A micro-mechanical structure of double-sided piezoelectric layer and a processing technology thereof

Abstract

The application provides a micro-mechanical structure with double-sided piezoelectric layers and a processing technology thereof, which comprises a structure layer with a first diaphragm, a second diaphragm with a third metal layer and a fourth metal layer, which is arranged on the structure layer and away from the first diaphragm, and a substrate with a fifth metal layer and a sixth metal layer, which is arranged on the second diaphragm, and the fifth metal layer is bonded with the fourth metal layer, and the sixth metal layer is bonded with the third metal layer. The micro-mechanical structure with double-sided piezoelectric layers and the processing technology thereof can solve the problem of difficult lead bonding of one side of the micro-mechanical structure with double-sided piezoelectric layers and the substrate, and improve the performance of the micro-mechanical structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of micro-mechanical structure technology, and in particular to a micro-mechanical structure with double-sided piezoelectric layer and a processing technology thereof. BACKGROUND

[0002] Micro Electro-Mechanical System (MEMS) is a new technology based on microelectronic technology and microprocessing technology. As early as in the 1960s, with the emergence and development of microelectronic technology, some creative scientists began to explore the use of silicon microprocessing method to manufacture sensors, actuators and controllers, and envisaged that they could be integrated in a small geometric space to form a highly automated, intelligent, mass-produced and low-cost microelectronic mechanical system. However, at this stage, there was no mature processing technology for manufacturing micro-mechanical structures and devices. Micro-mechanical was only a concept or design idea. In the 1980s, large-scale integrated circuit technology had matured, and people successfully manufactured micro-mechanical pressure sensors and a series of micro-mechanical parts such as micro-hinge, micro-link, micro-gear, etc. using IC technology. Micro-mechanical is a new and emerging frontier discipline that emerged in the late 1980s.

[0003] The micro-mechanical structure with double-sided piezoelectric layer can improve the performance of receiving signals and transmitting signals of the micro-mechanical structure because of the diaphragms on both sides. However, the micro-mechanical structure with double-sided piezoelectric layer is inconvenient for the electrical signal extraction of the diaphragm bonded to the substrate because of the diaphragm bonded to the substrate on one side. Usually, the electrical signal of the diaphragm bonded to the substrate can be extracted by punching a hole on the diaphragm not bonded to the substrate on the other side, which will damage the integrity of the diaphragm and affect the performance of the micro-mechanical structure. SUMMARY

[0004] The present application aims to overcome the above problems existing in the prior art and provide a micro-mechanical structure with double-sided piezoelectric layer and a processing technology thereof. The micro-mechanical structure extracts signals from the second diaphragm by bonding the fifth metal layer and the sixth metal layer to the fourth metal layer and the third metal layer on the substrate, thereby avoiding punching a hole on the first diaphragm, ensuring the integrity of the first diaphragm and improving the performance of the micro-mechanical structure.

[0005] To achieve the above technical purposes and effects, the present application realizes the following technical solutions:

[0006] The present application provides a micro-mechanical structure with double-sided piezoelectric layer, which comprises:

[0007] a structure layer with a first diaphragm;

[0008] A second diaphragm having a third metal layer and a fourth metal layer is disposed on the structural layer on the side away from the first diaphragm; and

[0009] A substrate having a fifth metal layer and a sixth metal layer is disposed on the second diaphragm, wherein the fifth metal layer is bonded to the fourth metal layer and the sixth metal layer is bonded to the third metal layer.

[0010] In one embodiment of the present invention, the first diaphragm includes:

[0011] A first metal layer is disposed on one side of the structural layer;

[0012] A first piezoelectric layer is disposed on the side of the first metal layer away from the structural layer; and

[0013] The second metal layer is disposed on the side of the first piezoelectric layer away from the first metal layer.

[0014] In one embodiment of the present invention, the first diaphragm further includes a first transition layer, which is located between the first metal layer and the first piezoelectric layer.

[0015] In one embodiment of the present invention, the second diaphragm further includes a second piezoelectric layer disposed between the third metal layer and the fourth metal layer.

[0016] In one embodiment of the present invention, the second diaphragm further includes a second transition layer, which is located between the third metal layer and the second piezoelectric layer.

[0017] In one embodiment of the present invention, a groove is provided on the substrate, and a cavity is formed between the groove and the structural layer.

