one of the plurality of photon absorbing regions for a reconstruction of at least one of color and brightness of at least one pixel (402) in an image.

Description

IMAGE SENSOR AND METHOD OF PRODUCING THE SAME

RELATED APPLICATIONS

This application claims priority from U.S. Provisional Patent Application No. 61/179,016 filed on May 18, 2009, U.S. Provisional Patent Application No. 61/244,454 filed on September 22, 2009 and U.S. Provisional Patent Application No. 61/301,063 filed on 3 February 2010. The contents of all of the above documents are incorporated by reference as if fully set forth herein.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to image sensors and, more particularly, but not exclusively, to active pixel image sensors, such as complementary metal oxide semiconductor (CMOS) image sensors and a method of producing the same.

During the last years the prevalence of CMOS image sensors (CISs), also known as CMOS active-pixel sensors (APSs), has increased substantially. The commonly used CMOS image sensor has an NxM matrix of photo sensors which absorb radiation and convert it into electrical charges that represent an electrically coded 2D digital image.

Reference is now made to FIG. 1 , which is a schematic illustration of a cross section of a segment of a known CMOS image sensor. The segment depicts three exemplary active pixels of a CIS having an NxM matrix of active pixels. Each active pixel, for example 70, has a photon absorbing region 89 which is made of a photo sensitive material for converting optical radiation into electrical signal. Examples of such materials are semiconductor materials such as, silicon, III-V semiconductors materials group and organic molecules, and/or polymer materials. Optionally the photon absorbing region 89 includes a bulk of an epitaxial silicon p-n diode (junction) that converts photons to electrons. The photon absorbing region 89 integrates an active transistor that processes the photo-electrons and forwards a signal to a signal processor, optionally via a circuitry 91 of conductors which are placed over the photon absorbing region 89. The epitaxial silicon p-n diodes are fabricated in a semiconducting layer 90. Usually, a color filter of a mosaic of color filters forming a color filter array (CFA) 92 is located above the semiconducting layer 90 and may be referred to herein as a pixel size filter. As the circuitry 91 and the color filter 92 are placed above the photon absorbing region 89, a layer of micro-lenses 93 is commonly added to focus the radiation toward the photon absorbing region 89.

Reduction of the size of an active pixel of a CIS fabricated as depicted in FIG. 1 usually leads to increase of the optical cross-talk between adjacent active pixels as well as the spectral cross talk and electrical crosstalk. In addition, the reduced pixel size reduces the fill-factor (FF), a ratio between the photon absorbing region and non- absorbing region in the pixel. The pixel size. reduction increases the interaction of radiation with the circuitry, an interaction that increases the optical loss and cross-talk. Current pixel size using standard of CIS fabricated as depicted in FIG. 1 reaches about l.l-1.4μm. During the last years, CMOS image sensors with new component arrangement have been developed in order overcome shortcomings of a CMOS image sensor with a reduced pixel size, enabling a higher resolution and/or a reduced image sensor size. For example, CMOS image sensors that have such new component arrangements are back-side illumination (BSI) CMOS image sensors and above integrated circuit (AIC) CMOS image sensors.

Reference is now made to FIG. 2, which is a schematic illustration of a known back-side illumination (BSI) CMOS image sensor. As depicted in FIG. 2, the photon absorbing region 89 of each active pixel, for example 71, is placed between the circuitry 91 and the color filter 92, which is usually placed behind one or more micro-lenses 93. As part of the BSI manufacturing process, the semiconducting wafer 90 is bonded to plastic or glass carrier substrates, such as a pyrex™ wafer and a silicon dioxide (SiO2) wafer. Once this bonding process is completed, the semiconducting wafer 90 is thinned down to several microns using techniques such as grinding, polishing and/or etching.

As depicted in FIG. 2, the circuitry 91 is located behind the semiconducting wafer 90. In such a manner, photons only travel via the color filter 92 and the layer of micro-lenses 93 before hitting the semiconducting wafer 90. In such a manner, the active portion of the photon absorbing region 89 is increased since there is no obstruction from the front side circuitry. This configuration allows reducing the pixel size without substantially increasing optical cross-talk between adjacent active pixels. It should be noted that shallow trench isolation (STI) structures 97 may be used to obtain electrical separation between adjacent active pixels. An AIC CMOS image sensor has a photon absorbing region that includes an absorbing material layer, for example a-Si, that is deposited on the CMOS electronics. The latter is formed above a specifically designed IC that is fabricated using standard IC fabrication tools, for example CMOS fabs. The IC includes some electrical connections and devices as well as conducting vias to the absorbing material layer. Light that hits the AIC sensor is absorbed in the deposited absorbing layer and the created electrical signals are transferred to the IC system through short electrical vias (about l-2μm). Thus, similarly to the BSI CMOS image sensor, no circuitry is placed in front of the photon absorbing region. Usually micro-lenses are not needed so that radiation almost directly heats the photon absorbing region. The AIC CMOS image sensor brings nearly to zero all cross-talk effects and dark currents.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present invention there is provided an active pixel image sensor. The active pixel image sensor comprises a semiconducting layer having a plurality of photon absorbing regions each separately converting radiation into electrical signal, a plurality of nanoparticles, each placed to scatter photons in an adjacent photon absorbing region of the plurality of photon absorbing regions, and a plurality of transistors each connected to receive and amplify the electrical signal from at least one of the plurality of photon absorbing regions for a reconstruction of at least one of color and brightness of at least one pixel in an image.

Optionally, the active pixel image sensor further comprises a plurality of isolation trenches for at least one of optically and electrically separating, at least partly, the plurality of photon absorbing regions from one another.

More optionally, a metallic strip is placed along the plurality of isolation trenches.

More optionally, the height dimension of the plurality of isolation trenches is at least as high as the height dimension of the semiconducting layer. More optionally, the heights difference of each the isolation trench and the semiconducting layer is less than about lOOnm.

Optionally, the plurality of nanoparticles are placed in a first layer, further comprising at least one additional nanoparticles layer placed on top of the first layer. Optionally, the semiconducting layer is between the plurality of nanoparticles and a circuitry connecting the plurality of transistors to a circuit performing the reconstruction.

Optionally, the plurality of nanoparticles is between the semiconducting layer and at least a portion of a circuitry connecting the plurality of transistors to a circuit performing the reconstruction.

Optionally, each the transistor independently receives and amplifies the electrical signal for the reconstruction.

Optionally, the active pixel image sensor further comprises a plurality of floating diffusion (FD) regions each formed in the semiconducting layer, between adjacent sides of two adjacent photon absorbing regions of the plurality of photon absorbing regions.

More optionally, the active pixel image sensor further comprises a plurality of isolation trenches for at least one of electrically and optically separating, at least partly, the two adjacent photon absorbing regions from one another, the plurality of isolation trenches being arranged to optically isolate each the FD region from one of the two adjacent photon absorbing regions while allowing electric charge to pass from another of the two adjacent photon absorbing regions thereto.

