WO2022062279A1 - 一种mems加速度传感器芯片低应力封装结构 - Google Patents

一种mems加速度传感器芯片低应力封装结构 Download PDF

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WO2022062279A1
WO2022062279A1 PCT/CN2021/071306 CN2021071306W WO2022062279A1 WO 2022062279 A1 WO2022062279 A1 WO 2022062279A1 CN 2021071306 W CN2021071306 W CN 2021071306W WO 2022062279 A1 WO2022062279 A1 WO 2022062279A1
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metal layer
acceleration sensor
sensor chip
mems acceleration
package
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PCT/CN2021/071306
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English (en)
French (fr)
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车录锋
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浙江大学
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Priority to US17/295,598 priority Critical patent/US11780727B2/en
Publication of WO2022062279A1 publication Critical patent/WO2022062279A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/0032—Packages or encapsulation
    • B81B7/0045—Packages or encapsulation for reducing stress inside of the package structure
    • B81B7/0048—Packages or encapsulation for reducing stress inside of the package structure between the MEMS die and the substrate
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/125—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by capacitive pick-up
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/0032—Packages or encapsulation
    • B81B7/0045—Packages or encapsulation for reducing stress inside of the package structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
    • B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
    • B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
    • B81C1/00261—Processes for packaging MEMS devices
    • B81C1/00325—Processes for packaging MEMS devices for reducing stress inside of the package structure
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P1/00—Details of instruments
    • G01P1/02—Housings
    • G01P1/023—Housings for acceleration measuring devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/0802—Details
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B2201/00—Specific applications of microelectromechanical systems
    • B81B2201/02—Sensors
    • B81B2201/0228—Inertial sensors
    • B81B2201/0235—Accelerometers

Definitions

  • the invention relates to a low-stress package structure of a sensor chip, in particular to a low-stress package structure of an acceleration sensor chip suitable for Micro-Electro-Mechanical Systems (MEMS), and belongs to the field of sensor chip package.
  • MEMS Micro-Electro-Mechanical Systems
  • MEMS accelerometer As a representative micro sensor, MEMS accelerometer has the advantages of small size, light weight, easy integration, low power consumption and cost, and mass production. It is widely used in consumer electronics, oil and gas exploration, aerospace, and defense industries. field.
  • the packaging of the chip is one of the key links in the manufacturing process of the acceleration sensor, which not only accounts for 30%-40% of the total cost, but also plays a vital role as a bridge between the sensor chip and the external processing circuit.
  • the accelerometer chip can establish electrical connection with the outside world through the tube-shell package, obtain mechanical support, and prevent damage or interference from harmful factors such as external force, heat, and chemistry.
  • the bottom surface of the acceleration sensor chip is simply bonded to the bottom surface of the casing cavity by gluing or soldering, and then the chip and the casing are wire-bonded, and finally the cavity is sealed by capping. Since the thermal expansion coefficients of the bonding material, the shell material and the chip material are different, when the external temperature changes, there will be different deformations among the three, resulting in thermal stress. The stress is transmitted to the inside of the acceleration sensor chip through the chip base plate, resulting in the deformation of the elastic beam of the sensor and the displacement of the movable structure, which will eventually affect the sensitivity, zero offset and temperature coefficient of the sensor. Therefore, how to reduce the thermal stress introduced by the packaging process is extremely important for the development of high-performance MEMS acceleration sensors.
  • the purpose of the present invention is to provide a low-stress packaging structure suitable for MEMS acceleration sensor chips, which can reduce the packaging stress of the sensor to a minimum, and has a simple process, high reliability, and ease of use. operation, high yield.
  • the present invention provides a low-stress packaging structure suitable for a MEMS acceleration sensor chip, including a tube shell and a MEMS sensor chip.
  • the two ends of the bottom of the MEMS acceleration sensor chip are respectively provided with a first metal layer and
  • a groove is arranged between the first metal layer and the second metal layer; and a third metal layer and a fourth metal layer are correspondingly arranged at both ends of the bottom of the tube case cavity.
