Targeted control of absorption behavior during laser resealing

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 of the substrate (3) or the cap (7) using a laser, characterized in that the introduction of the energy or heat is carried out by adjusting the extent of the absorbing part and by adjusting the strength of the absorption in the absorbing part to minimize stresses occurring in the substrate (3) or in the cap (7), wherein the adjustment of the extent of the absorbing part and the adjustment of the strength of the absorption in the absorbing part is carried out depending on a layer (1203) and / or structure in the substrate (3) or in the cap (7) such that the layer (1203) and / or the structure is a deposited layer and / or structure.

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. This method makes it particularly 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 10 2014 202 801 A1, US 2009 / 0205371 A1, and DE 10 2005 060 870 A1. 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 that of the prior art. Furthermore, the object of the present invention is to provide a compact, mechanically robust, and long-life micromechanical component compared to 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 The introduction of energy or heat is achieved by adjusting the extent of the absorbing part and by adjusting the strength of absorption in the absorbing part to minimize stresses occurring in the substrate or in the cap.

[0007] This provides a simple and cost-effective method for manufacturing a micromechanical component with which the introduction of energy or heat within the substrate or cap can be spatially controlled. Thus, a first transition of the material region from the solid to the liquid state and a subsequent second transition of the material region from the liquid to the solid state within the substrate or cap can be spatially controlled. Furthermore, due to the spatial distribution of energy or heat within the substrate or cap, the method according to the invention allows areas of the substrate or cap adjacent to the material region to be brought to a temperature higher than that achieved in the prior art.This allows the temperature gradients in the substrate or cap, particularly in the area of ​​the access opening, to be reduced compared to the prior art. This enables the thermal expansion during a temperature increase and / or the thermal shrinkage during a temperature decrease of adjacent areas in the substrate or cap, especially in the area of ​​the access opening, to be equalized. Consequently, the mechanical stresses or residual stresses occurring in the area of ​​the sealed access opening, particularly due to the cooling process after the third process step, can be reduced compared to the prior art. The reduction of locally occurring stresses or residual stresses is achieved through this process.Stress-relieving is particularly advantageous because, compared to the prior art, it increases resistance to cracking and thus reduces the probability of component failure immediately after sealing the access opening, during further processing of the micromechanical component, or during the product's lifetime. By preventing cracks, a hermetic seal of the access opening is made possible, thereby reducing the likelihood of the micromechanical component's functionality being impaired by a leaking seal compared to the prior art.

[0008] The inventive method allows, in particular, a reduction in temperature gradients between the recently solidified material region and the surrounding material, compared to the prior art, by spatially targeted temperature increases in the substrate or cap. Specifically, these temperature gradients can be reduced at the time of solidification of the material region and shortly thereafter. This advantageously enables the thermal shrinkage of the material region to essentially correspond to the thermal shrinkage of the surrounding material, or for the two thermal shrinkages to be aligned. Consequently, it is advantageously possible to reduce the mechanical stresses occurring in the area of ​​the sealed access opening, particularly after the material region has cooled, compared to the prior art.

[0009] According to the invention, temperature gradients are less critical when the material region is in a liquid state or in a molten state, since the material region is essentially stress-free at this time. However, the invention also provides, for example, that the temperature gradients are reduced compared to the prior art even when the material region is in a liquid state. In particular, the invention avoids or reduces the build-up of stresses after the material region has solidified because the recently solidified material region is significantly hotter than the surrounding material and therefore experiences greater or different thermal expansion during the cooling process than the colder surrounding material. The invention provides that the temperature gradient in the material or in the substrate is reduced.The temperature in the cap is kept as low as possible during the solidification of the material area and during cooling, so that the mechanical stresses remaining in the component after cooling are as low as possible.

[0010] A further advantage of the method according to the invention is that the movement of dislocations can be thermally activated by 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 at least partially, or at least partially locally in the area of ​​the access opening, particularly after the second transition, to be plastically deformable by thermally activated or facilitated dislocation movements. Therefore, compared to the prior art, locally occurring stresses or stress peaks resulting from plastic deformation can be reduced or eliminated by the targeted introduction of energy or heat.

