Optical apparatus

Abstract

The invention relates to an optical device. An optical apparatus, such as an imager, includes the following structures in order: a support having a through hole formed therein; a first electrode; an active layer capable of absorbing photons and converting the photons into electron-hole pairs; a second electrode; a conductive layer connecting the second electrode to one of the vias; and a microlens matrix. The device also includes an encapsulation layer disposed between the microlens matrix and the active layer. The encapsulation layer includes a first portion having a first density and a second portion having a second density. The first portion of the encapsulation layer is disposed between the active layer and the second portion of the encapsulation layer. The first density is lower than the second density.

Description

[0001] Priority claim

[0002] This application claims the benefit of priority of French patent application No. 2401385, filed on February 13, 2024, the contents of which are incorporated herein by reference in their entirety to the maximum extent permitted by law. Technical Field

[0003] The present description generally relates to optical devices, such as image acquisition devices or image sensors. More specifically, the present description relates to optical devices including pixels and microlenses. Background Art

[0004] Optical devices such as imagers include microlenses that focus light onto an active layer (also known as a quantum film (QF)), which converts photons into electron-hole pairs. An antireflection layer is placed between the microlens and the active layer. The antireflection layer also serves as a protective layer for the active layer.

[0005] A top electrode for collecting holes and a bottom electrode for collecting electrons are arranged on either side of the active layer. The top electrode contacts the upper portion of the active layer and is offset from a through-hole (called a built-in pad (BIP)) located in the substrate via a conductive layer, such as aluminum. To enable contact with the second electrode (called a contact on photodiode (CTPD)), an opening is formed in the antireflection layer.

[0006] Therefore, when the image acquisition device is exposed to radiation of a suitable wavelength (e.g., shortwave infrared (SWIR)), photons pass through the microlens and antireflection layer and penetrate the active layer. Electrons and holes are then generated. Electrons are guided through the vias and directed to the device's nodes (in other words, to the active area of the circuit). Holes are collected by the top electrode and guided through the conductive layer to the via (BIP).

[0007] To ensure the reliability of electronic components and achieve a quantum efficiency (QE) of more than 50% in the active layer, optical devices must meet multiple criteria: temperature resistance, humidity resistance, etc.

[0008] However, in current optical devices, oxidation of the active layer may occur due to their circuit manufacturing process or reliability testing (exposure to humidity).

[0009] On the one hand, it is observed that current antireflection coatings are not sufficiently effective in preventing oxidation of the active layer.

[0010] On the other hand, the conductive aluminum layer that enables the contacting can contain defects, particularly pits, resulting from its manufacturing process. These defects lead to a certain permeability in the aluminum layer, which can cause problems during structuring, particularly by wet etching. Indeed, the chemicals used to clean the photoresist resin can penetrate the aluminum layer and contaminate the active layer, particularly in the area where the second electrode makes contact, such as the contact to the photodiode (CTPD).

[0011] Exposure of the active layer to air, water, and / or other oxidizing agents causes its performance to degrade, and it may be difficult or even impossible to achieve an active layer quantum efficiency greater than 50%.

[0012] There is a need to improve the performance of optical devices, particularly to prevent oxidation of active layers. Summary of the Invention

[0013] Improvements are achieved by an optical device, such as an imager, comprising, in order: a support having a through-hole formed therein; a first electrode; an active layer capable of absorbing photons and converting them into electron-hole pairs; a second electrode; a conductive layer connecting the second electrode to one of the through-holes; and a microlens matrix. The device also includes an encapsulation layer disposed between the microlens matrix and the active layer, the encapsulation layer comprising a first portion having a first density and a second portion having a second density, the first portion of the encapsulation layer being disposed between the active layer and the second portion of the encapsulation layer, the first density being lower than the second density.

[0014] According to an embodiment, the encapsulation layer is based on silicon oxide.

[0015] According to an embodiment, the encapsulation layer is arranged between the active layer and the conductive layer.

