Abstract
A method is provided for manufacturing a micromechanical component including a substrate and a cap connected to the substrate and together with the substrate enclosing a first cavity, a first pressure prevailing and a first gas mixture with a first chemical composition being enclosed in the first cavity. An access opening, connecting the first cavity to surroundings of the micromechanical component, is formed in the substrate or in the cap. The first pressure and/or the first chemical composition are adjusted in the first cavity. The access opening is sealed by introducing energy and heat into an absorbing part of the substrate or the cap with the aid of a laser. A recess is formed in a surface of the substrate or of the cap facing away from the first cavity in the area of the access opening for reducing local stresses occurring at a sealed access opening.
Claims
1. A method for manufacturing a micromechanical component including a substrate and a cap connected to the substrate and together with the substrate enclosing a first cavity, a first pressure prevailing and a first gas mixture with a first chemical composition being enclosed in the first cavity, the method comprising: in a first step, forming an access opening connecting the first cavity to surroundings of the micromechanical component in the substrate or in the cap; in a second step, adjusting at least one of the first pressure and the first chemical composition in the first cavity; in a third step, sealing the access opening by introducing energy and heat into an absorbing part of the substrate or the cap with the aid of a laser; and in a fourth step, forming a recess in a surface of the substrate or of the cap facing away from the first cavity in the area of the access opening for reducing local stresses occurring at a sealed access opening.
2. The method as recited in claim 1, wherein the cap together with the substrate encloses a second cavity, a second pressure prevailing and a second gas mixture with a second chemical composition being enclosed in the second cavity.
3. The method as recited in claim 1, wherein the recess is formed in such a way that a first surface of a projection of the recess onto a plane extending in parallel to the surface and a second surface of a projection of the absorbing part of the substrate or of the cap onto the plane one of: i) do not overlap, or ii) only partially overlap.
4. The method as recited in claim 1, wherein in the fourth step, an additional recess or a plurality of additional recesses are formed in the surface in the area of the access opening to reduce local stresses occurring at a sealed access opening.
5. The method as recited in claim 1, wherein at least one of the recess, an additional recess, and a plurality of additional recesses is formed in a plane extending in parallel to the surface, one of rotationally symmetrical to the access channel or to the absorbing part of the substrate or of the cap.
6. The method as recited in claim 5, wherein the at least one of the recess, the additional recess, and the plurality of additional recesses is formed rotationally symmetrical to a center of mass of the absorbing part of the substrate or of the cap.
7. The method as recited in claim 5, wherein the at least one of the recess, the additional recess, and the plurality of additional recesses are etched anisotropically into the surface.
8. The method as recited in claim 5, wherein the at least one of the recess, the additional recess, and the plurality of additional recesses are isotropically etched into the surface after anisotropic etching.
9. The method as recited in claim 5, wherein the at least one of the recess, the additional recess, and the plurality of additional recesses are formed in such a way that a first extension of the at least one of the recess, the additional recess, and the plurality of additional recesses perpendicular to the surface corresponds to a second extension of the absorbing part of the substrate or of the cap.
10. The method as recited in claim 5, wherein the at least one of the recess, the additional recess, and the plurality of additional recesses, are formed chronologically after the third step, so that the at least one of the recess, the additional recess, and the plurality of additional recesses includes a ring-shaped cavity or a plurality of ring-shaped cavities.
11. A micromechanical component, comprising: a substrate; and a cap connected to the substrate and together with the substrate encloses a first cavity, a first pressure prevailing and a first gas mixture with a first chemical composition being enclosed in the first cavity, the substrate or the cap including a sealed access opening; wherein the substrate or the cap includes a recess situated in a surface of the substrate or of the cap facing away from the first cavity in the area of the access opening for reducing local stresses occurring at a sealed access opening.
12. The micromechanical component as recited in claim 11, wherein the cap together with the substrate encloses a second cavity, a second pressure prevailing and a second gas mixture and a second chemical compound being enclosed in the second cavity.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 shows a micromechanical component including an open access opening according to one exemplary specific embodiment of the present invention in a schematic representation.
[0033] FIG. 2 shows the micromechanical component according to FIG. 1 including a sealed access opening in a schematic representation.
[0034] FIG. 3 shows a method for manufacturing a micromechanical component according to one exemplary specific embodiment of the present invention in a schematic representation.
[0035] FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, and FIG. 9 show subareas of a micromechanical component according to exemplary specific embodiments of the present invention in schematic representations.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0036] In the different figures, identical parts are provided with identical reference numerals and are therefore generally also only named or mentioned once.
