Quantum-efficiency enhanced optical detector pixel having one or more optical scattering structures

Various optical detector pixel embodiments are described. One optical detector pixel includes a photodiode having a first end opposite a second end, a set of lateral walls joining the first end and the second end, and a depth parallel to the set of lateral walls. A lens is positioned to direct light toward the first end of the photodiode. A set of one or more optical scattering structures laterally extends at least partially into an illumination area defined by the lens and has a set of sidewalls extending away from the first end. The set of sidewalls includes a pair of sidewalls forming an included angle. The included angle extends perpendicular to the depth of the photodiode. The pair of sidewalls abut a portion of the photodiode.

FIELD

The described embodiments generally relate to optical detectors. More particularly, the described embodiments relate to optical detector pixels having one or more optical scattering structures that enhance their quantum efficiency (QE).

BACKGROUND

Sensors are included in many of today's electronic devices, including electronic devices such as smartphones, computers (e.g., tablet computers or laptop computers), wearable electronic devices (e.g., electronic watches, smart watches, or health monitors), game controllers, navigation systems (e.g., vehicle navigation systems or robot navigation systems), and so on. Sensors may variously sense the presence of objects, distances to objects, proximities of objects, movements of objects (e.g., whether objects are moving, or the speed, acceleration, or direction of movement of objects), compositions of objects, and so on. A sensor (e.g., an image sensor or a camera) may also or alternatively acquire an image of an object. One useful type of sensor is the optical detector.

SUMMARY

Embodiments of the systems, devices, methods, and apparatus described in the present disclosure pertain to optical detectors having one or more optical detector pixels (“detector pixels”) and, more particularly, to optical detectors having optical scattering structures that help to scatter received light within a photodiode of an optical detector pixel, so that the light is more fully absorbed by the photodiode, thereby increasing the quantum efficiency (QE) of both the photodiode and the optical detector pixel. Embodiments of the systems, devices, methods, and apparatus described in the present disclosure also pertain to optical scattering structures that are constructed and positioned to scatter light away from one or more semiconductor structures (e.g., memory nodes) that might be adversely impacted by scattered light.

In a first aspect, a pixel of an optical detector is described. The pixel may include a photodiode having a first end opposite a second end, a set of lateral walls joining the first end and the second end, and a depth parallel to the set of lateral walls. A lens may be positioned to direct light toward the first end of the photodiode. A set of one or more optical scattering structures may laterally extend at least partially into an illumination area defined by the lens, and may have a set of sidewalls extending away from the first end. The set of sidewalls may include a pair of sidewalls forming an included angle. The included angle may abut a portion of the photodiode.

In a second aspect, another pixel of an optical detector is a described. The pixel may include a first region including a photodiode, a second region including a memory node, an oxide wall positioned at least partly between the first region and the second region, and a set of one or more optical scattering structures positioned at least partially within the photodiode and defining a set of edges. The set of edges may include one or more of a curved edge, or a first edge oriented at an oblique angle with respect to a second edge.

In a third aspect, another pixel of an optical detector is described. The pixel may include a photodiode and an optical scattering structure positioned on or in the photodiode. The optical scattering structure may have a set of sidewalls. The set of sidewalls may include a first sidewall and a second sidewall. The first sidewall and the second sidewall may be adjoining sidewalls, and the first sidewall and the second sidewall may be non-orthogonal and define an included angle. The first sidewall and the second sidewall may abut a portion of the photodiode.

DETAILED DESCRIPTION

The systems, devices, methods, and apparatus described in the present disclosure pertain to both single-pixel optical detectors, as might be used for ambient light sensing (ALS), wireless communication, proximity sensing, and so on, and multiple-pixel optical detectors, as might be used in a camera and/or image sensor (e.g., a complementary metal-oxide semiconductor (CMOS) image sensor), fingerprint sensor, depth sensor, and so on. To improve the QE of such an optical detector, an optical scattering structure may be disposed in a trench formed in a first end (e.g., in a light-receiving end) of a photodiode of the optical detector. Alternatively, the optical scattering structure may be embedded under a light-receiving surface of the first end of the photodiode. In some cases, more than one optical scattering structure may be provided, in different trenches in the light-receiving end of the photodiode and/or at the same or different depths under the light-receiving surface of the photodiode.

