DE19931773C1 - Micromechanical component has contact ducts formed as metal wires which are recast from the molten glass during the manufacture of the first wafer - Google Patents

Abstract

The contact ducts in a micromechanical component are formed as metal wires which are recast from the molten glass during the manufacture of the first wafer. Micromechanical component comprises a first wafer (2) made of glass, a second wafer (3) connected to the first wafer to form an inner chamber (5), and one or more contact ducts (6a, 6b, 6c) for electrically connecting the inner chamber. The contact ducts are formed as metal wires which are recast from the molten glass during the manufacture of the first wafer. An Independent claim is also included for a process for the production of the micromechanical component.

Description

The present invention relates to a micromechanical component Contact bushings and a method for producing a micromechanical Component, according to the preambles of claims 1 and 13.

Micromechanical components are e.g. B. in the manufacture of sensors and Actuators needed. Especially with pressure sensors or also with acceleration and Rotation rate sensors become micromechanical or micro-electro-mechanical Components used. These are inexpensive to manufacture on a wafer basis, reliable in operation and have a small footprint.

In many cases it is necessary to use a micromechanical component To provide interior space, for example to create hermetically encapsulated structures. If this encapsulation takes place on a wafer basis, this can result in a considerable cost advantage be achieved. The encapsulations are often subject to high demands, for example with regard to mechanical strength, hermetic tightness, and with regard to the lateral space requirement, which should be as small as possible. A high mechanical resilience is necessary because e.g. B. in chip singling and Hybrid build-up process (e.g. wire bonding) considerable mechanical forces can occur. Likewise, the sensors often become considerable mechanical ones during operation Exposed to vibrations and thermal stress. Hermetic Tightness is required if there is a risk of dirt or moisture in the Interior of the sensor or actuator can get or the sensor or actuator vacuum, should be pressure-tight and / or chemically resistant. There is little lateral space requirement advantageous because the chip size is a decisive cost factor in batch processing is. Furthermore, electrical contact bushings inside the sensor have to be low parasitic loads, such as series resistance or stray capacitance, are provided his.  

For wafer-based encapsulation, e.g. B. the anodic bonding method known. Hermetically dense conductor bushings can either laterally, d. H. parallel to the wafer level, or also be produced vertically to the chip level. For example, are implanted Conductor paths possible as lateral contact bushings. However, are disadvantageous high stray capacities, high line resistance and in many cases high Space requirements. Lateral conductor bushings can also be passed through metal bushings will be realized. However, this requires a high manufacturing effort, being below Other special processes may be necessary, e.g. B. chemical mechanical Polishing. For the realization of vertical variants of the conductor track bushings known as via etching and their filling with metal. This However, processes are very expensive and take up a lot of space.

It is therefore the object of the present invention to provide a micromechanical component with an interior and contact bushings to create that simple and is inexpensive to produce, reliable operation and high durability guaranteed and has low electrical parasitic loads. Furthermore, a Method for producing micromechanical components with an interior are specified, which is simple and inexpensive to carry out and with one Hermetic encapsulation of the interior with improved electrical properties is possible.

This task is solved by the micromechanical component according to Claim 1 and by the method for producing a micromechanical Component according to claim 13. Further advantageous features, aspects and Details of the invention emerge from the dependent claims, the description and the drawings.

The micromechanical component according to the invention comprises an interior and a or several contact bushings for the electrical connection of the interior with the outside space, wherein at least two wafers are provided, which are together are connected to form the interior, and wherein at least a first wafer  is made of a glass in which to form the respective contact bushing at least one metal wire is cast in.

A high hermetic seal and chemical resistance of the component can be achieved. Since the Contact bushings are melted in glass, it is possible the interior to make it dirt, moisture, vacuum and pressure tight as well as chemically resistant, with a very high reliability and durability is guaranteed. The Contact bushings can be kept very short, so that improved electrical properties or reduced parasitic loads result. The stray capacity and the component size are extremely small. There can be simplified construction and Connection technologies are used, the manufacturing costs are reduced.

The wafers are advantageously arranged parallel to one another and the Contact bushings aligned perpendicular to the wafer level. That’s it Ratio of length to cross-sectional area of the contact bushings is very small, e.g. B. approx. 100 / cm to 200 / cm for vertical bushings compared to approx. 10000 / cm for lateral feedthroughs, which is why the ohmic resistance is about 100 times is smaller. Since the bushings do not run flat on or in the substrate, there are hardly any overlap with the substrate, which leads to a vanishingly low stray capacity leads.

