Thermal-Guided Chemical Etching of Substrates and Its Real-Time Monitoring

Abstract

A method (300) for controlling a substrate etching process includes disposing (301, 302) a bottom surface or a top surface of a substrate adjacent to a volume of etching fluid to create an etchant-substrate interface, and heating (305) the etchant-substrate interface via spatially controlled electromagnetic radiation. The method further includes transmitting (303) a monitoring beam through the substrate, the substrate and the volume of etching fluid being at least partially transparent at the wavelength range of the monitoring beam, and measuring (304) a property of the substrate surface via the monitoring beam during the substrate etching process to generate a real-time measured property of the substrate. A corresponding etching system (100A-100D) and a computer program product are also disclosed herein.

Description

[0001] Background

[0002] The present invention generally relates to methods and apparatuses for processing a substrate. More specifically, the present disclosure describes a manufacturing process for precisely forming an optical element from a substrate using thermally-assisted chemical etching and real-time, closed-loop process control.

[0003] Manufacturing processes traditionally used to machine optical elements (e.g., mirrors, flats, reflectors, and lenses) are laborious and time-consuming, which increases the cost of these elements. Processes such as single-point diamond turning, multi-axis computer numerical control (CNC) machining, and grinding and polishing are long operations that typically allow for the machining of only one or a few optical elements at a time. Additionally, after the initial manufacturing process, the optical element must be measured and tested to ensure compliance with design specifications. The manufacturing process and subsequent metrology may need to be repeated multiple times to obtain the desired dimensional accuracy and surface quality, which further extends the manufacturing time and cost. Summary of the Invention

[0005] A method of controlling a substrate etching process includes positioning a bottom or top surface of the substrate adjacent to a volume of etching fluid to create an etchant-substrate interface and heating the etchant-substrate interface via spatially controlled electromagnetic radiation. The method further includes transmitting a monitoring beam through the substrate, the substrate and the volume of etching fluid being at least partially transparent within the wavelength range of the monitoring beam, and measuring a property of the substrate surface via the monitoring beam during the substrate etching process to generate a real-time measured property of the substrate. A corresponding etching system and computer program product are also disclosed herein. Brief Description of the Drawings

[0007] 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, but rather emphasis is placed on clearly illustrating the principles of the invention. In the drawings, like reference numerals indicate corresponding parts throughout the several views.

[0008] Figures 1A - 1DIllustrates an etching system in which optical elements can be fabricated from a substrate using a localizable etch process;

[0009] Figure 2 Is a block diagram showing Figures 1A - 1D additional aspects of the etching system;

[0010] Figure 3 Is a flowchart depicting an example of a method for measuring the optical properties of an optical element being fabricated;

[0011] Figure 4A Shows a top view of a plurality of monitoring beam emitters disposed among etch assist emitters on an emitter support board;

[0012] Figure 4B Illustrates by Figure 4A a cross-section of the radiation pattern generated by an etch assist emitter;

[0013] Figure 4C Shows after moving Figure 4A the etch assist emitter closer to the etchant, the radiation pattern of the bottom surface of the etchant;

[0014] Figure 5 Shows an embodiment in which etch assist emitters are arranged in a circular pattern on the emitter support board;

[0015] Figure 6 Shows a side view of a monitoring beam emitter on an emitter support board for fabricating an optical element;

[0016] Figure 7 Illustrates an embodiment in which a microlens array (MLA) is used to focus etch assist radiation and monitoring beams;

[0017] Figure 8 Illustrates an embodiment in which the monitoring beam emitter is the second harmonic frequency of the etch assist emitter;

[0018] Figure 9 Depicts a monitoring beam emitter positioned adjacent to the emitter support board;

[0019] Figure 10 Illustrates etch assist radiation spatially modulated by a screen having a plurality of electronically - controllable modulating elements;

[0020] Figure 11Illustrated is an etching system having a radiation blocking screen;

[0021] Figure 12 Depicted is a movable lens for focusing and defocusing emitter-assisted radiation and monitoring beam radiation;

[0022] Figure 13 Illustrated is an etching system in which an optical profilometer is used to measure the surface profile of an optical component being manufactured;

[0023] Figure 14 Is a cross-sectional side view of a convex lens being manufactured within a substrate, wherein the output power of each etch-assist emitter is individually controlled;

[0024] Figure 15 Is a cross-sectional side view of a concave lens being manufactured within a substrate, wherein the output power of each etch-assist emitter is individually controlled;

[0025] Figure 16 Depicted is etch-assist radiation from a projector being directed by a dichroic mirror;

[0026] Figure 17 Depicted is manufacturing a window or a planar mirror in a substrate; and

[0027] Figure 18 Depicted is a projector that generates etch-assist radiation that passes through a cover plate and an etchant and is focused onto the surface of a substrate, where it is absorbed and converted to heat. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention recognizes the need to manufacture optical components such as lenses at lower cost and higher volume. Accordingly, an object of the present invention is to provide a simpler and less expensive method of manufacturing optical components without the need for multiple rounds of processing and metrology.

[0030] 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 manufacture optical lenses, those skilled in the art of optical component manufacturing will recognize that the disclosed method may be used to form other components such as elliptical reflectors and parabolic reflectors. It should also be understood that the optical components discussed herein may be used for electromagnetic radiation of multiple wavelengths, not limited to visible light.

[0031] Unless otherwise stated, the features shown in the embodiments can be combined with each other. In addition, an embodiment containing more than one feature should not be construed as meaning that all of these features are necessary for carrying out the present invention, since other embodiments may include fewer and / or alternative features.

[0032] Figures 1A - 1D An etching system 100 (i.e., 100A - 100D) is illustrated, in which optical elements can be fabricated from a substrate 103 using a localizable etching process. An optical measurement component can be used to monitor the localizable etching process. As Figure 1A and Figure 1D shown, a container wall 101 and a sealing element 102 (such as a gasket) can substantially surround and adjoin at least a portion of the surface of the substrate 103, forming a container for containing an etchant 104. The substrate 103 can be any number of solid materials, such as glass, ceramic, semiconductor, crystal, or rigid polymer. Preferably, the container wall material is substantially inert to the etchant 104, while the etchant reacts with the substrate 103 to remove material from the substrate surface. The container wall 101 can be covered with a lid 107 to form a closed container.

[0033] The depicted etchant 104 is a fluid, such as a liquid, gas, or plasma. The etchant 104 can be injected into the container through an inlet port 105 and can be removed from the container together with the material being etched via an outlet port 106. In some cases, multiple inlet and outlet ports can be used to transport the etchant. These ports can also be used to circulate the etchant 104 as needed. As shown in Figure 1C and Figure 1D respectively, the depth of the etchant 104 can be set by the position of the substrate 103 or the lid 107 sealed to the container wall 101. The lid 107 can be inert to the etchant 104.

[0034] In some embodiments, the etchant 104 is not covered with a lid 107. A liquid depth measuring device can be used to determine the etchant depth, which includes those devices known in the art, such as a hydrostatic pressure sensor, ultrasound, or laser time-of-flight sensor. The depth measuring device can be connected to a controller, such as a computer, or other digital processing device to which the device can send measurement data.

[0035] In some embodiments, before sealing the substrate 103 to the container wall 101, a thin film 108 is disposed on the surface of the substrate and the thin film is patterned. The thin film 108 can be deposited using physical or chemical vapor deposition or oxidation of the substrate surface and patterned using photolithography and chemical etching, as commonly performed in the semiconductor industry. The thin film 108 is preferably inert to the etchant 104 so as to prevent the covered portion of the substrate 103 from being etched. In some cases, the thin film 108 is etched by the etchant 104 at an etching rate slower than that of the substrate 103 and can be completely removed from the substrate before the etching process is completed.

