Manufacturing method of wafer-level packaged MEMS (Micro Electro Mechanical System) inertial device

Abstract

The invention relates to a manufacturing method of a wafer-level packaging MEMS (Micro Electro Mechanical System) inertial device, which comprises the following steps of: S1, manufacturing a substrate layer wafer with a plurality of grooves in the upper surface, and bonding a device layer wafer on the upper surface of the substrate layer wafer; s2, thinning and patterning the device layer wafer to obtain a movable sensitive structure which comprises an accelerometer structure and a gyroscope structure; s3, filling the movable sensitive structure with a sacrificial material, and growing a dielectric film layer on the sacrificial material; s4, releasing the sacrificial material to form an accelerometer structure cavity and a gyroscope structure cavity between the dielectric film layer and the substrate layer wafer; and S5, making the accelerometer structure cavity into a nitrogen chamber, and making the gyroscope structure cavity into a vacuum chamber. According to the invention, the processing of a cap wafer is saved, the process steps are reduced, the cost is reduced, devices in different atmosphere environments can be integrated on the same chip for manufacturing, the chip integration level is improved, and the final device volume is reduced.

Description

Technical Field

[0001] The present invention relates to the field of inertial sensing technology, and in particular to a method for manufacturing a wafer-level packaged MEMS inertial device. Background Art

[0002] MEMS inertial sensor is a miniaturized inertial measurement device manufactured using microelectronics and micromachining technologies. It is divided into accelerometers, gyroscopes and their combination. Accelerometers are used to measure the acceleration of an object, and gyroscopes are used to measure the angular velocity of an object. The combined test of acceleration and angular velocity can be used to describe the motion state of an object.

[0003] MEMS inertial sensors are generally composed of a MEMS sensor chip and an ASIC chip package. The MEMS sensor chip is generally composed of three functional layers: an electrically conductive substrate layer, a movable sensitive structure layer, and a sealed cavity cap layer. The three-layer structure is formed by bonding three wafers through a wafer bonding process.

[0004] Existing wafer-level packaged MEMS inertial sensor chips generally use multi-layer wafer bonding to seal the movable sensitive structure that detects inertial physical quantities into a micro cavity. The sealed cavity is made of a cap wafer with solder through a bonding process. The manufacturing process is complex and costly. At the same time, due to the different gas atmospheres in the accelerometer and gyroscope cavities, the two chips are generally manufactured separately and integrated together through tube and shell packaging. The final device is large in size, which is not conducive to miniaturization. Summary of the Invention

[0005] The object of the present invention is to provide a method for manufacturing a wafer-level packaged MEMS inertial device, which can at least solve some of the defects in the prior art.

[0006] To achieve the above objectives, an embodiment of the present invention provides the following technical solution: a method for manufacturing a wafer-level packaged MEMS inertial device, comprising the following steps: S1, manufacturing a substrate layer wafer having a plurality of grooves on its upper surface, and bonding a device layer wafer to the upper surface of the substrate layer wafer; S2, thinning and patterning the device layer wafer to obtain a movable sensitive structure, wherein the movable sensitive structure includes an accelerometer structure and a gyroscope structure; S3, filling the movable sensitive structure with a sacrificial material, and growing a dielectric film layer on the sacrificial material; S4, releasing the sacrificial material to form an accelerometer structure cavity and a gyroscope structure cavity between the dielectric film layer and the substrate wafer; S5, making the accelerometer structure cavity into a nitrogen chamber and making the gyroscope structure cavity into a vacuum chamber.

[0007] Furthermore, the S3 step is specifically as follows: Filling the movable sensitive structure with a sacrificial material until the sacrificial material covers the movable sensitive structure; performing patterning on the sacrificial material; Then, the dielectric thin film layer is grown on the sacrificial material.

[0008] Furthermore, in the step S4, the method of releasing the sacrificial material includes: opening a first release hole on the dielectric film layer above the accelerometer structure, and releasing the sacrificial material corresponding to the accelerometer structure through the first release hole to form an accelerometer structure cavity.

[0009] Furthermore, in step S5 , the accelerometer structure cavity is made into a nitrogen chamber by sealing the first release hole in a nitrogen atmosphere so that the accelerometer structure cavity is filled with nitrogen.

[0010] Furthermore, before growing the dielectric film layer on the sacrificial material, a getter is first produced on the upper surface of the sacrificial material corresponding to the gyroscope structure.

