Patent Application
20240118489
This disclosure relates generally to transfer printable micro-optical components.
Photonic systems use light-sensing, light-emitting, and light-modifying components to manipulate light (e.g., photons), typically for applications in telecommunications. Such systems often rely on integrated circuits using compound semiconductors to efficiently generate and amplify light, for example using lasers and optical amplifiers. The generated light can be modulated, for example with salts such as lithium niobate, and detected, for example with photodiodes having a semiconductor p-n junction that produces electrical current in response to light exposure. Light can also be directed, for example using wave guides or light pipes constructed with materials such as silicon nitride, or optical elements that are substantially transparent at a desired wavelength of light corresponding to emitted, modified, or detected light.
Modern silicon wafers are processed at a very high resolution, for example having features that are 10 nm or less in extent or having features that are separated by 10 nm or less, or both, to make dense and fast integrated circuits. Such small features sizes are a result of expensive photolithographic tools whose cost is justified in terms of the very large volumes of silicon integrated circuits, for example CMOS circuits, that can be processed by the tools. The very large volume of silicon integrated circuits has, in turn, led to the development of low-cost and relatively large source silicon wafers, for example 300 mm in diameter. The combination of low-cost and large silicon source materials and sophisticated process equipment (particularly high-resolution mask and exposure equipment) enables the low cost and ubiquitous silicon integrated circuits that are present in most electronic devices today.
However, silicon is not the optimal material for all desirable semiconductor devices and functions. For example, compound semiconductor materials, such as InP, GaAs, and GaN and many other III/V material combinations, can provide, for example, greater electron mobility, superior light emission, or superior sensor sensitivity and are therefore more suitable for certain applications, such as high-power electrical devices and photonic devices (e.g., lasers and light-emitting diodes) among others. Because these applications are often relatively recently developed and are manufactured at a relatively lower volume than silicon devices, the availability and cost of photolithographic processing equipment and wafer sizes for compound semiconductor materials is disadvantaged with respect to silicon. Essentially, compound semiconductor materials and processing are more expensive and are manufactured at lower resolutions (making larger and more expensive compound semiconductor components) than silicon. In some systems, photonic components are controlled by silicon circuits, for example CMOS circuits.
Optical elements, such as reflectors, refractors, or diffractors are also useful in photonic systems. Conventional optical elements can be too large for miniaturized optical and photonic systems. There is a need therefore, for structures, systems, and methods for small, high-resolution compound semiconductor devices, silicon devices, and optical elements for photonic and optical systems.
The present disclosure provides, inter alia, devices, structures, systems, and construction methods for micro-optical elements, micro-optical components, and micro-optical systems. The devices, structures, or systems can include light emitters, light detectors, light processors, light modifiers, and light transmitters such as lasers, photodiodes, phototransistors, optical modulators, optical amplifiers, and optical wave guides. Such micro-optical structures are useful in photonic systems, such as photonic integrated circuits that combine electrical integrated circuits (e.g., silicon circuits such as CMOS) with optical emitters (such as light-emitting diodes or LEDs and lasers), optical sensors (such as photodiodes) and optical structures (such as mirrors, partial mirrors, prisms, lenses, filters, diffusers, beam-shaping optics, and gratings) that provide one or more of reflection, refraction, polarization detection or modification, filters, or diffraction to light (e.g., photons), thereby processing or modifying the photons. Embodiments of the present disclosure can also comprise wave guides or light pipes for transmitting photons from one location to another.
According to embodiments of the present disclosure, a micro-optical component comprises a micro-substrate having a micro-substrate area and a micro-optical element disposed on the micro-substrate. The micro-optical element can be a passive optical component that modifies photons or one or more photon attributes but is not electrically active. At least a portion of a component tether can be physically attached to the micro-substrate or is physically attached to the micro-optical element. The component tether can be whole, e.g., for a micro-optical component on a component source wafer, or broken (e.g., fractured), or separated, e.g., for a micro-optical component micro-transfer printed to a system substrate.
The micro-optical component can have a thickness (e.g., a height or a depth or both) no greater than 250 μm (e.g., less than 250 μm, no greater than 200 μm, no greater than 150 μm, no greater than 100 μm, no greater than 75 μm, no greater than 50 μm, no greater than 25 μm, or no greater than 10 μm). A thickness, height, or depth of a micro-optical element can be the combined height, depth, or thickness of a micro-substrate and a micro-optical element together in a direction orthogonal to a micro-substrate surface on which the micro-optical element is disposed. The micro-optical element can have a micro-optical element area over the micro-substrate and the micro-substrate area can be greater than the micro-optical element area the micro-substrate area can be equal to the micro-optical element area, or the micro-substrate area can be smaller than the micro-optical element area. In some embodiments, the micro-substrate extends beyond a micro-optical element in only one dimension, e.g., in a direction parallel to the micro-substrate surface. In some embodiments, the micro-substrate extends beyond the micro-optical element in two dimensions, e.g., in orthogonal directions parallel to the micro-substrate surface.
According to embodiments of the present disclosure, the micro-optical element can be a reflection element, a refraction element, a diffraction element, a frequency filter, a phase-change element, a polarization detector, a polarization modifier (e.g., a polarization rotator or a polarization filter), a filter, a frequency converter, or any combination thereof. In some embodiments, the micro-optical element is a lens or a prism. The micro-optical element can be disposed on the micro-substrate surface or formed in the micro-substrate. The micro-optical element can extend away from the micro-substrate in a direction perpendicular to the micro-substrate surface.
