HERMETICALLY SEALED ENCLOSURE AND METHOD FOR MAKING THEM

Description

Field of invention

[0001] The present invention relates to a hermetically sealed enclosure, a substrate arrangement and a method for providing a hermetically sealed enclosure. Background and general description of the invention

[0002] Hermetically sealed enclosures are designed, for example, to protect a component or components inside the enclosure from adverse environmental conditions. This allows for the protection of sensitive electronics, circuits, or sensors located within the enclosure. In this way, sensors or medical implants, such as those used in the heart, retina, or for bioprocessors, can be manufactured and deployed. These can also be used, for example, as MEMS (microelectromechanical systems), barometers, blood gas sensors, glucose sensors, etc. Bioprocessors made of titanium are known to exist.

[0003] Further fields of application for an enclosure according to the invention can also be found in electronics applications, such as a case for a smartphone, in the field of virtual reality glasses and similar devices. An enclosure according to the invention can also be used for the production of flow cells, for example in the context of electromobility. But enclosures according to the invention can also be used in aerospace, in high-temperature applications, as well as in the field of micro-optics.

[0004] Since the aforementioned requirements for protecting the electronics housed within must be met by the enclosure, certain application areas are currently excluded from the use of an enclosure according to the invention. These include applications requiring a particularly thin enclosure or at least a thin side of the enclosure. Examples include fingerprint sensors, variable-focus contact lenses, pressure sensors for internal use, such as those measuring intracranial pressure, and ultra-thin enclosures for image sensors. Even in these applications, it can be advantageous to protect the electronics against adverse environmental influences. Optical communication with the interior of the enclosure can be advantageously ensured in this regard. For this purpose, the enclosure can be at least partially—i.e.,The cavity must be transparent, at least in certain areas and / or for a specific wavelength range. This transparency allows, for example, communication methods, data or energy transmission, and measurements by and with the electronics or sensors located within the cavity. In particular, optical communication methods, optical data transmission, or energy transmission may be enabled.

[0005] However, it is complicated, or even impossible, to use a thin substrate as is and mount it onto an enclosure. Thin substrates tend to warp when bonded with other substrate layers. The physical properties, such as the thermal conductivity of the thin substrate, can also change in the process. Furthermore, thin substrates can exhibit high internal stresses, making them unsuitable for enclosure fabrication. Laser joining processes cannot be used with thin substrates because, for example, material is burned or removed if the laser is aimed too close to the surface of the thin substrate. Therefore, it is difficult or even impossible to use thin substrates to create an enclosure that is both highly hermetically sealed and / or can be joined without additional bonding materials.

[0006] It is generally known to join several parts together and arrange them in such a way that a receiving area is created in the space between them, in which components can be housed. For example, European Patent EP 3 012 059 B1 discloses a method for manufacturing a transparent part for protecting an optical component. A novel laser process is used in this method.

[0007] European patent application EP 2 219 215 A1 relates to a semiconductor device and a method for its fabrication. In this process, a transparent substrate and a second substrate are joined together, with a functional element arranged on the second substrate. However, a thin transparent substrate is not used, nor is a laser process employed.

[0008] The present invention can be seen as improving known enclosures and, in particular, improving communication with the interior of the enclosure. Specifically, the optical communication with the interior of the enclosure or a sensitivity, such as pressure sensitivity, to the external environment of the enclosure is to be improved. Optionally, the enclosure according to the invention allows the use of more cost-effective components and / or more sensitive measurement of environmental data. The enclosures of the present invention are as reliable and durable as known enclosures.

[0009] A hermetically sealed enclosure according to the invention comprises at least one planar covering substrate, wherein the covering substrate has an outer flat side and a circumferential narrow side. In other words, the covering substrate has an outer surface oriented towards the environment, which is essentially planar or flat. Adjacent to the outer flat side and typically oriented at a right angle to the outer flat side, for example, extending around the edge of the outer flat side, is a circumferential narrow side. In one example, the covering substrate can be described as a plate or cuboid, having two large surfaces and four smaller surfaces arranged between the large surfaces, which are in particular perpendicular to and adjacent to the two large surfaces.The four smaller sides then together form the circumferential narrow side, and the top side forms the outer flat side of the covering substrate. The top side typically has a larger surface area than the smaller sides of the circumferential narrow side combined.

[0010] The hermetically sealed enclosure further comprises a second substrate arranged adjacent to the covering substrate and in direct contact with the covering substrate, which covers an area. The second substrate, together with the covering substrate, forms at least part of the enclosure. Preferably, the two substrates are arranged one above the other, i.e., stacked. For example, the substrates together form a substrate stack. The orientation above or below is merely descriptive, as the substrates can, of course, assume any orientation in space, and even a side-by-side arrangement should not leave the protected area. The two substrates are typically arranged with a larger side of their dimensions abutting each other.

[0011] The enclosure also includes a functional area enclosed within it, which is located, in particular, between the covering substrate and the second substrate. This functional area is, for example, a cavity or an active layer.

[0012] Furthermore, the housing features a laser bonding line by means of which the cover substrate is directly and hermetically bonded to the substrate located adjacent to it. A laser bonding line typically has a height HL perpendicular to its bonding plane. Preferably, the laser bonding line extends with height HL into the material of the substrate located above the laser bonding line. Opposite it, the laser bonding line extends into the material of the substrate located below the laser bonding line. For example, the cover substrate is fused to the second substrate directly by melting, without the need for intermediaries or adhesives. The laser bonding line can also be physically positioned within one of the two substrates to be joined, i.e., the laser's target point can be located within one of the two substrates, with the laser bonding line always extending into both substrates to be joined.During the joining step or in the laser bonding line, melting material from one substrate mixes with material from the other substrate to create a solid and inseparable hermetic bond between the two substrates.

[0013] If the enclosure consists only of the cover substrate and the second substrate to form the enclosure as a whole, the cover substrate is directly bonded to the second substrate, and the enclosure has a laser bond line. The enclosure then also has a bonding plane or joining area where the substrates are joined. In another example, the enclosure can be stacked from three substrates, with the cover substrate being directly bonded to the second substrate and the second substrate to a base substrate, which also forms the bottom of the enclosure. In this example, the enclosure has two contact zones or joining areas where the enclosure is joined.

[0014] The enclosure features a transparent thin-film substrate with a thickness of less than 200 µm. Such a thin-film substrate offers all the advantages of a conventional enclosure, particularly the hermetic seal of the enclosure's interior from the environment and the chemical inertness of the enclosure, which is especially advantageous for intracorporeal applications. Furthermore, the use of an enclosure according to the invention opens up application areas where conventional enclosures could not previously be used. For example, a pressure sensor can be made more sensitive, and particularly precise optical data transmissions, such as those required for a fingerprint sensor, can be achieved.

