EP1966078A1

EP1966078A1 - Method for sealing an opening

Info

Publication number: EP1966078A1
Application number: EP06830110A
Authority: EP
Inventors: Lutz Mueller; Ralf Hausner; Holger Hoefer; Udo Bischof; Volker Schmitz; Axel Grosse
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2005-12-20
Filing date: 2006-11-24
Publication date: 2008-09-10
Also published as: US8304845B2; JP2009520371A; WO2007071523A1; DE102005060870A1; US20090174148A1

Abstract

The invention relates to an integrated component with a substrate (1), wherein the substrate (1) has a cavity (10) enclosing a mechanical structure (11). The cavity (10) is filled with a fluid (14) of a given composition at a given pressure and the mechanical properties of the mechanical structure (11) are altered by the fluid (14).

Description

description

Method for closing an opening

The invention relates to a method for closing an opening in a substrate. The invention further relates to an integrated component with a substrate.

In addition to the integration of electronic circuits, technological progress has also led to the miniaturization of mechanical components and systems. So-called microelectromechanical systems (MEMS) realize mechanical units in the range of a few microns and below. In this case, the industrial production takes place via a multi-layer structure, often using materials from the semiconductor industry. In this case, cavities are formed in which micromechanical structures can be arranged. Furthermore, upper layers are generally provided which enclose the mechanical structure in the cavity in which a well-defined environment can be created. For this purpose, a corresponding liquid or gaseous fluid is introduced into the cavity through openings and the openings are closed. Thus, the cavity is also protected from external influences, and an undesirable temporal change, such as corrosion, is prevented. There is therefore a need to close off the openings and accordingly permanently entrap a fluid into the cavity.

Known methods include a fluid whose

Pressure and density are often unable to significantly influence the mechanical properties of the mechanical structure. Furthermore, in conventional methods, End material and sometimes aggressive components in the cavity, which then can lead to damage there. To close a mechanical structure in a cavity, for example, the closure of openings by a so-called. Refill process described in EP 1274648 Bl. Remaining openings of the substrate are grafted there and an internal pressure or an inner atmosphere is enclosed in the cavity, which is determined by the process conditions of the refining process. A decoupling of a certain internal atmosphere from this process is not possible. Furthermore, closure material, components thereof or even reaction products can penetrate into the cavity.

It is therefore an object of the present invention to provide an improved method for closing an opening in a substrate. It is a further object of the present invention to provide an improved integrated component having a mechanical structure. This object is achieved by the method according to claim 1 or by the integrated component according to claim 11. Further advantageous embodiments of the invention are specified in the dependent claims.

According to a first aspect of the present invention, there is provided a method of closing an opening in a substrate. The method comprises the following steps: First, a substrate is provided with a cavity, wherein the cavity is accessible through the opening. Furthermore, a fluid of a certain composition and under a certain pressure is introduced into the cavity. There is also provided a closure material which is applied to the opening and so the fluid dum into the cavity, preventing closure material from entering the cavity. The method of the invention has the advantage of including a fluid of a certain well-defined composition and under a certain well-defined pressure in the cavity. The pressure and composition of the fluid are decoupled from the provision and application of the closure material to the opening. Adverse environmental conditions during the provision and application of the sealing material thus do not or do not significantly affect the fluid that is trapped in the cavity. Neither closure material nor other - and sometimes harmful - components which are produced during the provision and application of the closure material thus penetrate into the cavity and damage to the cavity or any structures just contained therein is prevented.

According to one embodiment of the present invention, the provision of the closure material takes place by providing components. The said components form the closure material at the location of the opening by physical and / or chemical transformation, and the opening is thereby terminated so that neither closure material nor components penetrate into the cavity. It is thereby advantageously a well-defined fluid enclosed in the cavity, wherein neither closure material, nor components, or other reaction components in the cavity can lead to damage.

According to another embodiment of the present invention, the formation of the closure material by a plasma-enhanced vapor deposition process under atmospheric pressure (PECVD). In the case of a gas phase Divorce processes, the closure material is first brought in the form of components to the place of deposition, to form there just by a physical and / or chemical deformation of the closure material. In many cases, penetration into the cavity of components, of reaction products or of closure material itself leads to damage of structures provided there. However, the present invention carrying out the vapor deposition at atmospheric pressure advantageously prevents the diffusion of harmful substances through the opening in the cavity. Furthermore, the increased compared to conventional Abscheidungsverfah- ren atmospheric pressure, essentially in the range of 1 bar, to an advantageous effect on mechanical structures in the cavity. Thus, by the method according to the invention, two advantages can be achieved by one measure.

