Method of forming spatial light modulator
By using patternable materials to form predefined patterned structures in the fabrication of LCOS microdisplays, the problems of damage to the silicon backplane and moisture absorption by rigid spacer elements have been solved, enabling hermetic sealing and efficient manufacturing without spacers, thus improving optical performance and production efficiency.
Patent Information
- Application Number
- CN202510605006.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-08-01
- Filing Date
- 2025-05-12
- Publication Date
- 2026-02-03
AI Technical Summary
The rigid spacers used in existing LCOS microdisplay manufacturing can damage the silicon backplane, and moisture absorption leads to uneven optical performance, affecting image quality. Furthermore, the manufacturing process must be carried out on a per-device basis, which limits production speed.
A predefined patterned structure is formed on a silicon substrate using patternable materials. A hermetic seal is formed between the silicon substrate and the upper substrate through a bonding process, avoiding the use of rigid spacer elements. The patterning is performed using photosensitive patternable materials such as photoresists, and bonding is achieved through ultraviolet radiation or laser irradiation.
This achieves hermetic sealing without rigid spacers, reduces damage to the silicon backplane, improves manufacturing speed and optical performance uniformity, and enhances the hermeticity and production efficiency of the device.
Smart Images
Figure CN121454833A_ABST
Abstract
Description
Technical Field
[0001] This application relates to spatial light modulator devices, and more particularly to liquid crystal devices.
[0002] Embodiments of the present invention are particularly suitable for methods of forming liquid crystal on silicon (LCOS) microdisplay devices. However, it should be understood that the present invention can be applied to a wider range of contexts and other applications beyond liquid crystal displays. Background Technology
[0003] LCOS microdisplays are reflective devices that use a backplane, such as a silicon backplane, to reflect and manipulate light. They are used in consumer devices such as high-definition displays and in optical communications such as optical phase modulators used for optical switches.
[0004] The fabrication of these microdisplays requires bonding an upper transparent glass layer to a reflective or non-reflective silicon backplane or substrate. This bonding process typically involves applying a mixture of adhesive and spacer elements to form gaskets / sealants between the layers. This seal is then applied to the silicon backplane to bond the backplane to the upper transparent glass layer to house the liquid crystal material.
[0005] The mixture requires spacer elements, typically in the form of spherical spacers or microspheres, to maintain a constant spacing between layers. However, these spacer elements are formed from rigid materials such as plastic or glass and can potentially damage the sensitive silicon backplane. Furthermore, the process of applying the mixture must be performed on a per-device basis, which limits manufacturing speed.
[0006] It is also known that the mixture absorbs moisture, and that moisture alters the thickness and uniformity of the gasket. This will change the optical properties of the unit, and is evident in sensitive applications such as optical phase modulators.
[0007] Any discussion of the background art throughout this specification should not be construed as an admission that such art is well known in the art or constitutes part of common general knowledge. Summary of the Invention
[0008] According to a first aspect of this disclosure, a method for forming a spatial light modulator device is provided, the method comprising:
[0009] Provide planar silicon substrates;
[0010] Patternable materials are deposited onto the bonding surface of a silicon substrate;
[0011] Patternable materials are formed into predefined patterned structures on bonding surfaces;
[0012] Apply the upper substrate to a predefined patterned structure; and
[0013] A bonding process is performed to form a hermetically sealed structure between a predefined patterned structure and an upper substrate, thereby defining a cavity between the silicon substrate and the upper substrate to accommodate the light modulation material.
[0014] In some embodiments, the patternable material includes a photosensitive patternable material. In some embodiments, the photosensitive patternable material includes a photoresist material.
[0015] In some embodiments, the step of depositing a photosensitive patternable material includes spin-coating a layer of the photosensitive patternable material onto the bonding surface.
[0016] In some embodiments, the step of depositing a photosensitive patternable material includes spraying a layer of the photosensitive patternable material onto the bonding surface.
[0017] In some embodiments, the step of depositing a photosensitive patternable material includes pressing a layer of the photosensitive patternable material onto a bonding surface using a roll press.
[0018] In some embodiments, the steps of depositing patternable material and forming a predefined patterned structure include inkjet printing the patternable material onto a bonding surface at a predefined location to form a predefined patterned structure.
[0019] In some embodiments, the patternable material is an adhesive material. In other embodiments, the patternable material is a non-adhesive material.
[0020] In some embodiments, the steps of depositing patternable material and forming a predefined patterned structure include 3D printing the patternable material onto a bonding surface at a predefined location to form the predefined patterned structure.
[0021] In some embodiments, the patternable material is a non-adhesive material. In other embodiments, the patternable material is an adhesive material.
[0022] In some embodiments, the method further includes the following steps:
[0023] Depositing a thin metal film onto a predefined patterned structure and an exposed silicon substrate; and
[0024] A stripping process is performed to remove the predefined patterned structure and the metal film attached to the predefined patterned structure, thereby allowing the metal film to be directly attached to the exposed silicon substrate.
