CN221370643U

CN221370643U - Stress isolation packaging structure of MEMS device

Info

Publication number: CN221370643U
Application number: CN202323228848.3U
Authority: CN
Inventors: 苏佳乐; 郭中洋; 华亚平
Original assignee: Beijing Xindong Zhiyuan Microelectronics Technology Co ltd; Anhui Xindong Lianke Microsystem Co ltd
Current assignee: Beijing Xindong Zhiyuan Microelectronics Technology Co ltd; Anhui Xindong Lianke Microsystem Co ltd
Priority date: 2023-11-29
Filing date: 2023-11-29
Publication date: 2024-07-19
Anticipated expiration: 2033-11-29

Abstract

The utility model discloses a stress isolation packaging structure of an MEMS device, which comprises a packaging tube shell, an MEMS chip, a stress isolation substrate in a shape of T, an inverted T or I, a bonding adhesive and a packaging cover plate, wherein the MEMS chip is fixed in the packaging tube shell through the stress isolation substrate and the bonding adhesive, and a pressure welding block of the MEMS chip is connected with an inner bonding pad of the packaging tube shell through a bonding lead to lead out an electric signal of the MEMS chip. The utility model adopts the stress isolation base plate in the shape of T, inverted T or I, and the stress isolation base plate is respectively adhered with the packaging tube shell and the MEMS chip through the adhesive, and the stress transmitted to the MEMS chip is reduced by utilizing the characteristic of small contact area of the salient points of the stress isolation base plate, thereby realizing low-stress packaging and improving the performance of the product.

Description

Stress isolation packaging structure of MEMS device

Technical Field

The utility model belongs to the field of MEMS chip packaging, and particularly relates to a stress isolation packaging structure of an MEMS device.

Background

MEMS (Micro-Electro-MECHANICAL SYSTEMS) is an abbreviation of Micro-electromechanical systems, and MEMS manufacturing technology utilizes Micro-machining technology, particularly semiconductor wafer manufacturing technology, to manufacture various Micro-mechanical structures, and combines special control integrated circuits (ASICs) to form intelligent MEMS components such as Micro-MEMS, micro-actuators, micro-optical devices and the like. The MEMS component has the advantages of small volume, low cost, high reliability, strong capability of resisting severe environment, low power consumption, high intelligent degree, easy alignment and easy integration, and is widely applied to consumer electronic products represented by smart phones. With the increasingly vigorous competition of MEMS component markets and the great growth of wearable electronic products represented by smart watches, the requirements of customers on the performances of MEMS components are higher and higher, the volume is small, the power consumption is low, and the performance stability becomes the basic requirement, and the packaging structure of the electronic components has direct influence on the performances of the products.

Electronic components are typically packaged by interconnecting one or more electronic chips with electronic signals and encapsulating the electronic chips in a protective structure to provide mechanical or chemical corrosion protection and to provide electrical signal connection between the electronic chips and the outside of the package. Some electronic products, such as gyroscopes, accelerometers, oscillators, bulk acoustic wave filters, etc. in MEMS devices are very sensitive to stress, and their industrial-scale products require hermetic packaging with ceramic packages, metal packages, preformed plastic packages, etc. The common packaging method is that the back of the MEMS chip is fixed on a packaging bottom plate of a packaging tube shell through adhesive, front leads are interconnected to form a functional circuit, finally a packaging cover plate is added for sealing, so that components such as MEMS or an actuator and the like which can be used in electronic products are formed, only the back of the MEMS chip is contacted with the tube shell through the adhesive, the front of the MEMS chip is not contacted with any solid, and stress caused by packaging is only introduced from the back of the MEMS chip.

