WO2015085014A1 - Système et procédé pour obtenir des lames constituées d'un matériau ayant des caractéristiques de transparence optique connues - Google Patents

Système et procédé pour obtenir des lames constituées d'un matériau ayant des caractéristiques de transparence optique connues Download PDF

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WO2015085014A1
WO2015085014A1 PCT/US2014/068461 US2014068461W WO2015085014A1 WO 2015085014 A1 WO2015085014 A1 WO 2015085014A1 US 2014068461 W US2014068461 W US 2014068461W WO 2015085014 A1 WO2015085014 A1 WO 2015085014A1
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WIPO (PCT)
Prior art keywords
laminae
ingot
sacrificial layers
laser
pulsed laser
Prior art date
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PCT/US2014/068461
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English (en)
Inventor
David Callejo MUÑOZ
Joseph Adam
Harry Laswell
Original Assignee
Muñoz David Callejo
Joseph Adam
Harry Laswell
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from IT000232A external-priority patent/ITAN20130232A1/it
Priority claimed from IT000231A external-priority patent/ITAN20130231A1/it
Priority claimed from US14/558,535 external-priority patent/US20150158117A1/en
Application filed by Muñoz David Callejo, Joseph Adam, Harry Laswell filed Critical Muñoz David Callejo
Publication of WO2015085014A1 publication Critical patent/WO2015085014A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/0823—Devices involving rotation of the workpiece
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/0006—Working by laser beam, e.g. welding, cutting or boring taking account of the properties of the material involved
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/50—Working by transmitting the laser beam through or within the workpiece
    • B23K26/53—Working by transmitting the laser beam through or within the workpiece for modifying or reforming the material inside the workpiece, e.g. for producing break initiation cracks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
    • B23K2103/56—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26 semiconducting

Definitions

  • This patent application relates to the manufacture and processing of materials, according to one embodiment, and more specifically to a system and method for obtaining laminae made of a material having known optical transparency characteristics.
  • integrated circuits i.e., electronic components
  • the wafer is then cut, sometimes called diced, to singulate the integrated circuits from one another.
  • dicing methods do not work well for use in singulating wafers from an ingot or large block of material.
  • singulation is a material separation process that often involves the application of chemical processes and/or mechanical forces to materials, particularly brittle materials, such as strengthened glass.
  • materials that are often processed to create products via singulation include, but are not limited to, amorphous solid materials, crystalline materials, semiconducting materials, a crystalline ceramics, polymers, resins, and so forth. In some cases, materials having a monocrystalline structure are used. Such materials include synthetic corundum.
  • Corundum is a transparent material, with chemical formula AI2O3, which crystallizes in the trigonal system. Corundum has a high density (around 4 g/cm3). In nature, corundum is usually coloured, due to the presence of impurities. Among the different varieties of corundum found in nature are, in particular, ruby (whose red color is due to the presence of chromium) and sapphire (whose dark blue color is due to the presence of iron and titanium). Corundum has some interesting physico-chemical properties: high hardness (second only to that of diamond), high chemical inertia, and excellent transparency.
  • corundum ingots are well known.
  • synthetic corundum can be produced in the laboratory in the form of cylindrical bars by means of melt growth techniques, such as the Czochralski method, the Kyroupolus method, or in various forms, by means of the Stephanov method.
  • Synthetic corundum in the form of laminae singulated from corundum ingots because of its high breaking strength, scratch resistance, and its high chemical inertia, can be used, for example, to make transparent screens, such as screens of transparent lamination layers in which at least one of the lamination layers is composed of corundum.
  • Corundum can therefore be used to make screens for optical sensors (destined to be exposed to aggressive external agents) and transparent protective screens for the monitors of electronic devices, such as laptop computers, smartphones, tablets, and satellite-based navigation devices.
  • corundum laminae are based on using single wire saws or multi-wire saws with diamond impregnated metal wire.
  • this technology requires long machining times, is imprecise, and is quite expensive. As an example, using these traditional techniques, it takes about 18 hours of machining to cut 200 laminae of corundum, with a cross-section of about 150 mm and a thickness of 1 mm.
  • corundum laminae begin gradually to have an increasingly more flexible behavior with a minimum radius of curvature inversely proportional to the thickness of the lamina.
  • corundum laminae start to have sufficient flexibility to enable them to be used to make monitors with a curved geometry. Consequently, it is not possible to make monitors with corundum screens, with curved geometries, by adopting the technology of cutting by means of diamond impregnated wire.
  • Another drawback of the technology of cutting by means of diamond impregnated wire is the fact that the laminae obtained can only be laminae with flat large surfaces parallel to each other. Cutting by use of diamond impregnated wire cannot produce cuts in a curved or three-dimensional form.
  • Yet another drawback of the technology of cutting by means of diamond impregnated wire is the fact that the mechanical process of cutting causes structural damage beneath the surface of the material (so-called "subsurface damage") of a depth proportional to the particle size of the diamond dust present on the cutting wire. This thickness, indicatively 30 ⁇ on each side of the cut sheet, must be removed before polishing the sheet.
