Hybrid inductive proximity sensor based on semiconductor process and manufacturing method thereof

Abstract

The embodiment of the invention provides a hybrid inductive proximity sensor based on a semiconductor process and a manufacturing method thereof, the hybrid inductive proximity sensor comprises a planar induction coil and an electronic chip, the planar induction coil is a copper coil structure formed on a substrate through photoetching and electroplating processes, the plane induction coil is integrated with multiple sections of concentric annular sub-coils, and the multiple sections of concentric annular sub-coils are used for measuring magnetic field gradient changes caused by a target object in a segmented manner; the electronic chip is integrated with an oscillator circuit, and the oscillator circuit comprises an inductance branch with a series positive and negative temperature coefficient resistor combination, a capacitance branch with a parallel adjustable resistor, and a comparator unit for dynamically adjusting delay; the packaging structure of the hybrid inductive proximity sensor comprises a substrate which is inversely connected with an electronic chip through a carrier plate, and the surface of the substrate is covered with a protective layer; the packaging pretreatment of the hybrid inductive proximity sensor comprises the steps of bonding pad micromachining, gas protection reflow soldering and a composite adhesive buffer layer.

Description

Technical Field

[0001] The present application belongs to the technical field of micro-electromechanical system (MEMS) sensors, and in particular relates to a hybrid inductive proximity sensor based on semiconductor technology and a manufacturing method thereof. Background Art

[0002] As the core device for non-contact displacement detection in the industrial field, the technological evolution of inductive proximity sensors has always revolved around three major directions: miniaturization, temperature stability, and integration.

[0003] Traditional sensors use discrete negative temperature coefficient (NTC) thermistors for temperature compensation, requiring external components to adjust impedance matching. This not only takes up additional space but also limits mass production yield due to the uncontrollable mechanical adjustment. At the packaging level, the separate layout of the thick-film coil and electronics introduces significant parasitic effects. When an aluminum target approaches, the temperature-dependent drift of the coil's inductance (L) and resistance (R), resulting from the τ = L / R time constant, is on the same order of magnitude as the impedance change caused by target displacement, resulting in measurement errors up to micron levels. Furthermore, existing complementary metal oxide semiconductor (CMOS) processes make it difficult to implement thin-film resistors with both positive and negative temperature coefficients at the micron scale, making on-chip integration of temperature drift compensation circuitry impossible. For example, in a 750nm CMOS process, the metal layer resistance temperature coefficient is typically fixed at 0.18% / °C, while that of polysilicon resistors is -0.13% / °C. This material property difference renders traditional single-branch compensation circuits ineffective.

[0004] These technical bottlenecks have seriously restricted the large-scale application of high-precision, low-power proximity sensors in the field of intelligent manufacturing. Summary of the Invention

[0005] The present application proposes a hybrid inductive proximity sensor based on semiconductor technology and a manufacturing method thereof, which are used to address the above-mentioned defects of the prior art.

[0006] According to a first aspect of an embodiment of the present application, a hybrid inductive proximity sensor based on semiconductor technology is provided, comprising: a planar inductive coil and an electronic chip. The planar induction coil is a copper coil structure formed on a substrate through photolithography and electroplating processes. The planar induction coil integrates multiple concentric annular sub-coils, which are used to segmentally measure the magnetic field gradient changes caused by the target object; The electronic chip is integrated with an oscillator circuit, which includes an inductor branch having a combination of positive and negative temperature coefficient resistors connected in series, a capacitor branch having an adjustable resistor connected in parallel, and a comparator unit for dynamically adjusting delay; Among them, the packaging structure of the hybrid inductive proximity sensor includes the substrate that is flip-chip interconnected with the electronic chip through a carrier board, and the surface of the packaging structure of the hybrid inductive proximity sensor is covered with a protective layer; the pre-packaging treatment of the hybrid inductive proximity sensor includes pad micromachining, gas shielded reflow soldering and a composite glue buffer layer.

[0007] In some embodiments, the electronic chip is manufactured using a complementary metal oxide semiconductor process.

[0008] According to a second aspect of the present application, a method for manufacturing a hybrid inductive proximity sensor based on semiconductor technology is provided, which is used to manufacture the hybrid inductive proximity sensor based on semiconductor technology as described above, comprising: A planar induction coil is formed by electroplating a copper layer on a substrate and photolithography, and a plurality of concentric annular sub-coils are integrated; Prepare positive temperature coefficient resistors in the metal layer of electronic chips, and prepare negative temperature coefficient resistors in the polysilicon layer of electronic chips; Adjusting the resistance parameters of the positive temperature coefficient resistor and / or the negative temperature coefficient resistor to a target value by laser; Flip-chip interconnecting the substrate and the electronic chip via a carrier; A protective layer is applied to the surface of the interconnected structure.

[0009] In some embodiments, before flip-chip interconnecting the substrate with the electronic chip via the carrier, the method includes: A femtosecond laser is used to process a micro-groove structure in the pad area of ​​the carrier board to enhance solder wettability through capillary action; Performing local heating reflow soldering on the pad area in a nitrogen environment and starting plasma cleaning; A polyimide composite adhesive is printed between the carrier plate and the substrate and cured to form a buffer layer.

[0010] In some embodiments, after printing polyimide composite glue between the carrier and the substrate and curing it to form a buffer layer, the method includes: The buffer layer is subjected to a step-wise temperature-increasing annealing, wherein the step-wise temperature-increasing annealing includes a low-temperature matrix structure stabilization stage and a high-temperature grain boundary diffusion stage, and nitrogen protection is provided throughout the step-wise temperature-increasing annealing.

[0011] In some embodiments, the method further comprises: The impedance signal of each sub-coil is synchronously collected through a three-channel circuit; The impedance phase angle of each impedance signal is extracted independently using the discrete Fourier transform algorithm; Calculating a magnetic field gradient ratio according to the plurality of impedance phase angles; The magnetic field gradient ratio is compared with a pre-stored feature library and a target object material classification result is output for debugging the material recognition function of the hybrid inductive proximity sensor.

