Patent Description:
<CIT>, <CIT>, <CIT> and <CIT> disclose related art.

In a first aspect, an optical filter is provided.

The first optical channel and the second optical channel may each have a critical dimension that is less than or equal to <NUM> microns. The electromagnetic spectrum may comprise at least one of: one or more portions of ultraviolet light; one or more portions of visible light; one or more portions of near-infrared light; one or more portions of short-wave infrared light; one or more portions of mid-wave infrared light; or one or more portions of long-wave infrared light. The optical filter wherein: the first mirror may be configured to reflect a first range of the electromagnetic spectrum; the second mirror may be configured to reflect a second range of the electromagnetic spectrum; the third mirror may be configured to reflect a third range of the electromagnetic spectrum; the fourth mirror may be configured to reflect a fourth range of the electromagnetic spectrum; and the monolithic spacer may be configured to transmit greater than a threshold percentage of light that has a wavelength that is within each of the first range of the electromagnetic spectrum, the second range of the electromagnetic spectrum, the third range of the electromagnetic spectrum, and the fourth range of the electromagnetic spectrum. The monolithic spacer may be formed using an etching procedure.

In a second aspect, an optical sensor device is provided.

A difference between a thickness of the first portion of the monolithic spacer and a thickness of the second portion of the monolithic spacer may be less than or equal to a particular difference threshold. The first mirror and the second mirror may be each configured to reflect a same portion of the electromagnetic spectrum. The optical sensor device wherein: the first mirror may be configured to reflect a first range of the electromagnetic spectrum; the second mirror may be configured to reflect a second range of the electromagnetic spectrum; and the first portion of the monolithic spacer may be configured to transmit greater than a threshold percentage of light that has a wavelength that is within each of the first range of the electromagnetic spectrum, the second range of the electromagnetic spectrum. The critical dimension of the particular sensor element may be less than or equal to <NUM> microns.

In a third aspect, a method of manufacturing an optical filter is provided in accordance with claim <NUM>.

The multilevel etch mask may be formed using a grayscale lithography procedure. A first optical channel of the optical filter may comprise the first mirror, the first portion of the monolithic spacer, and the third mirror; a second optical channel of the optical filter may comprise the second mirror, the second portion of the monolithic spacer, and the fourth mirror; and the first optical channel and the second optical channel may each have a critical dimension that is less than or equal to <NUM> microns. The multilevel etch mask and the monolithic spacer may be etched using a single etching procedure. A difference between the first thickness of the first portion of the monolithic spacer and the second thickness of the second portion of the monolithic spacer may be less than or equal to a particular difference threshold.

The following description uses a spectrometer as an example. However, the techniques, principles, procedures, and methods described herein may be used with any sensor, including but not limited to other optical sensors and spectral sensors.

An optical device (e.g., comprising a spectrometer or one or more other optical sensors and/or spectral sensors) may use filtered light to perform a measurement associated with a particular wavelength. In a typical configuration of an optical device, an optical filter comprises an array of optical channels that are disposed over a set of sensor elements of an optical sensor of the optical device. The array of optical channels is configured to pass light associated with different ranges of an electromagnetic spectrum. However, in many cases, such as when the array of optical channels is formed using a conventional lift-off process, each optical channel has a critical dimension that is larger than respective critical dimensions of the set of sensor elements. Consequently, when the set of sensor elements are positioned closely together (e.g., when a pitch associated with the set of sensor elements is less than the respective critical dimensions of the set of sensor elements), each optical channel is disposed over multiple sensor elements of the set of sensor elements, which inhibits a resolution of the optical sensor. Further, in other cases, such as when the array of optical channels is formed using a multistage etching process, there is an increased likelihood of etch-induced defects being introduced to the array of optical channels, which negatively impacts a performance of the optical filter.

Some implementations described herein provide an optical sensor device that includes an optical filter with a plurality of optical channels. Each of the plurality of optical channels includes a bottom mirror, a top mirror, and a portion of a monolithic spacer positioned between the bottom mirror and the top mirror. The top mirror and the bottom mirror may be configured to reflect one or more ranges of an electromagnetic spectrum (e.g., a same range or different ranges of the electromagnetic spectrum). Further, in some implementations, the monolithic spacer may be formed using an etching procedure in coordination with a grayscale lithography procedure. This may cause the portion of the monolithic spacer between the top mirror and the bottom mirror to have a particular thickness, which allows (in coordination with the reflective properties of the top mirror and the bottom mirror) the optical channel to pass a particular range of the electromagnetic spectrum.

In this way, when using an etching procedure in coordination with a grayscale lithography procedure to form a monolithic spacer that is included in a plurality of optical channels, respective critical dimensions of the plurality of optical channels are reduced as compared to when optical channels are formed using a conventional lift-off process. Accordingly, in some implementations, respective critical dimensions of the plurality of optical channels may be less than or equal to respective critical dimensions of a plurality of sensor elements of an optical sensor in the optical sensor device. Thus, when the plurality of optical channels are disposed over the plurality of sensor elements, one or more of the optical channels may be disposed over a single sensor element of the plurality of sensor elements, which increases a resolution of the optical sensor included in the optical sensor device (as compared to when a single optical channel of a typical optical filter is disposed over multiple sensor elements of optical sensor device). Further, some implementations described herein provide a single etching procedure to form the monolithic spacer, which decreases a likelihood that etch-induced defects are introduced into the plurality of optical channels (as compared to when a plurality of optical channels are formed using a multistage etching process). This thereby improves a performance of the optical filter as compared to a typical optical filter formed using a multistage etching process.