  • the machining required to reduce surface roughness, in addition to requiring time is very delicate in that it can cause irreparable damage to the corundum sheet.
  • the protective monitor screens if made using corundum sheet-like elements, would be heavier than the monitors made using Gorilla® glass and therefore of little interest to the consumer electronics market, particularly in the case of monitors for portable devices, such as laptops and smartphones.
  • lasers can be used to facilitate the singulation process.
  • Conventional pulsed-laser machining uses the energy of the laser to ablate the material, cutting a block of the material from the outside into the interior of the block.
  • this conventional laser cutting technique creates ragged cuts that make it difficult to effect the separation of a sufficiently thin lamina from a block of material.
  • Femtosecond lasers offer several unique advantages over lasers of longer pulse duration.
  • the ultrashort pulse duration of femtosecond lasers makes it possible to produce extremely high target intensities with relatively low pulse energy.
  • the high target intensities in conjunction with ultrashort pulse duration, enable precise micron-level materials processing with minimal and/or manageable heat transfer to the target substrate per pulse. It is possible to take unique advantage of this latter property by controlling the rate of laser impact upon the target substrate.
  • a laser processing system is required, which integrates and coordinates the laser operations, beam manipulation, target positioning, and processing environment.
  • the laser processing system must also provide real-time process monitoring. This integration is very crucial to achieve the best possible processing results for a given application that uses the laser processing system.
  • an example system and method uses a laser with an energy density that is below that which will cause ablation of the material to instead modify the structure of the material.
  • an example embodiment uses a laser with an ultrashort pulse duration to modify the structure of a single-crystal material, transforming a portion of the material into a multi-crystalline or amorphous state, or a mixture of multi-crystalline and amorphous material. This modification of the structure of the material increases its chemical reactivity and decreases its mechanical strength relative to the surrounding single crystal material.
  • single-crystal corundum is almost entirely non-reactive to NaOH or KOH; but, amorphous and poly crystalline AI2O3 are highly reactive with these bases. The difference in reactivity is several orders of magnitude. Similarly, single-crystal corundum has very high mechanical strength compared to amorphous and poly crystalline AI2O3.
  • an example method employs a two- step process.
  • a laser with an ultrashort pulse duration e.g., a femtosecond or femtolaser or ultrafast laser
  • a laser with an ultrashort pulse duration e.g., a femtosecond or femtolaser or ultrafast laser
  • the second step one of several mechanisms as described herein is used to separate the material along this boundary layer.
  • these separation mechanisms include: chemical separation, thermal separation, thermo-mechanical separation, mechanical separation, water-jet separation, and secondary laser separation. The creation of the boundary layer and the various separation mechanisms are described in more detail below.
  • Figure 1 is a schematic view of a corundum ingot
  • Figure 2 is a schematic view of a corundum lamina obtained from the ingot as illustrated in Figure 1;
  • Figure 3 is a schematic view of a sacrificial layer made in the ingot as illustrated in Figure 1;
  • Figure 4 is a schematic view of a laser device for creating sacrificial layers in the ingot as illustrated in Figure 1 ;
  • Figure 5 is a schematic view of a focal point obtained with a pulsed laser
  • Figures 6 through 10 illustrate various examples of lenses for creation by an example embodiment
  • Figures 1 1 through 16 illustrate various example three-dimensional (3D) objects for creation by an example embodiment
  • Figures 17 through 19 illustrate other examples of lenses for creation by an example embodiment
  • Figure 20 is a processing flow chart illustrating an example embodiment of a method as described herein.
  • a system and method for obtaining laminae made of a material having known optical transparency characteristics.
  • the disclosure herein includes a description of a system and process for obtaining laminae, made of a material having monocrystalline structure, from an ingot made of a material having a monocrystalline structure.
  • the term “lamina” means an element having two large surfaces and a thickness of between 10 ⁇ and 1500 ⁇ .
  • the term “lamina” includes elements with two large surfaces that can be flat and substantially and/or generally parallel to each other.
  • the term “lamina made of crystalline material” includes crystalline materials having, on their two large surfaces which are flat and parallel to each other, the same crystallographic orientation.
  • the term “lamina” also includes elements in which at least one of the two large surfaces is generally curved and elements in which both of the large surfaces are generally curved, even with different radii of curvature.
  • the term “material having monocrystalline structure” includes synthetic corundum.
  • the term "material having monocrystalline structure” also includes a material from the group consisting of: corundum, sapphire, diamond, ruby, quartz, silicon, silicon carbide, carborundum, fluorite, copper, germanium, gallium nitride, gallium arsenide, indium phosphide, padparadscha, tungsten, molybdenum oxide, and pure, doped and codoped (Nd, Er, Er-Yb, Cr, Nd-Cr ...) yttrium aluminum garnet (YAG).
  • the term “ingot” includes bodies having an axis of symmetry and a cross- section that, at least in one section, is substantially and/or generally constant.
  • FIG. 1 An example embodiment of a system and method for obtaining laminae from a material having known optical transparency characteristics is described with reference to the accompanying drawings.