[0016] According to an embodiment, the encapsulation layer covers side surfaces and a portion of the upper surface of the active layer.

[0017] According to an embodiment, the encapsulation layer is arranged between and in contact with two metal nitride layers, the metal nitride preferably being silicon nitride.

[0018] According to an embodiment, the encapsulation layer is arranged between the electrically conductive layer and the microlens matrix.

[0019] According to an embodiment, the encapsulation layer is covered by a metal nitride layer, preferably silicon nitride.

[0020] According to an embodiment, the device comprises two encapsulation layers, wherein one encapsulation layer is arranged between the active layer and the conductive layer, and another encapsulation layer is arranged between the conductive layer and the microlens matrix.

[0021] According to an embodiment, the conductive layer is made of aluminum.

[0022] According to an embodiment, the first density is between 2.05 g / cm 3 and 2.13g / cm 3 between, for example, 2.09 g / cm 3 , and / or a second density between 2.20 g / cm 3 and 2.28g / cm 3 between, for example, 2.24 g / cm 3 .

[0023] According to an embodiment, the first portion of the encapsulation layer has a thickness between 50 and 250 nm and / or wherein the second portion of the encapsulation layer has a thickness between 3 and 50 nm.

[0024] This is also achieved by a method for manufacturing an optical device according to the present invention. The method comprises forming an encapsulation layer according to the following steps: depositing a first precursor at a first deposition rate to form a first portion of the encapsulation layer having a first density; depositing a second precursor at a second deposition rate to form a second portion of the encapsulation layer having a second density; the first deposition rate being greater than the second deposition rate, whereby the first density is less than the second density.

[0025] According to an embodiment, the first portion of the encapsulation layer and the second portion of the encapsulation layer are deposited by PECVD at a temperature less than or equal to 150°C.

[0026] According to an embodiment, the first precursor and the second precursor are silicon oxide precursors, preferably silicon alkoxides, more preferably TEOS.

[0027] According to an embodiment, the first deposition rate is at least 5 times greater than the second deposition rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The foregoing features and advantages, as well as other features and advantages, will be described in detail in the following description of specific embodiments given by way of illustration and not limitation, with reference to the accompanying drawings, in which:

[0029] Figure 1A shows a schematic cross section of an optical device;

[0030] Figure 1B shows a schematic cross section of an optical device;

[0031] Figure 1C shows a schematic cross section of an optical device;

[0032] Figure 2is a graph showing the variation in water content (in mg) over time for different layers: a SiON layer annealed at 300°C, a SiON layer annealed at 400°C, a 100 nm thick SiO2 layer deposited from TEOS at a low rate (referred to as TEOS low deposition rate (TEOS LDR)) and annealed at 400°C, a 142 nm thick SiO2 layer deposited by PECVD, and a 200 nm thick SiO2 layer;

[0033] Figure 3 is a graph showing tensile stress over time for a SiO2 layer;

[0034] Figure 4 is a graph showing changes in compressive stress over time for a SiON layer;

[0035] Figure 5 is a scanning electron microscope (SEM) image of a portion of an active layer, one side of which is sequentially covered by a SiN layer and then by a SiO2 layer; and

[0036] Figure 6 is a transmission electron microscopy (TEM-EDX) image of the BIP region of the optical device. DETAILED DESCRIPTION

[0037] Similar features are denoted by similar reference numerals in the various drawings. In particular, common structural and / or functional features between various embodiments may have the same reference numerals and may be arranged with the same structure, dimensions, and material properties.

[0038] For clarity, only operations and elements that are useful for understanding the embodiments described herein are illustrated and described in detail.

[0039] Unless otherwise stated, when two elements are referred to as being connected together, this means a direct connection without any intervening elements other than conductors, and when two elements are referred to as being coupled together, this means the two elements may be connected or they may be coupled via one or more other elements.

