MEMS sensor chip packaging stress isolation structure, MEMS sensor and preparation method

Abstract

The present invention discloses a MEMS sensor chip packaging stress isolation structure, a MEMS sensor and a preparation method, comprising a peripheral support frame and a stress isolation mass block located in the peripheral support frame, wherein the peripheral support frame and the stress isolation support block are connected by a supporting cantilever beam, the peripheral support frame, the stress isolation mass block and the supporting cantilever beam are all located on the same plane, and the peripheral support frame and the stress isolation mass block are respectively provided with a plurality of patch protrusions for connecting to the MEMS sensor chip or the packaging base. The present invention can effectively isolate the influence of patch stress or welding stress, and is compatible with integrated circuit processing technology, reduces sensor chip patch stress, has the characteristics of small size, low processing cost, and batch processing, and can be widely used in the integrated packaging of inertial sensor chips such as MEMS gyroscopes and accelerometers.

Description

Technical Field

[0001] The present invention relates to silicon micro sensor technology, and in particular to a MEMS sensor chip packaging stress isolation structure, a MEMS sensor and a preparation method thereof. Background Art

[0002] Gyroscopes and accelerometers are important components of MEMS sensors and are widely used in consumer electronic products such as mobile phones and pedometers, industrial and automotive products such as GPS-assisted navigation systems, robots, and engineering machinery, and military and aerospace products such as medium-range missile guidance and attitude control. They mainly realize acceleration measurement, angular velocity measurement, and vibration measurement of objects.

[0003] At present, MEMS sensor chips need to be packaged at the second level in product applications, mainly including plastic tube shell packaging, LTCC ceramic tube shell packaging, ceramic substrate COB packaging, etc. In this type of packaging process, the MEMS inertial sensor chip is generally directly mounted on the base of the packaging shell by adhesive or eutectic bonding. Due to the large difference in the thermal expansion coefficient CTE between the packaging shell material and the chip material, the thermal stress involved after packaging is large, and the MEMS inertial sensor chip is very sensitive to stress, especially when the working axis is parallel to the packaging plane, which directly affects the test performance, especially the full temperature range bias stability and other indicators. In addition, other MEMS sensors will also have similar problems as mentioned above. Summary of the invention

[0004] In view of the defects and shortcomings of the prior art, the purpose of the present invention is to provide a MEMS sensor chip packaging stress isolation structure, a MEMS sensor and a preparation method. The present invention can effectively isolate the influence of patch stress or welding stress, and is compatible with integrated circuit processing technology, reduces sensor chip patch stress, has small size, low processing cost, and can be processed in batches. It can be widely used in the integrated packaging of inertial sensor chips such as MEMS gyroscopes and accelerometers.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0006] A MEMS sensor chip packaging stress isolation structure comprises a peripheral support frame and a stress isolation mass block located in the peripheral support frame, wherein the peripheral support frame and the stress isolation support block are connected via a supporting cantilever beam, the peripheral support frame, the stress isolation mass block and the supporting cantilever beam are all located on the same plane, and the peripheral support frame and the stress isolation mass block are respectively provided with a plurality of patch protrusions for connecting to the MEMS sensor chip or the packaging base.

[0007] As a preferred solution of the present invention, the peripheral support frame and the stress isolation mass block are both symmetrical structures and their symmetry axes coincide with each other.

[0008] As a preferred solution of the present invention, the peripheral support frame is a square frame, and the number of patch protrusions arranged on the peripheral support frame is four, and the four patch protrusions are arranged at the four corners of the back side of the peripheral support frame.

[0009] As a preferred solution of the present invention, the stress isolation mass block is square, and there are three patch protrusions arranged on the stress isolation mass block, and the three patch protrusions are symmetrically distributed about the central axis of the stress isolation mass block.

[0010] As a preferred solution of the present invention, there are two supporting cantilever beams, and the two supporting cantilever beams are arranged on the same side between the peripheral supporting frame and the stress isolation mass block.

[0011] As a preferred solution of the present invention, the two supporting cantilever beams are symmetrically distributed about the central axis of the stress isolation mass block.

[0012] As a preferred solution of the present invention, the cross section of the supporting cantilever beam is rectangular.

