Bonded optical device

Abstract

To provide an improved bonded optical device which is miniaturized and has high resolution.SOLUTION: A bonded optical device may include a first optical element, a second optical element, and an optical pathway. The first optical element has a first array of optical emitters configured to emit light of a first color. The first optical element is bonded to at least one processor element, and the at least one processor element includes active circuitry configured to control operation of the first optical element. The second optical element has a second array of optical emitters configured to emit light of a second color different from the first color. The second optical element is bonded to the at least one processor element. The optical pathway is optically coupled with the first and second optical elements. The optical pathway is configured to transmit a superposition of light from first and second optical emitters to an optical output to be viewed by users.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] (Incorporation by reference of priority application) This application claims priority to U.S. Patent Application No. 17 / 124,408, filed December 16, 2020, and U.S. Provisional Patent Application No. 62 / 949,312, filed December 17, 2019, the entire contents of which are incorporated herein by reference in their entirety and for all purposes.

[0002] (Technical field) The present invention relates to bonded optical devices, and more particularly to bonded optical devices for use in wearable electronics. [Background technology]

[0003] For some types of display devices, extremely small and ultra-high resolution devices are desirable. Examples include direct-view display screens, such as those found on smartwatches and mobile phones, and applications using images projected from small screens, such as head-up displays (HUDs) and smart glasses. For example, in wearable smart glasses, such as augmented reality (AR) glasses, or other eyewear including electronic circuits and displays, the image may be located less than 1-2 cm (e.g., 1-1.2 cm) from the user's eyes. In such devices, for example, it may be desirable to utilize a display pixel pitch that is as small as possible (e.g., less than 5-6 μm) to provide the desired image quality. Some technologies, such as LCD (Light on Silicon), can provide low-pitch pixels, but can be inefficient in that a small amount of optical energy (e.g., light) is lost, may have low resolution with low manufacturing yields, and can be expensive.

[0004] Other technologies, such as micro light emitting diodes (microLEDs), can provide a sufficient amount of light energy (e.g., brightness) to provide a clear image that is visible in a sufficiently bright atmosphere, and thus can provide extremely bright images for AR / MR (mixed reality) applications. Light emitting diode (LED) wafers can be processed for one wavelength of light (red "R", green "G", or blue "B") at a time, and creating multicolor displays remains challenging for providing the desired level of image quality in the above applications.

[0005] Thus, there remains a continuing need for improved optical devices, for example, to create color images from monochromatic LED displays and to integrate these monochromatic micro LED displays into applications such as AR smart glasses, projection systems, car HUDs, smart watch displays, mobile phone displays, and others.

[0006] Specific implementations will now be described with reference to the accompanying drawings, which are provided by way of example and not limitation. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing an illustration of the relative distance between a display device and a user's eyes; [Figure 2] 1 is a schematic cross-sectional side view of a direct-bonded optical device according to one embodiment. [Figure 3] 10 is a schematic cross-sectional side view of a direct-bonded optical device according to another embodiment. [Figure 4] 1 is a schematic cross-sectional side view of an optical assembly, according to one embodiment. [Figure 5] 10 is a schematic cross-sectional side view of an optical assembly according to another embodiment. [Figure 6] 1 is a schematic diagram showing an illustration of the physical separation between pixels in an optical device, according to one embodiment. [Figure 7A] 1 is a schematic diagram showing an illustration of the physical separation between individual pixels of an optical device, according to one embodiment. [Figure 7B] FIG. 1 is a schematic diagram illustrating only the physical separation of pixels in an AxA matrix in an optical device, according to one embodiment. [Figure 8] 1 is a schematic diagram illustrating an optical system that can incorporate the optical assemblies described herein, according to one embodiment. [Figure 9] FIG. 1 is a schematic diagram illustrating a direct-coupled optical device to a waveguide with input and output coupling, according to one embodiment. [Figure 10] FIG. 10 is a schematic diagram illustrating an optical device configured to direct light into a waveguide having input and output couplings, according to another embodiment. [Figure 11] FIG. 1 is a schematic diagram illustrating an example of overlapping three color pixels. DETAILED DESCRIPTION OF THE INVENTION

[0008] FIG. 1 is a schematic diagram showing an illustration 100 of relative display distances between various display devices 104, 106, 108 and a user's eye 102. The fovea, the most sensitive part of the eye, contains the most retinal cones (which help distinguish color) and has a resolution of up to approximately 1 arc minute, which is 60 pixels per degree (PPD). PPD represents the pixel pitch required in a display based on the distance of the display device from the user's eye 102. For an AR smartglasses display 104 with a working distance of approximately 1 cm from the user's eye 102, a pixel pitch of up to approximately 5 μm produces what is perceived as a "sharp image." For a mobile phone display 106 with a working distance of approximately 20 cm from the user's eye 102, a pixel pitch of up to approximately 50 μm produces a sharp image. For a computer display 108 with a working distance of approximately 50 cm from the user's eye 102, a pixel pitch of up to approximately 300 μm produces a sharp image. DLP and LCoS based technologies are insufficient for several reasons including, for example, low brightness, pixel size, pitch, display size, etc. Therefore, microLED devices can be useful in some applications such as AR display applications.

[0009] Various embodiments disclosed herein relate to bonded optical devices 200, 300a-c (e.g., as shown in FIGS. 2 and 3). As described herein, some types of optical elements 202a-c, 302a-c (e.g., as shown in FIGS. 2 and 3), particularly light-emitting optical elements (e.g., light-emitting diodes, or LEDs), can be fabricated on wafers with devices configured to emit light of a single color (e.g., red, green, or blue), which can make it difficult to fabricate multicolor displays composed of hundreds of thousands or millions of LEDs from these separate wafers. In various embodiments, the optical elements 202a-c, 302a-c can be formed of semiconductor materials. For example, optical wafers (e.g., LED wafers) can be formed from III-V compound semiconductor material(s) such as InP, GaN, AlGaAs, InGaN, AlGalnP, etc. In various embodiments, direct bonding techniques enable such compound semiconductor materials to be bonded to different types of semiconductor processor elements (e.g., Si or CMOS processor dies), creating heterogeneous systems. Furthermore, it can be difficult to provide optical elements 202a-c, 302a-c (e.g., as shown in FIGS. 2 and 3) with pixels 602a-c (e.g., as shown in FIG. 6) (or display areas) with a pitch (e.g., space between pixels) small enough to display high-quality, high-brightness images directly displayed or projected onto a display (such as a small display or a display configured to be placed close to a user). In various embodiments, the pitch of the light emitters in the array can be less than 50 microns, e.g., less than 10 microns.

