Laser shutter with optimized intensity distribution

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 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 -- in a first method step (101), an access opening (11) connecting the first cavity (5) to an environment (9) of the micromechanical component (1) is formed in the substrate (3) or in the cap (7), wherein -- in a second method step (102), the first pressure and / or the first chemical composition in the first cavern (5) is adjusted, wherein -- in a third method step (103), the access opening (11) is closed by introducing energy or heat into an absorbing part of the substrate (3) or the cap (7) using a laser, wherein the introduction of the energy or heat is controlled by means of a laser beam (1005) comprising a spatial laser pulse extension (1001) extending essentially along a surface (1011) of the substrate (3) or the cap (7) facing away from the first cavity (5) and extending essentially parallel to a main extension plane (100) of the substrate (3) and a laser pulse intensity (1003) for reducing residual stresses in the substrate (3) or in the cap (7), wherein the introduction of the energy or heat is controlled by means of the laser beam (1005) such that the laser pulse extension (1001) comprises a first laser pulse extension region (1007) with at least a first laser pulse intensity and a second laser pulse extension region (1009) with at least a second laser pulse intensity,wherein a projection of the first laser pulse extension region (1007) onto the main extension plane (100) and a projection of the access opening (11) onto the main extension plane (100) at least partially overlap, characterized in that the introduction of the energy or heat is controlled by means of the laser beam (1005) such that the second laser pulse extension region (1009) comprises a first sub-region (1013) and a second sub-region (1015), wherein a projection of the first sub-region (1013) onto the main extension plane (100) and a projection of the second sub-region (1015) onto the main extension plane (100) are spaced apart from one another.

Description

State of the art

[0001] The invention is based on a method according to the preamble of claim 1.

[0002] Such a method is known from US 2011 / 0114830 A1 and US 2014 / 0022718 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 the 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 connected 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 specific internal pressure and / or the specific chemical composition in the cavity can be adjusted.

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

[0004] In the method for the targeted adjustment of 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 the desired internal pressure via the access channel. Finally, the area around the access channel is locally heated using a laser; the substrate material liquefies locally and, upon solidification, hermetically seals the access channel.

[0005] In gyroscopes, for example, a very low pressure is trapped, less than 1 mbar, for example. This is because some of the moving structures in gyroscopes are driven resonantly. At low pressure, oscillations can be easily excited with relatively low voltages due to the low damping.

[0006] With acceleration sensors, however, it is undesirable for the sensor to start vibrating, which would be possible if external acceleration were applied. Therefore, these sensors are operated at higher internal pressures. The internal pressure of an acceleration sensor, for example, is 500 mbar. Further disclosures can be found in the documents DE 102015220886A1, US 2011 / 0114840A1, and US 2014 / 0022718A1. Disclosure of the invention

[0007] It is an object of the present invention to provide a method for producing a micromechanical component that is mechanically robust and has a long service life compared to the prior art, in a simple and cost-effective manner compared to the prior art. Furthermore, it is an object of the present invention to provide a micromechanical component that is compact, mechanically robust and has a long service life compared to the prior art. According to the invention, this applies in particular to a micromechanical component with a (first) cavity. With the method according to the invention and the 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 if a first pressure is enclosed in a first cavity and a second pressure is enclosed in a second cavity, whereby the first pressure should be 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.

[0008] The task is solved by the introduction of the energy or heat is controlled by means of a laser beam comprising a spatial laser pulse extension and a laser pulse intensity for minimizing residual stresses in the substrate or in the cap, said laser beam extending essentially along a surface of the substrate or of the cap facing away from the first cavity and extending essentially parallel to a main extension plane of the substrate.

