Method for structuring glass element by etching at high etch rate

Abstract

Method for structuring a glass element by etching, in which the glass element (1) has at least one filiform damage (5) extending within the glass element (1), and in which the glass element (1) having the filiform damage (5) is exposed to an alkaline etching medium (14) suitable for removing glass of the glass element (1) by etching, and wherein the filiform damage (5) is widened by etching such that an opening (7) is created in the glass element, wherein the molar concentration of the etching medium (14) and the etching temperature thereof are determined by etching at least one test glass element (9) having a filiform damage (5) in at least one preceding etching process as a reference point and determining an edge height change at the opening (7) resulting from the filiform damage (5) in the etching process, the edge height change represents an increase or decrease in thickness at the edge (70) of the opening (7), and wherein, if the edge height change does not exceed a predetermined value, at least one parameter of the temperature and the molar concentration of the etching medium (14) is increased such that the rate of removal of the glass is increased but does not exceed the predetermined value of the edge height change, and wherein the thickness of the opening (7) is reduced. The glass element (1) is then etched using the values of the temperature and molar concentration thus determined.

Description

Field of the Invention

[0001] Generally speaking, the present invention relates to a method for structuring a glass element. In particular, the present invention relates to a method for structuring a glass element by means of a wet chemical etching process. Background Art

[0002] Structuring methods are known from the prior art, in which, for example, filamentous damage is introduced into a glass element by the action of laser radiation and the filamentous damage is subsequently subjected to a wet chemical etching process. In this case, in principle, the etching process can be carried out using HF or by the action of an alkaline etching medium.

[0003] Methods are known from the prior art in which a glass element with filamentous damage is widened by the action of an aqueous KOH solution. The widening of the filamentous damage generates openings in the glass element.

[0004] In an alkaline etching process, an alkali metal hydroxide solution is generally used as the etching medium. The etching of glass corresponds to the precipitation of various glass components (especially metal ions) from the glass network. In this case, the negatively charged hydroxide ions in the alkaline etching medium attack the Si-O-Si bonds of the glass network. The etching rate or the rate of glass dissolution depends on various factors. Thus, on the one hand, the glass composition of the glass affects the etching rate of the structuring process. Therefore, the number of bridging oxygens on the silicon atom affects its electrophilicity and thus its "reactivity". In addition, extra network formers and modifiers present in the glass form degradation products during glass dissolution, which affect the etching process. Thus, the degradation products sodium silicate or silicate anions have an accelerating effect on the etching process. The etching rate is also affected by external process parameters such as the pH value of the etching medium, the alkali used, and the etching temperature.

[0005] In large-scale etching, for example in the large-scale production of structured glass, the concentration of the etching medium and the etching temperature are generally kept constant during the etching process. Thus, during the etching process, the etching rate changes only due to the change in the relative amount of glass dissolved in the etching medium. Since the dissolved glass can no longer be "filtered out" from the etching solution, the amount of glass increases in each etching step. For a large amount of etching solution, the influence of the degradation products of glass dissolution can be neglected, and thus the etching rate can be considered substantially constant.

[0006] When etching very small structures, for example when etching filaments introduced into the glass using a laser, the etching solution penetrates structures with a diameter of only a few hundred nanometers and then etches the structures. Due to the small volume of these filaments, a relatively large amount of glass is locally dissolved in the filaments in a small amount of etching solution during the process. Correspondingly, the relative amount of dissolved glass increases and the etching rate decreases.

[0007] During the etching process, there is always an exchange of the etching solution in the filaments with the solution in the surrounding volume. At the "transition point", i.e., at the edges of the filaments, a region is created where the two concentrations are mixed and where etching thus occurs at an etching rate different from that in regions at a greater distance from the structure. Since the etching rate depends on the concentration, the glass is removed in this "mixing region" at an etching rate different from that inside the filaments, which can thus result in an edge height difference at the edges of the structure.

[0008] Especially in later applications of the etched structure (in which, for example, when the structured element is joined to other elements, the top structure of the element is of particular importance), the height difference between the edge region of the filaments and the more distant surface regions must not exceed a specific limit value.

