Image sensor with improved color accuracy

Abstract

An imaging device includes a plurality of optical sensors and a plurality of sets of interference filters disposed on an integrated circuit. One of the sets of interference filters includes a plurality of interference filters configured to allow light of different wavelength ranges to pass through. The invention also includes a plurality of sets of absorption filters. One of the sets of absorption filters includes a plurality of absorption filters configured to form an array. Each absorption filter is associated with one or more of the interference filters to form an absorption filter and interference filter pair. Each absorption filter and interference filter pair is associated with one or more of the optical sensors and is configured to allow light of a narrower wavelength range than the absorption filter alone.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to imaging, and more particularly to digital imaging with improved color accuracy. BACKGROUND

[0002] Most digital image sensors use color filters placed over a grid of photosensors to enable the reproduction of a variety of colors. For example, a red-green-blue (RGB) color sensor uses filters superimposed over three primary "channels" of red, green, and blue to represent the full spectrum. The filters used by RGB color sensors typically comprise organic "absorptive" filters that can include undesirable filter characteristics. Better filter characteristics can be used (e.g., interference filters), but interference filters are more complex to produce and can suffer from undesirable reflections of light outside the filter passband that create ghost images. Furthermore, while color accuracy can be improved by incorporating additional filters to provide more channels, adding too many additional channels can reduce the resolution of the image sensor. BRIEF DESCRIPTION OF DRAWINGS

[0003] Figure 1A An example of a passband response of an interference filter is shown;

[0004] Figure 1B An example of a reflectance response of an interference filter is shown;

[0005] Figure 2A A side view of an image sensor system is provided, showing the characteristic reflectance of an interference filter;

[0006] Figure 2B An example of a response of a longpass filter is shown;

[0007] Figure 3A An example of a passband response of an RGB absorptive filter is provided;

[0008] Figure 3B A top view of an RGGB filter mosaic array in accordance with the requirements of the present invention is provided;

[0009] Figure 4A Characteristic passband responses of selected shortpass and longpass interference filters overlaid on selected absorptive filter responses in accordance with the requirements of the present invention are provided;

[0010] Figure 4B Combined passband responses of selected shortpass and longpass interference filters with matching RGB absorptive filters in accordance with the requirements of the present invention are provided;

[0011] Figure 5 A top view of an example of a 6-channel color filter array in accordance with the requirements of the present invention is provided;

[0012] Figure 6 A side view of an image sensor with an absorbing filter overlaying an interference filter is provided in accordance with the present disclosure;

[0013] Figure 7 A side view of an image sensor with a microlens overlaying an absorbing filter and an interference filter is provided in accordance with the present disclosure;

[0014] Figure 8 A characteristic passband response of a multiband interference filter overlaid on each absorbing filter of an RGB filter configuration is provided.

[0015] Figure 9 A spectral results example of a combined passband response of a characteristic RGB absorbing filter and interference filter pair is provided in accordance with the present disclosure;

[0016] Figure 10 A side view of an image sensor with an absorbing filter overlaying an interference filter is provided in accordance with the present disclosure;

[0017] Figure 11 A flowchart of an example of a sensor production method in accordance with the present disclosure is provided. DETAILED DESCRIPTION

[0018] In various embodiments, a digital image sensor incorporates absorbing color filters in combination with interference filters to expand available color channels, providing additional color channels. In other embodiments, absorbing color filters are combined with interference filters to provide additional channels in the ultraviolet (UV), near-infrared (NIR), and infrared (IR) wavelengths. In some embodiments, interference filters are arranged in a stack above an array of photosensors with absorbing filters. In other embodiments, one or more interference filter passbands are selected and used in conjunction with each absorbing filter to provide additional color bands for each pixel of an image sensor. In other example embodiments, multiple absorbing filters are selected to reduce aliasing artifacts in a sensor system.

[0019] Figure 1A An example of a passband response of an interference filter is shown. In this example, the peak transmittance of the interference filter is centered on a target wavelength within the passband, which is the range of wavelengths that can pass through the interference filter. In this example, light in the passband passes through the interference filter to the pixel. For light outside the range of wavelengths that can pass through the interference filter, reflection occurs at the interference filter. Figure 1B An example of reflectance of an interference filter in Figure 1B is shown. In this example, the interference filter acts as a mirror for light outside the passband.

[0020] Figure 2AA side view of the image sensor system 10 is provided, showing the characteristic reflectivity of an interference filter. In this example, incident light received by the sensor system passes through one or more lens elements 44, which pass through the passband of an interference filter (such as interference filters 42A-42F), reach pixel elements (such as pixel element 52), and / or are reflected back as reflected light 62. Other elements of the image sensor system (such as a housing glass 40) can reflect this reflected light again, passing through the passband of another interference filter. In one example, the sensor system 10 may include additional elements such as the housing glass 40 of the image sensor, lens elements 44, encapsulation boundaries, or bonding lines (not shown), each of which can reflect light reflected by the interference filter outside the passband of the interference filter. For example, the image sensor 10 may employ a metal, plastic, glass, or ceramic housing (not shown), any of which can reflect unwanted light back. Multiple reflections or "bouncing" of light in the image sensor system 10 can produce ghosting and / or blur the image sensor because the reflected light will be canceled out by the incident light received at the interference filter. In one example, one or more band-stop filters may be disposed on the top surface of the protective glass 40 or on the top surface of the interference filters 42A–42F.

