IMAGE SENSOR WITH IMPROVED COLOR ACCURACY

Abstract

Imaging device, comprising: a plurality of optical sensors (62) on an integrated circuit; a plurality of sets of interference filters (242A, 242B), wherein a set of interference filters (242A, 242B) of the plurality of sets of interference filters (242A, 242B) includes a plurality of interference filters (42A - 42F) arranged in a pattern, wherein each interference filter (42A - 42F) of the plurality of filters is configured to transmit light in a different wavelength range; and a plurality of sets of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B), wherein a set of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) of the plurality of sets of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) comprises a plurality of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) arranged in a pattern, wherein each absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) are associated with two or more interference filters (42A - 42F) to form a pair of absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) and interference filter (42A - 42F), each pair of absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) and interference filter (42A - 42F) being configured to transmit light in a narrower wavelength range than the absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) alone,and wherein each absorption filter and interference filter pair is assigned to one or more optical sensors (62) of the plurality of optical sensors (62).

Description

BACKGROUND OF THE INVENTIONAL TECHNOLOGY FIELD OF INVENTION

[0001] This invention relates generally to imaging and in particular to digital imaging with improved color accuracy.

[0002] Most digital image sensors use color filters arranged on a grid of photosensors to enable the reproduction of a wide color range. A red-green-blue (RGB) color sensor, for example, uses filters for the three primary "channels"—red, green, and blue—additively to represent a complete light spectrum. The filters used in an RGB color sensor are typically organic absorption filters, which can exhibit undesirable filtering characteristics. Filters with better filtering characteristics, such as interference filters, can be used; however, interference filters are more complex to manufacture, and unwanted reflection of light outside the filter's transmission range can lead to ghosting.While providing more channels by inserting additional filters can improve color accuracy, adding too many additional channels can also degrade the resolution of an image sensor.

[0003] US 2015 / 0144770 A1 discloses a multispectral imager comprising a two-layer filter array monolithically integrated onto a detector array. The two-layer filter array comprises an upper layer of a pigment-based filter and a lower layer of a plasmonic nano-optical filter. Further state of the art is known from A. Kobylinskiy, B. Laue, E. Förster, B. Höfer, Y. Shen, H. Hillmer, and R. Brunner, “Substantial increase in detection efficiency for filter array-based spectral sensors”, Appl. Opt. 59, 2443-2451 (2020) and US 2015 / 0036046 A1. BRIEF DESCRIPTION OF MULTIPLE VIEWS OF THE DRAWING(S) Fig. Figure 1A illustrates an example passband response of an interference filter; Fig. Figure 1B illustrates an example of the reflection behavior of an interference filter; Fig. Figure 2A provides a side view of an image sensor system illustrating the characteristic reflectivity of an interference filter; Fig. 2B illustrates an example response of a long-pass filter; Fig. Figure 3A shows exemplary passband responses of RGB absorption filters; Fig. Figure 3B provides a top-down view of an arrangement of RGGB filter mosaics according to the present invention; Fig. 4A provides the characteristic passband responses of selected shortpass and longpass interference filters superimposed on the response of a selected absorption filter according to the present invention; Fig. 4B provides the combined passband responses of selected short-pass and long-pass interference filters with adapted RGB absorption filters according to the present invention; Fig. Figure 5 provides a top-down view of an exemplary 6-channel color filter pattern according to the present invention; Fig. Figure 6 provides a side view of an image sensor with absorption filters superimposed on interference filters according to the present invention; Fig. Figure 7 provides a side view of an image sensor with microlenses superimposed on absorption and interference filters according to the present invention; Fig. Figure 8 shows the characteristic passband responses of a multiband interference filter superimposed on each absorption filter of an RGB filter configuration. Fig. Figure 9 provides an exemplary spectral result from the combined passband responses of characteristic RGB absorption filters and interference filter pairs according to the present invention; Fig. Figure 10 provides a side view of an image sensor with absorption filters superimposed on interference filters according to the present invention; and Fig. Figure 11 is a flowchart illustrating an exemplary method for manufacturing a sensor according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0004] The invention is defined by the main claim and the dependent claim. Further embodiments of the invention are described by the dependent claims. In various embodiments, digital image sensors combine absorption-type color filters with interference-based filters to expand available color channels and provide additional color channels. In other embodiments, absorption-type color filters are combined with interference-based filters to provide additional channels in the ultraviolet (UV), near-infrared (NIR), and infrared (IR) wavelengths. In some embodiments, interference-based filters are stacked with absorption filters over an array of photosensors. In further embodiments, the passband of one or more interference filters is selected for use with each of several absorption filters to provide additional color bands for each pixel of an image sensor. In still other exemplary embodiments, a variety of absorption filters are selected to reduce ghosting artifacts in a sensor system.

[0005] Fig. Figure 1A illustrates an example passband response of an interference filter. In this example, the peak transmittance of the interference filter is centered on a target wavelength within a passband, where the passband is the range of wavelengths that can pass through the interference filter. In this example, light within the passband is directed through the interference filter and captured at the pixel. Light outside the wavelength range that can pass through the interference filter is reflected by the interference filter. Fig. Figure 1B illustrates an example of the reflectivity of the interference filter of Fig. 1B. In this example, the interference filter acts as a mirror for light outside the transmission range.

