JP7468182B2 - Film-attached substrate, submount, and optical device - Google Patents

Description

The present invention relates to a film-coated substrate, and a submount and an optical device using the film-coated substrate.

Conventionally, heat sinks with high heat dissipation properties have been used as submounts for optical elements such as LDs (Laser Diodes) and LEDs (Light Emitting Diodes). Such heat sinks efficiently dissipate heat generated when soldering optical elements and heat generated by the optical elements to the package. In addition, the following Patent Document 1 describes that materials such as CuW are used as materials for such heat sinks.

Japanese Patent Application Laid-Open No. 06-244358

In recent years, there has been a demand for thinner heat sinks to improve heat dissipation. However, when a heat sink such as that in Patent Document 1 is made thinner, it becomes more susceptible to the effects of heat during the firing process during manufacturing, and the heat sink may warp. If an optical element is mounted on a heat sink that has warped in this way, there is a problem that the heat cannot be dissipated sufficiently.

The object of the present invention is to provide a film-coated substrate capable of suppressing warping, as well as a submount and an optical device using the film-coated substrate.

The film-attached substrate according to the present invention is a film-attached substrate used in a submount for mounting an optical element, and is characterized by comprising a substrate having a first main surface and a second main surface facing each other, and a stress adjustment film disposed on at least one of the first main surface and the second main surface of the substrate.

In the present invention, it is preferable that the stress adjustment film is a sputtered film.

In the present invention, it is preferable that the stress adjustment film contains Ni.

In the present invention, it is preferable that the thickness of the stress adjustment film is 10 μm or less.

The present invention may further include a plating film provided between the substrate and the stress adjustment film.

In the present invention, it is preferable that the plating film contains Ni.

In the present invention, the semiconductor device may further include an adhesion film that is provided on the stress adjustment film and contains at least one of Au and Sn.

The submount according to the present invention is a submount for mounting an optical element, and is characterized by comprising a film-coated substrate constructed according to the present invention.

The submount of the present invention may be a heat sink.

The optical device according to the present invention is characterized by comprising a submount constructed according to the present invention, an optical element disposed on the stress adjustment film in the submount, and a package for housing the optical element.

The present invention provides a film-coated substrate capable of suppressing warping, as well as a submount and an optical device using the film-coated substrate.

1 is a schematic cross-sectional view showing a film-coated substrate according to a first embodiment of the present invention. 1A to 1C are schematic diagrams illustrating a method for measuring warpage in a film-coated substrate. FIG. 4 is a schematic cross-sectional view showing a film-coated substrate according to a second embodiment of the present invention. 1 is a schematic cross-sectional view showing an optical device according to an embodiment of the present invention.

The following describes preferred embodiments. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[Film-coated substrate]
First Embodiment
FIG. 1 is a schematic cross-sectional view showing a film-coated substrate according to a first embodiment of the present invention.

The film-coated substrate 1 is a substrate used for a submount of an optical element. In particular, the film-coated substrate 1 is preferably a substrate used for a submount having a heat sink function. The film-coated substrate 1 may be a submount for an element other than an optical element, or may be used for purposes other than a submount, and its use is not particularly limited.

The film-coated substrate 1 comprises a substrate 2, a first plating film 3, a stress adjustment film 4, a first adhesive film 5, a second plating film 8, and a second adhesive film 9. The substrate 2 has a first main surface 2a and a second main surface 2b that face each other.

A first plating film 3 is provided on the first main surface 2a of the substrate 2. A stress adjustment film 4 is provided on the first plating film 3. A first adhesive film 5 is provided on the stress adjustment film 4. Furthermore, a second plating film 8 is provided on the second main surface 2b of the substrate 2. A second adhesive film 9 is provided on the second plating film 8.

In this embodiment, the substrate 2 has a substantially rectangular plate shape. However, the substrate 2 may have a shape such as a substantially circular plate shape, and the shape is not particularly limited.

