Micromechanical optical component and method for manufacturing a micromechanical optical component

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 forming 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 fixed on the component substrate and serves 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 material-locking connection, - wherein the spacer and the component substrate are connected to one another by means of a second material-locking connection, - wherein, in a plan view of the optical window, the first material-locking connection is arranged below the optical window and the second material-locking connection is arranged beside the optical window. The invention also relates to a method for producing a micromechanical optical component.

Description

Technical Field

[0001] This invention relates to a micromechanical optical component in the form of a micromechanically packaged optical semiconductor assembly. Background Technology

[0002] Optical components must often operate in a sealed atmosphere. Some laser diodes, for example, must operate in a moisture-free and organic-free environment in order not to significantly reduce their lifespan.

[0003] The housings commonly used today to ensure this environment are very labor-intensive and expensive. Therefore, metal housings are often used, which on one hand have a ceramic through-guide that can guide electrical signals to the optical components, and on the other hand have at least one glass window to guide optical signals to and / or out of the optical components.

[0004] Furthermore, micromechanical accelerometers and speed sensors, along with their fabrication methods, are known. The sensors are fabricated at the wafer level—that is, in large numbers on a silicon substrate (wafer)—in parallel connection and are also encapsulated at the wafer level primarily in a hermetically sealed cavity via bonding methods, in which additional wafers are applied to the wafer containing the sensor. The fabrication process is relatively cost-effective because each otherwise expensive step is performed at the wafer level, i.e., simultaneously for the entire assembly of multiple individual sensors. The bonding methods typically used require high bonding temperatures but also achieve hermetically sealed and very robust connections.

[0005] Ideally, optical active components could also be hermetically and securely sealed at the wafer level. However, this simple utilization of the process used for optical components is not possible because optical active components typically do not withstand high bonding temperatures. Summary of the Invention

[0006] This invention seeks a component and a manufacturing method for hermetically encapsulating an optical component in a wafer composite. The method should be able to hermetically protect the optical component while minimizing the thermal load acting on the optical component during the manufacturing process.

[0007] This invention relates to a micromechanical optical component having an optical window, a spacer, and a component substrate. The spacer has a notch forming a cavity, which is defined by the optical window and the component substrate. An optical semiconductor assembly is disposed within the cavity, fixed to the component substrate, and configured to emit light radiation through the optical window. The optical window and the spacer are interconnected by a first material-locking connection, and the spacer and the component substrate are interconnected by a second material-locking connection. In a top view toward the optical window, the first material-locking connection is located below the optical window, and the second material-locking connection is located beside the optical window. The device is simply constructed.

[0008] Advantageously, the optical window is made of glass. The optical window allows for optical transmission while simplifying manufacturing. Advantageously, the component substrate is made of ceramic. Advantageously, components on the component substrate can make good contact and dissipate heat.

[0009] An advantageous configuration of the micromechanical optical component is that either the first or second material-locking connection is also a sealed glass bond. Advantageously, this enables the realization of a sealed cavity.

[0010] Advantageously, the cavity is tightly sealed. Thus, the optical semiconductor components are protected against dust, moisture, and other environmental influences.

[0011] Advantageously, the spacer retainer has a first absorption layer on the surface facing the component substrate. Advantageously, the device can be better manufactured by means of transmission welding.

[0012] However, it is also advantageous that the optical window has a second absorption layer on the surface adjacent to the cavity. Advantageously, this can prevent interference reflections of light within the cavity. Particularly advantageously, the first and second absorption layers are composed of the same material.

[0013] This invention also relates to a method for manufacturing micromechanical optical components. The invention proposes manufacturing spacer wafers with notches for each optical element. Furthermore, it proposes facet-bonding a glass wafer to the spacer wafer. The glass is then preferably removed via a simple sawing process in a track outside the bonding frame and also outside the notch. The individual optical elements, present on the respective substrates, are fitted into the notches and aligned with the wafer. A sealed connection between the individual substrates and the wafer is then established through a localized and very short heating process. This short and localized heating, on the one hand, produces a reliable sealed connection, and on the other hand, protects the optical components from excessively intense heating. The short and localized heating is preferably performed with a laser pulse from the front side of the wafer, which passes through the carrier wafer and appears on the substrate. The fitting, alignment, and mechanical pressure established during the bonding process are performed from the rear side of the wafer.

