Glass wafer and method for its manufacture

Abstract

The present invention relates generally to glass wafers for use as interposers, and more particularly to glass wafers including at least one opening.

Description

[Technical Field]

[0001] The present invention relates generally to glass wafers, particularly for use as interposers. Further applications include glass cores for packaging in MEMS, assembly and connection technologies, antennas in packaging concepts for GHz applications, and further similar applications. In particular, the present invention relates to glass wafers comprising at least one aperture. [Background technology]

[0002] Glass wafers used as interposers and / or for similar applications, e.g., as glass cores for MEMS or packaging applications, have at least one, and preferably a plurality of, openings and are generally metallized.

[0003] It is known to manufacture such glass wafers, for example by laser processing followed by an etching step, thus obtaining glass wafers with defined openings, which find application in the industrial production of semiconductors, for example.

[0004] Within the scope of the present disclosure, a glass wafer is generally understood to be a disk-shaped glass that may be designed, for example, circular, oval, or approximately rectangular, etc. In particular, the term glass wafer therefore also includes glass panels or glass disks.

[0005] Even if such glass interposers have already been known for some time, in practice certain difficulties always arise, for example with regard to the mechanical stability of these wafers or the durability of the metallization on these glass wafers, which also applies, for example, to the metallization within the openings themselves.

[0006] Therefore, the glass wafer - The metallization, e.g., metal electrodes, must be optimally adhered to the surface of the glass, especially within the openings in the glass wafer; - Thermal stresses that may occur during contact signal transmission on the glass wafer should be kept as low as possible to ensure long-term stability of the interposer, and in particular tensile stresses on the surface should be avoided. It must be optimized from the viewpoint of

[0007] Finally, it is important that the glass wafer is mechanically stable during semiconductor manufacturing and use, ie, in particular, has good mechanical strength.

[0008] However, it has been found so far that there is still a need for optimization, especially with regard to the adhesive strength of the metal layer to the glass and the mechanical strength of the glass wafer.

[0009] Glass wafers can generally be made more mechanically stable by a variety of methods, for example, U.S. Patent Application Publication No. 2009 / 0220761 describes a method for chemically strengthening glass.

[0010] It is also known that laser treatment can result in compositional changes in glass bodies, as described, for example, in U.S. Patent Application Publication No. 2020 / 024188.

[0011] Sun et al., in Optical Materials, Volume 108, 2020, report that etching of quartz glass with KOH can be performed, resulting in the formation of a diffusion layer of the etching medium on the surface of the quartz glass, which can increase the durability of the quartz glass against lasers.

[0012] Furthermore, there has been extensive research into the alteration of the mechanical and / or chemical properties of glass or glass-ceramics by etching, but no known studies have been conducted on structured glass wafers for use as interposers.

[0013] Therefore, there is a need in general for glass wafers that have improved mechanical strength while at the same time being made to be well coatable, particularly so that metallization will adhere well.

[0014] Problem to be solved by the invention It is an object of the present invention to provide a glass wafer which at least partially alleviates the drawbacks of the prior art. A further object is to provide a method for producing such a glass wafer.

[0015] Summary of the Invention This problem is solved by the subject matter of the independent claims. Preferred specific configurations can be found in the dependent claims, the description and the drawings of the present disclosure.

[0016] Thus, the present invention relates to a glass wafer, comprising at least one opening having a surface with two opposing side surfaces and an annular edge. The glass contained in the glass substrate comprises at least one network former and at least one metal oxide. The at least one opening has a maximum lateral dimension, particularly a diameter, of at most 400 μm, preferably at most 300 μm, particularly preferably at most 200 μm. Preferably, the maximum lateral boundary is at least 10 μm. The glass wafer has a thickness of at least 10 μm. Advantageously, the thickness of the wafer is limited to a maximum of 5 mm. A preferred lower limit for the wafer thickness is at least 30 μm, for example 50 μm or 100 μm. A preferred upper limit may be 3 mm or 1.5 mm, or even only 1 mm.

[0017] To achieve advantageous strength of the glass wafer, it is possible to envision that the thickness and maximum lateral dimension of the glass wafer are interrelated, and this aspect ratio between the maximum lateral dimension of the opening (e.g., the diameter of the opening) and the thickness of the glass wafer is preferably at least 1:100.

[0018] The leaching depth of the metal ions, in particular alkali metal ions, in particular lithium ions, sodium ions and / or potassium ions, is at least 1.1 times greater, preferably 1.5 times greater, particularly preferably 2 times greater, more preferably 5 times greater, very particularly preferably 10 times greater, at the surface of at least one opening than the leaching depth on both sides, preferably the leaching depth is at most 15 times greater than on both sides, this being preferably determined by ToF-SIMS measurements.

[0019] Preferably, the glass substrate comprises glass containing 30% to 75% by weight of SiO2, preferably up to 65% by weight of SiO2.