[0015] An enclosure typically forms a cavity, that is, a hollow space on an inner surface of the enclosure. For example, the cavity has a lateral rim, a bottom, and a top surface on which the cavity is enclosed by the enclosure. In other words, the cavity is completely enclosed by the enclosure, so that the inner surface of the enclosure also forms the boundary of the cavity, provided there is exactly one cavity in the enclosure. In the case of two or more cavities in the enclosure, the two or more cavities are jointly enclosed by the enclosure.

[0016] For the purposes of this application, the underside and top side are geometric constructs that, depending on the final orientation of the enclosure, can also be any other side. Alternatively, the top side can be described as a first side, the underside as a second side opposite the first, and the rim as an intermediate area between the first and second sides, with the rim typically being substantially perpendicular to the first and / or second side. The lateral rim typically connects the first side to the second side.

[0017] If the cavity is designed as a housing cavity, a housing component is arranged within it. This can be electronic circuits, sensors, or MEMS (microelectromechanical systems) or MOEMS (micro-optoelectromechanical systems).

[0018] The substrates are arranged directly adjacent to or on top of each other. This means that the at least two substrates are arranged or attached to each other in such a way that they lie in contact over their entire surface, without any other materials or layers being present or inserted between them. For technical reasons, minute gas inclusions or impurities, such as dust particles between the substrate layers, may be unavoidable. This can also result from any unevenness, even at the micro level, between the substrate layers or on the surfaces of the substrate layers. It is preferred if any such gap or space between the substrates is less than or equal to 5 µm, preferably less than or equal to 1 µm. In a further preferred embodiment, the joining zone or laser bond line created by the laser has a thickness between 10 and 50 µm.The laser bonding line thus ensures a hermetic seal, as it reliably bridges any gap that may occur between the two substrates.

[0019] One or more laser bond lines can encircle the functional area at a distance DF. This distance DF around the functional area can be constant, so that the laser bond line is positioned at approximately the same distance all around the functional area. Depending on the application, the distance DF can also vary, which may be advantageous from a production standpoint, for example, if multiple enclosures are joined in a single operation, or if the functional area has a round or arbitrary shape and the laser bond line is drawn in a straight line. Even if the cavity has optical properties, such as being shaped like a lens like a converging lens, the laser bond line can be formed around the cavity and may have varying distances from it. An enclosure can also encompass multiple cavities.

[0020] At the contact point between at least two substrates, the enclosure or contact area can be optically transparent or opaque in the visible wavelength range. Only the substrate through which the laser passes to form the laser bond line has at least one spectral window, allowing at least the wavelength of the laser to pass through the substrate, at least partially or in certain areas. The contact area is therefore designed to allow energy deposition via a laser joining process. The laser is thus at least partially absorbed there. This can be done so locally that the laser joining process can be described as a cold joining process.The heat energy provided for joining is therefore concentrated on the area of ​​the laser bonding line and diffuses only relatively slowly into the rest of the housing material, so that in particular no significant temperature increase occurs in the functional area.

[0021] Locally, in the area of ​​the laser bonding line, the laser melts material from both substrates, at least partially, so that the at least two substrates bond locally. The person skilled in the art can refer, for example, to EP 3 012 059 B1 for this purpose.

[0022] The covering substrate can have a thickness of less than 170 µm. Preferably, the thickness of the covering substrate is 150 µm or less, more preferably 125 µm or less. The covering substrate can also have a thickness of 10 µm or more, preferably 20 µm or more. In other words, the thickness of the covering substrate is preferably in the range of 10–170 µm, for example, preferably in the range of 20–150 µm.

[0023] An advantageous thickness for the cover substrate 3, when the housing is used as a pressure sensor, can be in the range of 100 µm to 150 µm. In principle, a thinner cover substrate 3 can achieve higher sensitivity, particularly for optical or pressure measurements (e.g., also for pressure measurements based on changes in the optical properties of the cover substrate 3). However, a lower limit to the thickness of the cover substrate 3, especially for a part 3a spanning a cavity 2, can be observed due to spontaneous material failure or decreasing resistance to shock or pressure loads with decreasing material thickness. Therefore, a suitable range for the present applications has been found to be between 100 µm and 150 µm.

[0024] The thickness of the covering substrate 3 can also depend on the area or size of the cavity 2 to be covered. For example, the cavity has an area that is covered by the covering substrate. This area of ​​the cavity or functional area can, for example, be in the range of 1 x 10⁻⁴ to 1 x 10⁻⁸ m², preferably 1 x 10⁻⁵ to 1 x 10⁻⁷, and more preferably 1 x 10⁻⁶ ± a certain order of magnitude. In other words, the area of ​​the cavity or functional area is 1 x 10⁻⁴ m² or less, preferably 1 x 10⁻⁵ or less, and more preferably in the range of 1 x 10⁻⁶ or less. The area of ​​the cavity or functional area is furthermore 1 x 10 8< or larger, preferably 1 x 10 -7< or larger, more preferably in the range of 1 x 10 -6< or larger.

[0025] A covering substrate for an enclosure can, for example, have a ratio of the thickness of the covering substrate 3 to the area of ​​the functional area 18 or cavity 2, wherein the ratio is in the range of 0.5 to 20,000, preferably in the range of 1 to 10,000, more preferably 5 to 1,000, and even more preferably 10 to 100. If the functional area can be covered in a supported manner, i.e., where part 3a is not self-supporting, the ratio of the thickness of the covering substrate 3 to the area of ​​the functional area 18 can be particularly small, since deflection is not to be expected.

[0026] The laser bond line has a width B in a direction parallel to the planar extension direction of the covering substrate. Specifically, the width W is measured at the surface of the covering substrate, i.e., the outer flat side.

[0027] In the state bonded to the substrate, the cover substrate exhibits surprisingly and unpredictably increased shear strength. It is therefore preferred that the shear strength of the cover substrate is increased precisely by being bonded to the second substrate via the laser bond line designed according to the invention. In other words, the increased shear strength is achieved precisely because the cover substrate is initially in a thicker form and is then bonded to the adjacent substrate in the thicker form by means of the laser. The laser bond line formed in this way differs from a laser bond line that would be obtained if the cover substrate were already provided as a thin-film substrate and were to be bonded by means of the laser. In that case, the laser bond line would be introduced into the material of the cover substrate (i.e.,(thus also the laser's target point) so close to the outer flat surface that the outer flat surface is damaged or altered by the laser and the improvement of the covering substrate is not achieved.