  • the third metal layer consists of two adjacent third metal layers.
  • the first metal layer and the second metal layer are Ti/Au (titanium/gold), and the third metal layer and the fourth metal layer are Ni/Au (nickel/gold).
  • the groove width is not less than 100 ⁇ m and the depth is not less than 10 ⁇ m.
  • the first metal layer of the MEMS acceleration sensor chip and the third metal layer of the casing are bonded together, and the second metal layer and the fourth metal layer are not bonded, only contact and fit , a certain active gap is left between the MEMS acceleration sensor chip and the side wall of the casing.
  • the first metal layer of the MEMS acceleration sensor chip and the third metal layer of the package are bonded together by a gold-tin solder layer.
  • the width of the active gap is not less than 0.1 mm.
  • the pads on the MEMS acceleration sensor chip and the pads in the package cavity are connected to each other by metal wires.
  • the package structure further includes a metal cover plate, and the metal cover plate is suitable for sealing the cavity of the case.
  • the tube shell is made of a ceramic material, and the material of the metal cover is a sealing alloy.
  • the present invention provides a semiconductor package including a MEMS acceleration sensor chip and a package.
  • the bottom of the MEMS acceleration sensor chip is respectively provided with a first metal layer and a second metal layer along the first direction, and a groove is provided between the first metal layer and the second metal layer.
  • a third metal layer and a fourth metal layer are respectively provided at the bottom of the tube-shell cavity along the first direction, the third metal layer is arranged opposite to the first metal layer, and the fourth metal layer is arranged opposite to the second metal layer.
  • two adjacent first metal layers are disposed along the second direction on the bottom of the MEMS acceleration sensor chip, and two adjacent first metal layers are disposed along the second direction on the bottom of the package cavity. With three metal layers, the second direction is perpendicular to the first direction.
  • a first metal layer is provided on the bottom of the MEMS acceleration sensor chip along the second direction, and two adjacent third metal layers are provided on the bottom of the package cavity along the second direction, The second direction is perpendicular to the first direction.
  • the first metal layer and the second metal layer are Ti/Au (titanium/gold), and the third metal layer and the fourth metal layer are Ni/Au (nickel/gold).
  • the groove width is not less than 100 ⁇ m and the depth is not less than 10 ⁇ m.
  • the first metal layer and the third metal layer are bonded together, the second metal layer and the fourth metal layer are not bonded, only contact and fit, and the periphery of the MEMS acceleration sensor chip is connected to the A gap is defined between the side walls of the casing.
  • the first metal layer and the third metal layer are bonded together by a gold-tin solder layer.
  • the width of the gap is not less than 0.1 mm.
  • the pads on the MEMS acceleration sensor chip and the pads in the package cavity are connected to each other by metal wires.
  • the package structure further includes a metal cover plate, and the metal cover plate is suitable for sealing the package cavity.
  • the tube shell is made of a ceramic material with good thermal conductivity and low thermal expansion coefficient
  • the material of the metal cover plate is a sealing alloy whose thermal expansion coefficient is closest to that of the ceramic tube shell.
  • FIG. 1 is a schematic structural diagram of a MEMS acceleration sensor chip as an embodiment of the present invention.
  • FIG. 2 is a top view of the package package of the MEMS acceleration sensor chip according to the present invention.
  • Fig. 3 is a cross-sectional view of the package structure of the MEMS acceleration sensor chip according to the present invention along the view angle AA' in Fig. 2 .
  • FIG. 4 is a cross-sectional view of the package structure of the MEMS acceleration sensor chip according to the present invention along the view angle of BB' in FIG. 2 .
  • FIG. 5 is a three-dimensional schematic diagram of the MEMS acceleration sensor chip packaged in a tube casing according to the present invention.
  • CV curve capacitor-voltage relationship curve
  • CV curve capacitance-voltage relationship curve
  • the first method is to choose the encapsulation material. Combined with the structural characteristics of the sensor chip, a low-stress adhesive is selected to effectively buffer the stress input from the outside world.
