Laser repair with stress-reducing pre-structuring

Abstract

Method for producing a micromechanical component (1) with a substrate (3) and with a cap (7) connected to the substrate (3) and enclosing a first cavern (5) with the substrate (3), wherein a first pressure prevails in the first cavern (5) and a first gas mixture with a first chemical composition is enclosed, wherein -- in a first process step (101) an access opening (11) connecting the first cavern (5) with a surrounding (9) of the micromechanical component (1) is formed in the substrate (3) or in the cap (7), wherein -- in a second process step (102) the first pressure and / or the first chemical composition is set in the first cavern (5), wherein -- in a third process step (103) the access opening (11) is closed by introducing energy or heat into an absorbing part (21) of the substrate (3) or the cap (7) using a laser, characterized in that -- in a fourth process step (104), wherein the fourth process step (104) is carried out before the third process step (103), a recess (17) is formed in a surface (19) of the substrate (3) or the cap (7) facing away from the first cavern (5) in the area of ​​the access opening (11) for receiving a material region (13) of the substrate (3) or the cap (7) that has been converted into a liquid state in the third process step (103), wherein the recess (17) is formed in a plane extending substantially parallel to the surface (19) and is rotationally symmetric to the access opening (11) or to the center of mass of the material region that has been converted into a solid state after the third process step or to the absorbing part (21) of the substrate (3) or the cap (7) and is annular in shape.

Description

State of the art

[0001] The invention relates to a method according to the preamble of claim 1.

[0002] Such a method is known from WO 2015 / 120939 A1. If a specific internal pressure is desired in a cavity of a micromechanical component, or if a gas mixture with a specific chemical composition is to be enclosed in the cavity, the internal pressure or chemical composition is often adjusted during the capping of the micromechanical component or during the bonding process between a substrate wafer and a cap wafer. During capping, for example, a cap is bonded to a substrate, whereby the cap and the substrate together enclose the cavity. By adjusting the atmosphere or the pressure and / or the chemical composition of the gas mixture present in the environment during capping, the desired internal pressure and / or chemical composition in the cavity can thus be set.

[0003] The method known from WO 2015 / 120939 A1 allows for the targeted adjustment of internal pressure in a cavity of a micromechanical component. In particular, this method makes it possible to produce a micromechanical component with a first cavity, in which a first pressure and a first chemical composition can be set that differ from a second pressure and a second chemical composition at the time of capping.

[0004] In the method for precisely controlling the internal pressure in a cavity of a micromechanical component according to WO 2015 / 120939 A1, a narrow access channel to the cavity is created in the cap or cap wafer, or in the substrate or sensor wafer. The cavity is then flooded with the desired gas and internal pressure via the access channel. Finally, the area around the access channel is locally heated using a laser, causing the substrate material to liquefy locally and, upon solidification, hermetically seal the access channel. Further disclosures are provided in publications DE 102014202801A1, US 2013 / 0265701A1, US 2013 / 0074596A1, and WO 2015 / 082952A1. Disclosure of the invention

[0005] The object of the present invention is to provide a method for manufacturing a mechanically robust and long-life micromechanical component in a manner that is simpler and more cost-effective than those found in the prior art. Furthermore, the object of the present invention is to provide a compact, mechanically robust, and long-life micromechanical component compared to those found in the prior art. According to the invention, this applies in particular to a micromechanical component with a (first) cavity. With the method and micromechanical component according to the invention, it is also possible to realize a micromechanical component in which a first pressure and a first chemical composition can be set in the first cavity and a second pressure and a second chemical composition can be set in a second cavity.For example, such a method is provided for the production of micromechanical components for which it is advantageous to have a first pressure enclosed in a first cavity and a second pressure enclosed in a second cavity, the first pressure being different from the second pressure. This is the case, for example, when a first sensor unit for measuring angular rate and a second sensor unit for measuring acceleration are to be integrated into a micromechanical component.