[0009] This provides a simple and cost-effective method for producing a micromechanical component, with which the introduction of energy or heat can be controlled using a laser beam comprising a spatial laser pulse extension and a laser pulse intensity in order to minimize residual stresses in the substrate or in the cap. This advantageously enables the energy or heat to be spatially introduced into the substrate or in the cap in a targeted manner. Thus, a first transition of the material region from the solid to the liquid state and a second transition of the material region from the liquid to the solid state following the first transition can be spatially controlled in the substrate or in the cap.Furthermore, due to the spatial distribution of the energy or heat, the method according to the invention can be used to bring regions of the substrate or cap that are adjacent to the material region of the substrate or cap to a higher temperature in a spatially targeted manner compared to the prior art. The temperature gradients in the substrate or cap, in particular in the region of the access opening, can therefore be reduced compared to the prior art. This makes it possible for the thermal expansion upon a temperature increase and / or the thermal shrinkage upon a temperature decrease of adjacent regions in the substrate or cap, in particular in the region of the access opening, to be equalized to one another and thus the mechanical stresses or strains that occur in the region of the closed access opening, in particular as a result of the cooling process after the third method step.Residual stresses can be reduced compared to the state of the art. The reduction or reduction of locally occurring stresses or strains is particularly advantageous because it increases the resistance to crack formation compared to the state of the art and thus reduces the probability of component failure immediately after the access opening is closed, during further processing of the micromechanical component, or during the product's lifetime compared to the state of the art. By avoiding cracks, a hermetic closure of the access opening is enabled, and thus the probability of a restriction of the functionality of the micromechanical component due to a leaky closure of the access opening is reduced compared to the state of the art.

[0010] With the method according to the invention, in particular, temperature gradients between the recently solidified material region and the material surrounding the material region can be reduced compared to the prior art by spatially targeted increases in the temperature in the substrate or in the cap. In particular, these temperature gradients can be reduced at the time of solidification of the material region shortly after the material region has solidified. This advantageously enables the thermal shrinkage of the material region to essentially correspond to the thermal shrinkage of the material surrounding the material region, or the two thermal shrinkages can be adjusted to match one another. This advantageously enables the mechanical stresses occurring in the region of the closed access opening, in particular after the material region has cooled down, to be reduced compared to the prior art.

[0011] According to the invention, temperature gradients at a time when the material region is in a liquid state or in a molten state are less critical because the material region is essentially stress-free at this time. However, according to the invention, for example, the temperature gradients are reduced compared to the prior art even at a time when the material region is in a liquid state. In particular, the invention avoids or reduces the build-up of stresses after the solidification of the material region because the recently solidified material region is hotter than the material surrounding the material region and therefore experiences greater / different thermal expansion during the cooling process than the colder material surrounding the material region. According to the invention, the temperature gradient in the material or in the substrate orin the cap during solidification of the material area and during cooling is kept as low as possible so that the mechanical stresses remaining in the component after cooling are as low as possible.

[0012] A further advantage of the method according to the invention is that the movement of dislocations can be thermally activated by means of the targeted spatial introduction of energy or heat into the substrate or cap. Thus, it is advantageously possible for the substrate or cap to be plastically deformed at least partially, or at least partially locally, in the region of the access opening, particularly after the second transition, through thermally activated dislocation movements or through facilitated dislocation movements. Thus, locally occurring stresses or stress peaks can be reduced or dissipated by plastic deformation using the targeted introduction of energy or heat, compared to the prior art.

[0013] The method according to the invention is also advantageous when surfaces of sensors or sensor cores are provided with organic coatings that prevent the adhesive bonding of movable structures, and these organic coatings degrade at the high temperatures, for example, during the bonding process, and are no longer fully effective. The method according to the invention can be used to counteract, in a simple and cost-effective manner, at least partial release of the organic layers into the cavity and the resulting increased internal pressure after the MEMS element is sealed.

[0014] Furthermore, the method according to the invention is also advantageous, for example, compared to a method in which different pressures p1 / p2 are required in a cavity of a yaw-rate sensor p1 and in a cavity of an acceleration sensor p2. In the cavity of the yaw-rate sensor, a high pressure initially trapped in both cavities is subsequently reduced to a low pressure by activating the getter via a temperature step in the cavity of the yaw-rate sensor. Compared to such a method, the method according to the invention is comparatively simple and cost-effective.