[0040] In the following disclosure, unless otherwise stated, when referring to absolute position qualifiers such as terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers such as terms "above", "below", "higher", "lower", etc., or orientation qualifiers such as "horizontal", "vertical", etc., reference is made to the orientation shown in the figures.

[0041] Unless otherwise indicated, the expressions "about," "approximately," "substantially," and "around" mean within 10%, and preferably within 5%.

[0042] Unless otherwise stated, values between X and Y mean that the endpoints X and Y are included in the range.

[0043] In the remainder of this description, unless stated otherwise, a layer or film is considered to be opaque to radiation when the transmittance of radiation through the layer or film is less than 30% and preferably less than 10%.

[0044] In the remainder of this description, a layer or film is considered transparent to radiation when the transmittance of radiation through the layer or film is greater than 50% and preferably greater than 70%.

[0045] Optical device embodiments will now be described with respect to an optical device comprising an array of micron-scale optical elements, wherein each micron-scale optical element corresponds to a micron-scale lens or microlens consisting of two diopters. However, it will be clear that these embodiments can also be implemented using other types of micron-scale optical elements, wherein each micron-scale optical element corresponds to, for example, a micron-scale Fresnel lens, a micron-scale gradient index lens, or a micron-scale diffraction grating.

[0046] The optical device may be an image acquisition device operating in the near infrared (NIR), i.e. for electromagnetic radiation with a wavelength between 800 nm and 2500 nm, and more particularly an image acquisition device operating in the short infrared (SWIR), i.e. for electromagnetic radiation with a wavelength between 800 nm and 2000 nm, preferably between 900 nm and 1700 nm, typically 1.4 µm.

[0047] The optical device may be an optical sensor, in particular a proximity sensor.

[0048] This is a device in which the photodiode is arranged above the integrated circuit (called an above-IC photodiode arrangement).

[0049] Optical devices are used in a wide range of applications, including the automotive market (e.g., fog sensors) and the telephony market (smartphones).

[0050] Now we will refer to Figure 1A 、 Figure 1B and Figure 1C The image acquisition system is described in more detail.

[0051] The device includes a support 10 with a through-hole 12 formed therein. Through-hole 12 is filled with a conductive material, such as copper. Support 10 may include a stack of insulating layers (not shown) and conductive tracks (not shown) between the insulating layers. The stack is preferably approximately 2µm thick. Through-hole 12 may be 3.2µm deep.

[0052] The substrate 10 is covered by an active layer 20. The active layer 20 converts photons received from the top of the device into electron / hole pairs.

[0053] The active layer 20 includes a first surface (bottom surface) partially in contact with the substrate 10 , a second surface (top surface), and lateral surfaces.

[0054] The active layer 20 is preferably made of a semiconductor material such as silicon.

[0055] Electronic components are formed beneath the vias (“viatops”). These components may be insulated-gate field-effect transistors or MOS transistors (“metal oxide semiconductor”), in particular manufactured using CMOS technology (“complementary metal oxide semiconductor”), and / or photodetectors.

[0056] The active layer 20 has a thickness of, for example, approximately 0.4 μm to 1 μm.

[0057] The active layer 20 is disposed between the first electrode 32 and the second electrode 34 .

[0058] The first electrode 32 collects, for example, electrons, and the second electrode 34 collects, for example, holes.

[0059] The first electrode 32 (or bottom electrode) is in contact with the first surface of the active layer 20 and the substrate 10 .

[0060] The first electrode 32 is made of metal, for example.

[0061] The first electrode 32 is, for example, in the form of a conductive stud.

[0062] The first electrode 32 is connected to the through hole 12 of the substrate 10 .

[0063] The second electrode 34 (or top electrode) preferably completely covers the second side of the active layer 20 .

[0064] The second electrode 34 has, for example, a double-layer or triple-layer (or triple-layer) structure and has a thickness of, for example, 40 to 60 nm.

[0065] The second electrode 34 is connected to one of the through-holes 12 (referred to as a built-in pad (BIP)) positioned in the substrate 10 via a conductive layer 35 that allows contact offset.