  • the second method is to design the chip structure. One is to appropriately increase the thickness of the bottom plate of the MEMS chip to reduce the influence of external stress on the deformation of the movable structure in the chip; the other is to introduce a stress isolation structure, although this method can effectively reduce the packaging stress. , but usually requires the fabrication of additional structural layers, which increases the complexity of the process and is not conducive to miniaturization.
  • the third method is to design the bonding position and bonding area of the chip. When packaging, select a position where the external stress has little influence on the deformation of the sensor structure for bonding, and minimize the bonding area without affecting the impact resistance.
  • the structure of the MEMS acceleration sensor chip 1 as an embodiment of the present invention is shown in Figure 1;
  • the elastic beam is deformed, and the position of the intermediate mass block changes, causing the differential capacitance value to change.
  • the detection circuit converts the differential capacitance change into a voltage signal to characterize the acceleration signal input from the outside;
  • the lower cover plate is introduced into the sensor, it will cause the deformation of the MEMS sensitive structure such as the elastic beam, which will cause the change of the plate gap and the torsion of the intermediate mass, which will ultimately affect the performance of the acceleration sensor.
  • the present invention relates to a low-stress packaging structure suitable for a MEMS acceleration sensor chip, comprising a MEMS acceleration sensor chip 1 and a package 2 .
  • Two ends of the bottom of the MEMS acceleration sensor chip 1 are respectively provided with a first metal layer 101, a second metal layer 102 and a groove 103, wherein the groove 103 is disposed between the first metal layer 101 and the second metal layer 102 and is close to the first metal layer 102.
  • Metal layer 101 ; the package package 2 of the MEMS acceleration sensor chip 1 is shown in FIG. 2 , and both ends of the bottom of the cavity of the package 2 are also respectively provided with a third metal layer 201 and a fourth metal layer 202 ; wherein, the third metal layer 201 consists of adjacent third metal layers 201a and third metal layers 201b.
  • the first metal layer 101 and the second metal layer 102 are made of Ti/Au (titanium/gold), and the third metal layer 201 and the fourth metal layer 202 are made of Ni/Au (nickel/gold).
  • FIGS 3 and 4 are shown for the cross-sectional views of the low-stress package structure of the MEMS acceleration sensor chip involved in the present invention
  • the first metal layer 101 of the MEMS acceleration sensor chip 1 and the third metal layer 201 of the package 2 are bonded together by the gold-tin solder layer 3, and the second metal layer 102 and the fourth metal layer 202 are only in contact without sticking Since only one end of the bottom of the MEMS sensor chip 1 is packaged with the shell 2 as a whole, and the other end is in a free state, the packaging stress can be fully released by the movement of the free end, thereby effectively reducing the packaging stress on the chip 1.
  • the second metal layer 102 and the fourth metal layer 202 which are only in contact with the bottom of the MEMS acceleration sensor chip 1 and the bottom of the cavity of the package 2 but not bonded, can provide mechanical support for the chip 1, compared with the isolated convex in the prior art.
  • the platform structure, the low stress package structure has high mechanical shock resistance and reliability.
  • a recess is provided on one side of the first metal layer 101 at the bottom of the MEMS sensor chip 1. Slot 103.
  • the width of the groove 103 is not less than 100 ⁇ m, and the depth is not less than 10 ⁇ m.
  • the width of the movement gap 5 is not less than 0.1 mm.
  • the pads 6 on the MEMS acceleration sensor chip 1 and the pads 7 in the cavity of the tube shell 2 are connected to each other through the metal leads 8 to realize the mutual transmission of electrical signals inside and outside the tube shell 2; finally, the metal cover plate 9 is used to vacuum seal the tube shell 2
  • the cavity is used to complete the low-stress packaging of the MEMS acceleration sensor chip 1 .