In some embodiments, a micro-optical component comprises a light-active element, for example an electrically active light-generating, light-modifying, or light-responsive element (e.g., a light-active element that generates, responds to, or modifies light in combination with received or generated electrical signals, e.g., a light-active component) disposed on the micro-substrate on a side of the micro-substrate opposite the micro-optical element. For example, the micro-optical element can be disposed on a first surface or first side of the micro-substrate and the light-active element can be disposed on a second surface or second side of the micro-substrate opposite and substantially parallel to the first surface or first side of the micro-substrate. The light-active element can send light to or receive light from the micro-optical element. A light-generating element can be a laser or light-emitting diode, a light-responsive element can be a photodiode or phototransistor, and a light-modifying element can be an optical amplifier or an optical modulator. In some embodiments, the micro-substrate comprises a micro-alignment mark disposed in the micro-substrate area exclusive of the micro-optical element area. The micro-substrate can be substantially transparent to light modified by the micro-optical element, the micro-substrate can be substantially reflective to light modified by the micro-optical element, or the micro-substrate can be substantially opaque to or absorb light modified by the micro-optical element or stray or ambient light.
In some embodiments of the present disclosure, the micro-substrate and the micro-optical element are unitary. For example, the micro-optical component can be monolithic and can comprise a common material made in a common construction or manufacturing step, for example by imprinting, two-photon polymerization, or photolithography.
In some embodiments, the micro-substrate and the micro-optical element comprise different materials, the micro-substrate and the micro-optical element comprise different structures adhered together, or both, and consequently are not unitary or monolithic. In some embodiments of the present disclosure, the micro-substrate has a micro-substrate area defined by the micro-substrate length times the micro-substrate width of no greater than 100,000 μm2 (e.g., no greater than 62,500 μm2, less than 62,500 μm2, no greater than 40,000 μm2, less than 40,000 μm2, no greater than 20,000 μm2, no greater than 10,000 μm2, no greater than 2,500 μm2, no greater than 400 μm2, or no greater than 100 μm2). In some embodiments, the micro-substrate has a large aspect ratio (length to width), for example no less than 2:1, no less than 4:1, no less than 5:1, no less than 8:1, or no less than 10:1. In some embodiments, the micro-substrate has a width of no greater than 50 μm and a length of no less than 100 μm, 200 μm, 250 μm, or 500 μm or a width of no greater than 100 μm and a length of no less than 500 μm, 750 μm, or 1000 μm. In some embodiments, the micro-substrate has a width of no greater than 200 μm and a length of no less than 400 μm, 600 μm, 800 μm, 1000 μm, 1200 μm, 1400 μm, 1600 μm, 1800 μm, or 2000 μm.
According to embodiments of the present disclosure, a micro-optical component comprises a protective layer or protective layers. The protective layer or layers can be constructed to desirably interact with light.
In some embodiments, the component tether comprises a portion of the protective layer. In some embodiments, the component tether is a hybrid organic-inorganic tether.
According to embodiments of the present disclosure, a micro-optical system comprises a system substrate and a micro-optical component disposed on the system substrate. The micro-optical component can be non-native to the system substrate. In some embodiments, the micro-optical element extends in a direction away from the system substrate. In some embodiments, the micro-optical system comprises a wave guide or light pipe disposed on or in the system substrate and in optical communication with the micro-optical element. In some embodiments, the system substrate comprises a cavity and the micro-optical element is at least partially disposed in the cavity.
In some embodiments, the micro-substrate is disposed in the cavity. In some embodiments either or both of the micro-optical element and the micro-substrate are adhered to a surface (e.g., side or floor) of the cavity, for example with an adhesive such as an optically clear adhesive or an optical-index matching adhesive. Some embodiments comprise a light pipe disposed in or on the system substrate disposed to transmit light into or out of the micro-optical element. In some embodiments, a micro-optical component comprises a light-active element disposed on the micro-substrate on a side of the micro-substrate opposite the micro-optical element, the system substrate is a semiconductor substrate, and the semiconductor substrate comprises an electronic circuit electrically connected to the light-active element. The electronic circuit can electrically control or respond to the light-active element.
In some embodiments of the present disclosure, the system substrate comprises a micro-alignment mark disposed on or in a surface of the system substrate. The micro-alignment mark can be disposed on or in the surface of the system substrate in alignment with an alignment mark disposed in or on the micro-optical component, for example on the micro-substrate outside the micro-optical element area.
In some embodiments of the present disclosure, the micro-optical system is a photonic integrated circuit.
In some embodiments, the system substrate comprises a cavity and the micro-optical element is disposed at least partially in the cavity. In some embodiments, the micro-optical system comprises adhesive that adheres the micro-optical element to the micro-substrate or adheres the micro-optical component to the system substrate or to a wall or floor (bottom) of a cavity in the system substrate. In some embodiments, the micro-optical system comprises an optical-index-matching material (e.g., an optically clear adhesive) disposed on any of the micro-optical element, micro-substrate, or system substrate. An optical-index-matching material or adhesive can fill a gap between the micro-optical element and the micro-substrate, or between the micro-optical component (e.g., the micro-optical element) and the system substrate, for example in a cavity in the system substrate.
