EP4028802A1

EP4028802A1 - Angular filter

Info

Publication number: EP4028802A1
Application number: EP20775825.1A
Authority: EP
Inventors: Tindara VERDUCI; Benjamin BOUTHINON; Emeline Saracco
Original assignee: Isorg SA
Current assignee: Isorg SA
Priority date: 2019-09-13
Filing date: 2020-09-08
Publication date: 2022-07-20
Also published as: WO2021048110A1; FR3100767B1; CN114424097A; FR3100767A1; US20220317351A1; JP2022548862A

Abstract

The present invention relates to an angular filter (2) for an image sensor, comprising opaque resin patterns (26) which are at least partially covered with a first moisture-proof layer (42).

Description

DESCRIPTION Angular filter

The present patent application claims the priority of the French patent application FR19 / 10119 which will be considered as forming an integral part of the present description.

Technical area

The present description relates to an angular filter for an image sensor.

Prior art

An angular filter is a device making it possible to filter incident radiation as a function of the incidence of this radiation and thus block the rays whose incidence is greater than a desired angle, called maximum incidence.

Summary of the invention

[0003] There is a need for improving angular filters.

[0004] One embodiment provides for an angular filter for an image sensor comprising patterns of opaque resin at least partially covered with a first moisture-proof layer.

[0005] According to one embodiment, the patterns are completely encapsulated between said first layer and a second moisture-proof layer.

[0006] One embodiment provides for a method of manufacturing an angular filter, comprising the following steps:

- forming opaque resin patterns; and

- Cover the patterns with a first moisture-proof layer. [0007] According to one embodiment, the method further comprises depositing a second moisture-proof layer before the formation of the resin patterns.

[0008] According to one embodiment, the layer or layers are opaque to UV.

[0009] According to one embodiment, the resin is black or colored.

[0010] According to one embodiment, the resin is positive.

According to one embodiment, the resin patterns have, in cross section, rectangular or trapezoidal shapes.

According to one embodiment, the layer or layers have a thickness between 1 and 200 nm, preferably between 10 and 50 nm.

[0013] According to one embodiment, the first layer, one of the layers or the layers are made of Al2O3.

According to one embodiment, the first layer, one of the layers or the layers are made of SiN / Si02 ·

According to one embodiment, the space between the resin patterns is filled with gas, preferably air.

According to one embodiment, the space between the resin patterns is filled with a material transparent at wavelengths between 400 nm and 1 mm, preferably between 400 and 700 nm.

[0017] According to one embodiment, the material is chosen from silicone, polydimethylsiloxane, an acrylate resin, an epoxy resin and an optically transparent adhesive.

According to one embodiment, the first and / or the second layer are deposited by a layer deposition process thin, plasma assisted chemical vapor deposition process or physical vapor deposition process.

[0019] According to one embodiment, the resin and the material are deposited by liquid, by centrifugation or by coating.

Brief description of the drawings

These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments made without limitation in relation to the accompanying figures, including:

Figure 1 is a sectional view, partial and schematic, of an implementation of an image acquisition system;

Figure 2 is a sectional view, partial and schematic, of an example of an angular filter;

[0023] FIG. 3 partially and schematically represents, by sectional views (A), (B) and (C), steps of a method of manufacturing an angular filter;

[0024] FIG. 4 partially and schematically represents, by sectional views (A), (B), (C) and (D), steps of another method of manufacturing an angular filter;

Figure 5 is a sectional view, partial and schematic, of an alternative implementation of an angular filter; and

Figure 6 is a sectional view, partial and schematic, of another variant implementation of an angular filter.

Description of the embodiments

The same elements have been designated by the same references in the various figures. In particular, the structural and / or functional elements common to the different embodiments and embodiments may have the same references and may have identical structural, dimensional and material properties.

For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been shown and are detailed. In particular, the embodiment of the image sensor and of the elements other than the angular filter have not been detailed, the embodiments and the embodiments described being compatible with the usual embodiments of the sensor and of these other elements. .

Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected or coupled together, it means that these two elements can be connected or be linked or coupled through one or more other elements.

In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "rear", "top", "bottom", "left", "right", etc., or relative, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc. ., Reference is made unless otherwise specified in the orientation of the figures.

Unless otherwise specified, the expressions "approximately", "approximately", "substantially", and "of the order of" mean within 10%, preferably within 5%.

Figure 1 is a sectional view, partial and schematic, of an embodiment of an image acquisition system 1. This figure illustrates the presence of an object 16, partially shown, whose image response is captured by the acquisition system 1. The image acquisition system 1 comprises, from bottom to top in orientation of the figure:

an image sensor 12, for example a CMOS sensor or a sensor based on thin film transistors (TFT, Thin Film Transistor), which can be coupled to inorganic photodiodes (crystalline silicon for a CMOS sensor or amorphous silicon for a TFT) or organic sensor;

- an angular filter 2; and

- a light source 14.