[0014] The method has a number of advantageous features and configurations.

[0015] Individual optical elements are applied to the wafer composite section, allowing for very precise adjustment of each individual element. During the final bonding process, which seals the optical elements within the notches of the spacer wafer, the bonding joint is heated only locally. This results in a very reliable bonding joint under locally high temperatures, while minimizing heating of the optical components. Localized heating is achieved through the spacer wafer. The surface of the spacer wafer is pre-treated to allow for good coupling by infrared laser. For this purpose, glass at that location is removed beforehand. The surface in the region of the second bonding joint is not damaged by sawing. An absorption layer can be provided beneath the spacer wafer. The first and second bonding frames are geometrically separated from each other. A single-crystal silicon wafer is preferably used as the spacer wafer.

[0016] The method comprises very few components and enables a device with a simple construction. In particular, it eliminates the need for a TSV carrier wafer. This novel manufacturing method achieves very high adjustment precision between the optical semiconductor components and the mirror. The resulting package is ultimately very small. Attached Figure Description

[0017] Figure 1 The micromechanical optical component according to the invention in the first embodiment is shown.

[0018] Figure 2a –2e illustrates a method for manufacturing micromechanical optical components according to the invention at different stages of the equipment.

[0019] Figure 3 The method according to the invention for manufacturing micromechanical optical components is illustrated schematically. Detailed Implementation

[0020] Figure 1 The micromechanical optical component according to the invention in the first embodiment is shown.

[0021] A micromechanical optical component having an optical window 140, a spacer 110, and a component substrate 19 is shown. The spacer 110 has a notch forming a cavity 30, which is defined by the optical window and the component substrate. An optical semiconductor assembly 18 is disposed in the cavity, which is fixed to the component substrate and configured to emit light radiation through the optical window in a beam path 40. The optical window and the spacer are interconnected by a first material-locking connection 5. The spacer and the component substrate are interconnected by a second material-locking connection 15. Here, in the top view 200 of the optical window, the first material-locking connection is arranged below the optical window and the second material-locking connection is arranged beside the optical window.

[0022] Figure 2a –2e illustrates a method for manufacturing micromechanical optical components according to the invention at different stages of the equipment.

[0023] First, spacer wafer 1 with notch 2 is manufactured ( Figure 2a For optical elements that output or receive signals not perpendicular to the wafer plane, it is advantageous to place passive optical elements, such as mirrors, within the spacer wafer to achieve a suitable beam path in a simple manner. For example, a defined beveled side 3 can be etched into a single-crystal silicon wafer with a defined crystal orientation using KOH etching; this side can be used as the mirror side. Furthermore, the mirror surface can also be provided with a reflective coating.

[0024] The glass wafer 4 is bonded to the spacer wafer. Figure 2b Preferably, the glass wafer is applied to the spacer wafer by a sealing glass bonding 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 a notch in the spacer wafer. In the region 6 surrounding this bonding region 5, i.e., the first material-locking connection, bonding between the glass wafer and the spacer wafer is intentionally not provided. This can be very easily achieved by a sealing glass bonding method using locally applied flux. However, additional localized material-locking connections 5 besides sealing glass bonding are also conceivable.

[0025] The glass wafer is partially or completely removed from the excess area 8 outside the bonding frame region. Figure 2cPreferably, this can be achieved by means of a simple cutting process. The result is that a window 140 is created from the glass wafer 4. During the cutting process, it is easy to cut into the spacer wafer, thereby creating a small notch 7 due to the sawing. This is technically simple to achieve. However, the cutting process can also be implemented in a more technically laborious variation, such that the cutting process stops at the height of the bonding joint. Then, no notch is created due to the sawing. This more laborious variation is preferred when particularly small components are desired.

[0026] Optionally, a first absorber layer 9 may be applied for the second bonding process. Preferably, the first absorber layer may be applied on the back side of the spacer wafer.

