Thermal flow velocity sensor for controlling temperature crosstalk through TGV structure and preparation method thereof

Abstract

The invention discloses a thermal flow velocity sensor for controlling temperature crosstalk through a TGV structure and a preparation method of the thermal flow velocity sensor. The TGV technology is adopted, a TGV through hole array is formed by filling metal on a glass substrate, an environment temperature measurement resistor is arranged in the peripheral area of a chip, a heat conduction through column is arranged below the environment temperature measurement resistor, a high-heat-conductivity packaging material is introduced on packaging to perceive the environment temperature in real time, a hot node of the sensor is anchored at the system environment temperature through the measures, and the heat conduction performance of the sensor is improved. The temperature crosstalk is effectively reduced, and the stable work of the sensor under different environmental conditions is ensured. Meanwhile, the thermal flow velocity sensor based on the TGV structure can also realize 3D packaging of the device and improve the I / O interface density, and solves the problems of poor reliability and micro-flow field damage caused by traditional lead bonding packaging. The sensor adopts MEMS and TGV technologies, and has the advantages of high-density integration, miniaturization, high reliability and low cost.

Description

Technical Field

[0001] This invention belongs to the field of thermal flow rate sensor design and fabrication technology, and particularly relates to a thermal flow rate sensor that controls temperature crosstalk through a TGV structure and its fabrication method. Background Technology

[0002] Thermal flow velocity sensors work by measuring changes in the thermal field near a heated body to determine flow velocity as fluid flows over it. The sign of the temperature gradient reflects the direction of the flow. Typical operating modes include heat loss and thermal temperature difference. The heat loss type reflects wind speed by measuring the temperature change of the heated body as the fluid flows over it, while the thermal temperature difference type reflects wind speed by measuring the temperature difference of a sensing structure surrounding a central heating resistor. Thermal flow velocity sensors fabricated using MEMS technology have seen rapid development in recent years due to their advantages such as the absence of moving mechanical components, mass production capability, and miniaturization. Based on the operating principle of the control circuit, they can be further divided into constant power circuits, constant voltage circuits, and constant temperature difference circuits. The constant temperature difference circuit effectively resists temperature drift caused by changes in ambient temperature, ensuring consistent output under different external ambient temperatures. Thermostatic circuits for thermal flow rate sensors require an ambient temperature sensing element to provide feedback. The advantage of an on-chip integrated ambient temperature sensing element compared to an off-chip element lies in enhanced system integrity, accurate real-time sensing of the flowing fluid temperature, and feedback to the control circuit, achieving consistent output across different ambient temperatures. However, the on-chip integrated ambient temperature sensing element is susceptible to temperature crosstalk from the heating resistor at the center of the thermal device, causing the thermostatic circuit to operate in a non-ideal state.

[0003] As chip sizes continue to shrink, the industry is pursuing high-density planar devices. The development of advanced packaging technologies like TSV or TGV is also driving MEMS chips towards integration and multifunctionality. Traditional MEMS thermal anemometers are manufactured on silicon substrates. While they benefit from mature silicon micromachining processes, offering advantages such as low cost and mass production, the subsequent packaging process typically uses wire bonding to connect external circuits. This can lead to long-term reliability issues and damage to the surface microfluidic field, causing measurement errors. The introduction of TGV technology not only solves the current problems with wire bonding but also expands packaging to the 3D dimension. Furthermore, the conductive pillars formed by TGV vias can provide denser I / O interfaces to meet the demands of device integration and multifunctionality. Simultaneously, the metal filling in the TGV structure provides a heat conduction channel. Placing an array of metal-filled TGV pillars below the ambient temperature sensing element anchors the element's hot junction to the system's ambient temperature, avoiding temperature crosstalk issues common in thermal devices. Summary of the Invention

[0004] The purpose of this invention is to provide a thermal flow velocity sensor that controls temperature crosstalk through a TGV structure and its fabrication method, so as to solve the technical problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows: A thermal flow rate sensor that controls temperature crosstalk through a TGV structure includes a TGV substrate, a TGV conductive post, a TGV thermally conductive post, a heating resistor, a temperature sensing resistor, a front bonding pad, a back bonding pad, an ambient temperature sensing resistor, a metal heat dissipation layer, a PCB board, an encapsulation adhesive layer, and an encapsulation shell. The TGV conductive pillar extends through the top and bottom sides of the TGV substrate. A front bonding pad is provided at the top of the TGV conductive pillar, and a back bonding pad is provided at the bottom of the TGV conductive pillar. The heating resistor is located at the middle of the upper end of the TGV substrate, and the temperature sensing resistor is located at the edge of the upper end of the TGV substrate. The TGV thermal conductive pillar runs through the top and bottom sides of the TGV substrate, with an ambient temperature sensing resistor at the top and a metal heat dissipation layer at the bottom. The left and right sides of the TGV substrate are connected to the package shell via an encapsulation adhesive layer; the PCB board and the back solder pad are connected via SMT surface mount technology.