[0011] The method according to the invention is particularly advantageous for a process in which a laser spot welding process is used in the third process step, since with the method according to the invention, stresses introduced locally into the material in the area of ​​the access opening or in the area of ​​the closed access opening due to spot welding can be effectively reduced or redistributed to areas further away from the access opening. The reduction of locally occurring stresses is particularly advantageous because, compared to the prior art, this increases the resistance to crack formation and thus reduces the probability of component failure immediately after closing the access opening, during further processing of the micromechanical component, or during the product's service life.

[0012] According to the invention, the extent of the absorbing part means, for example, an extent of the absorbing part substantially perpendicular to the principal extent plane. Alternatively or additionally, the extent of the absorbing part means, for example, an extent of the absorbing part substantially parallel to the principal extent plane. In this context, this refers in particular to a region of the substrate or cap in which the absorption of energy or heat is greater than zero or greater than a predetermined absorption value. In the context of the present invention, the strength of absorption means, for example, a spatial distribution of strength within the absorbing region that extends substantially perpendicular to the principal extent plane.Alternatively or additionally, the absorption strength can be understood, for example, as a spatially distributed strength distribution extending essentially parallel to the principal plane of extension within the absorbing region. The absorption strength values ​​of this distribution can be spatially precisely controlled. For example, the strength distribution can be constant or vary with increasing distance from the surface of the substrate or cap facing away from the first cavern. For example, the absorption strength can decrease steadily with increasing distance from the surface of the substrate or cap facing away from the first cavern. For example, 90% of the absorption in the substrate or cap can occur in a region between the surface and a distance of 1 µm from the surface.Furthermore, it is provided, for example, that the absorption strength decreases essentially exponentially with increasing distance from the surface of the substrate or cap facing away from the first cavern. It is provided, for example, that 90% of the absorption in the substrate or cap occurs in a region between the surface and a distance of 1 µm from the surface. It is also provided, for example, that the absorption strength initially increases with increasing distance from the surface of the substrate or cap facing away from the first cavern, then reaches a maximum, and subsequently decreases.It is provided, for example, that 90% of the absorption in the substrate or cap occurs in a region between a distance of 1 µm and a distance of 50 µm from the surface, preferably between a distance of 5 µm and a distance of 30 µm from the surface, and particularly preferably between a distance of 10 µm and a distance of 20 µm from the surface. Furthermore, it is provided, for example, that the strength of the absorption is initially essentially constant with increasing distance from the surface of the substrate or cap facing away from the first cavity, then decreases, and subsequently remains essentially constant. It is provided, for example, that 90% of the absorption in the substrate or cap occurs in a region between the surface and a distance of 1 µm from the surface.The extent of the absorbing portion and the strength of absorption within it, as described above, advantageously enable the introduction of energy or heat to be controlled essentially three-dimensionally within the substrate or cap. Finally, the term "absorbing portion" refers to a region of the substrate or cap in which 90% of the absorption occurs.

[0013] In the context of the present invention, the term “micromechanical component” is to be understood as encompassing both micromechanical components and microelectromechanical components.

[0014] 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.

[0015] 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.

[0016] Advantageous embodiments and further developments of the invention can be found in the dependent claims and in the description with reference to the drawings.

[0017] 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.

[0018] According to a preferred embodiment, the extent of the absorbing portion and the strength of the absorption within the absorbing portion are adjusted as a function of the laser wavelength used in the laser beam. This advantageously enables the global absorption behavior of the substrate or cap to be used to selectively introduce energy or heat into the substrate or cap.

