A multi-temperature-zone micro hot plate based on thermal cross and manufacturing method

Abstract

The application belongs to the technical field of MEMS, and particularly relates to a multi-temperature-zone micro hot plate based on heat cross and a manufacturing method. The micro hot plate integrates multiple heaters on a support layer, each heater corresponding to a working zone, and temperature control is realized by adjusting the input voltage or current of each heater; the working zones are interconnected, the heat cross effect between the working zones is further utilized, linkage control of multiple temperature working zones on a single micro hot plate is realized, and thus a working mode of single-micro-hot-plate multi-temperature-zone programmable control is formed; the working zones are interconnected, the heat cross effect is effectively utilized, and the overall power consumption of the micro hot plate is reduced.

Description

Technical Field

[0001] This invention belongs to the field of MEMS (Micro-Electro-Mechanical Systems) technology, specifically relating to a multi-temperature zone micro hot plate based on heat crossover and its manufacturing method. Background Technology

[0002] In the field of gas detection, metal-oxide-semiconductor (MOX) gas sensors have become the preferred solution for practical gas sensors due to their excellent physical and chemical properties. The working principle of MOX gas sensors is based on the response of gas-sensitive functional materials to a target gas. These materials typically exhibit optimal detection performance within an operating temperature range of 100℃–500℃. With the development of microelectromechanical systems (MEMS) technology, micro-hotplates (MHPs) are widely used in MOX gas sensors. These MHPs provide the required operating temperature environment for the gas-sensitive functional materials by embedding a heating wire into a dielectric thin film.

[0003] While micro-hotplate-based metal-oxide-semiconductor gas sensors offer significant advantages in providing heating conditions, practical applications still face challenges such as poor gas selectivity and cross-sensitivity. This means that the gas-sensitive functional materials exhibit non-unique responses to multiple gases, making accurate differentiation difficult. To address the selectivity issue, existing research often employs integrated sensor array designs, increasing the number of sensing elements to improve overall selectivity. However, a significant drawback of this approach is the substantial increase in power consumption. Furthermore, while integrating multiple sensors onto a single chip enables device miniaturization and high integration, it hinders precise temperature control of each operating region. Therefore, an innovative micro-hotplate design is urgently needed to optimize temperature control and balance power consumption, laying the foundation for the development and widespread application of high-performance portable gas sensors. Summary of the Invention

[0004] To overcome the problems in the prior art, this invention proposes a multi-temperature zone micro-hot plate based on heat cross-flow and its manufacturing method.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] In a first aspect, the present invention provides a multi-temperature zone micro hot plate based on thermal crossover, the micro hot plate comprising a silicon substrate, a support layer, a heating unit, an insulating layer, and a detection unit;

[0007] The support layer is located above the silicon substrate and is used to support the upper structure of the micro-hot plate and isolate the heat generated by the heating unit.

[0008] The heating unit is disposed above the support layer and includes multiple heaters, each corresponding to a working area, forming a coded multi-temperature region; the multiple heaters share a dielectric film, and heat is transferred between the working areas through the thermal cross-effect.

[0009] The insulating layer covers the heating unit for electrical isolation and to reduce heat conduction loss;

[0010] The detection unit is located above the insulating layer and includes multiple detection electrodes that correspond one-to-one with the heater, used to sense and read the response signal of the gas-sensitive functional material to the target gas.

[0011] Furthermore, the heater employs segmented, discontinuous heating electrodes with gradually varying widths.

[0012] Furthermore, the electrode width of the heating electrode gradually increases discontinuously from the edge to the center, and the electrode spacing of the heating electrode is uniform.

[0013] Furthermore, each heater corresponds to a working area, and temperature control is achieved by adjusting the input voltage or current of each heater, forming a coded multi-temperature zone, with each temperature zone interconnected.

[0014] Furthermore, the spacing between the heaters needs to be comprehensively considered and set based on the thermal cross-effect to ensure the uniformity of the temperature distribution of the micro-hot plate, power consumption, and mechanical deformation.

[0015] Furthermore, the peak temperature model of the micro-hot plate is as follows: the peak temperature T(d) of the micro-hot plate decreases non-linearly with the increase of the spacing d, and the temperature approaches the critical value d. critical The trend towards stability is represented as:

[0016] T(d) = a4d 4 +a3d 3 +a2d 2 +a1d+a0,d≤d critical ;

[0017] Where a4 represents the quartic coefficient, used to describe the nonlinear rapid change of peak temperature with increasing spacing; a3 represents the cubic coefficient, which reflects the secondary trend correction in the nonlinear change; a2 represents the quadratic coefficient, used to control the curvature of the peak temperature decrease curve; a1 represents the linear coefficient, which characterizes the basic trend of the peak temperature decreasing linearly with spacing, and is directly related to the linear part of the overall change; a0 represents the constant term, which is the theoretical peak temperature when the spacing approaches its minimum.

