HK1199144B - Sensor device including one or more metal-dielectric optical filters - Google Patents

Description

Sensor device comprising one or more metal-dielectric filters

Technical Field

The present invention relates to sensor devices comprising one or more optical filters, and more particularly to one or more metal-dielectric optical filters.

Background Art

Image sensors are sensor devices used in imaging devices (such as cameras, scanners, and copiers) to convert optical signals into electrical signals to allow image capture. Image sensors typically include multiple sensor elements and multiple filters arranged over the multiple sensor elements. A color image sensor includes multiple color filters arranged in an array, known as a color filter array (CFA). A CFA includes different types of color filters with different color passbands, such as 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 wide color passbands, resulting in less vivid colors. Alternatively, dichroic filters (i.e., interference filters) formed from stacked dielectric layers can be used as color filters. Such all-dielectric color filters have higher transmission levels and narrower color passbands, resulting in brighter and more vivid colors. However, the color passband of all-dielectric color filters experiences relatively large central wavelength shifts when the incident angle varies, resulting in undesirable color shifts.

Furthermore, all-dielectric color filters typically consist of 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. Therefore, lift-off processes are preferred for patterning. Examples of lift-off processes for patterning all-dielectric CFAs are disclosed in U.S. Patent Nos. 5,120,622 to Hanrahan, issued June 9, 1992; 5,711,889 to Buchsbaum, issued January 27, 1998; 6,238,583 to Edlinger et al., issued May 29, 2001; 6,638,668 to Buchsbaum et al., issued October 28, 2003; and 7,648,808 to Buchsbaum et al., issued January 19, 2010, which are incorporated herein by reference. However, lift-off processes are generally limited to filter spacing that is approximately twice the filter height, which makes it difficult to implement all-dielectric CFAs suitable for smaller color image sensors.

In addition to transmitting visible light in the color passband, dye-based color filters and all-dielectric color filters also transmit infrared (IR) light, which contributes to noise. Therefore, color image sensors generally also include an IR-blocking filter disposed on the CFA. Conventionally, an absorptive filter formed of colored glass or a dichroic filter formed of stacked dielectric layers is used as an IR-blocking filter. Alternatively, an induced-transmission filter formed of stacked metal and dielectric layers can be used as an IR-blocking filter. Examples of metal-dielectric IR-blocking filters are disclosed in U.S. Patent No. 5,648,653, issued on July 15, 1997, to Sakamoto et al., and U.S. Patent No. 7,133,197, issued on November 7, 2006, to Ockenfuss et al., both of which are incorporated herein by reference.

To avoid the use of IR-blocking filters, induced transmission filters formed from stacked metal and dielectric layers can be used as color filters. Such metal-dielectric color filters are inherently IR-blocking. Generally, metal-dielectric color filters have a relatively narrow color passband that does not significantly shift in wavelength with changes in the angle of incidence. In addition, metal-dielectric color filters are typically much thinner than all-dielectric color filters. Metal-dielectric color filters are disclosed in U.S. Patent No. 4,979,803 to McGuckin et al., issued on December 25, 1990, in U.S. Patent No. 6,031,653 to Wang, issued on February 29, 2000, in U.S. Patent Application No. 2009/0302407 to Gidon et al., published on December 10, 2009, in U.S. Patent Application No. 2011/0204463 to Grand, published on August 25, 2011, and in U.S. Patent Application No. 2012/0085944 to Gidon et al., published on April 12, 2012, which are incorporated herein by reference.

Typically, the metal layer in a metal-dielectric color filter is a silver layer, which is environmentally unstable and degrades when exposed to even small amounts of water or sulfur. Chemically etching the silver layer exposes the edges of the silver layer to the environment, allowing it to degrade. Therefore, in most cases, metal-dielectric CFAs are patterned by adjusting the thickness of only the dielectric layer to select different color passbands for the metal-dielectric color filter. In other words, different types of metal-dielectric color filters with different color passbands require the same number of silver layers and the same thickness of silver layers. Unfortunately, these requirements severely limit the possible optical designs of metal-dielectric color filters.