[0011] Furthermore, in the step S4, the method of releasing the sacrificial material further includes: opening a second release hole on the dielectric film layer above the gyroscope structure, and releasing the sacrificial material corresponding to the gyroscope structure through the second release hole to form a gyroscope structure cavity.

[0012] Furthermore, in the step S5 , the gyroscope structure cavity is made into a vacuum chamber by sealing the second release hole in a vacuum atmosphere and activating the getter.

[0013] Furthermore, in the step S1, the method for manufacturing a substrate layer wafer having a plurality of grooves on its upper surface is specifically as follows: Etching a plurality of grooves on the upper surface of the substrate wafer, wherein the grooves are spaced apart; An oxide layer is grown on the upper surface of the substrate wafer; Polysilicon is grown on the oxide layer outside the groove to form a conducting line.

[0014] Furthermore, the sacrificial material is polyimide or amorphous carbon.

[0015] Furthermore, the dielectric thin film layer is made of amorphous silicon, silicon oxide or silicon nitride, and has a thickness of 2-30 μm.

[0016] Compared with the existing technology, the beneficial effects of the present invention are: a method for manufacturing a wafer-level packaged MEMS inertial device saves the processing of a cap wafer, reduces process steps, and reduces costs, and can integrate devices in different atmosphere environments on the same chip, thereby improving chip integration and reducing the volume of the final device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of a method for manufacturing a wafer-level packaged MEMS inertial device according to an embodiment of the present invention, wherein a groove is formed on a substrate; Figure 2 A schematic diagram of the growing oxide layer in a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention; Figure 3 A schematic diagram of a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention, wherein polysilicon is grown on the oxide layer outside the groove; Figure 4 A schematic diagram of bonding a device layer wafer to the substrate layer wafer in a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention; Figure 5 A schematic diagram of thinning the device layer wafer in a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention; Figure 6 A schematic diagram of a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention, wherein a patterning process is performed on the device layer wafer; Figure 7 A schematic diagram of filling sacrificial material in a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention; Figure 8 A schematic diagram of a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention, wherein a getter is manufactured on the upper surface of the sacrificial material; Figure 9 A schematic diagram of a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention, wherein a patterning process is performed on the sacrificial material; Figure 10 A schematic diagram of growing a dielectric thin film layer in a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention; Figure 11 A schematic diagram of a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention, wherein a first release hole is opened above the accelerometer structure, and a sacrificial material in the accelerometer structure is released through the first release hole; Figure 12A schematic diagram of sealing the first release hole under a nitrogen atmosphere in a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention; Figure 13 A schematic diagram of a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention, wherein a second release hole is opened above the gyroscope structure, and a sacrificial material in the gyroscope structure is released through the second release hole; Figure 14 A schematic diagram of sealing the second release hole under a vacuum atmosphere in a method for manufacturing a wafer-level packaged MEMS inertial device provided by an embodiment of the present invention; In the accompanying drawings: 1-substrate layer wafer; 10-substrate layer; 12-oxide layer; 13-polysilicon; 2-device layer wafer; 3-sacrificial material; 4-getter; 5-dielectric film layer; 50-first release hole; 51-second release hole; 52-first sealing material; 53-second sealing material; 6-accelerometer structure; 60-first chamber; 61-first movable sensitive structure; 7-gyroscope structure; 70-second chamber; 71-second movable sensitive structure; 8-nitrogen chamber; 9-vacuum chamber. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] See also Figures 1 to 14 The embodiment of the present invention provides a method for manufacturing a wafer-level packaged MEMS inertial device, comprising the following steps: S1, manufacturing a substrate layer wafer 1 having a plurality of grooves 11 on the upper surface, and bonding a device layer wafer 2 to the upper surface of the substrate layer wafer, such as Figures 1 to 4 S2, the device layer wafer 2 is thinned and patterned to obtain a movable sensitive structure, the movable sensitive structure includes an accelerometer structure 6 and a gyroscope structure 7, as shown Figure 5 and Figure 6 S3, filling the movable sensitive structure with a sacrificial material 3, growing a dielectric film layer 5 on the sacrificial material, the dielectric film layer 5 covering the sacrificial material 3, as shown. Figures 7 to 10 S4, releasing the sacrificial material 3 to form an accelerometer structure cavity and a gyroscope structure cavity between the dielectric film layer 5 and the substrate wafer 1, as shown Figure 11S5, the accelerometer structure cavity is made into a nitrogen chamber 8 and the gyroscope structure cavity 7 is made into a vacuum chamber 9, as shown Figures 12 to 14 In this embodiment, this method saves the processing of a cap wafer, reduces the process steps, reduces the cost, and can integrate devices in different atmosphere environments on the same chip, improve the chip integration, and reduce the final device volume. Specifically, the dielectric film layer 5 can replace the cap wafer in the subsequent process, avoiding the need to process the cap wafer again. Figure 11 and Figure 13 In the embodiment, due to the coverage of the dielectric film layer 5, when the sacrificial material is released, the dielectric film layer 5 can cooperate with the sacrificial material 3 to form a square cavity at the position where the sacrificial material 3 disappears. The cavity is combined with the movable sensitive structure to form an accelerometer structure 6 and a gyroscope structure 7. Specifically, Figure 14 As shown, divided by the middle dotted line, the accelerometer structure 6 is on the left side of the dotted line, which includes a first chamber 60 and a first movable sensitive structure 61, the first chamber 60 and the first movable sensitive structure 61 are connected, and they are filled with nitrogen; the gyroscope structure 7 is on the right side of the dotted line, which includes a second chamber 70 and a second movable sensitive structure 71, the second chamber 70 and the second movable sensitive structure 71 are connected, and they are a vacuum environment.