[0036] The depicted etching system 100 includes an etching assist emitter 109, a monitoring beam emitter 116, and a monitoring beam detector 118. The etching system 100 is capable of positioning the bottom or top surface of the substrate 103 adjacent to a volume of etching fluid (i.e., the etchant 104) to create an etchant-substrate interface. The etching assist emitter 109 is capable of emitting spatially controlled electromagnetic radiation ( Figures 1A - 1C not shown in the figure), which selectively heats the etchant-substrate interface and thereby spatially controls or directs the etching rate along the etchant-substrate interface.

[0037] The monitoring beam emitter 116 transmits a monitoring beam ( Figures 1A - 1C not shown in the figure) through the substrate. The monitoring beam emitter 116 can include an array of individual emitters. Examples of the monitoring beam emitter 116 include lasers, light-emitting diodes (LEDs), incandescent lamps, gas discharge lamps, fluorescent lamps, radio elements, and thermal radiation emitters such as filaments, thin film microheaters, and microhotplates.

[0038] The substrate and a volume of etching fluid can be partially or completely transparent within the wavelength range of the monitoring beam. The monitoring beam detector 118 can measure properties of the substrate surface via the monitoring beam during the substrate etching process and thereby generate one or more real-time measured properties of the substrate. Examples of the measured properties include focal length, focal spot size, 2D dimensions and symmetry of the etched area, wavefront shape and phase, 3D profile (e.g., curvature) of the etched area, and surface roughness. Additionally, these properties can be measured with respect to monitoring beams having different wavelengths. The monitoring beam detector 118 can be an array of individual detectors or sensors. Examples of the monitoring beam detector include charge-coupled devices, CMOS image sensors, wavefront sensors, antenna elements, scanning confocal microscopy devices, and interferometry devices.

[0039] In some embodiments, such as Figure 1D depicted in, on the side of the substrate 103 opposite the etchant 104, a plurality of etch assist emitters 109 are arranged in a two-dimensional array (described below) on an emitter support plate 110. The emitter support plate 110 may be in contact with a heat sink 111. The emitter support plate 110 and the heat sink 111 may rest on a locator 112 that is controlled by a controller 113 such as a computer or other digital processing device. In some embodiments, the locator 112 has three-axis movement.

[0040] The etch assist emitter 109 may include any number of radiation sources such as lasers, LEDs, masers, gyrotrons, backward wave oscillators, or radio elements. In the latter case, the radio element is configured to emit millimeter-wave radiation from 10 GHz to 300 GHz in the form of a radiation beam. However, in some cases, the emitter 109 is a resistive heater such as a miniature filament or wire coil, a thin-film metal trace, a micromachined membrane through which current can pass to generate resistive heat, or a thin-film transparent conductor. The radiation generated by the resistive heater may be broadband radiation, and thus, a radiation filter (e.g., a bandpass filter or a cutoff filter) may be used to limit the radiation spectrum emitted by the heat source. Additionally, the etch assist emitter may be a radiation source including a plasmonic near-field transducer. In the case where the etchant is a liquid or a 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 the absorption peak of the liquid or gas.

[0041] The etch assist emitters 109 are individually controlled, whereby the radiation power of each etch assist emitter can be varied, or selected emitters can be turned off as needed. The controller 113 controls the etch assist emitters 109 through a drive circuit 114 that supplies electrical power to the etch assist emitters. Matrix addressing may be used to select individual emitters, as commonly used in semiconductor memory chips.

[0042] In some embodiments, the etch assist emitter 109 is substantially a Lambertian emitter that generates radiation 115 in a generally hemispherical pattern in a direction toward the substrate. In other embodiments, the etch assist emitter is a directional emitter that emits radiation in a highly directed manner. For example, the phase of the etch assist emitter can be controlled to direct the emitted radiation to a selected area by beam steering. Additionally, the etch assist emitter can be shaped or include reflective elements that increase the directivity of the emitted radiation. For example, a thermal emitter or a patch antenna element that is normally substantially Lambertian can be disposed within a parabolic reflective cavity that reflects radiation toward the substrate 103 to increase the directivity of the emitted radiation and the spatial selectivity of the etch process.

[0043] The radiation 115 can be continuous or quasi-continuous, and in the latter case, the pulse duration is preferably longer than 10 μs. In some embodiments, one or more etch assist emitters 109 generate radiation 115 having a wavelength different from that of other emitters within the array. The substrate 103 is transparent to the emitted radiation, which allows the radiation to pass through the substrate to the etchant 104, where most of the radiation is absorbed. The absorbed radiation is converted into 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 can be dispersed in the etchant to improve the conversion of electromagnetic energy to thermal energy.

[0044] By using an array of individually controllable etch assist emitters 109 and adjusting the radiation power and position of the etch assist radiation 115 incident on the etchant 104, the etch rate of a specified area of the substrate can be increased, and material can be selectively removed from the substrate 103, thereby shaping the substrate surface. The precision of the etch process is determined by the ability of the etch assist emitter 109 to heat a small volume of the etchant 102 at a specified location, which in turn is determined by various factors such as the radiation power, the area size of the radiation incident on the etchant 104, whether the radiation from neighboring emitters overlaps at the etchant, the packing density of the emitters on the emitter support plate 110, the temperature and flow rate of the etchant, and the absorption coefficient of the etchant.

[0045] At the wavelength of the etch assist emitter 109, the substrate 103 preferably has an absorption coefficient of less than 0.1 cm -1 and the etchant 104 preferably has an absorption coefficient greater than 1 cm -1Absorption coefficient. For an etchant having a water component, the wavelength of the etch assist emitter 109 is preferably close to any number of water absorption peaks in the ultraviolet (UV) spectrum, infrared (IR) spectrum, or radio frequency (RF) spectrum. For example, an emitter having a wavelength of approximately 1940 nm (which corresponds to a water absorption peak) can be used for an etchant containing water, such as a mixture of HF and water. The radiation absorbed by the etchant can be described by the Beer-Lambert law,

[0046] I = I o e -αx ,

[0047] where I is the radiation intensity at a distance x from the surface of the etchant, I o 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 having a linear absorption coefficient of 1 cm -1 or greater, approximately 90% of the etch assist radiation is absorbed within the first 2.3 cm of the etchant. Thus, one aspect of the present invention described herein is to perform precise thermally assisted chemical etching to process the substrate 103. The present invention can be used, for example, to etch raised or recessed shapes within a glass substrate to form an optical lens.

[0048] In other embodiments, the substrate 103 is opaque, and the etchant 104 in contact with the substrate surface is substantially transparent at the wavelength of the etch assist radiation 115 generated by the etch assist emitter 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 emitter 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 the drive circuit 114. By controlling the etch assist radiation 115 from the individual emitters within the array, selected regions of the substrate 103 can be locally heated, thereby increasing the etch rate of the substrate.

