HU227254B1 - Method of indirect working transparent materials by pulsed laser - Google Patents

Abstract

The present invention relates to a novel indirect pulsed laser machining process of a transparent material. The process according to the invention comprises the steps of bringing a transparent material (12), at least in a region (19) thereof to be machined, into coupling with an absorbing layer (18), said coupling ensuring intense heat exchange; directing a laser pulse of a laser light (20) emitted by a laser source (10) through the transparent material (12) into the absorbing layer (18); having the energy of the laser pulse absorbed within a portion of the absorbing layer (18) located in the vicinity of the transparent material's region (19) to be machined, and thereby heating up said absorbing portion of the absorbing layer (18) to boiling and removing mechanically material from the region (19) to be machined through a retroaction exerted on said region (19) by the boiling-away material of the absorbing layer (18), comprising (i) applying as the transparent material (12) such a material that is essentially fully transmissive at the wavelength of the laser light (20), (ii) making the absorbing layer (18) of such a material that is essentially fully absorbing at the wavelength of the laser light (20), (iii) setting the energy of the laser pulse so as to correspond to at least the transparent material's (12) threshold fluence value for etching, and (iv) forming the absorbing layer (18) with such a thickness that ensures boiling away of the absorbing layer (18) in its full thickness at the transparent material's region (19) to be machined as a consequence of absorbing the energy of the laser pulse by it.

Description

The present invention relates to a process for indirect laser machining of a transparent material and a workpiece made of such material, in particular to its indirect subtle laser processing.

For example, for machining various transparent materials in the nano and micrometer range (surface etching, drilling, punching), that is to say, fine machining, there are today several machining methods available. One of these machining modes is laser machining. In laser machining, the workpiece of the transparent material (s) is subjected to a laser beam emitted by a laser source. The laser source may be continuous or pulsed, and the exposure itself may be direct or indirect. In direct laser machining, the laser beam is directed directly to the workpiece surface to be machined, whereby the laser beam itself directly removes a designated portion of the workpiece surface without any auxiliary material. In indirect laser machining, the laser beam is not focused directly on the workpiece surface to be machined - the laser beam machining effect is achieved by the use of an auxiliary material. Hereinafter, the term "transparent material / workpiece" means a material / workpiece that is not or only marginally (preferably not more than 10% per cm, and preferably not more than 5% per cm) of the laser light used for machining. can absorb the laser light passing through it.

The main drawbacks of direct machining methods are that the cost of high power lasers / laser systems used in their case is relatively high and require high level of expertise to handle, and because of the laser beam penetration during machining the workpiece heated area thickness is difficult and difficult to control. resulting in extensive destruction and thus direct laser processing is not suitable for fine structures (such as surface elements).

In contrast, indirect laser machining methods require significantly less expensive lasers / laser systems and are therefore much more widespread in practice.

One of the most important direct laser processing methods is laser induced backside wet etching (LIBWE). This involves directly contacting the laser workpiece of the transparent workpiece to be etched on the wavelength of the laser beam with a strong absorbing liquid of small thickness, and then, through the workpiece, the laser light of the selected wavelength is exposed to the etching liquid. The laser light is absorbed by the thin layer of liquid in contact with the intended workpiece area of the workpiece and warmed up. As a result of the warming, a high pressure bubble is formed in the liquid layer. In parallel, the heated fluid layer heats and softens, and possibly melts, the area of the workpiece surface to be etched by contacting it through heat transfer. The surface is milled by the force applied to the workpiece material by the resulting high pressure and sudden expansion of the bubble, simply by removing / ejecting a portion of the softened material.

British Patent No. GB-2,341,580 A discloses a LIBWE method for finely machining a surface of a transparent workpiece (such as a bulk quartz plate) under industrial conditions, whereby the pulse is emitted in series by laser pulses successively over a period of time. Excimer lasers or dye lasers are generally used as laser sources in the ultraviolet (UV) range, which emit laser pulses with an energy density of 0.01 to 100 J / cm ² / pulse. The etching rate is 1-25 nm / pulse, depending on the absorbance of the laser light-absorbing solution (pyrene / acetone solution) and the energy density (0.5-1.5 J / cm ² / pulse) of the machining laser pulses emitted by the excimer laser source (KrF). size.