[0020] Such an arrangement has many advantages.

[0021] A glass wafer is generally designed to include a glass substrate. A glass substrate is understood to be a glass formed body that has not yet undergone a finishing step, such as coating, and / or further processing step, as well as shaping, such as cutting. Therefore, a wafer can generally be understood to be a finished substrate. In this sense, the sides and faces of a substrate and a wafer correspond to each other within the scope of the present disclosure. Therefore, when referring to the side face of a glass wafer or the edge face of a wafer, this also corresponds to the side face or edge face of a glass substrate.

[0022] In this case, the glass wafer or glass substrate is generally formed in the shape of a disk or plate, and therefore the thickness of the glass wafer or glass substrate is its smallest lateral dimension, in particular less than its length and width, or in the case of a circular wafer / substrate, its diameter.

[0023] The glass wafer has at least one opening, which has a maximum lateral dimension of at most 400 μm, preferably at most 300 μm, particularly preferably at most 200 μm, and may be made significantly smaller depending on the exact design. The opening can also generally be referred to as a "via."

[0024] The glass contained in the glass substrate and correspondingly the glass wafer is not a single-component glass and accordingly contains not only network formers but also generally, in particular metal oxides.

[0025] This is advantageous, since, unlike quartz glass, a simple and cost-effective production of the wafers by conventional melting methods is thus also possible.

[0026] At the surface of at least one opening, the leaching depth of metal ions, in particular alkali metal ions, in particular lithium ions, sodium ions and / or potassium ions, is at least 1.1 times greater, preferably 1.5 times greater, particularly preferably 2 times greater, more preferably 5 times greater, very particularly preferably 10 times greater, than the leaching depth on both sides, preferably the leaching depth is at most 15 times greater than on both sides.

[0027] This surprising configuration of the glass wafer according to the embodiment is very advantageous, since it has been found that it is possible to decisively improve the properties of the glass wafer in this way, in particular, it is surprisingly possible to improve the mechanical strength of the glass wafer, thereby improving its handling properties and its service life.

[0028] The reason for this is not entirely clear. For example, as mentioned above, it is known that ion exchange can increase the mechanical strength of glass, so-called chemical strengthening. However, in this case, ion exchange is not performed, but etching is performed. In this case, on the one hand, the glass is removed as a whole, but the dissolution of the glass network does not occur uniformly, so that certain ions, especially metal ions, are also dissolved from the glass network. In other words, in the surface region, the glass network remains together with the network former, but with a certain reduction in metal ions.

[0029] Surprisingly, it has not only been shown that this can be advantageous for the properties of the glass wafer, for example, with respect to subsequent adhesion on a metallization applied to the glass wafer or with respect to the strength obtained. Moreover, it has been shown that the percolation on the side surfaces is different from the percolation on the surface of at least one opening. In particular, it has been shown that the percolation depth at the penetration is at least 1.1 times greater than the percolation depth on both sides, preferably 1.5 times greater, particularly preferably 2 times greater, more preferably 5 times greater, very particularly preferably 10 times greater, and preferably the percolation depth is up to 15 times greater than on both sides of the wafer.

[0030] The reasons for this are not fully understood, however, the inventors believe that this is due to the particular implementation of the etch, whereby within the narrow opening, other concentration gradients result in the formation of this strong leachate compared to the leachate at the surface of the wafer.

[0031] The percolation depth and its different formation on the side of the wafer compared to the surface of the opening can be determined in particular by ToF-SIMS measurements.

[0032] This is particularly advantageous in the case of alkali-containing glasses, where alkali leaching occurs. For example, when using KOH-containing alkali solutions, sodium ions are preferably leached, and as mentioned above, this leaching has been shown to be different on the side and on the surface of the via. At the same time, in this case, a concentration of potassium ions can be seen on the surface of the wafer (see also Figures 8 to 11).

[0033] The inventors suspect a corresponding effect during leaching of lithium-containing glasses with KOH- and / or NaOH-containing alkaline solutions. Substituting glasses containing alkaline earth metal ions instead of or in addition to alkali ions may also produce a corresponding leaching pattern.

[0034] According to one embodiment, the glass substrate comprises glass containing 30-85% by weight of SiO2. A preferred range for the SiO2 content may be 60-84% by weight. Such glass has been found to be particularly advantageously suitable for forming glass wafers according to embodiments.

[0035] According to a further embodiment, the glass wafer is formed such that the breaking strength of the glass wafer is at least 400 MPa, preferably at most 650 MPa, and / or the Weibull modulus of the glass wafer is between 4.2 and 7.1.

[0036] In other words, according to this embodiment of the wafer, the wafer is designed to be particularly resistant to breakage.