More optionally, the active pixel image sensor further comprises a plurality of isolation trenches for at least one of optically and electrically separating, at least partly, the two adjacent photon absorbing regions from one another, the plurality of isolation trenches being placed in a plurality of common planes with the plurality of FD regions, each the common plane being substantially perpendicular to the a plane of the semiconducting layer.

More optionally, the active pixel image sensor of claim 12, wherein the plurality FD regions having a thickness less than the optical wavelength of the radiation.

More optionally, the active pixel image sensor further comprises a plurality of non continuous isolation trenches for at least one of optically and electrically separating, at least partly, the two adjacent photon absorbing regions from one another, the plurality of non continuous isolation trenches being mounted along one or both longitudinal sides of each the FD region.

More optionally, the plurality of non continuous isolation trenches having a plurality of apertures each having a width of less than the optical wavelength of the radiation.

Optionally, the plurality of nanoparticles are made of a member of a group consisting of gold, silver, copper, aluminum, silicon, silica and silicon nitride.

Optionally, the plurality of nanoparticles being placed to filter radiation in a non infrared range of frequencies, the image being an infrared image.

Optionally, the plurality of nanoparticles having a first group of nanoparticles formed to filter radiation in a first range of frequencies and a second group of nanoparticles formed to filter radiation in a second range of frequencies.

More optionally, the active pixel image sensor further comprises a plurality of a third group of nanoparticles formed to filter radiation in a third range of frequencies, the first, second and third ranges being respectively non red, non green, and blue frequencies.

More optionally, members of the first and second groups are placed in a mosaic arrangement in front of the plurality of photon absorbing regions. More optionally, the image is a color image and no color image array is placed in front of the active pixel image sensor.

Optionally, the semiconducting layer having a thickness of less than 400nm.

Optionally, the semiconducting layer having a thickness of less than lOOnm.

Optionally, the plurality of transistors and the semiconducting layer are fabricated in a back-side illumination process.

Optionally, the active pixel image sensor further comprises a color filter array (CFA).

Optionally, the plurality of nanoparticles are formed in the semiconducting layer. According to an aspect of some embodiments of the present invention there is provided a method of forming an active pixel image sensor. The method comprises fabricating a circuit comprising a plurality of transistors in a semiconducting layer, electronically separating the plurality of transistors from one another so as to form a plurality of discrete photon absorbing regions adapted to separately converting radiation into electrical signal, mounting a plurality of nanoparticles to scatter the radiation on or in at least some of the plurality of photon absorbing regions, and connecting the plurality of transistors to receive and amplify the electrical signal from at least one of the plurality of photon absorbing regions for a reconstruction of at least one of color and brightness of at least one pixel in an image.

Optionally, the electronically separating comprises forming a plurality of isolation trenching elements in the semiconducting layer. According to an aspect of some embodiments of the present invention there is provided an active pixel image sensor that comprises a semiconducting wafer having a plurality of photon absorbing regions each separately converting radiation into electrical signal, a plurality of nanoparticles, each placed to filter light with a certain wavelength range from an adjacent photon absorbing region of the plurality of photon absorbing regions, and a plurality of transistors each connected to receive and amplify the electrical signal from at least one of the plurality of photon absorbing regions for a reconstruction of at least one of color and brightness of at least one pixel in an image.

According to an aspect of some embodiments of the present invention there is provided an active pixel image sensor that comprises a semiconducting layer having a plurality of photon absorbing regions each separately converting radiation into electrical signal, a plurality of floating diffusion (FD) regions each formed in the semiconducting layer, between adjacent sides of two adjacent photon absorbing regions of the plurality of photon absorbing regions, and a plurality of isolation trenches for at least one of optically and electrically separating, at least partly, the two adjacent photon absorbing regions from one another, the plurality of isolation trenches being arranged to optically isolate, at least partly, each the FD region from one of the two adjacent photon absorbing regions while allowing electric charge to pass from another of the two adjacent photon absorbing regions thereto.

According to an aspect of some embodiments of the present invention there is provided an active pixel image sensor that comprises a semiconducting layer having a plurality of photon absorbing regions each separately converting radiation into electrical signal, a plurality of floating diffusion (FD) regions each formed in the semiconducting layer, between adjacent sides of two adjacent photon absorbing regions of the plurality of photon absorbing regions, and a plurality of isolation trenches for at least one of optically and electrically separating, at least partly, the two adjacent photon absorbing regions from one another, the plurality of isolation trenches being placed in a plurality of common planes with the plurality of FD regions, each the common plane being substantially perpendicular to the a plane of the semiconducting layer.

According to an aspect of some embodiments of the present invention there is provided an active pixel image sensor that comprises a semiconducting layer having a plurality of photon absorbing regions each separately converting radiation into electrical signal, a plurality of floating diffusion (FD) regions each formed in the semiconducting layer, between adjacent sides of two adjacent photon absorbing regions of the plurality of photon absorbing regions, and a plurality of non continuous isolation trenches for at least one of optically and electrically separating, at least partly, the two adjacent photon absorbing regions from one another, the plurality of non continuous isolation trenches being mounted along both longitudinal sides of each the FD region.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

Implementation of the method and/or system of embodiments of the invention can involve performing or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of embodiments of the method and/or system of the invention, several selected tasks could be implemented by hardware, by software or by firmware or by a combination thereof using an operating system.

For example, hardware for performing selected tasks according to embodiments of the invention could be implemented as a chip or a circuit. As software, selected tasks according to embodiments of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In an exemplary embodiment of the invention, one or more tasks according to exemplary embodiments of method and/or system as described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes a volitile memory for storing instructions and/or data and/or a non-volatile storage, for example, a magnetic hard-disk and/or removable media, for storing instructions and/or data. Optionally, a network connection is provided as well. A display and/or a user input device such as a keyboard or mouse are optionally provided as well.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced. It should be noted that although a number of similar components and/or elements may be depicted in each one of the figures herein, a single numeral may be used for identifying them jointly and severally.

