WO2024025475A1

WO2024025475A1 - Method of manufacturing an optical device, and optical device

Info

Publication number: WO2024025475A1
Application number: PCT/SG2023/050526
Authority: WO
Inventors: Shian Yeu Kam; Dongdong Li; Yuen Chin NG; Wee Leng ONG; Maciej BENEDICT
Original assignee: Ams-Osram Asia Pacific Pte. Ltd.
Priority date: 2022-07-29
Filing date: 2023-07-28
Publication date: 2024-02-01

Abstract

A method (100) of manufacturing an optical device (200) is provided. The method (100) includes forming (102) a lift-off mask (622p) on a predefined area of a carrier (620), wherein the lift-off mask (622p) comprises at least one opening (603) exposing the carrier (620); depositing (104) a material layer (624) through an opening (604) of a shadow mask (650), wherein at least a part of the material layer (624) is formed on the lift-off mask (622p) and the exposed carrier (620) in the opening (603) of the lift-off mask (622p); and removing (106) at least a part of the material layer by removing the lift-off mask (622p).

Description

METHOD OF MANUFACTURING AN OPTICAL DEVICE, AND OPTICAL DEVICE

Description

This disclosure generally relates to an optical device and a method to manufacture the same.

Glasses for displaying information (also denoted as smart glasses) , e.g. augmented reality glasses, and waveguide products usually require a mirror section, e.g. on a glass substrate. Most of the glass substrate is covered with a mask (also denoted as resist or resist mask) while forming the mirror section, e.g. 95 % of the glass substrate is supposed to remain free of the mirror section. The mask is usually lifted off in a further process step.

US 2014 342 102 Al discloses small feature size fabrication using a shadow mask deposition process having a conventional sputtering process with a shadow mask. However, a shadow mask process, however, is not able to achieve very small alignment requirements, e.g. less than 15 pm.

US 5 242 534 discloses a platinum lift-off process having a metal lift-off process. However, a lift-off process cannot be used if the resist coverage area is too large, e.g. about 95 % or more of the substrate area.

However, in smart glasses, the mirror section has to be aligned within a precision of 15 pm at maximum from a designated spot while having a very small opening in the lift-off mask, e.g. less than 5 % of the substrate area. Conventionally, it was not possible to achieve the alignment precision and the small opening size solely using a shadow mask or a conventional lift-off process. The large resist coverage area is too large for lift-off to finish the process in reasonable time as chemicals cannot seep through metal layers to resolve resist. Thus, it is economically not possible to complete large area lift-off processes in a reasonable time when the mask covers a substantial part of the substrate in a mirror patterning process.

The method to manufacture the optical device provides a cost-improved and more efficient method of manufacturing an optical device having a small-size mirror section, e.g. large sized lift-off areas of resist masks during manufacturing the device.

In various embodiments, a method for manufacturing an optical device is provided. The method includes: forming a lift-off mask on a predefined area of a carrier, wherein the lift-off mask includes at least one opening exposing (a surface of) the carrier; depositing a material layer through an opening of a shadow mask, wherein at least a part of the material layer is formed on the lift-off mask and the exposed carrier in the opening of the lift-off mask; and removing at least a part of the material layer by removing the lift-off mask.

Illustratively, a lift-off process is combined with a shadow mask in a sputtering process. This way, the resist coverage area can be reduced significantly. Thus, a mask lift-off is enabled that allows creating precise mirror patterning. As an example, the formed mirror may have a misalignment of equal to or less than 5 pm.

Hence, the lift-off mask may improve the final structure deposition precision to 0.5 pm or higher, depending on the alignment accuracy of photolithography tool. In comparison, a conventional shadow mask shows an accuracy of 1 mm to 2 mm. Thus, using the lift-off mask, a gap may be formed between the substrate and the shadow mask without having to worry about shadowing effect of sputtering.

In various embodiments, an optical device is provided including: a grating layer on a glass substrate; a material layer on or over the grating layer, wherein the material layer is formed of silver or aluminium; and wherein a surface estate of the material layer is less than 10 % of a surface estate of the surface of the glass substrate.

In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various aspects of the invention are described with reference to the following drawings, in which:

FIG. 1 is a flow diagram of a method of manufacturing an optical device;

FIG. 2A to FIG. 2C are schematic illustrations of optical devices having a small-sized mirror section .