Cs. Vass, T. Smausz and B. Hopp, Journal of Physics D: Applied Physics, Vol. 37, No. 2449-2454, 2004. The publication in pages 1 to 5 of this document deals with the LIBWE method of fine-work machining of transparent materials (for example, quartz plate in bulk). The working laser light source used is an ArF excimer laser operating at λ = 193 nm, the emitted laser pulses having a length of 20 ns and an energy density of 0.11-0.86 J / cm ² . The laser light scavenger is a highly toxic naphthalene / methyl methacrylate solution. Studies have shown that the etching rate is 4.7-49.5 nm / pulse at the applied energy densities.

In the LIBWE method, solutions of organic halogenated benzene derivatives (e.g., C ₆ H ₅ F, C ₈ H ₅ Cl, C ₆ H ₄ Cl ₂ ) and benzene, toluene, pyrene / acetone are generally used as a liquid forming a laser-absorbing excipient. solutions of naphthalene / methyl methacrylate, carbon tetrachloride, methanol, dimethylsulfoxide and the like are used. Therefore, the practical application of the LIBWE method requires a high degree of care, leak-proof handling of the absorbing fluid and adherence to appropriate safety standards, which makes the industrial application of the method extremely expensive.

A further disadvantage of the LIBWE method is that due to the use of the liquid laser-absorbing medium, special additional elements are used for etching, such as storing the liquid absorbing medium and directly contacting it with the intended surface of the workpiece.

A serving dish is also required. Its production requires the implementation of separate workflows, so its use also generally increases the cost of industrial application of the LIBWE method.

In addition, the etching rates available with the LIBWE method are typically up to several times ten nm, which is below the etching rates available with direct laser machining methods.

US 2004/0013951 discloses a process for laser processing of a transparent workpiece. According to the method, the workpiece is machined through a light-absorbing layer which is placed on a surface of the workpiece facing the machining beam incident on the workpiece. Accordingly, this process involves a front-side machining, which results in a low (up to 5%) light transmission area (up to 5%) at the machining site.

U.S. Patent No. 6,990,285 B2 discloses a method for finishing a transparent workpiece (for example, a molten quartz or crystalline sapphire), in particular a laser-triggered backsheet machining process for forming at least one through hole in its full thickness. The workpiece to be machined has a maximum thickness of a few mm. For processing, an ultra-short pulse laser is emitted at a wavelength of λ = 800 nm, that is, not more than 100 fs. The working laser pulses have an energy density equal to or less than 0.16 J / cm ² / pulse. The etching rate is 2.5 to 12.5 nm / pulse with a pulse energy of 7.5 to 10 pJ. In order to carry out the process, water is simply used as an absorbent medium, the main function of which is to remove the debris produced during machining. The use of water as an absorbent excipient is not appropriate for certain transparent materials because it has a refractive index that is too different from that of the material to be etched, resulting in a significant light reflection at the interface of the two materials. Accordingly, in such cases, water / methanol mixture or dimethylsulfoxide is preferably used as the absorption medium instead of water. One of the major drawbacks of this process is that the femtosecond laser source used for machining is extremely expensive and requires considerable expertise to operate.

U.S. Patent No. 5,987,920 describes a process for indirect laser machining of a transparent workpiece. In the process, a layer of excipient absorbing the wavelength of the machining laser is arranged on a surface to be machined on a wavelength transparent material of the processing laser beam, and a processing laser beam is directed through this transparent material. As a result of absorbing the energy of the laser beam in the excipient layer, this layer is heated locally and undergoes ablation. The debris formed during ablation and leaving the layer mechanically etches the surface of the transparent material to form a matte (i.e., reduced light transmission) region (s). High melting point ceramic materials are used as auxiliary material to prevent melting of the excipient during machining. The ceramic materials used are also relatively brittle, which facilitates the formation of debris that actually performs the processing of the transparent material.

In our investigations, it was concluded that the transparent material or workpiece is intended to be machined in close contact with a solid absorbent layer of a suitable thickness, and then exposed to the laser light through the transparent workpiece, at etching speeds even when using laser pulses of ns length.

In view of the foregoing, it is an object of the present invention to provide a novel type of process for fine laser indirect machining of a transparent material / workpiece which overcomes or at least significantly mitigates the above disadvantages of the above methods. It is also our goal to improve the efficiency of fine laser indirect machining of transparent material / workpiece.