The second wafer advantageously has one at the interface with the first wafer Recess or recess that is used to form the interior through the first wafer is closed like a lid. This allows for particularly simple and inexpensive Way an encapsulated interior can be created.

The first wafer preferably has on its side located in the interior and / or on the Interface to the second wafer interconnect structures connected to the contact bushings are connected. The electrical contacts can thus lie over the component, which is why no additional component area for the electrical contacts, e.g. B. in the form of wire bond pads. This leads in particular to the so-called  Batch processing at reduced manufacturing costs, since at reduced Component area more components can be processed at the same time.

The second wafer is preferably made of silicon and has at least one Contact bushing in the first wafer is electrically connected. In the interior, a Sensor and / or actuator element to be formed, which with the contact bushings the outside space is electrically connected. In particular, on the inside and / or one or more structured metal layers on the outside of the wafers be trained.

The wafers are advantageously connected to one another by anodic bonding. On the inner side of the first wafer is preferably an electrode surface formed, which is opposite a surface of the second wafer by a measuring capacity and / or to form an actuator element. The component can be used as a pressure, acceleration or rotation rate sensor. There is advantageously one on both sides Silicon wafers arranged a first wafer made of glass with cast metal wires. Thus, z. B. a layered structure of three wafers, the glass wafer is preferably configured as described above.

The glass wafer is preferred by dividing a glass block with the cast in it Metal wires made into individual disks.

The method according to the invention for producing a micromechanical component includes the steps:

Providing a glass wafer with metal wires cast into it and connecting the Glass wafers with a further wafer which has a depression on its surface, so that the recess forms an interior, the metal wires being positioned so that they have contact bushings for connecting the interior to the exterior form. This allows hermetically sealed components in particular Connections that lead into the interior of the component are simplified or less expensive are produced, the electrical properties of the components being improved and high reliability is guaranteed.  

A structured is preferred on one and / or both sides of the glass wafer Metal layer applied, which is in contact with the metal wires and after the Connect to the further wafer as a conductor track, contact and / or electrode surface serves.

When the metal wires are poured or poured into glass, the metal wires become preferably positioned so that taking thermal expansion into account the contact positions of the component to be produced. Preferably that Glass has a high sodium content and a coefficient of thermal expansion that largely corresponds to the expansion coefficient of silicon or as close as possible is coming.

To provide the glass wafer z. B. metal wires fixed and with melted Pouring glass, the resulting glass block is then divided into slices, such that the metal wires each lead from one side of the disc to the other side.

Another advantage of the invention is that simplified construction and Connection technologies are applicable. For example, because the contact bushings The known ones can lie on the surface of the lid or bottom wafer simplified construction and connection technologies for integration with others Components such as B. control and evaluation electronics can be used. In particular, the use of flip-chip technology is also more related simplified structure and connection technologies possible. This would be with lateral ones Contact bushings due to the thickness of the lid or bottom wafer, the z. B. must be at least 0.3 mm, not possible without further manufacturing steps.

The invention is described below with reference to the figures, in which:

Fig. 1 shows a first embodiment of the invention with a component assembly consisting of two wafers;

Fig. 2 shows another embodiment of the invention, which consists of three wafers; and

Fig. 3 shows steps for the manufacture of glass wafers with molded-in contact bushings as used according to the invention.

Fig. 1 shows a section through a component structure according to the invention. A micromechanical component 1 , which is designed as a pressure sensor, is formed from a glass wafer 2 and a silicon wafer 3 . The two wafers are aligned parallel to one another and connected to one another at an interface 4 by anodic bonds between glass and silicon. Inside the pressure sensor or component 1 there is a cavity or interior 5 , which is closed by the glass wafer 2 like a lid. In the glass wafer 2 there are contact bushings 6 a, 6 b, 6 c which electrically connect the outer space to the interior of the component and to the hollow or inner space 5 . The contact bushings 6 a, 6 b, 6 c are formed by metal wires, which are melted or cast in the glass material of the glass wafer 2 .

The metal wires or contact bushings 6 a, 6 b, 6 c run vertically or perpendicular to the wafer plane, ie perpendicular to the interface 4 between the glass wafer 2 and the silicon wafer 3 . On the top or outer side 21 of the glass wafer 2 there are connection or connection elements 7 a, 7 b, 7 c, the connection element 7 a being a wire bond, the connection element 7 b being a solder ball for flip-chip bonding and the connecting element 7 c is a metallization, which is arranged on the outside 21 for the configuration of conductor tracks, contact and / or electrode surfaces.