[0012] In some embodiments, the method further comprises: Fix the target position in a constant temperature environment, measure the oscillation frequency of the target fixed position, and dynamically adjust the capacitor branch voltage divider resistor ratio to make the inductance and capacitor branch voltage change rate consistent; The comparator bias current temperature coefficient is adjusted to offset residual linear drift and debug the temperature compensation function of the hybrid inductive proximity sensor.

[0013] In some embodiments, the method further comprises: Use a dual-output comparator to replace the reference voltage source; The power consumption and waveform stability of the hybrid inductive proximity sensor in the working mode and the standby mode are monitored for debugging the power supply function of the hybrid inductive proximity sensor.

[0014] In some embodiments, the method further comprises: Testing the minimum discernible displacement of the hybrid inductive proximity sensor by a micro-displacement driving device; measuring a frequency shift of the hybrid inductive proximity sensor at a fixed position during a temperature cycle; A long-term operation test of the hybrid inductive proximity sensor under mechanical shock and humidity environment is performed.

[0015] In some embodiments, the method further comprises: Copper pillar bumps and anisotropic conductive adhesive are used to achieve vertical interconnection between the carrier and the substrate; Define the epoxy resin coverage area through the mask and retain the coil sensing surface; Solder reflow is accomplished under localized laser heating.

[0016] The beneficial effects of the hybrid inductive proximity sensor based on semiconductor technology and the manufacturing method thereof according to the embodiments of the present application include at least: The embodiments of the present application utilize multi-segment concentric annular copper coils formed through photolithography and electroplating processes to capture magnetic field gradient changes caused by target objects in segments, significantly improving the positioning accuracy and distance resolution of metal objects and avoiding the detection blind spots caused by edge effects in traditional single coils. By integrating a positive and negative temperature coefficient resistor combination (PTC+NTC) in series with an adjustable resistor and capacitor branch in the oscillator circuit, ambient temperature drift is dynamically offset, ensuring stable output frequency over a wide temperature range and resolving the problem of false triggering caused by temperature fluctuations in industrial sites. By utilizing a flip-chip interconnect structure between the substrate and the electronic chip, combined with gas-shielded reflow soldering and a composite adhesive buffer layer packaging process, the coils are resistant to oil, dust, and high-pressure washing, with a lifespan of millions of operations, far exceeding that of mechanical contact sensors. By combining inductive and capacitive principles, the coils can simultaneously identify metal workpieces, plastic containers, or liquid levels, making them suitable for complex scenarios. Photolithography and electroplating processes enable high-precision batch manufacturing of coils, avoiding the yield loss associated with traditional winding processes. Pad micromachining technology improves packaging efficiency and significantly reduces unit cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic structural diagram of a hybrid inductive proximity sensor based on semiconductor technology according to an embodiment of the present application; Figure 2 Schematic diagram of a process for manufacturing a hybrid inductive proximity sensor based on semiconductor technology according to an embodiment of the present application; Figure 3 This is an integrated temperature compensation circuit diagram of the resistor combination according to an embodiment of the present application; Figure 4 Schematic diagram of the displacement of the intersection point of the inductor branch and the capacitor branch during the charging cycle as the temperature changes when no compensation is performed; Figure 5 Schematic diagram showing the displacement of the intersection point of the inductor branch and the capacitor branch after compensation according to an embodiment of the present application as the temperature changes during a charging cycle; Figure 6 A schematic diagram of a curve showing how the output frequency of the hybrid inductive proximity sensor according to an embodiment of the present application changes with the distance to the target object; Figure 7 FIG. 1 is a schematic diagram of a curve showing how the output frequency of the hybrid inductive proximity sensor varies with temperature according to an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical application of the present application, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0019] The following detailed description of the embodiments of the present application is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present application, but are not intended to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0020] An embodiment of the present application provides a hybrid inductive proximity sensor based on a semiconductor process. The hybrid inductive proximity sensor based on a semiconductor process is manufactured by a method for manufacturing a hybrid inductive proximity sensor based on a semiconductor process.

[0021] In some embodiments, a hybrid inductive proximity sensor based on semiconductor technology includes a planar inductive coil and an electronic chip.

[0022] In some embodiments, the planar induction coil is a copper coil structure formed on a substrate through photolithography and electroplating processes. The planar induction coil integrates multiple concentric annular sub-coils, and the multiple concentric annular sub-coils are used to segmentally measure the magnetic field gradient changes caused by the target object.

[0023] In one exemplary embodiment, the planar induction coil is made of copper and is a 3mm square with a line width of 20μm, a gap of 5μm, and a thickness of 25μm. The planar induction coil is formed by electroplating on a silicon substrate using a photolithography and electroplating process. The planar induction coil integrates a multi-segment heterogeneous coil structure. By segmentally measuring the local magnetic field gradient caused by the target object and combining it with a digital signal processing algorithm, it achieves real-time identification of the target material.

[0024] In some embodiments, the electronic chip integrates an oscillator circuit, which includes an inductor branch having a series combination of positive and negative temperature coefficient resistors, a capacitor branch having a parallel adjustable resistor, and a comparator unit for dynamically adjusting delay.

[0025] For example, the electronic chip is a 750nm complementary metal oxide semiconductor electronic chip, which integrates a differential relaxation oscillator circuit, and the differential relaxation oscillator circuit includes: an inductor branch, a capacitor branch and a comparator unit. Among them, the inductor branch is a coil resistor. , positive temperature coefficient resistor (Resistance is 10Ω, resistance temperature coefficient TCR = 0.18% / ℃) and negative temperature coefficient resistor (resistance is 8Ω, resistance temperature coefficient TCR = -0.13% / ℃) in series; the capacitor branch is connected with an adjustable resistor ( , NTC) and two sets of voltage resistors ( PTC and , NTC) in parallel, the time constant is calculated based on the following formula:

[0026] Where, represents the time constant, represents the capacitance value in the capacitance branch; the comparator unit adjusts the bias current The temperature characteristics of the oscillation frequency are dynamically compensated for the residual temperature drift.