Our aim is to implement a new type of laser etching process specifically designed for transparent material / workpiece that does not require the handling of auxiliary materials that are harmful to the environment and health, and which do not require additional equipment. Another object of the present invention is to provide a method that can be performed at a rate greater than the LIBWE method, i.e., having a single laser pulse etching rate (i.e., the etching rate) compared to LIBWE etching at substantially the same energy pulses as the LIBWE method. will. In addition, it is a particularly further object of our invention to develop an etching process that does not require the use of high-power and expensive femtosecond lasers / laser systems, which results in light transmission structures.

Our object to realize a new type of laser finishing process for a transparent material / workpiece has been achieved by developing a method according to claim 1. The process according to the invention is a possible preferred example. 2-19. claims. Further, the workpiece according to the invention is defined in claim 20.

The invention will now be described in more detail with reference to the accompanying drawings, in which:

Figure 1 for a new type of indirect laser back-finishing according to the invention / ma3

EN 227 254 1 schematically illustrates a possible arrangement for carrying out a method of drawing; the

Fig. 2 is a graphical representation of the etching rates obtained by machining a quartz surface by the method of the present invention and the known LIBWE method as a function of the energy density of the laser pulses used for machining; the

Figure 3 depicts the etching depths of a fine quartz workpiece machined according to the present invention as a function of the energy density of 30 ns laser pulses emitted at a wavelength λ = 248 nm using a nanosecond KrF excimer laser source for processing; the

Figure 4 illustrates a possible application of the method according to the invention, specifically as an example for forming an interferometric grid of a given lattice constant. illustrates layout; and that

5A. 5B and 5B. Figure 4A is a view of an interferometric lattice with a constant force 288 nm (Figure 5A) and 560 nm (Figure 5B) formed on a quartz plate surface, respectively, by atomic force microscopy (AFM).

Herein and hereinafter, we will refer to the inventive process for indirect laser finishing of transparent materials / workpieces, bearing in mind its essential details, which will be described in more detail below - laser induced backside dry etching (LIBDE). .

Figure 1 is a schematic diagram of one possible arrangement for carrying out the LIBDE process of the present invention. By means of the LIBDE method, the designated area 19 of the optically transparent workpiece 12, bounded by the first surface 13 and the second surface 14 overlapping therewith, is to be machined indirectly by laser light 20 emitted by laser sources 10, optionally in nano- and micrometer sizes. To this end, the work surface 12 of the workpiece 12 is in close contact with the intended surface to be machined away from the laser source 10, i.e. in this case the second surface 14 of the workpiece 12, with a predetermined thickness and solid absorbent layer 18. Preferably, in the light path defined by the workpiece 12 and the laser source 10, an optical imaging system 24 comprising at least one optical lens is disposed in order to provide control of the laser light 20 and, in some cases, the necessary focus. To process the area 19 of the workpiece 12, the laser light 20 exiting the laser source 10 and passing through the light path is directed through the imaging system 24. Note that the use of an optical imaging system 24 is not required.

If machining of workpiece 12 requires a pattern defined in the region 19 (e.g., a plurality of pits showing a given surface distribution or an optical grid or more complex structures such as microlens or sensor technology couplers or through holes), one or more of the desired patterns 22 a masking element can be arranged. The masking element 22 is generally located in a portion of the light path between the optical imaging system 24 and the laser source 10. It is to be noted here that the creation of a larger etching pattern on a larger portion of the workpiece surface 14, which is not radiated by a single laser beam emitted by the laser source 10, also requires that the laser light 20 be absorbed in the absorbent layer 18. place to move. This can be achieved, for example, by the relative movement of the workpiece 12 and the laser source 10 relative to one another or, if necessary, by modifying the light path of the laser light 20 with the optical imaging system 24. Physical devices (e.g., stage, stepper motor, and the like) required to perform precision movement or light path modification, and their operation / operation are known to those of ordinary skill in the art and are not specifically addressed herein.

