Patent Application
20250067686
The present invention relates, in general, to methods and an apparatus for processing a substrate. More specifically, the disclosure describes manufacturing processes using thermally-assisted chemical etching and real-time, closed-loop process control to precisely form optical elements from a substrate.
Manufacturing processes traditionally employed to machine optical elements (e.g. mirrors, flats, reflectors and lenses) are laborious and time-consuming, increasing the cost of these elements. Processes such as single-point diamond turning, multi-axis computer numerical control (CNC) machining, and grinding and polishing are protracted operations that typically allow only one or few optical elements to be machined at a time. Moreover, following the initial manufacturing process, the optical elements must be measured and tested to ensure compliance with design specifications. The manufacturing processes and ensuing metrology may need to be repeated multiple times to achieve a desired dimensional precision and surface quality, further extending the manufacturing time and cost.
Furthermore, optical components that are non-rotationally symmetric about an axis perpendicular to the surface of the component (i.e. freeform optics) can help to reduce the size and weight of an optical system and mitigate optical aberrations. Traditional methods of machining optics, however, use rotational tools that struggle to create non-rotationally symmetric surfaces. Rotary tools have constraints that leave imprints in the optical surface and produce errors in the desired optical surface shape. Due to the aforementioned weaknesses in optics manufacturing, there is a need for an improved method that is rapid, low-cost, more robust (i.e. less sensitive to environmental conditions) and capable of producing freeform optical surfaces.
A method of controlling a substrate etching process includes a surface of a substrate adjacent to etching fluid to produce an etchant-substrate interface and placing an electromagnetic radiation emitter on a moveable positioner. The method also includes focusing electromagnetic radiation from the electromagnetic radiation emitter to a portion of the etchant-substrate interface. The portion of the etchant-substrate interface having a surface area of not less than 0.05 squared micrometers (“μm2”) and not greater than 80 squared millimeters (“mm2”). The method includes selectively heating the portion of etchant-substrate interface using the focused electromagnetic radiation. The method includes transmitting a monitoring beam through the substrate, the substrate and volume of etching fluid being at least partially transparent over a wavelength range. The wavelength range includes a wavelength of the monitoring beam. The method includes measuring a property of the substrate surface, while selectively heating the portion, via the monitoring beam to produce a real-time measured property for the substrate. A corresponding etching system and computer-program product is also disclosed herein.
In some examples, the method includes moving the electromagnetic radiation emitter to selectively heat the portion of the etchant-substrate interface and increase an etching rate for the portion of the etchant-substrate interface.
In some examples, the method includes adjusting a power output of the electromagnetic radiation emitter to selectively heat the portion of the etchant-substrate interface and increase an etching rate for the portion of the etchant-substrate interface.
In some examples, the method includes adjusting one or more of a power output and position of the electromagnetic radiation emitter according to the measured property for the substrate. In some examples, adjusting the one or more of the power output and position of the electromagnetic radiation emitter changes an etching rate for the portion of the etchant-substrate interface.
In some examples, the method includes adjusting the surface area of the portion of the etchant-substrate interface by moving at least one of a focusing lens or a location of the electromagnetic radiation emitter according to the measured property for the substrate. In some examples, adjusting the surface area of the portion of the etchant-substrate interface changes an etched area of a portion of the substrate.
In some examples, the method includes placing the electromagnetic radiation emitter to a distance of not less than 1 mm and not greater than 150 mm away from the substrate and moving the electromagnetic radiation emitter using a multi-axis stage.
In some examples, the electromagnetic radiation emitter includes one or more of a laser, LED, lightbulb, or any combination thereof. In some examples, the electromagnetic radiation emitter includes one or more of a laser, LED, lightbulb, or any combination thereof. In some examples, the electromagnetic radiation emitter is configured to emit at least two beams from a single optical fiber, each laser beam of the at least two beams having a different wavelength.
In some examples, the method includes projecting a laser image onto the etchant-substrate interface concurrently with focusing the electromagnetic radiation to heat an additional portion of the etchant-substrate interface, the additional portion of the etchant-substrate interface having a surface area greater than the surface area of the portion of the etchant-substrate interface. In some examples, projecting the laser image includes emitting a first laser beam having a first wavelength. In some examples, focusing electromagnetic radiation from the electromagnetic radiation emitter includes emitting a second laser beam, the second laser beam having a second wavelength different from the first wavelength.
Examples of the present disclosure include a method for controlling a substrate etching process. The method includes disposing a surface of a substrate adjacent to a volume of etching fluid to produce an etchant-substrate interface. The method includes collimating a laser beam using at least one lens. The method includes directing the collimated laser beam onto at least one moveable mirror. The method includes focusing the laser beam from at the least one moveable mirror to a portion of the etchant-substrate interface. The portion of the etchant-substrate interface has a surface area of not less than 0.05 squared micrometers and not greater than 80 squared millimeters. The method includes heating the portion of the etchant-substrate interface with the focused laser beam. The method includes transmitting a monitoring beam through the substrate. The substrate and volume of etching fluid are at least partially transparent at a wavelength range. The wavelength range includes a wavelength of the monitoring beam. The method includes measuring a property of the substrate, after heating the portion, via the monitoring beam to produce a measured property for the substrate.
In some examples, one or more of the at least one moveable mirror includes a galvo-scan mirror. In some examples, the at least one lens includes an f-theta lens.
In some examples, the method includes projecting a laser image onto the etchant-substrate interface, concurrently with focusing the laser beam, to heat an additional portion of the etchant-substrate interface. The additional portion of the etchant-substrate interface has a surface area greater than the surface area of the portion of the etchant-substrate interface. In some examples, projecting the laser image includes emitting an additional laser beam having a wavelength different from a wavelength of the laser beam.
In some examples, the method includes adjusting the surface area of the portion of the etchant-substrate interface by adjusting the position of at least one lens relative to the etchant-substrate interface along an optical axis of the laser beam in response to the measured property. In some examples, the at least one lens is an electronically-controllable, zoom lens.