[0025] In some embodiments, the predefined patterned structure takes the form of a negative or inverse shape of an airtight seal.
[0026] In some embodiments, the steps of depositing patternable material and forming a predefined patterned structure include screen printing the patternable material onto the bonding surface at a predefined location to form the predefined patterned structure.
[0027] In some embodiments, the step of performing the bonding process includes exposing a predefined patterned structure to a heat source under pressure to perform a fusion bonding process between a silicon substrate and an upper substrate.
[0028] In some embodiments, the bonding process includes irradiating a predefined patterned structure with ultraviolet light to form an adhesive bond between a silicon substrate and an upper substrate.
[0029] In some embodiments, the step of performing the bonding process includes irradiating the predefined patterned structure with a laser at the interface between the upper substrate and the predefined patterned structure.
[0030] In some embodiments, the step of performing the bonding process includes irradiating a predefined patterned structure with infrared radiation to perform the welding process.
[0031] In some embodiments, the method further includes a step of cleaning the bonding surface of the silicon substrate prior to depositing a patternable material.
[0032] In some embodiments, the method further includes the step of depositing an optical modulation material onto a silicon substrate within a predefined patterned structure prior to applying an upper substrate.
[0033] In some embodiments, the predefined patterned structure includes openings that allow light modulation material to be added after the upper substrate has been applied.
[0034] In some embodiments, the patternable material comprises two or more constituent materials. A first of the two or more constituent materials may include a property defining a gasket height. A second of the two or more constituent materials may include a property defining a hermetic seal between a silicon substrate and an upper substrate. In some embodiments, one of the two or more constituent materials is adhesive to bond the patternable material to the bonding surface.
[0035] In some embodiments, the spatial light modulator device is a liquid crystal on silicon (LCOS) device.
[0036] In some embodiments, the patternable material is a homogeneous material.
[0037] In some embodiments, the patternable material does not have spacer elements.
[0038] In some embodiments, the predefined patterned structure is rectangular. In other embodiments, the predefined patterned structure is non-rectangular.
[0039] According to a second aspect of this disclosure, a liquid crystal microdisplay device formed by the method of the first aspect is provided.
[0040] According to a third aspect of this disclosure, a spatial light modulator apparatus is provided, comprising:
[0041] Lower substrate;
[0042] Upper substrate;
[0043] Active optical modulation material, which is disposed between a lower substrate and an upper substrate; and
[0044] A gasket material is disposed between a lower substrate and an upper substrate and generally surrounds an active light modulation material to seal the material between the lower substrate and the upper substrate.
[0045] The gasket material is a generally homogeneous material that does not contain rigid spacer elements. Attached Figure Description
[0046] Exemplary embodiments of this disclosure will now be described by way of example only with reference to the accompanying drawings, in which:
[0047] Figure 1 This is an exploded perspective cross-sectional view of the LCOS device;
[0048] Figure 2 This is an exploded perspective view of an LCOS device, showing the seal / gasket layer between the upper and lower substrates of the device;
[0049] Figure 3 This is a side view of a conventional seal or gasket used to house the spherical spacer element in an LCOS device.
[0050] Figure 4 This is a process flow diagram illustrating the main steps in a method for forming a liquid crystal microdisplay device;
[0051] Figure 5 This is a schematic diagram illustrating the different processing stages in forming a liquid crystal microdisplay device;
[0052] Figure 6A This is a front perspective view of the first patterned structure of a gasket deposited on a substrate during the process of forming a liquid crystal microdisplay device;
[0053] Figure 6B This is a front perspective view of a second patterned structure of a gasket deposited on a substrate during the process of forming a liquid crystal microdisplay device;
[0054] Figure 7A This is a top view of a liquid crystal microdisplay device, wherein the gasket is formed of a patternable material comprising two constituent materials;
[0055] Figure 7B yes Figure 7A A side view of a liquid crystal microdisplay device; and
[0056] Figure 8 This is a process flow diagram illustrating a specific implementation of the manufacturing process and example materials used in the process. Detailed Implementation
[0057] Embodiments of this disclosure will be described with reference to a liquid crystal spatial light modulator device. However, it should be understood that this disclosure is applicable to other spatial light modulator devices incorporating light modulation materials other than liquid crystal.
[0058] Device Overview
[0059] First refer to Figure 1 The figure illustrates a liquid crystal on silicon (LCOS) device 100, which can be used as a spatial light modulator, for example, in a microdisplay. Device 100 can also be referred to as an LCOS optical phase modulator because it modulates the phase and / or amplitude of an incident light signal propagating in the propagation dimension (z-dimension). Device 100 includes a silicon substrate 102 and a liquid crystal material layer 104 disposed between a pair of opposing electrodes 106 and 108. Here, the liquid crystal within layer 104 represents a light modulation material. An upper electrode 106 is disposed above the liquid crystal layer 104, and a lower electrode 108 is mounted to the silicon substrate 102. Electrode 106 is mounted to an upper transparent glass layer 107. The lower electrode 108 comprises a two-dimensional array 110 of independently electrically controllable pixels extending across device 100 in the first (x) and second (y) lateral dimensions. The liquid crystal layer 104 is configured to be electrically controllable into multiple electrical states by a voltage drive signal provided to the lower electrode 108 by an electrical controller 112.