<FIG> is a diagram of an example optical sensor device <NUM> described herein. The optical sensor device <NUM> may include a spectrometer device that performs spectroscopy, such as a spectral optical sensor device (e.g., a binary multispectral optical sensor device that performs vibrational spectroscopy (such as a near infrared (NIR) spectrometer), a mid-infrared spectroscopy (mid-IR), Raman spectroscopy, and/or the like). As shown in <FIG>, the optical sensor device <NUM> includes an optical filter <NUM> and an optical sensor <NUM>.

As further shown in <FIG>, the optical filter <NUM> may include a plurality of optical channels <NUM>. The plurality of optical channels <NUM> may be arranged in a one-dimensional or a two-dimensional array on a surface of the optical filter <NUM>. For example, as shown in <FIG>, the plurality of optical channels <NUM> may be arranged in a two-dimensional array (e.g., where each row of the array includes <NUM> optical channels <NUM> and each column includes <NUM> optical channels <NUM>). The plurality of optical channels <NUM> may respectively pass different ranges of an electromagnetic spectrum (e.g., pass light with different wavelength ranges).

The optical sensor <NUM> includes a device capable of sensing light. For example, optical sensor <NUM> may include an image sensor, a multispectral sensor, a spectral sensor, and/or the like. In some implementations, optical sensor <NUM> may include a silicon (Si) based sensor, an indium-gallium-arsenide (InGaAs) based sensor, a lead-sulfide (PbS) based sensor, or a germanium (Ge) based sensor, and may utilize one or more sensor technologies, such as a complementary metal-oxide-semiconductor (CMOS) technology, or a charge-coupled device (CCD) technology, among other examples. In some implementations, optical sensor <NUM> may include a front-side illumination (FSI) sensor, a back-side illumination (BSI) sensor, and/or the like.

As further shown in <FIG>, the optical sensor <NUM> may include a plurality of sensor elements <NUM>. The plurality of sensor elements <NUM> may be arranged in a one-dimensional or a two-dimensional array on a surface of the optical sensor <NUM>. In some implementations, an arrangement of the plurality of sensor elements <NUM> on the surface of the optical sensor <NUM> may correspond to an arrangement of the plurality of optical channels <NUM> on the surface of the optical filter <NUM>, such that an optical channel <NUM> may be configured to pass a range of particular electromatic frequencies (e.g., pass light associated with a particular wavelength range) to one or more sensor elements <NUM>. For example, as shown in <FIG>, the plurality of optical channels <NUM> and the plurality of sensor elements <NUM> may each be arranged in a corresponding two-dimensional array (e.g., an <NUM>×<NUM> array).

A sensor element <NUM> may be configured to obtain information regarding light that falls incident on the sensor element <NUM> (e.g., after passing through an optical channel <NUM>). For example, a sensor element <NUM> may provide an indication of intensity of light that falls incident on the sensor element <NUM> (e.g., active/inactive, or a more granular indication of intensity). The optical sensor <NUM> may be configured to collect the information obtained by the one or more sensor elements <NUM> to generate sensor data.

As further shown in <FIG>, the optical filter <NUM> may be disposed over the optical sensor <NUM> (e.g., such that an arrangement of the optical channels <NUM> is aligned with an arrangement of the sensor elements <NUM>). The optical filter <NUM> may be directly disposed on the optical sensor <NUM> or may be separated from the optical sensor <NUM> by a free space gap.

<FIG> is a diagram of a side-view of example optical sensor device <NUM> described herein. As shown in <FIG>, the optical sensor device <NUM> includes an optical filter <NUM> and an optical sensor <NUM> that respectively include a plurality of optical channels <NUM> (shown as optical channels <NUM>-<NUM> through <NUM>-<NUM>) and a plurality of sensor elements <NUM> (shown as sensor elements <NUM>-<NUM> through <NUM>-<NUM>). The optical filter <NUM>, the optical sensor <NUM>, the plurality of optical channels <NUM>, and the plurality of sensor elements <NUM> may be the same as, or similar to, the optical filter <NUM>, the optical sensor <NUM>, the plurality of optical channels <NUM>, and the plurality of sensor elements <NUM>, respectively, as described herein in relation to <FIG>.

As further shown in <FIG>, the optical filter <NUM> may include a plurality of bottom mirrors <NUM> (shown as bottom mirrors <NUM>-<NUM> through <NUM>-<NUM>), a monolithic spacer <NUM> (e.g., that includes a plurality of portions, shown as <NUM>-<NUM> through <NUM>-<NUM>), and/or a plurality of top mirrors <NUM> (shown as top mirrors <NUM>-<NUM> through <NUM>-<NUM>). The monolithic spacer <NUM> may be positioned between the plurality of bottom mirrors <NUM> and the plurality of top mirrors <NUM>. For example, as further shown in <FIG>, the monolithic spacer <NUM> may be disposed on the plurality bottom mirrors <NUM>, and the plurality of top mirrors <NUM> may be disposed on the monolithic spacer <NUM>.