[0009] Furthermore, the etching rate is severely affected by the process temperature. Thus, an increase in the etching temperature by 10 K approximately doubles the etching rate. Since the duration of the structuring process is inversely proportional to the etching rate, from an economic perspective, a high process temperature is advantageous because the process time can thus be reduced. In the structuring process where the height deviation in the edge region of the filaments must not exceed a specific value, the increase in the etching temperature is limited by the close relationship between the height difference and the etching temperature. Thus, there are limitations to more economical structuring at higher temperatures given the height difference specification. Summary of the Invention

[0010] Accordingly, an object of the present invention is to provide a method for determining optimal process parameters: the etching temperature and the concentration of the etching medium to accelerate the etching process while maintaining a desired maximum height difference. Another object of the present invention is to provide an etching method using the optimized process parameters.

[0011] Surprisingly, this object has been achieved by the subject matter of the independent claims. Advantageous designs and improvements are the subject matter of the dependent claims.

[0012] One aspect of the present invention relates to a method for structuring a glass element by etching, in which the glass element (1) has at least one filamentous damage (5) extending within the glass element (1), and in which the glass element (1) having the filamentous damage (5) is exposed to an alkaline etching medium (14). The alkaline etching medium is suitable for removing the glass of the glass element by etching and is preferably an alkaline hydroxide solution. In particular, the solution contains water or is an aqueous solution. One embodiment provides that the etching medium comprises an aqueous KOH solution.

[0013] The filamentous damage in a glass element is widened by etching to generate an opening in the glass element. By this method, multiple filaments can also be combined into one opening. In this case, channels are first formed by etching the filamentous damage. Through the etching process, these channels are further widened so that adjacent channels are combined.

[0014] The molar concentration of the etching medium or the concentration of the alkali in the etching medium and the etching temperature are determined as follows: In at least one prior etching process as a reference point, at least one test glass element having filamentous damage is etched and the change in the edge height at the opening generated due to the filamentous damage during the etching process is determined. The change in the edge height herein represents the increase or decrease in the glass thickness at the edge of the opening generated by the etching process. If the change in the edge height does not exceed a predetermined value in this reference measurement, at least one of the parameters of the etching temperature and the molar concentration of the etching medium is increased so that the glass removal rate or the etching rate increases, but does not exceed the predetermined value of the change in the edge height. Now, the glass element is etched using the etching temperature and the value of the molar concentration or concentration of the etching solution thus determined.

[0015] According to one embodiment, the temperature at which the etching process is carried out is selected as high as possible, but does not exceed the specified value of the maximum edge height change. The temperature that does not exceed the maximum allowable edge height change is called T max , and can be calculated by the following formula:

[0016] E A represents the activation energy of the etching reaction, R represents the universal gas constant, C represents the molar concentration or concentration of the etching medium, K ref represents the predetermined value of the edge height change, and K0 represents the value of the edge height change at a very low etching rate.

[0017] Since the etching rate follows the Arrhenius equation, there is the following relationship between the etching rate and the temperature:

[0018] The activation energy E A is a material parameter that is not affected by the etching process. The proportionality constant A takes into account the influence of the hydroxide concentration on the reaction rate of the etching process. Thus, when the hydroxide concentration increases beyond a certain limit value, the speed of the etching process decreases.

[0019] By measuring the etching rate at different temperatures, two parameters can be determined for the corresponding glass, where the parameters A and E A are obtained from the linear equation of the fitted line.

[0020] The variables a, b, g fit,1 and g fit,2is a fitting parameter that describes the relationship between the etching rate of the glass to be processed and the change in the edge height with respect to the concentration of the etching solution at a temperature In this case, the fitting parameters a and b describe the relationship between the change in the edge height K and the etching rate, and the relationship is as follows:

[0021] where R e represents the etching rate.