[0006] Furthermore, both the TGV conductive pillars and the TGV thermally conductive pillars are filled with metal. The TGV conductive pillars are used to transmit electrical signals, while the TGV thermally conductive pillars are used to transfer heat.

[0007] Furthermore, a thin first insulating layer is provided on the TGV substrate to prevent electrical short circuits.

[0008] Furthermore, the package housing is made of a material with high thermal conductivity, including metal or ceramic, and the surface of the package housing and the upper surface of the TGV substrate are on the same plane.

[0009] Furthermore, a metal heat dissipation layer covers the lower surface of the TGV heat-conducting pillar, separated by a thin third insulating layer.

[0010] Furthermore, the TGV thermal conductive pipes are in the form of TGV pipe arrays, with a single hole diameter of 20-80μm, an array spacing of 50-150μm, and an array coverage of no less than 70% of the projected area of ​​the ambient temperature measuring resistor.

[0011] This invention also discloses a method for fabricating a thermal flow velocity sensor that controls temperature crosstalk using a TGV structure, comprising the following steps: S1. Provide a double-sided polished TGV substrate and thoroughly clean the TGV substrate; S2. Use an ultrashort pulse laser to ablate the designated via locations. The laser focus should be in the center of the TGV substrate. S3. Use an etchant to etch the glass substrate in S2 to form TGV vias; S4. Implement the TGV through-hole filling process to fill the TGV through-hole formed in S3, forming a TGV conductive through-hole and a TGV thermally conductive through-hole that are connected vertically. S5. Deposit a first insulating layer on the upper surface of the TGV substrate; S6. Deposit metal on the first insulating layer and etch it to form the central heating resistor, the temperature measuring resistors symmetrically distributed on both sides, the ambient temperature measuring resistor, the bonding block, and the lead layer for connecting the resistors of the thermal flow sensor. S7. Deposit a second insulating layer to protect the central heating resistor, temperature sensing resistor, ambient temperature sensing resistor, bonding pad, and lead layer for connecting each resistor. S8. First, deposit a third insulating layer on the other side of the TGV substrate, then deposit metal and etch it to form a back bonding pad and a metal heat dissipation layer. S9. Provide a packaging shell with high thermal conductivity, which is connected to the prepared sensor die as a whole through a packaging adhesive layer, and ensures that they are on the same plane; S10. Provide a PCB board with the same solder pad distribution, and perform SMT packaging with the back solder pad formed in S8 to complete the complete fabrication of the flow rate sensor.

[0012] Furthermore, the TGV via filling process in S4 includes two parts: depositing a sidewall seed layer and electroplating a filler metal. The deposition is performed using magnetron sputtering technology, and the deposition material is Cu. After the sidewall seed layer is formed, the TGV substrate is placed in an electroplating device containing Cu electroplating solution for electroplating to form a TGV conductive via (and a TGV thermal via) that are open at both ends.

[0013] Furthermore, in S6, three metal layers of Ti, Pt, and Au are deposited in one step on the first insulating layer using magnetron sputtering technology. The thickness of Ti is 30 nm, the thickness of Pt is 300 nm, and the thickness of Au is 300 nm. Ti serves as the adhesive layer, Pt as the device layer, and Au as the lead layer. The central heating resistor, the temperature measuring resistors symmetrically distributed on both sides, and the ambient temperature measuring resistor are all composed of the adhesive layer, the device layer, and the lead layer.

[0014] The present invention provides a thermal flow velocity sensor that controls temperature crosstalk via a TGV structure and its fabrication method, which has the following advantages: 1. This invention innovatively combines TGV technology with MEMS thermal flow rate sensor to fabricate a TGV-based thermal flow rate sensor, which replaces the traditional silicon substrate and improves the reliability of the device.

[0015] 2. This invention combines TGV technology with MEMS chip design and manufacturing technology, and replaces the traditional MEMS chip surface wire bonding packaging process with high-density 3D stereo packaging. The sensor surface is free of the fine metal wires of traditional wire bonding, which avoids the problems of poor long-term reliability, the need to add additional packaging structure, and damage to the surface microflow field of thermal anemometer caused by surface wire bonding packaging, and provides a high-density I / O interface.

