CN117368271A - MEMS gas sensor and CMOS chip integrated packaging structure and preparation method thereof - Google Patents
MEMS gas sensor and CMOS chip integrated packaging structure and preparation method thereof Download PDFInfo
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Classifications
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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
- B81B7/0032—Packages or encapsulation
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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
- 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
- B81C1/00222—Integrating an electronic processing unit with a micromechanical structure
- B81C1/00238—Joining a substrate with an electronic processing unit and a substrate with a micromechanical structure
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- 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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
-
- 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
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- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Life Sciences & Earth Sciences (AREA)
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- General Health & Medical Sciences (AREA)
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Abstract
The invention discloses an integrated packaging structure of an MEMS gas sensor and a CMOS chip, wherein the MEMS gas sensor is inversely arranged on the CMOS chip, a heat insulation cavity is arranged in the integrated packaging structure, and gas enters the heat insulation cavity to be adsorbed on a gas sensing material of the MEMS gas sensor, so that the gas sensing material generates resistance change to realize detection of gas type and concentration; the gas sensing material of the MEMS gas sensor faces the CMOS chip and faces away from the gas inlet of the heat insulation cavity. The integrated packaging structure is a Wafer Level Chip Scale (WLCSP) package, is more integrated, miniaturized and low in cost, reduces dust accumulation of gas sensing materials, and increases the sensitivity of gas detection. The invention also discloses a preparation method of the integrated packaging structure.
Description
Technical Field
The invention belongs to the technical field of MEMS devices, and particularly relates to an integrated packaging structure of an MEMS gas sensor and a CMOS chip and a preparation method thereof.
Background
In the field of gas sensors, MEMS (micro-electromechanical systems) technology has been widely used for the manufacture and packaging of sensors. The MEMS gas sensor has the advantages of small volume, low power consumption, high sensitivity and the like, so that the MEMS gas sensor has great application potential in the fields of environmental monitoring, industrial safety, medical diagnosis, intelligent home furnishing and the like. And the packaging technology of the MEMS gas sensor is a key for ensuring the working stability and the testing reliability of the MEMS gas sensor.
Currently, common gas sensor packaging structures include conventional in-line pin type metal tube packages, chip-on-ceramic-base packages, and chip-on-pin-less surface plastic packages (DFNs). However, there are many limitations and disadvantages to these conventional gas sensor packages.
The metal tube shell package is similar TO the TO package of the transistor, but the gas-permeable metal grid is used at the top of the tube shell for communicating the gas sensitive element with the external gas environment, and the metal tube shell package is mainly limited in that the metal tube shell package is large in size, is not suitable for chip MEMS gas sensors, and is difficult TO be used in mobile electronic devices such as smart phones and the like.
The surface-mounted ceramic base is a package commonly used for MEMS gas sensors, the inside of the surface-mounted ceramic base is of a hollow structure, and after the MEMS gas sensor wafer is attached to the surface-mounted ceramic base, the surface-mounted ceramic base is connected to the base through bonding wires and then to pins at the bottom of the base, and the top of the surface-mounted ceramic base is commonly communicated with the internal and external gas environments through an open-pore metal cover plate. The ceramic base package is significantly smaller than the metal shell package, but still 4-5 times larger in size than the sensor die due to the built-in cavity plus bond wire linkage approach. In addition, dust can still enter the package through opening of the metal cover plate, and deposit on the surface of the gas sensitive material, so that the sensitivity of the sensor is reduced or the sensor is disabled.
The DFN package is similar to the ceramic base package in form, but can be made only about 2 times larger than the sensor wafer due to the adoption of custom-made substrates and plastic package molds, which further reduces the volume. The core part of the package is a cavity structure, the gas-sensitive structure of the wafer is exposed in the cavity, the opening communicated with the outside through the cavity is sealed by a dustproof breathable film, and dust can be prevented from entering the package while ventilation is realized. However, this method has a complex packaging process and high cost.
In view of the limitations of the existing gas sensor packaging technology, how to develop a MEMS gas sensor packaging method with further improved integration level, cost, reliability and the like is a technical problem to be solved by those skilled in the art.