[0028] The laser bond line forms part of the outer surface of the cover substrate, particularly when, for example, the cover substrate is initially provided and joined as a thicker substrate, and then the thickness is subsequently removed, for instance, by an abrasive process. If the laser bond line forms part of the outer surface of the cover substrate, or in other words, if the laser bond line extends into the outer surface of the cover substrate, then material stresses in the cover substrate can be reduced or relieved in a particularly advantageous manner. For example, stress reduction can be achieved through the advantageous combination of material removal, such as surface polishing. For instance, the stress present in the cover substrate material can be relieved by laser bonding or material removal, if necessary.The combination of the two steps reduces the stress by at least 15%, advantageously by at least 25%, more preferably by at least 50%, and possibly even by 65% ​​or more. In other words, the thinned cover substrate is even less stressed than a thin-layer substrate applied by other means, such as adhesive. As a result, the cover substrate can be more dimensionally stable and / or tolerate a higher degree of bending without breaking; it may also be more impact-resistant.

[0029] Preferably, the housing has a coating layer on its outer flat surface. In other words, the outer flat surface is coated, for example to improve its optical properties.

[0030] The outer flat surface can be given a nanoprint or nanoembossing. Furthermore, an external functional area can be arranged on the outer flat surface. For example, AR coatings, protective coatings, bioactive films, optical filters, and conductive layers, such as those made of ITO or gold, can be used as coating layers. Since the coating can advantageously be applied after the joining process, it is not necessary for the coating layer to be laser-penetrable.

[0031] The inner flat surface, that is, the side of the first substrate facing the second substrate, can also have a coating layer. If this inner coating layer is applied across the entire surface, it can become part of the laser bonding line in the area of ​​the laser bonding line. The coating layer can also be partially opaque, thus covering only a portion of the inner flat surface. An example of applying a coating layer to both sides is the application of an anti-reflective coating, at least partially or in certain areas, to both sides of the first substrate.

[0032] The cover substrate and / or the second substrate or further substrates can consist of wafers or be cut from materials such as glass, glass-ceramic, silicon, sapphire, or a combination of these materials. The material of the second substrate can differ from that of the cover substrate. It is particularly advantageous if the encapsulation material is chemically inert, for which borosilicate glass, for example, is well-suited. One or more of the substrates can also comprise or consist of Al₂O₃, sapphire, Si₃N₄, or Al₃.

[0033] The outer flat surface of the covering substrate is preferably flat, particularly planar. This means that the outer flat surface has no bulges and, furthermore, a maximum deviation from a flat plane of less than 5 µm. The outer flat surface has a mean roughness Ra of less than or equal to 20 nm.

[0034] The covering substrate is preferably thinner than 200 µm overall. Furthermore, the covering substrate is preferably planar overall and has a consistent thickness equal to that of its narrower circumferential edge.

[0035] The hermetically sealed enclosure preferably forms a contact plane or contact area between the covering substrate and the second substrate, where the covering substrate and the second substrate are in contact. The contact plane is preferably free of foreign materials, i.e., free of bonding materials such as, in particular, adhesives or glass frit. In other words, the covering substrate is in direct contact adjacent to the second substrate, with no foreign materials interposed between them.

[0036] The adjacent second substrate can be designed as a base substrate, with the base substrate and the cover substrate being hermetically bonded together with the same laser bonding line.

[0037] The second substrate can also be designed as an intermediate substrate, which is arranged between the cover substrate and a base substrate, wherein the base substrate is joined to the intermediate substrate in a first connection plane and the cover substrate is joined to the intermediate substrate in a second connection plane.

[0038] At least one laser bond line has a thickness in a direction perpendicular to the planar extent of the covering substrate. The thickness of the laser bond line perpendicular to the planar extent of the covering substrate defines the bonding zone of the enclosure. The laser bond line extends to the outer flat surface, and in particular, the laser bond line forms part of the outer flat surface. In other words, the outer flat surface is partially penetrated by the laser bond line.

[0039] In the area of ​​the laser bonding line, a material modification of the covering substrate and / or the adjacent second substrate is preferably present. This material modification can involve a change in the refractive index and / or a modified chemical composition. This modification preferably forms a region of the outer flat surface.

[0040] The width W of the laser bond line can be in a ratio to the thickness D of the covering substrate such as W : D greater than or equal to 1, in particular W : D greater than or equal to 0.5. Furthermore, the thickness ratio can also be specified as W : D greater than or equal to 0.1 or W : D greater than or equal to 0.05.

[0041] The functional area preferably comprises a hermetically sealed housing cavity, in a preferred embodiment for receiving a housing object, such as an electronic circuit, a sensor or MEMS or MOEMS.

[0042] The covering substrate is preferably at least partially and / or at least area-wise transparent for a wavelength range.

[0043] The invention also includes a hermetically sealed enclosure. The laser bonding line extends to the outer flat side, in particular forming part of the outer flat side.

[0044] The invention also includes a method for providing a hermetically sealed enclosure, in particular an enclosure as described above. The enclosure houses a functional area, which is specifically designed as a housing cavity for receiving at least one housing object. The method comprises the step of providing at least one cover substrate and a second substrate, the cover substrate comprising a transparent material. The at least two substrates are arranged directly adjacent to or on top of each other, so that a contact area or contact surface is formed between the at least two substrates. The cover substrate has an outer flat side and a circumferential narrow side.

[0045] The at least two substrates are hermetically sealed using a laser bonding line, whereby the at least two substrates are directly joined along at least one contact area of ​​the housing. In particular, the housing cavity or functional area is hermetically sealed with a laser bonding line around the functional area or housing cavity.

[0046] Furthermore, the process includes the removal of material from the covering substrate, in particular to reduce the thickness of the covering substrate. The removal of material from the covering substrate is carried out, in particular, abrasively, for example by grinding or sandblasting, resulting in the production of a thin-film substrate from the covering substrate, wherein the circumferential narrow side has a thickness of less than 200 µm.

[0047] In other words, the method presented in this application makes it possible to perform abrasive thinning or removal of the coating substrate without shearing, dissolving, or even destroying it. This enables a significant improvement in the manufacturing process and allows for the production of considerably improved coatings.

[0048] Of particular importance is the distance of the laser's target point, i.e., the location of the nonlinear energy input into the housing. This distance T is chosen to be large enough so that the material change introduced by the laser lies within the outer flat surface, i.e., does not extend to the surface of the cover substrate. This allows the deposited laser energy to be completely absorbed by the material of the adjacent substrates involved in the joining process, i.e., for example, the cover substrate and the second substrate, and creates a beneficial bond line or laser bond line that ultimately increases the shear strength of the cover substrate.