[0016] 3. This invention utilizes a TGV structure, with a TGV metal filling pillar below the ambient temperature sensing resistor forming a heat conduction channel. It also proposes a bottom metal heat dissipation layer and a high thermal conductivity package shell, which anchors the ambient temperature sensing resistor to the ambient temperature. This effectively solves the problem of temperature crosstalk in on-chip integrated ambient temperature sensing resistors and ensures the normal operation of the constant temperature difference circuit.

[0017] 4. This invention addresses the problem of temperature crosstalk affecting environmental temperature sensing resistors. By using a TGV metal heat dissipation channel, a bottom metal heat dissipation layer, a high thermal conductivity packaging shell, and a reasonable layout of the environmental temperature sensing resistors, it not only achieves the aforementioned goal of suppressing temperature crosstalk but also realizes complete sensor packaging in conjunction with process characteristics. Attached Figure Description

[0018] Figure 1 This is a side view of a thermal flow velocity sensor that controls temperature crosstalk using a TGV structure, as disclosed in an embodiment of the present invention. Figure 2 This is a schematic diagram of the cross-sectional structure of the structure obtained in step S1 of the preparation method disclosed in this invention. Figure 3 This is a schematic diagram of the cross-sectional structure of the structure obtained in step S2 of the preparation method disclosed in this invention; Figure 4 This is a schematic diagram of S3 being etched with an etchant in the preparation method disclosed in this invention; Figure 5 This is a schematic cross-sectional view of the structure obtained after S3 etching in the preparation method disclosed in this invention; Figure 6 This is a schematic diagram of the cross-sectional structure of the structure obtained in step S4 of the preparation method disclosed in this invention. Figure 7 This is a schematic diagram of the cross-sectional structure of the structure obtained in step S5 of the preparation method disclosed in this invention; Figure 8 This is a schematic diagram of the cross-sectional structure of the structure obtained in step S6 of the preparation method disclosed in this invention. Figure 9 This is a schematic diagram of the cross-sectional structure of the structure obtained in step S7 of the preparation method disclosed in this invention. Figure 10 This is a schematic diagram of the cross-sectional structure of the structure obtained in step S8 of the preparation method disclosed in this invention. Figure 11 This is a schematic diagram of the cross-sectional structure of the structure obtained in step S9 of the preparation method disclosed in this invention; Figure 12 This is a schematic diagram of the cross-sectional structure of the structure obtained in S10 of the preparation method disclosed in this invention; Figure 13 This is a step diagram of a thermal flow velocity sensor that controls temperature crosstalk through a TGV structure and its fabrication method, as disclosed in an embodiment of the present invention. Figure 14 This is a schematic diagram of a typical thermal flow rate sensor constant temperature difference circuit. Figure 15 This is a simulation cloud map of the thermal field distribution on the sensor surface of a thermal flow velocity sensor and its fabrication method that controls temperature crosstalk through a TGV structure, as disclosed in an embodiment of the present invention. The markings in the diagram are as follows: 1. Sensor die; 2. PCB board; 3. Encapsulation adhesive layer; 4. Encapsulation shell; 5. Etching solution; 21. Through-hole etch location; 22. TGV through-hole; 23. TGV conductive through-pillar; 24. TGV thermal through-pillar; 31. Center heating resistor; 32. Temperature sensing resistor; 33. Ambient resistor; 34. Bonding block; 51. Back bonding block; 52. Metal heat dissipation layer; 100. TGV substrate; 210. Sidewall seed layer; 220. Electroplated filler metal; 310. Adhesive layer; 320. Device layer; 330. Lead layer; 410. First insulating layer; 420. Second insulating layer; 430. Third insulating layer. Detailed Implementation

[0019] To better understand the purpose, structure, and function of this invention, the following description, in conjunction with the accompanying drawings, provides a more detailed account of a thermal flow velocity sensor that controls temperature crosstalk via a TGV structure and its fabrication method.

