CN112909728A

CN112909728A - Micromechanical optical component and method for producing a micromechanical optical component

Info

Publication number: CN112909728A
Application number: CN202011388558.3A
Authority: CN
Inventors: J·赖因穆特
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-12-03
Filing date: 2020-12-01
Publication date: 2021-06-04
Also published as: DE102019218820A1

Abstract

The invention relates to a micromechanical optical component having an optical window, a spacer and a component substrate, wherein the spacer has a recess which forms a cavity which is bounded by the optical window and the component substrate, wherein an optical semiconductor component is arranged in the cavity, which is fastened to the component substrate and serves for emitting light radiation through the optical window, wherein the optical window and the spacer are connected to one another by means of a first cohesive connection, wherein the spacer and the component substrate are connected to one another by means of a second cohesive connection, wherein, in a plan view of the optical window, the first cohesive connection is arranged below the optical window and the second cohesive connection is arranged next to the optical window. The invention also relates to a method for producing a micromechanical optical component.

Description

Micromechanical optical component and method for producing a micromechanical optical component

Technical Field

The invention relates to a micromechanical optical component in the form of a micromechanical encapsulated optical semiconductor component.

Background

Optically effective components must often operate in a sealed atmosphere. Some laser diodes, for example, must be operated in a moisture-free and organic-free environment in order not to significantly reduce their service life.

The housings that are common today to ensure this environment are very elaborate and expensive. For this purpose, metal housings are often used which have, on the one hand, a ceramic feedthrough which can conduct electrical signals to the optical component and, on the other hand, at least one glass window in order to be able to conduct optical signals to and/or from the optical component.

Furthermore, micromechanical acceleration sensors and rotation speed sensors and methods for their production are known. Sensors are produced at the wafer level, i.e. in large numbers on a silicon substrate (wafer), in parallel with one another, and are also encapsulated at the wafer level, predominantly by bonding methods in which a further wafer is applied to the wafer with the sensors, in a hermetically closed cavity. The production process is relatively cost-effective, since the individual, expensive working steps are carried out at the wafer level, i.e. simultaneously for the totality (ensembles) of a plurality of individual sensors. The bonding methods generally used require high bonding temperatures, but at the same time enable a sealed and very robust connection.

It is desirable that the optically effective components can also be hermetically and securely closed at the wafer level. However, simple use of such a process for optical components is not possible, since optically effective components are generally not subjected to high bonding temperatures.

Disclosure of Invention

The present invention seeks to provide an assembly and a method of manufacture for hermetically encapsulating optical components in a wafer compound. The method should be able to protect the optical component in a sealed manner and at the same time keep the thermal loads acting on the optical component during the production method as low as possible.

The invention relates to a micromechanical optical component having an optical window, a spacer and a component substrate, wherein the spacer has a recess which forms a cavity which is bounded by the optical window and the component substrate, wherein an optical semiconductor component is arranged in the cavity, which optical semiconductor component is fastened to the component substrate and is provided for emitting optical radiation through the optical window, wherein the optical window and the spacer are connected to one another by means of a first cohesive connection, and wherein the spacer and the component substrate are connected to one another by means of a second cohesive connection. In this case, the first adhesive bond connection is arranged below the optical window and the second adhesive bond connection is arranged next to the optical window in a plan view toward the optical window. The device is simple in construction.

Advantageously, the optical window is glass. The optical window allows optical transmission while being simple to manufacture. Advantageously, the component substrate is ceramic. Advantageously, the components on the component substrate can make good contact and conduct away heat.

An advantageous embodiment of the micromechanical optical component provides that the first material bond or the second material bond is also a sealing glass bond. Advantageously, this enables a sealed cavity.

Advantageously, the cavity is hermetically closed. Thereby, the optical semiconductor component is protected against dust, moisture and other environmental influences.

Advantageously, the spacer has a first absorption layer on the surface facing the component substrate. Advantageously, the device can be made better by means of transmission welding.

It is also advantageous, however, if the optical window has a second absorption layer on the surface adjoining the cavity. Advantageously, disturbing reflections of light in the cavity can thereby be avoided. It is particularly advantageous if the first absorption layer and the second absorption layer consist of the same material.

