Preparation method of piezoresistive triaxial accelerometer
Through the all-silicon structure design and stop structure, the existing three-axis accelerometers have been solved in impact overload and material stress mismatch, achieving higher impact resistance and detection accuracy, and avoiding mutual interference from acceleration detection.
Patent Information
- Application Number
- CN202411310146.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-19
- Publication Date
- 2024-12-31
AI Technical Summary
The existing piezoresistive three-axis accelerometers are prone to damage under impact overload and material stress mismatch, and there is mutual interference in acceleration detection in different directions, which reduces detection accuracy and stability.
Using a full silicon structure design, the stop structure and piezoresistive structure are produced through the combination of photolithography, silicon etching and oxide layer, and the X-axis, Y-axis and Z-axis sensitive structures are independently designed to avoid material stress mismatch, and through TSV Through holes and poly silicon filling improve overload resistance and form an independent acceleration detection system.
The impact resistance and long-term stability of the three-axis accelerometer are improved, the interference of acceleration detection in different directions is reduced, and the acceleration detection accuracy in each direction is improved.
Smart Images
Figure CN119224371A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductor technology, and in particular to a method for preparing a piezoresistive three-axis accelerometer. Background Art
[0002] The piezoresistive three-axis accelerometer measures the external acceleration environment based on the basic principle of the piezoresistive effect. It can measure spatial acceleration and reflect the movement of objects more comprehensively and accurately. It is widely used in fields such as robotics, automobiles, and medicine.
[0003] In actual applications, accelerometers are often subjected to shock overloads, such as falling, collision, etc. Shock overloads can easily damage the accelerometer structure; at the same time, the stress mismatch between different materials of the accelerometer reduces the long-term stability and reliability of the device; in addition, the acceleration detection in different directions of the traditional three-axis accelerometer often has a certain degree of mutual interference, thereby reducing the acceleration detection accuracy in each direction. Therefore, it is of great significance and practical value to study and improve the impact resistance, long-term stability and acceleration detection accuracy of the three-axis accelerometer in different directions. Summary of the invention
[0004] The purpose of the present invention is to solve the deficiencies in the prior art and to provide a method for preparing a piezoresistive three-axis acceleration sensor.
[0005] This application provides the following technical solutions: A method for preparing a piezoresistive three-axis accelerometer, characterized by comprising the following steps: (1) Take the first double-polished silicon wafer and make a cavity structure and a Z-axis direction stop structure by photolithography, silicon etching, and debonding. The cavity structure provides a movable space for the sensitive structure, and the Z-axis direction stop structure is used to limit the movement range of the Z-axis sensitive structure to prevent the structure from breaking due to excessive movement; (2) An oxide layer is provided on the surface of the first double-polished silicon wafer with the cavity structure and the Z-axis direction stop structure, and the oxide layer is an insulating dielectric layer; (3) Taking a second double-polished silicon wafer, bonding the second double-polished silicon wafer to the first double-polished silicon wafer having a cavity structure, a Z-axis stop structure, and an oxide layer; (4) After the bonding is completed, the second double-polished silicon wafer is subjected to photolithography, silicon etching, and debonding to manufacture an X-axis sensitive structure, a Y-axis sensitive structure, a Z-axis sensitive structure, an X-axis stop structure, and a Y-axis stop structure; (5) On the second double-polished silicon wafer with the X-axis sensitive structure, the Y-axis sensitive structure, the Z-axis sensitive structure, the X-axis stop structure and the Y-axis stop structure, a piezoresistive structure and a lead structure are manufactured by photolithography, implantation, degumming, etc. The piezoresistive structure is used to sense the change of external acceleration, and the lead is used to connect the piezoresistive structure to form a Wheatstone bridge; (6) Take the third double-polished silicon wafer, and make a cavity structure and a Z-axis direction stop structure by photolithography, silicon etching, and degumming. The cavity structure can provide a space for the sensitive structure to move, and the Z-axis direction stop structure is used to limit the movement range of the Z-axis sensitive structure to prevent the structure from breaking due to excessive movement; (7) Taking a third double-polished silicon wafer with a cavity structure and a Z-axis stop structure, and making TSV through holes on the third double-polished silicon wafer by photolithography, silicon etching, and debonding; (8) Take the third double-polished silicon wafer with TSV through holes, oxidize it to form an oxide layer, and the oxide layer is an insulating dielectric layer; (9) Take the third double-polished silicon wafer after oxidation and fill the TSV through hole with poly silicon, which is used to connect the lead and the pad; (10) Bonding the third double-polished silicon wafer after filling with poly silicon, the second double-polished silicon wafer after making the piezoresistor and lead structure, and the first double-polished silicon wafer after setting the oxide layer together; (11) A metal pad is fabricated on the non-bonded side of the third double-polished silicon wafer, thereby finally forming a piezoresistive three-axis accelerometer as described in the present invention.
