Ocean thermohaline film sensing chip based on multi-layer island type isolation structure

Abstract

The invention relates to the technical field of marine environment monitoring and sensors, in particular to a marine thermohaline film sensing chip based on a multi-layer island type isolation structure. The temperature measurement function island and the salt measurement function island are manufactured on the insulating substrate and are separated by a physical isolation groove; the public regulation and control cover plate covers the temperature measurement function island, the salt measurement function island and the physical isolation groove; the temperature measurement function island comprises a platinum film thermal resistor and a zinc oxide porous protective layer covering the platinum film thermal resistor; the salt measuring functional island comprises a boron-doped diamond film interdigital electrode; and a micropore array is arranged on the public regulation and control cover plate. Through the combination of the three-dimensional partition layout, the functional film material and the composite protection structure, the problems of corrosion, fouling and crosstalk are relieved, and the working stability and measurement reliability of the sensor in a complex marine environment are improved.

Description

Technical Field

[0001] This invention relates to the field of marine environmental monitoring and sensor technology, specifically a marine temperature and salinity thin-film sensing chip based on a multi-layer island-type isolation structure. Background Technology

[0002] Marine environmental monitoring is a core component of modern marine science, climate research, and resource development. Temperature and salinity, as fundamental parameters, directly impact ocean density, circulation patterns, ecological balance, and engineering safety. However, in practical applications, traditional sensors face numerous common challenges. First, the strong corrosiveness of seawater (such as high chloride ion concentrations and oxidizing environments) causes rapid degradation of electrodes or sensitive materials, shortening equipment lifespan and reducing measurement reliability. Second, biofouling is a significant problem, including the attachment of microorganisms, algae, seaweed, or small marine organisms, which can cover the sensing surface, hindering ion transport or heat exchange, leading to signal distortion or complete failure. Furthermore, potential interference between temperature and salinity measurements is another key challenge: in integrated designs, localized thermal effects generated by the temperature sensing unit can alter the conductivity of the surrounding seawater, introducing salinity measurement errors. These problems not only increase maintenance frequency and costs but can also lead to discontinuous or inaccurate data, affecting the reliability of scientific research and engineering decisions. To address these challenges, existing technologies often employ single protective measures, such as surface coatings or material replacements, but these often struggle to simultaneously solve multiple problems, resulting in limited effectiveness. Therefore, a comprehensive and innovative design solution is needed to improve the overall performance of the sensor from multiple dimensions, including structural layout, material selection, and protection mechanisms, to ensure long-term stability and measurement accuracy in harsh marine environments. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and propose a marine temperature and salinity thin-film sensor chip based on a multi-layer island isolation structure. By combining a three-dimensional partitioned layout, functional thin-film materials and a composite protective structure, the invention alleviates corrosion, fouling and crosstalk problems, and improves the working stability and measurement reliability of the sensor in complex marine environments.

[0004] To achieve the above objectives, the technical solution specifically adopted by the present invention is as follows: A marine temperature and salinity thin-film sensing chip based on a multi-layer island-type isolation structure includes, from bottom to top, a substrate, temperature measuring islands and salinity measuring islands located on the substrate and physically isolated from each other, and a common control cover plate covering the temperature measuring islands and salinity measuring islands.

[0005] Furthermore, the substrate is a double-sided polished single-crystal silicon wafer, on which a high-quality silicon dioxide insulating layer with a thickness of 0.8-1.2 micrometers is grown through a thermal oxidation process to ensure electrical isolation between the electrodes.

[0006] Furthermore, the temperature measuring island includes: a platinum thin-film micro-thermal resistor fabricated on the substrate surface, forming a serpentine or other extended pattern; and a zinc oxide porous protective layer that completely covers the platinum thin-film thermal resistor, covering the platinum resistor, preferably a zinc oxide-based protective layer with nano- to micron-level pores (thickness of 1-1.5 microns), which allows for rapid heat transfer while preventing direct contact with contaminants.

[0007] Furthermore, the platinum thin-film micro-thermal resistor adopts a four-wire connection method.