The interior 5 is formed, for example, by a rectangular recess in the silicon wafer 3 on the side adjacent to the glass wafer 2 . On the underside 22 or the inner side of the glass wafer 2 there is an electrode surface 8 a and a conductor 8 b, which electrically connects the electrode surface 8 a with the contact bushing 6 b. The electrode surface 8 a and the conductor track 8 b are formed in one piece by a metal layer. Furthermore, a further metal layer 8 c is provided on the underside 22 of the glass wafer 2 in the region of the adjacent silicon substrate of the Si wafer 3 , which forms an electrical contact between the silicon substrate and the metal of the contact bushing 6 a. The contact bushing 6 c, which is in the right area of the glass wafer 2 in FIG. 1, is in electrical contact with a further conductor track or metal layer 8 d, which is likewise arranged on the underside 22 of the glass wafer 2 in the area of the interior 5 and in the contact or interface 4 of the anodic bond protrudes between glass and silicon.

The electrode surface 8 a on the underside 22 of the glass wafer 2 is arranged essentially parallel to the underlying substrate of the silicon wafer 3 and spaced from it. By means of suitable electrical connections via the contact bushing 6 b on the one hand and the contact bushings 6 a and 6 c on the other hand, the electrode surface 8 a forms a measuring capacitance 81 together with the silicon wafer 3 underneath. When the distance between the electrode surface 8 a and the top 31 of the silicon wafer 3 changes, the capacitance 81 changes accordingly. Thus, a pressure acting on the silicon wafer 3 from outside can be measured via the encapsulated cavity 5 with the measuring capacitance 81 arranged therein.

FIG. 2 shows a section through a micromechanical component 10 according to a further embodiment of the invention. In this case, elements that are the same or have the same function as in the embodiment shown in FIG. 1 are identified by the same reference numerals. In the embodiment shown here, a glass wafer 2 a, 2 b is arranged on each side of the silicon wafer 3 a. Thus, the device structure consists of three wafers, ie a glass cap wafer 2 a, a silicon wafer 3 a and a bottom glass wafer 2 b. Both glass wafers 2 a, 2 b have cast-in contact bushings 6 a, 6 b, 6 c, each of which form an electrical connection from the outside into the interior of the component. An upper interior 5 a is electrically conductively connected to the top 21 a of the glass lid wafer 2 a, while a lower interior 5 b is electrically conductively connected to the bottom 21 b of the glass bottom wafer 2 b. This structure can also be used as a pressure sensor, two capacitances 81 being present in the hermetically sealed interior of the sensor 10 for pressure measurement, so that, for. B. sensor drift effects can be taken into account in the measurement.

In a further embodiment of the invention, which is not shown in the figures, the micromechanical component forms an acceleration sensor. For this purpose, a mass is suspended asymmetrically on two opposite torsion bars inside the sensor. The surface of the mass, which lies inside the sensor and in principle corresponds to the surface 31 of the component shown in FIG. 1, is advantageously flat and serves as an electrode surface for measuring capacitors. The capacitor arrangement advantageously consists of two electrodes arranged symmetrically to the axis of rotation. An acceleration perpendicular to the wafer plane leads to a tilt of the mass and thus to an opposite change in capacitance of the two capacitors and advantageously the magnitude of the acceleration acting can be determined from the difference.

The micromechanical device shown in Fig. 1 and Fig. 2 1, 10 is used in a further variant, as well as an acceleration sensor. For this purpose, the location inside the device 1, the silicon wafer substrate 10 is 3 or 3 a on one side only with the remaining silicon substrate is connected, while it floats freely at the other side. For example, the component 10 shown in FIG. 2 and discussed above can easily be designed as an acceleration sensor in that the silicon substrate located between the cavity 5 a and the cavity 5 b only on the right or on the left with the remaining part of the silicon wafer 3 a connected is. In this case, a silicon bar is obtained which bends due to its inertia when accelerated perpendicular to the wafer surface or interface 4 . This changes the capacitances 81 on both sides of the silicon beam, from which the acceleration can be derived.

Even in the construction as discussed in FIG. 1, the component 1 can be configured as an acceleration sensor by slight modification. For this purpose, only the cavity or interior 5 on the right-hand side in FIG. 1 has to be open, so that there is no connection between the silicon wafer 3 and the glass wafer 2 in this part. The part of the silicon wafer 3 below the electrode surface 8 a is then designed as a bar, which is connected or fixed only in the left part of the sensor to the rest of the silicon substrate. When accelerating perpendicular to the interface 4 , the capacitance 81 changes due to the inertia of the silicon bar formed in this way.

