JP2022112336A - Lid of light emitting device - Google Patents

Abstract

To obtain a lid with a suitable base film that does not degrade the bonding performance of the metal brazing material that serves as the bonding material and does not cause lid peeling or airtightness defects when using a lid body with light emitting device transparency.SOLUTION: The light emitting device A consists of a substrate 1, a lid 2 with an inverted concave cross-sectional shape, and an LED element 3 that serves as the light emitting element, and the substrate and lid are joined by a metal brazing material. The lid 2 is provided with a base layer, and the second group layer of the base layer has a multilayer structure including a Ni alloy film, a Ni diffusion suppression film, and an Au film.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a lid used in a light emitting device having an LED (Light Emitting Diode).

A light-emitting device using an LED generally has a structure in which the LED is sealed inside a package to improve reliability. As a specific structural example, there is a structure in which the LED is housed in a cavity of a package base (for example, a ceramic package) and the cavity opening of the package base is sealed with a lid.

In such a structure, the lid must be transparent to the LED illumination. When the LED is a deep-ultraviolet LED that emits deep ultraviolet rays, it has been conventionally considered suitable to use quartz glass for the lid. In addition, the present applicant has proposed the use of crystal for the lid. (Patent document 1).

PCT/JP2020/026073

In the above-mentioned patent document, when crystal or the like is used for the lid of the light emitting device, a lid having a suitable base film that does not cause peeling of the lid or poor airtightness can be obtained. However, Ni in the Ni alloy film may diffuse into the upper Au film and form Ni oxide on the Au film surface depending on the usage environment of the light emitting device.

In such a case, the wettability of the metallic brazing material, for example, an Au--Sn alloy, which joins the package and the lid may be lowered, and the sealing performance of the lid may be lowered.

The present invention has been made in view of the above problems. An object of the present invention is to provide a lid having a suitable underlying film that does not cause defects.

In order to solve the above problems, the lid of the light-emitting device according to the first aspect of the present invention is a lid used in a light-emitting device in which an LED is sealed in a package with a metal brazing material, and a base film formed on a sealing surface of the lid body, wherein the base film comprises a first group layer directly formed on the lid body, and the first group layer. a second group layer formed on the It is characterized by having a laminated structure including a Ni alloy film, a Ni diffusion suppression film and an Au film, which are laminated in order from the side closest to the .

According to the above configuration, since the Ni diffusion suppression film is interposed between the Ni alloy film and the uppermost Au film, the diffusion of Ni into the uppermost Au film is suppressed, and the uppermost Au film Ni oxide is not formed on the film surface. As a result, it is possible to obtain a lid having a suitable base film that does not degrade the bonding performance of the metal brazing material that serves as a bonding material, and does not cause peeling of the lid or poor airtightness when the lid body having translucency of the light emitting device is used. be able to.

Further, in the above lid, the Ti film included in the first group layer may be a Ti film having a thickness of 200 to 300 nm.

According to this configuration, it is possible to reduce the occurrence of detachment of the lid and poor airtightness in the light emitting device, and improve the reliability of hermetic sealing by the lid.

In addition, a metal brazing material may be formed on the upper surface of the Au film.

According to this configuration, it is possible to obtain a lid provided with a brazing metal material having improved bondability between the Au film and the brazing metal material.

Also, the brazing metal may be made of an Au--Sn alloy.

According to this configuration, it is possible to obtain a lid with improved bondability between the Au film and the Au—Sn alloy.

In addition, an alloy film of the Au film and the brazing metal may be formed on the Ni diffusion suppression film of the second group layer.

According to this configuration, it is possible to obtain a lid on which an alloy film having improved bonding properties of a brazing metal is formed.

Also, the Ni diffusion suppressing film of the second group layer can be a Ti film.

According to this configuration, since the Ti material efficiently suppresses the diffusion of Ni, it is possible to obtain a lid with improved hermetic sealing performance.

Further, the Ni diffusion suppressing film of the second group layer may be made of a Ti film having an oxide film made of titanium oxide on its surface.