FIG. 3A to FIG. 3E illustrate schematic cross-sections of an optical device while forming a smallsized mirror section.

FIG. 4A to FIG. 4F illustrate schematic cross-sections of an optical device while forming a smallsized mirror section.

FIG. 5 illustrates a schematic top view of an optical device while forming a smallsized mirror section.

FIG. 6A to FIG. 6C illustrate schematic cross-sections of an optical device while forming a smallsized mirror section.

FIG. 7A to FIG. 7E illustrates schematic top views of an optical device while forming a smallsized mirror section. FIG. 8A to FIG. 8B illustrates schematic top views of an optical device while forming a smallsized mirror section.

FIG. 9A to FIG. 9B illustrates schematic top views of an optical device while forming a small- sized mirror section.

FIG. 10A to FIG. 10B illustrates schematic top views of an optical device while forming a smallsized mirror section.

FIG. 11A to FIG. 11C illustrates schematic top views of an optical device while forming a smallsized mirror section.

The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and aspects in which the disclosure may be practiced. One or more aspects are described in sufficient detail to enable those skilled in the art to practice the disclosure. Other aspects may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the disclosure. The various aspects described herein are not necessarily mutually exclusive, as some aspects can be combined with one or more other aspects to form new aspects. Various aspects are described in connection with methods and various aspects are described in connection with devices. However, it may be understood that aspects described in connection with methods may similarly apply to the devices, and vice versa. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

FIG.l illustrates a flow diagram of a method 100 of manufacturing an optical device. The method 100 may include forming 102 a li ft-of f mask on a predefined area of a carrier, wherein the li ft-of f mask comprises at least one opening exposing the carrier ; depositing 104 a material layer through an opening of a shadow mask, wherein at least a part of the material layer is formed on the li ft-of f mask and the exposed carrier in the opening of the li ft-of f mask; and removing 106 at least a part of the material layer by removing the li ft-of f mask .

In other words and illustratively, the method 100 for manufacturing an optical device may include forming 102 a patterned li ft-of f mask on a predefined area of a carrier .

The method 100 may include depositing 104 a material layer on or over the predefined area of the carrier using a sputtering process utili zing a shadow mask, wherein at least a part of the material layer may be formed on the li ft-of f mask .

Depositing 104 of the material layer may include a positioning of the shadow mask on or over the predefined area of the carrier, wherein an opening of the shadow mask may be arranged over the predefined area may extend through at least a part of the patterned li ft-of f mask . Material of the material layer may be sputtered through the opening in the shadow mask on the carrier and at least a part of the li ftof f mask .

The method 100 may include forming 106 a patterned material layer by removing the material layer in a part of the predefined area by removing the li ft-of f mask adhering to the material layer .

The optical device may be a smart glass and/or a waveguide structure .

The carrier may include a glass carrier . Alternatively, or in addition, the carrier may include a grating structure , and wherein the li ft-of f mask and the material layer may be formed on the grating structure. As an example, the carrier may include a glass carrier and a grating structure.

The grating structure may include a plurality of titanium oxide pillars or may be any other kind of optical grating.

The lift-off mask and the material layer may be formed on the grating structure. As an example, the lift-off mask and the material layer may be formed on and between the pillars.

The lift-off mask may be a photoresist structure.

The shadow mask may include at least one opening in the predefined area.

The patterned material layer may be formed as a mirror for visible light. As an example, the patterned material layer may be formed of silver or aluminium.

The patterned lift-off mask may be formed by depositing a lift-off mask structure on the carrier, and subsequently patterning the lift-off mask structure. The lift-off mask may be removed using a wet chemical process.

The method may further include forming a coating layer on or above the patterned material layer.

FIG.2A to FIG.2C show schematic illustrations of optical devices having a small-sized mirror section.

FIG.2A illustrates a glass of a smart glass 200 as an example of an optical device, e.g. an augmented reality glass.

The glass 200 includes a small-sized mirror section 206 in a on a glass area 206. The glass area 206 without mirror section may be about 95 % or more of the area of the glass. As illustrated, the mirror section 206 is to be aligned in a distinct, predetermined area of the glass 200. As an example, a permitted misalignment of the mirror section may be less than 15 pm regardless of the flatness of the substrate, e.g. the glass area 206.