Each mirror, of the plurality of bottom mirrors <NUM> and/or the plurality of top mirrors <NUM>, may comprise one or more metals, one or more dielectric materials, and/or one or more semiconductor materials, among other examples. Each mirror may be configured to reflect a particular range of an electromagnetic spectrum (e.g., reflect light with a wavelength that is within a particular wavelength range). The electromagnetic spectrum may include, for example, one or more portions of ultraviolet light (e.g., one or more portions of light with a wavelength that is within <NUM> to <NUM>), one or more portions of visible light (e.g., one or more portions of light with a wavelength that is within <NUM> to <NUM>), one or more portions of near-infrared light (e.g., one or more portions of light with a wavelength that is within <NUM> to <NUM>), one or more portions of short-wave infrared light (e.g., one or more portions of light with a wavelength that is within <NUM> to <NUM>), one or more portions of mid-wave infrared light (e.g., one or more portions of light with a wavelength that is within <NUM> to <NUM>), or one or more portions of long-wave infrared light (e.g., one or more portions of light with a wavelength that is within <NUM> to <NUM>).

The monolithic spacer <NUM> may comprise one or more materials, such as at least one of a silicon (Si) material, a hydrogenated silicon (Si:H) material, an amorphous silicon (a-Si) material, a silicon nitride (SiN) material, a germanium (Ge) material, a hydrogenated germanium (Ge:H) material, a silicon germanium (SiGe) material, a hydrogenated silicon germanium (SiGe:H) material, a silicon carbide (SiC) material, a hydrogenated silicon carbide (SiC:H) material, a silicon dioxide (SiO<NUM>) material, a tantalum pentoxide (Ta<NUM>O<NUM>) material, a niobium pentoxide (Nb<NUM>O<NUM>) material, a niobium titanium oxide (NbTiOx) material, a niobium tantalum pentoxide (Nb<NUM>TaO<NUM>) material, a titanium dioxide (TiO<NUM>) material, an aluminum oxide (Al<NUM>O<NUM>) material, a zirconium oxide (ZrO<NUM>) material, an yttrium oxide (Y<NUM>O<NUM>) material, an aluminum nitride (AlN), or a hafnium oxide (HfO<NUM>) material, among other examples. The monolithic spacer <NUM> may be formed as a single spacer (e.g., rather than a spacer comprising discrete parts or layers). Additionally, or alternatively, the monolithic spacer <NUM> may have a uniform, or substantially uniform, crystal lattice structure (e.g., the monolithic spacer <NUM> may not include any interfaces within the monolithic spacer <NUM>). For example, the monolithic spacer <NUM> may be formed as a single spacer using an etching procedure (e.g., in coordination with a grayscale lithography procedure), as further described herein in relation to <FIG>.

In some implementations, a particular optical channel <NUM>, of the plurality of optical channels <NUM>, may include a particular bottom mirror <NUM>, of the plurality of bottom mirrors <NUM>; a particular top mirror <NUM>, of the plurality of top mirrors <NUM>; and a particular portion of the monolithic spacer <NUM> (e.g., that is positioned between the particular bottom mirror <NUM> and the particular top mirror <NUM>). For example, as shown in <FIG>, the optical channel <NUM>-<NUM> may include the bottom mirror <NUM>-<NUM>, the top mirror <NUM>-<NUM>, and a first portion of the monolithic spacer <NUM>-<NUM> that is positioned between the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM>; the optical channel <NUM>-<NUM> may include the bottom mirror <NUM>-<NUM>, the top mirror <NUM>-<NUM>, and a second portion of the monolithic spacer <NUM>-<NUM> that is positioned between the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM>; and the optical channel <NUM>-<NUM> may include the bottom mirror <NUM>-<NUM>, the top mirror <NUM>-<NUM>, and a first portion of the monolithic spacer <NUM>-<NUM> that is positioned between the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM>.

In some implementations, the particular bottom mirror <NUM> and the particular top mirror <NUM> of the particular optical channel <NUM> may be configured to reflect one or more ranges of the electromagnetic spectrum (e.g., a same range of the electromagnetic spectrum or different ranges of the electromagnetic spectrum). For example, as shown in <FIG>, for the optical channel <NUM>-<NUM>, the bottom mirror <NUM>-<NUM> may be configured to reflect a first range of the electromagnetic spectrum (as indicated by a left-to-right diagonal line pattern), and the top mirror <NUM>-<NUM> may be configured to reflect a second range of the electromagnetic spectrum (as indicated by a right-to-left diagonal line pattern), where the first range and the second range are different (e.g., at least some of the first range and the second range are not coextensive); for the optical channel <NUM>-<NUM>, the bottom mirror <NUM>-<NUM> may be configured to reflect a third range of the electromagnetic spectrum (as indicated by a horizontal line pattern) and the top mirror <NUM>-<NUM> may be configured to reflect a fourth range of the electromagnetic spectrum (as indicated by a vertical line pattern), where the third range and the fourth range are different (e.g., at least some of the third range and the fourth range are not coextensive); and for the optical channel <NUM>-<NUM>, the bottom mirror <NUM>-<NUM> may be configured to reflect a fifth range of the electromagnetic spectrum (as indicated by a square line pattern) and the top mirror <NUM>-<NUM> may be configured to reflect a sixth range of the electromagnetic spectrum (as indicated by a diamond line pattern), where the fifth range and the sixth range are different (e.g., at least some of the fifth range and the sixth range are not coextensive). In a particular example, the bottom mirror <NUM>-<NUM> may be configured to reflect light with a wavelength that is within a <NUM> to <NUM> range, the top mirror <NUM>-<NUM> may be configured to reflect light with a wavelength that is within a <NUM> to <NUM> range, the bottom mirror <NUM>-<NUM> may be configured to reflect light with a wavelength that is within a <NUM> to <NUM> range, the top mirror <NUM>-<NUM> may be configured to reflect light with a wavelength that is within a <NUM> to <NUM> range, the bottom mirror <NUM>-<NUM> may be configured to reflect light with a wavelength that is within a <NUM> to <NUM> range, and the top mirror <NUM>-<NUM> may be configured to reflect light with a wavelength that is within a <NUM> to <NUM> range.