According to a further embodiment of the present invention, the closure material is provided in the form of a paste. Furthermore, while the closure material in a

Carrier medium may be introduced, which can be resolved after application again. By dissolving the carrier medium, the closure material remains in a porous form, and the cavity is still advantageously accessible through the opening. So it can be done further process steps that require access to the cavity.

In accordance with a further embodiment of the present invention, the closure material is applied to the opening in a liquid manner, so that the cavity is closed by solidification of the closure material on the opening. The liquefaction of many conventional sealing materials can advantageously be carried out under almost any environmental conditions. consequences. This makes it possible to include a well-defined fluid of certain compositions under a certain pressure in the cavity.

According to another embodiment of the present invention, a wetting layer is formed on the substrate at least in an environment of the opening. The wetting layer according to the invention advantageously favors the accumulation of sealing material around and on the opening. Preferably, for this purpose, a metallosis may be provided as a wetting surface for a solder around the opening.

According to a further embodiment of the present invention, the pressure of the trapped fluid is between 500 mbar and 2 bar. On the one hand, this pressure according to the invention prevents the diffusion of harmful substances into the cavity and, on the other hand, can favorably influence the structural properties of the cavity and mechanical properties of structures therein. Further, the temperature-can temperature during the application of the closing material between 175 ° C and 400 ⁰ C. Advantageously, a reliable application of the closure material, for example by liquefaction, is ensured, while the temperature is insufficient to damage components in and on the substrate.

According to another embodiment of the present invention, a non-stick coating is applied to an inner wall of the cavity and to a surface of the mechanical structure. This non-stick coating prevents the mechanical structure from sticking even when in mechanical contact with a surface of the cavity. Since sticking of the mechanical structure to surfaces of the cavity is a frequent Cause of an unstable operation of the integrated component or even a total failure desselbigen represents, the provision of the non-stick coating according to the invention leads to a significant improvement in the operation and the reliability of the integrated component.

According to a second aspect of the present invention, an integrated component is provided. The integrated component has a substrate with a cavity, the latter surrounding a mechanical structure. The cavity is further filled with a fluid of a certain composition and under a certain pressure. The mechanical properties of the mechanical structure are significantly influenced by the fluid. The integrated component according to the invention makes it possible to significantly influence the mechanical properties of the mechanical structure. Advantageously, a targeted tuning of mechanical parameters is thus possible, such as the tuning of the damping. At the same time, the integrated component is reliable and sturdy. Furthermore, the production of the integrated component according to the invention is considerably simplified by a well-defined fluid of specific compositions and under a certain pressure, since the penetration of harmful substances into the cavity during production is prevented. Thus, the performance and reliability of integrated components with mechanical structures can be significantly improved.

FIGS. 1A to 1D show a schematic sectional view of an integrated component according to a first embodiment of the present invention; FIGS. 2A to 2D show a schematic sectional view of an integrated component according to a second embodiment of the present invention; and

3A and 3B show a schematic sectional view of an integrated component according to a third embodiment of the present invention.

FIG. 1A shows an integrated component in a substrate 1 with a mechanical structure 11, which is arranged in a cavity 10. A substrate surface 100 has openings 12 with inner walls 112. The inner surface of the cavity 10 is designated 110, and the surface of the mechanical structure 11 is designated 111. Such an integrated component is manufactured by a number of per se known process techniques. The substrate 1 often comprises silicon, silicon oxide, silicon nitride and other conventional materials in the form of structured layers. For example, the mechanical structure 11 is freed by removing an underlying silicon oxide layer. The openings 12 in the substrate surface 100 also serve to supply process-related liquids and gases. So that the function of the integrated component is not impaired even when the mechanical structure 11 is in mechanical contact with the walls of the cavity 10, an anti-static coating (ASC) 13 is applied to a surface 111 of the mechanical structure 11 on an inner wall 110 of the cavity 10, applied to an inner wall 112 of the openings 12 and to the substrate surface 100, as shown in Fig. IB. This non-stick coating significantly increases the reliability of the integrated component. However, the provision of a non-stick coating 13 is not necessary for this embodiment. In a further step, as shown in FIG. 1C, a fluid 14 is introduced through the openings 12 into the cavity 10. For the purposes of the present invention, a fluid means both gases and liquids, which may also advantageously interact with the mechanical system 11. Thus, for example, the pressure and the composition of the fluid 14 can be chosen such that a certain mechanical damping of the mechanical structure 11 is achieved. Modern deposition techniques, such as, for example, chemical vapor deposition (CVD), initially bring components to the location of deposition, at which the material to be deposited then forms by chemical and / or physical transformation. Starting components, materials used or reaction products can thereby damage the mechanical structure 11, the cavity 10, or also coatings, such as the non-stick coating 13. The fluid 14 also prevents the penetration of such harmful components and substances.