Summary of the Invention

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

Therefore, the present invention relates to a sensor device comprising: one or more sensor elements; and one or more filters arranged on the one or more sensor elements, wherein each of the one or more filters comprises: a plurality of dielectric layers; and a plurality of metal layers stacked alternately with the plurality of dielectric layers, wherein each of the plurality of metal layers has a tapered edge at the periphery of the filter, which is protectively covered by one or more of the plurality of dielectric layers.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in more detail with reference to the accompanying drawings, in which:

FIG1A is a schematic diagram of a cross section of a first embodiment of an optical filter of the present invention;

1B to 1G illustrate various steps in a method of manufacturing the optical filter of FIG. 1A ;

FIG2 is a schematic diagram of a cross section of a second embodiment of an optical filter of the present invention;

FIG3 is a schematic diagram of a cross section of multiple optical filters;

FIG4A is a table of the number of layers, materials, and thicknesses of an exemplary red filter;

FIG4B is a table of the number of layers, materials, and thicknesses of an exemplary green filter;

FIG4C is a table of the number of layers, materials, and thicknesses of an exemplary blue filter;

FIG4D is a table of the number of layers, materials, and thicknesses of exemplary photopic filters;

5A and 5B are graphs of the transmission spectra of the exemplary red, green, and blue filters of FIGS. 4A to 4C ;

FIG5C is a graph of the transmission spectrum of the exemplary photopic filter of FIG4D at incident angles of 0° to 60°;

6A is a graph of the color gamut of the exemplary red, green, and blue (RGB) filter set of FIGS. 4A through 4C and a conventional dye-based RGB filter set;

6B is a graph of the color loci of the exemplary red filter of FIG. 4A and a conventional all-dielectric red filter at incident angles of 0° to 60°;

FIG6C is a graph of the color locus of the exemplary photopic filter of FIG4D at incident angles of 0° to 60°;

FIG7 is a schematic diagram of a cross-section of a first embodiment of a sensor device of the present invention; and

FIG8 is a schematic diagram of a cross section of a second embodiment of a sensor device of the present invention.

Detailed description of the invention

The present invention provides a metal-dielectric filter having a protected metal layer, which is particularly suitable for use in sensor devices. The filter comprises a plurality of dielectric layers and a plurality of metal layers stacked alternately. 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 dielectric layers. As a result, the metal layers increase resistance to environmental degradation, resulting in a more durable filter.

In some embodiments, dielectric layers and metal layers are stacked without any intermediate layers. Referring to FIG1A , a first embodiment of an optical filter 100 disposed on a substrate 110 includes three dielectric layers 120 and two metal layers 130 stacked alternately. Each metal layer 130 is disposed between and adjacent to two dielectric layers 120, and is thereby protected from environmental influences.

The metal layer 130 has a tapered edge 131 at the periphery 101 of the filter 100. In other words, the thickness of the metal layer 130 is substantially uniform throughout the central portion 102 of the filter 100, but tapers off at the periphery 101 of the filter 100. Similarly, the thickness of the dielectric layer 120 is substantially uniform throughout the central portion 102 of the filter 100, but tapers off at the periphery 101 of the filter 100. Thus, the central portion 102 of the filter 100 is substantially uniform in height, while the periphery 101 of the filter 100 is sloped. In other words, the filter 100 has a substantially flat top and sloped sides.

Advantageously, the tapered edge 131 of the metal layer 130 is not exposed to the environment. Instead, the tapered edge 131 of the metal layer 130 is covered by one or more dielectric layers 120. The one or more dielectric layers 120 inhibit environmental degradation (e.g., corrosion) of the metal layer 130, for example, by preventing sulfur and water from diffusing into the metal layer 130. Preferably, the metal layer 130 is substantially encapsulated by the dielectric layers 120. More preferably, the tapered edge of the metal layer 130 is protectively covered by the adjacent dielectric layer 120, and the metal layer 130 is substantially encapsulated by the adjacent dielectric layer 120.

1B to 1G , a first embodiment of an optical filter 100 can be manufactured using a lift-off process. Specifically referring to FIG. 1B , in a first step, a substrate 110 is provided. Specifically referring to FIG. 1C , in a second step, a photoresist layer 140 is applied to substrate 110. Typically, photoresist layer 140 is applied by spin coating or spray coating.

With specific reference to FIG1D , in the third step, photoresist layer 140 is patterned to expose the area of substrate 110 where optical filter 100 will be disposed, i.e., the filter region. Other areas of substrate 110 remain covered by patterned photoresist layer 140. Typically, photoresist layer 140 is patterned by first exposing the areas of photoresist layer 140 covering the filter region of substrate 110 to ultraviolet (UV) light using a mask, and then developing (i.e., etching) the exposed areas of photoresist layer 140 using a suitable developer or solvent.