Thus, according to embodiments of the present disclosure, a cavity in a system substrate has one or more cavity sides (e.g., walls) extending into the system substrate and the micro-optical element is disposed in contact with one or more of the cavity sides. In some embodiments, the micro-optical element is disposed in the cavity but does not contact any of the cavity sides or floor. In some embodiments, the micro-optical element extends out of the cavity, for example above a surface of the system substrate. In some embodiments, the micro-substrate is disposed at least partially in the cavity. In some embodiments, the micro-substrate is disposed exclusively in the cavity. A surface of the micro-substrate can be substantially (e.g., within manufacturing tolerances) in a common plane with a surface of the system substrate. In some embodiments, the cavity has one or more cavity sides or walls extending into the system substrate and the micro-substrate is disposed in contact with one or more of the cavity sides or walls. In some embodiments, the cavity has a cavity floor (e.g., cavity bottom) in the system substrate and the micro-substrate is disposed in contact with the cavity floor, e.g., adhered to the cavity floor with an adhesive such as an optical-index matching adhesive.
In some embodiments of a micro-optical system according to the present disclosure, the system substrate comprises a structural (e.g., mechanical) stop disposed on a surface of the system substrate and the micro-optical component is in contact with or adhered to the structural stop. The structural stop can be formed, e.g., photolithographically, in or on the system substrate surface or can be a side (e.g., wall) of a cavity formed in the system substrate, for example by pattern-wise etching or imprinting the system substrate. The micro-substrate or the micro-optical element (or both) can be adjacent to, in contact with, or adhered to structural stop.
According to embodiments of the present disclosure, a micro-optical component source wafer comprises a source wafer comprising one or more sacrificial portions separated by one or more anchor portions and a micro-optical component disposed entirely and directly over each of the one or more sacrificial portions and physically attached to one of the one or more anchor portions by a tether.
According to embodiments of the present disclosure, a method of making a micro-optical system comprises providing a micro-optical component source wafer, providing a stamp, providing a system substrate, contacting the stamp to the micro-optical component, removing the micro-optical component from the micro-optical component source wafer with the stamp, contacting the micro-optical component to the system substrate with the stamp, and removing the stamp from the micro-optical component and the system substrate. In some embodiments, an adhesive layer is disposed on the system substrate and the micro-optical component contacted and adhered to the adhesive layer and system substrate.
According to embodiments of the present disclosure, a method of making a micro-optical system comprises providing a micro-optical component source wafer, providing a first stamp and a second stamp, providing a system substrate, contacting the first stamp to a first side of the micro-optical component, removing the micro-optical component from the micro-optical component source wafer with the first stamp, contacting the micro-optical component to a second side of the micro-optical component opposite the first side with the second stamp, contacting the first side of the micro-optical component to the system substrate with the second stamp, and removing the second stamp from the micro-optical component and the system substrate.
A method of making a system (e.g., a micro-optical system) according to the present disclosure can comprise providing a micro-optical component source wafer having one or more sacrificial portions separated by one or more anchor portions, coating at least a portion of the one or more sacrificial portions with a liquid curable polymer, forming a structure (e.g., a micro-optical component), wherein forming the structure comprises using two-photon polymerization to cure only a portion of the liquid curable polymer to form at least a portion of the structure, such as a micro-optical component, forming a component tether between the micro-optical component and one of the one or more anchor portions, and removing an uncured portion of the liquid curable polymer to form a gap between the structure and the component source wafer and make a micro-transfer-printable structure. In some embodiments, the sacrificial portion is a cavity and embodiments comprise disposing at least a portion of the liquid curable polymer in the cavity and curing only a portion of the liquid curable polymer in the cavity to form at least a portion of the structure (e.g., a micro-optical component) in the cavity. In some embodiments of the present disclosure, methods can comprise providing a micro-optical component source wafer comprising a cavity adjacent to one or more anchor portions, disposing at least a portion of a liquid curable polymer in the cavity, forming a structure (e.g., a micro-optical component), wherein forming the structure comprises using two-photon polymerization to cure only a portion of the liquid curable polymer to form at least a portion of the structure, forming a component tether between the structure and one of the one or more anchor portions, and removing an uncured portion of the liquid curable polymer (e.g., from the cavity).
According to embodiments of the present disclosure a method of making a system (e.g., a micro-optical system) can comprise providing a micro-optical component source wafer comprising one or more sacrificial portions separated by one or more anchor portions, coating at least a portion of the one or more sacrificial portions with a liquid curable polymer, forming a structure (e.g., a micro-optical component), wherein forming the structure comprises using imprint lithography to form at least a portion of the structure (e.g., a micro-optical component), and forming a component tether between the micro-optical component and one of the one or more anchor portions.
According to embodiments of the present disclosure a method of making a system (e.g., a micro-optical system) can comprise providing a micro-optical component source wafer comprising one or more sacrificial portions separated by one or more anchor portions, forming a mold in one of the one or more sacrificial portions, coating at least a portion of the sacrificial portions including the mold with a liquid curable polymer, forming a structure (e.g., a micro-optical component), wherein forming the structure comprises curing the liquid curable polymer, and forming a component tether between the structure and one of the one or more anchor portions. The mold can be made by etching a solid material in the sacrificial portion.