In the drawings: FIG. 1 is a schematic illustration of a cross section of a segment of a known APS

CMOS image sensor;

FIG. 2 is a schematic illustration of a known back-side illumination (BSI) CMOS image sensor;

FIG. 3A is a cross section view of a segment of a backside illuminated CMOS image sensor having a layer of nanoparticles, according to some embodiments of the present invention;

FIG. 3 B is a schematic illustration of an active pixel image sensor having a nanoparticles, according to some embodiments of the present invention;

FIG. 3 C is a schematic illustration of a segment of an active pixel image sensor having floating diffusion (FD) regions between active pixels;

FIGs. 3D-3E, are schematic top view illustrations of a segment of an image sensor having floating diffusion regions and isolation trenches sized and shaped to isolate each FD region from active pixels which are not assigned thereto, according to some embodiments of the present invention;

FIGs. 3F-3G, are top view schematic illustrations of a segment of an image sensor having floating diffusion regions and non continuous isolation trenches for at least partly isolating them, according to some embodiments of the present invention;

FIG. 3H is a top view schematic illustration of a segment of an active pixel image sensor having lateral floating diffusion regions and continuous isolation trenches which do not completely isolate the space between two active pixels and an isometric view blowup of two active pixels thereof, according to some embodiments of the present invention;

FIG. 4 is a schematic illustration of the backside illuminated CMOS image sensor that is depicted in FIG. 3A, with a color filter array (CFA), according to some embodiments of the present invention;

FIG. 5 is schematic illustration of a segment of a semiconducting wafer bounded between two STI structures, in front of an exemplary active pixel and behind of a nanoparticle(s) and a buffer layer, according to some embodiments of the present invention;

FIG. 6 A is a flowchart of a method of forming an image sensor having a plurality of nanoparticles, according to some embodiments of the present invention; FIG. 6B is another flowchart of a method of forming an image sensor having a plurality of nanoparticles, according to some embodiments of the present invention;

FIG. 7 is a schematic illustration of a cross section of a segment of an AIC CMOS image sensor having a layer of nanoparticles, according to some embodiments of the present invention; FIG. 8 is a schematic illustration of a cross section of a segment of an AIC

CMOS image sensor, as shown at FIG. 7 where the nanoparticles are embedded in transparent electrodes thereof , according to some embodiments of the present invention; and

FIG. 9 is a graph that depicts the outcome of an experiment performed with a CMOS image sensor having the structure according to some embodiments of the present invention. DESCRIPTION OF EMBODIMENTS OF THE INVENTION

According to some embodiments of the present invention there is provided an active pixel image sensor having a plurality of active pixels, where some or all of the pixels have one or more nanoparticles which are placed on the active pixels to scatter radiation and/or to enhance the optical absorption thereof in their photon absorbing regions and/or to filter the radiation from their photon absorbing regions. The active pixel image sensor includes a semiconducting layer in which the photon absorbing regions are formed and separately convert radiation into electrical signal. The photon absorbing regions are optionally optically and/or electronically separated or partially separated from one another by isolation trenches, such as deep trench isolation (DTI) and/or shallow trench isolation (STI) structures. The active pixel image sensor further includes a plurality of electrical devices/circuits which are connected to receive and amplify the electrical signal from one or more of the photon absorbing regions for a reconstruction of color and/or brightness of one or more pixels in an image. The active pixel image sensor further may include a plurality of nanoparticles, each placed to scatter the optical radiation in one of the photon absorbing regions. Optionally, the nanoparticles are mounted as a non-homogeneous layer on top of the semiconducting material layer.

Optionally, the nanoparticles are selected to filter certain wavelengths, for example, red, blue, and/or green light. Groups-of such nanoparticles may be placed above the photon absorbing regions in a mosaic pattern, such as a Bayer filter pattern. In such a manner, the active pixel image sensor may be used to capture a color image without using a color filter array.

Optionally, the nanoparticles are metal nanoparticles, such as gold, silver, copper, and aluminum nanoparticles sized to scatter predominately radiation.

Optionally, the shape, size, material and relative location of the nanoparticles are adjusted to scatter, enhance or filter light in certain wavelength ranges. According to some embodiments of the present invention there is provided a method of forming an active pixel image sensor. The method is based on forming a plurality of electrical devices/circuits in a semiconducting layer and electronically separating the electrical circuits from one another so as to form a plurality of discrete photon absorbing regions adapted to separately converting radiation into electrical signal. Then one or more nanoparticles are placed to scatter the radiation in some or all of the photon absorbing regions and the transistor circuits are connected to receive and amplify the electrical signal from one or more of the photon absorbing regions for a reconstruction of color and/or brightness of one or more pixels in an image. Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

Reference is now made to FIG. 3 A that shows a cross section view of a segment of an active pixel image sensor 100, such as a CMOS image sensor, having a non- homogeneous layer of nanoparticles 401, according to some embodiments of the present invention. The active pixel image sensor 100 is optionally fabricated as a backside illuminated CMOS image sensor where the nanoparticles 401 are added thereto, for example as described below.

The active pixel image sensor 100 integrates an array of active pixels, for example as shown at 402. Optionally, has a photon absorbing region, as shown at 89, which includes a transistor circuit, such as a 4T architecture pixel transistors having a photodetector, a transfer gate, reset gate, selection gate and source-follower readout transistor (not shown). Each transistor circuit receives and amplifies electrical signal which is converted from absorbed optical radiation at the photon absorbing region 89. In such a manner, the active pixel image sensor 100 reconstructs the color and/or the brightness of a respective pixel in an image that is captured thereby. The array of active pixels is fabricated on one side of a semiconducting layer and/or a semiconducting wafer 403, referred to herein as semiconducting layer 403 such as silicon, GaAs etc., as known in the art. Optionally, Silicon-On-Insulator (SOI) is used as the substrate. The thickness of the active semiconductor layer 403 is less than about 10 microns.

One or more nanoparticles 407 are placed on some or all of the active pixels, optionally on the opposing side of the photon absorbing region 89 of the active pixel, in the semiconducting layer 403. For brevity, a nanoparticle is a particle having at least two dimensions and in most cases three dimensions less than 250 run. Optionally, the size of each nanoparticle is between about 50nm and about 250nm in diameter and between about 20nm and about 150nm in thickness. In some embodiments, the nanoparticles are metal nanoparticles, such as gold, silver, copper, and aluminum nanoparticles sized to predominately scatter radiation. Optionally, an adhesive layer, such as an adhesion promoter layer (for example, HDMS), is used to strongly attach the nanoparticles 401 to the semiconducting wafer 403.

Optionally, a buffer layer 404 separates between the nanoparticles layer 401 and the semiconducting layer 403. Optionally, the buffer layer 404 is made of a non- absorbing material and/or of low refractive index. Such materials are, for example, silicon dioxide, silicon nitride, a polymer or a combination of polymers, for example PMMA, and/or a coating produced by the sol-gel process. The thickness of the buffer is optionally between about 2nm and about lOOnm. Optionally, the space between the nanoparticles is covered with the same material as the buffer. As depicted in FIG. 3 A, shallow trench isolation (STI) structures 405 are- formed or otherwise placed to separate between different active pixels 402 so that the photon absorbing region 89 is bounded, or partially bounded, by STI structures, such as shown by 409. The STI structures are stretched along the semiconducting wafer 403 so as to create a mesh that defines the active pixels 402. Optionally each STI structure is between about 50nm and about 450nm deep. The STI structures are formed during the fabrication of active pixels 402 on the semiconducting layer 403, as commonly known in the art.