Conventional techniques using solely a shadow mask sputtering process only provide an accuracy of 1 mm to 2 mm. Conventional techniques using solely a lift-off mask are not usable when the lift-off area, e.g. the glass area 206, is large, e.g. about 95 % of the substrate area or larger. Thus, a glass 200 as illustrated in FIG.2A cannot be formed using such conventional techniques.

In a smart glass 200, the glass area 206 may include a plurality of grating structures 252, 254, 256. The grating structures 252, 254, 256 may be configured to guide light 260 (e.g. an image) from a light source 250 to the eye of a person wearing the smart glass (in FIG.2B illustrated by the arrow 262) . Here, the mirror section would be arranged above a part of the first grating structure 252 receiving the light 260 from the light source. Thus, the mirror section prevents a direct transmission of light 260 through the first grating structure 252.

FIG.2C illustrates a schematic cross-section of the portion of glass 200 having the mirror section 226.

Here, the glass 200 includes a grating layer 220 between a first substrate 214-1 and a second substrate 214-2.

The grating layer 220 may include a plurality of titanium oxide structures, e.g. pillars. The first and second substrates 214-1, 214-2 may be glass substrates as an example . One or more optically functional layers may be formed on the outside of the first and second substrate 214-1, 214-2, e.g. an anti-reflection coating 212.

Further, the glass 200 may include one or more of a spacer 204, a sealing 202, and an adhesive etc. at the sides of the glass 200. The mirror section illustrated in FIG.2A may be formed by a patterned material layer 224 on, above and between the grating 220 and the substrates 214-1, 214-2. The material layer 224 may be coating reflective for visible light. As an example, the material layer 224 may be formed of aluminium or silver.

FIG.3A to FIG.3E illustrate schematic cross-sections of an optical device while forming a small-sized mirror section.

FIG.3A illustrates an example of a substrate 301 on which the mirror section is to be formed. The substrate 301 may include a glass substrate 314. The glass substrate 314 may have a thickness of about 800 pm as an example. The glass substrate 314 may be a 6" glass wafer for example.

An anti-reflection coating (ARC) 312 may be formed on an outside of the glass substrate 314.

An optical layer structure may be formed on the opposite side of the glass substrate 314. The optical layer structure may include one or more layers 316, 318 of different refractive indices, e.g. a titanium oxide (TiO2) layer 316 and an alumina (A12O3) layer 318. A grating layer 320 may be formed at the outside surface of the optical layer structure. The grating layer 320 may have a thickness in a range from about 10 nm to about 700 nm, e.g. in a range from about 25 nm to 500 nm, e.g. in a range from about 50 nm to 200 nm, e.g. 100 nm.

The grating layer 320 may include a plurality of grating structures, e.g. a plurality of pillars and/or lamellae of various size and spacing. The grating structure may be formed of Ti02 as an example.

As illustrated in FIG.3B, a lift-off mask 322 (also denoted as lift-off resist or lift-off resist mask) is formed on a part of the grating layer 320. As an example, the lift-off mask 322 may be formed on top of the grating structures of the grating layer, on their sidewalls and/or in the spacing between the grating structures.

The lateral extension of the lift-off mask depends on the size of the mirror section to be formed and the alignment precision of a shadow mask of a sputtering process above the area in which the mirror section is to be formed.

Further, as illustrated in FIG.3C, the lift-off mask is patterned, e. g. removed, in the area in which the mirror section is to be formed. Thus, a patterned lift-off mask 322p is formed.

Thus, the material layer 324 may be formed using a sputtering process using a shadow mask. The shadow mask includes an opening having about the size or smaller than the lateral dimension of the opening in the patterned lift-off mask 322p. This way, it may not be necessary to have an opening in the shadow mask having the size as small as the mirror section to be formed (e.g. the opening can be larger) . Alternatively, or in addition, may not be necessary to arrange the opening of the shadow mask exactly above the area in which the mirror section is to be formed (e.g. the lift-off mask provides a wiggle room for the alignment for the shadow mask) .

