Patent Description:
Image sensors are sensor devices that are used in imaging devices, such as cameras, scanners, and copiers, to convert optical signals into electrical signals, allowing image capture. An image sensor, generally, includes a plurality of sensor elements and a plurality of optical filters disposed over the plurality of sensor elements. A color image sensor includes a plurality of color filters disposed in an array, i.e., a color filter array (CFA). The CFA includes different types of color filters having different color passbands, e.g., red, green, and blue (RGB) filters.

Conventionally, absorption filters formed using dyes are used as color filters. Unfortunately, such dye-based color filters have relatively broad color passbands, resulting in less brilliant colors. Alternatively, dichroic filters, i.e., interference filters, formed of stacked dielectric layers may be used as color filters. Such all-dielectric color filters have higher transmission levels and narrower color passbands, resulting in brighter and more brilliant colors. However, the color passbands of all-dielectric color filters undergo relatively large center-wavelength shifts with changes in incidence angle, resulting in undesirable shifts in color.

Furthermore, all-dielectric color filters, typically, include a large number of stacked dielectric layers and are relatively thick. Consequently, all-dielectric color filters are expensive and difficult to manufacture. In particular, all-dielectric color filters are difficult to etch chemically. Lift-off processes are, therefore, preferred for patterning. Examples of lift-off processes for patterning all-dielectric CFAs are disclosed in <CIT>, in <CIT>, in <CIT>, in <CIT>, in <CIT>, and in <CIT>. However, lift-off processes are, generally, limited to a filter spacing of about twice the filter height, which makes it difficult to achieve all-dielectric CFAs suitable for smaller color image sensors.

In addition to transmitting visible light in color passbands, both dye-based and all-dielectric color filters also transmit infrared (IR) light, which contributes to noise. Therefore, a color image sensor, typically, also includes an IR-blocking filter disposed over the CFA. Conventionally, absorption filters formed of colored glass or dichroic filters formed of stacked dielectric layers are used as IR-blocking filters. Alternatively, induced transmission filters formed of stacked metal and dielectric layers may be used as IR-blocking filters. Examples of metal-dielectric IR-blocking filters are disclosed in <CIT>, and in <CIT>.

To avoid the use of an IR-blocking filter, induced transmission filters formed of stacked metal and dielectric layers may be used as color filters. Such metal-dielectric color filters are inherently IR-blocking. Typically, metal-dielectric color filters have relatively narrow color passbands that do not shift significantly in wavelength with changes in incidence angle. Furthermore, metal-dielectric color filters are, generally, much thinner than all-dielectric color filters. Examples of metal-dielectric color filters are disclosed in <CIT>, in <CIT>, in <CIT>, in <CIT>, and in <CIT>.

Typically, the metal layers in metal-dielectric color filters are silver layers, which are environmentally unstable and which deteriorate when exposed to even small amounts of water or sulfur. Chemically etching the silver layers exposes the edges of the silver layers to the environment, allowing deterioration. Therefore, in most instances, metal-dielectric CFAs are patterned by adjusting the thicknesses of only the dielectric layers to select different color passbands for the metal-dielectric color filters. In other words, different types of metal-dielectric color filters having different color passbands are required to have the same number of silver layers as one another and the same thicknesses of the silver layers as one another. Unfortunately, these requirements severely limit the possible optical designs for the metal-dielectric color filters.

The present invention provides a sensor device including metal-dielectric optical filters that are not subject to these requirements, and which are particularly suitable for use in image sensors and other sensor devices.

Accordingly, the present invention relates to a sensor device as defined in the Claims.

The present invention will be described in greater detail with reference to the accompanying drawings wherein:.

The present invention includes a metal-dielectric optical filter having protected metal layers, which is particularly suitable for use in a sensor device of the present invention. The optical filter includes a plurality of dielectric layers and a plurality of metal layers stacked in alternation. The metal layers are intrinsically protected by the dielectric layers. In particular, the metal layers have tapered edges that are protectively covered by one or more of the dielectric layers. Accordingly, the metal layers have increased resistance to environmental degradation, resulting in a more durable optical filter.