In some implementations, the monolithic spacer <NUM> may be configured to be transparent for one or more ranges of the electromagnetic spectrum. For example, the monolithic spacer <NUM> may be configured to transmit greater than a threshold percentage of light that has a wavelength that is within at least one of the first range of the electromagnetic spectrum, the second range of the electromagnetic spectrum, the third range of the electromagnetic spectrum, the fourth range of the electromagnetic spectrum, the fifth range of the electromagnetic spectrum, or the sixth range of the electromagnetic spectrum described in the example above. As another example, when the particular portion of the monolithic spacer <NUM> is positioned between the particular bottom mirror <NUM> and the particular top mirror <NUM> in the particular optical channel <NUM>, the particular portion of the monolithic spacer <NUM> may be configured to transmit greater than the threshold percentage of light that has a wavelength that is within each of a first particular range of the electromagnetic spectrum that the particular bottom mirror <NUM> is configured to reflect and a second particular range of the electromagnetic spectrum that the particular top mirror <NUM> is configured to reflect. The threshold percentage of light may be greater than or equal to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%, for example.

In some implementations, the plurality of bottom mirrors <NUM> may be disposed on a first side of the monolithic spacer <NUM> (e.g., a bottom side of the monolithic spacer <NUM>), and the plurality of top mirrors <NUM> may be disposed on a second side of the monolithic spacer <NUM> (e.g., a top side of the monolithic spacer <NUM>). Any two bottom mirrors <NUM>, of the plurality of bottom mirrors <NUM>, may be configured to reflect one or more ranges of the electromagnetic spectrum wherein the ranges are different ranges of the electromagnetic spectrum. For example, as shown in <FIG>, the bottom mirror <NUM>-<NUM> may be configured to reflect a first range of the electromagnetic spectrum (as indicated by the left-to-right diagonal line pattern), and the bottom mirror <NUM>-<NUM> may be configured to reflect a second range of the electromagnetic spectrum (as indicated by the horizontal line pattern), where the first range and the second range are different (e.g., at least some of the first range and the second range are not coextensive). Any two top mirrors <NUM>, of the plurality of top mirrors <NUM>, may be configured to reflect one or more ranges of the electromagnetic spectrum (e.g., a same range of the electromagnetic spectrum or different ranges of the electromagnetic spectrum). For example, as shown in <FIG>, the top mirror <NUM>-<NUM> may be configured to reflect a third range of the electromagnetic spectrum (as indicated by the right-to-left diagonal line pattern), and the top mirror <NUM>-<NUM> may be configured to reflect a fourth range of the electromagnetic spectrum (as indicated by the vertical line pattern), where the third range and the fourth range are different (e.g., at least some of the third range and the fourth range are not coextensive).

In some implementations, two or more portions of the monolithic spacer <NUM> may have different thicknesses. For example, as shown in <FIG>, a thickness <NUM>-<NUM> of the first portion of the monolithic spacer <NUM>-<NUM> may be different than a thickness <NUM>-<NUM> of the second portion of the monolithic spacer <NUM>-<NUM>. Further, the thickness <NUM>-<NUM> and the thickness <NUM>-<NUM> may each be different than a thickness <NUM>-<NUM> of the third portion of the monolithic spacer <NUM>-<NUM>. In some implementations, a difference between a thickness of a particular portion of the monolithic spacer <NUM> and a thickness of another portion of the monolithic spacer <NUM> may be less than or equal to a particular difference threshold. The particular difference threshold may be less than or equal to <NUM> nanometers (nm), <NUM>, or <NUM>, among other examples.

