Multistage structure and method for manufacturing same

Abstract

Techniques for making multi-level structures are described. For example, in accordance with some implementations, techniques for making a multi-level master are described, from which optical elements can be replicated, either directly or through a sub-master. Multi-level optical elements and processes for making these multi-level optical elements are also described.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 022,005, filed May 8, 2020, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention relates to multi-level structures, such as optical elements and master molds (e.g., tools or dies) for manufacturing these optical elements. Background Technology

[0004] In principle, arbitrary wavefronts can be generated, for example, from diffraction structures that have high diffraction efficiency at the design wavelength. Such diffraction structures typically have a surface relief depth that varies continuously over every 2π phase interval. This phase profile with a continuous depth is not easily fabricated. However, multi-level phase structures can offer a trade-off between relatively high diffraction efficiency and ease of fabrication. Furthermore, optical elements with multi-level structures (i.e., three or more levels) can provide superior performance in some cases compared to single-level or double-level structures. For example, a diffractive optical element (DOE) consisting of three levels can exhibit better optical performance in some cases than a diffractive optical element with only one or two levels.

[0005] The first task in the entire fabrication process involves generating a set of one or more masks containing phase profile information. The second task is to transfer the phase profile information from the masks to the surface of the element as specified by the design of the optical element. In some manufacturing methods, master molds (e.g., tools or dies) or sub-master molds are used to form multiple optical elements by replication, where replication refers to the technique used to reproduce a given structure. Attached Figure Description

[0006] Figures 1 to 7 Describe the operations in an example method for generating a master mold or optical element with a multi-level structure.

[0007] Figure 8 and Figure 9 Examples of single-channel and multi-channel modules, including optical elements with multi-level structures, are shown respectively.

[0008] Figures 10 to 12 An example of the operation is shown in the replication process using a master mold with a multi-level structure. Summary of the Invention

[0009] This invention describes techniques for fabricating multilevel structures. For example, according to some implementations, the invention describes techniques for fabricating multilevel master molds (e.g., tools or molds) from which optical elements (e.g., diffractive optical elements) can be replicated directly or by means of sub-molds. The invention also describes multilevel optical elements and processes for fabricating such multilevel optical elements.

[0010] For example, in one aspect, the present invention describes a method for manufacturing an optical element or master mold having a multi-level structure. The method includes: providing a substrate including a first substrate portion and a second substrate portion. The first substrate portion is on the second substrate portion and has a composition different from that of the second substrate portion. The method includes: forming a first trench and a second trench through a surface of the substrate, wherein the first trench extends through the second substrate portion and partially extends into the first substrate portion, and wherein the depth of the first trench is different from the depth of the second trench. Forming the second trench includes: etching through the second substrate portion, wherein the first substrate portion serves as an etch stop layer during the formation of the second trench.

[0011] Some implementations include one or more of the following features. For example, in some implementations, the method further includes: providing a passivation material that at least partially fills the first trench and covers the surface of the substrate; and depositing a mask on a portion of the passivation material. In some cases, providing the passivation material that at least partially fills the first trench includes: conformally coating the bottom and side surfaces of the first trench with the passivation material. In some cases, after depositing the mask, a second trench is formed, wherein the second trench is disposed in a portion of the substrate in which the mask is not present. Furthermore, in some cases, before forming the second trench, the portion of the passivation material not covered by the mask is removed. In some implementations, after forming the second trench: the mask and the passivation material are removed.

[0012] In some implementations, after the first trench is formed, a mask is deposited on a portion of the surface of the substrate; and then the second trench is formed, wherein the second trench is disposed in a portion of the substrate in which the mask is not present.

[0013] In some implementations, the first substrate portion is at least partially made of chromium, and the second substrate portion is at least partially made of silicon. The mask may, for example, be at least partially made of a polymer material. In some cases, the polymer material is a photoresist. The passivation material may, for example, be at least partially made of aluminum oxide. In some instances, filling the first trench at least partially with the passivation material includes depositing the passivation material by atomic layer deposition.

[0014] The present invention also describes a master mold for replicating a master mold or optical element. The master mold includes a substrate having a first substrate portion and a second substrate portion. The first substrate portion is on the second substrate portion and has a composition different from that of the second substrate portion. The substrate has a multi-level structure comprising at least three different levels. The upper surface of the second substrate portion defines a first level of the levels. A surface in the same plane as the boundary between the first substrate portion and the second substrate portion defines a second level of the levels. A surface in the plane between the upper and lower surfaces of the first substrate portion defines a third level of the levels. In some implementations, the first substrate portion is at least partially made of chromium, and the second substrate portion is at least partially made of silicon.