According to embodiments of the present disclosure a method of making a system (e.g., a micro-optical system) can comprise providing a micro-optical component source wafer comprising a cavity adjacent to an anchor portion, using imprint lithography to form a mold in the cavity, wherein using imprint lithography comprises coating the cavity with a liquid curable polymer and curing the liquid curable polymer, forming a structure (e.g., a micro-optical component), wherein forming the structure comprises disposing a material in the mold that is differentially etchable from the mold, forming a component tether between the micro-optical component and one of the anchor portions, and etching the cured polymer to release the transfer-printable structure. The cavity can be a sacrificial portion.
In some embodiments of the present disclosure, a micro-optical component comprises a micro-substrate having a micro-substrate area and a micro-optical element disposed on the micro-substrate area of the micro-substrate. The micro-optical element can have a micro-optical element area over the micro-substrate and the micro-substrate area can be greater than the micro-optical element area. According to embodiments of the present disclosure, the component tether can be made in a common step with forming the structure (e.g., micro-optical component) or can be made in additional deposition and processing (e.g., patterning) steps. In some embodiments, the component tether comprises tether portions made in a common step with forming the structure and comprises additional tether portions including different materials made using additional deposition and processing (e.g., patterning) steps, e.g., to make a hybrid tether comprising multiple, different materials, such as organic (e.g., polymer) and inorganic (e.g., silicon oxide or nitride) materials.
Methods described herein can be used to make micro-optical systems, but are not limited to such and can, for example, be used to make non-optical micro-systems. Structures of the present disclosure can be, in some embodiments, non-optical micro-components for example micro-transfer-printable non-optical micro-components having dimensions in the micron range, e.g., any combination of a height, width, or length less than or equal to 250 μm, less than 250 μm, no greater than 200 μm, no greater than 150 μm, no greater than 10 μm, no greater than 75 μm, no greater than 50 μm, no greater than 25 μm, or no greater than 10 μm.
In some embodiments, components of the present disclosure include a broken (e.g., fractured) or separated tether after the micro-optical component is printed to a component substrate, for example by micro-transfer printing.
Embodiments of the present disclosure provide micro-transfer-printable micro-optical components, systems, sources, and methods useful in highly integrated optical and photonic systems.
Drawings are presented herein for illustration purposes, not for limitation. Drawings are not necessarily drawn to scale. The foregoing and other objects, aspects, features, and advantages of the disclosure will become more apparent and may be better understood by referring to the following description taken in conjunction with the accompanying drawings, in which:
Certain embodiments of the present disclosure provide, inter alia, devices, structures, systems, and methods for micro-optical elements, micro-optical components, and micro-optical systems. Micro-optical structures are useful in photonic systems, such as photonic integrated circuits that combine electrical integrated circuits (e.g., silicon circuits such as CMOS) with optical emitters (such as light-emitting diodes and lasers), optical sensors (such as photodiodes and phototransistors), optical amplifiers, optical modulators, and passive optical structures (for example reflectors such as mirrors, partial mirrors, diffusers, and prisms, refractors, such as lenses, beam-shaping optics, filters, frequency converters, and diffractors, such as gratings) that provide reflection, refraction, diffraction, conversion, or filtering to photons, thereby redirecting, processing, or modifying the photons. Embodiments of the present disclosure can also comprise optical wave guides or light pipes for transmitting photons from one location to another. Photons propagating through free space (e.g., a vacuum or gas such as the atmosphere) or through a solid or liquid material having a constant optical index are also referred to herein as light, light rays, or light beams. Processed or modified light is light (e.g., photons, light rays, or light beams) whose direction, frequency, phase, frequency distribution, polarization, or propagation characteristics are changed, for example by reflection, refraction, conversion, filtering, or diffraction with an optical structure. Optical devices or structures interact with photons. Embodiments of the present disclosure provide micro-optical elements that are too small to construct and locate in photonic systems using known methods and material and can be used, therefore, to construct photonic systems that cannot be made using methods of the prior art.
Optical emitters, amplifiers, modulators, or sensors can comprise semiconductor components made with semiconductors such as silicon or compound semiconductors such as GaN, GaAs, or InP, or other light-sensitive materials such as lithium niobate using fabrication facilities and materials, for example compatible with silicon fabrication facilities. The semiconductors can comprise active circuits or devices, for example transistors, optical sensors, optical amplifiers, or optical light emitters such as lasers, light-emitting diodes (LEDs), or photodiodes. In some embodiments, the devices, structures, and systems disclosed herein comprise a silicon substrate or a silicon substrate comprising a silicon circuit. The silicon circuit can be connected to non-silicon semiconductor components to make a heterogeneous module, for example a light-control circuit, light-modifying circuit, or light-responsive circuit for light emitters or light responders.