[0060] The upper electrode 106 is formed of transparent or partially transparent indium tin oxide or other at least partially transparent conductive oxides, and allows optical signals to be transmitted into and out of the device 100. The lower electrode 108 is reflective and comprises an array 110 of individually controllable aluminum pixels (e.g., 114). The pixels of electrode 108 are electrically driven by supplying a potential (V) across liquid crystal layer 104 between the upper electrode 106 and the lower electrode 108 to drive local liquid crystals within the layer 104 in a predetermined configuration. Each pixel in the array 110 can be individually driven by an electrical controller 112 at one of several predetermined voltage levels to provide local phase modulation to the incident light signal. Electrical control of the pixels is provided by an interconnect via silicon substrate 102 to the electrical controller 112.
[0061] Pre-alignment of the liquid crystal material within layer 104 can be provided by alignment layers 118 and 120. Layers 118 and 120 contain a plurality of small grooves aligned along a predetermined direction to define the slow axis of the liquid crystal material.
[0062] See now Figure 2 In a conventional LCOS device, layers 118 and 120 are sealed together using a gasket / seal 140 to encapsulate liquid crystal layer 104. Liquid crystal material is not shown in this figure. A gap in the gasket / seal 140 is shown because liquid crystal material can be added through this gap before the final sealing layer. However, in some embodiments, liquid crystal filling occurs before sealing between layers 118 and 120. In these embodiments, a gap in the gasket / seal 140 may not be necessary. In other embodiments, liquid crystal layer 104 is sealed with gasket / seal 140 between upper electrode 106 or upper transparent glass layer 107 and lower electrode 108 or substrate 102.
[0063] Figure 3 A close-up side view of a portion of a conventional gasket / seal 140 is shown, which is formed from a mixture of adhesive material 142 and spacer elements 144, 146, and 148. Although shown as formed on alignment layers 118 and 120, it should be understood that the gasket / seal 140 may be formed on other layers, such as between substrate 102 or lower electrode 108 and upper transparent glass layer 107 or upper electrode 106. Spacer elements 144, 146, and 148 may be spherical, cylindrical, or other shapes, and are preferably formed of a rigid material such as plastic, silicon dioxide, or another conductive or non-conductive material inert to the liquid crystal material. The spacer elements are used to maintain a uniform gap or cell thickness between the two glass substrates that enclose the liquid crystal material. The thickness of this gap is typically on the order of several micrometers (μm). The uniformity of this gap is important for the proper functioning of the device. If the gap is non-uniform, it may cause variations in the electric field across the liquid crystal layer, which may result in non-uniform optical properties and degrade image quality. However, as mentioned above, the introduction of rigid spacer elements can damage the sensitive silicon backplane. Therefore, this invention seeks to reduce or completely eliminate the need for spacer elements while maintaining the gasket height / space.
[0064] Although only three spacer elements are shown, these elements are distributed throughout the gasket / seal 140 to provide reinforcement to the adhesive material 142 and maintain a fixed spacing between elements 118 and 120 (or between other elements in the device 100) to accommodate the liquid crystal material 104.
[0065] Embodiments of the present invention will be described with reference to LCOS microdisplay devices. However, it should be understood that the present invention is also applicable to other types of microdisplay devices.
[0066] Manufacturing method
[0067] See now Figure 4This illustrates a method 400 for forming a liquid crystal microdisplay device, such as an LCOS device. By implementing method 400, the use of spacer elements in the manufacturing process can be reduced or completely avoided. (See reference...) Figure 5 Describe the steps of method 400. Figure 5 The fabrication stages of a microdisplay device are schematically illustrated. Figure 5 In this context, the silicon substrate 502 can also be referred to as the backplane, and is collectively known as... Figure 1 Layers 102, 108, and 118, and the top substrate 504 are collectively referred to as Figure 1 106, 107 and 120.
[0068] At initial step 401, a silicon substrate 502 is provided. The substrate 502 forms the backplate of the apparatus. In some embodiments, the substrate 502 is pre-cleaned and prepared for subsequent bonding processes to have, for example, Figure 5 The bonding surface 506 is shown. The area of the top substrate 504 across the substrate 502 that is bonded to the substrate 502 forms the bonding surface 506.