[0018] The peak temperature is obtained by using the spacing d to evaluate the peak temperature and its variation law of the micro-hot plate under different spacings, providing a reference for optimizing the structural design and performance control of the micro-hot plate.

[0019] Furthermore, the mechanical deformation model of the micro-hot plate is as follows: the mechanical deformation D(d) decreases with the increase of the spacing d, and the relationship is expressed as:

[0020] D(d) = b4d 4 +b3d 3 +b2d 2 +b1d+b0,d≤d critical ;

[0021] Wherein, b4 represents the quartic coefficient, used to describe the increasing nonlinearity of mechanical deformation as the spacing increases, reflecting the influence of the higher-order nonlinear part during the deformation decrease process; b3 represents the cubic coefficient, characterizing the second-order nonlinearity trend of deformation change, used to adjust the overall smoothness of the deformation curve; b2 represents the quadratic coefficient, controlling the intermediate trend of deformation change, affecting the curvature characteristics of mechanical deformation as the spacing decreases; b1 represents the linear coefficient, depicting the part of deformation decrease that is linearly related to the spacing, providing support for the linear baseline trend of the curve; b0 represents the constant term, i.e., the theoretical initial value of mechanical deformation at the minimum spacing;

[0022] By inputting the spacing d, the corresponding mechanical deformation is calculated, thereby analyzing the mechanical response characteristics of the micro-hot plate under different spacings.

[0023] Furthermore, the temperature distribution model of the micro-hot plate: temperature distribution The relationship gradually flattens out as the spacing d increases, and can be expressed as follows:

[0024]

[0025] Where x represents the lateral distance; w1 and w2 represent the magnitude weights of the two Gaussian distributions, used to characterize the influence of lateral distance and spacing on the temperature distribution; μ1 and μ2 represent the center positions of the two Gaussian distributions, corresponding to the peak positions of the temperature distribution; σ1 and σ2 represent the standard deviations of the Gaussian distributions, reflecting the breadth and range of the peak temperature.

[0026] The quadratic function part Q(x,d) is defined as:

[0027] Q(x,d)=[α1x 2 d 2 +β1xd 2 +γ1d 2 ]+[α2x 2 d+β2xd+γ2d]+[α3x2 +β3x+γ3];

[0028] In the above formula, α1, β1, and γ1 are coupling coefficients of high-order nonlinear changes in temperature distribution related to spacing and lateral distance, reflecting the specific influence of high-order nonlinearity on temperature distribution; α2, β2, and γ2 are coefficients used to describe medium nonlinear changes in temperature distribution, reflecting the medium nonlinear trend of temperature distribution with spacing and lateral distance, and playing a smoothing and regulating role in the overall distribution; α3, β3, and γ3 are coefficients describing the overall linear change trend in temperature distribution, characterizing the variation law of temperature with lateral distance and the overall distribution characteristics with spacing.

[0029] Furthermore, the material used for the support layer is SiO2; the insulating layer comprises Si3N4, a material with high thermal conductivity, and SiO2, a material with low thermal conductivity, forming a Si3N4-SiO2 composite film.

[0030] Furthermore, the support layer and the insulating layer form a SiO2-Si3N4-SiO2 composite dielectric film, and a plurality of rectangular etching windows penetrating the composite dielectric film are distributed on the composite dielectric film.

[0031] In a second aspect, the present invention provides a method for manufacturing a multi-temperature zone micro-hot plate based on thermal crossover according to the first aspect, comprising the following steps:

[0032] Step 1: Prepare a silicon substrate;

[0033] Step 2: Form a support layer on a silicon substrate using a thermal oxidation process;

[0034] Step 3: Fabricate heating units using sputtering and photolithography-lift processes, with each heater in the heating unit corresponding to a working area;

[0035] Step 4: Chemical vapor deposition of Si3N4 above the heating unit;

[0036] Step 5: Continue to deposit a layer of SiO2 on top of Si3N4 to form a Si3N4-SiO2 composite film;

[0037] Step 6: Introduce annealing and chemical mechanical polishing processes to eliminate residual forces and planarize the surface;

[0038] Step 7: A detection unit is formed on the insulating layer using sputtering and photolithography-lifting processes, with the detection electrodes in the detection unit corresponding one-to-one with the heater;

[0039] Step 8: Wet etching, dry etching, or a combination of both are used to form the back etching area, and a front etching window structure is formed on the front side.