The mechanical stress introduced by the package is mainly derived from unequal volume changes between the MEMS chip and the packaging material caused by temperature changes, and mechanical deformation of the PCB board during use. The most commonly used material for MEMS chips is silicon, which has a thermal expansion coefficient of 2.6ppm/K at room temperature, and the same material is difficult to find; the aluminum oxide ceramic with the coefficient of thermal expansion closest to that of silicon (the coefficient of thermal expansion is 7 ppm/k) in the common packaging shell material is also much larger than that of silicon; since the thermal expansion coefficients of the adhesive and the package shell material are different from those of the MEMS chip material (mainly silicon), during the packaging process and the high temperature process used later, such as the curing of the adhesive, capping, SMT and daily use of an end user, when the temperature changes, the volume changes of the MEMS chip and the package shell and the adhesive are inconsistent, so that mechanical stress is generated, which is also called thermal mismatch stress. Besides temperature change, the PCB deformation caused in the assembly process, the PCB deformation caused by mechanical vibration and mechanical impact in the use process of an end user can be conducted to the MEMS chip through the packaging tube shell, so that abnormal deformation is caused to the MEMS structure sensitive to stress, even the MEMS structure is seriously adhered, the MEMS chip falls off or breaks, the zero point and the sensitivity drift are shown on the output signal of the MEMS, and the output signal is saturated or has no output signal.

Therefore, considering that the performance and reliability of the device are changed due to the fact that the device is extremely easily influenced by external stress in the packaging process and the using process, the impact and influence of the external stress on the micro-mechanical structure, which are borne by the MEMS chip, are fully considered on the packaging structure, and meanwhile, the electric signal generated by the MEMS can be completely led out to the outside through the packaging body.

For packaging of MEMS devices, reducing or isolating package stress is an important consideration. The existing methods for reducing or isolating package stress generally include the following methods: (1) The contact area between the MEMS chip and the packaging tube shell is reduced, and the defect of the contact area is that the mechanical strength of the chip and the tube shell is low and the mechanical impact resistance is weak; in addition, the contact area of the two is small, so that unbalanced deformation of the MEMS chip is caused, and the performance is worse; (2) The MEMS chip is installed in the tube shell through the elastic packaging lining plate, and the defects of the MEMS chip are that the lining plate has high cost, complex packaging process and weak mechanical impact resistance, and can possibly cause signal delay.

In order to improve the performance of the MEMS chip, a stress isolation structure can be added between the MEMS chip and the packaging tube shell, so that the stress generated by packaging is reduced, and the yield and the performance of the product are improved. Several ways of stress isolation are presently disclosed: patent EP2653443B1 proposes a stress isolation cavity formed by bonding an isolation substrate with a base wafer and bonded with a pressure MEMS chip to achieve stress isolation. The stress isolation structure is complex to process, and a single-end clamped beam is formed between the isolation structure and the substrate wafer, and is easily influenced by external low-frequency resonance.

Patent CN110723713a shows a method for printing a stress buffer layer on a packaging substrate by using 3D, an array type stress isolation layer with a certain thickness is added between the packaging substrate and the MEMS packaging sheet layer, so as to relieve the stress transferred by the substrate, and the criss-cross columnar strips are buffered layer by layer, so that the stress from the packaging tube shell substrate can be eliminated very well, but the bonding between the MEMS and the isolation layer is seriously uneven due to the concave between the strips, so that the bonding surface between the packaging sheet adhesive and the MEMS is seriously uneven, the MEMS chip is unbalanced when the top columnar strip generates stress, the MEMS chip receives a large tensile force along the strip direction of the uppermost isolation layer, and in the vertical direction, no or small stress is generated due to the existence of gaps between the strips, so that the tensile deformation received by the MEMS chip is unbalanced, and the influence on the device with a symmetrical MEMS structure is obvious. In addition, the package cavity height and size are typically limited, so the spacer layer thickness is very limited, and 3D printing is as challenging as mass production.