[0015] The present invention also describes optical elements. For example, an optical element may include a substrate having a first substrate portion and a second substrate portion. The first substrate portion is on the second substrate portion and has a composition different from that of the second substrate portion. The substrate has a multi-level structure comprising at least three different levels. The upper surface of the second substrate portion defines a first level of the levels. A surface in the same plane as the boundary between the first substrate portion and the second substrate portion defines a second level of the levels. A surface in the plane between the upper and lower surfaces of the first substrate portion defines a third level of the levels. The depth and position of the first, second, and third levels relative to each other can, for example, be configured to provide predefined optical functions.

[0016] The present invention also describes an optoelectronic module including optical elements having a multi-level structure and aligned with an active optoelectronic component.

[0017] Other aspects, features, and advantages will become apparent from the following detailed description, accompanying drawings, and claims. Detailed Implementation

[0018] This invention describes techniques for fabricating multilevel structures. For example, according to some implementations, the invention describes techniques for fabricating multilevel master molds (e.g., tools or molds) from which optical elements (e.g., diffractive optical elements) can be replicated directly or by means of sub-molds. The invention also describes multilevel optical elements and processes for fabricating such multilevel optical elements.

[0019] like Figure 1As shown, substrate 10 has a first substrate portion 12 and a second substrate portion 14. The first substrate portion 12, disposed on the second substrate portion 14, has a thickness t. The first substrate portion 12 may, for example, be at least partially made of chromium. In some implementations, the first substrate portion 12 may be made of other materials. The second substrate portion 14 may, for example, be made of silicon. However, in some implementations, the second substrate portion 14 may be made of other materials (e.g., molten or polycrystalline silicon dioxide, or one or more dielectric or metallic materials). In some cases, substrate 10 is a wafer with a lateral dimension substantially greater than its thickness. Substrate 10 has a substrate surface on which a first level L1 of a multi-level structure is established.

[0020] like Figure 2 As shown, the method includes creating a first trench 16 in a substrate 10. The first trench 16 has a first depth D1 relative to the substrate surface and extends through the thickness of a first substrate portion 12 and partially extends into a second substrate portion 14. Another stage of a multi-level structure is established at the bottom of the first trench 16. This stage may be referred to as a third stage L3. The first trench 16 can be created, for example, by electron beam lithography and etching, but other techniques can be used in some implementations. For some implementations, the width of the first trench 16 can range from a few nanometers to a few micrometers. In some instances, the dimensions of the first trench 16 and its corresponding arrangement can be related to predetermined optical functions such as diffractive optical functions.

[0021] Next, as Figure 3 As shown, the method includes: partially filling the first trench 16 with a passivation material 18 (i.e., conformally coating the bottom and side surfaces of the first trench), and simultaneously covering at least a portion of the substrate surface at level L1 with the passivation material. In some implementations, the passivation material 18 is at least partially composed of aluminum oxide. In some implementations, other materials may be used for the passivation material 18. The passivation material 18 may be deposited, for example, in the first trench 16 and on top of the substrate surface by atomic layer deposition, but other techniques may be used in some implementations.

[0022] like Figure 3 As further shown, the method also includes selectively providing a mask 20 on portions of the passivation material 18 on the substrate surface and on portions of the passivation material conformally coated with the first trench 16. The mask 20 may, for example, be at least partially composed of a polymeric material such as a resist (e.g., a photoresist). In some cases, the mask material is coated onto the substrate surface (e.g., by spin coating) and then patterned (e.g., via standard photolithography) to form the mask 20.

[0023] like Figure 4As shown, the method includes: removing passivation material 18 from the substrate surface not covered by mask 20. Similarly, removing passivation material 18 coated on the bottom and side surfaces of the first trench 16 and not covered by mask 20. Removal of passivation material 18 may include, for example, argon sputtering. Figure 4 In the example, the passivation material not covered by mask 20 is completely removed. In some instances, the passivation material can be removed by wet etching.

[0024] like Figure 5 As shown, the method includes creating a second trench 22 through the surface of the substrate, such that the second trench has a second depth D2 relative to the substrate surface (i.e., relative to stage L1). The depth D2 may be equal to (or substantially equal to) the thickness t1 of the first substrate portion 12 of the substrate 10. The second trench 22 is created in a region of the substrate where the mask 20 is not present. The second trench 22 extends to the upper surface of the second substrate portion 14 of the substrate 10, such that the bottom of the second trench 22 establishes another stage of a multi-level structure. This other stage may be referred to as the second stage L2. In the method shown, the first trench 16 is deeper than the second trench 22. That is, D1 > D2, and the second stage L2 is closer to the first stage L1 than the third stage L3.