Examples of the present disclosure include a system for controlling a substrate etching process. The system includes a substrate receiver configured to receive and hold a substrate such that a surface of the substrate is adjacent to a volume of etching fluid to produce an etchant-substrate interface. The system includes a moveable positioner and an electromagnetic radiation emitter located on the moveable positioner and configured to focus electromagnetic radiation to a portion of the etchant-substrate interface and selectively heat the portion of the etchant-substrate interface using the focused electromagnetic radiation. The portion of the etchant-substrate interface has a surface area of not less than 0.05 squared micrometers and not greater than 80 squared millimeters. The system includes a monitoring beam emitter configured to transmit a monitoring beam through the substrate. The substrate and volume of etching fluid is at least partially transparent over a wavelength range. The wavelength range includes a wavelength of the monitoring beam. The system includes a monitoring beam detector configured to measure a property of the substrate surface, after the electromagnetic radiation emitter selectively heats the portion, via the monitoring beam to produce a measured property for the substrate.
Many aspects of the disclosed invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the present invention. In the drawings, like reference numerals designate corresponding parts throughout the several views.
The present invention recognizes the need to manufacture optical elements such as lenses with less expense and greater throughput. It is accordingly an object of the present invention to provide a simpler and less expensive method to fabricate optical components without the need for multiple rounds of machining and metrology.
The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or uses. For example, while the disclosed invention may be used to create optical lenses, those skilled in the art of optical element manufacturing will be aware that other elements such as elliptical and parabolic reflectors may be fashioned using the disclosed methods. It should also be understood that the optical elements discussed herein may be used with various wavelengths of electromagnetic radiation, not limited to visible light.
The features exhibited in the embodiments may be combined with each other unless noted otherwise. Moreover, an embodiment containing a plurality of features should not be construed to mean that all those features are necessary for practicing the invention, as other embodiments may comprise less and/or alternative features.
The depicted etchant 104 is a fluid such as a liquid, gas or plasma. The etchant 104 may be injected into the vessel through an inlet port 105 and may be removed from the vessel along with etched material via an outlet port 106. In some cases, multiple inlet and outlet ports may be used to transport the etchant. The ports may also be used to circulate the etchant 104 as desired. As shown in
In some embodiments, the etchant 104 is not covered with a cover 107. The etchant depth may be determined using a liquid depth measurement device including those commonly known within the art such as a hydrostatic pressure sensor, ultrasonic or laser time-of-flight sensor. The depth measurement device may be connected to a controller such as a computer or other digital processing apparatus to which the device can send measurement data.
In some embodiments, prior to sealing the substrate 103 to the vessel wall 101, a thin film 108 is disposed on the surface of the substrate and the thin film is patterned. The thin film 108 may be deposited using physical or chemical vapor deposition or oxidation of the substrate surface, and patterned using photolithography and chemical etching, as commonly performed within the semiconductor industry. The thin film 108 is preferably inert to the etchant 104 in order to prevent covered portions of the substrate 103 from being etched. In some cases, the thin film 108 is etched by the etchant 104 at a slower etch rate than the substrate 103 and may be completely removed from the substrate before the etch process is complete.
The depicted etching system 100 includes etch-assist emitter(s) 109, monitoring beam emitter(s) 116 and monitoring beam detector(s) 118. The etching system 100 enables placing the bottom surface or top surface of the substrate 103 adjacent to a volume of etching fluid (i.e., etchant 104) to produce an etchant-substrate interface. The etch-assist emitter(s) 109 are able to emit spatially controlled electromagnetic radiation (not shown in
The monitoring beam emitter(s) 116 transmit a monitoring beam (not shown in
The substrate and volume of etching fluid may be partially or fully transparent at the wavelength range of the monitoring beam. The monitoring beam detector(s) 118 may measure a property of the substrate surface during the substrate etching process via the monitoring beam and thereby produce one or more real-time measured properties for the substrate. Examples of measured properties include focal length, focal spot size, 2D size and symmetry of the etched area, wavefront shape and phase, 3D profile of the etched area (e.g. curvature), and surface roughness. Additionally, in some examples, these properties are measured with monitoring beams having different wavelengths. The monitoring beam detectors(s) 118 may be an array of individual detectors or sensors. Examples of monitoring beam detector(s) include charge coupled devices, CMOS image sensors, wavefront sensors, antenna elements, scanning confocal microscopy devices, and interferometry devices.
In some embodiments, such as depicted in
The etch-assist emitters 109 may comprise any number of radiation sources such as lasers, LEDs, masers, gyrotrons, backward wave oscillators, or radio elements. In the latter case, the radio elements are configured to emit millimeter wave radiation from 10 GHz to 300 GHz in the form of radiation beams. Still, in some cases, the emitters 109 are resistive heaters such as miniature filaments or wire coils, thin film metal traces, micromachined membranes through which an electrical current may be passed to create resistive heat, or thin film transparent conductors. The radiation generated by the resistive heaters may be broad spectrum radiation, and as such, a radiation filter (e.g., a bandpass or cutoff filter) may be used to limit the radiation spectrum emitted by the heat sources. Further still, the etch-assist emitters may be radiation sources comprised of plasmonic near-field transducers. In the case where the etchant is a liquid or gas, the wavelength of the etch-assist radiation may be highly absorbed by the etchant. Preferably the wavelength of the etch-assist radiation is at or near an absorption peak of the liquid or gas.
The etch-assist emitters 109 are individually controlled whereby the radiation power of each etch-assist emitter may be varied or select emitters may be turned off as desired. The controller 113 controls the etch-assist emitters 109 through a driver circuit 114 which supplies the etch-assist emitters with electrical power. An individual emitter may be selected using matrix addressing, as commonly used in semiconductor memory chips.