[0006] Fig. Figure 2A provides a side view of an image sensor system 10, illustrating the characteristic reflectivity of an interference filter. In the example, incident light rays received at the sensor system pass through one or more lens elements 44, where they either pass through the transmission band of an interference filter, such as interference filters 42A-42F, to a pixel element, such as pixel elements 52, and / or are reflected back as reflected light 62, where they can be reflected again by other elements of the image sensor system, such as the cover glass 40, to pass through the transmission band of another interference filter.In one example, the sensor system 10 can include additional elements, such as a cover glass 40 for the image sensor, lens elements 44, packaging boundaries, or bond wires (not shown), any of which can reflect light outside the interference filter's passband that has been reflected by the interference filter. For example, an image sensor 10 can be implemented in a metal, plastic, glass, or ceramic housing (not shown), any of which can reflect unwanted light back. The multiple reflections or "light reflections" in the image sensor system 10 can lead to ghosting and / or blurring at the image sensor because the reflected light is offset from the incident light received at the interference filter. In one example, one or more blocking filters can be provided on the top surface of the cover glass 40 or on the top surface of the interference filters 42A-42F.

[0007] Typical absorption-type color filters, such as the red, green, and blue (RGB) filters in an RGB (or RGGB) image sensor, absorb light that lies outside the filter's transmission range, resulting in very few, if any, reflections. Accordingly, absorption-type filters exhibit limited ghosting; however, they are made of materials such as pigmented organic photoresists (like crosslinkable acrylate copolymers with photoinitiators), which may not have ideal filtering properties. Interference filters, on the other hand, can offer useful filtering properties, in addition to flexible design options for filter response compared to absorption-type filters. However, interference filters are relatively complex to manufacture and can result in thick layers on a photosensor (pixels), in addition to ghosting.

[0008] In addition to the red, green, and blue (RGB) filters, other image sensor configurations in an RGB (or RGGB)-based image sensor use absorption filters, all of which exhibit similar performance issues. Examples include: the cyan, magenta, and yellow filters of a CMY-based image sensor; the red, green, blue, and white filters of an RGBW-based image sensor; the cyan, yellow, green, and magenta filters of a CYGM-based image sensor, etc.

[0009] Fig. Figure 2B illustrates an example response of an interference-based longpass filter. Interference filter arrays designed for a broad spectral response require additional fabrication layers to suppress unwanted out-of-band light. In the example response of Fig. 2B's long-pass response for light with wavelengths above approximately 700 nm also exhibits several harmonics and other unwanted transmission anomalies below approximately 500 nm, all of which necessitate additional filter layers for removal. Accordingly, a given interference-based filter for an image sensor may include thick filter layers that exhibit unwanted crosstalk between filter elements when implemented in a pixelated pattern on a sensor. Furthermore, the thick filter layers required by interference filters designed for a broad spectral response can increase substrate stress during fabrication and complicate the production of small-form-factor pixels for high-resolution image sensors.For example, thick filter layers during manufacturing can cause “wafer warping” by adding stress to one side of the semiconductor wafer, leading to handling problems with tools and other issues.

[0010] Fig. Figure 3A shows exemplary passband responses for each absorption filter of red, green, and blue (RGB) filters. RGB filters are typically implemented in a pattern of three or four filters repeated in an array over a grid or array of photosensor elements or pixels. When four filters are used in the pattern, the green filter is typically repeated to create an RGGB filter pattern. Fig. 3B provides a top-down view of a repeating RGGB filter pattern, where filters 22A are green filters and filters 22B and 22C are red and blue filters, respectively.

[0011] Fig. Section 4A provides the characteristic passband responses 72 and 74 of selected short-pass and long-pass interference filters, superimposed on the response 76 of a selected absorption filter. In the example, a first interference filter is configured to transmit wavelengths 72 at desired wavelengths below the peak absorption wavelengths of the selected absorption filter response. A second interference filter is configured to transmit wavelengths 74 at desired wavelengths above the peak absorption wavelengths of the selected absorption filter response 76. In an example, the combination of the first interference filter and the second interference filter with a fitted absorption filter results in two transmission peaks for the absorption filter: one just below the transmission peak for the absorption filter and one just above the transmission peak for the absorption filter.

[0012] In one example, a fitted absorption filter can absorb out-of-band wavelengths for each of the second and first interference filters, preventing out-of-band wavelengths from being reflected back to create ghost images. Furthermore, the complexity of the filter stack for the first and second interference filters can be reduced, as unwanted transmission wavelengths no longer need to be compensated for with additional filter layers. In one example, the resulting reduction in the Fig. 4A illustrated filter layers lead to thinner and less complex filter stacks, which in turn can lead to less expensive filters with reduced optical crosstalk.

[0013] Fig. 4B provides the combined passband responses of selected short-pass / long-pass interference filters with matched RGB absorption filters. In an example, as explained with reference to 4A, each of the red, green, and blue (RGB) absorption filters, when used in combination with two matched interference filters, results in two transmission peaks, as shown. In one example, the two transmission peaks can result in three additional color channels for each filter mosaic, for a total of 6 color channels (b'λ, bλ (blue), g'λ, gλ (green), r'λ, and rλ (red)). In other examples, various filter configurations can be used to add additional channels to RGB filters and other filter configurations, including but not limited to cyan, magenta and yellow (CMY) filters, red, green, blue and white (RGBW) filters, cyan, yellow, green and magenta (CYGM) filters, etc.

[0014] Fig. Figure 5 provides a top-down view of an example 6-channel color filter pattern. In the example, each of the red, green, and blue filters of a typical RGGB filter pattern contains an additional filter response. In the example shown, the filter pattern includes the filters b'λ, bλ (blue), g'λ, gλ (green), r'λ, and rλ (red). Other examples (not shown) include absorption filters tuned with interference filters to provide additional channels in ultraviolet (UV), visible (VIS), near-infrared (NIR), and infrared (IR) wavelengths. In one example, an absorption filter, such as an organic filter, can be tuned with selected interference filters to provide additional channels in the UV, VIS, NIR, and IR wavelength bands. In another example, the interference filters can be Fabry-Perot filters and / or plasmonic interference filters.In yet another example, the absorption-based filters and / or interference filters of the . Fig. 4B and Fig. 5 include one or more short-pass, long-pass, band-pass or band-stop filters.