The one or more nanoparticles 407, which are placed on the photon absorbing region 89 of some or all of the active pixels, for example as shown at FIG. 3 A, increase the optical absorption of incident photons and/or the photocurrent generation of the respective active pixel, see H. R. Stuart and D. G. Hall, "Absorption Enhancement in

Silicon-on-Insulator Waveguides Using Metal Island Films," Appl. Phys. Left. 69, 2327 (1996); "Island Size Effects in Nanoparticle-Enhanced Photodetectors," Appl. Phys.

Lett. 73, 3815 (1998) and D. M. SCHAADT, B. FENG, and E. T. YU, "enhanced semiconductor optical absorption via surface plasmon excitation in metal nanoparticles," appl. phys. lett. 86, 063106 (2005), which are incorporated herein by reference. Optionally, the nanoparticles 407 increase the optical absorption of light with a certain wavelength range, for example as described below.

Additionally or alternatively, the nanoparticles 407 placed on the photon absorbing regions 89, for example as shown at FIG. 3A, decrease the optical absorption of light with a certain wavelength range. Optionally, the STI structures 405 are stretched all along the semiconducting layer 403, between the buffer layer 404 and the metals layer 91. In such an embodiment, the electric cross-talk between active pixels is eliminated or substantially reduced.

It should be noted that if the semiconducting wafer 403 is thicker than about 400nm, deep trench isolation (DTI) structures may formed or placed instead of the STI structures 405. The DTI structures are similar to STI structures however can go as deep as about 5μm. The fabrication of DTI is known in the art. In such embodiments, the optical cross-talk is reduced or eliminated as the radiation scattering from one pixel to an adjacent pixel is substantially reduced. In other words, the STI or DTI structures 405 block most of the optical radiation entering a certain active pixel from reaching an adjacent active pixel. In such an embodiment, microlenses may be removed, reducing the cost of the image sensor and its overall thickness. Alternatively, microlenses are added to further reduce the optical cross-talk by focusing radiation inside in each active pixel. Optionally, the PN junction of each active pixel has a thinner, about one order of magnitude, photon absorbing region 89 than the photon absorbing region 89 of common CIS active pixel. In such a manner, a lower voltage application is required for fully depleting the PN junction, a depletion performed for efficiently collecting charges when radiation is absorbed. In such a manner, a higher doping concentration, of between about 1 and about 3 orders of magnitude, may be used to provide larger full-well-capacity (FWC) that is equal to the amount of charge the photon absorbing region 89 accumulates before it saturates. Larger FWC means larger dynamic range. As the semiconducting wafer is thin, relatively low power consumption and improved high frequency performance are obtained. Also, thin absorbing region requires only STI for optical cross-talk elimination and does not require harder for fabrication DTI.

According to some embodiments of the present invention, the nanoparticles 401 form red, green and/or blue color filters on the array of active pixels 402. In such a manner, the Active pixel image sensor 100 may be used for capturing a color image without a color filter array (CFA), such as a Bayer filter. As described above, the semiconducting layer 403 may be a thin layer of c-Si, for example between 50nm and 300nm. Placing one or more nanoparticles 407 in front of the photon absorbing region 89 of some or all of the active pixels enhances, for example, by about ten times, the absorption thereof in a certain wavelength range, for example red or green wavelengths, without enhancing other wavelengths, for example, respectively, green and blue or red and blue wavelengths. Optionally, the active pixels above which one or more nanoparticles 401 are selected according to a mosaic arrangement, such as a Bayer filter mosaic. In such an embodiment, nanoparticles that increase red wavelengths are placed above active pixels as if they were red filters in a Bayer filter mosaic and nanoparticles that increase green wavelengths are placed above active pixels as if they were green filters in the Bayer filter mosaic. In such an embodiment, the nanoparticles 401 replace a color blocks of the CFA and increase the sensitivity of the active pixels, as. outlined above and described below. The forming of an active pixel array, as described above, allows generating an active pixel image sensor. For example, FIG. 3 B depicts an active pixel image sensor 50 that includes the semiconducting layer 403 having a plurality of photon absorbing regions 51, each separately converting radiation into electrical signal, as shown at 89 and described above. The photon absorbing regions 51 are separated from one another, optionally by a set of STI structures and/or DTI structures. The active pixel image sensor 50 further includes a plurality of nanoparticles 52, each placed to scatter photons in an adjacent photon absorbing region, such as 89, for example as shown in FIG. 5. Optionally, as shown at FIG. 3B, groups of nanoparticles, such as 53, are formed on some, optionally all, of the photon absorbing regions 51. The active pixel image sensor further includes a plurality of transistor circuits, such as shown in 54. Each transistor circuit is connected to receive and amplify the electrical signal from one or more of the plurality of photon absorbing regions 51. For example, in the segment depicted in FIG. 3 A each transistor circuit is connected to receive and amplify the electrical signal from a separate photon absorbing region. In such a manner, the color and/or the brightness of different pixels may be reconstructed, facilitating the forming of an image based thereupon. It should be noted that the plurality of nanoparticles 52 may enhance absorption of optical radiation in their vicinity, tens of nanometers around them. This enhancement is an outcome of surface waves resonance. As such, the placing of the nanoparticles on the photon absorbing regions 51 enhances their radiation absorption capacity. As used herein to scatter photons means to scatter photons and to enhance radiation absorption of a respective photon absorbing region.

As commonly known, floating diffusion (FD) regions may be formed between different active pixels in some image sensor architectures, for example as shown at FIG. 3C. In CIS which are formed according to these architectures, the photo-generated charge which is accumulated in the active pixel is transferred to a proximate FD region which is formed on one of its sides. The charge is translated to voltage and then read by the CIS readout network. The FD regions are formed in a lateral physical connection in the semiconducting layer where the charge transfer is controlled by a gate contact. Usually, the FD regions are placed between two adjacent pixels and shared by them.

Optionally, if the active pixel is fabricated with FD regions between the active pixels, the nanoparticles are arranged to scatter light away from the FD region. This may be done by locating the nanoparticles farther from the FD region and also by generating a non-symmetrical pattern of nanoparticles on the pixel so to create destructive interference of light radiation at the pixel's area closer to the FD region.

Additionally or alternatively, the image captured by the image sensor is processed to reduce the effect of the cross talk. Such a processing may be based on the expected cross talk effect in the side of the active pixel which is in touch with the FD region. This effect is expected to be stronger than the cross talk effect at the other sides of the active pixels.