In some implementations, each optical channel <NUM>, of the plurality of optical channels <NUM>, may have a critical dimension <NUM> (e.g., a maximum dimension, such as a width, of the optical channel <NUM>), and each sensor element <NUM>, of the plurality of sensor elements <NUM>, may have a critical dimension <NUM> (e.g., a maximum dimension, such as a width, of the sensor element <NUM>). For example, as shown in <FIG>, the optical channel <NUM>-<NUM> may have a critical dimension <NUM>-<NUM>, the optical channel <NUM>-<NUM> may have a critical dimension <NUM>-<NUM>, and the optical channel <NUM>-<NUM> may have a critical dimension <NUM>-<NUM>. Further, the sensor element <NUM>-<NUM> may have the critical dimension <NUM>-<NUM>, the sensor element <NUM>-<NUM> may have the critical dimension <NUM>-<NUM>, and the sensor element <NUM>-<NUM> may have the critical dimension <NUM>-<NUM>. In some implementations, the respective critical dimensions <NUM> of the plurality optical channels <NUM> and the respective critical dimensions <NUM> of the sensor elements <NUM> may be less than or equal to a critical dimension threshold. The critical dimension threshold may be, for example, less than or equal to <NUM> microns, <NUM> microns, or <NUM> microns. Additionally, or alternatively, the respective critical dimensions <NUM> of the plurality optical channels <NUM> may be less than or equal to the respective critical dimensions <NUM> of the sensor elements <NUM>. Accordingly, when the plurality of optical channels <NUM> are disposed over the plurality of sensor elements <NUM> (e.g., as described herein in relation to <FIG>), one or more of the optical channels <NUM> may disposed over a single sensor element <NUM> of the plurality of sensor elements <NUM>.

<FIG> is a diagram of a side-view of an example optical sensor device <NUM> described herein. As shown in <FIG>, the optical sensor device <NUM> includes an optical filter <NUM> that includes a plurality of optical channels <NUM> (shown as optical channels <NUM>-<NUM> and <NUM>-<NUM>) that are the same as, or similar to, corresponding elements described herein in relation to <FIG>. For example, the optical filter <NUM> may include a plurality of bottom mirrors <NUM> (shown as bottom mirrors <NUM>-<NUM> and <NUM>-<NUM>), a monolithic spacer <NUM> (e.g., that includes a plurality of portions, shown as <NUM>-<NUM> and <NUM>-<NUM>), and/or a plurality of top mirrors <NUM> (shown as top mirrors <NUM>-<NUM> and <NUM>-<NUM>). The monolithic spacer <NUM> may be positioned between the plurality of bottom mirrors <NUM> and the plurality of top mirrors <NUM>. Accordingly, a particular optical channel <NUM>, of the plurality of optical channels <NUM>, may include a particular bottom mirror <NUM>, of the plurality of bottom mirrors <NUM>; a particular top mirror <NUM>, of the plurality of top mirrors <NUM>; and a particular portion of the monolithic spacer <NUM> (e.g., that is positioned between the particular bottom mirror <NUM> and the particular top mirror <NUM>).

As shown in <FIG>, the optical channel <NUM>-<NUM> may include the bottom mirror <NUM>-<NUM>, the top mirror <NUM>-<NUM>, and a first portion of the monolithic spacer <NUM>-<NUM> that is positioned between the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM>, and the optical channel <NUM>-<NUM> may include the bottom mirror <NUM>-<NUM>, the top mirror <NUM>-<NUM>, and a second portion of the monolithic spacer <NUM>-<NUM> that is positioned between the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM>. As further shown in <FIG>, for the optical channel <NUM>-<NUM>, the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM> may each be configured to reflect a first range of the electromagnetic spectrum (e.g., a same range of the electromagnetic spectrum, as indicated by a right-to-left diagonal line pattern), and, for the optical channel <NUM>-<NUM>, the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM> may each be configured to reflect a same range of the electromagnetic spectrum (a same range of the electromagnetic spectrum, as indicated by a dot pattern).

The monolithic spacer <NUM> may be configured to be transparent for the first range and the second range of the electromagnetic spectrum. For example, the monolithic spacer <NUM> may be configured to transmit greater than a threshold percentage of light (e.g., greater than <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% of light) that has a wavelength that is within the first range and the second range of the electromagnetic spectrum. In some implementations, two or more portions of the monolithic spacer <NUM> may have different thicknesses. For example, as shown in <FIG>, a thickness <NUM>-<NUM> of the first portion of the monolithic spacer <NUM>-<NUM> may be different than a thickness <NUM>-<NUM> of the second portion of the monolithic spacer <NUM>-<NUM>. In some implementations, a difference between a thickness of a particular portion of the monolithic spacer <NUM> and a thickness another portion of the monolithic spacer <NUM> may be less than or equal to a particular difference threshold. The particular difference threshold may be less than or equal to <NUM>, <NUM>, or <NUM>, among other examples.

<FIG> is a diagram of a side-view of an example optical sensor device <NUM> that does not fall within the scope of the appended claims but is provided for exemplary purposes. As shown in <FIG>, the optical sensor device <NUM> includes an optical filter <NUM> that includes a plurality of optical channels <NUM> (shown as optical channels <NUM>-<NUM> and <NUM>-<NUM>) that are the same as, or similar to, corresponding elements described herein in relation to <FIG>. For example, the optical filter <NUM> may include a plurality of bottom mirrors <NUM> (shown as bottom mirrors <NUM>-<NUM> and <NUM>-<NUM>), a monolithic spacer <NUM> (e.g., that includes a plurality of portions, shown as <NUM>-<NUM> and <NUM>-<NUM>), and/or a plurality of top mirrors <NUM> (shown as top mirrors <NUM>-<NUM> and <NUM>-<NUM>). The monolithic spacer <NUM> may be positioned between the plurality of bottom mirrors <NUM> and the plurality of top mirrors <NUM>. Accordingly, a particular optical channel <NUM>, of the plurality of optical channels <NUM>, may include a particular bottom mirror <NUM>, of the plurality of bottom mirrors <NUM>; a particular top mirror <NUM>, of the plurality of top mirrors <NUM>; and a particular portion of the monolithic spacer <NUM> (e.g., that is positioned between the particular bottom mirror <NUM> and the particular top mirror <NUM>).