[0021] Typical absorptive color filters in RGB (or RGGB) image sensors (such as red-green-blue (RGB) filters) absorb light outside the passband of a given filter, thus minimizing reflections. Therefore, absorptive filters rarely exhibit ghosting. However, absorptive filters are composed of materials such as colored organic photoresists (e.g., crosslinkable acrylic polymers containing photoinitiators), whose filtering properties are not ideal. On the other hand, interference filters offer more flexible filter response designs compared to absorptive filters. However, aside from ghosting, the manufacturing process for interference filters is relatively complex and can lead to thick layers (pixels) on the photoelectric sensor.

[0022] Besides RGB (red, green, blue) filters, other image sensor configurations in RGB (or RGGB) based image sensors use absorption filters, each exhibiting similar performance issues. Examples include: cyan, magenta, and yellow filters in CMY imagers; red, green, blue, and white filters in RGBW imagers; and cyan, yellow, green, and magenta filters in CYGM imagers, etc.

[0023] Figure 2B An example of the response of an interference long-pass filter is shown. Interference filter arrays used to provide a wider spectral response require additional manufacturing layers to suppress unwanted out-of-band light. Figure 2BIn response to the example of the long pass response of wavelengths longer than about 700 nm, multiple harmonics and other undesirable transmission anomalies also occur below about 500 nm, all of which require additional filter layers to remove. Thus, a given interference filter for an image sensor can include thick filter layers, which when implemented in a pixelated array on a sensor, can result in undesirable cross-talk between filter elements. Further, the thick filter layers required to provide a wide spectral response for an interference filter can increase substrate stress during production, complicating the production process for high resolution imagers in small form factor pixels. For example, thick filter layers can increase stress on one side of a semiconductor wafer during production, causing "wafer bowing" that can result in tool handling problems and other issues.

[0024] Figure 3A An example of a passband response for each red, green, and blue (RGB) absorption filter is provided. A typical implementation of an RGB filter is to repeat an array of three or four filters across a grid or array of photosensor elements or pixels. When four filters are used in the array, a green filter is typically repeated, resulting in an RGGB filter array. Figure 3B A top view of a repeating RGGB filter array is provided, where filter 22A is a green filter, and filters 22B and 22C are red and blue filters, respectively.

[0025] Figure 4A The characteristic passband responses 72 and 74 of a selected short pass interference filter and a long pass interference filter are provided overlaid on a selected absorption filter response 76. In this example, the first interference filter is configured to allow wavelengths 72 to pass when the desired wavelengths are lower than the peak absorption of the selected absorption filter response 76. The second interference filter is configured to allow wavelengths 74 to pass when the desired wavelengths are higher than the peak absorption of the selected absorption filter response 76. In one example, the combination of the first and second interference filters with the matching absorption filter results in two transmission peaks for the absorption filter, one slightly lower and one slightly higher than the transmission peak of the absorption filter.

[0026] In one example, the matching absorption filter can absorb the out-of-band wavelengths of the first and second interference filters, so that the out-of-band wavelengths are not reflected back to create ghost images. Further, the filter stack complexity of the first and second interference filters can be reduced since there is no need for additional filter layers to compensate for undesirable transmission wavelengths. In one example, Figure 4A The reduction in filter layers reduces filter stack thickness and complexity, which in turn reduces filter cost and reduces optical cross-talk.

[0027] Figure 4BThe combined passband responses of selected short and long pass interference filters and matching RGB absorption filters are shown. In one example, according to the explanation referenced in Figure 4A , two transmission peaks are present when each red-green-blue (RGB) absorption filter is used in combination with two matching interference filters, as shown. In one example, the two transmission peaks can result in three additional color channels per filter mosaic, for a total of six color channels b'λ, bλ (blue), g'λ, gλ (green), r'λ, and rλ (red). In other examples, different filter configurations can be employed to add additional channels to the RGB filter and other filter configurations, including but not limited to cyan, magenta, and yellow (CMY) filters, red, green, blue, and white (RGBW) filters, and cyan, yellow, green, and magenta (CYGM) filters, among others.

[0028] Figure 5 A top view of a 6-channel color filter array example is provided. In this example, each red-green-blue filter of a typical RGGB filter array includes an additional filter response. In the example shown, the filter array includes filters b'λ, bλ (blue), g'λ, gλ (green), r'λ, and rλ (red). Other examples (not shown) include absorption filters that are matched to interference filters, which can provide additional channels for ultraviolet (UV), visible (VIS), near-infrared (NIR), and infrared (IR) wavelengths. In one example, absorption filters (such as organic filters) can be matched to selected interference filters to provide additional channels for the UV, VIS, NIR, and IR bands. In another example, the interference filters can be Fabry-Perot filters and / or plasma interference filters. In another example, Figure 4B and Figure 5 , the absorption filters and / or interference filters can include one or more short pass filters, long pass filters, band pass filters, or band stop filters.

[0029] In one particular implementation and operational example, the output of an image sensor (such as image sensor 10 in Figure 2A ) can be processed to de-mosaic an image produced when a particular filter array (such as the 6-channel filter array example described in Figure 5 ) is applied. In one example, a de-mosaic process can be employed to extract spectral bandpass responses from a set of filters. The de-mosaic process can be accomplished using one or more processors that use an algorithm or digital image process to reconstruct the bandpass response of an optical sensor associated with an individual filter in a set of filters. In one example, if two sets of optical sensors are interspersed, a de-mosaic process can be used to retrieve spectral information from a subset of interspersed sets or arrays of filters.