[0037] According to a preferred embodiment, the glass comprises the following components in weight percent on an oxide basis: B2O3 5-25, preferably 8-25 Al2O3 0-25, preferably 0-10 Includes:

[0038] According to another further aspect, the glass wafer has a roughness of at least one surface, in particular at least one of the two sides, of at most 1000 nm. Preferably, the roughness may be less than 100 nm or even less than 10 nm. According to one embodiment, the roughness is at most 1 nm or even less.

[0039] The glasses listed below have been found to be particularly suitable for the manufacturing method involving laser irradiation, formation, filamentary damage, and subsequent etching with integration of widened channels along the filamentary damage.

[0040] According to a first embodiment, the composition comprises the following components in weight percent based on oxides: [Table 1] Includes:

[0041] The following ranges in weight percent based on oxide: [Table 2] is advantageous.

[0042] Further advantageous embodiments are those containing, in weight percent based on oxides: [Table 3] Includes:

[0043] Another further advantageous embodiment is one comprising the following in weight percent based on oxide: [Table 4] Includes:

[0044] Another further advantageous embodiment is one comprising the following in weight percent based on oxide: [Table 5] Includes:

[0045] Further advantageous embodiments of the same are those in weight percent based on oxides: [Table 6] Includes:

[0046] It can be said that for all the aforementioned glass compositions, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, CuO, Cr2O3, etc. can be added in some cases. 0-2 wt.% of As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 can be added as refining agents, and the total amount of each of the total compositions is 100 wt.%.

[0047] According to a further advantageous embodiment, the glass comprises the following components in % by weight, based on oxides: SiO2 30-75, preferably 30-65 B2O3 6-25, preferably 6-10.5 Al2O31~15 Na2O 1 to 15, preferably 3 to 15 K2O 0.5 to 15, preferably 3 to 15 ZnO 0-12 TiO20-10, preferably 0.5-10 CaO 0~0.1 Includes:

[0048] According to a further advantageous embodiment, the glass comprises the following components in % by weight, based on oxides: SiO258~65 B2O36~10.5 Al2O314~25 MgO 0-3 CaO 0-9 BaO 3-8 ZnO 0-2 Includes:

[0049] In general, it can be said to be advantageous that the total content of MgO, CaO and BaO is in the range of 0 to 18% by weight, or 0 to 10% by weight, or 0 to 4% by weight.

[0050] It has proven particularly advantageous for all embodiments if the total alkali content is limited, which means that the sum of Li2O+Na2O+K2O is advantageously less than 15% by weight, particularly advantageously less than 5% by weight.

[0051] The preferred content of Na2O for all embodiments is 0 to 8% by weight, in particular 1 to 5% by weight. The preferred content of K2O for all embodiments is 0 to 8% by weight, in particular 0 to 3% by weight.

[0052] Although this applies to all embodiments, it has been observed to be particularly advantageous if the LiO content is less than the NaO and / or KO content. This means that LiO / NaO<1 and / or LiO / KO<1. The glasses mentioned herein are particularly advantageously LiO-free. Of course, unavoidable impurities, which may typically range up to 5 ppm, may also be present.

[0053] Surprisingly, it has been found that wafers according to embodiments of the present disclosure are particularly well suited for connection technologies, in particular for providing very high data rates, for which rather small vias are particularly required. Furthermore, it has been found that the selective leaching of metal ions, in particular alkali ions, results in particularly good adhesion of the metallization to the wafer, especially also in the region of the vias or through-openings themselves.

[0054] Metallizations comprising or consisting of Ni, Cr, Ti, Pd, etc., which may also function as adhesion promoters between the glass substrate or wafer and further layers, e.g., further metal layers, can be applied, for example, without electricity (electroless plating) or galvanically.

[0055] According to preferred embodiments, the metallization comprises copper, silver, gold, or aluminum. The copper-containing layer may be applied directly to the glass wafer or to an adhesion-promoting layer comprising or consisting of Ni, Cr, Ti, Pd, etc., applied between the glass wafer and the copper-containing layer. According to further embodiments, the metallization may consist mainly, i.e., more than 50% by weight, or substantially, i.e., more than 90% by weight, or entirely of copper.

[0056] The excellent adhesion of the metallization can be demonstrated, for example, by a scratch test on the surface of the metallized wafer, as will be explained in more detail below. A further method is the "Tesa test", in which an adhesive strip is applied to a sample and the force required to peel the adhesive strip together with the coating is measured.

[0057] The present invention also relates to a method.