The photoresist layer 140 is patterned so that an overhang 141 (i.e., an undercut portion) is formed around the patterned photoresist layer 140 of the filter region. Typically, the overhang 141 is formed by chemically modifying the top portion of the photoresist layer 140, for example using an appropriate solvent, so that the top portion develops more slowly than the bottom portion of the photoresist layer 140. Alternatively, the overhang 141 can be formed by applying a double-layer photoresist layer 140 to the substrate 110, the double-layer photoresist layer 140 consisting of a slower-developing top layer and a faster-developing bottom layer.

With specific reference to FIG. 1E , in a fourth step, multilayer stack 103 is deposited on patterned photoresist layer 140 and the filter region of substrate 110. The portion of multilayer stack 103 disposed on the filter region of substrate 110 forms optical filter 100. The layers of multilayer stack 103 corresponding to the layers of optical filter 100 can be deposited using various 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. Furthermore, different layers can be deposited using different deposition techniques. For example, metal layer 130 can be deposited by sputtering a metal target, and dielectric layer 120 can be deposited by reactive sputtering of a metal target in the presence of oxygen.

Because the overhang 141 obscures the perimeter of the filter area of the substrate 110, the deposited layers taper in thickness toward the perimeter 101 of the filter 100. When the dielectric layer 120 is deposited on the metal layer 130, the dielectric layer 120 covers not only the top surface of the metal layer 130 but also the tapered edge 131 of the metal layer 130, thereby protecting the metal layer 130 from environmental influences.

1F , in a fifth step, a portion of the multilayer stack 103 on the patterned photoresist layer 140 is removed, i.e., stripped, along with the photoresist layer 140. Typically, the photoresist layer 140 is stripped using a suitable stripper or solvent. The optical filter 100 remains on the filter region of the substrate 110. The substrate 110 may be, for example, a conventional sensor element.

It should be noted that the lift-off process of Figures 1B to 1F can also be used to simultaneously form multiple filters 100 of the same type (i.e., having the same optical design) on a substrate 110. Furthermore, the lift-off process can be repeated to subsequently form one or more filters of different types (i.e., having different optical designs) on the same substrate 110. Thus, an array of filters can be formed on the substrate 110. The substrate 110 can be, for example, a conventional sensor array.

1G , in an optional sixth step, an additional dielectric coating 150 is deposited on the filter 100. The dielectric coating 150 can be deposited using one of the previously mentioned deposition techniques. The dielectric coating 150 covers the central portion 102 and the periphery 101 of the filter 100, i.e., all exposed portions of the filter 100, thereby protecting the filter 100 from environmental influences.

In other embodiments, the optical filter includes multiple corrosion-inhibiting layers disposed between the dielectric layer and the metal layer, which further protect the metal layer. Referring to FIG2 , a second embodiment of an optical filter 200 disposed on a substrate 210 is similar to the first embodiment of the optical filter 100 but further includes four corrosion-inhibiting layers 260 interposed between three dielectric layers 220 and two metal layers 230.

Each of the metal layers 230 is disposed between and adjacent to two corrosion-inhibiting layers 260, and is thus further protected from environmental influences. The corrosion-inhibiting layers 260 primarily inhibit corrosion of the metal layers 230 during the deposition process. In particular, the corrosion-inhibiting layers 260 protect the portion of the metal layer 230 that is in the optical path, preventing degradation of the optical properties of the metal layer 230. Preferably, the tapered edge 231 of the metal layer 230 is protectively covered by the adjacent corrosion-inhibiting layers 260 and by the proximate dielectric layer 220. Thus, the metal layer 230 is preferably substantially encapsulated by the adjacent corrosion-inhibiting layers 260 and by the proximate dielectric layer 220.

The second embodiment of the optical filter 200 can be manufactured by a lift-off process similar to the lift-off process used to manufacture the first embodiment of the optical filter 100. However, the layers of the multilayer stack deposited in the fourth step correspond to the layers of the optical filter 200. In particular, the corrosion-inhibiting layer 260 is deposited before and after each metal layer 230. Advantageously, the corrosion-inhibiting layer 260 inhibits corrosion, i.e., oxidation, of the metal layer 230 during the deposition of the dielectric layer 220.