[0049] In addition, as Figure 1D shown, the device 100D enables the operator to monitor the surface of the substrate 103 in real time during the etching process. On the emitter support plate 110, the monitoring beam emitter 116 generates a monitoring beam 117 in the direction of the substrate. The substrate 103, the etchant 104, and the cover 107 are transparent at the wavelength of the monitoring beam 117, preferably having an absorption coefficient less than 0.1 cm -1Absorption coefficient. Accordingly, at least a portion of the monitoring beam 117 passes through the substrate 103, the etchant 104, and the lid 107 and is incident on the monitoring beam detector 118, which is positioned on the opposite side of the substrate 103 from the monitoring beam emitter 116. The monitoring beam detector 118 may include a camera that captures an image of the monitoring beam 117 and sends the image to the controller 113 for processing and display. The controller 113 may use the robotic arm 119 to control the position of the monitoring beam detector 118 in three dimensions and may control various operations of the monitoring beam detector, such as exposure, signal, gain, and frame rate. The monitoring beam detector 118 may include one or more of a charge-coupled device (CCD) sensor, a complementary metal-oxide semiconductor (CMOS) image sensor, an optical profiler, or a Shack-Hartmann wavefront sensor.

[0050] When the monitoring beam 117 passes through the optical element being fabricated within the substrate 103, beam characteristics such as position, 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 118, and the image is sent to the controller 113, which then calculates various optical properties of the optical element being fabricated. For example, a collimated monitoring beam passing through the substrate 103 in which a convex lens is being etched will reach a focused spot at the focal length of the lens. To obtain a lens with a specific focal length, the monitoring beam detector 118 may be moved to a position at a specific distance from the substrate 103, i.e., at the desired focal length of the lens, and the etching process continues until the minimum monitoring beam spot size is recorded by the monitoring beam detector 118, which indicates that the lens has the desired focal length.

[0051] In some embodiments, the monitoring beam detector 118 may be moved in a direction perpendicular to the surface of the substrate 103 using the robotic arm 119 to measure the spot size of the monitoring beam 117 at multiple distances from the substrate 103. These measurements may be used to calculate the angle of incidence θ of the monitoring beam 117 and the focal length f of an optical element such as a lens reflector or a parabolic reflector. By way of example, the optical properties of a lens may be measured using the following procedure. The spot size of the monitoring beam is measured at an image plane located at a distance z1 from the substrate 103, having a spot size diameter d1, and a second monitoring beam spot size is measured at an image plane at a greater distance z2 (z2 > z1) from the substrate 103, having a spot size diameter d2. The angle of incidence θ of the monitoring beam 117 is calculated using the following formula,

[0052]

[0053] Assume that the spot size of the monitoring beam is reduced to a negligible small point at the focal length, and the focal length f can be calculated from the incident angle. For a light converging lens,

[0054]

[0055] And for a light diverging lens, the virtual focal length f v is,

[0056]

[0057] The ability to calculate rather than measure the focal length is necessary in the following cases: where the lens has a focal length shorter than the depth of the etchant 104 such that the monitoring beam detector 118 cannot be moved to the focus to directly measure the focal length, or when a diverging lens is being fabricated and the virtual focal length cannot be directly measured.

[0058] It should be understood that the optical properties of the lens measured during the etching 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 that correlates the measured properties of the lens in the disclosed etching apparatus with the properties of the lens in air can be used. Alternatively, if the refractive indices and thicknesses of the substrate 103, the etchant 104, and the cover 107 are known, the optical properties of the lens in air can be calculated based on the optical measurements of the lens during the etching process, using Snell's law.

[0059] The monitoring beam detector 118 also records the baseline intensity of the monitoring beam 117 that passes through the substrate 103, the etchant 104, and the glass cover 107 before the etching process begins. As etching starts, the change in the intensity of the monitoring beam due to specular reflection from the surface of the substrate 103 can be used to infer information about the surface roughness of the substrate.

[0060] The measured characteristics of the monitoring beam are used for closed-loop process control. The aforementioned monitoring beam measurement provides feedback to the controller 113 in real time regarding the progress of surface etching, such that the controller can dynamically adjust the radiation power generated by the separate etch assist emitter 109 and the position of the emitter, thereby modifying the etching process as needed. The controller 113 compares the measured optical properties of the optical element being manufactured with the design specifications of the optical element. The etching process can be adjusted manually by an operator or automatically by the controller 113 to make the measured optical properties closer to the desired optical properties. For example, by comparing the measured optical properties of a lens with the design specifications of the lens and then using a computer to adjust the substrate etching to minimize the differences, an optical lens with a desired focal length, numerical aperture, size, and shape can be fabricated within the substrate. Closed-loop feedback eliminates many post-fabrication metrologies by performing metrology during the manufacturing process, thereby increasing manufacturing yield and reducing the cost of optical elements.

[0061] In some embodiments, a Shack-Hartmann wavefront sensor is used as the monitoring beam detector 118. The wavefront sensor can be used to measure the wavefront distortion of the monitoring beam 117 caused by the surface of the substrate as the monitoring beam passes through the substrate 103. The shape of the wavefront can be mathematically described using Zernike polynomials. Zernike polynomials can be used to model the optical aberrations of the optical element being manufactured. The wavefront sensor can be used to monitor the etching process in real time and provide process feedback to the controller 113 using the following loop: First, the controller 113 uses the wavefront sensor to record the wavefront distortion during the substrate etching process; second, the wavefront is modeled using Zernike polynomials; third, the computer adjusts the etch assist radiation power and / or radiation position incident on the etchant to change the substrate etching process and minimize the optical aberrations modeled using Zernike polynomials; and fourth, the controller observes the change in the wavefront when the substrate is etched using the new radiation power and / or position settings.

[0062] Those skilled in the art of lens design will recognize that the methods and apparatuses described herein can be used to fabricate many different optical elements. For example, spherical or aspherical lenses that focus or defocus light can be machined. In addition, beam shaping lenses can be fabricated, such as lenses that transform a monitoring beam having an elliptical two-dimensional cross-section into a monitoring beam having a circular shape. Freeform lenses can also be fabricated, where the lens does not have translational or rotational symmetry about an axis perpendicular to the surface of the substrate 103. In some embodiments, the disclosed invention is used to fabricate a mold. For example, a concave trough can be etched in 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 together as a single optical element having desired chromatic and / or achromatic properties.

[0063] It should be noted that the apparatuses disclosed herein can be used to fabricate optical elements on both sides of a substrate. For example, after fabricating an optical element on a first side of the 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) abuts and seals the container 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 position of the monitoring beam. As etching begins, the position of the etching assist radiation can be adjusted so that the optical element being fabricated maintains the central position of the initial monitoring beam on the monitoring beam detector. Thus, the optical axis of the optical element fabricated on the second side of the substrate is aligned with the optical axis of the optical element fabricated on the first side of the substrate.

[0064] It should be noted that alternative arrangements of the components of the apparatus 100D can exist without departing from the methods of the present invention. For example, the etching assist emitter 109 and the monitoring beam emitter 116 can be placed above the substrate 103, and the etchant 104 can be sealed on the bottom side of the substrate 103. In this embodiment, the monitoring beam detector 118 is placed on the substrate below the etchant 104, opposite the monitoring beam emitter 116.

[0065] Figure 2FIG. is a block diagram showing additional aspects of the etching systems 100A - 100D. As shown, a user may interact with a software program to control the substrate etching process. The software program consists of a graphical user interface (GUI) through which the user may observe a monitoring beam as measured by a monitoring beam detector and manually change the power supplied to individual etch assist emitters and the position of the emitters (via a positioner) to adjust substrate etching. Additionally, the software program allows the user to manually adjust the monitoring beam detector settings, move the monitoring beam detector using a robotic arm, and control the electrical power supplied to the monitoring beam emitter.

