Thin film for semiconductor laser bonding and method for producing same

Abstract

This thin film for semiconductor laser bonding has a solder layer that contains 7.2-14.0 wt% Au, 0.1-4.4 wt% Ag, and 0.1-10.1 wt% Cu, with the remainder excluding unavoidable impurities being Sn.

Description

Thin film for semiconductor laser bonding and its manufacturing method

[0001] The present disclosure relates to a thin film for semiconductor laser bonding and a method for manufacturing the same.

[0002] Various techniques are known for improving the performance of thin solder films used when mounting light-emitting elements such as laser diodes on submount substrates. For example, Non-Patent Document 1 ("Development of a Low-Melting-Point Sn-Based Thin-Film Solder for Fluxless Bonding," Sakamoto et al., Journal of the Japan Institute of Electronics Packaging, Vol. 14, No. 3, 2011, pp. 179-188) describes a thin solder film that does not use flux, which may degrade the performance of light-emitting elements. The thin solder film described in Non-Patent Document 1 has an Ag layer disposed between the Sn layer and the Au layer, which prevents the Au contained in the Au layer from diffusing into the Sn layer and suppresses poor wetting and the occurrence of Kirkendall voids due to surface oxidation.

[0003] Furthermore, Patent Document 1 (JP 2007-288001 A) describes a solder thin film in which an Ag layer and a Cu layer are disposed between three Sn layers, and the Ag content is 5.5 wt % or less, the Cu content is 1.5 wt % or less, and the Sn content is 93.0 wt % or more. The solder thin film described in Patent Document 1 is bonded to an Au electrode to form a SnAgCuAu alloy, which achieves a melting point of 250°C or less.

[0004] The solder thin film described in Non-Patent Document 1 can suppress poor wetting and the occurrence of voids, and the solder thin film described in Patent Document 1 can achieve a melting point of 250°C or less, but there is a demand for even higher performance and lower melting points for thin films for semiconductor laser bonding.

[0005] The present disclosure solves these problems and provides a thin film for semiconductor laser bonding that can achieve high performance and a low melting point.

[0006] The thin film for semiconductor laser bonding according to the present disclosure has a solder layer containing 7.2 wt % or more and 14.0 wt % or less of Au, 0.1 wt % or more and 4.4 wt % or less of Ag, 0.1 wt % or more and 10.1 wt % or less of Cu, and the remainder, excluding unavoidable impurities, being made of Sn.

[0007] Furthermore, in the semiconductor laser bonding thin film according to the present disclosure, Cu preferably forms a Cu layer that is disposed over the entire surface of one side of the solder layer.

[0008] Furthermore, the semiconductor laser bonding thin film according to the present disclosure preferably contains 7.2 wt % to 14.0 wt % of Au.

[0009] Furthermore, the semiconductor laser bonding thin film according to the present disclosure preferably contains 0.1 wt % to 4.4 wt % of Ag and 0.1 wt % to 6.7 wt % of Cu.

[0010] Furthermore, the semiconductor laser bonding thin film according to the present disclosure preferably contains 0.1 wt % to 10.1 wt % of Cu and 0.1 wt % to 3.1 wt % of Ag.

[0011] Furthermore, the semiconductor laser bonding thin film according to the present disclosure preferably further comprises a diffusion prevention layer that contains Pt and is disposed so as to face the surface of the solder layer on which Cu is disposed.

[0012] Furthermore, in the semiconductor laser bonding thin film according to the present disclosure, the diffusion prevention layer preferably has a Cr layer containing Cr and a Pt layer containing Pt and disposed between the Cr layer and the solder layer.

[0013] Furthermore, the present disclosure provides a method for manufacturing a thin film for semiconductor laser bonding, which has a solder layer containing 7.2 wt % to 14.0 wt % Au, 0.1 wt % to 4.4 wt % Ag, and 0.1 wt % to 10.1 wt % Cu, with the remainder being Sn except for unavoidable impurities, and includes processes of forming a Cu layer, forming an Ag layer on the Cu layer, forming a Sn layer on the Ag layer, and forming an Au layer on the Sn layer.

[0014] The semiconductor laser bonding thin film according to the present disclosure can achieve high performance and a low melting point.

[0015] 1A is a diagram showing a semiconductor laser bonding thin film according to a first embodiment; FIG. 1B is a diagram showing a reaction state between Cu contained in a Cu layer and Sn contained in a Sn layer when the semiconductor laser bonding thin film shown in FIG. 1 is heated; and FIG. 1B is a cross-sectional photograph of the semiconductor laser bonding thin film shown in FIG. 1 before and after melting. FIG. 1C is a Sn—Ag—Cu phase diagram; and FIG. 1D is a Au—Sn phase diagram. FIG. 1A is a flowchart showing a method for manufacturing the semiconductor laser bonding thin film shown in FIG. 1; and FIG. 1D is a flowchart showing more detailed processing of step S104 shown in FIG. 1A. FIG. 1D is a diagram showing a semiconductor laser bonding thin film according to a second embodiment; FIG. 1E is a diagram showing a semiconductor laser bonding thin film according to a third embodiment; and FIG. 1F is a diagram showing a semiconductor laser bonding thin film according to a fourth embodiment. (a) is a surface image of sample 1 during RTA treatment, (b) is an SEM image of the cross section of sample 1 after RTA treatment, (c) is a surface image of sample 2 during RTA treatment, (d) is an SEM image of the cross section of sample 2 after RTA treatment, (e) is a surface image of sample 3 during RTA treatment, (f) is an SEM image of the cross section of sample 3 after RTA treatment, (g) is a surface image of sample 4 during RTA treatment, and (h) is an SEM image of the cross section of sample 4 after RTA treatment. (a) is a surface image of Example 1 during RTA treatment, (b) is an SEM image of a cross section of Example 1 after RTA treatment, (c) is a surface image of Example 2 during RTA treatment, (d) is an SEM image of a cross section of Example 2 after RTA treatment, (e) is a surface image of Example 3 during RTA treatment, (f) is an SEM image of a cross section of Example 3 after RTA treatment, (g) is a surface image of Example 4 during RTA treatment, (h) is an SEM image of a cross section of Example 4 after RTA treatment, (i) is a surface image of Example 5 during RTA treatment, and (j) is an SEM image of a cross section of Example 5 after RTA treatment.(a) is a surface image of Example 6 during RTA treatment, (b) is a surface image of Example 7 during RTA treatment, (c) is a surface image of Example 8 during RTA treatment, (d) is a surface image of Example 9 during RTA treatment, (e) is a surface image of Comparative Example 1 during RTA treatment, (f) is a surface image of Comparative Example 2 during RTA treatment, (g) is a surface image of Comparative Example 3 during RTA treatment, (h) is a surface image of Comparative Example 4 during RTA treatment, (i) is a surface image of Comparative Example 5 during RTA treatment, and (j) is a surface image of Comparative Example 6 during RTA treatment.