  • the package shell 2 adopts a ceramic material with good thermal conductivity and low thermal expansion coefficient, such as alumina ceramics; the material of the metal cover plate 9 is a thermal expansion coefficient equal to Ceramic shell 2 is the closest sealing alloy, such as iron-nickel alloy, iron-nickel-cobalt alloy, iron-nickel-chromium alloy, iron-chromium alloy, iron-nickel-copper alloy, nickel-molybdenum alloy, nickel-molybdenum-tungsten alloy Wait.
  • a ceramic material with good thermal conductivity and low thermal expansion coefficient such as alumina ceramics
  • the material of the metal cover plate 9 is a thermal expansion coefficient equal to Ceramic shell 2 is the closest sealing alloy, such as iron-nickel alloy, iron-nickel-cobalt alloy, iron-nickel-chromium alloy, iron-chromium alloy, iron-nickel-copper alloy, nickel-molybdenum alloy, nickel-molybdenum-tungsten alloy Wait.
  • the CV curve (capacitance-voltage relationship curve) of the capacitor formed by the upper cover plate and the middle mass block
  • the curve can be seen in Figure 7.
  • the curve is calculated and analyzed, and the deflection angle of the intermediate mass block is 3.783E-4 degrees, and the offset is 0.032 microns. It can be seen that the deflection angle and offset of the intermediate mass block caused by the packaging stress are greatly reduced.
  • the metal layer that is only in contact with the bottom of the MEMS acceleration sensor chip and is not bonded can provide mechanical support for the chip and improve the impact resistance and reliability of the package structure.
  • first and second are used for descriptive purposes only and should not be construed to indicate or imply relative importance.