[0058] A method for manufacturing a glass wafer, particularly a glass wafer according to an embodiment of the present disclosure, comprising: a glass substrate including at least one opening, the glass substrate having two opposing side surfaces and an annular edge surface; - providing a disk-shaped glass substrate; - directing a laser beam of an ultrashort pulse laser at one of the side surfaces of the disk-shaped glass substrate, the laser beam being shaped by a focusing optical system to form an elongated focus within the disk-shaped glass substrate, so that irradiation energy of the laser beam generates a filament-like damage within the volume of the disk-shaped glass substrate, the longitudinal direction of which is perpendicular to at least one of the side surfaces of the disk-shaped glass substrate, and the ultrashort pulse laser emitting pulses or pulse packets having at least two consecutive laser pulses to generate the filament-like damage; - etching the disk-shaped glass substrate in a liquid etching medium at least in the areas where filamentary damage is formed in the disk-shaped glass substrate, the filamentary damage widening to form channels, the liquid etching medium being or comprising an alkaline liquid, preferably a potassium-containing alkaline liquid. Includes:

[0059] The inventors have found that such a procedure, particularly using alkaline etching, is particularly advantageous.

[0060] That is, it has been found that the metallization applied to the wafer is better preserved when etching with an alkaline solution compared to etching with an acid.

[0061] That is, the alkaline etching treatment is believed to result in fewer metal ions overall, and fewer alkali and / or alkaline earth ions in particular, being leached from the glass network, which is believed to result in better adhesion of the metallization on the glass, and the inventors suspect that this is due to a diffusion process from the glass to the metallization.

[0062] As already mentioned above, it has been found that in this way it is possible to obtain glass wafers in which the exudation at the openings differs significantly from the exudation at the surface of the glass wafer, ie in particular on both side surfaces.

[0063] In particular, the percolation depth at the opening is greater than the percolation depth on the surface.

[0064] In other words, it appears that there is stronger leaching in the openings than on the surface of the glass wafer, however, it was found that very good contact of the metallization on the glass surface is still possible in the openings.

[0065] Etching with a potassium-containing alkali, preferably an aqueous potassium-containing alkali, is considered particularly advantageous here, i.e., a particularly advantageous leaching profile is thus prepared, which can prove advantageous in subsequent processing steps in the manufacture of interposers. Particular attention should be paid here to the good adhesion of the metallization on the etched glass surface.

[0066] Preferably, etching can be carried out at a temperature of at least 110°C, for example 115°C or 120°C, ie with an etching medium having a temperature of at least 110°C, preferably at least 115°C, preferably at most 150°C.

[0067] In this way, it is believed that the special surface structure of the glass wafer can be obtained particularly easily.

[0068] Surprisingly, it has been found that changing other parameters of the method operation is not necessarily necessary to achieve the advantageous properties of the glass wafer. In particular, to improve the strength of the glass wafer compared to, for example, prior art glass wafers, it is not necessary to adapt the laser parameters for creating the filaments required to subsequently obtain corresponding openings in the glass wafer. Rather, surprisingly, it appears that adapting the etching parameters, i.e., in particular the temperature of the etching bath, is sufficient to achieve the improved properties.

[0069] According to one embodiment, the glass material of the disk-shaped glass substrate is removed at a removal rate of less than 5 μm per hour. This is considered advantageous because it is believed that a different surface structure is formed than in the case of a higher removal rate. In particular, this is considered to result in selective removal of the glass substrate, which is considered advantageous in terms of the mechanical properties of the resulting glass wafer. The slower removal is also considered advantageous in terms of the resulting adhesive strength. The inventors believe that this results in more selective removal, resulting in a correspondingly more favorable surface structure, and that the leaching of certain substances, especially metal ions, may be less severe. The inventors believe that this may potentially result in a kind of "strengthening effect," or that the glass structure is not weakened as much as in the case of a strong, rapid, full-surface removal, which is advantageous for the subsequent handling of the glass wafer.

[0070] According to one embodiment, the etching time is at least 12 hours. Even slower or longer etching processes can result in an advantageous increase in the mechanical stability of the resulting glass wafer.

[0071] According to one embodiment, the number of pulses in the burst for introducing the filamentary lesion is at least 2 or at most 7.

[0072] However, it is also possible, and in some cases preferable, to generate filamentary damage with only a single laser pulse rather than in the form of a pulse packet.

[0073] According to another further embodiment, the pulse duration of the laser is in the range of 0.5 ps to 2 ps.

[0074] According to another embodiment, mechanical polishing of at least one surface is carried out. This is particularly advantageous for achieving a low roughness and can also contribute to an even greater increase in the mechanical strength of the glass wafer. Particularly preferably, polishing is carried out after etching.