In some embodiments, the etch-assist emitters 109 are substantially Lambertian emitters that generate radiation 115 in a largely hemispherical pattern in a direction toward the substrate. In other embodiments, the etch-assist emitters are directional emitters that emit radiation in a highly directional manner. For example, the phase of the etch-assist emitters may be controlled to direct the emitted radiation toward a selected area via beam steering. Furthermore, the etch-assist emitters may be shaped in a manner, or comprise reflective elements, that increase(s) the directionality of the emitted radiation. For example, thermal emitters or patch antenna elements that are normally substantially Lambertian may be disposed within a parabolic reflective cavity that reflects radiation toward the substrate 103 in order to increase the directionality of the emitted radiation and the spatial selectivity of the etch process.
The radiation 115 may be continuous or quasi-continuous, in the case of the latter, the pulse duration is preferably longer than 10 μs. In some embodiments, one or more etch-assist emitters 109 produce radiation 115 having a wavelength different from the wavelength of the other emitters within the array. The substrate 103 is transparent to the emitted radiation allowing the radiation to pass through the substrate to the etchant 104 where the radiation is largely absorbed. The absorbed radiation is converted to heat thereby raising the local temperature of the etchant 104 and increasing the etch rate of the substrate 103. In some embodiments, nanoparticles that are highly absorptive of the radiation may be dispersed in the etchant to increase the conversion of electromagnetic energy to thermal energy.
By using an array of individually controllable etch-assist emitters 109 and adjusting the radiation power and location of the etch-assist radiation 115 incident on the etchant 104, the etch rate at specified areas of the substrate may be increased and material may be selectively removed from the substrate 103 thereby shaping the substrate surface. The precision of the etching process is determined by the ability of the etch-assist emitters 109 to heat a small volume of etchant 104 at a specified location, which, in turn, is determined by a variety of factors such as the radiation power, the areal size of the radiation incident on the etchant 104, whether radiation from adjacent emitters overlap at the etchant, the packing density of the emitters on the emitter support board 110, the temperature and inflow rate of the etchant, and the absorption coefficient of the etchant.
At the wavelength of the etch-assist emitters 109, the substrate 103 preferably has an absorption coefficient less than 0.1 cm−1 and the etchant 104 preferably has an absorption coefficient greater than 1 cm−1. For etchants with a water component, the wavelength of the etch-assist emitters 109 are preferably near any number of water absorption peaks in the ultraviolet (UV), infrared (IR) or radio frequency (RF) spectrum. For example, emitters with a wavelength of approximately 1940 nm (which corresponds to an absorption peak of water) may be used for etchants that comprise water such as a mixture of HF and water. The radiation absorbed by the etchant may be described by the Beer-Lambert law,
where I is the radiation intensity at distance x from the surface of the etchant, Io is the radiation intensity incident on the etchant surface at x=0, and α is the linear absorption coefficient of the etchant. For an etchant with a linear absorption coefficient of 1 cm−1 or greater, about 90% of the etch-assist radiation is absorbed within the first 2.3 cm of the etchant. Thus, one aspect of the invention described herein is to perform precise thermally-assisted chemical etching to machine a substrate 103. The invention may be used, for example, to etch a convex or concave shape within a glass substrate thereby forming an optical lens.
In other embodiments, the substrate 103 is opaque and the etchant 104, which is in contact with the substrate surface, is generally transparent at the wavelength of the etch-assist radiation 115 generated by the etch-assist emitters 109. In this case, the etch-assist radiation 115 is directed through the etchant 104 to the substrate surface. The substrate 103 absorbs the etch-assist radiation 115 and the substrate is heated according to the radiation intensity. At the wavelength of the etch-assist emitters 109, the substrate 103 preferably has an absorption coefficient greater than 1 cm−1 and the etchant 104 preferably has an absorption coefficient less than 0.1 cm−1. The etch-assist emitters 109 are arranged in an array and each emitter is individually controllable by the controller 113 through a driver circuit 114. By controlling the etch-assist radiation 115 from individual emitters within the array, select areas of the substrate 103 may be locally heated thereby increasing the etch rate of the substrate.
Furthermore, as illustrated in
As the monitoring beams 117 pass through optical elements under fabrication within the substrate 103, beam characteristics such as location, intensity, cross-sectional diameter (i.e. spot size) and shape may change during the fabrication process. The beam characteristics are recorded by the monitoring beam detector(s) 118 and the images are sent to the controller 113 which then calculates various optical properties of the optical elements under fabrication. For example, collimated monitoring beams passing through the substrate 103 in which a convex lens is being etched will come to a focused spot at the focal length of the lens. To obtain a lens with a specific focal length, the monitoring beam detector(s) 118 may be moved to a location at a specific distance from the substrate 103, the desired focal length of the lens, and the etch process proceeds until a minimum monitoring beam spot size is recorded by the monitoring beam detector(s) 118 indicating the lens has the desired focal length.
In some embodiments, the monitoring beam detector(s) 118 may move in a direction normal to the substrate 103 surface using the robotic arm 119 to measure the spot sizes of the monitoring beams 117 at multiple distances from the substrate 103. These measurements may be used to calculate the incident angle θ of the monitoring beams 117 and the focal length f of an optical element such as a lens or parabolic reflector. By way of example, the optical properties of a lens may be measured using the following procedure. The spot size of a monitoring beam is measured at an image plane located a distance z1 from the substrate 103 having a spot size diameter of d1 and a second monitoring beam spot size is measured at an image plane further away from the substrate 103 at z2 (z2>z1) having spot size diameter d2. The incident angle θ of the monitoring beam 117 is calculated using the equation,
The focal length f may be calculated from the incident angle, assuming the monitoring beam spot size decreases to a negligibly small point at the focal length. For a light converging lens,
and for a light diverging lens, the virtual focal length fv is,
The ability to calculate, rather than measure, the focal length is necessary in situations where a lens has a focal length shorter than the depth of the etchant 104 such that the monitoring beam detector(s) 118 could not be moved to the focal point to measure the focal length directly or when a diverging lens is being fabricated and the virtual focal length cannot be measured directly.