  • the terms “installed”, “connected” and “connected” should be understood in a broad sense, for example, it may be a fixed connection, an integral connection, or a It can be a detachable connection; it can be a mechanical connection or an electrical connection, or it can be a connection between two components; it can be directly connected or indirectly connected through an intermediate medium. situation to understand the specific meaning of the above terms.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
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Abstract

一种适用于MEMS加速度传感器芯片的低应力封装结构，包括传感器芯片（1）和管壳（2），传感器芯片（1）底部两端分别设有第一金属层（101）和第二金属层（102），管壳（2）腔体底部两端也设有对应的第三金属层（201）和第四金属层（202）；第一金属层（101）与第三金属层（201）粘接，第二金属层（102）与第四金属层（202）仅接触但不粘接；为阻止粘接材料高温封装时溢向另一侧金属层，在传感器芯片（1）底部的第一金属层（101）和第二金属层（102）之间设有凹槽（103）。高温封装时，芯片材料具有膨胀空间，从而将传感器的封装应力降低到最小。还提供了一种半导体封装体。

Description

一种MEMS加速度传感器芯片低应力封装结构
相关申请的交叉引用
本申请要求申请号为202011001239.2、申请日为2020年9月22日的中国专利申请的优先权，该中国专利申请的全部内容通过引用并入本文。
技术领域
本发明涉及一种传感器芯片低应力封装结构，尤其涉及一种适用于微电子机械系统(Micro-Electro-Mechanical Systems,MEMS)加速度传感器芯片低应力封装结构，属于传感器芯片封装领域。
背景技术
MEMS加速度传感器作为具有代表性的微传感器，具有体积小、重量轻、易集成、功耗和成本低、可批量生产等优点，被广泛地应用于消费电子、油气勘探、航空航天、国防工业等领域。而芯片的封装是加速度传感器制作过程中的关键环节之一，其不仅占据着总成本的30％-40％，还在传感器芯片与外部处理电路之间扮演着至关重要的桥梁角色。加速度传感器芯片通过管壳封装可建立与外界的电学连接，获得机械支撑，防止外部力、热、化学等有害因素的损害或干扰。
传统的封装首先是通过胶粘或焊料粘接的方式将加速度传感器芯片底面与管壳腔体底面进行简单的粘合，再对芯片与管壳进行引线键合，最后封盖实现腔体密封。由于粘接材料、管壳材料与芯片材料之间的热膨胀系数各不相同，当外部温度变化时，三者之间便呈现出不同的形变量，从而产生热应力。该应力通过芯片底板传递到加速度传感器芯片内部，导致传感器弹性梁变形和可动结构偏移，最终会影响传感器的灵敏度、零点偏移和温度系数等性能。因此，如何减小封装过程引入的热应力，对高性能MEMS加速度传感器的研制极其重要。
发明内容
为解决现有封装技术中存在的问题，本发明的目的在于提供一种适用于MEMS加速度传感器芯片的低应力封装结构，能够将传感器的封装应力降低到最小，且工艺简单，可靠性高，易于操作，成品率高。
为实现上述目的，在一方面，本发明提供了一种适用于MEMS加速度传感器芯片的低应力封装结构，包括管壳和MEMS传感器芯片，MEMS加速度传感器芯片底部两端分别设 有第一金属层和第二金属层，第一金属层与第二金属层之间设有凹槽；管壳腔体底部两端对应设有第三金属层和第四金属层。
在一些实施例中，第三金属层由相邻的两个第三金属层组成。
在一些实施例中，第一金属层和第二金属层为Ti/Au(钛/金)，第三金属层和第四金属层为Ni/Au(镍/金)。
在一些实施例中，凹槽宽度不小于100μm，深度不小于10μm。
基于所述MEMS加速度传感器芯片与管壳，MEMS加速度传感器芯片的第一金属层与管壳的第三金属层粘接在一起，第二金属层与第四金属层不粘接，只进行接触配合，MEMS加速度传感器芯片与管壳的侧壁之间留有一定的活动间隙。