[0069] Before substrate 502 has been cleaned and prepared for bonding, an initial substrate fabrication process is performed at optional step 402. This includes preparing substrate 502 and upper substrate 504 for bonding. Step 402 may include cleaning bonding surface 506, surface activation if necessary, and pre-coating an alignment layer. A polyimide coating may be added to substrate 502 or bonding surface 506, providing chemical and thermal stability as well as electrical isolation. The polyimide layer may form alignment layer 118. An initial baking process may also be performed during this initial process. This initial process at step 402 facilitates proper adhesion of the gasket to the substrate. The cleaning process may involve chemical cleaning, for example, using detergents, and / or may include plasma cleaning. A similar process may be applied to the bonding surface on upper substrate 504.
[0070] During or before step 402, the lower alignment layer 118 is applied to the substrate 502. Similarly, the upper alignment layer 120 is applied to the top substrate 504 at an appropriate time before the liquid crystal material is added to the device.
[0071] At step 403, a patternable material 508 is deposited onto the bonding surface 506 of the silicon substrate 502. In some embodiments, this includes baking the material if necessary. A patternable material refers to a material that can be manipulated, applied, or modified to produce a shape with a predefined thickness (in...). Figure 1Any material with a specific pattern or design (in the z-direction). Patternable materials must possess properties that allow them to maintain their structure and thickness with high precision in a stable or operable state (e.g., cured), and to withstand pressure from the upper electrode 106 or the alignment layer 120 bonded to it. Therefore, patternable materials have sufficient strength and hermeticity to eliminate the need for rigid spacer elements. The foregoing discussion of patternable material 508 addresses additional properties related to material characteristics suitable for sealing. Patternable materials can have their physical or chemical properties modified in a controlled manner to produce the desired pattern via processes such as photolithography, etching, or deposition. Preferably, patternable material 508 is a generally homogeneous material. Specifically, patternable material 508 preferably does not contain rigid materials such as spacer elements.
[0072] In some embodiments, the patternable material 508 comprises a polymer. In other embodiments, the patternable material 508 may comprise a metallic material that can be applied in liquid form.
[0073] Preferably, the patternable material 508 can meet the following four requirements:
[0074] 1) Can be patterned into a washer-like structure;
[0075] 2) It can be manipulated to accurately limit the height of the washer;
[0076] 3) Provide airtight seals; and
[0077] 4) Adhesive / bondable to other materials.
[0078] In some embodiments, the patternable material 508 may include two or more constituent materials. When the patternable material 508 includes more than one constituent material, each of the constituent materials may be responsible for fulfilling a subgroup of the four requirements described above, such that, in combination, the sum of the constituent materials forming the patternable material 508 collectively provides the four requirements. When the patternable material 508 includes more than one constituent material, the resulting gasket / seal 140 is also formed from more than one constituent material. This is in Figure 8 It is illustrated schematically and described below.
[0079] exist Figure 2 , 3 In Figures 6 and 7, the patternable material 508 and the subsequent gasket / seal 140 are shown inserted from the outer edges of the substrate 102 and the glass layer 107. However, it should be understood that in some embodiments, the patternable material 508 and the subsequent gasket / seal 140 may be positioned close to or flush with the outer edges of the substrate 102 and the glass layer 107.
[0080] As mentioned below, in some embodiments, the patternable material 508 may include a photosensitive patternable material. In some embodiments, the photosensitive patternable material includes a photoresist material designed to be rigid and permanently form part of the final structure, unlike typical photoresist materials designed to be temporary and removable by solvents. In one example, such a patternable material comprises SU-8 or a derivative thereof. SU-8 is an epoxy-negative photoresist available from Kayaku Advanced Materials, Inc., Westborough, MA, or Gersteltec Engineering Solutions, Inc. (https: / / www.gersteltec.ch / ). Different patternable materials may have different trade-offs between their patternability, rigidity, bonding ability, and hermeticity. Therefore, some structures may require greater rigidity but less hermeticity, etc. For example, SU-8 has higher rigidity than conventional photoresists. Furthermore, as another example, SU-8 can have different viscosities (e.g., SU-8 2-25 or SU-8 50-100). Higher viscosity formulations can be used during application to achieve thicker structures after they have been imparted with permanence. Photoresist is typically a type of polymer that can be applied to a surface and then selectively exposed (usually to ultraviolet light). Depending on the type of photoresist used, this exposure causes a chemical change in the photoresist. Photoresists can be positive or negative. When a positive photoresist is exposed to UV or other light, the exposed material becomes soluble and is thus removed by the developer solution, while the unexposed areas remain on the substrate. Conversely, a negative photoresist becomes insoluble upon exposure to UV or other light, and the unexposed areas can be washed away by the developer solution.
[0081] When the patternable material 508 includes a permanent patternable material and one or more constituent materials, the patternable material 508 may include:
[0082] A first permanent patternable material, which is suitable for a) forming patternable washer-like structures; b) providing washer height definition; and c) bonding / bonding to other materials.
[0083] A second material, which is not a permanently patternable material, is applied such that it surrounds and conforms to the first material to produce a hybrid structure that provides an airtight seal.