As shown in <FIG>, the optical channel <NUM>-<NUM> may include the bottom mirror <NUM>-<NUM>, the top mirror <NUM>-<NUM>, and a first portion of the monolithic spacer <NUM>-<NUM> that is positioned between the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM>, and the optical channel <NUM>-<NUM> may include the bottom mirror <NUM>-<NUM>, the top mirror <NUM>-<NUM>, and a second portion of the monolithic spacer <NUM>-<NUM> that is positioned between the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM>. As further shown in <FIG>, for the optical channel <NUM>-<NUM>, the bottom mirror <NUM>-<NUM> may be configured to reflect a first range of the electromagnetic spectrum (as indicated by a right-to-left diagonal line pattern) and the top mirror <NUM>-<NUM> may be configured to reflect a second range of the electromagnetic spectrum (as indicated by a diamond line pattern) that is different than the first range. For the optical channel <NUM>-<NUM>, the bottom mirror <NUM>-<NUM> may be configured to reflect the first range of the electromagnetic spectrum (as indicated by the right-to-left diagonal line pattern) and the top mirror <NUM>-<NUM> may be configured to reflect a third range of the electromagnetic spectrum (as indicated by a dot pattern) that is different than the first range. In this way, each of the plurality of bottom mirrors <NUM> (e.g., that are disposed on a same side of the monolithic spacer <NUM>) may be configured to reflect a same portion of the electromagnetic spectrum.

The monolithic spacer <NUM> may be configured to be transparent for the first range, the second range, and the third range of the electromagnetic spectrum. For example, the monolithic spacer <NUM> may be configured to transmit greater than a threshold percentage of light (e.g., greater than <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% of light) that has a wavelength that is the first range, the second range, and the third range of the electromagnetic spectrum. In some implementations, two or more portions of the monolithic spacer <NUM> may have different thicknesses. For example, as shown in <FIG>, a thickness <NUM>-<NUM> of the first portion of the monolithic spacer <NUM>-<NUM> may be different than a thickness <NUM>-<NUM> of the second portion of the monolithic spacer <NUM>-<NUM>. In some implementations, a difference between a thickness of a particular portion of the monolithic spacer <NUM> and a thickness another portion of the monolithic spacer <NUM> may be less than or equal to a particular difference threshold. The particular difference threshold may be less than or equal to <NUM>, <NUM>, or <NUM>, among other examples.

As shown in <FIG>, the optical channel <NUM>-<NUM> may include the bottom mirror <NUM>-<NUM>, the top mirror <NUM>-<NUM>, and a first portion of the monolithic spacer <NUM>-<NUM> that is positioned between the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM>, and the optical channel <NUM>-<NUM> may include the bottom mirror <NUM>-<NUM>, the top mirror <NUM>-<NUM>, and a second portion of the monolithic spacer <NUM>-<NUM> that is positioned between the bottom mirror <NUM>-<NUM> and the top mirror <NUM>-<NUM>. As further shown in <FIG>, for the optical channel <NUM>-<NUM>, the bottom mirror <NUM>-<NUM> may be configured to reflect a first range of the electromagnetic spectrum (as indicated by a right-to-left diagonal line pattern) and the top mirror <NUM>-<NUM> may be configured to reflect a second range of the electromagnetic spectrum (as indicated by a diamond line pattern) that is different than the first range. For the optical channel <NUM>-<NUM>, the bottom mirror <NUM>-<NUM> may be configured to reflect a third range of the electromagnetic spectrum (as indicated by a dot pattern) and the top mirror <NUM>-<NUM> may be configured to reflect the second range of the electromagnetic spectrum (as indicated by a diamond line pattern) that is different than the third range. In this way, each of the plurality of top mirrors <NUM> (e.g., that are disposed on a same side of the monolithic spacer <NUM>) may be configured to reflect a same portion of the electromagnetic spectrum.

The monolithic spacer <NUM> may be configured to be transparent for the first range, the second range, and the third range of the electromagnetic spectrum. For example, the monolithic spacer <NUM> may be configured to transmit greater than a threshold percentage of light (e.g., greater than <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% of light) that has a wavelength that is within the first range, the second range, and the third range of the electromagnetic spectrum. In some implementations, two or more portions of the monolithic spacer <NUM> may have different thicknesses. For example, as shown in <FIG>, a thickness <NUM>-<NUM> of the first portion of the monolithic spacer <NUM>-<NUM> may be different than a thickness <NUM>-<NUM> of the second portion of the monolithic spacer <NUM>-<NUM>. In some implementations, a difference between a thickness of a particular portion of the monolithic spacer <NUM> and a thickness another portion of the monolithic spacer <NUM> may be less than or equal to a particular difference threshold. The particular difference threshold may be less than or equal to <NUM>, <NUM>, or <NUM>, among other examples.