[0015] Furthermore, the method according to the invention is advantageous when sealing a MEMS structure arranged in the first cavity with a cap wafer at high temperatures, for example, using a sealing glass as the bonding material or with various other bonding materials or bonding systems such as eutectic aluminum-germanium (AlGe) or copper-tin-copper (CuSnCu) systems. Even if the bonding process is carried out under vacuum and at high temperatures, gases from the bonding system evaporate at high temperatures and cause a residual pressure in the cavity that is independent of the very low pressure prevailing in the bonding chamber and thus in the cavity during the bonding process. This residual pressure can be significantly reduced with the method according to the invention compared to the prior art.

[0016] In particular, the method according to the invention is also advantageous, for example, if outgassing of noble gases or other gases from the wafers or from the substrate or from the cap or from a bonding layer occurs during the bonding process, if the noble gases or other gases cannot be pumped through the getter or can only be pumped with difficulty, since the method according to the invention can be used to set the first pressure after the bonding process using the access opening. Thus, such outgassing can be effectively counteracted with the method according to the invention. This is advantageous because outgassing of noble gases or other gases that cannot be pumped through the getter or can only be pumped with difficulty would limit the minimum achievable pressure and, even at higher pressures, this outgassing could cause significant, undesirable variation in the internal pressure.

[0017] In the context of the present invention, a laser beam is understood to mean electromagnetic radiation emitted continuously or discontinuously by a laser. The laser can be, for example, a pulsed laser or a continuous-wave laser. Furthermore, the invention provides that the continuous-wave laser is operated such that the electromagnetic radiation is continuously emitted or continuously incident on the absorbing part of the substrate or cap. Furthermore, the invention provides that the electromagnetic radiation incident on the absorbing part of the substrate or cap and is at least partially absorbed by it.

[0018] According to the invention, a laser beam comprising a spatial laser pulse extension and a laser pulse intensity is understood to mean that the laser beam comprises a spatial intensity distribution, wherein the laser pulse intensity within the spatial laser pulse extension is greater than zero or greater than a minimum laser pulse intensity. In other words, the spatial laser pulse extension is defined such that the laser pulse intensity spatially within the laser pulse extension is greater than zero or greater than the minimum laser pulse intensity, and that the laser pulse intensity spatially outside the laser pulse extension is equal to zero or less than the minimum laser pulse intensity.In the context of the present invention, the laser pulse extension and the laser pulse intensity are meant essentially along the surface of the substrate or the cap facing away from the first cavity and running essentially parallel to the main extension plane of the substrate.

[0019] In the context of the present invention, the term “micromechanical component” is to be understood as encompassing both micromechanical components and microelectromechanical components.

[0020] The present invention is preferably intended for the production 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, ie, three, four, five, six, or more than six, cavities.

[0021] Preferably, the access opening is closed by introducing energy or heat into a part of the substrate or cap that absorbs this energy or heat, using a laser. In this case, energy or heat is preferably introduced sequentially into the absorbing part of the substrate or cap of several micromechanical components, which are manufactured jointly on a wafer, for example. Alternatively, however, a temporally parallel introduction of the energy or heat into the respective absorbing part of the substrate or cap of several micromechanical components is also provided, for example using several laser beams or laser devices.

[0022] Advantageous embodiments and further developments of the invention can be found in the dependent claims and the description with reference to the drawings.

[0023] According to a preferred development, it is provided that the cap with the substrate encloses a second cavity, wherein a second pressure prevails in the second cavity and a second gas mixture with a second chemical composition is enclosed.

[0024] According to the invention, the introduction of energy or heat is controlled by means of the laser beam in such a way that the laser pulse extension comprises a first laser pulse extension range with at least a first laser pulse intensity and a second laser pulse extension range with at least a second laser pulse intensity, wherein a projection of the first laser pulse extension range onto the main extension plane and a projection of the access opening onto the main extension plane at least partially overlap. This advantageously enables the absorbing part to be spatially divided across the first laser pulse extension range and the second laser pulse extension range using the first laser pulse intensity and the second laser pulse intensity. This advantageously enables the material region to transition into a liquid aggregate state only in certain regions of the absorbing part.

[0025] According to the invention, the laser pulse extension comprising a first laser pulse extension range with at least a first laser pulse intensity and a second laser pulse extension range with at least a second laser pulse intensity is to be understood as meaning that the first laser pulse intensity within the first laser pulse extension range and the second laser pulse intensity within the second laser pulse extension range are each greater than zero or greater than a minimum laser pulse intensity. Furthermore, this is to be understood as meaning that the first laser pulse intensity outside the first laser pulse extension range and the second laser pulse intensity outside the second laser pulse extension range are each equal to zero or less than a minimum laser pulse intensity.