[0010] In some micro LED displays, each pixel 704 (e.g., as shown in FIG. 7A) may utilize an individual LED chip (e.g., optical element) as the pixel 704 (e.g., as shown in FIG. 7A) or as a subpixel. For example, the micro LED chips (e.g., optical elements including an array of emitters) may be separately manufactured and placed using pick-and-place techniques. Transfer and place techniques and color conversion schemes may also be used, but these techniques may be uneconomical or may be very lossy. Thus, there remains a continuing need for improved optical devices.

[0011] Embodiments disclosed herein can enable displays with fine pixel pitch by bonding (e.g., direct bonding or hybrid bonding) optical elements 202a-c, 302a-c (e.g., as shown in FIGS. 2 and 3) (particularly light-emitting elements such as LED devices including multiple LEDs) to at least one carrier 204, 304a-c (e.g., as shown in FIGS. 2 and 3) such as a processor, e.g., an image processor element, which may include active circuitry (e.g., one or more transistors) configured to control the operation of the optical elements 202a-c, 302a-c (e.g., as shown in FIGS. 2 and 3). In various embodiments, the light emitters of the emitter array can be independently controllable. Beneficially, in some embodiments, direct bonding or hybrid bonding can be used to physically and electrically connect the optical elements 202a-c, 302a-c (e.g., as shown in FIGS. 2 and 3) to the carrier 204, 304a-c (e.g., as shown in FIGS. 2 and 3) (e.g., a processor element) without the use of adhesives. The use of direct bonding can enable pixel pitches of less than 5 microns, or even less than 1 micron. At least one of the carriers 204, 304a-c has a coefficient of thermal expansion (CTE) of less than 7 ppm.

[0012] FIG. 2 is a schematic cross-sectional side view of a bonded optical device 200 in which multiple optical elements 202a-c are bonded (e.g., directly bonded) to a common carrier 204, according to one embodiment. In some embodiments, the common carrier 204 can comprise an integrated device die, such as a processor die, having circuitry for controlling the operation of the optical elements 202a-c. FIG. 3 is a schematic cross-sectional side view of multiple bonded optical devices 300a-c in which multiple optical elements 302a-c are bonded (e.g., directly bonded) to corresponding multiple carriers 304a-c. The optical elements can be fabricated in wafer form and singulated to define the optical elements 202a-c, 302a-c shown in FIGS. 2-3. As shown in FIG. 2, the optical elements 202a-c (which can comprise emitter dies, such as LEDs) can be directly bonded to the common carrier 204 without an intervening adhesive, for example, in a die-to-wafer (D2W) process. In some embodiments (see, e.g., FIG. 11), the optical elements 202a-c, 302a-c and the carriers 204, 304a-c can be integrated into a larger optical system. For example, the bonded optical device 200 (e.g., including the optical elements 202a-c and the common carrier 204 bonded directly thereto) can be attached to a waveguide or other structure.

[0013] In other embodiments, carriers 304a-c can be singulated to form multiple bonded optical devices 300a-c, as shown in Figure 3. In other embodiments, singulated optical elements 302a-c can be bonded to singulated carriers 304a-c in a die-to-die (D2D) process to obtain the bonded optical devices 300a-c shown in Figure 3. In yet other embodiments, optical elements in wafer form (not shown) can be bonded (e.g., directly bonded) to a carrier (e.g., a processor wafer) in wafer form (not shown) in a wafer-to-wafer (W2W) process (not shown). The bonded wafer can then be singulated to form multiple bonded optical devices 300a-c.

[0014] The optical elements 202a-c, 302a-c can be directly bonded to at least one carrier 204, 304a-c (such as a processor element) without adhesive (e.g., using a dielectric-dielectric bonding technique such as ZiBond®, DBI, or DBI Ultra technology used by Xperi Corporation of San Jose, Calif.) For example, the dielectric-dielectric bond can be formed without adhesive using the direct bonding techniques disclosed in at least U.S. Pat. No. 9,391,143 and U.S. Pat. No. 10,434,749, the entire contents of each of which are incorporated herein by reference in their entirety and for all purposes.

[0015] In various embodiments, the direct bond can be formed without an intervening adhesive. For example, the dielectric bonding surfaces 206, 306a-c can be polished to a high degree of smoothness. The bonding surfaces 206, 306a-c can be cleaned and exposed to plasma and / or etchants to activate the surfaces. In some embodiments, the surfaces can be terminated with a chemical species after or during activation (e.g., during the plasma and / or etch process). In various embodiments, the termination chemical species can include nitrogen. Additionally, in some embodiments, the bonding surfaces can be exposed to fluorine. For example, one or more fluorine peaks can be present near the layers and / or bonding interface. Without being limited by theory, in some embodiments, the activation process can be performed to break chemical bonds at the bonding surface, and the termination process can provide additional chemical species at the bonding surface that improve the bonding energy during direct bonding. Thus, in a direct bond structure, the bonding interface between two dielectric materials can have a very smooth interface with a higher nitrogen content and / or fluorine peak at the bonding interface.