  • an example embodiment of the disclosed method can be used for obtaining a plurality of laminae 3, 3, ...3 made of a material having a monocrystalline structure, such as corundum.
  • the plurality of laminae 3, 3, ...3 is obtained from an ingot 2 made of monocrystalline material having an axis of symmetry X, a lateral surface 20, which develops around the axis of symmetry X of the ingot 2, a first distal end 21, and a second distal end 22 (crossed by the axis of symmetry X).
  • the ingot 2 has a substantially and/or generally straight axis of symmetry X and a cross-section that, at least in one section, is substantially and/or generally constant.
  • the ingot 2 is a bar of monocrystalline corundum, for example a bar of corundum with a circular or rectangular cross-section obtained by means of the Czochralski process, or any other known process for producing synthetic corundum.
  • At least one distal end 22 of the ingot 2 can have a surface 23 that is substantially flat and/or generally orthogonal to the axis of symmetry X of the ingot 2.
  • the flat surface 23 can be obtained, for example, by cutting, with a diamond impregnated wire, a distal end of a corundum bar 2 obtained using the Czochralski method or other known method for producing synthetic corundum.
  • the example embodiment disclosed herein provides a step of creating a plurality of sacrificial layers 4, 4, ...A that develop in a manner substantially and/or generally orthogonally to the axis of symmetry X of the ingot 2.
  • the sacrificial layers 4, 4, ...4 have a modified thermal expansion coefficient and a modified chemical reactivity compared to that of the original monocrystalline material.
  • the sacrificial layers 4, 4, ...4 can be distributed along the axis of symmetry (X) of the ingot 2 so as to define a plurality of intermediate layers 3, 3, ...3, with an unchanged thermal coefficient or chemical reactivity, interspersed with the sacrificial layers 4, 4, ...4.
  • the distance between the successive sacrificial layers 4 determines the thickness of the intermediate layers 3 and, therefore, the thickness of the laminae that is desired.
  • the form of each intermediate layer 3 is conjugated to the forms of each pair of sacrificial layers 4 between which the intermediate layer 3 is located. [0035] In the example embodiment illustrated in Fig.
  • each sacrificial layer 4 is delimited by two flat surfaces 41, 42 that are parallel to each other and orthogonal to the axis X of the ingot 2, and by a portion 201 of the lateral surface 20 of the ingot 2, located between the intersections of the two flat surfaces 41, 42 with the lateral surface 20.
  • a separation method uses a thermal or heating process to separate the sacrificial layers 4, 4, ...4 and laminae 3, 3, ...3 formed by the intermediate layers interposed between the sacrificial layers.
  • the thermal process causes the breakage, sequential or contemporaneous, of the sacrificial layers 4, 4, ...4 and the consequent creation, sequential or contemporaneous, of a plurality of laminae 3, 3, ...3 made of monocrystalline material.
  • the plurality of sacrificial layers 4, 4, ...4, with a modified thermal expansion coefficient compared to the thermal expansion coefficient of the original monocrystalline structure is obtained by irradiating the ingot 2 with a pulsed laser beam 61 (also known as "femtosecond laser” or “ultrafast laser") as shown in Fig. 4.
  • the pulsed laser creates a modification of the crystalline structure which, in turn, causes a variation of the thermal expansion coefficient inside the sacrificial layer 4.
  • the crystalline material is irradiated with a pulsed laser beam 61 (so-called “femtosecond laser” or “ultrafast laser”).
  • a laser generator 6 which comprises a laser source 62, a system for transporting the laser beam 63, a focuser 64, and a system for moving the laser beam 65.
  • the pulsed laser beam 61 has an optical axis Y on which there is a focal point P.
  • the pulsed laser beam 61 has a sufficiently high pulse power/average power ratio to minimize the induced thermal load on the material of the ingot 2 and thus limit the transmission of heat.
  • the crystalline material suffers structural damage and, consequently, a variation in the thermal expansion coefficient and chemical reactivity in the crystalline material.
  • the high energy density in a time on the order of femtoseconds, generates a multi-photon absorption process, able to ionize the material inside the focus area, generating micro voids on the crystal structure.
  • Those micro voids generate an expansion wave that creates a pressure above the Young's modulus of the material, breaking the atomic bonds and generating an amorphous or poly crystalline material, without generating micro-fractures, thus modifying the thermal expansion coefficient and chemical reactivity of the crystalline material.
  • Young's modulus also known as the tensile modulus or elastic modulus, is a measure of the stiffness of an elastic material and is a quantity used to characterize materials.
  • the system for moving the laser beam 61 may comprise an optical movement system, with a variable- focus lens 66 and one and/or more movable mirrors 65, to alter the depth of the focal point P in the ingot 2.
  • a system of alternating linear rotation or movement of the ingot 2 (not shown) may be provided.
  • the laser beam 61 may have an elliptical cross-section, with a small axis 611 (parallel to the axis of symmetry X of the ingot 2) and a large axis 612 (orthogonal to the axis of symmetry X of the ingot 2) as shown in Fig. 5.