The light source 14 is illustrated above the object 16. It can however, as a variant, be located between the object 16 and the angular filter 2.

The radiation emitted by the light source 14 can be visible radiation, from 400 to 700 nm and / or infrared from 700 nm to 1 mm. In the case of an application to the determination of fingerprints, the object 16 corresponds to the finger of a user.

Figure 2 is a sectional view, partial and schematic, of an example of a conventional angular filter 2 '.

The angular filter 2 'is composed, from top to bottom in the orientation of the figure:

- 22 microlenses;

- a substrate or support 24; and

- walls or patterns 26 resting on the substrate 24 and delimiting holes 28.

For the purposes of the present description, the term

“Transparent” a material allowing more than 1% of the radiation to pass in the wavelengths concerned and “opaque” a material allowing less than 1% of the radiation to pass in the wavelengths concerned. The walls correspond to patterns 26 of resin.

This resin is composed of an absorbent material at least at the wavelengths to be filtered. The resin may be a black resin absorbing in the visible and infrared range or a colored resin absorbing visible light of a given color. The resin patterns 26 may, in cross section, be rectangular or trapezoidal in shape. The space between two patterns 26 is defined as a hole 28.

The substrate 24 can be made of a transparent polymer which does not absorb at least the wavelengths considered, here in the visible and infrared range. This polymer can in particular be made of poly (ethylene terephthalate) PET, poly (methyl metacrylate) PMMA, cyclic olefin polymer (COP), polyimide (PI), polycarbonate (PC). The thickness of the substrate 24 can, for example, vary from 1 to 100 µm, preferably between 20 and 100 µm. The substrate 24 can correspond to a color filter, to a polarizer, to a half-wave plate or to a quarter-wave plate.

Opposite each hole 28 is a microlens 22. Each hole 28 is centered substantially on the focus of the associated microlens 22. The microlenses 22 can be made of silica, PMMA, epoxy resin or acrylate resin.

Thus, the rays emitted by the light source 14 are focused by the microlenses 22 at their contacts. The rays focused in the holes 28 of the angular filter 2 ′ are picked up by photodetectors present at the outlet of the filter, in the image sensor 12. The rays focused on the resin patterns 26 are absorbed by the latter.

The inventors have found that outside of normal conditions of use corresponding to an ambient temperature of 0 to 40 ° C, at an atmospheric pressure of about 1013 hPa and at a relative humidity of between 20 and 50%, typically at an ambient temperature of about 80 ° C with a relative humidity of about 80%, the angular filter 2 'undergoes accelerated aging. The resin 26 becomes unstable and the holes 28 close, which damages the properties of the filter 2 '. Exposure to UV radiation, which is electromagnetic radiation with a wavelength between 10 and 400 nm, can further accelerate this phenomenon.

The embodiments and embodiments described provide for partially or totally encapsulating the resin patterns 26 of the filter 2 ', in order to protect them at least from humidity and, preferably, UV. The material encapsulating the patterns can also, depending on its nature, be airtight.

For the purposes of the present description, the term “waterproof” denotes a material whose water vapor transmission rate (WVTR, Water Vapor Transmission Rate) is less than 10 g / day / m ² .

FIG. 3 partially and schematically shows, by views (A), (B) and (C), of the steps of a method of manufacturing an angular filter 2.

View (A) partially and schematically shows a stack 61 of microlenses 22 and a substrate 24.

View (B) partially and schematically shows a stack 63 of substrate 24 and microlenses 22, and patterns 26 of resin.

This stack 63 may correspond to a usual angular filter such as the filter 2 ′ of FIG. 2.

An embodiment of a method of manufacturing the stack 63 shown in view (B) of Figure 3 comprises the following steps: - deposition of a positive opaque resin (colored or black) on the substrate 24, by centrifugation or coating;

- photolithography of patterns to be etched in the resin; and

- development of the resin (photolithography) to keep only the patterns 26.

Another embodiment of a method of manufacturing the stack 63 shown in view (B) of Figure 3 comprises the following steps: formation on the substrate 24 and by photolithography steps, d a transparent resin mold, of complementary shape to the desired shape of the patterns 26;

- filling of the mold with the resin (colored or black) making up the patterns 26; and

- removal from the mold, for example by a "lift-off" process.

Another embodiment of a method of manufacturing the stack 63 shown in view (B) of Figure 3 comprises the following steps:

- deposition of a resin film (black or colored) on the substrate 24, by coating or centrifugation; and

- perforation of the resin film.

The perforation can be carried out using a micro-perforation tool comprising, for example, micro needles to obtain the dimensions of the holes 28 and the pitch of the holes 28 desired, corresponding to the patterns 26.