[0027] It is generally desirable that the optical window 140 be configured to be opaque in areas where no beam path is provided, in order to suppress scattering. In a particularly advantageous variant, the first absorption layer 9 can be deposited simultaneously on the back side of the spacer wafer 1 and the second absorption layer 10 for suppressing scattering can be deposited on the glass wafer 4 or the underside of the window 140 by directional deposition, for example by sputtering or vapor deposition. This can be achieved by planar deposition of such a layer on the back side of the spacer wafer to which the glass wafer has already been bonded. Here, the mirror surface can be used as a self-adjusting shading area so that the glass wafer is not coated at the points where the optical beam enters or exits.

[0028] Optical components, particularly optical semiconductor components 18, are applied onto a component substrate 19 (not specifically shown, see [link]). Figure 2d Advantageously, a ceramic substrate is used. This offers low cost and good thermal conductivity. It is also advantageous to use a substrate with electrically conductive contacts to create electrical channels early and cost-effectively. Furthermore, a substrate with pre-prepared rear-side contacts 20 is advantageous. Preferably, the components on the substrate can already be inspected and selected based on measurements, allowing only the best components to be further processed.

[0029] Each optical component is introduced into cavity 30 on the rear side of spacer wafer 1, which is established through notch 2. Component substrate 19 is not a wafer, but a single substrate. Thus, the component substrate can be individually adjusted within the notch. Component substrate 19 is connected to the spacer wafer by means of a second material-locking connection 15, using a bonding method. The bonding connection surrounds the notch 2 in the spacer wafer 1 and thereby surrounds the cavity 30, and is located wholly or partially in the region where no glass is present on the spacer wafer. A sealing connection is then created between the spacer wafer 1 and component substrate 19 by means of a short thermal pulse 11. Figure 2dPreferably, the material for the bonding connection is arranged on the spacer wafer or component substrate. Particularly advantageous is a sealing glass, which is applied, for example, by means of a screen printing method.

[0030] In a particularly advantageous variant, the adjustment of the component substrate relative to the spacer wafer can be performed immediately following the adjustment of the features of the optical components with respect to the features of the mirror in the spacer wafer. This allows for the elimination of inaccuracies in mirror manufacturing, notch fabrication, or application of the optical elements to the ceramic substrate that affect the accuracy of the optical beam between the mirror and the optical elements. In a particularly advantageous variant, this fine adjustment from the front can be achieved through an optical window, where both the mirror element and the optical element can be observed simultaneously, thus enabling exceptionally high adjustment accuracy.

[0031] Preferably, the new sealing glass bonding frame is heated by a short laser pulse. A laser pulse shorter than 200 milliseconds is preferred. The laser pulse can also be a multi-pulse. A laser with a wavelength greater than 600 nm is preferred. The laser pulse is preferably introduced only locally into a region of the new sealing glass bonding frame. The laser pulse is preferably introduced from the front side. The laser pulse is preferably introduced into a region outside the first bonding frame.

[0032] In an optional additional step, the contact surface 20 can be formed and further processed on the back side of the individual substrate 19. Advantageously, for example, the individual substrate is first provided with a flat contact surface, and then solder balls are applied to the contact surface in the wafer recombination section in this step, i.e., after bonding to the spacer wafer. In this sequence, the solder balls are not damaged during bonding, simpler processing is achieved during bonding, and the solder balls can be cost-effectively applied to all contact surfaces simultaneously in the wafer recombination section.

[0033] In the final step, the micromechanical optical components are separated. For this purpose, the spacer wafer 1 is diced to produce individual components with spacer retainers 110. Figure 2e ).turn out, Figure 2e A micromechanical optical component according to the invention is shown in the second embodiment. The device shown is compared to... Figure 1 The device shown has a first absorption layer 9 additionally on the surface of the spacer holder 110 facing the substrate 19 and a second absorption layer 10 additionally on the surface of the optical window 140 adjacent to the cavity 30. Here, the second absorption layer is also structured. The second absorption layer does not cover the entire window, but only a portion of it. The other part of the window remains open relative to the mirror side, allowing light to pass through the window unobstructed along the beam path 40.

[0034] Figure 3The illustration schematically depicts a method for manufacturing micromechanical optical components according to the present invention.