[0013] As a preferred solution of the present invention, the peripheral support frame, the supporting cantilever beam and the stress isolation mass block are made of processing materials having the same or similar thermal expansion coefficient as that of the processing materials used in the MEMS sensor chip.

[0014] As a preferred solution of the present invention, the processing material having the same or similar thermal expansion coefficient as that of the processing material used in the MEMS sensor chip is one of single crystal silicon wafer, prex7740 glass and Schott glass.

[0015] Another aspect of the present invention provides a MEMS sensor, comprising a packaging base, a MEMS sensor chip and any one of the above-mentioned MEMS sensor chip packaging stress isolation structures, wherein the MEMS sensor chip is connected to the packaging base via the MEMS sensor chip packaging stress isolation structure.

[0016] The type of the MEMS sensor chip of the present invention is not limited and is not general. The MEMS sensor chip may be an inertial sensor chip.

[0017] Another aspect of the present invention provides a method for preparing any one of the above-mentioned MEMS sensor chip packaging stress isolation structures, comprising:

[0018] A substrate prepared for use as a processing material for a stress isolation structure of a MEMS sensor chip package;

[0019] Spin-coat a layer of photoresist on the back of the substrate, bake and solidify it, and then photolithograph the pattern of multiple patch protrusions on the peripheral support frame; after photolithography development and drying, etch out multiple patch protrusions on the peripheral support frame;

[0020] A layer of photoresist is spin-coated on the front side of the substrate, baked and cured, and then a pattern of a plurality of patch protrusions on the stress isolation mass block is photoetched; after photolithography development and drying, a plurality of patch protrusions on the stress isolation mass block are etched;

[0021] A layer of photoresist is spin-coated on the front side of the substrate, baked and solidified, and then the patterns of the supporting cantilever beam and the stress isolation mass block are photoetched; after photolithography development and drying, the supporting cantilever beam and the stress isolation mass block are etched.

[0022] Furthermore, the present invention selects a suitable process to etch the patch protrusions, the supporting suspension plate and the stress isolation mass block at the corresponding positions in the corresponding steps according to the material used for the substrate. If the substrate material is a single crystal silicon wafer, a deep silicon etching process is used for etching; if the substrate is a glass material such as prex7740 glass or Schott glass, a wet etching process is used for etching.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The present invention can effectively isolate the influence of patch stress or welding stress, and at the same time play a high overload impact buffering role. Specifically, the suspension plate structure designed by the present invention can release the stress of the patch package on the suspension plate through the deformation of the suspension plate, thereby isolating the influence of stress on the structure. At the same time, under impact, the deformation of the suspension plate can also play a buffering role, improve the impact resistance of the overall packaging structure, and is compatible with integrated circuit processing technology, reduces sensor chip patch stress, has small size, processing cost points, and can be processed in batches. It can be widely used in the integrated packaging of inertial sensor chips such as MEMS gyroscopes and accelerometers. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0026] Figure 1 It is a schematic diagram of the three-dimensional structure of the front side of the stress isolation structure of the MEMS sensor chip package in one embodiment of the present invention;

[0027] Figure 2 It is a schematic diagram of the three-dimensional structure of the back side of the stress isolation structure of the MEMS sensor chip package in one embodiment of the present invention;

[0028] Figure 3 for Figure 2The cross-sectional structure diagram of AA in the middle;

[0029] Figure 4 A schematic diagram of the structure of a MEMS sensor in one embodiment of the present invention;

[0030] Figure 5 It is a schematic diagram of overall stress simulation of the assembly of a MEMS sensor chip and a stress isolation structure in one embodiment of the present invention;

[0031] Figure 6 The present invention is a process schematic diagram of a method for preparing a stress isolation structure for a MEMS sensor chip package in an embodiment of the present invention, wherein: (a) represents a prepared substrate; (b) represents a pattern of multiple patch protrusions on a peripheral support frame photoetched on the back side of the substrate; (c) represents a pattern of multiple patch protrusions on the peripheral support frame etched; (d) represents a pattern of multiple patch protrusions on a stress isolation mass block photoetched on the front side of the substrate; (e) represents a pattern of multiple patch protrusions on the stress isolation mass block etched; (f) represents a pattern of supporting cantilever beams and stress isolation mass blocks photoetched; (g) represents a pattern of supporting cantilever beams and stress isolation mass blocks etched.