[0084] When providing an airtight seal, in one example, the second material (and / or a combination of permanently patternable materials) may have a water vapor transmission rate (WVTR) of less than 5 g / m² / day, for example, according to ASTM F1249, at a thickness of 500 micrometers at 60°C and 90% indoor humidity. In another example, the second material (and / or a combination of permanently patternable materials) may have a water vapor transmission rate (WVTR) of less than 1 g / m² / day at a thickness of 500 micrometers at 60°C and 90% indoor humidity.
[0085] In another example, the second material (and / or the combination of permanently patternable materials) has a boiling water absorption rate of less than 3% by weight when immersed in boiling water for up to 2 hours, or less than 1% by weight when immersed in boiling water for up to 2 hours. The example boiling water absorption rate standard is ASTM D570.
[0086] In another example, when immersed in water at 25 degrees Celsius for 24 hours, the room temperature water absorption rate of the second material (and / or the combination of permanently patternable materials) is less than 1% by weight, or less than 0.1% by weight. The example room temperature water absorption rate standard is ASTM D570.
[0087] The patternable material 508 preferably includes an adhesive material, but may include a material that becomes adhesive only after processing such as baking. Thus, the patternable material 508 may initially include a non-adhesive material.
[0088] The deposition process in step 403 can include a variety of different deposition processes, depending on the application and the specific patternable material to be used. In some embodiments, where the patternable material 508 is photosensitive, deposition step 403 includes spin-coating a layer of photosensitive patternable material onto the bonding surface. Spin-coating is a procedure for applying a uniform film to a flat substrate using centrifugal force. Typically, excess solution is placed at the center of the substrate, which is held in place on a rotatable support, and then the substrate is rotated at high speed to diffuse the fluid by centrifugal force. Excess material is ejected from the edges of the rotating substrate, leaving a generally uniform film on the surface.
[0089] In other embodiments where the patternable material 508 is photosensitive, the deposition step 403 includes spraying a layer of photosensitive patternable material onto the bonding surface 506. Spraying involves directly spraying the patternable material 508 onto the bonding surface 506 in a spray form using a nozzle that atomizes the material into fine droplets.
[0090] When the patternable material is photosensitive, deposition step 402 may include rolling a layer of photosensitive patternable material onto the bonding surface 506. This process may include roll deposition, wherein rolls of patternable material 508 are selectively rolled onto the bonding surface 506. This process can be performed accurately and at high speed using a robotic deposition system. One such example is in flexographic printing.
[0091] At step 404, the patternable material 508 is formed into a predefined patterned structure on the bonding surface 506. An example patterned structure is shown in Figure 6. This patterning process can include various processes outlined below. The predefined patterned structure can include the final desired structure for forming a gasket / seal on a device. For example, this can include a circumferentially extending seal, such as... Figure 2 The seal shown. Alternatively, the predefined patterned structure can include a negative or inverse pattern of the final desired structure for forming the gasket / seal on the device. For example, the predefined patterned structure can be in the form of a negative of the shape of the hermetic seal to be formed. This is especially likely to occur when using photoresist patternable materials.
[0092] When the patternable material 508 includes a photoresist, a photoresist etching or development process can be performed at step 404. Once the photoresist is deposited onto the substrate 102, it is exposed to a light source (typically ultraviolet light) via a mask carrying the desired predefined patterned structure. The light induces a chemical change in the exposed areas of the photoresist. After exposure, the photoresist is developed. This involves immersing the substrate in a solution that dissolves either the exposed or unexposed areas of the photoresist, depending on whether a positive or negative photoresist is used. The result is an embossed image of the mask pattern in the photoresist.
[0093] In some embodiments, deposition step 403 and patterning step 404 are bonded together and performed as a single step. For example, steps 403 and 404 may together include inkjet-spraying patternable material 508 onto bonding surface 506 at a predefined location to form a predefined patterned structure. During inkjet deposition, patternable material 508 is deposited directly from the printhead onto bonding surface 506 with the desired patterned structure, and no separate patterning process is required.
[0094] Similarly, in other embodiments, steps 403 and 404 together include 3D printing patternable material 508 onto bonding surface 506 at predefined locations to form a predefined patterned structure. In some embodiments, patternable material 508 is formed on bonding surface 506 via an additive manufacturing process to directly form the predefined patterned structure. In other embodiments, a layer of patternable material 508 is first deposited on bonding surface 506, and subtractive 3D printing processes such as etching are used to selectively remove segments of the layer to form the predefined patterned structure.
[0095] When the patternable material 508 comprises multiple constituent materials, the inkjet or 3D printing process can include:
[0096] The first material is suitable for a) forming a patternable washer-like structure (patterning is performed by 3D printing process); and b) providing washer height limitation.
[0097] A second material is applied such that it surrounds and conforms to the first material, and a) provides an airtight seal; and b) is bonded / bonded to other materials.