The material of the substrate 2 is not particularly limited, but it is preferable that the substrate 2 is made of a material with high heat dissipation properties. Specific examples of the material of the substrate 2 include CuW, CuMo, AlN, Cu-Diamond, Mo, Al-SiC, and Mg-SiC. One of these materials may be used alone, or multiple types may be used in combination.

The thickness of the substrate 2 is not particularly limited, but is preferably 0.1 mm or more, more preferably 0.2 mm or more, and preferably 1.0 mm or less, and more preferably 0.5 mm or less. When the thickness of the substrate 2 is equal to or greater than the lower limit, the heat dissipation properties can be further improved. When the thickness of the substrate 2 is equal to or less than the upper limit, the device in which it is used can be made even thinner.

The first plating film 3 and the second plating film 8 are used to improve adhesion to the substrate 2.

The material of the first plating film 3 and the second plating film 8 is not particularly limited, but in this embodiment, it is Ni. However, the material of the first plating film 3 and the second plating film 8 is not limited to Ni, and may be Cr, Ti, W, TiW, Mo, Ni-Cr, etc. These materials may be used alone or in combination. Note that the first plating film 3 and the second plating film 8 desirably contain 95% or more of the above-mentioned materials. However, the first plating film 3 and the second plating film 8 may contain impurities and additives as long as they do not impair the effects of the present invention.

The thickness of each of the first plating film 3 and the second plating film 8 is not particularly limited, but can be, for example, 0.5 μm or more and 5 μm or less.

The stress adjustment film 4 is a film for adjusting the stress applied to the entire film-coated substrate 1 by its film stress and suppressing the warping of the film-coated substrate 1. Specifically, the stress adjustment film 4 is a film that adjusts the warping of the film-coated substrate 1 as a whole by causing warping in the opposite direction to the direction in which warping occurs when the stress adjustment film 4 is not provided. Therefore, the stress adjustment film 4 may be provided on the first main surface 2a side as in this embodiment, or on the second main surface 2b side, taking into account the direction in which warping occurs when the stress adjustment film 4 is not provided. It may also be provided on both the first main surface 2a and the second main surface 2b. Even when provided on the second main surface 2b side, it may be provided on the second main surface 2b, or it may be provided between the second plating film 8 and the second adhesive film 9.

The degree of warping in the stress adjustment film 4 can be adjusted by the film stress. Therefore, the degree of warping in the stress adjustment film 4 can be adjusted, for example, by the thickness of the stress adjustment film 4. This will be explained using the following experimental example.

In the experimental example, as shown in FIG. 2(a), first, a Cr plating film (thickness 100 nm) was formed as the first plating film 13 on a substrate 12 (manufactured by Nippon Electric Glass Co., Ltd., BDA, thickness: 0.5 mm). Next, a Ni film was formed as the stress adjustment film 14 on the first plating film 13 by a sputtering method. The Ni films produced had thicknesses of 300 nm, 1000 nm, and 1500 nm, respectively. In this way, three types of film-coated substrates 11 were produced.

The dimensions of the film-coated substrate 11 were length a: 25 mm and width b: 25 mm, as shown in Figures 2(a) and 2(b). The first plating film 13 and the stress adjustment film 14 were not deposited in the portions of the film-coated substrate 11 at a length c: 0.2 mm from the first end 11b and the second end 11c in the longitudinal direction.

The amount of warping of the film-coated substrate 11 thus obtained was measured. Specifically, the film-coated substrate 11 was placed on the stage 10 shown in FIG. 2(c) and left at 25° C. for 1 hour, after which the amount of warping L was measured. The film-coated substrate 11 was placed with the film surface 11a facing upward. The difference in height between the first end 11b and the second end 11c and the center of the length direction of the non-film surface 11d of the film-coated substrate 11 was taken as the amount of warping L. The amount of warping L was taken as the average of the amounts of warping L of the two ends 11b and 11c. The non-film surface 11d is the surface opposite the film surface 11a.

The results are shown in Table 1 below.

As shown in Table 1, the greater the thickness of the Ni film used as the stress adjustment film 14, the greater the absolute value of the amount of warping.