Reference is now also made to FIGs. 3D-3E, which are schematic top view illustrations of a segment of an image sensor having lateral floating diffusions and isolation trenches 310 which are sized and shaped to isolate each FD region from active pixels which are not assigned thereto, according to some embodiments of the present invention. In FIGs. 3D and 3E, each FD region is connected to a single active pixel. For example, in FIG. 3D active pixel 312 is connected to FD region 313 and in FIG. 3E active pixel 314 is connected to FD region 315. In such a manner, the FD region can be electrically and optically isolated from other active pixels. Optionally, an FD region between two active pixels is split by the designated isolation tranches. The designated trenches 310 may be fabricated in a common CMOS process technology similar to STI or DTI.

Reference is now also made to FIGs. 3F-3G, which are top view schematic illustrations of a segment of an image sensor having lateral floating diffusion regions and non continuous isolation trenches, according to some embodiments of the present invention. Optionally, designated trenches 311, such as designated STI structures, are placed to prevent from light to pass from one pixel to and while allowing charge thereto.

In such a manner, the functioning of the FD regions is not annulled while electrical current leakage between adjacent active pixels is reduced and the optical isolation is increased. The designated trenches 311 may be fabricated in a common CMOS process technology, optionally the same one used for STI or DTI. As a rule of thumb, non isolating spaces in each non-continuous isolation trench barrier may be between about

50nm and about 150nm, however wider spaces are also possible. The trade-off is between electrical properties of the charge transfer from an active pixel to its FD region and Cross-Talk / Quantum Efficiency (CT/QE).

Optionally, one or more non-continuous isolation trench barriers 311 are placed in the semiconducting layer. Optionally, one non-continuous isolation trench barrier 316 is place along one side of an FD region line 318 and another non-continuous isolation trench barrier 317 is place along an opposing side of the FD region line 318. The non- continuous isolation trench barriers 317, 318 are optionally placed, optionally in parallel to one another, so as to form a continuous isolation barrier along a common axis, as shown at FIGs. 3 F and 3 G. In such embodiments, the continuous isolation barriers serve as continuous light reflectors without blocking the electrical path between an active pixel and an adjacent FD region. Specific sizes and shapes may be determined per specific pixel design.

Reference is now made to FIG. 3H, which is a top view schematic illustration of a segment of an active pixel image sensor 319 having lateral floating diffusion regions and continuous isolation trenches which do not completely isolate the space between two active pixels and an isometric view blowup of two active pixels thereof, encircled by a dashed line, according to some embodiments of the present invention. As shown at 323, the active pixel image sensor 319 includes a layer of nanoparticles, optionally as described above. In such embodiments, the FD region 327 is placed in proximity to the circuitry, metal and poly-Si contacts layer 325, facilitating the fabrication of isolation trenches 326 above them. In such a manner, the isolation trenches 326 do not stretch through the entire semiconducting layer 324. Optionally, the thickness of silicon in the FD region 327 is relatively thin in relation to common FD regions. The isolation trenches 326 may be fabricated after the semiconducting layer 324 is flipped and before the fabrication of the nanoparticles 323 on a buffer layer 328. During the fabrication, the silicon thickness at the FD region is reduced from w to w - h. When w - h <100nm, light confinement in the PD is relativity high and the CT/QE problem is solved. The trade-off is between optical CT reduction and electrical properties of the FD region. Reference is now made to FIG. 4, which is a schematic illustration of the backside illuminated active pixel image sensor 100 that is depicted in FIG. 3 A with a color filter array (CFA) 501, such as a Bayer color filter, according to some embodiments of the present invention.

The CFA 501 has a plurality of pixel size filters that filter radiation by wavelength range, such that active pixels receive different separate filtered intensities that include information about the color of light (captured radiation), for example red, green, and blue (RGB). The raw image data captured by the image sensor 100 may be converted to a full-color image by a demosaicing algorithm tailored for the pattern of the pixel size filters. Optionally, a buffer 503 separates between the nanoparticles 401 and the CFA 501. Optionally, the buffer layer is similar to the buffer layer described above.

Reference is now also made to FIG. 5, which shows schematic illustration of an exemplary photon absorbing region, such as shown at 89 of FIG. 3 A, according to some embodiments of the present invention. The photon absorbing region 89 is in a segment of a semiconducting wafer 403 bounded between two STI or DTI structures 601, sandwiched between a respective circuitry 602 and one or more nanoparticles 503 and optionally a buffer layer (not shown). FIG. 5 further depicts an exemplary trajectory 604 of a photon trapped in the photon absorbing region 89. Trapped photons are scattered in the photon absorbing region 89, between by the STI structures 601 and the nanoparticles

503, until they are converted to electrical signal by the photon absorbing region 89. As such, the distance that these photons pass in the active pixel space 600 is averagely longer than the thickness of the semiconducting wafer 403 that defines the distance between the nanoparticles 503 and the photon absorbing region of the active pixel 602. In such a manner, the absorption of the photon absorbing region 89 is higher than the absorption of a similar absorbing region without the nanoparticles 503 though the thickness of the photon absorbing region 89 is not larger in size and/or space.

Optionally, the STI structures 601 are filled with an isolation material, such as SiO2 and the like. Optionally, a metallic strip is placed in the center of each STI structure 601 so as to increase the isolation coefficient thereof and to reduce further the optical cross-talk between the active pixels.

The scattering of the photons, which is promoted by the nanoparticles and the isolation trenches lengthen the trajectory of light in the photon absorbing regions 89. This increases the light absorption in each active pixel individually. As the light absorption of each pixel is increased thinner absorbing layers may be used without reducing its sensitivity. Thin layers have advantages over thicker layers which are commonly used in front side illumination (FSI) and back side illuminated (BSI) CMOS image sensors. For example, thinner absorbing layers have less cross-talk as light in wider range of angles of incidence does not pass to adjacent active pixels. In addition, when using the thinner layers optical and electrical crosstalk are drastically reduced so that it may allow not using a micro-lenses array. In such a manner, the cost of the image sensor may be reduced. Also, when using common absorbing layers which are thicker than about 2 microns in BSI sensors, short wavelength light, such as light in the blue range, is absorbed close to the surface of the absorbing layers and relatively far from the electrical signal collecting circuit. Therefore, the photo-electrons created by the short wavelength light have relatively higher probability to cross over to the adjacent pixel circuitry and produce cross-talk. This phenomenon is practically diminished when using thin absorbing layers of less than 400nm and STI for the formation of the pixels. Optionally, thickness of the semiconducting absorbing layer 91 is less than about

300nm. In such a manner, the power consumption and frequency performance are greatly improved. Also, in such manner, easier and more flexible fabrication of either NMOS or PMOS is obtained since N or P - well are not required to override the substrate doping as the case is with standard, thicker than 2 micrometers CMOS image sensors.

