Spectrometer

A spectrometer includes a plurality of photodetectors, an anti-reflection layer, a grating layer, a distant layer, and a collimator. The anti-reflection layer is disposed on the plurality of photodetectors. The grating layer is disposed above the anti-reflection layer and includes a plurality of grating structures to spread a light into a spectrum to the plurality of photodetectors through the distant layer. The distant layer continuously extends from the grating layer to the anti-reflection layer, the distant layer has a thickness in a range from 400 μm to 2000 μm, and a refractive index of the grating layer is greater than a refractive index of the distant layer. The collimator is disposed above the grating layer, in which the collimator is configured to confine an incident angle of the light from a first micro-lens.

BACKGROUND

Field of Invention

The present disclosure relates to a spectrometer with high resolution. More particularly, the present disclosure relates to a spectrometer with high resolution having a distant layer.

Description of Related Art

In the field of optics, a light spectrum could be analyzed by a variety of analytical instruments, such as a spectrometer or an interferometer. Despite the fact that a traditional grating spectrometer has high spectral sensitivity and large bandwidth of light, a volume of a traditional grating spectrometer is relatively large because it needs sufficient optical path length for coupling of light. An interferometer, such as Fabry-Perot interferometer, selectively transmits light with specific wavelengths, such that spectrum analysis could be achieved with a single filter. However, a cavity in the interferometer limits the spectral range, and so it may not be suitable in a broadband spectrum.

A waveguide grating device also could be used for analyzing a spectrum of light, but it is limited by specific incident angles and specific light wavelength, so the coupling efficiency of light on the waveguide grating may be poor. Therefore, there is a need to solve the above problems.

SUMMARY

One aspect of the present disclosure is to provide a spectrometer. The spectrometer includes a plurality of photodetectors, an anti-reflection layer, a grating layer, a distant layer, and a collimator. The anti-reflection layer is disposed on the plurality of photodetectors. The grating layer is disposed above the anti-reflection layer and includes a plurality of grating structures to spread a light into a spectrum to the plurality of photodetectors through the distant layer. The distant layer continuously extends from the grating layer to the anti-reflection layer, the distant layer has a thickness in a range from 400 μm to 2000 μm, and a refractive index of the grating layer is greater than a refractive index of the distant layer. The collimator is disposed above the grating layer, in which the collimator is configured to confine an incident angle of the light from a first micro-lens and increase a coupling efficiency of the light from the grating layer to the plurality of photodetectors.

According to some embodiments of the present disclosure, the collimator includes a pin hole aligned with the plurality of grating structures of the grating layer.

According to some embodiments of the present disclosure, the pin hole has a width in a range from 0.1 μm to 10 μm.

According to some embodiments of the present disclosure, the spectrometer further includes a second micro-lens aligned with the pin hole of the collimator, in which a second light-receiving surface of the second micro-lens is a concave surface.

According to some embodiments of the present disclosure, a projection of the plurality of grating structures on the anti-reflection layer overlaps a portion of the anti-reflection layer and a portion of the plurality of photodetectors.

According to some embodiments of the present disclosure, the spectrometer further includes an absorption layer disposed in the anti-reflection layer, in which the absorption layer is disposed below the grating structures and aside the plurality of photodetectors. The light has a critical angle between the grating layer and the distant layer, and the critical angle is in a range from 22 to 50 degrees. The light includes a second order diffraction light after the light propagates from the collimator and couples in the grating layer, and an incident angle of the second order diffraction light is greater than the critical angle. The light includes a zero order diffraction light and a first order diffraction light after the light couples out from the grating layer and couples in the distant layer, the absorption layer is configured to receive the zero order diffraction light, and the plurality of photodetectors are configured to receive the first order diffraction light.

According to some embodiments of the present disclosure, the anti-reflection layer is a conformal coating on the absorption layer and the plurality of photodetectors.

According to some embodiments of the present disclosure, calculating an optical resolution of the light is based on the following equation:

Δ⁢λΔ⁢L
where Δλ is a wavelength range of the light, ΔL is a length difference between L1and L2, where L1equals T×tan(θ1), L2equals T×tan(θ2), T is the thickness of the distant layer, and θ1and θ2respectively are minimum and maximum emergent angles of the light.