[0049] By carefully selecting the temperature T, it can also be improved to ensure that the zone of nonlinear absorption (nlA; i.e., in particular the laser's target point) does not extend into the covering substrate. It has been shown that at the target point, the laser can generate foreign particles, which may manifest, for example, as a blackening and / or a change in the refractive index in the nlA.

[0050] Surprisingly, this can create a laser bond line that is particularly wide after grinding on the outer flat side.

[0051] The hermetically sealed enclosure can be achieved using a laser joining process. The hermetically sealed cavities or the enclosure can be sealed at a temperature lower or higher than the enclosure's eventual operating temperature.

[0052] In this process, at least two substrates are preferably provided as wafer stacks in order to produce, for example, a plurality of hermetically sealed enclosures together in the same work process.

[0053] The process can further include singulating the encapsulation from a wafer stack, wherein this step is carried out in particular by means of a laser cutting or laser separation step. The same laser used for the joining process can be used for singulation.

[0054] The previously described method can be used to produce an enclosure with a hermetically sealed housing cavity enclosed within it.

[0055] A housing produced according to the above method can also be used as a medical implant or as a sensor.

[0056] The invention also includes a sensor unit and / or medical implant with a housing as described above, or with a substrate arrangement as also described above.

[0057] The height HL of the laser bond line is preferably in a range greater than 10 µm, more preferably greater than 50 µm, greater than 100 µm or even greater than 200 µm.

[0058] The invention will now be explained in more detail with reference to exemplary embodiments and the figures, whereby identical and similar elements are partially provided with the same reference numerals and the features of the different exemplary embodiments can be combined with one another. Brief description of the characters

[0059] They show: Fig. 1 Section through a first embodiment of an enclosure according to the invention, Fig. 2a, 2b Examples of results with disadvantageous manufacturing processes, Fig. 3 Exemplary process steps for manufacturing an enclosure according to the invention, Fig. 4a, 4b Detailed section of the joining zone, Fig. 5 Top view of an enclosure according to the invention, Fig. 6 Side sectional view through the joining zone, Fig. 7a to 7d Different embodiments of a substrate arrangement not according to the invention or of an enclosure according to the invention, Fig. 8 Further embodiment of an enclosure according to the invention, Fig. 9 Schematic sketch of a joining zone, Fig. 10a, b Different designs of laser bond lines, Fig. 11 Photographic representation of an enclosure to be manufactured according to the invention, Fig. 12 Top view of an enclosure according to the invention, Fig. 13 Side sectional view of the Fig. 12 shown enclosure, Fig. 14 side view of the in Fig. 12 shown enclosure, Fig. 15 Top view of the in Fig. 12shown enclosure, Fig. 16 Side sectional view of a laser welding zone with a plurality of parallel laser welding lines, before material removal of the cover substrate, Fig. 17 Side sectional view of a laser welding zone with a plurality of parallel laser welding lines, after material removal of the cover substrate, Fig. 18 Grayscale legend to Figures 19 , 20 and 21 Fig. 19 Side section after polishing the surface of the covering substrate, Fig. 20 Analysis result before polishing the surface of the covering substrate, Fig. 21 Analysis result after polishing the surface of the covering substrate, Fig. 22 Further analysis result before polishing the surface of the covering substrate, Fig. 23 Further analysis result after polishing the surface of the covering substrate. Detailed description of the invention

[0060] Fig. 1Figure 1 shows an embodiment of an enclosure according to the invention in a side sectional view. The enclosure 1 comprises a first substrate 3 as a thin glass layer 3 and a second substrate 24, wherein the first substrate 3 and the second substrate 24 are hermetically joined around their circumference by means of the joining zone 6. An outer flat surface 4 of the first substrate 3 faces the surroundings. The joining zone 6 is located in the contact area 10 between the first substrate 3 and the second substrate 24. The enclosure 1 encloses a cavity 2 in which a housing object 5 is arranged. For example, the cavity 2 is abrasively formed into the second substrate 24, i.e., hollowed out from the second substrate 24.

[0061] Referring to Fig. 2aAn embodiment is shown which does not represent the invention, but rather depicts the bonding of two substrates using an adhesive or frit. The problem here is that the bonding areas cannot be realized equidistantly; instead, the thickness of the adhesive or frit 11 varies or is subject to fluctuations in the finished product. This results either in a lack of hermetic seal or in the cover 30 not lying flat or evenly, leading to an overall poorer bond and reduced durability of the cover. Arrows 12 illustrate the distance from the bottom of the cavity shown to the cover 30, which is not uniform within the cavity. Arrow 13 illustrates the distance from the top of an object in the cavity to the cover 30.

[0062] Referring to Fig. 2bAnother inferior embodiment is shown, which is not intended to illustrate the invention, in which the curvature 14 is visible in the cover 30, which occurs, for example, in a conventional ultrashort pulse process. The disadvantage of this embodiment is that the top surface of the cover 30 is not uniform or flat, and this curvature 14 is extremely difficult to treat. This leads to higher costs or to the fact that the process is not fully functional. Fig. 2b The product shown cannot be used for the applications according to the invention.

[0063] Fig. 3Figure 1 shows exemplary steps for the production of an enclosure 1 according to the invention. Several enclosures 1 are produced from common substrates of a substrate spatula 9, for example in the form of wafers, in the same operation to reduce production costs and / or minimize material waste. In a preparatory step 110, the stack of substrates 7, 24 and the housing object 5 are prepared for the completion of the enclosure 1. Before final production, the first substrate 7 has a thickness greater than 200 µm, so that the subsequent joining process can be carried out more easily and precisely. In other words, the substrate is not yet a thin-film substrate before the joining process is carried out. The second substrate 24 and the first substrate 7 form the wafer stack 9.

[0064] In joining step 120, a laser is used to introduce the joining zone or laser bond line 6 into the enclosure 1, whereby in this example the wafer stack 9 has a plurality of cavities 2, namely three cavities 2. Several enclosures 1 are later separated from the wafer stack 9. A laser bond line 6 is applied around each cavity 1, hermetically sealing the respective cavity 2.

[0065] In a reduction step 130, the finished cover substrate 3 is produced as a thin glass layer from the first substrate 7 prior to final production, for example, by means of abrasive material removal. This can be a polishing step, a sandblasting step, or similar ablation to reduce the thin-film substrate 3 to a thickness of less than 200 µm. In ablation step 130, the laser bond line 6 is also at least partially removed, so that the laser bond line 6 forms part of the surface 4 of the thin glass layer 3, thus creating a suitable bonding zone 6a. The cover substrate 3 is formulated such that it exhibits particularly high shear strength in the state bonded to the second substrate 24.