<FIG> are diagrams of an example implementation <NUM> of a formation process for manufacturing an optical filter (e.g., an optical filter that is the same as, or similar to, the optical filters <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM> described in relation to <FIG>). As shown in <FIG>, the optical filter may be formed by forming, on a substrate <NUM>, a plurality of bottom mirrors <NUM> (e.g., that are the same as, or similar to, the bottom mirrors <NUM>, <NUM>, <NUM>, and/or <NUM> described herein in relation <FIG>, shown as bottom mirrors <NUM>-<NUM> through <NUM>-N, where N ≥ <NUM>), a monolithic spacer <NUM> (e.g., that is the same as, or similar to, the monolithic spacer <NUM>, <NUM>, <NUM>, and/or <NUM> described herein in relation <FIG>, shown with portions of the monolithic spacer <NUM>-<NUM> through <NUM>-N), a plurality of top mirrors <NUM> (e.g., that are the same as, or similar to, the top mirrors <NUM>, <NUM>, <NUM>, and/or <NUM> described herein in relation <FIG>, shown as top mirrors <NUM>-<NUM> through <NUM>-N), and a multilevel etch mask <NUM> (shown with portions of the multilevel etch masks <NUM>-<NUM> through <NUM>-N). In some implementations, one or more layers and/or structures may be fabricated using a sputtering procedure, a photolithographic procedure, a grayscale lithography procedure, an etching procedure, a lift off procedure, a scraping procedure, an annealing procedure, a molding procedure, a casting procedure, a machining procedure, and/or a stamping procedure, among other examples.

The substrate <NUM> may include a silicon (Si) substrate, a gallium arsenide (GaAs) substrate, an indium phosphide (InP) substrate, a germanium (Ge) substrate, and/or another type of substrate. As shown in <FIG>, and by reference number <NUM>, the formation process may include forming the plurality of bottom mirrors <NUM> on the substrate <NUM>. For example, the formation process may include forming a first bottom mirror <NUM>-<NUM> on a first region of a surface of the substrate <NUM> (e.g., a first region of a top surface of the substrate <NUM>), a second bottom mirror <NUM>-<NUM> on a second region of the surface of the substrate <NUM>, and so on. In this way, the one or more bottom mirrors <NUM> may be formed on the substrate <NUM> such that the one or more bottom mirrors <NUM> do not overlap each other.

As further shown in <FIG>, and by reference number <NUM>, the formation process may include forming the monolithic spacer <NUM> on the one or more bottom mirrors <NUM>. For example, the formation process may include forming the monolithic spacer <NUM> on respective surfaces of the one or more bottom mirrors <NUM> (e.g., respective top surfaces of the one or more bottom mirrors <NUM>). For example, a first portion of the monolithic spacer <NUM>-<NUM> may be formed over the top surface of the first bottom mirror <NUM>-<NUM>, a second portion of the monolithic spacer <NUM>-<NUM> may be formed over the top surface of the second bottom mirror <NUM>-<NUM>, and so on. As further shown in <FIG>, the monolithic spacer <NUM> may be formed with a uniform, or substantially uniform, thickness. For example, a thickness of a portion of the monolithic spacer <NUM> may be the same as, within a tolerance (e.g., that is less than or equal to <NUM> microns), a thickness of any other portion of the monolithic spacer <NUM>.

The multilevel etch mask <NUM> may comprise a photo-sensitive material, such as a photo-sensitive polymer. As shown in <FIG>, the formation process may include forming the multilevel etch mask <NUM> on the monolithic spacer <NUM>. In some implementations, the multilevel etch mask <NUM> may be formed using a grayscale lithography procedure, such as a grayscale electron beam lithography procedure or a grayscale photolithography procedure. For example, as shown in <FIG>, and by reference number <NUM>, when using the grayscale lithography procedure, the formation process may include depositing the multilevel etch mask <NUM> on the monolithic spacer <NUM>. As shown in <FIG>, and by reference number <NUM>, when using the grayscale lithography procedure, the formation process may further include exposing the multilevel etch mask <NUM> to different amounts of light (e.g., ultraviolet (UV) light) to cause one or more portions of the multilevel etch mask <NUM> (shown as portions of the multilevel etch mask <NUM>-<NUM> through <NUM>-N) to have different thicknesses (e.g., to have multiple levels). The one or more portions of the multilevel etch mask <NUM> may correspond with the one or more bottom mirrors <NUM> and the one or more portions of the monolithic spacer <NUM>. For example, a first portion of the multilevel etch mask <NUM>-<NUM> may be disposed over the first bottom mirror <NUM>-<NUM>, and the first portion of the monolithic spacer <NUM>-<NUM>, a second portion of the multilevel etch mask <NUM>-<NUM> may be disposed over the second bottom mirror <NUM>-<NUM> and the second portion of the monolithic spacer <NUM>-<NUM>, and so on.