As a variant, the perforation of the film can be performed by laser ablation.

The view (C) of Figure 3 shows, partially and schematically, an angular filter 2.

According to this embodiment, the resin patterns 26 of the stack 63 of the view (B) of Figure 3 are covered by a first layer 42 impervious to at least moisture and, preferably, opaque to UV.

An embodiment of a method of manufacturing the angular filter 2 shown in view (C) of FIG.

3 comprises the conformal deposition of a layer 42 of Al2C> 3 by a thin film deposition process (ALD - Atomic Layer Deposition). Layer 42 then has, for example, a thickness of between approximately 1 and 50 nm, preferably between 10 and 50 nm.

Another embodiment of a method of manufacturing the angular filter 2 shown in view (C) of Figure 3 comprises the conformal deposition of a layer 42 of

SiN / Si02 by a plasma-assisted chemical vapor deposition process (PECVD - Plasma-Enhanced Chemical Vapor Deposition). Layer 42 then has, for example, a thickness of between approximately 10 and 200 nm, preferably between 10 and 50 nm.

FIG. 4 partially and schematically represents, by sectional views (A), (B), (C) and (D), steps of another method of manufacturing an angular filter

2.

View (A) partially and schematically shows the stack 61 of microlenses 22 and of the substrate 24.

View (B) partially and schematically shows a stack 65 of the substrate 24 and the microlenses 22, and of a second layer 44 impervious to at least moisture and, preferably, opaque to UV.

An embodiment of a method of manufacturing the stack 65 shown in view (B) of Figure 4 comprises the full plate deposition, on the substrate 24, of a 44 Al2O3 layer by a thin film deposition process (ALD

- Atomic Layer Deposition). Layer 44 then has, for example, a thickness of between approximately 1 and 50 nm, preferably between 10 and 50 nm.

Another embodiment of a method of manufacturing the stack 65 shown in view (B) of Figure 4 comprises the full plate deposition on the substrate

24, a layer 44 of SiN / SiO 2 by a plasma-assisted chemical vapor deposition process (PECVD - Plasma-Enhanced Chemical Vapor Deposition). Layer 44 then has, for example, a thickness of between approximately 10 and 200 nm, preferably between 10 and 50 nm.

View (C) of Figure 4 shows, partially and schematically, a stack 67 of the layer 44, the substrate 24 and the microlenses 22, and patterns 26 of resin.

An embodiment of a method of manufacturing the stack 67 shown in view (C) of Figure 4 comprises, as for step (B) of Figure 3, the following steps:

- deposition of a positive opaque resin (colored or black) on the sealed layer 44, by coating or centrifugation;

- photolithography of patterns to be engraved in the colored or black resin; and

- development of the resin (photolithography) to keep only the patterns 26.

Another embodiment of a method of manufacturing the stack 67 shown in view (C) of Figure 4 comprises, as for step (B) of Figure 3, the following steps : formation of a transparent resin mold, on the waterproof layer 44, by photolithography steps, of shape complementary to the desired shape of the patterns 26;

- filling of the mold with the resin (black or colored) making up the patterns 26; and

- removal from the mold, for example by a "lift-off" process.

Another embodiment of a method of manufacturing the stack 67 shown in view (C) of Figure 4 comprises, as for step (B) of Figure 3, the following steps :

- deposition of a resin film (black or colored) on the waterproof layer 44, by coating or centrifugation; and

- perforation of the resin film.

As a variant, the perforation of the film can be carried out by laser ablation.

View (D) of Figure 4 shows, partially and schematically, an angular filter 2.

According to this embodiment, the resin patterns 26 of the stack 67 of view (C) of FIG. 4 are covered by a layer 42 impervious to at least moisture and, preferably, opaque to UV. .

Thus, with respect to the embodiment of FIG.

3, the embodiment of FIG. 4 provides for complete encapsulation of the patterns 26 of resin.

An embodiment of a method of manufacturing the angular filter 2 shown in view (D) of FIG.

4 comprises the conformal deposition of a layer of Al2C> 3 by a thin film deposition process (ALD - Atomic Layer Deposition). Layer 42 then has, for example, a thickness of between approximately 1 and 50 nm, preferably between 10 and 50 nm.

Another embodiment of a method of manufacturing the angular filter 2 shown in view (D) of Figure 4 comprises the conformal deposition of a layer of

In the embodiments of Figures 3 and 4, the holes 28 are left empty or filled with air or a gas, the sensor 12 (Figure 1) resting on the patterns 26.

FIG. 5 is a partial and schematic sectional view of an alternative embodiment of an angular filter 2.