[0006] The task is solved by the fact that -- in a fourth procedural step -- a recess is formed in one of the surfaces of the substrate or cap facing away from the first cavern in the area of ​​the access opening to receive a material area of ​​the substrate or cap that has been converted into a liquid state in the third process step and / or -- a raised area on the surface of the substrate or cap facing away from the first cavern in the area of ​​the access opening to guide away the material area of ​​the substrate or cap that has been converted into a liquid state in the third process step, essentially away from the access opening and essentially parallel to the surface, and / or -- a reflection area is formed on or in the surface of the substrate or cap facing away from the first cavern in the area of ​​the access opening, resulting in increased reflection of laser radiation used in the third process step to introduce energy or heat, in contrast to the rest of the surface, and / or -- an absorption area is formed on or in the surface of the substrate or cap facing away from the first cavern in the area of ​​the access opening, resulting in increased absorption of the laser radiation used in the third process step to introduce the energy or heat, in contrast to the rest of the surface.

[0007] This provides a simple and cost-effective method for manufacturing a micromechanical component in which the solidified material region can be recessed into the substrate or cap relative to the surface. Compared to a method without forming the recess, the method according to the invention has the advantage, for example, that the solidified material region protrudes less far above the surface, thus offering less surface area for mechanical impacts. This makes the solidified material region and / or the interfaces between the solidified material region and the remaining substrate or cap, and / or the area around the interfaces, less susceptible to cracking.In other words, the solidified material area is less susceptible to damage and unintentional contact, for example during the production flow, thanks to the inventive method, and is therefore less of a cause and starting point for cracks. Furthermore, the inventive method makes it less problematic if the substrate material is only heated locally and contracts relative to its surroundings during both solidification and cooling. The fact that a very high tensile stress can thus arise in the sealing area is also less problematic, since, for example, lowering the solidified material area minimizes the surface area exposed to mechanical impacts. Consequently, spontaneous cracking, which can occur depending on the stress and material, is also less likely.Crack formation under thermal or mechanical stress of the micromechanical component during further processing or in the field is also less likely, since, for example, the area of ​​the sealed access opening is better protected. In particular, the method according to the invention makes it possible for the melt zone, especially immediately surrounding the access opening, to have a shallower melt depth compared to the surrounding area of ​​the access opening, particularly areas of the cap or substrate further away from the access opening, with or after the introduction of energy or heat, for example by means of a laser pulse, than without pretreatment according to one or a selection of the alternatives in the fourth process step. In particular, the method according to the invention makes it possible to prevent cracking during solidification of the material area due to the recrystallization dynamics in the center of the melted zone.The recess prevents the formation of a tip in the center of the solidified material area or any protrusion of the tip beyond the surface of the substrate or cap. This also eliminates the likelihood of damage to such a tip or unintentional contact during the subsequent manufacturing process. Thus, a simple and cost-effective method is provided for manufacturing a micromechanical component that is mechanically robust and has a long service life compared to prior art.

[0008] In the context of the present invention, the term “micromechanical component” is to be understood as encompassing both micromechanical components and microelectromechanical components.

[0009] The present invention is preferably intended for the manufacture of a micromechanical component with one cavity. However, the present invention is also intended, for example, for a micromechanical component with two cavities or with more than two, i.e., three, four, five, six or more than six, cavities.

[0010] Preferably, the access opening is closed by introducing energy or heat into an energy- or heat-absorbing part of the substrate or cap using a laser. Preferably, energy or heat is introduced sequentially into the absorbing part of the substrate or cap of several micromechanical components, which are, for example, manufactured together on a wafer. Alternatively, however, simultaneous introduction of energy or heat into the respective absorbing part of the substrate or cap of several micromechanical components is also possible, for example, using multiple laser beams or laser devices.

[0011] Advantageous embodiments and further developments of the invention can be found in the dependent claims and in the description with reference to the drawings.

[0012] According to a preferred embodiment, the cap with the substrate encloses a second cavern, wherein a second pressure prevails in the second cavern and a second gas mixture with a second chemical composition is enclosed.

