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 a WTi mixed metal layer, an Au metal layer, a Ni metal layer, a WTi mixed metal layer, an Au metal layer and an Au metal layer. 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, and 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 researched and applied in large quantities. 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 easily causes the 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 easily causes the tearing of the capacitor medium at the edge of the upper plate, the separation of the capacitor medium from the lower plate, and the device without 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 adhesion and high bonding tensile strength, and can still maintain excellent performance after high-strength reliability tests.

[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, a fifth metal layer arranged on the fourth metal layer, and a sixth metal layer arranged on the fifth metal layer. The first metal layer is a WTi mixed metal, the second metal layer is an Au metal, the third metal layer is a Ni metal, the fourth metal layer is a WTi mixed metal, the fifth metal layer is an Au metal, and the sixth metal layer is an Au metal.

[0006] A preparation method of the metal thin layer structure for surface bonding according to claim 1, comprising 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 regions where the third metal layer is not needed are coated and the photoresist is cured by a photolithography process, and the regions where the third metal layer is needed are exposed;

[0010] S4. The third metal layer is prepared by using a Ni metal target and an electroplating process;

[0011] S5. The fourth metal layer is prepared by using a WTi mixed metal target and a magnetron sputtering process;

[0012] S6. The fifth metal layer is prepared by using an Au metal target and a magnetron sputtering process;

[0013] S7. The sixth metal layer is prepared by using an Au metal target and a photo-plating process;

[0014] S8. The photoresist is removed by peeling off;

[0015] S9. The excess second metal layer and the first metal layer under the regions without the third metal layer are removed by a wet process.

[0016] Further, the mass ratio of the W metal and the Ti metal in the WTi mixed metal target is 2:8-5:5.

[0017] 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.

[0018] Further, the first metal layer serves as a seed layer, and the second metal layer serves as a seed layer for electroplating of the third metal layer.

[0019] Further, in S8, the third metal layer, the fourth metal layer, the fifth metal layer, and the sixth metal layer on the photoresist are peeled off together with the photoresist.

[0020] Further, the sixth metal layer serves as a gold wire bonding layer.

[0021] Further, the thickness of the first metal layer (1) is 40-150 nm, the thickness of the second metal layer (2) is 20-160 nm, the thickness of the third metal layer (3) is 350-1300 nm, the thickness of the fourth metal layer (4) is 40-150 nm, the thickness of the fifth metal layer (5) is 20-160 nm, and the thickness of the sixth metal layer (6) is 1.1-5 μm.

[0022] Further, in S9, the wet process is used to remove the excess metal layer 2 under the non-metal layer 3 area, the wet solution used is potassium cyanide: 647 gold removal concentrated solution: water volume ratio of 1:5:200 mixture; the wet process is used to remove the excess metal layer 1 under the non-metal layer 3 area, the wet solution used is hydrogen peroxide, the temperature is 60℃, and the concentration is 26%.

[0023] Further, the purity of the Au metal target is higher than 99.999%.

[0024] 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, Ni metal, WTi mixed metal, Au metal, Au metal in turn upwards as the upper plate of the capacitor has higher adhesion and high bonding tensile strength, and can still maintain excellent performance after experiencing high-strength reliability test. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the present application.

[0026] Figure 2 It is a schematic diagram of the position of the first metal layer.

[0027] Figure 3 It is a schematic diagram of the position of the photoresist.

[0028] Figure 4 It is a schematic diagram of the position of the second metal layer.

[0029] Figure 5 It is a schematic diagram of the position of the third metal layer.

[0030] Figure 6 It is a schematic diagram of the position of the fourth metal layer.

[0031] Figure 7 It is a schematic diagram of the position of the fifth metal layer.

[0032] Figure 8 It is a schematic diagram of the position of the sixth metal layer.

[0033] Figure 9 It is a schematic diagram of the overall structure when the excess metal layer is not removed. DETAILED DESCRIPTION

[0034] The present application discloses a metal thin layer structure for surface bonding and a preparation method. Figure 1As shown below, the metal thin-layer structure for surface bonding provided by the present invention will be further described in detail: The metal thin-layer structure for surface bonding includes a first metal layer 1, a second metal layer 2 disposed on the first metal layer 1, a third metal layer 3 disposed on the second metal layer 2, a fourth metal layer 4 disposed on the third metal layer 3, a fifth metal layer 5 disposed on the fourth metal layer 4, and a sixth metal layer 6 disposed on the fifth metal layer 5; the first metal layer 1 is a WTi mixed metal, the second metal layer 2 is Au metal, the third metal layer 3 is Ni metal, the fourth metal layer 4 is a WTi mixed metal, the fifth metal layer 5 is Au metal, and the sixth metal layer 6 is Au metal.