[0066] Optionally, the method for producing the enclosure 1 according to the invention can include a tempering or coating step 140, in which, for example, a coating 20 is applied, in which an outer functional layer 16 is deposited on the outer surface 4 of the first substrate 3. In the separation step 150, the individual enclosures 1 are separated by means of a cutting tool 22, which can also be a laser, such as the laser that is also used for joining the enclosure. In other words, a plurality of enclosures 1 are separated from the wafer stack 9. Therefore, in this example, several enclosures 1 are produced together, which further reduces the costs of the manufacturing process.

[0067] Referring to Fig. 4aFigure 1 shows a detail of a longitudinal section through the laser bonding zone 6, where the laser bonding zone extends to the outer flat side 4 of the first substrate 3 and has a width W at the outer flat side 4. The first substrate 3 has a thickness D, for example, less than 200 µm. In this example, the thickness of the first substrate 3 can be less than 100 µm, less than 70 µm, preferably less than 50 µm, or even less than 30 µm. The width or diameter of the laser bond line 6, here denoted by W, is wider than the thickness of the thin glass layer 3. For example, W is 200 µm when the thin glass layer is 130 µm thick. For example, W / D is greater than 1, so that the width of the laser bond line 6 on the outer surface 4 is greater than the thickness D of the thin glass layer 3. The ratio W / D is further preferably 0.5, so that W is half the thickness D of the thin glass layer 3 or greater.The W / D ratio can also be greater than or equal to 0.1, but preferably greater than or equal to 0.05.

[0068] Typical current laser bonding lines have a width ranging from 10 µm to 50 µm. A W / D ratio of 0.05 would be achieved, for example, with W = 10 µm and D = 200 µm. However, larger W / D values ​​can also be useful, such as 0.25, which results from W = 50 µm and D = 200 µm.

[0069] The inventive method, by means of which, among other things, the thin glass layer 3 is developed during the manufacturing process, leads to a particularly usable surface of the outer flat side 4, in which, in particular, no curvature or bump on the outside 4 protrudes beyond the mean thickness D of the thin glass layer 3.

[0070] Referring to Fig. 4b is in addition to Fig. 4aThe target area 8 of the bonding laser is shown, which is inserted at a depth T measured from the outer surface 4. T can be, for example, greater than or equal to 10 µm, greater than or equal to 50 µm, greater than or equal to 100 µm, or greater than or equal to 200 µm. T is always greater than the thickness D of the thin glass layer used to hermetically bond the first substrate 3 to the second substrate 24. The target point 8 represents the region of nonlinear absorption in the material and / or avalanche ionization, i.e., for example, the depth set for the Keldysh parameter. It is the region of the laser bond line where optical damage is introduced, such as a locally altered refractive index or a darkening.

[0071] Referring to Fig. 5Figure 1 shows a top view of an enclosure 1 according to the invention, wherein a functional area 2 is arranged inside the enclosure 1. The laser bonding line 6 is arranged circumferentially around the functional area 2 and hermetically seals the functional area 2, here designed as a cavity, on all sides. The width of the laser bonding line B on the outer surface 4 of the first substrate 3 is shown by way of example around the laser bonding line 6.

[0072] Referring to Fig. 6 Figure 1 shows a side section view through an enclosure or substrate arrangement according to the invention along a laser bonding line 6. The laser bonding line 6 is modified on its upper side to form the adapted joining zone 6a, which forms part of the outer surface 4 of the first substrate. The laser bonding line 6 extends into both the first substrate 3 and the second substrate 24.

[0073] Referring to Fig. 7aA substrate arrangement is shown with a thin-layer substrate 3 and a second substrate 24 hermetically connected to it, which are hermetically joined by means of the laser bonding line 6.

[0074] Referring to Fig. 7b is the arrangement according Fig. 7a shown, which additionally has an outer functional layer 16, for example an optical coating 16. The outer functional layer 16 has a homogeneous, i.e. uniform, thickness and also covers the modified functional layer 6, 6a. The laser bond line 6 is introduced into the contact area 10 between the first and second substrate 3, 24.

[0075] Referring to Fig. 7c is the arrangement according Fig. 7aThe diagram shows an additional internal functional layer 18 or an internal functional area 18, which, for example, is incorporated into the second substrate 24, arranged between the first substrate 3 and the second substrate 24, or can be applied to the underside of the first substrate 3. This layer 18 can be part of the contact surface or form the contact surface. The layer 18 can, for example, be an AR coating on the inside of the cover substrate 3. If the layer 18 is formed over the entire surface, it will be damaged in the area of ​​the laser bonding line 6, 6a. This can be tolerated if the functionality of the layer 18 is not impaired, for example, if the coating in the area of ​​the cavity 2 remains intact.

[0076] Referring to Fig. 7dAnother embodiment is shown, wherein the housing 1 contains a cavity 2 or a functional area 18. The functional area 18 can be a lens-shaped recess in the second substrate 24, which, for example, can already have optical properties due to the shape of the recess, i.e., function as a lens. In contrast to the Figures 7c and 7d show the Figures 7a and 7b no embodiments of the claimed invention.

[0077] With Fig. 8A further embodiment of the enclosure 1 is shown, wherein a first laser bonding line 6 hermetically joins the second substrate 24 to a third substrate 25, and wherein a second laser bonding line 6a joins the second substrate 24 to the first substrate or cover substrate 3. In this example, the two laser bonding lines 6, 6a are arranged directly one above the other. While this arrangement has advantages, the invention is not intended to be limited to this arrangement. Among the advantages of this arrangement is the desired maximum yield of the cavity 2 portion of the enclosure. The laser bonding line preferably has a minimum distance to each interface or surface surrounding the laser bonding line 6, 6a.Since, on the one hand, the cavity 2 should extend as close as possible to the outer surface of the housing 1, and on the other hand, the laser bonding lines 6, 6a should maintain a minimum distance from both the cavity 2 and the outer surface of the housing 1, the advantageous arrangement of the two laser bonding lines 6, 6a directly above one another or offset from each other as little as possible results. The laser bonding line 6a has a flattened upper surface, which results from the fact that the cover substrate 3 is abrasively thinned after the bonding process to form the outer surface 4 of the cover substrate 3. In this process, material from the laser bonding line 6a is also removed.

[0078] With Fig. 9A detailed sketch of the setup of a laser bond line 6, 6a is shown. W denotes the maximum (lateral) width of the melting region 36, where plane 34 represents the plane at which W is measured. HL is the height of the melting region 36, and CN is the distance of the laser focus, i.e., the area / point of nonlinear absorption, from plane 34 in which W is measured. The inner melting region 32 is located inside the laser bond line 6, 6a.