[0020] Traditionally, MEMS thermal flow rate sensors have been fabricated using silicon substrates. Silicon MEMS sensors have seen extensive research and development due to their compatibility with CMOS technology. However, with increasing demands for miniaturization, integration, and measurement accuracy, silicon-based MEMS thermal flow rate sensors suffer from severe heat dissipation. Furthermore, the need for multi-functional measurement applications has led to an increasingly urgent demand for monolithic integration of multiple sensors. The emergence of TGV technology largely solves these problems. Firstly, for thermal sensors, the low thermal conductivity of the glass substrate prevents heat loss through the substrate, significantly reducing ineffective heat dissipation and improving sensor performance. Secondly, with the growing demand for multiple sensors, monolithic integrated manufacturing of multiple sensors is a future trend. The introduction of TGV technology allows for denser I / O interfaces and brings traditional planar wire bonding packaging to the 3D packaging field. Finally, monolithic integrated thermal devices inevitably suffer from temperature crosstalk. Thermal devices are affected by interference from heating elements, and monolithically integrated ambient temperature sensing elements cannot accurately reflect the true temperature of the flowing fluid. The introduction of TGV technology in this invention not only offers the aforementioned advantages but also provides a thermal conductivity channel, reducing the temperature crosstalk effect of the ambient temperature sensing resistor in on-chip integrated thermal flow velocity sensors, thus enabling them to maintain a constant temperature difference operating state. Furthermore, this invention achieves these functions through a combination of TGV metal heat dissipation channels, a bottom metal heat dissipation layer, a high thermal conductivity packaging shell, and a rational layout of the ambient temperature sensing resistor. It also utilizes process characteristics to achieve complete sensor packaging, providing guidance for the true commercialization of thermal flow velocity sensors.

[0021] A thermal flow rate sensor that controls temperature crosstalk through a TGV structure includes a TGV substrate 100, a TGV conductive post 23, a TGV thermal conductive post 24, a heating resistor 31, a temperature sensing resistor 32, a front bonding pad 34, a back bonding pad 51, an ambient temperature sensing resistor 33, a metal heat dissipation layer 52, a PCB board 2, an encapsulation adhesive layer 3, and an encapsulation shell 4. The TGV conductive post 23 penetrates the upper and lower sides of the TGV substrate 100. The upper end of the TGV conductive post 23 is provided with a front bonding block 34, and the lower end of the TGV conductive post 23 is provided with a back bonding block 51. The heating resistor 31 is located at the middle of the upper end of the TGV substrate 100, and the temperature measuring resistor 32 is located at the edge of the upper end of the TGV substrate 100. The TGV thermal conductive pillar 24 runs through the upper and lower sides of the TGV substrate 100, with an ambient temperature sensing resistor 33 at the upper end and a metal heat dissipation layer 52 at the lower end. The left and right sides of the TGV substrate 100 are connected to the package shell 4 via the encapsulation adhesive layer 3; the PCB board 2 and the back solder pad 51 are connected via SMT surface mount technology.

[0022] Both the TGV conductive post 23 and the TGV thermal conductive post 24 are filled with metal. The TGV conductive post 23 is used to transmit electrical signals, and the TGV thermal conductive post 24 is used to transfer heat.

[0023] A thin first insulating layer 410 is disposed on the TGV substrate 100 to prevent electrical short circuits.

[0024] The package housing 4 is made of a material with high thermal conductivity, including metal or ceramic, and the surface of the package housing 4 and the upper surface of the TGV substrate 100 are on the same plane.

[0025] A metal heat dissipation layer 52 covers the lower surface of the TGV heat-conducting pillar 24, separated by a thin third insulating layer 430.

[0026] The TGV thermal conductive column 24 is in the form of a TGV column array, with a single hole diameter of 20-80μm, an array spacing of 50-150μm, and an array coverage of not less than 70% of the projected area of ​​the ambient temperature sensing resistor 33. Example

[0027] A thermal flow velocity sensor that controls temperature crosstalk using a TGV structure, the complete structure of which is as follows: Figure 1 As shown in the diagram. The steps of its preparation method are illustrated in the diagram below. Figure 13 As shown, the specific implementation steps include the following: Step 1: Provide fused silica glass, Corning 7980, 500μm thick, as TGV substrate 100. Before proceeding to the next step, ultrasonically clean it with acetone, isopropanol, and deionized water for at least 15 minutes each. After cleaning, remove the sample and dry it with a nitrogen gun to reduce the impact of surface contaminants on subsequent process steps. Figure 2 As shown; Step 2: Use an ultrashort pulse laser to ablate the designated via location 21. The laser wavelength is 1030nm and the pulse width is 10ps. Before performing the laser operation, check that the laser focusing plane is in the middle of the 100mm thickness of the TGV substrate. Figure 3 As shown; Step 3: Use etchant 5 to perform wet etching on the TGV substrate 100 after ultrashort pulse laser ablation. The etching time must be longer than the time required for the etchant to penetrate the upper and lower ends of the via. In step three, the etching solution 5 is either hydrofluoric acid or KOH solution. In this example 1, a low-concentration hydrofluoric acid solution with a concentration of 5% is selected as the etching solution. Figure 4 As shown; In step three, to enhance the etching effect, the etching process is carried out in a water bath at a temperature of 80°C.