[0030] In one particular related example, an optimized color filter configuration can be employed to improve the demosaicing algorithm. In one particular example, a multi-channel filter array can be configured appropriately so that each channel is as isolated as possible from the nearest wavelength channel, thereby avoiding interference from adjacent filters from propagating to other channels in the filter array.

[0031] In another example, all or a portion of the output of an image sensor example, such as image sensor 10 in FIG. 1, can be processed to perform spectral correction and / or provide white balance correction to the image and / or discrete portions of the image produced by the image sensor. In another example, an optimized color filter configuration can be employed to enhance the spectral correction of a white balance specific algorithm. Figure 2A

[0032] A side view of an image sensor, such as image sensor 10 in FIG. 1, is provided in which the absorption filters 64A, 64B, 66A, 66B, 68A, and 68B cover the interference filters 42A-42F. In one example, each absorption filter 64A, 64B, 66A, 66B, 68A, and 68B matches one of the interference filters in a filter pair. In this example, the absorption filters 64A and 64B are configured to allow the same wavelength to pass as the center wavelength of a red absorption filter in a typical red-green-green-blue (RGGB) filter array. In one example, each absorption filter 64A, 64B, 66A, 66B, 68A, and 68B matches a different interference filter, combining the filter responses of the filter pair to produce two color channels that can be sensed by the sensor 62. In one example, although illustrated as separate filters, the absorption filters 64A and 64B can be made into one filter. In another example, an interference filter can be added underneath the two different absorption filters 64A and 64B to allow different portions of the interference band to pass. Figure 6 Figure 2A A side view of an image sensor is provided in which the absorption filters and interference filters are covered by micro-lenses, in which the arrangement of FIGS. 4-6 is employed. In one example, the micro-lenses 90 can be positioned over one or more of the absorption filters 64A, 64B, 66A, 66B, 68A, and 68B, as well as the interference filter pairs containing the interference 42A-42F. In another example (not shown), a light baffle or shade is used in place of the micro-lenses 90.

[0033] Figure 7 Figure 7 ​​In other examples, a micro-lens 90 in FIG. 4-7, or an additional light barrier or shade, can be added to prevent stray light from affecting sensor performance. The light barrier or shade example is composed of one or more metals, a pseudo-metal, an opaque deposited material, and / or any other light absorbing material. In other examples, light pipes and / or deep trench isolation (DTI) techniques can be employed to direct light and prevent crosstalk light from degrading system performance. In another example, the absorbing and interference filters in FIGS. 4-7 can be implemented in a backside illuminated sensor (BSI or BI). A BSI-based imager can use an image sensor arrangement on the backside of an integrated circuit. In another example, planarization layers (such as organic spin-on materials), oxide deposition layers, and other planarization layers can be employed to compensate for non-planarity of the filter layers.

[0034] In one implementation and operational example, an imaging device includes a plurality of optical sensors disposed on an integrated circuit, and a plurality of sets of interference filters disposed on top of the optical sensors. In one example, the plurality of sets of interference filters are separated from the plurality of optical sensors by an etch stop layer. In an alternative example, the plurality of sets of interference filters are separated from the plurality of optical sensors by an air gap or substantially transparent material. In one example, the material includes one or more organic materials. In another example, the material can be optimized to limit reflections, and / or can include an alloy gradient or layer stack. In one example, a set of interference filters of the plurality of sets of interference filters includes a plurality of interference filters that form an array, where each interference filter is configured to allow light of a different wavelength range to pass. In one particular example, each interference filter is one or more short-pass, long-pass, band-pass, or band-stop filter, each configured to allow light of at least one of an ultraviolet spectral range, a visible spectral range, a near-infrared spectral range, and an infrared spectral range to pass. In another particular example, one or more of the plurality of sets of interference filters includes a Fabry-Perot filter. In another particular example, one or more of the plurality of sets of interference filters includes a plasma interference filter. In another particular example, at least some of the plurality of sets of absorbing filters are configured to allow infrared light to pass, or are configured to block infrared light. Filter examples include IR band-pass and IR cut-off filters, respectively. In another particular example, an interference filter or set of interference filters can only be disposed at certain locations of the image sensor array, some pixels are associated with one or more absorbing filters, and have no underlying interference filter.

[0035] In one example, a plurality of sets of absorption filters are disposed on top of a plurality of sets of interference filters, each absorption filter being one or more of a short pass filter, a long pass filter, a band pass filter, or a band stop filter, each interference filter being configured to allow light in at least one of an ultraviolet spectral range, a visible spectral range, a near infrared spectral range, and an infrared spectral range to pass. The absorption filters can include organic filters and / or plasma filters. In one example, the plurality of sets of absorption filters are separated from the plurality of sets of interference filters by an etch stop layer. In an alternative example, the plurality of sets of absorption filters are also separated from the plurality of sets of interference filters by an air gap or a substantially transparent material. In one example, the transparent material can also be optimized to limit reflection, and / or can include an alloy gradient and / or a layer stack.