It should be understood that the optical properties of the lens measured during the etch process are not equivalent to the optical properties of the lens in air. To determine the properties of the lens in air, a look-up table correlating measured properties of a lens in the disclosed etching apparatus to the properties of a lens in air may be used. Alternatively, if the refractive indices and thicknesses of the substrate 103, etchant 104 and cover 107 are known, Snell's law may be used to calculate the optical properties of the lens in air based on the optical measurements of the lens made during the etch process.
The monitoring beam detector(s) 118 also records a baseline intensity of the monitoring beam 117 passing through the substrate 103, etchant 104 and glass cover 107 before the etch process. As the etch commences, changes in monitoring beam intensity due to specular reflection from the surface of the substrate 103 may be used to infer information regarding the substrate's surface roughness.
The measured monitoring beam characteristics are used for closed-loop process control. The aforementioned monitoring beam measurements provide feedback on the progression of the surface etch to the controller 113 in real-time such that the controller may dynamically adjust the radiation power generated by individual etch-assist emitters 109 and the location of the emitters thereby modifying the etch process as needed. The controller 113 compares the measured optical properties of an optical element under fabrication to the design specifications for that optical element. The etch process may be adjusted manually by an operator or automatically by the controller 113 to bring the measured optical properties closer to the desired optical properties. For example, an optical lens with a desired focal length, numerical aperture, size, and shape may be machined within a substrate by comparing the measured optical properties of the lens with the design specifications of the lens and then using the computer to adjust the substrate etch to minimize the difference. Closed-loop feedback eliminates much post-fabrication metrology by performing the metrology during the manufacturing process thereby increasing manufacturing throughput and reducing optical element cost.
In some embodiments, a Shack Hartman wavefront sensor is used as the monitoring beam detector 118. The wavefront sensor may be used to measure the wavefront distortion of the monitoring beams 117 caused by the surface of the substrate as the monitoring beams pass through the substrate 103. The shape of the wavefront may be described mathematically using Zernike polynomials. The Zernike polynomials may be used to model optical aberrations in the optical elements under fabrication. The wavefront sensor may be used to monitor the etch process in real-time and provide process feedback to the controller 113, using the following cycle: first the controller 113 records the wavefront distortion during the substrate etch process using the wavefront sensors; second Zernike polynomials are used to model the wavefront; third, the computer adjusts the etch-assist radiation power and/or radiation location incident on the etchant to alter the substrate etch process and minimize the optical aberrations as modeled using Zernike polynomials; and, fourth the controller observes the changes to the wavefront as the substrate is etched using the new radiation power and/or location settings.
Those skilled in the art of lens design will recognize that many diverse optical elements may be fabricated using the methods and apparatus described herein. For example, spherical or aspherical lenses that focus or de-focus light may be machined. Furthermore, beam shaping lenses may be fabricated such as lenses that convert a monitoring beam with an elliptical two-dimensional cross-section to one with a circular shape. Freeform lenses in which a lens has no translational or rotational symmetry about an axis normal to the surface of the substrate 103 may also be fabricated. In some embodiments, the disclosed invention is used to fabricate a mold. For example, a concave trough may be etched into the substrate 103 and the trough is filled with a second material. In one aspect of the invention, the mold and the second material are used jointly as a single optical element having desirable chromatic and/or achromatic properties.
It should be noted that the apparatus disclosed herein may be used to fabricate optical elements on both sides of a substrate. For example, following the fabrication of an optical element on the first side of a substrate, the substrate is removed from the apparatus and cleaned. The side of the substrate without the optical element (i.e. the second side of the substrate) is abutted and sealed to a vessel wall and an etchant is injected onto the second substrate surface. In this case, the monitoring beam passes through the previously fabricated optical element and the monitoring beam detector records the central location of the monitoring beam. As the etching commences, the position of the etch-assist radiation may be adjusted such that the optical element under fabrication maintains the central position of the initial monitoring beam on the monitoring beam detector. Thereby the optical axis of the optical element fabricated on the second side of the substrate is aligned to the optical axis of the optical element fabricated on the first side of the substrate.
It should be noted that alternative arrangements of the parts of the apparatus 100D may exist without departing from the methods of the invention. For example, the etch-assist emitters 109 and monitoring beam emitters 116 may be placed above the substrate 103, and the etchant 104 may be sealed on the bottom side of the substrate 103. The monitoring beam detector(s) 118, in this embodiment, is placed on the opposite of the substrate as the monitoring beam emitters 116, below the etchant 104.
In some embodiments, a software program automatically controls the substrate etch process using feedback from the monitoring beam measurements to create an optical element matching the specifications input into the program by a user. For example, specifications for a lens may include focal length, minimum spot size to which the lens must focus light, the diameter of the lens, and a radius of curvature or a surface profile. The software program calculates the properties of the optical element under fabrication using the measured monitoring beam characteristics and compares the measured optical element properties to the user-defined specifications and minimizes the difference. The software program accomplishes this task by controlling the etch-assist emitter array which may entail changing the radiation power of individual etch-assist emitters 109, turning the etch-assist radiation 115 of some emitters off or moving the emitter array relative to the substrate 103 using the positioner 112. Many multivariate optimization algorithms, as known within the art, may be used to control the etch-assist emitter array and minimize the difference between the optical element specifications and measured optical properties of the optical elements.
In some embodiments, machine learning may be used to improve the etching process. For example, an artificial neural network using reinforcement learning may be used to dynamically adjust the inputs to the etch process (e.g. etch-assist radiation power and emitter location) in response to positive or negative reinforcement (i.e. a reward). The strength of the reinforcement is based on the difference between the calculated optical properties of the optical element under fabrication and user-specified optical properties of the optical element where actions that minimize the difference result in a positive reward.