Therefore, in this embodiment, by adjusting the surface on which the stress adjustment film 4 is provided and the amount of warping in accordance with the design of components other than the stress adjustment film 4 that constitutes the film-coated substrate 1, it is possible to adjust the amount of warping of the entire film-coated substrate 1 to be reduced. Therefore, warping can be suppressed in the film-coated substrate 1.

The material of the stress adjustment film 4 is not particularly limited, and Ni, Ti, W, Mo, TiW, Ni-Cr, Pt, Pd, Au, etc. can be used. These materials may be used alone or in combination. From the viewpoint of making it easier to adjust the amount of warping of the entire film-coated substrate 1, it is preferable that the stress adjustment film 4 is a film whose main component is Ni. The material of the stress adjustment film 4 may also be an alloy of Ni and another metal. The above-mentioned main component means that the component is contained in the stress adjustment film 4 at 95% or more. However, the stress adjustment film 4 may contain impurities and additives as long as they do not impair the effects of the present invention.

The thickness of the stress adjustment film 4 is not particularly limited and can be appropriately designed according to the required amount of warping. The thickness of the stress adjustment film 4 can be, for example, 0.05 μm or more and 10 μm or less. From the viewpoint of thinning and reducing manufacturing costs, the thickness of the stress adjustment film 4 is preferably 1.0 μm or less, and more preferably 0.5 μm or less.

The method for forming the stress adjustment film 4 is not particularly limited, but it is preferable to form it by a sputtering method. Therefore, it is preferable that the stress adjustment film 4 is a sputtered film. In this case, a denser film is formed, making it easier to adjust the amount of warping of the entire film-coated substrate 1. The thickness of the stress adjustment film 4 can also be made thinner.

The stress adjustment film 4 is preferably provided over the entire main surface of the substrate 2 in a plan view, but may be provided over only a portion of the main surface of the substrate 2. The stress adjustment film 4 may also be provided on the side surface of the substrate 2 in addition to at least a portion of the main surface of the substrate 2.

The first adhesive film 5 has a first layer 6 and a second layer 7. Specifically, the first layer 6 is provided on the stress adjustment film 4. Furthermore, the second layer 7 is provided on the first layer 6.

The first layer 6 preferably functions as a diffusion prevention layer. For example, it is preferably a layer for preventing the components of the second layer 7 from diffusing into the first plating film 3 or the stress adjustment film 4. This can improve the adhesion of the first adhesive film 5 to the optical element or the like. However, the first layer 6 does not necessarily have to be provided in the first adhesive film 5.

The material of the first layer 6 is not particularly limited, but in this embodiment, it is Pt. In this case, it is possible to further suppress the components of the second layer 7 from diffusing into the first plating film 3 and the stress adjustment film 4. However, the material of the first layer 6 is not limited to Pt, and may be Au, Pd, or the like. These materials may be used alone or in combination. Note that the first layer 6 preferably contains 95% or more of the above-mentioned materials. However, the first layer 6 may contain impurities or additives to the extent that they do not impair adhesion.

The thickness of the first layer 6 is not particularly limited, but can be, for example, 0.05 μm or more and 1.0 μm or less.

The method for forming the first layer 6 is not particularly limited, and it can be formed by, for example, a sputtering method or a vapor deposition method.

The second layer 7 is, for example, a layer that is in direct contact with an optical element, etc.

The material of the second layer 7 is not particularly limited, but examples thereof include Au, Sn, and the like. In particular, the material of the second layer 7 is preferably at least one of Au and Sn. In this case, by melting the second layer 7, it is possible to more easily bond it to an optical element, etc., and it is also possible to bond it at a lower temperature. The second layer 7 may be made of an alloy of Au and Sn. It may also be made of an alloy of Au and Ge, an alloy of Au and Si, or an alloy of Sn, Ag, and Cu. It is desirable that the second layer 7 contains 95% or more of the above-mentioned materials. However, the second layer 7 may contain impurities or additives to the extent that they do not impair adhesion.