[0036] In one particular example, a set of absorption filters of the plurality of sets of absorption filters includes absorption filters arranged in an array, wherein each absorption filter of the set of absorption filters is associated with one or more interference filters to form an absorption filter and interference filter pair. In one particular example, the interference filter of at least one absorption filter and interference filter pair includes a plurality of interference filters. In one example, the response of each absorption filter and interference filter pair is configured to allow light in a narrower wavelength range than the individual absorption filter to pass. In another example, each absorption filter and interference filter pair can be optically aligned with at least one optical sensor of a plurality of optical sensors. In one example, a microlens assembly can include absorption filter and interference filter pairs, each absorption filter and interference filter can be disposed distally from respective optical sensors in an image sensor plane such that light passing through a particular chief ray associated microlens substantially passes through the associated absorption filter and interference filter, respectively. In one example, the microlens 90 can reduce cross talk when matched with the absorption filter and interference filter pair.

[0037] In another example, the imaging device includes a plurality of microlenses disposed on top of a plurality of sets of absorption filters, each microlens being associated with at least one absorption filter. In another example, one or more of a light blocking, light pipe, and / or deep trench isolation techniques are employed to reduce the effect of stray light on light in one or more absorption and interference pairs.

[0038] In one implementation and operational example, in addition to improving color accuracy, the image sensor and image sensor system described herein with reference to Figure 4A 、 Figure 4B 、 Figure 5 and Figure 6The additional color channels of the illustration can also be used to improve white balance. In one particular related example, a first image sensor with increased spectral resolution is configured to operate simultaneously in an imaging system with a second image sensor configured to image the same scene. In this example, the first image sensor provides increased color accuracy information to correct the image of the second image sensor. In one related example, the second image sensor can increase spatial resolution compared to the first image sensor while reducing spectral information.

[0039] In one related implementation and operation example, an image sensor is configured to include some absorption filters that are not paired with an interference filter, and other absorption filters that are paired with an interference filter. In one particular example, a green absorption filter G of the image sensor is not configured with an underlying paired interference filter, while another absorption filter Ga is configured with an underlying paired interference filter. In this example, the missing spectral filter response can be calculated as Gb = G - Ga. An image sensor that implements paired and unpaired interference filters (such as the filters shown in Figure 4A 、 Figure 4B 、 Figure 5 and Figure 6 The image sensor that implements paired and unpaired interference filters can provide good performance in low light conditions, with the filter G in the relationship Gb = G - Ga providing a wider optical bandwidth and thus being more sensitive in low light conditions that include one or more additional color channels. In a particular implementation and operation related example, filters without an underlying absorption filter are configured for use in low light conditions. In another particular related example, interference filters that are sparsely distributed across the sensor array can be used to increase color accuracy while limiting the overall impact of the additional color channels on light sensitivity. In one related implementation and operation example, an image sensor is configured to include some interference filters that are not paired with an absorption filter, and other interference filters that are paired with an absorption filter.

[0040] In another implementation and operational example, one or more of the cavity layers in any of the interference filters 42A-42F can be composed of a material or composite that absorbs at least some unwanted wavelengths while allowing desired wavelengths to pass. In one example, the material can include a porous optical material with a refractive index close to 1.0 (low n material) and / or a high refractive index optical material. In one example, the cavity material can be a semiconductor with a refractive index of 2.5-3.5, which has a different optical propagation than a cavity containing air (n=l.0). In one particular example, the cavity can include an amorphous or semi-crystalline direct bandgap III-V material, where the absorption characteristics of the cavity material can be changed by varying the III-V material alloy ratio or by replacing a different alloy. In one example, the cavity material can absorb photons with energy above the bandgap and allow photons with lower energy to pass.

[0041] Figure 8 The characteristic passband response of a multi-band interference filter overlaid on each absorbing filter of an RGB filter configuration is shown. In one implementation and operational example, the interference filter is configured as a multi-band filter that, when combined with an absorbing filter, can select one spectral band of the multi-band filter to define a small portion of the absorbing filter. In one example, fewer interference filters are needed in the production of an 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 wavelength of each red-green-blue absorbing filter response. In one implementation example, a second interference filter is configured to provide a wavelength response 140B in a narrow band above the peak absorption wavelength of each absorbing filter associated with response peaks 164A (blue), 164B (green), and 164C (red). In one example, the combination of the first multi-band interference filter and the second multi-band interference filter with a matching absorbing filter results in two transmission peaks for each absorbing filter, one slightly below the transmission peak of the absorbing filter and one slightly above the transmission peak of the absorbing filter. In one implementation example, a supplemental interference filter is configured to allow wavelengths in a narrow band for each blue and green filter in a similar manner. In one related example, Figure 8 An embodiment is shown in which one or more absorbing filters can be selected for a target harmonic of a selected interference filter. In another example, only one interference filter or set of interference filters can be placed in a particular location of an image sensor array, resulting in the image sensor array including an unmodified RGB or RGGB filter structure and a modified RGB or RGGB filter structure, where the responses of the unmodified RGB or RGGB filter structure and the modified RGB or RGGB filter structure can be used to calculate a compensated RGB value.

