A pad structure of a MEMS device and a method of manufacturing the same

Abstract

The application provides a preparation method of a pad of a MEMS device, which comprises 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-throw silicon wafer. The application increases the transition metal layer and the transition dielectric layer structure in the pad, reduces the risk of pad failure caused by stress mismatch between the metal layers and between the metal layer and the dielectric layer, and increases the reliability of the pad.

Description

TECHNICAL FIELD

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

[0002] The pad is one of the key components of a micro-electro-mechanical 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 the MEMS pad directly affects the performance, reliability, service life, environmental adaptability, and yield of the chip. A high-quality MEMS pad can ensure a high-stability 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, a high-quality MEMS pad can improve the environmental adaptability of the chip, such as temperature, humidity, vibration, etc., so that the chip has a wider application prospect. A high-quality pad can ensure the stable performance of the chip during the service life, reduce the failure rate, and improve the user's satisfaction. A high-quality MEMS pad can improve the production yield of the chip, thereby reducing production costs and improving the competitiveness of enterprises. In order to ensure the high performance, reliability, service life, and environmental adaptability of the chip, attention must be paid to the design, production, and quality control of the MEMS pad.

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

[0005] For traditional MEMS devices, no transition metal layer or transition dielectric layer is added in the pad to reduce stress, so when the pad is subjected to temperature and force during packaging and wire bonding, stress mismatch between different metals or between the metal and the dielectric layer is prone to occur, resulting in pad failure. SUMMARY

[0006] The present application is to overcome the deficiencies in the prior art, and to provide a pad structure of a MEMS device that can improve the quality of the MEMS pad, save the cost of tape-out, and improve the performance of the product.

[0007] The present application provides the following technical solutions:

[0008] A preparation method of a pad of a MEMS device, characterized in that it comprises the following steps: S1, taking a double-etched silicon wafer, and preparing a first dielectric layer on the upper surface of the double-etched silicon wafer;

[0009] S2, a group of first through holes are prepared on the first dielectric layer by photoetching, dielectric etching and adhesive removing process in sequence;

[0010] S3, the first transition metal layer is formed on the first dielectric layer and fills the first through holes completely, so that the first transition metal layer is electrically connected to the double-polished silicon wafer;

[0011] S4, the first metal layer is prepared on the upper surface of the first transition metal layer and is in communication with the internal circuit of the MEMS chip;

[0012] S5, the second transition metal layer is prepared on the upper surface of the first metal layer;

[0013] S6, the second dielectric layer is prepared on the upper surface of the second transition metal layer;

[0014] S7, a group of second through holes are prepared on the second dielectric layer by photoetching, dielectric etching and adhesive removing process in sequence;

[0015] S8, the third transition metal layer is formed on the second dielectric layer and fills the second through holes completely, so that the third transition metal layer is electrically connected to the second transition metal layer;

[0016] S9, the second metal layer is prepared on the third transition metal layer and is in communication with the internal circuit of the MEMS chip;

[0017] S10, the transition dielectric layer is formed on the second metal layer;

[0018] S11, the third through hole is prepared on the transition dielectric layer by photoetching, dielectric etching and adhesive removing process in sequence to form the wire bonding area of the pad.

[0019] On the basis of the above technical solutions, the following further technical solutions can be provided:

[0020] The first dielectric layer and the second dielectric layer are made of the same material, i.e. silicon dioxide, and are prepared by different methods.

[0021] The first transition metal layer, the second transition metal layer and the third transition metal layer are made of the same material, i.e. titanium, and are prepared by sputtering.

[0022] The first metal layer and the second metal layer are prepared by sputtering, and are made of different materials.

[0023] The second dielectric layer and the transition dielectric layer are prepared by chemical reaction deposition, and are made of different materials.

[0024] The preparation method of a pad of a MEMS device comprises the following steps: S1, taking a double-etched silicon wafer 1, and preparing a first dielectric layer 2 of silicon dioxide on the upper surface of the double-etched silicon wafer 1 by an oxidation method.

[0025] Advantages of the application:

[0026] The preparation steps are clear and convenient to implement, the risk of pad failure caused by stress mismatch between metal layers and between metal layers and dielectric layers is reduced by adding suitable transition metal layers and transition dielectric layer structures in the pad, and the reliability of the pad is increased. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The structure diagram of the pad prepared after the preparation steps are completed. DETAILED DESCRIPTION

[0028] A preparation method of a pad of a MEMS device comprises the following steps: S1, taking a double-etched silicon wafer 1, and preparing a first dielectric layer 2 of silicon dioxide on the upper surface of the double-etched silicon wafer 1 by an oxidation method.

[0029] S2, a group of first through holes 3 penetrating through the first dielectric layer 2 are prepared on the first dielectric layer 2 by photoetching, dielectric etching and adhesive removing processes in sequence.