[0016] Hereinafter, a thin film for semiconductor laser bonding and a manufacturing method thereof according to an embodiment will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to the embodiments, but extends to the inventions set forth in the claims and their equivalents.

[0017] (Configuration and Function of Semiconductor Laser Bonding Thin Film According to First Embodiment) FIG. 1 is a diagram showing a semiconductor laser bonding thin film according to the first embodiment.

[0018] The semiconductor laser bonding thin film 1 is mounted on a submount substrate 10, and has an electrode layer 20, a diffusion prevention layer 30, and a solder layer 40. A light emitting element such as a laser diode is mounted on the solder layer 40 of the semiconductor laser bonding thin film 1.

[0019] The submount substrate 10 is an aluminum nitride (AlN) substrate having a rectangular planar shape and a thermal expansion coefficient smaller than that of metal, and has a semiconductor laser bonding thin film 1 disposed on its surface. The submount substrate 10 may also be formed of ceramics other than AlN, such as silicon carbide (SiC). The electrode layer 20 of the submount substrate 10 has a wiring pattern, and is connected to a light-emitting element mounted on the solder layer 40 via a bonding wire (not shown). Furthermore, the submount substrate 10 is mounted on a metal stem such as a CAN package, and is connected via a bonding wire to the wiring pattern of the electrode layer and to leads or the like disposed on the metal stem.

[0020] The electrode layer 20 includes a titanium (Ti) layer 21, an electrode platinum (Pt) layer 22 laminated on the Ti layer 21, and an electrode gold (Au) layer 23 laminated on the electrode Pt layer 22. The electrode layer 20 has a wiring pattern and is connected to one electrode of the light-emitting element mounted on the solder layer 40 via a bonding wire (not shown). The Ti layer 21 is formed of Ti, the electrode Pt layer 22 is formed of Pt, and the electrode Au layer 23 is formed of Au. The Ti layer 21 and the electrode Pt layer 22 are diffusion prevention layers that prevent the diffusion of Au contained in the electrode Au layer 23, and the electrode Au layer 23 is a pad layer connected to the bonding wire. The Ti layer 21 also functions as an adhesion layer with the submount substrate 10.

[0021] The diffusion prevention layer 30 is formed of Pt and is laminated on the electrode layer 20. The diffusion prevention layer 30 prevents tin (Sn) and Au contained in the solder layer 40 laminated on the diffusion prevention layer 30 from diffusing into the electrode layer 20. The thickness of the diffusion prevention layer 30 is preferably 0.01 μm or more and 0.6 μm or less, and more preferably 0.1 μm or more and 0.3 μm or less. If the thickness of the diffusion prevention layer 30 is thicker than 0.6 μm, burrs may occur when forming a wiring pattern by a lift-off method or the like. Furthermore, if the thickness of the diffusion prevention layer 30 is thinner than 0.01 μm, the diffusion prevention effect cannot be sufficiently obtained.

[0022] The solder layer 40 has a copper (Cu) layer 41, a silver (Ag) layer 42, a Sn layer 43, and an Au layer 44, and melts when heated to a predetermined temperature, thereby mounting the light-emitting element to the submount substrate 10 via the electrode layer 20 and the diffusion prevention layer 30.

[0023] The Cu layer 41 is made of Cu and is disposed over the entire surface of one side of the solder layer 40 so as to face one side of the diffusion prevention layer 30. The Cu layer 41 is a layer for generating an appropriate intermetallic compound between the diffusion prevention layer 30 and the solder layer 40 when the solder layer 40 is heated. By disposing the Cu layer 41 over the entire surface of one side of the solder layer 40, the rate at which Cu is mixed into the Sn layer 43 can be suppressed, and the rise in the melting point of the solder layer 40 can be made gradual.

[0024] The Cu content of the solder layer 40 is preferably 0.1 wt % or more and 10.1 wt % or less. When the Cu content is less than 0.1 wt %, the reaction between the diffusion barrier layer 23 and the Sn layer 43 occurs early when the solder layer 40 is heated, significantly reducing the melting duration, which is the time during which the solder layer 40 remains molten. When the Cu content of the solder layer 40 is 0.1 wt % or more and 10.1 wt % or less, a large number of voids do not occur, enabling high reliability. When the Cu content is greater than 10.1 wt %, a large number of voids may occur at the interface between the diffusion barrier layer 30 and the solder layer 40 when the solder layer 40 is heated.

[0025] 2(a) is a diagram showing the reaction state between Cu contained in the Cu layer 41 and Sn contained in the Sn layer 43 when the semiconductor laser bonding thin film 1 is heated, and FIG. 2(b) is a cross-sectional photograph of the semiconductor laser bonding thin film 1 before and after melting. In the solder layer 40, an Ag layer 42 is disposed between the Cu layer 41 and the Sn layer 43, but the Ag content of the Ag layer 42 in the solder layer 40 is small, and even in the presence of the Ag layer 42, a reaction occurs between the Cu contained in the Cu layer 41 and the Sn contained in the Sn layer 43, and the effect of this reaction is significant. Therefore, the reaction state will be described here without the Ag layer 42.

[0026] As the semiconductor laser bonding thin film 1 is heated, Cu and Sn react to generate Cu6Sn5, strengthening the bond between the Cu layer 41 and the Sn layer 43 and ultimately enhancing the adhesion between the diffusion barrier layer 30 and the solder layer 40. After the formation of Cu6Sn5, Cu and Sn further react to generate Cu3Sn instead of Cu6Sn5. While Cu6Sn5 is being generated, the diffusion amounts of Cu and Sn are approximately the same. However, when Cu3Sn is generated instead, the diffusion amount of Cu is greater than the diffusion amount of Sn, increasing the risk of voids occurring within the Cu layer 41 and Cu3Sn. The thickness of the Cu layer 41 and the Cu content in the solder layer 40 are adjusted so that Cu6Sn5 is generated and Cu3Sn is not generated.