[0018] In one embodiment of the present invention, a boss is further provided on the substrate, and the sixth metal layer is grown on the bonding surface of the boss and the third metal layer.

[0019] In one embodiment of the present invention, the micromechanical structure further includes a first pad and a second pad, wherein the first pad is disposed on the first metal layer and located on one side of the first piezoelectric layer, and the second pad is located on the second metal layer.

[0020] In one embodiment of the present invention, the micromechanical structure further includes a third pad located on the sixth metal layer and on one side of the third metal layer.

[0021] In one embodiment of the present invention, the micromechanical structure further includes a fourth pad, which is located on the fifth metal layer and on one side of the fourth metal layer.

[0022] The present invention also provides a fabrication process for micromechanical structures, the fabrication process comprising:

[0023] The sampling sheet has a double-sided piezoelectric layer structure;

[0024] The front and back sides of the sample are patterned and etched to obtain the first diaphragm and the second diaphragm;

[0025] The fifth metal layer and the sixth metal layer are grown on the substrate; and

[0026] The substrate and the second diaphragm are bonded together to obtain the micromechanical structure.

[0027] In summary, this invention provides a micromechanical structure with a double-sided piezoelectric layer and its fabrication process. This micromechanical structure, by setting a sixth metal layer and a fifth metal layer on a substrate, with the sixth metal layer bonded to the third metal layer and the fifth metal layer bonded to the fourth metal layer, allows the electrical signals of the third and fourth metal layers to be led out, facilitating wire connection. This solves the problem of difficult wire connection on one side of the double-sided piezoelectric layer micromechanical structure bonded to the substrate. Furthermore, it eliminates the need for drilling holes in the first diaphragm, maintaining the integrity of the micromechanical structure and improving its performance. Attached Figure Description

[0028] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0029] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0030] Figure 2 This is an exploded view of the overall structure of the present invention;

[0031] Figure 3 This is a partial structural schematic diagram of the present invention;

[0032] Figure 4 This is the present invention. Figure 4 The front view;

[0033] Figure 5 This is a schematic diagram of the structure of a substrate according to an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of the structure of the second diaphragm of the present invention;

[0035] Figures 7-1 to 7-4 This is a process diagram of the present invention.

[0036] The labels in the diagram are as follows: 1-substrate, 2-bore, 3-sixth metal layer, 4-first metal layer, 5-first piezoelectric layer, 6-second metal layer, 7-first diaphragm, 8-first pad, 9-second pad, 10-fourth pad, 11-third metal layer, 12-fourth metal layer, 13-second piezoelectric layer, 14-second diaphragm, 15-first transition layer, 16-structural layer, 17-second transition layer, 18-fifth metal layer, 19-groove, 20-third pad, 21-piezoelectric layer structure. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Please see Figures 1 to 4 This invention provides a micromechanical structure with a double-sided piezoelectric layer. The micromechanical structure includes a structural layer 16, which has a first diaphragm 7. The material of the structural layer 16 can be monocrystalline silicon, polycrystalline silicon, silicon nitride, or glass, but is not limited thereto. The first diaphragm 7 is disposed on one side of the structural layer 16. Specifically, the first diaphragm 7 includes a first metal layer 4, a first piezoelectric layer 5, and a second metal layer 6. The first metal layer 4 is disposed on one side of the structural layer 16. The thickness of the first metal layer 4 can be tens to hundreds of nanometers. This application does not limit the material of the first metal layer 4. In one embodiment of this invention, the first metal layer 4 can be gold, platinum, or aluminum. The first piezoelectric layer 5 is disposed on the first metal layer 4 and on the side away from the structural layer 16. The first piezoelectric layer 5 can be an aluminum nitride layer, a potassium sodium niobate layer, or lead zirconate titanate, but is not limited thereto. The second metal layer 6 is disposed on the first piezoelectric layer 5 on the side away from the first metal layer 4. The material of the second metal layer 6 can be tin, copper, or cobalt, but is not limited thereto. The second metal layer 6, the first piezoelectric layer 5, and the first metal layer 4 are etched away to remove excess portions, exposing a portion of the first metal layer 4. A passivation layer (not shown in the figure) may also be disposed on the second metal layer 6, located on the side of the second metal layer 6 away from the first piezoelectric layer 5, which serves to protect the second metal layer 6. In one embodiment of the invention, the first diaphragm 7 further includes a first transition layer 15, which is located between the first metal layer 4 and the first piezoelectric layer 5.