According to some embodiments of the present disclosure, Δλ is in a range from 300 nm to 600 nm, and θ1and θ2ranges from 22.62° to 50.29°.

According to some embodiments of the present disclosure, Δλ is in a range from 500 nm to 900 nm, and θ1and θ2ranges from 22.62° to 43.81°.

According to some embodiments of the present disclosure, Δλ is in a range from 800 nm to 1200 nm, and θ1and θ2ranges from 23.58° to 36.87°.

According to some embodiments of the present disclosure, each of the plurality of grating structures include a binary grating structure, a step grating structure, a blazed grating structure, or a slanted grating structure.

According to some embodiments of the present disclosure, the binary grating structure includes a first vertical sidewall, a second vertical sidewall, and a first top surface. The first vertical sidewall is parallel to the second vertical sidewall, the first vertical sidewall adjoins and is perpendicular to the first top surface, and the second vertical sidewall adjoins and is perpendicular to the first top surface. A height of the binary grating structure is in a range from 0.25 μm to 0.4 μm.

According to some embodiments of the present disclosure, the step grating structure includes a first vertical sidewall, a second vertical sidewall, a third vertical sidewall, a fourth vertical sidewall, a first top surface, a second top surface, and a third top surface. The first vertical sidewall, the second vertical sidewall, the third vertical sidewall, and the fourth vertical sidewall are parallel to each other. The first top surface, the second top surface, and the third top surface adjoin and are perpendicular to the first vertical sidewall, the second vertical sidewall, the third vertical sidewall, and the fourth vertical sidewall.

According to some embodiments of the present disclosure, the blazed grating structure includes an oblique sidewall extending from a top of the blazed grating structure to a bottom of the blazed grating structure, and a width of the blazed grating structure gradually increases from the top of the blazed grating structure to the bottom of the blazed grating structure.

According to some embodiments of the present disclosure, the slanted grating structure includes a first oblique sidewall, a second oblique sidewall, and a top surface adjoining the first oblique sidewall and the second oblique sidewall.

According to some embodiments of the present disclosure, the grating layer further includes a grating substrate between the plurality of grating structures and the distant layer, and the plurality of grating structures protruding from the grating substrate.

According to some embodiments of the present disclosure, the first micro-lens is disposed above the collimator, and a first light-receiving surface of the first micro-lens is a convex surface.

According to some embodiments of the present disclosure, the spectrometer further includes a buffer layer disposed between the first micro-lens and the collimator, and a refractive index of the buffer layer is in a range from 1.5 to 2.2.

According to some embodiments of the present disclosure, the spectrometer further includes a cladding layer disposed between the grating layer and the collimator, wherein the refractive index of the grating layer is greater than a refractive index of the cladding layer, the refractive index of the cladding layer is in a range from 1.5 to 2.2, and the refractive index of the distant layer is in a range from 1.5 to 2.2.

DETAILED DESCRIPTION

As mentioned in the description of related art above, the traditional grating spectrometer may have the disadvantage of having a large size, the interferometer may be limited by the spectral range of light, and the waveguide grating device has the problem of low coupling efficiency of light. The present disclosure provides a spectrometer having miniaturization of a high-resolution grating spectrometer on a chip to solve the above problems. The spectrometer of the present disclosure includes a distant layer having a thickness at least 400 μm, and the spectrometer has the advantages of a miniaturized size, high resolution of the analysis results, readily integrated with complementary metal-oxide-semiconductor (CMOS) electronics, capable of covering a wide spectral range.

Hereinafter, several embodiments of the present invention will be disclosed with the accompanying drawings. Many practical details will be described in the following description for a clear description. However, it should be understood that these practical details should not be used to limit the present invention. That is, in some embodiments of the present invention, these practical details are unnecessary. In addition, in order to simplify the drawings, some conventional structures and elements will be shown in the drawings in a simple schematic manner.