The invention also relates to a method for producing a micromechanical optical component. The invention proposes to produce a Spacer Wafer (Spacer-Wafer) with cutouts for the individual optical elements. It is also proposed that the glass wafer be surface-bonded to the spacer wafer. The glass is then removed, preferably by means of a simple sawing process, in the track outside the bonding frame and also outside the gap. The individual optical elements present on the individual substrates are inserted into the recesses and adjusted with respect to the wafer. A hermetic connection between the individual substrates and the wafer is then established by means of a local and very short heating process. By means of short-term and local heating, on the one hand a reliable sealing connection can be produced and, on the other hand, the optical component can be protected against excessively intense heating. The short-term and local heating is preferably carried out from the front side of the wafer with laser pulses which emerge through the carrier wafer onto the substrate. The preparation, adjustment and mechanical pressure build-up during the bonding process is done from the wafer backside.

The method has a number of advantageous features and configurations.

The individual optical elements are applied to the wafer compound, whereby very precise adjustment can be made for each individual element. During the final bonding process, in which the optical element is sealed closed in the gap of the spacer wafer, the bonding connection is heated only locally. This makes it possible to produce a very reliable bonding connection at locally high temperatures and nevertheless to heat the optical component less significantly. Local heating is achieved through the spacer wafer. The surface of the spacer wafer is pretreated in such a way that good coupling-in by means of infrared laser light is possible. For this purpose, the glass at this location is removed beforehand. The surface in the region of the second bond connection is not damaged by sawing. An absorber layer may be disposed below the spacer wafer. The first and second bond frames are geometrically separated from each other. The spacer wafer is preferably a single crystal silicon wafer.

The method involves very few components and enables a simply constructed device. In particular, the use of a TSV carrier wafer is also unnecessary. This new production method enables a very high degree of adjustment precision between the optical semiconductor component and the mirror. The package produced is ultimately very small.

Drawings

Fig. 1 shows a micromechanical optical component according to the present invention in a first embodiment.

Fig. 2a to 2e show a method for producing a micromechanical optical component according to the present invention in different stages of the device.

Fig. 3 schematically shows a method according to the invention for producing a micromechanical optical component.

Detailed Description

A micromechanical optical component with an optical window 140, a spacer 110 and a component substrate 19 is shown. The spacer 110 has an indentation forming a cavity 30 which is bounded by the optical window and the component substrate. An optical semiconductor component 18 is arranged in the cavity, which semiconductor component is fixed to the component substrate and is provided for emitting optical radiation in a beam path 40 through the optical window. The optical window and the spacer are connected to each other by means of a first material-locking connection 5. The spacer and the component substrate are connected to one another by means of a second material-locking connection 15. In a top view 200 of the optical window, the first adhesive bond connection is arranged below the optical window and the second adhesive bond connection is arranged next to the optical window.

First, a spacer wafer 1 with notches 2 is manufactured (fig. 2 a). For optical elements which output or receive signals which do not run perpendicular to the wafer plane, it is advantageous to provide passive optical elements, such as mirrors, in the spacer wafer in order to achieve a suitable beam path in a simple manner. The defined inclined side 3 can be etched into a monocrystalline silicon wafer with a defined crystal orientation, which can be used as a mirror side, for example by KOH etching. Furthermore, the mirror surface may also be provided with a reflective coating.

The glass wafer 4 is bonded to the spacer wafer (fig. 2 b). Preferably, the glass wafer is applied to the spacer wafer by a sealing glass soldering method. The sealing glass 5 can be applied to the glass wafer or spacer wafer by a screen printing method. The glass wafer is accordingly bonded to the spacer wafer in a manner surrounding the gap in the spacer wafer. In the region 6 surrounding the bonding region 5, i.e. the first material bond, the bond between the glass wafer and the spacer wafer is intentionally not provided. This can be achieved very simply by means of a sealing glass welding method with locally applied flux. However, other local cohesive connections 5 than sealing glass bonds are also conceivable.

The glass wafer is partially or completely removed outside the bonding frame region in the excess region 8 (fig. 2 c). Preferably, this can be done by means of a simple cutting process. As a result, the window 140 is established from the glass wafer 4. During the cutting process, the spacer wafer can be simply cut into, whereby small gaps 7 are achieved as a result of the sawing. This is technically simple to implement. However, the cutting process can also be carried out in a technically more complex variant in such a way that it is stopped at the level of the bonded connection. No gaps then arise due to sawing. This more elaborate variant is preferably used when particularly small components are desired.