[0015] In a specific example of the execution and operation, the output of an image sensor, such as image sensor 10, can be... Fig. 2A, processed to make an image demosaic, which was generated by applying a specific filter pattern, such as the one in Fig. Figure 5 describes an example of a 6-channel filter pattern. In this example, a demosaicing process can be used to extract the spectral bandpass response from a set of filters. The demosaicing process can be enabled using one or more processors, where the processors use an algorithm or digital image processing to reconstruct a bandpass response from optical sensors associated with individual filters in a filter set. In an example where two groups of optical sensors are dispersed, a demosaicing process can be used to retrieve spectral information from a subset of filters in a dispersed group or array.

[0016] In a specific related example, an optimized configuration of color filters can be used to improve the demosaicing algorithm. In this particular example, a multi-channel filter pattern can be configured so that each channel is separated as much as possible from the channels with the nearest wavelengths, thus reducing the likelihood of interference propagating from a neighboring filter to the other channels in the filter pattern.

[0017] In another example, all or part of the output of an exemplary image sensor, such as image sensor 10, can be... Fig. 2A, processed to perform spectral correction and / or to provide white balance correction for an image generated by the image sensor and / or for discrete parts of an image. In yet another example, an optimized configuration of the color filters can be used to improve the spectral correction of a particular algorithm used for white balance.

[0018] Fig. Figure 6 shows a side view of an image sensor, such as image sensor 10. Fig. 2A, with absorption filters 64A, 64B, 66A, 66B, 68A, and 68B ready to superimpose the interference filters 42A-42F. In one example, each absorption filter 64A, 64B, 66A, 66B, 68A, or 68B is matched to an interference filter in a filter pair. In this example, the absorption filters 64A and 64B are configured to transmit wavelengths with the same center wavelength, such as the red absorption filters in a typical red-green-green-blue (RGGB) filter pattern. In another example, each of the absorption filters 64A, 64B, 66A, 66B, 68A, and 68B is matched to a different interference filter, with the filter response of the combined filter pairs producing two color channels for detection by the sensor 62. In one example, the absorption filters 64A and 64B, although shown as separate filters, can be manufactured as a single filter.In another example, a single interference filter can be made under two different absorption filters 64A and 64B to allow a different section of an interference band to pass through.

[0019] Fig. Figure 7 shows a side view of an image sensor using the arrangement of Fig. 4 to 6 with microlenses superimposed on absorption and interference filters. In one example, a microlens 90 may be included over one or more absorption filters 64A, 64B, 66A, 66B, 68A, and 68B, and interference filter pairs with interference filters 42A-42F. In another (not shown) example, a light-deflecting plate or cover is used either instead of or in addition to the microlens 90. Fig. 7 is provided to prevent stray light from impairing sensor performance. Exemplary light covers or deflection plates include one or more made of a metal, pseudometal, opaque deposited material, and / or any other material capable of absorbing light. In other examples, fiber optics and / or deep trench insulation (DTI) may be used to channel light and prevent crosstalk from degrading system performance. In yet another example, the absorption filters and interference filters of the Fig. 4 to 7 can be implemented in a back-illuminated sensor, also known as a back-illuminated sensor (BSI or BI). BSI-based imagers can utilize an array of imaging elements on the back side of the integrated circuit containing an image sensor. In yet another example, planarization layers, such as organic spin-on materials, oxide deposition layers, and other planarization layers, can be used to compensate for the non-planarity of filter layers.

[0020] In one embodiment and operation, an imaging device comprises a plurality of optical sensors on an integrated circuit, wherein a plurality of sets of interference filters are arranged on the optical sensors. In one example, the interference filter sets are separated from the multiple optical sensors by an etch stop layer. In an alternative example, the interference filter sets are further separated from the multiple optical sensors by an air gap or a substantially transparent material. In one example, this material comprises one or more organic materials. In another example, this material may be optimized to limit reflection and / or may comprise an alloy gradient or a stack of layers.In one example, a set of interference filters of a plurality of sets of interference filters comprises a plurality of interference filters arranged in a pattern, each interference filter configured to transmit light in a different wavelength range. In one specific example, each interference filter is one or more of a short-pass, long-pass, band-pass, or band-stop filter, and each interference filter is configured to transmit light in at least one of the ultraviolet, visible, near-infrared, or infrared spectral ranges. In another specific example, one or more interference filters of the plurality of sets of interference filters comprise a Fabry-Perot filter.In yet another specific example, one or more interference filters from the plurality of sets of interference filters include a plasmonic interference filter. In another specific example, at least some absorption filters from the plurality of sets of absorption filters are configured to transmit infrared light or are configured to cut off infrared light. Example filters include IR-pass filters and IR-cut filters, respectively. In yet another specific example, an interference filter or set of interference filters may be present only at some locations within the image sensor array, with some pixels being assigned to one or more absorption filters without underlying interference filters.

[0021] In one example, a plurality of sets of absorption filters are arranged over a plurality of sets of interference filters, each absorption filter being one or more of a shortpass, longpass, bandpass, or bandstop filter, and each absorption filter being configured to transmit light in at least one of the ultraviolet, visible, near-infrared, or infrared spectral ranges. The absorption filters may include organic filters and / or plasmonic filters. In one example, the sets of absorption filters are separated from the multiple interference filters by an etch stop layer. In an alternative example, the sets of absorption filters are further separated from the multiple interference layers by an air gap or a substantially transparent material.In one example, the transparent material may also be optimized to limit reflection and / or may include an alloy gradient and / or a stack of layers.