Optical structures such as micro-optical elements of the present disclosure that modify light can comprise, for example, glass, polymers, or silicon. Micro-optical elements can be at least partially transparent (e.g., at least 50% transparent, at least 60% transparent, at least 70% transparent, at least 80% transparent, at least 90% transparent, or at least 95% transparent) to light of a desired frequency or frequencies, such as light modified, generated, or sensed by micro-optical elements, light emitters, or light sensors of the present disclosure. The optical structures can comprise multiple layers or coatings disposed on one or more surfaces of the optical structures, such as index-matching coatings, reflective coatings such as thin silver or aluminum layers, phase-change layers, polarization-sensitive layers, or anti-reflection layers. Light can be, for example, visible light, infrared light, ultraviolet light, any electromagnetic radiation having a frequency between 300 GHz and 3000 THz or a wavelength from 10 nm to 1000 μm, and generally any electromagnetic wave of any frequency that can be or is intentionally modified or otherwise processed with a micro-optical element. Substrates on which one or more micro-optical elements are disposed can be at least partially transparent (e.g., transparent) (e.g., at least 50% transparent, at least 60% transparent, at least 70% transparent, at least 80% transparent, at least 90% transparent, or at least 95% transparent) to light of a desired frequency or frequencies. In some embodiments, substrates on which one or more micro-optical elements are disposed can be at least partially reflective (e.g., reflective) (e.g., at least 50% reflective, at least 60% reflective, at least 70% reflective, at least 80% reflective, at least 90% reflective, or at least 95% reflective) to light of a desired frequency or frequencies. In some embodiments, substrates on which one or more micro-optical elements are disposed can be at least partially absorptive (e.g., opaque) (e.g., at least 50% absorptive, at least 60% absorptive, at least 70% absorptive, at least 80% absorptive, at least 90% absorptive, or at least 95% absorptive) to light of a desired frequency or frequencies.
According to embodiments of the present disclosure and as illustrated in
Micro-optical element 14 can be a passive optical structure that does not require external power (e.g., electrical power). Micro-optical component 10 can comprise at least a portion of a component tether 11 physically attached to micro-substrate 12 or physically attached to micro-optical element 14. Component tether 11 can be broken (e.g., fractured) or separated. Micro-optical component 10 can have a thickness H (e.g., a height or depth of micro-optical component 10) no greater than 250 μm (e.g., less than 250 μm, no greater than 200 μm, no greater than 150 μm, no greater than 100 μm, no greater than 75 μm, no greater than 50 μm, no greater than 25 μm, or no greater than 10 μm) in a direction D orthogonal to a surface of micro-substrate 12 on which micro-optical element 14 is disposed. Micro-optical components 10 having such a size or thickness are not readily or accurately micro-assembled into a micro-optical system using techniques of the prior art. Thus, embodiments of the present disclosure enable the precise micro-assembly of micro-optical components 10 in large volumes into photonic systems that are smaller and less expensive.
Micro-optical element 14 can have a micro-optical element area 18 on or over micro-substrate surface 13. Micro-substrate surface 13 can have a micro-substrate area 16 that is greater than micro-optical element area 18, as shown in
Micro-optical component 10 can comprise micro-alignment marks 15 (fiducial marks) disposed on or in micro-substrate 12 to assist in aligning micro-optical components 10 on a system substrate 40 in a micro-optical system 70, as discussed further below. Micro-substrate surface 13 can have a micro-substrate area 16 exclusive of micro-optical element area 18 that absorbs or diffuses stray light 50, for example to reduce unwanted reflections in a micro-optical system 70. Such an area of micro-substrate surface 13 can be black, for example coated with a light 50 absorbing material such as carbon black. Thus, micro-substrate 12 can have portions that are light-transparent or light-reflective and portions that are light-absorptive (e.g., light absorbing or light absorbent). In some embodiments, micro-substrate 12 can have portions that are light-transparent and other portions that are light-reflective. Patterned micro-substrates 12 can be made, for example, by pattern-wise material deposition such as evaporation of light-reflective or light-absorbing materials, for example using photolithographic, coating, or inkjet deposition methods.
In some embodiments of the present disclosure, micro-substrate 12 can transmit but does not intentionally modify (e.g., redirect or transform) light 50, in contrast to micro-optical element 14. In particular, in some embodiments, micro-substrate area 16 exclusive of micro-optical element area 18 is not intended to manipulate light 50 or otherwise modify light 50 and, in some embodiments, does not receive light 50. Those knowledgeable in optical design will appreciate that any real-world system is subject to ambient light 50 or unwanted light 50 reflection, or propagation and such light 50 can impinge on micro-substrate area 16 exclusive of micro-optical element area 18. To reduce such unwanted effects, micro-substrate area 16 exclusive of micro-optical element area 18 can absorb light 50, for example with a coating of a black material such as carbon black. In some embodiments, micro-optical element area 18 of micro-substrate 12 can be a portion of micro-optical element 14 (e.g., micro-optical element 14 can comprise the portion of micro-substrate 12 that is in micro-optical element area 18).