[0027] In some embodiments, the hybrid inductive proximity sensor's packaging structure includes a substrate flip-chip-connected to the electronic chip via a carrier board. The surface of the hybrid inductive proximity sensor's packaging structure is covered with a protective layer. Pre-packaging processing for the hybrid inductive proximity sensor includes pad micromachining, gas-shielded reflow soldering, and a composite adhesive buffer layer. The electronic chip is manufactured using a complementary metal oxide semiconductor (CMOS) process.

[0028] For example, the substrate of the packaging structure is flip-chip interconnected with the complementary metal oxide semiconductor electronic chip through a 100μm thick printed circuit board (PCB) as a carrier board. The top sensing surface is unobstructed and the entire structure is coated with a 200μm epoxy resin protective layer.

[0029] Pre-packaging processing steps may include, for example, solder joint pretreatment, flip-chip integration, and stress buffering. Solder joint pretreatment involves using a femtosecond laser to create micro-nanoscale grooves (2μm deep, 5μm pitch) in the pad area before ball placement on the printed circuit board substrate. This enhances solder wettability through capillary action, thereby increasing solder joint strength. Flip-chip integration involves using localized heating reflow (peak temperature 245°C, nitrogen shielding) and simultaneously performing a plasma clean (Ar / O2 mixture, pressure 0.5Pa) for 10 minutes during the reflow phase to remove organic contaminants and activate surface hydroxyl groups, thereby improving interfacial peel strength after epoxy resin encapsulation. The stress buffer layer includes: screen-printing polyimide silver nanoparticle composite glue between the printed circuit board carrier and the substrate to form a 0.5μm thick buffer layer after curing. After the stress buffer layer is cured, a step-by-step annealing process (150℃ / 30min to 250℃ / 15min) is added to improve the thermal conductivity of the buffer layer through the grain boundary diffusion effect of silver nanoparticles, thereby preventing warping caused by thermal mismatch.

[0030] In some embodiments, the aforementioned stepped annealing process includes placing the cured stress buffer layer in a nitrogen oven and heating the temperature from room temperature to 150°C at a rate of 10°C / min for 30 minutes. This low-temperature annealing phase initially stabilizes the polyimide matrix structure and promotes the formation of a preliminary dispersed network of silver nanoparticles in a low-energy state. The temperature is then increased at a rate of 15°C / min to 250°C and held for 15 minutes. During this high-temperature phase, the silver nanoparticles utilize the grain boundary diffusion effect to form a denser thermal conductivity pathway within the polyimide matrix. Following annealing, the temperature is gradually decreased to room temperature at a rate of 5°C / min to avoid sudden cooling that could cause new stresses within the buffer layer. The heating and cooling rates and holding time must be strictly controlled throughout the entire process. The nitrogen environment prevents oxidation of the silver particles and ensures sufficient grain boundary diffusion. Ultimately, through stepped temperature control, the thermal conductivity of the buffer layer is significantly improved without compromising the properties of the polyimide, effectively suppressing thermal mismatch warping between the printed circuit board and the substrate.

[0031] In some embodiments, a temperature compensation circuit with stepped temperature control is constructed by the following constraints. The temperature compensation circuit is directly integrated into the differential relaxation oscillator circuit, and the inductor branch ( 、 series) and the capacitor branch ( 、 、 The collaborative application of parallel connection achieves temperature characteristic matching.

[0032] For example, the time constant temperature characteristics of the inductor and capacitor branches are matched by the following formula: ; in, , , in, Indicates the coil inductance, represents the temperature change rate of the inductor branch time constant, represents the temperature change rate of the time constant of the capacitor branch, 、 are the time constants of the inductor branch and the capacitor branch respectively.

[0033] For example, the branch voltage Umax temperature drift is consistent with the following formula: ; Where, , , 、 They represent the maximum voltage of the inductor branch and the maximum voltage of the capacitor branch respectively.

[0034] In some embodiments, the dynamic delay compensation mechanism of the comparator unit is implemented in the following manner: The temperature coefficient is inversely related to the temperature drift of the oscillation frequency, offsetting and Uncovered linear temperature error; within the temperature range of −40°C to 80°C, the maximum absolute error is ≤18 μm when the target position is 450 μm.

[0035] The embodiments of the present application utilize multi-segment concentric annular copper coils formed through photolithography and electroplating processes to capture magnetic field gradient changes caused by target objects in segments, significantly improving the positioning accuracy and distance resolution of metal objects and avoiding the detection blind spots caused by edge effects in traditional single coils. By integrating a positive and negative temperature coefficient resistor combination (PTC+NTC) in series with an adjustable resistor and capacitor branch in the oscillator circuit, ambient temperature drift is dynamically offset, ensuring stable output frequency over a wide temperature range and resolving the problem of false triggering caused by temperature fluctuations in industrial sites. By utilizing a flip-chip interconnect structure between the substrate and the electronic chip, combined with gas-shielded reflow soldering and a composite adhesive buffer layer packaging process, the coils are resistant to oil, dust, and high-pressure washing, with a lifespan of millions of operations, far exceeding that of mechanical contact sensors. By combining inductive and capacitive principles, the coils can simultaneously identify metal workpieces, plastic containers, or liquid levels, making them suitable for complex scenarios. Photolithography and electroplating processes enable high-precision batch manufacturing of coils, avoiding the yield loss associated with traditional winding processes. Pad micromachining technology improves packaging efficiency and significantly reduces unit cost.

[0036] The present invention provides a method for manufacturing a hybrid inductive proximity sensor based on semiconductor technology, which is used to manufacture the hybrid inductive proximity sensor based on semiconductor technology as described above. The method includes the following steps 210-250.

[0037] In step 210 , a copper layer is electroplated on the substrate and a planar induction coil is formed by photolithography, and a plurality of concentric annular sub-coils are integrated.

[0038] In some embodiments, the copper layer is 25 μm thick, the planar induction coil is a planar spiral coil, and the terminals of the planar induction coil are interconnected with the electronic chip via a substrate that is a 100 μm thick printed circuit board.