[0040] Compared with the prior art, the present invention has the following technical effects:

[0041] (1) This invention integrates multiple heaters on the support layer. The heaters adopt a segmented, discontinuous, gradually varying width heating electrode design. By changing the width of the heating electrodes, the uniformity of temperature distribution in the working area is improved, while the mechanical deformation of the micro-hot plate is reduced, ensuring structural stability. The thermal cross-effect between the working areas allows heat to be effectively transferred to other working areas when one working area is in operation, achieving thermal compensation. This reduces the input power required for other working areas to reach the target temperature, thereby reducing overall power consumption. In addition, the etching window design in the micro-hot plate utilizes the excellent thermal insulation properties of air to concentrate heat in the heating area, further reducing heat loss and improving heat conduction efficiency.

[0042] (2) This invention achieves flexible temperature adjustment of each working zone of the micro-hot plate through coded multi-temperature zone control. The input voltage or current of each working zone can be adjusted independently. Combined with the thermal cross-effect between working zones, the working zones are interconnected, realizing the linkage control of multiple temperature working zones on a single micro-hot plate, thus forming a single micro-hot plate multi-temperature zone coded control working mode. The array design of the heater expands the working area of ​​the micro-hot plate, enabling multiple temperature zones to be generated on a single micro-hot plate. This allows the sensor to capture the multiple response characteristics of various gases in a single operation, achieving higher detection selectivity and response speed for different gases. Attached Figure Description

[0043] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of a multi-temperature zone micro-hot plate structure based on heat crossover according to the present invention;

[0045] Figure 2 This is a schematic diagram of the segmented discontinuous gradient width heater of the present invention;

[0046] Figure 3 This is a schematic diagram of the fitting results between peak temperature and working zone spacing in an embodiment of the present invention;

[0047] Figure 4 This is a schematic diagram showing the fitting results of mechanical deformation and working area spacing in an embodiment of the present invention;

[0048] Figure 5 This is a schematic diagram showing the fitting results of temperature distribution and working area spacing in an embodiment of the present invention;

[0049] Figure 6 These are schematic diagrams of the micro-hot plates of different heating units in embodiments of the present invention;

[0050] Figure 7 This is a diagram showing the effect of different working zone spacings on the temperature distribution at the center of the micro-hot plate in an embodiment of the present invention.

[0051] Figure 8 This is a graph showing the relationship between the peak temperature and mechanical deformation of the micro-hot plate and the working area spacing in an embodiment of the present invention;

[0052] Figure 9 This is a comparison diagram of the temperature distribution of micro-hot plates with and without etching windows under the same heating voltage in the embodiments of the present invention;

[0053] Figure 10 This is a schematic diagram of an experimental method for studying heat cross-contamination between working areas in an embodiment of the present invention;

[0054] Figure 11 This is a multi-temperature zone control curve diagram of a single micro-hot plate in an embodiment of the present invention;

[0055] Figure 12 This is the temperature distribution curve of the midline cutoff line when the input voltage of the three heaters in the micro-hot plate in this embodiment of the invention is 2.3V.

[0056] Figure label:

[0057] 1. Silicon substrate; 2. Support layer; 3. Heating unit; 4. Insulating layer; 5. Detection unit; 6. Front etching window; 7. Back etching area. Detailed Implementation

[0058] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the specific implementation methods, structures, features, and effects of the technical solutions proposed according to the present invention are described in detail below with reference to the accompanying drawings and preferred embodiments. Specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0059] In one embodiment of the present invention, a multi-temperature zone micro-hotplate based on thermal crossover is provided, such as... Figure 1 As shown, from bottom to top, it includes: silicon substrate 1, support layer 2, heating unit 3, insulating layer 4, and detection unit 5.

[0060] The support layer 2 is located above the silicon substrate 1 and is used to support the upper structure of the micro-hot plate and isolate the heat generated by the heating unit 3 to reduce heat loss. The material used for the support layer 2 is SiO2, and the thickness is 0.1μm to 3μm.

[0061] The heating unit 3 is disposed above the support layer 2. The heating unit 3 includes multiple heaters, each employing a segmented, discontinuously tapered heating electrode. By varying the electrode width, the uniformity of temperature distribution in the working area is improved. Simultaneously, the discontinuous tapered design helps reduce localized overheating and temperature gradients, thereby minimizing mechanical deformation of the micro-heat plate and ensuring structural stability. Each heater has independent voltage or current input control; by adjusting the input voltage or current of each heating electrode, temperature control can be achieved, forming coded multi-temperature regions. The heater thickness is set between 100nm and 500nm to ensure optimal performance and efficiency.