In some embodiments of the present disclosure, micro-substrate 12 can modify (e.g., redirect or transform) light 50, in combination with micro-optical element 14. For example, micro-substrate 12 can have a reflective coating 19 (or be reflective as shown in
Micro-optical element 14 can be a passive optical element that modifies light 50 by, for example, reflecting, partially reflecting, filtering, frequency converting, phase changing, polarization changing, refracting, or diffracting light 50 incident on micro-optical element 14, for example modifying a light ray, light beam, or photons 50 that intersect with micro-optical element 14, for example on an optical surface or face of micro-optical element 14. Micro-optical element 14 can be a mirror, partial mirror, or diffraction grating and can be coated with optical coatings such as anti-reflection coatings, to reduce unwanted optical effects, or can incorporate passive optical materials such as filters or multiple layers that filter desired frequencies of light 50 through optical interference. In some embodiments, micro-optical element 14 is a lens (e.g., a lenslet, that has optical power) or a prism. In some embodiments, micro-optical element 14 is a micro-lens, an array of micro-lenses, or comprises multiple micro-lenses. In some embodiments, micro-optical element 14 is an array of micro-optics (e.g., micro-lenses or micro-diffractive gratings). Micro-optical element 14 can comprise fluorescent or phosphorescent material coatings to absorb and re-emit light 50. Micro-optical element 14 can change the phase or frequency distribution, or both, of incident light 50. Micro-optical element 14 can be a light filter. Micro-optical element 14 can focus or defocus incident light 50. Micro-optical element 14 can be a Fresnel lens. In some embodiments, micro-optical element 14 can redirect light 50 from a direction parallel to micro-substrate surface 13 (horizontal) to a direction D orthogonal to micro-substrate surface 13 (vertical), for example as shown in
In the embodiments illustrated in
In some embodiments and as illustrated in
In some embodiments of the present disclosure, micro-substrate 12 and micro-optical element 14 are unitary and integral, for example comprise a single structure having different portions, can comprise a same material, can be a same material, or can be made in a common process, for example in a common manufacturing step or steps with common materials. Micro-optical component 10 can be monolithic. For example, in some embodiments, micro-optical component 10 comprises a curable polymer, such as a photoresist, epoxy, or resin. In some embodiments, micro-substrate 12 comprises a different material from micro-optical element 14 and can be made using different steps at different times or can comprise different structures made at different times in different places of different materials adhered together, for example micro-optical element 14 can be adhered to micro-substrate surface 13 of micro-substrate 12 with an optically clear adhesive. In some embodiments, the adhesive can be a metal, e.g., a reflective metal or a solder. Micro-substrate 12 can have substantially parallel opposing sides (as shown in the Figures) or can have opposing sides that are not parallel. For example, in some embodiments, micro-substrate 12 comprises a substantially transparent oxide such as silicon dioxide and micro-optical element 14 comprises a curable polymer. In some embodiments, micro-substrate 12 is not substantially transparent to light 50 and can comprise, for example, a ceramic or light-absorbing resin. Either or both of micro-substrate 12 and micro-optical element 14 of micro-optical component 10 can be made by injection molding, stamping, etching, two-photon polymerization, micro- or nano-imprinting, imprint lithography (e.g., nanoimprint lithography) or any of various photolithographic processing steps separately or at the same time, including but not limited to any one or combination of spray coating, spin coating, blade coating, hopper coating, curtain coating, evaporative coating, sputtering, ablation, masking, etching, and curing.
In some embodiments, micro-optical component 10 is coated with a material, such as a polymer or inorganic oxide or nitride, such as silicon dioxide or silicon nitride that is differentially etchable from a material of sacrificial portions 34 or micro-optical component source wafer 30. The material is processed, for example using photolithographic methods and materials including masking and etching or, in some embodiments, by rinsing. Such a method is particularly useful for inorganic materials but can also be used by organic materials. In some embodiments, the material is coated in a liquid state, photolithographically processed, and then cured. (The liquid material can be soft-cured before photolithographic processing.) In some embodiments, the material is coated in a liquid state, shaped, and then cured. The material can be, but is not necessarily, soft-cured before shaping. Organic materials, for example polymers, can be shaped by micro-imprinting (micro-molding), for example with a master mold such as a photolithographically constructed silicon master mold, and then cured (either with the mold in place or after the mold is removed), or shaped by two-photon polymerization, to form micro-optical component 10. Micro-optical components 10 can be photolithographically processed after micro-molding, for example to segment multiple micro-optical components 10 from each other over the surface of component source wafer 30 or to provide additional optical or protective encapsulating layers. The additional layers can be patterned.
Once micro-optical components 10 are constructed, they can be under-etched by etching sacrificial portions 34 to form a gap 36 and suspend micro-optical components 10 over gap 36 and component source wafer 30 by a component tether 11. In some embodiments, micro-substrate 12 or micro-optical element 14 is differentially etchable from a material comprising sacrificial portion 34. For example, micro-substrate 12 or micro-optical element 14 can comprise a layer of silicon dioxide or silicon nitride disposed and patterned over sacrificial portion 34 and component source wafer 30 and sacrificial portion 34 can comprise a semiconductor such as silicon. Micro-optical element 14 is then formed, for example by micro-imprinting and curing a polymer layer or using two-photon polymerization to cure a polymer layer, and then encapsulated to protect the cured polymer material from the sacrificial portion 34 etching process.
In some embodiments, sacrificial portion 34 of component source wafer 30 is photolithographically processed to form physical structures such as indentations or pits, for example inverted pyramids, as a mold in a material of sacrificial portion 34, for example a material such as crystalline silicon. The structured surface of sacrificial portion 34 is coated, e.g., by sputtering, evaporation, spin coating, spray coating, or slot coating with a material of micro-optical component 10, and then shaped, for example by photolithographic processing or by micro-imprinting and curing, to construct micro-optical component 10 on sacrificial portion 34. Sacrificial portion 34 is then etched to suspend micro-optical component 10 over sacrificial portion 34 and component source wafer 30. Thus, micro-optical element 14 can extend from micro-substrate 12 towards micro-optical component source wafer 30 or away from micro-optical component source wafer 30, depending on the method of construction used. The specific angle of the mold and, hence, micro-optical element 14 with respect to micro-substrate 12 can be defined by the crystalline nature of sacrificial portion 34, for example due to crystallographic orientation of (e.g., fast) etch planes relative to a crystallographic orientation of micro-optical component source wafer 30.
