Voltage reduction during laser resealing through time-shaped laser pulses and pulse sequences

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 controlled by means of a time-shaped laser pulse (905) comprising a laser pulse duration (901) and a laser pulse intensity (903) in comparison to an unshaped laser pulse to reduce temperature gradients in the substrate (3) or in the cap (7), wherein the introduction of the energy or heat using the time-shaped laser pulse (905) is controlled such that the time-shaped laser pulse (905) includes a further laser pulse intensity (909) during a further laser pulse duration (907) preceding the laser pulse duration (901), wherein the further laser pulse intensity (909) is lower than the laser pulse intensity (903),wherein the introduction of energy or heat by means of the time-shaped laser pulse (905) is controlled in such a way that the further laser pulse duration (907) is at least partially temporally preceded by a first transition of the material region of the absorbing part from the solid to the liquid state of matter,

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.

[0005] Further disclosures are found in the printed documents DE 102011103516A1, DE 102014202801A1 and US 20050189621A1. Disclosure of the invention

[0006] 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.

[0007] The task is solved by controlling the introduction of energy or heat using a time-shaped laser pulse comprising a laser pulse duration and a laser pulse intensity to reduce temperature gradients in the substrate or cap.

[0008] This provides a simple and cost-effective method for manufacturing a micromechanical component that allows the controllable introduction of energy or heat using a time-shaped laser pulse to reduce temperature gradients in the substrate or cap. This advantageously enables energy or heat to be selectively introduced into the substrate or cap both before and after the first transition of the material from the solid to the liquid state. Thus, due to thermal conduction in the substrate or cap, it is possible to target the material region or cap.Areas of the substrate or cap adjacent to the absorbing part can be heated to a higher temperature than in the prior art both before and after the first transition. This reduces the temperature gradients in the substrate or cap, particularly in the area of ​​the access opening, compared to the prior art. This allows 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, thus reducing the mechanical stresses occurring in the area of ​​the sealed access opening compared to the prior art.

[0009] The method according to the invention allows, in particular, temperature gradients between the recently solidified material area or weld point and the material surrounding the material area or weld point to be reduced compared to the prior art by selectively increasing the temperature in the material surrounding the material area or weld point. In particular, these temperature gradients can be reduced at the time of solidification of the weld point or shortly thereafter. Thus, it is advantageously possible to ensure that the thermal shrinkage of the material area or weld point essentially corresponds to the thermal shrinkage of the material surrounding the material area, or that the two thermal shrinkages can be aligned.This advantageously enables the reduction of mechanical stresses occurring in the area of ​​the sealed access opening, particularly after the material area has cooled down, compared to the prior art.

[0010] 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 hotter and therefore experiences greater / different thermal expansion during the cooling process than the colder material surrounding it. The invention provides that the temperature gradient in the material, the substrate, or the cap during the solidification of the material region is reduced.to keep the stresses at the welding point and during cooling as low as possible so that the mechanical stresses remaining in the component after cooling are as low as possible.

[0011] A further advantage of the method according to the invention is that, by selectively introducing energy or heat into the substrate or cap, the movement of dislocations can be thermally activated even before the first transition and / or after the second transition. 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 before the first transition and / or after the second transition, to be plastically deformable through thermally activated or facilitated dislocation movements. Consequently, locally occurring stresses or stress peaks resulting from plastic deformation can be reduced or eliminated by selectively introducing energy or heat, compared to the prior art.

[0012] 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 can be effectively reduced or redistributed to areas further away from the access opening due to spot welding. 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.