In some embodiments, the dielectric layers and the metal layers are stacked without any intervening layers. With reference to <FIG>, a first embodiment of the optical filter <NUM>, disposed on a substrate <NUM>, includes three dielectric layers <NUM> and two metal layers <NUM> stacked in alternation. The metal layers <NUM> are each disposed between and adjacent to two dielectric layers <NUM> and are, thereby, protected from the environment.

The metal layers <NUM> have tapered edges <NUM> at a periphery <NUM> of the optical filter <NUM>. In other words, the metal layers <NUM> are substantially uniform in thickness throughout a central portion <NUM> of the optical filter <NUM>, but taper off in thickness at the periphery <NUM> of the optical filter <NUM>. Likewise, the dielectric layers <NUM> are substantially uniform in thickness throughout the central portion <NUM> of the optical filter <NUM>, but taper off in thickness at the periphery <NUM> of the optical filter <NUM>. Accordingly, the central portion <NUM> of the optical filter <NUM> is substantially uniform in height, whereas the periphery <NUM> of the optical filter <NUM> is sloped. In other words, the optical filter <NUM> has a substantially flat top and sloped sides.

The tapered edges <NUM> of the metal layers <NUM> are not exposed to the environment. Rather, the tapered edges <NUM> of the metal layers <NUM> are covered by one or more of the dielectric layers <NUM>. The one or more dielectric layers <NUM> suppress environmental degradation, e.g., corrosion, of the metal layers <NUM>, e.g., by inhibiting the diffusion of sulfur and water into the metal layers <NUM>. The metal layers <NUM> are substantially encapsulated by the dielectric layers <NUM>. The tapered edges <NUM> of the metal layers <NUM> are protectively covered by adjacent dielectric layers <NUM>, and the metal layers <NUM> are substantially encapsulated by adjacent dielectric layers <NUM>.

With reference to <FIG>, the first embodiment of the optical filter <NUM> may be fabricated by a lift-off process. With particular reference to <FIG>, in a first step, the substrate <NUM> is provided. With particular reference to <FIG>, in a second step, a photoresist layer <NUM> is applied onto the substrate <NUM>. Typically, the photoresist layer <NUM> is applied by spin coating or spray coating.

With particular reference to <FIG>, in a third step, the photoresist layer <NUM> is patterned to uncover a region of the substrate <NUM> where the optical filter <NUM> is to be disposed, i.e., a filter region. Other regions of the substrate <NUM> remain covered by the patterned photoresist layer <NUM>. Typically, the photoresist layer <NUM> is patterned by first exposing a region of the photoresist layer <NUM> covering the filter region of the substrate <NUM> to ultraviolet (UV) light through a mask, and then developing, i.e., etching, the exposed region of the photoresist layer <NUM> by using a suitable developer or solvent.

The photoresist layer <NUM> is patterned in such a manner that an overhang <NUM>, i.e., an undercut, is formed in the patterned photoresist layer <NUM> surrounding the filter region. Typically, the overhang <NUM> is formed by chemically modifying, e.g., by using a suitable solvent, a top portion of the photoresist layer <NUM>, so that the top portion develops more slowly than a bottom portion of the photoresist layer <NUM>. Alternatively, the overhang <NUM> may be formed by applying a dual-layer photoresist layer <NUM>, consisting of a top layer that develops more slowly and a bottom layer that develops more quickly, to the substrate <NUM>.

With particular reference to <FIG>, in a fourth step, a multilayer stack <NUM> is deposited onto the patterned photoresist layer <NUM> and the filter region of the substrate <NUM>. A portion of the multilayer stack <NUM> disposed on the filter region of the substrate <NUM> forms the optical filter <NUM>. The layers of the multilayer stack <NUM>, which correspond to the layers of the optical filter <NUM>, may be deposited by using a variety of deposition techniques, such as: evaporation, e.g., thermal evaporation, electron-beam evaporation, plasma-assisted evaporation, or reactive-ion evaporation; sputtering, e.g., magnetron sputtering, reactive sputtering, alternating-current (AC) sputtering, direct-current (DC) sputtering, pulsed DC sputtering, or ion-beam sputtering; chemical vapor deposition, e.g., plasma-enhanced chemical vapor deposition; and atomic layer deposition. Moreover, different layers may be deposited by using different deposition techniques. For example, the metal layers <NUM> may be deposited by sputtering of a metal target, and the dielectric layers <NUM> may be deposited by reactive sputtering of a metal target in the presence of oxygen.