[0035] Please see Figures 2 to 9 As shown below, the method for preparing the metal thin-film structure for surface bonding provided by the present invention will be further described in detail:

[0036] Step 1: A first metal layer 1 with a thickness of 100 nm is prepared on the surface of the capacitor dielectric 8 using a WTi hybrid metal target and a magnetron sputtering process. The W to Ti mass ratio of the WTi hybrid metal target is 3:7. The first metal layer 1 serves as a seed layer to increase the adhesion between the capacitor dielectric (8) and the metal. Figure 2 As shown.

[0037] Step 2: A second metal layer 2 with a thickness of 95 nm is prepared using an Au metal target and a magnetron sputtering process. The Au metal target has a purity higher than 99.999%. The second metal layer 2 serves as a seed layer for the electroplating of the third metal layer 3, enhancing adhesion. Figure 3 As shown.

[0038] Step 3: Apply and cure photoresist 7 to the areas where the third metal layer 3 does not need to be prepared using photolithography, leaving the areas where the third metal layer 3 needs to be prepared exposed, such as... Figure 4 As shown.

[0039] Step 4: A third metal layer 3 with a thickness of 800 nm is prepared using a Ni metal target and electroplating process. The third metal layer 3 can improve the bonding strength of the overall structure, such as... Figure 5 As shown.

[0040] Step 5: A fourth metal layer 4 with a thickness of 100 nm is prepared using a WTi hybrid metal target and magnetron sputtering. The W to Ti mass ratio of the WTi hybrid metal target is 3:7. Figure 6 As shown.

[0041] Step 6: A fifth metal layer 5 with a thickness of 95 nm is prepared using an Au metal target and a magnetron sputtering process. The Au metal target has a purity higher than 99.999%. Figure 7as shown.

[0042] Step 7: A sixth metal layer 6 with a thickness of 1.5 μm is prepared by using an Au metal target and a photo-plating process, and the sixth metal layer 6 is used as a gold wire bonding layer, which is used for gold wire bonding and simultaneously releases stress during the bonding process, as shown in Fig. 6. Figure 8

[0043] Step 8: The photoresist 7 is removed by a wet solvent, and the third metal layer 3, the fourth metal layer 4, the fifth metal layer 5 and the sixth metal layer 6 on the photoresist 7 are removed, as shown in Fig. 7. Figure 9

[0044] Step 9: The excess second metal layer 2 under the area without the third metal layer 3 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 90 seconds, as shown in Fig. 8. Figure 9

[0045] Step 10: The excess first metal layer 1 under the area without the third metal layer 3 is removed by a wet process, and the wet solution used is hydrogen peroxide, the temperature of the hydrogen peroxide is 60°C, the concentration is 26%, and the corrosion time is 110 seconds, as shown in Fig. 9. Figure 9

[0046] The bonding strength of the prepared metal thin layer is tested and compared with a metal thin layer sheet in the prior art: 22 points on the metal thin layer prepared by the present application are measured for bonding strength, and the results are all greater than 60 grams, which meets the characteristics of high bonding tensile strength; and the bonding strength of 22 points at the same position of the metal thin layer sheet in the prior art is between 12.5 grams and 19.9 grams, which has a large gap from the index of the bonding strength of the metal thin layer structure prepared by the present application.​​​​

Claims

1. A thin metal layer structure for surface bonding, characterized in that, It includes a first metal layer (1), a second metal layer (2) disposed on the first metal layer (1), a third metal layer (3) disposed on the second metal layer (2), a fourth metal layer (4) disposed on the third metal layer (3), a fifth metal layer (5) disposed on the fourth metal layer (4), and a sixth metal layer (6) disposed on the fifth metal layer (5); the first metal layer (1) is a WTi mixed metal, the second metal layer (2) is Au metal, the third metal layer (3) is Ni metal, the fourth metal layer (4) is a WTi mixed metal, the fifth metal layer (5) is Au metal, and the sixth metal layer (6) is Au metal. The first metal layer (1) is prepared using a WTi mixed metal target and a magnetron sputtering process; the WTi mixed metal target contains... The mass ratio of W metal to Ti metal is 2:8 to 5:5; the capacitor dielectric (8) is formed on the surface of the capacitor dielectric (8) by magnetron sputtering; the first metal layer (1) is used as a seed layer, the second metal layer (2) is used as a seed layer for electroplating the third metal layer (3); the sixth metal layer (6) is used as a gold wire bonding layer; the thickness of the first metal layer (1) is 40 to 150 nm, the thickness of the second metal layer (2) is 20 to 160 nm, the thickness of the third metal layer (3) is 350 to 1300 nm, the thickness of the fourth metal layer (4) is 40 to 150 nm, the thickness of the fifth metal layer (5) is 20 to 160 nm, and the thickness of the sixth metal layer (6) is 1.1 to 5 μm.

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