Pad structure of MEMS device and preparation method thereof

Abstract

The invention provides a preparation method of a bonding pad of an MEMS device. The preparation method comprises the step of sequentially preparing a first dielectric layer, a first transition metal layer, a first metal layer, a second transition metal layer, a second dielectric layer, a third transition metal layer, a second metal layer (10) and a transition dielectric layer (11) on a double-parabolic silicon wafer. The proper transition metal layer and transition dielectric layer structures are additionally arranged in the bonding pad, so that the risk of bonding pad failure caused by stress mismatch between the metal layers and between the metal layers and the dielectric layers is reduced, and the reliability of the bonding pad is improved.

Description

Technical Field

[0001] The present invention relates to the field of chip manufacturing, and in particular to a pad structure of a MEMS device and a preparation method thereof. Background Art

[0002] The pad is one of the key components of the micro-electromechanical system (MEMS) chip. During the chip packaging process, the pad can realize the electrical connection between the chip and the external ASIC circuit.

[0003] The quality of MEMS pads directly affects the performance, reliability, service life, environmental adaptability, and yield of the chip. High-quality MEMS pads can ensure a highly stable electrical connection between the chip and the external circuit, which helps to reduce signal transmission loss, improve the signal transmission speed of the circuit and the overall performance of the chip. At the same time, high-quality MEMS pads can improve the environmental adaptability of the chip, such as temperature, humidity, vibration, etc., so that the chip has a wider application prospect. High-quality pads can ensure that the chip has stable performance during its service life, reduce the failure rate, and improve user satisfaction. High-quality MEMS pads can improve the production yield of the chip, thereby reducing production costs and improving the competitiveness of the enterprise. In order to ensure the high performance, reliability, service life and environmental adaptability of the chip, it is necessary to pay attention to the design, production and quality control of MEMS pads.

[0004] During the manufacturing process, MEMS pads need to go through processes such as metal evaporation, metal sputtering, eutectic bonding, metal patterning and annealing. Different processes will directly change the stress between metal and metal in the pad or the stress between metal and dielectric layer, resulting in stress mismatch between different metals or between metal and dielectric layer, and reducing the adhesion between different metals or between metal and dielectric layer.

[0005] For traditional MEMS devices, no transition metal layer and transition dielectric layer are added to the pad to reduce stress. Therefore, when the pad is subjected to temperature and force during packaging and wire bonding, stress mismatch is easily generated between different metals or between metal and dielectric layers, resulting in pad failure. Summary of the invention

[0006] The present invention aims to overcome the deficiencies in the prior art and to provide a pad structure for a MEMS device that improves the quality of a MEMS pad, can save wafer fabrication costs, and improves product performance.

[0007] This application provides the following technical solutions: A method for preparing a pad of a MEMS device, characterized in that it comprises the following steps: S1, taking a double-polished silicon wafer, and preparing a first dielectric layer on the upper surface of the double-polished silicon wafer; S2, preparing a group of first through holes on the first dielectric layer by sequentially performing photolithography, dielectric etching, and resist stripping processes; S3, a first transition metal layer is covered on the first dielectric layer, and the first transition metal layer completely fills the first through hole, so that the first transition metal layer is electrically connected to the double-polished silicon wafer; S4, preparing a first metal layer on the upper surface of the first transition metal layer that is connected to and coordinated with the internal circuit of the MEMS chip; S5, preparing a second transition metal layer on the upper surface of the first metal layer; S6, preparing a second dielectric layer on the upper surface of the second transition metal layer; S7, preparing a group of second through holes on the second dielectric layer by sequentially performing photolithography, dielectric etching, and resist stripping processes; S8, a third transition metal layer is covered on the second dielectric layer, and the third transition metal layer completely fills the second through hole, so that the third transition metal layer is electrically connected to the second transition metal layer; S9, preparing a second metal layer on the third transition metal layer to communicate with the internal circuit of the MEMS chip; S10, a transition dielectric layer is covered on the second metal layer; S11, preparing a third through hole on the transition dielectric layer by sequentially performing photolithography, dielectric etching, and resist stripping processes to form a bonding area of ​​a pad.