Because the overhang <NUM> shadows a periphery of the filter region of the substrate <NUM>, the deposited layers taper off in thickness towards the periphery <NUM> of the optical filter <NUM>. When a dielectric layer <NUM> is deposited onto a metal layer <NUM>, the dielectric layer <NUM> covers not only the top surface of the metal layer <NUM>, but also the tapered edges <NUM> of the metal layer <NUM>, thereby, protecting the metal layer <NUM> from the environment.

With particular reference to <FIG>, in a fifth step, a portion of the multilayer stack <NUM> on the patterned photoresist layer <NUM> is removed, i.e., lifted off, together with the photoresist layer <NUM>. Typically, the photoresist layer <NUM> is stripped by using a suitable stripper or solvent. The optical filter <NUM> remains on the filter region of the substrate <NUM>. The substrate <NUM> may, for example, be a conventional sensor element.

It should be noted that the lift-off process of <FIG> may also be used to simultaneously form a plurality of optical filters <NUM> of the same type, i.e., having the same optical design, on the substrate <NUM>. Moreover, the lift-off process may be repeated to subsequently form one or more optical filters of a different type, i.e., having a different optical design, on the same substrate <NUM>. Thereby, an optical filter array may be formed on the substrate <NUM>. The substrate <NUM> may, for example, be a conventional sensor array.

With reference to <FIG>, in an optional sixth step, an additional dielectric coating <NUM> is deposited onto the optical filter <NUM>. The dielectric coating <NUM> may be deposited by using one of the deposition techniques mentioned heretofore. The dielectric coating <NUM> covers both the central portion <NUM> and the periphery <NUM> of the optical filter <NUM>, i.e., all exposed portions of the optical filter <NUM>, thereby, protecting the optical filter <NUM> from the environment.

According to the invention, the optical filter includes a plurality of corrosion-suppressing layers, disposed between the dielectric layers and the metal layers, which further protect the metal layers. With reference to <FIG>, a second embodiment of the optical filter <NUM>, disposed on a substrate <NUM>, is similar to the first embodiment of the optical filter <NUM>, but further includes four corrosion-suppressing layers <NUM> inserted between the three dielectric layers <NUM> and the two metal layers <NUM>.

The metal layers <NUM> are each disposed between and adjacent to two corrosion-suppressing layers <NUM> and are, thereby, further protected from the environment. The corrosion-suppressing layers <NUM> suppress corrosion of the metal layers <NUM>, principally during the deposition process. In particular, the corrosion-suppressing layers <NUM> protect portions of the metal layers <NUM> in the optical path, inhibiting degradation of the optical properties of the metal layers <NUM>. The tapered edges <NUM> of the metal layers <NUM> are protectively covered by adjacent corrosion-suppressing layers <NUM>, as well as by nearest dielectric layers <NUM>. Thus, the metal layers <NUM> are, substantially encapsulated by adjacent corrosion-suppressing layers <NUM>, as well as by nearest dielectric layers <NUM>.

The second embodiment of the optical filter <NUM> may be fabricated by a lift-off process similar to that used to fabricate the first embodiment of the optical filter <NUM>. However, the layers of the multilayer stack deposited in the fourth step correspond to the layers of the optical filter <NUM>. In particular, corrosion-suppressing layers <NUM> are deposited before and after each metal layer <NUM>. Advantageously, the corrosion-suppressing layers <NUM> suppress corrosion, i.e., oxidation, of the metal layers <NUM> during deposition of the dielectric layers <NUM>.