As shown in <FIG>, and by reference number <NUM>, the formation process may include etching the multilevel etch mask <NUM> and/or the monolithic spacer <NUM> using an etching procedure. For example, the formation process may include using a single etching procedure, such as a single reactive ion etching procedure, to etch the multilevel etch mask <NUM> and/or the monolithic spacer <NUM>. In some implementations, etching the multilevel etch mask <NUM> eliminates the multilevel etch mask <NUM> (e.g., none, or substantially none, of the multilevel etch mask <NUM> remains after completion of the etching procedure). Additionally, or alternatively, etching the monolithic spacer <NUM> may cause two or more portions of the monolithic spacer <NUM> to have different thicknesses. For example, etching the monolithic spacer <NUM> may cause the first portion of the monolithic spacer <NUM>-<NUM> that is disposed on the first bottom mirror <NUM>-<NUM> to have a first thickness and the second portion of the monolithic spacer <NUM>-<NUM> that is disposed on the second bottom mirror <NUM>-<NUM> to have a second thickness that is different than the first thickness. The respective thicknesses of the portions of the monolithic spacer <NUM> (e.g., after completion of the etching procedure) may be related to the respective thicknesses of corresponding portions of the multilevel etch mask <NUM> (e.g., prior to elimination of the multilevel etch mask <NUM> via the etching procedure). For example, a thickness of a particular portion of the monolithic spacer <NUM> (e.g., after completion of the etching procedure) may be a particular percentage of a thickness of a particular portion of the multilevel etch mask <NUM> that is disposed on the particular portion of the monolithic spacer <NUM> prior to the etching procedure.

As shown in <FIG>, and by reference number <NUM>/, the formation process may include forming the one or more top mirrors <NUM> on the monolithic spacer <NUM>. For example, the formation process may include forming a first top mirror <NUM>-<NUM> on a first region of a surface of the monolithic spacer <NUM> (e.g., a top surface of the first portion of the monolithic spacer <NUM>-<NUM>), a second top mirror <NUM>-<NUM> on a second region of the surface of the monolithic spacer <NUM> (e.g., a top surface of the second portion of the monolithic spacer <NUM>-<NUM>), and so on.

In this way, the optical filter may formed with a plurality of optical channels <NUM> (e.g., that are the same as, or similar to, the plurality of optical channels <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM> described herein in relation to <FIG>). For example, a first optical channel <NUM>-<NUM> may comprise the first bottom mirror <NUM>-<NUM>, the first portion of the monolithic spacer <NUM>-<NUM>, and the first top mirror <NUM>-<NUM>; a second optical channel <NUM>-<NUM> may comprise the second bottom mirror <NUM>-<NUM>, the second portion of the monolithic spacer <NUM>-<NUM>, and the second top mirror <NUM>-<NUM>; and so on.

As an example, "at least one of: a, b, or c" is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiple of the same item.

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles "a" and "an" are intended to include one or more items, and may be used interchangeably with "one or more. " Further, as used herein, the article "the" is intended to include one or more items referenced in connection with the article "the" and may be used interchangeably with "the one or more. " Furthermore, as used herein, the term "set" is intended to include one or more items (e.g., related items, unrelated items, or a combination of related and unrelated items), and may be used interchangeably with "one or more. " Where only one item is intended, the phrase "only one" or similar language is used. Also, as used herein, the terms "has," "have," "having," or the like are intended to be open-ended terms. Further, the phrase "based on" is intended to mean "based, at least in part, on" unless explicitly stated otherwise. Also, as used herein, the term "or" is intended to be inclusive when used in a series and may be used interchangeably with "and/or," unless explicitly stated otherwise (e.g., if used in combination with "either" or "only one of").

Claim 1:
A method of manufacturing (<NUM>) an optical filter (<NUM>), comprising:
forming, on a substrate (<NUM>), a first mirror (<NUM>-<NUM>) and a second mirror (<NUM>-<NUM>),
wherein the first mirror (<NUM>-<NUM>) and the second mirror (<NUM>-<NUM>) do not overlap each other;
forming, on the first mirror (<NUM>-<NUM>) and the second mirror (<NUM>-<NUM>), a monolithic spacer (<NUM>);
forming a multilevel etch mask (<NUM>) on the monolithic spacer (<NUM>);
etching the multilevel etch mask (<NUM>) and the monolithic spacer (<NUM>), wherein:
etching the multilevel etch mask (<NUM>) eliminates the multilevel etch mask (<NUM>), and
etching the monolithic spacer (<NUM>) causes a first portion (<NUM>-<NUM>) of the monolithic spacer disposed on the first mirror (<NUM>-<NUM>) to have a first thickness and a second portion (<NUM>-<NUM>) of the monolithic spacer disposed on the second mirror (<NUM>-<NUM>) to have a second thickness that is different than the first thickness;
forming, on the first portion (<NUM>-<NUM>) of the monolithic spacer, a third mirror (<NUM>-<NUM>),
wherein the first mirror (<NUM>-<NUM>) and the third mirror (<NUM>-<NUM>) are configured to reflect one or more ranges of an electromagnetic spectrum; and
forming, on the second portion (<NUM>-<NUM>) of the monolithic spacer, a fourth mirror (<NUM>-<NUM>),
wherein the second mirror (<NUM>-<NUM>) and the fourth mirror (<NUM>-<NUM>) are configured to reflect one or more ranges of the electromagnetic spectrum.