[0022] The parameter g fit,1 and g fit,2 describe the relationship between the etching rate and the temperature and concentration, and the relationship is as follows:

[0023] According to another embodiment, the following temperature is determined by performing a reference measurement at an etching temperature of 98 °C: at this temperature, maximum etching can be performed in the etching bath at a given hydroxide concentration C without exceeding the predetermined maximum value for the change in the edge height K ref The fitting parameters a, b, g fit,1 and g fit,2 described above are determined such that the maximum etching temperature T max is:

[0024] Here, E A also represents the activation energy of the etching reaction (J / mol), C represents the concentration of hydroxide ions in the etching medium (mol / l). K ref is the predetermined maximum value of the change in the edge height, K0 represents the change in the edge height at a very low etching rate, both in units of nm and can be approximately equal to zero. R is the universal gas constant, in units of J / (mol·K).

[0025] According to one embodiment, the maximum value of the change in the edge height or the predetermined or fixed maximum value of the edge height increase K ref is less than 10 μm, preferably less than 5 μm, preferably less than 2 μm, and very particularly preferably less than 1 μm. In particular, K less than 0.8 μm, less than 0.5 μm or even less than 0.3 μm can also be selected ref .

[0026] One embodiment provides for etching a glass element at the following temperatures and molar concentrations of the etching medium: at these temperatures and molar concentrations, the etching rate is at least as high as the etching rate in an etching medium in the form of a KOH lye (having a molar concentration or concentration in the range from 0.5 to 5 mol / l and a temperature in the range from at least 85 °C up to the boiling point). By increasing the hydroxide concentration, the boiling point of the etching solution shifts to a higher temperature. Thus, in this embodiment, a temperature can be achieved that is higher than the boiling point of the etching medium in a reference process (i.e., having a hydroxide ion concentration in the range from 0.5 to 5 mol / l). Thus, according to one embodiment, the etching temperature is determined by and does not exceed the boiling temperature of the etching solution used. Preferably, the glass is etched in an aqueous solution of an alkali, in particular an aqueous solution of an alkali metal hydroxide. It has proven particularly advantageous to use an aqueous KOH solution.

[0027] With increasing hydroxide concentration, the viscosity of the etching solution increases, which in particular makes it difficult to exchange the etched volume inside the filaments with the etched volume outside the filaments when etching very small structures (such as laser filaments). In addition, due to the high viscosity, the mobility of the dissolved glass components is adversely affected, so that local concentration gradients may form inside the filaments. Thus, according to one embodiment, an etching solution having a concentration of less than 24 mol / l, preferably less than 20 mol / l, particularly preferably less than 18 mol / l is used to etch the glass element.

[0028] At a given temperature, the etching medium has a maximum etching rate that depends on the concentration of the etching solution. At the same time, at a given etching temperature, with increasing concentration of the etching solution, the amount of edge height variation decreases significantly. This effect is particularly pronounced at higher temperatures, where generally larger edge height variations occur. By increasing the concentration, the etching rate initially decreases, but at the same time, due to the positive effect of the concentration on the edge height variation, the maximum temperature at which the etching process can be carried out can be increased at a predetermined maximum value of the edge height variation. Here, due to the exponential temperature influence, the influence of the temperature increase on the etching rate is greater than the influence of the hydroxide ion concentration or the molar concentration of the etching solution (see formula IV). In addition, by increasing the concentration of the etching medium, its boiling point is increased. Thus, the maximum etching temperature at which the etching reaction can still be carried out practically is also increased. Thus, one embodiment of the invention provides for etching a glass element at a molar concentration of the etching medium that is higher than the molar concentration at which the maximum etching rate is achieved. In particular, the molar concentration of the etching solution used is at least 3 mol / l higher than the molar concentration of the etching solution at which the maximum etching rate is achieved. It has been found that it is particularly advantageous if the etching solution is a KOH solution, in particular an aqueous KOH solution and has a molar concentration of at least 8 mol / l. Description of the Drawings

[0029] The following is in accordance with Figures 1 to 15Describe the present invention. Shown therein are:

[0030] Figure 1 A schematic diagram showing the generation of filaments,

[0031] Figure 2 A schematic diagram showing the etching process of a glass element,

[0032] Figure 3 A schematic diagram showing an etched glass element with a negative edge height change,

[0033] Figure 4 A schematic diagram showing the relationship between the etching rate and the concentration of the etching solution according to various embodiments,