[0022] In one specific example, the set of absorption filters in the plurality of sets of absorption filters comprises absorption filters arranged in a pattern, with each absorption filter in the set being associated with one or more interference filters to provide an absorption-interference filter pair. In another specific example, the interference filter in at least one absorption-interference filter pair comprises a plurality of interference filters. In yet another example, the response of each absorption-interference filter pair is configured to transmit light in a narrower wavelength range than the absorption filter alone would transmit. In yet another example, each absorption-interference filter pair can be optically aligned with at least one optical sensor in the plurality of optical sensors.In one example, microlens arrays can include absorption filter and interference filter pairs, where each of the absorption filter and interference filter can be shifted by the individual optical sensors in the plane of the image sensor, so that light passing through the microlens associated with a specific principal beam essentially passes through an associated absorption filter or interference filter, respectively. In one example, the microlens can reduce crosstalk when tuned with an absorption filter and interference filter pair.

[0023] In yet another example, the imaging device comprises a plurality of microlenses arranged on multiple sets of absorption filters, each microlens being connected to at least one absorption filter. In another example, one or more light guide plates, light guides, or deep trench isolation are used to reduce the influence of stray light on the light in one or more absorption and interference pairs.

[0024] In an operational and implementation example, additional color channels can be used, as described in the Fig. 4A, Fig. 4B, Fig. 5 and Fig. As described in Section 6, these filters can be used to provide improved white balance in addition to improved color accuracy compared to image sensors and image sensor systems that use only absorption-type filters. In a specific related example, a first image sensor with increased spectral resolution can be configured to work in conjunction with a second image sensor configured to image the same scene in an imaging system. In this example, the first image sensor provides information with increased color accuracy to correct the image from the second image sensor. In a related example, the second image sensor can have increased spatial resolution while providing reduced spectral information compared to the first image sensor.

[0025] In a related example of operation and execution, an image sensor can be configured to include some absorption filters that are not paired with interference filters, along with other absorption filters that are paired with interference filters. In a specific example, one green absorption filter G of an image sensor can be configured without an underlying paired interference filter, while another absorption filter G a It can be configured with an underlying paired interference filter. In the example, the missing spectral filter response can then be converted to G. b = G - G a be calculated. An image sensor that implements paired and unpaired interference filters, as used in the Fig. 4A, Fig. 4B, Fig. 5 and Fig. Figure 6 shows that it can offer advantageous performance in poor lighting conditions, for example, the filter G from the relationship G b= G - G a providing a wider optical bandwidth and therefore potentially more sensitive in low-light conditions, the inclusion of one or more additional color channels. In one specific related example of design or operation, filters without underlying absorption filters can be configured for use in low-light conditions. In another specific related example, interference filters sparsely distributed across a sensor array can be used to provide improved color accuracy while limiting the overall effect that additional color channels can have on light sensitivity. In a related operational and design example, an image sensor can be configured to include some interference filters not paired with absorption filters, along with other interference filters that are paired with absorption filters.

[0026] In another operational and embodiment, one or more cavity layers in one of the interference filters 42A–42F can comprise a material or a composite of materials adapted to absorb at least some unwanted wavelengths while transmitting desired wavelengths. In one example, the materials can include porous optical materials with a refractive index closer to 1.0 (low-n materials) and / or optical materials with a higher refractive index. In another example, the cavity material can be a semiconductor with a refractive index of 2.5–3.5, exhibiting light propagation that differs from that of an air-filled cavity (n = 1.0).In a specific example, the cavity can comprise an amorphous or semi-amorphous material with a direct band gap of III-V, where the absorption properties of the cavity material can be modified by changing the III-V material alloy ratios or by substituting different alloys. In one example, the cavity material can be tailored to absorb photons with higher energies than the band gap and transmit photons with lower energies.

[0027] Fig. Figure 8 shows the characteristic passband responses of a multiband interference filter superimposed on each absorption filter of an RGB filter configuration. In one operational and implementation example, interference filters are configured as multiband filters so that when the interference filters are combined with an absorption filter, one of the spectral bands of the multiband filter can be selected to define a smaller portion of the absorption filter. In one example, fewer interference-type filters are required during the fabrication of the image sensor, thus reducing complexity. Referring to Figure 8, a first interference filter is configured to provide a wavelength response 140A in a narrow band below the peak absorption wavelengths for each of the blue, green, and red absorption filter responses.In one embodiment, a second interference filter is configured to provide a wavelength response 140B in a narrow band above the wavelengths of the peak absorption for each of the absorption filters associated with the response peaks 164A (blue), 164B (green), and 164C (red). In another example, combining the first and second multiband interference filters with matched absorption filters results in two transmission peaks for each absorption filter: one just below the transmission peak for the absorption filter and one just above the transmission peak for the absorption filter. In yet another embodiment, complementary interference filters can be configured to transmit wavelengths in a narrow band for each of the blue and green filters in a similar manner. This is illustrated in a related example. Fig. 8 An embodiment in which one or more absorption filters are adapted to select a specific harmonic of a chosen interference filter. In yet another example, an interference filter or a set of interference filters can be included only at some locations of the image sensor array, such that the image sensor array comprises both unmodified RGB or RGGB filter structures and modified RGB or RGGB filter structures, wherein the response from the unmodified and modified RGB or RGGB filter structures can be used to compute compensated RGB values.