在一些实施例中，MEMS加速度传感器芯片的第一金属层与管壳的第三金属层通过金锡焊料层粘接在一起。
在一些实施例中，活动间隙的宽度不小于0.1mm。
在一些实施例中，MEMS加速度传感器芯片上的焊盘与管壳腔体内的焊盘通过金属引线相互连接。
在一些实施例中，封装结构还包括金属盖板，金属盖板适于密封管壳腔体。
在一些实施例中，管壳采用陶瓷材料，金属盖板的材料为封接合金。
在另一方面，本发明提供了一种半导体封装体，包括MEMS加速度传感器芯片和管壳。MEMS加速度传感器芯片的底部沿第一方向分别设有第一金属层和第二金属层，第一金属层与第二金属层之间设有凹槽。管壳腔体的底部沿第一方向分别设有第三金属层和第四金属层，第三金属层与第一金属层相对设置，第四金属层与第二金属层相对设置。
在一些实施例中，在MEMS加速度传感器芯片的底部上沿第二方向设置有两个相邻的第一金属层，在管壳腔体的底部上沿第二方向设置有两个相邻的第三金属层，第二方向与第一方向垂直。
在一些实施例中，在MEMS加速度传感器芯片的底部上沿第二方向设置有一个第一金属层，在管壳腔体的底部上沿第二方向设置有两个相邻的第三金属层，第二方向与第一方向垂直。
在一些实施例中，第一金属层和第二金属层为Ti/Au(钛/金)，第三金属层和第四金属层为Ni/Au(镍/金)。
在一些实施例中，凹槽宽度不小于100μm，深度不小于10μm。
基于所述MEMS加速度传感器芯片与管壳，第一金属层与第三金属层粘接在一起，第二金属层与第四金属层不粘接，只进行接触配合，MEMS加速度传感器芯片的周边与管壳 的侧壁之间限定有间隙。
在一些实施例中，第一金属层与第三金属层通过金锡焊料层粘接在一起。
在一些实施例中，间隙的宽度不小于0.1mm。
在一些实施例中，MEMS加速度传感器芯片上的焊盘与管壳腔体内的焊盘通过金属引线相互连接。
在一些实施例中，封装结构还包括金属盖板，金属盖板适于密封管壳腔体。
在一些实施例中，管壳采用导热性好、热膨胀系数低的陶瓷材料，金属盖板的材料为热膨胀系数与陶瓷管壳最为接近的封接合金。
上述说明仅是本发明技术方案的概述，为了能够更清楚了解本发明的技术手段，并可依照说明书的内容予以实施，以下以本发明的实施例并配合附图详细说明如后。
附图说明
图1是作为本发明实施例的MEMS加速度传感器芯片的结构示意图。
图2是本发明所涉及的MEMS加速度传感器芯片封装管壳的俯视图。
图3是本发明所涉及的MEMS加速度传感器芯片封装结构沿图2中AA’视角的剖面图。
图4是本发明所涉及的MEMS加速度传感器芯片封装结构沿图2中BB’视角的剖面图。
图5是本发明所涉及的MEMS加速度传感器芯片封装在管壳中的三维示意图。
图6是本发明所涉及的MEMS加速度传感器芯片完成低应力封装后，上盖板和中间质量块构成电容的CV曲线(电容电压关系曲线)图。
图7是本发明所涉及的MEMS加速度传感器芯片完成低应力封装后，下盖板和中间质量块构成电容的CV曲线(电容电压关系曲线)图。
具体实施方式
下面结合附图对本发明作进一步描述。以下实施例的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。以下实施例仅用于更加清楚地说明本发明的技术方案，而不能以此来限制本发明的保护范围。
为了降低封装热应力，相关技术通常从以下几个角度采取办法。第一种方法是选择封装材料。结合传感器芯片的结构特点，选择低应力的粘片胶，对外界输入的应力起有效的缓冲作用。第二种方法是设计芯片结构，其一是适当增加MEMS芯片底板的厚度，降低外部应力对芯片内可动结构变形的影响；其二是引入应力隔离结构，该法虽能有效的降低封装应力，但通常需要制作额外的结构层，增加了工艺的复杂性且不利于实现微型化。第三种方法是设 计芯片的粘接位置与粘接面积。封装时要选择外部应力对传感器结构变形影响较小的位置进行粘接，在不影响抗冲击特性的情况下尽量减小粘接面积。
作为本发明实施例的MEMS加速度传感器芯片1的结构如图1所示；MEMS加速度传感器1采用电容检测原理，由上盖板、弹性梁、中间质量块、下盖板组成一对差分电容；当外界输入加速度信号时，弹性梁发生形变，中间质量块位置发生变化引起差分电容值变化，通过检测电路将差分电容变化量转换为电压信号，来表征外界输入的加速度信号；当有封装热应力通过下盖板引入传感器时，会导致弹性梁等MEMS敏感结构发生形变，从而造成极板间隙变化以及中间质量块的扭转，最终影响加速度传感器的性能。