[0042] In one example, a matching absorption filter (such as the absorption filters associated with response peaks 164A, 164B, and 164C) can absorb the out-of-band wavelengths of each of the first and second interference filters described above, and thus the out-of-band wavelengths are not reflected back to create ghost images. In one example, the filter stack complexity of the first and second interference filters can be reduced because the adverse transmission wavelengths are substantially attenuated, and thus additional filter layers are not needed to compensate for the adverse transmission wavelengths. In another example, this filter layer reduction can reduce filter stack thickness and / or complexity, which in turn can reduce filter cost and reduce cross-talk.

[0043] Figure 9 Spectral results examples of combined passband responses of feature RGB absorption filter and interference filter pairs are provided. In this example, a 6 filter array can achieve a spectral result with a doubled number of color channels. In Figure 9 In a particular example, one absorption filter and interference filter pair combination provides two color channel responses 364A and 364B associated with a blue color channel, another absorption filter and interference filter pair combination provides two color channel responses 366A and 366B associated with a green color channel, and a third absorption filter and interference filter pair combination provides two color channel responses 366A and 366B associated with a green color channel.

[0044] In an implementation example, an RGB-IR sensor can be formed using an interference infrared (IR) cut filter paired with R, G, and B absorption filters on an optical sensor array. In another example, the optical sensor is not covered by an IR cut filter and is configured to allow IR light to pass. In another example, the optical sensor is covered by an absorption IR bandpass filter (such as an IR bandpass filter), forming an IR optical sensor. In another example, the associated optical sensor is not covered by a filter and is configured to allow all wavelengths to pass, forming a substantially white optical sensor. In another example, the optical sensor is covered by an interference filter configured to allow a selected wavelength band to pass. In another example, the optical sensor is covered by an interference filter and an absorption filter. In another example, the filters are arranged in a Bayer mosaic array, forming an RGB-IR sensor. In another example, any of the examples described with reference to Figure 9 the optical sensor is covered by an absorption filter configured to allow a selected wavelength band to pass, forming an RGB-UV sensor (in addition to or in place of an RGB-IR sensor).

[0045] In one implementation and operational example, several Fabry-Perot filters can be arranged in an array on an image sensor, causing different optical sensors in the image sensor to be paired with different Fabry-Perot passband filters. In one example, the filters form a Bayer mosaic array on the sensor. In this example, the plurality of Fabry-Perot filters can belong to a predefined filter group, each filter group can be formed using a common mirror layer and alternative cavities. In one example, the cavity thickness of the Fabry-Perot filters in this group will determine the center wavelength of the Fabry-Perot filters. In one example, the mirror layer can be implemented by a reflective material and / or a Bragg stack. In another example, the cavities can be arranged in an array (e.g., by a lift-off or etching process) to replace the thickness covering different optical sensors, causing each filter group to contain Fabry-Perot filters with different cavity thicknesses, where each Fabry-Perot filter substantially matches at least one optical sensor. In one example, several optical sensors are adjusted to collect part of the incident wavelengths, depending on the specific Fabry-Perot filter on that optical sensor.

[0046] In another implementation and operational example, multiple groups of Fabry-Perot filters can be produced, each filter group containing at least one Fabry-Perot filter with a predetermined cavity thickness. In one example, when the spectral transmission of Fabry-Perot filters outside the 500-600 nm wavelength range is useless due to Bragg mirror leakage or due to the multiple harmonics of the Fabry-Perot filters, a first filter group implements a set of four Fabry-Perot filters in the 500-600 nm range. In one example, when the spectral transmission of Fabry-Perot filters outside the 600-700 nm wavelength range is useless, a second filter group is configured to implement another set of four Fabry-Perot filters in the 600-700 nm range. In one specific example, the 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 filters will act as band-stop filters for the first group of Fabry-Perot filters. In another example, the second group of filters is paired with an absorption filter configured to attenuate wavelengths outside the 600-700 nm passband. In this example, the absorption filter or filters can act as band-stop filters for the second group of Fabry-Perot filters. In a related example, three or more groups paired with absorption filters can manage the wavelength response in the visible and infrared spectrum.

[0047] Figure 10 A side view of the image sensor 62 with the absorption filters 264A and 264B covering the interference filter groups 242A and 242B is provided. Referring to Figure 6 , Figure 10may be considered to include additional layers Figure 6 A sensor, such additional layers provide space for sensor system production. In one example, a stop layer 280 is deposited over the pixel layer of the sensor 62 to protect the pixel layer from subsequent photolithographic production processes. In one example, interference filter sets 242A and 242B are formed on the first stop layer, and a second stop layer is deposited on top of the interference filter sets 242A and 242B to protect the interference filter sets 242A and 242B from subsequent production processes. In one example, production of interference filters can result in uneven topography due to different filter thicknesses. Accordingly, one or more planarization layers can be provided to planarize the surface prior to formation of the absorptive filters.

[0048] In one implementation and mode of operation, one or more anti-reflective coatings or layers can be included between functional elements of an image sensor. For example, the stop layer 280 can include an anti-reflective coating. In one particular example, an anti-reflective coating can be applied to the pixel layer of the image sensor 62, and in another particular example, the stop layer 280 includes an anti-reflective coating that functions as a stop layer during subsequent photolithographic steps. In another implementation and mode of operation, an anti-reflective coating or layer 282 can be located on top of the absorptive filters 264A and 264B. In one example, the anti-reflective coating can reduce light reflected from the surface of underlying structural elements, such as the pixel layer or the interference filter sets 242A and 242B.