At times, an optical scattering structure can scatter light in undesirable directions, such as toward a memory node, transistor, or other structure of an optical detector pixel. This can result in increased optical crosstalk, increased parasitic light sensitivity (PLS), decreased modulation transfer function (MTF), and so on, and can in some cases degrade the performance (or even change the output) of an optical detector pixel. For example, undesirable scatter of light may result in a global shutter image sensor pixel (e.g., a pixel of a camera) or time-of-flight image sensor pixel producing an incorrect output. To reduce the scattering of light in undesirable directions, the optical detector pixels described herein include optical scattering structures having sidewalls, edges, and positions that can mitigate the scattering of light in undesirable directions and sometimes increase the scattering of light in desirable directions.

Directional terminology, such as “top”, “bottom”, “upper”, “lower”, “front”, “back”, “over”, “under”, “above”, “below”. “left”, “right”, etc. is used with reference to the orientation of some of the components in some of the figures described below. Because components in various embodiments can be positioned in a number of different orientations, directional terminology is used for purposes of defining relative positions of various structures, and may not always define absolute positions. For example, a first structure described as being “above” a second structure and “below” a third structure is also “between” the second and third structures, and would be “above” the third structure and “below” the second structure if the stack of structures were to be flipped. Also, as used herein, the phrase “at least one of” preceding a series of items, with the term “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list. The phrase “at least one of” does not require selection of at least one of each item listed; rather, the phrase allows a meaning that includes one or more of any of the items, or one or more of any combination of the items, or one or more of each of the items. By way of example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to one or more of only A, only B, or only C; any combination of A, B, or C; and one or more of each of A, B, and C. Similarly, it may be appreciated that an order of elements presented for a conjunctive or disjunctive list provided herein should not be construed as limiting the disclosure to only that order provided.

As used herein, a “layer” refers to one or more materials that are typically, but not necessarily, parallel to the top surface and/or bottom surface of a substrate or another layer.

FIG.1shows an isometric view of an example single-pixel optical detector100. By way of example, the optical detector100may be configured as an ALS, a wireless signal receiver, a proximity sensor, a display pixel health or calibration sensor, a reflected light sensor (e.g., a sensor that detects light emitted by a device and reflected off of one or more of a component of a device, a user of a device, or an object around which the device or a user of the device wants to navigate), and so on.

The optical detector100may include a photodiode102. In some cases, the photodiode102may be formed on or in a substrate104(e.g., a semiconductor substrate, such as a silicon (Si) or gallium arsenide (GaAs) substrate). The photodiode102may be formed by means of epitaxial growth of one or more layers on the substrate104, diffusion of ions into the substrate104, implantation of ions into the substrate104(i.e., ion implantation), and so on. One or more other semiconductor structures (e.g., transistors, memory nodes, and so on) and/or layers of electrical interconnect (e.g., one or more patterned metal layers) may also be formed on or in the substrate104. The other semiconductor structure(s) or layers of electrical interconnect may be used to bias the photodiode102, clear (reset) a charge on the photodiode102, read a charge from the photodiode102, and so on.

A lens106may be positioned to direct light toward a first end (or light-receiving end, or light-receiving surface) of the photodiode102. The light-receiving end of the photodiode102may have a light-receiving surface that is generally parallel to a top or bottom surface of the substrate104. In some embodiments, and as shown, the lens106may be formed in a dielectric material and attached to the optical detector100(e.g., in a frontside illumination (FSI) configuration of the optical detector100). In other embodiments, the lens106may be formed (e.g., etched) into the substrate104(e.g., in a backside illumination (BSI) configuration of the optical detector100), and the photodiode102may receive light through the substrate104.

Optionally, an anti-reflective material108may be deposited or grown on the light-receiving end of the photodiode102, between the photodiode102and the lens106.

A controller110may be directly or indirectly connected to the optical detector100, and may provide signals (or instructions) for operating the optical detector100. The signals (or instructions) may cause the optical detector100to be reset, enabled during a light integration period or light detection period, read, and so on.

FIG.2shows an isometric view of an example multiple-pixel optical detector200. The optical detector200may include a set or an array of pixels202. By way of example, the array of pixels202are shown to be arranged in m columns and n rows (i.e., in an m×n array of pixels202, where m and n are the same or different integers). However, the array of pixels202may alternatively be arranged in a single column or row, in concentric circles or other patterns, or in other ways.