[0079] Referring to Fig. 10a and Fig. 10bFigure 1 shows a comparison of different depths T of exemplary laser bonding zones 6, 6a, labeled a, b, c, d, and e, which are partially embedded into a raw substrate 7, i.e., the thin-film substrate 3 before material removal. The laser bonding zones 6, 6a differ in the depth T to which they are embedded from above through the first substrate 7 into the substrate stack 1 or the enclosure 1. The future outer surface 4 is shown with a dashed line; this surface will form the outer flat side 4 of the final enclosure. The depths T are measured as the distance of the focal point 8 from the future outer flat side 4. D denotes the thickness of the cover substrate 3 after the final treatment. In the case of the laser bonding line 6, 6a labeled a, the melting area 36 extends only slightly into the cover substrate 3.Although this arrangement already provides a sufficient bond, it has been found that such an arrangement may be sensitive to potential material defects, so that if a material defect or a weakening of one of the substrates 3, 24, 25 is present, a detachment of the covering substrate or a breaking of the hermetic seal could result.

[0080] In the laser bonding lines 6, 6a designated b, c, and d, the convection zone 36 extends sufficiently far into the cover substrate 7, i.e., into the subsequent thin-film substrate 3, whereby in c and d, material from the melt bubble 36 is already being removed to produce the thin-film substrate 3. However, in the laser bonding line 6, 6a designated d, the zone of nonlinear absorption 8 already approaches the contact surface 10 between the substrates 3, 24 considerably. In the zone of nonlinear absorption 8, a visible material change was observed, with clouding of the material and / or a change in the refractive index. Therefore, it is preferred to keep the laser target area 8 at a distance from the contact surface 10, which is still the case in embodiments a, b, and c. In this case, sufficient material from the two substrates 3, 24 is also convectively mixed with each other.The embodiment designated by e finally shows a laser bonding line 6, 6a which no longer extends into the second substrate 24 and is no longer able to create a bond between the two substrates.

[0081] The preferred position of the laser bonding line 6, 6a for producing a thin-film substrate stack or an enclosure 1 was found to be when T equals D + CN. The region where T is less than D + WH is preferable; conversely, it is preferable to choose T larger than CN to create a bond between the first and second substrates 3, 24. If the plane 34 of the widest extent W of the melt bubble 36 lies approximately in the middle of the subsequent thin-film substrate, i.e., at approximately D / 2, then T - CN = D / 2. In all the aforementioned regions and at the intermediate heights, the thin-film substrate stack 1 or the enclosure 1 can be successfully produced.

[0082] Referring to Fig. 11 Figure 1 shows a side view of an enclosure 1 or a substrate stack 1, 9, in which a plurality of laser bond lines 6, 6a are applied as examples. An upper thickness region 42 is shown hatched, which is to be removed down to the later outer flat surface 4 for the production of the thin-film substrate 3. The sufficient material thickness of the upper region 42 ensures that the laser bond lines 6, 6a can be applied to the enclosure 1 or the substrate stack 1, 9 without interference or disturbance, and that a secure bond between the thin-film substrate 3 and the second substrate 24 can be achieved.

[0083] Functional area 18 can perform various tasks; for example, it can be an optical receptor or a technical, electromechanical, and / or electronic component, which can be arranged in a cavity 2. As the Fig. 6To illustrate, a laser bond line 6 consists of a plurality of laser pulse hit areas 26, which are placed so close together that the material of the second substrate 24 merges seamlessly with the material of the first substrate 3.

[0084] With regard to the Figures 12 to 15 Another embodiment of an enclosure 1 is shown, in which a cavity 2 or a functional area 18 is hermetically sealed inside the enclosure 1. Fig. 12 Figure 1 shows a top view of the enclosure 1, with the thin cover substrate 3 spanning the cavity 2. The cavity 2 can be irregularly shaped, as in this example, and optimized with regard to the installation space or other requirements of the components 5 to be housed within it. The embodiment of the enclosure 1 shown here can be configured as a pressure sensor 1.

[0085] Fig. 13Figure 1 shows the pressure sensor 1 in a side view. The cover substrate 3 is thinned or polished to a thickness of approximately 100 to 150 µm, specifically 130 µm in this case. The cover substrate 3, with its section 3a, spans the cavity 2. The cover substrate 3 is thin enough that it can compensate for pressure fluctuations or pressure values ​​in the unsupported section 3a by deformation. The deformation of the unsupported section 3a can, in turn, be detected, for example, by optical measurement, and a pressure absolute value, relative value, or pressure change can be derived from this.

[0086] The construction of the cover substrate 3, in which a thicker substrate is first joined to the second substrate 24 and the cover substrate 3 is then thinned to the desired thickness after laser bonding, for example by polishing, can provide an even stronger or more suitable cover substrate 3 that is capable of withstanding higher pressure differentials between the interior of the cavity 2 and the environment without being destroyed. This is particularly because the step of removing material from the cover substrate 3 reduces material stresses in the cover substrate 3 and thereby improves the strength and / or deformability of the cover substrate 3. The hermetic sealing of the cavity 2 by means of the circumferential laser bond line 6a, which completely encloses the cavity 2, is a key element for ensuring that pressure differentials between the interior of the cavity 2 and the environment are reliably maintained and that pressure measurements can be reliably carried out.

[0087] Due to the flexibility K of the cover substrate 3 in the area of ​​the cavity 2, which is spanned by the cover substrate 3 with part 3a, optical properties can also be realized if part 3a is considered a lens or generally possesses optical properties. On the one hand, the prevailing pressure or pressure difference can be measured optically, since the optical properties of part 3a change with increasing bending; on the other hand, a desired optical property can also be set by adjusting the pressure or pressure difference. For example, an optical system can be focused, i.e., the focal point of part 3a can be adjusted. Similarly, an optical sensor could be arranged inside the cavity 2, and the optical focus of the radiation incident on the cavity 2 could be varied by changing the pressure.For this purpose, an adjustable passage 52 can also be provided, by means of which pressure equalization and / or pressure changes can be achieved in the interior of the housing 1 or in the cavity 2. For example, a pump or valve can be arranged on or in the passage 52 for this purpose. For example, a liquid can also be arranged in the interior or cavity 2, and the optical properties of part 3a can be adjusted by the inflow or outflow of liquid through the passage 52.

[0088] The second substrate 24 can either be a continuous substrate 24, for example made from a wafer which has "holes" or recesses at the locations of the later cavities 2, or "spacers" can be used, i.e. spacers between the first substrate 3 and the third substrate 25. Fig. 14 Finally, the figure shows the housing in side view, showing the layer arrangement of the three layers 3, 24, 25.