The patent CN201911000389.9 adopts spring type flexible connection, the MEMS bearing platform is etched by a silicon wafer to form a plane corrugated spring mechanism, two ends of the spring mechanism are stretched and suspended on the supporting frame, the structure is similar to the bearing platform with two ends suspended by springs, the MEMS chip is arranged on the MEMS bearing platform, the stress transmitted by the packaging body is completely relieved through micro deformation of the plane corrugated elastic mechanism, and the MEMS chip arranged on the bearing platform is basically not influenced by the stress of the packaging body. The structure has remarkable effect in relieving the stress of the package shell, but the defect of the method is obvious, and the method is difficult to realize in practice, because of the following reasons: 1) The rigidity of the corrugated spring structure formed by etching is limited, the subsequent MEMS is difficult to assemble on the MEMS bearing table to ensure that the planar corrugated mechanism is not damaged, and if the rigidity of the planar corrugated spring is improved, the stress transmitted by the packaging tube shell is difficult to ensure not to be transmitted to the bearing table; 2) Because the MEMS bearing table suspending mechanism adopts flexible connection, external vibration is extremely easy to be transmitted to the MEMS bearing mechanism through the corrugated spring structure, the resonance effect of the MEMS chip and the MEMS bearing table can be overlapped with MEMS signals, the MEMS signals are greatly interfered, the stability of MEMS signal output is seriously affected, and the linear output of the MEMS signals is difficult to ensure; 3) The inherent resonance characteristics of the spring structure also have a hysteresis effect on certain types of MEMS frequency response.

Patent CN112225168a adopts a stress isolation structure, a step is required to be made on the bottom plate of the packaging tube, one end of the stress isolation substrate is fixed on the step, the other end is suspended above the packaging bottom plate, a gap is formed between the stress isolation substrate and the packaging bottom plate, the fixed area is connected with the suspended area through the neck of the rigid substrate, the isolation groove is positioned between the suspended area and the fixed area, the MEMS chip is fixed in the suspended area and is not in direct contact with the packaging tube, and the mechanical stress transmitted to the MEMS chip by the packaging tube is isolated through the substrate isolation groove. The scheme can realize stress isolation, but has poor impact resistance, when impacted by the direction vertical to the isolation plate, the isolation plate is suspended and can collide with the packaging bottom plate, so that the isolation plate needs to be made thicker, the processing difficulty is higher, the whole packaging thickness is thicker, and the size of the electronic element is smaller, so that the packaging form is not suitable for mass production.

Disclosure of utility model

The utility model aims to solve the technical problem of overcoming the defects existing in the prior art, and provides a stress isolation packaging structure of an MEMS device, wherein a stress isolation substrate in a shape of T, inverted T or I is adopted, and is respectively bonded with a packaging tube shell and an MEMS chip through a piece of adhesive, so that the stress transmitted to the MEMS chip is reduced by utilizing the characteristic of small contact area of the salient points of the stress isolation substrate, the low-stress packaging is realized, and the performance of a product is improved.

In order to solve the technical problems, the utility model provides a stress isolation packaging structure of an MEMS device, which comprises a packaging tube shell, an MEMS chip, a bonding adhesive and a packaging cover plate, wherein an inner bonding pad is arranged in the packaging tube shell, an outer bonding pad is arranged outside the packaging tube shell, and the inner bonding pad and the outer bonding pad are electrically connected through an internal circuit of the packaging tube shell; the MEMS chip is fixed in the packaging tube shell through the stress isolation substrate and the adhesive sheet glue, and the pressure welding block of the MEMS chip is connected with the inner bonding pad of the packaging tube shell through the bonding lead wire to lead out the electric signal of the MEMS chip; the stress isolation substrate consists of a substrate and protruding points, and is in a T shape, an inverted T shape or an I shape.

Specifically, the bump is in a shape of a straight column, a cylinder, a hollow straight column or a hollow cylinder, and at least one bump is arranged.

The stress isolation substrate is made of a material with the same or similar thermal expansion coefficient to that of a silicon material, and preferably monocrystalline silicon wafer, polycrystalline silicon or low-expansion glass.

Preferably, the stress isolation substrate is provided with an anti-glue overflow groove on the surface bonded with the MEMS chip.