[0026] According to a preferred development, the introduction of energy or heat is controlled by means of the laser beam in such a way that a projection of the first laser pulse extension region onto the main extension plane and a projection of the second laser pulse extension region onto the main extension plane are spaced apart from one another. This advantageously enables the introduction of energy or heat into spatially separated regions in the substrate or in the cap.

[0027] According to a preferred development, the introduction of energy or heat is controlled by means of the laser beam in such a way that a projection of the second laser pulse extension region onto the main extension plane and a projection of the access opening onto the main extension plane are spaced apart from one another. This advantageously enables energy or heat to be introduced into a region of the substrate or cap spaced apart from the access opening.

[0028] According to a preferred development, the introduction of energy or heat is controlled by means of the laser beam in such a way that a first material region of a first absorbing region of the absorbing part of the substrate or the cap transitions into a liquid state due to the first laser pulse intensity of the first laser pulse extension range, while a second material region of a second absorbing region of the absorbing part of the substrate or the cap transitions into a liquid state or remains in a solid state due to the second laser pulse intensity of the second laser pulse extension range. This advantageously makes it possible to generate local mechanical stresses, in particular compressive stresses, in the substrate or in the cap, which counteract stresses, in particular tensile stresses, occurring in the region of the access opening.

[0029] According to a preferred development, the introduction of energy or heat is controlled by means of the laser beam in such a way that the spatial laser pulse extension is formed over the entire surface of the hollow cylinder or as a cut surface of the hollow cylinder running perpendicular to the longitudinal axis of the hollow cylinder, wherein the longitudinal axis essentially coincides with the center of the access opening. This advantageously enables the energy or heat to be introduced into the substrate or cap in a particularly targeted manner.

[0030] According to the invention, the introduction of energy or heat is controlled by means of the laser beam such that the second laser pulse extension region comprises a first subregion and a second subregion, wherein a projection of the first subregion onto the main extension plane and a projection of the second subregion onto the main extension plane are spaced apart from one another. This advantageously enables the energy or heat to be introduced into several regions of the substrate or cap spaced apart from the access opening.

[0031] According to a preferred development, the introduction of energy or heat is controlled by means of the laser beam in such a way that the first subregion and the second subregion are formed substantially parallel to the surface and substantially rotationally symmetrically. This advantageously enables the energy or heat to be introduced particularly symmetrically into the substrate or cap.

[0032] According to a preferred development, the introduction of energy or heat is controlled by means of the laser beam such that the second laser pulse expansion region comprises further subregions, in particular three or four or five or six or seven or eight or nine or ten further subregions, wherein the subregions are formed substantially parallel to the surface and substantially rotationally symmetrically and are arranged with the first subregion and the second subregion substantially parallel to the surface and substantially rotationally symmetrically around the access opening. This advantageously enables the energy or heat to be introduced into the substrate or into the cap in a particularly symmetrical and targeted manner.

[0033] According to a preferred development, the introduction of energy or heat is controlled by means of the laser beam in such a way that the laser beam comprises a laser pulse duration and the laser pulse intensity is provided so that it can be varied over time. This advantageously makes it possible for energy or heat to be introduced in a targeted manner into the substrate or cap before a first transition of the material region from the solid to the liquid state and after a second transition of the material region from the liquid to the solid state. Thus, due to heat conduction in the substrate or cap, it is possible for regions of the substrate or cap adjacent to the material region or to the absorbing part of the substrate or cap to be brought to a temperature that is higher than in the prior art before the first transition and after the second transition.Thus, the temperature gradients in the substrate or in the cap, particularly in the area of ​​the access opening, are reduced compared to the prior art. This allows the thermal expansion upon a temperature increase and / or the thermal shrinkage upon a temperature decrease of adjacent regions in the substrate or in the cap, particularly in the area of ​​the access opening, to be equalized, thus reducing the mechanical stresses occurring in the area of ​​the closed access opening compared to the prior art.