[0098] Both inkjet and 3D printing processes can be used to produce adhesive / non-adhesive predefined patterned structures. For example, both inkjet and 3D printing processes can print height-defined gasket structures (but not adhesive ones). Furthermore, both inkjet and 3D printing processes can also print adhesive epoxy gasket structures.
[0099] Figure 7A and 7B A patternable structure formed from a patternable material 508 comprising two constituent materials 508A and 508B is schematically shown. As shown, the two materials are arranged horizontally side-by-side relative to each other. Note that in some embodiments, the positions of the adhesive material and the sealing material can be interchanged. That is, the adhesive material can be an inner structure / layer (as shown in Figure 7) or an outer structure / layer. The adhesive material comprises a permanently patternable material and forms the inner layer, while the outer layer is formed of a material with good moisture-barrier properties to provide a seal.
[0100] In some embodiments, steps 403 and 404 together include screen printing a patternable material 508 onto a bonding surface 506 at predefined locations to form a predefined patterned structure. This process involves first placing a mask or stencil structure, which is the negative of the predefined patterned structure, onto the bonding surface 506. Then, the patternable material 508 is deposited onto the mask / stencil to fill the voids and create the predefined patterned structure on the bonding surface 506. The mask / stencil is then removed.
[0101] In some embodiments, additional steps may be performed after steps 403 and 404. For example, after performing deposition step 403, a metal stripping process is performed, wherein a metal film is deposited onto a predefined patterned structure formed by a patterned material 508 on surface 506 and an exposed silicon substrate 502. The predefined patterned structure may be formed using one of the processes described above (e.g., using a photoresist). Next, a stripping process may be performed to remove the predefined patterned structure and the metal film attached to it. This stripping process is typically performed using a solvent. The metal deposited on top of the patterned structure is stripped off along with the patterned structure, thereby allowing the metal film to be directly attached to the exposed silicon substrate.
[0102] When the patternable material 508 comprises a metallic material, a metal sintering process can be performed. Initially, the metallic patternable material is deposited onto the bonding surface 506 to form a layer of patternable material. Next, the metallic material is patterned into a desired predefined patterned structure. This patterning may include projecting a laser beam onto the patternable material at locations corresponding to the predefined patterned structure. Energy from the laser beam is used to bond the metallic material to the bonding surface 506 to form the predefined patterned structure. After this, any remaining unbonded metallic material not bonded to the bonding surface 506 is washed away, leaving only the predefined patterned structure used to form the gasket.
[0103] In each of the above processes, the patternable material 508 is formed such that it has a predefined patterned structure, the predefined patterned structure including a predefined thickness and sufficient strength and minimum compressibility to support the upper substrate 504 in operation.
[0104] At step 405, an upper substrate 504 is applied to a predefined patterned structure formed of a patternable material 508. In some embodiments, liquid crystal material 104 is added after step 404 and before step 405. This can be achieved by including, for example, liquid crystal material 104 in the predefined patterned structure. Figure 6A Execution occurs when the complete circumferential structure is shown. Or, as... Figure 6B As shown, gap 602 can remain within a predefined patterned structure, such as... Figure 6B As shown. This gap 602 allows for the addition of liquid crystal material 104 after the upper substrate 504 has been applied and bonded in step 406 below. After filling with liquid crystal material 104, the gap is filled with additional material, which is preferably the same material as the patternable material 508.
[0105] Finally, at step 406, a bonding process is performed such that the predefined patterned structure forms a hermetically sealed element between the silicon substrate 502 and the upper substrate 504. After bonding, the patternable material itself forms a seal or gasket between the silicon substrate 502 and the upper substrate 504. This defines a cavity between the silicon substrate 502 and the upper substrate 504 to accommodate the liquid crystal material 104. In one example, the shear bond strength of the patternable material to the glass and silicon is greater than approximately 10 Newtons per square millimeter (N / mm²). 2 ) or 10 MPa.
[0106] The bonding process used will depend on the material used for the patternable material 508. The bonding process may include exposing a predefined patterned structure to a heat source under pressure to perform a fusion bonding process between the silicon substrate 502 and the upper substrate 504. The bonding process may include irradiating the predefined patterned structure with ultraviolet radiation to form an adhesive bond between the silicon substrate and the upper substrate. The bonding process may include irradiating the predefined patterned structure with a laser at the interface between the upper substrate 502 and the predefined patterned structure. The bonding process may include irradiating the predefined patterned structure with infrared radiation to perform a welding process.
[0107] Following the process of method 400, a liquid crystal microdisplay device is formed, which enables it to be hermetically sealed and free of destructive spacer materials / elements. Method 400 can be performed wholly or partially by an automated manufacturing apparatus or system. This apparatus or system can be programmed to repeat method 400 on multiple devices to mass-produce liquid crystal microdisplay devices.