Disclosure of Invention
The invention provides an integrated packaging structure of an MEMS gas sensor and a CMOS chip, which is a Wafer Level Chip Scale (WLCSP) packaging, is more integrated, miniaturized and low in cost, reduces dust accumulation of a gas sensing material, and increases the sensitivity of gas detection.
The embodiment of the invention provides an integrated packaging structure of an MEMS gas sensor and a CMOS chip, which is characterized in that the MEMS gas sensor is inversely arranged on the CMOS chip, a heat insulation cavity is arranged in the integrated packaging structure, and gas enters the heat insulation cavity to be adsorbed on a gas sensing material of the MEMS gas sensor, so that the gas sensing material generates resistance change to realize detection of gas type and concentration;
the gas sensing material of the MEMS gas sensor faces the CMOS chip and faces away from the gas inlet of the heat insulation cavity.
Further, the MEMS gas sensor is flip-chip mounted on the CMOS chip through the bonding layer, and the resistance signal output by the MEMS gas sensor is transmitted to a reading circuit of the CMOS chip through the bonding layer, so that the detection result of the gas type and the concentration can be read.
Further, the heating electrode and the interdigital electrode of the MEMS gas sensor are respectively connected with the CMOS chip through bonding layers.
Further, the CMOS chip includes a read circuit, TSV via, and an underlying PAD, wherein:
the reading circuit is connected with the interdigital electrode to read a resistance signal and is connected with the heating electrode to control the heating temperature;
one end of the TSV through hole is connected with the bonding layer, and the other end is connected with the bottom PAD;
the other end of the bottom PAD is connected with a solder ball for board-level welding.
Further, the heat insulation cavity comprises a back etching cavity formed in the MEMS gas sensor and a bonding cavity formed between the MEMS gas sensor and the CMOS chip, and the back etching cavity is connected with the bonding cavity.
Further, the bonding cavity has a height of not less than 5 μm.
Further, the section of the heat insulation cavity is any one or combination of a trapezoid, a triangle, a rectangle and a square, the transverse width is 5-400 mu m, and the depth is 0.3-500 mu m.
Further, the MEMS gas sensor includes:
the dust-proof breathable film is internally provided with a porous structure, and can be breathable while isolating dust;
the lower surface of the substrate is covered with the dust-proof breathable film, a back etching cavity is formed in the substrate, and the back etching cavity is connected with a bonding cavity formed between the CMOS chip and the MEMS chip;
the support layer is formed on the upper surface of the substrate;
the heating electrode is formed on the upper surface of the supporting layer in a patterning way;
an insulating layer formed on upper surfaces of the heating electrode and the supporting layer;
the interdigital electrode is formed on the upper surface of the insulating layer in a patterning way;
the gas sensing material is formed on the interdigital electrodes of the island and the upper surface of the insulating layer, the island is obtained by etching part of the insulating layer and the supporting layer, and the back etching cavity is communicated with the bonding cavity after etching the insulating layer and the supporting layer around the island.
The embodiment of the invention also provides a preparation method of the MEMS gas sensor and CMOS chip integrated packaging structure, which is characterized by comprising the following steps:
obtaining a substrate, and forming a supporting layer on the substrate by adopting a thermal oxidation process;
forming a patterned heating electrode on the supporting layer by a magnetron sputtering and etching method in sequence;
forming an insulating layer on the supporting layer and the heating electrode by adopting a magnetron sputtering or chemical vapor deposition method;
forming interdigital electrodes on the insulating layer sequentially through magnetron sputtering and etching methods;
etching part of the insulating layer and the supporting layer by adopting a plasma etching or wet etching method to form Pad grooves and islands, wherein the Pad grooves are connected with the surface of the heating electrode;
forming bonding layers on the Pad grooves and the interdigital electrodes respectively by adopting an electroplating or thermal evaporation method;
etching the substrate to the supporting layer by adopting an etching process to form a back etching cavity, wherein the back etching cavity is communicated with a space around the island, which is obtained by etching away part of the supporting layer and the insulating layer, so that the island becomes a suspension structure;
covering gas sensing materials on the interdigital electrodes and the insulating layer of the island by adopting a dripping method to obtain the MEMS gas sensor;
the method comprises the steps of obtaining a CMOS chip with TSV, and flip-chip mounting an MEMS gas sensor on the CMOS chip through a bonding layer by adopting a metal bonding or ball-implanted ultrasonic bonding method, wherein a bonding cavity is formed between the MEMS gas sensor and the CMOS chip;
and covering the dust-proof breathable film on the back surface of the substrate of the MEMS gas sensor, thereby obtaining the integrated packaging structure of the MEMS gas sensor and the CMOS chip.