[0030] S3, a first transition metal layer 4 is prepared on the first dielectric layer 2, the first transition metal layer 4 completely fills the first through holes 3, and the first transition metal layer 4 forms an electrical connection with the double-etched silicon wafer 1. The first transition metal layer 4 is made of titanium and is prepared by sputtering.

[0031] S4, a first metal layer 5 made of tungsten is prepared on the upper surface of the first transition metal layer 4 by sputtering, and the first metal layer 5 covers the upper surface of the entire first transition metal layer 4. The first metal layer 5 forms an electrical connection with the internal circuit of the MEMS chip.

[0032] S5, a second transition metal layer 6 made of titanium is prepared on the upper surface of the first metal layer 5 by sputtering, and the second transition metal layer 6 covers the upper surface of the entire first metal layer 5.

[0033] S6, a second dielectric layer 7 made of silicon dioxide is prepared on the upper surface of the second transition metal layer 6 by a chemical reaction deposition method.

[0034] S7. A set of second through holes 8 penetrating the second dielectric layer 7 are sequentially prepared on the second dielectric layer 7 by photolithography, dielectric etching and resist removal processes.

[0035] S8. A third transition metal layer 9 covering the second dielectric layer 7 is prepared on the second dielectric layer 7 by sputtering. A portion of 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 form an electrical connection.

[0036] S9. A second metal layer 10 of metallic material is prepared on the surface of the third transition metal layer 9 by sputtering. The second metal layer 10 forms an electrical connection with the internal circuit of the MEMS chip.

[0037] S10. A transition dielectric layer 11 is prepared on the surface of the second metal layer 10 by chemical reaction deposition. The material of the transition dielectric layer 11 is silicon nitride.

[0038] S11. A third via 12 is formed on the transition dielectric layer 11 by photolithography, dielectric etching and resist removal processes, thereby forming the bonding area of ​​the pad.

[0039] like Figure 1 As shown, a bonding pad for a MEMS device is fabricated using the above-described fabrication method. The bonding pad comprises, from bottom to top, 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. The first transition metal layer 4 forms an electrical connection with the double-polished silicon wafer 1, and the second transition metal layer 6 and the third transition metal layer 9 form an electrical connection. A third via 12 is provided on the transition dielectric layer 11 to form the wire bonding area of ​​the bonding pad.

[0040] By using the first transition metal layer 4, the second transition metal layer 6, and the third transition metal layer 9, the adhesion between the metal layer and the dielectric layer is improved, while the stress on the solder pads is reduced.

Claims

1. A method for fabricating pads for a MEMS device, characterized in that: It includes the following steps: S1. Take a double-polished silicon wafer (1) and prepare a first dielectric layer (2) on the upper surface of the double-polished silicon wafer (1). S2. A set of first through holes (3) are prepared on the first dielectric layer (2) by photolithography, dielectric etching and resist removal processes in sequence. S3. A first transition metal layer (4) is covered on the first dielectric layer (2). The first transition metal layer (4) completely fills the first through hole (3), so that the first transition metal layer (4) and the double-polished silicon wafer (1) form an electrical connection. S4. A first metal layer (5) that communicates and cooperates with the internal circuit of the MEMS chip is prepared on the upper surface of the first transition metal layer (4). S5. A second transition metal layer (6) is prepared on the upper surface of the first metal layer (5). S6. A second dielectric layer (7) is prepared on the upper surface of the second transition metal layer (6). S7. A set of second through holes (8) are prepared on the second dielectric layer (7) by photolithography, dielectric etching and resist removal processes in sequence. S8. A third transition metal layer (9) is covered on the second dielectric layer (7). 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) form an electrical connection. S9. A second metal layer (10) is fabricated on the third transition metal layer (9) to communicate and cooperate with the internal circuit of the MEMS chip. S10. A transition dielectric layer (11) is covered on the second metal layer (10). S11. A third via (12) is formed on the transition dielectric layer (11) by photolithography, dielectric etching and resist removal processes to form the bonding area of ​​the pad; 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 and reduce the stress on the pads.

2. The method for fabricating a bonding pad for 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, silicon dioxide, but they are prepared by different methods.

3. The method for fabricating a bonding pad for 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 all made of titanium metal and are prepared by sputtering.

4. The method for fabricating a bonding pad for 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 they are made of different materials.

5. The method for fabricating a bonding pad for 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 the two are made of different materials.

6. A pad fabricated using the method for fabricating a MEMS device pad as described in claim 1, characterized in that: It 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) arranged sequentially from bottom to top. The first transition metal layer (4) forms an electrical connection with the double-polished silicon wafer (1), and the second transition metal layer (6) and the third transition metal layer (9) form an electrical connection. A third through-hole (12) is provided on the transition dielectric layer (11) to form the wire bonding area of ​​the solder pad.

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