In Fig. ID, finally, the integrated component is shown with a sealing layer 15, which closes the openings 12 tight and includes the fluid 14 at a certain pressure and with a certain composition in the cavity 10. The application method of the sealing layer 15 can remove the non-stick coating 13 on the substrate surface 100. The pressure of the fluid 14, preferably in the range of 1 bar, can both prevent the ingress of harmful substances and at the same time can influence the mechanical properties of the mechanical structure 11. It has been found that an integrated component, as shown in FIG. 1D, can be produced by a plasma-enhanced chemical vapor deposition (PECVD) process at one pressure, which substantially corresponds to the atmospheric pressure of 1 bar, can be completed without damaging material or harmful substances damaging the mechanical structure 11, the non-stick coating 13, or other components in the cavity 10. Preferably, a low frequency plasma frequency in the range of 10 Hz to 200 kHz can be used in the PECVD process.

FIG. 2A shows a further integrated component with a substrate 2 with a cavity 20, in which a mechanical

Structure 21 is provided. A surface 220 of the cavity 20 and a surface 221 of the mechanical system 21 are coated with a non-stick coating 23. The cavity 20 is accessible via openings 22 with inner walls 222. On a surface 200 of the substrate 2, a wetting layer 26 has been partially applied, at least in an environment of the openings 22. An advantageous environment of an opening 22 is formed by an annular, the opening 22 enclosing area, wherein the width of the ring amounts to between one and ten times the opening diameter. In the context of the present invention, the environment can thereby maintain a minimum distance to the edge of the opening 22, to reach directly to the opening 22, or also include the opening 22 with.

In the context of an advantageous embodiment, a conductive closure material is selected, for example so-called solder bumps, which, in addition to the closure of the openings 22, also provide electrical contact to a further substrate arranged above the substrate 3. The further substrate may then also include an electrical drive circuit. In the sense of a further advantageous embodiment, the integrated component is provided in such a way with the non-stick coating 23. layers, so that also forms on the surface 200, the material of the non-stick coating 23. This material can then be removed locally in the area around the openings 22 and can not allow any further coating on coated areas. For example, the material of the non-stick coating 23 on the surface 200 then acts as Lotstoplack.

In a manufacturing step, a sealing material 28 in the form of a paste is applied to the surface 200 of the substrate 2, as shown in FIG. 2B. The closure material 28 may be present in a granular form and form the paste in a carrier medium 27. Examples include solder pastes or glass frit pastes in which a granular metal or a granular seal glass is in a binder. The carrier medium 27 is not absolutely necessary in the context of the present invention, but it simplifies the application of the closure material 28. If a carrier medium 27 is provided, it is removed in a subsequent production step, as shown in Fig. 2C. For example, an organic carrier medium 27 may be ashed. There remains a porous arrangement of the closure material 28 on the surface 200 back. Therefore, the openings 22 are still permeable and the cavity 20 is accessible even after the application of the closure material 28. Thus, further process steps can also be performed at this stage, such as the application of the non-stick coating 23.

As further shown in FIG. 2C, a fluid 24 is introduced into the cavity 20 of the substrate 2. Both the composition and the pressure of the fluid 24 are selected so that the fluid 24 enclosed in the cavity 20 does not damage the mechanical structure 21 or its coating and advantageously adjust the mechanical properties of the mechanical system 21 in the desired manner. In addition, the fluid 24 may prevent diffusion of harmful substances into the cavity 20. By shallow or local heating, the sealing material is liquefied, which then collects preferably at the locations of the wetting layer 26 and forms a cap over the openings 22. The solidified closure material 28 thus forms tight closure caps 29, as shown in FIG. 2D. The melting of the sealing material 28 allows for the utmost independence of the pressure and composition of the fluid 24. It is therefore possible to seal a desired fluid 24 or even a vacuum in the cavity 20 tightly. It is also possible to dispense with the application of the closure material 28 and the carrier medium 27, and to provide only a liquid closure material which advantageously adheres to the wetting layer 26, as may be done, for example, by wave soldering or a solder bath. The liquefied closure material should advantageously have a surface tension which on the one hand promotes the formation of a cap over the openings 22 and on the other hand suppresses penetration into the openings. It can thus be dispensed with the wetting layer 26.