The MEMS chip can be a measurement mode which is not contacted with the external environment, such as an accelerometer, a gyroscope, an image MEMS and the like; but also in a measurement mode in contact with the external environment, such as pressure MEMS, flow MEMS, microphones, etc. The MEMS chip is easy to be influenced by external stress due to small volume and high sensitivity, and when in packaging, the stress generated by thermal mismatch of the packaging tube shell and the adhesive sheet glue and the stress introduced by welding on the PCB board can have larger influence on the performance of the MEMS chip, and even the product is invalid. According to the utility model, the stress isolation substrate is added between the packaging tube shell and the MEMS chip, and when the stress isolation substrate is in a T shape, the contact area between the packaging tube shell and the salient point of the stress isolation substrate is smaller, so that the stress transmitted to the MEMS chip is reduced; when the stress isolation is basically in an inverted T shape, the contact area between the MEMS chip and the salient points of the stress isolation substrate is smaller, so that the stress transferred to the MEMS chip is reduced; when the stress isolation is basically in an I shape, the MEMS chip, the packaging tube shell and the stress isolation substrate have enough contact surfaces, but the contact areas of the upper substrate and the lower substrate and the salient points are smaller, the stress transmitted to the MEMS chip is reduced, namely, the stress transmitted to the MEMS chip can be reduced in the three modes, and the low-stress packaging is realized.

Drawings

FIG. 1 is a cross-sectional view of a stress isolation substrate in a "T" shape according to an embodiment.

FIG. 2 is a cross-sectional view of a package structure employing a T-shaped stress isolation substrate according to an embodiment.

FIG. 3 is a cross-sectional view of a stress isolation substrate in the shape of an inverted "T" in accordance with the second embodiment.

FIG. 4 is a cross-sectional view of a package structure employing an inverted T-shaped stress isolation substrate according to a second embodiment.

Fig. 5 is a cross-sectional view of a stress isolation substrate in the shape of an "i" of the third embodiment.

Fig. 6 is a cross-sectional view of a package structure employing an i-shaped stress isolation substrate according to a third embodiment.

Fig. 7 is a schematic view of the bump shape: (a) a straight cylindrical shape; (b) a plurality of cylinders; (c) hollow right cylindrical shape.

Fig. 8 is a process flow diagram of a stress isolation substrate in the shape of an "i" in accordance with the third embodiment.

Detailed Description

The utility model is further described below with reference to the drawings and examples.

Example 1

The stress isolation packaging structure of the MEMS device comprises a packaging tube shell 222, an MEMS chip 212, a stress isolation substrate, adhesive sheets 221 and 213 and a packaging cover plate 211, wherein an inner bonding pad is arranged in the packaging tube shell 222, an outer bonding pad is arranged outside the packaging tube shell 222, and the inner bonding pad and the outer bonding pad are electrically connected through an internal circuit of the packaging tube shell 222; the MEMS chip 212 is fixed in the package case 222 by the stress isolation substrate and the adhesive sheets 221 and 213, and the bonding pads of the MEMS chip 212 are connected with the inner bonding pads of the package case 222 by bonding wires 214, so as to lead out the electrical signals of the MEMS chip 212.

The stress isolation substrate of this embodiment is in a T shape, and is composed of a substrate 111 and bumps 112, wherein the substrate 111 may be a silicon wafer, a glass sheet or a material sheet of other materials, the bumps 112 are prepared on the substrate, the bumps 112 may be designed into a shape of a straight column 112A, a plurality of cylinders 112B, a hollow straight column 112C or the like according to the requirement (as shown in fig. 7 (a), 7 (B) and 7 (C)), and the number of the bumps 112 may be 1, 2 or more according to the requirement. The bump 112 and the package shell 222 of this embodiment are bonded by the adhesive 221, the substrate 111 and the MEMS chip 212 are bonded by the adhesive 213, the surface of the substrate 111 bonded to the MEMS chip 212 is provided with an anti-adhesive overflow groove 113, the MEMS chip 212 realizes the electrical connection between the package shell 222 and the MEMS chip 212 by the lead 214, and finally, the package cover 211 is used for sealing.