Similarly to the optical detector described with reference toFIG.1, the optical detector200may be configured as an ambient light sensor, a wireless signal receiver, a proximity sensor, a display pixel health or calibration sensor, a reflected light sensor (e.g., a sensor that detects light emitted by a device and reflected off of one or more of a component of a device, a user of a device, or an object around which the device or a user of the device wants to navigate), and so on. The optical detector200may also be used as a camera, image sensor, fingerprint sensor, depth sensor, and so on. Each pixel202of the optical detector200may be configured the same as, or similarly to, the single-pixel optical detector described with reference toFIG.1, and may include a photodiode204, a substrate206, a lens208, and/or an anti-reflective material210.

A controller212may be directly or indirectly connected to the optical detector200, and may provide signals (or instructions) for operating the optical detector200. The signals (or instructions) may cause the array of pixels202of the optical detector200to be reset, enabled during a light integration period or light detection period, read, and so on. In some cases, the pixels202may be operated individually. In other cases, the pixels202may be operated collectively or in different subsets.

FIGS.3A and3Bshow a first example pixel300including a set of one or more optical scattering structures308.FIG.3Ashows an elevation of the pixel300(from view III-B—III-B inFIG.3B), andFIG.3Bshows a top-down plan view of the pixel300(from view III-A-III-A inFIG.3A). The pixel300may be used as, or in, an optical detector. In some embodiments, the pixel300may take the form of the single-pixel optical detector described with reference toFIG.1, or one of the pixels in the multiple-pixel optical detector described with reference toFIG.2.

The pixel300may include a first region302and a second region304. By way of example, the second region304is shown to surround the first region302. In alternative embodiments, the second region304may be adjacent the first region302(e.g., to the side, under, and/or over the first region302).

The first region302may include a photodiode306and/or one or more other structures (e.g., one or more optical scattering structures308, transistors, and so on). In some cases, the first region302may only include the photodiode306and one or more optical scattering structures308. The second region304may include one or more semiconductor structures, such as one or more semiconductor structures310, and/or one or more other structures. Each semiconductor structure310may be or include a memory node, a transistor, or another type of structure. In some embodiments, the second region304may include multiple (i.e., two or more) semiconductor structures310.

The photodiode306may have a first end336opposite a second end338. The first end336may include a light-receiving surface314, or a surface on which at least some light initially impinges after passing through a lens312. The first end336may also have one or more optical scattering structures308embedded therein or positioned thereon (or in some cases embedded close under the light-receiving surface314). The photodiode306may also include a set of one or more lateral walls340that join the first end336and the second end338. In some cases, the set of one or more lateral walls340may include a single wall having a circular lateral cross-section, or a square or rectangular lateral cross-section with arcuate turns at the corners of the square or rectangular lateral cross-section. In other cases, the set of one or more lateral walls340may include multiple walls that meet at ninety degree corners. The set of one or more lateral walls340may also take other forms. The photodiode306may have a depth, D, parallel to the set of lateral walls340, and perpendicular to the lateral cross-section shown inFIG.3B.

In some embodiments, a lens312(e.g., a microlens) may be positioned to direct light toward the first end336of the photodiode338(e.g., toward a light-receiving surface314of the photodiode306) and/or one or more optical scattering structures308embedded in or under the first end336or light-receiving surface314. In a BSI embodiment of the pixel300, the lens312may be formed (e.g., etched) in the backside of a substrate on (or in) which the photodiode306is formed. In an FSI embodiment of the pixel300, the lens312may be formed in a dielectric that is attached to the pixel300. The lens312may in some cases focus (or direct) received light into an illumination area316(e.g., into a beam or spot of light) on the first end336, or on the light-receiving surface314of the photodiode306, and/or on surfaces or edges of the optical scattering structure(s)308. Without the lens312, light may still be received by the first end336or light-receiving surface314of the photodiode306and/or surfaces or edges of the optical scattering structure(s)308, but without being directed into the illumination area316(e.g., without being focused into a beam or spot of light).

Optionally, an oxide wall or an oxide/metal wall318, such as a deep trench isolation (DTI) wall or a shallow trench isolation (STI) wall, may be positioned at least partly between the first region302and the second region304(e.g., positioned around at least part of a lateral periphery of the photodiode306or first region302, and/or extending at least partially around the set of lateral walls340of the photodiode306). For purposes of this description, oxide/metal walls are walls that include both oxide and metal portions, such as oxide walls with embedded metal walls, metal conductors, or other metal structures. In some cases, the oxide (or oxide/metal) wall318may be positioned between the photodiode306and the semiconductor structure310. In some cases, the oxide (or oxide/metal) wall318may extend partly and laterally around (e.g., 50%, 75%, or more of the way around) the first region302and/or the photodiode306. In other cases, the oxide (or oxide/metal) wall318may laterally surround the first region302and/or the photodiode306.