According to this configuration, the oxide film made of titanium oxide more efficiently suppresses the diffusion of Ni, so that a lid with improved hermetic sealing performance can be obtained.

Also, the first group layer may be configured to be in contact with the crystal plate and consist of the Ti film, the Au film, and another Ti film.

According to this configuration, since the first group layer is secured as a layer structure at the time of hermetic sealing, it is possible to obtain a lid capable of performing stable hermetic sealing.

The Au film, which is the uppermost layer of the second group layer, has an inner peripheral edge that is pulled down further than the inner peripheral edge of the Ni alloy film, and an outer peripheral edge of the Au film that is lower than the Ni alloy film. It can be configured to have a pull-down structure that is pulled down inside the outer peripheral edge.

According to this configuration, it is possible to obtain a lid capable of suppressing the alloy material from reaching other layers at the time of airtight sealing and performing stable airtight sealing.

Further, in the structure of pulling down the Au film, the width of pulling down on the inner peripheral edge side can be made smaller than the width of pulling down on the side of the outer peripheral edge.

In addition, it is possible to adopt a configuration in which the pulling width of the inner peripheral edge side of the pulling structure of the Au film is 25 μm or more.

In order to solve the above problems, a method for manufacturing a lid according to a second aspect of the present invention is a method for manufacturing a lid used in a light-emitting device in which an LED is sealed in a package. A first step of forming a first group layer containing a Ti film having a thickness of 20 to 700 nm on the sealing surface of the lid body having light properties, and a top layer of the first group layer formed in the first step a second step of oxidizing a certain Ti film to form an oxide film made of titanium oxide on the surface; and a third step of forming a second group layer including the Ni alloy film, the Ni diffusion suppression film, and the Au film.

According to the lid manufacturing method described above, the bonding performance of the metal brazing material used as the bonding material is not deteriorated, and when the lid body having translucency of the light-emitting device is used, the lid is not peeled off or the airtightness is not good. A lid with a film can be obtained.

Further, in the lid manufacturing method, the Ti film formed in the first step may have a thickness of 200 to 300 nm.

According to this configuration, it is possible to reduce the occurrence of detachment of the lid and poor airtightness in the light emitting device, and improve the reliability of hermetic sealing by the lid.

Further, in the method for manufacturing the lid, in the first step, a buffer film composed of an Au film and another Ti film, which are laminated in order from the side closer to the Ti film, is formed on the Ti film. be able to.

According to this configuration, since the first group layer is secured as a layer structure at the time of hermetic sealing, it is possible to obtain a lid capable of performing stable hermetic sealing.

Further, in the lid manufacturing method, the Au film, which is the uppermost layer of the second group layer, has an inner peripheral edge that is pulled down more inward than an inner peripheral edge of the Ni alloy film, and an outer peripheral edge of the Au film. A configuration may be employed in which the peripheral edge is pulled down to the outside of the outer peripheral edge of the Ni alloy film.

According to this configuration, it is possible to obtain a lid capable of suppressing the alloy material from reaching other layers at the time of airtight sealing and performing stable airtight sealing.

According to the present invention, there is provided a suitable base film that does not degrade the bonding performance of the brazing metal used as the bonding material and that does not cause peeling of the lid or poor airtightness when the lid body having translucency of the light-emitting device is used. You can get a lid.

It is a sectional view showing an example of composition of a light-emitting device to which the present invention is applied. It is a bottom view (joint surface) of a lid. 4 is a partial cross-sectional view showing the structure of an underlying film in the lid of Embodiment 1; FIG. FIG. 2 is a cross-sectional view showing a configuration in which a metal brazing material is provided on the base film of Embodiment 1; 4 is an SEM photograph of a partial cross-section of a film state in which a metal brazing material is provided on the base film of Embodiment 1. FIG. FIG. 8 is a cross-sectional view showing a lid configuration of Embodiment 2;

[First Embodiment]
BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment according to the present invention will be described in detail below with reference to the drawings.