[0039] In some embodiments, the planar induction coil is electroplated on a silicon substrate using a photolithography and electroplating process (photolithography and electroplating), has an inductance of 4.3 μH and a resistance of 18 Ω, and its magnetic field distribution characteristics determine an effective measurement range of 100-1500 μm.

[0040] For example, the fabrication process for a planar induction coil involves first fabricating a planar copper coil on a silicon substrate using photolithography and electroplating. The core of this process is the formation of a high-precision microstructure through a combination of photolithography and electroplating. Specifically, a photoresist approximately 25μm thick is spin-coated on the silicon substrate. UV lithography is performed using a mask to create a groove structure corresponding to the coil pattern. Pure copper is then electroplated within the grooves, controlling the current density (approximately 2A / dm²) and plating time (approximately 90 minutes) to ensure a uniform copper layer thickness of 25μm. The coil in this application features a square spiral structure with a side length of 3mm, a line width of 20μm, and a 5μm gap between adjacent coils. The resulting parameters are 4.3μH inductance and 18Ω resistance. After electroplating, the copper layer undergoes a de-smearing and annealing treatment (at 300°C for 30 minutes) to eliminate internal stress in the copper layer and improve conductivity. This step must be performed in a Class 100 cleanroom to prevent contamination of micron-scale line widths that could cause shorts or open circuits.

[0041] In some embodiments, a multi-segment heterogeneous coil structure is integrated into the planar induction coil, and the local magnetic field gradient change caused by the target object is measured in segments, and the real-time identification function of the target material is realized in combination with a digital signal processing algorithm. Specifically, the original single coil is divided into three groups of concentric annular sub-coils (inner ring, middle ring, and outer ring), and the line width and gap of each group of sub-coils are increased in a ratio of 1:1.5:2 to form differentiated magnetic field sensitive areas; a three-channel synchronous sampling circuit (corresponding to the inner ring, middle ring, and outer ring sub-coils) is integrated into the chip using a 2M / 2PCMOS process to respectively collect the impedance change of each sub-coil. Each channel includes: generating a 10MHz excitation signal through a switched capacitor network (SCM), injecting it into the sub-coil after passing through a programmable gain amplifier (PGA), and detecting the impedance The real part of and the imaginary part ; and output material classification signal by calculating the magnetic field gradient ratio and comparing it with the pre-stored material feature library.

[0042] Among them, the detection impedance The real part of and the imaginary part It is expressed by the following formula: , Where j represents the inner ring, middle ring or outer ring, and the real part of the impedance is obtained and the imaginary part .

[0043] Then, the impedance phase angle is calculated by the following inverse tangent function: , , Calculate the impedance phase angle , the phase angle reflects the phase relationship between the inductive reactance and resistance caused by the change of magnetic field.

[0044] In some embodiments, the magnetic field gradient ratio is calculated as follows: Data normalization, that is, the impedance change of each sub-coil Normalization is performed according to the following formula: , In the formula This is the baseline impedance when there is no target.

[0045] And, the gradient ratio calculation, that is, the magnetic field gradient ratio is defined according to the following formula : , The material classification signal is output by matching the pre-stored material feature library (G threshold range of metals such as aluminum, copper, and steel) through the table lookup method.

[0046] Step 220 : preparing a positive temperature coefficient resistor on the metal layer of the electronic chip, and preparing a negative temperature coefficient resistor on the polysilicon layer of the electronic chip.

[0047] In some embodiments, the processing of the electronic chip includes: constructing a relaxation oscillator using a 2M / 2P / HR process; preparing positive / negative temperature coefficient resistors on the metal layer (M1) and the polysilicon layer (P+); laser trimming 、 and parameter.

[0048] Step 230 : Adjust the resistance parameters of the positive temperature coefficient resistor and / or the negative temperature coefficient resistor to a target value by laser.

[0049] In some embodiments, referring to Figure 3 As shown, the electronic chip is a metal oxide semiconductor electronic chip, which integrates a differential relaxation oscillator circuit and includes two branches with temperature matching characteristics: the inductor branch is a coil resistor. Series positive temperature coefficient resistor (Resistance is 10Ω, TCR=0.18% / ℃) and negative temperature coefficient resistor (resistance is 8Ω, TCR=-0.13% / ℃); the capacitor branch is composed of NTC resistor (resistance is 5kΩ) and the voltage divider resistor ( , PTC and , NTC) in parallel. The time constant of the two branches is and By adjusting the resistance parameters, the temperature characteristics of , while ensuring the voltage divider ratio , The temperature drift of the sensors is consistent, thus eliminating the influence of temperature change on measurement accuracy. is the maximum voltage of the inductor branch (due to the coil resistance and 、 Determined by the partial pressure of is the maximum voltage of the capacitor branch (given by and 、 is determined by the partial pressure of

[0050] In an exemplary embodiment, an electronic interface circuit is constructed based on a 750nm complementary metal oxide semiconductor (2M / 2P / HR) process. First, the circuit is completed using an electronic design automation (EDA) tool, including: laying out a differential relaxation oscillator with two branches, the two branches being an inductor branch and a coil resistor. Series positive temperature coefficient resistor (Resistance is 10Ω, TCR=0.18% / ℃) and negative temperature coefficient resistor (8Ω, TCR=-0.1300% / ℃); the capacitor branch is composed of NTC resistors (5kΩ) and the voltage divider resistor (PTC), (NTC) in parallel. In addition, ensure that the time constant of the two branches 、 The temperature characteristics match and the voltage divider ratio and Chip processing can be done using a standard tape-out process, which includes, for example, first depositing a metal layer 1 (M1, an aluminum-copper alloy layer (containing 0.5% Cu in Al), approximately 500nm thick) and a polysilicon layer (P+) on a silicon wafer, defining the resistor pattern through photolithography, and then performing ion implantation and annealing to adjust the temperature coefficient of the thin layer resistance. Laser trimming equipment is also used to precisely adjust R L1 、R L2 、R C The resistance value was adjusted to the target parameter with a control error of less than ±0.5%. Finally, the electronic chip size was optimized to 1.2mm×1.2mm to match the coil area.