  • the size of the small axis 61 1 is as small as possible, so as to minimize the thickness of the sacrificial layer 4, whereas the maximum size of the large axis 612 is such as always to maintain a density of light output such as to damage the crystalline structure of the material of the ingot 2.
  • the small axis 61 1 measures about 2 ⁇ while the large axis 612 measures about 30 ⁇ .
  • the thickness of the sacrificial layer 4 is as small as possible. In practice, the average thickness of the sacrificial layer 4 can be between 2 ⁇ and 10 ⁇ . In other embodiments, the thickness of the sacrificial layer 4 can be between 2 ⁇ and 40 ⁇ .
  • the interaction between the laser beam and the material of the ingot 2 is influenced by the absorption coefficient of the material which, in turn, depends on the wave length of the incident radiation.
  • the pulsed laser beam 61 used to create the sacrificial layer 4 has a wavelength ⁇ inside or within the transparency range of the material.
  • the pulsed laser beam 61 has a wavelength ⁇ of about 258 nm, 343 nm, 515 nm, 780 nm, 800 nm, or 1,030 nm.
  • the repetition frequency f of the pulsed laser beam 61 is at least 10 kHz and, preferably, is higher than 1 MHz.
  • the duration ⁇ of the pulses of the laser beam 61 can be between lxlO 15 seconds and lxlO 14 seconds and, preferably, between lxlO "15 and lxlO "10 seconds.
  • the peak energy density of the pulsed laser beam is at least 0.5 ⁇ ⁇ pulse. Every material can be characterized for an energy band gap; so, the ionization process and consequently the corresponding laser parameters can be tuned for each material.
  • Energy per pulse, pulse duration, power spatial density, laser wavelength and pulse spatial overlapping can be defined for every single material in the range of the multiphoton absorption.
  • This set of parameters, energy per pulse, pulse duration, peak power spatial density, laser wavelength, and pulse spatial overlapping can determine when the material will suffer a phase transformation from crystalline to amorphous or poly crystalline, and when the material will suffer undesirable micro or macro fractures.
  • the second region, existing between the first parameter level threshold and the third parameter level threshold corresponds to second region parameter settings that cause a desirable phase transformation in the material without causing micro or macro fractures in the material.
  • the spatial energy density per pulse can be determined for every different material to transfer to the material enough energy to ionize the material's structure, but not enough to fracture it.
  • the spatial energy density per pulse for each different material depends on the energy band gap for each different material.
  • the desired laser wavelength for each material can be chosen to be inside or within the highest optical transparency region of each different material.
  • the femtosecond laser material ionization techniques described herein can be used on any material, given the optical transparency characteristics of the material and the second region parameter settings described above.
  • multi-crystalline or polysilicon materials can also be used.
  • the multi-crystalline or polysilicon materials can be irradiated with a femtosecond laser as described above to create the sacrificial layers 4.
  • the use of the femtosecond laser provides several benefits over the conventional methods of applying a photoresist layer and etchant to the material.
  • the etchant will break out of the area defined by the photoresist layer and follow the multi-crystalline boundaries beneath the etch leaving "ragged" walls in the trenches rather than straight, flat walls.
  • the use of the femtosecond laser as described herein provides a solution to this problem.
  • the embodiments described herein use the femtosecond laser to convert the polysilicon to amorphous silicon in the areas being removed. Then, as described in more detail below, a chemical etch, or other separation techniques described herein, can be used to remove the amorphous silicon selectively without damaging the remaining polysilicon.
  • Femtosecond lasers represent a source of electric field pulses, which can have field intensities approaching and even exceeding the atomic binding field. Working with a high energy confined in a very short period of time, very strong non-linear effects are generated. For an electric field of this order, the polarization response of the medium changes from linear to non-linear.
  • the laser pulse is either non- linearly absorbed or, at lower field intensities, modifies the medium as it propagates, modulating its own spectrum.
  • This selectivity is the main difference between the femtosecond laser interaction and the longer pulse laser interaction. This fact makes femtosecond laser systems able to manufacture intra-bulk transparent materials (e.g., structures deep inside the base material) with the highest spatial resolution and the minimum of collateral thermal damage.
  • Pulsed laser technology has evolved over the past four decades to the point that exawatt (10 18 ) powers are now achievable with commercially available tabletop lasers. Tightly confining the beam to micrometer areas leads to intensities far beyond 10 17 W/m 2 .
  • the current laser technology is pushing the upper limit of the generated intensities, allowing new non-linear optical mechanisms to be measured and manufactured.
  • the availability of high power laser sources pushed far beyond the limit of perturbative nonlinear optics, beyond non-linearly ionizing electrons to relativistic non-linear optics.
  • the electric field is capable of not only ionizing the material, but also accelerating the ionized electron to relativistic speeds all within a single pulse time duration.
  • the laser pulses should be focused on areas on the order of 10 ⁇ 2 .
  • short pulse laser systems are characterized in that the irradiation duration is shorter than the material energy propagation time. So, there are no thermal propagation effects inside the material, limiting the collateral damage around the working area, and allowing the working area to be limited to the focus volume. In this way, the spatial resolution increases dramatically, and the quality of the finished piece improves in parallel.