[0066] In some embodiments, the software program automatically controls the substrate etching process using feedback from the monitoring beam measurements to produce an optical element that matches the specifications input by the user into the program. For example, the specifications of a lens may include the focal length, the minimum spot size to which the lens must focus light, the diameter of the lens, and the radius of curvature or surface profile. The software program uses the measured monitoring beam characteristics to calculate the properties of the optical element being manufactured and compares the measured optical element properties to the user - defined specifications and minimizes the differences. The software program accomplishes this task by controlling the etch assist emitter array, which may require changing the radiation power of individual etch assist emitters 109, turning off the etch assist radiation 115 of some emitters, or moving the emitter array relative to the substrate 103 using a positioner 112. As is known in the art, many multi - variable optimization algorithms may be used to control the etch assist emitter array and minimize the differences between the optical element specifications and the measured optical properties of the optical element.

[0067] 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 etching process (e.g., etch assist radiation power and emitter position) in response to positive or negative reinforcement (i.e., reward). The intensity of the reinforcement is based on the difference between the calculated optical properties of the optical element being manufactured and the user - specified optical properties of the optical element, where actions that minimize the difference result in a positive reward.

[0068] Now refer to Figure 3 , Figure 3 FIG. is a flow chart 300 that shows a method for processing a substrate using the methods and apparatuses disclosed herein. Figure 3The method begins with a first step 301 of placing a substrate in contact with the container wall and sealing the substrate surface against the container wall to form a container for holding an etchant. In step 302, the etchant is dispensed onto the surface of the substrate in the container. In step 303, one or more monitoring beams are generated and directed through the substrate to a monitoring beam detector on the opposite side of the substrate. The substrate is substantially transparent at the wavelength of the monitoring beam. Next, in step 304, a computer uses the monitoring beam detector to record the properties of the monitoring beam. Properties of the monitoring beam such as diameter size, shape, intensity, and wavefront shape and phase can be recorded to collect baseline measurements of the monitoring beam at the start of etching. Steps 301 - 304 are considered initialization steps for establishing the manufacturing process.

[0069] In step 305, an array of individually controllable etch assist emitters located on the opposite side of the substrate from the etchant directs radiation to a plurality of selectable locations on the etchant surface at the substrate - etchant interface. The substrate is substantially transparent at the wavelength of the radiation. In step 306, the radiation power of the selected emitters is adjusted to selectively heat the etchant and form a target etch shape in the substrate. In step 307, when etching the substrate, at least one property of the monitoring beam (e.g., beam diameter size, shape, intensity, wavefront shape, or wavefront phase) is measured. The features etched in the substrate change the properties of the monitoring beam recorded by the monitoring beam detector. In step 308, if the properties of the monitoring beam are not as desired (e.g., if the beam shape is asymmetric, the beam size increases in size instead of decreasing in size, or the wavefront is not shaped as desired), the radiation power from the plurality of etch assist emitters can be adjusted to change the etching process by repeating steps 306 and 307.

[0070] In some cases, steps 309, 310, and 311 can be performed. As listed in step 309, the monitoring beam detector is moved a predetermined distance from the substrate, and the monitoring beam detector 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 (e.g., the focal length of a lens) about the optical element being formed in the substrate can be calculated. If the optical element does not have the desired properties, according to step 311, the etching process continues and the measurement of the monitoring beam is repeated starting from step 307. Otherwise, once the desired monitoring beam properties have been obtained, the process is complete. In step 312, the etch assist radiation and the monitoring beam are turned off. Then the etchant is flushed out of the container and the substrate is washed with water. In some embodiments, the etchant is flushed before each measurement of the monitoring beam or other substrate - related measurement, and if the etching process continues, the container is refilled with etchant.

[0071] In some embodiments, more than one etch assist emitter array is used to process a substrate. Figure 4A A top view shows a plurality of monitoring beam emitters 116 scattered among etch assist emitters 109 on emitter support plate 110. The emitter support plate 110 is a rigid, planar platform, preferably a printed circuit board (PCB) with metal traces that provide electrical contact to the monitoring beam emitters 116 and the etch assist emitters 109. It should also be noted that the monitoring beam emitters 116 and the etch assist emitters 109 can be in different planes. For example, the monitoring beam emitters 116 can be recessed into the support plate. The etch assist emitters 109 and the monitoring beam emitters 116 are arranged in a two-dimensional pattern, forming a rectangular array 403 scattered on the emitter support plate 110. Each array 403 is used to etch a different area of the substrate, whereby multiple etch shapes can be generated simultaneously. In some embodiments, the surface of the emitter support plate 110 is covered by a single large array. By turning off selected etch assist emitters, this large array can be configured into smaller arrays, thus dividing the group of emitters into active arrays separated by deactivated emitters.

[0072] In one aspect of the present invention, each monitoring beam emitter 116 can generate a monitoring beam 117 having substantially the same wavelength or multiple different wavelengths. For example, the monitoring beam emitters 116 forming the array can include LEDs of red, green, or blue. By using a combination of wavelengths, the monitoring beam detector can record how light of different wavelengths passes through the optical elements being manufactured during the etching process. For example, a lens being manufactured can have different focal lengths for light of different wavelengths (i.e., chromatic aberration). The monitoring beam detector 118 can record the focal length at each wavelength of each monitoring beam 117. In addition, the monitoring beam detector can detect monitoring beams having different wavelengths by using filters. For example, a monitoring beam detector with a green bandpass filter can detect the green monitoring beam, and another monitoring beam detector with a red bandpass filter can detect the red monitoring beam.

[0073] In some embodiments, the disclosed methods and apparatus are used to simultaneously fabricate a plurality of optical elements on a surface of a substrate. A plurality of emitter arrays can be used to etch a number of optical elements on a region of the substrate in contact with an etchant. The optical elements can be the same, or multiple types of optical elements can be fabricated across the substrate. In one case, a plurality of monitoring beams pass through the optical elements, and a monitoring beam detector is moved to a position above each optical element to measure the optical properties of the optical element. In other cases, a large monitoring beam can pass through a plurality of optical elements. A computer independently controls each etch assist emitter in the array. Radiation from each etch assist emitter can be adjusted based on feedback from the monitoring beam as recorded by the monitoring beam detector such that the etch process for each lens can be completed substantially simultaneously. Thus, the etch processes and feedback systems described herein can be scalable to enable mass production.

[0074] The completed optical elements are removed from the substrate by a variety of means. For example, individual optical elements can be removed from the substrate by dicing or laser cutting. In some cases, optical elements can be removed from a wafer by setting a barrier material on the surface of the substrate and patterning the barrier material. The substrate can then be etched at an opening in the barrier material where the substrate is exposed using wet etching and / or dry etching until the optical element is released from the substrate or the optical element is held in the substrate by a small tab or bridge connecting the optical element to the substrate body. The barrier material can then be selectively removed from the optical element using a wet etchant that dissolves the barrier material without etching the optical element.

[0075] In some embodiments, after fabricating the optical elements, the substrate can be coated with at least one thin film to produce an optical coating, such as one or more anti-reflection coatings, IR filter coatings, 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 can be patterned to create holes over the optical elements within the substrate. The light-blocking thin film is patterned, for example, using photolithography and the thin film is removed using a lift-off process, which is a process commonly performed within the semiconductor electronics industry. In some embodiments, the light-blocking thin film can be used as a thin film barrier 108 during the fabrication of the optical elements. After fabricating the optical elements, the thin film barrier 108 can remain on the surface of the substrate, thereby forming holes.