The corrosion-suppressing layers <NUM> may be deposited as metal compound, e.g., metal nitride or metal oxide, layers by using one of the deposition techniques mentioned heretofore. Alternatively, the corrosion-suppressing layers <NUM> may be formed by first depositing suitable metal layers, by using one of the deposition techniques mentioned heretofore, and subsequently oxidizing the metal layers. Preferably, the corrosion-suppressing layers <NUM> are each formed by first depositing a suitable metal layer, oxidizing the metal layer, and then depositing a metal oxide layer. For example, the corrosion-suppressing layers <NUM> may be formed by sputtering of a suitable metal target followed by oxidation, followed by reactive sputtering of a suitable metal target in the presence of oxygen. Further details of methods of forming corrosion-suppressing layers are disclosed in <CIT>.

The optical filter useable in the present invention may have a variety of optical designs. The optical designs of exemplary optical filters will be described in further detail hereafter. In general, the optical design of the optical filter is optimized for a particular passband by selecting suitable layer numbers, materials, and/or thicknesses.

Typically, the optical filter includes <NUM> to <NUM> metal layers, <NUM> to <NUM> dielectric layers, and, optionally, <NUM> to <NUM> corrosion-suppressing layers. In general, increasing the number of metal layers provides a passband with steeper edges, but with a lower in-band transmittance.

The first layer in the optical design, i.e., the first layer deposited on the substrate, may be a metal layer or a dielectric layer. The last layer in the optical design, i.e., the last layer deposited on the substrate, is usually a dielectric layer. When the first layer is a metal layer, the optical filter may consist of n metal layers (M) and n dielectric layers (D) stacked in a sequence of (M/D)n, where n ≥ <NUM>. Alternatively, the optical filter may consist of n metal layers (M), n dielectric layers (D), and <NUM>n corrosion-suppressing layers (C), stacked in a sequence of (C/M/C/D)n, where n ≥ <NUM>. When the first layer is a dielectric layer, the optical filter may consist of n metal layers (M) and n + <NUM> dielectric layers (D) stacked in a sequence of D(M/D)n, where n ≥ <NUM>. Alternatively, the optical filter may consist of n metal layers (M), n + <NUM> dielectric layers (D), and 2n corrosion-suppressing layers (C), stacked in a sequence of D(C/M/C/D)n, where n ≥ <NUM>.

The metal layers are each composed of silver or silver alloy. For example, a silver alloy consisting essentially of about <NUM> wt% gold, about <NUM> wt% tin, and a balance of silver may provide improved corrosion resistance. Typically, the metal layers each have a physical thickness between about <NUM> and about <NUM>, preferably, between about <NUM> and about <NUM>.

The dielectric layers are each composed of a dielectric material. Typically, the dielectric layers are each composed of a high-index dielectric material, i.e., a dielectric material having a refractive index greater than about <NUM> at <NUM>, that is transparent in the visible spectral region. Suitable examples of high-index dielectric materials include titanium dioxide (TiO<NUM>), zirconium dioxide (ZrO<NUM>), niobium pentoxide (Nb<NUM>O<NUM>), tantalum pentoxide (Ta<NUM>O<NUM>), and mixtures thereof. Preferably, the high-index dielectric material is also UV-absorbing, i.e., absorbing in the near-UV spectral region. For example, a high-index dielectric material including or consisting of TiO<NUM> and/or Nb<NUM>O<NUM> may provide enhanced UV blocking, i.e., lower out-of-band transmittance in the near-UV spectral region. Preferably, the high-index dielectric material has a refractive index greater than about <NUM> at <NUM>, more preferably, greater than about <NUM> at <NUM>. A higher refractive index is usually desirable. However, the transparent high-index dielectric materials that are currently available, generally, have refractive indices less than about <NUM> at <NUM>.

Generally, but not necessarily, the dielectric layers are composed of the same dielectric material, but have different thicknesses. Typically, the dielectric layers each have a physical thickness between about <NUM> and about <NUM>. This physical thickness is selected to correspond with a quarter wave optical thickness (QWOT) required by an optical design. The QWOT is defined as <NUM>nt, where n is the refractive index of the dielectric material and t is the physical thickness. Typically, the dielectric layers each have a QWOT between about <NUM> and about <NUM>.