[0025] The second trench 22 can be created, for example, by etching. Preferably, the etching used to create the second trench 22 does not (or does not significantly) cause etching of the second substrate portion 14 of the substrate. That is, the second substrate portion 14 is preferably used as an etch stop layer. As a result, the depth of the second trench 22 can be precisely controlled. Furthermore, by allowing the second substrate portion 14 to serve as an etch stop layer relative to the etch used during the formation of the second trench 22, the etch used during the formation of the second trench 22 will not change the depth of the first trench 16, which also helps to maintain precise control over the final depth of the first trench 16.

[0026] Next, as Figure 6 As shown, the method includes, for example, removing material from mask 20 using a peeling technique. Furthermore, as... Figure 7 As shown, the method includes, for example, removing the remaining passivation material 18 by a stripping technique.

[0027] In some implementations, providing a layer of passivation material 18 has the advantage of helping to eliminate or reduce the need for high-precision alignment during subsequent photolithography steps. Furthermore, the presence of passivation material 18 during the etching of the second trench 22 helps prevent lateral etching into the first substrate portion 12 (see [link to documentation]). Figure 5 However, in some implementations, it is not necessary to provide passivation material 18, and mask 20 can be directly deposited onto substrate 10.

[0028] like Figure 7As shown in the example, the resulting structure 30 has three different levels, L1, L2, and L3, wherein the second level L2 is deeper in the substrate than the first level L1, and the third level L3 is deeper in the substrate than the second level L2 (i.e., farther from the first level L1). The resulting multi-level structure 30 is formed in a substrate consisting of two or more portions 12, 14 arranged one on top of the other, each portion being made of a different material than the others. At least one level in the multi-level structure 30 (i.e., the second level L2 in the illustrated example) lies in the same plane as the boundary between the first portion 12 and the second portion 14 of the substrate, wherein the first portion 12 and the second portion 14 have different compositions from each other.

[0029] In some implementations, the resulting multi-level structure 30 can be used as an optical element (e.g., a DOE), that is, an optical element having a multi-level structure wherein the number of levels is at least three. Depending on the material of the multi-level structure, the optical element can be configured to be operable for, for example, infrared (IR) or visible radiation. The depth and position of each level relative to each other can be configured according to predefined optical functions.

[0030] In some implementations, optical elements having the multi-level structure described above can be integrated into a module that houses one or more optoelectronic devices (e.g., light-emitting and / or light-sensing devices). The optical elements can be used to modify or redirect emitted or incident light waves as they pass through the optical elements.

[0031] For example, such as Figure 8 As shown, in some implementations, the light sensing module (e.g., an ambient light sensor module) 800 includes an active optoelectronic device 802 mounted on a substrate 803. The optoelectronic device 802 may be, for example, a light sensor (e.g., a photodiode, pixel, or image sensor) or a light emitter (e.g., a laser such as a vertical-cavity surface-emitting laser, or a light-emitting diode). The module housing may, for example, include a spacer 810 separating the optoelectronic device 802 and / or the substrate 803 from the optical element 804 having the multi-level structure described above.

[0032] exist Figure 8In a single-channel module, optical element 804 can be arranged to intersect the path of incident light or the path of outgoing light. The optical element can be aligned with active optoelectronic component 802 and can be mounted into a housing. In some cases (e.g., where the optoelectronic component is a photosensor), light incident on module 800 is modified or redirected by optical element 804. For example, in some cases, optical element 804 modifies one or more characteristics of the light before it is received and sensed by optoelectronic component 802. In some instances, for example, optical element 804 can focus patterned light onto optoelectronic component 802. In some cases, optical element 804 can separate, diffuse, and / or polarize the light before it is received and sensed by optoelectronic component 802.

[0033] In some cases (e.g., when the optoelectronic component 802 is a light emitter), the light generated by the optoelectronic component 802 passes through the optical element 804 and exits the module. Figure 8 In the single-channel module, optical element 804 can be arranged to intersect the path of the emitted light 806. Optical element 804 can modify or redirect the light. For example, in some cases, one or more characteristics of the light are modified before it leaves module 800 after striking the optical element. In some cases, module 800 is operable to generate one or more of, for example, structured light, diffused light, and patterned light.

[0034] The multi-channel module can also incorporate at least one optical element having the multi-level structure described above. For example... Figure 9 As shown, such a multi-channel module 900 may include, for example, a light sensor 902A and a light emitter 902B, both of which can be mounted on the same printed circuit board (PCB) or other substrate 903. In the example shown, an optical element 904 having the multi-level structure described above is mounted on a housing above the light emitter 902B. The multi-channel module may include a light emission channel and a light detection channel, which can be optically isolated from each other by a wall forming part of the module housing. A lens 905 may be disposed above the light sensor 902A.

[0035] In some cases, one or more of the above modules may be integrated into mobile phones, laptops, televisions, wearable devices, or motor vehicles.