In other words, the lift-off mask may have a lateral extension that may be larger than the opening of the shadow mask, in a range of 5 mm to 1 cm. Thus, the lift-off mask provides a wiggle room for the alignment of the opening of the shadow mask. The lateral extension of the lift-off mask may be smaller than the shadow mask. This way, the amount of lift-off mask can be reduced further.

The material layer 324 may include silver as an example. The material layer may have a thickness in a range from about 10 nm to about 500 nm, e.g. in a range from about 50 nm to 400 nm, e.g. in a range from about 100 nm to 200 nm, e.g. 170 nm.

A coating layer 326 may be formed on the material layer 324. The coating layer 326 may be formed subsequently to the material layer 324 in the sputtering process. The coating layer may include silicon oxide (SiO2) , e.g. having a thickness of about 30nm. The coating layer 326 may prevent an oxidation of the material layer 324.

The remaining lift-off layer 322p may be removed in a wet chemical process thereby removing an excess of material layer 324 adhering to the lift-off layer 322p, as illustrated in FIG.3E. This way, a patterned material layer 324p is formed.

FIG.4A to FIG.4F illustrate schematic cross-sections of an optical device while forming a small-sized mirror section.

FIG.4A illustrates an example of a substrate 401 on which the mirror section is to be formed. The substrate 401 may include a glass substrate 414. The glass substrate 414 may have a thickness of about 600 pm as an example. The glass substrate 414 may be an 8" glass wafer for example.

An anti-reflection coating (ARC) 412 may be formed on an outside of the glass substrate 414.

A grating layer 420 may be formed on the opposite side of the glass substrate 414. The grating layer 420 may have a thickness in a range from about 10 nm to about 700 nm, e.g. in a range from about 25 nm to 500 nm, e.g. in a range from about 50 nm to 200 nm, e.g. 100 nm. The grating layer 420 may include a plurality of grating structures, e.g. a plurality of pillars and/or lamellae of various size and spacing. The grating structure may be formed of TiO2 as an example.

As illustrated in FIG.4B, a lift-off mask 422 (also denoted as lift-off resist or lift-off resist mask) is formed on a part of the grating layer 420. As an example, the lift-off mask 422 may be formed on top of the grating structures of the grating layer, on their sidewalls and/or in the spacing between the grating structures.

Further, as illustrated in FIG.4C, the lift-off mask is patterned, e.g. removed, in the area in which the mirror section is to be formed. Thus, a patterned lift-off mask 422p is formed.

Thus, the material layer 424 may be formed using a sputtering process using a shadow mask. The shadow mask includes an opening having about the size or smaller than the lateral dimension of the lift-off mask. This way, it may not be necessary to have an opening in the shadow mask having the size of the mirror section (e.g. the opening can be larger) . Alternatively, or in addition, it may not be necessary to arrange the opening of the shadow mask precisely above the area in which the mirror section is to be formed (e.g. the lift-off mask provides a wiggle room for the alignment for the shadow mask) .

The material layer 424 may include aluminium for example. The material layer may have a thickness in a range from about 10 nm to about 500 nm, e.g. in a range from about 50 nm to 400 nm, e.g. in a range from about 100 nm to 200 nm, e.g. 200 nm. The remaining lift-off layer 422p may be removed in a wet chemical process thereby removing an excess of material layer 424 adhering to the lift-off layer 422, as illustrated in FIG.4E. This way, a patterned material layer 424p is formed.

A coating layer 426 may be optionally formed 406 on the patterned material layer 424p, as illustrated in FIG.4F. The coating layer 426 may be formed subsequently after forming the patterned material layer 424p, e.g. in a spin on glass coating and baking process (SOG) . The coating layer may include silicon as an example, e.g. having a thickness of about 120 nm. The coating layer 426 may prevent an oxidation and/or prevent a mechanical damaging of the patterned material layer 424p. Alternatively, or in addition, the coating layer 426 may provide a planar surface.

FIG.5 illustrates a schematic top view of an optical device 506 after forming a patterned material layer 524p, e.g. a small-sized mirror section, on a grating layer 520 on a substrate 518. As illustrated in FIG.5, a plurality of smallsized mirror sections can be formed on the same wafer at the same time.