[0020] See also Figure 6 、 Figure 7 and Figure 9 , the step S3 specifically comprises: filling the movable sensitive structure with a sacrificial material 3 until the sacrificial material 3 covers the movable sensitive structure; patterning the sacrificial material 3; and then growing the dielectric film layer 5 on the sacrificial material 3. In this embodiment, Figure 5 After the device layer wafer 2 is thinned and polished, it is as shown in FIG. Figure 6 As shown, the device layer wafer 2 is patterned. The patterning process includes photolithography, etching, cleaning and other processes. A movable sensitive structure can be made on the device layer wafer 2. Figure 7 As shown, the sacrificial material 3 is filled into the movable sensitive structure. When it is full, the sacrificial material 3 is continued to be filled until the sacrificial material 3 forms a sacrificial structure covering the upper surface of the movable sensitive structure. Figure 9 As shown, the sacrificial material is patterned. The patterning process here is the key to separating the accelerometer structure 6 and the gyroscope structure 7. It can be said that the positions of the accelerometer structure 6 and the gyroscope structure 7 are divided. Subsequently, through the processes of making the dielectric film layer 5, releasing the sacrificial material 3, making the nitrogen cavity and the vacuum cavity, etc., the final accelerometer structure 6 and gyroscope structure 7 can be obtained.

[0021] See also Figure 11 and Figure 12In step S4, the method for releasing the sacrificial material 3 includes: opening a first release hole 50 in the dielectric film layer 5 above the accelerometer structure 6, and releasing the sacrificial material 3 corresponding to the accelerometer structure 6 through the first release hole 50 to form an accelerometer structure cavity. Preferably, in step S5, the method for forming the accelerometer structure cavity into a nitrogen chamber 8 includes: sealing the first release hole 50 with a first sealing material 52 under a nitrogen atmosphere, so that the cavity of the accelerometer structure 6 is filled with nitrogen 8. In this embodiment, the accelerometer structure 6 is ultimately filled with nitrogen. Therefore, after first releasing the sacrificial material 3 through the first release hole 50, the first release hole 50 is then sealed under a nitrogen atmosphere, so that the cavity of the accelerometer structure 6 is filled with nitrogen.

[0022] See also Figure 8 and Figure 9 In step S2, before growing the dielectric film layer 5 on the sacrificial material 3, a getter 4 is formed on the upper surface of the sacrificial material 3 corresponding to the gyroscope structure. In this embodiment, the getter 4 is formed so that the getter 4 can be subsequently activated to maintain the vacuum environment of the gyroscope structure 7.