[0034] A further, unclaimed subject matter 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 having a first chemical composition is enclosed, wherein the substrate or the cap comprises a closed access opening,wherein the substrate or cap comprises a material region that solidifies after a controlled introduction of energy or heat into an absorbing part of the substrate or cap using a laser beam extending substantially along a surface of the substrate or cap facing away from the first cavity and extending substantially parallel to a main extension plane of the substrate, and a laser pulse intensity that minimizes residual stresses in the substrate or cap, and closes the access opening. This advantageously provides a compact, mechanically robust, and cost-effective micromechanical component with a set first pressure. The aforementioned advantages of the method according to the invention also apply correspondingly to the micromechanical component according to the invention.

[0035] According to a preferred embodiment, the substrate or cap comprises silicon. This advantageously enables the micromechanical component to be manufactured using standard semiconductor layer technology methods.

[0036] According to a preferred development, the cap encloses a second cavity with the substrate, wherein a second pressure prevails in the second cavity and a second gas mixture with a second chemical composition is enclosed. This advantageously provides a compact, mechanically robust, and cost-effective micromechanical component with a set first pressure and a second pressure.

[0037] According to a preferred development, the first pressure is lower than the second pressure, with a first sensor unit for measuring the yaw rate being arranged in the first cavity and a second sensor unit for measuring acceleration being arranged in the second cavity. This advantageously provides a mechanically robust micromechanical component for measuring yaw rate and acceleration with optimal operating conditions for both the first sensor unit and the second sensor unit. Short description of the drawings Fig. 1 shows a schematic representation of a micromechanical component with an open access opening according to an exemplary embodiment of the present invention. Fig. 2 shows a schematic representation of the micromechanical component according to Fig. 1 with closed access opening. Fig. 3 shows a schematic representation of a method for producing a micromechanical component according to an exemplary embodiment of the present invention. Fig. 4 shows a schematic representation of a micromechanical component with an open access opening according to a further exemplary embodiment of the present invention. Fig. 5 shows a schematic representation of the micromechanical component according to Fig. 4 with closed access opening. Fig. 6, Fig. 7, Fig. 8 and Fig. 9 show schematic representations of spatial laser pulse extensions according to exemplary embodiments of the present invention. Embodiments of the invention

[0038] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0039] In Fig. 1 and Fig. 2 is a schematic representation of a micromechanical component 1 with open access opening 11 in Fig. 1 and with closed access opening 11 in Fig. 2 according to 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 designed 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 is not shown.

[0040] For example, in the first cavern 5, especially as in Fig. 2, a first pressure. In addition, a first gas mixture with a first chemical composition is enclosed in the first cavity 5. Furthermore, a second pressure prevails, for example, 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, for example, in the cap 7. According to the invention, however, it can also be provided alternatively that the access opening 11 is arranged in the substrate 3.

[0041] For example, it is provided that the first pressure in the first cavern 5 is lower than the second pressure in the second cavern. For example, it is also provided that in the first cavern 5 a Fig. 1 and Fig. 2 not shown first micromechanical sensor unit for angular rate measurement and in the second cavern a Fig. 1 and Fig. 2 not shown second micromechanical sensor unit for acceleration measurement are arranged.

[0042] In Fig. 3 shows a schematic representation of a method for producing the micromechanical component 1 according to an exemplary embodiment of the present invention. -- in a first method step 101, the access opening 11, in particular a narrow one, connecting the first cavity 5 with an environment 9 of the micromechanical component 1 is formed in the substrate 3 or in the cap 7. Fig. 1 shows an example of the micromechanical component 1 after the first method step 101. In addition, -- in a second method step 102, the first pressure and / or the first chemical composition in the first cavern 5 is adjusted 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 method step 103, the access opening 11 is closed by introducing energy or heat into an absorbing part of the substrate 3 or the cap 7 using a laser. Alternatively, it is also provided, for example, that -- in the third method step 103, the area around the access channel is only locally heated, preferably by a laser, and the access channel is hermetically sealed. Thus, it is advantageously possible to provide the method according to the invention with energy sources other than a laser for closing the access opening 11. Fig. 2 shows an example of the micromechanical component 1 after the third method step 103.