[0108] Figure 8 A specific embodiment of a manufacturing process and example materials used in said process is illustrated schematically. Figure 8 In this process, the gasket application step corresponds to the deposition of the patternable material 508 in method 400 and the subsequent formation of the patterned structure (steps 403 and 404). As shown in the figure, in addition to the main steps of method 400 described above, additional steps such as cleaning, baking, and curing can be performed. Figure 8 The PI Rub step involves forming grooves in alignment layers 118 and 120 to provide pre-alignment of the liquid crystal material within layer 104.
[0109] The advantages of the preferred embodiments of this disclosure include:
[0110] Improve the airtightness of liquid crystal microdisplay assemblies;
[0111] Reduce damage to the sensitive back panel of the display. The disclosed technology uses materials and / or techniques that enable it to be hermetically tight and free of potentially destructive spacer materials;
[0112] Higher productivity than conventional processes achieved through the use of standard wafer-level semiconductor processes; and
[0113] It is possible to print "special" features. Specifically, conventional washers have a rectangular shape. Using the process of this invention, different and more complex washer structures can be formed, for example, as additional lines within the framework of an improved LCOS device.
[0114] explain
[0115] The term "infrared" is used in the specification and claims. Within the scope of this specification, infrared refers to the overall infrared region of the electromagnetic spectrum, which includes near-infrared, infrared, and far-infrared frequencies or light waves.
[0116] Throughout this specification, references to "one embodiment," "some embodiments," or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of this disclosure. Therefore, the phrases "in one embodiment," "in some embodiments," or "in one embodiment" appearing throughout this specification do not necessarily refer to the same embodiment. Furthermore, it will be apparent to those skilled in the art, based on this disclosure, that particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.
[0117] As used herein, unless otherwise specified, the ordinal adjectives “first,” “second,” “third,” etc., used to describe common objects merely indicate different instances of the same object and are not intended to imply that the objects described in this way must be in a given sequence in time, space, hierarchy, or in any other way.
[0118] In the appended claims and the description herein, either the term "comprising" or "comprising thereof" is an open-ended term meaning that at least the element / feature that follows the term is included, but other elements / features are not excluded. Therefore, when used in the claims, the term "comprising" should not be construed as limited to the components or elements or steps listed thereafter. For example, the statement "the apparatus comprises A and B" should not be limited to the apparatus consisting only of elements A and B. As used herein, either the term "comprising" or "comprising thereof" is also an open-ended term meaning that at least the element / feature that follows the term is included, but other elements / features are not excluded. Therefore, "comprising" is synonymous with "including" and means "comprising".
[0119] It should be understood that in the above description of exemplary embodiments of this disclosure, various features of this disclosure are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of simplifying the disclosure and aiding in the understanding of one or more aspects of the invention. However, this disclosure approach should not be construed as reflecting an intention that the claims require more features than expressly recited in each claim. In fact, as reflected in the appended claims, inventive aspects lie in less than all the features of a single or more disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into this detailed description, wherein each claim is independently a separate embodiment of this disclosure.
[0120] Furthermore, while some embodiments described herein include features that are not included in other embodiments, combinations of features from different embodiments are intended to be within the scope of this disclosure and to form different embodiments, as will be understood by those skilled in the art. For example, any combination of any of the claimed embodiments may be used in the appended claims.
[0121] Many specific details are set forth in the description provided herein. However, it should be understood that embodiments of this disclosure can be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.
[0122] Similarly, it should be noted that the term "coupling" when used in the claims should not be construed as limited to a direct connection. The terms "coupling" and "connection," as well as their derivatives, may be used. It should be understood that these terms are not intended to be synonyms with each other. Therefore, the scope of the expression "device A coupled to device B" should not be limited to devices or systems in which the output of device A is directly connected to the input of device B. This means that there is a path between the output of A and the input of B, which may be a path containing other devices or components. "Coupling" can mean two or more elements in direct physical, electrical, or optical contact, or two or more elements that are not in direct contact with each other but still cooperate or interact with each other.
[0123] The embodiments described herein are intended to cover any adaptations or variations of the invention. Although the invention has been described and explained with reference to specific exemplary embodiments, those skilled in the art will recognize that additional embodiments within the scope of the invention can be readily conceived.
Claims
1. A method for forming a spatial light modulator device, the method comprising: Provide planar silicon substrates; Patternable materials are deposited onto the bonding surface of the silicon substrate; The patternable material is formed into a predefined patterned structure on the bonding surface; The upper substrate is applied to the predefined patterned structure; as well as A bonding process is performed such that the predefined patterned structure forms a hermetically sealed element between the silicon substrate and the upper substrate, thereby defining a cavity between the silicon substrate and the upper substrate to accommodate the optical modulation material.
2. The method according to claim 1, wherein the patternable material comprises a photosensitive patternable material.
3. The method of claim 2, further comprising exposing the photosensitive patternable material to convert the photosensitive patternable material into a permanent patternable material.