[0076] Figure 4B Shown by Figure 4AThe cross-section of the radiation pattern 404 generated by the etch-assisted emitter 109 in a plane perpendicular to the radiation propagation direction, which plane is at the substrate-etchant interface. The size and shape of the output radiation pattern 404 are for illustrative purposes, as various sources of etch-assisted radiation will have different cross-sectional profiles and the radiation can diverge at greater angles in one direction relative to another. The boundary of the radiation can be defined as the 1 / e value of the maximum radiation intensity or the half-power beam width where the power has dropped to -3 dB of the maximum power. The radiation from one etch-assisted emitter 109 can overlap with the radiation from adjacent etch-assisted emitters. Figure 4C shows the Figure 4B radiation pattern 406 of the bottom surface of the etchant after moving the etch-assisted emitter 109 closer to the etchant. Since the radiation beam 407 diverges less over the shorter distance between the etch-assisted emitter 109 and the substrate-etchant interface, the surface area covered by the radiation 407 is Figure 4C less in Figure 4B than the radiation in Figure 4C . It should be understood that Figure 4B the power density of the radiation beam 407 in

[0077] Figure 5 shows an embodiment of the present invention in which the etch-assisted emitters 109 are arranged in a circular pattern 503 on the emitter support plate 502. A single monitoring beam emitter 116 is used in this embodiment of the present invention. The monitoring beam generated by the monitoring beam emitter can be collimated or the beam can be expanded outward to cover an area substantially equal to the area covered by the radiation from the etch-assisted emitter 501. In some embodiments, multiple monitoring beam emitters are scattered throughout the etch-assisted emitter array. The circular emitter array is useful for etching having a circular outer boundary or a radially symmetric shape, such as a conventional lens.

[0078] Figure 6 shows a side view of the monitoring beam emitter 116 on the emitter support plate 110 for manufacturing an optical element using the disclosed method. For clarity, the etch-assisted emitters are not shown. The monitoring beam 117 generated by the monitoring beam emitter is uncollimated and divergent such that the beam substantially covers the entire area of the optical element being manufactured. The monitoring beam 117 passes through the transparent substrate 103, the etchant 104, and the cover plate 107 to reach the monitoring beam detector 118. The monitoring beam emitter 116 is positioned at a known distance d o from the substrate 103, where d o is greater than the desired focal length f of the optical element being manufactured. In the case where the optical element is a converging lens, the Thin Lens Equation can be used,

[0079]

[0080] to find the distance d i (i.e., the image distance), the monitoring beam detector 118 should be placed at this distance d i such that when the lens under fabrication has achieved the desired focal length f, the monitoring beam emitter 116 will appear at the focal point. In other words, the monitoring beam detector is placed at the distance d i such that the image of the monitoring beam emitter 116 as recorded by the monitoring beam detector 118 is sharpest when the lens has been fabricated to have the desired focal length f.

[0081] In some embodiments, the monitoring beam emitter 116 is positioned at a distance from the substrate that is equal to the desired focal length of the lens under fabrication. As the etching process proceeds, the monitoring beam 117 passing through the substrate begins to converge and eventually becomes collimated, indicating that 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.

[0082] It should be understood that the focal length of the lens determined by the foregoing method is not equal to the focal length of the lens in air. To determine the properties of the lens in air, a look-up table that correlates the measured focal length with the focal length of the lens in air can be used.

[0083] Figure 7 An embodiment of the present invention is illustrated in which a microlens array (MLA) 700 is used to focus the etch assist radiation 115 and the monitoring beam 117. The etch assist emitter 109 can be any number of radiation energy sources such as LEDs, vertical cavity surface emitting lasers (VCSELs), superluminescent light emitting diodes, diode pumped solid state (DPSS) lasers, semiconductor laser diodes, or laser coupled optical fibers. The lenses within the MLA 700 are identical lenses and thus these lenses focus the etch assist radiation 115 and the monitoring beam 117 differently because they typically have different wavelengths. In some embodiments, the MLA 700 can have two different lens types, one type for the etch assist emitter 109 and one type for the monitoring beam emitter 116. In this case, both the etch assist emitter and the monitoring beam emitter can be collimated.

[0084] In some embodiments, as Figure 8As depicted, the etch assist emitter 109 is a laser, and the monitor beam emitter 116 is generated by a non-linear process using the etch assist radiation 115 output from the etch assist emitter 109. For example, the etch assist emitter can be a diode laser, and the monitor beam emitter 116 is a DPSS laser generated at the second harmonic frequency of the etch assist emitter. The etch assist radiation 115 and the monitor beam 117 thus substantially originate from the same location on the emitter support plate 110.

[0085] In some embodiments, as Figure 9 shown, the monitor beam emitter 116 is positioned adjacent to the emitter support plate 110. The monitor beam emitter 116 can be, for example, an LED, a laser diode, a fiber-coupled laser, a gas laser, a VCSEL, or any other light source. The lens 901 collimates the monitor beam 117 generated by the monitor beam emitter 116. In the case where the monitor beam emitter 116 is a fiber laser, the fiber can carry several different wavelengths of light simultaneously. The monitor beam 117 is directed by the dichroic mirror 902 towards the substrate 103. The etch assist emitter 109 is located on top of the emitter support plate 110. The lens 903 above the etch assist emitter focuses the etch assist radiation 115 onto the etchant at the substrate-etchant interface. The etch assist radiation 115 passes relatively unimpeded through the dichroic mirror 902.

[0086] Figure 10 An embodiment of the invention is illustrated in which the etch assist radiation 115 emitted from a single etch assist emitter 109 is spatially modulated by a screen 1010 having a plurality of electronically controllable modulation elements. The screen 1010 selectively prevents different amounts of radiation from reaching the etchant 104, ranging from complete blockage (i.e., opaque) to having substantially no effect on the intensity of the radiation (i.e., transparent). Preferably, each modulation element is computer-addressable by a computer having a user interface through which an operator can input commands to the computer to control the transparency of the modulation element. Thus, the operator can selectively block the etch assist radiation 115 from specific regions of the etchant 104 according to the need to fabricate optical elements within the substrate 102. Figure 10The thickness of the solid arrows shown represents the relative power of the etch assist radiation 115, where the thicker arrows represent higher power than the thinner arrows. The monitoring beam 117 generated by the monitoring beam emitter 116 can also be blocked by the screen 1010 to varying degrees. The thickness of the dashed arrows represents the relative power of the monitoring beam 117, where the thicker dashed arrows represent higher power than the thinner dashed arrows. Optical measurements of the optical element can be made by temporarily rendering the screen 1010 transparent and allowing the monitoring beam 117 to pass relatively unimpeded through the screen 1010. During this time, the monitoring beam detector records the characteristics of the monitoring beam 117 passing through the optical element under manufacture.

[0087] The screen 1010 can include 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) known in the art, or an electrochromic screen that undergoes a change in optical transparency in response to an applied current or potential. In the case of an electrochromic screen, the screen is segmented into addressable elements.

[0088] 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 can be coupled into an optical fiber. In some cases, radiation having different wavelengths can be generated by more than one etch assist emitter coupled into the optical fiber. Similarly, multiple monitoring beams having different wavelengths (e.g., red, green, and blue) can be coupled into the optical fiber. An electronic driver controlled by a computer is used to control the radiation emitters and monitoring beam emitters at the input side of the optical fiber. In some cases, multiple such optical fibers can be used for thermally assisted chemical etching and etch monitoring in accordance with the disclosed invention. In other cases, multiple optical fibers can be bundled together in a tube or ferrule and fixed in place using epoxy. The optical fibers are terminated in the ferrule such that the ends of the optical fibers are substantially in the same plane within the ferrule.