[0013] A further object of the present invention is a method for manufacturing a micromechanical component comprising a substrate and a cap connected to the substrate and enclosing a first cavity and a second cavity, wherein a first pressure prevails in the first cavity and a first gas mixture with a first chemical composition is enclosed, wherein a second pressure prevails in the second cavity and a second gas mixture with a second chemical composition is enclosed, wherein -- in a first process step an access opening connecting the first cavern with an environment of the micromechanical component is formed in the substrate or in the cap, wherein -- in a second process step the first pressure and / or the first chemical composition is set in the first cavern, whereby -- in a third process step the access opening is closed by introducing energy or heat into an absorbing part of the substrate or cap using a laser, wherein -- in a fourth procedural step -- a recess is formed in one of the surfaces of the substrate or cap facing away from the first cavern in the area of ​​the access opening to receive a material area of ​​the substrate or cap that has been converted into a liquid state in the third process step and / or -- a raised area on the surface of the substrate or cap facing away from the first cavern in the area of ​​the access opening to guide away the material area of ​​the substrate or cap that has been converted into a liquid state in the third process step, essentially away from the access opening and essentially parallel to the surface, and / or -- a reflection area on or in the surface of the substrate or cap facing away from the first cavern in the area of ​​the access opening to the

[0014] In contrast to the rest of the surface, increased reflection of the laser radiation used in the third process step to introduce energy or heat is formed and / or -- an absorption area is formed on or in the surface of the substrate or cap facing away from the first cavern in the area of ​​the access opening, resulting in increased absorption of the laser radiation used in the third process step to introduce the energy or heat, in contrast to the rest of the surface.

[0015] According to a preferred embodiment, the recess is designed such that the solidified material region is situated between a plane extending substantially along the surface and the first cavity. This advantageously prevents the solidified material region from projecting beyond the surface, thus further reducing its exposure to mechanical impacts. Consequently, the solidified material region and / or the interfaces between the solidified material region and the remaining substrate or cap, and / or the area around the interfaces, are even less susceptible to cracking.

[0016] According to a preferred embodiment, the recess is designed such that a first area of ​​a projection of the recess onto a plane extending substantially along the surface is smaller than a second area of ​​a projection of the solidified material region or the absorbing part of the substrate or cap onto the plane. This advantageously allows the amount of the substrate or cap material region that has been converted into the liquid state to be reduced, and enables a melt pool generated by the energy input to flow more freely without requiring an unnecessarily large area of ​​the surface for the recess's formation.

[0017] According to a preferred embodiment, the recess is designed to be in a plane extending substantially parallel to the surface, rotationally symmetrical to the access channel or to the center of mass of the solidified material area or to the absorbing part of the substrate or cap, and / or to be ring-shaped. This allows the melt pool to flow particularly advantageously.

[0018] According to a preferred embodiment, the recess in a further plane extending substantially parallel to the surface is positioned at a distance from the center point of the access channel in that further plane that is substantially twice as far as the maximum extent of the access channel in that further plane is from the center point. This allows the melt pool to flow particularly efficiently.

[0019] According to a preferred embodiment, a raised area of ​​the solidified material is formed in a plane extending substantially parallel to the surface, and is rotationally symmetrical to the access channel, the center of mass of the solidified material area, the absorbing part of the substrate or cap, and / or is ring-shaped. This advantageously allows the solidified material area to lie beneath an otherwise (i.e., except for the area of ​​the access opening) substantially flat surface of the cap or substrate. Furthermore, this reduces the maximum stress in the solidified material area, the cap, or the substrate. It also advantageously prevents the area of ​​maximum mechanical stress from being located directly above the sealed access opening.Furthermore, the inventive method advantageously enables the positioning between the access opening and the melting bath to be determined not only by the laser's alignment accuracy, but, for example, primarily by the pre-structuring in the case of a slightly wider laser beam. This allows the pre-structuring to be carried out with high precision, unlike in previously known methods. Thus, the melt pool, for example, can be reproduced very accurately in its shape and its shape relative to the access opening, even with minor variations in laser accuracy. This provides an effective way to reduce the probability that the solidified material area is the cause or starting point of cracks.