[0051] Step 240 , flip-chip interconnecting the substrate and the electronic chip via a carrier.

[0052] In some embodiments, before the substrate is flip-chip interconnected with the electronic chip through the carrier, the process includes: using a femtosecond laser to process a micro-groove structure in the pad area of ​​the carrier to enhance solder wettability through capillary action; performing local heating reflow soldering on the pad area in a nitrogen environment, and starting plasma cleaning; and printing a polyimide composite glue between the carrier and the substrate and curing it to form a buffer layer.

[0053] In some embodiments, after printing the polyimide composite glue between the carrier and the substrate and curing it to form a buffer layer, the buffer layer is subjected to a step-by-step temperature rising annealing, wherein the step-by-step temperature rising annealing includes a low-temperature matrix structure stabilization stage and a high-temperature grain boundary diffusion stage, and nitrogen protection is provided throughout the step-by-step temperature rising annealing.

[0054] For example, the substrate is flip-chip soldered to a printed circuit board carrier; gold wire bonding connects the complementary metal oxide semiconductor electronic chip to the printed circuit board; and a 200μm epoxy resin protective layer is applied.

[0055] In some embodiments, a hybrid inductive proximity sensor is constructed by vertically interconnecting a 3 mm square planar copper coil (20 μm line width, 5 μm gap, and 25 μm copper layer thickness) with a 750 nm metal oxide semiconductor electronic chip.

[0056] Step 250: coating a protective layer on the surface of the interconnected structure.

[0057] In some embodiments, a "sandwich" packaging structure is used to integrate a planar induction coil and an electronic chip. The specific process involves flip-chip soldering the silicon-based planar induction coil to a 100μm-thick flexible printed circuit board substrate. Tin-silver solder balls (50μm diameter) are deposited on the pads using a ball placement machine. The reflow profile is set to a peak of 245°C (hold temperature for 30 seconds) to ensure a reliable electrical connection between the planar induction coil and the printed circuit board. The electronic chip, processed in the second step, is then interconnected to the printed circuit board substrate via wire bonding. Gold wire with a diameter of 25μm is used for the bonding, and the bonding pressure is controlled within the range of 80-100mN to avoid damaging the chip's passivation layer. During the packaging process, special care is taken to keep the top of the coil clear of obstructions to maximize the sensitivity of the sensing surface. Finally, epoxy resin is used for encapsulation, with a coating thickness of 200μm controlled by a dispenser. Curing conditions are 120°C for 60 minutes. After packaging is completed, an air tightness test (helium mass spectrometer leak detector detects leakage rate <1×10-9Pa·m³ / s) and a mechanical shock test (performed in accordance with IEC60068-2-27 standard) are carried out.

[0058] In some embodiments, in order to improve the packaging quality, the present application is implemented by the following means, including: flip-chip soldering instead of gold wire bonding, for example, using copper pillar bumps (CuPillar) and anisotropic conductive adhesive (ACA) between the electronic chip and the printed circuit board substrate to achieve vertical interconnection, which can reduce the parasitic inductance to below 0.1nH; local selective encapsulation, such as defining the epoxy resin coverage area through photolithography to protect only the chip and solder joints, leaving the top 0.5mm of the coil without a covering layer to improve the sensing sensitivity; laser-assisted reflow soldering, for example, during the reflow process of the tin-silver solder ball, local laser heating (peak temperature 245°C) is used to prevent the silicon-based coil from deforming due to the overall high temperature.

[0059] The embodiment of the present application integrates multiple concentric annular sub-coils through electroplating copper layer and photolithography technology, realizing high-precision coil patterning and avoiding the risk of inter-turn short circuit in traditional winding process; the multi-segment coil structure can capture the magnetic field gradient change in segments, significantly improving the positioning accuracy of metal targets, while supporting the detection of non-metallic targets and expanding the application scenarios; by preparing positive temperature coefficient resistors in the metal layer of the electronic chip and negative temperature coefficient resistors (NTC) in the polysilicon layer, the intrinsic characteristics of the material are used to achieve resistance temperature drift complementarity; it provides a physical basis for the temperature compensation circuit, eliminates the need for external compensation components, simplifies the chip structure and reduces thermal coupling interference; by dynamically adjusting the PTC / NTC resistance value to the target parameter by laser, it can accurately The time constant temperature drift rate of the inductive branch and the capacitive branch is matched, which solves the problem of sensing distance drift caused by individual differences of components in mass production and ensures the consistency of detection in the entire temperature range; the substrate and the electronic chip are interconnected through the carrier flip-chip, which replaces the wire bonding, shortens the signal transmission path and reduces parasitic inductance; this structure enhances the ability to resist mechanical vibration, and is compatible with the mounting process, improves the production line efficiency, and is suitable for high-vibration scenarios such as automotive welding; after the interconnection, this application is coated with an epoxy resin or polyimide protective layer to achieve sealing, moisture-proof, chemical corrosion resistance and mechanical protection; the composite adhesive layer buffers thermal stress, avoids solder joint cracking caused by temperature cycling, and extends the service life of the sensor in oily and high-pressure flushing environments.

[0060] In some embodiments, the method further includes: synchronously collecting the impedance signal of each sub-coil through a three-channel circuit; independently extracting the impedance phase angle of each impedance signal using a discrete Fourier transform (DFT) algorithm; calculating a magnetic field gradient ratio based on the multiple impedance phase angles; comparing the magnetic field gradient ratio with a pre-stored feature library and outputting a target object material classification result for debugging the material recognition function of the hybrid inductive proximity sensor.

[0061] In an exemplary embodiment, the specific steps of using the discrete Fourier transform algorithm to extract the impedance phase angle include: First, a three-channel synchronous sampling circuit collects the time-domain voltage and current signals of each sub-coil under a 10 MHz excitation, and converts them into digital signals through an analog-to-digital converter (ADC). Then, the digital signals are input into the Fourier transform algorithm module, and the frequency-domain transformation is performed on N sampling points within each period to calculate the complex amplitude components (real part and imaginary part) of the signal at a 10 MHz frequency.