[0016] In various embodiments, the conductive contact pads 208a-c, 308a-c of the optical elements 202a-c, 302a-c or LED elements can be directly bonded to the corresponding conductive contact pads 210a-c, 310a-c of the carrier 204, 304a-c (e.g., processor element). In various embodiments, one LED pixel in an LED chip can have two contact pads or electrodes (positive and negative). In various embodiments, the carrier 204, 304a-c (e.g., processor element) can generate identical images on the corresponding optical elements 302a-c. As described herein, each optical element 302a-c can comprise a monochromatic optical element, generating identical images such that a multicolor image can be viewed when the images are superimposed. For example, hybrid bonding techniques can be used to provide direct conductor-conductor bonding along the bonding interfaces 206, 306a-c, including covalently bonded dielectric-dielectric surfaces. In various embodiments, direct conductor-to-conductor (e.g., contact pad-to-contact pad) and dielectric-to-dielectric bonds can be formed using direct bonding techniques disclosed in at least U.S. Pat. Nos. 9,716,033 and 9,852,988, the entire contents of each of which are incorporated herein by reference in their entirety and for all purposes.

[0017] For example, the dielectric bonding surfaces 206, 306a-c can be pre-treated and directly bonded to one another without an intervening adhesive. The conductive contact pads 208a-c, 210a-c, 308a-c, 310a-c (which can be surrounded by non-conductive dielectric field regions) can also be directly bonded to one another without an intervening adhesive. In some embodiments, each contact pad 208a-c, 210a-c, 308a-c, 310a-c can be recessed below the dielectric field region, e.g., by less than 20 nm, less than 15 nm, or less than 10 nm, e.g., in the range of 2 nm to 20 nm, or in the range of 4 nm to 10 nm. The dielectric field regions can be directly bonded to one another without an adhesive at room temperature in some embodiments, after which the bonded structure can be annealed. Upon annealing, the contact pads 208a-c, 210a-c, 308a-c, 310a-c can expand and contact one another, forming a direct metal-metal bond. Beneficially, the use of direct bond interconnect, or DBI® and / or ZiBond technology, as described above, can enable fine pixel pitches. In some embodiments, the pitch of the bond pads 208a-c, 210a-c, 308a-c, 310a-c can be less than 300 microns, less than 40 microns, less than 10 microns, or less than 2 microns. In some applications, it is desirable for the ratio of the pitch of the bond pads 208a-c, 210a-c, 308a-c, 310a-c to one of the dimensions of the bond pads 208a-c, 210a-c, 308a-c, 310a-c to be less than 5, or less than 3, and in some cases less than 2. In various embodiments, the contact pads 208a-c, 210a-c, 308a-c, 310a-c can include copper, although other metals may be suitable.

[0018] The embodiments disclosed herein can also be used in combination with the apparatus and methods disclosed throughout U.S. Patent Application Nos. 15 / 919,570 (issued April 21, 2020 as U.S. Patent No. 10,629,577); 16 / 219,693; and 16 / 176,191, the entire contents of each of which are incorporated herein by reference in their entirety and for all purposes. U.S. Patent Application No. 15 / 919,570 teaches direct hybrid bonding of CMOS logic wafers or dies to LED wafers or dies, for example, for direct control of emitters (active matrix drive). U.S. Application No. 16 / 176,191 teaches direct bonding of optically transparent substrates.

[0019] The embodiments disclosed herein can also be used in combination with the apparatus and methods disclosed throughout U.S. Patent No. 10,629,577, which describes how optical elements can be bonded to a processor die, the entire contents of which are incorporated herein by reference in their entirety and for all purposes. U.S. Patent No. 10,629,577 teaches directly bonded arrays of optical elements, such as directly bonded LED arrays.

[0020] Thus, in a direct bonding process, a first element (e.g., optical element 202a-c, 302a-c) can be bonded directly to a second element (e.g., carrier 204, 304a-c, such as a processor die) without an intervening adhesive. In some arrangements, the first element can comprise a singulation element, such as a singulated optical device die. In other arrangements, the first element can comprise a carrier or substrate (e.g., a wafer) that includes a plurality (e.g., tens, hundreds, or more) of device regions that, upon singulation, form a plurality of integrated device dies. Similarly, the second element can comprise a singulation element, such as a singulated integrated device die (e.g., a processor die). In other arrangements, the second element can comprise a substrate (e.g., a wafer).

[0021] As described herein, the first and second components (e.g., optical elements 202a-c, 302a-c and carriers 204, 304a-c or processor die) can be directly bonded to one another without adhesive, which differs from a vapor deposition process. The first and second components can accordingly comprise non-deposited components. Furthermore, unlike deposited layers, direct bond structures can include defect regions (not shown) along the bonded interfaces 206, 306a-c where nanovoids exist. The nanovoids may form due to activation (e.g., exposure to plasma) of the bonded surfaces. As described above, the bonded interfaces 206, 306a-c can include condensation of material from the activation and / or final chemical treatment process. For example, in embodiments utilizing nitrogen plasma for activation, nitrogen peaks can form at the bonded interfaces 206, 306a-c. In embodiments utilizing oxygen plasma for activation, oxygen peaks can form at the bonded interfaces 206, 306a-c. In some embodiments, the bonding interface 206, 306a-c can include silicon oxide, silicon nitride, silicon oxynitride, silicon oxynitride, or silicon carbonitride. As described herein, the direct bond can include a covalent bond that is stronger than a van der Waals bond. The bonding layer can also include a polished surface that has been planarized to a high degree of smoothness.

[0022] In various embodiments, the metal-to-metal bond between the contact pads 208a-c, 210a-c, or 308a-c, 310a-c can be bonded such that the copper grains grow together across the bond interface 206, 306a-c. In some embodiments, the copper can have grains oriented along crystal planes to improve copper diffusion across the bond interface 206, 306a-c. The bond interface 206, 306a-c can extend substantially completely to at least a portion of the bond contact pads 208a-c, 210a-c, 308a-c, 310a-c, such that there are substantially no gaps between non-conductive bond regions at or near the bond contact pads 208a-c, 210a-c, 308a-c, 310a-c. In some embodiments, a barrier layer (not shown) may be provided below the contact pads 208a-c, 210a-c, 308a-c, 310a-c (e.g., it may comprise copper). However, in other embodiments, there may be no barrier layer underneath the contact pads 208a-c, 210a-c, 308a-c, 310a-c, as described, for example, in U.S. Patent Application Publication No. 2019 / 0096741, which is incorporated herein by reference in its entirety for all purposes.