The workpiece 12 may be made of any solid material which is optically transparent at the operating wavelength of the laser source used for machining, and may soften (possibly melt) under the influence of heat, but does not require excessively high temperatures. The softening (melting) temperature of the workpiece material 12 is preferably not more than 4000 K. Since the workpiece 12 is made of a transparent material that has only a slight absorption at the wavelength of the processing laser 20, the LIBDE method of the present invention is also suitable for machining. For example, when using laser light 20 in the visible spectral range, preferably having a wavelength of λ = 500 nm, the method can successfully quartz beam up to one meter in thickness. However, if the workpiece 12 is to be subjected to volumetric machining, for example to form through-holes, openings, gaps of any shape between the second surfaces 14 and the first surfaces 13, the workpiece 12 is preferably formed to a thickness of up to several hundred nm, preferably 100-300 nm. Who. Optically transparent inorganic materials such as bulk or crystalline quartz, common glass, calcium fluoride, magnesium fluoride, lithium fluoride, silicon carbide, alumina, sapphire, diamonds, etc., are optically transparent. polycarbonate, acrylic or vinyl resins or organic glass. The workpiece 12 may be of any shape; the workpiece 12 may be formed, for example, in the form of a sheet, an array, a block or even a tube of a given wall thickness.

HU 227 254 Β1

The absorbent layer 18 is made up of a material which absorbs almost completely, but preferably at least 95-99%, of the laser light 20, which passes through the optically transparent workpiece 12 almost absorptively over a relatively short distance. The absorbent layer 18 is preferably formed of a metal. Metals are particularly advantageous for this purpose because, in their case, the condition is met in almost the entire range of UV-visible light. Silver and aluminum are particularly preferred as the absorbent layer 18 in the process of the invention. Generally speaking, any metal having a boiling point greater than the melting point of the material of the workpiece 12 to be machined may be used as the absorbent layer 18, but does not need to be made of metal. For example, thin films made of carbon are advantageously used as absorbers 18 in the process of the present invention, since they have sufficient absorptivity in the infrared, visible and UV ranges. However, in the case of a non-metallic absorbent layer 18, it is essential that the absorbance of the material used should be relatively high at the wavelength of the laser being processed. In the case of UV treatment 20 laser processing, a layer made of a polymer (e.g., polycarbonate, polyethylene terephthalate, polymethylmethacrylate, polyhydroxybutyrate, polyimide and other similar polymers) and biopolymers can also be advantageously used. The thickness of the absorbing layer 18 is selected such that the energy of the incident laser light 20 in the absorbing layer 18 is substantially completely absorbed. At the same time, the absorbent layer 18 should be thin enough to be removed from the surface 14 of the workpiece 12 at its intended thickness 19 by laser irradiation and thereby ensure the etching of the region 19 at the same time. With this in mind, the thickness of the absorbent layer 18 is selected from 50 to 150 nm, more preferably from 80 to 120 nm, and more preferably about 100 nm, depending on the energy of the working laser light 20 and the particular material of the absorbent layer 18. The absorbent layer 18 is typically formed by physical or chemical vapor deposition (PVD, CVD), vacuum evaporation, vaporization, or spraying, which also provide a natural contact between the workpiece 12 and the absorbent layer 18.

In order to carry out the LIBDE method of the present invention, the laser source 10 may be any pulsed laser capable of emitting pulses having an energy density of 0.01 to 10 J / cm ² . Preferably, the emitted laser pulses are 10-100 ns long, more preferably 20-50 ns long. Of course, the energy density and the length of the laser pulses forming the laser light 20 used for machining depend on the material of the workpiece 12 and the absorbent layer 18 to be machined. It is noted that pulses of too high energy density can result in volumetric destruction of the workpiece 12, whereas pulses of too low energy density lead to low efficiency etching. Preferred pulsed lasers include, for example, an ArF excimer laser (λ = 193 nm), a KrCl excimer laser (λ = 222 nm), a KrF excimer laser (λ = 248 nm), an XeCl excimer laser (λ = 308 nm), an XeF excimer laser (λ = 351 nm), various dye lasers, a Kr ion laser, an Ar ion laser and a Cu gas laser can be used. The higher harmonics of the YAG and YLF lasers, which can be obtained with suitable non-linear optical elements, can also be used effectively. However, in our experiments, the LIBDE method can be successfully performed with a visible laser, such as green light (λ = 500 nm), that is, it enables the processing of materials which are opaque to UV light (eg glass).

The following is a brief description of the implementation of the LIBDE method according to the invention. Prior to the start of the process, the surface 14 of the transparent workpiece 12 to be machined (at least in the region 19) is brought into close contact with an appropriate (preferably 50-150 nm) absorbent layer 18 of laser light absorbing auxiliary material. To ensure close contact, the absorbent layer 18 is preferably applied to the surface 14 by vacuum evaporation. Subsequently, the absorbent layer 18 is illuminated by the optically transparent workpiece 12, in accordance with the pattern to be etched into the surface 14, by the laser light used for machining. The structure to be etched is optionally provided in the form of a masking element 22 disposed in the light path of the laser light 20. If necessary, the laser light 20 is also routed through the optical imaging system 24 prior to falling onto the workpiece 12 for concentration.