[0062] In some embodiments, the three-channel synchronous sampling circuit is integrated based on a two-layer metal interconnect and / or two-layer polysilicon (2M / 2P) CMOS process. Each channel first generates a 10 MHz excitation signal by a switched-capacitor network, injects it into the corresponding sub-coil after being amplified by a programmable gain amplifier, and detects the real and imaginary parts of the impedance. The collected time-domain electrical signals are converted into digital signals by an analog-to-digital converter, and then the digital demodulation module uses the discrete Fourier transform algorithm to extract the impedance phase angle θ, calculates the magnetic field gradient ratio, and compares it with a pre-stored material feature library, and finally outputs a material classification signal to achieve material identification for the regions corresponding to different sub-coils.

[0063] In some embodiments, the method further includes: fixing the target position in a constant-temperature environment, measuring the oscillation frequency of the target fixed position, and dynamically adjusting the capacitance branch voltage-dividing resistor ratio to make the voltage change rates of the inductor and the capacitance branch consistent; adjusting the temperature coefficient of the comparator bias current to cancel the residual linear drift and debug the temperature compensation function of the hybrid inductive proximity sensor.

[0064] Refer to the appendix Figure 4-5 As shown, T1 and T2 represent the first temperature and the second temperature, where T1 < T2, and P(T1) and P(T2) are the intersection points of the voltage waveforms of the inductor branch and the capacitance branch corresponding to T1 and T2 respectively. The positions of these P(T1) and P(T2) points directly determine the oscillation period of the relaxation oscillator. During the operation of the relaxation oscillator, when the voltage of the capacitance branch reaches the same as that of the inductor branch, that is, at the P(T1) and P(T2) points, the comparator flips, triggering the start or end of the oscillation period. Figure 4 It shows the situation where the intersection point P(T1) of the inductor branch and the capacitance branch during the charging cycle without compensation changes to P(T2) as the temperature changes (from T1 to T2): When the temperature rises, due to the temperature coefficient of the coil resistance (about 0.18% / °C), the time constant of the inductor branch changes, and the position of the intersection point changes significantly, causing the oscillation frequency to drift. This drift will cause a measurement error of up to the micron level in industrial applications. Figure 5The figure shows that the intersection point P(T1) of the inductor branch and the capacitor branch after compensation according to the embodiment of the present application changes and shifts to P(T2) as the temperature changes (from T1 to T2) during the charging cycle: the positive / negative temperature coefficient resistor ( and ) and the capacitor branch matching adjustable resistor ( 、 ) to ensure that the temperature characteristics of the two branches' time constants match (this condition is already met in the present embodiment), while also ensuring that the temperature drift of the voltage divider ratio is consistent. Therefore, even with temperature fluctuations, the intersection point position remains relatively stable, significantly reducing the impact of temperature on the oscillation frequency and achieving a technical indicator of temperature drift ≤ 0.07% / °C.

[0065] In an exemplary embodiment, circuit calibration is performed based on the solution of a set of equations. The set of equations is established based on the following three constraints: Constraint 1: Time constant matching: , in, is the time constant of the inductor branch, is the time constant of the capacitor branch; Constraint 2: Voltage division matching: and The temperature coefficient is consistent; Constraint 3: Satisfaction =10Ω, =8Ω, =5kΩ and other measured parameters.

[0066] In an exemplary embodiment, the circuit calibration process includes: fixing the target at 450 μm in a constant temperature box at -40°C, 25°C, and 80°C, and measuring the output frequency; fine-tuning the output frequency by a digital potentiometer. and The resistance ratio makes and The temperature curve of Figure 7 The temperature-frequency curve shown in Figure 1 adjusts the temperature coefficient of the comparator bias current to offset the residual linearity error.

[0067] In an exemplary embodiment, referring to the attached Figure 7As shown in the figure, the temperature compensation circuit debugging steps are as follows: First, set three temperature points in the constant temperature chamber: −40°C, 25°C, and 80°C. Fix an aluminum target at a distance of 450μm (this distance is the vertical distance between the aluminum target object and the top sensing surface of the sensor (the coil plane)). Measure the output frequency change curve with temperature. Use an oscilloscope to record the oscillation frequency (nominal value 10.5-30MHz) and calculate the temperature drift (formula: Δf / f·ΔT, where T is the chamber temperature). If the measured drift exceeds 0.07% / °C, fine-tune the circuit. and The resistance ratio makes The temperature characteristics of Dynamic comparator delay compensation is achieved by adjusting the temperature coefficient of the bias current. Using a digital potentiometer to change the reference resistance, the temperature slope of the comparator propagation delay and the residual linearity error are inversely offset. After debugging, verify that the frequency fluctuation at the same target position does not exceed ±0.3% within the −40°C to 80°C range.

[0068] In some embodiments, the method further includes: replacing a reference voltage source with a dual-output comparator; and monitoring the power consumption and waveform stability of the hybrid inductive proximity sensor in operating mode and standby mode to debug a power supply function of the hybrid inductive proximity sensor.

[0069] In one exemplary embodiment, this application utilizes a dual-output comparator in place of a reference voltage source, leveraging complementary output terminals to maintain circuit balance. This reduces power consumption to just 85μW in standby mode and 100mW in active mode. This makes the application compatible with industry-standard 5V control systems, addressing the poor interface compatibility between existing sensors and printed circuit board devices. The package structure employs a "sandwich" stacking layout, where the coil substrate is flip-chip soldered to the electronic chip via a 100μm-thick printed circuit board carrier, leaving the top sensing surface unobstructed. The overall dimensions are optimized to 3mm × 3mm × 1.2mm. Gold wire bonding provides the electrical connection between the electronic chip and the printed circuit board, while a 200μm epoxy protective layer ensures environmental resistance. Tests have shown that the device maintains stable functionality under 80% humidity and 100,000 mechanical shock cycles.