With reference toFIG.1,FIG.1is a cross-sectional view of a spectrometer1000in accordance with some embodiments of the present disclosure. The spectrometer1000includes a plurality of photodetectors1100, an anti-reflection layer1200, a grating layer1300, a distant layer1400, and a collimator1500. The photodetector1100may be a Si photodetector, a Ge photodetector, or an organic photodetector. The plurality of photodetectors1100could be isolated by a plurality of deep trench insulation (DPI), as shown inFIG.1. The anti-reflection layer1200is disposed on the plurality of photodetectors1100. The anti-reflection layer1200is an anti-reflection coating (ARC) film. The anti-reflection layer1200is configured to increase the transmittance of the light L from the distant layer1400to the plurality of photodetectors1100. A refractivity of the anti-reflection layer is less than 15%. The material of the anti-reflection layer1200may include organic multi-film material or inorganic multi-film material, such as SiO2, SiH, or other suitable material. The grating layer1300is disposed above the anti-reflection layer1200and includes a plurality of grating structures1310to spread a light L into a spectrum to the plurality of photodetectors1100through a distant layer1400.

The distant layer1400inFIG.1continuously extends from the grating layer1300(including the plurality of the grating structures1310and the grating substrate1320) to the anti-reflection layer1200. The distant layer1400has a thickness T in a range from 400 μm to 2000 μm, such as 600, 800, 1000, 1200, 1400, 1600, or 1800 μm. If the thickness T of the distant layer1400is less than 400 μm, it may not provide a high resolution of the spectrometer1000. If the thickness T of the distant layer1400is greater than 2000 μm, it may not have the advantage of miniaturization of a high-resolution grating spectrometer on a chip. The distant layer1400having a thickness T at least 400 μm leads to the high-resolution spectrometer1000of the present disclosure. A refractive index of the distant layer1400is in a range from 1.5 to 2.2, such as 1.6, 1.8, or 2.0. The distant layer1400may be made from a low n polymer. A refractive index of the grating layer1300is greater than a refractive index of the distant layer1400. The collimator1500is disposed above the grating layer1300. The collimator1500is configured to confine an incident angle of the light L from a first micro-lens1600assuring the incident angle is around zero and increase a coupling efficiency of the light L from the grating layer1300to the plurality of photodetectors1100. In other words, the collimator1500could revise the light L to increase the coupling efficiency of image pixels.

With reference toFIG.2A,FIG.2Ais a top view of the collimator1500of the spectrometer1000inFIG.1. The collimator1500inFIG.1andFIG.2Aincludes a pin hole1510to confine the incident angle of the light L. The pin hole1510is served as a narrow entrance slit. The incident angle of the light L is in a range from 0 to ±3 degrees, such as 0.5, 1, 1.5, 2, or 2.5 degrees. Preferably, the incident angle of the light L is 0 degree. When the incident angle of the light L is 0 degree, the light L is vertical to a top surface1502of the collimator1500. The pin hole1510of the collimator1500has a width W in a range from 0.1 to 10 μm, such as 0.5, 1, 2, 4, 6, or 8 μm. If the width W is smaller than 0.1 μm, it may not have sufficient amount of light transmitted into the grating layer1300below. If the width W is greater than 10 μm, the incident angle of the light L may be beyond a tolerance value, which leads to unexpected results of the optical resolution of the light L. Although the collimator1500illustrated inFIG.2Ahas three pin holes1510, the number of the pin hole1510is not limited in the present disclosure.