[0062] The insulating layer 4 covers the heating unit 3; the insulating layer includes a high thermal conductivity material Si3N4 and a low thermal conductivity material SiO2 to form a Si3N4-SiO2 composite film, which is used for electrical isolation and to reduce heat conduction loss. The total thickness of the Si3N4-SiO2 composite film is controlled between 0.2μm and 1μm.

[0063] The material used for the support layer 2 is SiO2, and the insulating layer 4 is a Si3N4-SiO2 composite film. The support layer 2 and the insulating layer 4 form an Oxide-Nitride-Oxide sandwich structure to regulate the residual stress of the micro hot plate. This sandwich structure design can effectively avoid stress mismatch caused by a single dielectric material and reduce the risk of breakage of the micro hot plate.

[0064] The detection unit 5 is located above the insulating layer 4 and includes multiple detection electrodes that correspond one-to-one with the heater, used to sense and read the response signal of the gas-sensitive functional material to the target gas.

[0065] The etched windows are located on the sandwich structure formed by the support layer 2 and the insulating layer 4, and include multiple small rectangular etched windows that penetrate the sandwich structure to improve the thermal efficiency of the micro-hot plate.

[0066] In this embodiment, the heating unit 3 consists of multiple heaters with identical structures, and the geometry of each heater is referenced. Figure 2 Where W1, W2, and W3 represent the widths of the heating electrodes, which increase discontinuously from the edge W1 towards the center W2 and W3; W a This indicates the spacing between the heating electrodes; all spacing is uniform.

[0067] Electrode width and electrode spacing are two key parameters in heater design, jointly determining the temperature characteristics of the heating zone. For a heater with constant electrode width and electrode spacing, the power P distribution per unit area S is consistent, according to the formula... The heating power density of the concentric circular heater is uniformly distributed within the heating region, where σ represents the heating power density of the heating region. However, a uniform heating power density can lead to uneven temperature distribution in the micro-hotplate. By changing the electrode width of the heater, the heating power density distribution within the heating region can be optimized, thereby improving the temperature uniformity of the micro-hotplate.

[0068] The heater employs a segmented, discontinuous, gradually increasing width design, where the heating electrode width gradually increases from the edge to the center, but not continuously. By progressively adjusting the electrode width in segments, the heating power density distribution of the micro-hotplate is optimized, resulting in a more uniform temperature within the heating area. This design improves temperature distribution uniformity while effectively reducing mechanical deformation, contributing to the stability of the micro-hotplate during gas detection.

[0069] There is a thermal cross-effect between the working areas corresponding to the heaters in the heating unit 3. When one working area is working, heat can be transferred to other working areas to achieve thermal compensation, reducing the input power required for other working areas to reach the set temperature and significantly reducing the overall power consumption. In addition, the heating unit 3 can be expanded into an array layout to increase the number of heaters. The temperature of different working areas can be adjusted by partition control. Specifically, the input voltage or current of each heater can be controlled independently. Combined with the thermal cross-effect, each working area can reach the required temperature, generating multiple response characteristics to the target gas at different temperatures, thereby improving the selectivity and efficiency of gas detection.

[0070] The spacing between the working areas is set based on the impact of the thermal cross-contamination effect on the performance of the micro-hotplate, ensuring that temperature distribution uniformity is maintained while reducing power consumption, and mechanical deformation is controlled within an acceptable range. Under constant input voltage or current, appropriately reducing the spacing can enhance the thermal cross-contamination effect, increase the working area temperature, and optimize power consumption; however, too small a spacing can lead to local hot spots, thus affecting temperature uniformity, while too large a spacing will weaken the thermal cross-contamination effect. Taking into account the temperature distribution, power consumption, and mechanical performance of the micro-hotplate, the reasonable setting of the heater spacing achieves the best balance between thermal and mechanical performance, significantly improving the overall thermal efficiency of the micro-hotplate.

[0071] The thermal cross-contamination effect between working zones is a key factor affecting the performance of micro-hotplates. When the spacing between working zones is small, the thermal cross-contamination effect is significant, resulting in high heat transfer efficiency and reducing the power consumption required for each working zone to reach its set temperature. However, excessively small spacing can lead to localized overheating, causing uneven temperature distribution and significant mechanical deformation. As the spacing increases, the thermal cross-contamination effect gradually weakens, power consumption increases significantly, but the temperature distribution becomes more even, and mechanical deformation also decreases. When the spacing reaches a certain critical spacing d... critical Subsequently, the thermal cross-effect almost completely disappears, and the performance between the working zones becomes independent, with peak temperature, mechanical deformation, and temperature distribution all tending to stabilize. Therefore, the design of the working zone spacing needs to find the optimal balance between thermal and mechanical properties while satisfying the constraints of the critical spacing.