In this embodiment, a "T" shaped isolation substrate is added between the package case 222 and the MEMS chip 212, and since the contact area between the package case 222 and the bump 112 of the "T" shaped isolation substrate is small, the stress transferred to the MEMS chip 212 is reduced, and the performance of the product can be improved.

Example two

The stress isolation packaging structure of the MEMS device comprises a packaging tube shell 222, an MEMS chip 212, a stress isolation substrate, adhesive sheets 221 and 213 and a packaging cover plate 211, wherein an inner bonding pad is arranged in the packaging tube shell 222, an outer bonding pad is arranged outside the packaging tube shell 222, and the inner bonding pad and the outer bonding pad are electrically connected through an internal circuit of the packaging tube shell; the MEMS chip 212 is fixed in the package case 222 by the stress isolation substrate and the adhesive sheets 221 and 213, and the bonding pads of the MEMS chip 212 are connected with the inner bonding pads of the package case by bonding wires 214, so as to lead out the electrical signals of the MEMS chip 212.

The stress isolation substrate of this embodiment is in an inverted "T" shape, and is composed of a substrate 111 and bumps 112, wherein the substrate 111 may be a silicon wafer, a glass sheet or a material sheet of other materials, the bumps 112 are prepared on the substrate, the bumps 112 may be designed into the shapes of a straight column 112A, a plurality of cylinders 112B, a hollow straight column 112C, etc. according to the requirements (as shown in fig. 7 (a), 7 (B) and 7 (C)), and the number of the bumps 112 may be 1, 2 or more according to the requirements. The substrate base 111 and the package case 222 of this embodiment are bonded by the adhesive 221, the bump 112 and the MEMS chip 212 are bonded by the adhesive 213, the MEMS chip 212 realizes the electrical connection between the package case 222 and the MEMS chip 212 by the leads 214, and finally, the package cover 211 is used for sealing.

In this embodiment, an inverted "T" shaped isolation substrate is added between the package case 222 and the MEMS chip 212, and since the contact area between the MEMS chip 212 and the bump 112 of the inverted "T" shaped isolation substrate is small, the stress transferred to the MEMS chip 212 is reduced, and the performance of the product can be improved.

Example III

The stress isolation substrate of this embodiment is in an "i" shape, and is composed of an upper substrate 111a, a lower substrate 111b and a bump 112, where the bump 112 is formed on the upper substrate 111a by etching or depositing a thin film and then etching, and the upper substrate 111a and the lower substrate 111b may be silicon chips, glass sheets or material sheets of other materials, and the same material of the upper substrate 111a and the lower substrate 111b may be bonded by a material bonding method, for example, silicon-silicon bonding, anodic bonding or eutectic bonding. The bumps 112 may be designed into a shape of a straight column 112A, a plurality of cylinders 112B, a hollow straight column 112C, etc. as required (as shown in fig. 7 (a), 7 (B) and 7 (C)), and the number of the bumps 112 may be 1, 2 or more as required. In fig. 7, the side length dimension of the bump 112 is Amm when it is a straight column 112A or a hollow straight column 112C, the radius of the column is Amm when it is a plurality of columns 112B, and the shape of the bump 112 is a hollow straight column 112C in the third embodiment, because it is preferable to simulate the stress isolation of the bumps 112 of different shapes and normalize the resulting stress values, as shown in table 1, since the hollow straight column 112C has the best stress isolation effect.

TABLE 1 maximum stress after different isolation structures are packaged

	Straight column	Hollow straight column	Cylindrical array
				Column top size (mm ²)	A*A	A*A	Radius A
Maximum stress (normalization)	0.924	0.264	0.440

In this embodiment, the lower substrate 111b is bonded to the package case 222 through the adhesive 221, the upper substrate 111a is bonded to the MEMS chip 212 through the adhesive 213, the adhesive overflow preventing groove 113 is disposed on the surface of the upper substrate 111a bonded to the MEMS chip 212, the MEMS chip 212 realizes the electrical connection between the package case 222 and the MEMS chip 212 through the leads 214, and finally, the package cover 211 is used for sealing.