[0089] Referring to Fig. 15 A further relationship is explained. The boundary of cavity 2 or functional area 18 is described by the continuous or discrete (with a number U of points) 2D function of points f(u). A K-factor can be defined using the thickness D of the covering substrate 3 as follows: K = min f x u − c x 2 + f y u − c y 2 D

[0090] c corresponds to the coordinates of the center point 48, or barycenter, of cavity 2 and can be obtained as follows: c → = ∫ f → du or in the case of a disputed case: c → = 1 U ∑ u f →

[0091] The K-factor provides a measure for estimating or calculating the flexibility of the covering substrate 3. The flexibility K is then preferably in the range of 5 to 15, more preferably in the range of 7 to 12.

[0092] With a thickness of the covering substrate of 150 µm, the K-value can then be obtained in an example as K = 1.25 mm / 0.15 mm = 8.33.

[0093] In other words, the enclosure 1 has a flexibility K with respect to the covering substrate, wherein the calculated value for the flexibility K ≥ 3, preferably K ≥ 5, less preferably K ≥ 7, and / or wherein K ≤ 18, preferably K ≤ 15, and less preferably K ≤ 12. Possible intervals for the flexibility of a covering substrate 3, which have been determined to be advantageous within the scope of the invention, can then be 3 ≤ K ≤ 18, preferably 5 ≤ K ≤ 15, or more preferably 7 ≤ K ≤ 12, wherein the other numerical combinations for the value interval of K can also be advantageous.

[0094] Figures 16 to 23 Referring to a further embodiment of an enclosure 1, the surprising improvement with regard to the residual stresses in the material of the cover substrate 3 is clearly illustrated. Thus, it shows Fig. 16A cross-section through an enclosure 1 before material removal from the cover substrate 7. For testing purposes, to better determine the material stress, a plurality of laser welding lines 6 are introduced parallel and more or less equidistant from each other into the composite material of cover substrate 7 and base substrate 24. Before final processing, the cover substrate 7 initially has a thickness of 1800 µm, matching the thickness of the base substrate 24, which also has a thickness of 1800 µm. The cover substrate 7 is removed, for example by abrasive polishing or sandblasting, down to the indicated reduction line 135 and then becomes the thin cover substrate 3, for example a thin glass layer. The reduction line 135 thus represents a removal target. In this case, the removal target 135 is set to a residual thickness of 100 µm for the cover substrate 3, so that the enclosure has a total thickness of 1900 µm.

[0095] The laser joining lines 6 extend approximately the same distance into the two substrates 7, 24, the shape of the laser joining lines 6 being described in detail with Figures 4a, 4b , Fig. 9 , 10a and 10b This is explained and shown. The features of the laser welding lines shown in the aforementioned figures are also inherent in the Figures 16 to 23The reference symbols are not repeated in these figures, and only for the sake of clarity are they not used. For example, the target point of the laser focus is located in the base substrate 24, and the point of nonlinear absorption 26 is also located there. The convection zone 36 extends from the base substrate 24 to the cover substrate 7, where material from the base substrate 24 is mixed with material from the cover substrate 7. This creates a permanent bond between the two substrates 3 and 24. At the same time, as already explained, the laser bond lines 6 can be reliably generated if the cover substrate 7 has a greater thickness before final processing, since no material is burned off and a complete and coherent material exchange takes place in the convection zones 36. Subsequently, material 130 is removed from the cover substrate 7.

[0096] With Fig. 17The housing 1 with the removed cover substrate 3 is shown, with modified laser welding lines 6a being generated. The cover substrate 3 has been removed down to the ablation target 135, thus having a thickness of 100 µm. The base substrate still has a thickness of 1800 µm (the drawing is accordingly not to the Figures 19 to 23 (to scale, since at exact scale the cover substrate 3 would hardly be visible anymore). How with Fig. 17 As can be seen in this example, a significant portion of the outer surface 4 of the cover substrate 3 is formed by the modified laser welding lines 6a, which extend to or into the outer surface 4. The Fig. 17 The embodiment shown also corresponds in structure to the one for with Figures 19 to 23 shown measurement results.

[0097] Referring to Fig. 18 A grayscale is shown, by means of which the in Figures 19 , 20 and 21 A delay value can be assigned to the displayed grayscale levels. For the Figures 20 and 21The scale ranges from a delay of 0 nm for white to 70 nm for black, and the value range is linearly resolved between 0 and 70 nm. In the case of the Figure 19 The value white also corresponds to 0 nm, while black corresponds to a delay of 180 nm. The range from 0 to 180 nm delay is used for representing the Fig. 19 also linearly resolved from white to black across the displayed shades of gray.

[0098] Referring to Figures 19 , 20 and 21 are representations of delay measurements of a joined and, in the case of the Fig. 19 and 21 polished, housing 1 shown. Housing 1, which is in Fig. 20 As shown, its structure corresponds to the cross-sectional representation of the Fig. 16 , whereby the in Fig. 21 The diagram shown in the structure is described in Fig. 17 The cross-section shown corresponds to this. The majority of adjacent laser welding lines 6, 6a are in the Figures 19 ,20, 21 clearly visible. The retardance refers to the delay that occurs, for example, in a birefringent crystal or other birefringent medium between the two perpendicularly polarized light rays. As explained previously, this can provide information about the flexural strength K of the cover substrate 3 in this case.

[0099] Fig. 19Figure 1 shows a cross-section through the enclosure 1, illustrating the measured retardation in the material. The laser bonding lines 6a, with their laser target points (i.e., the nonlinear absorption region 26, the inner melting zone 32, and the convection zone 36), can be clearly identified based on the retardation. The contact area 10 between the cover substrate 3 and the base substrate 24 is also visible. Even areas that previously exhibited high retardation values ​​are homogenized across several laser bonding lines 6a in the ground substrate 3 of the enclosure 1.

[0100] In a direct comparison between the images of the Figures 20 and 21 It becomes apparent that the Fig. 20 is significantly darker, thus exhibiting a greater delay. From this, it can be concluded that the material of the cover substrate 3 contains the in Fig. 20 The depicted housing 1 has a greater residual stress or internal stress than after material removal, which condition is associated with Fig. 21The same relationship is shown in the two graphs of the Figures 22 and 23 further clarifies where the obtained deceleration values ​​are shown over a cross-section of the housing 1. It becomes clear that the residual stress, which influences the basis of the measured deceleration values, can be reduced by a factor of approximately 2 after material removal to the removal target 135. That is, in the case with Fig. 22 In the case shown, before material removal, the measured delay is approximately twice as large as in the case with Fig. 23 Case shown after material removal.