[0043] For example, it is provided that in a fourth method step the substrate 3 is connected to the cap 7, wherein the fourth method step is carried out before or after the first method step 101.

[0044] After the third method step 103, in a Fig. 2, mechanical stresses occur in the lateral region 15 shown by way of example on a surface of the cap 7 facing away from the first cavity 5, as well as in the depth perpendicular to a projection of the lateral region 15 onto the surface, i.e. along the access opening 11 and in the direction of the first cavity 5, of the micromechanical component 1. These mechanical stresses, in particular local mechanical stresses, prevail in particular at and in the vicinity of an interface between a material region 13 of the cap 7, which changes into a liquid state of aggregation in the third method step 103 and, after the third method step 103, changes into a solid state of aggregation and closes the access opening 11, and a residual region of the cap 7 remaining in a solid state of aggregation during the third method step 103. In this case, Fig. 2 the material region 13 of the cap 7 closing the access opening 11 is to be regarded or shown schematically only, in particular with regard to its lateral extension or shape, in particular running parallel to the surface, and in particular with regard to its extension or configuration perpendicular to the lateral extension, in particular running perpendicular to the surface.

[0045] In Fig. 4 and Fig. 5 is a schematic representation of a micromechanical component 1 with open access opening 11 in Fig. 4 and with closed access opening 11 in Fig. 5 according to another exemplary embodiment of the present invention. This shows, by way of example, that a first micromechanical sensor unit for yaw rate measurement 1017 or a MEMS element is arranged in the first cavity 5. In Fig. 4 and Fig. 5 also shows an example of a main extension plane 100 of the substrate 3. In addition, Fig. 5 shows, by way of example, a surface 1011 extending essentially parallel to the main extension plane 100 and a laser beam 1005. Furthermore, Fig. 5 exemplary laser pulse intensities 1003 of the laser beam 1005 are shown. In Fig. 5 shows, by way of example, a Gaussian laser pulse intensity 1019 or a Gaussian beam profile and a uniform or top hat laser pulse intensity 1021 or a uniform or top hat beam profile.

[0046] For example, it is provided that the spatial intensity profile or the laser pulse intensities 1003 of the laser radiation 1005 used for the sealing process or the third method step is designed in such a way that residual stresses in the material occurring, in particular during the cooling process, are minimized.

[0047] According to the invention, the introduction of energy or heat is controlled by means of the laser beam 1005 comprising a spatial laser pulse extension 1001 running essentially along the surface 1011 of the substrate 3 or the cap 7 and the laser pulse intensity 1003 in order to minimize residual stresses in the substrate 3 or in the cap 7.

[0048] In Fig. 6, Fig. 7, Fig. 8 and Fig. 9 shows schematic representations of spatial laser pulse extensions 1001 according to exemplary embodiments of the present invention. Fig. 6 shows an example of a full-area spatial laser pulse extension 1001. Fig. 7, Fig. 8 and Fig. 9 show, in the left area, side views or sectional views of a partial area of ​​the micromechanical component 1 and, in the right area, top views or views of a plane substantially parallel to surface 1011.

[0049] Furthermore, in Fig. 7 shows, by way of example, that the spatial laser pulse extension 1001 comprises a first laser pulse extension region 1007 with at least a first laser pulse intensity and a second laser pulse extension region 1009 with at least a second laser pulse intensity. A projection of the first laser pulse extension region 1007 onto the main extension plane 100 and a projection of the access opening 11 onto the main extension plane 100 overlap at least partially. Furthermore, FIG. Fig. 7 shows, by way of example, that a projection of the first laser pulse extension region 1007 onto the main extension plane 100 and a projection of the second laser pulse extension region 1009 onto the main extension plane 100 are spaced apart from each other. Furthermore, Fig. 7 exemplifies that a projection of the second laser pulse extension region 1009 onto the main extension plane 100 and a projection of the access opening 11 onto the main extension plane 100 are spaced apart from each other.