[0023] Although the illustrated embodiment shows a direct bonded optical element, in other embodiments the optical element can be attached to the carrier with an adhesive, for example a transparent adhesive.

[0024] As shown and described herein, in some embodiments, the bonded optical devices 200, 300a-c can include optical elements 202a-c, 302a-c that include multiple image or display areas (e.g., pixels 602a-c, as shown in FIG. 6). Each image area can include a monochromatic image area including an optical emitter 614 configured to emit light of a single color. The optical emitter 614 can include a light-emitting diode, which can emit light from a region or surface within the optical element on which the LED is formed. The optical elements 202a-c, 302a-c can include LED wafers including III-V materials, such as GaAs, GaN, GaP, InGaN, AlGalnP, AlGaAs, and the like. For example, the optical elements 202a-c, 302a-c can include monochromatic LED chips in various embodiments. Each LED chip can be configured to emit light of a single color. The LED chips can be configured to emit different colors. For example, a first LED chip (such as optical element 202a) can be configured to emit red light, a second LED chip (such as optical element 202b) can be configured to emit green light, and a third LED chip (such as optical element 202c) can be configured to emit blue light. It should be understood that the LED chips can emit any suitable color.

[0025] The optical elements 202a-c, 302a-c can be bonded, e.g., directly bonded without an intervening adhesive, to at least one carrier 204, 304a-c (e.g., at least one processor element) that includes active circuitry for controlling operation of the pixels of the optical elements 202a-c, 302a-c. The at least one carrier 204, 304a-c can be constructed of semiconductor elements, such as silicon, in various configurations. For example, the carrier 204, 304a-c can function as a silicon-based backplane in some embodiments. The carrier 204, 304a-c can include a processor die with driver circuitry electrically connected to the light emitters via contact pads 208a-c, 210a-c, 308a-c, 310a-c. The driver circuitry can control light emission from the multiple light emitters of the optical elements 202a-c, 302a-c.

[0026] As described herein, multiple image regions (such as pixels 602a-c shown in FIG. 6) can be positioned relative to each other and a common optical path (such as light guide 804 shown in FIG. 8) such that monochromatic light from each image region is combined into the optical path. In some embodiments, multiple such bonded optical devices 200, 300a-c can be combined into a common optical path. Multiple bonded optical devices 200, 300a-c can be configured to emit different colored light (e.g., a red bonded optical device, a green bonded optical device, and a blue bonded optical device). The superimposed light beams from the multiple bonded optical devices can be forwarded along an optical path to an optical output that is viewed by a user. Multiple monochromatic images can be superimposed into a multicolor image in the waveguide that represents the combined contribution of each pixel of the multiple bonded optical devices.

[0027] In various embodiments, the overlapping of light from multiple monochromatic image areas can provide redundancy in case one image area is damaged or unused, in which case light from other pixels can compensate for the color of light in the damaged image area.

[0028] Beneficially, the embodiments disclosed herein can utilize bonded optical elements 202a-c, 302a-c containing multiple arrays or pixels of LEDs without separately singulating and re-growing singulated LEDs on a substrate. The array of LED chips can be directly bonded to an array of processing elements configured to control the operation of the LEDs. In contrast, other methods require singulating and stacking individual LED pixels on a substrate with a high pitch, potentially complicating the assembly process. The use of direct-bonded optical elements containing arrays of LEDs can correspondingly improve the manufacturability of display devices. In one example, arrays of red (R), green (G), and blue (B) LED wafers are each separately directly or hybrid-bonded to a silicon (Si) backplane or imager wafer. These stacks can then be singulated to form red, green, and blue monochromatic imagers, which can be combined to form multicolor images. In another example, red, green, and blue LED wafers can be separately singulated to form R, G, and B LED chips and directly bonded to a silicon backplane or imager. Elements in the silicon backplane can be electrically connected to the LED pixels in the R, G, and B chips to provide pixel-level control. The LED wafers can be directly or hybrid bonded to the silicon backplane, although any other suitable backplane (e.g., thin film transistor, or TFT) backplane can also be used. In some embodiments, an optical assembly, as described herein, can include at least one red LED chip, at least one green LED chip, and at least one blue LED chip. In some embodiments, an optical system can include a plurality or array of such optical assemblies to direct image data to a user.

[0029] In some embodiments, the monochromatic image regions can be oriented parallel to one another. For example, in some embodiments, the image regions can be arranged side-by-side on a waveguide. Light from the image regions can be coupled into the waveguide, which can transmit the multiple-color superimposed image to a user. In other embodiments, the image regions can be arranged non-parallel to one another (e.g., perpendicular to one another), and combiner optics can be provided to transmit the multiple-color superimposed image to a user.

[0030] 4 is a schematic cross-sectional side view of an optical assembly of combined optical devices (e.g., monochromatic emitter chips), according to one embodiment. The optical assembly 400 includes a plurality of optical devices 400a-c formed by a plurality of optical elements 402a-c (e.g., monochromatic LED chips) directly bonded to a corresponding plurality of carrier elements 404a-c (e.g., silicon-based backplanes). The optical assembly 400 can include as redirection elements or mirroring devices 406a-b (e.g., mirrors, beam splitters, or other suitable optical redirection devices) and an optical combiner device 408 (e.g., a lens).

[0031] In one embodiment, optical devices 400a-c (including optical elements 402a-c (e.g., single-color LED chips for R, G, and B, respectively)) can be combined with corresponding carrier elements 404a-c (e.g., silicon backplanes) to form a color image or part of a color image. That is, instead of an RGB microLED display, for example, separate single-color LED chips can be combined as shown in FIG. 4. With three displays used, gang bonding of millions of pixels is not an issue. Multiple optical assemblies 400 can be integrated into an array in various optical systems.