  • One more advantage of the short pulse laser is that the beam can be focused inside the bulk material, deep into the bulk material (e.g., several millimeters or more deep), with very low optical losses.
  • Using a laser beam focused within the material transparency region means that the machining process can be done inside the volume of the material from outside, without interaction or damage the rest of the material where the beam is passing.
  • the only laser/material interaction happens inside the focus volume, where the energy is high enough to generate non-linear absorption into the material.
  • Longer pulse lasers will interact linearly with the material; so, the energy will be linearly absorbed by the material on the laser path through the material.
  • no intra-bulk manufacturing can be performed with normal long pulse lasers, as for example, lasers in the pico-second range.
  • Femtosecond lasers have been used for micro machining and optical manufacturing on several materials, such as glass, crystals, etc. But, these prior uses of femtosecond lasers have always been for small pieces, on micro areas of the pieces, and close to the surface of the material. Femtosecond lasers have been used on structures no bigger than a few microns. These prior uses of femtosecond lasers have gone no deeper than a few tens of microns from the irradiation surface. Small piping, waveguides, and the like are the typical structures generated by the traditional use of femtosecond lasers in the micro-fluidics and micro-optics fields.
  • femtosecond lasers Some industrial applications of femtosecond lasers are focused on drilling, mostly metallic parts for the automotive industry; but, even in this industrial case, the holes drilled by femtosecond lasers have diameters of around 200 microns with about 200 microns in depth, thus remaining within the micro world.
  • the technology described herein aims to work the bulk material from the inside to the outside, interacting several millimeters or more deep into the material, using the material transparency and the non-linear interaction of the femtosecond laser as described herein.
  • the application of a set of optimized laser wavelength, pulse duration, and delivered spatial energy density parameters to achieve a successful phase transformation is highly dependent on consistent control of delivered energy within an integrated optical path and sample movement system.
  • the system as described herein, can be configured to move the laser beam through the use of galvo scanners, multi-axis linear drive systems for the optical delivery structure, or combinations of these systems with multi-axis motion systems to move the materials being irradiated.
  • the system control processes must coordinate precise and consistent focal size, pulse-to-pulse overlap, and energy delivery to achieve consistent phase transformation in the desired pattern.
  • a Gaussian beam is a light beam where the beam intensity follows a Gaussian distribution, centered and symmetrically distributed. This kind of beam is useful for maintaining the machining symmetry, as well as to understand the laser/material interaction.
  • this kind of beam with a typical dimension of 5 to 10 microns in diameter, allows generation of small pieces with a high spatial resolution, shaped corners, and straight lines. These small pieces can be machined very precisely, depending only on the beam diameter. So, for many 3D applications, the use of Gaussian beams can be beneficial.
  • a defocused beam with an elliptical shape can be used for this purpose.
  • a defocused beam with an elliptical shape can be generated using a long focal distance lens.
  • Long focal distance f-theta lenses typical for use in laser marking scanners, can achieve a good focal distance, thereby introducing a very long optical field with a linear distance where the beam can be considered almost focused.
  • Bessel beams have a cylindrical shape, which have a limited kerf perpendicular to the cutting direction, but allow a deep cut parallel to the cut direction. So, low kerf and fast scanning speeds can be generated by using this type of beam shape.
  • a spatial light modulator SLM
  • SLM spatial light modulator
  • the beam front acts like a cylinder from the point of view of the laser/material interaction.
  • Using a Bessel beam with a 10 micron diameter and a 20 micron height can speed up the scanning process by a factor of 10 in comparison with traditional Gaussian beams for some applications.
  • the sacrificial layers 4, 4, ...4 can be removed by means of chemical etching.
  • Chemical etching may be done in a particular example embodiment using hydrofluoric acid (HF), at a concentration by volume higher than 50%, at boiling temperature (about 150°C), or a mixture of 50% by volume of sulphuric acid (H2SO4) and phosphoric acid (H3PO4), at boiling temperature (200°C or above).
  • HF hydrofluoric acid
  • H2SO4 sulphuric acid
  • H3PO4 phosphoric acid
  • the ingot is arranged on a grid, for example, a grid made of polytetrafluoroethylene (PTFE), that holds the laminae 3, 3, ...3 after dissolving the sacrificial layers 4, 4, ...4.
  • PTFE polytetrafluoroethylene
  • corundum laminae 3 with a minimum thickness of 5 ⁇ can be produced or thicknesses up to 5mm.
  • chemical separation relies on the increased chemical reactivity of the modified material compared to the unmodified material.
  • Chemical separation takes advantage of the difference in chemical reactivity between the unmodified and modified material as produced by exposure of the material to the femtosecond laser as described above.
  • a block of processed material can be immersed into a tank of a chemical agent or mixtures of multiple chemical agents to chemically remove the modified material. This results in the block being converted into a number of laminae of the material, where the quantity is dependent on the size of the block, the thickness of the modified layers, and the thickness of the unmodified layers.