Optionally, a first absorption layer 9 for the second bonding process may be applied. Preferably, the first absorption layer can be applied on the rear side of the spacer wafer.

It is also generally desirable for the optical window 140 to be opaquely formed in places where no beam path is provided, in order to suppress scattering. In a particularly advantageous variant, the first absorber layer 9 can be deposited simultaneously on the rear side of the spacer wafer 1 and the second absorber layer 10 for suppressing scattering on the underside of the glass wafer 4 or the window 140 by directional deposition, for example by a sputtering method or an evaporation method. This can be achieved by planar deposition of such a layer on the rear side of the spacer wafer on which the glass wafer has been bonded. In this case, the mirror can be used as a self-adjusting obscuration (abschatting) in order not to coat the glass wafer at the point where the optical beam enters or exits.

An optical component, in particular an optical semiconductor assembly 18, is applied on a component substrate 19 (not shown in particular, see fig. 2 d). Advantageously, a ceramic substrate is used. This has little expense and good thermal conductivity. It is advantageous to use a substrate with electrical through-contacts in order to generate electrical vias early and cost-effectively. It is advantageous to use a substrate with a previously prepared backside contact 20. Preferably, the components on the substrate can already be inspected and sorted out on the basis of the measured values, so that only good components can be further processed.

The individual optical components are introduced on the rear side of the spacer wafer 1 into the cavity 30, which has been set up through the gap 2. The component substrate 19 is not a wafer but a single substrate. The component substrate can thereby be individually adjusted in the recess. The component substrate 19 is connected to the spacer wafer by means of a second material-locking connection 15 by means of a bonding method. The bond connections surround the gap 2 in the spacer wafer 1 and thus the cavity 30 and are located completely or partially in the region in which no glass is present on the spacer wafer. A sealed connection between the spacer wafer 1 and the component substrate 19 is then produced by means of a short heat pulse 11 (fig. 2 d). Preferably, the material for the bonding connection is arranged for this purpose on the spacer wafer or the component substrate. Particularly advantageous is a sealing glass, which is applied, for example, by means of a screen printing method.

In a particularly advantageous variant, the adjustment of the component substrate relative to the spacer wafer can be carried out immediately after: the characteristics of the optical assembly are adjusted with respect to the characteristics of the mirrors in the spacer wafer. It is thereby possible to achieve that inaccuracies in the production of the mirror or in the production of the recess or in the application of the optical element to the ceramic substrate have an influence on the accuracy of the optical beam between the mirror and the optical element. In a particularly advantageous variant, such a fine adjustment from the front side can be achieved by means of an optical window, wherein the mirror element and the optical element can be viewed at the same time and therefore a particularly high adjustment accuracy can be achieved.

Preferably, the new sealing glass bonding frame is heated by means of a short laser pulse. Laser pulses shorter than 200 milliseconds are preferably applied. The laser pulses may also be applied as multiple pulses. Preferably, a laser having a wavelength greater than 600nm is used. The laser pulse is preferably introduced only locally in the region of the new sealing glass bonding frame. The laser pulses are preferably introduced from the front side. The laser pulses are preferably introduced in a region outside the first bond frame.

In an optional further step, the contact surfaces 20 can be produced and further processed on the rear side of the individual substrates 19. For example, it is advantageous to first provide the individual substrates with flat contact surfaces and then to apply solder balls to the contact surfaces in the wafer compound in this step, i.e. after bonding to the spacer wafer. In this sequence, the solder balls are not damaged during the bonding process, simpler handling during the bonding process is enabled, and the solder balls can be applied to all contact surfaces simultaneously in the wafer compound part at a cost-effective rate.

In a final step, the micromechanical optical component is separated. For this purpose, the spacer wafer 1 is cut open and a single component with the spacer 110 is produced (fig. 2 e). As a result, fig. 2e shows a micromechanical optical component according to the invention in a second embodiment. In contrast to the device shown in fig. 1, the device shown additionally has a first absorption layer 9 on the surface of the spacer 110 facing the component substrate 19 and a second absorption layer 10 on the surface of the optical window 140 adjacent to the cavity 30. The second absorption layer is also structured here. The second absorbent layer does not cover the entire window but only a portion. Another portion of the window remains open with respect to the mirror side so that light can pass through the window along beam path 40 unimpeded.