[0019] In the context of the present invention, the laser beam is understood to be electromagnetic radiation emitted continuously or intermittently by a laser. The laser can be, for example, a pulsed laser or a continuous-wave laser. Furthermore, according to the invention, the continuous-wave laser is operated such that the electromagnetic radiation is emitted continuously or falls continuously onto the absorbing part of the substrate or cap. It is also provided that the electromagnetic radiation falls onto the absorbing part of the substrate or cap and is at least partially absorbed by it.

[0020] According to a preferred embodiment, the extent of the absorbing part and the strength of the absorption in the absorbing part are adjusted depending on the material of the substrate or the cap. This advantageously enables the adjustment of spatially structured absorption behaviors.

[0021] According to a preferred embodiment, the extent of the absorbing portion and the strength of the absorption within that portion are adjusted as a function of the doping of the substrate or the cap. This advantageously allows for particularly precise adjustment of the extent of the absorbing area and the strength of the absorption within that area.

[0022] According to a preferred embodiment, the extent of the absorbing part and the strength of the absorption in the absorbing part are adjusted as a function of the temperature of the substrate or the cap. This advantageously provides a further means of influencing the overall absorption behavior of the substrate or the cap.

[0023] According to a preferred embodiment, the extent of the absorbing part and the strength of the absorption within the absorbing part are adjusted depending on a layer and / or structure in and / or on the substrate or in and / or on the cap. This advantageously makes it possible to provide different depth profiles of the absorbing part and different strengths of absorption within these depth profiles.

[0024] According to a preferred embodiment, the adjustment of the extent of the absorbing part and the adjustment of the absorption strength within the absorbing part are carried out as a function of the layer and / or the structure, such that the layer and / or the structure is a deposited layer and / or structure. This advantageously enables the production of different depth profiles using layer technology methods known from the prior art.

[0025] According to a preferred embodiment, the adjustment of the extent of the absorbing part and the adjustment of the absorption intensity within the absorbing part are carried out as a function of the layer and / or structure, such that the layer and / or structure is a doped layer and / or structure. This advantageously allows the absorption coefficient to be adjusted very sensitively.

[0026] A further 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 comprises a material region which solidifies after the introduction of energy or heat into an absorbing part of the substrate or the cap by adjusting the extent of the absorbing part and by adjusting the strength of the absorption in the absorbing part in order to minimize stresses occurring in the substrate or in the cap and which seals the access opening.This advantageously provides a compact, mechanically robust, and cost-effective micromechanical component with a preset first pressure. The aforementioned advantages of the method according to the invention also apply accordingly to the micromechanical component according to the invention.

[0027] According to a preferred further development, it is provided that the micromechanical component -- a material of the substrate or cap for introducing the energy or heat and / or -- doping the substrate or cap to introduce energy or heat and / or -- comprises a layer and / or structure in and / or on the substrate or in and / or on the cap for introducing energy or heat. This advantageously enables the micromechanical component to exhibit particularly low mechanical stresses, or only mechanical stresses below a critical level, in the area of ​​the access opening, and is therefore particularly robust against cracking.

[0028] According to a preferred embodiment, the cap containing the substrate encloses a second cavity, in which a second pressure prevails 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 controlled first and second pressures.

[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. 4, Fig. 5 and Fig. Figure 6 shows schematic representations of adjusting the extent of an absorbing part and adjusting the strength of absorption in the absorbing part according to exemplary embodiments of the present 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 of the substrate 3 or the cap 7 using a laser. Alternatively, it is also provided, for example, 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, on a surface of the cap 7 facing away from the cavern 5, and in 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 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, and in particular with regard to its extent or configuration perpendicular to the lateral extent, especially perpendicular to the surface.

[0036] In Fig. 4, Fig. 5 and Fig. Figure 6 schematically illustrates the adjustment of the extent of the absorbing part and the adjustment of the absorption intensity in the absorbing part according to exemplary embodiments of the present invention. It is provided that the introduction of energy or heat is achieved by adjusting the extent of the absorbing part substantially perpendicular to a principal extension plane 100 of the substrate 3 or the cap 7 and by adjusting the absorption intensity in the absorbing part substantially perpendicular to the principal extension plane 100 in order to minimize mechanical stresses occurring in the substrate 3 or in the cap 7. In other words, in Fig. 4, Fig. 5 and Fig. Six process variants of the third process step 103 are shown, wherein the heat or energy input, for example by a laser beam 1201, is carried out by targeted influence on the absorption behavior of the substrate 3 or the cap 7 in such a way that the stresses left in the substrate 3 or in the cap 7 are minimized or reduced to a non-critical level.