[0006] Advantages of the invention: The beneficial effect of the present invention is that the present invention provides a method for preparing a piezoresistive three-axis acceleration sensor. The piezoresistive three-axis accelerometer adopts an all-silicon structure, which avoids stress mismatch between different materials. The overload resistance of the accelerometer is improved by designing a stop structure. At the same time, the acceleration sensitive structures in different directions are independent of each other, avoiding interference in acceleration detection in different directions. BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 A schematic diagram of the structure of the first double-polished silicon wafer 1; Figure 2 Schematic diagram of a first double-polished silicon wafer 1 with a cavity structure and a Z-axis direction stop structure; Figure 3 Schematic diagram of the first double-polished silicon wafer 1 with a cavity structure, a Z-axis stop structure and an oxide layer; Figure 4 A schematic diagram of the structure of the second double-polished silicon wafer 2; Figure 5 Schematic diagram of the second double-polished silicon wafer 2 after bonding with the first double-polished silicon wafer 1 having a cavity structure, a Z-axis direction stop structure and an oxide layer; Figure 6 Schematic diagram of the second double-polished silicon wafer 2 after bonding after the sensitive structure and the stopper structure are made; Figure 7 yes Figure 6 Schematic diagram of the X-axis and Y-axis sensitive structures and stop structures described in; Figure 8 Schematic diagram of the second double-polished silicon wafer 2 after bonding after the sensitive structure, stopper structure, lead wire and piezoresistive structure are fabricated; Fig. 9 A schematic diagram of the structure of the third double-polished silicon wafer 3; Fig.10 Schematic diagram of the structure of the third double-polished silicon wafer 3 after the cavity structure and the Z-axis stop structure are manufactured; Fig.11 Schematic diagram of the structure of the third double-polished silicon wafer 3 after TSV through holes are made; Fig.12 A schematic diagram of the structure of the third double-polished silicon wafer 3 after TSV through holes are made and oxidized; Fig.13 Schematic diagram of the third double-polished silicon wafer 3 being filled with poly silicon after TSV through holes are made; Fig.14 A schematic diagram of a structure after bonding together a third double-polished silicon wafer 3 filled with poly silicon, a second double-polished silicon wafer 2 after manufacturing piezoresistors and lead structures, and a first double-polished silicon wafer 1; Fig.15 Schematic diagram of the structure after the bonding pad is made on the unbonded side of the third double-polished silicon wafer 3. Specific implementation plan
[0008] like Figure 1-14 As shown, a method for preparing a piezoresistive three-axis accelerometer is characterized in that it comprises the following steps: (1) If Figure 1 , Figure 2 As shown, a first double-polished silicon wafer 1 is taken, and a cavity structure 4 and a Z-axis direction stop structure 5 are manufactured by photolithography, silicon etching, and degumming. The cavity structure 4 provides a movable space for the sensitive structure, and the Z-axis direction stop structure 5 is used to limit the movement amplitude of the Z-axis sensitive structure 9 to prevent the structure from being broken due to excessive movement amplitude.
[0009] (2) Figure 3 As shown, an oxide layer 6 is disposed on the surface of the first double-polished silicon wafer 1 with the cavity structure 4 and the Z-axis direction stop structure 5. The oxide layer 6 is an insulating dielectric layer (such as silicon oxide).
[0010] (3) If Figure 4-5 As shown, a second double-polished silicon wafer 2 is taken and bonded to a first double-polished silicon wafer 1 having a cavity structure 4 , a Z-axis direction stop structure 5 and an oxide layer 6 .
[0011] (4) If Figure 6As shown, after the bonding is completed, the second double-polished silicon wafer 2 is fabricated by photolithography, silicon etching, and degumming to form an X-axis sensitive structure 7, a Y-axis sensitive structure 8, a Z-axis sensitive structure 9, an X-axis stop structure 10, and a Y-axis stop structure 11. The X-axis sensitive structure 7 is used to sense the acceleration in the X-axis direction, the Y-axis sensitive structure 8 is used to sense the acceleration in the Y-axis direction, the Z-axis sensitive structure 9 is used to sense the acceleration in the Z-axis direction, the X-axis stop structure 10 is used to limit the movement amplitude of the X-axis sensitive structure 7 in the X-axis direction to prevent the structure from being broken due to excessive movement amplitude, and the Y-axis stop structure 11 is used to limit the movement amplitude of the Y-axis sensitive structure 8 in the Y-axis direction to prevent the structure from being broken due to excessive movement amplitude. Figure 7 It is a schematic diagram of the X-axis and Y-axis sensitive structures and the stop structure, wherein 7 is the X-axis sensitive structure, which is a beam structure, and 10 is the X-axis direction stop structure; 8 is the Y-axis sensitive structure, which is a beam structure, and 11 is the Y-axis direction stop structure.