The set of one or more optical scattering structures308may be positioned at least partially within the photodiode306(e.g., the optical scattering structure(s)308may extend at least partially below a portion of the light-receiving surface314of the photodiode306). The optical scattering structure(s)308may laterally extend at least partially into the illumination arca316defined by the lens312. By way of example, only one optical scattering structure308is shown. In alternative embodiments, there may be more than one optical scattering structure308, positioned in the same or different planes (or between different starting and ending depths from the light-receiving surface314of the photodiode306).

In some embodiments, a set of one or more trenches320may be formed in the light-receiving surface314of the photodiode306, and may extend into the photodiode306. The set of one or more optical scattering structures308may be disposed in the set of trenches320. As shown, a light-receiving surface322of an optical scattering structure308may be flush with the light-receiving surface314of the photodiode306. Alternatively, the optical scattering structure308may be fully embedded within the photodiode306(e.g., under the light-receiving surface314of the photodiode306), or the optical scattering structure308may project above the light-receiving surface314of the photodiode306.

Each optical scattering structure308may have a light-receiving surface322, a set of sidewalls324, and a set of edges326. The sidewalls324may extend away from the light-receiving surface322of the optical scattering structure308, and away from the first end336(or light-receiving surface314) of the photodiode306. For example, the sidewall(s)324of the optical scattering structure308may extend perpendicularly to the first end336, the light-receiving surface314, and the light-receiving surface322. Each edge326may 1) define a transition between a surface (e.g., the surface322) and a sidewall324of the optical scattering structure308, or 2) define an inside or outside corner between two sidewalls324of the optical scattering structure308. Light that impinges on the edges326or sidewalls324of an optical scattering structure308may be redirected (or scatter) within the photodiode306differently than light that impinges on the light-receiving surface314of the photodiode306(the latter of which may cause light to refract but not scatter). When the lens312is present, and in some cases, one or more optical scattering structures308may be positioned such that they laterally extend at least partially into the illumination area316defined by the lens312.

The sidewalls324and edges326of the optical scattering structure(s)308may in some cases be positioned and/or oriented to direct (e.g., scatter) light in desired directions. For example, it may be desirable to direct light into the photodiode306, to increase light absorption by the photodiode306, but to direct light away from the semiconductor structure310and/or the second region304, to prevent optical crosstalk and interference.

By way of example, and as shown, an optical scattering structure308may have a pair of sidewalls324(e.g., a pair of adjoining sidewalls324) that form an included angle328, with the included angle328extending perpendicular to the depth, D, of the photodiode306, and with the pair of sidewalls324abutting a portion of the photodiode306. For purposes of this description, an “included angle” is an angle formed between two structures (e.g., two surfaces, sidewalls, or edges) that intersect at an angle of one-hundred-eighty degrees (180°) or less. Although the included angle328is shown to be an obtuse angle formed by non-orthogonal sidewalls324, the included angle328could alternatively be an acute angle or a right angle.

The optical scattering structure may also have a second pair of sidewalls324that form a second included angle330. The included angle330may also extend perpendicular to the depth, D. of the photodiode306, and may abut a different portion of the photodiode306.

In the example shown, the optical scattering structure308has a lateral cross-section, parallel to the light-receiving surface314of the photodiode306and parallel to the light-receiving surface322of the optical scattering structure308(e.g., in a plane, or in all planes, that intersect the optical scattering structure308parallel to the light-receiving surface322), defined by two intersecting triangles332,334.

In alternative embodiments of the pixel300, the optical scattering structure308could take any of the forms described with reference toFIGS.4A-5E, or the set of one or more optical scattering structures308could include multiple optical scattering structures, as described with reference toFIGS.6A-7B.

FIGS.4A-4Cshow a second example pixel400including a set of one or more optical scattering structures410.FIG.4Ashows an elevation of the pixel400(from view IV-B-IV-B inFIG.4B);FIG.4Bshows a top-down plan view of the pixel400(from view IV-A-IV-A inFIG.4A); andFIG.4Cshows an enlarged top down plan view of the optical scattering structure410. The pixel400may be used as, or in, an optical detector. In some embodiments, the pixel400may take the form of the single-pixel optical detector described with reference toFIG.1, or one of the pixels in the multiple-pixel optical detector described with reference toFIG.2.