[0037] For example, alternative or additional process variants of the third process step 103 are also provided, wherein the energy or heat input, for example by a laser beam 1201, is carried out by targeted influence on the reflection behavior and / or the transmission behavior of the substrate 3 or the cap 7 in such a way that the stresses left in the substrate 3 or in the cap 7 are minimized or reduced to a non-critical level.

[0038] For example, it is provided that the extent of the absorbing part and the strength of the absorption in the absorbing part are adjusted depending on the laser wavelength used for the laser beam 1201. This makes it possible, for example, to influence the absorption behavior of the substrate or the cap using the laser wavelength during laser material processing. A change in wavelength or laser wavelength has a global effect on the absorption behavior of the substrate or the cap. For example, it is provided that the amount of heat introduced into the material or substrate 3 or the cap 7 is adjusted by precisely controlling the laser wavelength such that, after cooling, i.e., after the third process step 103, the material or substrate 3 or the cap 7 is at a specific temperature.The stresses remaining in the cap 7 are reduced compared to the prior art. Furthermore, it is also provided, for example, that the substrate 3 or the cap 7 comprises silicon. Here, for example, it is provided that the laser wavelength is less than 1000 nm. In this case, the energy or heat is absorbed particularly strongly on a surface of the substrate or the cap facing away from the first cavern 5. Here, for example, the resulting heat distribution into the depth of the substrate 3 or the cap 7, i.e., from the surface facing away from the first cavern 5 towards the first cavern 5, is determined by the thermal conductivity in the substrate 3 or in the cap 7. This is exemplified in [reference missing]. Fig. 4 shown.

[0039] When controlling the energy or heat input by using a laser wavelength of the laser beam 1201 and a silicon-containing substrate 3 or a silicon-containing cap 7, the fact that silicon is a semiconductor material is utilized, and thus the absorption behavior of the substrate 3 or the cap 7 is strongly dependent on the wavelength and therefore the quantum energy of the photons. For example, it is intended that the laser wavelength is greater than 1000 nm. It is advantageous here that for wavelengths greater than 1000 nm, the absorption of silicon decreases significantly, since the photon energy is no longer sufficient to overcome the direct band gap. For example, a deeper penetration of the laser light can thus be specifically achieved by using a longer wavelength. This is exemplified in Fig. 5 is shown here. Fig. 5. The extent of the absorbing part shown is essentially perpendicular to the principal extension plane 100 compared to that shown in Fig. Figure 4 shows the extent of the absorbing part, which is essentially perpendicular to the principal extension plane 100, enlarged. An enlarged extent is achieved here, for example, by using a longer laser wavelength.

[0040] According to the present invention, the energy penetration depth is controlled, for example, by adjusting the laser wavelength. The laser wavelength is selected such that the desired energy penetration depth is achieved. The invention provides, for example, for the use of an infrared laser. Here, it is provided, for example, that the laser wavelength is between 780 nm and 1600 nm, preferably between 1030 nm and 1500 nm, and particularly preferably between 1080 nm and 1100 nm. Alternatively, it is also provided, for example, that the laser wavelength is between 1030 nm and 1080 nm. Furthermore, it is alternatively provided that the laser wavelength is between 1100 nm and 1500 nm. However, the invention also provides, for example, that the laser wavelength can be adjusted via nonlinear optical effects and tunable light sources.Elements of tunable light sources, such as an optical parametric oscillator (OPO) and / or an optical parametric amplifier (OPV or OPA), are specifically tuned to the material used in the substrate or in the cap, or to the desired extent of the absorbing part and strength of absorption in the absorbing part.