[0050] At the Fig. 7, it is provided, for example, that a first material region of a first absorbing region of the absorbing part of the substrate 3 or of the cap 7 changes into a liquid state of aggregation due to the first laser pulse intensity of the first laser pulse expansion region 1007, wherein a second material region of a second absorbing region of the absorbing part of the substrate 3 or of the cap 7 changes into a liquid state of aggregation due to the second laser pulse intensity of the second laser pulse expansion region 1009 or remains in a solid state of aggregation.

[0051] In other words, in Fig. 7 shows by way of example that, in addition to the melted region around the ventilation hole or to the material region 13 arranged in the region of the access opening 11, additional regions in the material are heated or melted in the immediate or wider surroundings. This is particularly advantageous because, for example, local compressive stresses can be generated which counteract the formation of tensile stresses in the closure region or in the immediate region of the access opening 11. For example, a combination of a high first laser pulse intensity with a high second laser pulse intensity is provided. For example, the second laser pulse extension region 1009 encloses the closure region or the access opening 11 in a ring-shaped or circular manner at a defined distance.In this case, the second laser pulse intensity is set, for example, in such a way that no melting but only heating occurs in the second laser pulse expansion region 1009.

[0052] Fig. 8 shows, by way of example, that the second laser pulse extension region 1009 comprises a first sub-region 1013 and a second sub-region 1015. For example, it is provided that a projection of the first sub-region 1013 onto the main extension plane 100 and a projection of the second sub-region 1015 onto the main extension plane 100 are spaced apart from one another. Furthermore, Fig. 8 shows, by way of example, that the first sub-region 1013 and the second sub-region 1015 are formed substantially parallel to the surface 1011, essentially rotationally symmetrical or point-shaped. Finally, Fig. 8 shows, by way of example, that the second laser pulse expansion region 1009 comprises six further subregions. It is shown here, by way of example, that the subregions are formed substantially parallel to the surface 1011, substantially rotationally symmetrical or point-shaped, and are arranged with the first subregion 1013 and the second subregion 1015, substantially parallel to the surface 1011, substantially rotationally symmetrical around the access opening 11. In other words, Fig. 8 shows, for example, that several locations in the additional area or in the second laser pulse extension area 1009 are irradiated point-like.

[0053] According to the invention, it is also provided, for example, that the first laser pulse expansion region 1007 is a spatial laser pulse expansion of a first laser beam, and that the second laser pulse expansion region 1009 is a spatial laser pulse expansion of a second laser beam. Furthermore, it is also provided, for example, that the first subregion 1013 is a spatial laser pulse expansion of a third laser beam, and that the second subregion 1015 is a spatial laser pulse expansion of a fourth laser beam. Furthermore, it is provided, for example, that the further subregions are spatial laser pulse expansions of further laser beams.

[0054] Finally, Fig. 9 that the spatial laser pulse extension 1001 is formed as a sectional surface of the hollow cylinder running perpendicular to the longitudinal axis of the hollow cylinder, wherein the longitudinal axis essentially coincides with the center of the access opening 11. For example, Fig. 9, a high laser intensity or laser pulse intensity 1003 is applied to the substrate 3 or to the cap 7 only in the closure region or in the region of the access opening 11, wherein the high laser pulse intensity 1003 is arranged in a ring around the actual ventilation hole or around the access opening 11. For example, such a beam profile is a donut beam profile.

[0055] The spatial laser pulse extensions 1001 shown here are merely exemplary. According to the invention, individual or multiple spatial laser pulse extensions 1001 of any shape are provided, which heat or melt the substrate 3 or the cap 7 and reduce the local tensile stresses in the closure region or in the region of the access opening 11 compared to the prior art.

[0056] For example, it is also provided that, in order to minimize the stresses, the temporal sequence of the laser irradiation of the substrate 3 or the cap 7 in the closure region or in the region around the access opening 11 and in the additional region or in regions spaced apart from the access opening 11 is suitably controlled.

[0057] Further advantages of the method according to the invention and the micromechanical component 1 according to the invention compared to the prior art are as follows: -- Different sensor cores with different internal pressure requirements can easily be combined on one chip. -- Any internal pressure, even very low internal pressures, can be set in a MEMS cavern or in the first cavern 5. -- Residual stresses caused by the laser process used are reliably reduced, thus significantly increasing the robustness of the components. -- The technology is simple, robust and cost-effective. -- The manufacturing process is compatible with known manufacturing processes, for example with capping processes such as aluminum-germanium (AlGe) eutectic bonding and seal glass bonding. -- The method according to the invention allows a particularly stable closure of the MEMS cavity over its lifetime.