[0013] In the context of the present invention, the term "time-shaped laser pulse" refers to electromagnetic radiation emitted by a laser either intermittently or continuously over a period of time with variable intensity. In the context of the present invention, the term "time-shaped laser pulse" can refer, for example, to a single laser pulse or, alternatively, to an envelope comprising several laser pulses. The laser can be, for example, a pulsed laser or a continuous-wave laser, the continuous-wave laser preferably being operated such that the electromagnetic radiation is emitted continuously or intermittently over a period of time, or is directed onto the absorbing part of the substrate or cap continuously or intermittently over a period of time.In other words, in the context of the present invention, the time-shaped laser pulse is understood to be electromagnetic radiation which falls on the absorbing part of the substrate or cap in time-limited portions or in a single time-limited portion and is at least partially absorbed by it. Furthermore, according to the invention, the total duration of the time-shaped laser pulse is the duration between a first time point at which the intensity of the time-shaped laser pulse is zero and a second time point at which the intensity of the time-shaped laser pulse is zero.Alternatively, according to the invention, the total duration of the time-shaped laser pulse is also provided for as the duration between a third time point at which the intensity of the time-shaped laser pulse has a first local minimum and a fourth time point at which the intensity of the time-shaped laser pulse has a second local minimum.

[0014] In the context of the present invention, the term “micromechanical component” is to be understood as encompassing both micromechanical components and microelectromechanical components.

[0015] 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.

[0016] 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.

[0017] Advantageous embodiments and further developments of the invention can be found in the dependent claims and in the description with reference to the drawings.

[0018] 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.

[0019] According to a preferred embodiment, the introduction of energy or heat using the time-shaped laser pulse is controlled such that the time-shaped laser pulse includes a further laser pulse intensity during a subsequent laser pulse duration preceding the main laser pulse duration, wherein the subsequent laser pulse intensity is lower than the main laser pulse intensity. This advantageously enables energy or heat to be selectively introduced into the substrate or cap even before the first transition. Thus, due to thermal conduction in the substrate or cap, it is possible to bring areas of the substrate or cap adjacent to the material region or the absorbing part of the substrate or cap to a higher temperature than in the prior art before the first transition.Thus, the temperature gradients in the substrate or cap, particularly in the area of ​​the access opening and especially during the solidification of the material, are reduced compared to the prior art. This is achieved, in particular, without the material transitioning to the liquid state earlier than in the prior art, and without the adjacent areas transitioning to the liquid state.

[0020] According to a preferred embodiment, the introduction of energy or heat using the time-shaped laser pulse is controlled such that the time-shaped laser pulse includes a third laser pulse intensity during a third laser pulse duration following the first, wherein the third laser pulse intensity is lower than the first. This advantageously enables energy or heat to be selectively introduced into the substrate or cap before, during, and after the second transition. Thus, due to thermal conduction in the substrate or cap, areas adjacent to the material region or the absorbing part of the substrate or cap can be brought to a higher temperature after the second transition compared to the prior art.This reduces the temperature gradients in the substrate or cap, particularly in the area of ​​the access opening and especially during and shortly after the point at which the material solidifies, compared to the prior art. This is achieved, in particular, without keeping the material in the liquid state for an unnecessarily long time compared to the prior art, and without the adjacent areas transitioning into the liquid state.

[0021] According to a preferred embodiment, the laser pulse intensity and / or the subsequent laser pulse intensity and / or the third laser pulse intensity are kept constant over time and / or increased and / or decreased. This advantageously enables particularly precise control of the energy or heat input, thus allowing for a targeted reduction of temperature gradients, especially in the area of ​​the sealed access opening.

[0022] According to a preferred embodiment, the introduction of energy or heat using the time-shaped laser pulse is controlled such that the subsequent laser pulse duration is at least partially prior to the first transition of the material region from the solid to the liquid state. This advantageously enables areas 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 higher temperature, compared to the prior art, even before the first transition.

[0023] According to a preferred embodiment, the introduction of energy or heat using the time-shaped laser pulse is controlled such that the third laser pulse duration at least partially follows a second transition of the material region from the liquid to the solid state. This advantageously enables areas 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 higher temperature, compared to the prior art, after the second transition.

[0024] According to a preferred embodiment, the introduction of energy or heat is controlled by means of a further time-shaped laser pulse, which is placed temporally prior to the time-shaped laser pulse and comprises a fourth laser pulse duration and a fourth laser pulse intensity, in order to reduce temperature gradients in the substrate or in the cap.

[0025] This advantageously allows energy or heat to be introduced into the material region or the absorbing region even before the time-shaped laser pulse. Thus, through thermal conduction, the areas of the substrate or cap adjacent to the material region or the absorbing part of the substrate or cap can be brought to a higher temperature than in the prior art before the absorption of the time-shaped laser pulse, thereby efficiently reducing temperature gradients.