[Basic structure of light-emitting device]
A configuration example of a light emitting device A to which the present invention is applied will be described with reference to FIG. As shown in FIG. 1, the light-emitting device A is composed of a substrate 1, a lid 2 having an inverted concave cross section, and an LED element 3 serving as a light-emitting element.

The substrate 1 has a rectangular flat plate structure in plan view, and is made of alumina (Al2O3), aluminum nitride (AlN), or the like. A metal layer 11 serving as a lid and internal terminals 12 on which the LED elements 3 are mounted are provided on the upper surface of the substrate 1 , and external terminals 14 are provided on the lower surface of the substrate 1 . The internal terminals 12 and the external terminals 14 are electrically connected by metal vias 13 penetrating the substrate. It should be noted that the substrate 1 is preferably made of a material having high thermal conductivity so as to allow heat generated during operation of the LED element 3 to escape, and the above-mentioned aluminum nitride is suitable.

The lid 2 is made of crystal (translucent lid body) having substantially the same size as the substrate 1 in plan view, and has at least a lid body 20 and a base film 23 . The lid body 20 is made of a plurality of crystals, and has a configuration in which a crystal plate 21 having a rectangular flat plate shape in plan view and a crystal frame plate 22 having a rectangular frame shape in plan view are joined together. This bonding is performed by forming an Au film on each bonding surface of the crystal plate 21 and the crystal frame 22 and performing metal-to-metal bonding. Specifically, an Au film (thickness: 300 nm) corresponding to the circumferential shape of the crystal frame plate is formed on one main surface of the crystal plate 21, and an Au film (thickness: 300 nm) is formed on the crystal frame plate on the joint surface with the crystal plate. thickness of 300 nm), and the two Au films are bonded together under heat and pressure.

The structure of the lid body may be any structure as long as the cross section has an inverted concave shape. In direct bonding, hydrophilic treatment causes the substrates to adhere to each other due to intermolecular forces such as hydroxyl groups and hydrogen attached to the substrate surface of each crystal plate, and subsequent heat treatment bonds silicon and oxygen, which are constituent elements of each crystal. It is a joining method that promotes

Further, as a structure having an inverted concave shape in cross section, only the outer peripheral portion of the crystal plate may be thickened, and the central portion forming the cavity may be half-etched in the thickness direction. This half-etching is a technique for thinning by etching only a selected portion using a photolithographic technique.

In FIG. 1, a base film 23 is formed on the opposite surface of the crystal frame plate 22 to the joint portion with the crystal plate 21 . Although the configuration of the base film 23 will be described later, the lid 2 and the base film 23 are included in the lid. This embodiment shows an example in which the brazing material 24 is formed on the surface of the base film 23, and an Au--Sn material is used as an example of the brazing material 24 as an alloy material. The brazing material forming structure will also be described later.

FIG. 2 shows a bottom view (joint surface) of the lid. A crystal frame plate 22 is bonded to a crystal plate 21 , a base film 23 is formed in a circumferential shape on the crystal frame plate, and a brazing material 24 is formed on the base film 23 . As is clear from FIG. 2, the base film is formed so as to be pulled inward with respect to the width d1 of the crystal frame plate. Further, the metal brazing material 24 is formed to have a width d3 with a configuration that is pulled inward with respect to the width d2 of the underlying film 23 . Such a pull-down structure has the effect of suppressing protrusion of the base film and/or metal brazing material from the lid or substrate when the LED element is hermetically sealed.

As shown in FIG. 1, in the light emitting device A, the LED element 3 is electrically and mechanically bonded to internal terminals of the substrate by FCB (Flip Chip Bonding). However, the present invention is not limited to this, and the LED element 3 may be die-bonded to the substrate 1 and electrically connected to the internal terminals by wire bonding.

The LED element 3 is, for example, a deep ultraviolet LED that emits deep ultraviolet light. Deep ultraviolet rays refer to ultraviolet rays with relatively short wavelengths, and are mainly used for sterilization and disinfection. Quartz has a good transmittance to deep ultraviolet rays, so when the LED element 3 is an LED for deep ultraviolet rays, it is preferable to form the lid from quartz.