[0012] (5) If Figure 8 As shown, on the second double-polished silicon wafer 2 with the X-axis sensitive structure 7, the Y-axis sensitive structure 8, the Z-axis sensitive structure 9, the X-axis stop structure 10 and the Y-axis stop structure 11, a piezoresistive structure 12 and a lead structure 13 are manufactured by photolithography, injection, degumming, etc. The piezoresistive structure 12 is used to sense the change of external acceleration, and the lead 13 is used to connect the piezoresistive structure to form a Wheatstone bridge.
[0013] (6) Figure 8-10 As shown, the third double-polished silicon wafer 3 is taken, and the cavity structure 14 and the Z-axis direction stop structure 15 are manufactured by photolithography, silicon etching, and degumming. The cavity structure 14 can provide a moving space for the sensitive structure, and the Z-axis direction stop structure 15 is used to limit the movement range of the Z-axis sensitive structure 9 to prevent the structure from being broken due to excessive movement range.
[0014] (7) Fig.11 As shown, a third double-polished silicon wafer 3 with a cavity structure 14 and a Z-axis direction stop structure 15 is taken, and a TSV through hole 16 is manufactured on the third double-polished silicon wafer 3 by photolithography, silicon etching, and debonding.
[0015] (8) Fig.12 As shown, the third double-polished silicon wafer 3 with TSV through holes 16 is taken, and the third double-polished silicon wafer 3 is oxidized to form an oxide layer 17, and the oxide layer 17 is an insulating dielectric layer (such as silicon oxide).
[0016] (9) Fig.13 As shown, the oxidized third double-polished silicon wafer 3 is taken, and poly silicon 18 is filled in the TSV through hole. The poly silicon 18 is used to connect the lead 13 and the pad 19.
[0017] (10) Fig.14As shown, the third double-polished silicon wafer 3 after filling with poly silicon 18, the second double-polished silicon wafer 2 after manufacturing the piezoresistor 12 and the lead structure 13, and the first double-polished silicon wafer 1 after setting the oxide layer 6 are bonded together.
[0018] (11) Fig.15 As shown, a metal pad 19 is made on the side of the third double-polished silicon wafer 3 that is not bonded, and finally a piezoresistive three-axis accelerometer described in the present invention is formed.
Claims
1. A method for preparing a piezoresistive three-axis accelerometer, characterized in that The following steps are involved: 1) Take a first double-polished silicon wafer (1), and manufacture a cavity structure (4) and a Z-axis direction stop structure (5) by photolithography, silicon etching, and degumming processes; 2) performing oxidation treatment on the surface of the first double-polished silicon wafer (1) having the cavity structure (4) and the Z-axis direction stop structure (5), so as to form an oxide layer (6) on the surface of the double-polished silicon wafer (1); 3) taking a second double-polished silicon wafer (2), and bonding the second double-polished silicon wafer (2) to the first double-polished silicon wafer (1) having a cavity structure (4), a Z-axis direction stop structure (5), and an oxide layer (6); 4) On the bonded second double-polished silicon wafer (2), an X-axis sensitive structure (7), a Y-axis sensitive structure (8), a Z-axis sensitive structure (9), an X-axis stop structure (10) and a Y-axis stop structure (11) are manufactured by photolithography, silicon etching and degumming processes; 5) On the second double-polished silicon wafer (2), a piezoresistive structure (12) and a lead structure (13) are manufactured by photolithography, implantation, and degumming processes; 6) Take the third double-polished silicon wafer (3), and manufacture the cavity structure (14) and the Z-axis direction stop structure (15) through photolithography, silicon etching, and degumming processes; 7) Forming TSV through holes (16) on the third double-polished silicon wafer (3) by photolithography, silicon etching, and degumming processes; 8) performing oxidation treatment on the third double-polished silicon wafer (3) to form an oxide layer (17) on the surface of the double-polished silicon wafer, the surface of the cavity structure and the surface of the TSV through hole; 9) Filling the TSV through-holes in the oxidized third double-polished silicon wafer (3) with poly silicon (18), where the poly silicon (18) is used to connect the leads (13) and the pads (19); 10) bonding together the third double-polished silicon wafer (3) after filling with poly silicon (18), the second double-polished silicon wafer (2) after manufacturing the piezoresistor (12) and the lead structure (13), and the first double-polished silicon wafer (1) after setting the oxide layer (6); 11) A metal pad (19) is fabricated on the side of the third double-polished silicon wafer (3) that is not bonded, thereby finally forming a piezoresistive three-axis accelerometer according to the present invention.