The method comprises the following main steps:

a, providing a spacer wafer with a gap;

b, connecting the spacer wafer and the glass wafer through the first material locking connection part;

c, manufacturing the window by sawing the glass wafer and removing the redundant glass part;

providing a component substrate having an optical semiconductor component fixed thereon;

e, placing the component substrate on the spacer wafer in such a way that the optical semiconductor component is arranged in the recess,

connecting the component substrate to the spacer wafer by means of transmission bonding (Durchstrahl-Bonden), wherein the beam is directed from the side of the window, alongside the window and through the spacer wafer.

List of reference numerals

1 spacer wafer

2 gap

3 mirror surface

4 glass wafer

5 first material-locking connection, sealing glass bond

6 surrounding area beside the sealing glass bond

7 by sawing notches

8 redundant glass wafer area

9 first absorbent layer

10 second absorbent layer

11 pulse of heat radiation

15 second material locking connection

18 optical assembly

19 member substrate

20 rear side contact

30 cavities

40 beam path

110 spacer, spacer holder

140 glass window

200 top view

Claims

1. A micromechanical optical component having an optical window (140), a spacer (110) and a component substrate (19),

-wherein the spacer holder (110) has a gap forming a cavity (30) bounded by the optical window and the component substrate,

-wherein an optical semiconductor component (18) is arranged in the cavity, which optical semiconductor component is fixed on the component substrate and is arranged for emitting optical radiation through the optical window,

-wherein the optical window and the spacer are connected to each other by means of a first material-locking connection (5),

-wherein the spacer and the component substrate are connected to each other by means of a second material-locking connection (15),

-wherein, in a top view towards the optical window, the first cohesive connection is arranged below the optical window and the second cohesive connection is arranged beside the optical window.

2. Micromechanical optical component according to claim 1, characterized in that the optical window (140) is glass.

3. Micromechanical optical component according to claim 1 or 2, characterized in that the component substrate (19) is ceramic.

4. Micromechanical optical component according to any one of the preceding claims, characterized in that the first and/or the second material-locking connection (5, 15) is a sealing glass bond.

5. Micromechanical optical component according to any one of the preceding claims, characterized in that the cavity (30) is hermetically closed.

6. Micromechanical optical component according to any one of the preceding claims, characterized in that the spacer (110) has a first absorption layer (9) on the surface facing the component substrate (19) and/or the optical window (140) has a second absorption layer (10) on the surface adjoining the cavity (30).

7. Micromechanical optical component according to claim 6, characterized in that the first absorption layer (9) and the second absorption layer (10) consist of the same material.

8. Method for producing a micromechanical optical component, comprising the following steps:

a, providing a spacer wafer with a gap;

b, connecting the spacer wafer and the glass wafer through a first material locking connection part;

c manufacturing a window by sawing the glass wafer and removing excess glass portions;

providing a component substrate having an optical semiconductor assembly fixed thereon;

e, placing the component substrate on the spacer wafer such that the optical semiconductor component is arranged in the recess,

connecting the component substrate to the spacer wafer by means of transmission bonding, wherein the beam is directed from the side of the window, next to the window and through the spacer wafer.

9. Method for producing an optical component according to claim 8, characterized in that in step B the first material bond is produced by means of a sealing glass bond after sealing glass has been applied to the spacer wafer and/or the glass wafer.

10. Method for manufacturing an optical component according to claim 8 or 9, characterized in that in step F a second material bond is manufactured by means of a sealing glass bond after sealing glass has been applied to the spacer wafer and/or the component substrate.

11. Method for manufacturing an optical component according to one of the claims 8 to 10, characterized in that a first absorption layer is applied to the side of the spacer wafer facing away from the optical window before step E.

12. Method for manufacturing an optical component according to one of the claims 8 to 11, characterized in that a second absorption layer is applied onto the side of the optical window facing the spacer wafer before step E.

13. Method for manufacturing an optical component according to claims 11 and 12, characterized in that after step B the first and the second absorption layer are applied simultaneously, wherein in particular the spacer wafer is used as a mask for the structured application of the second absorption layer onto the optical window.