Further, as a material having transparency to deep ultraviolet rays, there is quartz glass that has been conventionally used, but if quartz glass is used as the lid of the light-emitting device A, the number of test steps in the airtightness test may increase. . When quartz is used for the lid 2 of the light-emitting device A, there is an advantage that the airtightness test can be performed more easily because the number of test steps is reduced when performing the airtightness test.

[Construction of the lid]
Next, the configuration of the lid will be described.
As described above, the lid 2 is made of crystal having substantially the same size as the substrate 1 in plan view. The lid body 20 is made of a plurality of crystals, and has a structure in which a crystal plate 21 having a rectangular flat plate shape in plan view and a crystal frame plate 22 having a rectangular frame shape in plan view are joined together. This bonding is performed by metal-to-metal bonding of an Au film previously formed on the bonding surfaces of the crystal plate 21 and the crystal frame 22 .

As shown in FIG. 3, a base film 23 is formed on the surface of the crystal frame 22 of the lid 2 (the side of the bonding surface with the substrate 1). The base film 23 has a first group layer 231 formed in contact with the crystal frame 22 and a second group layer 232 laminated on the upper surface of the first group layer.

The first group layer 231 directly formed on the crystal frame 22 is in contact with the crystal frame 22 and a Ti film 2311 is circumferentially formed over the entire circumference of the crystal frame 22 . An Au film 2312 is formed on the entire upper surface of the Ti film 2311 . A Ti film 2313 is further formed on the entire upper surface of the Au film 2312 . Each of these metal films is formed by, for example, a vacuum deposition method or a sputtering method, but other film formation methods may be used. It has been confirmed that if the thickness of the Ti film 2313 is too thin or too thick, reliable airtightness cannot be obtained in the light-emitting device A. More preferably, it is in the range of 300 nm.

The second group layer 232 is formed on the first group layer 231, and is formed in the order of the Ni alloy film 2321, the Ni diffusion suppression film 2322, and the Au film 2323. As shown in FIG. A Ni-Ti (nickel-titanium) film, for example, is formed as a Ni alloy layer on the entire upper surface of the Ti film 2313 of the first group layer 231 . A Ti film, for example, is formed as a Ni diffusion suppression film 2322 on the entire upper surface of the Ni alloy film 2321 . An Au film 2323 is formed on the upper surface of the Ni diffusion suppression film 2322 . Each of these metal films is formed by, for example, a vacuum deposition method or a sputtering method, but other film formation methods may be used.

The thickness of the Ti film (Ni diffusion suppressing film 2322) is approximately 10 nm. This film thickness does not have to be in a final film-forming state. For example, it has been confirmed that the diffusion of Ni can be suppressed even when Ti molecules are formed like islands, and the diffusion of Ni can be suppressed when the thickness is about 8 to 50 nm.

Also, the Ti film (Ni diffusion suppression film 2322) may be oxidized on its surface to form an oxide film made of titanium oxide (TiO2) on the surface of the Ti film. For example, in this embodiment, an oxide film made of titanium oxide (TiO2) is formed only on the edge region of the Ti film (Ni diffusion suppression film 2322) where the Au film 2323 is not formed on the upper surface. According to this configuration, the alloy material formed together with the brazing material 24 and the like during hermetic sealing is suppressed from reaching other layers (Ti film 2311, Au film 2312, Ti film 2313, Ni alloy film 2321, etc.), A lid capable of stably hermetic sealing can be obtained.

The Au film 2323 is recessed from both ends of the Ni diffusion suppression film 222 in the width direction, and the width of the Au film 2323 is smaller than the width of the Ni diffusion suppression film 2322 . By arranging the metal brazing material on the Au film 2323 which is pulled down in this way, it is possible to prevent the alloy formed by the eutectic bonding of the metal brazing material from reaching the first group layer 231 from the side surface. As a result, peeling off of the lid and airtightness failure can be prevented.

The Ni alloy layer (NiTi film) 2321 in the second group layer 232 preferably has a film thickness in the range of 50 to 1000 nm. Also, the Ni alloy layer (NiTi film) 2321 can be replaced with another Ni alloy film.

