A metal thin layer structure for surface bonding and a method of manufacturing

Abstract

The application discloses a metal thin layer structure for surface bonding and a preparation method. The metal thin layer comprises two WTi mixed metal layers and three Au metal layers. The metal thin layer is prepared by a magnetron sputtering process, an electroplating process and the like. Compared with the prior art, the metal thin layer structure is used as an upper plate of a capacitor, has higher adhesion and high bonding tensile strength, and can still maintain excellent performance after experiencing high-strength reliability tests.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a metal thin layer structure for surface bonding and a preparation method thereof. BACKGROUND

[0002] Modern wireless communication technology develops rapidly, and GaN microwave power devices are widely researched and applied. Inductors, capacitors, thin film resistors and other passive devices, as key components of microwave matching circuits, have also become important research hotspots.

[0003] The Ni / Pd / Au plating layer structure has been widely used in the packaging field, and can meet the requirements of wire bonding and solder assembly at the same time, but when this structure is introduced into the preparation process of the upper plate of the capacitor, it has several problems. First, Ni cannot be closely combined with the capacitor medium, which is prone to risk of metal separation of the upper plate; second, the stress of the capacitor upper plate prepared by the Ni / Pd / Au plating layer is too large, which is prone to cause tearing of the capacitor medium at the edge of the upper plate, and the capacitor medium and the lower plate are separated, and the device has no capacitor characteristics; third, the capacitor device prepared by the Ni / Pd / Au plating layer will be broken or separated from the capacitor medium after high storage and temperature cycle reliability verification. Therefore, a new type of metal thin layer structure for surface bonding and a preparation method thereof are needed to solve the above problems. SUMMARY

[0004] The present application provides a metal thin layer structure for surface bonding and a preparation method thereof to solve the above problems. The metal thin layer structure is used as the upper plate of the capacitor, has high ductility and high bonding tensile strength, and can still maintain excellent performance after high-strength reliability test.

[0005] The metal thin layer structure for surface bonding comprises a first metal layer, a second metal layer arranged on the first metal layer, a third metal layer arranged on the second metal layer, a fourth metal layer arranged on the third metal layer, and a fifth metal layer arranged on the fourth metal layer. The first metal layer is a WTi mixed metal, the second metal layer is Au metal, the third metal layer is a WTi mixed metal, the fourth metal layer is Au metal, and the fifth metal layer is Au metal.

[0006] A preparation method of a metal thin layer structure for surface bonding, characterized in that it comprises the following steps:

[0007] S1. The first metal layer is prepared by using a WTi mixed metal target and a magnetron sputtering process;

[0008] S2. The second metal layer is prepared by using an Au metal target and a magnetron sputtering process;

[0009] S3. The third metal layer is prepared by using a WTi mixed metal target and a magnetron sputtering process;

[0010] S4. The fourth metal layer is prepared by using an Au metal target and a magnetron sputtering process;

[0011] S5. The area where the fifth metal layer is not needed is coated and the photoresist is cured by a photoetching process, so that the area where the fifth metal layer is needed is exposed;

[0012] S6. The fifth metal layer is prepared by using an Au metal target;

[0013] S7. The photoresist is removed;

[0014] S8. The excess fourth metal layer, third metal layer, second metal layer and first metal layer under the area without the fifth metal layer are removed.

[0015] Further, the mass ratio of W metal to Ti metal in the WTi mixed metal target is 5:5-2:8.

[0016] Further, in S1, a piece of capacitor dielectric is prepared, and the first metal layer is formed on the surface of the capacitor dielectric by a magnetron sputtering process.

[0017] Further, the first metal layer serves as a seed layer, and the fourth metal layer serves as a seed layer of the fifth metal layer.

[0018] Further, the third metal layer serves as a bonding buffer layer.

[0019] Further, in S7, the fifth metal layer on the photoresist is removed together with the photoresist.

[0020] Further, the thickness of the first metal layer is 50-150 nm, the thickness of the second metal layer is 20-100 nm, the thickness of the third metal layer is 0.5-2 μm, the thickness of the fourth metal layer is 20-100 nm, and the thickness of the fifth metal layer is 1-5 μm.

[0021] Further, in S8, when the excess fourth metal layer and second metal layer under the area without the fifth metal layer are removed by a wet process, the wet solution used is a mixed solution of potassium cyanide: 647 gold removal concentrated solution: water with a volume ratio of 1:5:200; when the excess third metal layer and first metal layer under the area without the fifth metal layer are removed by a wet process, the wet solution used is hydrogen peroxide with a concentration of 26% and a temperature of 60°C.