[0037] FIG. 1 and FIG. 2 show a schematic depiction of a micromechanical component 1 including an open access opening 11 in FIG. 1, and including a sealed access opening 11 in FIG. 2 according to one exemplary specific embodiment of the present invention. Micromechanical component 1 hereby includes a substrate 3 and a cap 7. Substrate 3 and cap 7 are connected to one another, preferably hermetically, and together enclose a first cavity 5. For example, micromechanical component 1 is formed in such a way that substrate 3 and cap 7 additionally together enclose a second cavity. The second cavity is, however, not shown in FIG. 1 and FIG. 2.
[0038] For example, a first pressure prevails in first cavity 5, in particular in the case of sealed access opening 11, as shown in FIG. 2. In addition, a first gas mixture with a first chemical composition is enclosed in first cavity 5. Furthermore, 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. Access opening 11 is preferably situated in substrate 3 or in cap 7. In the case of the exemplary embodiment presented here, access opening 11 is situated for example in cap 7. According to the present invention, however, it may also be alternatively provided that access opening 11 is situated in substrate 3.
[0039] It is provided, for example, that the first pressure in first cavity 5 is lower than the second pressure in the second cavity. It is also provided, for example, that a first micromechanical sensor unit for measuring the rotation rate is situated in first cavity 5, not shown in FIG. 1 and FIG. 2, and a second micromechanical sensor unit for measuring the acceleration is situated in the second cavity, not shown in FIG. 1 and FIG. 2.
[0040] A method for manufacturing micromechanical component 1 according to an exemplary specific embodiment of the present invention is shown in a schematic representation in FIG. 3. For this purpose, [0041] in a first method step 101, in particular, narrow access opening 11 in substrate 3 or in cap 7 is formed connecting first cavity 5 to surroundings 9 of micromechanical component 1. FIG. 1 shows, for example, micromechanical component 1 after first method step 101. In addition, [0042] in a second method step 102, the first pressure and/or the first chemical composition is adjusted in first cavity 5, or first cavity 5 is flooded with the desired gas and the desired internal pressure via the access channel. Furthermore, for example, [0043] in a third method step 103, access opening 11 is sealed by introducing energy and heat into an absorbing part 21 of substrate 3 or cap 7 with the aid of a laser. It is, for example, alternatively also provided that [0044] in third method step 103, the area around the access channel is merely preferably locally heated by a laser and the access channel is hermetically sealed. Thus, it is advantageously possible to also provide the method according to the present invention with other energy sources besides a laser for sealing access opening 11. FIG. 2 shows, for example, micromechanical component 1 after third method step 103.
[0045] Chronologically after third method step 103, mechanical stresses may occur in a lateral area 15, shown, for example, in FIG. 2, on surface 19, and in the depth perpendicular to a projection of lateral area 15 onto surface 19, i.e. along access opening 11 and in the direction of first cavity 5 of micromechanical component 1. These mechanical stresses, in particular local mechanical stresses, prevail in particular on or in the vicinity of an interface between a material area 13 of cap 7, which seals access opening 11 in a liquid aggregate state in third method step 103 and transitions into a solid aggregate state after third method step 103, and a residual area of cap 7, which remains in a solid aggregate state during third method step 103. In FIG. 2, material area 13 of cap 7 sealing access opening 11 is hereby merely indicated schematically or schematically depicted, in particular with respect to its lateral extension or form extending in particular in parallel to surface 19, and in particular with respect to its expansion or configuration running perpendicular to the lateral extension, in particular perpendicular to surface 19.
[0046] In FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, and FIG. 9, subareas of a micromechanical component 1 according to exemplary specific embodiments of the present invention are schematically depicted. In FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, and FIG. 9, different recesses 17 or structures are hereby situated for reducing the stresses in or around absorbing part 21 of substrate 3 or of cap 7 or in or around the area which is melted. The structures are hereby formed in such a way that the material directly around absorbing part 21 of substrate 3 or of cap 7 or around molten area 21 may reduce the stresses in the solidified melting area due to elastic deformation. For this purpose, for example, one single structure or also a plurality of structures is situated preferably rotationally symmetrical with respect to the center of mass of the melt. In FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, and FIG. 9, for example, recesses 17 or structures are provided. However, differently shaped and differently extending recesses 17 may also be provided which meet the objective according to the present invention. The structures provided in FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, and FIG. 9 are preferably etched anisotropically into surface 19. In addition, for example, a lower part of the structures shown in FIG. 9 is isotropically etched after the anisotropic etching. For example, surface 19 hereby includes a silicon surface. For example, a first extension of recesses 17 is perpendicular to surface 19, or the depth, to which recesses 17 of the structures extend into surface 19 or into the silicon surface, is in the area of a second extension of absorbing part 21, perpendicular to surface 19 or to the melting depth, for example, of the silicon. However, it is alternatively also provided that the first extension is smaller than the second extension. Alternatively, it is additionally also provided that the second extension is smaller than the first extension.