The grating layer1300inFIG.1includes a plurality of grating structures1310. In some embodiments, the grating layer1300includes a grating substrate1320and the plurality of grating structures1310protruding from the grating substrate1320. In other words, in some examples, the grating layer1300may have the grating substrate1320and the grating structures1310on the grating substrate1320, as shown inFIG.1. In other examples, the grating layer1300may not have the grating substrate1320below the grating structures1310(please refer toFIG.9A), depending on the manufacturing process of the spectrometer1000. In the case of the grating layer1300includes the grating substrate1320and the grating structures1310, as shown inFIG.1, the refractive index of the grating structures1310and a refractive index of the grating substrate1320may be the same or different. The refractive index of the grating structures1310and the refractive index of the grating substrate1320are in a range from 1.5 to 3.5, such as 1.8, 2.0, 2.2, 2.5, 2.8, 3.0, or 3.2. The grating structures1310and the grating substrate1320may be made from a high n polymer, such as SiNx, NbOx, TaOx, TiOx, SiHx. The material of the grating structures1310and the grating substrate1320may be the same (please refer toFIG.8E) or different (please refer toFIG.1andFIG.9B). The various grating structures1310of the grating layer1300will be described in detail inFIG.5AtoFIG.5Dbelow.

With reference toFIG.2B,FIG.2Bis a top view of the plurality of grating structures1310of the spectrometer1000inFIG.1. As shown inFIG.1,FIG.2A, andFIG.2B, the pin holes1510of the collimator1500are aligned with the grating structures1310of the grating layer1300. The vertical layout of the pin holes1510of the collimator1500could prevent T−1diffraction light and/or high order diffraction light from propagating into the grating layer1300below the collimator1500. Similarly, the vertical layout of the grating structures1310could prevent T−1diffraction light and/or high order diffraction light from propagating into the distant layer1400below the grating structures1310.

Still refer toFIG.1, the first micro-lens1600of the spectrometer1000is disposed above the collimator1500, and a first light-receiving surface1602of the first micro-lens1600is a convex surface. Specifically, the first micro-lens1600refracts and converges external light to the internal of the spectrometer1000.

As shown inFIG.1, the spectrometer1000further includes a buffer layer1700, a cladding layer1800, and an absorption layer1900. The buffer layer1700is disposed between the first micro-lens1600and the collimator1500. A refractive index of the buffer layer1700is in a range from 1.5 to 2.2, such as 1.6, 1.8, or 2.0. The material of the buffer layer1700may be an organic material or inorganic material. The light transmittance of the buffer layer1700is greater than 80%. The cladding layer1800is disposed between the collimator1500and the grating layer1300. Specifically, the cladding layer1800is disposed on the grating layer1300. The refractive index of the grating layer1300is greater than a refractive index of the cladding layer1800. In some embodiments, the refractive index of the grating structures1310of the grating layer1300is greater than the refractive index of the cladding layer1800. In some embodiments, the refractive index of the cladding layer1800is in a range from 1.5 to 2.2, such as 1.6, 1.8, or 2.0.

The absorption layer1900inFIG.1is disposed in the anti-reflection layer1200and is disposed under the grating structures1310. The absorption layer1900is disposed aside the plurality of photodetectors1100. The absorption layer1900is configured to absorb a zero order (T0) diffraction light, thereby avoiding T0diffraction light passing to the plurality of photodetectors1100. The T0diffraction light herein is optical noise. The absorption coefficient K of the absorption layer1900is greater than 0.1. In some embodiments, the anti-reflection layer1200is a conformal coating on the absorption layer1900and the plurality of photodetectors1100, and so a thickness of a first portion1200aof the anti-reflection layer1200over the plurality of photodetectors1100is substantially the same as a thickness of a second portion1200bof the anti-reflection layer1200over the absorption layer1900. The absorption layer1900may be made from metal or other absorption material.

With reference toFIG.3,FIG.3is a partial view of the grating layer1300, the distant layer1400, the collimator1500, and the cladding layer1800of the spectrometer1000inFIG.1. After the light L passes through the pin hole1510of the collimator1500, the light L passes through the cladding layer1800and propagates from the grating structures1310and the grating substrate1320of the grating layer1300into the distant layer1400. The light L has a critical angle θcbetween the grating substrate1320and the distant layer1400. Specifically, if the incident angle θT1of a first order (T1) diffraction light is less than the critical angle θc, the light L will transmit into the distant layer1400. If the incident angle θT1of T1diffraction light is greater than the critical angle θc, the light L will occur total internal reflection (TIR) at the interface between the grating substrate1320and the distant layer1400. The T1diffraction light is the light that could be received by the plurality of photodetectors1100(please refer toFIG.1). As shown inFIG.3, an incident angle θT2of a second order (T2) diffraction light is greater than the critical angle θc, so that the T2diffraction light will occur TIR to filter out the T2diffraction light. In some embodiments, the critical angle θcis in a range from 22 to 50 degrees, for example, 22.62 to 50 degrees. In some embodiments, the refractive index of the grating structures1310is greater than the refractive index of the distant layer1400. The more the difference between the refractive index of the grating structures1310and the refractive index of the distant layer1400, the coupling efficiency of the grating structures1310to the distant layer1400would be better.