Further, the substrate is any one or combination of silicon, silicon carbide, sapphire and ceramic.
Compared with the prior art, the invention has the beneficial effects that:
the MEMS gas sensor is arranged on the CMOS chip in a flip-chip mode, so that the gas sensing material at the top of the MEMS gas sensor faces the CMOS chip and faces away from the gas inlet of the heat insulation cavity, and the risk of dust accumulation on the gas sensor material is reduced.
Because the MEMS gas sensor is vertically inverted on the CMOS chip, the MEMS gas sensor and the CMOS chip are integrally packaged by the WLCSP, the size of the device is greatly reduced, and the integration is easier to realize.
Drawings
FIG. 1 shows a support layer according to an embodiment of the present invention, 100 is a substrate, 101 is a support layer;
FIG. 2 shows a heater electrode according to an embodiment of the present invention, 100 is a substrate, 101 is a supporting layer, and 102 is a heater electrode;
FIG. 3 shows an embodiment of the present invention, wherein 100 is a substrate, 101 is a supporting layer, 102 is a heating electrode, and 103 is an insulating layer;
FIG. 4 shows a schematic diagram of a detection interdigital electrode according to an embodiment of the present invention, wherein 100 is a substrate, 101 is a supporting layer, 102 is a heating electrode, 103 is an insulating layer, and 104 is a detection interdigital electrode;
FIG. 5 shows an embodiment of the present invention, wherein 100 is a substrate, 101 is a supporting layer, 102 is a heating electrode, 103 is an insulating layer, 104 is a detection interdigital electrode, 105 is a pad groove connected with the heating electrode, and 105-1 is a through cavity;
FIG. 6 shows a bonding layer preparation according to an embodiment of the present invention, wherein 100 is a substrate, 101 is a supporting layer, 102 is a heating electrode, 103 is an insulating layer, 104 is a detection interdigital electrode, 105 is a pad groove, and is connected to the heating electrode, and 105-1 is a through cavity; 106 is a bonding layer;
FIG. 7 shows a back etching of a substrate, 100 being a substrate, 101 being a supporting layer, 102 being a heating electrode, 103 being an insulating layer, 104 being a detection interdigital electrode, 105 being a pad groove and being connected to the heating electrode, 105-1 being a through cavity, according to an embodiment of the present invention; 106 is a bonding layer, 107 is a back etching cavity;
FIG. 8 shows a gas sensor material according to an embodiment of the present invention, wherein 100 is a substrate, 101 is a supporting layer, 102 is a heating electrode, 103 is an insulating layer, 104 is a detection interdigital electrode, 105 is a pad groove, and is connected to the heating electrode, and 105-1 is a through cavity; 106 is a bonding layer, 107 is a back etching cavity, and 108 is a gas sensing material;
fig. 9 shows WLCSP package bonding provided in an embodiment of the invention, 100 is a substrate, 101 is a supporting layer, 102 is a heating electrode, 103 is an insulating layer, 104 is a detection interdigital electrode, 105 is a pad groove, and is connected to the heating electrode, 105-1 is a through cavity; 106 is a bonding layer, 107 is a back etching cavity, 108 is a gas sensing material, 109 is a final bonding layer formed after the bonding of the 106 bonding layer and the CMOS part bonding layer is completed, 200 is a CMOS chip with a reading circuit, 201 is a TSV through hole which is processed in the CMOS chip in advance and is communicated with the back of the CMOS chip, 202 is a bottom PAD connected with the through hole, and 110 is a heat insulation cavity formed by bonding a gas sensor and the CMOS chip;
FIG. 10 shows a device film according to an embodiment of the present invention, wherein 100 is a substrate, 101 is a supporting layer, 102 is a heating electrode, 103 is an insulating layer, 104 is a detection interdigital electrode, 105 is a pad groove, the heating electrode is connected, 105-1 is a through cavity, 107 is a back etching cavity, 108 is a gas sensing material, 109 is a final bonding layer, 200 is a CMOS chip with a reading circuit, 110 is a heat insulation cavity formed by bonding a gas sensor and the CMOS chip, 111 is a dust-proof and air-permeable film, and can have a water absorption function, and 203 is a solder ball for board level welding;