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 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 -- in a first method step (101), an access opening (11) connecting the first cavity (5) to an environment (9) of the micromechanical component (1) is formed in the substrate (3) or in the cap (7), wherein -- in a second method step (102), the first pressure and / or the first chemical composition in the first cavern (5) is adjusted, wherein -- in a third method step (103), the access opening (11) is closed by introducing energy or heat into an absorbing part of the substrate (3) or the cap (7) using a laser, wherein the introduction of the energy or heat is controlled by means of a laser beam (1005) comprising a spatial laser pulse extension (1001) extending essentially along a surface (1011) of the substrate (3) or the cap (7) facing away from the first cavity (5) and extending essentially parallel to a main extension plane (100) of the substrate (3) and a laser pulse intensity (1003) for reducing residual stresses in the substrate (3) or in the cap (7), wherein the introduction of the energy or heat is controlled by means of the laser beam (1005) such that the laser pulse extension (1001) comprises a first laser pulse extension region (1007) with at least a first laser pulse intensity and a second laser pulse extension region (1009) with at least a second laser pulse intensity,wherein a projection of the first laser pulse extension region (1007) onto the main extension plane (100) and a projection of the access opening (11) onto the main extension plane (100) at least partially overlap, characterized by that the introduction of the energy or heat is controlled by means of the laser beam (1005) such that the second laser pulse extension region (1009) comprises a first sub-region (1013) and a second sub-region (1015), wherein a projection of the first sub-region (1013) onto the main extension plane (100) and a projection of the second sub-region (1015) onto the main extension plane (100) are spaced apart from one another. [2] Method according to one of the preceding claims, wherein the introduction of the energy or heat is controlled by means of the laser beam (1005) such that a projection of the first laser pulse extension region (1007) onto the main extension plane (100) and a projection of the second laser pulse extension region (1009) onto the main extension plane (100) are spaced apart from one another. [3] Method according to one of the preceding claims, wherein the introduction of the energy or heat is controlled by means of the laser beam (1005) such that a projection of the second laser pulse extension region (1009) onto the main extension plane (100) and a projection of the access opening (11) onto the main extension plane (100) are spaced apart from one another. [4] Method according to one of the preceding claims, wherein the introduction of the energy or heat is controlled by means of the laser beam (1005) in such a way that a first material region of a first absorbing region of the absorbing part of the substrate (3) or of the cap (7) changes into a liquid state due to the first laser pulse intensity of the first laser pulse expansion region (1007), wherein a second material region of a second absorbing region of the absorbing part of the substrate (3) or of the cap (7) changes into a liquid state or remains in a solid state due to the second laser pulse intensity of the second laser pulse expansion region (1009). [5] Method according to one of the preceding claims, wherein the introduction of the energy or heat is controlled by means of the laser beam (1005) such that the spatial laser pulse extension (1001) is formed over the entire surface or as a sectional surface of the hollow cylinder running perpendicular to the longitudinal axis of a hollow cylinder, wherein the longitudinal axis substantially coincides with the center of the access opening (11). [6] Method according to one of the preceding claims, wherein the introduction of the energy or heat is controlled by means of the laser beam (1005) such that the first sub-region (1013) and the second sub-region (1015) are formed substantially parallel to the surface (1011) in a substantially rotationally symmetrical manner. [7] Method according to one of the preceding claims, wherein the introduction of the energy or heat is controlled by means of the laser beam (1005) such that the second laser pulse expansion region (1009) comprises further sub-regions, in particular three or four or five or six or seven or eight or nine or ten further sub-regions, wherein the sub-regions are formed substantially parallel to the surface (1011) in a substantially rotationally symmetrical manner and are arranged with the first sub-region (1013) and with the second sub-region (1015) substantially parallel to the surface (1011) in a substantially rotationally symmetrical manner around the access opening (11).

Images