[0032] Legend:

[0033] 1. Peripheral support frame; 2. Support cantilever beam; 3. Stress isolation mass block; 4. Patch protrusion.

[0034] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0036] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0037] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0038] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0040] like Figure 1 and Figure 2 As shown, this embodiment provides a MEMS sensor chip packaging stress isolation structure, including a peripheral support frame 1, a supporting cantilever beam 2, a stress isolation mass block 3 and a patch protrusion 4.

[0041] The peripheral support frame 1 is a square frame structure with a square hole inside. A square stress isolation mass block 3 is arranged in the square hole of the peripheral support frame 1. The peripheral support frame 1, the supporting cantilever beam 2, and the stress isolation mass block 3 are on the same plane. The four sides of the stress isolation mass block 3 correspond to the four sides of the peripheral support frame 1, and the spacing between the four sides of the stress isolation mass block 3 and the corresponding four sides of the peripheral support frame 1 is equal.

[0042] The peripheral support frame 1 and the stress isolation support block 3 are connected by a supporting cantilever beam 2. The peripheral support frame 1 and the stress isolation mass block 3 are respectively provided with a plurality of patch protrusions 4 for connecting with the MEMS sensor chip or the packaging base. The connection process of the patch protrusion 4 and the MEMS sensor chip or the packaging base can be bonding or bonding as needed.

[0043] Reference Figure 1, the number of patch protrusions 4 arranged on the stress isolation mass block 3 is three, and the three patch protrusions 4 are symmetrically distributed about the central axis of the stress isolation mass block 3. This can reduce the bonding area of ​​the stress isolation mass block 3 connected to the MEMS sensor chip or the packaging base, further reduce the impact of the patch glue, and ensure the flatness of the chip patch.

[0044] Reference Figure 2 , the number of patch protrusions 4 arranged on the peripheral support frame 1 is four, and the four circular patch protrusions 4 are arranged at the four corners of the back of the peripheral support frame 1. This can reduce the bonding area between the peripheral support frame 1 and the MEMS sensor chip or the packaging base, further reduce the impact of the patch glue, and ensure the flatness of the chip patch.

[0045] Reference Figure 1 , Figure 2 and Figure 3 There are two supporting cantilever beams 2, and the two supporting cantilever beams 2 are arranged on the same side between the peripheral supporting frame 1 and the stress isolation mass block 3. The two supporting cantilever beams 2 are symmetrically distributed about the central axis of the stress isolation mass block 3. The cross section of the supporting cantilever beam 2 is rectangular.

[0046] It can be understood that the shapes of the peripheral support frame 1 and the stress isolation mass block 3 in the present invention are not limited to Figure 1 and Figure 2 The square shape in the illustrated embodiment may also be other shapes. Preferably, the peripheral support frame and the stress isolation mass block are both symmetrical structures and their axes of symmetry coincide with each other.

[0047] It can be understood that the shape of the patch protrusion 4 in the present invention is not limited and can be Figure 1 , Figure 2 The circular patch protrusions in the embodiment may also be patch protrusions of other shapes. The number of patch protrusions 4 in the present invention is not limited and can be set according to actual needs. It is preferred that all patch protrusions 4 located on the same side are symmetrically distributed about the central axis of the stress isolation mass block 3 or the central axis of the peripheral support frame 1.

[0048] The peripheral support frame 1, the supporting cantilever beam 2 and the stress isolation mass block 3 in the present invention are made of processing materials with the same or similar thermal expansion coefficient as the processing materials used in the MEMS sensor chip, so as to effectively avoid thermal stress caused by the difference in the thermal expansion coefficient CTE of the materials, such as using one of single crystal silicon wafers, prex7740 glass and Schott glass. Figure 1 and Figure 2 In the illustrated embodiment, the manufacturing material used is a single crystal silicon wafer.