[0028] In step three, the final structure of the vertically penetrating TGV through-hole 22 is formed, as shown below. Figure 5 As shown.

[0029] Step 4: Implement the TGV through-hole filling process, filling the vertically extending TGV through-hole 22 with metal to form vertically conductive TGV through-hole 23 and thermally conductive TGV through-hole 24, as shown below. Figure 6 As shown; In step four, the TGV via filling process includes two parts: depositing a sidewall seed layer 210 and electroplating a filler metal 220. To ensure the adhesion of the sidewall seed layer 210, magnetron sputtering technology is used for deposition, and Cu is used as the deposition material. After the sidewall seed layer 210 is formed, the glass substrate 100 is placed in an electroplating apparatus containing Cu electroplating solution for electroplating processing to form TGV conductive vias 23 and TGV thermally conductive vias 24 that are connected vertically.

[0030] Step 5: Deposit the first insulating layer 410 on the surface using the PECVD method, such as... Figure 7 As shown.

[0031] Step Six: Deposit and etch metal on the first insulating layer (410) to form the central heating resistor 31, the symmetrically distributed temperature sensing resistors 32 on both sides, the ambient temperature sensing resistor 33, the bonding pad 34, and the lead layer 330 for connecting the resistors, as shown. Figure 8 As shown; Three layers of Ti / Pt / Au metal were deposited in one step using magnetron sputtering technology, with thicknesses of 30 / 300 / 300 nm, which served as the adhesion layer 310, the device layer 320, and the lead layer 330, respectively. The purpose of the adhesive layer 310 is to enhance the adhesion between the device and the glass substrate 100. The device layer 320 is formed by dry etching to form a central heating resistor 31, a temperature sensing resistor 32 and an ambient temperature sensing resistor 33. The lead 330 is formed by wet etching with potassium iodide solution on top of the central heating resistor 31, the temperature measuring resistor 32 and the ambient temperature measuring resistor 33, with an etching time of 30s. The pressure welding block 34 also includes the above three-layer metal structure and is located above the TGV conductive post 23; To reduce the impact of temperature crosstalk on the ambient temperature sensing resistor, the ambient temperature sensing resistor 33 should be placed near the edge of the chip.

[0032] Step 7: Deposit a second insulating layer 420 to protect the central heating resistor 31, the temperature sensing resistor 32, the ambient temperature sensing resistor 33, the bonding pad 34, and the lead layer 330 for connecting the resistors, as shown below. Figure 9 As shown; The second insulating layer 420 was deposited using PECVD technology. The deposition material was silicon oxide, and the thickness was 600 nm.

[0033] Step 8: First, deposit a third insulating layer 430 on the other side, then deposit metal and etch it to form the back bonding pad 51 and the metal heat dissipation layer 52, as shown. Figure 10 As shown; For the same TGV conductive post 23, its upper and lower ends correspond to the pressure welding block 34 and the back pressure welding block 51, respectively; The fabrication process of the back bonding pad 51 is the same as that of the bonding pad 34, that is, the Ti / Pt / Au three-layer metal is deposited in one step using magnetron sputtering technology, with thicknesses of 30 / 300 / 300nm respectively, and then etched to form the back bonding pad 51.

[0034] Step Nine: Provide a packaging shell 4 with high thermal conductivity. The prepared TGV substrate 100 serves as the sensor die 1. It is connected to the prepared TGV substrate 100 as a whole through the packaging adhesive layer 3, ensuring they are on the same plane. Figure 11 As shown; Step 10: Provide a PCB board 2 with the same solder pad distribution, and perform SMT packaging with the back solder pad 51, as shown. Figure 12 As shown; The position and size of the Pad on PCB board 2 are consistent with those of the back solder pad 51; The sensor die 1 is connected to the PCB board 2 via SMT packaging, and the process includes solder paste printing, automatic placement, and reflow soldering. Example