The corrosion inhibition layer 260 can be deposited as a metal compound, such as a metal nitride or metal oxide layer, using one of the previously mentioned deposition techniques. Alternatively, the corrosion inhibition layer 260 can be formed by first depositing a suitable metal layer using one of the previously mentioned deposition techniques, and then oxidizing the metal layer. Preferably, each corrosion inhibition layer 260 is formed by first depositing a suitable metal layer, oxidizing the metal layer, and then depositing a metal oxide layer. For example, the corrosion inhibition layer 260 can be formed by sputtering a suitable metal target, followed by oxidation, and then reactive sputtering of the suitable metal target in the presence of oxygen. Further details of the method of forming the corrosion inhibition layer are disclosed in U.S. Patent No. 7,133,197.

The optical filter of the present invention can have various optical designs. The optical design of exemplary optical filters will be described in more detail below. In general, the optical design of the filter is optimized by selecting the appropriate number of layers, materials and/or thicknesses for a specific passband.

Typically, the filter comprises 2 to 6 metal layers, 3 to 7 dielectric layers and optionally 4 to 12 corrosion inhibition layers. In general, increasing the number of metal layers provides a passband with steeper edges but lower in-band transmission.

The first layer in an optical design (i.e., the first layer deposited on the substrate) can be a metal layer or a dielectric layer. The last layer in an optical design (i.e., the last layer deposited on the substrate) is typically a dielectric layer. When the first layer is a metal layer, the filter can consist of n metal layers (M) and n dielectric layers (D), stacked in the order (M/D)n, where n ≥ 2. Alternatively, the filter can consist of n metal layers (M), n dielectric layers (D), and 2n corrosion-inhibiting layers (C), stacked in the order (C/M/C/D)n, where n ≥ 2. When the first layer is a dielectric layer, the filter can consist of n metal layers (M) and n+1 dielectric layers (D), stacked in the order D(M/D)n, where n ≥ 2. Alternatively, the filter may consist of n metal layers (M), n+1 dielectric layers (D), and 2n corrosion-inhibiting layers (C) stacked in the order D(C/M/C/D)n, where n≥2.

Each metal layer is composed of a metal or alloy. Typically, each metal layer is composed of silver. Alternatively, each metal layer may be composed of a silver alloy. For example, a silver alloy consisting essentially of approximately 0.5 weight percent (wt%) gold, approximately 0.5 wt% tin, and a balance of silver may provide improved corrosion resistance. Typically, but not necessarily, the metal layers are composed of the same metal or alloy, but have different thicknesses. Typically, each metal layer has a physical thickness between approximately 5 nm and approximately 50 nm, preferably between approximately 10 nm and approximately 35 nm.

Each dielectric layer is composed of a dielectric material. Generally, each dielectric layer is composed of a high-refractive-index dielectric material that is transparent in the visible light spectral region (i.e., a dielectric material having a refractive index greater than approximately 1.65 at 550 nm). Suitable examples of high-refractive-index dielectric materials include _titanium dioxide ( _TiO₂ ), zirconium dioxide ( _ZrO₂ ), niobium pentoxide ( _Nb₂O₅ ), _tantalum pentoxide ( _Ta₂O₅ ), and mixtures thereof. Preferably, the high-refractive-index dielectric material is also UV-absorbing, i.e., absorbing in the near-UV spectral region. For example, a high-refractive-index dielectric material comprising or consisting _{of TiO₂ and} /or _{Nb₂O₅ can} provide enhanced _UV blocking, i.e., lower out-of-band transmittance in the near-UV spectral region. Preferably, the high-refractive-index dielectric material has a refractive index greater than approximately 2.0 at 550 nm, more preferably greater than approximately 2.35 at 550 nm. A higher refractive index is generally desirable. However, currently available transparent high-refractive-index dielectric materials generally have a refractive index of less than about 2.7 at 550 nm.

Typically, but not necessarily, the dielectric layers are composed of the same dielectric material but have different thicknesses. Typically, each dielectric layer has a thickness between approximately 20 nm and approximately 300 nm. This physical thickness is selected to correspond to the quarter-wave optical thickness (QWOT) required by the optical design. QWOT is defined as 4 nt, where n is the refractive index of the dielectric material and t is the physical thickness. Typically, each dielectric layer has a QWOT between approximately 200 nm and approximately 2400 nm.