Instead of the embodiment shown above with measuring capacitances 81 in the cavity 5 or 5 a, 5 b, an embodiment with actuator elements can also be provided. For example, a silicon beam located in the cavity 5 , 5 a, 5 b can be excited to vibrate via the electrical connections to the exterior, for example by electrostatic forces or by piezoelectric elements which are additionally arranged in the interior or cavity. Such vibrating structures can e.g. B. serve as part of a rotation rate sensor, wherein when the system rotates due to the Coriolis force by the periodically oscillating structure, a further vibration is generated, the deflection of which is a measure of the rotation rate.

The component according to the invention can also be used, for example, as a Be designed acceleration sensor that is sensitive parallel to the wafer level. At this sensor, the silicon wafer is provided with interdigital structures, i. H. on the lateral movable structures are attached to finger structures. Are parallel to these fingers fixed fingers connected to the surrounding silicon. Acceleration leads then a change in these capacities. The metal surfaces inside then serve only as conductor tracks and as contact areas, no longer as electrode areas. It understands it goes without saying that a variety of sensor types according to the present invention can be designed.

The manufacture of glass wafers 2 , 2 a, 2 b or bond glasses with melted-in electrical contact bushings will now be described with reference to FIG. 3. For this purpose, wires with a diameter of z. B. 0.2 mm, which later represent the electrical feedthroughs. The lateral arrangement of the wires corresponds to the desired position of the contact bushings for the finished component. In order to achieve a corresponding accuracy of the contact position, the thermal expansion during production is taken into account.

Now the fixed wires are poured into a glass or with melted glass cast around. In order for the glass to be suitable for anodic bonding, it has a high one Sodium content and a coefficient of thermal expansion that the Expansion coefficient of silicon comes as close as possible. To pour it in Material of the wires, e.g. As tungsten or molybdenum, a higher melting point than that Have used glass.

The electrical conductivity of the melted wires and the insulation of the wires can be tested very easily after melting and solidification. Then the resulting glass block with the vertically melted wires sawn into slices in such a way that the desired wires are melted out electrical contact bushings are made from one side of the respective washer lead to the other side of the disc.

The disks are then planarized and polished so that they are small Thickness fluctuation, plane-parallel surfaces and the smallest possible Show surface roughness. This step is comparable to polishing Glass or silicon wafers. However, there are two in the method described here Materials, the bond glass on the one hand and the contact bushings on the other, edit at the same time. Finally, the panes are cleaned to remove residues, such as B. remove metal or abrasive residues and particles from the surface.

The bond glasses produced in this way are used according to the present invention for producing the described actuators or sensors. A silicon wafer is connected to a lid wafer made of glass. In the case of a structure comprising more than two wafers, as shown in FIG. 2, an additional glass bottom wafer is used. Here, a cavity is formed between the wafers, in which the sensor and / or actuator element z. B. is designed by metallic layers. This sensor and / or actuator element or the conductor tracks, electrode surfaces and / or the silicon wafer contained therein are electrically connected via contact bushings which lead from the interior of the component to the exterior of the component. The connection is made via the melted-in contact bushings, which run vertically to the lid or bottom wafer. In this case, the inside and / or the outside of the top or bottom wafer can additionally be provided with at least one structured metal layer, which serve as conductor tracks, contact and / or electrode surfaces. The lid or bottom wafer is connected to the silicon wafer by means of an anodic bonding process in order to obtain the finished component structure.

The bond area between the glass wafer 2 , 2 a, 2 b and the silicon wafer 3 , 3 a has a closed bond frame. The electrical contact bushings 6 a, 6 b, 6 c do not cross this bond frame, but run vertically to the bond surface.

The advantages of the present invention are summarized:

• - Simplified manufacture, in particular of hermetically sealed components with electrical connections that lead into the interior of the component;
• - great hermetic tightness and chemical resistance of the Contact bushings;
• - low ohmic resistance of the contact bushings;
• - low substrate capacities or low stray capacities;
• - Small component size and thus low manufacturing costs;
• - Simplified construction and connection technology.