[0020] Furthermore, another object of the present invention is a micromechanical component comprising a substrate and a cap connected to the substrate and enclosing a first cavity with the substrate, wherein a first pressure prevails in the first cavity and a first gas mixture with a first chemical composition is enclosed, wherein the substrate or the cap comprises a sealed access opening, wherein the substrate or the cap -- a recess located in one of the first caverns facing away from the substrate or cap and in the area of ​​the access opening for receiving a material area of ​​the substrate or cap that has been converted into a liquid state during the closing of the access opening and / or. -- a raised area arranged on the surface of the substrate or cap facing away from the first cavern and in the area of ​​the access opening, for diverting the portion of the substrate or cap material that has been converted into a liquid state during the closing of the access opening substantially away from the access opening and substantially parallel to the surface and / or -- comprising a reflection area arranged on or in the surface of the substrate or cap facing away from the first cavern and in the area of ​​the access opening for increased reflection of laser radiation used to introduce energy or heat during the closing of the access opening, in contrast to the rest of the surface, and / or -- comprising an absorption area located on or in the surface of the substrate or cap facing away from the first cavern and in the area of ​​the access opening, for increased absorption of the laser radiation used to introduce energy or heat during the closing of the access opening, in contrast to the rest of the surface.

[0021] According to a preferred embodiment, the cap with the substrate encloses a second cavern, wherein a second pressure prevails in the second cavern and a second gas mixture with a second chemical composition is enclosed.

[0022] Furthermore, another object of the present invention is a micromechanical component comprising a substrate and a cap connected to the substrate and enclosing a first cavity and a second cavity, wherein a first pressure prevails in the first cavity and a first gas mixture with a first chemical composition is enclosed, wherein a second pressure prevails in the second cavity and a second gas mixture with a second chemical composition is enclosed, wherein the substrate or the cap comprises a sealed access opening, wherein the substrate or the cap -- a recess located in one of the first caverns facing away from the substrate or cap and in the area of ​​the access opening for receiving a material area of ​​the substrate or cap that has been converted into a liquid state during the closing of the access opening and / or -- a raised area arranged on the surface of the substrate or cap facing away from the first cavern and in the area of ​​the access opening, for diverting the portion of the substrate or cap material that has been converted into a liquid state during the closing of the access opening substantially away from the access opening and substantially parallel to the surface and / or -- comprising a reflection area arranged on or in the surface of the substrate or cap facing away from the first cavern and in the area of ​​the access opening for increased reflection of laser radiation used to introduce energy or heat during the closing of the access opening, in contrast to the rest of the surface, and / or -- an absorption area located on or in the surface of the substrate or cap facing away from the first cavern and in the area of ​​the access opening, which is raised in contrast to the rest of the surface

[0023] The process includes absorbing the laser radiation used to introduce energy or heat during the closing of the access opening. This advantageously provides a compact, mechanically robust, and cost-effective micromechanical component with preset first and second pressures. The aforementioned advantages of the method according to the invention also apply accordingly to the micromechanical component according to the invention.

[0024] According to a preferred embodiment, the recess is designed such that the solidified material region is situated between a plane extending substantially along the surface and the first cavity. This advantageously provides a micromechanical component that is particularly robust against mechanical impacts.

[0025] According to a preferred embodiment, a raised area of ​​the solidified material is arranged in a plane extending substantially parallel to the surface, and is rotationally symmetrical to the access channel, the center of mass of the solidified material, the absorbing part of the substrate or cap, and / or is ring-shaped. This advantageously allows maximum stresses to be located further away from the access channel and are less concentrated, in contrast to known micromechanical components. Furthermore, it is advantageously achieved that the solidified material area is located only below a plane extending substantially along the surface.

[0026] According to a preferred further development, it is provided that an elevation of the solidified material area is arranged on one of the sides of the solidified material area facing away from the first cavern.

[0027] According to a preferred further development, the substrate and / or the cap is provided for to comprise silicon.

[0028] According to a preferred embodiment, the reflection area comprises an additional layer. According to a preferred embodiment, for example, the reflection area or the additional layer comprises aluminum or gold or Al or Au. According to a preferred embodiment, for example, the reflection area or the additional layer comprises a reflective layer of defined thickness made of oxide or nitride.