[0008] On the basis of the above technical solutions, there are also the following further technical solutions: The first dielectric layer and the second dielectric layer are made of the same material, namely silicon dioxide, and are prepared in different ways.

[0009] The first transition metal layer, the second transition metal layer and the third transition metal layer are made of the same material, namely titanium metal, and are prepared by sputtering.

[0010] The first metal layer and the second metal layer are both prepared by sputtering, and the materials of the two are different.

[0011] The second dielectric layer and the transition dielectric layer are both prepared by chemical reaction deposition, and the two are made of different materials.

[0012] A pad prepared by a method for preparing a pad for a MEMS device is characterized in that: it includes a double-polished silicon wafer, a first dielectric layer, a first transition metal layer, a first metal layer, a second transition metal layer, a second dielectric layer, a third transition metal layer, a second metal layer and a transition dielectric layer distributed in sequence from bottom to top, an electrical connection is formed between the first transition metal layer and the double-polished silicon wafer, and an electrical connection is formed between the second transition metal layer and the third transition metal layer; a third through hole is provided in the transition dielectric layer to form a wiring area of ​​the pad.

[0013] Advantages of the invention: The preparation steps of the present invention are clear and easy to implement. By adding a suitable transition metal layer and transition dielectric layer structure in the pad, the risk of pad failure caused by stress mismatch between metal layers and between the metal layer and the dielectric layer is reduced, thereby increasing the reliability of the pad. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of the solder pad obtained after the preparation steps provided by the present invention are completed. DETAILED DESCRIPTION

[0015] A method for preparing a pad of a MEMS device comprises the following steps: S1, taking a double-polished silicon wafer 1, and preparing a first dielectric layer 2 of silicon dioxide material on the upper surface of the double-polished silicon wafer 1 by oxidation.

[0016] S2, preparing a group of first through holes 3 penetrating the first dielectric layer 2 on the first dielectric layer 2 by sequentially using photolithography, dielectric etching, and resist stripping processes.

[0017] S3, a first transition metal layer 4 is covered on the first dielectric layer 2, and the first transition metal layer 4 completely fills the first through hole 3, so that the first transition metal layer 4 forms an electrical connection with the double-polished silicon wafer 1. The first transition metal layer 4 is made of titanium metal and is prepared by sputtering.

[0018] S4, a first metal layer 5 made of tungsten metal is prepared on the upper surface of the first transition metal layer 4 by sputtering, and the first metal layer 5 covers the entire upper surface of the first transition metal layer 4. The first metal layer 5 is electrically connected with the internal circuit of the MEMS chip.

[0019] S5 . Prepare a second transition metal layer 6 made of titanium metal on the upper surface of the first metal layer 5 by sputtering. The second transition metal layer 6 covers the entire upper surface of the first metal layer 5 .

[0020] S6. A second dielectric layer 7 made of silicon dioxide is prepared on the upper surface of the second transition metal layer 6 by chemical reaction deposition.

[0021] S7 , preparing a group of second through holes 8 penetrating the second dielectric layer 7 on the second dielectric layer 7 by sequentially performing photolithography, dielectric etching, and resist stripping processes.

[0022] S8. Prepare a third transition metal layer 9 covering the second dielectric layer 7 on the second dielectric layer 7 by sputtering, and a portion of the third transition metal layer 9 completely fills the second through hole 8, so that the third transition metal layer 9 is electrically connected to the second transition metal layer 6.

[0023] S9. A second metal layer 10 made of metal is prepared on the upper surface of the third transition metal layer 9 by sputtering. The second metal layer 10 is electrically connected with the internal circuit of the MEMS chip.

[0024] S10, preparing a transition dielectric layer 11 on the upper surface of the second metal layer 10 by chemical reaction deposition, and the material of the transition dielectric layer 11 is silicon nitride.

[0025] S11 , preparing a third through hole 12 on the transition dielectric layer 11 by sequentially performing photolithography, dielectric etching, and resist stripping processes to form a bonding area of ​​a pad.