[0039] Please see Figures 1 to 4 , Figure 6In one embodiment of the present invention, the micromechanical structure further includes a second diaphragm 14, which is disposed on the structural layer 16 on the side away from the first diaphragm 7. Specifically, the second diaphragm 14 includes a third metal layer 11, a second piezoelectric layer 13, and a fourth metal layer 12, with the third metal layer 11 disposed on the other side of the structural layer 16. The material of the third metal layer 11 can be gold, molybdenum, or tungsten, but is not limited thereto. The second piezoelectric layer 13 is disposed on the third metal layer 11 on the side away from the structural layer 16. The second piezoelectric layer 13 can be an aluminum nitride layer, a scandium-doped aluminum nitride layer, or a lead zirconate titanate layer, but is not limited thereto. The fourth metal layer 12 is disposed on the second piezoelectric layer 13 on the side away from the third metal layer 11. This application does not limit the material of the fourth metal layer 12; in one embodiment of the present invention, the fourth metal layer 12 can be gold, platinum, or chromium. The second piezoelectric layer 13 and the fourth metal layer 12 are etched away to remove excess portions, exposing a portion of the third metal layer 11. The materials of the first transition layer 15 and the second transition layer 17 can be multiple layers, such as silicon dioxide, lead oxide, and silicon nitride, but are not limited thereto.

[0040] Please see Figures 1 to 5 In one embodiment of the present invention, the micromechanical structure further includes a substrate 1 having a fifth metal layer 18 and a sixth metal layer 3. The substrate 1 is disposed on the second diaphragm 14, and the fifth metal layer 18 is bonded to the fourth metal layer 12, and the sixth metal layer 3 is bonded to the third metal layer 11. In one embodiment of the present invention, a groove 19 is provided on the substrate 1, forming a cavity between the groove 19 and the structural layer. A boss 2 is also provided on the substrate 1, and the bonding surface of the boss 2 with the third metal layer 11 is used for growing the sixth metal layer 3. The inner wall of the boss 2 surrounds one end of the second piezoelectric layer 13 and the fourth metal layer 12. The fifth metal layer 18 is disposed on the bonding surface of the substrate 1 and the fourth metal layer 12, and the fifth metal layer 18 is bonded to the fourth metal layer 12 and extends to the outside of the fourth metal layer 12, thereby electrically communicating with the fourth metal layer 12 and extracting the electrical signal of the fourth metal layer 12. The sixth metal layer 3 is bonded to the third metal layer 11 and extends to the outside of the third metal layer 11, thereby electrically communicating with the third metal layer 11 and extracting the electrical signal of the third metal layer 11. The substrate 1 can be obtained from a silicon substrate wafer through two etching processes. Specifically, firstly, excess portions on the surface of the silicon substrate wafer are etched away to form a protrusion 2, and then a groove 19 is etched on the silicon substrate wafer to form the substrate 1. In one embodiment of the present invention, the groove 19 can also be etched through to form a substrate 1 with a through-groove.

[0041] Please see Figures 1 to 4In one embodiment of the present invention, the micromechanical structure further includes a first pad 8, a second pad 9, a third pad 20, and a fourth pad 10. The first pad 8 is disposed on the first metal layer 4 and is located on one side of the first piezoelectric layer 5. The second pad 9 is located on the second metal layer 6. The third pad 20 is located on the sixth metal layer 3 and is located on one side of the third metal layer 11. The third pad 20 can extract signals from the third metal layer 11. The fourth pad 10 is located on the fifth metal layer 18 and is located on one side of the fourth metal layer 12. The fourth pad 10 can extract signals from the fourth metal layer 12.

[0042] Please see Figures 7-1 to 7-4 The present invention also provides a fabrication process for micromechanical structures, the fabrication process comprising steps S1-S4:

[0043] The S1 sample sheet has a double-sided piezoelectric layer structure 21. The sample sheet includes a structural layer 16 and a two-layer piezoelectric layer structure 21.

[0044] S2 patterns both the front and back sides of the sample and etches the first diaphragm 7 and the second diaphragm 14. Specifically, the second metal layer 6, the first piezoelectric layer 5 and the first metal layer 4 are etched sequentially from top to bottom, and the lateral cross-sectional area of ​​the first metal layer 4 is larger than that of the first piezoelectric layer 5.