[0027] The Ag layer 42 is formed of Ag and is disposed so as to cover the entire upper surface of the Cu layer 41. By including Ag in the solder layer 40, deterioration of the solder layer 40 due to heat cycle tests and the like is mitigated, improving reliability. The Ag content in the solder layer 40 is preferably 0.1 wt% or more and 4.4 wt% or less. When the Ag content is less than 0.1 wt%, the effect of improving reliability due to the inclusion of Ag is substantially absent. When the Ag content is 0.1 wt% or more and 4.4 wt% or less, a lower melting point is possible. Figure 3 is a Sn-Ag-Cu phase diagram. The melting point decrease due to the inclusion of a small amount of Ag can be qualitatively explained using the Sn-Ag-Cu phase diagram. In Figure 3, the horizontal axis represents the Cu content in the Sn-Ag-Cu alloy, the vertical axis represents the Ag content in the Sn-Ag-Cu alloy, and the numbers in the diagram represent melting points. It can be seen that the melting point increases as the Ag content increases above 4.5 wt %. In the solder layer 40, which contains Au from the Au layer 44 in addition to Sn, Ag, and Cu and is also affected by the inclusion of Pt from the diffusion prevention layer 30, when the Ag content is greater than 4.5 wt %, the melting point of the solder layer 40 exceeds 210° C., making it difficult to lower the melting point.

[0028] The Sn layer 43 is formed of Sn and is disposed so as to cover the entire upper surface of the Ag layer 42. Sn is the primary component of the solder layer 40, and the Sn content in the solder layer 40 is preferably 83.1 wt % or more and 92.0 wt % or less, and more preferably 83.1 wt % or more and 88.7 wt % or less. The solder layer 40 is a low-melting-point solder primarily composed of Sn. AuSn (8:2 wt %) thin-film solder, commonly used for mounting laser diodes, has high reliability. However, AuSn (8:2 wt %) thin-film solder has a high melting point of 278°C, and thermal stress generated during mounting of the laser diode may degrade the laser diode's light-emitting characteristics, such as blue shift in the emission wavelength and reduced optical output due to active layer migration. By using Sn as the primary component, the solder layer 40 can achieve a low melting point, increased ductility, and reduced stress.

[0029] The Au layer 44 is formed of Au and is disposed so as to cover the entire upper surface of the Sn layer 43. The inclusion of a small amount of Au in the solder layer 40 allows the solder layer 40 to have a lower melting point. FIG. 4 is an Au-Sn phase diagram. The lowering of the melting point due to the inclusion of a small amount of Au can be qualitatively explained using the Au-Sn phase diagram. From the Au-Sn phase diagram, it can be seen that in an Au-Sn alloy, when the Au content is less than 14.0 wt %, the melting point is approximately 240°C or less. Therefore, the Au content in the solder layer 40 is preferably 0.1 wt % or more and 14.0 wt % or less. When the Au content is less than 0.1 wt %, the effect of adding Au to lower the melting point is not substantially apparent. In the solder layer 40, which contains Sn, Ag, and Cu in addition to Au and is also affected by the Pt contamination of the diffusion prevention layer 30, when the Au content is 0.1 wt % or more and 14.0 wt % or less, the melting point of the semiconductor laser bonding thin film 1 becomes 210° C. or less, making it possible to lower the melting point. When the Au content is more than 14.0 wt %, the melting point of the semiconductor laser bonding thin film 1 becomes higher than 210° C., making it difficult to lower the melting point.

[0030] The remainder of the semiconductor laser bonding thin film 1 other than the above-mentioned component composition is made up of impurities. The impurities are components that are mixed in due to various factors in the manufacturing process when the semiconductor laser bonding thin film 1 is industrially manufactured, and are contained in an amount that does not affect the characteristics of the semiconductor laser bonding thin film 1.

[0031] The solder layer 40 has favorable properties and is usable when it contains 7.2 to 14.0 wt. % Au, 0.1 to 4.4 wt. % Ag, 0.1 to 10.1 wt. % Cu, and the remainder, excluding unavoidable impurities, is Sn. By having this composition, the solder layer 40 can have favorable properties, such as a melting point of 210°C or less, no significant voids, and a melting duration of 5 seconds or more. Optical elements such as semiconductor lasers are mounted within a few seconds of solder melting, so a melting duration of 5 seconds or more is desirable.

[0032] It is more preferable that the Cu content in the solder layer 40 is 0.1 wt% or more and less than 10.1 wt% and the Ag content in the solder layer 40 is 0.1 wt% or more and 3.1 wt% or less. When the Cu content in the solder layer 40 is 0.1 wt% or more and less than 10.1 wt% and the Ag content in the solder layer 40 is 0.1 wt% or more and 3.1 wt% or less, there is no risk of voids occurring, a lower melting point is possible, and further higher reliability is possible. The melting point decrease due to the small amount of Cu content can be qualitatively explained by the Sn—Ag—Cu phase diagram shown in Figure 3. It can be seen that when a small amount of Cu is contained in an Sn—Ag—Cu alloy, the melting point decreases as the Cu content decreases.

[0033] It is more preferable that the Ag content is 0.1 wt % or more and 3.1 wt % or less, and the Cu content is 0.1 wt % or more and 6.7 wt % or less in the solder layer 40. When the Ag content is 0.1 wt % or more and 3.1 wt % or less, and the Cu content is 0.1 wt % or more and 6.7 wt % or less, a low melting point is possible, and voids are not generated, resulting in high reliability.

[0034] It is more preferable that the Au content in the solder layer 40 is 7.3% by weight or more and 14.0% by weight or less. When the Au content is 7.3% by weight or more and 14.0% by weight or less, the melting point of the semiconductor laser bonding thin film 1 becomes 205° C., which can be further lowered.

[0035] The Au content in the solder layer 40 is preferably 7.3 wt % or more and 8.0 wt % or less, and more preferably 7.3 wt % or more and 7.7 wt % or less. When the Au content is 7.3 wt % or more and 7.7 wt % or less, the melting duration is 15 seconds or more.