[0070] In one exemplary embodiment, the ability of a dual-output comparator to replace a reference voltage source was verified to address the industrial field's need for a 0-5V unipolar power supply. The specific method involved: In operating mode, the chip current (nominal 20mA) was monitored using a power load meter to calculate power consumption. In standby mode, a 0V logic signal was applied to shut down the oscillator and the leakage current was measured (<17μA, corresponding to 85μW power consumption). An oscilloscope was used to observe the duty cycle stability of the output square wave. For a ±5% power supply voltage fluctuation, the frequency offset should be less than ±0.1%. Furthermore, the circuit must ensure that the oscillator can maintain oscillation without a reference voltage. The comparator threshold voltage (VTH) and hysteresis width (>10mV) were adjusted to prevent false triggering due to noise interference.

[0071] In some embodiments, the method further includes: testing the minimum discernible displacement of the hybrid inductive proximity sensor using a micro-displacement drive device; measuring the frequency offset of the hybrid inductive proximity sensor at a fixed position during a temperature cycle; and performing a long-term operation test of the hybrid inductive proximity sensor under mechanical shock and humidity environments.

[0072] In some embodiments, referring to Figure 6 As shown, the performance verification data of this application shows that the sensor's longitudinal resolution for aluminum targets reaches 120nm (within a range of <500μm), the full-scale nonlinear error is ≤0.25%, and the response frequency covers 10.5-30MHz (corresponding to changes in target distance). Compared with existing technologies, this application reduces parasitic inductance by 60% through three-dimensional integration, reduces mass production costs by 40%, and can meet the complex working conditions of industrial sites without the need for external adjustment. This technology has been verified by the prototype and is suitable for scenarios such as precision positioning, robot joint monitoring, and gap control of semiconductor equipment in the field of intelligent manufacturing. It has significant technical advantages and industrial prospects.

[0073] In one exemplary embodiment, the resolution test includes: using piezoelectric ceramics to drive an aluminum target (1 mm thick) to move within a range of 500 μm in 5 μm steps, recording the frequency-displacement curve, and calculating the minimum resolvable displacement (120 nm).

[0074] In an exemplary embodiment, referring to the attached Figure 7 As shown in Figure 2, the temperature drift test involves fixing the target at 450 μm and infinity in a −40 to 80°C temperature chamber, measuring the output frequency change, and verifying that the drift is ≤ 0.07% / °C.

[0075] In an exemplary embodiment, the long-term stability test includes: continuous operation for 1000 hours, recording the zero drift (frequency offset when the target is removed) every 24 hours, and requiring it to be less than ±0.5 MHz.

[0076] In an exemplary embodiment, the environmental resistance test includes: performing 85% humidity storage (240 hours) and a vibration test (10-2000 Hz sweep frequency, acceleration 15g).

[0077] In some embodiments, the method further includes: using copper pillar bumps and anisotropic conductive adhesive to achieve vertical interconnection between the carrier and the substrate; defining the epoxy resin coverage area through a mask and retaining the coil sensing surface; and completing solder reflow under local laser heating.

[0078] The embodiment of the present application addresses the technical bottleneck of the difficulty in directly realizing micron-level negative temperature coefficient resistors in complementary metal oxide semiconductor processes, and adopts a combined compensation strategy of positive and negative temperature coefficient resistors. By establishing a five-variable equation system (including two time constant matching equations, two voltage divider matching equations, and three boundary condition equations), the solution is obtained. 、 、 、 and The optimal parameter combination. Experimental verification shows that within the temperature range of −40°C to 80°C, this compensation application controls the temperature drift within 0.07% / °C, improving stability by more than 60% compared to the traditional negative temperature coefficient resistor external compensation application. To eliminate residual linear temperature errors, a dynamic comparator delay compensation mechanism is further introduced, that is, by adjusting the temperature characteristics of the comparator bias current so that it acts in the opposite direction to the oscillation frequency temperature drift, ultimately achieving stable output over the entire temperature range. In terms of power supply architecture, this application abandons the traditional three-wire power supply mode (−2.5V / GND / +2.5V) and adopts a 0-5V single-polarity power supply.

[0079] The hybrid inductive proximity sensor proposed in this application achieves the following significant technical effects: experimentally verified, the sensor's longitudinal resolution for aluminum targets reaches 120nm (within a range of <500μm), and the full-scale nonlinear error is ≤0.25%, effectively solving the accuracy bottleneck problem caused by temperature drift in traditional sensors; within the temperature range of −40~80℃, the dual-branch temperature compensation circuit (R L1 =10Ω, R L2 =8Ω, R C=5kΩ) and dynamic comparator delay adjustment, temperature drift is controlled within 0.07% / °C, achieving over 60% stability improvement compared to traditional NTC external compensation solutions. This performance meets the requirements of high-precision industrial scenarios such as semiconductor equipment precision positioning (±50nm level) and robotic joint monitoring (<1μm displacement detection). In terms of integration, a three-dimensional stacked package structure vertically interconnects a planar copper coil (square side length 3mm) with the CMOS chip. A 100μm-thick PCB substrate eliminates parasitic effects, resulting in an optimized overall size of 3mm × 3mm × 1.2mm, a 75% reduction compared to traditional split-type solutions. Gold wire bonding and a 200μm epoxy resin protective layer ensure environmental tolerance, maintaining stable functionality in 80% humidity and 100,000 mechanical shock cycles. The single-power supply (0-5V) architecture eliminates reliance on the reference voltage through a dual-output comparator, resulting in standby power consumption as low as 85μW and operating mode power consumption of 100mW. This application reduces energy consumption by 40% compared to traditional three-wire power supplies and is compatible with industrial standard PLC control systems. This application reduces mass production costs by 40% through the hybrid integration of planar induction coils using photolithography and electroplating processes with complementary metal oxide semiconductor processes, and can meet the complex working conditions of industrial sites without external calibration. After actual scenario testing in printing machinery roller gap monitoring and semiconductor wafer handling robots, the sensor maintained a repeatability accuracy of ±0.3μm after 1000 hours of continuous operation, demonstrating its value for large-scale promotion and application.