[0045] S3 grows a fifth metal layer 18 and a sixth metal layer 3 on the substrate 1. Metal layers are grown on the upper surface of the substrate to form the fifth metal layer 18 and the sixth metal layer 3. Specifically, before growing the fifth metal layer 18 and the sixth metal layer 3, the substrate 1 is etched. First, excess portions of the silicon substrate wafer surface are etched away to form a protrusion 2. Then, a groove 19 is etched on the silicon substrate wafer to form the substrate 1. In one embodiment of the invention, the groove 19 can be etched through to form a substrate 1 with a through-groove.

[0046] The S4 bonding substrate 1 and the second diaphragm 14 are bonded together, and the first pad 8, the second pad 9, the third pad 20, and the fourth pad 10 are grown and etched to obtain the micromechanical structure. Specifically, the sixth metal layer 3 is bonded to the third metal layer 11, and the fifth metal layer 18 is bonded to the fourth metal layer 12. The first pad 8 is grown and etched on the first metal layer 4, the second pad 9 is grown and etched on the second metal layer 6, the third pad 20 is grown and etched on the sixth metal layer 3, and the fourth pad 10 is grown and etched on the fifth metal layer 18.

[0047] In summary, this invention provides a micromechanical structure with a double-sided piezoelectric layer and its fabrication process. This micromechanical structure, by setting a sixth metal layer and a fifth metal layer on a substrate, with the sixth metal layer bonded to the third metal layer and the fifth metal layer bonded to the fourth metal layer, allows the electrical signals of the third and fourth metal layers to be led out, facilitating wire connection. This solves the problem of difficult wire connection on one side of the double-sided piezoelectric layer micromechanical structure bonded to the substrate. Furthermore, it eliminates the need for drilling holes in the first diaphragm, maintaining the integrity of the micromechanical structure and improving its performance.

[0048] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A micromechanical structure with double-sided piezoelectric layers, characterized in that, The micromechanical structure includes: A structural layer having a first diaphragm; A second diaphragm having a third metal layer and a fourth metal layer is disposed on the structural layer on the side away from the first diaphragm; and A substrate having a fifth metal layer and a sixth metal layer is disposed on the second diaphragm, wherein the fifth metal layer is bonded to the fourth metal layer and the sixth metal layer is bonded to the third metal layer; The substrate is also provided with a boss, and the bonding surface of the boss with the third metal layer is used to grow the sixth metal layer. The first diaphragm includes: A first metal layer is disposed on one side of the structural layer; A first piezoelectric layer is disposed on the side of the first metal layer away from the structural layer; and A second metal layer is disposed on the side of the first piezoelectric layer away from the first metal layer; The second diaphragm further includes a second piezoelectric layer disposed between the third metal layer and the fourth metal layer.

2. The micromechanical structure according to claim 1, characterized in that, The first diaphragm further includes a first transition layer, which is located between the first metal layer and the first piezoelectric layer.

3. The micromechanical structure according to claim 1, characterized in that, The second diaphragm further includes a second transition layer, which is located between the third metal layer and the second piezoelectric layer.

4. The micromechanical structure according to claim 1, characterized in that, A groove is provided on the substrate, and a cavity is formed between the groove and the structural layer.

5. The micromechanical structure according to claim 1, characterized in that, The micromechanical structure further includes a first pad and a second pad, wherein the first pad is disposed on the first metal layer and located on one side of the first piezoelectric layer, and the second pad is located on the second metal layer.

6. The micromechanical structure according to claim 1, characterized in that, The micromechanical structure also includes a third pad, which is located on the sixth metal layer and on one side of the third metal layer.

7. The micromechanical structure according to claim 1, characterized in that, The micromechanical structure also includes a fourth pad, which is located on the fifth metal layer and on one side of the fourth metal layer.

8. A fabrication process for the micromechanical structure according to any one of claims 1-7, characterized in that, The processing technology includes: The sampling sheet has a double-sided piezoelectric layer structure; The front and back sides of the sample are patterned and etched to obtain the first diaphragm and the second diaphragm; The fifth metal layer and the sixth metal layer are grown on the substrate; and The substrate and the second diaphragm are bonded together to obtain the micromechanical structure.

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