[0049] In one related example, referring to Figure 6 and Figure 7 If necessary, an anti-reflective coating and / or material can be added to reduce light reflected from any underlying structure. For example, an anti-reflective coating can be included on one or more top surfaces of the absorptive filters, on the bottom surface of the absorptive filters, or on any of the top surfaces of the sensor pixel layer. Figure 6 , Figure 7 or Figure 10 An anti-reflective coating can be applied on top of any of the sensor pixel layers to reduce light reflected from the underlying structure.

[0050] Figure 11 A flowchart is provided to illustrate one example of a method of producing a sensor. The method begins at step 100 by depositing a first set of thin film layers on a pre-produced semiconductor wafer substrate to provide optical sensors (pixels) of an image sensor. In one implementation and mode of operation, prior to depositing the thin film layers of the first set of thin film layers, the substrate has been prepared (e.g., as described with reference to Figure 10The substrates mentioned can have or not have a passivation layer. In one example, the first set of thin film layers can start at a first stop layer and / or end at a second stop layer. The method continues at step 102 where the first set of thin film layers are removed in areas where no first filter is needed. The first set of thin films can be removed first using a photolithography process and then using a dry and / or wet etching process that will stop at the stop layer or passivation layer.

[0051] The method continues at step 104 where a second set of thin film layers are deposited on the semiconductor wafer substrate and then continues at step 106 where the second set of thin film layers are removed in areas where no second filter is needed. The second set of thin film layers can be removed first using a photolithography process and then using a dry and / or wet etching process that will stop at the stop layer provided during the production of the first set of thin film layers. At step 108, the method repeats steps 104 to 106 as needed for additional filter layers. For example, if 6 different interference filters are needed, step 108 will include repeating steps 104 to 106 (4 times).

[0052] The method continues at step 110 where a planarization layer is added. The planarization can be achieved first using an oxidation deposition step and then using chemical mechanical planarization (CMP). Other planarization options include using spin-on (e.g. spin-on glass) and then etching the topography peaks introduced during the filter production or selective etching of the topography peaks. At step 112, the method continues with the application of the absorbing color filter layers. In one example, the absorbing color filters can be applied in sequence: using a spin-on colored resist layer, then using light to cure the resist in areas where the filter is needed and finally dissolving the areas of the resist that were not cured. For example, red, green and blue (RGB) filters can be applied in 3 separate photolithography processes, each with three different filters.

[0053] It is noted that in all the embodiments described, one or more of the absorbing filters can be replaced by a plasma filter, typically implemented using an array of metal layers to define a passband.

[0054] It is noted that the terms such as bitstream, stream, signal sequence, etc. or their counterparts can be used herein in an interchangeable manner to describe data information, the content of which corresponds to the type of content, e.g. data, video, speech, text, graphics, audio, etc., any of which can be generally referred to as "data".

[0055] In this document, the terms“substantially” and“approximately” provide an industry-accepted tolerance for its respective term and / or element it describes. In some industries, a tolerance less than 1% is acceptable, in other industries, a tolerance of 10% or more is acceptable. Other examples of industry-accepted tolerance are between less than 1% and 50%. Industry-accepted tolerance corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, thermal noise, dimensions, signal errors, packet loss, temperature, pressure, material composition, and / or performance metrics. Within an industry, the difference in accepted tolerance can be greater or less than a percentage level (e.g., a dimension tolerance of less than + / - 1%). The correlation between elements can vary from less than a percentage level difference to several percentages. Other correlations between elements can vary from several percentage differences to orders of magnitude differences.

[0056] Further, in this document, the terms“configured,”“operably coupled to,”“coupled to,” and / or“coupled” include direct coupling and / or indirect coupling through intervening elements (e.g., elements including, but not limited to, components, elements, circuits, and / or modules), where, for indirect coupling, the intervening elements do not modify the signal information but can adjust its current level, voltage level, and / or power level. In this document, inferred coupling (i.e., where, according to an inference, an element is coupled to another element) includes direct and indirect coupling between two elements in the same manner as“coupled to.”

[0057] In this document, the terms“configured,”“operable,”“coupled to,” or“operably coupled to” mean that a component includes one or more power connections, inputs, outputs, and when activated, can perform one or more corresponding functions, and further that an inferred coupling to one or more other components. In this document, the term“related to” includes direct and / or indirect coupling independent components and / or embedding one component in another component.

[0058] In this document, the term“favorable comparison” indicates that a comparison between two or more components, signals, etc. provides a desired relationship. For example, if the desired relationship is that the magnitude of signal 1 is greater than signal 2, a favorable comparison can be achieved when the magnitude of signal 1 is greater than signal 2 or the magnitude of signal 2 is less than signal 1. In this document, the term“unfavorable comparison” indicates that a comparison between two or more components, signals, etc. fails to provide a desired relationship.

[0059] In this document, one or more claims may include the phrase "at least one of a, b, and c" (a specific form of this general form) or "at least one of a, b, or c" (this general form), wherein the elements may be more or less than "a," "b," and "c." In either wording, the phrase should 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 should refer to a, b, and / or c. For example, it should refer to: only "a," only "b," only "c," "a" and "b," "a" and "c," "b" and "c," and / or "a," "b," and "c."