[0047] FIG. 3 shows by way of example that, [0048] in a fourth method step 104, recess 17 or a stress-release structure is formed in a surface 19 of substrate 3 or of cap 7 facing away from first cavity 5 in the area of access opening 11 to reduce local stresses occurring at a sealed access opening 11.
[0049] In FIG. 4 and FIG. 5, different recesses 17 or structures or ring-shaped structures for reducing stresses are depicted. For example, a distance of a recess 17 to the outer edge of absorbing part 21 of substrate 3 or of cap 7 hereby corresponds maximally to the radius of absorbing part 21 or of melting area 21. In particular, it is provided, for example, that the distance of recess 17 to the outer edge of absorbing part 21 of substrate 3 or of cap 7 corresponds to half of the radius of absorbing part 21 or of melting area 21. Furthermore, it is provided, for example, that recess 17 is formed as a circular ring, as a square frame, or as a polygon, in particular as a quadrilateral, hexagon, octagon, decagon, or dodecagon, or as a polygon with more than twelve sides. For example, the square frame or the polygon may also be aligned arbitrarily according to the crystal orientation, in particular according to the silicon crystal orientation, and/or formed as an additional polygon.
[0050] In FIG. 6, two additional possible designs of recess 17 are shown by way of example. In particular, a plurality of recesses 17 is shown in FIG. 6. For example, recess 17 or the plurality of recesses 17 or the stress-release structure for adjusting the mechanical properties include one or multiple nested, interrupted ring structures. These ring structures, for example, do not intersect or intersect at least partially with melting area 21 or with absorbing part 21 or extend into melting area 21 or into absorbing part 21.
[0051] In FIG. 7, two additional possible designs of recess 17 are shown by way of example. For example, in this case, recess 17 includes a ring structure running around melting area 21 or absorbing part 21 and trenches connected to the ring structure and running in a spoke-like fashion or radially to the center or to the center of mass of melting area 21. The trenches hereby extend, for example, merely partially into absorbing part 21 and are situated at least partially outside of absorbing part 21. It is also provided, for example, that the trenches are formed to be connected to one another in the area of access opening 11. In other words, the trenches may meet in the center or preferably end prior to that. For example, it is to be further ensured, taking into account all tolerances, that the ends lie within melting area 21. Furthermore, an additional possible design of a plurality of additional recesses 17 is shown in FIG. 7. A plurality of individual structures 17 are hereby situated in and around melting area 21, which make the material more flexible and tolerant for adjustment offsets due to the matrix-like arrangement. It is provided, for example, that individual structures 17 are formed from quadrilaterals, hexagons, or octagons, or a combination of the same.
[0052] FIG. 8 shows by way of example an additional possible design of recess 17. Recess 17 hereby includes, for example, a ring-shaped structure or multiple individual structures formed with ring shapes and situated within melting area 21 around access channel 11. The depth of recess 17 or the structure or the extension of recess 17 perpendicular to surface 19 is hereby greater than the extension of absorbing part 21 or of the melting depth. It is thus possible that after a material area solidified in the area of absorbing part 21, after the melting of the material area, a ring-shaped cavity 301 or multiple ring-shaped cavities 301 situated around access channel 11 is/are formed and remain underneath the melt symmetrically around access channel 11. Due to these cavities 301, stress or mechanical stress in the area of the underside of the access hole seal or on a side of absorbing part 21 facing first cavity 5 may be reduced. For example, the width or an extension of recess 17 is hereby formed in such a way that, for example, the laser in third method step 103 does not reach the etching base or an interface between recess 17 and cap 7, or that the laser does not irradiate the etching base or the interface.
[0053] Alternatively, it is also provided that the angle of incidence of the laser beam in third method step 103 is set in such a way that the laser beam or the laser pulse does not perpendicularly strike the recess surface or the interface between recess 17 and cap 7.
[0054] It is provided according to the present invention that, for example, recesses 17 or structures are optionally combined with stress release structures or additional recesses 17 or structures outside of melting area 21 or absorbing part 21. Different etching depths may hereby be implemented, for example, with the aid of the aspect ratio dependent etch (rate) (ARDE) effect.
[0055] Finally, FIG. 9 shows recesses 17, the recesses 17 each including an isotropic area 303. It is hereby provided, for example, that isotropic area 303 is situated in particular on a side of recess 17 facing away from surface 19. For example, recesses 17 or the structures shown in FIG. 9 are etched in such a way that, at the end of the etching or on a side of recess 17 facing first cavity 5, an isotropic etching step is carried out, due to which an undercut 305 is formed at the etching base. It is provided, in particular, that undercut 305 is formed in such a way that undercut 305 extends essentially in parallel to surface 19 or, in comparison to remaining recess 17, projects at least partially into cap 7 in parallel to the surface.
