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 Pd metal layer, a Ni metal layer, a Pd metal layer and an Au metal layer. The metal thin layer is prepared by a magnetron sputtering process, an electroplating process or 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 a high-strength reliability test.

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 elements 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 Pd metal, the fourth metal layer is a Ni metal, the fifth metal layer is a Pd metal, and the sixth metal layer is an Au metal.

[0006] A preparation method of the metal thin layer structure for surface bonding 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. Photoresist is coated and cured on the areas where a third metal layer does not need to be prepared using photolithography, thus exposing the areas where a third metal layer needs to be prepared.

[0010] S4. Prepare the third metal layer;

[0011] S5. Prepare the fourth metal layer;

[0012] S6. Prepare the fifth metal layer;

[0013] S7. Prepare the sixth metal layer;

[0014] S8. Remove the photoresist;

[0015] S9. Remove the excess second metal layer and first metal layer below the area without the third metal layer.

[0016] Furthermore, the mass ratio of W metal to Ti metal in the WTi mixed metal target is 6:4 to 2:8.

[0017] Furthermore, in S1, a capacitor dielectric is prepared, and a first metal layer is formed on the surface of the capacitor dielectric by magnetron sputtering.

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

[0019] Furthermore, in S8, while removing the photoresist, the third, fourth, fifth, and sixth metal layers on the photoresist are also peeled off along with the photoresist.

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

[0021] Furthermore, the thickness of the first metal layer is 40–140 nm, the thickness of the second metal layer is 20–150 nm, the thickness of the third metal layer is 50–400 nm, the thickness of the fourth metal layer is 300–1200 nm, the thickness of the fifth metal layer is 50–400 nm, and the thickness of the sixth metal layer is 1.1–5.5 μm.

[0022] Furthermore, in S9, when using a wet process to remove the excess second metal layer below the region without the third metal layer, the wet solution used is a mixture of potassium cyanide, 647 gold removal concentrate, and water in a volume ratio of 1:5:200; when using a wet process to remove the excess first metal layer below the region without the third metal layer, the wet solution used is hydrogen peroxide at a temperature of 60°C and a concentration of 26%.

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

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: The metal thin layer structure prepared by WTi mixed metal, Au metal, Pd metal, Ni metal, Pd metal and Au metal in sequence upwards is used as the upper electrode of the capacitor, which has high adhesion and high bonding tensile strength, and can still maintain excellent performance after undergoing high-strength reliability test. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention.

[0026] Figure 2 This is a schematic diagram showing the location of the first metal layer in this invention.

[0027] Figure 3 This is a schematic diagram showing the location of the photoresist described in this invention.

[0028] Figure 4 This is a schematic diagram showing the location of the second metal layer in this invention.

[0029] Figure 5 This is a schematic diagram showing the location of the third metal layer described in this invention.

[0030] Figure 6 This is a schematic diagram showing the location of the fourth metal layer described in this invention.

[0031] Figure 7 This is a schematic diagram showing the location of the fifth metal layer described in this invention.

[0032] Figure 8 This is a schematic diagram showing the location of the sixth metal layer described in this invention.

[0033] Figure 9 This is a schematic diagram of the overall structure of the present invention when the excess metal layer has not been removed. Detailed Implementation

[0034] This invention discloses a thin metal layer structure for surface bonding and its preparation method. Please refer to [link / reference]. Figure 1 As 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 Pd metal, the fourth metal layer 4 is Ni metal, the fifth metal layer 5 is Pd metal, and the sixth metal layer 6 is Au metal.

[0035] Please seeFigures 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 105 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 dielectric and the metal. Figure 2 As shown.

[0037] Step 2: A second metal layer 2 with a thickness of 80 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 200 nm is prepared using Pd metal and electroplating or magnetron sputtering. The third metal layer 3 can improve the adhesion between the second metal layer 2 and the fourth metal layer 4, such as... Figure 5 As shown.