Each optional corrosion-inhibiting layer is composed of a corrosion-inhibiting material. Typically, the corrosion-inhibiting layer is composed of a corrosion-inhibiting dielectric material. Examples of suitable corrosion-inhibiting dielectric materials include silicon _nitride ( _Si3N4 ), _TiO2 , _Nb2O5 , zinc oxide (ZnO), and mixtures thereof. Preferably, the corrosion-inhibiting dielectric material is a compound of a metal having a higher galvanic potential than the _metal or alloy of the metal layer, such as a nitride or oxide.

Corrosion inhibition layers are typically suitably thin to avoid substantially contributing to the optical design of the filter, particularly when they absorb in the visible light spectral region. Typically, each corrosion inhibition layer has a physical thickness between about 0.1 nm and about 10 nm, preferably between about 1 nm and about 5 nm. Further details of suitable corrosion inhibition layers are disclosed in U.S. Patent No. 7,133,197.

The optional dielectric coating is composed of a dielectric material. The dielectric coating can be composed of the same dielectric material and can have the same thickness as the dielectric layer. Generally, the dielectric coating is composed of the same dielectric material as the last dielectric layer and has a thickness that is a fraction of the design thickness of the last dielectric layer (i.e., the thickness required by the optical design). In other words, the last dielectric layer of the optical design is split between the dielectric layer and the 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., 250 QWOT, then the actual thickness ta of the last dielectric layer is given by ta = td - tc.

Referring to FIG. 3 , the optical filter 300 generally has a filter height h (i.e., the height of the center portion of the optical filter 300 from the substrate 310) that is less than 1 μm, preferably less than 0.6 μm. Furthermore, the optical filter 300 generally has a filter width w (i.e., the width of the center portion of the optical filter 300) that is less than 2 μm, preferably less than 1 μm. Advantageously, when multiple optical filters 300 are formed using a lift-off process, the relatively small filter height allows for smaller filter spacing. The optical filter 300 generally has a filter spacing d (i.e., the spacing between the center portions of the closest optical filters 300) that is less than 2 μm, preferably less than 1 μm.

The filter is a metallo-dielectric bandpass filter with high in-band transmittance and low out-of-band transmittance, i.e., an induced transmission filter. Typically, the filter has a maximum in-band transmittance greater than approximately 50%, an average out-of-band transmittance less than approximately 2% between approximately 300 nm and approximately 400 nm, i.e., in the near-UV spectral region, and an average out-of-band transmittance less than approximately 0.3% between approximately 750 nm and approximately 1100 nm, i.e., in the infrared (IR) spectral region. Typically, the filter also has low angular shift, i.e., the center wavelength shift with varying angles of incidence from 0°. Typically, for a filter centered at 600 nm, the filter has an angular shift of less than approximately 5% in magnitude, or less than approximately 30 nm, at a 60° angle of incidence.

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

The optical designs (i.e., number of layers, materials, and thicknesses) of exemplary red, green, and blue filters, i.e., exemplary RGB filter sets, are tabulated in Figures 4A, 4B, and 4C, respectively. The optical design of an exemplary photopic filter is tabulated in Figure 4D. The layers of each optical design are numbered starting with the first layer deposited on the substrate.

Each metal layer is composed of silver and has a physical thickness between approximately 13 nm and approximately 34 nm. Each dielectric layer is composed of a high-refractive-index dielectric material (H) and has a QWOT between approximately 240 nm and approximately 2090 nm. For example, the high-refractive-index dielectric material may be a mixture of _Nb2O5 and _TiO2 having a refractive index of approximately 2.43 at 550 nm. Each corrosion-inhibiting layer _is composed of ZnO and has a physical thickness of approximately 2 nm.

When the high-refractive-index dielectric material has a refractive index of approximately 2.43 at 550 nm, the filter height of the red filter is 606 nm, the filter height of the green filter is 531 nm, the filter height of the blue filter is 252 nm, and the filter height of the photopic filter is 522 nm. These filter heights are significantly smaller than those of conventional all-dielectric filters.

5A and 5B , the transmission spectra 570, 571, and 572 of exemplary red, green, and blue filters are plotted. The transmission spectrum 570 of the exemplary red filter includes a red passband centered at approximately 620 nm, the transmission spectrum 571 of the exemplary green filter includes a green passband centered at approximately 530 nm, and the transmission spectrum 572 of the exemplary blue filter includes a blue passband centered at approximately 445 nm.