[0049] Reference Figure 4In one embodiment of the present invention, a MEMS sensor is provided, comprising a packaging base, a MEMS sensor chip and any one of the above-mentioned MEMS sensor chip packaging stress isolation structures, wherein the MEMS sensor chip is connected to the packaging base via the MEMS sensor chip packaging stress isolation structure.

[0050] It should be noted that the MEMS sensor chip does not depend on a specific MEMS sensor type. As a specific implementation example, Figure 4 The MEMS sensor chip in the illustrated embodiment is an inertial sensor chip.

[0051] Figure 4 In the embodiment shown, the existing chip size is used as a benchmark, and the overall design of the package base is 5mm*5mm. Considering the depth of the ceramic tube shell of the external package, the overall thickness of the package base is designed to be 800um at most. According to the simulation results, it can be found that the frequency is mainly determined by the thickness of the stress isolation mass block 3. When the thickness of the stress isolation mass block 3 is 700um, the frequency is 8135Hz. If the frequency is further increased (above 10K), the MEMS sensor chip package stress isolation structure needs to be thickened. According to the simulation results, under a 10000g impact, the displacement of the stress isolation mass block 3 in the z direction is less than 1.5um, and the higher the resonant frequency of the stress isolation mass block 3, the smaller the displacement. When the thickness of the MEMS sensor chip package stress isolation structure is 700um, the frequency is 8135hz and the impact displacement is 1um. Therefore, it is sufficient for the thickness of the circular patch protrusions 4 protruding at the four corners of the peripheral support frame 1 to be greater than 10um. Considering processing deviations and redundancy, this design is 20um. Figure 5 As shown, when the size of the triangularly distributed circular patch protrusions 4 on the stress isolation mass block 3 is φ1mm, the height of the circular patch protrusions 4 changes very little from 20um to 120um on the displacement caused by stress; based on the comprehensive simulation results, this embodiment determines that the thickness of the circular patch protrusions 4 protruding at the four corners of the peripheral support frame 1 is 20um, the height of the circular patch protrusions 4 on the stress isolation mass block 3 is designed to be 20um, the size is φ1mm, and the thickness of the overall stress isolation structure is designed to be 760um, and the frequency is 9300hz at this time.

[0052] In addition, see Figure 6 An embodiment of the present invention further provides a method for preparing a MEMS sensor chip packaging stress isolation structure, comprising:

[0053] 1) Prepare a substrate for processing materials used as a stress isolation structure for MEMS sensor chip packaging, such as Figure 6 As shown in (a) in .

[0054] 2) Spin-coat a layer of photoresist on the back of the substrate, bake and cure, and then photoetch out a plurality of circular patch protrusions on the peripheral support frame 1, such as Figure 6 As shown in (b), B is the photoresist on the upper side of the pattern of multiple circular patch protrusions produced by photolithography.

[0055] 3) After photolithography and development, the product is dried and then a deep silicon etching process is used to etch out a plurality of circular patch protrusions on the peripheral support frame, such as Figure 6 As shown in (c) in .

[0056] 4) Spin-coat a layer of photoresist on the front side of the substrate, bake and cure it, and then photoetch out the pattern of multiple circular patch protrusions on the stress isolation mass block, such as Figure 6 As shown in (d), B is the photoresist on the upper side of the pattern of multiple circular patch protrusions produced by photolithography.

[0057] 5) After photolithography and development, the product is dried and then a deep silicon etching process is used to etch out a plurality of circular patch protrusions on the stress isolation mass block 3, such as Figure 6 As shown in (e) in .

[0058] 6) Spin-coat a layer of photoresist on the front side of the substrate, bake and cure, and then photoetch the pattern of the supporting cantilever beam and the stress isolation mass block, such as Figure 6 As shown in (f), B is the photoresist on the upper side of the pattern supporting the cantilever beam and the stress isolation mass block.

[0059] 7) After photolithography and development, the product is dried and then a deep silicon etching process is used to etch out the supporting cantilever beam and the stress isolation mass block, such as Figure 6 As shown in (g), C represents the etched groove structure.