[0040] Step 5: A fourth metal layer 4 with a thickness of 600 nm is prepared using Ni metal and electroplating or magnetron sputtering processes. This fourth metal layer 4 can improve the bonding strength of the overall structure, such as... Figure 6 As shown.

[0041] Step 6: A fifth metal layer 5 with a thickness of 200 nm is prepared using Pd metal and electroplating or magnetron sputtering. The fifth metal layer 5 improves the adhesion between the fourth metal layer 4 and the sixth metal layer 6. Figure 7 As shown.

[0042] Step 7: A sixth metal layer 6 with a thickness of 1.5 μm is prepared using Au metal through electroplating, evaporation, or magnetron sputtering. The sixth metal layer 6 serves as the gold wire bonding layer, not only for gold wire bonding but also for stress relief during the bonding process. Figure 8 As shown.

[0043] Step 8: The photoresist 7 is stripped using a wet solvent stripping process. The third metal layer 3, fourth metal layer 4, fifth metal layer 5, and sixth metal layer 6 on the photoresist 7 are then stripped away. Figure 9 As shown.

[0044] Step 9: Remove the excess second metal layer 2 below the area without the third metal layer 3 using a wet process. The wet solution used is a mixture of potassium cyanide, 647 gold removal concentrate, and water at a volume ratio of 1:5:200, and the etching time is 95 seconds. Figure 9 As shown.

[0045] Step 10: Remove the excess first metal layer 1 below the area without the third metal layer 3 using a wet process. The wet solution used is hydrogen peroxide, with a temperature of 60℃, a concentration of 26%, and an etching time of 90 seconds. Figure 9 As shown.

[0046] By testing the bonding strength of the prepared metal thin layer and comparing it with a metal thin layer sheet in the prior art: the bonding strength of 22 points on the metal thin layer prepared by the present invention was measured, and the results were all greater than 60 grams, which is consistent with the characteristics of high bonding tensile strength; while the bonding strength of the 22 points at the same location of the prior art metal thin layer sheet was between 12.5 grams and 19.9 grams, which is significantly different from the bonding strength index of the metal thin layer structure prepared by the present invention.

Claims

1. A method for preparing a thin metal 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 (8) is prepared, and the first metal layer (1) is formed on the surface of the capacitor dielectric (8) by magnetron sputtering process. The mass ratio of W metal to Ti metal in the WTi hybrid metal target is 6:4~2:8; the thickness of the first metal layer (1) is 40~140nm. 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 20~150nm. S3. Photoresist (7) is applied and cured to the area where the third metal layer (3) does not need to be prepared by photolithography, exposing the area where the third metal layer (3) needs to be prepared. S4. The third metal layer (3) is made of Pd metal and prepared by electroplating or magnetron sputtering process. The thickness of the third metal layer (3) is 50~400nm. S5. The fourth metal layer (4) is made of Ni metal and prepared by electroplating or magnetron sputtering. The thickness of the fourth metal layer (4) is 300~1200nm. S6. The fifth metal layer (5) is made of Pd metal and prepared by electroplating or magnetron sputtering. The thickness of the fifth metal layer (5) is 50~400nm. S7. The sixth metal layer (6) is made of Au metal and prepared by electroplating, evaporation or magnetron sputtering process. The thickness of the sixth metal layer (6) is 1.1~5.5μm. S8. Remove the photoresist (7). While removing the photoresist (7), the third metal layer (3), fourth metal layer (4), fifth metal layer (5), and sixth metal layer (6) on the photoresist (7) are peeled off along with the photoresist (7). S9. Remove the excess second metal layer (2) and first metal layer (1) below the area without the third metal layer (3); The first metal layer (1) serves as a seed layer, the second metal layer (2) serves as a seed layer for electroplating the third metal layer (3), and the sixth metal layer (6) serves as a gold wire bonding layer.

2. The method for preparing a metal thin-film structure for surface bonding according to claim 1, characterized in that, In S9, when the wet process is used to remove the excess second metal layer (2) below the region without the third metal layer (3), the wet 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 first metal layer (1) below the region without the third metal layer (3), the wet 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.

Images