[0026] According to a preferred embodiment, the introduction of energy or heat is controlled by means of a third time-shaped laser pulse, which follows the time-shaped laser pulse and comprises a fifth laser pulse duration and a fifth laser pulse intensity, to reduce temperature gradients in the substrate or cap. This advantageously enables energy or heat to be introduced into the material region or the absorbing region after the time-shaped laser pulse. Thus, thermal conduction allows the areas of the substrate or cap adjacent to the material region or the absorbing part of the substrate or cap to be heated to a higher temperature than in the prior art after the absorption of the time-shaped laser pulse, thereby efficiently reducing temperature gradients.

[0027] According to a preferred embodiment, the introduction of energy or heat is controlled such that the fourth laser pulse intensity is lower than the laser pulse intensity. This advantageously allows energy or heat to be introduced into the material region or the absorbing region even before the time-shaped laser pulse without the material region transitioning into a liquid state.

[0028] According to a preferred embodiment, the introduction of energy or heat is controlled such that the fifth laser pulse intensity is lower than the laser pulse intensity. This advantageously allows energy or heat to be introduced into the material region or the absorbing region after the time-shaped laser pulse without the material region reverting to a liquid state.

[0029] According to a preferred embodiment, the total duration of the time-shaped laser pulse is between 10 fs and 10 s, preferably between 1 µs and 100 ms, and particularly preferably between 10 µs and 10 ms. According to a preferred embodiment, the laser pulse duration is substantially equal to the second laser pulse duration and / or substantially equal to the third laser pulse duration. Alternatively, according to a preferred embodiment, the laser pulse duration is substantially equal to half the second laser pulse duration and / or substantially equal to half the third laser pulse duration. Furthermore, according to a preferred embodiment, the laser pulse duration is also substantially equal to one-third of the second laser pulse duration and / or substantially equal to one-third of the third laser pulse duration.Furthermore, according to a preferred embodiment, the laser pulse duration is substantially one-quarter of the subsequent laser pulse duration and / or substantially one-quarter of the third laser pulse duration. Finally, alternatively, according to a preferred embodiment, the laser pulse duration is substantially one-fifth of the subsequent laser pulse duration and / or substantially one-fifth of the third laser pulse duration. Brief description of the drawings Fig. Figure 1 shows a schematic representation of a micromechanical component with an open access opening according to the state of the art. 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, Fig. 6, Fig. 7 and Fig. Figure 8 shows schematic representations of time-shaped laser pulses 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, Fig. 6, Fig. 7 and Fig. Figure 8 shows schematic representations of time-shaped laser pulses according to exemplary embodiments of the present invention. Here, in Fig. 4, Fig. 5, Fig. 6, Fig. 7 and Fig. Figure 8 shows the intensity Y over time X of exemplary time-shaped laser pulses.

[0037] This shows Fig. 4. For example, a time-shaped laser pulse 905, wherein the time-shaped laser pulse 905 comprises a laser pulse duration 901 and a laser pulse intensity 903. In other words, in Fig. Figure 4 shows a commonly used simple pulse shape, such as approximately a so-called rectangular pulse. According to the invention, the time-shaped laser pulse 905 comprises any pulse shapes that can be realized, for example, with modern laser sources.

[0038] Fig. Figure 5 shows, by way of example, a further embodiment of the time-shaped laser pulse 905, by means of which the introduction of energy or heat is controlled such that the time-shaped laser pulse 905 comprises a further laser pulse intensity 909 during a further laser pulse duration 907 preceding the laser pulse duration 901, wherein the further laser pulse intensity 909 is lower than the laser pulse intensity 903. In other words, according to the invention, it is provided, for example, that a laser power preceding the actual welding pulse is used to introduce the energy or heat. Here, it is provided, for example, that an emission preceding the actual welding pulse, or the laser power preceding the actual welding pulse, is applied with a significantly lower power or intensity compared to the welding pulse.This makes it advantageous to allow the material adjacent to the welding point to preheat through heat conduction, thereby reducing the temperature gradient compared to the state of the art.