[0066] The conductive layer contacts the second electrode 34 in an area referred to as the contact on the photodiode (CTPD).

[0067] In order to enable contacting on the second electrode (contact on photodiode (CTPD)), an opening is formed in the antireflection coating covering the second electrode 34 .

[0068] As we will see later, the antireflection coating may also serve as a protective layer for the active layer 20 .

[0069] The device further comprises a planarisation layer 60 covering the anti-reflective coating. Preferably this is a resin layer.

[0070] An array of micron-sized lenses 70 (or a microlens matrix) covers the planarization layer 60. The lenses are formed, for example, by elements having a convex surface and a flat surface. The flat surfaces of the microlenses are preferably located on top of the resin layer and in contact with the resin layer.

[0071] An array of microlenses 70 focuses the radiation onto the pixels.

[0072] The array of microlenses 70 is preferably arranged in a matrix, with the optical axis of each microlens coinciding with the center of the resin block. The microlenses are, for example, made of organic resin. The microlenses are preferably transparent at the wavelength of interest.

[0073] In one embodiment, the microlenses are identical, ie, they have the same chemical composition and the same dimensions. Alternatively, the microlenses may not have the same dimensions.

[0074] The device may include a protective layer 71 covering the microlens 70. The protective layer 71 may be made of an inorganic material such as silicon oxide (SiO2) or silicon oxynitride (SiON). In one embodiment, the protective layer is substantially impermeable to moisture. For example, the protective layer has a thickness between 100 nm and 600 nm.

[0075] The device may include a resin layer 80, referred to as black resin, which strongly absorbs incident light of interest at wavelengths. Black resin 80 is also known as logical light blocking (LOBO) resin. Black resin 80 covers a portion of the microlens, while other portions are uncovered. Resin layer 80 may be protected by a protective layer 81. Protective layer 81 may be made of an inorganic material such as silicon oxide (SiO2) or silicon oxynitride (SiON). In one embodiment, the protective layer is substantially impermeable to moisture. For example, the protective layer has a thickness between 100 nm and 600 nm.

[0076] The device further includes at least one encapsulation layer 50, 55 disposed between the active layer 20 and the matrix of microlenses 70. The encapsulation layers 50, 55 may be SiO2 or SiON layers. Preferably, the encapsulation layers 50, 55 are made of SiO2. Typically, each encapsulation layer 50, 55 is made of a single (dielectric) material.

[0077] Each encapsulation layer 50, 55 comprises two sections (or portions): a first section (lower section) having a first density and a second section (upper section) having a second density. Because the first and second sections form part of the encapsulation material itself, they are each made of the same (dielectric) material. The first section is positioned between the active layer and the second section. In other words, the first section is positioned on the underside of the device, opposite the active layer 20, and the second section is positioned on the upper side of the device, opposite the matrix of microlenses 70.

[0078] The first density is lower than the second density.

[0079] For example, the first density (i.e., the density of the lower portion) is 2.05 g / cm 3 and 2.13g / cm 3 between and / or the second density (i.e., the upper density) at 2.20 g / cm 3 and 2.28g / cm 3 For example, for an encapsulation layer made of SiO2, the first density may be 2.09 g / cm 3 And / or the second density may be 2.24 g / cm 3 .

[0080] The upper part forms a dense layer (or hard shell) that encapsulates the lower part.

[0081] The second portion has a thickness of, for example, between 3 and 50 nm, preferably between 10 and 50 nm, and even more preferably between 10 and 30 nm, such as around 20 nm.

[0082] The thickness of the first portion is greater than the thickness of the second portion. The thickness of the first portion is for example between 50 and 250 nm, preferably between 150 and 250 nm, even more preferably between 180 and 230 nm, for example around 210 nm.

[0083] For example, the first portion has a refractive index between 1.43 and 1.45 (for a wavelength of 633 nm).For example, the second portion has a refractive index between 1.47 and 1.48 (for a wavelength of 633 nm).