[0023] See also Figure 13 and Figure 14 In step S4, the method of releasing the sacrificial material 3 further includes: opening a second release hole 51 on the dielectric film layer 5 above the gyroscope structure 7, and releasing the sacrificial material 3 corresponding to the gyroscope structure 7 through the second release hole 51 to form a gyroscope structure cavity. Preferably, in step S5, the method of making the gyroscope structure cavity into a vacuum chamber 9 is: sealing the second release hole 51 under a vacuum atmosphere, and activating the getter 4 to maintain the vacuum level in the cavity of the gyroscope structure 7. In this embodiment, the gyroscope structure 7 ultimately requires a vacuum 9 environment in the cavity, so the sacrificial material 3 in the cavity of the gyroscope structure 7 can be first released using the second release hole 51, and then the air in the vacant cavity can be evacuated. Then, the second release hole 51 can be sealed with a second sealing material 53. In order to maintain the vacuum level, the getter 4 can be activated. The fabrication of the gyroscope structure 7 of this embodiment and the fabrication of the accelerometer structure 6 described above can be performed sequentially. Either the first release hole 50 or the second release hole 51 can be opened first. This prevents both structures from being filled with nitrogen or becoming a vacuum in a nitrogen or vacuum environment, thereby improving fabrication efficiency. For example, if both the first release hole 50 and the second release hole 51 are opened simultaneously, then in a nitrogen-filled environment, both the cavity of the accelerometer structure 6 and the cavity of the gyroscope structure 7 will be filled with nitrogen. Therefore, after the release hole of the accelerometer structure 6 is sealed, the nitrogen in the gyroscope structure 7 must be removed.

[0024] See also Figure 1 、 Figure 2 and Figure 3 In step S1, the method for fabricating a substrate wafer 1 having a plurality of grooves 11 on its upper surface is as follows: etching the upper surface of the substrate wafer 1 to form a plurality of grooves 11, with the grooves 11 spaced apart; growing an oxide layer 12 on the upper surface of the substrate wafer 1; and growing polysilicon on the oxide layer 12 outside the grooves 11 to form conductive circuits. In this embodiment, the substrate wafer is processed before being bonded to the device wafer 2 to facilitate fabrication of a movable sensitive structure with the device wafer 2.

[0025] The following are specific embodiments of the present invention: Combine Figures 1 to 14 , each step of the manufacturing method of the wafer-level packaged MEMS inertial device is described one by one: See also Figure 1 A plurality of grooves 11 are formed on the upper surface of the substrate, and the grooves 11 are arranged at intervals. Specifically, the substrate is formed into grooves 11 by photolithography, etching, cleaning and other processes, and the depth of the grooves 11 is 0.5~20μm.

[0026] See also Figure 2 An oxide layer 12 is grown on the upper surface of the substrate where the groove 11 is formed. Specifically, the thickness of the oxide layer 12 is 0.5-4 μm.

[0027] See also Figure 3 , polysilicon 13 is grown on the oxide layer 12 outside the groove 11 and a conductive circuit is formed to form a substrate layer wafer 1. Specifically, polysilicon 13 is grown on the surface and patterned to form a conductive circuit, and the resistance of the polysilicon 13 is less than 0.1Ω.cm.

[0028] See also Figure 4 The device layer wafer 2 is bonded to the substrate layer wafer 1. Specifically, the substrate layer wafer 1 and the device layer wafer 2 are directly melt-bonded without pattern alignment, and the resistance of the device layer wafer 2 is less than 0.1Ω.cm.

[0029] See also Figure 5 , thinning the device layer wafer 2. Specifically, the device layer wafer 2 is thinned and polished to a thickness of 10-100 μm.

[0030] See also Figure 6 The device layer wafer 2 is patterned to obtain a movable sensitive structure. Specifically, the patterning process includes photolithography, etching, and cleaning to produce a movable sensitive structure on the device layer wafer 2. The structure is the prototype of the accelerometer structure 6 and the gyroscope structure 7.

[0031] See also Figure 7The movable sensitive structure is filled with a sacrificial material until the sacrificial material covers the movable sensitive structure. Specifically, the sacrificial material is polyimide (PI) or amorphous carbon (aC) to perform surface flattening.

[0032] See also Figure 8 A getter 4 is formed on the upper surface of the sacrificial material 3. Specifically, the getter 4 (a titanium-based or thorium-based material) is deposited on the surface and patterned.

[0033] See also Figure 9 , a patterning process is performed on the sacrificial material 3 to form an accelerometer structure 6 and a gyroscope structure 7. Specifically, the patterning process includes processes such as photolithography, etching, and cleaning.

[0034] See also Figure 10 , growing a dielectric thin film layer 5, said dielectric thin film layer 5 covering said sacrificial material 3 and said getter 4. Specifically, the dielectric thin film layer 5 (amorphous silicon or silicon oxide or silicon nitride) is grown at a low temperature and the surface is planarized, with a thickness of 2-30 μm.