The pixel400may include a photodiode402formed on a substrate404. By way of example, the pixel400is configured as a BSI pixel, with the photodiode402receiving light through the substrate404.

The photodiode402may have a first end446opposite a second end448. The first end446may include a light-receiving surface408, or a surface on which at least some light initially impinges after passing through the lens406. The first end446may also have one or more optical scattering structures410embedded therein or positioned thereon (or in some cases embedded close under the light-receiving surface408). The photodiode402may also include a set of one or more lateral walls450that join the first end446and the second end448. In some cases, the set of one or more lateral walls450may include a single wall having a circular lateral cross-section, or a square or rectangular lateral cross-section with arcuate turns at the corners of the square or rectangular lateral cross-section. In other cases, the set of one or more lateral walls450may include multiple walls that meet at ninety degree corners. The set of one or more lateral walls450may also take other forms. The photodiode402may have a depth, D, parallel to the set of lateral walls450.

The lens406(e.g., a microlens) may be positioned to direct light toward the first end446of the photodiode402(e.g., toward a light-receiving surface408of the photodiode402) and/or one or more optical scattering structures410embedded in or under the first end446or light-receiving surface408. The lens406may be formed (e.g., etched) in the backside of the substrate404. The lens406may in some cases focus (or direct) received light into an illumination area412(e.g., into a beam or spot of light) on the first end446, or on the light-receiving surface408of the photodiode402, and/or on surfaces or edges of the optical scattering structure(s)410. Without the lens406, light may still be received by the first end446or light-receiving surface408of the photodiode402and/or surfaces or edges of the optical scattering structure(s)410, but the light may not be directed into the illumination area412on the first end446or light-receiving surface408.

One or more oxide (or oxide/metal) walls414, such as one or more deep trench isolation (DTI) walls, may be positioned laterally around part of the photodiode402. For example, a first oxide (or oxide/metal) wall414-1may form a first U-shaped wall (e.g., a squared-off U-shaped wall) around the photodiode402, and a second oxide (or oxide/metal) wall414-2may form a second and larger U-shaped wall (e.g., a squared-off U-shaped wall) around part of the photodiode402, with the bottom portions of the first and second U-shaped oxide (or oxide/metal) walls414-1,414-2disposed on opposite lateral sides of the photodiode402, and with the uprights of the U-shaped oxide (or oxide/metal) walls414-1,414-2overlapping on opposite lateral sides of the photodiode402. In some embodiments, the pixel400may include additional oxide (or oxide/metal) walls414. Each of the oxide (or oxide/metal) walls414,414-1,414-2may be continuous or discontinuous. A discontinuous oxide (or oxide/metal) wall may include gaps through which conductive traces are routed. Each of the oxide (or oxide/metal) walls414,414-1,414-2may also extend from the front to the back of the pixel400, or may have a depth that is shallower than the full depth of the pixel400. An oxide (or oxide/metal) wall414that is shallower than the full depth of the pixel400may provide areas through which conductive traces may be routed, areas in which transistors418,438,440,442,444or other semiconductor structures may be formed, and so on.

By way of example, a memory node416may be disposed between each pair of overlapping uprights of the first and second U-shaped oxide (or oxide/metal) walls414-1,414-2. That is, different memory nodes416may be positioned to the left and to the right of the photodiode402shown inFIGS.4A and4B. A pair of transistors418may be simultaneously or sequentially pulsed to transfer all or a portion of a charge integrated by the photodiode402to one or both of the memory nodes416. In some cases, a memory node416may be blocked from receiving light by a shield452placed between the lens406and the memory node416. Additionally or alternatively, the lens406may direct received light away from the memory node(s)416. In some cases, an anti-reflective (AR) coating454may be disposed between the lens/substrate406/404and photodiode/shields402/452.

A set of one or more optical scattering structures410may be positioned at least partially within the photodiode402(e.g., the optical scattering structure(s)410may extend at least partially below a portion of the light-receiving surface408of the photodiode402). The optical scattering structure(s)410may laterally extend at least partially into the illumination arca412defined by the lens406. By way of example, only one optical scattering structure410is shown. In alternative embodiments, there may be more than one optical scattering structure410, positioned in the same or different planes (or between different starting and ending depths from the light-receiving surface408of the photodiode402).