[0035] A thermal flow velocity sensor that controls temperature crosstalk using a TGV structure and its fabrication method, the complete structure as follows: Figure 1 As shown in the diagram. The steps of its preparation method are illustrated in the diagram below. Figure 13 As shown, the specific implementation steps include the following: Step 1: Provide borosilicate glass 100, model SCHOTT BOROFLOAT 33, with a thickness of 500 μm, as the TGV substrate 100. Before proceeding to the next step, ultrasonically clean it with acetone, isopropanol, and deionized water for at least 15 minutes each. After cleaning, remove the sample and dry it with a nitrogen gun to reduce the impact of surface contaminants on subsequent process steps, such as... Figure 2 As shown; Step 2: Use an ultrashort pulse laser to ablate the designated via location 21. The laser wavelength is 1030nm and the pulse width is 10ps. Before performing the laser operation, check that the laser focusing plane is in the middle of the 100mm thickness of the TGV substrate. Figure 3 As shown; Step 3: Use etchant 5 to perform wet etching on the TGV substrate 100 after ultrashort pulse laser ablation. The etching time must be longer than the time required for the etchant to penetrate the upper and lower ends of the via. In step three, the etching solution 5 is either hydrofluoric acid or KOH solution. In this example 2, a low-concentration hydrofluoric acid solution with a concentration of 2.5% is selected as the etching solution. Figure 4 As shown; In step three, to enhance the etching effect, the etching process is carried out in a water bath at a temperature of 90°C.

[0036] In step three, the final structure of the vertically penetrating TGV through-hole 22 is formed, as shown below. Figure 5 As shown.

[0037] Step 4: Implement the TGV through-hole filling process, filling the vertically extending TGV through-hole 22 with metal to form vertically conductive TGV through-hole 23 and thermally conductive TGV through-hole 24, as shown below. Figure 6 As shown; In step four, the TGV via filling process includes two parts: depositing a sidewall seed layer 210 and electroplating a filler metal 220. To ensure the adhesion of the sidewall seed layer 210, magnetron sputtering technology is used for deposition, and Cu is used as the deposition material. After the sidewall seed layer 210 is formed, the glass substrate 100 is placed in an electroplating apparatus containing Cu electroplating solution for electroplating processing to form TGV conductive vias 23 and TGV thermally conductive vias 24 that are connected vertically.

[0038] Step 5: Deposit the first insulating layer 410 on the surface using the PECVD method, such as... Figure 7 As shown.

[0039] Step Six: Deposit and etch metal on the first insulating layer 410 to form the central heating resistor 31, the symmetrically distributed temperature sensing resistors 32 on both sides, the ambient temperature sensing resistor 33, the lead wire 330, and the bonding pad 34 of the thermal flow sensor, as shown. Figure 8 As shown; Three layers of Ti / Pt / Au metal were deposited in one step using metal evaporation technology, with thicknesses of 30 / 300 / 300 nm, respectively, serving as the adhesion layer 310, the device layer 320, and the lead layer 330. The purpose of the adhesive layer 310 is to enhance the adhesion between the device and the glass substrate 100. The device layer 320 is formed by dry etching to form a central heating resistor 31, a temperature sensing resistor 32 and an ambient temperature sensing resistor 33. The lead 330 is formed by wet etching with potassium iodide solution on top of the central heating resistor 31, the temperature measuring resistor 32 and the ambient temperature measuring resistor 33, with an etching time of 30s. The pressure welding block 34 also includes the above three-layer metal structure and is located above the TGV conductive post 23; Furthermore, to reduce the impact of temperature crosstalk on the ambient temperature sensing resistor, the ambient temperature sensing resistor 33 should be placed near the edge of the chip.

[0040] Step 7: Deposit a second insulating layer 420 to protect the central heating resistor 31, temperature sensing resistor 32, ambient temperature sensing resistor 33, lead layer 330, and bonding pad 34, as shown. Figure 9 As shown; A passivation layer of 400 was deposited using PECVD technology. The deposited material was silicon nitride, and the thickness was 600 nm.

[0041] Step 8: First, deposit a third insulating layer 430 on the other side, then deposit metal and etch it to form the back bonding pad 51 and the metal heat dissipation layer 52, as shown. Figure 10 As shown; The back bonding block 51 is different from the bonding block 34. For the same TGV conductive post 23, its upper and lower ends correspond to the bonding block 34 and the back bonding block 51, respectively. The fabrication process of the back bonding pad 51 is the same as that of the bonding pad 34, that is, the three layers of Ti / Pt / Au metal are deposited in one step using metal vapor deposition technology, with thicknesses of 30 / 300 / 300nm respectively, and are formed after etching.

[0042] Step Nine: Provide a packaging shell 4 with high thermal conductivity. The prepared TGV substrate 100 serves as the sensor die 1. It is connected to the prepared TGV substrate 100 as a whole through the packaging adhesive layer 3, ensuring they are on the same plane. Figure 11 As shown; Step 10: Provide a PCB board 2 with the same solder pad distribution, and perform SMT sealing with the back solder pad 51, such as... Figure 12 As shown; The position and size of the Pad on PCB board 2 are consistent with those of the back solder pad 51; The sensor die 1 is connected to the PCB board 2 via SMT packaging, and the process includes solder paste printing, automatic placement, and reflow soldering.