According to some embodiments of the present invention, the one or more nanoparticles, which are placed on a certain active pixel, are adapted to a wavelength range that a certain active pixel is designated to absorb. Optionally, the size, shape, and/or material of the nanoparticles and/or the location thereof on the surface of the active pixel increase the optical absorption of the active pixel to which they are attached. Optionally, nanoparticles, which are designed to increase the absorption of red green and blue light, are distributed according to a mosaic pattern, such as Bayer pattern, above the photon absorbing regions. In such a manner, the photon absorbing regions may absorb light as if a CFA is mounted on the semiconducting wafer 91. For example, metallic cylindrical particles with a diameter of between about 60nm and about 1 lOnm enhance the optical absorption of blue light; metallic cylindrical particles with a diameter of between about HOnm and about 160nm enhance the optical absorption of green light; and metallic cylindrical particles with a diameter of between about 130nm and about 200nm are suitable to enhance the optical absorption of red light. Metallic cylindrical particles with larger diameter, between about 150nm and about 250nm, are suitable to enhance the optical absorption of IR radiation. Optionally, the shape of the some or all of the nanoparticles is cylindrical, spherical, having a U-shaped front, having an r-shaped front, and/or semi spherical. For example, the cylindrical shape is good for polarization independent sensors while U- shaped can be used for polarized light and for string light focusing.

As described above, some or all of the nanoparticles are made of metals, such as aluminum (Al), silver (Ag) and/or gold (Au). Optionally, the nanoparticles are made of an alloy that comprises one or more of the aforementioned metals. For example, a nanoparticle may be made of an alloy of Al and Ag or an alloy of Al, Ag and Au. Such alloys improve the spectral response of the nanoparticles, for example, alloy of Al and Ag may enhance the optical absorption of short wavelength radiation and IR radiation. Au and Ag may be used to enhance the optical absorption of IR radiation. Also, alloys may prevent physical shortcomings, for example reduce the oxidation tendency of Al particles. In such case Ag can be used to cover Al. Additionally or alternatively, the location of the nanoparticles on the surface of a certain active pixel is determined according to the location of the active pixel in the image sensor 100. The location of the active pixel in the image sensor 100 affects the incidence angle in which radiation from a source in front of the sensor impinges its photon absorbing region. For example, photon absorbing regions of active pixels in the center of the image sensor 100 are hit with radiation in vertical, about 0° incidence angle and photon absorbing regions of active pixels at the edges of the image sensor 100 sensor are hit with in an oblique incidence angle as high as 25°. For example, if the average distance between particles in a red pixel with normal incidence may be about 270nm then, for oblique incidence as described above this distance is slightly larger, for example about 300nm.

Optionally, the nanoparticles may be located on the same side of the absorbing layer as the electronic circuitry. The fabrication of the nanoparticles in such case is done as part of a common CMOS fabrication process, such as FSI and/or BSI fabrication processes. It is also optional to place nanoparticles in both sides of the semiconducting layers, increasing the radiation scattering and the enhancement of light absorption.

According to some embodiments of the present invention, the image sensor 100 functions as an infrared (IR) image sensor. Optionally, an IR-pass filter is placed in front of the layer of nanoparticles. The IR-pass filter filters radiation not in the infrared (IR) area, namely not in the range between about 0.7 and about 300 micrometers, which equates to a frequency range between approximately 1 and 430 terahertz (THz). As described above, in each active pixel, the nanoparticles 401 trap photons between STI structures, for example as shown at FIG. 5. As such, the distance each photon pass in the semiconducting wafer increases. In such a manner, a backside illuminated Active pixel image sensor 100 with nanoparticles, as shown at 401, captures radiation centered on higher wavelengths than a backside illuminated CMOS image sensor having a similar semiconducting wafer however without the layer of nanoparticles 401. As the nanoparticles 401 trap photons in the active pixel so as to increase the distance they pass in the semiconducting wafer 403, the thickness of the IR image sensor may be reduced in relation to an IR image sensor without a layer of nanoparticles. For example, a sensor with absorbing layer thickness of 5-6 microns may be reduced down to about 400nm thickness. According to some embodiments of the present invention, the image sensor 100 functions both as an IR sensor and as a visible light sensor. The absorption of IR radiation by the image sensor 100 is higher by a factor of about ten folds than the absorption of IR radiation by a similar image sensor without the layer of nanoparticles 401. For example, absorption of IR in a 300nm thick layer of c-Si is about 3% and may be increased up to 30% when a layer of nanoparticles is added as described above. As described above, some active pixels may be adjusted, using appropriate design of the nanoparticles, to enhance the light absorption of a limited part of the spectrum. These pixels do not absorb, or substantially not absorb, IR radiation and thus the IR absorption is low, for example about 3%. Consequently, IR noise is reduced or eliminated without using filters that filter out IR radiation. This allows using the same image sensor 100 for capturing visible light and infrared light simultaneously.

Reference is now also made to FIG. 6A, which is a flowchart 450 of a method of forming an image sensor having a plurality of nanoparticles, according to some embodiments of the present invention.

Fh"st, as shown at 451 , the transistors are formed in a semiconducting wafer. The fabrication may be performed in any known method of fabricating back side illuminated photodiodes and/or front side illuminated photodiodes.

Now, a shown at 452, the transistors are electronically separated from one another so as to form a plurality of discrete photon absorbing regions adapted to separately converting radiation into electrical signal. The separation may be performed by forming STI structures and/or DTI structures, as commonly known in the art. Optionally, the fabrication of the isolation structures and the transistors is performed in a common process. Now, a shown at 453, the one or more nanoparticles are placed to scatter the converted radiation on top and/or below at least some photon absorbing regions, for example as shown at FIG. 3B. The fabrication of nanoparticles may be performed using different methods. For example a layer of nanoparticles may be fabricated on the semiconducting wafer 403 by using photolithography followed by metal evaporation and lift-off process. In such a manufacturing process, a 90nm CMOS fabrication process or a finer fabrication process is used to shape the nanoparticles. Another technique is nano- imprint lithography (NIL) followed by evaporation and liftoff. Optionally, fine alignment is performed.

According to some embodiments of the present invention, one or more additional layers of nanoparticles are bonded to the layers of nanoparticles 401 which are attached to the semiconducting wafer 403 of the image sensor 100. As described above, nanoparticles may be placed in a buffer layer, for example a layer of a non-absorbing material or low-absorbing material with low refractive index. A number of these layers may be fabricated in front of the semiconducting wafer 403, one upon the other.

Now, as shown at 454, a plurality of transistors are connected to receive and amplify the electrical signal from one or more of the plurality of photon absorbing regions for a reconstruction of color and/or brightness of one or more pixels in an image.

Optionally, a CFA is mounted on top of the nanoparticles, for example as shown at FIG. 4, as known in the art. Additionally or alternatively, microlenses are mounted on top of the nanoparticles, for example as shown at FIG. 4, as known in the art. Reference is also made to FIG. 6B, which is another flowchart 460 of an exemplary method of forming an image sensor having a plurality of nanoparticles, according to some embodiments of the present invention.