[0041] Furthermore, it is provided, for example, that the extent of the absorbing part and the strength of the absorption in the absorbing part are adjusted depending on the material of the substrate 3 or the cap 7. In particular, it is provided that the material of the substrate 3 or the cap 7 comprises silicon. For example, it is provided that a spatially structured absorption behavior can be achieved through local material modifications and changes.

[0042] Furthermore, it is also provided, for example, that the extent of the absorbing region and the strength of the absorption in the absorbing region are adjusted depending on the doping of the substrate 3 or the cap 7. This advantageously results in an increase in the electron density in the conduction band and / or the hole density in the valence band, thereby increasing absorption in the long-wavelength region. This is achieved, for example, by having the substrate 3 or the cap 7 comprise silicon and be doped with foreign atoms.

[0043] Furthermore, it is provided, for example, that the extent of the absorbing part and the strength of the absorption in the absorbing part are adjusted depending on the temperature of the substrate 3 or the cap 7. Here, it is provided, for example, that the substrate 3 or the cap 7 is heated with a heat source before and / or during the third process step 103. This is provided, for example, with heat sources that contact the substrate 3 or the cap 7, such as a heating plate, or with heat sources that do not contact the substrate 3 or the cap 7, such as an infrared lamp. Alternatively or additionally, a combination of a contacting and a non-contacting heat source, such as an oven, is also provided.When using a temperature of substrate 3 or cap 7, for example, when using silicon, the fact that silicon absorbs more strongly in the long-wavelength region with increasing temperature is advantageously utilized. This is achieved advantageously because more phonons are present at elevated temperature to enable a transition across the indirect band gap, and because more electrons are located in the conduction band, thus making intraband transitions available for absorption.

[0044] Furthermore, it is also provided, for example, that the adjustment of the extent of the absorbing part and the adjustment of the strength of the absorption in the absorbing part is carried out depending on a layer 1203 and / or structure in the substrate 3 and / or on the substrate 3 or in the cap 7 and / or on the cap 7. Fig. Figure 6 shows an example of layer 1203 in the cap 7. This advantageously allows, in contrast to the use of a homogeneous material, for the majority of the energy to be absorbed further inside the material, i.e., not at the surface of the substrate 3 or the cap 7. With homogeneous materials, most of the energy is absorbed at the irradiated surface according to the Lambert-Beer law.

[0045] When using absorbing layers and / or structures, it is intended, for example, that a maximum of energy deposition is provided at the depth of the component. In other words, it is intended, for example, that the strength of absorption in the absorbing part has a maximum in a region facing away from the first cavern 5 and substantially spaced in the direction of the first cavern 5. For this purpose, it is intended, for example, that -- low-doped silicon is used as the base material, or that substrate 3 or the cap comprises low-doped silicon, and that -- a laser wavelength, for example a laser wavelength between 1200 nm and 1400 nm, is used, for which the low-doped silicon is essentially transparent and that -- a highly absorbent layer or structure is deposited at the target depth, whereby the desired energy distribution is achieved using the highly absorbent layer. This is used, for example, in Fig. Figure 6 illustrates this. This advantageously allows the laser light to penetrate to the absorption layer / structure without significant attenuation and is selectively absorbed within the absorption layer / structure. For example, the highly absorbent layer or structure may comprise heavily doped silicon and / or an impurity material and / or a metal.