[0060] Furthermore, in this document, the terms "processing module," "processing circuit," "processor," and / or "processing unit" may refer to one or more processing devices. Such processing devices may include microphones, microcontrollers, digital signal processors, microcomputers, central processing units, field-programmable gate arrays, programmable logic devices, state machines, logic circuits, analog circuits, digital circuits, and / or any device that manipulates signals (analog and / or digital) according to circuit hard-coded and / or operational instructions. The processing module, module, processing circuit, and / or processing unit may be or further include memory and / or integrated storage elements, which may be one storage device, multiple storage devices, and / or embedded circuitry of another processing module, module, processing circuit, and / or processing unit. Such storage devices may include read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and / or any device storing digital information. Please note that if the processing module, module, processing circuit, and / or processing unit comprises more than one processing device, the processing device may be centrally located (e.g., directly coupled together via a wired and / or wireless bus structure) or may be distributed (e.g., cloud computing indirectly coupled via a local area network and / or wide area network). It should be further noted that if the processing module, module, processing circuit, and / or processing unit implements one or more of its functions through state machines, analog circuits, digital circuits, and / or logic circuits, the memory and / or storage element storing the corresponding operation instructions may be embedded within or outside the circuitry composed of state machines, analog circuits, digital circuits, and / or logic circuits. It should also be noted that the storage element may store, and the processing module, module, processing circuit, and / or processing unit may execute hard-coded and / or operation instructions corresponding at least to some of the steps and / or functions shown in one or more figures. Such a storage device or storage element may be included in a single product.

[0061] The above detailed description has discussed one or more embodiments in terms of the performance of particular functions and relationships between those functions. For ease of discussion, the boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined. Alternative boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are therefore within the scope and spirit of the claims. In addition, the boundaries of these functional building blocks have been arbitrarily defined, for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships of the alternatives are appropriately performed. Similarly, flow diagram blocks can be arbitrarily arranged, as long as the specified functionality of the blocks is appropriately performed.

[0062] Other ways of defining the flow diagram block boundaries and sequence can also be used, to the extent that the specified functions and relationships are appropriately performed. Accordingly, such alternative definitions of the functional building blocks and flow diagram blocks are within the scope and spirit of the claims. One of ordinary skill in the art will further appreciate that the functional building blocks and other illustrative blocks, modules and components herein can be implemented as illustrated, by discrete components, by an application specific integrated circuit, by a processor executing appropriate software, and / or the like, or any combination(s) thereof.

[0063] In addition, flow diagrams can include a "start" and / or "continue" indication. The "start" and "continue" indications indicate where, in the specified flows, the specified steps can be initiated, in accordance with any of the embodiments. Also, flow diagrams can include a "end" and / or "continue" indication. The "end" and / or "continue" indications indicate where, in the specified flows, the steps can be ended, and / or where the steps can be joined by one or more flows, in accordance with any of the embodiments. In this case, "end" can indicate the end of one specific flow, portion of a flow and / or sub-flow, and "continue" can indicate where the flow can continue with another of the steps, and / or with another flow, in accordance with any of the embodiments. Additionally, while a flow diagram indicates a particular order of steps, alternative embodiments can perform the steps in any order, unless otherwise specifically limited by certain embodiments. Finally, these flow diagrams illustrate a flow of steps for processes performed affirmatively by parties. Other flow diagrams illustrate a flow of steps for processes performed affirmatively and / or negatively by parties.

[0064] In this document, the terms "embodiment" or "embodiments" are used to describe one or more aspects, features, concepts and / or examples. The one or more embodiments can be implemented in hardware, software and / or firmware, and can be used with one or more devices, systems and / or processes. The terms "first," "second," "third," etc. can be used herein to describe various elements, components, regions, steps and / or the like. However, such elements, components, regions, steps and / or the like should not be limited by these terms. Such terms are only used to distinguish one element, component, region, step and / or the like from another element, component, region, step and / or the like. Terms such as "first," "second," "third," etc. are not necessarily used herein to describe separate, independent and / or distinct elements, components, regions, steps and / or the like. Rather, such terms can be used herein interchangeably, to describe a particular element, component, region, step and / or the like.

[0065] Unless specifically stated otherwise, in any of the drawings herein, signals and / or connections between elements and / or components can be analog or digital, continuous-time or discrete-time, and single-ended or differential. For example, if a signal path is shown as a single-ended path, it also represents a differential signal path. Likewise, if a signal path is shown as a differential path, it also represents a single-ended signal path. Although one or more specific architectures are described herein, other architectures can also be implemented. For example, one or more data buses can be used instead of a single data bus, direct connections between elements can be used instead of indirect connections, and other elements can be used instead of those shown, which do not affect the intended functionality of the described architecture. Those skilled in the art will recognize how to implement such alternative architectures given the benefit of this disclosure.

[0066] The term "module" is used in one or more implementation examples described herein. A module implements one or more functions through a device such as a processor or other processing device, possibly including a memory storing operational instructions or other hardware operating in conjunction with the same. A module can operate independently and / or in conjunction with software and / or firmware. In this context, a module can include one or more sub-modules, each of which can be one or more modules.

[0067] Further, in this context, a computer-readable memory includes one or more storage elements. A storage element can be a standalone storage device, multiple storage devices, or a set of storage locations within a storage device. Such storage devices include 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 devices include solid-state memory, hard disk memory, cloud memory, thumb drives, server memory, computing device memory, and / or other physical media used to store digital information.