[0035] The method comprises the following main steps: A: Provide spacer wafers with notches; B: The spacer wafer and the glass wafer are connected by the first material locking connection part; C: Window is made by sawing glass wafers and removing excess glass. D: Provides a component substrate with optical semiconductor components fixed thereon; E: The component substrate is placed on the spacer wafer in this way, so that the optical semiconductor components are arranged in the notch. F: The component substrate and the spacer wafer are connected by transmission bonding (Durchstrahl-Bonden), wherein the beam originates from the side of the window, is oriented next to the window and passes through the spacer wafer.

[0036] List of reference numerals 1 Spacer wafer 2 gaps 3 Mirror 4 Glass wafers 5. First material locking connection part, sealing glass keying part 6. Surrounding area next to the sealing glass bonding part 7. Through the saw cut notch 8. Excess glass wafer area 9 First Absorption Layer 10 Second Absorption Layer 11 Thermal radiation pulse 15 Second material locking connection part 18 Optical Components 19 Component Substrate 20 Rear contact area 30 cavities 40 Beam Path 110 Spacer, Spacer Retention Component 140 glass windows 200 Top View

Claims

1. A micromechanical optical component having an optical window (140), a spacer (110), and a component substrate (19). -in, The spacer (110) has a notch that forms a cavity (30), which is defined by the optical window and the component substrate. -An optical semiconductor assembly (18) is disposed in the cavity, the optical semiconductor assembly being fixed on the component substrate and configured to emit light radiation through the optical window. -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), In a top view toward the optical window, the first material locking connection is arranged below the optical window, and the second material locking connection is arranged beside the optical window and located in a region where the first material locking connection is not present on the spacer, such that the thermal pulse for generating the second material locking connection can be oriented beside the optical window and through the spacer. The spacer (110) has a first absorption layer (9) on the surface facing the component substrate (19) and the optical window (140) has a second absorption layer (10) on the surface adjacent to the cavity (30), wherein the second absorption layer (10) only covers a portion of the optical window (140) so that light can pass through the optical window (140) unimpeded along the beam path (40).

2. The micromechanical optical component according to claim 1, characterized in that, The optical window (140) is made of glass.

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

4. The micromechanical optical component according to claim 1 or 2, characterized in that, The first material locking connection part (5) and / or the second material locking connection part (15) are sealed glass bonding parts.

5. The micromechanical optical component according to claim 1 or 2, characterized in that, The cavity (30) is tightly sealed.

6. The micromechanical optical component according to claim 1 or 2, characterized in that, The first absorption layer (9) and the second absorption layer (10) are composed of the same material.

7. A method for manufacturing micromechanical optical components, comprising the following steps: A: Provide spacer retainers with notches; B: The spacer and the glass wafer are connected by a first material locking connection; C: An optical window is manufactured by sawing the glass wafer and removing excess glass portions; D: Provide a component substrate having an optical semiconductor assembly fixed on the component substrate; E: Place the component substrate onto the spacer holder, such that the optical semiconductor assembly is arranged in the notch. F: The component substrate and the spacer are connected by transmission bonding, wherein... The beam originates from the side of the optical window, is oriented beside the optical window, and passes through the spacer, such that a second material-locking connection is formed between the spacer and the component substrate. This second material-locking connection is disposed beside the optical window and located in a region where the first material-locking connection is not present on the spacer. Prior to step E, a first absorption layer is applied to the side of the spacer that is away from the optical window and a second absorption layer is applied to the side of the optical window that faces the spacer. The second absorption layer (10) covers only a portion of the optical window (140) so that light can pass through the optical window (140) unimpeded along the beam path (40).

8. The method for manufacturing micromechanical optical components according to claim 7, characterized in that, In step B, after the sealing glass has been coated onto the spacer and / or the glass wafer, the first material locking connection is manufactured by the sealing glass bonding portion.

9. The method for manufacturing micromechanical optical components according to claim 7 or 8, characterized in that, In step F, after the sealing glass has been coated onto the spacer and / or the component substrate, a second material locking connection is manufactured through the sealing glass bonding portion.

10. The method for manufacturing micromechanical optical components according to claim 7 or 8, characterized in that, After step B, the first absorption layer and the second absorption layer are coated simultaneously, wherein the spacer is used as a mask for structured coating of the second absorption layer onto the optical window.

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