[0075] The invention will be explained in more detail below on the basis of the drawings. [Brief explanation of the drawings]

[0076] [Figure 1] FIG. 1 is a perspective view of a glass wafer according to one embodiment. [Figure 2] FIG. 1 is a cross-sectional view of a glass wafer according to one embodiment. [Figure 3] FIG. 1 is a schematic diagram of a method for manufacturing a glass wafer according to one embodiment. [Figure 4] FIG. 1 is a diagram of the probability of breakage of various glass wafers. [Figure 5] FIG. 1 is a diagram of the probability of breakage of various glass wafers. [Figure 6] 10 is a ToF-SIMS profile showing different leaching of a glass wafer depending on the etching medium. [Figure 7] 10 is a ToF-SIMS profile showing different leaching of a glass wafer depending on the etching medium. [Figure 8] 10 is a ToF-SIMS profile showing different surface structures within an aperture and on the side of a glass wafer according to an embodiment. [Figure 9] 10 is a ToF-SIMS profile showing different surface structures within an aperture and on the side of a glass wafer according to an embodiment. [Figure 10] 10 is a ToF-SIMS profile showing different surface structures within an aperture and on the side of a glass wafer according to an embodiment. [Figure 11] 10 is a ToF-SIMS profile showing different surface structures within an aperture and on the side of a glass wafer according to an embodiment. [Figure 12]10. ToF-SIMS profiles of differently pretreated and metallized glass wafers. [Figure 13] 10. ToF-SIMS profiles of differently pretreated and metallized glass wafers. [Figure 14] 10. ToF-SIMS profiles of differently pretreated and metallized glass wafers. [Figure 15] 10. ToF-SIMS profiles of differently pretreated and metallized glass wafers. [Figure 16] FIG. 1 is a diagram of a scratch mark on a metallized glass wafer. [Figure 17] FIG. 1 is a diagram of a scratch mark on a metallized glass wafer.

[0077] FIG. 1 shows a schematic, not-to-scale, perspective view of a glass wafer 1 according to one embodiment. The glass wafer 1 includes a glass substrate (not shown) containing at least one opening 7, which may also be referred to as a "via" within the scope of this disclosure. The glass substrate, or equivalently, the glass wafer 1, includes two opposing side surfaces 3, 5. The glass wafer 1, or equivalently, the glass substrate, includes a glass containing at least one network former, preferably SiO2, and at least one metal oxide. This glass is therefore also formed as a multicomponent glass, which offers significant advantages over, for example, pure quartz glass. In particular, the glass can therefore be used for manufacturing and forming processes in conventional melting processes.

[0078] FIG. 2 shows a cross-sectional view of a glass wafer 1 according to one embodiment. Two openings 7 are shown in cross section, visible as holes 71 and 72 on the respective side surfaces 3 and 5 of the glass wafer 1. Also shown is a depletion region 9 resulting from the etching process. This is divided into two regions: a region 91 with only a small depletion or leaching depth, formed on both side surfaces 3 and 5 of the glass wafer 1, and a region 92 within the opening 7 with a significantly larger leaching depth. The leaching depth, particularly for metal ions in the region of the opening 7, is at least 1.1 times greater, preferably 1.5 times greater, particularly preferably 2 times greater, more particularly preferably 5 times greater, and very particularly preferably 10 times greater; preferably, the leaching depth is 15 times greater than on both side surfaces 3 and 5 of the glass wafer 1. This can be determined preferably by ToF-SIMS measurements.

[0079] 3 shows, in a schematic, not-to-scale view, an exemplary method for producing a glass wafer 1 (not shown here). For this purpose, a glass substrate 2 is provided. Side surfaces 3, 5 of the glass substrate 2 correspond to the side surfaces of the subsequent glass wafer 1.

[0080] A laser beam 13 is generated by an ultrashort pulse laser 11, and this laser beam 13 is directed onto a glass substrate 2. A focusing optical system 15 shapes an elongated focus 17 within the disk-shaped glass substrate 2, so that the irradiation energy of the laser beam 13 generates a filament-like damage 19 within the volume of the disk-shaped glass substrate 2, the longitudinal direction of which is perpendicular to the surface of the glass substrate 2 or at least one of both side surfaces 3 and 5 of the glass substrate 2.

[0081] This process can then be repeated at other locations on the glass substrate. In a further method step, openings are created from the filamentary damage 19, which serve as interlayer connections in the interposer.

[0082] FIG. 4 shows a diagram of the strength of glass wafers depending on the etching medium used or the glass substrate subjected to other pretreatments. All measurement data was obtained without drilling any openings in the wafer or substrate in question. As is customary when illustrating the strength of materials that undergo brittle fracture, the points are plotted in a double logarithmic Weibull diagram. This also applies to FIG. 5 accordingly.

[0083] Measurement point a) (solid point) is the break probability of a glass substrate that has not been etched or otherwise pretreated and therefore represents a benchmark for the break probability. Point b) (solid triangle) represents the break probability determined for a glass wafer etched with KOH. Point c) (open square with its apex below) is the break probability for a wafer etched with HF. Finally, point d) (square with a cross inside) shows the break probability for a polished wafer.

[0084] There is a significant difference here, as shown by the fracture probability as a function of the stress acting on the substrate or wafer. Thus, the KOH-etched wafers show improved mechanical stability even compared to unetched substrates, and especially compared to the HF-etched samples.