The optional corrosion-suppressing layers are each composed of a corrosion-suppressing material. Typically, the corrosion-suppressing layers are composed of a corrosion-suppressing dielectric material. Examples of suitable corrosion-suppressing dielectric materials include silicon nitride (Si<NUM>N<NUM>), TiO<NUM>, Nb<NUM>O<NUM>, zinc oxide (ZnO), and mixtures thereof. Preferably, the corrosion-suppressing dielectric material is a compound, e.g., a nitride or an oxide, of a metal having a higher galvanic potential than the metal or alloy of the metal layers.

The corrosion-suppressing layers are, generally, suitably thin to substantially avoid contributing to the optical design of the optical filter, especially when they are absorbing in the visible spectral region. Typically, the corrosion-suppressing layers each have a physical thickness between about <NUM> and about <NUM>, preferably, between about <NUM> and about <NUM>. Further details of suitable corrosion-suppressing layers are disclosed in <CIT>.

The optional dielectric coating is composed of a dielectric material. The dielectric coating may be composed of the same dielectric materials and may have the same range of thicknesses as the dielectric layers. Typically, the dielectric coating is composed of the same dielectric material as the last dielectric layer and has a thickness that is a portion of the design thickness, i.e., the thickness required by the optical design, of the last dielectric layer. In other words, the last dielectric layer of the optical design is split between a dielectric layer and a dielectric coating. For example, if the last dielectric layer has a design thickness td and the dielectric coating has a coating thickness tc, e.g., <NUM> QWOT, the actual thickness ta of the last dielectric layer is given by: ta = td - tc.

With reference to <FIG>, the optical filter <NUM>, typically, has a filter height h, i.e., a height of the central portion of the optical filter <NUM> from the substrate <NUM>, of less than <NUM>, preferably, of less than <NUM>. Also typically, the optical filter <NUM> has a filter width w, i.e., a width of the central portion of the optical filter <NUM>, of less than <NUM>, preferably, of less than <NUM>. Advantageously, the relatively small filter height allows a smaller filter spacing when a plurality of optical filters <NUM> are formed by a lift-off process. Typically, the optical filters <NUM> have a filter spacing d, i.e., a spacing between the central portions of nearest optical filters <NUM>, of less than <NUM>, preferably, of less than <NUM>.

The optical filter is a metal-dielectric bandpass filter, i.e., an induced transmission filter, having a high in-band transmittance and a low out-of-band transmittance. Typically, the optical filter has a maximum in-band transmittance of greater than about <NUM> %, an average out-of-band transmittance of less than about <NUM> % between about <NUM> and about <NUM>, i.e., in the near-UV spectral region, and an average out-of-band transmittance of less than about <NUM> % between about <NUM> and about <NUM>, i.e., in the infrared (IR) spectral region. Generally, the optical filter also has a low angle shift, i.e., center-wavelength shift with change in incidence angle from <NUM>°. Typically, the optical filter has an angle shift at an incidence angle of <NUM>° of less than about <NUM>% or about <NUM> in magnitude for an optical filter centered at <NUM>.

In some embodiments, the optical filter is a color filter having a relatively narrow color passband in the visible spectral region. For example, the optical filter may be a red, green, blue, cyan, yellow, or magenta filter. In other embodiments, the optical filter is a photopic filter having a photopic passband, i.e., a passband that mimics the spectral response of the human eye to relatively bright light, in the visible spectral region. In yet other embodiments, the optical filter is an IR-blocking filter having a relatively broad passband in the visible spectral region.

Optical designs, i.e., layer numbers, materials, and thicknesses, for exemplary red, green, and blue filters, i.e., an exemplary RGB filter set, are tabulated in <FIG>, <FIG>, and <FIG>, respectively. An optical design for an exemplary photopic filter is tabulated in <FIG>. The layers of each optical design are numbered starting from the first layer deposited on the substrate.