[0022] Further, the purity of the Au metal target is higher than 99.999%.

[0023] Beneficial effects: Compared with the prior art, the present application has the following remarkable effects: the metal thin layer structure prepared by using WTi mixed metal, Au metal and sequentially upward based on the capacitor dielectric as the capacitor upper plate has higher ductility and high bonding tensile strength, and can still maintain excellent performance after experiencing high strength reliability test. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present application.

[0025] Figure 2 It is a schematic diagram of the position of the first metal layer of the present application.

[0026] Figure 3 It is a schematic diagram of the position of the second metal layer of the present application.

[0027] Figure 4 It is a schematic diagram of the position of the third metal layer of the present application.

[0028] Figure 5 It is a schematic diagram of the position of the fourth metal layer of the present application.

[0029] Figure 6 It is a schematic diagram of the position of the photoresist of the present application.

[0030] Figure 7 It is a schematic diagram of the position of the fifth metal layer of the present application.

[0031] Figure 8 It is a schematic diagram of the overall structure when the excess metal layer is not removed of the present application. DETAILED DESCRIPTION

[0032] The present application discloses a metal thin layer structure for surface bonding and a preparation method thereof. Figure 1 As shown in the figure, the metal thin layer structure for surface bonding provided by the present application is further described in detail as follows: the metal thin layer structure for surface bonding comprises a first metal layer 1, a second metal layer 2 arranged on the first metal layer 1, a third metal layer 3 arranged on the second metal layer 2, a fourth metal layer 4 arranged on the third metal layer 3, and a fifth metal layer 5 arranged on the fourth metal layer 4; the first metal layer 1 is WTi mixed metal, the second metal layer 2 is Au metal, the third metal layer 3 is WTi mixed metal, the fourth metal layer 4 is Au metal, and the fifth metal layer 5 is Au metal.

[0033] As shown in the figure, the preparation method of the metal thin layer structure for surface bonding provided by the present application is further described in detail as follows: Figures 2 to 8

[0034] ​First step: a first metal layer 1 with a thickness of 90 nm is prepared on the surface of the capacitor dielectric 7 by using a WTi mixed metal target and a magnetron sputtering process, wherein the mass ratio of W to Ti in the WTi mixed metal target is 3:7, and the first metal layer 1 serves as a seed layer to increase the adhesion between the dielectric and the metal, as shown in FIG. 1. Figure 2

[0035] Second step: a second metal layer 2 with a thickness of 60 nm is prepared by using an Au metal target and a magnetron sputtering process, wherein the purity of the Au metal target is higher than 99.999%, and the second metal layer 2 serves as an interlayer between the first metal layer 1 and the third metal layer 3 to enhance adhesion and release stress, as shown in FIG. 2. Figure 3

[0036] Third step: a third metal layer 3 with a thickness of 800 nm is prepared by using a WTi mixed metal target and a magnetron sputtering process, wherein the mass ratio of W to Ti in the WTi mixed metal target is 3:7, and the third metal layer 3 serves as a bonding buffer layer to prevent the gold wire bonding point from penetrating into the capacitor dielectric 7, as shown in FIG. 3. Figure 4

[0037] Fourth step: a fourth metal layer 4 with a thickness of 60 nm is prepared by using an Au metal target and a magnetron sputtering process, wherein the purity of the Au metal target is higher than 99.999%, and the fourth metal layer 4 serves as an interlayer between the third metal layer 3 and the fifth metal layer 5 to enhance adhesion and release stress, as shown in FIG. 4. Figure 5

[0038] Fifth step: the photoresist 6 is coated and cured on the areas where the fifth metal layer 5 is not needed by a photolithography process, and the areas where the fifth metal layer 5 is needed are exposed, as shown in FIG. 5. Figure 6

[0039] Sixth step: the fourth metal layer 4 serves as a seed layer for the fifth metal layer 5, and the fifth metal layer 5 with a thickness of 2 μm is prepared by using an Au metal target and a plating, evaporation, or magnetron sputtering process, and the fifth metal layer 5 serves as a gold wire bonding layer to release stress during the bonding process, as shown in FIG. 6. Figure 7

[0040] Seventh step: the photoresist 6 is removed by a wet solvent, and the fifth metal layer 5 on the photoresist 6 is removed together with the photoresist 6, as shown in FIG. 7. Figure 8

[0041] Eighth step: the excess fourth metal layer 4 under the area without the fifth metal layer 5 is removed by a wet process, and the wet solution used is a mixed solution of potassium cyanide: 647 gold removal concentrated solution: water with a volume ratio of 1:5:200, and the corrosion time is 100 seconds, as shown in FIG. 8.​​​​​​​Figure 8 as shown.