FIG. 11 shows a ball-bonded package design according to an embodiment of the present invention, wherein 100 is a substrate, 101 is a supporting layer, 102 is a heating electrode, 103 is an insulating layer, 104 is a detection interdigital electrode, 105 is a pad groove, and the heating electrode is connected, 105-1 is a through cavity; 106 is a bonding layer, 107 is a back etching cavity, 108 is a gas sensing material, 109 is gold ball bonding, 200 is a CMOS chip with a reading circuit, 110 is a heat insulation cavity formed by bonding a gas sensor and the CMOS chip, 111 is a dust-proof and breathable film, and 203 is a solder ball for board level welding;
FIG. 12 is another cross-sectional view showing the bonding cavity 110 in communication with the back-etched cavity 107 through the through-cavity 105-1, i.e., the A-A interface of FIG. 13, in accordance with an embodiment of the present invention;
FIG. 13 is a top view of a gas sensor according to an embodiment of the present invention, showing the relative positions of the through cavity 105-1, the sensitive material 108, the heater electrode 102, and the detector electrode 104.
Detailed Description
The MEMS gas sensor and CMOS chip integrated packaging structure provided by the embodiment of the invention is specifically described with reference to the accompanying drawings.
According to the embodiment of the invention, the MEMS gas sensor is bonded with the CMOS chip, so that the CMOS-MEMS integrated Wafer Level Chip Scale Package (WLCSP) of the gas sensor is realized, the device is more integrated, miniaturized and low-cost, and meanwhile, the packaging structure is that the gas sensor is inverted on the CMOS chip, so that the risk of detection sensitivity reduction of a gas sensing material caused by dust accumulation is reduced.
The MEMS gas sensor and CMOS chip integrated packaging structure provided by the embodiment of the invention comprises: the MEMS gas sensor is inversely arranged on the CMOS chip, a heat insulation cavity is arranged in the integrated packaging structure, gas passes through the heat insulation cavity and is adsorbed on a gas sensing material of the MEMS gas sensor, so that the gas sensing material is subjected to resistance change to realize the detection of the gas type and concentration. The gas sensing material of the MEMS gas sensor is opposite to the gas inlet of the heat insulation cavity, so that dust accumulation on the gas sensing material is reduced, and the gas sensing material can generate resistance change based on sensitivity of the introduced gas.
According to the embodiment of the invention, the MEMS gas sensor is inversely arranged on the CMOS chip through the bonding layer, so that the MEMS gas sensor is vertically bonded on the CMOS chip, compared with the prior art that the MEMS gas sensor is connected with the CMOS chip through the tiled conducting wire, the size is smaller, the integration is better, and the resistance signal output by the MEMS gas sensor can be transmitted into the reading circuit of the CMOS chip through the bonding layer, so that the detection result of the gas type and the concentration can be read.
In a specific embodiment, the bonding layer provided in this embodiment connects the heating electrode and the interdigital electrode of the MEMS gas sensor with the CMOS chip, respectively. The change in resistance of the gas sensing material is detected by the interdigitated electrodes to form a resistance signal, and the resistance signal is transferred to the read circuit through the bonding layer.
The CMOS chip provided by the embodiment of the invention is connected with the lead led out from the periphery of the heating electrode, and the input current controls the heating electrode to generate heat. Insulation is achieved by means of islands and cavities around them. The connection lines of the heating electrode and the interdigital electrode are led out through the support structure of the island.
In a specific embodiment, the CMOS chip provided in this embodiment includes a read circuit, a TSV via, and an underlying PAD, where: the reading circuit is connected with the interdigital electrode to read the resistance signal and connected with the heating electrode to control the heating temperature; one end of the TSV through hole is connected with the bonding layer, and the other end is connected with the bottom PAD; the other end of the bottom PAD is connected with a solder ball for board-level welding.