[0034] Figure 5 A schematic diagram showing the relationship between the etching rate and the amount of glass dissolved in the etching solution,

[0035] Figure 6 A schematic diagram showing the respective edge height changes at different temperatures and in different filament cross-sections,

[0036] Figure 7 A schematic diagram showing the relationship between the concentration and the boiling temperature of an aqueous KOH solution,

[0037] Figure 8 A schematic diagram showing the relationship between the etching rate and the temperature,

[0038] Figure 9 A schematic diagram showing the relationship between the etching rate and the concentration of the etching solution,

[0039] Figure 10 A schematic diagram showing the relationship between temperature, the concentration of the etching solution, and the etching rate,

[0040] Figure 11 A schematic diagram showing the relationship between the edge height increase and the etching rate at different etching solution concentrations and the corresponding fitted curves,

[0041] Figure 12 A schematic diagram showing the relationship between the edge height increase and the concentration of the etching solution at different temperatures and the corresponding fitted curves,

[0042] Figure 13 A schematic diagram showing the relationship between the edge height increase and the temperature at different etching solution concentrations and the corresponding fitted curves,

[0043] Figure 14 A graphical illustration of the optimized process range for a process operating at 98 °C at 5 M, and

[0044] Figure 15A graphical illustration showing an optimized process range of a process with a maximum edge height difference of 1000 μm. Detailed Description

[0045] Figure 1 Schematically shows the introduction of filamentous damage 5 into the glass element 1 by laser irradiation. Here, the laser 2 is aligned with the surface 10 of the glass element 1. By using the focusing optics 3, the laser beam 4 has a sufficiently high energy density when bombarding the glass element 1, thereby generating filamentous damage 5 in the glass element 1. The diameter of the filament 5 is determined by the diameter of the laser beam 4 bombarding the glass element 5. The irradiation of the laser beam 4 causes an ablation process, which results in the formation of the filamentous damage 5. In this case, the filament 5 can extend through the entire glass thickness. By realigning the glass element 1 relative to the laser 2, for example, a plurality of adjacent filaments 5 can be generated. By a subsequent etching process for widening each filament 5, these filaments can be merged with each other, thereby generating an opening 7 in the glass element. Figure 2 Schematically shows the etching process of widening the filament into a channel 7. In Figure 2 In the illustrated embodiment, the glass element 1 or the test glass element 9 is placed in a container 15 having an etching solution 14. In this case, the filament 5 expands into a channel 7. The channel 7 penetrates the two surfaces 10, 11 of the glass elements 1, 9. In this case, the etching rate and thus the removal of the glass are not the same at all parts on the glass elements 1, 9. In particular, in the edge region 70 around the opening 7, the local etching rate may be different from the overall etching rate at the surfaces 10, 11. This results in an edge height variation in the edge region 70. In this case, the edge height variation is derived from the difference between the thickness d2 of the glass in the edge region 70 and the thickness d1 of the glass in the region of the glass element spaced apart from the edge region. Therefore, the edge height variation K applies: K = |d1 - d2| (VI).

[0046] In Figure 2 In the illustrated example, the edge region 70 has a greater thickness d2 than the region 7 spaced apart from the opening. Therefore, Figure 2 the illustrated edge height variation is an edge height increase. Conversely, in Figure 3 the embodiment of the glass element 1 shown in, the edge region 70 has a smaller thickness d2 than the total thickness d1. Therefore, Figure 3 the illustrated glass element has a reduced edge height in the edge region 70.

[0047] Figure 4The relationship between the etching rate and the concentration of the dissolved glass in the etching solution is shown for three different glasses. It is obvious here that the etching rate depends on the respective glass composition. The concentration of the dissolved glass is plotted logarithmically, and accordingly, during the structuring process, only minor changes occur in the relative amount of dissolved glass. Therefore, the etching rate in the etching solution can in principle be considered constant.