[0008] Furthermore, the zinc oxide porous protective layer is a zinc oxide-based protective layer with a thickness of 1-1.5 micrometers and nanometer- to micrometer-level pores, which allows for rapid heat transfer while preventing direct contact with contaminants.

[0009] Furthermore, the salt measurement island and the temperature measurement island are physically isolated from each other by a physical isolation trench.

[0010] Furthermore, the physical isolation trench is located between the two islands, with a width of 150-250 micrometers and a depth penetrating to the silicon substrate. It is made of a low thermal conductivity material to reduce thermal crosstalk.

[0011] Furthermore, the core component of the salt measurement island is a boron-doped diamond thin-film interdigitated electrode. Utilizing its chemical inertness, wide electrochemical window, and extremely low adsorption characteristics, it is resistant to the electrochemical corrosion of seawater, avoiding problems such as surface oxidation and ion adsorption of traditional metal electrodes.

[0012] Furthermore, the common control cover plate is deposited on the temperature measurement island and the salt measurement island, using a silicon nitride thin film with a regularly etched array of micropores. The pore size is 0.5-1.5 micrometers, ensuring that the ion migration required for conductivity measurement is unimpeded, while still being significantly smaller than typical marine planktonic larvae or larger particles. This silicon nitride cover plate can cover the entire chip area with uniform thickness and low stress, greatly improving the density and long-term reliability of the encapsulation layer.

[0013] The chip of this invention is suitable for marine scientific observation, environmental monitoring systems, underwater unmanned equipment, marine engineering platforms, and other applications requiring real-time, high-precision temperature and salinity measurements. It has the following characteristics and beneficial effects: 1) Achieved inherent corrosion resistance and long-term stability: By using boron-doped diamond, an intrinsically inert material, as the electrode, the problems of electrochemical corrosion and ion adsorption of traditional metal electrodes are fundamentally avoided, providing a stable sensitive interface for conductivity measurement, and the expected lifespan far exceeds that of existing metal electrode sensors.

[0014] 2) Significantly suppresses measurement crosstalk: The unique "island isolation" design, combined with physical isolation trenches, establishes an effective thermal barrier between the temperature and salinity measurement units. Combined with the lateral thermal diffusion effect of the zinc oxide layer on the temperature island, the influence of platinum resistance thermometer self-heating on the conductivity of adjacent micro-area seawater is minimized, thereby greatly improving the accuracy of simultaneous temperature and salinity measurement.

[0015] 3) A highly efficient composite antifouling mechanism was constructed: the zinc oxide nanoporous layer and the silicon nitride microporous cover plate constitute a "nano-micro" dual-scale physical filtration barrier. This structure ensures the rapid passage of water molecules and ions for measurement while effectively blocking the initial attachment of most microorganisms, algal spores, and suspended particles to the sensitive surface, structurally extending the maintenance-free cycle of the sensor. Attached Figure Description

[0016] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic cross-sectional view of the overall structure of an embodiment of the present invention.

[0017] Figure 2 This is a top view of the layout of an embodiment of the present invention (the common cover plate is hidden).

[0018] In the figure, 1 is the insulating substrate; 2 is the platinum thin film resistance thermometer; 3 is the zinc oxide porous protective layer; 4 is the boron-doped diamond thin film interdigitated electrode; 5 is the common control cover plate; 6 is the micropore array; and 7 is the physical isolation trench. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0020] like Figures 1-2 The first aspect of the present invention provides a marine temperature and salinity thin-film sensing chip based on a multi-layer island-type isolation structure, comprising: an insulating substrate 1; a temperature measuring functional island and a salinity measuring functional island fabricated on the insulating substrate 1 and separated by a physical isolation trench 7; and a common control cover plate covering the temperature measuring functional island, the salinity measuring functional island and the physical isolation trench; the temperature measuring functional island includes a platinum thin-film thermistor 2 and a zinc oxide porous protective layer 3 covering it; the salinity measuring functional island includes a boron-doped diamond thin-film interdigitated electrode 4; and the common control cover plate 5 is provided with a micropore array 6.