In a specific embodiment, the heat insulation cavity provided by the embodiment of the invention comprises a back etching cavity formed in the MEMS gas sensor and a bonding cavity formed between the MEMS gas sensor and the CMOS chip, wherein the back etching cavity is connected with the bonding cavity.
In one embodiment, the bonding cavity provided in this embodiment has a height of not less than 5 μm. Thereby isolating heat dissipation, improving the efficiency of heating the gas sensing material of the heating electrode and reducing the heat loss.
The MEMS gas sensor provided by the embodiment of the invention comprises a dust-proof gas-permeable film, a substrate, a supporting layer, a heating electrode, an insulating layer, an interdigital electrode and a gas sensing material, wherein:
the dust-separation breathable film provided by the embodiment has the functions of ventilation, dust prevention and water absorption, and is of a loose porous structure inside the dust-separation breathable film, so that the dust-separation breathable film can be ventilated while isolating dust.
The lower surface of the substrate provided by the embodiment is covered with the dust-proof breathable film, a back etching cavity is formed in the substrate, and the back etching cavity is connected with a bonding cavity formed between the CMOS chip and the MEMS chip.
The supporting layer provided in this embodiment is formed on the upper surface of the substrate.
The heating electrode pattern provided in this embodiment is formed on the upper surface of the supporting layer.
The insulating layer provided in this embodiment is formed on the upper surfaces of the heating electrode and the supporting layer.
The interdigital electrode pattern provided in this embodiment is formed on the upper surface of the insulating layer.
The gas sensing material provided by the embodiment is formed on the interdigital electrode of the island and the upper surface of the insulating layer, the island is obtained by etching the insulating layer and the supporting layer, and after etching the insulating layer and the supporting layer around the island, the back etching cavity is communicated with the bonding cavity, and the communicated back etching cavity and the bonding cavity jointly form a heat insulation cavity inside the sensor.
The embodiment of the invention also provides a preparation method of the MEMS gas sensor and CMOS chip integrated packaging structure, which comprises the following steps: the method comprises the steps of preparing a supporting layer, a heating electrode, an insulating layer, an interdigital electrode for detection, a heat insulation cavity formed by etching the insulating layer, a heat insulation cavity formed by etching a substrate, a gas sensing material, a heat insulation cavity formed by bonding a gas sensor and a CMOS chip and the like.
The preparation of the supporting layer provided by the embodiment of the invention is formed by a thermal oxidation method, and the supporting layer is positioned between the substrate and the heating electrode; the heating electrode is formed by sputtering coating and etching and is positioned between the supporting layer and the insulating layer; the insulating layer is formed by chemical vapor deposition and is positioned between the heating electrode and the interdigital electrode for detection; the interdigital electrode for detection is formed by sputtering coating and etching and is positioned between the insulating layer and the sensing material; the central island is formed by etching the insulating layer and the supporting layer around the central island; the cavity is formed by etching the back of the substrate and is positioned below the supporting layer, the cavity, the insulating layer and the supporting layer which are etched around the island are partially formed to be communicated with the cavity, the insulating layer and the supporting layer are further connected to the cavity formed by bonding, and gas is diffused to the surface of the gas sensing material through the communicated cavity; the gas sensing material is covered on the interdigital electrode for detection in a dripping or sputtering mode, and a bonding cavity formed by bonding the gas sensor and the CMOS chip is realized by bonding layer metal or ball implantation, and the heat loss generated by heating the electrode can be reduced by the bonding cavity.
The substrate provided by the embodiment of the invention is one or any combination of silicon, silicon carbide, sapphire, ceramic and the like;
the heat insulation cavity provided by the embodiment of the invention can be one or any combination of a ladder shape, a triangle shape and a rectangular square shape, and has the transverse width of 5-400 mu m and the depth of 0.3-500 mu m;
the metal bonding layer and the electrode provided by the embodiment of the invention are deposited by adopting methods such as thermal evaporation or magnetron sputtering, electroplating and the like, and the material is one or any combination of molybdenum, gold, platinum, copper, aluminum, silver, titanium, tungsten and nickel, and the thickness is 0.1-50 mu m; forming patterns by adopting processes such as plasma etching, lift-off, wet etching and the like; the line width of the electrode is 0.5-10 μm
The material of the supporting layer and the insulating layer provided by the embodiment of the invention is one or any combination of silicon oxide, doped silicon oxide, silicon nitride, doped silicon nitride and the like, and the thickness is 0.1-3 mu m.