[0036] It is more preferable that the Ag content is 0.1 wt % or more and 4.4 wt % or less, and the Cu content is 0.1 wt % or more and 6.7 wt % or less in the solder layer 40. When the Ag content is 0.1 wt % or more and 4.4 wt % or less, and the Cu content is 0.1 wt % or more and 6.7 wt % or less, the melting point of the solder layer 40 becomes 205°C, making it possible to lower the melting point.

[0037] More preferably, the solder layer 40 contains 7.3 to 7.7 wt % Au, 0.1 to 3.1 wt % Ag, 0.5 to 6.7 wt % Cu, and the remainder, excluding unavoidable impurities, Sn. By having this composition, the solder layer 40 can have even more preferable properties, such as a melting point of 205°C, no voids, and a melting duration of 15 seconds or more.

[0038] In addition, since the Ag contained in the Ag layer 42 and the Au contained in the Au layer 44 diffuse into the Sn layer 43 even at room temperature, the Ag layer 42, the Sn layer 43 and the Au layer 44 may be an integrated layer.

[0039] FIG. 5A is a flowchart showing a method for manufacturing the semiconductor laser bonding thin film 1.

[0040] First, in a substrate preparation step, an aggregate substrate is placed inside a vacuum chamber of the manufacturing apparatus (S101). The aggregate substrate is a flat plate-shaped member made of AlN that forms the submount substrate 10. After the aggregate substrate is placed inside the vacuum chamber, the inside of the vacuum chamber is evacuated.

[0041] Next, in the electrode layer formation step, the electrode layer 20 is formed (S102). The electrode layer 20 is formed by sequentially depositing a Ti layer 21, an electrode Pt layer 22, and an electrode Au layer 23 by a vacuum deposition process such as sputtering.

[0042] Next, in the diffusion prevention layer forming step, the diffusion prevention layer 30 is formed (S103). Similar to the electrode layer forming step, the diffusion prevention layer 30 is formed by depositing Pt on the electrode layer 20 by vacuum deposition. Note that the region where the diffusion prevention layer 30 is not to be deposited is covered with a resist film.

[0043] Next, in the solder layer forming step, the solder layer 40 is formed on the diffusion prevention layer 30 (S104).

[0044] FIG. 5B is a flowchart showing the process of S104 in more detail.

[0045] First, in the Cu layer formation step, the Cu layer 41 is formed (S201). The Cu layer 41 is formed by depositing Cu on the diffusion prevention layer 30 by a vacuum deposition process. The thickness of the deposited Cu layer 41 is determined depending on the Cu content of the solder layer 40.

[0046] Next, in the Ag layer formation step, the Ag layer 42 is formed (S202). The Ag layer 42 is formed by depositing Ag on the Cu layer 41 by vacuum deposition. The thickness of the Ag layer 42 to be formed is determined depending on the Ag content of the solder layer 40.

[0047] Next, in the Sn layer formation step, the Sn layer 43 is formed (S203). The Sn layer 43 is formed by vacuum deposition of Sn on the Ag layer 42. The thickness of the Sn layer 43 is determined depending on the Sn content of the solder layer 40.

[0048] Then, in the Au layer formation step, the Au layer 44 is formed (S204). The Au layer 44 is formed by depositing Au on the Sn layer 43 by vacuum deposition. The thickness of the Au layer 44 is determined depending on the Au content of the solder layer 40.

[0049] Then, in the aggregate substrate cutting step, the aggregate substrate is cut (S105) to form a plurality of semiconductor laser bonding thin films 1, thereby completing the manufacturing step of the semiconductor laser bonding thin film 1. In the aggregate substrate cutting step, the resist film covering the electrode layer 20 is removed before cutting the aggregate substrate.

[0050] (Configuration and Function of Semiconductor Laser Bonding Thin Film According to Second Embodiment) FIG. 6 is a diagram showing a semiconductor laser bonding thin film according to a second embodiment.

[0051] The semiconductor laser bonding thin film 2 differs from the semiconductor laser bonding thin film 1 in that it has a diffusion prevention layer 31 instead of the diffusion prevention layer 30. The configurations and functions of the components of the semiconductor laser bonding thin film 2 other than the diffusion prevention layer 31 are the same as the configurations and functions of the components of the semiconductor laser bonding thin film 1 with the same reference numerals, and therefore detailed explanations will be omitted here.

[0052] The diffusion prevention layer 31 includes a chromium (Cr) layer 32 and a Pt layer 33. The Cr layer 32 is an adhesive layer that enhances adhesion between the electrode layer 20 and the diffusion prevention layer 31. The Cr layer 32 prevents the electrode layer 20 and the solder layer 40 from intermixing, even if the Pt layer 33 is completely consumed in a reaction with the solder layer 40, thereby providing a sufficient diffusion prevention effect. The thickness of the Cr layer 32 is preferably 0.01 μm or more and 0.2 μm or less, and more preferably 0.03 μm or more and 0.1 μm or less. If the thickness of the Cr layer 32 is thicker than 0.2 μm, the strong stress of the Cr itself may induce peeling from the electrode layer 20. Furthermore, if the thickness of the Cr layer 32 is thinner than 0.01 μm, a sufficient diffusion prevention effect is not substantially achieved.

[0053] The Pt layer 33 prevents Sn and Au contained in the solder layer 40 from diffusing into the electrode layer 20. The thickness of the Pt layer 33 is preferably 0.01 μm or more and 0.6 μm or less, and more preferably 0.1 μm or more and 0.3 μm or less.

[0054] The manufacturing method of the semiconductor laser bonding thin film 2 is the same as the manufacturing method of the semiconductor laser bonding thin film 1 except that it includes the step of laminating the diffusion prevention layer 31 on the electrode layer 20, so a detailed description thereof will be omitted here.

[0055] (Configuration and Function of Semiconductor Laser Bonding Thin Film According to Third Embodiment) FIG. 7 is a diagram showing a semiconductor laser bonding thin film according to a third embodiment.

[0056] The semiconductor laser bonding thin film 3 differs from the semiconductor laser bonding thin film 1 in that it has a solder layer 45 instead of the solder layer 40. The configurations and functions of the components of the semiconductor laser bonding thin film 3 other than the solder layer 45 are the same as the configurations and functions of the components of the semiconductor laser bonding thin film 1 with the same reference numerals, and therefore detailed explanations will be omitted here.