[0084] exist Figure 1A In the first embodiment shown in , the encapsulation layer 50 is positioned between the active layer 20 and the conductive contact layer 35 .

[0085] The encapsulation layer 50 covers the top electrode 34 and the active layer 20 and protects the sides of the active layer 20. It may also cover a portion of the substrate 10.

[0086] In this first embodiment, the encapsulation layer 50 also acts as an antireflection layer.

[0087] In such Figure 1B In the second embodiment shown in , the encapsulation layer 55 is positioned between the conductive contact layer 35 and the matrix of microlenses 70. More specifically, it is in contact with the conductive layer 35. Preferably, it completely covers the conductive layer 35. This protects not only the PTCD area, but also the BIP area.

[0088] In such Figure 1C In a third embodiment shown in , the device may comprise two encapsulation layers 50 , 55 : a first encapsulation layer 50 is positioned between the active layer 20 and the conductive layer 35 , and a second encapsulation layer 55 is positioned between the conductive layer 35 and the matrix of microlenses 70 .

[0089] The device may also include one or more metal nitride layers 51, 52, 56. For example, the encapsulation layer 50 may be between two metal nitride layers (e.g., Figure 1A and Figure 1C and 52), and the encapsulation layer 55 may be formed with a metal nitride layer (e.g., Figure 1B and Figure 1C Assembling the packaging layer and the metal nitride layer(s) forms a packaging component.

[0090] The metal nitride is preferably silicon nitride.Each metal nitride layer 51 , 52, 56 has a thickness of, for example, between 300 and 400 nm, preferably between 350 nm and 380 nm.

[0091] In particular, the encapsulation element can be a double layer (e.g., SiO2 / SiN) or a triple layer (SiN / SiO2 / SiN). A double layer is advantageous when the encapsulation layer is located between the conductive layer 35 and the matrix of microlenses 70. A triple layer is advantageous when the encapsulation layer is located between the active layer 20 and the conductive layer 35. The triple layer can function not only as an encapsulation element but also as an anti-reflection element.

[0092] The encapsulating element has, for example, a total thickness between 30 nm and 200 nm, preferably between 40 nm and 130 nm, and more preferably about 40 nm. The thickness of the resulting encapsulating element (double or triple layer) will depend, in particular, on its location. The thickness of the encapsulating element is advantageously adapted so that the layer is transparent in the visible range.

[0093] In particular, we will describe the fabrication of the encapsulation layers 50, 55 of the device.

[0094] The encapsulation layer 50 , 55 is formed according to the following steps: deposition of a first portion of the encapsulation layer 50 , 55 ; and deposition of a second portion of the encapsulation layer 50 , 55 on the first portion of the encapsulation layer 50 , 55 .

[0095] The first portion of the encapsulation layer 50 , 55 and the second portion of the encapsulation layer 50 , 55 are preferably deposited using a plasma assisted chemical vapor deposition (PECVD) technique.

[0096] In order to form each encapsulation layer 50, 55 with a different density, the respective first and second portions of the encapsulation layer are formed at different deposition rates.

[0097] The first portion is formed at a first deposition rate and the second portion is formed at a second deposition rate. The first deposition rate is higher than the second deposition rate. The first deposition rate is at least five times the second deposition rate. For example, the first deposition rate is approximately ten times the second deposition rate.

[0098] For example, in PECVD deposition, the deposition rate can be modified by adjusting one or more of the following parameters: the power of the high frequency, the use of the low frequency (in addition to the high frequency), and / or the heating temperature.

[0099] A first precursor may be used to form a first portion of the encapsulation layer 50, 55, and a second precursor may be used to form a second portion of both the encapsulation layers 50, 55. Preferably, the first and second portions of the encapsulation layers 50, 55 are deposited using the same precursor.

[0100] The encapsulation layers 50, 55 are preferably deposited at a temperature of 150° C. or lower. Advantageously, they are carried out at a temperature higher than 100° C. Even more preferably, they are carried out at a temperature between 120° C. and 150° C.