The metal layers are each composed of silver, and have physical thicknesses between about <NUM> and about <NUM>. The dielectric layers are each composed of a high-index dielectric material (H), and have QWOTs between about <NUM> and about <NUM>. For example, the high-index dielectric material may be a mixture of Nb<NUM>O<NUM> and TiO<NUM> having a refractive index of about <NUM> at <NUM>. The corrosion-suppressing layers are each composed of ZnO and each have a physical thickness of about <NUM>.

When the high-index dielectric material has a refractive index of about <NUM> at <NUM>, the filter height of the red filter is <NUM>, that of the green filter is <NUM>, that of the blue filter is <NUM>, and that of the photopic filter is <NUM>. These filter heights are considerably smaller than those of conventional all-dielectric optical filters.

Transmission spectra <NUM>, <NUM>, and <NUM> for the exemplary red, green, and blue filters are plotted in <FIG>. The transmission spectrum <NUM> for the exemplary red filter includes a red passband centered at about <NUM>, the transmission spectrum <NUM> for the exemplary green filter includes a green passband centered at about <NUM>, and the transmission spectrum <NUM> for the exemplary blue filter includes a blue passband centered at about <NUM>.

Transmission spectra <NUM> and <NUM> for the exemplary photopic filter at incidence angles of <NUM>° to <NUM>° are plotted in <FIG>. The transmission spectrum <NUM> for the exemplary photopic filter at an incidence angle of <NUM>° includes a photopic passband centered at about <NUM>. In the transmission spectrum <NUM> for the exemplary photopic filter at an incidence angle of <NUM>°, the photopic passband is centered at about <NUM>. In other words, the angle shift of the exemplary photopic filter at an incidence angle of <NUM>° is about -<NUM>.

The exemplary optical filters each have a maximum in-band transmittance of greater than about <NUM> %. Advantageously, the exemplary optical filters provide improved IR blocking relative to conventional dye-based and all-dielectric optical filters, reducing noise caused by IR leaking. Specifically, the exemplary optical filters each have an average out-of-band transmittance of less than about <NUM> % between about <NUM> and about <NUM>, i.e., in the IR spectral region. The exemplary optical filters, particularly the exemplary red filter, also provide improved UV blocking relative to some conventional metal-dielectric color filters, reducing noise caused by UV leaking. Specifically, the exemplary optical filters each have an average out-of-band transmittance of less than about <NUM> % between about <NUM> and about <NUM>, i.e., in the near-UV spectral region.

A color gamut <NUM> for the exemplary RGB filter set is plotted on a CIE xy chromaticity diagram in <FIG>, along with a color gamut <NUM> for a conventional dye-based RGB filter set for comparison. Advantageously, the color gamut <NUM> of the exemplary RGB filter set is considerably larger than the color gamut <NUM> of the conventional dye-based RGB filter set.

A color trajectory <NUM> for the exemplary red filter at incidence angles of <NUM>° to <NUM>° is plotted on a CIE xy chromaticity diagram in <FIG>, along with a color trajectory <NUM> for a conventional all-dielectric red filter at incidence angles of <NUM>° to <NUM>°. A color trajectory <NUM> for the exemplary photopic filter at incidence angles of <NUM>° to <NUM>° is plotted on a CIE xy chromaticity diagram in <FIG>. Advantageously, the angle shift of the exemplary optical filters is considerably smaller than the angle shift of conventional all-dielectric optical filters.

The optical filter is part of a sensor device of the present invention. The sensor device may be any type of sensor device including a plurality of sensor elements, in addition to a plurality of optical filters described herein. For example, the sensor device may be an ambient light sensor, a proximity sensor, or an image sensor. The sensor elements may be any type of conventional sensor elements. Typically, the sensor elements are photodetectors, such as photodiodes, charge-coupled device (CCD) sensor elements, or complementary metal-oxide semiconductor (CMOS) sensor elements. The sensor elements may be front- or back-illuminated.

The optical filters are disposed over the one or more sensor elements, so that the optical filters filter light provided to the sensor elements. Typically, each optical filter is disposed over one sensor element. In other words, each pixel of the sensor device, typically, includes one optical filter and one sensor element. Preferably, the optical filters are disposed directly on the sensor elements. For example, the optical filters may be formed on the sensor elements by a lift-off process. However, in some instances, there may be one or more coatings disposed between the optical filters and the sensor elements.