[0048] Figure 5 The relationship between the etching rate and the amount of dissolved glass at high glass concentrations is shown here. When the amount of glass dissolved in the etching solution per liter exceeds 1.5 kg of glass, the etching process does not stop, but the etching rate decreases significantly. Since the volume of the filaments is very small, relatively high glass concentrations can also form within the filaments during the structuring process described herein. Therefore, the etching rate in the filaments is lower than the etching rate of the glass surface regions spaced apart from the filaments. During the etching process, the etching solution in the filaments is constantly exchanged with the solution in the surrounding volume. In the edge region, i.e., at the edges of the filaments, there appears the following region: in this region, the two concentrations are mixed and thus the etching rate is different from that of the regions farther away from the structure. Therefore, there is a change in the edge height around structure 70. In Figure 2 the illustrated embodiment, less glass is removed in the edge region 70, which is the "mixing region", resulting in an increase in the edge height in the edge region around structure 7.

[0049] Figure 6 The relationship between the edge height change and the etching temperature is shown. Here, each column corresponds to a different cross-sectional geometry of structure 7, and these geometries are also shown in Figure 6 this figure. For each structure, the etching process is carried out at 80 °C and 125 °C, with all other parameters remaining unchanged. It can be clearly seen from Figure 6 this figure that the degree of the edge height difference is temperature-dependent. The degree of this correlation is also affected by the cross-sectional geometry of the structure. Therefore, for a given geometry and maximum edge height difference, the possibility of increasing the etching rate by increasing the etching temperature is limited.

[0050] Figure 7 The influence of the concentration or molarity of the etching solution on the boiling point of an aqueous KOH solution is shown. In this case, the boiling point of the etching solution increases with increasing concentration. This can be explained by the effect of boiling point elevation.

[0051] The concentration of the etching solution affects the etching rate. This can be clearly seen from Figure 8 this figure. Figure 8The relationship between the etching rate and temperature is shown correlatively with the concentration of an exemplary glass and an etching rate. To this end, test glasses of the same glass composition are etched in three different etching solutions at different temperatures, and the etching rate is determined by the weight loss of the glass. From Figure 8 It can be clearly seen that increasing the concentration of the etching solution will slow down the etching process. Figure 8 This effect can be seen from the parallel shift of the three curves in

[0052] Figure 8 The parallelism of the lines in A indicates that the variable E Figure 8 is not affected by the concentration of the medium. By increasing the KOH concentration, the process window related to the process temperature shifts significantly upward due to the higher boiling point, making a faster process possible. From A the three curves in

[0053] the activation energy value of the exemplary glass can be determined and applied: E e,98℃ = 87 kJ / mol. Figure 9

[0054] Ref Here, R Figure 9 is in the unit of μm / h. The values 1.145 μm / h and 0.046 (μm·l) / (h·mol) are obtained from the curve fitting shown in Figure 9 and depend on the specific glass composition and the temperature under the curve shown in Ref i.e., the temperature T

[0055] Therefore, for this exemplary glass, the etching rate for a given temperature and different concentrations can be calculated as follows:

[0056] This formula thus describes the etching rate of the exemplary glass at each etching solution concentration in the range of 6 to 18 mol / l and at each temperature. It should be noted that the fitting parameter refers to the temperature at which the etching rate is measured, i.e., 98 °C. The formula is then determined by corresponding initial measurements for all further calculations.

[0057] For glasses of different compositions and reference measurements not carried out at 98 °C, the correlation between the concentration of the etching solution and the etching rate must also be determined experimentally, and the parameters are calculated by curve fitting of the corresponding curves. Thus, more generally, the following applies to the etching rate:

[0058] Using the method according to the invention, the optimal process parameters can be determined in order to achieve the highest possible etching rate with a given maximum variation in the edge height. To obtain a given reference etching rate R e,Ref , the temperature at which etching must be carried out at a given concentration is:

[0059] Thus, for the exemplary glass, the relationship between the etching temperatures to be set at a given concentration of etching solution C is:

[0060] Here R e,Ref is in the unit of μm / h.

[0061] Figure 10 shows the relationship between the etching temperature and the etching rate and the KOH concentration of the etching solution. It can be seen that although the comparison temperature increases, the maximum etching rate increases significantly at higher concentrations. This is partly due to the exponential term in the Arrhenius equation, and the influence of the exponential term on the etching rate is greater than the linear part with the increase in temperature. In addition, the boiling temperature also increases exponentially.