[0028] In one example, a tailored absorption filter, such as those associated with response peaks 164A, 164B, and 164C, can absorb out-of-band wavelengths for each of the first and second interference filters discussed above, preventing out-of-band wavelengths from being reflected back as ghost images. In another example, the complexity of the filter stack for the first and second interference filters can be reduced because unwanted transmission wavelengths are significantly attenuated and therefore no longer need to be compensated for by adding filter layers. In yet another example, a resulting reduction in filter layers can allow for thinner and / or less complex filter stacks, which in turn can lead to more cost-effective filters with reduced crosstalk.

[0029] Fig. Figure 9 shows an exemplary spectral result of the combined passband responses of characteristic RGB absorption and interference filter pairs. In the example, a 6-filter pattern leads to a spectral result that doubles the number of color channels. In the specific example of Fig. 9. An absorption filter and an interference filter pair are combined to provide two color channel responses 364A and 364B, which are assigned to a blue channel, while another pair of absorption filters and interference filters is combined to provide two color channel responses 366A and 366B, which are assigned to a green channel, and a third pair of absorption filters and interference filters is combined to provide two color channel responses 366A and 366B, which are assigned to a green channel.

[0030] In one embodiment, an RGB-IR sensor can be formed by using an interference infrared (IR) blocking filter paired with R, G, and B absorption filters on an optical sensor array. In an alternative example, an optical sensor is not covered by the IR blocking filter and is configured to transmit IR light. In another example, the optical sensor is superimposed with an absorbing IR pass filter, such as an IR pass filter, to implement an optical IR sensor. In yet another example, an associated optical sensor is left uncovered by a filter and transmits all wavelengths to provide an essentially white optical sensor. In still another example, an optical sensor is superimposed with an interference filter configured to transmit a selected wavelength band.In another example, an optical sensor is superimposed with both interference and absorption filters. In another example, filters are patterned in a Bayer-like mosaic pattern to provide an RGB-IR sensor. In yet another example, an RGB-UV sensor is created using one of the methods described in [reference to be added]. Fig. 9 discussed examples were formed (either instead of or in addition to an RGB-IR sensor).

[0031] In one implementation and operational example, multiple Fabry-Perot filters can be patterned on an image sensor, allowing different optical sensors to be paired with different Fabry-Perot passband filters within the image sensor. In one example, the filters on the sensor form a Bayer-like mosaic pattern. In the example, multiple Fabry-Perot filters can belong to a predefined filter group, with each filter group being formed using common mirror layers with alternative cavities. In one example, the cavity thickness of a Fabry-Perot filter in the group determines the center wavelength of the Fabry-Perot filter. In another example, mirror layers can be implemented using reflective materials and / or Bragg stacks. In yet another example, a cavity can be structured (e.g.,(using lifting or etching processes) to change the thickness superimposed on different optical sensors, such that each filter group has multiple Fabry-Perot filters with different cavity thicknesses, each of the Fabry-Perot filters being essentially matched to at least one optical sensor. In one example, multiple optical sensors can be matched to collect a portion of incoming wavelengths, depending on a specific Fabry-Perot filter on the optical sensor.

[0032] In another implementation and operating example, multiple filter groups of Fabry-Perot filters can be fabricated, each filter group containing at least one Fabry-Perot filter with a predetermined cavity thickness. In one example, a first filter group implements a set of four Fabry-Perot filters in the 500–600 nm range when spectral transmission of the Fabry-Perot filters outside this wavelength range is undesirable, for example, due to Bragg mirror leakage or multiple harmonics of the Fabry-Perot filter. In another example, a second filter group can be configured to implement another set of four Fabry-Perot filters in the 600–700 nm range when spectral transmission of the Fabry-Perot filters outside this wavelength range is undesirable.In one specific example, a first group of filters is paired with one or more absorption filters configured to attenuate wavelengths outside the 500–600 nm passband. In this example, the absorption filter acts as a stop filter for the first group of Fabry-Perot filters. In another example, the second group of filters is paired with an absorption filter tuned to attenuate wavelengths outside the 600–700 nm passband. In this example, one or more absorption filters can act as stop filters for the second group of Fabry-Perot filters. In a related example, three or more groups paired with absorption filters can be tuned to manage wavelength responses in the visible and infrared spectrum.

[0033] Fig. Figure 10 provides a side view of an image sensor 62 with absorption filters 264A and 264B superimposed on interference filter sets 242A and 242B. With reference to Fig. 6 can Fig. 10 as the sensor of Fig. Figure 6 is considered, where additional layers are provided to enable the fabrication of a sensor system. In one example, the stop layer 280 is deposited on the pixel layer of the sensor 62 to protect the pixel layer from subsequent lithography-based fabrication processes. In another example, interference filter sets 242A and 242B are formed on the first stop layer, and a second stop layer is deposited on the interference filter sets 242A and 242B to protect them from subsequent fabrication processes. In yet another example, the fabrication of interference filters can lead to a non-uniform topography due to the varying thicknesses associated with the different filters. Accordingly, one or more planarization layers can be provided to planarize the surface before absorption filters are formed.

[0034] In one embodiment and operating example, one or more antireflective coatings or layers may be included between the functional elements of an image sensor. For example, the stop layer 280 may include an antireflective coating. In one specific example, the antireflective coating may be applied over the pixel layer of the image sensor 62, and in another specific example, the stop layer 280 includes an antireflective coating that can act as a stop layer for subsequent lithography steps. In another embodiment and operating example, an antireflective coating or layer 282 may be provided on the absorption filters 264A and 264B. In one example, the antireflective coatings may be adapted to attenuate light reflected from underlying structural elements, such as the pixel layer or the surface of the interference filter sets 242A and 242B.