Reference is now made to
In step 305, an array of etch-assist emitters, each individually controllable, located on the opposite side of the substrate as the etchant direct radiation toward a multiplicity of selectable locations on the surface of the etchant at the substrate-etchant interface. The substrate is substantially transparent at the wavelength of the radiation. In step 306, the radiation power of select emitters is adjusted to selectively heat the etchant and form a target etch shape in the substrate. In step 307, at least one property of the monitoring beam (e.g. beam diameter size, shape, intensity, wavefront shape or wavefront phase) is measured as the substrate is etched. The feature etched in the substrate changes properties of the monitoring beam recorded by the monitoring beam detector(s). In step 308, if the property of the monitoring beam is not as desired (e.g. if the beam shape is asymmetric, the beam size is increasing in size rather than decreasing in size, or the wavefront is not shaped as desired), the radiation power from various etch-assist emitters may be adjusted to change the etching process by repeating steps 306 and 307.
In some cases, steps 309, 310, and 311 may be performed. As listed in step 309, the monitoring beam detector(s) is moved a predetermined distance from the substrate and the monitoring beam detector(s) records at least one property of the monitoring beam at the new location. In step 310, based on the change in at least one property of the monitoring beam, additional information about the optical element being formed in the substrate may be calculated (e.g. focal length of a lens). If the optical element does not possess the desired property, according to step 311, the etch process continues and the measurement of the monitor beam is repeated starting from step 307. Otherwise, once the desired monitor beam property has been achieved, the process is complete. In step 312, the etch-assist radiation and the monitoring beam are turned off. The etchant is then flushed from the vessel and the substrate is rinsed with water. In some embodiments, the etchant is flushed previous to each measurement of the monitor beam or other substrate related measurement and the vessel is refilled with etchant if the etching process is continued.
In some embodiments, more than one etch-assist emitter array is used to machine a substrate.
In one aspect of the invention, each of the monitoring beam emitters 116 may generate monitoring beams 117 having substantially identical wavelengths or a variety of different wavelengths. For example, the monitoring beam emitters 116 forming the array may comprise red, green or blue LEDs. By using a combination of wavelengths, the monitoring beam detector(s) can record how different wavelengths of light pass through the optical element under fabrication during the etch process. For example, a lens being fabricated may have different focal lengths for different wavelengths of light (i.e. a chromatic aberration). The monitoring beam detectors 118 may record the focal length at each wavelength of each monitoring beam 117. Furthermore, monitoring beam detectors may detect monitoring beams with different wavelengths by using filters. For example, a monitoring beam detector with a green bandpass filter may detect a green monitoring beam and another monitoring beam detector with a red bandpass filter may detect a red monitoring beam.
In some embodiments, the disclosed methods and apparatus are used to fabricate a multiplicity of optical elements concurrently on the surface of a substrate. A multiplicity of emitter arrays may be used to etch many optical elements over the area of the substrate in contact with the etchant. The optical elements may be identical or various types of optical elements may be fabricated throughout the substrate. In one case, a multiplicity of monitoring beams passes through the optical elements and the monitoring beam detector(s) moves to a position above each optical element to measure the optical properties of the optical elements. In other cases, a large monitoring beam may pass through multiple optical elements. The computer controls each etch-assist emitter in the arrays independently. The radiation from each etch-assist emitter may be adjusted based on the feedback from the monitoring beam as recorded by the monitoring beam detector(s), such that the etch process for each lens may be completed at substantially the same time. Thus, the etching process and feedback system described herein may be scalable to enable batch fabrication.
Completed optical elements are removed from the substrate through various means. For example, an individual optical element may be removed from the substrate by dicing or laser cutting. In some cases, optical elements may be removed from the wafer by disposing a barrier material on the substrate surface and patterning the barrier material. The substrate may then be etched using wet etching and/or dry etching at the openings in the barrier material, where the substrate is exposed, until the optical elements are freed from the substrate or held in the substrate with small tabs or bridges connecting the optical elements to the body of the substrate. The barrier material may then be selectively removed from the optical elements using a wet etchant that dissolves the barrier material without etching the optical elements.
In some embodiments, following fabrication of the optical elements, the substrate may be coated with at least one thin film to create an optical coating such as one or more anti-reflection, IR filter, and mirror coatings. In another aspect of the invention, the surface of the substrate is coated with a light-blocking thin film. The light-blocking thin film may be patterned to create an aperture on the optical elements within the substrate. The light-blocking thin film is patterned for example using photolithography and a lift-off process to remove the thin film, a process commonly performed within the semiconductor electronics industry. In some embodiments the light-blocking thin film may be used as the thin film barrier 108 during optical element fabrication. The thin film barrier 108 may be left on surface of the substrate following the fabrication of the optical elements thereby forming an aperture.
may be used to find the distance di (i.e. image distance) at which the monitoring beam detector 118 should be placed such that the monitoring beam emitters 116 will appear in focus when the lens under fabrication has obtained the desired focal length f. In other words, the monitoring beam detector is placed at the distance di whereby the images of the monitoring beam emitters 116, as recorded by the monitoring beam detector 118, are sharpest when a lens has been fabricated having the desired focal length f.
In some embodiments, the monitoring beam emitters 116 are positioned at a distance from the substrate, equal to the desired focal length of a lens under fabrication. As the etch process proceeds, the monitoring beams 117 passing through the substrate begin to converge, eventually becoming collimated, indicating a lens with the desired focal length has been etched into the substrate. The monitoring beam detector 118 is used to determine when the beam is collimated by measuring the monitoring beam spot size at multiple distances from the substrate 103. Monitoring beam collimation is achieved when the spot size is substantially the same for each measurement.
It should be understood that the focal length of the lens as determined by the aforementioned methods is not equivalent to the focal length of the lens in air. To determine the properties of the lens in air, a look-up table correlating the measured focal length to the focal length of a lens in air may be used.