According to this variant, following the steps detailed in FIG. 3, a deposition is carried out by spreading, by centrifugation or by coating, of a moisture-proof filling material 46. The material 46 is completely transparent in the visible and the infrared. The thickness of the material 46 is, for example, between 1 nm and 50 μm, preferably between 1 nm and 25 μm. The material 46 can be silicone, polydimethylsiloxane PDMS, an epoxy resin, an acrylate resin or an optically transparent adhesive (OCA - Optical Clear Adhesive).

An advantage induced by the filling of the holes 28 is that this makes it possible to perform, in step (C) of FIG. 3, a non-conforming deposit at the level of the covering of the patterns 26 of resin. Thus, this step (C) can consist of a deposit (non-compliant) of SiN / Si02 by physical vapor deposition (PVD

- Physical Vapor Deposition).

Figure 6 is a sectional view, partial and schematic, of another variant implementation of an angular filter 2.

According to this variant, following the steps detailed in FIG. 4, a deposition is carried out by spreading, by centrifugation or by coating, of a moisture-proof filling material 46. The material 46 is completely transparent in the wavelengths of interest for the image sensor, preferably transparent in the visible. The thickness of the material 46 is, for example, between 1 nm and 25 μm, preferably between 10 nm and 3 μm. The material 46 can be silicone, polydimethylsiloxane PDMS, an epoxy resin, an acrylate resin or an optically transparent adhesive (OCA - Optical Clear Adhesive).

As for the variant of Figure 5, such filling of the holes 28 allows to perform in step (D) of Figure 4, a non-conforming deposit at the level of the covering of the patterns 26 of resin.

Thus, this step (D) can consist of a deposit (non-compliant) of SiN / Si02 by physical vapor deposition (PVD

- Physical Vapor Deposition).

In the embodiments of Figures 5 and 6, the sensor 12 rests on the surface of the material 46.

An advantage of the embodiments and implementation described is to improve the stability of the form factor of the holes 28 of the angular filter. The angular filters 2 do not undergo accelerated aging and their lifespans are thereby extended. Another advantage of the embodiments and implementation described is that they are compatible with the usual techniques of deposition and etching.

Various modes of implementation and variants have been described. Those skilled in the art will understand that certain characteristics of these various embodiments and variants could be combined, and other variants will be apparent to those skilled in the art. In particular, the choice between the different methods of depositing the encapsulation layers depends on the application and, for example, on the technologies available. In addition, the level of opacity and transparency depends on the materials used.

Finally, the practical implementation of the embodiments and variants described is within the abilities of those skilled in the art based on the functional indications given above.

Claims

1. Angular filter (2) for an image sensor comprising patterns (26) of opaque resin at least partially covered with a first layer (42) impervious to humidity.

2. Filter (2) according to claim 1, wherein the patterns (26) are fully encapsulated between said first layer and a second layer (42, 44) impervious to moisture.

3. Filter according to claim 1 or 2, wherein the layer or layers (42, 44) are opaque to UV.

4. Filter according to any one of claims 1 to 3, wherein the resin is black or colored.

5. Filter according to any one of claims 1 to 4, wherein the resin is positive.

6. Filter according to any one of claims 1 to 5, wherein the patterns (26) of resin have, in cross section, rectangular or trapezoidal shapes.

7. Filter according to any one of claims 1 to 6, wherein the layer or layers (42, 44) have a thickness between 1 and 200 nm, preferably between 10 and 50 nm.

8. Filter according to any one of claims 1 to 7, wherein the first layer (42), one of the layers (42,

44) or the layers (42, 44) are in AI2O3.

9. Filter according to any one of claims 1 to 8, wherein the first layer (42), one of the layers (42,

44) or the layers (42, 44) are made of SiN / Si02

10. Filter according to any one of claims 1 to

9, wherein the space (28) between the resin patterns (26) is filled with gas, preferably air.

11. Filter according to any one of claims 1 to

10, wherein the space (28) between the resin patterns (26) is filled with a material (46) transparent at wavelengths between 400 nm and 1 mm, preferably between 400 and 700 nm.

12. The filter of claim 11, wherein the material (46) is selected from silicone, polydimethylsiloxane, an acrylate resin, an epoxy resin and an optically transparent adhesive.

13. The filter of claim 11 or 12, wherein the resin and the material (46) are deposited by liquid by centrifugation or by coating.

14. Filter according to any one of claims 1 to 13, wherein the first (42) and / or the second layer (44) are deposited by a thin film deposition process, an assisted chemical vapor deposition process. by plasma or a physical vapor deposition process.

15. A method of manufacturing an angular filter (2), according to any one of claims 1 to 14, comprising the following steps:

- Forming patterns (26) of opaque resin; and

- Covering the patterns (26) with a first moisture-proof layer (42).

16. The method of claim 15, further comprising depositing a second moisture-proof layer (44) prior to patterning (26) of resin.