[0035] In a related example, referring to the Fig. 6 and Fig. 7. Antireflective coatings and / or materials may be added if required to attenuate light reflected from an underlying structure. For example, an antireflective coating applied to one or more of the top surface of an absorption filter, the bottom surface of an absorption filter, or the top surface of the pixel layer of one of the sensors of Fig. 6, Fig. 7 or Fig. 10 is applied, to dampen light reflected from an underlying structure.

[0036] Fig. Figure 11 is a flowchart illustrating an exemplary procedure for fabricating a sensor system. The procedure begins at step 100, where an initial set of thin-film layers is deposited onto a previously fabricated semiconductor wafer substrate to provide the optical sensors (pixels) for image sensors. In an implementation and operating example, a fabricated substrate, such as the one referenced in Figure 11, can be used to create a sensor system. Fig.The first set of thin-film layers, as mentioned in step 10, can be provided with or without a passivation layer prior to deposition. In one example, the first set of thin-film layers can begin with a first stop layer and / or end with a second stop layer. The process continues with step 102, removing the first set of thin-film layers in areas that do not require the first filter. The first set of thin films can be removed using a lithography process, followed by dry and / or wet etching processes designed to stop at a stop layer or passivation layer.

[0037] The process continues with step 104, in which a second set of thin-film layers is deposited onto the semiconductor wafer substrate, and proceeds with step 106, in which the second set of thin-film layers is removed in areas that do not require a second filter. The second set of thin-film layers can be removed using a lithography process, followed by dry and / or wet etching processes designed to stop at a stop layer provided during the fabrication of the first set of thin-film layers. In step 108, the process repeats steps 104 through 106 as needed for additional filter layers. For example, if six different interference filters are required, step 108 would involve repeating steps 104 through 106 four times.

[0038] The process continues with step 110, adding a planarization layer. Planarization can be achieved, for example, using an oxide deposition step followed by planarization using chemical-mechanical planarization (CMP). Other planarization options include the use of spin coating (such as spin-on glass) followed by etching the topographic peaks introduced during filter fabrication or selective etching of the topographic peaks. In step 112, the process continues with the application of absorption color filter layers. In one example, the absorption color filters can be applied sequentially using spin-deposited pigmented resist layers, followed by exposure to cure the resist in areas requiring a filter, followed by dissolving uncured resist areas.For example, red, green and blue (RGB) filters can be applied in 3 separate lithographic processes, one for each of the three different filters.

[0039] It should be noted that in all described embodiments, one or more absorption filters can be replaced by a plasmonic filter, with filters typically being implemented using structured metal layers to define passbands.

[0040] It should be noted that terminologies such as those used herein, such as bitstream, stream, signal sequence, etc. (or their equivalents), have been used interchangeably to describe digital information whose content corresponds to a number of desired types (e.g., data, video, speech, text, graphics, audio, etc., which may be generally referred to as "data").

[0041] As used here, the terms "essentially" and "approximately" provide an industry-accepted tolerance for the respective term and / or the relativity between the elements. For some industries, an industry-accepted tolerance is less than one percent, and for others, it is 10 percent or more. Other examples of industry-accepted tolerances range from less than one percent to fifty percent. Industry-accepted tolerances correspond to, but are not limited to, component values, process variations in integrated circuits, temperature variations, rise and fall times, thermal noise, dimensions, signal errors, lost packets, temperatures, pressures, material compositions, and / or performance characteristics. Within an industry, tolerance deviations from accepted tolerances may be more or less than one percent (e.g.,Dimensional tolerance of less than + / - 1%). A certain degree of relativity between elements can range from a difference of less than one percent to several percent. Other relativities between elements can range from a difference of a few percent to the order of magnitude of the differences.

[0042] As may also be used herein, the terms “configured to”, “operationally coupled to”, “coupled to”, and / or “coupling” include direct coupling between objects and / or indirect coupling between objects via an intermediary object (e.g., an element includes, but is not limited to, a component, element, circuit, and / or module), where, in an example of indirect coupling, the intermediary element does not modify the information of a signal but may adjust its current level, voltage level, and / or power level. As may also be used herein, inferred coupling (i.e., when an element is coupled to another element by inference) includes direct and indirect coupling between two elements in the same way as “coupled to”.

[0043] As may be further used herein, the terms "configured to", "operational to", "coupled to", or "operationally coupled to" indicate that an item includes one or more power connections, input(s), output(s), etc., to perform one or more of its corresponding functions when activated, and may further include a derived coupling with one or more other elements. As may be further used herein, the term "associated with" includes the direct and / or indirect coupling of separate elements and / or the embedding of one element within another.

[0044] As used here, the term "comparable" indicates that a comparison between two or more elements, signals, etc., provides a desired relationship. For example, if the desired relationship is that signal 1 has a larger magnitude than signal 2, a favorable comparison can be achieved if the strength of signal 1 is greater than that of signal 2, or if the strength of signal 2 is less than that of signal 1. As used here, the term "unfavorable comparison" indicates that a comparison between two or more elements, signals, etc., does not provide the desired relationship.

[0045] As used herein, one or more claims in a specific form of this generic form may include the expression "at least one of a, b, and c" or this generic form "at least one of a, b, or c," with more or fewer elements than "a," "b," and "c." In both formulations, the expressions are to be interpreted identically. In particular, "at least one of a, b, and c" is equivalent to "at least one of a, b, or c" and is intended to mean a, b, and / or c. For example, it means: only "a," only "b," only "c," "a" and "b," "a" and "c," "b" and "c," and / or "a," "b," and "c."