[0057] The solder layer 45 differs from the solder layer 40 in that the solder layer 45 has a first Au layer 46 and a second Au layer 47 instead of the Au layer 44. The configurations and functions of the components of the solder layer 45 other than the first Au layer 46 and the second Au layer 47 are the same as the configurations and functions of the components of the solder layer 40 with the same reference numerals, and therefore detailed description thereof will be omitted here.

[0058] The first Au layer 46 and the second Au layer 47 are formed of Au. The first Au layer 46 is disposed between the Ag layer 42 and the Sn layer 43, and the second Au layer 47, like the Au layer 44, is disposed on the upper surface of the Sn layer 43. The first Au layer 46 and the second Au layer 47 are disposed such that the total amount of Au contained in the first Au layer 46 and the second Au layer 47 is such that the Au content in the solder layer 45 is 0.1 wt % or more and 14.0 wt % or less. Note that the first Au layer 46 is disposed between the Ag layer 42 and the Sn layer 43, but may also be disposed between the Cu layer 41 and the Ag layer 42.

[0059] The manufacturing method of the semiconductor laser bonding thin film 3 is the same as the manufacturing method of the semiconductor laser bonding thin film 1 except that it includes a step of stacking the first Au layer 46 between the Ag layer 42 and the Sn layer 43, so detailed explanation will be omitted here.

[0060] (Configuration and Function of Semiconductor Laser Bonding Thin Film According to Fourth Embodiment) FIG. 8 is a diagram showing a semiconductor laser bonding thin film according to a fourth embodiment.

[0061] The semiconductor laser bonding thin film 4 differs from the semiconductor laser bonding thin film 2 in that it does not have an electrode layer 20. The Cr layer 32 of the diffusion prevention layer 31, which is an adhesion layer, adheres to the submount substrate 10, so that the semiconductor laser bonding thin film 4 adheres to the submount substrate 10.

[0062] The method for manufacturing the semiconductor laser bonding thin film 4 is the same as the method for manufacturing the semiconductor laser bonding thin film 1 except that it does not include the electrode layer forming step, so a detailed description thereof will be omitted here.

[0063] (Layer Structure of Diffusion Barrier Layer and Solder Layer) Table 1 shows the layer structure of the diffusion barrier layer disposed below the Sn layer and the Au layer disposed on the Sn layer, and the layer below the solder layer. In each of Samples 1 to 4 shown in Table 1, a 3.0 μm-thick Sn layer is laminated on a lower layer laminated on an AlN substrate, and a 0.16 μm-thick Au layer is sequentially laminated on the Sn layer.

[0064]

[0065] In Table 1, the "Layer structure of lower layers" column indicates the layer structure of the layers below the Sn layer and the Au layer, "First layer" indicates the bottom layer, "Second layer" indicates the layer stacked on the "First layer," "Third layer" indicates the layer stacked on the "Second layer," and "Fourth layer" indicates the layer stacked on the "Third layer."

[0066] The "Melting Property" column indicates the melting property when subjected to rapid thermal annealing (RTA) at 220°C. The RTA treatment was performed using a pulse heater manufactured by Ichinen Seisakusho Co., Ltd., where the temperature was raised to 220°C within a few seconds and maintained at 220°C for 20 seconds. In the "Melting Property" column, "◯" indicates that the sample remained in a molten state for 15 seconds or more when heated at 220°C, and "×" indicates that the sample remained in a molten state for less than 1 second when heated at 220°C. The "Void" column indicates the occurrence of voids when subjected to RTA treatment at 220°C. In the "Void" column, "◯" indicates that no voids were generated, "Δ" indicates that a small number of voids were generated, and "×" indicates that a large number of voids were generated. The "Evaluation" column provides an overall evaluation of melting property and voids. In the "Evaluation" column, "◯" indicates good, and "×" indicates poor.

[0067] Sample 1 has a 0.05 μm thick Cr layer as the first layer, a 0.20 μm thick nickel (Ni) layer as the second layer, a 3.0 μm thick Sn layer stacked on the Ni layer, and a 0.16 μm thick Au layer stacked on the Sn layer in this order.

[0068] FIG. 9( a ) is a surface image of sample 1 during RTA treatment, and FIG. 9( b ) is a scanning electron microscope (SEM) image of a cross section of sample 1 after RTA treatment.

[0069] For sample 1, the molten state continued for less than 1 second during the RTA treatment, and a large number of voids were generated after the RTA treatment, resulting in an "X" in both the "Melting property" and "Voids" columns and an "X" in the "Evaluation" column.

[0070] Sample 2 has a first layer made of a Ti layer with a thickness of 0.05 μm, a second layer made of a Pt layer with a thickness of 0.20 μm, a Sn layer with a thickness of 3.0 μm laminated on the Pt layer, and an Au layer with a thickness of 0.16 μm laminated on the Sn layer.

[0071] FIG. 9(c) is a surface image of sample 2 during the RTA treatment, and FIG. 9(d) is an SEM image of the cross section of sample 2 after the RTA treatment.

[0072] In sample 2, no voids were generated after the RTA treatment, and the "Void" column was marked "Good", but the molten state continued for less than 1 second during the RTA treatment, and the "Melting property" column was marked "Poor", and the "Evaluation" column was marked "Poor".

[0073] Sample 3 has a 0.05 μm thick Ti layer as the first layer, a 0.20 μm thick Pt layer as the second layer, and a 0.74 μm thick Ag layer as the third layer. A 3.0 μm thick Sn layer is stacked on the Ag layer, and a 0.16 μm thick Au layer is stacked on the Sn layer in this order.

[0074] FIG. 9(e) is a surface image of sample 3 during the RTA treatment, and FIG. 9(f) is an SEM image of the cross section of sample 3 after the RTA treatment.

[0075] For sample 3, the molten state continued for 15 seconds or more during the RTA treatment, and the "Melting property" column was marked "Good." However, a large number of voids were generated after the RTA treatment, and the "Void" column was marked "Poor," and the "Evaluation" column was marked "Poor."

[0076] Sample 4 has a layer structure corresponding to the semiconductor laser bonding thin film 2. Sample 4 has a 0.05 μm-thick Cr layer as the first layer, a 0.20 μm-thick Pt layer as the second layer, a 0.1 μm-thick Cu layer as the third layer, and a 0.74 μm-thick Ag layer as the fourth layer. A 3.0 μm-thick Sn layer is laminated on the Ag layer, and a 0.16 μm-thick Au layer is laminated on the Sn layer in this order.