The energy of the laser pulses of sufficient energy density is absorbed in a thin layer of the irradiated region of the absorber layer 18 extending near the surface 14 of the workpiece 12. The layer in question invokes a portion of the energy absorbed to heat the environment, which causes local warming or boiling of the material of the absorbent layer, essentially the entire thickness of the absorbent layer. At the same time, the area 19 of the workpiece 12 in contact with the absorption region is also heated by intense heat transfer and softens / melts or even boils to a depth depending on the energy of the irradiation. The material of the absorbent layer 18 exiting the surface 14 at high speed exerts a rebound effect on the molten material of the region 19. As a result, some of the material in the region 19 is ejected from the workpiece block 12 resulting in etching. After ejection, the remainder of the workpiece 12 rapidly cools and solidifies. The dotted pattern / structure has sharp edges.

Note that etching itself takes place only when the boiling point of the material of the absorbent layer 18 is the melting of the material of the workpiece 12.

EN 227 254 Β1 points. It is further noted that etching, on the other hand, only occurs when the laser pulses of the laser light 20 used for processing have an energy density of a threshold. According to our investigations, the energy density of the etching threshold of the LIBDE method according to the invention is typically 100-500 mJ / cm ² / pulse, which depends on the parameters (wavelength, pulse length) of the laser source 10 employed and the material of the workpiece 12 and absorbent layer.

Finally, after forming the desired pattern / structure in the region 19 of the workpiece 12, the remaining absorbent layer 18 is removed from the surface 14 by physical (e.g., grinding) or chemical (e.g., dissolution) methods if required for subsequent use of the workpiece.

The greater efficiency of the LIBDE process of the present invention over the LIBWE method is illustrated in Figure 2, which shows the etching rates measured during the machining of bulk quartz workpieces as a function of the energy density of the machining laser pulses. The measurement results used are in the following articles, and the labels used for reference in Figure 2 have the following meaning:

- 'Vass [1]: Naphthalene / MMA': Comparing study of subpicosecond and nanosecond wet etching of fused silica by Cs. Vass, D. Sebők and B. Hopp (Applied Surface Science, in print, online, 2005). October 27), wherein the excipient is a naphthalene / methyl methacrylate solution;

- 'Nino [2]: toluene' and 'Nino [2]: pyrene / acetone' by H. Nino, Y. Yasui, X. Ding, A. Narazaki, T. Sato, Y. Kawaguchi and A. Yabe. Surface microfabrication of silica glass by excimer laser irradiation of organic solvent, Journal of Photochemistry and Photobiology A: Chemistry 158 (2003) 179-182, wherein the excipient is a toluene or pyrene / acetone solution, respectively;

- 'Böhme [3]: Pyrene / toluene' by R. Böhme and K. Zimmer, "The Influence of Laser Spot Size and Pulse Number on Laser-Induced Backside Wet Etching" [Applied Surface Science 247 (2005) 256-261], wherein the excipient is a pyrene / toluene solution; and

- 'Dry etching': data obtained by the LIBDE method according to the invention, wherein the excipient is metallic silver.

It can be clearly seen from Figure 2 that the LIBDE method developed by us produces significantly higher etching rates at any energy density. Further, Figure 2 also shows that for LIBDE, the etching threshold is about half of the etching threshold for the LIBWE method. This means that, under the same external conditions, the size of the LIBDE machinable surface of the invention is about twice the size of the LIBWE machinable surface. That is, a much simpler and cheaper setup is enough to achieve the same effect.

The process of the present invention and its possible uses are illustrated by the following examples.