First, as shown at 461, standard electronics fabrication processes are performed in a semiconducting layer, as known in the art. Then, as shown at 462, a plastic/acrylic wafer is attached to one of the sides of the semiconductor wafer. Now, as shown at 463, the semiconducting layer is flipped and thinned. Then, as shown at 463, a buffer layer is added and the nanoparticles are mounted thereon, for example as described above. The nanoparticles are optionally covered with a protective layer. Optionally, as shown at 464, a CFA and microlenses are added to the image sensor. Reference is now made to FIG. 7, which is a schematic illustration of a cross section of a segment of an AIC CMOS image sensor 700 having a plurality of nanoparticles 701, optionally in one or more layers, according to some embodiments of the present invention. Optionally, the nanoparticles 701 may be used to enhance an above-integrated-circuit (AIC) image sensor, such as shown at 700. The AIC sensor 700 is constructed as follows. First, electronics 702 needed for the sensor is fabricated on a semiconducting layer 703, such as a standard silicon substrate, using a standard CMOS process. After the CMOS process is over, the semiconducting layer 703 has a metal layer(s) 702 thereabove for signal transmissions. On top of the metal layer 702, a thin layer of light absorbing material is mounted 704, for example a layer of amorphous silicon (a-Si). Optionally, photodiodes are fabricated in the light absorbing material 704 to create separated pixels. Each photodiode is connected electrically to a metal electrode of the metal layer 702. This electrode connects the photodiode to the electronic circuits below. Since each photodiode needs at least two connecting electrodes, positive and negative, a transparent electrode 705 is placed on top of the photodiode. This transparent electrode is also connected to the metal layer.

As commonly known, the thinner is the a-Si photodiode, the higher are the electronic performances of the respective active pixel. The electronic efficiency is increased and the Stabler- Wronski effect is reduced. However, a thin a-Si photodiode yields low absorption and thus have lower sensitivity. The addition of nanoparticles 701 to the AIC sensor 700 increases the absorption of the absorbing material 704 and enable the use of thin absorbing material 704. As shown at FIG. 7, the nanoparticles 701 may be embedded in the transparent electrode 705 above the absorbing material 704 and/or in the oxide surrounding the metal layers 702, as shown at FIG. 8.

In such an embodiment, the AIC CMOS image sensor 700 is fabricated in a known process for fabricating an AIC CMOS image sensor, such as depicted in FIG. 1 where a thin buffer layer 702 is deposited on top of the semiconducting wafer 89 and then a layer of nanoparticles 701 is fabricated on top of the thin buffer layer 701. A transparent electrode may be used in the AIC. The layer of nanoparticles 702 may be fabricated in the transparent electrode layer 91. The optical effect is as described above in relation to the embodiments described in relation to FIGs. 4-6. The nanoparticles 702 significantly improve the optical absorption of the AIC CMOS image sensor 700.

Additionally or alternatively, the thin buffer layer 701 and the layer of nanoparticles 702 are deposited on top of the CFA 92, optionally instead of a layer of microlenses, as shown at FIG. 8. Optionally, the positioning of the nanoparticles in the layer of nanoparticles 702 is calculated as a function of the location of the PN junctions 91 in front of the semiconducting wafer 89. Optionally, STI or DTI structures are used for separating between the active pixels, similarly to the described above. It is expected that during the life of a patent maturing from this application many relevant systems and methods will be developed and the scope of the term a semiconducting wafer, a nanoparticle, and a circuitry is intended to include all such new technologies a priori. As used herein the term "about" refers to ± 10 %.

The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to". This term encompasses the terms "consisting of and "consisting essentially of.

The phrase "consisting essentially of means that the composition or method may include additional ingredients and/or steps, but only if the additional ingredients and/or steps do not materially alter the basic and novel characteristics of the claimed composition or method.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". Any particular embodiment of the invention may include a plurality of "optional" features unless such features conflict.

Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases "ranging/ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples. Reference is now made to an example, which together with the above descriptions, illustrates some embodiments of the invention in a non limiting fashion and to FIG. 9 which depicts a graph that depicts the outcome of a simulation performed to an image sensor having the structure according to some embodiments of the present invention. The example provides an exemplary numerical evaluation of the technology described above. Finite differences time domain (FDTD) simulations have been used to predict a realistic behavior of electro-magnetic waves in a CMOS image sensor defined as described above. The results of the FDTD simulations are presented in graph depicted in FIG. 9. The graph compares between an optical absorption of two CMOS image sensors. A first CMOS image sensor has a relatively thin semiconducting wafer of 290nm and 20nm SiO2 buffer layers. The second CMOS image sensor is identical to the first CMOS image sensor apart of having a layer of nanoparticles, as depicted in FIG. 3 A. The layer of nanoparticles includes cylindrical Al nanoparticles each having 120nm in diameter and 60nm in thickness and arranged in a cubic periodic array with a 270nm period length. The optical absorption of the CMOS image sensors is compared for blue, red, and green wavelengths. As shown in FIG. 9, a significant increase in the optical absorption is clear where a layer of nanoparticles is used. The image sensor, which is attached with a layer of nanoparticles, absorbed in the blue, green and red wavelength ranges as much as 2, 3.5 and 4 times the amount of light absorbed by the image sensor without the layer of nanoparticles. The layer of nanoparticles allows an image sensor with a semiconducting wafer of 290nm to absorb light as an image sensor with a semiconducting wafer having a thickness of about 2000 nm.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.

Claims

WHAT IS CLAIMED IS:

1. An active pixel image sensor, comprising: a semiconducting layer having a plurality of photon absorbing regions each separately converting radiation into electrical signal; a plurality of nanoparticles, each placed to scatter photons in an adjacent photon absorbing region of said plurality of photon absorbing regions; and a plurality of transistors each connected to receive and amplify said electrical signal from at least one of said plurality of photon absorbing regions for a reconstruction of at least one of color and brightness of at least one pixel in an image.

2. The active pixel image sensor of claim 1, further comprising a plurality of isolation trenches for at least one of optically and electrically separating, at least partly, said plurality of photon absorbing regions from one another.

3. The active pixel image sensor of claim 2, wherein a metallic strip is placed along said plurality of isolation trenches.

4. The active pixel image sensor of claim 2, wherein the height dimension of said plurality of isolation trenches is at least as high as the height dimension of said semiconducting layer.

5. The active pixel image sensor of claim 2, wherein the height difference of each said isolation trench and said semiconducting layer is less than about lOOnm.

6. The active pixel image sensor of claim 1, wherein said plurality of nanoparticles are placed in a first layer, further comprising at least one additional nanoparticles layer placed on top of said first layer.

7. The active pixel image sensor of claim 1, wherein said semiconducting layer is between said plurality of nanoparticles and a circuitry connecting said plurality of transistors to a circuit performing said reconstruction.