[0062] Figure 11 shows the relationship between the increase in the edge height of the exemplary glass and the etching rate in etching solutions of different concentrations. Figure 12 shows the relationship between the increase in the edge height of the exemplary glass and the concentration of the etching solution, Figure 13 shows the relationship between the increase in the edge height and the etching temperature.

[0063] From Figures 11 to 13 it can be clearly seen that: surprisingly, for high-concentration etching solutions, the correlation between the increase in the edge height and the etching rate and the etching temperature is significantly lower than that of low-concentration etching solutions. Figure 12It is also shown that at the same etching temperature, as the concentration of the etching medium increases, the Kirby height decreases significantly. This effect is more pronounced at high temperatures than at low temperatures, with a stronger Kirby effect at high temperatures. Therefore, by adjusting the concentration of the etching solution, etching can be carried out at a higher temperature and thus at a higher etching rate without degrading the specification of the edge height variation achieved by the previously selected parameter set consisting of the concentration of the etching solution and the etching temperature.

[0064] According to Figures 11 to 13 , the following relationship can be determined for the example glass:

[0065] By fitting this formula to the experimentally determined data shown in Figures 11 to 13 , the following fitting parameters were obtained: a = 1616 (nm·mol·h) / (μm·1), b = 74.4 (nm·h) / μm, and K0 = 30 nm. The unit of K is nm, and the unit of Re is μm / h.

[0066] Using the fitting parameters A, g fit,i , g fit,2 , a, b, and K0 obtained from various reference measurements, the temperature T max can finally be determined at which etching can be carried out without exceeding the specified value of the edge height variation K ref :

[0067] The optimal process range can now be defined. In this case, it can be determined by the maximum edge height difference K ref , or it can be determined based on a previously used process with a sufficiently good quality, i.e., with a satisfactory edge height difference.

[0068] Figure 14 Shows the determination of the optimal process range for the process of etching the example glass with a 5 - molar etching solution at a temperature of 98°C. The optimized process range is shown in hatching and is located above the "comparison temperature" curve here because the etching rate there is higher than the current process, and at this etching rate, the process can be run more economically. Therefore, it is advantageous to carry out the etching of the glass element at the following temperature and concentration of the etching medium: at which the etching rate is at least as high as the etching rate in the etching medium in the form of KOH lye (with a concentration in the range of 0.5 to 5 Mol / l and a temperature in the range of at least 85°C up to the boiling point). Further, it is advantageous that the process range is located below the curve "K ref , 5mol / 1, 98°C" because the edge height difference here is less than the current process.

[0069] Figure 15 Shows the determination of the optimal process range for an etching process with a maximum edge height variation defined as 1000 nm. Here, the optimal process range is above the "comparison temperature" curve because the etching rate there is higher than that of the current process, and the process can operate more economically at this etching rate. The upper limit of the process range is defined by the curve "K rcf = 1000 μm" because at process temperatures above this curve, the edge height variation is greater than the set limit value of 1000 μm. Additionally, this temperature is also limited by the boiling temperature of the etching solution. List of reference numerals 1 Glass element 2 Laser 3 Focusing optics 4 Laser beam 5 Filamentary damage 7 Opening 9 Test glass element 10、11 Side of glass element 1 14 Etching medium 15 Container of 14 70 Edge of 7

Claims

1. A method for structuring a glass element by etching, wherein the glass element (1) has at least one filamentary damage (5) extending within the glass element (1), and wherein, A glass element (1) having a filamentary damage (5) is exposed to an alkaline etching medium (14) which is suitable for removing the glass of the glass element (1) by etching, and wherein the filamentary damage (5) is widened by etching to generate an opening (7) in the glass element, and wherein the molar concentration and the temperature of the etching medium (14) are determined by etching at least one test glass element (9) having a filamentary damage (5) in at least one preceding etching process as a reference point and determining the change in the edge height at the opening (7) resulting from the etching process of the filamentary damage (5), the change in the edge height representing the increase or decrease in the thickness at the edge (70) of the opening (7), and wherein if the change in the edge height does not exceed a predetermined value, at least one of the temperature and the molar concentration of the etching medium (14) is increased such that the removal rate of the glass is increased but does not exceed the predetermined value of the change in the edge height, and wherein the glass element (1) is subsequently etched with the values of the temperature and the molar concentration thus determined.