The gas sensing material provided by the embodiment of the invention is tin oxide, tungsten oxide, zinc oxide and some composite materials doped with platinum or other metals.
Example 1
The embodiment of the invention provides a preparation method of an integrated packaging structure of an MEMS gas sensor and a CMOS chip, which comprises the following steps:
(1) The substrate 100 is ultrasonically cleaned using an SPM solution.
(2) As shown in fig. 1, a silicon oxide support layer 101 of 300nm is formed on a silicon substrate 100 using a thermal oxygen process.
(3) As shown in fig. 2, a magnetron sputtering method is adopted to deposit 300nm of metal platinum on the silicon oxide supporting layer 101, an IBE etching method is adopted to form the heating electrode 102, the etching process of the heating electrode 102 is that RF power is 500W, the chamber pressure is 7mT, the beam current is 460mA, the voltage is 400eV, the etching rate is about 30nm/min, and the line width of the heating electrode is 500nm.
(4) As shown in fig. 3, a silicon oxide insulating layer 103 having a thickness of about 1 μm is deposited on the support layer 101 and the heating electrode 102 by magnetron sputtering or chemical vapor deposition.
(5) As shown in fig. 4, a magnetron sputtering method is adopted to deposit 300nm of metal platinum on the insulating layer 103, an IBE etching method is adopted to form the interdigital electrode 104 for detection, the etching process of the interdigital electrode 104 for detection is that RF power is 500W, the chamber pressure is 7mT, the beam current is 460mA, the voltage is 400eV, the etching rate is about 30nm/min, and the line width of the interdigital electrode for detection is 500nm.
(6) As shown in fig. 5, a portion of the insulating layer 103 and the supporting layer 102 are etched by plasma etching or wet etching, etc., to form Pad grooves 105, through cavities 105-1 and islands. The etching process of the insulating layer 103 is that the RF power is 1000W, the chamber pressure is 20mT, and the etching gas is CF 4 /O 2 100/20Sccm, an etching rate of about 200nm/min, pad grooves 105 connected to the surface of the heater electrode 102, through cavities 105-1 connected to the substrate 100, and a lateral width of the through cavities 105-1 of 60 μm. Not visible in this cross section through cavity 105-1, and is thus framed using a dashed frame;
(7) As shown in fig. 6, a 50 μm gold bonding layer 106 is formed in the pad groove 105 and the pad region of the detection interdigital electrode by electroplating or thermal evaporation.
(8) As shown in fig. 7, the substrate 100 is etched by using a Bosch process to form the back-etched cavity 107, wherein the single cycle of the Bosch process is performed with RF power 3000/1000/140W, chamber pressure 50mT, and the etching gas is SF6/O2 200/90Sccm, and about 300 cycles are required to be etched. The back-etched cavity 107 is connected to the support layer and has a lateral width of 110 μm.
(9) As shown in fig. 8, a layer of gas sensing material 108 is coated on the detection interdigital electrode 104 by a drop-coating method.
(10) As shown in fig. 9 or 11, the prepared gas sensor device and the CMOS chip 200 with the read circuit are bonded together by adopting a metal bonding or ball-implanted ultrasonic bonding method, 109 is a final bonding layer or gold ball, the depth of a bonding cavity 110 generated by bonding the gas sensor and the CMOS chip 200 is 50 μm, heat dissipation is isolated, the CMOS chip comprises the read circuit, one end of a TSV through hole 201 is connected with the bonding layer, and the other end is connected with a bottom PAD202; the other end of the bottom PAD202 is connected to a solder ball 203 for board level soldering, and the back etched cavity 107 is connected to the bonding cavity 110 by penetrating the cavity 105-1 to form a thermally insulating cavity inside the integrated package structure.