With reference toFIG.4,FIG.4is a partial view of the distant layer1400of the spectrometer1000inFIG.1after the light L transmits from the grating layer1300into the distant layer1400. Specifically, calculating an optical resolution of the light L is based on the following equation:

Δ⁢λΔ⁢L
where Δλ is a wavelength range of the light L, ΔL is a length difference between a length L1and a length L2. The length L1equals T×tan(θ1), the length L2equals T×tan(θ2), the thickness T is a thickness of the distant layer1400, and a emergent angle (diffraction angle) θ1and a emergent angle (diffraction angle) θ2respectively are minimum and maximum emergent angles of the light L. More specifically, a range that the length difference between the length L1and the length L2could be received by the light L spreading into a spectrum to the plurality of photodetectors1100.

For example, please refer toFIG.4, the optical resolution of the light L having a wavelength in a range from 300 nm to 600 nm when the thickness T of the distant layer1400is 400 μm (T=400 μm), where the emergent angle θ1=50.29° and the emergent angle θ2=22.62°. The optical resolution

(Δ⁢λΔ⁢L)
of the spectrometer1000would be obtained by the dispersion in nm/pixel. Length L1=400 μm×tan(50°)=476 μm, length L2=400 μm×tan(22.62°)=166 μm, and length difference L1−L2=476 μm−166 μm=310 μm. The optical resolution at wavelengths from 300 nm to 600 nm would be about

6⁢0⁢0-300⁢(nm)4⁢7⁢6-166⁢(μm)=0.97(nmμm).
With the similar calculation method mentioned above, the light L having a wavelength in a range from 500 nm to 900 nm and the thickness T of the distant layer1400is 400 μm, the optical resolution would be about

1.83(nmμm)
The light L having a wavelength in a range from 800 nm to 1200 nm, the optical resolution would be about

It can be seen from Table 1 below. Table 1 shows examples of the optical resolutions of the light L in various wavelength ranges and various thicknesses T of the distant layer1400. In some embodiments, the thickness T of the distant layer1400in a range from 400 μm to 2000 μm. In some embodiments, Δλ is in a range from 300 nm to 600 nm, θ1and θ2ranges from 22.62° to 50.29°, and the resulted optical resolution of the light L is in a range from 0.317 nm/μm to 0.97 nm/μm. In some embodiments, Δλ is in a range from 500 nm to 900 nm, θ1and θ2ranges from 22.62° to 43.81°, and the resulted optical resolution of the light L is in a range from 0.61 nm/μm to 1.83 nm/μm. In some embodiments, Δλ is in a range from 800 nm to 1200 nm, θ1and θ2ranges from 23.58° to 36.87°, and the resulted optical resolution of the light L is in a range from 1.06 nm/μm to 3.2 nm/μm.

With reference toFIG.5AtoFIG.5D,FIG.5AtoFIG.5Dare enlargement views of various grating structures1310of the grating layer1300of the spectrometer1000inFIG.1. As shown inFIG.5A, the binary grating structure1310aincludes a first vertical sidewall SW1, a second vertical sidewall SW2, and a first top surface S1. The first vertical sidewall SW1is substantially parallel to the second vertical sidewall SW2, the first vertical sidewall SW1is substantially perpendicular to the first top surface S1, and the second vertical sidewall SW2is substantially perpendicular to the first top surface S1. The binary grating structure1310ahas a width W, a height H, and a period P, in which the period P is defined by a distance between two binary grating structures1310a. In some embodiments, the period P is in a range from 0.25 to 0.4 μm, such as 0.3, or 0.35 μm. In some embodiments, the height H is in a range from 0.25 to 0.4 μm, such as 0.3 μm. In some embodiments, a fill factor (FF=width/period) is in a range from 0.4 to 0.6, such as 0.45, 0.5, or 0.55. In some embodiments, the binary grating structures1310ainclude different periods P, but have the same height H.