[0101] The layers 50 , 55 deposited in this way have very good consistency, which ensures better protection of the underlying pixels, in particular with regard to sealing, thereby avoiding oxidation phenomena.

[0102] Preferably, the encapsulation layers 50, 55 are made of SiO2, and the precursor is a silicon oxide precursor, such as silicon alkoxide.

[0103] The first portion of the silicon oxide encapsulation layer 50, 55 may be deposited from a plasma comprising the first silicon alkoxide, preferably from a plasma comprising the first silicon alkoxide, oxygen, and helium.

[0104] The second portion of the silicon oxide encapsulation layer 50, 55 can be deposited by plasma including the second silicon alkoxide. Preferably, it is deposited by plasma including the second silicon alkoxide, oxygen, and helium.

[0105] The first and second silicon alkoxides are preferably silicon alkoxides having all hydrolyzable functional groups. The use of compounds having hydrolyzable functional groups results in a layer made of silicon oxide. In particular, the silicon alkoxide has the formula (R1O)(R2O)Si(OR3)(OR4), where R1, R2, R3, and R4 are linear alkyl chains, preferably C1 to C5 linear alkyl chains. Preferably, R1, R2, R3, and R4 are identical.

[0106] The first and second silicon alkoxides are preferably the same.The first and second silicon alkoxides are preferably tetraethyl orthosilicate (TEOS).

[0107] Other layers of the package component may be deposited by chemical vapor deposition (CVD), such as low pressure chemical vapor deposition (LPCVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or PECVD.

[0108] The various layers of the package component are preferably deposited at a temperature of 150° C. or lower.

[0109] Over the entire board, ie over the entire structure, a layer is formed.

[0110] A description of illustrative and non-limiting examples of embodiments is now provided.

[0111] In order to demonstrate the performance improvements resulting from the presence of the encapsulation layers 50, 55 within the optical device, comparative moisture and / or temperature resistance tests were performed on different devices or structures.

[0112] In the first test, the watertightness of different layers was tested: a SiON layer annealed at 300°C and 400°C, a SiO2 layer obtained from TEOS LDR (TEOS Low Deposition Rate) and annealed at 400°C, and two SiO2 layers of 142nm and 200nm obtained from TEOS deposited by PECVD. In each case, the layers were formed on a silicon substrate. The curves clearly show that the SiON layer is permeable to water, while the SiO2 layer is hermetically sealed ( Figure 3 ). Unlike the SiON layer, the SiO2 layer does not absorb water significantly even after 600 hours.

[0113] The SiO2 layer obtained by PECVD deposition of TEOS ( Figure 3 ) and SiON layer annealed at 150°C ( Figure 4 ) performed mechanical testing.

[0114] These values are obtained based on Stoney's formula, which establishes the relationship between the radius of curvature, stress, and the thickness of the layer and substrate.

[0115] Since the SiO2 layer is completely waterproof and does not absorb moisture, unlike the SiON layer, there is no significant change in stress after 600 hours.

[0116] Figure 5 An SEM image of a device showing the first layer of an antireflective element deposited on it: a SiN layer and a SiO2 layer obtained by PECVD deposition of TEOS at 150°C. The deposition is uniform: the thickness variation on the sides and above the electrodes is less than 10%. The SiO2 layer provides uniform protection at all points: not only the top of the structure is protected, but also the sides.

[0117] To test their heat and humidity resistance, two devices underwent highly accelerated stress testing (HAST). In a specific embodiment, one device had a SiN / SiON / SiN antireflection element, and the other had a SiN / SiO2 / SiN antireflection element. The HAST test involved exposing the devices to a temperature of approximately 110°C and 85% relative humidity for 60 hours, and then to a pressurized enclosure at 2 atm for 144 hours. The devices were then subjected to several characterizations. The device with the SiN / SiO2 / SiN antireflection element demonstrated improved BIP resistance, better post-lithography BIP definition, better dark current, and better mechanical stability.