[0043] A complete thermal flow rate sensor includes a sensor chip and matching interface circuitry. At the circuit level, constant bias and constant temperature difference are the two most common forms. Compared to a constant bias circuit, a constant temperature difference circuit can use negative feedback to control and adjust the resistance heating temperature of the sensor's heating area, maintaining a constant temperature difference with the actual ambient fluid. A typical constant temperature difference control circuit schematic is shown below. Figure 14 As shown, it mainly includes matching resistors. and Central heating resistor Ambient temperature measuring resistor Used for regulation and Temperature difference between Thermostatic adjustment resistor Because they are manufactured under the same process conditions, the central heating resistance and ambient temperature measuring resistor Having the same temperature coefficient, denoted as And at the calibrated temperature The resistance values ​​of the following resistors are respectively and ,and , and It is a resistor with a low temperature drift coefficient, located outside the sensor chip. , , , , When placed in a Wheatstone bridge, the bridge remains balanced due to the action of the operational amplifier, and according to the relationship of the temperature coefficient of resistance, we have: (1) Among them, the constant temperature difference regulating resistor It can be set to: (2) Equation (1) can be written as: (3) If the ambient fluid temperature changes at this time Then we have: (4) It can be seen that equation (4) still maintains the equilibrium condition of the constant temperature difference control circuit, that is, the circuit still maintains and Temperature difference between The working state of the thermostatic flow rate sensor is as follows. This demonstrates that the thermostatic control circuit can adapt to different working environments and maintain a constant temperature difference under different fluid temperatures, thus ensuring that the output of the thermostatic flow rate sensor is a stable value.

[0044] However, as chip sizes continue to shrink, the thermal field of the central heating resistor in thermal devices will inevitably affect the ambient temperature sensing resistor in the constant temperature difference circuit. Temperature crosstalk can occur, affecting the normal operation of devices and reducing the measurement accuracy of thermal flow rate sensors. To address the temperature crosstalk problem in the design and fabrication of existing thermal flow rate sensors, this invention proposes a thermal flow rate sensor that controls temperature crosstalk through a TGV structure. This involves utilizing the metal filling formed by TGV technology to create a through-pillar for heat conduction and proposing a high thermal conductivity packaging structure. The layout of the ambient temperature sensing resistor is adjusted to anchor its temperature to the ambient fluid temperature, ensuring the normal operation of the constant temperature difference control circuit.

[0045] like Figure 15As shown in the simulated thermal field cloud diagram, under a constant temperature difference of 100K above the ambient temperature at the central heating resistor, the lowest temperature point of the flow velocity sensor chip appears in the surrounding ambient temperature sensing resistor region, at 292.953K. This structure allows the thermal flow velocity sensor to not only possess a smaller size with more complex interconnect structures and functions, thanks to the advanced TGV packaging technology, meeting the needs of sensor chip integration, but also effectively solves the problem of temperature crosstalk in the heating resistor of the on-chip integrated ambient temperature sensing element, ensuring the normal operation of the constant temperature difference circuit. This enables the thermal flow velocity sensor to adapt to various complex working environments.

[0046] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A thermal flow velocity sensor that controls temperature crosstalk via a TGV structure, characterized in that, It includes a TGV substrate (100), TGV conductive pillars (23), TGV thermally conductive pillars (24), heating resistors (31), temperature sensing resistors (32), front bonding pads (34), back bonding pads (51), ambient temperature sensing resistors (33), metal heat dissipation layer (52), PCB board (2), encapsulation adhesive layer (3), and encapsulation shell (4); The TGV conductive post (23) penetrates the upper and lower sides of the TGV substrate (100). The upper end of the TGV conductive post (23) is provided with a front bonding block (34), and the lower end of the TGV conductive post (23) is provided with a back bonding block (51). The heating resistor (31) is located at the middle position of the upper end of the TGV substrate (100), and the temperature measuring resistor (32) is located at the edge position of the upper end of the TGV substrate (100). The TGV thermal conductive pillar (24) runs through the top and bottom sides of the TGV substrate (100), with an ambient temperature sensing resistor (33) at the top and a metal heat dissipation layer (52) at the bottom. The left and right sides of the TGV substrate (100) are connected to the package shell (4) through the encapsulation adhesive layer (3); the PCB board (2) and the back solder pad (51) are connected through the SMT surface mount process.