[0029] According to a preferred embodiment, the first pressure is lower than the second pressure, with a first sensor unit for measuring the angular rate being arranged in the first cavern and a second sensor unit for measuring the acceleration being arranged in the second cavern. This advantageously provides a mechanically robust micromechanical component for measuring angular rate and acceleration, with optimal operating conditions for both the first and second sensor units. Brief description of the drawings Fig. Figure 1 shows a schematic representation of a micromechanical component with an open access opening according to an exemplary embodiment of the present invention. Fig. Figure 2 shows a schematic representation of the micromechanical component according to Fig. 1 with a closed access opening. Fig. Figure 3 shows a schematic representation of a method for manufacturing a micromechanical component according to an exemplary embodiment of the present invention. Fig. Figure 4 shows a schematic representation of a previously known micromechanical component. Fig. 5, Fig. 6, Fig. 7, Fig. 8 and Fig. Figure 9 shows a schematic representation of a section of the micromechanical component according to Fig. 4 at different times of a previously known manufacturing process. Fig. 10, Fig. 11, Fig. 12, Fig. 13 and Fig. Figure 14 shows schematic representations of a partial area of ​​a micromechanical component according to an exemplary embodiment of the present invention at different times of a method according to the invention. Embodiments of the invention

[0030] In the various figures, identical parts are always marked with the same reference symbols and are therefore usually only named or mentioned once.

[0031] In Fig. 1 and Fig. Figure 2 is a schematic representation of a micromechanical component 1 with an open access opening 11 in Fig. 1 and with closed access opening 11 in Fig. Figure 2 shows an exemplary embodiment of the present invention. Here, the micromechanical component 1 comprises a substrate 3 and a cap 7. The substrate 3 and the cap 7 are connected to each other, preferably hermetically, and together enclose a first cavity 5. For example, the micromechanical component 1 is configured such that the substrate 3 and the cap 7 additionally enclose a second cavity. The second cavity is in Fig. 1 and in Fig. 2, however, is not shown.

[0032] For example, in the first cavern 5, especially in situations like those in Fig. Figure 2 shows a sealed access opening 11, and a first pressure is present. Furthermore, a first gas mixture with a first chemical composition is enclosed in the first cavity 5. Additionally, for example, a second pressure prevails in the second cavity, and a second gas mixture with a second chemical composition is enclosed in the second cavity. Preferably, the access opening 11 is arranged in the substrate 3 or in the cap 7. In the present embodiment, the access opening 11 is arranged in the cap 7 by way of example. However, according to the invention, it can alternatively be provided that the access opening 11 is arranged in the substrate 3.

[0033] For example, it is planned that the initial pressure in the first cavern 5 will be lower than the second pressure in the second cavern. It is also planned, for example, that a [missing text] will be installed in the first cavern 5. Fig. 1 and Fig. 2 not shown first micromechanical sensor unit for measuring rotation rate and in the second cavern a in Fig. 1 and Fig. 2 second micromechanical sensor units for acceleration measurement are arranged, not shown.

[0034] In Fig. Figure 3 shows a schematic representation of a method for manufacturing the micromechanical component 1 according to an exemplary embodiment of the present invention. In this process, -- in a first process step 101 the access opening 11 connecting the first cavern 5 with an environment 9 of the micromechanical component 1, in particular narrow, is formed in the substrate 3 or in the cap 7. Fig. Figure 1 shows, as an example, the micromechanical component 1 after the first process step 101. Furthermore, -- in a second process step 102, the first pressure and / or the first chemical composition is set in the first cavern 5, or the first cavern 5 is flooded with the desired gas and the desired internal pressure via the access channel. Furthermore, for example -- in a third process step 103, the access opening 11 is closed by introducing energy or heat into an absorbing part 21 of the substrate 3 or the cap 7 using a laser. Alternatively, for example, it is also provided that -- in the third process step 103, the area around the access channel is preferably heated locally by a laser and the access channel is hermetically sealed. Thus, it is advantageously possible to provide the process according to the invention with energy sources other than a laser for sealing the access opening 11. Fig. Figure 2 shows, by way of example, the micromechanical component 1 after the third process step 103.

[0035] After the third procedural step 103, in a Fig. Mechanical stresses occur in the lateral region 15 of the micromechanical component 1, as illustrated by example in Figure 2, both on the surface 19 and in depth perpendicular to a projection of the lateral region 15 onto the surface 19, i.e., along the access opening 11 and in the direction of the first cavern 5. These mechanical stresses, in particular local mechanical stresses, prevail especially at and near an interface between a material region 13 of the cap 7 that transitions into a liquid state in the third process step 103 and into a solid state after the third process step 103, closing the access opening 11, and a residual region of the cap 7 that remains in a solid state during the third process step 103. Fig. 2 the material area 13 of the cap 7 closing the access opening 11 is to be regarded as merely schematic or is shown schematically, in particular with regard to its lateral extent or shape, especially parallel to the surface 19, and in particular with regard to its extent or configuration perpendicular to the lateral extent, especially perpendicular to the surface 19.