[0046] According to the invention, it is further provided, for example, that the adjustment of the extent of the absorbing part and the adjustment of the absorption strength in the absorbing part are carried out as a function of the layer 1203 and / or the structure, such that the layer 1203 and / or the structure is a deposited layer and / or structure. For example, absorption control by one or more absorbing layers is provided. It is further provided, for example, that the layer or layers are embedded in the micromechanical component 1 or spaced apart from the surfaces of the micromechanical component 1. -- in a fourth process step the substrate 3 or the cap 7 is coated with one or more absorbing layers and that -- in a fifth process step, the absorbing layer or layers are coated with another layer. For example, this additional layer may comprise silicon, polysilicon, or polycrystalline silicon. It is also possible, for example, that -- in a sixth process step, another absorbing layer is deposited on top of the other layer, and that In a seventh process step, a third layer is deposited on top of the additional absorbing layer. For example, it is also possible to deposit further absorbing layers and yet more layers on top of corresponding absorbing layers or layers. In this way, arbitrary depth profiles can be advantageously generated.

[0047] Furthermore, according to the invention, the extent of the absorbing portion and the strength of the absorption within the absorbing portion are adjusted as a function of layer 1203 and / or the structure, such that layer 1203 and / or the structure is a doped layer and / or structure. This allows for different absorption profiles to be achieved through corresponding doping profiles. For example, the doped layer and / or structure comprises doped silicon. In this case, the degree of absorption can be very sensitively influenced by the doping concentration. This advantageously makes it possible to set arbitrary depth profiles of absorption or energy deposition by adjusting doping profiles.For example, it is envisaged that the doping profiles are generated by building up corresponding layers on a silicon substrate by thermally activated diffusion of an applied dopant source or by ion implantation.

[0048] According to the invention, it is also provided, for example, that the amount of heat introduced for a given desired melting depth is minimized. The stresses introduced into the material and remaining after cooling are highly dependent on the amount of heat introduced, so these too can be reduced by appropriately adapted absorption management. In addition to the magnitude, sign, and direction of the stresses occurring in the substrate 3 or in the cap 7 after the third process step 103, their location or spatial distribution is also crucial for their influence on crack initiation and component failure. Thus, stresses deep within a component are generally less critical than those at the surface. By "burying" the absorption zone deep within the component, the tendency to crack can therefore be reduced.

[0049] Finally, according to the invention, it is also provided, for example, that the absorption behavior or the transmission behavior or the reflection behavior of the substrate 3 or the cap 7 is determined as a function of further parameters.

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 of the substrate (3) or the cap (7) using a laser, characterized by , that the introduction of energy or heat is carried out by adjusting the extent of the absorbing part and by adjusting the strength of absorption in the absorbing part to minimize stresses occurring in the substrate (3) or in the cap (7), wherein the adjustment of the extent of the absorbing part and the adjustment of the strength of absorption in the absorbing part is carried out depending on a layer (1203) and / or structure in the substrate (3) or in the cap (7) such that the layer (1203) and / or the structure is a deposited layer and / or structure. [2] Method according to claim 1, wherein the adjustment of the extent of the absorbing part and the adjustment of the strength of the absorption in the absorbing part is carried out as a function of a laser wavelength of a laser beam (1201) used. [3] Method according to one of the preceding claims, wherein the adjustment of the extent of the absorbing part and the adjustment of the strength of the absorption in the absorbing part is carried out depending on a material of the substrate (3) or the cap (7). [4] Method according to one of the preceding claims, wherein the adjustment of the extent of the absorbing part and the adjustment of the strength of the absorption in the absorbing part is carried out as a function of doping the substrate (3) or the cap (7). [5] Method according to one of the preceding claims, wherein the adjustment of the extent of the absorbing part and the adjustment of the strength of the absorption in the absorbing part is carried out as a function of the temperature of the substrate (3) or the cap (7). [6] Micromechanical component (1) produced by the method according to one of the preceding claims, 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 material region (13) that solidifies after the introduction of energy or heat into an absorbing part of the substrate (3) or the cap (7) by adjusting the extent of the absorbing part and by adjusting the strength of the absorption in the absorbing part to minimize stresses occurring in the substrate (3) or in the cap (7) and that closes the access opening (11), wherein the micromechanical component (1) - comprising a layer (1203) and / or structure in the substrate (3) or in the cap (7) for introducing the energy or heat, wherein the layer (1203) and / or the structure is a deposited layer and / or structure.

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