[0060] The preparation method of the above-mentioned MEMS sensor chip packaging stress isolation structure of this embodiment adopts dry etching, which can be formed by photolithography dry etching with a mask plate, which can greatly reduce the device area, achieve high-quality, high-precision, large-scale processing, improve consistency, and reduce corresponding costs; at the same time, it can effectively buffer the impact of high-load shock on the chip and ensure the reliability of the product. The MEMS sensor chip packaging stress isolation structure is processed using integrated circuit processing technology. The stress isolation structure can be directly bonded to the chip in the front-end process of wafer tape-out, which improves product consistency and assembly accuracy. It can be cut into pieces together with the chip for later secondary packaging.

[0061] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A MEMS sensor chip packaging stress isolation structure, characterized in that: It comprises a peripheral support frame and a stress isolation mass block located in the peripheral support frame, wherein the peripheral support frame and the stress isolation support block are connected via a supporting cantilever beam, the peripheral support frame, the stress isolation mass block and the bottom surface of the supporting cantilever beam are all located on the same plane, the peripheral support frame and the stress isolation mass block are respectively provided with a plurality of patch protrusions for connecting with a MEMS sensor chip or a packaging base, the peripheral support frame and the stress isolation mass block are both symmetrical structures and the symmetry axes of the two coincide, the peripheral support frame is a square frame, the number of patch protrusions arranged on the peripheral support frame is four, and the four patch protrusions are arranged at the four corners of the back side of the peripheral support frame, the stress isolation mass block is square, the number of patch protrusions arranged on the stress isolation mass block is three, and the three patch protrusions are symmetrically distributed about the central axis of the stress isolation mass block, and the patch protrusions are circular patch protrusions; The thickness of the stress isolation mass block is 700um, the thickness of the circular patch protrusions at the four corners of the peripheral support frame is 20um, the height of the circular patch protrusions on the stress isolation mass block is designed to be 20um, and the size is φ1mm.

2. The MEMS sensor chip packaging stress isolation structure according to claim 1, characterized in that: There are two supporting cantilever beams, and the two supporting cantilever beams are arranged on the same side between the peripheral supporting frame and the stress isolation mass block.

3. The MEMS sensor chip packaging stress isolation structure according to claim 2, characterized in that: The two supporting cantilever beams are symmetrically distributed about the central axis of the stress isolation mass block.

4. The MEMS sensor chip packaging stress isolation structure according to claim 1 or 2, characterized in that: The cross section of the supporting cantilever beam is rectangular.

5. The MEMS sensor chip packaging stress isolation structure according to claim 4, characterized in that: The peripheral support frame, the supporting cantilever beam and the stress isolation mass block are made of processing materials having the same or similar thermal expansion coefficient as that of the processing materials used in the MEMS sensor chip.

6. The MEMS sensor chip packaging stress isolation structure according to claim 5, characterized in that: The processing material having the same or similar thermal expansion coefficient as that of the processing material used in the MEMS sensor chip is one of single crystal silicon wafer, prex7740 glass and Schott glass.

7. A MEMS sensor, characterized in that: The invention comprises a packaging base, a MEMS sensor chip and the MEMS sensor chip packaging stress isolation structure according to claim 1, wherein the MEMS sensor chip is connected to the packaging base through the MEMS sensor chip packaging stress isolation structure.

8. The MEMS sensor according to claim 7, characterized in that: The MEMS sensor chip is an inertial sensor chip.

9. A method for preparing the MEMS sensor chip packaging stress isolation structure according to claim 1, characterized in that: include: A substrate prepared for use as a processing material for a stress isolation structure of a MEMS sensor chip package; Spin-coat a layer of photoresist on the back of the substrate, bake and solidify it, and then photoetch a plurality of patch protrusion patterns on the peripheral support frame; After photolithography development and drying, a plurality of patch protrusions on the peripheral support frame are etched; A layer of photoresist is spin-coated on the front side of the substrate, baked and cured, and then a pattern of a plurality of patch protrusions on the stress isolation mass block is photoetched; After photolithography development and drying, a plurality of patch protrusions on the stress isolation mass block are etched; A layer of photoresist is spin-coated on the front side of the substrate, baked and cured, and then a pattern of supporting cantilever beams and stress isolation quality blocks is photoetched; After photolithography development and drying, the supporting cantilever beam and the stress isolation mass block are etched out.

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