[0026] like Figure 1 As shown, a pad for a MEMS device is prepared by the above-mentioned preparation method, which includes a double-polished silicon wafer 1, a first dielectric layer 2, a first transition metal layer 4, a first metal layer 5, a second transition metal layer 6, a second dielectric layer 7, a third transition metal layer 9, a second metal layer 10 and a transition dielectric layer 11, which are distributed in sequence from bottom to top. An electrical connection is formed between the first transition metal layer 4 and the double-polished silicon wafer 1, and an electrical connection is formed between the second transition metal layer 6 and the third transition metal layer 9; a third through hole 12 is provided on the transition dielectric layer 11 to form a wiring area of ​​the pad.

[0027] The first transition metal layer 4 , the second transition metal layer 6 and the third transition metal layer 9 improve the adhesion between the metal layer and the dielectric layer, while achieving the technical effect of reducing the pad stress.

Claims

1. A method for preparing a pad of a MEMS device, characterized in that: It includes the following steps: S1, taking a double-polished silicon wafer (1), and preparing a first dielectric layer (2) on the upper surface of the double-polished silicon wafer (1); S2, preparing a group of first through holes (3) on the first dielectric layer (2) by sequentially using photolithography, dielectric etching, and degumming processes; S3, a first transition metal layer (4) is covered on the first dielectric layer (2), the first transition metal layer (4) completely filling the first through hole (3), so that the first transition metal layer (4) and the double-polished silicon wafer (1) are electrically connected; S4, preparing a first metal layer (5) on the upper surface of the first transition metal layer (4) that is connected to and cooperates with the internal circuit of the MEMS chip; S5, preparing a second transition metal layer (6) on the upper surface of the first metal layer (5); S6. Preparing a second dielectric layer (7) on the upper surface of the second transition metal layer (6); S7, preparing a group of second through holes (8) on the second dielectric layer (7) by sequentially performing photolithography, dielectric etching, and resist stripping processes; S8. A third transition metal layer (9) is covered on the second dielectric layer (7), and the third transition metal layer (9) completely fills the second through hole (8), so that the third transition metal layer (9) and the second transition metal layer (6) are electrically connected and matched; S9, preparing a second metal layer (10) on the third transition metal layer (9) to communicate with the internal circuit of the MEMS chip; S10, a transition dielectric layer (11) is covered on the second metal layer (10); S11, preparing a third through hole (12) on the transition dielectric layer (11) by sequentially performing photolithography, dielectric etching, and degumming processes to form a bonding area of ​​a pad.

2. The method for preparing a pad of a MEMS device according to claim 1, characterized in that: The first dielectric layer (2) and the second dielectric layer (7) are made of the same material, namely silicon dioxide, but are prepared in different ways.

3. The method for preparing a pad of a MEMS device according to claim 1, characterized in that: The first transition metal layer (4), the second transition metal layer (6) and the third transition metal layer (9) are made of the same material, namely titanium metal, and are prepared by sputtering.

4. The method for preparing a pad of a MEMS device according to claim 1, characterized in that: The first metal layer (5) and the second metal layer (10) are both prepared by sputtering, and are made of different materials.

5. The method for preparing a pad of a MEMS device according to claim 1, characterized in that: The second dielectric layer (7) and the transition dielectric layer (11) are both prepared by chemical reaction deposition, and are made of different materials.

6. A soldering pad made by the method for making a soldering pad for a MEMS device as claimed in claim 1, characterized in that: The invention comprises a double-polished silicon wafer (1), a first dielectric layer (2), a first transition metal layer (4), a first metal layer (5), a second transition metal layer (6), a second dielectric layer (7), a third transition metal layer (9), a second metal layer (10) and a transition dielectric layer (11) which are sequentially arranged from bottom to top; an electrical connection is formed between the first transition metal layer (4) and the double-polished silicon wafer (1); and an electrical connection is formed between the second transition metal layer (6) and the third transition metal layer (9); and a third through hole (12) is provided on the transition dielectric layer (11) to form a wiring area of ​​a pad.

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