In addition, although the Ti film is exemplified as the Ni diffusion suppression film 2322, it may be a metal film such as an Al film that can suppress the diffusion of Ni.

As described above, the LED element 3 is electrically and mechanically joined to the internal terminals of the substrate 1, and the metal layer 11 of the substrate and the base film 23 of the lid body are joined with the metal brazing material 24, thereby hermetically sealing the LED element. A stopped light emitting device can be obtained.

The structure of the present invention prevents the Ni material contained in the Ni alloy layer from diffusing into the Au film and reaching the surface of the Au film. As a result, in the conventional structure, deterioration in the wettability of the brazing metal used for hermetic sealing is suppressed, and the brazing metal is alloyed with the Au film, so that suitable hermetic sealing can be maintained.

The present invention may have a configuration in which the metal brazing material is previously bonded to the base film.
FIG. 4 shows a configuration in which brazing material is formed on the lid. The basic structure of the underlying film is the same as the structure described in FIG. A material alloy film 24 is formed. The metal brazing material is an Au—Sn alloy brazing material, which is formed to have the same width and thickness as the uppermost Au film 2323 in FIG. . The composition ratio of the Au—Sn alloy can be adjusted according to the temperature environment in which the light emitting device is used to raise or lower the melting point. FIG. 5 is a SEM photograph of a partial cross-section of the film thus formed.

According to the present invention, since Ni does not precipitate on the surface of the Au film 2323, metal brazing filler metals such as Au—Sn alloy brazing filler metals can be joined with good wettability.

[Method for manufacturing lid]
A manufacturing method for manufacturing lids at the wafer level will be described with an example of manufacturing a large number of lids at once. A rectangular plate-shaped crystal wafer is prepared. In addition, a multi-frame crystal wafer having the same outer shape as the crystal wafer and having through holes formed in a matrix is prepared. Each through-hole of this multi-piece quartz crystal wafer is formed using a photolithographic technique.

Thereafter, the Ti film 2311 is formed on the multi-frame crystal wafer side by physical vapor deposition such as vacuum deposition or sputtering. The thickness of the Ti film 2311 is, for example, about 250 nm. After that, an Au film 2312 is formed on the Ti film 2311 by a similar method. The thickness of the Au film 2312 is, for example, approximately 500 nm. After that, a Ti film 2313 is formed by a similar method. The thickness of the Ti film 2313 is, for example, about 50 nm. As described above, the first group layer in the underlying film is formed.

After the Ti film 2313 is formed, these crystal wafers are once taken out from the film forming apparatus, and the surface of the Ti film is exposed to the air. good. With such a configuration, only the second group layer 232 melts to form a eutectic bond with the sealing brazing material (bonding material), and the first group layer 231 does not form a eutectic bond.

The method of oxidizing the Ti film to form an oxide film on its surface is not limited to the method of exposing the surface of the Ti film to air. For example, a method of forming a Ti oxide film (TiO2) by introducing oxygen when forming a Ti film by sputtering, or a method of promoting oxidation of the formed Ti film surface by oxygen plasma are also possible.

After that, a Ni--Ti film with a thickness of about 300 nm is formed on the Ti film 2313 (or TiO2 film), which is the uppermost layer of the first group layer 231, by physical vapor deposition such as vacuum deposition or sputtering. A Ni alloy layer 2321 is thus formed. Then, a Ti film 2322 having a thickness of about 10 nm is formed on this Ni--Ti film by a physical vapor deposition method such as vacuum deposition or sputtering.

After that, an Au film 2323 is formed on the Ti film 2322 to a thickness of about 300 nm. Although this Au film 2323 is formed to be smaller in width than the underlying Ti film, the film width is reduced by photolithography. Note that the width of this Au film 2323 may be the same as the width of the underlying Ti film 2322 . Thus, the second group layer 232 in the underlying film 23 is formed.