[0077] FIG. 9( g ) is a surface image of sample 4 during the RTA treatment, and FIG. 9( f ) is an SEM image of the cross section of sample 4 after the RTA treatment.

[0078] In Sample 4, a small amount of voids were generated after the RTA treatment, and the "Void" column was marked "△", but the molten state continued for 15 seconds or more during the RTA treatment, so the "Fusibility" column was marked "◯" and the "Evaluation" column was marked "◯". The difference between Sample 4 and Sample 3 is whether or not a Pt layer is disposed between the Cr layer and the Cu layer; in Sample 4, the amount of void generation is reduced by disposing the Pt layer. Sample 4 has a layer structure similar to that of the semiconductor laser bonding thin film 4. However, the effect of the layer structure in Sample 4 is also exerted in the semiconductor laser bonding thin films 1 to 3 in the same way as in the semiconductor laser bonding thin film 4.

[0079] (Regarding the Au, Sn, Ag, and Cu Contents in the Solder Layer) Table 2 shows the Au, Sn, Ag, and Cu contents in the solder layer. Each of Examples 1 to 9 and Comparative Examples 1 to 6 shown in Table 2 is formed by sequentially laminating a Cu layer, an Ag layer, a Sn layer, and an Au layer on a diffusion prevention layer made of a Cr layer and a Pt layer that is laminated on a submount substrate made of AlN. Each of Examples 1 to 9 and Comparative Examples 1 to 6 has a layer structure similar to that of the semiconductor laser bonding thin film 4. However, the effects of the Au, Sn, Ag, and Cu contents in the solder layers of Examples 1 to 9 and Comparative Examples 1 to 6 are also achieved in the semiconductor laser bonding thin films 1 to 3 in the same manner as in the semiconductor laser bonding thin film 4.

[0080]

[0081] In Table 2, the "Content" column indicates the content of Au, Sn, Ag, and Cu in the solder layer. The "Au" column indicates the Au content in the solder layer in weight percent, the "Sn" column indicates the Sn content in the solder layer in weight percent, the "Ag" column indicates the Ag content in the solder layer in weight percent, and the "Cu" column indicates the Cu content in the solder layer in weight percent.

[0082] The "Melting Point" column indicates whether the melting point was good or bad when subjected to RTA treatment. The RTA treatment was carried out by gradually raising the temperature from room temperature to 240°C using a pulse heater manufactured by Ichinen Manufacturing Co., Ltd. In the "Melting Point" column, "◯" indicates that the melting point was 205°C, "△" indicates that the melting point was 210°C, and "X" indicates that the melting point was higher than 210°C. The "Void" column indicates the occurrence of voids when subjected to RTA treatment at 220°C. In the "Void" column, "◯" indicates that no voids were generated, "△" indicates that a small number of voids were generated, and "X" indicates that a large number of voids were generated. The "Melting Duration" column indicates the time the molten state continued when subjected to RTA treatment at 220°C. In the "Melting duration" column, "◯" indicates that the melted state continued for 15 seconds or more, "△" indicates that the melted state continued for 5 seconds or more but less than 15 seconds, and "×" indicates that the melted state continued for less than 5 seconds.

[0083] The "Evaluation Score" column is a score value for the overall evaluation combining melting property, voids, and melting duration. The values ​​shown in the "Evaluation Score" column are scored as follows: "○" shown in the "Melting Point", "Voids", and "Melting Duration" columns is scored as 2 points, "△" is scored as 1 point, and "×" is scored as 0 point. When the evaluation score is 6 points, the composition of the solder layer is considered to be in the optimum composition range. When the evaluation score is 5 points, the composition of the solder layer is considered to be in a composition range that is not optimum but usable. When the evaluation score is 4 points or less, the composition of the solder layer is considered to be in an unusable composition range.

[0084] Example 1 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 8.0 wt % Au, 91.8 wt % Sn, 0.1 wt % Ag, and 0.1 wt % Cu.

[0085] FIG. 10(a) is a surface image of Example 1 during RTA treatment, and FIG. 10(b) is an SEM image of a cross section of Example 1 after RTA treatment.

[0086] In Example 1, the melting point was 205°C, so the "Melting Point" column was marked "Good", no voids were generated after the RTA treatment, so the "Void" column was marked "Good", and the molten state continued for about 5 seconds, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Good", and the "Melting Duration" column was marked "Good", the evaluation score for Example 1 was 5 points.

[0087] Example 2 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 7.7 wt % Au, 88.6 wt % Sn, 3.1 wt % Ag, and 0.5 wt % Cu.

[0088] FIG. 10(c) is a surface image of Example 2 during the RTA treatment, and FIG. 10(d) is an SEM image of the cross section of Example 2 after the RTA treatment.

[0089] In Example 2, the melting point was 205°C, so the "Melting Point" column was marked "Good", no voids were generated after the RTA treatment, so the "Void" column was marked "Good", and the molten state continued for 15 seconds or more, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Good", and the "Melting Duration" column was marked "Good", the evaluation score for Example 2 was 6 points.

[0090] Example 3 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 7.6 wt % Au, 87.5 wt % Sn, 3.1 wt % Ag, and 1.8 wt % Cu.

[0091] FIG. 10(e) is a surface image of Example 3 during RTA treatment, and FIG. 10(f) is an SEM image of the cross section of Example 3 after RTA treatment.

[0092] In Example 3, the melting point was 205°C, so the "Melting Point" column was marked "Good", no voids were generated after the RTA treatment, so the "Void" column was marked "Good", and the molten state continued for 15 seconds or more, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Good", and the "Melting Duration" column was marked "Good", Example 3 was evaluated as having 6 points.

[0093] Example 4 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 7.5 wt % Au, 86.0 wt % Sn, 0.3 wt % Ag, and 3.5 wt % Cu.

[0094] FIG. 10( g ) is a surface image of Example 4 during the RTA treatment, and FIG. 10( h ) is an SEM image of the cross section of Example 4 after the RTA treatment.

[0095] In Example 4, the melting point was 205°C, so the "Melting Point" column was marked "Good", no voids were generated after the RTA treatment, so the "Void" column was marked "Good", and the molten state continued for 15 seconds or more, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Good", and the "Melting Duration" column was marked "Good", the evaluation score for Example 4 was 6 points.