As shown inFIG.5B, the step grating structure1310bincludes a third vertical sidewall SW3, a fourth vertical sidewall SW4, a fifth vertical sidewall SW5, a sixth vertical sidewall SW6, a second top surface S2, a third top surface S3, and a fourth top surface S4. The third vertical sidewall SW3, the fourth vertical sidewall SW4, the fifth vertical sidewall SW5, and the sixth vertical sidewall SW6are substantially parallel to each other. The second top surface S2, the third top surface S3, and the fourth top surface S4are substantially perpendicular to the fourth vertical sidewall SW4, the fifth vertical sidewall SW5, and the sixth vertical sidewall SW6. In some embodiments, a step number of the step grating structures1310bis greater than 3. In some embodiments, the step grating structures1310binclude different periods P, but have the same height H. As shown inFIG.5C, the blazed grating structure1310cincludes a seventh vertical sidewall SW7and an eighth sidewall SW8. The eighth sidewall SW8is an inclined sidewall. The seventh vertical sidewall SW7and the eighth sidewall SW8form an angle. In some embodiments, the blazed grating structures1310cinclude different periods P, but have the same height H.

As shown inFIG.5D, the slanted grating structure1310dincludes a ninth sidewall SW9, a tenth sidewall SW10, and a fifth top surface S5. The ninth sidewall SW9and the tenth sidewall SW10are inclined sidewalls. The slanted grating structure1310dhas a height H. In some embodiments, the height H is 0.5 μm. The fifth top surface S5connects to the ninth sidewall SW9and the tenth sidewall SW10. With reference toFIG.6,FIG.6is an enlargement view of the slanted grating structure1310dof the spectrometer1000inFIG.1. The slanted grating structure1310dis defined by the ninth sidewall SW9, the tenth sidewall SW10, and the fifth top surface S5. The ninth sidewall SW9, the tenth sidewall SW10, and the fifth top surface S5are defined by a bottom left point BL, a bottom right point BR, an upper left point UL, and an upper right point UR. The ninth sidewall SW9and a surface1322of the slanted grating structure1310dforms a bottom angle BA, and the tenth sidewall SW10and the surface1322of the slanted grating structure1310dforms a front angle FA. In some embodiments, the coupling efficiency of the slanted grating structure1310dis between 60% and 90% in the T1diffraction light and a spectral range of 300˜600 nm with the optical resolution of

0.97(nmμm)
for the distant layer1400having the thickness T of 400 μm. In some embodiments, the slanted grating structures1310dinclude different periods P, but have the same slanted angles (such as the bottom angle BA and front angle FA).

Each of the grating structures1310includes the binary grating structure1310a, the step grating structure1310b, the blazed grating structure1310c, or the slanted grating structure1310d. In other words, the grating structures1310illustrated inFIG.1could be substituted by the grating structures1310a-1310dillustrated inFIG.5AtoFIG.5D. It is understood that the higher the order of the diffraction light, the greater the diffraction angle. Therefore, the high order of the diffraction light (such as T2diffraction light, T3diffraction light, and so on) would be filtered by changing the width W, the height H, and/or the period P of the grating structures1310. In some embodiments, the light L having a wavelength in a range from 300 nm to 600 nm diffracts into the distant layer1400when the grating structures1310have a period around 0.4 μm±0.01 μm. In some embodiments, the light L having a wavelength in a range from 500 nm to 900 nm diffracts into the distant layer1400when the grating structures1310have a period around 0.65 μm±0.01 μm. In some embodiments, the light L having a wavelength in a range from 800 nm to 1200 nm diffracts into the distant layer1400when the grating structures1310have a period around 0.9 μm±0.01 μm. In some embodiments, the thickness T of the distant layer1400could be adjusted by the incident angle θT1of T1diffraction light transmitted out from the grating substrate1320.