[0036] As in Fig. 3 is shown as an example; additionally, -- in a fourth procedural step 104 -- a recess 17 in one of the first caverns 5 on the surface 19 of the substrate 3 or the cap 7 facing away from the access opening 11 for receiving a material area 13 of the substrate 3 or the cap 7 that has been converted into a liquid state in the third process step 103 and / or -- a raised area on the surface 19 of the substrate 3 or the cap 7 facing away from the first cavern 5 in the area of ​​the access opening 11 for directing the material area 13 of the substrate 3 or the cap 7, which was converted into a liquid state in the third process step 103, substantially away from the access opening 11 and substantially parallel to the surface 19 and / or -- a reflection area on or in the surface 19 of the substrate 3 or the cap 7 facing away from the first cavern 5 in the area of ​​the access opening 11 for increased reflection of a laser radiation 211 used in the third process step 103 for introducing the energy or heat, in contrast to the rest of the surface 19, is formed and / or -- an absorption area on or in the surface 19 of the substrate 3 or the cap 7 facing away from the first cavern 5 in the area of ​​the access opening 11 for increased absorption of the laser radiation 211 used in the third process step 103 to introduce the energy or heat is formed in contrast to the rest of the surface 19.

[0037] In Fig. 4 or in Fig. Figure 4A shows an example of a previously known micromechanical component 1. This example shows a micromechanical component 1 with a combined acceleration and yaw rate sensor, which are hermetically sealed with a cap wafer. During the capping process, a high internal pressure is set in the second cavity 205 of the acceleration sensor. Using the previously known method, a low internal pressure is set in the first cavity 5 of the yaw rate sensor. If a crack forms in the cap 7, for example, after the internal pressure in the first cavity 5 has been set, the first cavity 5 of the yaw rate sensor will be flooded with air, and the yaw rate sensor will no longer be able to oscillate due to the air damping and may fail. Finally, in Fig. 4 B and in Fig. Figure 4C shows an area of ​​the sealed access opening 11 or the solidified material area. Fig. 4 B and Fig. 4 C areas with high mechanical stresses or high tensile stresses or high tensile stress.

[0038] In Fig. 5, Fig. 6, Fig. 7, Fig. 8 and Fig. 9 is, in schematic representations, a sub-area of ​​the already known micromechanical component 1 according to Fig. 4. A previously known procedure is presented at different times.

[0039] In Fig. Figure 6 shows, by way of example, the absorbing part 21, or the area of ​​laser energy that is absorbed, which at least partially absorbs the laser radiation 211 shown schematically by arrows. The laser radiation 211, or a laser pulse 211 or several laser pulses 211, heats the material around the access hole, or the material around the access hole is melted by a laser pulse 211. The laser pulse 211 is preferably positioned centrally above the access hole in order to minimize the melting zone and thus the laser power required.

[0040] In Fig. Figure 7 shows the material area 13 in the liquid state or as molten material 13. Fig. Figure 7 shows how the molten material spreads within the molten area and seals the access hole. The molten material then solidifies (Figure 13).

[0041] In Fig. Figure 8 also shows a point in time at which material 13 has already partially transitioned from the liquid to the solid state. The portion of material 13 that has already solidified is depicted as a solidification front.

[0042] Finally, it shows Fig. Figure 9 shows, by way of example, how the entire material area 13 has transitioned into the solid state and a protrusion 213 of the solidified material area has formed centrally above the access opening 11, which projects out over a plane extending along the surface 19. Here, the protrusion 213 is shown by way of example as a conical bulge with a projection towards the substrate.