[0032] In one implementation, the bonded optical devices 400a-c can be oriented at an angle relative to one another. For example, the optical elements 402a-c can be approximately perpendicular to one another. In another implementation, the optical elements 402a-c can form a predetermined angle greater than or less than 90° relative to one another. The optical devices 400a-c can each be mounted to a frame or other structure (not shown) and aligned with one or more mirroring devices 406a-b (which can be, for example, beam splitters for redirecting the light). As shown in FIG. 4, the mirroring devices 406a-b can redirect light from the optical elements 402a-c along a common channel to overlap the colored light from each optical element 402a-c. The light from each optical element 402a-c can be varied, for example, based on control via circuitry in the carrier elements 404a-c, to generate overlapping light of various colors. The light image data from each optical element 402a-c passes through an optical combiner device 408 (eg, a lens) to collect the light so that it can be transmitted to a user.

[0033] In one embodiment, hybrid direct bonding (such as DBI®) can be implemented to bond carrier elements 404a-c (e.g., CMOS circuitry) to control each pixel / diode with optical elements 402a-c, such as large R, G, B chips based on the size of the display, with approximately 5 μm pitch.

[0034] In another implementation, the colors as produced by the optical elements 402a-c driven by the carrier elements 404a-c can be used to deliver an image or a portion of an image to the user's eye by the optical combiner device 408 (e.g., via a curved combiner or waveguide).

[0035] In other implementations, D2D, W2W or D2W junctions can be used based on the application.

[0036] 5 is a schematic cross-sectional side view of an optical assembly 500 including combined optical elements, according to another embodiment. The optical assembly 500 includes individual optical elements 502a-c (e.g., optical wafers) and carrier elements 504a-c, as well as mirroring devices 506a-c and an optical combiner device 508.

[0037] As shown, individual optical elements (e.g., R, G, B wafers, etc.) 502a-c can be stacked and singulated onto carrier elements 504a-c to form three large optical devices, e.g., monochrome display chips measuring 5 mm x 8 mm.

[0038] In one embodiment, the optical elements 502a-c can be arranged side-by-side. In some embodiments, the optical elements 502a-c can be mounted on a common carrier (not shown). In other embodiments, the optical elements 502a-c can be mounted on separate carrier elements 504a-c to form the optical devices 500a-c.

[0039] In one implementation, the optical devices 500a-c can be arranged (e.g., mounted on a frame or structure) so that they are laterally offset by a predetermined amount. In such an arrangement, the optical elements 502a-c are laterally offset from one another by a predetermined distance along a direction parallel to a major surface of at least one carrier element 504a-c. Here, the light-emitting surfaces can also be parallel to one another. In another implementation, the light-emitting surfaces may not be parallel to one another, but can be angled relative to one another.

[0040] As shown, light from each optical element 502a-c can be redirected by a corresponding mirroring device 506a-c to superimpose image data, which can be collected via an optical combiner device 508 (e.g., a combiner optic such as a lens) to generate different colors. Additionally, the light from each optical element 502a-c can be varied based on control via carrier elements 504a-c to generate different colors based on how much of each color is emitted and combined from each optical element 502a-c.

[0041] 6 is a diagram illustrating physical separation between pixels in an optical device. The optical device includes a plurality of pixels 602a-c, a plurality of light guides 604, a plurality of physical separation portions 606, a carrier element 608, an optical element 610, a bonding interface 612 between the carrier element 608 and the optical element 610, a plurality of emitters 614 (light-emitting regions), and a plurality of contact pads 616 between the carrier element 608 and the optical element 610. Light is emitted from the light-emitting surface of the emitter 614 and can propagate through the pixel area as shown.

[0042] In various embodiments, each pixel 602a-c (e.g., a monochrome image region) can include one or more optical physical isolation or pixel isolation structures configured to limit crosstalk between adjacent regions of the optical element 610. For example, the isolation structures can include trenches formed through at least a portion of the optical element 610. The isolation structures can be similar to deep trench isolation structures implemented in back-illuminated image sensors.

[0043] As shown, in one embodiment, the physical separation 606 between pixels 602a-c in an optical device 610, such as a chip, can comprise a deep trench isolation feature for an integrated micro LED array. Such deep trench isolation features can prevent light received by one pixel from entering another pixel, and the micro LEDs can also be fabricated to prevent light 604 generated by one diode / pixel from inter-scattering to an adjacent pixel / diode, for example, based on the physical separation 606. Based on such individually controllable pixels 602a-c, for example, light emitted from one pixel 602c via an emitter 614 (which can be configured to emit light of a single predetermined color and constitute or define at least a portion of pixels 602a-c) is physically separated from adjacent pixel 602b by the physical separation 606.

[0044] 7A and 7B illustrate embodiments with different physical separations. FIG. 7A is a schematic diagram illustrating an example of a physical separation 702 between all pixels 704, while FIG. 7B is an illustration of a physical separation 706 in only an A×A matrix (e.g., 2×2, 3×3, etc.) 708 of pixels 710. The embodiment of FIG. 7B can produce higher yields because the physical separation is between the A×A matrix 708 and not between individual pixels 710, such that a single malfunctioning pixel is not a problem for emitted light. Such an embodiment can also enable improved control of the brightness of emitted light, for example. A processor element (e.g., a CMOS or Si backplane) can turn on or off a select number of pixels from the matrix 708 to control brightness, allowing the matrix 708 to function as one large pixel in a display containing multiple smaller pixels 710. Thus, in various embodiments, the processor element can independently control the pixels 710 as part of the matrix 708 to create the desired image data, where the matrix 708 functions as a larger pixel and the pixels 710 function as subpixels. Accordingly, the pixels 710 within the optical element can be divided into matrices of pixels, and the processor element can be configured to selectively control the brightness of the pixels within each matrix accordingly. In various embodiments, isolation features can be configured to optically isolate adjacent matrices 708 of pixels 710 (e.g., to prevent crosstalk). In some embodiments, adjacent pixels 710 within a matrix 708 may not be separated by isolation features. In other embodiments, adjacent pixels 710 may be separated by isolation features.

[0045] 8 is a schematic diagram illustrating an optical system 800 configured to direct light into a waveguide. The optical system 800 includes an input coupling 802, a waveguide 804, and an output coupling 806.