[0096] Example 5 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 7.3 wt % Au, 83.1 wt % Sn, 2.9 wt % Ag, and 6.7 wt % Cu.

[0097] FIG. 10(i) is a surface image of Example 5 during RTA treatment, and FIG. 10(j) is an SEM image of the cross section of Example 5 after RTA treatment.

[0098] In Example 5, the melting point was 205°C, so the "Melting Point" column was marked "Good", no voids were generated after the RTA treatment, so the "Void" column was marked "Good", and the molten state continued for 15 seconds or more, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Good", and the "Melting Duration" column was marked "Good", Example 5 was evaluated to have a score of 6.

[0099] Example 6 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 14.0 wt % Au, 80.0 wt % Sn, 2.8 wt % Ag, and 3.2 wt % Cu.

[0100] FIG. 11(a) is a surface image of Example 6 during the RTA treatment.

[0101] In Example 6, the melting point was 205°C, so the "Melting Point" column was marked "Good", no voids were generated after the RTA treatment, so the "Void" column was marked "Good", and the molten state continued for about 5 seconds, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Good", and the "Melting Duration" column was marked "Good", the evaluation score for Example 6 was 5 points.

[0102] Example 7 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 7.7 wt % Au, 88.6 wt % Sn, 0.1 wt % Ag, and 3.6 wt % Cu.

[0103] FIG. 11(b) is a surface image of Example 7 during the RTA treatment.

[0104] In Example 7, the melting point was 205°C, so the "Melting Point" column was marked "Good", no voids were generated after the RTA treatment, so the "Void" column was marked "Good", and the molten state continued for about 5 seconds, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Good", and the "Melting Duration" column was marked "Good", the evaluation score for Example 7 was 5 points.

[0105] Example 8 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 7.4 wt % Au, 84.7 wt % Sn, 4.4 wt % Ag, and 3.4 wt % Cu.

[0106] FIG. 11(c) is a surface image of Example 8 during the RTA treatment.

[0107] In Example 8, the melting point was 205°C, so the "Melting Point" column was marked "Good", no voids were generated after the RTA treatment, so the "Void" column was marked "Good", and the molten state continued for about 5 seconds, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Good", and the "Melting Duration" column was marked "Good", the evaluation score for Example 8 was 5 points.

[0108] Example 9 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 7.2 wt % Au, 82.7 wt % Sn, 0.1 wt % Ag, and 10.1 wt % Cu.

[0109] FIG. 11(d) is a surface image of Example 9 during the RTA treatment.

[0110] In Example 9, the melting point was 210°C, so the "Melting Point" column was marked "△", no voids were generated after the RTA treatment, so the "Void" column was marked "〇", and the molten state continued for 15 seconds or more, so the "Melting Duration" column was marked "〇". Since the "Melting Point" column was marked "〇", the "Void" column was marked "〇", and the "Melting Duration" column was marked "△", the evaluation score for Example 9 was 5 points.

[0111] Comparative Example 1 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 7.0 wt % Au, 80.4 wt % Sn, 2.8 wt % Ag, and 9.8 wt % Cu.

[0112] FIG. 11( e ) is a surface image of Comparative Example 1 during the RTA treatment.

[0113] In Comparative Example 1, the melting point was 205°C, so the "Melting Point" column was marked "Good", a large number of voids were generated after the RTA treatment, so the "Void" column was marked "Poor", and the molten state continued for about 5 seconds, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Poor", and the "Melting Duration" column was marked "Good", the evaluation score for Comparative Example 1 was 3 points.

[0114] Comparative Example 2 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 6.8 wt % Au, 77.8 wt % Sn, 2.7 wt % Ag, and 12.6 wt % Cu.

[0115] FIG. 11(f) is a surface image of Comparative Example 2 during the RTA treatment.

[0116] In Comparative Example 2, the melting point was 205°C, so the "Melting Point" column was marked "Good", a large number of voids were generated after the RTA treatment, so the "Void" column was marked "Poor", and the molten state continued for about 5 seconds, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Poor", and the "Melting Duration" column was marked "Good", the evaluation score for Comparative Example 2 was 3 points.

[0117] Comparative Example 3 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 6.6 wt % Au, 77.5 wt % Sn, 2.7 wt % Ag, and 15.3 wt % Cu.

[0118] FIG. 11( g ) is a surface image of Comparative Example 3 during the RTA treatment.

[0119] In Comparative Example 3, the melting point was 205°C, so the "Melting Point" column was marked "Good", a large number of voids were generated after the RTA treatment, so the "Void" column was marked "Poor", and the molten state continued for about 5 seconds, so the "Melting Duration" column was marked "Good". Since the "Melting Point" column was marked "Good", the "Void" column was marked "Poor", and the "Melting Duration" column was marked "Good", the evaluation score for Comparative Example 3 was 3 points.

[0120] Comparative Example 4 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 19.6 wt % Au, 74.8 wt % Sn, 2.6 wt % Ag, and 3.0 wt % Cu.

[0121] FIG. 11(h) is a surface image of Comparative Example 4 during the RTA treatment.

[0122] In Comparative Example 4, the melting point was 210°C, so the "Melting Point" column was marked "△", no voids were generated after the RTA treatment, so the "Void" column was marked "◯", and the molten state continued for less than 1 second, so the "Melting Duration" column was marked "X". Since the "Melting Point" column was marked "△", the "Void" column was marked "◯", and the "Melting Duration" column was marked "X", the evaluation score for Comparative Example 4 was 3 points.

[0123] Comparative Example 5 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 24.5 wt % Au, 70.2 wt % Sn, 2.5 wt % Ag, and 2.8 wt % Cu.

[0124] FIG. 11(i) is a surface image of Comparative Example 5 during the RTA treatment.

[0125] In Comparative Example 5, the melting point was higher than 210°C, so the "Melting Point" column was marked with "X", no voids were generated after the RTA treatment, so the "Void" column was marked with "O", and the molten state continued for less than 1 second, so the "Melting Duration" column was marked with "X". Since the "Melting Point" column was marked with "X", the "Void" column was marked with "O", and the "Melting Duration" column was marked with "X", the evaluation score for Comparative Example 5 was 2 points.

[0126] Comparative Example 6 was formed by sequentially stacking Cu, Ag, Sn, and Au, and contained 6.9 wt % Au, 79.0 wt % Sn, 4.5 wt % Ag, and 9.6 wt % Cu.