  • a disk of material can be converted into a simple convex lens by separating the disk of material into three separate pieces, the lens and two pieces of scrap material.
  • a block of material can be converted into a three- dimensional shape by separating the block of material into multiple separate pieces, the desired three-dimensional shape and multiple pieces of scrap material.
  • the breakage of the sacrificial layers 4, 4, ...4 occurs by creating a spatial temperature gradient along the axis of symmetry of the ingot 2.
  • a distal end 22 of the ingot 2 is heated so as to generate a temperature gradient along the axis X which passes through the sacrificial layers 4, 4, ...4 in succession causing the breakage, in succession, of the sacrificial layers and thus the creation of the laminae 3, 3, ...3.
  • the stresses inside the sacrificial layer 4 reach sufficiently high values to exceed the breaking stresses, causing the fracture of the sacrificial layer 4.
  • the spatial thermal gradient can have a value of at least 100°C/mm.
  • the distal end 22 of the ingot 2 is heated to a temperature in the range between 600°C and 1,300°C, for example by means of an electric heating element or by a CO2 laser. Heating can occur, for example, by irradiation using an electrically -heated metal plate, or by exposure to an infrared laser, such as a CO2 laser.
  • the sacrificial layer 4 closest to the distal end 22 is stressed in compression by the intermediate layer 3, which is at a higher temperature, and is stressed in traction by the intermediate layer 3, which is at a lower temperature. This causes a breakage of the ingot 2, due to thermal load, at the sacrificial layer.
  • the laminae made of monocrystalline material 3, 3, ...3 are detached sequentially from the distal end 22.
  • the breakage of the sacrificial layers occurs by creating a uniform temporal temperature gradient inside the ingot 2, until a contemporaneous breaking of the sacrificial layers 4, 4, ...4 occurs.
  • the ingot 2 is heated to a temperature in the range between 600°C and 1,300°C and the temporal thermal gradient must be at least l°C/minute.
  • the thermal gradient, spatial or temporal passes through the sacrificial layer 4, (in which the thermal expansion coefficient has been modified), and the areas adjacent to the sacrificial layer 4 (in which the thermal expansion coefficient has remained unchanged).
  • corundum laminae 3 By means of the various embodiments of the methods described herein, it is possible to obtain corundum laminae 3 with a minimum thickness of 10 ⁇ . It is therefore possible to obtain corundum laminae of a thickness suitable to make transparent screens with a flat or curved geometry that are scratch resistant and have a higher breaking strength than that of state-of-the-art screens (such as Gorilla® glass).
  • the lamina 3 thus obtained has no subsurface damage and has lower roughness which is a function of the small diameter 61 1 of the laser beam, in practice the surface roughness is less than 10 ⁇ .
  • the thermal separation techniques described above take advantage of the difference in the coefficient of thermal expansion between the unmodified material and the modified material to exert physical force through expansion to separate the material.
  • a temperature gradient is created along the axis of symmetry of the ingot 2.
  • This temperature gradient can be a temporal temperature gradient created over time (e.g., temp cycling the material), a spatial temperature gradient created over space (e.g., one end of a block cold and one end hot), or a thermal impulse applied with another laser step to one end of the ingot 2 to "pop off a layer, for example.
  • a variety of other techniques can be used to create a temperature gradient to cause separation of the material between the unmodified material and the modified material.
  • thermo-mechanical process can be used to cause separation of the material between the unmodified material and the modified material.
  • a thermo-mechanical process can be used to process one lamina at a time.
  • the laser is used, as described above, to modify a portion of the material block thereby creating a boundary layer defining one lamina.
  • a hot vacuum chuck can be attached to a surface of the unmodified material of the material block, thereby causing the surface to heat up to a pre-defined temperature.
  • a mechanical force can be exerted using the vacuum chuck to pop off the lamina.
  • the vacuum chuck can then transport the separated lamina to a delivery area while the material block is indexed and the laser process is repeated.
  • the next boundary layer is created in the material block using the laser followed by a second hot vacuum chuck operation. This process can be repeated until the material block is fully processed and a plurality of laminae are produced therefrom.
  • the material block can be processed by the laser in a single step.
  • a plurality of boundary layers can be created in the material block to define a corresponding plurality of laminae.
  • the processed material block can be processed with the hot vacuum chuck in a second process step.
  • the hot vacuum chuck can be attached to a portion of the material block, thereby causing the portion to heat up to a pre-defined temperature.
  • a mechanical force can be exerted using the vacuum chuck to pop off each of the plurality of laminae one at a time.
  • This variation of the thermo- mechanical process would decouple the laser processing time from the separation processing time as the timing associated with the process steps may be substantially different.
  • thermo-mechanical process as described herein is not limited to just creating laminae from a material block.
  • the thermo-mechanical process can be used, for example, to create a lens from a disk of material or other arbitrary shapes from an initial piece of material.
  • the thermo-mechanical process can be used if there is a surface to which a vacuum chuck can be attached to enable the material to be held tightly enough.