[0036] In some implementations, Figure 7The resulting multilevel structure 30 can be used as a master mold (e.g., a tool or die) to create sub-master molds or to replicate optical elements having a multilevel structure corresponding to that of the master mold. For example, in some implementations, the replicated optical element has the same multilevel structure as the master mold, while in another implementation, the replicated optical element has the reverse of the multilevel structure of the master mold (i.e., a negative). Figures 10 to 13 This shows that it can be done directly from (e.g., having combinations such as those above) Figure 7 The operation of a multi-level master mold replicating optical element with a multi-level structure. In this context, replication refers to the technique used to reproduce a given structure. Specifically, a structured surface can be imprinted into a liquid or plastically deformable material (“replica material”), and then the material can be hardened, for example, by using ultraviolet (UV) radiation or heating. The structured surface can then be removed, thereby obtaining a negative (replica) of the structured surface.

[0037] Figure 10 An example of a female mold 1000 having the multi-level structure described above is shown. The multi-level female mold 1000 can be, for example, by combining... Figures 1 to 7 The method described above is used to obtain it. Then, as... Figure 11 As shown, a polymer replication material (e.g., uncured epoxy resin) 1010 is deposited between a multi-level master mold 1000 and a replication substrate 1012. The multi-level master mold 1000 and the replication substrate 1012 are brought into close proximity, such that the multi-level structure of the master mold 1000 is pressed into the replication material 1010. The polymer replication material 1010 can be cured (e.g., by exposure to ultraviolet radiation and / or by heat). Figure 12 A replica 1014 depicts a multi-level master mold 1000 formed in a cured replica material. The replica 1014 includes multiple multi-level elements (e.g., optical elements such as DOEs). Figure 13 As shown, replica 1014 (e.g., by cutting along cut line 1016) is separated to create multiple individual multilevel optical elements. One or more of the unified optical elements (each having a multilevel structure corresponding to the multilevel structure of the master mold 1000) can be incorporated, for example, into a combination such as described above. Figure 8 and Figure 9 In the single-channel or multi-channel optoelectronic modules of the aforementioned.

[0038] In some implementations, the master mold 1000 can be used to replicate the sub-mold, which is then used to replicate multi-level optical elements.

[0039] Although the foregoing examples describe a multi-level structure with three levels, similar techniques can be used to create multi-level structures with more than three levels. For example, by appropriately selecting the material of a portion of the substrate and by appropriately selecting the etchant, the starting substrate may include additional layers that can be selectively etched, wherein one or more of these layers serve as etch stop layers during the etching of other layers.

[0040] Although a particular implementation has been described in detail, various modifications are possible. Therefore, other implementations are also within the scope of the claims.

Claims

1. A method for manufacturing an optical element or master mold having a multi-level structure, the method comprising: A substrate is provided that includes a first substrate portion and a second substrate portion, wherein the first substrate portion is on the second substrate portion and the first substrate portion has a composition different from that of the second substrate portion; A first trench is formed through the surface of the substrate, wherein the first trench extends through the first substrate portion and partially extends into the second substrate portion; After the first trench is formed, a mask is deposited on a portion of the surface of the substrate; as well as A second trench is then formed through the surface of the substrate, wherein the second trench is disposed in the portion of the substrate in which the mask is not present. The depth of the first trench is different from the depth of the second trench. The formation of the second trench includes etching through the first substrate portion, wherein the second substrate portion serves as an etch stop layer during the formation of the second trench, and The method further includes: A passivation material is provided, which at least partially fills the first trench and covers the surface of the substrate; A mask is selectively deposited on the passivation material portions on the surface of the substrate and within the first trench; and After depositing the mask on a portion of the passivation material, the portion of the passivation material not covered by the mask is removed, and then the second trench is formed, wherein the second trench is disposed in a portion of the substrate in which the mask is not present.

2. The method according to claim 1, wherein, Providing a passivation material that at least partially fills the first trench includes conformally coating the bottom and side surfaces of the first trench with the passivation material.

3. The method according to claim 1, further comprising: After the second trench is formed: Remove the mask; as well as Remove the passivation material.

4. The method according to any one of claims 1 to 3, wherein, The first substrate portion is at least partially made of chromium, and the second substrate portion is at least partially made of silicon.

5. The method according to any one of claims 1 to 3, wherein, The mask is at least partially made of polymer material.

6. The method according to claim 5, wherein, The polymer material is a corrosion inhibitor.

7. The method according to any one of claims 1 to 3, wherein, The passivating material is at least partially composed of aluminum oxide.

8. The method according to any one of claims 1 to 3, wherein, Filling the first trench at least partially with a passivation material includes depositing the passivation material by atomic layer deposition.

9. The method according to any one of claims 1-3, wherein, Providing the passivation material includes partially filling the first trench.

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