[0089] Figure 11 Illustrated is a configuration of an etch system where an optical fiber 1101 is used with a radiation blocking screen 1010. The thickness of the solid arrows represents the power of the etch assist radiation 115, where the thicker arrows represent relatively higher power than the thinner arrows. Similarly, the thicker dashed arrows represent the monitoring beam 117 having relatively higher power than the thinner dashed arrows. By electronically changing the entire screen to a transparent state, the monitoring beam 117 can be allowed to pass through the screen 1010 temporarily unimpeded. In some embodiments, lenses can be used to collimate or focus the etch assist radiation 115 and the monitoring beam 117 exiting the optical fiber 1101.

[0090] In some embodiments, as Figure 12 shown, the optical fiber 1101 and the movable lens 1201 are used to focus and defocus the radiation and the monitoring beam exiting the optical fiber. The movable lens 1201 moves closer to or farther from the optical fiber 1101 in a direction perpendicular to the surface of the optical fiber to focus the radiation onto the etchant 104. The focused radiation incident on the etchant 104 has a higher power density than the defocused radiation and increases the etching rate of the substrate 103 more. Thus, in order to form a recessed optical element within the substrate 103, the movable lens 1201 can focus the etch-assist radiation 115 onto a small area on the etchant at the center of the optical element being fabricated to form the apex of the groove, and then gradually defocus the radiation over time (by moving the lens relative to the etch-assist emitter) to controllably form the outer edge of the recessed shape. As described above, the lens can also be used to collimate the monitoring beam 117 for measuring certain properties of the optical element being fabricated. The monitoring beam 117 is collimated for only a short period of time, just long enough to perform the optical measurement. During the time of performing the optical measurement, the etch-assist radiation emitter can be temporarily turned off. Additionally, in some embodiments, the optical fiber 1101 moves in two dimensions in a plane parallel to the fixed lens 1201. The optical fiber can also move rotationally about an imaginary central axis extending through the length of the optical fiber 1101.

[0091] In one case, the etch-assist radiation 115 from the lens 1201 is incident on at least one galvanometer scan mirror. The angular position of the galvanometer scan mirror is controlled by a computer, whereby the computer directs the etch-assist radiation incident on the mirror to a desired position on the etchant.

[0092] In some embodiments, the etch-assist emitter can be positioned on a emitter support plate while using a non-contact optical profiler to monitor the etching process, and the optical profiler provides feedback to a controller that controls the etch-assist emitter. Figure 13The configuration of an etching system is illustrated, in which an optical profiler 1301 is used to measure the surface profile of an optical element being manufactured. The optical profiler may use an incident radiation beam 1302 and focus the incident radiation beam 1302 onto the surface of the substrate using an objective lens 1303. The etchant 104 and the cover 107 are substantially transparent at the wavelength of the incident beam of the optical profiler. In some cases, the cover plate 107 is removed from the device to prevent the incident radiation beam 1302 of the profiler from reflecting off the cover and interfering with the operation of the profiler. In other cases, the cover plate 107 may have an anti-reflection coating to minimize the reflected light of the incident radiation 1302 from the profiler. Additionally, in other cases, a transparent liquid having a refractive index substantially matching that of the cover plate may be injected onto the surface of the cover plate 107, and the objective lens 1303 of the profiler may be immersed in the transparent fluid. Further, in other embodiments, the optical profiler 1301 may include a material-compensated objective lens, and optical profiling may be performed by focusing the incident beam of the optical profiler located on the side of the substrate 103 opposite the etchant 104 onto the surface of the substrate in contact with the etchant. For example, in the case where the substrate is glass, the objective lens may be glass-compensated such that the profiler can measure the machined surface of the substrate.

[0093] The devices and methods described in this disclosure can be used to fabricate many types of optical elements. By way of example, Figure 14 A cross-sectional side view of a convex lens being fabricated within a substrate 103 is shown. The output power of each etch assist emitter 109 is controlled individually. The width of the solid arrows illustrates the power of the etch assist emitter 109, whereby the thicker arrows represent relatively higher power compared to the thinner arrows. The outermost etch assist emitters 109 have a higher output power than the two central emitters, whereby the outer edges of the etch region are heated more than the central region, which results in a faster etch rate at the edges. The patterned thin film 108 is used to protect the regions of the transparent substrate outside the etch region. Below the emitter support plate 110 are a number of monitoring beam emitters 116 and optical lenses 901 that collimate the monitoring beam 117 generated by the monitoring beam emitters. The emitter support plate 110 has openings extending through the top and bottom surfaces of the emitter support plate, whereby the monitoring beam 117 passes through the support plate. The convex-shaped surface of the substrate 103 focuses the monitoring beam 117. As the etching progresses, the convergence position of the monitoring beam 117 generally moves closer to the substrate 103.

[0094] By way of example, Figure 15A cross-sectional side view of a concave lens being fabricated within a substrate is shown. The output power of each etch assist emitter 109 is controlled individually. The width of the solid arrows illustrates the power of the etch assist emitters 109, where the thicker arrows represent relatively higher power compared to the thinner arrows. The radiation from the innermost etch assist emitter has a higher power than the radiation from the two outer emitters, whereby the inner working area is heated more than the outer areas, which results in a faster etch rate at the center of the substrate 103. The patterned thin film 108 is used to protect the areas of the substrate 103 outside the etch area. Below the emitter support plate 110 are a number of monitoring beam emitters 116 with optical lenses 901 that collimate the output monitoring beams 117. The emitter support plate 110 has openings extending through the support plate, whereby the monitoring beams 117 pass through the support plate. The monitoring beams 117 are defocused by the convex-shaped surface of the substrate 103. As the etching progresses, the monitoring beams 117 diverge from the virtual focus on the underside of the substrate 103.

[0095] In some aspects of the present invention, Figure 15 the substrate therein is used as a mold. After fabricating the grooves, the substrate 103 is removed from the etchant, washed with water and cleaned. A glass preform or glass glob having a melting temperature lower than that of the substrate 103 is placed within the grooves. The substrate 103 and the preform are heated to the softening temperature of the preform. The preform can be pressed with a suitable force to distribute the preform within the grooves such that the grooves are filled with the preform. Thereafter, chemical mechanical polishing (CMP) is used to planarize the preform and the substrate surface.

[0096] In some cases, the substrate 103 and the preform are heated to the melting temperature of the preform. The preform melts under its own weight to fill the grooves. Then, chemical mechanical polishing (CMP) is used to planarize the preform and the substrate surface. The preformed glass can remain within the mold, whereby the mold and the preformed glass form a single optical element having a flat surface. In some embodiments, the flat surface of the optical element can 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 known in the art.

[0097] In another embodiment, the etch assist radiation can emanate from a projector. For example, the projector can be a laser or an LED projector as is known in the art. The projector can 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 Figure 16 shown in Figure 16 , the etch assist radiation 115 from the projector 1601 is directed by the dichroic mirror 1602 to the etchant 104. The projector includes a focusing lens that is used to focus the etch assist radiation 115 onto the substrate-etchant interface.