For reference purposes, <FIG> shows a sensor device <NUM> including a sensor element <NUM> and an optical filter <NUM> disposed on the sensor element <NUM>. For example, the sensor device <NUM> may be an ambient light sensor, the sensor element <NUM> may be a photodiode, and the optical filter <NUM> may be a photopic filter, such as the exemplary photopic filter of <FIG>, or an IR-blocking filter.

According to the present invention, the sensor device includes a plurality of sensor elements, and a plurality of optical filters disposed over the plurality of sensor elements. The sensor elements are disposed in an array. In other words, the sensor elements form a sensor array, such as a photodiode array, a CCD array, a CMOS array, or any other type of conventional sensor array. The optical filters are also disposed in an array. In other words, the optical filters form an optical filter array, such as a color filter array (CFA). ,The sensor array and the optical filter array are corresponding two-dimensional arrays, i.e., mosaics. For example, the arrays may be rectangular arrays having rows and columns.

Usually, the optical filters are substantially separate from one another. In other words, the peripheries of the optical filters are not usually in contact with one another. However, in some instances, the dielectric layers of the optical filters may unintentionally touch, while the metal layers, particularly, the tapered edges, remain separate from one another.

The plurality of optical filters includes different types of optical filters having different passbands from one another. For example, the plurality of optical filters may include color filters, such as red, green, blue, cyan, yellow, and/or magenta filters, photopic filters, IR-blocking filters, or a combination thereof. In some embodiments, the plurality of optical filters includes different types of color filters, forming a CFA. For example, the plurality of optical filters may include red, green, and blue filters, such as the exemplary red, green, and blue filters of <FIG>, forming an RGB filter array, such as a Bayer filter array.

Advantageously, the different types of optical filters may have different numbers of metal layers and/or different thicknesses of the metal layers from one another. In some embodiments, at least two of the different types of optical filters include different numbers of metal layers from one another. In the same or other embodiments, at least two of the different types of optical filters have different metal-layer thicknesses from one another. For example, the exemplary blue filter of <FIG> has a different number of metal layers from the exemplary red and green filters of <FIG> and <FIG>. Moreover, all of the exemplary red, green, and blue filters of <FIG> have different metal-layer thicknesses from one another.

Claim 1:
A sensor device (<NUM>) comprising:
a plurality of sensor elements ( <NUM>); and
a plurality of optical filters (<NUM>) disposed over the the plurality of sensor elements (<NUM>), wherein each of the optical filters (<NUM>) includes:
a plurality of dielectric layers (<NUM>); and
a plurality of silver or silver alloy metal layers (<NUM>) stacked in alternation with the plurality of dielectric layers (<NUM>), wherein each of the plurality of metal layers (<NUM>) is substantially uniform in thickness throughout a central portion (<NUM>) of the optical filter (<NUM>), and tapers off in thickness at a periphery (<NUM>) of the optical filter (<NUM>) to has a tapered edge (<NUM>), at the periphery (<NUM>) of the optical filter (<NUM>,), that is protectively covered by one or more of the plurality of dielectric layers (<NUM>), and each of the plurality of metal layers (<NUM>) is separated from a substrate (<NUM>) of an optical filter (<NUM>), of the one or more optical filters, using at least one the plurality of dielectric layers (<NUM>), and each of the plurality of metal layers (<NUM>) is encapsulated by two nearest of the plurality of dielectric layers (<NUM>); and
wherein each of the one or more optical filters (<NUM>) further includes a plurality of corrosion-suppressing layers (<NUM>) disposed between the plurality of dielectric layers (<NUM>) and the plurality of metal layers (<NUM>), and the metal layers are encapsulated by the corrosion-suppressing layers,
characterised in that the plurality of sensor elements (<NUM>) are disposed in a two-dimensional array, and the plurality of optical filters (<NUM>) are disposed in a corresponding two-dimensional array, and the plurality of optical filters (<NUM>) includes different types of optical filters (<NUM>) having different passbands from one another.