[0085] This is particularly true when the temperature of the etching bath, i.e., the alkali solution used, for example, the KOH-containing alkali solution, is adjusted to at least 110°C, preferably at least 115°C, for example, 120°C. As mentioned above, it has been found that the glass break probability can be significantly influenced by the choice of etching medium and also by its temperature. This can also be shown for the structured substrate, i.e., the resulting glass wafer.

[0086] FIG. 5 shows the fracture probability as a function of the stress acting on the wafer for two different types of wafer. Here, a) (open circles) shows fracture probability data for a glass wafer, obtained for a wafer 1 mm thick with openings 50 μm in diameter. Etching was performed with HF. Point b) (open triangles with their apex pointing downwards) serves as a contrast, showing the fracture probability for a wafer 1 mm thick, etched with KOH, with openings 10 μm in diameter.

[0087] The characteristic strength σ for these samples c and Weibull coefficients are given in the table below: [Table 7] The results are summarized in Table 1, with confidence intervals in parentheses.

[0088] The characteristic strength and the Weibull modulus are two parameters of the Weibull distribution. The strength of brittle materials is usually described by the Weibull distribution. The characteristic strength is one of the two parameters that define the distribution.

[0089] As can be seen from these data, the characteristic strength and Weibull modulus data depend on the etching method, whereby glass wafers etched with an alkaline solution, here KOH, have higher strength.

[0090] Here, it can be shown that samples etched with HF show a significantly increased leaching and loss of metal ions, especially alkali metal ions such as sodium and potassium ions, compared to etching with an alkaline solution such as KOH.

[0091] This is exemplarily illustrated in Figures 6 and 7, which show the ToF-SIMS profiles of glass wafers etched with HF (filled circles) or KOH (open circles), respectively, where it is clearly seen that the sample etched with KOH shows a less intense depletion of metal ions, here sodium and potassium ions, than the glass wafer etched with HF.

[0092] The inventors speculate that this smaller reduction in the surface area of the glass wafer is responsible for the observed strength improvement. In general, for glass, it is believed that reducing the sodium in the surface area increases crack propagation within the glass. The sodium-depleted surface layer has a lower density compared to non-sodium-depleted glass, which should lead to the formation of tensile stresses at the surface. This, in turn, should increase the probability of crack formation and crack growth, ultimately leading to fracture failure.

[0093] Similarly, while all etching methods inherently result in the leaching and depletion of metal ions, such as sodium ions, in the case of structured substrates or wafers containing openings, the precise formation of this depletion zone is believed to be important. The inventors speculate that this may be relevant to laser structuring methods, since laser processing initially induces microcracks in the substrate / wafer. However, here, etching initially acts rather advantageously, since the etching and associated material removal first remove such microcracks and initially suppress further crack propagation. However, as observed and described, HF or acid etching clearly results in significantly stronger metal ion depletion, thereby somewhat reducing this advantageous effect. Here, alkaline etching has the advantage that metal ions, especially sodium, do not leach as strongly, thereby better assisting in minimizing crack propagation. The inventors speculate that the relationship of reduced sodium resulting in increased fracture probability, which applies to glass in general, applies not only to sodium but also to metal ions in general, and therefore that the overall improvement in mechanical strength of structured glass wafers compared to prior art wafers can be attributed to an overall reduction in leaching compared to known wafers.

[0094] The inventors speculate that this may be due to an acid etching mechanism, such as with HF, which initially involves the adsorption of fluorine anions on the glass surface, followed by the leaching of metal ions, particularly alkali and / or alkaline earth ions, so that a porous layer develops on the glass surface, followed by the rapid breaking of Si-O-Si or XO-Si bonds (where X represents a further network former, e.g., aluminum or boron).

[0095] In contrast, the inventors speculate that alkaline etching results in more uniform removal, whereby bonds are not as severely weakened by the network former. Thus, the surface chemistry of the glass is left more intact than with etching with an acid such as HF. This has the advantage of being a faster process, but clearly has significant drawbacks with respect to the resulting product, such as reduced mechanical strength.

[0096] Interestingly, this lower surface leaching also proved to be an advantage when considering subsequent processing steps, allowing for better adhesion on the glass wafer, possibly due to interdiffusion of metal ions in the subsequently applied metallization.

[0097] The difference in leaching depth between the side and the surface at the opening is noted in Figures 8-11. Here, the ToF-SIMS profiles of metal ions can be seen, respectively: in Figures 8 and 9, the ToF-SIMS profile of sodium ions, and in Figures 10 and 11, the ToF-SIMS profile of potassium ions. In the case of sodium ions, it is clearly recognizable that leaching is stronger inside the opening (Figure 9) than at the side (Figure 8) during leaching with an alkaline solution containing KOH. Figures 10 (side) and 11 (inside the opening) show the enrichment of potassium ions in the near-surface region.