[0039] Fig. Figure 6 shows, by way of example, a further embodiment of the time-shaped laser pulse 905, by means of which the input of energy or heat is controlled such that the time-shaped laser pulse 905 comprises a third laser pulse intensity 913 during a third laser pulse duration 911 following the laser pulse duration 901, wherein the third laser pulse intensity 913 is lower than the laser pulse intensity 903. In other words, according to the invention, it is provided, for example, that a power trailing the actual laser pulse delays the cooling of the weld point. This also reduces the temperature gradient at the time of solidification of the material region 13. For example, an emission or power trailing the actual welding pulse comprises a significantly lower power or intensity compared to the welding pulse.

[0040] Fig. Figure 7 shows another exemplary embodiment of the time-shaped laser pulse 905, wherein the laser pulse intensity 903 is first increased and then decreased. Furthermore, the second laser pulse intensity 909 is increased and the third laser pulse intensity 913 is decreased. In other words, the time-shaped laser pulse 905 comprises Fig. 7 ramps of pulse power. Fig. Figure 7 shows, by way of example, an emission with increasing power preceding the actual welding pulse or laser pulse intensity 903, and an emission with decreasing power following the actual welding pulse or laser pulse intensity 903. According to the invention, it is provided, for example, that the slope of the intensity Y increases with time X of the time-shaped laser pulse 905, or that the time-shaped laser pulse 905 comprises several slope segments, each containing a slope. It is provided, for example, that the slopes increase with time X before a maximum intensity 927 of the time-shaped laser pulse 905 and decrease with time X after the maximum intensity 927 of the time-shaped laser pulse 905.For example, it is also intended that the laser pulse intensity 903 and / or the further laser pulse intensity 909 and / or the third laser pulse intensity 913 is kept constant over time and / or increased and / or decreased.

[0041] For example, it is also provided that the introduction of energy or heat using the time-shaped laser pulse 905 is controlled in such a way that the subsequent laser pulse duration 907 is at least partially temporally preceding a first transition of the material region 13 from the solid to the liquid state. Furthermore, it is also provided, for example, that the introduction of energy or heat using the time-shaped laser pulse 905 is controlled in such a way that the third laser pulse duration 911 is at least partially temporally following a second transition of the material region 13 from the liquid to the solid state.

[0042] Fig. Figure 8 shows, by way of example, a further time-shaped laser pulse 919, which precedes the time-shaped laser pulse 905 and comprises a fourth laser pulse duration 915 and a fourth laser pulse intensity 917, for controlling the introduction of energy or heat to reduce temperature gradients in the substrate 3 or in the cap 7. Furthermore, it shows Fig. 8 For example, a third time-shaped laser pulse 925, following the time-shaped laser pulse 905 and comprising a fifth laser pulse duration 921 and a fifth laser pulse intensity 923, for controlling the introduction of energy or heat to reduce temperature gradients in the substrate 3 or in the cap 7. Furthermore, shows Fig. 8 for example, that the fourth laser pulse intensity 917 is lower than the laser pulse intensity 903 and that the fifth laser pulse intensity 923 is lower than the laser pulse intensity 903.

[0043] Furthermore, it shows Fig.8 a plurality of additional laser pulses, wherein the additional laser pulses precede or lag behind the time-shaped laser pulse 905. For example, the plurality of additional laser pulses includes a fourth time-shaped laser pulse 929, which precedes the time-shaped laser pulse 905 and comprises a sixth laser pulse duration and a sixth laser pulse intensity; a fifth time-shaped laser pulse 931, which precedes the time-shaped laser pulse 905 and comprises a seventh laser pulse duration and a seventh laser pulse intensity; a sixth time-shaped laser pulse 933, which follows the time-shaped laser pulse 905 and comprises an eighth laser pulse duration and an eighth laser pulse intensity; and a seventh time-shaped laser pulse 935, which follows the time-shaped laser pulse 905 and comprises a ninth laser pulse duration and a ninth laser pulse intensity.In other words, for example, the actual welding pulse or the time-shaped laser pulse 905 is preceded by pulses with significantly lower, possibly increasing, energy, power, or intensity compared to the welding pulse or the time-shaped laser pulse 905. Furthermore, for example, the actual welding pulse or the time-shaped laser pulse 905 is followed by pulses with significantly lower, possibly decreasing, energy, power, or intensity compared to the welding pulse or the time-shaped laser pulse 905.