In some embodiments, as depicted in
In some embodiments, as shown in
The thickness of the solid arrows shown in
The screen 1010 may comprise any electronically controllable transmissive spatial light modulator such as a liquid crystal (LC) screen or liquid crystal display (LCD) with individually addressable elements (i.e. pixels), as commonly known within the art, or an electrochromic screen which undergoes a change in optical transparency in response to an applied electrical current or electric potential. In the case of an electrochromic screen, the screen is segmented into addressable elements.
In some embodiments, the etch-assist radiation 115 from at least one etch-assist emitter 109 and at least one monitoring beam 117 from at least one monitoring beam emitter 116 may be coupled into an optical fiber. In some cases, radiation, having different wavelengths, may be generated by more than one etch-assist emitter coupled into the optical fiber. Likewise, multiple monitoring beams with different wavelengths (e.g. red, green and blue) may be coupled into the optical fiber. The radiation emitter(s) and monitoring beam emitter(s) at the input side of the optical fiber are controlled using an electronic driver which is controlled by a computer. In some cases, a multiplicity of these optical fibers may be used to perform thermally-assisted chemical etching and etch monitoring according to the disclosed invention. In other cases, multiple optical fibers may be bundled together in a tube or ferrule and held in place using an epoxy. The optical fibers are terminated in the ferrule such that the ends of the fibers are at substantially the same plane in the ferrule.
In some embodiments, as illustrated in
In one case, the etch-assist radiation 115 from the lens 1201 is incident on at least one galvo scan mirror. The angular position of the galvo scan mirror(s) is controlled by a computer whereby the computer directs the etch-assist radiation incident on the mirror(s) to a desired location on the etchant.
In some embodiments, etch-assist emitters may be positioned on an emitter support board while the etch processes is monitored using a non-contact optical profilometer, the optical profilometer providing feedback to a controller which controls the etch-assist emitters.
The apparatus and methods described in this disclosure may be used to fabricate many types of optical elements.
In some aspects of the invention, the substrate in
In some cases, the substrate 103 and preform are heated to the melting temperature of the preform. The preform melts under the its own weight to fill the trough. The preform and substrate surfaces are then planarized using chemical mechanical polishing (CMP). The preform glass may remain in the mold whereby the mold and preform glass form a single optical element having planar surfaces. In some embodiments, the planar surfaces of the optical element may be used as a substrate for thin film transistors (TFTs), microelectromechanical systems (MEMS), organic light emitting diodes, transparent micro-heaters or electrodes, LEDs or any other opto-electro-mechanical device commonly known within the art.
In another embodiment, the etch-assist radiation may emanate from a projector. For example, the projector may be a laser or LED projector as commonly known within the art. The projector may utilize a reflective LC screen such as a liquid crystal on silicon (LCOS) chip or a digital micro mirror device (DMD) for spatially modulating a laser beam or projecting a “scene” onto the etchant at the substrate-etchant interface. As illustrated in
Below the dichroic mirror 1602 may be at least one monitoring beam emitter 116. The monitoring beam 117 generated by the monitoring beam emitter is collimated by a lens 1603. The collimated beam size is approximately the same areal size as the etch-assist radiation at the substrate 103. The collimated monitoring beam passes through the dichroic mirror 1602, substrate 103, etchant 104 and a cover plate 107 with relatively little absorption. On the side of the cover plate, opposite to the monitoring beam emitter(s), beam reducer lenses 1604 are used to decrease the size of the monitoring beam such that the monitoring beam is approximately the same size as a monitoring beam detector(s) 118, the detector also being on the side of the cover plate opposite the monitoring beam emitters. As an example, the beam reducer lenses 1604 may be comprised of two convex lenses that form a Keplerian beam reducer or a concave and convex lens forming a Galilean beam reducer. The monitoring beam detector(s) 118 may be comprised of a CCD or CMOS camera or a wavefront sensor such as a Shack-Hartmann wavefront (SHW) sensor.
In the case where the monitoring beam detector 118 is a wavefront sensor, three-dimensional optical profilometry of the substrate may be performed during the etch process. In general, the phase of an incident wavefront passing through a material is delayed by an amount proportional the material's thickness and refractive index (i.e. the optical path length). By comparing the phase of the wavefront incident on the material with the phase of the wavefront after passing through the material, one can calculate the material's thickness.
In the system described herein, the surface profile of the substrate 103 may be calculated by comparing the phase of the wavefront before etching has commenced (i.e. initial wavefront phase) with the measured phase of the wavefront after etching the substrate.
Referring again to
where λ is the wavelength of the monitoring beam and n1 and n2 are the refractive indices of the substrate and etchant, respectively. The controller 113 may be used to calculate the surface profile using the above equation.
In some cases, the surface profile of the substrate 103 is only measured when the fluid vessel is filled with water. The etch process proceeds using the following cycle: first, the fluid vessel is filled with water; second a monitoring beam 117 is generated and directed through the dichroic mirror 1602, substrate 103, etchant 104, and cover 107; third, the wavefront at the exit pupil of the substrate is relayed to the monitoring beam detector 118 and the controller 113 records the initial wavefront; fourth, the water is removed from the fluid vessel and etchant 104 is injected into the fluid vessel; fifth, etch-assist radiation 115 is projected onto the substrate-etchant interface for a specified time and the substrate 103 is controllably etched; sixth, the etch-assist radiation is turned off; seventh, the etchant 104 is removed from the fluid vessel and the vessel is filled with water; eighth, a new wavefront at the exit pupil of the substrate 103 is relayed to the monitoring beam detector 118 and the controller 113 records the new wavefront; ninth, using the initial wavefront measurement and the new wavefront measurement, the surface profile of the substrate is calculated by the controller 113 and compared to a desired surface profile; tenth, based on the difference between the desired surface profile and the calculated surface profile, the power and/or location of the etch-assist radiation is adjusted; eleventh, the water is removed from the fluid vessel, replaced with etchant and the etch-assist radiation 115 is projected onto the substrate-etchant interface. The foregoing steps may repeat multiple times until the surface profile of the etched substrate is within tolerance of the desired surface profile.