In some embodiments, a set of one or more trenches420may be formed in the light-receiving surface408of the photodiode402, and may extend into the photodiode402. The set of one or more optical scattering structures410may be disposed in the set of trenches420. As shown, a light-receiving surface422of an optical scattering structure410may be flush with the light-receiving surface408of the photodiode402. Alternatively, the optical scattering structure410may be fully embedded within the photodiode402(e.g., under the light-receiving surface408of the photodiode402), or the optical scattering structure410may project above the light-receiving surface408of the photodiode402.

Each optical scattering structure410may have a light-receiving surface422, a set of sidewalls424, and a set of edges426. The sidewalls424may extend away from the light-receiving surface422of the optical scattering structure410, and away from the first end446(or light-receiving surface408) of the photodiode402. For example, the sidewall(s)424of the optical scattering structure410may extend perpendicularly to the first end446, the light-receiving surface408, and the light-receiving surface422. Each edge426may1) define a transition between a surface (e.g., the light-receiving surface422) and a sidewall424of the optical scattering structure410, or2) define an inside or outside corner between two sidewalls424of the optical scattering structure410. Light that impinges on the edges426or sidewalls424of an optical scattering structure410may be redirected (or scatter) within the photodiode402differently than light that impinges on the light-receiving surface408of the photodiode402(the latter of which may cause light to refract but not scatter). When the lens406is present, and in some cases, one or more optical scattering structures410may be positioned such that they extend at least partially into the illumination area412defined by the lens406.

The sidewalls424and edges426of the optical scattering structure(s)410may in some cases be positioned and/or oriented to direct (e.g., scatter) light in desired directions. For example, it may be desirable to direct light into the photodiode402, to increase light absorption by the photodiode402, but to direct light away from the memory nodes416, to prevent optical crosstalk and interference between the integration of light by the photodiode402and the storage of charge by the memory nodes416.

By way of example, and as shown, an optical scattering structure410may have one or more pairs of sidewalls424(e.g., pairs of adjoining sidewalls424), with each pair of sidewalls424forming an included angle428extending perpendicular to the depth, D, of the photodiode406, and with the pair of sidewalls424abutting a portion of the photodiode402. Although the included angles428are shown to be obtuse angles formed by non-orthogonal pairs of sidewalls424, the included angles428could alternatively be acute angles or right angles. A set of three sidewalls424-1,424-2,424-3may be arranged such that a first intersection between a first sidewall424-1and a second sidewall424-2defines a first obtuse angle, and such that a second intersection between a third sidewall424-3and the second sidewall424-2defines a second obtuse angle. Respective normals430-1,430-2,430-3to the first sidewall424-1, the second sidewall424-2, and the third sidewall424-3intersect. A second set of three sidewalls424may be disposed in a mirrored relationship with respect to the first set of three sidewalls424-1,424-2,424-3.

In the example shown, the optical scattering structure410has a lateral cross-section, parallel to the light-receiving surface408of the photodiode402and parallel to the light-receiving surface422of the optical scattering structure410(e.g., in a plane, or in all planes, that intersect the optical scattering structure410parallel to the light-receiving surface422), defined by two triangles432,434joined by a bridge436.

In alternative embodiments of the pixel400, the optical scattering structure410could take any of the forms described with reference toFIGS.4A-5E, or the set of one or more optical scattering structures408could include multiple optical scattering structures, as described with reference toFIGS.6A-7B.

FIG.4Cshows how light incident on the edges426or sidewalls424of the optical scattering structure410may scatter. As shown, the light reflecting off of the edges426-1and426-2and sidewalls424-1and424-3may scatter primarily toward the interior of the photodiode402, in directions that are less likely to result in light scattering between the first and second U-shaped oxide walls414-1,414-2and changing the state of one or both of the memory nodes416.

FIGS.5A-5Eshow additional example optical scattering structures that may be used in one or more of the optical detector pixels described with reference toFIG.1,2,3A-3B, or4A-4C, or in other optical detector pixels.

The optical scattering structures shown inFIGS.3A-3B and4A-4Care symmetric about first, second, and third orthogonal axes (e.g., x and y axes parallel to the light-receiving surface of the photodiode, and a z axis perpendicular to the light-receiving surface of the photodiode). In contrast,FIG.5Ashows an optical scattering structure500that is symmetric about first and second orthogonal axes (x and z axes), and asymmetric about a third axis (y axis) orthogonal to each of the first and second orthogonal axes. The z axis may be the axis perpendicular a light-receiving surface of a photodiode.