[0101] It is evident to the person skilled in the art that the embodiments described above are to be understood as examples and that the invention is not limited to these, but can be varied in many ways without leaving the scope of protection of the claims.

[0102] In all figures, the same reference symbols denote the same features, so that descriptions of features that may only be mentioned in one figure, or at least not with regard to all figures, can also be applied to those figures for which the feature is not explicitly described.

Claims

1. Hermetically sealed enclosure (1) comprising at least one flat cover substrate (3) having an outer flat face (4) and a circumferential edge face, and a second substrate (24) arranged adjacent to the cover substrate and in direct contact with the flat cover substrate, at least one functional area (2, 18) enclosed by the enclosure which is arranged in particular between the cover substrate and the second substrate, wherein the cover substrate is configured as a transparent thin-film substrate, wherein the cover substrate has a thickness of less than 200 µm, characterized in that the hermetically sealed enclosure (1) comprises a laser bonding line (6, 6a) by means of which the cover substrate (3) is directly hermetically sealed to the second substrate (24) arranged adjacent to the cover substrate.

2. Hermetically sealed enclosure (1) according to the preceding claim, wherein the thickness of the cover substrate (3) is measured at the circumferential edge face of the cover substrate, and / or wherein the cover substrate (3) has a thickness of less than 170 µm, preferably less than 150 µm, more preferably less than 125 µm, and / or a thickness greater than 10 µm, further preferably greater than 20 µm.

3. Hermetically sealed enclosure (1) according to at least one of the preceding claims, having at least one of the following features - The laser bonding line has a width W in a direction parallel to the planar surface direction of extension of the cover substrate, in particular a width at the circumferential edge face of the cover substrate, and the cover substrate exhibits increased shear strength when bonded to the second substrate; the laser bonding line (6, 6a) has an original height HL, and the cover substrate (3) has less than half the thickness compared to HL, and / or T < D+WH and / or T > CN; - the outer flat face (4) has at least one of the following features: a coating layer (16) and / or a nanoimprint or nanoembossing (16), and / or a functional area (16); - the outer flat face (4) of the cover substrate (3) is characterized in that it is flat, in particular planar, in particular has no bulges, further in particular has a maximum deviation from the flat plane that is less than 5 pm, further in particular has an arithmetic mean deviation of the roughness profile Ra of less than or equal to 20 nm, and / or the cover substrate (3) has an overall thickness of less than 200 µm, is in particular planar, and consistently exhibits the thickness of the circumferential edge face throughout; - the cover substrate (3) forms a contact plane or contact area (10) with the second substrate (24) at which the cover substrate is in contact with the second substrate, wherein the contact plane is free of foreign materials, in particular free of bonding materials such as adhesive or glass frit; - the adjacent second substrate (24) is a base substrate, and the base substrate is hermetically sealed to the cover substrate with the same laser bonding line (6, 6a), or the second substrate arranged adjacent thereto is an intermediate substrate which is arranged between the cover substrate and a base substrate, the base substrate being connected to the intermediate substrate in a first bonding plane, and the cover substrate is bonded to the intermediate substrate in a second bonding plane; - the at least one laser bonding line (6, 6a) has a thickness WH in a direction perpendicular to the planar direction of extension of the cover substrate (3), and the laser bonding line extends to the outer flat face (4), wherein in particular the laser bonding line forms part of the outer flat face; - the area of the laser bonding line (6, 6a) exhibits a material modification of the cover substrate (3) and / or the adjacent second substrate (24), in particular a change in refractive index and / or a modified chemical composition, and this material modification forms an area of the outer flat face (4).

4. Hermetically sealed enclosure (1) according to claim 3, wherein the width W of the laser bonding line (6, 6a) is greater than the thickness D of the cover substrate (3), and / or wherein the width W of the laser bonding line (6, 6a) has a relation to the thickness D of the cover substrate (3) such as W / D greater than or equal to 1, in particular W / D greater than or equal to 0.05.

5. Hermetically sealed enclosure (1) according to at least one of the preceding claims, wherein the functional area (2, 18) has a hermetically sealed housing cavity for accommodating a housing object (5), such as an electronic circuit, a sensor, or MEMS.

6. Hermetically sealed enclosure (1) according to at least one of the preceding claims, wherein the cover substrate (3) is at least partially and / or at least in some areas transparent in a wavelength range.

7. Hermetically sealed enclosure (1) according to at least one of the preceding claims, wherein the cover substrate (3) consists of glass, glass-ceramic, silicon, sapphire, or a combination of the aforementioned materials, or wherein the cover substrate consists of ceramic material, in particular oxide ceramic material.

8. Hermetically sealed enclosure (1) according to one of claims 1 to 7, wherein the laser bonding line (6, 6a) extends to the outer flat face (4), wherein in particular the laser bonding line (6, 6a) forms part of the outer flat face (4).

9. Method for providing a hermetically sealed enclosure (1), wherein a functional area (2, 18) is housed by the enclosure, wherein the functional area is designed in particular as a housing cavity (2) for accommodating at least one housing object (5), comprising the steps: - providing at least one cover substrate (3) and a second substrate (24), wherein the cover substrate comprises a transparent material, wherein the at least two substrates are arranged directly adjacent to or on top of each other, so that a contact area (10) is formed between the at least two substrates, and wherein the cover substrate has an outer flat face (4) and a circumferential edge face, - hermetically sealing the enclosure by directly joining the at least two substrates together along at least one contact area of the housing by means of a laser bonding line (6, 6a), - removing material from the cover substrate, in particular removing abrasively, for example by grinding, thereby producing a thin-film substrate from the cover substrate, wherein the circumferential edge face has a thickness of less than 200 µm.

10. Method according to claim 9, wherein the hermetically sealing of the enclosure (1) and / or the cavity (2) is carried out by means of a laser joining process, and / or wherein the hermetically sealing of the enclosure (1) and / or cavity (2) is carried out at a temperature that is lower or higher than the subsequent operating temperature of the enclosure.

11. Method according to at least one of the preceding method claims, wherein the at least two substrates (3, 24, 25) are provided as a wafer stack (9) so that a plurality of hermetically sealed enclosures (1) can be manufactured simultaneously from the wafer stack in a single processing step.

12. Method according to at least one of the preceding method claims, further comprising the step of separating the enclosure (1) from a wafer stack (9), wherein the step is carried out in particular by means of a laser cutting or laser separation step, wherein, in particular, the same laser is used that is also used for the joining step.

13. Use of an enclosure (1) manufactured according to the above method comprising a hermetically sealed housing cavity (2) enclosed therein as a medical implant or as a sensor.

14. Sensor unit and / or medical implant comprising an enclosure (1) according to at least one of claims 1 to 8