  • a purely mechanical process can be used to cause separation of the material between the unmodified material and the modified material.
  • the process is similar to the thermo-mechanical process described above, except the vacuum chuck is used with no heat. If enough damage or modification of the material at the boundary layer is caused by the laser, the vacuum chuck can be used to remove the lamina from the block without the application of heat. For example, if the material in the modified layer is converted to a fully amorphous powder, a purely mechanical process can be used.
  • a water-jet separation process can be used to cause separation of the material between the unmodified material and the modified material.
  • the process takes advantage of the fact that the modified material is not as strong as the unmodified material.
  • a femtosecond laser can be used to create the modified material in a block of material at the boundary layers.
  • the block of material with the modified material can then be transferred to a water jet machine.
  • the water jet machine can be controlled or programmed to follow the path defined by the boundary layers either programmatically or by using machine vision to recognize the visual difference between the modified material at the boundary layers and the unmodified material of the remainder of the material block. Because the modified material is softer than the unmodified material as a result of the action of the femtosecond laser, the water jet can remove the modified material thereby separating the lamina from the material block without damaging the lamina.
  • the water jet can use pure water or water with one or more additives.
  • water with an abrasive additive can be used to separate the lamina from the material block.
  • the abrasive additive can be hard enough to remove the modified material, but not hard enough to damage the surface of the unmodified material.
  • water with a chemical additive can be used with the water jet. Chemical additives, such as NaOH or KOH, combine the physical water jet action with chemical action.
  • the various separation processes described herein can be used, for example, to create a lens from a disk of material or other arbitrary shapes from an initial piece of material.
  • a secondary laser irradiation step can be used to separate a desired structure from a bulk block of material after the material has been irradiated with the femtosecond laser in a primary laser irradiation step as described above.
  • the primary laser irradiation step the transparency of the material in the specific areas irradiated has been reduced.
  • the same areas of the material irradiated and modified in the primary laser irradiation step are irradiated again with a secondary laser.
  • the second pass with the secondary laser can be at a much lower power than the first pass with the femtosecond laser.
  • the secondary laser can be a femtosecond laser or another type of laser. Because the modified material is no longer transparent, by virtue of the primary laser irradiation step, the energy of the second laser irradiation at the specific areas of the material is all absorbed, providing localized heating of the modified material. This localized heating causes the modified material to expand and separates the unmodified material along this modified layer corresponding to the irradiated specific areas of the material. If the power level of the second laser is optimized appropriately, the material can be separated without introducing any undesired thermal effect (e.g., cracking) in the unmodified material.
  • Cutting blades such as scalpels or razor blades made from single-crystal
  • the various embodiments described herein can achieve near-net shape machining of three-dimensional (3D) shapes using a combination of three axis or five axis movement of the material block, independent movement of the laser beam delivery mechanism, and adjustment of the laser focal distance to control the location where the laser is focused inside of a block of material to submicron accuracy.
  • the various embodiments described herein enable placement of the focal point anywhere inside the block of material. By placement of the laser focal point at any desired position on or within the block of material and with controlled movement of the material block and/or the laser beam delivery mechanism, a boundary can be traced in three-dimensions to define a desired 3D shape within the block of material.
  • the laser modifies the material at the boundary relative to the surrounding unmodified material.
  • the laser can be used to create regions of modified material within the block of material such that the desired two-dimensional (2D) or 3D shape is outlined by the boundary.
  • the material is then separated along the modified region or boundary to expose the desired shape from the original block of material.
  • the surface finish of the separated material is very good with less than 10 ⁇ of variation and no sub-surface damage; so, the amount of polishing needed is substantially reduced.
  • an initial block of material can be configured as a circular disk of sapphire.
  • the laser beam delivery mechanism and the position of the circular disk of sapphire can be controlled to cause the laser to trace a curved boundary layer through the circular disk of sapphire.
  • the modified disk can be separated into two pieces along the modified boundary layer.
  • the result is a simple plano-concave lens as shown in Fig. 17.
  • the other piece of the modified disk would be a simple plano-convex lens.
  • Each lens can be polished after the separation to render a useful lens and an example of a 3D shape produced by the example embodiment disclosed herein.
  • More complex lenses can be created by tracing two modified curved boundary layers within the circular disk of sapphire using the laser. This allows production of double-concave, convex, convexo-concave, or other lenses.
  • Various example lenses produced by the example embodiments disclosed herein are illustrated in Fig. 18.
  • the resulting 3D shapes can be simple spherical lenses, aspherical lenses, or complex lenses, such as an eyeglass lens that includes correction for astigmatism and/or provides a progressive bifocal function.
  • Lens elements produced using the techniques and systems described herein can be combined to make more complex lenses as shown in Fig. 19.
  • example embodiments can produce much more complex shapes than can be cost-effectively produced with conventional machining.
  • an embodiment can convert a cylinder of single-crystal sapphire into a sapphire champagne flute or coupe thereby creating an entirely new type of luxury good.
  • the techniques disclosed herein can be used to trace boundary layers within the cylinder of single-crystal sapphire using the laser and then separate the sapphire champagne flute or coupe from the remaining material using the separation methods described above.