Moreover, the controller 113 may be used to compare the measured surface profile to an ideal surface profile specified by a user. The difference between the specified and measured surface profiles may be used to change the location of the etch-assist radiation 115 incident on the etchant or turn off the etch-assist radiation at certain areas of the etchant-substrate interface. Hereby, the profile of the etched substrate may be controlled and the difference between the measured profile and the specified profile (i.e. the profile error) may be minimized. Thus, the measured surface profile may provide real-time feedback for controlling the etch process.
In some aspects of the invention, a window or a flat may be fabricated in the substrate as illustrated in
In another embodiment, the etchant and the cover plate are transparent to the etch-assist radiation and the substrate is highly absorbing of the etch-assist radiation. The substrate is locally heated, and thermal energy from the substrate accelerates the etch process. In this case, illustrated in
In some examples, opposite to the etchant 104 with respect to the substrate 103, an electromagnetic radiation emitter 109 is located on a positioning stage 112. In some embodiments, the positioning stage 112 has at least two axes of movement. In some examples, the positioning stage 112 is configured to move in a virtual plane substantially parallel to the substrate 103. In some examples, the positioning stage 112 is configured to rotate the emitter 109 about an axis, and the axis is substantially parallel to the substrate 103. Additionally, and/or alternatively, in some examples, the positioning stage 112 is configured to move the emitter 109 toward and/or away from the substrate 103.
The electromagnetic radiation emitter 109 includes, in some examples, any number of radiation sources, including, but not limited to, a laser, light emitting diode (LED), a tungsten bulb, a reflector, and/or a combination thereof. In some examples, the substrate 103 is transparent to the emitted radiation 115, allowing the radiation 115 to pass through the substrate 103 to the etchant 104, where the radiation 115 is absorbed.
Referring to
In some examples, the surface area of the portion 140 is a two-dimensional area of the etchant-substrate interface 138. The surface area, in some examples, is as spot size of the focused radiation 115 incident on the etchant-substrate interface 138.
In some examples, the etchant 104 absorbs the electromagnetic radiation 115 and creates heat, thereby raising the local temperature of the etchant 104 at the selected portion 140 and increasing the etch rate of the substrate 103 at the selected portion 140. In some examples, the system 1900 includes a current driver to control the power of the radiation 115. In some examples, a controller 113 (e.g., a computer) controls the current driver. In some examples, by adjusting the power (e.g., via the controller 113) and/or location (e.g., via the positioning stage 112) on the substrate 103 of the radiation 115, the etch rate at specified areas (e.g., portion 140) of the substrate 103 is increased, and material is selectively removed from the substrate 103, thereby shaping the substrate surface.
In some examples, the removal of material from the substrate is monitored using monitoring beam detector 118. In some examples, the monitoring beam detector 118 includes a sensor. The sensor includes any number of sensing elements. Sensing elements include, for example, a charge coupled device (CCD), complementary metal oxide semiconductor (CMOS) imaging sensor, a wavefront sensor, an interferometer, a photodiode, and/or any combination thereof. In some examples, the monitoring beam detector 118 is moveable via a positioning stage 119 controlled by a controller 113.
In some examples, the system 1900 includes a monitoring beam emitter 116 configured to illuminate the substrate 103. In some examples, the monitoring beam emitter 116 emits a monitoring beam 117, which is collimated by a lens 122 and directed toward the substrate 103 using a beamsplitter 124. In some examples, the monitoring beam 117 passes through the substrate 103 and reflects from a dichroic mirror 126. In some examples, the dichroic mirror 126 is transparent to the radiation 115 and reflective to the monitoring beam 117. In some examples, the position and/or focus of the collimating lens 122 is electronically controllable via the controller 113.
In some examples, the focusing lens 134 includes an f-theta lens. In some examples, the focusing lens 134 includes an electronically-controllable, zoom lens. In some examples, the lens 134 includes a lens within a lens housing, and the position of the lens within the lens housing can be mechanically controlled. In some examples, a diffractive optical element is placed in the path of the radiation 115 adjacent to the focusing lens 134 such that the diffractive element splits the radiation 115 into multiple beams.
In some examples, the substrate 103 and etching fluid 104 are at least partially transparent over a wavelength range. In some examples, the wavelength range is within the visible spectrum. In some examples, the wavelength range is not less than 400 and not greater than 700 nanometers (“nm”). In some examples, the wavelength range is not less than 440 and not greater than 650 nm. In some examples, that wavelength range includes a wavelength of the monitoring beam 117. In some examples, the wavelength of the monitoring beam 117 is approximately 450 nm. In some examples, the wavelength of the monitoring beam 117 is approximately 515 nm. In some examples, the wavelength of the monitoring beam 117 is approximately 633 nm.
In some examples, the substrate 103, etchant 104 and cover plate 107 are transparent at the wavelength of the monitoring beam 117. In some examples, the substrate 103, etchant 104, and cover plate 107 have absorption coefficients less than 0.1 cm−1. The monitoring beam 117 thus passes through the substrate 103, etchant 104 and cover plate 107, reflects from the dichroic mirror 126 and is incident on the monitoring beam detector 118, which is positioned on the opposite to the radiation emitter 109 with respect to the substrate 103. In some examples, the monitoring beam detector 118 includes a sensor configured to measure properties of the substrate 103, and the monitoring beam detector 118 is configured to transmit data (e.g., data including such measurements) to the controller 113 for processing and/or display. The controller 113, in some examples, controls the position of the monitoring beam detector 118 in three dimensions using a robotic arm or positioning stage(s) 112.