[0043] Through the in Fig. 5, Fig. 6, Fig. 7, Fig. 8 and Fig. The nine process steps depicted, for example, cause stresses in the cap material, specifically in the cap 7 or substrate 3. These stresses, or mechanical stresses, arise particularly during the solidification of the material. For instance, the greatest stress occurs at the deepest point of the melt zone. This can be visualized by the fact that the melt is most surrounded by a solid at this point and therefore reacts least effectively to the different expansion movements. Directly at the surface, the material can react, for example, with a bulge or contraction. This can also be observed very clearly in the center of the melt zone. Since, for example, the silicon solidifies from the edge and expands during solidification, a phenomenon such as the one shown in [reference missing] occurs in the center of the melt zone. Fig. 9 shows a cone-shaped protrusion. This is, for example, so high that it can extend a few µm above the substrate.

[0044] Critical of the in Fig. For example, two points in the arrangement shown in 9 are: 1. The area of ​​highest stress in the material lies precisely in and above the area of ​​the access hole 11. The now-sealed access hole 11 is a disturbance in the bulk material. It therefore acts, for example, as a starting point for cracks and thus weakens the material. 2. Above the access hole, for example, a conical tip 213 is formed that extends significantly beyond the substrate. This poses a risk for further processing and field application, as the tip can be subjected to mechanical stress and thus cause cracks in the material.

[0045] In Fig. 10, Fig. 11, Fig. 12, Fig. 13 and Fig. Figure 14 schematically depicts a partial area of ​​a micromechanical component according to an exemplary embodiment of the present invention at different points in time of a method according to the invention. For example, the recess 17 or a pre-structuring of the substrate 3 around the access opening 11 or around the access channel 11 is formed such that the solidified material area is arranged between a plane extending substantially along the surface 19 and the first cavity 5. This is shown in Fig. 14 are shown as examples.

[0046] Additionally or alternatively, for example, the recess 17 is designed such that a first surface of a projection of the recess 17 onto a plane extending substantially along the surface 19 is smaller than a second surface of a projection of the solidified material area or the absorbing part 21 of the substrate 3 or the cap 7 onto the plane.

[0047] Furthermore, the recess 17 is preferably formed in a plane extending substantially parallel to the surface 19, essentially rotationally symmetric to the access channel 11 or to the center of mass of the solidified material area or to the absorbing part 21 of the substrate 3 or the cap 7 and / or in an annular form.

[0048] Furthermore, in Fig. Figure 10 shows how the recess 17 in a further plane 201 extending substantially parallel to the surface 19 is formed at a distance of substantially twice as far from a center point 203 of the access channel 11 in the further plane 201 as the maximum extent 207 of the access channel 11 in the further plane 201 is from the center point 203. In particular, it is provided that an inner radius of the ring or the annular recess 17 is at least twice as large as a radius of the access hole or the access channel 11. Furthermore, for example, the protrusion 213 of the solidified material region in the plane extending substantially parallel to the surface 19 is formed substantially rotationally symmetrical with respect to the access channel 11 or to the center of mass of the solidified material region or to the absorbing part 21 of the substrate 3 or the cap 7 and / or is annular. Fig. Figure 14 shows the elevation 213 as an example of a ring-shaped protrusion without overhang to the substrate.

[0049] In Fig. Figure 13 schematically illustrates an area 215 with reduced stress or reduced mechanical tension and an evasive movement 215 intended to reduce tension.

[0050] Through the in Fig. 10, Fig. 11, Fig. 12, Fig. 13 and Fig. The process steps, as schematically illustrated in 14, achieve the formation of a melt pool 13 after the laser pulse 211 by pre-treating the material in the area of ​​the access hole 11, which no longer has a classic trough shape. The process according to the invention is possible, for example, by means of a process as shown in Fig. Figure 10 shows pre-structuring, such as etching, of the area to be melted with laser pulse 211. Areas that are to be melted particularly deeply can be etched to a greater depth. For example, the laser light penetrates deeper into the material relative to the height of the substrate surface. Molten material from higher areas flows into lower areas as soon as the material becomes liquid. The opposite behavior applies to areas that are not structured. In particular, as shown in Fig. Figure 12 shows that a shape of the melting zone or of the material area 13 in the liquid state is chosen such that the material area 13 melts in a ring shape around the access hole 11 to a greater depth.