[0127] FIG. 11(h) is a surface image of Comparative Example 6 during the RTA treatment.

[0128] In Comparative Example 6, the melting point was 210°C, so the "Melting Point" column was marked "△", a small number of voids were generated after the RTA treatment, so the "Void" column was marked "△", and the molten state continued for 15 seconds or more, so the "Melting Duration" column was marked "〇". Since the "Melting Point" column was marked "△", the "Void" column was marked "△", and the "Melting Duration" column was marked "〇", the evaluation score for Comparative Example 6 was 4 points.

[0129] Examples 1, 6, 8, and 9 received a rating of 5 points, and Examples 2 to 5 and 7 received a rating of 6 points. On the other hand, Comparative Examples 1 to 4 received a rating of 3 points, Comparative Example 5 received a rating of 2 points, and Comparative Example 6 received a rating of 4 points.

[0130] Examples 1 to 9 received evaluation scores of 5 or more, and are usable as solder layers. The composition range encompassing Examples 1 to 9 is a range containing 7.2 wt% to 14.0 wt% Au, 0.1 wt% to 4.4 wt% Ag, 0.1 wt% to 10.1 wt% Cu, and the remainder, excluding unavoidable impurities, consisting of Sn. A solder layer containing 7.2 wt% to 14.0 wt% Au, 0.1 wt% to 4.4 wt% Ag, 0.1 wt% to 10.1 wt% Cu, and the remainder, excluding unavoidable impurities, consisting of Sn is usable as a solder layer according to the present application.

[0131] Examples 1 to 5 and 7 received a perfect score of 6 points, making them ideal for use as solder layers. The composition range encompassing Examples 1 to 5 and 7 is a range containing 7.3 wt% to 7.7 wt% Au, 0.1 wt% to 3.1 wt% Ag, 0.5 wt% to 6.7 wt% Cu, and the remainder, excluding unavoidable impurities, consisting of Sn. A solder layer containing 7.3 wt% to 7.7 wt% Au, 0.1 wt% to 3.1 wt% Ag, 0.5 wt% to 6.7 wt% Cu, and the remainder, excluding unavoidable impurities, consisting of Sn is ideal for use as a solder layer according to the present application.

[0132] The melting points of Examples 1 to 9, which contain 7.2 wt% to 14.0 wt% Au, are 210°C. The solder layer can have a lower melting point by containing 7.2 wt% to 14.0 wt% Au. The melting points of Examples 1 to 8, which contain 7.3 wt% to 14.0 wt% Au, are 205°C. The solder layer can have a further lower melting point by containing 7.3 wt% to 14.0 wt% Au. Examples 2 to 5, 7, and 8, which contain 7.3 wt% to 7.7 wt% Au, have a melting duration of 15 seconds or more. The solder layer can have a melting duration of 15 seconds or more by containing 7.3 wt% to 7.7 wt% Au.

[0133] The melting points of Examples 1 to 8, which contain 0.1 wt% to 4.4 wt% Ag and 0.1 wt% to 6.7 wt% Cu, are 205°C. The solder layer contains 0.1 wt% to 4.4 wt% Ag and 0.1 wt% to 6.7 wt% Cu, which allows for a low melting point. The melting points of Examples 1 to 7, which contain 0.1 wt% to 3.1 wt% Ag and 0.1 wt% to 6.7 wt% Cu, are 205°C, and no voids occur in Examples 1 to 7. The solder layer contains 0.1 wt% to 3.1 wt% Ag and 0.1 wt% to 6.7 wt% Cu, which allows for a low melting point, no voids, and high reliability.

[0134] Examples 1 to 9, which contain 0.1 wt% to 10.1 wt% Cu, do not generate a large number of voids. High reliability can be achieved by including 0.1 wt% to 10.1 wt% Cu in the solder layer. Examples 1 to 7 and 9, which contain 0.1 wt% to 10.1 wt% Cu and 0.1 wt% to 3.1 wt% Ag, do not generate voids. Further high reliability can be achieved by including 0.1 wt% to 10.1 wt% Cu and 0.1 wt% to 3.1 wt% Ag in the solder layer.

Claims

1. A thin film for semiconductor laser bonding, comprising a solder layer containing 7.2% or more and 14.0% or less by weight of Au, 0.1% or more and 4.4% or less by weight of Ag, 0.1% or more and 10.1% or less by weight of Cu, and the remainder being Sn except for unavoidable impurities.

2. A thin film for semiconductor laser bonding as described in claim 1, wherein Cu forms a Cu layer disposed over the entire surface of one side of the solder layer.

3. A thin film for semiconductor laser bonding according to claim 1 or 2, containing 7.3% by weight or more and 14.0% by weight or less of Au.

4. A thin film for semiconductor laser bonding according to claim 1 or 2, containing 0.1% by weight or more and 4.4% by weight or less of Ag and 0.1% by weight or more and 6.7% by weight or less of Cu.

5. A thin film for semiconductor laser bonding according to claim 1 or 2, containing 0.1% by weight or more and 10.1% by weight or less of Cu and 0.1% by weight or more and 3.1% by weight or less of Ag.

6. A thin film for semiconductor laser bonding as described in claim 1 or 2, wherein the solder layer contains 7.3 wt % or more and 7.7 wt % or less of Au, 2.9 wt % or more and 3.1 wt % or less of Ag, and 0.5 wt % or more and 6.7 wt % or less of Cu.

7. A thin film for semiconductor laser bonding as described in claim 1 or 2, further comprising a diffusion prevention layer containing Pt and arranged so as to face the surface of the solder layer on which the Cu is arranged.

8. A thin film for semiconductor laser bonding as described in claim 7, wherein the diffusion prevention layer has a Cr layer containing Cr and a Pt layer containing Pt and disposed between the Cr layer and the solder layer.

9. A method for manufacturing a thin film for semiconductor laser bonding having a solder layer containing 7.2% by weight or more and 14.0% by weight or less of Au, 0.1% by weight or more and 4.4% by weight or less of Ag, 0.1% by weight or more and 10.1% by weight or less of Cu, and the remainder consisting of Sn except for unavoidable impurities, comprising the steps of forming a Cu layer, forming an Ag layer on the Cu layer, forming a Sn layer on the Ag layer, and forming an Au layer on the Sn layer.

Images