Example 1

In order to illustrate the LIBDE method of the present invention, in the arrangement of Figure 1, 1 mm thick sheets of melted quartz were machined. A 100 nm thick silver layer was applied to the second surface 14 of each workpiece 12 by vacuum evaporation. The laser source 10 was a KrF excimer laser operating at λ = 248 nm wavelength. The absorption coefficient of the silver layer at the wavelength in question is 71 1 / μΐτι, which means a penetration depth of 14 nm for 20 laser light. The areas 19 of the surfaces 14 to be etched were patches of 0.0105 cm ² . A single 10 cm focal length lens made of quartz was also included in the light path to concentrate the laser light 20. The silver layers were irradiated through the quartz plates. The energy density of the laser pulses was varied in the range of 90-4030 mJ / cm ² . The tests showed that when the laser light used for machining 20 had an energy density of a lower so-called etching threshold (which in this experiment was about 192 mJ / cm ² ), the irradiated spot was simply evaporated and simultaneously that is, quartz has left the 19 provinces. Figure 3 shows the etching depth as a function of the energy density of the laser pulses used for machining, which in this case (since it is a single shot method) is the etching speed. Figure 3 shows that the etching rate above the etching threshold energy is linearly dependent on the energy density of the machining laser pulse. Based on this relation, the energy density of the machining laser pulses can be unambiguously determined / controlled by adjusting the energy density, which means that the LIBDE method can be easily and reliably automated in bulk applications.

Example 2

Our method is also suitable for the production of fine submicrometer structures. To illustrate this, Figure 4 schematically illustrates a possible arrangement for performing interferometric lattice etching according to the LIBDE method of the present invention. The optically transparent workpiece 12 delimited by the first 13 and second surfaces 14 is in this case formed by a 1 mm thick quartz billet, on which the absorbent layer 18 of metal silver is deposited by vacuum evaporation on its intended surface 14. The energy densities of Example 1 were used for etching. It is intended to provide a surface 14 for the workpiece 12

To produce an interferometric lattice 29, the laser light emitted by a laser source (not shown) is divided into two beams by a beam splitter 25 arranged in a light path (e.g., a semi-transparent mirror). The two beams are then guided into the absorber layer 18 of the same length, but in two different light paths, where the energy of the two interfering beams is absorbed in accordance with the desired interferometric pattern (series of quench and reinforcement lines) when there is a corresponding phase difference between the beams. In this case, one of the two beams is transmitted through an optical delay 27. The optical retarder 27 can be implemented in its simplest form by means of mirrors 27b, 27a arranged in the light path of one beam and perpendicular to one skilled in the art. The direction of said beam outside the optical delay 27 and the direction of the other beam into the absorbing layer 18 are accomplished by additional mirrors 28a, 28b arranged in the light paths of the beams.

5A. 5B and 5B. Figures 3A and 4B show atomic force microscopy images of interferometric gratings 29 immersed in the surface 14 of a quartz workpiece 12 using the laser light 20 of different wavelengths using the LIBDE method of the present invention. 5A. Figure 28B is a 288 nm lattice constant; Figure 5A shows an interferometric grid with a grid constant of 560 nm.

In contrast to the currently known laser machining methods (e.g. ablation, LIBWE), the machining method of the present invention is a so-called single shot method. This means that each part of the pattern / structure to be etched is created by a laser pulse. In the irradiated region, the absorbent layer is also removed with the milled material, so that a second impulse in the same region of the workpiece is no longer effective. From this region, the absorbent layer evaporates and the workpiece's sputtering material splashes out. There is no way to recover. Due to the single shot nature of the LIBDE, the possible movement of the workpiece from shot to shot is not a problem at all, so the "noise" does not interfere with the intended submicrometer structure. This is extremely important for the applicability of the LIBDE method in nanotechnology.

Further, if the creation of a particular etching pattern requires multi-pulse machining and the coating of the machined surface can be accomplished by vacuum evaporation without having to remove the workpiece from the arrangement, the workpiece is etched in a suitably designed vacuum chamber and indirectly etched The surface may be re-coated with the absorbent layer after successive steps of laser etching followed by vacuum evaporation, which may be repeated as many times as desired to achieve the desired pattern. This allows you to create multi-level volumetric patterns in the workpiece.

The LIBDE process of the present invention allows for fine laser indirect processing of transparent materials / workpieces, nanostructured structures, microlens (laser beam homogenizers), Fresnel lenses, high-destructive optical lattices, and sensor coupling. In addition, through the process according to the invention, through-holes, openings, gaps can be successfully formed in transparent workpieces of suitable thickness.