[0080] The embodiments of this application aim to address the technical difficulties of traditional industrial sensors in miniaturization, temperature stability, and integration, particularly for the needs of non-contact displacement detection in industrial automation. This application adopts a three-dimensional stacked packaging structure, achieving high-precision displacement detection through the collaborative design of planar electroplated coils and complementary metal oxide semiconductor electronic chips. Through the hybrid integration of planar induction coils using complementary metal oxide semiconductor processes and etching and electroplating processes, this solves the miniaturization bottleneck and temperature drift problems caused by discrete components in traditional sensors, making it suitable for high-precision, low-power, single-power smart manufacturing scenarios. The planar copper coils and complementary metal oxide semiconductor electronic chips are integrated through a three-dimensional stacked structure. A dual-branch temperature compensation circuit is used, with the inductor branch connected in series with positive / negative temperature coefficient resistors and the capacitor branch matched with an adjustable resistor. Through the collaborative compensation of the temperature characteristics of the time constant and voltage divider, a temperature drift of ≤0.07% / °C is achieved in the range of −40°C to 80°C. Combined with dynamic comparator delay adjustment and a single-power architecture, it is suitable for industrial high-precision displacement detection.

[0081] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present application, and the present application is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present application, and such modifications and improvements are also considered to be within the scope of protection of the present application.

Claims

1. A hybrid inductive proximity sensor based on semiconductor technology, characterized in that: include: Planar induction coil and electronic chip, The planar induction coil is a copper coil structure formed on a substrate through photolithography and electroplating processes. The planar induction coil integrates multiple concentric annular sub-coils, which are used to segmentally measure the magnetic field gradient changes caused by the target object; The electronic chip is integrated with an oscillator circuit, which includes an inductor branch having a combination of positive and negative temperature coefficient resistors connected in series, a capacitor branch having an adjustable resistor connected in parallel, and a comparator unit for dynamically adjusting delay; Among them, the packaging structure of the hybrid inductive proximity sensor includes the substrate that is flip-chip interconnected with the electronic chip through a carrier board, and the surface of the packaging structure of the hybrid inductive proximity sensor is covered with a protective layer; the pre-packaging treatment of the hybrid inductive proximity sensor includes pad micromachining, gas shielded reflow soldering and a composite glue buffer layer.

2. The hybrid inductive proximity sensor based on semiconductor technology according to claim 1, characterized in that: The electronic chip is manufactured using a complementary metal oxide semiconductor process.

3. A manufacturing method for manufacturing the hybrid inductive proximity sensor based on semiconductor technology according to claim 1 or 2, characterized in that: include: A planar induction coil is formed by electroplating a copper layer on a substrate and photolithography, and a plurality of concentric annular sub-coils are integrated; Positive temperature coefficient resistors are prepared in the metal layer of electronic chips, and negative temperature coefficient resistors are prepared in the polysilicon layer of electronic chips; Adjusting the resistance parameters of the positive temperature coefficient resistor and / or the negative temperature coefficient resistor to a target value by laser; Flip-chip interconnecting the substrate and the electronic chip via a carrier; A protective layer is applied to the surface of the interconnected structure.

4. The manufacturing method according to claim 3, characterized in that Before flip-chip interconnecting the substrate with the electronic chip via the carrier, the method includes: A femtosecond laser is used to process a micro-groove structure in the pad area of ​​the carrier board to enhance solder wettability through capillary action; Performing local heating reflow soldering on the pad area in a nitrogen environment and starting plasma cleaning; A polyimide composite adhesive is printed between the carrier plate and the substrate and cured to form a buffer layer.

5. The manufacturing method according to claim 3, characterized in that After printing polyimide composite glue between the carrier plate and the substrate and curing it to form a buffer layer, the method includes: The buffer layer is subjected to a step-wise temperature-increasing annealing, wherein the step-wise temperature-increasing annealing includes a low-temperature matrix structure stabilization stage and a high-temperature grain boundary diffusion stage, and nitrogen protection is provided throughout the step-wise temperature-increasing annealing.

6. The manufacturing method according to claim 3, characterized in that The method further comprises: The impedance signal of each sub-coil is synchronously collected through a three-channel circuit; The impedance phase angle of each impedance signal is extracted independently using the discrete Fourier transform algorithm; Calculating a magnetic field gradient ratio according to the plurality of impedance phase angles; The magnetic field gradient ratio is compared with a pre-stored feature library and a target object material classification result is output for debugging the material recognition function of the hybrid inductive proximity sensor.

7. The manufacturing method according to claim 3, characterized in that The method further comprises: Fix the target position in a constant temperature environment, measure the oscillation frequency of the target fixed position, and dynamically adjust the capacitor branch voltage divider resistor ratio to make the inductance and capacitor branch voltage change rate consistent; The comparator bias current temperature coefficient is adjusted to offset residual linear drift and debug the temperature compensation function of the hybrid inductive proximity sensor.

8. The manufacturing method according to claim 3, characterized in that The method further comprises: Use a dual-output comparator to replace the reference voltage source; The power consumption and waveform stability of the hybrid inductive proximity sensor in the working mode and the standby mode are monitored for debugging the power supply function of the hybrid inductive proximity sensor.

9. The manufacturing method according to claim 3, characterized in that: The method further comprises: Testing the minimum discernible displacement of the hybrid inductive proximity sensor by a micro-displacement driving device; measuring a frequency shift of the hybrid inductive proximity sensor at a fixed position during a temperature cycle; A long-term operation test of the hybrid inductive proximity sensor under mechanical shock and humidity environment is performed.

10. The manufacturing method according to claim 4, characterized in that: The method further comprises: Copper pillar bumps and anisotropic conductive adhesive are used to achieve vertical interconnection between the carrier and the substrate; Define the epoxy resin coverage area through the mask and retain the coil sensing surface; Solder reflow is accomplished under localized laser heating.

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