2. The method according to claim 1, wherein The temperature at which the glass element (1) is etched in the etching medium (14) is not higher than the temperature T given by the following formula max : where E A represents the activation energy of the etching reaction, R represents the universal gas constant, C represents the molar concentration of the etching medium, K ref represents a predetermined value of the edge height change and K0 represents the edge height change value at a very low etching rate, where K0 can in particular be set equal to zero, where a, b, g fit,1 and g fit,2 are fitting parameters which describe the dependence of the etching rate and the edge height change of the glass to be processed on the concentration of the etching solution at a temperature where the fitting parameters a, b describe the relationship between the edge height change K and the etching rate, and the relationship is: where R e represents the etching rate, and wherein the parameter g fit,1 and g fit,2 describe the relationship between the etching rate and temperature and concentration, and the relational expression is:

3. The method according to claim 2, wherein The temperature at which the glass element (1) is etched in the etching medium (14) is not higher than the temperature T given by the following formula max : where E A represents the activation energy of the etching reaction, in J / mol, R represents the universal gas constant, in J / (mol·K), C represents the molar concentration of the etching medium, in mol / l, K ref represents a predetermined value of the edge height change, and K0 represents the edge height change at a very low etching rate, both in nm, where K0 can in particular be set equal to zero.

4. The method according to any one of claims 1 to 3, characterized in that The etching of the glass element (1) is carried out at the following temperature and molar concentration of the etching medium: at the temperature and molar concentration, the etching rate is at least as high as the etching rate in an etching medium (14) in the form of a KOH alkaline solution with a molar concentration in the range of 0.5 to 5 mol / l and a temperature in the range of at least 85 °C up to the boiling point.

5. The method according to any one of claims 1-4, characterized in that, During the etching of the glass element (1), the temperature of the etching medium (14) does not exceed the boiling temperature of the etching medium (14).

6. The method according to any one of claims 1-5, characterized in that, The glass element (1) is etched with an etching solution having a molar concentration less than 24 mol / l, preferably less than 20 mol / l, and particularly preferably less than 18 mol / l.

7. The method according to any one of claims 1-6, wherein The etching solution contains a solvent, preferably water, and the etching solution is particularly preferably an aqueous solution.

8. The method according to any one of claims 1-7, characterized in that, Etching is carried out using a KOH-containing solution, preferably an aqueous KOH solution, as the etching medium.

9. A method for structuring a glass element by etching, in particular the method according to any one of claims 1 - 8, wherein the glass element (1) has at least one filamentary damage (5) extending within the glass element (1), and wherein, A glass element (1) having a filamentary damage (5) is exposed to an alkaline etching medium which is suitable for removing the glass of the glass element (1) by etching, and wherein the filamentary damage (5) is widened by etching to generate an opening (7) in the glass element, and wherein at a given temperature, the etching medium (14) has a maximum etching rate depending on the molar concentration, and wherein the etching of the glass element (1) is carried out at a molar concentration of the etching medium (14) higher than the molar concentration at which the maximum etching rate is achieved.

10. The method according to claim 9, wherein During the etching of the glass element (1), the molar concentration of the etching medium is at least 3 mol / l higher than the molar concentration giving the maximum etching rate.

11. The method according to any one of claims 9-10, characterized in that, The etching medium is a KOH alkaline solution having a molar concentration of at least 8 mol / l.

12. The method according to any one of claims 1-11, characterized in that, The opening (7) is generated by merging adjacent widened channels (8), wherein the channels (8) are respectively produced by etching the filamentary damage (5).

13. The method according to any one of claims 1 to 12, characterized in that, Predetermined maximum value K of the edge height variation ref K that is less than 10 μm, preferably less than 5 μm, preferably less than 2 μm, and very particularly preferably less than 1 μm, and in particular may also be selected to be less than 0.8 μm, less than 0.5 μm or even less than 0.3 μm ref .

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