[0098] Below the dichroic mirror 1602 can be at least one monitoring beam emitter 109. The monitoring beam 117 generated by the monitoring beam emitter is collimated by the lens 1603. The collimated beam size is approximately the same as the area size of the etch assist radiation at the substrate 103. The collimated monitoring beam passes through the dichroic mirror 1602, the substrate 103, the etchant 104, and the cover plate 107 with relatively little absorption. On the side of the cover plate opposite the monitoring beam emitter, beam reducer lenses 1604 are used to reduce the size of the monitoring beam such that it is approximately the same size as the monitoring beam detector 118, which is also on the side of the cover plate opposite the monitoring beam emitter. As an example, the beam reducer lenses 1604 can include two convex lenses forming a Keplerian beam reducer or a concave lens and a convex lens forming a Galilean beam reducer. The monitoring beam detector 118 can include a CCD or CMOS camera or a wavefront sensor, such as a Shack-Hartmann wavefront (SHW) sensor.

[0099] In the case where the monitoring beam detector 118 is a wavefront sensor, three-dimensional optical profilometry of the substrate can be performed during the etching process. Generally, the amount by which the phase of an incident wavefront passing through a material is delayed is proportional to the thickness and refractive index of the material (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, the thickness of the material can be calculated.

[0100] In the system described herein, the surface profile of the substrate 103 can be calculated by comparing the phase of the wavefront before the start of etching (i.e., the initial wavefront phase) with the measured phase of the wavefront after etching the substrate.

[0101] Referring again to Figure 16, the monitoring beam 117 is collimated by the collimating lens 1602, generating a substantially planar wavefront incident on the substrate. The wavefront at the substrate is relayed to the wavefront sensor by a beam expander lens 1603. In other words, the wavefront at the exit pupil of the substrate is imaged onto the wavefront sensor. The controller 118 records the initial phase of the wavefront. As the substrate is etched, the initial wavefront phase is changed by the shape of the substrate. The phase of the wavefront after etching is measured by the wavefront sensor 118 and recorded by the controller 113. The controller is used to calculate the phase difference, Δφ(x,y), between the initial phase of the wavefront and the phase of the wavefront after etching. The 3D surface profile z(x,y) of the substrate can be calculated using the following formula,

[0102]

[0103] where λ is the wavelength of the monitoring beam, and n1 and n2 are the refractive indices of the substrate and the etchant, respectively. The controller 113 can be used to calculate the surface profile using the above formula.

[0104] In some cases, the surface profile of the substrate 103 is measured only when the fluid container is filled with water. The etching process is carried out using the following cycle: First, the fluid container is filled with water; Second, the monitoring beam 117 is generated and directed through the dichroic mirror 1602, the substrate 103, the etchant 104, and the lid 107; Third, the wavefront at the exit pupil of the substrate is relayed to the wavefront sensor 118, and the controller 113 records the initial wavefront; Fourth, the water is removed from the fluid container, and the etchant 104 is injected into the fluid container; Fifth, the etching assist radiation 115 is projected onto the substrate-etchant interface for a specified time, and the substrate 103 is controllably etched; Sixth, the etching assist radiation is turned off; Seventh, the etchant 104 is removed from the fluid container, and the container is filled with water; Eighth, the new wavefront at the exit pupil of the substrate 103 is relayed to the wavefront sensor 118, and the controller 113 records the new wavefront; Ninth, the initial wavefront measurement and the new wavefront measurement are used, and the controller 113 calculates the surface profile of the substrate and compares it with the desired surface profile; Tenth, based on the difference between the desired surface profile and the calculated surface profile, the power and / or position of the etching assist radiation is adjusted; Eleventh, the water is removed from the fluid container, replaced with the etchant, and the etching assist radiation 115 is projected onto the substrate-etchant interface. The foregoing steps can be repeated multiple times until the surface profile of the etched substrate is within the tolerance of the desired surface profile.

[0105] In addition, the controller 113 can be used to compare the measured surface profile with an ideal surface profile specified by the user. The difference between the specified and measured surface profiles can be used to change the position of the etch assist radiation 115 incident on the etchant, or to turn off the etch assist radiation at certain regions of the etchant-substrate interface. Accordingly, the profile of the etched substrate can be controlled and the difference (i.e., profile error) between the measured profile and the specified profile can be minimized. Thus, the measured surface profile can provide real-time feedback for controlling the etching process.

[0106] In some aspects of the present invention, a window or a flat mirror can be fabricated in the substrate, as Figure 17 shown. "Two-pass" measurements using a wavefront sensor can be used to measure the flatness of the substrate 103 during processing. The monitoring beam emitter 109 generates a monitoring beam 117. The monitoring beam is collimated by a lens 1701, and the collimated beam is directed to the substrate by a beam splitter 1702. The collimated beam is expanded by an expanding lens 1603. The expanded beam passes through the cover plate 107, the etchant 104, the substrate 103, and the dichroic mirror 1602. A mirror 1703 that is substantially perpendicular to the collimated beam reflects the collimated beam along the same path to the wavefront sensor 118. As long as the surface of the substrate is parallel to the mirror, the collimated beam 117 will follow the same path to the beam splitter 1702, where a portion of the beam will pass through the beam splitter and be incident on the wavefront sensor 118. The expanding lens 1603 relays the wavefront from the substrate 103 to the wavefront sensor 118, where the phase of the wavefront is measured and the surface profile of the substrate 103 can be calculated. The controller 113 uses the profile measurement to adjust the etch assist radiation 115 emitted from the projector 1601 to maintain a flat surface on the substrate 103 such that the substrate surface remains parallel to the surface of the mirror 1703.

[0107] In another embodiment, the etchant and the cover plate are transparent to the etch assist radiation, and the substrate is highly absorptive of the etch assist radiation. The substrate is locally heated, and the thermal energy from the substrate accelerates the etching process. In Figure 18In this case as shown, the projector 1601 generates the etch assist radiation 115, and the etch assist radiation passes through the cover plate 107 and the etchant 104. The etch assist radiation 115 is focused onto the surface of the substrate 103, where the radiation is absorbed and converted into heat. Depending on the radiation pattern emitted by the projector 1601, the etching can be controlled spatially. Opposite the projector, on the other side of the substrate, a monitoring beam detector or profilometer 118 can be used to measure at least one property of the substrate 103. For example, vertical scanning interferometry or scanning laser confocal microscopy can be used to measure the surface profile of the substrate 103 during etching. The substrate 103 is transparent to the monitoring beam 117 of the monitoring beam detector or profilometer 118. Using profilometry, the computer 113 can compare the measured surface profile with an ideal surface shape specified by the user, and the difference between the specified and measured shapes can be used to modify the position and intensity of the etch assist radiation 115 incident on the substrate by controlling the radiation emitted from the projector 1601, thereby correcting the profile error.

[0108] Since other variations and combinations of the embodiments of the invention set forth above and the features previously discussed can be utilized without departing from the invention, the foregoing description of the preferred embodiments should be considered illustrative rather than limiting of the invention as defined by the claims.

[0109] The invention can be a system, method, and / or computer program product. The computer program product can include a computer-readable storage medium (or media) having computer-readable program instructions thereon for causing a processor to perform aspects of the invention.

[0110] A computer-readable storage medium can be a tangible device that can hold and store instructions for use by an instruction execution device. The computer-readable storage medium can be, for example but 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 devices. A non-exhaustive list of more specific examples of the computer-readable storage medium includes the following items: a portable computer disk, 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 disc (“DVD”), a memory stick, a floppy disk, a mechanically encoded device (such as a punched card or a raised structure having instructions recorded thereon in grooves), and any suitable combination of the foregoing items. As used herein, a computer-readable storage medium should not be construed as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., an optical pulse passing through an optical fiber cable), or an electrical signal transmitted through a wire.