In this embodiment, an i-shaped isolation substrate is added between the package shell 222 and the MEMS chip 212, the package shell 222 is bonded to the lower substrate 111b, the MEMS chip 212 is bonded to the upper substrate 111a, and the bump 112 is isolated between the upper substrate 111a and the lower substrate 111b, so that the contact area is small, the stress transferred to the MEMS chip 212 is reduced, and the performance of the product can be improved. And the contact surfaces of the lower substrate 111b and the package tube shell, and the contact surfaces of the upper substrate 111a and the MEMS chip 212 are provided with enough areas, so that the problems that the chip loading is difficult and the high G impact and vibration resistance are poor due to the small contact area on one surface of the T-shaped isolation structure or the inverted T-shaped isolation structure are solved. The bump 112 not only isolates the upper substrate 111a from the lower substrate 111b, but also leaves room for observing the glue-climbing condition between the stress isolation structure and the package case 222 during mounting, so that the glue process can be better controlled. The stress isolation structure of the present embodiment, in the same area as the package can 222 and the MEMS chip 212, not only isolates the stress conducted from the package can 222 to the MEMS chip 212, but also ensures that the product can resist high G impact and vibration environments.

The processing flow of the stress isolation substrate in the shape of an "i" is shown in fig. 8, and the processing flow of the stress isolation substrate in the shape of an "i" is shown in fig. 8, in which a double-sided polished silicon wafer 131 shown in fig. 8 (a) is adopted, one surface of the silicon wafer 131 is processed into the shape of an anti-glue overflow groove through processing steps such as gluing, photoetching, developing, etc., and a groove is etched in an etching manner to realize the anti-glue overflow groove, as shown in fig. 8 (b); processing the appearance of the hollow straight column 112C on the other surface of the silicon wafer 131 through the processing steps of gluing, exposing, developing and the like, and etching a bump structure with a certain depth through deep groove etching, such as a Bosch DRIE processing process or a KOH etching process, wherein the structure depth is 100-200 mu m, as shown in fig. 8 (C); bonding another silicon wafer or glass sheet 132 to the bump, as shown in fig. 8 (d), the bonding may be anodic bonding, silicon-silicon bonding or eutectic bonding; finally, the silicon wafer or glass sheet 132 is thinned to 100 to 200 μm, and the thickness of the entire stress isolation structure is controlled to 400 to 600 μm as shown in fig. 8 (e).

The foregoing is only the best mode of carrying out the utility model. It should be noted that it is also possible for those skilled in the art to make several modifications or equivalent substitutions to the technical solution of the present utility model without departing from the principle of the present utility model, and shall be considered as falling within the protection scope of the present utility model.

Claims

1. The utility model provides a stress isolation packaging structure of MEMS device, includes encapsulation shell, MEMS chip, viscose and encapsulation apron, encapsulation apron is located encapsulation shell, its characterized in that:

The MEMS chip is fixed in the packaging tube shell through the stress isolation substrate and the adhesive sheet glue, and the pressure welding block of the MEMS chip is connected with the inner bonding pad of the packaging tube shell through the bonding lead wire to lead out the electric signal of the MEMS chip;

The stress isolation substrate consists of a substrate and protruding points, and is in a T shape, an inverted T shape or an I shape.

2. The stress isolation package of a MEMS device of claim 1, wherein: the convex points are in the shape of straight column, cylinder, hollow straight column or hollow cylinder.

3. The stress isolation package of a MEMS device of claim 2, wherein: at least one of the bumps is arranged.

4. The stress isolation package of a MEMS device of claim 1, wherein: the stress isolation substrate is made of a material with the same or similar thermal expansion coefficient to that of a silicon material.

5. The stress isolation package of a MEMS device of claim 4, wherein: the stress isolation substrate is made of monocrystalline silicon piece, polycrystalline silicon or low-expansion glass.

6. The stress isolation package of a MEMS device of claim 1, wherein: one surface of the stress isolation substrate, which is bonded with the MEMS chip, is provided with an anti-glue overflow groove.