2. The thermal flow velocity sensor for controlling temperature crosstalk via TGV structure according to claim 1, characterized in that, Both the TGV conductive column (23) and the TGV thermal conductive column (24) are filled with metal. The TGV conductive column (23) is used to transmit electrical signals, and the TGV thermal conductive column (24) is used to transfer heat.

3. The thermal flow velocity sensor for controlling temperature crosstalk via TGV structure according to claim 1, characterized in that, A thin first insulating layer (410) is disposed on the TGV substrate (100) to prevent electrical short circuits.

4. The thermal flow velocity sensor for controlling temperature crosstalk via TGV structure according to claim 1, characterized in that, The package housing (4) is made of a material with high thermal conductivity, including metal or ceramic, and the surface of the package housing (4) and the upper surface of the TGV substrate (100) are on the same plane.

5. The thermal flow velocity sensor for controlling temperature crosstalk via a TGV structure according to claim 1, characterized in that, A metal heat dissipation layer (52) covers the lower surface of the TGV heat-conducting column (24), separated by a thin third insulating layer (430).

6. The thermal flow velocity sensor for controlling temperature crosstalk via TGV structure according to claim 1, characterized in that, The TGV thermal conductive column (24) is in the form of a TGV column array, with a single hole diameter of 20-80μm, an array spacing of 50-150μm, and an array coverage of not less than 70% of the projected area of ​​the ambient temperature measuring resistor (33).

7. A method for fabricating a thermal flow velocity sensor that controls temperature crosstalk via a TGV structure, used in the thermal flow velocity sensor that controls temperature crosstalk via a TGV structure as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Provide a double-sided polished TGV substrate (100) and thoroughly clean the TGV substrate (100). S2. Use an ultrashort pulse laser to ablate the designated via (21) ablation location. The laser focusing position should be in the middle of the TGV substrate (100). S3. Use etchant (5) to etch the glass substrate (100) in S2 to form TGV via (22). S4. Implement the TGV through-hole filling process to fill the TGV through-hole (22) formed in S3 to form a TGV conductive through-hole (23) and a TGV thermally conductive through-hole (24) that are connected vertically. S5. Deposit a first insulating layer (410) on the upper surface of the TGV substrate (100). S6. Deposit metal on the first insulating layer (410) and etch it to form a central heating resistor (31), temperature measuring resistors (32) symmetrically distributed on both sides, an ambient temperature measuring resistor (33), a bonding pad (34), and a lead layer (330) for connecting each resistor. S7. Deposit a second insulating layer (420) to protect the central heating resistor (31), temperature sensing resistor (32), ambient temperature sensing resistor (33), bonding pad (34) and lead layer (330) for connecting each resistor. S8. First, deposit a third insulating layer (430) on the other side of the TGV substrate (100), then deposit metal and etch it to form a back bonding pad (51) and a metal heat dissipation layer (52). S9. Provide a packaging shell (4) with high thermal conductivity, which is connected to the prepared TGV substrate (100) as a whole through the packaging adhesive layer (3) and ensures that they are on the same plane; S10. Provide a PCB board (2) with the same solder pad distribution, and perform SMT packaging with the back solder pad (51) formed in S8 to complete the complete fabrication of the flow rate sensor.

8. The method for fabricating a thermal flow velocity sensor with temperature crosstalk controlled by a TGV structure according to claim 7, characterized in that, The TGV via filling process in S4 includes two parts: depositing a sidewall seed layer (210) and electroplating a filler metal (220). The deposition is performed using magnetron sputtering technology, and the deposition material is Cu. After the sidewall seed layer (210) is formed, the TGV substrate (100) is placed in an electroplating device containing Cu electroplating solution for electroplating processing to form a TGV conductive via (23) and a TGV thermal via (24) that are connected vertically.

9. The method for fabricating a thermal flow velocity sensor with temperature crosstalk controlled by a TGV structure according to claim 7, characterized in that, In S6, three metal layers of Ti, Pt and Au are deposited in one step on the first insulating layer (410) using magnetron sputtering technology. The thickness of Ti is 30nm, the thickness of Pt is 300nm, and the thickness of Au is 300nm. Ti is used as the adhesive layer (310), Pt is used as the device layer (320), and Au is used as the lead layer (330). The central heating resistor (31), the temperature measuring resistors (32) symmetrically distributed on both sides, and the ambient temperature measuring resistor (33) are all composed of the adhesive layer (310), the device layer (320) and the lead layer (330).

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