By way of example, the optical scattering structure500has first, second, and third sidewalls502-1,502-2,502-3positioned similarly to the first set of three sidewalls described with reference toFIGS.4A-4C, and a singular, flat sidewall502-4facing in a direction opposite the second sidewall502-2.

FIG.5Bshows an optical scattering structure510similar to the optical scattering structure described with reference toFIG.5A, but with a singular curved sidewall512(bounded by curved edges) replacing the set of three sidewalls502-1,502-2, and502-3. The curved sidewall512(and its upper and lower edges) are shown to have a concave shape, but could alternatively have a convex or other curved shape. An optical scattering structure may also have a sidewall having a different curved shape, more than one sidewall having a curved shape, or a perimeter having a continuously curved shape.

FIG.5Cshows an optical scattering structure520similar to the optical scattering structure described with reference toFIG.5A, but with a multiple-step wall522replacing the first, second, and third sidewalls502-1,502-2,502-3. By way of example, the multiple-step wall522includes multiple “inward steps”524extending toward a planar center of gravity of the optical scattering structure520, and an equal number of “outward steps”526extending away from the planar center of gravity of the optical scattering structure520. In alternative embodiments, the inward and outward steps524,526may be of different size and different number, or the inward or outward steps524,526may not have orthogonal sidewalls, or the optical scattering structure520may only have one set of steps (e.g., the inward or outward steps524,526shown inFIG.5C, but not both), or the optical scattering structure520may have steps formed on additional or different sidewalls, or the optical scattering structure520may have steps that give the optical scattering structure an overall different shape.

FIG.5Dshows a set of optical scattering structures530that is similar to the optical scattering structure described with reference toFIGS.3A and3B, but with the lateral cross-section of the optical scattering structure530, parallel to a light-receiving surface of a photodiode, defined by two laterally spaced apart optical scattering structures532,534. By way of example, the two laterally spaced apart optical scattering structures532,534are each shown to have a triangular lateral cross-section. In other embodiments, one or both of the optical scattering structures532,534may have a differently shaped lateral cross-section, or the set of optical scattering structures530may include more than two optical scattering structures.

Each ofFIGS.3A-3B,4A-4C,5A, and5Dshow a set of one or more optical scattering structures that defines a set of edges (and sidewalls), with each set of edges (and sidewalls) including at least a first edge (and associated first sidewall) that is oriented at an oblique angle with respect to a second edge (and associated second sidewall). Some of the sets of one or more optical scattering structures have two or more pairs of edges (and associated sidewalls) that are oriented at oblique angles with respect to each other.FIGS.5D and5Ecach show a set of optical scattering structures having two or more optical scattering structures, in which a first optical scattering structure includes a first edge; a second optical scattering structure, laterally spaced apart from the first optical scattering structure, includes a second edge; and the first edge of the first optical scattering structure is oriented at an oblique angle with respect to the second edge of the second optical scattering structure. In particular,FIG.5Eshows a set of optical scattering structures540including three laterally spaced apart optical scattering structures542-1,542-2,542-3. By way of example, each of the optical scattering structures542-1,542-2,542-3is shown to have a rectangular cross-section parallel to a light-receiving surface of a photodiode. In alternative embodiments, one or more of the optical scattering structures may have a differently shaped cross-section and/or there may be more than three optical scattering structures.

As an example, the optical scattering structures542-1,542-2,542-3are laid out to mimic the set of three sidewalls described with reference toFIGS.4A-4C and5A, but the optical scattering structures542-1,542-2,542-3are laterally spaced apart such that portions of a photodiode may fill the spaces between them. In some cases, it may be easier to form three separate rectangular trenches to hold three separate optical scattering structures542-1,542-2,542-3than to form a single trench having non-orthogonal sidewalls.

FIGS.6A and6Bshow a third example pixel600. The pixel600includes optical scattering structures410-1,410-2positioned at different depths within the pixel600.FIG.6Ashows an elevation of the pixel600, andFIG.6Bshows a top-down plan view of the pixel600. The pixel600may be used as, or in, an optical detector. In some embodiments, the pixel600may take the form of the single-pixel optical detector described with reference toFIG.1, or one of the pixels in the multiple-pixel optical detector described with reference toFIG.2. By way of example, the pixel600is shown and described as a variation of the pixel described with reference toFIGS.4A-4C, and the same reference numerals are used below when appropriate. Like structures that are already shown inFIGS.4A-4Cmay not be referenced or described further below.