本发明涉及的一种适用于MEMS加速度传感器芯片的低应力封装结构，包括MEMS加速度传感器芯片1和管壳2。
MEMS加速度传感器芯片1底部两端分别设有第一金属层101，第二金属层102和凹槽103，其中凹槽103设置于第一金属层101和第二金属层102之间并靠近第一金属层101；MEMS加速度传感器芯片1的封装管壳2如图2所示，管壳2腔体底部两端同样分别设有第三金属层201，第四金属层202；其中，第三金属层201由相邻的第三金属层201a和第三金属层201b组成。
所述第一金属层101，第二金属层102采用Ti/Au(钛/金)制成，第三金属层201、第四金属层202采用Ni/Au(镍/金)制成。
本发明所涉及的MEMS加速度传感器芯片低应力封装结构剖面图可参见图3和图4；本发明所涉及的MEMS加速度传感器芯片封装在管壳中的三维示意图可参见图5。
所述MEMS加速度传感器芯片1的第一金属层101与管壳2的第三金属层201通过金锡焊料层3粘接在一起，第二金属层102与第四金属层202仅接触而不粘接；由于MEMS传感器芯片1仅底部一端与管壳2封装为一体，另一端呈自由状态，封装应力可依靠自由端的活动进行充分释放，从而有效的降低了芯片1上的封装应力。
MEMS加速度传感器芯片1底部和管壳2腔体底部仅接触而未粘接的第二金属层102和第四金属层202，可为芯片1提供机械支撑，相较于现有技术中孤立的凸台结构，所述低应力封装结构具有较高的抗机械冲击能力和可靠性。
为阻止金锡焊料高温封装时溢向MEMS传感器芯片1底部另一侧，造成第二金属层102与第四金属层202的粘接，MEMS传感器芯片1底部第一金属层101一侧设有凹槽103。
所述凹槽103宽度不小于100μm，深度不小于10μm。
MEMS加速度传感器芯片1与管壳侧壁4之间留有一定的活动间隙5，保证了高温封装时，MEMS加速度传感器芯片1材料有一定裕度的膨胀空间，从而MEMS加速度传感器芯 片1的封装应力能够降低到最小。
为留有足够裕度的活动空间，所述活动间隙5的宽度不小于0.1mm。
MEMS加速度传感器芯片1上的焊盘6与管壳2腔体内的焊盘7通过金属引线8相互连接，实现电信号在管壳2内外的相互传输；最后采用金属盖板9真空密封管壳2腔体，完成MEMS加速度传感器芯片1的低应力封装。
在一些实施例中，为降低封装外壳对传感器芯片1上热应力的影响，管壳2采用导热性好、热膨胀系数低的陶瓷材料，例如氧化铝陶瓷；金属盖板9的材料为热膨胀系数与陶瓷管壳2最为接近的封接合金，例如铁镍系合金、铁镍钴系合金、铁镍铬系合金、铁铬系合金、铁镍铜系合金、镍钼系合金、镍钼钨系合金等。
本发明所涉及的MEMS加速度传感器芯片1完成低应力封装后，上盖板和中间质量块构成电容的CV曲线(电容电压关系曲线)可参见图6，下盖板和中间质量块构成电容的CV曲线可参见图7。对曲线进行计算分析得到中间质量块偏转角度为3.783E-4度，偏移为0.032微米，可见由封装应力造成的中间质量块偏转角度和偏移大大减小。
本发明至少具有以下有益效果：
MEMS传感器芯片仅底部一端与管壳粘接为一体，另一端呈自由状态，封装应力可依靠自由端的活动进行充分释放，从而有效的降低了封装过程引入的热应力。
管壳腔体底部和MEMS加速度传感器芯片底部仅接触而未粘接的金属层，可为芯片提供机械支撑，提高封装结构的抗冲击能力和可靠性。
MEMS加速度传感器芯片与管壳腔体侧壁留有一定的活动间隙，保证了高温封装时，芯片材料有一定裕度的膨胀空间，从而将传感器的封装应力降低到最小。
在本发明的描述中，需要理解的是，术语“上”、“下”、“竖直”、“水平”、“顶”、“底”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本发明和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本发明的限制。
此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性。
在本发明的描述中，需要说明的是，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，一体地连接，也可以是可拆卸连接；可以是机械连接或电连接，也可以是两个元件内部的连通；可以是直接相连，也可以通过中间媒介间接相连，对于本领域的普通技术人员而言，可以根据具体情况理解上述术语的具体含义。