FIG5C shows transmission spectra 573 and 574 of an exemplary photopic filter at angles of incidence ranging from 0° to 60°. Transmission spectrum 573 of the exemplary photopic filter at an angle of incidence of 0° includes a photopic passband centered at approximately 555 nm. Transmission spectrum 574 of the exemplary photopic filter at an angle of incidence of 60° includes a photopic passband centered at approximately 520 nm. In other words, the angular offset of the exemplary photopic filter at an angle of incidence of 60° is approximately −25 nm.

Each exemplary filter has a maximum in-band transmittance greater than approximately 60%. Advantageously, the exemplary filters provide improved IR rejection relative to conventional dye-based and all-dielectric filters, reducing noise caused by IR leakage. Specifically, each exemplary filter has an average out-of-band transmittance of less than approximately 0.3% between approximately 750 nm and approximately 1100 nm (i.e., in the IR spectral region). The exemplary filters, particularly the exemplary red filter, also provide improved UV rejection relative to some conventional metal-dielectric color filters, reducing noise caused by UV leakage. Specifically, each exemplary filter has an average out-of-band transmittance of less than approximately 2% between approximately 300 nm and approximately 400 nm (i.e., in the near-UV spectral region).

The color gamut 680 of the exemplary RGB filter set is plotted in the CIE xy chromaticity diagram in FIG6A for comparison, along with the color gamut 681 of a conventional dye-based RGB filter set. Advantageously, the color gamut 680 of the exemplary RGB filter set is significantly larger than the color gamut 681 of the conventional dye-based RGB filter set.

The color locus 682 of the exemplary red filter at an incident angle of 0° to 60° is plotted in the CIE xy chromaticity diagram in FIG6B , along with the color locus 683 of a conventional all-dielectric red filter at an incident angle of 0° to 60°. The color locus 684 of the exemplary photopic filter at an incident angle of 0° to 60° is plotted in the CIE xy chromaticity diagram in FIG6C . Advantageously, the angular offset of the exemplary filter is significantly less than that of a conventional all-dielectric filter.

The optical filters of the present invention are particularly useful when included as part of a sensor device. The sensor device can be any type of sensor device that, in addition to including one or more optical filters of the present invention, also includes one or more sensor elements. For example, the sensor device can be an ambient light sensor, a proximity sensor, or an image sensor. The one or more sensor elements can be any type of conventional sensor element. Typically, the one or more sensor elements are photosensors, such as photodiodes, charge-coupled device (CCD) sensor elements, or complementary metal oxide semiconductor (CMOS) sensor elements. The one or more sensor elements can be front- or back-illuminated.

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

In some embodiments, the sensor device includes a single sensor element and a single optical filter disposed on the sensor element. Referring to FIG7 , a first embodiment of a sensor device 790 includes a sensor element 711 and an optical filter 700 disposed on the sensor element 711. For example, the sensor device 790 can be an ambient light sensor, the sensor 711 can be a photodiode, and the optical filter 700 can be a photopic filter, such as the exemplary photopic filter of FIG4D , or an IR blocking filter.

In other embodiments, the sensor device includes a plurality of sensor elements and a plurality of filters arranged on the plurality of sensor elements. Generally, the sensor elements are arranged 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. Furthermore, generally, the filters are arranged in an array. In other words, the filters form a filter array, such as a color filter array (CFA). Preferably, the sensor array and the filter array are corresponding two-dimensional arrays, i.e., mosaics. For example, the array can be a rectangular array having rows and columns.

Typically, these filters are substantially separated from each other. In other words, the perimeters of the filters generally do not touch each other. However, in some instances, the dielectric layers of the filters may inadvertently touch while the metal layers, particularly the tapered edges, remain separated from each other.

Generally, the plurality of filters includes different types of filters having different passbands. For example, the plurality of filters may include color filters, such as red, green, blue, cyan, yellow, and/or magenta filters, photopic filters, IR-blocking filters, or combinations thereof. In some embodiments, the plurality of filters includes different types of color filters forming a CFA. For example, the plurality of filters may include red, green, and blue filters forming an RGB filter array (e.g., a Bayer filter array), such as the exemplary red, green, and blue filters of Figures 4A to 4C.