[0068] Although specific combinations of functions and features of one or more embodiments are described herein, other combinations of such functions and features can be used. The present invention is not limited to the specific examples disclosed herein and expressly includes such other combinations.

Claims

1. An imaging device comprising: a plurality of optical sensors disposed on an integrated circuit; a plurality of sets of interference filters, wherein a set of interference filters includes a plurality of interference filters arranged in an array, wherein each interference filter is configured to allow light of a different wavelength range to pass; and a plurality of sets of absorption filters, wherein a set of absorption filters includes a plurality of absorption filters arranged in an array, wherein each absorption filter is associated with two or more interference filters to form an absorption filter and interference filter pair, wherein each absorption filter and interference filter pair is configured to allow light of a narrower wavelength range than the absorption filter alone to pass, wherein each absorption filter and interference filter pair is associated with one or more of the plurality of optical sensors.

2. The imaging apparatus of claim 1, wherein, the plurality of sets of interference filters are separated from the plurality of optical sensors by an etch stop layer.

3. The imaging apparatus of claim 1, wherein, the plurality of sets of interference filters are further separated from the plurality of optical sensors by an air gap or a transparent material.

4. The imaging apparatus of claim 3, wherein, the transparent material includes one or more organic materials.

5. The imaging apparatus of claim 3, wherein, the transparent material is optimized to limit reflection, and / or includes an alloy gradient or a layer stack.

6. The imaging apparatus of claim 1, wherein, each interference filter is selected from a set of filters including a short pass filter, a long pass filter, a band pass filter, or a band stop filter, wherein each interference filter is configured to allow light of at least one of an ultraviolet spectral range, a visible spectral range, a near infrared spectral range, and an infrared spectral range to pass.

7. The imaging apparatus of claim 1, wherein, one or more of the plurality of sets of interference filters includes a Fabry-Perot filter.

8. The imaging apparatus of claim 1, wherein, at least some of the plurality of sets of absorption filters are configured to block light of an infrared wavelength range.

9. The imaging apparatus of claim 1, wherein, at least some of the plurality of sets of absorption filters include at least one organic filter or a plasma filter.

10. The imaging apparatus of claim 1, wherein, the plurality of sets of absorption filters are separated from the plurality of interference filters by an etch stop layer.

11. The imaging apparatus of claim 1, wherein, the absorption filters are further separated from the plurality of interference filters by an air gap or a transparent material.

12. The imaging apparatus of claim 1, wherein, a first interference filter of a set of interference filters and a second interference filter of a set of interference filters are associated with an absorption filter of a set of absorption filters, wherein the first and second interference filters are configured to provide a response when combined with the absorption filter that includes a first transmission peak and a second transmission peak, respectively, wherein the first transmission peak is at a lower wavelength than a peak response of the absorption filter and the second transmission peak is at a higher wavelength than the peak response of the absorption filter.

13. The imaging device of claim 1, further comprising: a plurality of microlenses disposed on top of a set of absorption filters of the plurality of sets of absorption filters, wherein each microlens is associated with at least one absorption filter.

14. The imaging apparatus of claim 1, wherein, the plurality of optical sensors are arranged in an array of optical sensors, wherein a plurality of interference filters of the plurality of sets of interference filters are associated with not all of the plurality of optical sensors of the array of optical sensors.

15. The imaging device of claim 1, further comprising: a plurality of light blocking pieces, wherein the plurality of light blocking pieces are adapted to attenuate light reflected between one or more adjacent pairs of absorbing and interference filters.

16. The imaging apparatus of claim 1, wherein, each of the plurality of sets of interference filters includes a top surface and a bottom surface, wherein one or more of the plurality of interference filters includes a cavity between the top surface and the bottom surface, wherein the cavity contains at least one amorphous or semi-crystalline material.

17. The imaging apparatus of claim 1, wherein, each of the plurality of sets of interference filters includes a top surface and a bottom surface, wherein one or more of the plurality of interference filters includes a cavity between the top surface and the bottom surface, wherein the cavity includes one or more materials adapted to at least absorb some unwanted wavelengths while at least allowing some desired wavelengths to pass through.

18. The imaging apparatus of claim 1, wherein, at least some of the plurality of sets of interference filters are configured to allow a plurality of wavelength bands of light to pass through.

19. A method of producing an imaging device according to any one of claims 1-18, comprising the steps of: depositing a first set of thin film layers on a semiconductor substrate, wherein the semiconductor substrate includes a plurality of arrays of optical sensors, wherein the first set of thin film layers includes a first mirror layer, a cavity layer, and a second mirror layer; removing the first set of thin film layers from a plurality of predetermined regions of a semiconductor wafer substrate; depositing a second set of thin film layers on the semiconductor wafer substrate, wherein the second set of thin film layers includes a cavity layer and a second mirror layer; removing the second set of thin film layers from the plurality of predetermined regions of the semiconductor wafer substrate; applying a first absorbing filter layer; applying a second absorbing filter layer; and applying a third absorbing filter layer.

20. The method of claim 19, further comprising the steps of: depositing a third set of thin film layers on the semiconductor wafer substrate, wherein the third set of thin film layers includes a cavity layer and a second mirror layer; and removing the third set of thin film layers from the plurality of predetermined regions of the semiconductor wafer substrate.

Images