显然，上述说明并非是本发明的限制，本发明也并不仅限于上述举例，本技术领域的技术人员在本发明的实质范围内所做的变化、改型、添加或替换，也应属于本发明的保护范围。

Claims (19)

  1. 一种适用于MEMS加速度传感器芯片的低应力封装结构，包括MEMS加速度传感器芯片和管壳，其特征在于：所述MEMS加速度传感器芯片底部两端分别设有第一金属层和第二金属层，所述第一金属层与所述第二金属层之间设有凹槽；管壳腔体底部两端对应设有第三金属层和第四金属层。
  2. 根据权利要求1所述的适用于MEMS加速度传感器芯片的低应力封装结构，其特征在于：所述第三金属层由相邻的两个第三金属层组成。
  3. 根据权利要求1所述的适用于MEMS加速度传感器芯片的低应力封装结构，其特征在于：所述第一金属层和所述第二金属层为Ti/Au(钛/金)，所述第三金属层和所述第四金属层为Ni/Au(镍/金)。
  4. 根据权利要求1所述的适用于MEMS加速度传感器芯片的低应力封装结构，其特征在于：所述凹槽宽度不小于100μm，深度不小于10μm。
  5. 根据权利要求1所述的适用于MEMS加速度传感器芯片的低应力封装结构，其特征在于：所述MEMS加速度传感器芯片的所述第一金属层与所述管壳的所述第三金属层粘接在一起，所述第二金属层与所述第四金属层不粘接，只进行接触配合，所述MEMS加速度传感器芯片与所述管壳的侧壁之间留有一定的活动间隙。
  6. 根据权利要求5所述的适用于MEMS加速度传感器芯片的低应力封装结构，其特征在于：所述MEMS加速度传感器芯片的所述第一金属层与所述管壳的第三金属层通过金锡焊料层粘接在一起。
  7. 根据权利要求5所述的适用于MEMS加速度传感器芯片的低应力封装结构，其特征在于：所述活动间隙的宽度不小于0.1mm。
  8. 根据权利要求1所述的适用于MEMS加速度传感器芯片的低应力封装结构，其特征在于：所述MEMS加速度传感器芯片上的焊盘与所述管壳腔体内的焊盘通过金属引线相互连接。
  9. 根据权利要求1所述的适用于MEMS加速度传感器芯片的低应力封装结构，其特征在于：所述封装结构还包括金属盖板，所述金属盖板适于密封所述管壳腔体。
  10. 一种半导体封装体，包括：
    MEMS加速度传感器芯片，所述MEMS加速度传感器芯片的底部沿第一方向分别设有第一金属层和第二金属层，所述第一金属层与所述第二金属层之间设有凹槽；
    管壳，所述管壳腔体的底部沿所述第一方向分别设有第三金属层和第四金属层，所述第 三金属层与所述第一金属层相对设置，所述第四金属层与所述第二金属层相对设置。
  11. 根据权利要求10所述的半导体封装体，其特征在于：在所述MEMS加速度传感器芯片的底部上沿第二方向设置有两个相邻的第一金属层，在所述管壳腔体的底部上沿所述第二方向设置有两个相邻的第三金属层，所述第二方向与所述第一方向垂直。
  12. 根据权利要求10所述的半导体封装体，其特征在于：在所述MEMS加速度传感器芯片的底部上沿第二方向设置有一个第一金属层，在所述管壳腔体的底部上沿所述第二方向设置有两个相邻的第三金属层，所述第二方向与所述第一方向垂直。
  13. 根据权利要求10所述的半导体封装体，其特征在于：所述第一金属层和所述第二金属层为Ti/Au(钛/金)，所述第三金属层和所述第四金属层为Ni/Au(镍/金)。
  14. 根据权利要求10所述的半导体封装体，其特征在于：所述凹槽宽度不小于100μm，深度不小于10μm。
  15. 根据权利要求10所述的半导体封装体，其特征在于：所述第一金属层与所述第三金属层粘接在一起，所述第二金属层与所述第四金属层不粘接，只进行接触配合，所述MEMS加速度传感器芯片的周边与所述管壳的侧壁之间限定有间隙。
  16. 根据权利要求15所述的半导体封装体，其特征在于：所述第一金属层与所述第三金属层通过金锡焊料层粘接在一起。
  17. 根据权利要求15所述的半导体封装体，其特征在于：所述间隙的宽度不小于0.1mm。
  18. 根据权利要求10所述的半导体封装体，其特征在于：所述MEMS加速度传感器芯片上的焊盘与所述管壳腔体内的焊盘通过金属引线相互连接。
  19. 根据权利要求10所述的半导体封装体，其特征在于：所述封装结构还包括金属盖板，所述金属盖板适于密封所述管壳腔体。
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