[0118] Finally, the BIP region of the device obtained according to a specific embodiment was observed by MET-EDX. The metal layer 35 made of aluminum is in turn covered by an encapsulation layer 55 made of SiO2 (as described above) and by a SiN layer 56. The SiO2 layer is clearly visible and conformal ( Figure 6 ).

[0119] One advantage of the described methods is that they improve the temperature and humidity performance of image acquisition equipment.

[0120] Various embodiments and variations have been described. Those skilled in the art will appreciate that certain features of these embodiments may be combined, and those skilled in the art will readily conceive of other variations.

[0121] Finally, actual implementation of the embodiments and variations described herein is well within the capabilities of those skilled in the art based on the functional description provided above.

Claims

1. An optical device comprising: a support member having a through hole formed therein; a first electrode on the support member; an active layer of the first electrode, the active layer being configured to absorb photons and convert the absorbed photons into electron-hole pairs; a second electrode on the active layer; a conductive layer over the second electrode, connecting the second electrode to one of the through holes; a microlens matrix on the conductive layer; as well as an encapsulation layer, arranged between the microlens matrix and the active layer; The encapsulation layer includes a first portion with a first density and a second portion with a second density, the first portion of the encapsulation layer is arranged between the active layer and the second portion of the encapsulation layer, and the first density is lower than the second density.

2. The device according to claim 1, wherein The encapsulation layer is based on silicon oxide.

3. The device according to claim 1, wherein The encapsulation layer is disposed between the active layer and the conductive layer.

4. The device according to claim 3, wherein The encapsulation layer covers the side surfaces and a portion of the top surface of the active layer.

5. The apparatus according to claim 3, wherein The encapsulation layer is disposed between and in contact with the two metal nitride layers.

6. The apparatus according to claim 1, wherein The encapsulation layer is arranged between the conductive layer and the microlens matrix.

7. The apparatus according to claim 6, wherein The encapsulation layer is covered by a metal nitride layer.

8. The apparatus according to claim 1, wherein The encapsulation layer includes: a first encapsulation layer disposed between the active layer and the conductive layer; and A second packaging layer is arranged between the conductive layer and the microlens matrix.

9. The apparatus according to claim 1, wherein The conductive layer is made of aluminum.

10. The apparatus according to claim 1, wherein The first density is between 2.05 and 2.

13.

11. The apparatus according to claim 1, wherein The second density is between 2.20 and 2.

28.

12. The apparatus according to claim 1, wherein The first portion of the encapsulation layer has a thickness between 50 and 250 nm.

13. The apparatus according to claim 1, wherein The second portion of the encapsulation layer has a thickness between 3 and 50 nm.

14. A method of manufacturing an optical device, the optical device comprising: a support member having a through hole formed therein; a first electrode on the support member; an active layer of the first electrode, the active layer being configured to absorb photons and convert the absorbed photons into electron-hole pairs; a second electrode on the active layer; a conductive layer above the second electrode, connecting the second electrode to one of the through holes; a microlens matrix above the conductive layer; and an encapsulation layer disposed between the microlens matrix and the active layer; The method comprises forming the encapsulation layer according to the following steps: depositing a first precursor at a first deposition rate to form a first portion of the encapsulation layer having a first density; as well as depositing a second precursor at a second deposition rate to form a second portion of the encapsulation layer having a second density; The first deposition rate is greater than the second deposition rate, so that the first density is less than the second density.

15. The method of claim 14, further comprising depositing the first portion of the encapsulation layer and the second portion of the encapsulation layer by PECVD at a temperature less than or equal to 150°C.

16. The method according to claim 14, wherein The first precursor and the second precursor are silicon oxide precursors.

17. The method according to claim 16, wherein: The first precursor and the second precursor are TEOS.

18. The method according to claim 14, wherein The first deposition rate is at least 5 times greater than the second deposition rate.

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