In some examples, as the monitoring beam 117 passes through optical elements under fabrication within the substrate 103, beam characteristics such as location, intensity, cross-sectional diameter (i.e. spot size) and shape may change during the fabrication process. In some examples, the monitoring beam detector 118 is configured to record the beam characteristics and send data to the controller 113. In some examples, the controller 113 is configured to calculate one or more optical properties of the optical components under fabrication based at least in part on the received data. In some examples, the controller 113 is configured to use the detector to monitor the surface (e.g., a surface at the etchant-substrate interface 138) of the substrate 103 in real-time during the etch process and modify the position of the focused radiation 115 and/or radiation power in response to a measured property of the substrate 103.
Referring to
In some examples, the method 2200 includes a step 2210 of transmitting a monitoring beam 117 through the substrate 103. In some examples, the substrate 103 and the etching fluid 104 are at least partially transparent over a wavelength range. In some examples, the wavelength range includes a wavelength of the monitoring beam 117. In some examples, the method 2200 includes a step 2212 of measuring a property of the substrate 103. In some examples, measuring a property of the substrate 103. In some examples, the step 2212 is performed concurrently with the step 2208 of selectively heating the selected portion 140. In some examples, measuring 2212 the property of the substrate 103 surface includes measuring 2212 the property via the monitoring beam 117 to produce a measured property for the substrate 103.
In some examples, the method 2300 includes a step 2305 of moving and/or scanning the electromagnetic radiation emitter 109 and/or a focusing lens 134. In some examples, the step 2305 includes moving the electromagnetic radiation emitter 109 to selectively heat a portion 140 of the etchant-substrate interface 138 and/or to increase an etching rate for the portion 140 of the etchant-substrate interface 138.
In some examples, the method 2300 includes a step 2314 of projecting a laser image 302 onto the etchant-substrate interface 138. In some examples, the method 2300 includes a step 2306 of focusing electromagnetic radiation 115 from the electromagnetic radiation emitter 109 to a selected portion 140 of the etchant-substrate interface 138. In some examples, the method 2300 includes performing the step 2306 concurrently with the step 2314. In some examples, the step 2314 heats an additional portion 142 of the etchant-substrate interface 138. In some examples, the additional portion 142 of the etchant-substrate interface 138 has a surface area greater than the surface area of the selected portion 140 of the etchant-substrate interface 138. In some examples, the additional portion 142 overlaps with and/or encompasses the selected portion 140.
In some examples, the method 2300 includes a step 2308 of selectively heating the portion 140 of the etchant-substrate interface 138 using focused electromagnetic radiation 115. In some examples, the method 2300 includes a step 2310 of transmitting the monitoring beam 117 through the substrate 103. In some examples, the method 2300 includes a step 2312 of measuring a property of the substrate 103. In some examples, the step 2312 is performed concurrently with the step 2208 of selectively heating the selected portion 140. In some examples, measuring 2312 the property of the substrate 103 surface includes measuring 2312 the property via the monitoring beam 117 to produce a measured property for the substrate 103.
In some examples, the step 2305 of moving and/or scanning the electromagnetic radiation emitter 109 and/or the focusing lens 134 is in response to the measured property of the substrate 103.
In some examples, the method 2500 includes a step 2508 of focusing the laser beam from at the least one moveable mirror 303 to a portion 140 of the etchant-substrate interface 138, the portion 140 of the etchant-substrate interface 138 having a surface area of not less than 0.05 μm2 and not greater than 80 mm2. In some examples, the focusing 2508 is performed concurrently with the projecting 2507. In some examples, the projecting 2507 heats an additional portion 142 of the etchant-substrate interface 138, the additional portion 142 of the etchant-substrate interface 138 having a surface area greater than the surface area of the portion 140 of the etchant-substrate interface 138. In some examples, the additional portion 142 overlaps with and/or encompasses the portion 140.
In some examples, the method 2500 includes a step 2510 of heating the portion of the etchant-substrate interface 138 with the focused laser beam. In some examples, the method 2500 includes a step 2512 of transmitting a monitoring 117 beam through the substrate 103. In some examples, the substrate 103 and volume of etching fluid 104 are at least partially transparent at a wavelength range that includes a wavelength of the monitoring beam 117. In some examples, the method 2500 includes a step 2514 of measuring a property of the substrate 103, while heating 2510 the portion 140, via the monitoring beam 117 to produce a measured property for the substrate 103.
In some examples, the method 2500 includes a step 2503 of adjusting the surface area of the portion 140 of the etchant-substrate interface 138 by adjusting the at least one lens 122 in response to the measured property.
As the embodiments of the invention presented above and other variations and combinations of the features previously discussed can be utilized without departing from the present invention, the foregoing description of the preferred embodiments should be taken by way of illustration rather than by way of limitation of the invention as defined by the claims.
The present invention may be a system, a method, and/or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention.
The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (“RAM”), a read-only memory (“ROM”), an erasable programmable read-only memory (“EPROM” or Flash memory), a static random access memory (“SRAM”), a portable compact disc read-only memory (“CD-ROM”), a digital versatile disk (“DVD”), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.
Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device.
Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention.
Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions.
These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks.
The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks.
The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.
In the preceding description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of an embodiment.
The description of elements in each figure may refer to elements of proceeding figures. Like numbers refer to like elements in all figures, including alternate embodiments of like elements. The embodiments may be practiced in other specific forms. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
This application claims the benefit of and is a continuation-in-part of U.S. patent application Ser. No. 17/728,467, filed Apr. 25, 2022, which is a continuation of U.S. Pat. No. 11,313,813, filed Mar. 19, 2020, U.S. Provisional Patent Application No. 63/598,946, filed Nov. 15, 2023, and U.S. Provisional Patent Application No. 62/820,754, filed Mar. 3, 2019, which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63598946 | Nov 2023 | US | |
| 62820754 | Mar 2019 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16823552 | Mar 2020 | US |
| Child | 17728467 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17728467 | Apr 2022 | US |
| Child | 18949147 | US |