[0021] In one embodiment, the platinum thin-film micro-thermal resistor 2 adopts a four-wire connection method to eliminate the influence of wire resistance and contact resistance, thereby improving the accuracy and stability of temperature measurement.

[0022] In one embodiment, the zinc oxide porous protective layer 3 is a zinc oxide-based protective layer with nano- to micron-level pores and a thickness of 1-1.5 micrometers. On the one hand, the porous structure allows for rapid heat transfer, ensuring the response speed of the temperature sensor; on the other hand, the protective layer can effectively prevent pollutants in seawater from directly contacting the platinum film, preventing corrosion and pollution, and extending the sensor's lifespan.

[0023] In one embodiment, the physical isolation trench 7 is located between the two islands, with a width of 150-250 micrometers and a depth penetrating to the silicon substrate. It is made of a low thermal conductivity material to reduce thermal crosstalk. Through physical isolation and the use of a low thermal conductivity filling material, the heat conduction between the temperature measurement island and the salinity measurement island is significantly reduced, avoiding mutual interference between temperature and salinity measurements and improving measurement accuracy.

[0024] In one embodiment, the common control cover plate 6 is deposited on the temperature measurement island and the salt measurement island, and is made of silicon nitride thin film with a regular array of micropores etched on it. The pore size is 0.5-1.5 micrometers, ensuring that the ion migration required for conductivity measurement is not hindered, but is significantly smaller than typical marine planktonic larvae or larger particles. This silicon nitride cover plate can cover the entire chip area with uniform thickness and low stress, greatly improving the density and long-term reliability of the packaging layer.

[0025] In summary, based on the aforementioned multi-layer island isolation structure, this invention enables the chip to achieve high-precision synchronous measurement through physical separation and functional coordination. Temperature measurement mechanism Platinum thin film resistance thermometer (serpentine structure): Based on the temperature coefficient of platinum resistance (TCR≈0.00385 / ℃), changes in seawater temperature → linear changes in the resistance of the platinum resistance → the four-wire connection eliminates the resistance error of the wires and outputs a precise temperature signal.

[0026] Zinc oxide porous protective layer (1-1.5μm): Nano / micron-level pores allow heat to pass through rapidly (thermal conductivity >30W / mK), while blocking suspended matter and biological adhesion in seawater, thus preventing platinum resistance thermometers from becoming contaminated and failing.

[0027] Salinity measurement mechanism Boron-doped diamond interdigitated electrode: Applying AC voltage → Measuring seawater ionic conductivity → Salinity inversion. The chemical inertness (wide electrochemical window > 3V) and low adsorption characteristics of diamond electrodes completely avoid the corrosion / polarization problems of traditional metal electrodes.

[0028] Isolation and encapsulation collaboration Physical isolation trench (150-250μm deep): filled with low thermal conductivity material (such as polyimide, κ<0.5W / mK) to block thermal crosstalk between the temperature island heating and the salinity electrode (thermal isolation efficiency >90%).

[0029] Silicon nitride common cover plate (micropores 0.5-1.5μm): Microporous array: allows ions to migrate freely (ion permeability >95%), but intercepts plankton / particulate matter (size >2μm); Low-stress encapsulation: Maintains the stability of the electrode-seawater interface and prevents delamination during long-term immersion.

[0030] Core strengths: The physical isolation of the dual-function islands ensures that temperature / salinity measurements do not interfere with each other (crosstalk error <1%), while the common cover plate synchronously protects both sensors, enabling long-term reliable operation in marine environments (>5 years of lifespan).

[0031] In a second aspect, the present invention provides a method for fabricating a marine temperature and salinity thin-film sensing chip based on a multi-layer island isolation structure as described in the first aspect, comprising the following steps: Step 1: Substrate Pretreatment A 500μm single-crystal silicon wafer was selected, and a 1.0μm SiO2 insulating layer was grown by wet oxygen oxidation (1100℃) after cleaning.