[0098] 12-17 illustrate the differences between glass wafers of the prior art with glass wafers corresponding to embodiments of the present disclosure, where the glass wafers were each metallized, since this most clearly shows the differences in the glass wafers and the type of pretreatment that corresponds to the application.

[0099] The metallized glass wafers are illustratively glass wafers obtained by a conventional method, here etching with HF, and by the method described in this disclosure. Each was metallized at 100°C, first applying a chromium layer, then a titanium layer, and then a copper metallization. The deposition temperature was 100°C. Adhesion strength can generally be improved at higher deposition temperatures, so the beneficial effects of etching are preferably demonstrated at this lower temperature. However, metallization deposition temperatures of up to 400°C or higher are generally possible.

[0100] 12 and 13 show ToF-SIMS profiles for a wafer metallized at 100°C with chromium as an adhesion-promoting layer between the glass and copper. As can be seen, the sodium (FIG. 12) and potassium (FIG. 13) levels in the glass, i.e., in the bulk region of the metallized glass wafer, are identical. However, there are differences in the sodium or potassium content (illustrated in the signal of the single positively charged sodium or potassium ion, respectively). The sodium or potassium levels are higher in the copper metallization region after etching with KOH than after etching with HF. We speculate that this is due to less leaching of the glass surface by the KOH treatment, allowing the corresponding metal ions to diffuse more quickly into the metallization, thus resulting in better overall adhesion. Because this effect of leaching depth is even more pronounced at the surface of the opening, we believe that the metallization within the opening itself adheres even better than if it were already adhered in the side regions of the wafer.

[0101] Corresponding diagrams are shown for the use of an adhesion-promoting titanium layer between the glass surface and the copper layer in Figures 14 and 15. Again, the sodium (Figure 14) and potassium (Figure 15) levels in the glass, i.e., in the bulk region of the metallized glass wafer, are identical. However, there are similar differences in the sodium or potassium content (illustrated in the signal of the single positively charged ion of sodium or potassium, respectively). The sodium or potassium levels are higher in the copper metallization region after etching with KOH than after etching with HF. The inventors speculate that this is due to the fact that the glass surface is less leached by the KOH treatment, allowing the corresponding metal ions to diffuse more quickly into the metallization, thus resulting in better adhesion overall. Because this effect of leaching depth is even more pronounced at the surface of the opening, the inventors believe that the metallization within the opening itself adheres even better than if it were already adhered in the side region of the wafer.

[0102] Finally, Figures 16 and 17 show images of scratch marks on variously etched and subsequently metallized glass wafers. Titanium was used as the adhesion-promoting layer.

[0103] The scratch resistance of metallizations is generally determined by the Knoop scratch test, a standard procedure for determining the scratch resistance and simultaneously the adhesive strength of metallizations in the coating and metallization industries. Such a test involves applying a diamond tip to the surface of the coating to be tested and moving the tip at a constant speed along a certain distance. The force acting on the tip can be constant or continuously increased along the test section. In the case of the samples depicted in Figures 16 and 17, the force was continuously increased along the test section. The corresponding forces are shown in the respective figures. The load at which the layer fails is recorded. Layer failure is characterized by the appearance of initial cracks in the layer next to the scratch itself. These cracks can often lead to beach marks or even delamination over time. The load at which failure due to crack formation occurs is determined by visual inspection under a microscope. This load is also referred to as the "critical load" (LC).

[0104] In Figure 16, a metallization is shown in which a glass wafer was etched with KOH. Afterwards, an adhesion-promoting titanium layer was applied, followed by a copper layer. The temperature during metallization was 100°C, since this represents a more critical case, as already explained above.

[0105] The illustration in Figure 16 is as follows: - 0.03N and 1N (5mm) no delamination (a,b) - 1N and 2N (5mm) no delamination (c,d) - 2N and 3N (5mm) no delamination (e,f) - 3N and 4N (5mm) no delamination (g,h) Shows.

[0106] In comparison, Figure 17 shows scratch marks on a metallized glass wafer similar to that of Figure 16, but where the etching of the glass wafer was performed with HF. - 0.03N and 1N (5mm) no delamination (a,b) - 1N and 2N (5mm) no delamination (c,d) - 2N and 3N (5mm) - Delamination (e,f) in one of two measurements after the critical force of approximately 2.9N - 3N and 4N (5mm) Delamination in one of two measurements after the critical force of 3N (g, h) Shows.