Claims (20)

PATENT CLAIMS A method for indirectly pulsed laser processing of a transparent material, comprising contacting the transparent material with an absorbent layer (18) at least in the area (19) to be processed; directing to the absorbing layer (18) a laser pulse formed by a laser light (20) emitted by a laser source (10) through the transparent material; the energy of the laser pulse is absorbed in the region of the absorbent layer (18) close to the intended working area (19) of the transparent material, wherein the transparent material is substantially transmissive material at the wavelength of the laser light (20); the laser pulse energy is set at least equal to the etching threshold energy of the transparent material, characterized in that the absorption region of the absorption layer (18) is heated to the source by the absorption of the laser pulse energy and the material is absorbed by (19) mechanically removing material from the area to be machined (19), wherein the absorbent layer (18) is formed with a thickness which by absorbing the energy of the laser pulse, the absorbent layer (18) is boiled to full thickness at the intended area (19) of the transparent material. Method according to Claim 1, characterized in that the workpiece (12) having a first surface (13) and a second surface (14) opposite to it is formed from the transparent material, and the area (19) to be machined is so formed. is placed on the surface of the resulting workpiece (12) through which the laser light (20) leaves the workpiece (12). Method according to claim 1 or 2, characterized in that the heat exchange connection is achieved by close contact between the absorbent layer (18) and the transparent material. A method according to claim 3, characterized in that the surface contact is formed by the material of the absorbent layer (18). It is produced by applying physical vapor deposition (PVD), chemical vapor deposition (CVD), vacuum evaporation, evaporation or atomisation. 5. A method according to any one of claims 1 to 4, characterized in that the laser pulse directed to the absorber layer (18) has a duration of 10-100 ns, more preferably 20-50 ns, and an energy density of 0.01-10 J / cm ² . 6. A method according to any one of claims 1 to 3, characterized in that the laser source (10) is a pulsed nanosecond laser source which produces a laser pulse having an energy density of 0.01 to 10 J / cm ² . 7. The method of claim 6, wherein the laser source is an ArF excimer laser (λ = 193 nm), a KrCl excimer laser (λ = 222 nm), a KrF excimer laser (λ = 248 nm), XeCI excimer laser (λ = 308 nm), XeF excimer laser (λ = 351 nm), various dye lasers, Kr ion laser, Ar ion laser and Cu gas laser. The method of claim 6, wherein the laser source is a YAG or YLF laser, and the laser light (20) is a higher harmonic thereof obtained by nonlinear optical elements. 9. A process according to any one of claims 1 to 4, characterized in that the absorbent layer (18) is formed at a thickness of 50-150 nm, more preferably 80-120 nm, more preferably about 100 nm. 10. A process according to any one of claims 1 to 3, characterized in that the absorbent layer (18) is made of a metal or carbon or polymer having a boiling point above the melting point of the transparent material. A method according to claim 10, characterized in that the absorbent layer (18) is made of aluminum or silver. 12. 1-1! A process according to any one of claims 1 to 5, characterized in that the transparent material is a bulk or crystalline quartz, common glass, calcium fluoride, magnesium fluoride, lithium fluoride, silicon carbide, alumina, sapphire, selected from the group consisting of diamond, cured polycarbonate, acrylic or vinyl resins and organic glass. 13. A method according to any one of claims 1 to 6, characterized in that in the area to be machined (19) the degree of material removal is adjusted by the energy of a laser pulse directed to the absorbent layer (18). 14. Method according to any one of claims 1 to 3, characterized in that the laser pulse is directed to the absorbing layer (18) by means of an optical imaging system (24). 15. A method according to any one of claims 1 to 3, characterized in that by removing material in the area to be machined (19) of the transparent material, a milling pattern and / or a through hole in the volume of the transparent material is formed. 16. A method according to any one of claims 1 to 4, characterized in that the material removal in the area to be machined (19) of the transparent material produces a pattern in the nano or micrometer range. 17. A method according to any one of claims 1 to 5, characterized in that it is repeated several times to form a multilevel volumetric pattern in the transparent material. Method according to claim 15 or 16 or 17, characterized in that the patterning is facilitated by placing a masking element (22) in the path of the laser pulse. 19. Method according to any one of claims 1 to 3, characterized in that after the desired processing of the transparent material, the remaining absorbent layer (18) is removed from the surface of the transparent material by physical or chemical contact. 20. A workpiece which is transparent at the emission wavelength of the laser source used for machining, characterized in that the surface and / or volume of the laser source used in the method of FIG. Substance deficiency sites formed according to the desired pattern by the method of any one of claims 1 to 6.