4. The method according to claim 2, wherein the photosensitive patternable material comprises a photoresist material.
5. The method of claim 2, wherein the step of depositing the photosensitive patternable material comprises spin-coating a layer of the photosensitive patternable material onto the bonding surface.
6. The method of claim 2, wherein the step of depositing the photosensitive patternable material comprises spraying a layer of the photosensitive patternable material onto the bonding surface.
7. The method of claim 2, wherein the step of depositing the photosensitive patternable material comprises rolling the photosensitive patternable material onto the bonding surface.
8. The method of claim 1, wherein the steps of depositing the patternable material and forming the predefined patterned structure include inkjet printing the patternable material onto the bonding surface at a predefined location to form the predefined patterned structure.
9. The method of claim 8, wherein the patternable material is an adhesive material.
10. The method of claim 8, wherein the patternable material is a non-adhesive material.
11. The method of claim 1, wherein the steps of depositing the patternable material and forming the predefined patterned structure include 3D printing the patternable material onto the bonding surface at a predefined location to form the predefined patterned structure.
12. The method of claim 10, wherein the patternable material is an adhesive material.
13. The method of claim 11, wherein the patternable material is a non-adhesive material.
14. The method of claim 1, further comprising the following steps: A thin metal film is deposited onto the predefined patterned structure and the exposed silicon substrate; as well as A stripping process is performed to remove the predefined patterned structure and the metal film attached to the predefined patterned structure, thereby allowing the metal film to be directly attached to the exposed silicon substrate.
15. The method of claim 14, wherein the predefined patterned structure is in the form of a negative or inverse of the shape of the hermetic seal.
16. The method of claim 1, wherein the steps of depositing the patternable material and forming the predefined patterned structure include screen printing the patternable material onto the bonding surface at a predefined location to form the predefined patterned structure.
17. The method of claim 1, wherein the step of performing the bonding process includes exposing the predefined patterned structure to a heat source under pressure to perform a fusion bonding process between the silicon substrate and the upper substrate.
18. The method of claim 1, wherein the step of performing the bonding process includes irradiating the predefined patterned structure with ultraviolet radiation to form an adhesive bond between the silicon substrate and the upper substrate.
19. The method of claim 1, wherein the step of performing the bonding process includes irradiating the predefined patterned structure with a laser at the interface between the upper substrate and the predefined patterned structure.
20. The method of claim 1, wherein the step of performing the bonding process includes irradiating the predefined patterned structure with infrared radiation to perform the welding process.
21. The method of claim 1, further comprising the step of cleaning the bonding surface of the silicon substrate prior to depositing the patternable material.
22. The method of claim 1, further comprising the following steps: Before applying the upper substrate, an optical modulation material is deposited onto the silicon substrate within the predefined patterned structure.
23. The method of claim 1, wherein the predefined patterned structure includes openings that allow the addition of an optical modulation material after the upper substrate has been applied.
24. The method of claim 1, wherein the patternable material comprises two or more constituent materials.
25. The method of claim 24, wherein at least one of the two or more constituent materials includes the characteristic of defining the height of the washer.
26. The method of claim 3, wherein when formed as the permanent patternable material, the photosensitive patternable material has a shrinkage rate of less than 5 vol.%.
27. The method of claim 24, wherein at least one of the two or more constituent materials includes the characteristics of the hermetic seal defining the space between the silicon substrate and the upper substrate.
28. The method of claim 26, wherein the material has a water vapor transmission rate (WVTR) of less than 5 g / m² / day at a thickness of 500 micrometers at 60 degrees Celsius and 90% indoor humidity.
29. The method of claim 26, wherein when immersed in boiling water for 2 hours, the material has a boiling water absorption rate of less than 3% by weight.
30. The method of claim 26, wherein when immersed in water at 25 degrees Celsius for 24 hours, the material has a room temperature water absorption rate of less than 1% by weight.
31. The method of claim 24, wherein at least one of the two or more constituent materials is adhesive in order to bond the patternable material to the bonding surface.
32. The method of claim 31, wherein the shear bond strength between the material and the glass and silicon is greater than 10 Newtons per square millimeter or 10 MPa.
33. The method of claim 1, wherein the spatial light modulator device is a liquid crystal on silicon (LCOS) device.
34. The method of claim 1, wherein the patternable material is a homogeneous material.
35. The method of claim 1, wherein the patternable material does not contain spacer elements.
36. The method of claim 1, wherein the predefined patterned structure is rectangular.
37. The method of claim 1, wherein the predefined patterned structure is non-rectangular.
38. A liquid crystal microdisplay device formed by the method according to claim 1.
39. A spatial light modulator device, comprising: Lower substrate; Upper substrate; An active optical modulation material is disposed between the lower substrate and the upper substrate; as well as A gasket material disposed between the lower substrate and the upper substrate and substantially surrounding the active light modulation material to seal the material between the lower substrate and the upper substrate; The gasket material is a generally homogeneous material that does not contain rigid spacer elements.