[0046] In one implementation, optical assemblies 400 and / or 500, such as the composite LED-CMOS structure optical assemblies described herein (including monochrome micro LED displays), can be mounted as separate units or can be mounted directly onto the waveguide 804 (e.g., via multiple input couplings 802) in a direct side or angle configuration. In one or more implementations, this can be implemented in, for example, projectors (projection systems), automotive HUDs, smartwatch displays, and mobile phone displays, which include multiple output couplings 806 used to transmit image data to the user's eye 102.

[0047] 9 and 10 are schematic diagrams illustrating an optical device, such as a micro LED, directly bonded to a waveguide 906, 1006 with input and output couplings. The devices each include an optical assembly 902, 1002 (e.g., as described in detail herein with respect to FIGS. 2-3 ) configured to couple light into the waveguide 906, 1006 at the input coupling (904 and 1004, respectively) and to a user at the output coupling (908 and 1008, respectively). In some implementations (e.g., FIG. 9 ), the bonded optical device (e.g., assembly 902) can be directly bonded to the waveguide 906 without an intervening adhesive, mechanically and optically coupling the optical device to the waveguide 906. In other embodiments, the optical assembly can be mounted to a frame or other structure that connects to the waveguide.

[0048] The input couplings 904, 1004 allow image data from the optical assemblies 902, 1002 to enter the waveguides 906, 1006 (e.g., made of a dielectric material), which are used to transmit the image data to the user's eye 102 via the output couplings 908, 1008 via light (e.g., including superimposed light emitted from the optical assemblies 902, 1002 via corresponding arrays of emitters) traveling through the waveguides 906, 1006, e.g., by total internal reflection (TIR).

[0049] 10, an optical device 1010 (e.g., a prism, etc.) can be used to redirect the light transmitted from the optical assembly 1002 so that it travels through the waveguide 1006. In some embodiments, the optical assembly 1002 can be mounted on another structure that is angled relative to the waveguide 1006, and the light can be redirected to the optical device 1010 by mirrors and combiner optics, as shown.

[0050] 11 is a schematic diagram showing an example of a three-color pixel superposition, which includes a plurality of optical elements (e.g., LED dies (R, G, B)) 1102a-c comprising a plurality of pixels 1106, a carrier element 1104, a plurality of optical coupling elements 1108 (e.g., lenses), a plurality of connecting waveguides 1110, a plurality of mirroring devices 1112a-c, an optical combiner device 1114, and a waveguide 1116.

[0051] In one embodiment, the plurality of optical elements 1102a-c can emit monochromatic light via a plurality of emitters (not shown), which can travel through a corresponding optical combining element 1108 and connecting waveguide 1110 and be reflected by a corresponding mirroring device 1112a-c. As shown, the plurality of optical elements 1102a-c can be disposed between the carrier element 1104 and the connecting waveguide 1116. The optical elements 1102a-c can be directly bonded to the carrier element 1104 without an intervening adhesive. Furthermore, the mirroring devices 1112a-c can be disposed at an angle relative to the connecting waveguide 1110 to direct incident light passing through the optical combiner device 1114 and the waveguide 1116 toward a user's eye (not shown).

[0052] In one embodiment, the carrier element 1104 is a silicon / glass carrier, or in another embodiment, an active silicon die that drives the pixels 1106 and optical elements (e.g., LED dies) 1102a-c. In some embodiments, the optical elements can be bonded directly to the waveguides, e.g., connecting waveguides 1110, without an intervening adhesive. In other embodiments, the optical elements can be attached to the waveguides with a transparent adhesive.

[0053] Thus, in various embodiments, a bonded optical device is disclosed. The bonded optical device can include a first optical element having a first array of light emitters configured to emit light of a first color. The first optical element can be bonded to at least one processor element, the at least one processor element including active circuitry configured to control operation of the first optical element. The bonded optical element can include a second optical element having a second array of light emitters configured to emit light of a second color different from the first color. The second optical element can be bonded to the at least one processor element, the at least one processor element including active circuitry configured to control operation of the second optical element. The bonded optical device can include an optical path optically coupled to the first and second optical elements, the optical path configured to transmit a superposition of light from the first and second light emitters to an optical output viewed by a user.

[0054] In some embodiments, the first optical element is directly bonded to the at least one processor element without an intervening adhesive, and the second optical element is directly bonded to the at least one processor element without an intervening adhesive. The respective dielectric bonding surfaces of the first optical element and the at least one processor element can be directly bonded to each other without an intervening adhesive. The corresponding conductive contact pads of the first optical element and the at least one processor element can be directly bonded to each other without an intervening adhesive. Each optical emitter in the first and second arrays of optical emitters can be electrically connected to a corresponding driver circuit on the at least one processor element.

[0055] In some embodiments, a first light emitter of the first array of light emitters and a second light emitter of the second array of light emitters at least partially define a pixel, and the light path can be configured to transmit a superposition of light from the first and second light emitters of the pixel. The at least one processor element can include a first processor element and a second processor element separate from the first processor element. The first optical element can be bonded to the first processor element, and the second optical element can be bonded to the second processor element. In some embodiments, at least one processor element comprises a common carrier.

[0056] In various embodiments, the optical path comprises an optical waveguide. The first optical element can be disposed between the optical waveguide and the first processor element. The second optical element can be disposed between the optical waveguide and the second processor element. In some embodiments, the first and second optical elements are bonded directly to the optical waveguide without an intervening adhesive. In some embodiments, the first and second optical elements are bonded with one or more adhesives that are transparent to the first and second colors of light, respectively.

[0057] In some embodiments, the first and second optical elements may be laterally offset from one another along a direction parallel to a major surface of the at least one processor element. In some embodiments, the emitting surfaces of each of the first and second optical elements may be substantially parallel to one another. In some embodiments, the emitting surfaces of each of the first and second optical elements may be positioned non-parallel to one another.

[0058] The bonded optical device can include one or more optical isolation structures in the first optical element, which can be configured to limit crosstalk between adjacent optical emitters.