Advantageously, different types of filters can have different numbers of metal layers and/or different thicknesses of metal layers. In some embodiments, at least two of the different types of filters include different numbers of metal layers. In the same or other embodiments, at least two of the different types of filters have different metal layer thicknesses. For example, the exemplary blue filter of FIG. 4C has a different number of metal layers than the exemplary red and green filters of FIG. 4A and 4B. Furthermore, all of the exemplary red, green, and blue filters of FIG. 4A through 4C have different metal layer thicknesses.

8 , a second embodiment of a sensor device 890 includes a plurality of sensor elements 811 and a plurality of optical filters 800 and 804 arranged on the plurality of sensor elements 811. The plurality of optical filters 800 and 804 include a first type of optical filter 800 having a first passband and a second type of optical filter 804 having a second passband different from the first passband. For example, the sensor device 890 may be an image sensor, the plurality of sensor elements 811 may form a CCD array, and the plurality of optical filters 800 and 804 may form a Bayer filter array, of which only a portion of a row is shown. The first type of optical filter 800 may be a green filter, such as the exemplary green filter of exemplary FIG. 4B , and the second type of optical filter 804 may be a blue filter, such as the exemplary blue filter of exemplary FIG. 4C .

Of course, numerous other embodiments can be envisaged without departing from the spirit and scope of the invention.

Claims (20)

1. A sensor device, comprising: One or more sensor elements; and One or more filters, said one or more filters being disposed on said one or more sensor elements, wherein each of said one or more filters includes: Multiple dielectric layers; and Multiple metal layers stacked alternately with the plurality of dielectric layers, wherein Each of the plurality of metal layers has a tapered edge at the periphery of the filter, which is substantially encapsulated by one or more of the plurality of dielectric layers. Each of the plurality of metal layers is separated from the substrate of the filter in the one or more filters using at least one of the plurality of dielectric layers, and Each of the plurality of metal layers has a physical thickness between 5 nm and 50 nm, and each of the plurality of dielectric layers has a thickness between 20 nm and 300 nm. 2. The sensor device of claim 1, wherein the one or more filters are disposed directly on the one or more sensor elements. 3. The sensor device of claim 2, wherein the one or more filters are formed on the one or more sensor elements by a stripping process. 4. The sensor device of claim 1, wherein the one or more filters have a substantially flat top and sloping sides. 5. The sensor device of claim 1, wherein each of the plurality of metal layers is substantially encapsulated by the two closest dielectric layers of the plurality of dielectric layers. 6. The sensor device of claim 1, wherein each of the plurality of metal layers is composed of silver. 7. The sensor device of claim 1, wherein each of the plurality of dielectric layers is composed of a high refractive index dielectric material having a refractive index greater than 2.0 at 550 nm. 8. The sensor device of claim 7, wherein the high refractive index dielectric material is ultraviolet absorbing, and wherein each of the one or more filters has an average out-of-band transmittance of less than 2% between 300 nm and 400 nm. 9. The sensor device of claim 1, wherein each of the plurality of dielectric layers is composed of titanium dioxide, zirconium dioxide, niobium pentoxide, tantalum pentoxide, or mixtures thereof. 10. The sensor device of claim 1, wherein each of the one or more filters further comprises a plurality of corrosion-inhibiting layers disposed between the plurality of dielectric layers and the plurality of metal layers. 11. The sensor device of claim 10, wherein the dielectric layer D, the plurality of corrosion inhibition layers C and the plurality of metal layers M are stacked in the order D(C/M/C/D) _n , and wherein n≥2. 12. The sensor device of claim 10, wherein each of the plurality of corrosion inhibition layers is composed of ZnO. 13. The sensor device of claim 1, further comprising a dielectric coating that protectively covers the one or more filters. 14. The sensor device of claim 1, wherein the one or more filters are one or more color filters, photosensitive filters, infrared blocking filters, or combinations thereof. 15. The sensor device of claim 1, wherein the one or more sensor elements are composed of a plurality of sensor elements, and wherein the one or more filters are composed of a plurality of filters. 16. The sensor device of claim 15, wherein the one or more sensor elements are arranged in a two-dimensional array, and wherein the plurality of filters are arranged in a corresponding two-dimensional array. 17. The sensor device of claim 15, wherein the plurality of filters are substantially separate from each other. 18. The sensor device of claim 15, wherein the plurality of filters comprises different types of filters having different passbands. 19. The sensor device of claim 18, wherein at least two of the different types of filters comprise different numbers of metal layers. 20. The sensor device of claim 18, wherein at least two of the different types of filters have metal layer thicknesses that differ from each other.