Micro-optical components 10 can be constructed in a variety of ways. In some embodiments of the present disclosure and as shown in
In some embodiments of the present disclosure and as shown in
In some embodiments and as illustrated in
According to embodiments of the present disclosure, different two-photon polymerization, micro-imprint, and/or photolithographic methods can be combined to make different micro-optical elements 14 in a micro-optical component 10 or different portions of micro-optical component 10, for example to make the different micro-optical elements 14 in micro-optical component 10 of
In some embodiments, component tethers 11 can comprise only organic materials, e.g., as shown in
Those knowledgeable in two-photon polymerization, micro-imprinting, and photolithography will appreciate that the methods described herein for making micro-optical components 10 are not limited in the different micro-optical structures that can be formed. In particular, a great variety of micro-optical elements 14 can be constructed using these techniques. Furthermore, a variety of materials can used in, and coatings applied to, micro-optical elements 14 of the present disclosure. Non-optical micro-transfer-printable components, devices, and structures can also be constructed using these techniques.
The location of a light beam 50 that reflects or refracts from a surface of micro-optical element 14 can be accommodated by a correspondingly located light-active element 20 or light-transmissive element such as a light pipe 44 (e.g., an optical wave guide) in a micro-optical system 70 comprising micro-optical component 10, as shown in
In some embodiments and as shown in
Moreover, in some embodiments, for micro-optical systems 70 and as shown in
Micro-optical elements 14 can extend in a direction toward system substrate 40 (e.g., into system substrate 40) or away from system substrate 40 (e.g., away from system-substrate surface 43 in direction D as shown in
In some embodiments, cavity 42 can be filled or partially filled with a material, such as an optical-index-matching material to reduce stray reflections from surfaces of cavity 42 or micro-optical element 14. The optical-index-matching material can be a curable polymer disposed as a liquid in cavity 42 before or after micro-optical component 10 is disposed on system substrate 40 and micro-optical element 14 is disposed in cavity 42, e.g., as shown in
In various embodiments, system substrate 40 can be a semiconductor (e.g., silicon or a compound semiconductor), glass, polymer, resin, ceramic, sapphire, or a printed circuit board. Micro-electronic components 22 disposed on system substrate 40 can be integrated circuits, e.g., micro-transfer printed unpackaged bare die, and can process electrical signals received from or provided to light-active elements 20. Micro-electronic components 22 can be constructed using photolithographic processes on silicon (or other semiconductor) wafers. Light-active elements 20 can be constructed using photolithographic processes for compound semiconductor wafers such as InP, GaAs, GaN and various alloys thereof.
In general, components of the present disclosure can be assembled using micro-transfer printing to remove components (e.g., micro-optical components 10, light-active elements 20, and micro-electronic components 22) from a component source wafer 30 and disposing them on a system substrate 40, thereby breaking (e.g., fracturing) or separating component tethers 11 used to hold the component in place over an etched sacrificial portion 34 or cavity 42 (e.g., gap 36) of the component source wafer 30 to an anchor portion (anchor 32) of the component source wafer 30. Micro-transfer printing is useful for micro-assembling micron-scale components. For example, any of micro-optical components 10, light-active elements 20, and micro-electronic components 22 can have a lateral extent over system-substrate surface 43 of no greater than two hundred μm, no greater than one hundred μm, no greater than fifty μm, no greater than twenty μm, no greater than ten μm, no greater than five μm, no greater than three μm, or no greater than two μm and a thickness no greater than one hundred μm, no greater than fifty μm, no greater than twenty μm, no greater than ten μm, no greater than five μm, no greater than two μm, or no greater than one micron.
In some embodiments, it can be desirable to construct micro-optical element 14 extending away from component source wafer 30 (for example due to fabrication constraints) but to dispose it onto system substrate 40 in cavity 42. In some such embodiments, micro-optical component 10 can be inverted (e.g., flipped over) after picking up micro-optical component 10 with micro-transfer printing stamp 60 and before printing micro-optical component 10 onto system substrate 40. This inversion can be accomplished with a stamp-to-stamp transfer. In such a transfer, a first micro-transfer printing stamp 60A is used to pick up micro-optical component 10 from component source wafer 30 (step 140 shown in
Micro-optical component 10 can be constructed in any of a variety of ways, examples of which are illustrated in
In step 230, micro-optical element 14 or micro-substrate 12 (or both, comprised in micro-optical component 10) are formed. In some embodiments, micro-optical element 14 or micro-substrate 12, or both, are formed using two-photon polymerization to cure liquid uncured polymer 37 to make a three-dimensional structure forming a solid structure comprising cured polymer 38, for example as shown in
Once liquid uncured polymer 37 is cured to make the three-dimensional cured polymer 38 structure, sacrificial portion 34 can be removed in step 240 to form gap 36, for example by rinsing (e.g., where two-photon polymerization was used as in
In some embodiments and as shown in
In some embodiments, sacrificial portion 34 can be made by depositing a liquid, curable polymer in a cavity 42 in micro-optical component source substrate 30, for example as in
The components (e.g., micro-optical components 10) transfer printed to system substrate 40 are non-native to system substrate 40. In embodiments in which system substrate 40 is a semiconductor (e.g., silicon), a circuit (e.g., a native micro-electronic component 24 as shown in
As used herein, a device native to a substrate is formed on the substrate, for example by photolithographically processing layers of material that were directly deposited on the substrate, for example by sputtering or vapor deposition. A device formed on a native substrate (e.g., component source substrate 30) and then transferred to a second substrate is non-native to the second substrate (e.g., system substrate 40).