[0059] In some embodiments, the first color has a first peak at a first wavelength, and the second color has a second peak at a second wavelength. The difference between the first and second wavelengths can be at least 25 nm. Thus, in various embodiments, the wavelengths can be separated by a sufficient amount such that the colors emitted by the optical element are distinguishable from one another. In some embodiments, the optical path can include one or more redirecting elements (e.g., mirrors, beam splitters, etc.) for redirecting light from the first and second image regions. In some embodiments, the optical path includes a lens configured to act on the superimposed light.

[0060] The bonded optical device may include a third optical element optically coupled to the optical path and bonded to at least one processor element. The third optical element may be configured to emit light of a third color different from the first and second colors. The first, second, and third colors may include red, green, and blue, respectively. In various embodiments, the light emitters of the first array are independently controllable. The first and second arrays of light emitters may comprise respective arrays of light emitting diodes (LEDs). The pitch of the light emitters of the first array may be less than 50 microns. The pitch of the light emitters of the first array may be less than 10 microns.

[0061] In another embodiment, a bonded optical device is disclosed. The bonded optical device can include a first optical element bonded directly to at least one carrier without an adhesive, the first optical element configured to emit light of a first color. The bonded optical device can include a second optical element bonded directly to the at least one carrier without an adhesive. The second optical element can be configured to emit light of a second color different from the first color. The first and second optical elements can be laterally offset from each other along a direction parallel to a major surface of the at least one carrier. The bonded optical device can include an optical path optically coupled to the first and second optical elements, the optical path configured to transmit a superposition of light from the first and second optical elements to an optical output viewed by a user.

[0062] In some embodiments, the at least one carrier comprises a first carrier and a second carrier separate from the first carrier. In some embodiments, the at least one carrier comprises at least one processor element including active circuitry configured to control operation of at least one of the first and second optical elements. In some embodiments, the first optical element can be directly bonded to the at least one carrier without an intervening adhesive, and the second optical element can be directly bonded to the at least one carrier without an intervening adhesive. In some embodiments, the dielectric bonding surfaces of the first optical element and the at least one carrier are directly bonded to each other without an intervening adhesive. In some embodiments, the conductive contact pads of the first optical element and the at least one carrier are directly bonded to each other without an intervening adhesive. In various embodiments, the at least one carrier can include at least one of silicon or glass. In some embodiments, the at least one carrier can have a coefficient of thermal expansion (CTE) of less than 7 ppm.

[0063] In some embodiments, the optical path can comprise an optical waveguide. In some embodiments, the third optical element can be optically coupled to the optical path. The third optical element can be directly bonded to the at least one carrier without adhesive. The third optical element can be configured to emit light of a third color different from the first and second colors.

[0064] In some embodiments, the first, second, and third colors include red, green, and blue, respectively. The first and second optical elements can comprise respective arrays of light emitters. The light emitters can be independently controllable. The light emitters can comprise light emitting diodes (LEDs).

[0065] In another embodiment, a method of bonding at least one optical element to at least one processor element is disclosed. The method can include bonding a first optical element to the at least one processor element, the first optical element comprising a first array of optical emitters configured to emit light of a first color, the at least one processor element comprising active circuitry configured to control operation of the first optical element; bonding a second optical element to the at least one processor element, the second optical element comprising a second array of optical emitters configured to emit light of a second color different from the first color, the at least one processor element comprising active circuitry further configured to control operation of the second optical element; and bonding the first and second optical elements to an optical path configured to convey a superposition of light from the first and second optical emitters to an optical output viewed by a user. In some embodiments, at least one carrier comprises a processor die.

[0066] Although disclosed in connection with certain embodiments and examples, those skilled in the art will recognize that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses, as well as obvious modifications and equivalents thereof. Furthermore, unless otherwise specified, illustrated components may be the same as or substantially similar to one or more different illustrated components bearing the same number. Moreover, while certain variations have been shown and described in detail, other modifications that are within the scope of this disclosure will be readily apparent to those skilled in the art based on this disclosure. It is also contemplated that various combinations or subcombinations of specific features and aspects of the embodiments can be made and still fall within the scope of this disclosure. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another to form varying aspects of the disclosed invention. Accordingly, it is intended that the scope of the invention disclosed herein should not be limited by the specific disclosed embodiments described above, but should be determined only by a fair interpretation of the following aspects. [Explanation of symbols]

[0067] 602a~c pixels 604 Light Guide 606 Physical separation section 608 Carrier element 610 Optical Elements 612 Carrier element 614 Emitter 616 Contact Pad

Claims

1. A bonded optical device, a first optical element having a first array of light emitters configured to emit light of a first color, the first optical element being directly bonded to at least one processor element without an intervening adhesive, the at least one processor element including active circuitry configured to control operation of the first optical element; a second optical element having a second array of light emitters configured to emit light of a second color different from the first color, the second optical element being directly bonded to at least one processor element without an intervening adhesive, the at least one processor element including active circuitry configured to control operation of the second optical element; an optical path optically coupled to the first and second optical elements, the optical path configured to convey a superposition of light from the first and second light emitters into a light output viewed by a user; A bonded optical device comprising:

2. 2. The bonded optical device according to claim 1, wherein respective dielectric bonding surfaces of the first optical element and the at least one processor element are directly bonded to each other without any intervening adhesive.

3. 3. The bonded optical device of claim 2, wherein the conductive contact pads of the first optical element and the at least one processor element are directly bonded and electrically connected to each other without any intervening adhesive.

4. 4. The bonded optical device of claim 3, wherein each light emitter in said first and second arrays of light emitters is electrically connected to a corresponding driver circuit on said at least one processor element.

5. 5. The bonded optical device of claim 1, wherein a first light emitter of the first array of light emitters and a second light emitter of the second array of light emitters at least partially define a pixel, and wherein the optical path is configured to transmit a superposition of light from the first and second light emitters of the pixel.

6. The at least one processor element comprises a first processor element and a second processor element separate from the first processor element, the first optical element being bonded to the first processor element, and the second optical element being bonded to the second processor element. A bonded optical device according to any one of claims 1 to 5.

7. The bonded optical device according to any one of claims 1 to 5, wherein the at least one processor element comprises a common carrier.