FIG. 3A shows a further integrated component in a substrate 3 with a mechanical structure 31 which is arranged in a cavity 30. The cavity 30 is accessible via openings 32 with inner walls 332. Both a surface 330 of the cavity 30 and a surface 331 of the mechanical structure 31 are coated with a non-stick coating 33. Furthermore, a fluid 34 is introduced into the cavity 30. By local melting, such as by a laser beam, a previously applied closure material or an upper part of the substrate 3 is liquefied and closes off by openings 39, the openings 32, as shown in Fig. 3B. The closure material can be formed by the substrate 3 in this embodiment. Thus, a well-defined fluid 34 can be introduced into the cavity 30 under a certain pressure and with a specific composition, without the need for further process steps for applying further closure materials. Another advantage is that a gentle processing of the previously structured integrated component can take place. Also, this method allows a selective closing of the openings 32, for example by first closing a first part of the openings 32, then carrying out further process steps which still require access to the cavity 30 and then closing the remaining openings 32. In addition to the melting of parts of the substrate 3, a separate material for forming the plugs 39 can be used by local heating, such as metals, which are deposited around the openings 32 before melting in an environment. Alternatively, material in the form of a film, for. B. of metal, a thermoset or thermosets, are provided.

In all embodiments, the temperature during the application or the melting of the closure material is preferably in a range of 175 ° C to 400 ⁰ C. Further, as a sealing material, for example SiO 2 or Si 3 N ₄ are used and as a fluid, for example, nitrogen, neon, mixtures from it, SF ₆ , or other inert gases or mixtures thereof included. The openings 12, 22, 32 may further have different sizes.

Claims

claims

A method of closing an opening (12, 22, 32) in a substrate (1, 2, 3), the method comprising the steps of:

Providing a substrate (1, 2, 3) having a cavity (10, 20, 30), the cavity (10, 20, 30) being accessible through the opening (12, 22, 32); Introducing a fluid (14, 24, 34) of a specific composition and / or under a certain pressure into the cavity (10, 20, 30);

Providing a closure material (3, 15, 28); Applying the closure material (3, 15, 28) to the opening (12, 22, 32) so that the fluid (14, 24, 34) is trapped in the cavity (10, 20, 30) and preventing the Closure material (3, 15, 28) in the cavity (10, 20, 30) penetrates.

2. The method of claim 1, wherein providing the closure material (3, 15, 28) by providing

Components, wherein the components form the closure material (3, 15, 28) by physical and / or chemical deformation, and wherein the formation of the closure material (3, 15, 28) on the opening (12, 22, 32) takes place, so that no components penetrate into the cavity (10, 20, 30).

3. The method of claim 2, wherein providing the components and forming the closure material (3, 15, 28) is performed by a plasma enhanced vapor deposition process under an atmospheric pressure.

4. The method according to any one of claims 1 to 2, wherein the provision of the closure material (3, 15, 28) takes place as a paste, in particular with a carrier medium (27), which is dissolved after application.

5. The method according to any one of claims 1 to 4, wherein the closure material (3, 15, 28) is applied liquid to the opening (12, 22, 32), so by solidification of the closure material (3, 15, 28) on the opening (12, 22, 32) of the cavity (10, 20, 30) is completed.

6. The method according to any one of claims 1 to 5, wherein additionally a step for forming a wetting layer (26) on the substrate (1, 2, 3) takes place at least in an environment of the opening (12, 22, 32).

7. The method according to any one of claims 1 to 6, wherein the pressure of the fluid (14, 24, 34) is between 500 mbar and 2 bar.

8. The method according to any one of claims 1 to 7, wherein the temperature during the application of the closure material

(3, 15, 28) on the opening (12, 22, 32) between 175 ° C and 400 ⁰ C.

9. The method according to any one of claims 1 to 8, wherein prior to the application of the closure material (3, 15, 28) on the opening (12, 22, 32), a non-stick coating (13, 23, 33) on an inner wall (110, 220 , 330) of the cavity (10, 20, 30) and on a surface (111, 221, 331) of a mechanical structure (11, 21, 31) is applied.

10. An integrated component comprising a substrate (1, 2, 3) having a cavity (10, 20, 30), which is completed by a method according to any one of claims 1 to 9.