8. The active pixel image sensor of claim 1, wherein said plurality of nanoparticles is between said semiconducting layer and at least a portion of a circuitry connecting said plurality of transistors to a circuit performing said reconstruction.

9. The active pixel image sensor of claim 1, wherein each said transistor independently receives and amplifies said electrical signal for said reconstruction.

10. The active pixel image sensor of claim 1, further comprising a plurality of floating diffusion (FD) regions each formed in said semiconducting layer, between adjacent sides of two adjacent photon absorbing regions of said plurality of photon absorbing regions.

11. The active pixel image sensor of claim 10, further comprising a plurality of isolation trenches for at least one of electrically and optically separating, at least partly, said two adjacent photon absorbing regions from one another, said plurality of isolation trenches being arranged to optically isolate each said FD region from one of said two adjacent photon absorbing regions while allowing electric charge to pass from another of said two adjacent photon absorbing regions thereto.

12. The active pixel image sensor of claim 10, further comprising a plurality of isolation trenches for at least one of optically and electrically separating, at least partly, said two adjacent photon absorbing regions from one another, said plurality of isolation trenches being placed in a plurality of common planes with said plurality of FD regions, each said common plane being substantially perpendicular to said a plane of said semiconducting layer.

13. The active pixel image sensor of claim 12, wherein said plurality FD regions having a thickness less than the optical wavelength of said radiation.

14. The active pixel image sensor of claim 10, further comprising a plurality of non continuous isolation trenches for at least one of optically and electrically separating, at least partly, said two adjacent photon absorbing regions from one another, said plurality of non continuous isolation trenches being mounted along one or both longitudinal sides of each said FD region.

15. The active pixel image sensor of claim 14, wherein said plurality of non continuous isolation trenches having a plurality of apertures each having a width of less than the optical wavelength of said radiation.

16. The active pixel image sensor of claim 1, wherein said plurality of nanoparticles are made of a member of a group consisting of gold, silver, copper, aluminum, silicon, silica and silicon nitride.

17. The active pixel image sensor of claim 1, wherein said plurality of nanoparticles being placed to filter radiation in a non infrared range of frequencies, said image being an infrared image.

18. The active pixel image sensor of claim 1, wherein said plurality of nanoparticles are divided to a plurality of groups each placed to increase the scattering of radiation in a first range of frequencies, in relation to the scattering of radiation in a second range of frequencies, in a different region of said plurality of photon absorbing regions, said first and second ranges of frequencies are different.

19. The active pixel image sensor of claim 18, wherein said first and second ranges of frequencies are selected from a group consisting of red, green, and blue frequencies.

20. The active pixel image sensor of claim 1, wherein said plurality of nanoparticles are divided to a plurality of groups each set to increase the scattering of radiation in a different region of said plurality of photon absorbing regions, each said group being adapted to the relative location of said respective different region in said semiconducting layer.

21. The active pixel image sensor of claim 1, wherein said plurality of nanoparticles having a first group of nanoparticles formed to filter radiation in a first range of frequencies and a second group of nanoparticles formed to filter radiation in a second range of frequencies.

22. The active pixel image sensor of claim 18, further comprises a plurality of a third group of nanoparticles formed to filter radiation in a third range of frequencies, said first, second and third ranges being respectively non red, non green, and non blue frequencies.

23. The active pixel image sensor of claim 18, wherein members of said first and second groups are placed in a mosaic arrangement in front of said plurality of photon absorbing regions.

24. The active pixel image sensor of claim 23, wherein said image is a color image and no color image array is placed in front of said active pixel image sensor.

25. The active pixel image sensor of claim 1, wherein said semiconducting layer having a thickness of less than 400nm.

26. The active pixel image sensor of claim 1, wherein said semiconducting layer having a thickness of less than lOOnm.

27. The active pixel image sensor of claim 1, wherein said plurality of transistors and said semiconducting layer are fabricated in a back-side illumination process.

28. The active pixel image sensor of claim 1, further comprising a color filter array (CFA).

29. The active pixel image sensor of claim 1, wherein said plurality of nanoparticles are formed in said semiconducting layer.

30. A method of forming an active pixel image sensor, comprising: fabricating a circuit comprising a plurality of transistors in a semiconducting layer; electronically separating said plurality of transistors from one another so as to form a plurality of discrete photon absorbing regions adapted to separately converting radiation into electrical signal; mounting a plurality of nanoparticles to scatter said radiation on or in at least some of said plurality of photon absorbing regions; and connecting said plurality of transistors to receive and amplify said electrical signal from at least one of said plurality of photon absorbing regions for a reconstruction of at least one of color and brightness of at least one pixel in an image.

31. The method of claim 30, wherein said electronically separating comprises forming a plurality of isolation trenching elements in said semiconducting layer.

32. An active pixel image sensor, comprising: a semiconducting wafer having a plurality of photon absorbing regions each separately converting radiation into electrical signal; a plurality of nanoparticles, each placed to filter light with a certain wavelength range from an adjacent photon absorbing region of said plurality of photon absorbing regions; and a plurality of transistors each connected to receive and amplify said electrical signal from at least one of said plurality of photon absorbing regions for a reconstruction of at least one of color and brightness of at least one pixel in an image.

33. An active pixel image sensor, comprising: a semiconducting layer having a plurality of photon absorbing regions each separately converting radiation into electrical signal; a plurality of floating diffusion (FD) regions each formed in said semiconducting layer, between adjacent sides of two adjacent photon absorbing regions of said plurality of photon absorbing regions; and a plurality of isolation trenches for at least one of optically and electrically separating, at least partly, said two adjacent photon absorbing regions from one another, said plurality of isolation trenches being arranged to optically isolate, at least partly, each said FD region from one of said two adjacent photon absorbing regions while allowing electric charge to pass from another of said two adjacent photon absorbing regions thereto.

34. An active pixel image sensor, comprising: a semiconducting layer having a plurality of photon absorbing regions each separately converting radiation into electrical signal; a plurality of floating diffusion (FD) regions each formed in said semiconducting layer, between adjacent sides of two adjacent photon absorbing regions of said plurality of photon absorbing regions; and a plurality of isolation trenches for at least one of optically and electrically separating, at least partly, said two adjacent photon absorbing regions from one another, said plurality of isolation trenches being placed in a plurality of common planes with said plurality of FD regions, each said common plane being substantially perpendicular to said a plane of said semiconducting layer.

35. An active pixel image sensor, comprising: a semiconducting layer having a plurality of photon absorbing regions each separately converting radiation into electrical signal; a plurality of floating diffusion (FD) regions each formed in said semiconducting layer, between adjacent sides of two adjacent photon absorbing regions of said plurality of photon absorbing regions; and a plurality of non continuous isolation trenches for at least one of optically and electrically separating, at least partly, said two adjacent photon absorbing regions from one another, said plurality of non continuous isolation trenches being mounted along both longitudinal sides of each said FD .