(11) As shown in fig. 10, a film 111 having a ventilation, dust-proof and water-absorbing function is coated on the back surface of the substrate 100. As shown in fig. 13, a top view of an integrated package structure of a MEMS gas sensor and a CMOS chip is obtained, as shown in fig. 12, which is A-A cross-sectional view of a top view of an integrated package structure of a MEMS gas sensor and a CMOS chip, and fig. 1 to 11, which are B-B cross-sectional views of a top view of an integrated package structure of a MEMS gas sensor and a CMOS chip, as shown in fig. 11, which is a structure diagram of a device formed by ultrasonic bonding using gold-implanted balls.
Wherein 100 is a substrate, and the material is one or any combination of silicon, silicon carbide, sapphire, ceramic and the like.
101 is a supporting layer deposited on the surface of the substrate 100, and the material may be one or any combination of silicon oxide, doped silicon oxide, silicon nitride, doped silicon nitride, and the like, and the thickness is 100-500nm.
102 is a heating electrode deposited on the supporting layer 101, and the material may be one or any combination of molybdenum, gold, platinum, copper, aluminum, silver, titanium, tungsten and nickel, and the thickness is 50-500nm, and the heating electrode is formed into a designed pattern by IBE etching, wet etching and other methods, and the linewidth of the heating electrode is 0.5-10 μm.
103 is an insulating layer deposited on the supporting layer 101 and the heating electrode 102, and the material may be one or any combination of silicon oxide, doped silicon oxide, silicon nitride, doped silicon nitride, and the like, and the thickness is 0.1-3 μm.
104 is an interdigital electrode for detection deposited on the insulating layer 103, the material can be one or any combination of molybdenum, gold, platinum, copper, aluminum, silver, titanium, tungsten and nickel, the thickness is 50-500nm, the designed pattern is formed by IBE etching, wet etching and other methods, and the line width of the heating electrode is 0.5-10 μm.
105 and 105-1 are Pad grooves and heat insulation cavities formed by etching the insulating layer 103 and the supporting layer 101, respectively, the Pad grooves 105 are connected with the surface of the heating electrode 102, the penetrating cavities 105-1 are connected with the substrate 100, and the transverse width of the penetrating cavities 105-1 is 20-500 μm.
106 is a bonding layer filled in pad groove 105 and the pad area of the detection interdigital electrode, and is made of one or any combination of molybdenum, gold, platinum, copper, aluminum, silver, titanium, tungsten and nickel, and the thickness is 0.5-100 μm.
107 is a heat insulation cavity formed after etching the substrate 100, the depth of the cavity is 50-500 μm, and the lateral width is 30-400 μm.
108 are gas sensing materials that are dripped onto the sensing interdigital electrodes, which may be tin oxide, tungsten oxide, zinc oxide, and some composite materials doped with platinum or other metals.
And 109 is a bonding layer or bonding alloy ball formed after the gas sensor device is bonded with the CMOS chip.
And 110 is a bonding cavity formed by bonding the gas sensor device and the CMOS chip, and the depth of the cavity is 0.3-100 mu m.
111 is a layer of film with ventilation, dust prevention and water absorption functions, which is covered on the 100 substrates, and the material can be polytetrafluoroethylene which is formed by special process treatment.
200 is a CMOS chip with a read circuit.
201 is a pre-processed TSV via inside a CMOS chip.
202 is a bottom PAD of the bottom of the CMOS chip connected to the TSV via for subsequent board level solder ball placement.
203 are solder balls for board level soldering.
Claims (10)
1. The integrated packaging structure of the MEMS gas sensor and the CMOS chip is characterized in that the MEMS gas sensor is inversely arranged on the CMOS chip, a heat insulation cavity is arranged in the integrated packaging structure, and gas enters the heat insulation cavity to be adsorbed on a gas sensing material of the MEMS gas sensor, so that the gas sensing material generates resistance change to realize detection of gas type and concentration;
the gas sensing material of the MEMS gas sensor faces the CMOS chip and faces away from the gas inlet of the heat insulation cavity.
2. The MEMS gas sensor and CMOS chip integrated package structure of claim 1, wherein the MEMS gas sensor is flip-chip mounted on the CMOS chip through the bonding layer, and the resistance signal output from the MEMS gas sensor is transferred to a reading circuit of the CMOS chip through the bonding layer, so that the detection result of the gas type and concentration can be read.