8. The optical path includes an optical waveguide, the first optical element is disposed between the optical waveguide and the first processor element, and the second optical element is disposed between the optical waveguide and the second processor element. A bonded optical device according to any one of claims 1 to 7.

9. 9. The bonded optical device of claim 8, wherein the first and second optical elements are bonded directly to the optical waveguide without any intervening adhesive.

10. 9. The bonded optical device according to claim 8, wherein the first and second optical elements are bonded together with one or more adhesives that are transparent to the first and second color lights, respectively.

11. A bonded optical device according to any one of claims 1 to 10, wherein the first and second optical elements are laterally offset from each other along a direction parallel to a major surface of the at least one processor element, and the light-emitting surfaces of the first and second optical elements are approximately parallel to each other.

12. 11. The junction optical device according to claim 1, wherein the light emitting surfaces of the first and second optical elements are arranged non-parallel to each other.

13. 13. The bonded optical device of claim 1, further comprising one or more optical isolation structures within the first optical element, the optical isolation structures configured to limit crosstalk between adjacent optical emitters.

14. 14. The bonded optical device of claim 1, wherein the first color has a first peak at a first wavelength and the second color has a second peak at a second wavelength, and the difference between the first and second wavelengths is at least 25 nm.

15. The bonded optical device of any preceding claim, wherein the optical path comprises one or more redirecting elements that redirect light from the first and second image regions.

16. The junction optical device according to any one of claims 1 to 15, wherein the optical path comprises a lens configured to act on the superimposed light.

17. 17. The bonded optical device of claim 1, further comprising a third optical element optically coupled to the optical path and bonded to the at least one processor element, the third optical element configured to emit light of a third color different from the first and second colors.

18. 20. The bonded optical device of claim 17, wherein the first, second, and third colors comprise red, green, and blue, respectively.

19. 19. A bonded optical device according to any preceding claim, wherein the light emitters of the first array are independently controllable.

20. A bonded optical device according to any preceding claim, wherein the first and second arrays of light emitters comprise respective arrays of light emitting diodes (LEDs).

21. 21. The bonded optical device of claim 1, wherein the pitch of the light emitters of the first array is less than 50 microns.

22. 21. The bonded optical device of claim 1, wherein the pitch of the light emitters of the first array is less than 10 microns.

23. 23. The bonded optical device of claim 1, wherein each of the first and second arrays of light emitters comprises a plurality of matrices, each matrix comprising a plurality of pixels, and wherein the at least one processor element is configured to selectively control the brightness of the pixels in each matrix.

24. 24. The bonded optical device of claim 23, further comprising isolation features between adjacent matrices of said pixels.

25. 25. The bonded optical device of any preceding claim, wherein each of the first and second optical elements is configured to produce a respective monochromatic image.

26. A bonded optical device, a first optical element bonded directly to the at least one carrier without adhesive, the first optical element configured to emit light of a first color; a second optical element bonded directly to the at least one carrier without adhesive, the second optical element being configured to emit light of a second color different from the first color, the first and second optical elements being laterally offset from each other along a direction parallel to a major surface of the at least one carrier; and an optical path optically coupled to the first and second optical elements, the optical path configured to convey a superposition of light from the first and second optical elements into a light output viewed by a user; A bonded optical device comprising:

27. 27. The bonded optical device of claim 26, wherein the at least one carrier comprises a first carrier and a second carrier separate from the first carrier.

28. 28. The bonded optical device of claim 26 or 27, wherein the at least one carrier comprises at least one processor element including active circuitry configured to control operation of at least one of the first and second optical elements.

29. 29. The bonded optical device of claim 26, wherein the first optical element is bonded directly to the at least one carrier without any intervening adhesive, and the second optical element is bonded directly to the at least one carrier without any intervening adhesive.

30. 30. The bonded optical device of claim 29, wherein respective dielectric bonding surfaces of the first optical element and the at least one carrier are directly bonded to each other without an intervening adhesive.

31. 31. The bonded optical device of claim 30, wherein the respective conductive contact pads of the first optical element and the at least one carrier are bonded directly to one another without an intervening adhesive.

32. 32. The bonded optical device according to any one of claims 26 to 31, wherein the at least one carrier comprises at least one of silicon or glass.

33. 33. The bonded optical device of any one of claims 26 to 32, wherein the at least one carrier has a coefficient of thermal expansion (CTE) of less than 7 ppm.

34. The bonded optical device according to any one of claims 26 to 33, wherein the optical path comprises an optical waveguide.

35. 35. The bonded optical device of claim 26, further comprising a third optical element optically coupled to the optical path, the third optical element being bonded directly to the at least one carrier without adhesive, and the third optical element being configured to emit light of a third color different from the first and second colors.

36. 36. The bonded optical device of claim 35, wherein the first, second, and third colors comprise red, green, and blue, respectively.

37. 37. A bonded optical device according to any one of claims 26 to 36, wherein the first and second optical elements comprise respective arrays of light emitters.

38. 38. The bonded optical device of claim 37, wherein the light emitters are independently controllable.

39. 39. The bonded optical device of claim 37 or 38, wherein the light emitter comprises a light emitting diode (LED).

40. 1. A method of bonding at least one optical element and at least one processor element, comprising: directly bonding a first optical element to at least one processor element without an intervening adhesive, the first optical element comprising a first array of light emitters configured to emit light of a first color, the at least one processor element comprising active circuitry configured to control operation of the first optical element; directly bonding a second optical element to the at least one processor element without an intervening adhesive, the second optical element comprising a second array of light emitters configured to emit light of a second color different from the first color, and the at least one processor element comprising active circuitry further configured to control operation of the second optical element; coupling the first and second optical elements with an optical path, the optical path configured to transmit an overlap of light from the first and second light emitters into an optical output viewable by a user; A method comprising:

41. directly bonding the dielectric bonding surfaces of the first optical element and the at least one processor element together without any intervening adhesive; directly bonding respective conductive contact pads of the first optical element and the at least one processor element without an intervening adhesive; 41. The method of claim 40, further comprising:

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