Claims (17)

1. Micromechanical component, with:
a first wafer ( 2 ; 2 a, 2 b) made of glass,
at least one second wafer ( 3 ; 3 a), which is connected to the first wafer ( 2 ; 2 a, 2 b) to form an interior ( 5 ; 5 a, 5 b), and
one or more contact bushings ( 6 a, 6 b, 6 c) for the electrical connection of the interior ( 5 ; 5 a, 5 b) to the exterior,
characterized by
that the one or more contact bushings ( 6 a, 6 b, 6 c) are formed by one or more metal wires which were cast in molten glass during the manufacture of the first wafer ( 2 a, 2 b, 2 c). 2. Micromechanical component according to claim 1, characterized in that the wafers ( 2 , 3 ; 2 a, 2 b, 3 a) are arranged parallel to one another and the contact bushings ( 6 a, 6 b, 6 c) are aligned perpendicular to the wafer plane . 3. Micromechanical component according to claim 1 or 2, characterized in that the second wafer ( 3 ; 3 a) at the interface ( 4 ) to the first wafer ( 2 ; 2 a, 2 b) has a recess and / or lateral structuring, which is closed to form the interior ( 5 ; 5 a, 5 b) by the first wafer ( 2 ; 2 a, 2 b) like a lid. 4. Micromechanical component according to one of the preceding claims, characterized in that the first wafer ( 2 ; 2 a, 2 b) on its inside ( 5 ; 5 a, 5 b) located side ( 22 ) and / or at the interface ( 4 ) for the second wafer ( 3 ; 3 a) has metal or conductor track structures ( 8 a, 8 b, 8 c, 8 d) which are connected to the contact bushings ( 6 a, 6 b, 6 c). 5. Micromechanical component according to one of the preceding claims, characterized in that in the interior ( 5 ; 5 a, 5 b) a sensor and / or actuator element ( 81 ) is formed, which via the contact bushings ( 6 a, 6 b, 6 c) is electrically connected to the outside space. 6. Micromechanical component according to one of the preceding claims, characterized in that the second wafer ( 3 ; 3 a) is made of silicon and with at least one contact bushing ( 6 a, 6 c) in the first wafer ( 2 ; 2 a, 2 b ) is electrically connected. 7. Micromechanical component according to one of the preceding claims, characterized in that on the inside ( 22 ) and / or the outside ( 21 ; 21 a, 21 b) of the wafer ( 2 ; 2 a, 2 b) one or more structured metal layers ( 7 a, 7 b, 7 c, 8 a, 8 b, 8 c, 8 d) are formed. 8. Micromechanical component according to one of the preceding claims, characterized in that the wafers ( 2 , 3 ; 2 a, 2 b, 3 a) are connected to one another by anodic bonding. 9. Micromechanical component according to one of the preceding claims, characterized in that an electrode surface ( 8 a) is formed on the side of the first wafer ( 2 ) located in the interior ( 5 ), which is opposite to a surface of the second wafer ( 3 ) by one Measuring capacity ( 81 ) and / or to form an actuator element. 10. Micromechanical component according to one of the preceding claims, characterized in that the first wafer made of glass ( 2 a, 2 b) with the cast-in metal wires ( 6 a, 6 b, 6 c) arranged on both sides of a silicon wafer ( 3 a) is. 11. Micromechanical component according to one of the preceding claims, characterized characterized in that it is used as a pressure, acceleration or rotation rate sensor is trained. 12. Micromechanical component according to one of the preceding claims, characterized in that the wafer or wafers are made of glass ( 2 ; 2 a, 2 b) by dividing a glass block with metal wires cast therein into individual disks. 13. A method for producing a micromechanical component, comprising the steps:
Providing a glass wafer ( 2 ; 2 a, 2 b),
Connecting the glass wafer to a further wafer ( 3 ; 3 a, 3 b), which has a depression and / or lateral structuring on its surface, so that the depression or lateral structuring forms an interior ( 5 ; 5 a, 5 b), characterized in that during the manufacture of the glass wafer ( 2 ; 2 a, 2 b) metal wires are fixed and cast with molten glass in order to make contact bushings ( 6 a, 6 b, 6 c) for connecting the interior ( 5 ; 5 a, 5 b) to form with the outside space. 14. The method according to claim 13, characterized in that on one and / or both sides ( 21 ; 21 a, 21 b) of the glass wafer ( 2 ; 2 a, 2 b) a structured metal layer ( 7 a, 7 b, 7 c ) is applied, which is in contact with the metal wires and, after being connected to the further wafer ( 3 ; 3 a), serves as a conductor track, contact and / or electrode surface. 15. The method according to claim 13 or 14, characterized in that when casting the metal wires with glass the metal wires are positioned so that under Taking thermal expansion into account the contact positions of the produce component to be produced. 16. The method according to one or more of claims 13 to 15, characterized characterized in that the glass has a coefficient of thermal expansion which comes as close as possible to the coefficient of expansion of silicon. 17. The method according to one or more of claims 13 to 16, characterized in that to provide the glass wafer ( 2 ; 2 a, 2 b) metal wires are fixed and cast with molten glass, the resulting glass block is then divided into slices, so that the metal wires run from one side of the disc to the other.