After that, these two wafers are metal-to-metal bonded via an Au film. Specifically, in the crystal wafer, an Au film is formed on the joint surface with at least a large number of frame crystal wafers. Also, an Au film is formed on the entire surface of the multi-frame crystal wafer. These Au films are formed to have a film thickness of 100 to 400 nm on each main surface.

Next, while the surfaces of the Au films of both wafers are activated, the bonding surfaces of the two wafers are thermocompression-bonded. As a result, it is possible to obtain a crystal wafer on which a large number of lid bodies having recesses are formed.

As described above, it is possible to obtain a crystal wafer on which a large number of lid bodies each having an underlying layer are formed. Thereafter, the crystal wafer is individually cut by means such as dicing to obtain individual lids.

[Other embodiments]
In the above-described embodiment, the recess is formed in the lid as a structure for housing the LED element, and this recessed area is used as a cavity for housing the LED element. In this case also, the above-described structure is applied to the base film structure formed on the lid. The brazing material used for sealing may be formed on the lid side or may be formed on the package side.

As shown in FIG. 6, a light-emitting element 6 may be mounted in a package 4 having a concave cross section and hermetically sealed with a lid 5 made of crystal. Specifically, the package 4 is made of ceramics made of aluminum nitride, for example, and a metal film 41 is formed on the upper side wall around the package. A plurality of internal terminals 42, metal vias 43 leading the internal terminals 42 to the outer bottom surface of the package, and external terminals 44 connected to the metal vias and provided on the outer bottom surface of the package are provided on the inner bottom of the package. The light emitting element 6 is electrically and mechanically connected to the internal terminals by means of metal brazing material or metal bumps.

A base film 53 is formed in a circumferential shape on the outer periphery of the lid 5 . The base film 53 has a first group layer formed in contact with the crystal of the lid, and a second group layer laminated on the upper surface of the first group layer.

The structure of the first group layer is such that a Ti film, an Au film, and a Ti film are formed in contact with the crystal. Each of these metal films is formed by, for example, a vacuum deposition method or a sputtering method, but other film formation methods may be used.

The structure of the second group layer is formed on the first group layer, and the Ni alloy film, the Ni diffusion suppression film, and the Au film are formed in this order. An example of the Ni alloy film is a Ni--Ti (nickel-titanium) film. Also, as the Ni diffusion suppressing film, for example, a Ti film can be used. Each of these metal films is formed by, for example, a vacuum deposition method or a sputtering method, but other film formation methods may be used.

The metal layer 41 of the package 4 and the base film 53 of the lid 5 are joined with a metal brazing material to obtain a hermetically sealed light emitting device.

In the above embodiment, the lids 2 and 5 are disclosed to be quartz, but the lids 2 and 5 are not limited to this, and quartz glass may be used.

The embodiments disclosed this time are exemplifications in all respects and are not grounds for restrictive interpretation. Therefore, the technical scope of the present invention is not to be interpreted only by the above-described embodiments, but is defined based on the claims. In addition, all changes within the meaning and range of equivalence to the claims are included.

A Light emitting device 1 Substrate 11 Metal film 12 Internal terminal 14 External terminals 2 and 5 Lid 20 Lid main body
21 crystal plate 22 crystal frame plate 23 base film 24 brazing alloy films 3, 6 LED element 14 bonding layer 4 package

Claims (3)

A lid for a light-emitting device in which an LED is sealed in a package with a metallic brazing material,
including a translucent lid body and a base film formed on a sealing surface of the lid body,
The base film includes a first group layer formed directly on the lid body and a second group layer formed on the first group layer,
The first group layer has a structure including a Ti film with a thickness of 20 to 700 nm,
A lid of a light-emitting device, wherein the second group layer has a laminated structure including a Ni alloy film, a Ni diffusion suppression film, and an Au film, which are laminated in order from the side closer to the first group layer. 2. The lid of a light emitting device according to claim 1, wherein a metal brazing material is formed on the upper surface of said Au film. 2. The lid of a light emitting device according to claim 1, wherein an alloy film of said Au film and a metal brazing material is formed on said Ni diffusion suppression film of said second group layer.

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