[0111] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to a corresponding computing / processing device, or downloaded to an external computer or an external storage device via a network (such as the Internet, a local area network, a wide area network, and / or a wireless network). The network can include a copper transmission cable, an optical transmission fiber, a wireless transmission, a router, a firewall, a switch, a gateway computer, and / or an edge server. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium within the corresponding computing / processing device.

[0112] The computer-readable program instructions for performing the operations of the present invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state-setting data, or source code or object code written in any combination of one or more programming languages, including, for example, object-oriented programming languages such as Smalltalk, C++, and the like, and conventional procedural programming languages such as the "C" programming language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, executed partially on the user's computer, executed partially on the user's computer and partially on a remote computer, or executed 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 connection, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., through the Internet using an Internet service provider). In some embodiments, an electronic circuit system, including, for example, a programmable logic circuit, a field-programmable gate array (FPGA), or a programmable logic array (PLA), may execute the computer-readable program instructions by utilizing the state information of the computer-readable program instructions to personalize the electronic circuit system in order to perform aspects of the present invention.

[0113] 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 should be understood that each block in 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.

[0114] These computer-readable program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to create a means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram via the processor of the computer or other programmable data processing apparatus. These computer-readable program instructions may also be stored in a computer-readable storage medium, which may 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 storing the instructions comprises an article of manufacture including instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0115] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other devices to produce a computer-implemented process, such that the instructions executed on the computer, other programmable apparatus, or other devices implement the functions / acts specified in one or more blocks of the flowchart and / or block diagram.

[0116] The flowcharts 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 diagram may represent a module, segment, or portion of instructions, which may include one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may not occur in 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 should also be noted that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

[0117] In the foregoing description, numerous specific details such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc. are provided to provide a thorough understanding of the embodiments. However, those skilled in the relevant art will recognize that the embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments.

[0118] The description of the elements in each figure may refer to the elements in the previous figures. In all the figures, the same numerals refer to the same elements, including alternative embodiments of the same element. These embodiments may be implemented in other specific forms. The described embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

1. A method for controlling a substrate etching process, the method comprising: Positioning a bottom surface or a top surface of a substrate adjacent to a volume of etching fluid to create an etchant - substrate interface such that the substrate is disposed between the etching fluid and an etching - assisting emitter; Heating the etchant-substrate interface via spatially controlled electromagnetic radiation emitted by the etch assist emitter, wherein the substrate is at least partially transparent to the spatially controlled electromagnetic radiation such that at least a portion of the spatially controlled electromagnetic radiation passes through the substrate and the portion passing through the substrate is at least partially absorbed by the etch fluid, and the etch fluid has an absorption coefficient greater than 1 cm -1 ; Transmitting a monitoring beam through the substrate, the substrate and the volume of etching fluid being at least partially transparent at the wavelength range of the monitoring beam; During the substrate etching process, measuring a property of the substrate surface via the monitoring beam to produce a measured property for the substrate; and During the substrate etching process, adjusting the spatially - controlled electromagnetic radiation in response to the measured property for the substrate to provide electromagnetic radiation in some regions of the etchant - substrate interface that is greater than in other regions of the etchant - substrate interface.

2. The method according to claim 1, wherein The volume of etching fluid includes one or more of a liquid, a gas, and a plasma.

3. The method according to claim 1, wherein, Adjusting the spatially - controlled electromagnetic radiation raises the temperature of a selected portion of the etching fluid relative to other portions of the etching fluid and raises the etching rate of the selected portion of the etching fluid relative to the other portions of the etching fluid.

4. The method according to claim 1, wherein Adjusting the spatially - controlled electromagnetic radiation during the substrate etching process to achieve a desired surface profile for the substrate.

5. The method according to claim 1, wherein Adjusting the spatially - controlled electromagnetic radiation changes the etching rate of a selected portion of the substrate relative to other portions of the substrate.

6. The method according to claim 1, further comprising placing the substrate under a container wall to form an etching container.

7. The method according to claim 1, further comprising placing an energy source for the spatially - controlled electromagnetic radiation close to the substrate.

8. The method according to claim 7, wherein The energy source includes one or more of the following: a laser, a maser, an LED, a radio component, a gyrotron, a backward - wave oscillator, and a thermal radiation emitter.

9. The method according to claim 8, wherein The thermal radiation emitter includes a filament, a thin - film micro - heater, and a micro - hotplate.

10. The method according to claim 7, wherein, The energy source includes an array of etching - assisting emitters.

11. The method according to claim 1, further comprising placing a monitoring beam detector close to the substrate and measuring the measured property of the substrate via the monitoring beam detector.

12. The method according to claim 11, wherein, The monitoring beam detector includes one or more of the following: a charge - coupled device, a CMOS image sensor, a wave - front sensor, a scanning confocal microscopy device, an antenna array, and an interferometric device.

13. The method according to claim 12, wherein, The monitoring beam detector includes an array of sensors.

14. The method according to claim 1, further comprising flushing the etchant from a holding container before measuring the property of the substrate surface.

15. The method according to claim 1, further comprising using spatial light modulation to produce the spatially - controlled electromagnetic radiation incident on the etchant - substrate interface.

16. The method according to claim 1, further comprising using a wave - front sensor to measure the property of the substrate surface during the substrate etching process.

17. A system for controlling a substrate etching process, the system comprising: A substrate receiver configured to receive a substrate and hold the substrate adjacent to a volume of etching fluid to create an etchant-substrate interface; An etch assist emitter configured to heat the etchant-substrate interface via spatially controlled electromagnetic radiation, wherein the substrate is disposed between the etch fluid and the etch assist emitter and is at least partially transparent to the spatially controlled electromagnetic radiation such that at least a portion of the spatially controlled electromagnetic radiation passes through the substrate and the portion passing through the substrate is at least partially absorbed by the etch fluid, and the etch fluid has an absorption coefficient greater than 1 cm -1 ; A monitoring beam emitter configured to transmit a monitoring beam through the substrate, the substrate and the volume of etching fluid being at least partially transparent at the wavelength range of the monitoring beam; A monitoring beam detector configured to measure a property of the substrate surface via the monitoring beam during substrate etching to produce a measured property for the substrate; and wherein the etch assist emitter is further configured to adjust the spatially controlled electromagnetic radiation during substrate etching in response to the measured property of the substrate to provide greater electromagnetic radiation in some regions of the etchant-substrate interface than in other regions of the etchant-substrate interface.

18. The system of claim 17, further comprising a controller configured to receive the property of the substrate surface and control the etch assist emitter to achieve a desired profile for the etchant-substrate interface.

19. The system of claim 17, further comprising an etch vessel configured to hold the volume of etching fluid.

20. The system according to claim 19, wherein The substrate encloses the etch vessel.

21. The system according to claim 17, wherein The monitoring beam emitter includes one or more of: a laser, a maser, an LED, an incandescent lamp, a gas discharge lamp, a fluorescent lamp, a radio element, and a thermal radiation emitter.

22. The system according to claim 21, wherein, The thermal radiation emitter includes a filament, a thin film microheater, and a microhotplate.

23. The system according to claim 17, wherein, The monitoring beam detector includes one or more of: a charge coupled device, a CMOS image sensor, a wavefront sensor, a scanning confocal microscopy device, an antenna array, and an interferometric device.

24. A computer program product for controlling a substrate etching process, the computer program product including a computer-readable storage medium having program instructions embodied therein, wherein the computer-readable storage medium itself is not a transient signal, the program instructions being executable by a digital processing device to cause the digital processing device to implement the method of claim 1.

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