FIG.6A, FIG.6B, and FIG.6C illustrate schematic cross sections of an optical device while forming a patterned material layer 624p.

As illustrated in FIG.6A, a patterned lift-off mask 622p may be formed on a surface of a carrier 620.

The carrier 620 may include one or more of structures of a grating layer, a substrate, and one or more further functional layers as described above, e.g. an anti-reflection coating . The lift-off mask 622p may be patterned as described above in FIG.3C or FIG.4C, e.g. by developing an illuminated photoresist layer.

The patterned lift-off mask 622p may have a first lateral extension 602 and an opening 603.

A shadow mask 650 is arranged above the surface of the carrier having the patterned lift-off mask 622p. The shadow mask 650 may have a second lateral extension 601 and an opening 604.

Material 630 for forming the material layer 624 is deposited through the opening 604 on the surface of the carrier in the opening of the patterned lift-off mask 622p and on the patterned lift-off mask 622p, as illustrated in FIG.6B.

The first lateral extension 602 of the patterned lift-off mask 622p may be in a range of 0.1 mm to 10 mm larger than the opening 604 of the shadow mask 650. This way, the material layer 624 deposited in the penumbra of the shadow mask 650, e.g. adjacent to the deepest shadow formed by the opening 604 of the shadow mask, forms still on the patterned lift-off mask 622p. Alternatively, or in addition, the first lateral extension 602 provides a wiggle room for the alignment precision of the shadow mask 650.

However, the first lateral extension 602 of the patterned lift-off mask 622p may be equal or smaller than the second lateral extension 601 of the shadow mask 650. This way, the amount of patterned lift-off mask 622p can be reduced, and thus may improve the patterning process of the material layer 624.

As illustrated in FIG.6C, material 630 of the material layer 624 that has been formed on the patterned lift-off mask 622p can be removed while removing the patterned lift-off mask 622p. This way, a patterned material 624p can be formed having structural features that are smaller, e.g. having a lateral extension of about the opening 603 in the patterned lift-off mask 622p, than the lateral extension of the opening 604 of the shadow mask.

FIG.7A to FIG.11C illustrate top views of a carrier in a method to provide an optical device.

FIG.7A illustrates a carrier 718 on which the optical device is to be formed. The carrier 718 may include one or more of structures of a grating layer 720, a substrate, and one or more further functional layers as described above, e.g. an anti-reflection coating.

The grating layer 720 may be structured (see also FIG.2B) having a 100 nm grating, e.g. a 100 nm line width and a 200 nm spacing between adjacent lines, for example .

An edge clearance 701 of about 15 mm may be considered.

The (unpatterned) lift-off mask may be formed using a negative mask 706 illustrated in FIG.7E. The alignment 704 of the negative mask 706 on the carrier 718 may be performed by aligning (illustrated in FIG.7D) alignment marks 703 on the negative mask (see FIG.7C) and alignment marks 702 of the carrier mask (see FIG.7B) relative to each other. The wiggle room for the alignment marks 702, 703 may be equal or less than 5 pm.

The alignment marks 702, 703 may be arranged in a distance 708, 709 from the area in which the lift-off mask is to be formed on the carrier, e.g. a first distance 708 of about 7 mm and a second distance 709 of about 18 mm, for example.

The lift-off mask may be patterned as illustrated in FIG.8A exposing the carrier 718. The patterned lift-off mask 822p may have a transmission ratio of equal to or less than 5 %. Note that the grating layer 720 is covered by the patterned lift-off mask 706 as illustrated in FIG.8B (see also FG.6A) .

FIG.9A illustrates a shadow mask 901 having opening 902 (see also FIG.6A) that is mounted in material deposition device illustrated in FIG.9B.

The material deposition device may be a sputtering device having a magnetron 905 and a platen 904, and the shadow mask 901 is arranged between the magnetron 905, the target 906 and the carrier 903 having the lift-off mask (see also FIG.6A) . The alignment of the shadow mask 901 and the carrier 903 may depend on the precision of the robot arm of the material deposition device.

FIG.10A and FIG.10B illustrate the openings 902 of the shadow mask overlaying the patterned lift-off mask 822p on the carrier, e.g. corresponding to FIG.6A. FIG.10B illustrates a magnified illustration of this area of FIG.10A. There may be maximum allowed offsets in x-direction 1012 and y-direction 1014 of the openings and the opening in the lift-off mask that can be adjusted based on an accuracy of the robot arm placement of the material deposition device, and a shadowing effect of the material deposition (see also FIG.6B) .