[0032] Step 2: Define functional areas and trenches simultaneously. Defined in the SiO2 layer by photolithography: Temperature measuring island area (platinum resistance zone) Salt measurement island area (diamond electrode area) Isolation trench area (150-250μm wide).

[0033] Step 3: Stepwise preparation of the temperature measuring island Platinum resistance thermometer fabrication: Magnetron sputtering of a 200nm platinum film → stripping process to form a serpentine pattern (four-wire connection) Zinc oxide protective layer: Sol-gel spin-coating of zinc oxide precursor → annealing at 450℃ → formation of a 1.2μm porous layer (nanoscale pores).

[0034] Step 4: Stepwise preparation of salt islands Diamond electrode growth: Hot-filament CVD deposition of a 1.0 μm boron-doped diamond film (800℃, boron source). Electrode patterning: Reactive ion etching is used to form interdigitated electrodes (finger width / spacing = 10 μm).

[0035] Step 5: Trench filling and cover plate integration Trenching treatment: Fill with a low thermal conductivity material (such as polyimide) → polish smooth after curing (this step was missing in the original procedure).

[0036] Public cover preparation: PECVD deposition of 1.0μm silicon nitride film → photolithography + deep reactive ion etching → formation of a micropore array with a pore size of 1.0μm and a period of 3μm.

[0037] Step 6: Backend encapsulation Individual chips are obtained through dicing and packaged in ceramic or metal casings to ensure that only the front side (cover side) of the chip is exposed to the measurement environment.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A marine temperature and salinity thin-film sensing chip based on a multi-layer island isolation structure, characterized in that, The chip, from bottom to top, includes a substrate, temperature measurement islands and salt measurement islands located on the substrate and physically isolated from each other, and a common control cover plate covering the temperature measurement islands and salt measurement islands.

2. The marine temperature and salinity thin-film sensing chip based on a multi-layer island isolation structure as described in claim 1, characterized in that, The substrate is a double-sided polished monocrystalline silicon wafer, on which a high-quality silicon dioxide insulating layer with a thickness of 0.8-1.2 micrometers is grown through a thermal oxidation process to ensure electrical isolation between the electrodes.

3. The marine temperature and salinity thin-film sensing chip based on a multi-layer island isolation structure as described in claim 1, characterized in that, The temperature measurement island includes: a platinum thin film micro-thermal resistor fabricated on the substrate surface, forming a serpentine or other extended pattern; and a porous zinc oxide protective layer that completely covers the platinum thin film thermal resistor, covering the platinum resistor.

4. The marine temperature and salinity thin-film sensing chip based on a multi-layer island isolation structure as described in claim 3, characterized in that, The platinum thin-film micro-thermal resistor adopts a four-wire connection method.

5. A marine temperature and salinity thin-film sensing chip based on a multi-layer island isolation structure as described in claim 3, characterized in that, The zinc oxide porous protective layer is a zinc oxide-based protective layer with a thickness of 1-1.5 micrometers and nanometer- to micrometer-level pores.

6. The marine temperature and salinity thin-film sensing chip based on a multi-layer island isolation structure as described in claim 1, characterized in that, The salt measurement island and the temperature measurement island are physically isolated from each other by a physical isolation trench.

7. A marine temperature and salinity thin-film sensing chip based on a multi-layer island isolation structure as described in claim 6, characterized in that, The physical isolation trench is located between the two islands, with a width of 150-250 micrometers and a depth penetrating to the silicon substrate. It uses a low thermal conductivity material to reduce thermal crosstalk.

8. A marine temperature and salinity thin-film sensing chip based on a multi-layer island isolation structure as described in claim 1, characterized in that, The core component of the salt measurement island is a boron-doped diamond thin-film interdigitated electrode.

9. A marine temperature and salinity thin-film sensing chip based on a multi-layer island isolation structure as described in claim 1, characterized in that, The common control cover plate is deposited on the temperature measurement island and the salt measurement island, and is made of silicon nitride thin film with a regular array of micropores etched on it, with a pore size of 0.5-1.5 micrometers.

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