[0046] As they may be used herein, the terms "processing module," "processing circuit," "processor," "processing circuit," and / or "processing unit" can refer to a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, microcontroller, digital signal processor, microcomputer, central processing unit, field-programmable gate array, programmable logic device, state machine, logic circuit, analog circuit, digital circuit, and / or any device that manipulates signals (analog and / or digital) based on a hard-coded circuit and / or operating instructions.The processing module, module, processing circuit, processing circuit, and / or processing unit may be a memory and / or an integrated memory element, or may further include a single memory element, multiple memory elements, and / or embedded circuitry of another processing module, module, processing circuit, processing circuit, and / or processing unit. Such a memory device may be read-only memory, random-access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and / or any device that stores digital information.It should be noted that if the processing module, module, processing circuit, processing circuit and / or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly connected to each other via a wired and / or wireless bus structure) or distributed (e.g., cloud computing via indirect coupling over a local area network and / or a wide area network).It should also be noted that if the processing module, module, processing circuit, and / or processing unit implements one or more of its functions via a state machine, analog circuit, digital circuit, and / or logic circuit, the memory and / or storage element that stores the corresponding operating instructions may be embedded within or outside the circuit comprising the state machine, analog circuit, digital circuit, and / or logic circuit. Furthermore, it should be noted that hard-coded operating instructions corresponding to at least some of the steps and / or functions depicted in one or more of the figures may be stored by the memory element and executed by the processing module, module, processing circuit, and / or processing unit.Such a storage device or storage element may be included in a manufactured article.

[0047] One or more embodiments have been described above using process steps that illustrate the execution of specified functions and their relationships. The boundaries and sequence of these function blocks and process steps have been arbitrarily defined here for the sake of simplicity. Alternative boundaries and sequences may be defined as long as the specified functions and relationships are adequately executed. All such alternative boundaries or sequences are thus within the scope and spirit of the claims. Furthermore, the boundaries of these function blocks have been arbitrarily defined for the sake of simplicity. Alternative boundaries could be defined as long as the certain significant functions are adequately executed. Similarly, flowchart blocks may also have been arbitrarily defined here to illustrate a particular significant functionality.

[0048] Where used, the block boundaries and flowchart sequence could be defined differently and still perform the specific significant functionality. Such alternative definitions of both function blocks and flowchart blocks and sequences are thus within the scope and spirit of the claims. A person skilled in the art will also recognize that the function blocks and other illustrative blocks, modules, and components herein, as shown, can be implemented or by discrete components, application-specific integrated circuits, processors, executing appropriate software, and the like, or any combination thereof.

[0049] Furthermore, a flowchart may include a "Start" and / or "Continue" indicator. The "Start" and "Continue" indicators reflect that the presented steps can optionally be integrated into one or more other routines or otherwise used in conjunction with them. A flowchart may also include an "End" and / or "Continue" indicator. The "End" and / or "Continue" indicators reflect that the presented steps can end as described and shown, or can optionally be integrated into one or more other routines or otherwise used in conjunction with them. In this context, "Start" denotes the beginning of the first presented step and may be preceded by other activities not explicitly shown. Furthermore, "Continue" reflects that the depicted steps can be performed multiple times and / or followed by other activities not specifically shown.While a flowchart shows a specific sequence of steps, other sequences are also possible, provided that the principles of causality are adhered to.

[0050] The one or more embodiments are used here to illustrate one or more aspects, features, concepts, and / or examples. A physical embodiment of a device, article, machine, and / or process may include one or more of the aspects, features, concepts, examples, etc., described with reference to one or more of the embodiments discussed herein. Furthermore, the embodiments from figure to figure may include the same or similarly named functions, steps, modules, etc., which may use the same or different reference numerals, and as such, the functions, steps, modules, etc., may be the same or similar, or different.

[0051] Unless explicitly stated otherwise, signals to, from, and / or between elements in any of the figures shown herein can be analog or digital, continuous-time or discrete-time, and asymmetric or differential. For example, where a signal path is represented as a single-ended path, it also represents a differential signal path. Similarly, where a signal path is represented as a differential path, it also represents a single-ended signal path. While one or more specific architectures are described here, other architectures may also be implemented, employing one or more data buses not explicitly shown, direct connectivity between elements, and / or indirect coupling between other elements, as would be recognized by a person skilled in the art.

[0052] The term "module" is used in the description of one or more embodiments. A module implements one or more functions via a device such as a processor or other processing device or other hardware, which may include or operate in conjunction with memory that stores operating instructions. A module may operate independently and / or in conjunction with software and / or firmware. As also used herein, a module may contain one or more submodules, each of which may be one or more modules.

[0053] As may be used further herein, computer-readable memory comprises one or more memory elements. A memory element can be a separate storage device, multiple storage devices, or a set of memory locations within a storage device. Such a storage device can be read-only memory, random-access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and / or any device that stores digital information. The storage device can be in the form of solid-state storage, hard disk storage, cloud storage, a USB flash drive, server storage, computer device storage, and / or any other physical medium for storing digital information.