FIG.11A illustrates a top view after depositing the material layer 1024 on the patterned lift-off mask 882p and the carrier in the opening of the lift-off mask. FIG.11B illustrates a magnified illustration of the area of deposition of the material layer of FIG.11A corresponding to the state illustrated e.g. in FIG.6B. FIG.11C illustrates the patterned material layer 1124p, e.g. corresponding to the state illustrated e.g. in FIG.5 and FIG.6C.

In the following some examples are described, which relate to what is described herein and shown in the figures. Example 1 is a method of providing an optical device, the method including: forming a lift-off mask on a predefined area of a carrier, wherein the lift-off mask includes at least one opening exposing the carrier; depositing a material layer through an opening of a shadow mask, wherein at least a part of the material layer is formed on the lift-off mask and the exposed carrier in the opening of the lift-off mask; and removing at least a part of the material layer by removing the lift-off mask.

In Example 2, the subject matter of Example 1 can optionally include that the material of the material layer is sputtered through the opening of the shadow mask.

In Example 3, the subject matter of Example 1 or 2 can optionally include that the opening of the shadow mask is arranged above the opening of the lift-off mask.

In Example 4, the subject matter of any one of Examples 1 to 4 can optionally include that the lift-off mask includes a lateral extension equal to or smaller than a lateral extension of the shadow mask.

In Example 6, the subject matter of any one of Examples 1 to

5 can optionally include that the lift-off mask includes a lateral extension larger than the opening of the shadow mask.

In Example 7, the subject matter of any one of Examples 1 to

6 can optionally include that the optical device is a smart glass or a waveguide structure.

In Example 8, the subject matter of any one of Examples 1 to

7 can optionally include that the carrier includes a glass substrate .

In Example 9, the subject matter of any one of Examples 1 to

8 can optionally include that the carrier includes a grating layer, and wherein the lift-off mask and the material layer are formed on the grating layer.

In Example 10, the subject matter of Example 9 can optionally include that the grating layer includes a plurality of titanium oxide pillars and/or titanium oxide lines.

In Example 11, the subject matter of any one of Examples 1 to

10 can optionally include that the lift-off mask is a photoresist structure.

In Example 12, the subject matter of any one of Examples 1 to

11 can optionally include that a surface estate of the liftoff mask is less than 10 % of a surface estate of the surface of the carrier.

In Example 13, the subject matter of any one of Examples 1 to

12 can optionally include that the material layer is formed of silver or aluminium.

In Example 14, the subject matter of any one of Examples 1 to 12 can optionally include that the opening in the lift-off mask is formed by depositing a lift-off mask structure on the carrier, and subsequently forming the opening in the lift-off mask structure.

In Example 15, the subject matter of any one of Examples 1 to 13 can optionally include that the lift-off mask is removed using a wet chemical process.

In Example 16, the subject matter of any one of Examples 1 to 15 can optionally further include: forming a coating layer on or above the material layer.

Example 17 is an optical device, the including: a grating layer on a glass substrate; a material layer on or above the grating layer, wherein the material layer is formed of silver or aluminium; and wherein a surface estate of the material layer is less than 10 % of a surface estate of the surface of the glass substrate.

In Example 18, the subject matter of Example 17 can optionally include that the surface estate of the material layer is less than 5 % of the surface estate of the surface of the glass substrate.

In Example 19, the subject matter of Example 17 or 18 can optionally include that the glass substrate includes a bow shape .

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any example or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other examples or designs .

The words "plurality" and "multiple" in the description or the claims expressly refer to a quantity greater than one. The terms "group (of) ", "set [of] ", "collection (of) ", "series (of)", "sequence (of)", "grouping (of)", etc., and the like in the description or in the claims refer to a quantity equal to or greater than one, i.e. one or more. Any term expressed in plural form that does not expressly state "plurality" or "multiple" likewise refers to a quantity equal to or greater than one.