[0044] For example, it is provided that the total duration of the pulse train is between 100 ns and 1 s, preferably between 1 µs and 100 ms, and particularly preferably between 10 µs and 10 ms. According to the present invention, the total duration of the pulse train is defined as the time between a fifth point in time at which the intensity of a first-occurring shaped laser pulse is just zero and a sixth point in time at which the intensity of a last-occurring shaped laser pulse is just zero. For example, it is also provided that the laser pulse intensities in a first third of the total duration of the pulse train are lower than the laser pulse intensities in a second third of the total duration of the pulse trains. For example, it is also provided that the laser pulse intensities in a third third of the total duration of the pulse train are lower than the laser pulse intensities in the second third of the total duration of the pulse trains.For example, it is planned that the third third follows the second third in time, and the second third follows the first third in time.

[0045] According to the invention, a multitude of different pulse shapes or pulse sequences are provided, which are coordinated such that residual mechanical stresses in the area of ​​the access opening are minimized after the access opening has been closed, compared to the prior art. For this purpose, virtually any temporal pulse shape and pulse sequence are proposed, which fulfill the purpose of minimizing the residual stresses. It is also provided, by way of example, that the pulse shapes and pulse sequences shown here can be combined arbitrarily. For instance, it is also provided that any (free) pulse shape can be used to adjust the temperature gradients around the welding point during the solidification and cooling process.

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 controlled by means of a time-shaped laser pulse (905) comprising a laser pulse duration (901) and a laser pulse intensity (903) in comparison to an unshaped laser pulse to reduce temperature gradients in the substrate (3) or in the cap (7), wherein the introduction of energy or heat by means of the time-shaped laser pulse (905) is controlled such that the time-shaped laser pulse (905) includes a further laser pulse intensity (909) during a further laser pulse duration (907) preceding the laser pulse duration (901), wherein the further laser pulse intensity (909) is lower than the laser pulse intensity (903), wherein the introduction of energy or heat by means of the time-shaped laser pulse (905) is controlled such thatthat the further laser pulse duration (907) is at least partially temporally preceded by a first transition of the material region of the absorbing part from the solid to the liquid state of matter, [2] Method according to claim 1, wherein the introduction of energy or heat using the time-shaped laser pulse (905) is controlled such that the time-shaped laser pulse (905) comprises a third laser pulse intensity (913) during a third laser pulse duration (911) following the laser pulse duration (901), wherein the third laser pulse intensity (913) is lower than the laser pulse intensity (903). [3] Method according to one of the preceding claims, wherein the laser pulse intensity (903) and / or the further laser pulse intensity (909) and / or the third laser pulse intensity (913) is kept constant over time and / or increased and / or decreased. [4] Method according to claim 2, wherein the introduction of energy or heat using the time-shaped laser pulse (905) is controlled such that the third laser pulse duration (911) is at least partially temporally following a second transition of the material region of the absorbing part from the liquid to the solid state. [5] Method according to one of the preceding claims, wherein the introduction of energy or heat is controlled by means of a further time-shaped laser pulse (919) preceding the time-shaped laser pulse (905) and comprising a fourth laser pulse duration (915) and a fourth laser pulse intensity (917) to reduce temperature gradients in the substrate (3) or in the cap (7). [6] Method according to one of the preceding claims, wherein the introduction of energy or heat is controlled by means of a third time-shaped laser pulse (925) following the time-shaped laser pulse (905) and comprising a fifth laser pulse duration (921) and a fifth laser pulse intensity (923) to reduce temperature gradients in the substrate (3) or in the cap (7). [7] Method according to claim 5, wherein the input of energy or heat is controlled such that the fourth laser pulse intensity (917) is lower than the laser pulse intensity (903). [8] Method according to claim 6, wherein the input of energy or heat is controlled such that the fifth laser pulse intensity (923) is lower than the laser pulse intensity (903).

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