The second layer 7 may be a laminate in which Au layers and Sn layers are laminated. In this case, the Au layers and Sn layers may be laminated alternately. The number of layers in the laminate may be, for example, 3 layers or more and 200 layers or less. An alloy layer of Au and Sn may be formed between the Au layer and the Sn layer. In this case, by melting the second layer 7, it is possible to bond it to an optical element, etc. more easily and at a lower temperature.

The thickness of the second layer 7 is not particularly limited, but can be, for example, 1 μm or more and 30 μm or less.

The method for forming the second layer 7 is not particularly limited, and it can be formed by, for example, a sputtering method or a vapor deposition method. The second layer 7 may also be a plating film.

The second adhesive film 9 is, for example, an adhesive film that is adhered to a package or the like. The second adhesive film 9 may be the same as the first adhesive film 5 described above. Therefore, the second adhesive film 9 may be composed of the first layer 6 and the second layer 7 described above, or may be composed of only the second layer 7.

As described below, an Au film may be provided on the inner surface of the package. In this case, it is preferable that the second adhesive film 9 contains Au. In addition, in the case of a laminate in which an Au layer and an Sn layer are laminated, it is preferable that the Au layer is the outermost layer. This can further increase the bonding strength with the package.

Second Embodiment
FIG. 3 is a schematic cross-sectional view showing a film-coated substrate according to a second embodiment of the present invention.

As shown in FIG. 3, the film-coated substrate 21 does not have a first plating film 3. Also, no film is provided on the second main surface 2b of the substrate 2. The other points are the same as those of the first embodiment.

As in the second embodiment, the first plating film 3 does not have to be provided between the substrate 2 and the stress adjustment film 4, and no film needs to be provided on the second main surface 2b of the substrate 2. It is sufficient that the stress adjustment film 4 is disposed on one of the first main surface 2a and the second main surface 2b of the substrate 2.

Also in the second embodiment, a stress adjustment film 4 is provided on the first main surface 2a of the substrate 2, so that the amount of warping applied to the entire film-coated substrate 21 can be adjusted to reduce. Therefore, warping can be suppressed even in the film-coated substrate 21.

[Optical Devices]
Fig. 4 is a schematic cross-sectional view showing an optical device according to one embodiment of the present invention. As shown in Fig. 4, an optical device 31 includes the film-coated substrate 1 of the first embodiment, an optical element 37, a prism 38, and a package 32. The film-coated substrate 1, the optical element 37, and the prism 38 are housed in the package 32.

More specifically, the package 32 is a container-shaped member having a bottom 33 and a side wall 34 disposed on the bottom 33. The package 32 can be made of, for example, a ceramic material. Examples of the ceramic material that can be used include alumina and aluminum nitride. Among these, aluminum nitride is preferable from the viewpoint of further improving heat dissipation.

The bottom 33 has a mounting surface 33a. The sidewall 34 has an inner surface 34a. A metal film 36 is provided on the mounting surface 33a of the bottom 33 and the inner surface 34a of the sidewall 34.

In this embodiment, the optical element 37 and the prism 38 are arranged on the metal film 36 on the mounting surface 33a. More specifically, the film-coated substrate 1 is provided on the metal film 36, and the optical element 37 is arranged thereon. At this time, the second main surface 2b side of the film-coated substrate 1 is bonded to the metal film 36. Meanwhile, the first main surface 2a side of the film-coated substrate 1 is bonded to the optical element 37. The prism 38 is also bonded to the metal film 36. The prism 38 can be bonded to the metal film 36 by, for example, soldering, without any particular limitation.

The package 32 does not necessarily have to have the metal film 36. However, it is preferable that the package 32 has the metal film 36 as in this embodiment. This configuration is particularly effective when the difference in thermal expansion coefficient between the film-coated substrate 1 or the prism 38 and the package 32 is relatively large.

The metal film 36 is preferably an Au film. In this case, since the metal film 36 is less susceptible to oxidation, the bonding strength between the film-coated substrate 1 or prism 38 and the package 32 can be further increased when manufacturing the optical device 31.