Embodiments of the present disclosure provide devices and methods for micro-assembling heterogeneous components, e.g., micro-optical components 10, non-native micro-electronic components 22, and light-active elements 20, that can all comprise materials different from a material of system substrate 40. In some embodiments, heterogeneous micro-optical system 70 comprises different materials, e.g., different components comprising semiconductor materials such as different compound semiconductor materials such as GaAs, InP, GaN disposed on a common system substrate 40, for example glass, ceramic, printed-circuit boards, or silicon. System substrate 40 can comprise native semiconductor circuits. Using non-native materials enables the best material to be used for each component and avoids component photolithographic processing incompatibilities.
Various embodiments of structures and methods are described herein that include (e.g., were made by) printing components such as micro-optical components 10. Printing may include or be micro-transfer printing. As used herein, micro-transfer-printing involves using a transfer device (e.g., a visco-elastic elastomeric micro-transfer printing stamp 60, such as a polydimethylsiloxane (PDMS) micro-transfer printing stamp 60) to transfer a component using controlled adhesion. For example, an exemplary transfer device can use kinetic, rate-dependent, or shear-assisted control of adhesion between a transfer device (e.g., micro-transfer printing stamp 60) and a component such as micro-optical component 10. It is contemplated that, in certain embodiments, where a method is described as including micro-transfer-printing a component, other analogous embodiments exist using a different transfer method. In methods according to certain embodiments, a vacuum tool, electrostatic tool, or other transfer device is used to print a micro-optical component 10, for example by contacting micro-substrate 12 in a micro-substrate area 16 exclusive of micro-optical element area 18.
System substrate 40 can be a module substrate, for example of a micro-transfer printable module. For example, printing (e.g., micro-transfer printing) and other processing (e.g., photolithographic processing) can be used in combination to assemble and optically interconnect micro-optical components 10 on system substrate 40 to form a module that itself can be transferred (e.g., printed, such as micro-transfer printed) to another, larger target substrate. In some such embodiments where system substrate 40 is a module substrate, system substrate 40 can be native to a module source wafer. System substrate 40 can then be released from the module source wafer by etching (e.g., with gas or liquid etchant) (e.g., such that it is suspended from the module source wafer by a tether) and then printed (e.g., with an elastomeric stamp).
In some embodiments, micro-substrate 12 comprises a micro-optical element 14 disposed therein. For example, micro-substrate 12 and micro-optical element 14 can be integral with each other.
In some embodiments, a stamp used to print micro-optical component 10 has a structured post to avoid contacting delicate micro-optical element 14, which could damage it or otherwise impair its subsequent performance. For example, a stamp may have a suction cup profile. In some embodiments, micro-optical component 10 having micro-optical element 14 extending from micro-substrate 12 towards component source wafer 30 allows for stamps with unstructured posts, or other analogous transfer devices, to be used without risking damage to micro-optical element 14.
Examples of micro-transfer printing processes suitable for printing components onto system substrates 40 are described in U.S. Pat. No. 8,722,458 entitled Optical Systems Fabricated by Printing-Based Assembly, U.S. Pat. No. 9,362,113 entitled Engineered Substrates for Semiconductor Epitaxy and Methods of Fabricating the Same, U.S. Pat. No. 9,358,775 entitled Apparatus and Methods for Micro-Transfer-Printing, U.S. patent application Ser. No. 14/822,868, filed on Aug. 10, 2015, entitled Compound Micro-Assembly Strategies and Devices, and U.S. Pat. No. 9,704,821 entitled Stamp with Structured Posts, each of which is hereby incorporated by reference herein in its entirety.
It is contemplated that systems, devices, methods, and processes of the disclosure encompass variations and adaptations developed using information from the embodiments described herein. Adaptation and/or modification of the systems, devices, methods, and processes described herein may be performed by those of ordinary skill in the relevant art.
Throughout the description, where articles, devices, and systems are described as having, including, or comprising specific components, or where processes and methods are described as having, including, or comprising specific steps, it is contemplated that, additionally, there are articles, devices, and systems according to certain embodiments of the present disclosure that consist essentially of, or consist of, the recited components, and that there are processes and methods according to certain embodiments of the present disclosure that consist essentially of, or consist of, the recited processing steps.
It should be understood that the order of steps or order for performing certain actions is immaterial so long as operability is not lost. Moreover, two or more steps or actions may be conducted simultaneously.
Certain embodiments of the present disclosure were described above. It is, however, expressly noted that the present disclosure is not limited to those embodiments, but rather the intention is that additions and modifications to what was expressly described in the present disclosure are also included within the scope of the disclosure. Moreover, it is to be understood that the features of the various embodiments described in the present disclosure were not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations were not made express, without departing from the spirit and scope of the disclosure. Having described certain implementations of heterogeneous wafer structures, heterogeneous semiconductor structures, methods of their fabrication, and methods of their use, it will now become apparent to one of skill in the art that other implementations incorporating the concepts of the disclosure may be used. Therefore, the disclosure should not be limited to certain implementations, but rather should be limited only by the spirit and scope of the following claims.
This application claims the benefit of U.S. Provisional Patent No. 63/414,423 filed on Oct. 7, 2022, the disclosure of which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63414423 | Oct 2022 | US |