  • example embodiments can produce even more complex shapes.
  • Fig. 16 illustrates an example of a complete watchcase that can be produced from single-crystal sapphire.
  • the techniques disclosed herein can be used to trace complex boundary layers within a block of single-crystal sapphire using the laser and then separate the complex 3D shape from the remaining material using the separation methods described above.
  • the femtosecond laser can be used to modify all of the material that needs to be removed, rather than just a boundary layer.
  • the modified material produced by the femtosecond laser has different properties than the unmodified material.
  • the modified material is less transparent, or perhaps even opaque at some wavelength(s).
  • a secondary laser can be used to ablate the modified material at an energy level to which the unmodified material is transparent.
  • the secondary laser can be a femtosecond laser or a lower power picosecond or nanosecond laser.
  • the modified material can be removed using the secondary laser and the unmodified material remains intact.
  • a processing flow diagram illustrates an example embodiment of a method as described herein.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Laser Beam Processing (AREA)

Abstract

L'invention porte sur un procédé pour obtenir une pluralité de lames, constituées d'un matériau ayant des caractéristiques de transparence optique connues, à partir d'un lingot constitué du matériau, le lingot ayant un axe de symétrie (X), le procédé comprenant : la création, dans le lingot par utilisation d'un faisceau laser à impulsions, d'une pluralité de couches sacrificielles avec une structure modifiée, la pluralité de couches sacrificielles étant distribuée le long de l'axe de symétrie (X), la pluralité de couches sacrificielles divisant le lingot en une pluralité de couches résiduelles ; la soumission de la pluralité de couches sacrificielles à une gravure chimique, provoquant ainsi une séparation des couches résiduelles ; et le détachement des couches résiduelles pour produire la pluralité de lames constituées du matériau.
PCT/US2014/068461 2013-12-05 2014-12-03 Système et procédé pour obtenir des lames constituées d'un matériau ayant des caractéristiques de transparence optique connues WO2015085014A1 (fr)

Applications Claiming Priority (10)

Application Number Priority Date Filing Date Title
ITAN2013A000231 2013-12-05
ITAN2013A000232 2013-12-05
IT000232A ITAN20130232A1 (it) 2013-12-05 2013-12-05 Metodo per ottenere una pluralita' di lamine da un lingotto di materiale con struttura monocristallina
IT000231A ITAN20130231A1 (it) 2013-12-05 2013-12-05 Procedimento per ottenere una pluralita' di lamine da un lingotto di materiale con struttura monocristallina
US14/481,691 US20150158255A1 (en) 2013-12-05 2014-09-09 Method for obtaining laminas made of a material having monocrystalline structure
US14/481,667 2014-09-09
US14/481,667 US20150159279A1 (en) 2013-12-05 2014-09-09 Process for obtaining a plurality of laminas made of a material having monocrystalline structure from an ingot
US14/481,691 2014-09-09
US14/558,535 US20150158117A1 (en) 2013-12-05 2014-12-02 System and method for obtaining laminae made of a material having known optical transparency characteristics
US14/558,535 2014-12-02

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110773871A (zh) * 2019-11-08 2020-02-11 合肥工业大学 一种在空速管的非平表面上制备防结冰表面的制备方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09141645A (ja) * 1995-11-21 1997-06-03 Daido Hoxan Inc ウエハの製法およびそれに用いる装置
JPH09272119A (ja) * 1996-04-04 1997-10-21 Daido Hoxan Inc ウエハの製法およびそれに用いる装置
US20060027531A1 (en) * 2001-07-05 2006-02-09 Nobuo Kawase Base material cutting method, base material cutting apparatus, ingot cutting method, ingot cutting apparatus and wafer producing method
US20100136766A1 (en) * 2007-05-25 2010-06-03 Hamamatsu Photonics K.K. Working method for cutting
JP2011082546A (ja) * 2004-06-11 2011-04-21 Showa Denko Kk 化合物半導体素子ウェハーの製造方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09141645A (ja) * 1995-11-21 1997-06-03 Daido Hoxan Inc ウエハの製法およびそれに用いる装置
JPH09272119A (ja) * 1996-04-04 1997-10-21 Daido Hoxan Inc ウエハの製法およびそれに用いる装置
US20060027531A1 (en) * 2001-07-05 2006-02-09 Nobuo Kawase Base material cutting method, base material cutting apparatus, ingot cutting method, ingot cutting apparatus and wafer producing method
JP2011082546A (ja) * 2004-06-11 2011-04-21 Showa Denko Kk 化合物半導体素子ウェハーの製造方法
US20100136766A1 (en) * 2007-05-25 2010-06-03 Hamamatsu Photonics K.K. Working method for cutting

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110773871A (zh) * 2019-11-08 2020-02-11 合肥工业大学 一种在空速管的非平表面上制备防结冰表面的制备方法
CN110773871B (zh) * 2019-11-08 2021-10-12 合肥工业大学 一种在空速管的非平表面上制备防结冰表面的制备方法

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