Claims

[1] Imaging device comprising: a plurality of optical sensors (62) on an integrated circuit; a plurality of sets of interference filters (242A, 242B), wherein a set of interference filters (242A, 242B) of the plurality of sets of interference filters (242A, 242B) includes a plurality of interference filters (42A - 42F) arranged in a pattern, wherein each interference filter (42A - 42F) of the plurality of filters is configured to transmit light in a different wavelength range; and a plurality of sets of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B), wherein a set of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) of the plurality of sets of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) includes a plurality of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) arranged in a pattern, wherein each absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) are associated with two or more interference filters (42A - 42F) to form a pair of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) and interference filters (42A - 42F), each pair of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) and interference filters (42A - 42F) being configured to transmit light in a narrower wavelength range than the absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) alone,and wherein each absorption filter and interference filter pair is associated with one or more optical sensors (62) of the plurality of optical sensors (62). [2] The imaging device of claim 1, wherein the sets of interference filters (242A, 242B) are separated from the plurality of optical sensors (62) by an etch stop layer (282). [3] The imaging device of claim 1 or 2, wherein the sets of interference filters (242A, 242B) are additionally separated from the plurality of optical sensors (62) by an air gap or a substantially transparent material. [4] The imaging device of claim 3, wherein the substantially transparent material comprises one or more organic materials. [5] An imaging device according to claim 3 or 4, wherein the substantially transparent material is optimized to limit reflection and / or may comprise an alloy gradient or a layer stack. [6] An imaging device according to any preceding claim, wherein each interference filter (42A-42F) is selected from a group consisting of short-pass filters, long-pass filters, band-pass filters, or band-stop filters, wherein each interference filter (42A-42F) is configured to transmit light in at least one of an ultraviolet spectral range, a visible light spectral range, a near-infrared spectral range, and an infrared spectral range. [7] An imaging device according to any preceding claim, wherein one or more interference filters (42A - 42F) of the plurality of sets of interference filters (242A, 242B) comprise a Fabry-Perot filter. [8] An imaging device according to any preceding claim, wherein at least some absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) of the plurality of sets of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) are configured to cut off light in an infrared wavelength range. [9] An imaging device according to any preceding claim, wherein at least some absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) of the plurality of sets of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) comprise at least one of organic filters or plasmonic filters. [10] An imaging device according to any preceding claim, wherein the sets of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) are separated from the plurality of interference filters (42A - 42F) by an etch stop layer. [11] An imaging device according to any preceding claim, wherein the absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) are additionally separated from the plurality of interference filters (42A - 42F) by an air gap or a substantially transparent material. [12] Imaging device according to one of the preceding claims, wherein a first interference filter (42A - 42F) of a set of interference filters (242A, 242B) and a second interference filter (42A - 42F) of a set of interference filters (242A, 242B) are associated with an absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) of a set of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) of the plurality of sets of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B), wherein the first interference filter (42A - 42F) and the second interference filter (42A - 42F) are configured to provide a response comprising a first transmission peak (140A) anda second transmission peak (140B) when combined with the absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B), wherein the first transmission peak (140A) is at a wavelength lower than a peak response for the absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) and the second transmission peak (140B) is at a wavelength higher than the peak response for the absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B). [13] Imaging device according to one of the preceding claims, further comprising: a plurality of microlenses (90) arranged on a set of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B) of the plurality of sets of absorption filters (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B), each microlens (90) being associated with at least one absorption filter (64A, 64B, 33A, 66B, 68A, 68B, 264A, 264B). [14] An imaging device according to any preceding claim, wherein the plurality of optical sensors (62) are arranged in an optical sensor array, wherein a plurality of interference filters (42A - 42F) of the plurality of sets of interference filters (42A - 42F) are associated with fewer than all of the plurality of optical sensors (62) in the optical sensor array. [15] Imaging device according to one of the preceding claims, further comprising: a plurality of light guide plates, the plurality of light guide plates being adapted to attenuate light reflected between one or more adjacent absorption and interference pairs. [16] An imaging device according to any preceding claim, wherein each interference filter (42A - 42F) of the plurality of sets of interference filters (242A, 242B) has a respective upper surface and a respective lower surface, wherein one or more interference filters (42A - 42F) of the plurality of interference filters (42A - 42F) include a cavity between the upper surface and the lower surface, the cavity comprising at least one of an amorphous or semi-amorphous material. [17] The imaging device of any one of claims 1 to 15, wherein each interference filter (42A-42F) of the plurality of sets of interference filters (242A, 242B) has a respective top surface and a respective bottom surface, wherein one or more interference filters (42A-42F) of the plurality of interference filters (42A-42F) include a cavity between the top surface and the bottom surface, the cavity comprising one or more materials adapted to absorb at least some unwanted wavelengths while transmitting at least some desired wavelengths. [18] An imaging device according to any preceding claim, wherein at least some interference filters (42A - 42F) of the plurality of sets of interference filters (242A, 242B) are configured to transmit light in multiple wavelength bands. [19] A method of manufacturing the imaging device according to any one of the preceding claims, comprising: Depositing (100) a first set of thin film layers on a semiconductor substrate, wherein the semiconductor substrate includes a plurality of optical sensor arrays, wherein the first set of thin film layers comprises a first mirror layer, a cavity layer, and a second mirror layer; removing (102) the first set of thin film layers from a plurality of predetermined regions of the semiconductor wafer substrate; depositing (104) a second set of thin film layers on the semiconductor wafer substrate, wherein the second set of thin film layers comprises a cavity layer and a second mirror layer; removing (106) the second set of thin film layers from a plurality of predetermined regions of the semiconductor wafer substrate; Applying (112) a first absorption filter layer; Applying (112) a second absorption filter layer; and Applying (112) a third absorption filter layer. [20] The method of claim 19, further comprising: Depositing a third set of thin film layers on the semiconductor wafer substrate, the third set of thin film layers comprising a cavity layer and a second mirror layer; and Removing the third set of thin film layers from a plurality of predetermined regions of the semiconductor wafer substrate.

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