[0042] Ninth step: removing the excess third metal layer 3 under the area without the fifth metal layer 5 by a wet process, using a wet solution of hydrogen peroxide, with a temperature of 60°C and a concentration of 26%, for a corrosion time of 6 minutes, as shown in Figure 6. Figure 8 as shown.

[0043] Tenth step: removing the excess second metal layer 2 under the area without the fifth metal layer 5 by a wet process, using a wet solution of potassium cyanide: 647 gold removal concentrate: water in a volume ratio of 1:5:200, for a corrosion time of 100 seconds, as shown in Figure 7. Figure 8 as shown.

[0044] Eleventh step: removing the excess first metal layer 1 under the area without the fifth metal layer 5 by a wet process, using a wet solution of hydrogen peroxide, with a temperature of 60°C and a concentration of 26%, for a corrosion time of 1 minute, as shown in Figure 8. Figure 8 as shown.

[0045] By testing the bonding strength of the prepared metal thin layer and comparing it with a metal thin layer sheet in the prior art: 22 points on the metal thin layer prepared by the present application were measured for bonding strength, and the results were all greater than 60 grams, meeting the characteristics of high bonding tensile strength; while the bonding strength of 22 points at the same position of the metal thin layer sheet in the prior art was between 12.5 grams and 19.9 grams, which was quite different from the index of the bonding strength of the metal thin layer structure prepared by the present application.

Claims

1. A method for producing a metal thin layer structure for surface bonding, characterized in that Includes the following steps: S1. The first metal layer (1) is prepared by using a WTi hybrid metal target and magnetron sputtering process. A capacitor dielectric (7) is prepared, and the first metal layer (1) is formed on the surface of the capacitor dielectric (7) by magnetron sputtering process. The mass ratio of W metal to Ti metal in the WTi hybrid metal target is 5:5~2:

8. The thickness of the first metal layer (1) is 50~150nm. S2. The second metal layer (2) is prepared by using an Au metal target and magnetron sputtering process. The thickness of the second metal layer (2) is 20~100nm. S3. The third metal layer (3) is prepared by WTi mixed metal target and magnetron sputtering process, and the thickness of the third metal layer (3) is 0.5~2μm; S4. The fourth metal layer (4) is prepared by using an Au metal target and magnetron sputtering process. The thickness of the fourth metal layer (4) is 20~100nm. S5. Photoresist (6) is applied and cured to the area where the fifth metal layer (5) does not need to be prepared by photolithography, thus exposing the area where the fifth metal layer (5) needs to be prepared. S6. The fifth metal layer (5) is prepared by magnetron sputtering using an Au metal target. The thickness of the fifth metal layer (5) is 1~5μm. S7. Remove the photoresist (6). While removing the photoresist (6), the fifth metal layer (5) on the photoresist (6) is peeled off along with the photoresist (6). S8. Remove the excess fourth metal layer (4), third metal layer (3), second metal layer (2) and first metal layer (1) below the area without the fifth metal layer (5); The first metal layer (1) serves as a seed layer, the fourth metal layer (4) serves as a seed layer for the fifth metal layer (5), and the third metal layer (3) serves as a bonding buffer layer.

2. The method for preparing a metal thin-film structure for surface bonding according to claim 1, characterized in that, In S8, when the wet process is used to remove the excess fourth metal layer (4) and second metal layer (2) below the region without the fifth metal layer (5), the wet process solution used is a mixture of potassium cyanide: 647 gold removal concentrate: water in a volume ratio of 1:5:200; when the wet process is used to remove the excess third metal layer (3) and first metal layer (1) below the region without the fifth metal layer (5), the wet process solution used is hydrogen peroxide, at a temperature of 60°C and a concentration of 26%.

3. The method for preparing a metal thin-film structure for surface bonding according to claim 1, characterized in that, The purity of the Au metal target is higher than 99.999%.

4. A thin metal layer structure for surface bonding obtained by the preparation method according to any one of claims 1-3.

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