The pixel600includes a first optical scattering structure410-1and a second optical scattering structure410-2. The first optical scattering structure410-1may be the optical scattering structure described with reference toFIGS.4A-4C, and may have a light-receiving surface422positioned flush with a light-receiving surface408of the photodiode402. Alternatively, the first optical scattering structure410-1may be positioned entirely below the light-receiving surface408of the photodiode402. The first optical scattering structure410-1may extend to a first depth (e.g., depth “A”) within the photodiode402.

By way of example, the second optical scattering structure410-2is shown to be shaped and constructed similarly to the first optical scattering structure410-1. In alternative embodiments, the first and second optical scattering structures410-1,410-2may have different shapes and/or constructions. The second optical scattering structure410-2may have a light-receiving surface602positioned below the light-receiving surface408of the photodiode402. Alternatively, the light-receiving surface602of the second optical scattering structure410-2may be positioned flush with the light-receiving surface408of the photodiode402. The second optical scattering structure410-2may extend to a second depth (e.g., depth “B”) within the photodiode402. The depth B may be farther away from the light-receiving surface408of the photodiode402than the depth A.

In some embodiments of the pixel600, the second optical scattering structure410-2may be laterally offset from the first optical scattering structure410-1(sec, e.g.,FIG.6B). In alternative embodiments, the second optical scattering structure410-2may be vertically aligned with, or overlap a portion of, the first optical scattering structure410-1.

FIGS.7A and7Bshow a fourth example pixel700. The pixel700includes optical scattering structures410-1,410-3positioned at different depths within the pixel700.FIG.7Ashows an elevation of the pixel700, andFIG.7Bshows a top-down plan view of the pixel700. The pixel700may be used as, or in, an optical detector. In some embodiments, the pixel700may take the form of the single-pixel optical detector described with reference toFIG.1, or one of the pixels in the multiple-pixel optical detector described with reference toFIG.2. By way of example, the pixel700is shown and described as a variation of the pixel described with reference toFIGS.4A-4C, and the same reference numerals are used below when appropriate. Like structures that are already shown inFIGS.4A-4Cmay not be referenced or described further below.

The pixel700includes a first optical scattering structure410-1and a second optical scattering structure410-3. The first optical scattering structure410-1may be the optical scattering structure described with reference toFIGS.4A-4C, and may have a light-receiving surface422positioned flush with a light-receiving surface408of the photodiode402. Alternatively, the first optical scattering structure410-1may be positioned entirely below the light-receiving surface408of the photodiode402.

By way of example, the second optical scattering structure410-3is shown to be shaped differently from the first optical scattering structure410-1. In alternative embodiments, the first and second optical scattering structures410-1,410-3may have the same or different shapes and/or constructions. The second optical scattering structure410-3may have a light-receiving surface702positioned flush with the light-receiving surface422of the first optical scattering structure410-1.

The first and second optical scattering structures410-1,410-3may extend to the same depth within the photodiode402. Because the light-receiving surfaces422,702of the first and second optical scattering structures410-1,410-3are flush, and because the light-receiving surfaces422,702of the first and second optical scattering structures410-1,410-3extend to the same depth, the first and second optical scattering structures410-1,410-3may be referred to as co-planar.

In some alternative embodiments, the pixel described with reference toFIGS.6A-6B or7A-B may include additional optical scattering structures, which additional optical scattering structures are co-planar, non-co-planar, overlapping, or non-overlapping with other optical scattering structures.

The foregoing description, for purposes of explanation, uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art, after reading this description, that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art, after reading this description, that many modifications and variations are possible in view of the above teachings.

As described above, one aspect of the present technology may be the gathering and use of data, including optical data. The present disclosure contemplates that, in some instances, this gathered data may include personal information data (e.g., biological information) that uniquely identifies or can be used to identify, locate, contact, or diagnose a specific person. Such personal information data can include demographic data, location-based data, telephone numbers, email addresses, home addresses, data or records relating to a user's health or level of fitness (e.g., vital signs measurements, medication information, exercise information), date of birth, or any other identifying or personal information.

The present disclosure recognizes that the use of such personal information data, in the present technology, can be used to the benefit of users. For example, the personal information data can be used to activate or deactivate various functions of the user's device, or gather performance metrics for the user's device or the user. Further, other uses for personal information data that benefit the user are also contemplated by the present disclosure. For instance, health and fitness data may be used to provide insights into a user's general wellness, or may be used as positive feedback to individuals using technology to pursue wellness goals.