Although each of the grating structures1310a-1310dillustrated inFIG.5AtoFIG.5Dhas three grating structures1310a-1310d, the number of the grating structures1310a-1310dis not limited in the present disclosure. In addition, the grating structures1310a-1310dcould be mirror structures in a lateral symmetry ofFIG.5AtoFIG.5D. In some embodiments, the grating structures1310(including the binary grating structure1310a, the step grating structure1310b, the blazed grating structure1310c, or the slanted grating structure1310d) could include multiple periods for multiple wavelength regions. The wavelength regions may cover 300 nm to 1200 nm. Therefore, the spectrometer1000of the present disclosure could cover a wide spectral range.

With reference toFIG.7,FIG.7is a cross-sectional view of a spectrometer1000ain accordance with other embodiments of the present disclosure. Specifically, the spectrometer1000inFIG.1further includes a second micro-lens1610to form the spectrometer1000ainFIG.7. With similar features being labeled by similar numerical references, and descriptions of the similar features are not repeated herein. The second micro-lens1610is configured to confine the incident angle of the light L and increase the light L entering into the grating structures1310. The incident angle of the light L is in a range between 0 and ±3 degrees, such as 0.5, 1, 1.5, 2, or 2.5 degrees. Preferably, the incident angle of the light L is 0 degree. The second micro-lens1610is aligned with the pin hole1510of the collimator1500, and a second light-receiving surface1612of the second micro-lens1610is a concave surface. Please refer toFIG.2A,FIG.2B, andFIG.7, it is understood that the plurality of the pin holes1510of the collimator1500, the plurality of the second micro-lens1610above the collimator1500, and the grating structures1310are aligned with each other.

FIG.8AtoFIG.8Eare cross-sectional views of various stages of manufacturing a spectrometer in accordance with some embodiments of the present disclosure. It is understood that additional operations can be provided before, during, and after processes shown byFIG.8AtoFIG.8E, and some of the operations described below can be replaced or eliminated, for additional embodiments of the process. The order of the operations/processes may be interchangeable.

As shown inFIG.8A, a substrate2000is provided, and the anti-reflection layer1200is deposited on the substrate2000. The substrate2000could include the plurality of photodetectors1100and the plurality of deep trench insulation (DPI) between the photodetectors1100. The anti-reflection layer1200could be formed by depositing multiple films of anti-reflection material, and the deposition method could be physical vapor deposition (PVD). As shown inFIG.8B, the distant layer1400is taped on the anti-reflection layer1200. As shown inFIG.8C, the grating layer1300(including the grating structures1310and the grating substrate1320) is disposed on the distant layer1400. Specifically, the grating layer1300inFIG.8Chas undergone coating, exposure, development, and etching processes. As shown inFIG.8D, the cladding layer1800is disposed on the grating layer1300. Specifically, the cladding layer1800inFIG.8Dhas undergone coating and backing processes. As shown inFIG.8E, the collimator1500with the pin hole1510aligned with the grating structures1310is disposed on the cladding layer1800. Specifically, the collimator1500inFIG.8Ehas undergone coating, exposure, and development processes. It is noticed that the grating structures1310and the grating substrate1320of the grating layer1300inFIG.8Eare formed by the same material.

FIG.9AandFIG.9Bare cross-sectional views of other examples of spectrometers in accordance with some embodiments of the present disclosure. Specifically, inFIG.9A, the grating substrate1320has been completely removed, thereby remaining the grating structures1310on the distant layer1400. InFIG.9B, the grating structures1310and the grating substrate1320of the grating layer1300are formed by different material.

The spectrometer of the present disclosure includes a distant layer having a thickness at least 400 μm, and the spectrometer has the advantages of a miniaturized size, high resolution of the analysis results, readily integrated with complementary metal-oxide-semiconductor (CMOS) electronics, capable of covering a wide spectral range.