3. The MEMS gas sensor and CMOS chip integrated package of claim 2, wherein the heating electrode and the interdigital electrode of the MEMS gas sensor are respectively connected to the CMOS chip by bonding layers.
4. The MEMS gas sensor and CMOS chip integrated package of claim 3, wherein the CMOS chip comprises a read circuit, TSV via, and underlying PAD, wherein:
the reading circuit is connected with the interdigital electrode to read a resistance signal and is connected with the heating electrode to control the heating temperature;
one end of the TSV through hole is connected with the bonding layer, and the other end is connected with the bottom PAD;
the other end of the bottom PAD is connected with a solder ball for board-level welding.
5. The MEMS gas sensor and CMOS chip integrated package structure of claim 1, wherein the thermally insulating cavity comprises a back etched cavity formed inside the MEMS gas sensor and a bonding cavity formed between the MEMS gas sensor and the CMOS chip, the back etched cavity being connected to the bonding cavity.
6. The MEMS gas sensor and CMOS chip integrated package of claim 5, wherein the bonding cavity has a height of not less than 5 μm.
7. The MEMS gas sensor and CMOS chip integrated package structure of claim 1, wherein the cross section of the thermally insulating cavity is any one or a combination of a trapezoid, triangle, rectangle, square, with a lateral width of 5-400 μm and a depth of 0.3-500 μm.
8. The MEMS gas sensor and CMOS chip integrated package of claim 1, wherein the MEMS gas sensor comprises:
the dust-proof breathable film is internally provided with a porous structure, and can be breathable while isolating dust;
the lower surface of the substrate is covered with the dust-proof breathable film, a back etching cavity is formed in the substrate, and the back etching cavity is connected with a bonding cavity formed between the CMOS chip and the MEMS chip;
the support layer is formed on the upper surface of the substrate;
the heating electrode is formed on the upper surface of the supporting layer in a patterning way;
an insulating layer formed on upper surfaces of the heating electrode and the supporting layer;
the interdigital electrode is formed on the upper surface of the insulating layer in a patterning way;
the gas sensing material is formed on the interdigital electrodes of the island and the upper surface of the insulating layer, the island is obtained by etching part of the insulating layer and the supporting layer, and the back etching cavity is communicated with the bonding cavity after etching the insulating layer and the supporting layer around the island.
9. A method of manufacturing a MEMS gas sensor and CMOS chip integrated package according to any one of claims 1-8, comprising:
obtaining a substrate, and forming a supporting layer on the substrate by adopting a thermal oxidation process;
forming a patterned heating electrode on the supporting layer by a magnetron sputtering and etching method in sequence;
forming an insulating layer on the supporting layer and the heating electrode by adopting a magnetron sputtering or chemical vapor deposition method;
forming interdigital electrodes on the insulating layer sequentially through magnetron sputtering and etching methods;
etching part of the insulating layer and the supporting layer by adopting a plasma etching or wet etching method to form Pad grooves and islands, wherein the Pad grooves are connected with the surface of the heating electrode;
forming bonding layers on the Pad grooves and the interdigital electrodes respectively by adopting an electroplating or thermal evaporation method;
etching the substrate to the supporting layer by adopting an etching process to form a back etching cavity, wherein the back etching cavity is communicated with a space around the island, which is obtained by etching away part of the supporting layer and the insulating layer, so that the island becomes a suspension structure;
covering gas sensing materials on the interdigital electrodes and the insulating layer of the island by adopting a dripping method to obtain the MEMS gas sensor;
the method comprises the steps of obtaining a CMOS chip with TSV, and flip-chip mounting an MEMS gas sensor on the CMOS chip through a bonding layer by adopting a metal bonding or ball-implanted ultrasonic bonding method, wherein a bonding cavity is formed between the MEMS gas sensor and the CMOS chip;
and covering the dust-proof breathable film on the back surface of the substrate of the MEMS gas sensor, thereby obtaining the integrated packaging structure of the MEMS gas sensor and the CMOS chip.
10. The method for manufacturing the integrated package structure of the MEMS gas sensor and the CMOS chip according to claim 9, wherein the substrate is any one or a combination of silicon, silicon carbide, sapphire, and ceramic.
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