[0051] As in Fig. 13 and Fig. As shown in Figure 14, during the solidification process, the areas of highest stress are no longer located above or directly above the access hole 11, as in the previously known method, but rather in a ring-shaped pattern around the access hole 11, particularly at a lateral distance from the access hole 11. Furthermore, the maximum stress or maximum mechanical stress in the material is reduced, since the position of maximum mechanical stress is no longer concentrated at a single point in the center as in Figure 14. Fig. 7, Fig. 8 and Fig. 9 depicted tub, but is distributed over a ring, for example essentially along the elevation 213.

[0052] Due to the modified melting zone 13 in contrast to the previously known method, no conical tip 213 is formed in the middle of the melting zone 13, but rather a ring-shaped elevation 213 around the center of the melting zone, which has a significantly lower height due to its radial extent and is significantly less sensitive to mechanical stresses due to its locally larger extent.

Claims

[1] Method for producing a micromechanical component (1) with a substrate (3) and with a cap (7) connected to the substrate (3) and enclosing a first cavern (5) with the substrate (3), wherein a first pressure prevails in the first cavern (5) and a first gas mixture with a first chemical composition is enclosed, wherein -- in a first process step (101) an access opening (11) connecting the first cavern (5) with a surrounding (9) of the micromechanical component (1) is formed in the substrate (3) or in the cap (7), wherein -- in a second process step (102) the first pressure and / or the first chemical composition is set in the first cavern (5), wherein -- in a third process step (103) the access opening (11) is closed by introducing energy or heat into an absorbing part (21) of the substrate (3) or the cap (7) using a laser, characterized by , that -- in a fourth process step (104), wherein the fourth process step (104) is carried out before the third process step (103), a recess (17) is formed in a surface (19) of the substrate (3) or the cap (7) facing away from the first cavern (5) in the area of ​​the access opening (11) for receiving a material region (13) of the substrate (3) or the cap (7) that has been converted into a liquid state in the third process step (103), wherein the recess (17) is formed in a plane extending substantially parallel to the surface (19) and is rotationally symmetric to the access opening (11) or to the center of mass of the material region that has been converted into a solid state after the third process step or to the absorbing part (21) of the substrate (3) or the cap (7) and is annular in shape. [2] Method according to claim 1, wherein the cap (7) with the substrate (3) encloses a second cavern, wherein a second pressure prevails in the second cavern and a second gas mixture with a second chemical composition is enclosed. [3] Method according to one of the preceding claims, wherein the recess (17) is formed such that the material region which has transitioned into a solid state of matter after the third method step is arranged between a plane extending substantially along the surface (19) and the first cavern (5). [4] Method according to one of the preceding claims, wherein the recess (17) is designed such that a first surface of a projection of the recess (17) onto a plane extending substantially along the surface (19) is smaller than a second surface of a projection of the material region or the absorbing part (21) of the substrate (3) or the cap (7) that has transitioned into a solid state after the third method step onto the plane. [5] Method according to one of the preceding claims, wherein the recess (17) in a further plane (201) extending substantially parallel to the surface (19) is formed at a distance substantially twice as far from a center point (203) of the access opening (11) in the further plane (201) as a maximum extent (207) of the access opening (11) in the further plane (201) is formed at a distance from the center point (203). [6] Micromechanical component (1) comprising a substrate (3) and a cap (7) connected to the substrate (3) and enclosing a first cavity (5) with the substrate (3), wherein a first pressure prevails in the first cavity (5) and a first gas mixture with a first chemical composition is enclosed, wherein the substrate (3) or the cap (7) comprises a sealed access opening (11), characterized by, that the substrate (3) or the cap (7) comprises a recess (17) located in one of the first caverns (5) facing away from the substrate (3) or the cap (7) and in the region of the access opening (11) for receiving a material region (13) of the substrate (3) or the cap (7) that has been converted into a liquid state during the closing of the access opening (11), wherein the recess (17) is substantially rotationally symmetrical to the access opening (11) or to the center of mass of the material region that has been converted into a solid state after the third process step or to the absorbing part (21) of the substrate (3) or the cap (7) and is annular in shape. [7] Micromechanical component (1) according to claim 6, wherein the cap (7) encloses a second cavity with the substrate (3), wherein a second pressure prevails in the second cavity and a second gas mixture with a second chemical composition is enclosed

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