[0035] See also Figure 11 A first release hole 50 is opened on the dielectric film layer 5 above the accelerometer structure 6 , and the sacrificial material 3 in the accelerometer structure 6 is released through the first release hole 50 .

[0036] See also Figure 12 The first release hole 50 is sealed in a nitrogen atmosphere to fill the accelerometer structure 6 with nitrogen. Specifically, a hole-filling material (a dense metal material such as aluminum or titanium) is grown in a nitrogen atmosphere at normal pressure or negative pressure to seal the release hole.

[0037] See also Figure 13 A second release hole 51 is opened on the dielectric film layer 5 above the gyroscope structure 7 , and the sacrificial material 3 in the gyroscope structure 7 is released through the second release hole 51 .

[0038] See also Figure 14 The second release hole 51 is sealed in a vacuum atmosphere, and the getter 4 is activated to maintain the vacuum level in the gyroscope structure 7. Specifically, a filling material (a dense metal material such as aluminum or titanium) is grown in a vacuum atmosphere to seal the release hole, and the getter 4 is activated by heating to maintain a high vacuum inside the cavity.

[0039] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a wafer-level packaged MEMS inertial device, characterized in that: The steps include: S1, manufacturing a substrate layer wafer having a plurality of grooves on its upper surface, and bonding a device layer wafer to the upper surface of the substrate layer wafer; S2, thinning and patterning the device layer wafer to obtain a movable sensitive structure, wherein the movable sensitive structure includes an accelerometer structure and a gyroscope structure; S3, filling the movable sensitive structure with a sacrificial material, and growing a dielectric film layer on the sacrificial material; S4, releasing the sacrificial material to form an accelerometer structure cavity and a gyroscope structure cavity between the dielectric film layer and the substrate wafer; S5, making the accelerometer structure cavity into a nitrogen chamber and making the gyroscope structure cavity into a vacuum chamber.

2. The method for manufacturing a wafer-level packaged MEMS inertial device according to claim 1, wherein: The S3 step is specifically as follows: Filling the movable sensitive structure with a sacrificial material until the sacrificial material covers the movable sensitive structure; performing patterning on the sacrificial material; Then, the dielectric thin film layer is grown on the sacrificial material.

3. The method for manufacturing a wafer-level packaged MEMS inertial device according to claim 1, wherein: In the step S4, the method of releasing the sacrificial material includes: opening a first release hole on the dielectric film layer above the accelerometer structure, and releasing the sacrificial material corresponding to the accelerometer structure through the first release hole to form an accelerometer structure cavity.

4. The method for manufacturing a wafer-level packaged MEMS inertial device according to claim 3, wherein: The method of making the accelerometer structure cavity into a nitrogen chamber in the step S5 is: sealing the first release hole in a nitrogen atmosphere so that the accelerometer structure cavity is filled with nitrogen.

5. The method for manufacturing a wafer-level packaged MEMS inertial device according to claim 1, wherein: Before growing the dielectric film layer on the sacrificial material, a getter is firstly produced on the upper surface of the sacrificial material corresponding to the gyroscope structure.

6. The method for manufacturing a wafer-level packaged MEMS inertial device according to claim 5, wherein: In the step S4, the method of releasing the sacrificial material further includes: opening a second release hole on the dielectric film layer above the gyroscope structure, and releasing the sacrificial material corresponding to the gyroscope structure through the second release hole to form a gyroscope structure cavity.

7. The method for manufacturing a wafer-level packaged MEMS inertial device according to claim 6, wherein: The method of manufacturing the gyroscope structure cavity into a vacuum chamber in the step S5 is: sealing the second release hole under a vacuum atmosphere and activating the getter.

8. The method for manufacturing a wafer-level packaged MEMS inertial device according to claim 1, wherein: In the step S1, the method for manufacturing a substrate layer wafer having a plurality of grooves on its upper surface is specifically as follows: Etching a plurality of grooves on the upper surface of the substrate wafer, wherein the grooves are spaced apart; An oxide layer is grown on the upper surface of the substrate wafer; Polysilicon is grown on the oxide layer outside the groove to form a conducting line.

9. The method for manufacturing a wafer-level packaged MEMS inertial device according to claim 1, wherein: The sacrificial material is polyimide or amorphous carbon.

10. The method for manufacturing a wafer-level packaged MEMS inertial device according to claim 1, wherein: The dielectric thin film layer is made of amorphous silicon, silicon oxide or silicon nitride, and has a thickness of 2-30 μm.

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