In this embodiment, the metal film 36 is provided on the entire mounting surface 33a of the bottom 33 and the entire inner surface 34a of the side wall 34. However, it is sufficient that the metal film 36 is provided at least on the portion where the film-coated substrate 1 and the prism 38 are arranged.

A lid 35 is provided on the side wall 34 of the package 32 to seal the optical element 37 and the prism 38. The lid 35 is not particularly limited, but in this embodiment is a glass lid.

The method for joining the lid 35 and the side wall 34 is not particularly limited, but they can be joined, for example, by soldering with AuSn, SnAg, SnAgCu, or the like. In this case, since no gas is generated after joining, impurities are less likely to adhere to the reflective film 39 of the prism 38, and deterioration of the reflection characteristics is less likely to occur.

In this embodiment, the optical element 37 is a light source that emits light to the prism 38. The light source is not particularly limited, but may be, for example, an LD or an LED. As shown in FIG. 4, light A emitted from the optical element 37 is reflected by the prism 38, passes through the cover 35, and is emitted outside the optical device 31. The optical element 37 may be a light receiving element that receives light from the prism 38.

In the optical device 31, the film-coated substrate 1 is used as a submount for the optical element 37. The film-coated substrate 1 also functions as a heat sink. Therefore, heat generated in the optical element 37 can be efficiently dissipated to the package 32 side through the film-coated substrate 1. This can be explained as follows.

Heat sinks often undergo a firing process during their manufacture. Therefore, when heat sinks are made thinner in order to miniaturize devices, warping can occur during the firing process. If the heat sink is mounted in a package in this state, gaps will form, resulting in a problem of reduced heat dissipation to the package.

In contrast, in the optical device 31 of this embodiment, the film-coated substrate 1 is used as a heat sink, so the above-mentioned warping can be suppressed. Therefore, even when the film-coated substrate 1 is mounted on the package 32, gaps are unlikely to occur and the heat dissipation to the package 32 is unlikely to decrease. Therefore, in the optical device 31, it is possible to efficiently dissipate heat generated in the optical element 37 to the package 32 side through the film-coated substrate 1. In addition, the positional deviation in the height direction of the optical element 37, which is the light source, can also be suppressed.

DESCRIPTION OF SYMBOLS 1, 11, 21...film-coated substrate 2, 12...substrate 2a...first main surface 2b...second main surface 3, 13...first plating film 4, 14...stress adjustment film 5...first adhesion film 6...first layer 7...second layer 8...second plating film 9...second adhesion film 10...stage 11a...film surface 11b...first end 11c...second end 11d...non-film surface 31...optical device 32...package 33...bottom 33a...mounting surface 34...side wall 34a...inner surface 35...lid 36...metal film 37...optical element 38...prism 39...reflective film

Claims (10)

A film-attached substrate used in a submount for mounting an optical element, comprising:
a substrate having opposing first and second major surfaces;
a stress adjustment film that is a sputtered film disposed on at least one of the first main surface and the second main surface of the substrate;
a plating film provided between the substrate and the stress adjustment film;
The film-attached substrate comprises: The film-coated substrate according to claim 1 , wherein the stress adjustment film contains Ni. The film-coated substrate according to claim 1 , wherein the stress adjustment film has a thickness of 10 μm or less. The film-coated substrate according to any one of claims 1 to 3 , wherein the plating film contains Ni. The film-coated substrate according to claim 1 , further comprising an adhesion film provided on the stress adjustment film and containing at least one of Au and Sn. The film-coated substrate according to any one of claims 1 to 4, further comprising an adhesion film having a first layer provided on the stress adjustment film and containing Pt or Pd, and a second layer provided on the first layer and containing at least one of Au and Sn. The film-coated substrate according to claim 6 , wherein the first layer comprises Pt. A submount for mounting an optical element,
A submount comprising the film-coated substrate according to any one of claims 1 to 7. The submount of claim 8, which is a heat sink. A submount according to claim 8 or 9;
an optical element disposed on the stress adjustment film of the submount;
a package for housing the optical element;
An optical device comprising:

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