[0107] That is, as noted, adhesion of the metallization is better for glass wafers according to embodiments etched by basic etching. [Explanation of symbols]

[0108] 1 glass wafer 2. Glass substrate 3,5 1 aspect 7 aperture 71,72 Holes on the side 9 Depletion region 91 Area of 9 on side 3 or 5 92 Area 9 in Aperture 7 11 Ultrashort pulse laser 13 Laser beam 15 Condensing optical system 17 focus 19 Filamentous lesions

Claims

1. a glass wafer comprising a glass substrate including at least one opening having a surface with two opposing side surfaces and an annular edge surface, the glass substrate comprising glass including a network former and at least one metal oxide; the at least one opening has a maximum lateral dimension, in particular a diameter, of at most 400 μm, preferably at most 300 μm, particularly preferably at most 200 μm; the glass wafer has a thickness of at least 10 μm; the leaching depth of alkali metal ions, in particular lithium ions and / or sodium ions, at the surface of the at least one opening, preferably determined by ToF-SIMS measurements, is at least 1.1 times greater, preferably 1.5 times greater, particularly preferably 2 times greater, more preferably 5 times greater, very particularly preferably 10 times greater, than the leaching depth on both side surfaces, preferably the leaching depth is at most 15 times greater than on both side surfaces, Preferably, the glass substrate contains 30% to 85% by weight of SiO ２ , preferably 60 to 84% by weight of SiO ２ Glass containing Glass wafer.

2. a glass wafer comprising a glass substrate including at least one opening having a surface with two opposing side surfaces and an annular edge surface, the glass substrate comprising glass including a network former and at least one metal oxide; the at least one opening has a maximum lateral dimension, in particular a diameter, of at most 400 μm, preferably at most 300 μm, particularly preferably at most 200 μm; the glass wafer has a thickness of at least 10 μm; the leaching depth of metal ions, in particular alkali metal ions, in particular potassium ions and / or sodium ions, at the surface of the at least one opening, preferably determined by ToF-SIMS measurements, is at least 1.1 times greater, preferably 1.5 times greater, particularly preferably 2 times greater, more preferably 5 times greater, very particularly preferably 10 times greater, than the leaching depth on both side surfaces, preferably the leaching depth is at most 15 times greater than on both side surfaces, Preferably, the glass wafer has a characteristic strength of at least 400 MPa, preferably at most 650 MPa; and / or The Weibull coefficient of the glass wafer is 4.2 to 7.

1. In particular, a glass wafer according to claim 1.

3. The glass comprises the following components in weight percent on an oxide basis: B ２ O ３ 5 to 25, preferably 8 to 25 Al ２ O ３ 0 to 25, preferably 0 to 10 3. The glass wafer of claim 1, comprising:

4. 4. The glass wafer according to claim 1, wherein the glass wafer has, on at least one surface, in particular on at least one of the two side surfaces, a roughness of at most 1000 nm, preferably less than 100 nm or even less than 10 nm, in particular a roughness of at most 1 nm or even less.

5. The glass comprises the following components in weight percent on an oxide basis: 【Table 1】 Including, Preferably, Li ２ O + Na ２ O+K ２ O is 0 to less than 15% by weight, and particularly preferably Li ２ O / Na ２ O<1 and / or Li ２ O / K ２ 5. The glass wafer according to claim 1, wherein O<1.

6. The glass comprises the following components in weight percent on an oxide basis: 【Table 2】 6. The glass wafer of claim 1, comprising:

7. 7. The glass wafer according to claim 1, comprising a metallization in at least one region of at least one side surface and / or in at least one region of the surface of the opening.

8. 10. A method for producing a glass wafer, in particular a glass wafer according to any one of claims 1 to 6, comprising a glass substrate having at least one opening, the glass substrate having two mutually opposing side surfaces and an annular edge surface, the method comprising: - providing a disk-shaped glass substrate; - directing a laser beam of an ultrashort pulse laser at one of the side surfaces of the disk-shaped glass substrate, the laser beam being shaped by a focusing optical system to form an elongated focus within the disk-shaped glass substrate, so that irradiation energy of the laser beam generates a filament-like damage within the volume of the disk-shaped glass substrate, the longitudinal direction of which is perpendicular to at least one of the side surfaces of the disk-shaped glass substrate, and the ultrashort pulse laser emitting pulses or pulse packets having at least two consecutive laser pulses to generate the filament-like damage; - etching the disk-shaped glass substrate in a liquid etching medium at least in the areas where filamentary damage is formed in the disk-shaped glass substrate, the filamentary damage widening to form channels, the liquid etching medium being or comprising an alkaline liquid, preferably a potassium-containing alkaline liquid. A method comprising:

9. Features include: the glassy material of the disk-shaped glass substrate is removed at a removal rate of less than 5 μm per hour, and / or the etching time is at least 12 hours, and / or said etching medium has a temperature of at least 110°C, preferably at most 150°C, and / or the number of pulses in the burst for inducing filamentary lesions is at least 2 or at most 7, and / or the pulse duration of said laser is in the range of 0.5 ps to 2 ps; - mechanical polishing of at least one surface is carried out; 9. The method of claim 8, characterized by at least one of:

10. A glass wafer produced or producible by a method according to claim 8 or 9, preferably a glass wafer according to any one of claims 1 to 7.

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