The term "connected" can be understood in the sense of a (e.g. mechanical, optical and/or electrical) , e.g. direct or indirect, connection and/or interaction. For example, several elements can be connected together mechanically such that they are physically retained (e.g., a plug connected to a socket) and electrically such that they have an electrically conductive path (e.g., signal paths exist along a communicative chain) . While the above descriptions and connected figures may depict optical device components as separate elements , skilled persons will appreciate the various possibilities to combine or integrate discrete optical functions into a single element . Such may include combining two or more components from a single component . Conversely, skilled persons will recogni ze the possibility to separate a single element into two or more discrete elements , such as splitting a single component into two or more separate component .

It is appreciated that implementations of methods detailed herein are exemplary in nature , and are thus understood as capable of being implemented in a corresponding device . Likewise , it is appreciated that implementations of devices detailed herein are understood as capable of being implemented as a corresponding method . It is thus understood that a device corresponding to a method detailed herein may include one or more components configured to perform each aspect of the related method .

All acronyms defined in the above description additionally hold in all claims included herein .

While the disclosure has been particularly shown and described with reference to speci fic embodiments , it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims . The scope of the disclosure is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced .

Claims

CLAIMS A method (100) of manufacturing an optical device (200) , the method (100) comprising: forming (102) a lift-off mask (622p) on a predefined area of a carrier (620) , wherein the lift-off mask (622p) comprises at least one opening (603) exposing the carrier (620) ; depositing (104) a material layer (624) through an opening (604) of a shadow mask (650) , wherein at least a part of the material layer (624) is formed on the liftoff mask (622p) and the exposed carrier (620) in the opening (603) of the lift-off mask (622p) ; and removing (106) at least a part of the material layer by removing the lift-off mask (622p) . The method of claim 1, wherein the material (630) of the material layer (624) is sputtered through the opening (604) of the shadow mask (650) . The method of claim 1 or 2, wherein the opening (604) of the shadow mask (650) is arranged laterally at least partially overlapping above the opening (603) of the lift-off mask (622p) . The method of any one of claims 1 to 3, wherein the lift-off mask (622p) comprises a lateral extension (602) equal to or smaller than a lateral extension (601) of the shadow mask (650) . The method of any one of claims 1 to 4, wherein the lift-off mask (622p) comprises a lateral extension (602) larger than the opening (604) of the shadow mask (650) . The method of any one of claims 1 to 5, wherein the optical device (200) is a smart glass or a waveguide structure . The method of any one of claims 1 to 6, wherein the carrier (620) comprises a glass substrate (314, 414) . The method of any one of claims 1 to 7, wherein the carrier (620) comprises a grating layer (320, 420) , and wherein the lift-off mask (622p) and the material layer (624) are formed on the grating layer (320, 420) . The method of claim 8, wherein the grating layer (320, 420) comprises a plurality of titanium oxide pillars and/or titanium oxide lines.

The method of any one of claims 1 to 9, wherein the lift-off mask (622p) is a photoresist structure. The method of any one of claims 1 to 10, wherein a surface estate of the lift-off mask (622p) is less than or equal to 10 % of a surface estate of the surface of the carrier (620) . The method of any one of claims 1 to 11, wherein the material layer (624) is formed of silver or aluminium. The method of any one of claims 1 to 12, wherein the opening (603) in the lift-off mask (622p) is formed by depositing a lift-off mask structure (322, 422) on the carrier (620) , and subsequently forming the opening (603) in the lift-off mask structure. The method of any one of claims 1 to 13, wherein the lift-off mask (622p) is removed using a wet chemical process . The method of any one of claims 1 to 13, further comprising: forming a coating layer (326, 426) on or above the material layer (324p, 424p) . An optical device, the comprising: a grating layer (320, 420) on a glass substrate (314, 414) ; a material layer (324p, 424p) on or over the grating layer (314, 414) , wherein the material layer (324p, 424p) is formed of silver or aluminium; and wherein a surface estate of the material layer (324p. 424p) is less than or equal to 10 % of a surface estate of the surface of the glass substrate (314, 414) . The optical device of claim 16, wherein the surface estate of the material layer is less than or equal to 5 % of the surface estate of the surface of the glass substrate (314, 414) . The optical device of claim 16 or 17, wherein the glass substrate comprises a bow shape.