[0072] To investigate the effects of the spacing *d* between working zones on peak temperature, mechanical deformation, and temperature distribution, mathematical models for each parameter were established to quantify their relationship with the spacing. For example... Figure 3 , Figure 4 , Figure 5 The figures shown are schematic diagrams illustrating the fitting results of peak temperature, mechanical deformation, and temperature distribution with the working zone spacing.

[0073] Peak temperature model: The peak temperature T(d) of the micro-hotplate decreases non-linearly with the increase of the spacing d, but the temperature increases when the spacing approaches the critical value d. critical The trend towards stability can be represented as:

[0074] T(d) = a4d 4 +a3d 3 +a2d 2 +a1d+a0,d≤d critical ;

[0075] Wherein, a4 represents the quartic coefficient, used to describe the nonlinear rapid change of peak temperature with increasing spacing; a3 represents the cubic coefficient, which reflects the secondary trend correction in the nonlinear change; a2 represents the quadratic coefficient, used to control the curvature of the peak temperature decrease curve; a1 represents the linear coefficient, which characterizes the basic trend of the peak temperature decreasing linearly with spacing, and is directly related to the linear part of the overall change; a0 represents the constant term, which is the theoretical peak temperature when the spacing approaches its minimum.

[0076] Preferably, a4 = 1.4 × 10 -6 a3 = -4.8 × 10 -4 a² = 5.9 × 10 -2 a1 = -3.9, a0 = 5.3 × 10 2The peak temperature is obtained by inputting the spacing d, thereby evaluating the peak temperature and its variation law of the micro-hot plate under different spacings, and providing a reference for optimizing the structural design and performance control of the micro-hot plate.

[0077] Mechanical deformation model: The mechanical deformation D(d) decreases with increasing spacing d, and the relationship can be expressed as:

[0078] D(d) = b4d 4 +b3d 3 +b2d 2 +b1d+b0,d≤d critical ;

[0079] Wherein, b4 represents the quartic coefficient, used to describe the increasing nonlinearity of mechanical deformation as the spacing increases, reflecting the influence of the higher-order nonlinear part during the deformation decrease process; b3 represents the cubic coefficient, characterizing the second-order nonlinearity trend of deformation change, used to adjust the overall smoothness of the deformation curve; b2 represents the quadratic coefficient, controlling the intermediate trend of deformation change, affecting the curvature characteristics of mechanical deformation as the spacing decreases; b1 represents the linear coefficient, depicting the part of deformation decrease that is linearly related to the spacing, providing support for the linear baseline trend of the curve; b0 represents the constant term, i.e., the theoretical initial value of mechanical deformation at the minimum spacing;

[0080] Preferably, b4 = 1.3 × 10 -10 b3 = -3.8 × 10 -8 b² = 4.5 × 10 -6 b1 = -4.1 × 10 -4 b0 = 7.0 × 10 -2 By inputting the spacing d, the corresponding mechanical deformation is calculated, thereby analyzing the mechanical response characteristics of the micro-hot plate under different spacings.

[0081] Temperature distribution model: Temperature distribution The relationship gradually flattens out as the spacing d increases, and can be expressed as:

[0082]

[0083] Where x represents the lateral distance; w1 and w2 represent the magnitude weights of the two Gaussian distributions, used to characterize the influence of lateral distance and spacing on the temperature distribution; μ1 and μ2 represent the center positions of the two Gaussian distributions, corresponding to the peak positions of the temperature distribution; σ1 and σ2 represent the standard deviations of the Gaussian distributions, reflecting the breadth and range of the peak temperature.

[0084] The quadratic function part Q(x,d) is defined as:

[0085] Q(x,d)=[α1x2 d 2 +β1xd 2 +γ1d 2 ]+[α2x 2 d+β2xd+γ2d]+[α3x 2 +β3x+γ3];

[0086] In the above formula, α1, β1, and γ1 are coupling coefficients of high-order nonlinear changes in temperature distribution related to spacing and lateral distance, reflecting the specific influence of high-order nonlinearity on temperature distribution; α2, β2, and γ2 are coefficients used to describe medium nonlinear changes in temperature distribution, reflecting the medium nonlinear trend of temperature distribution with spacing and lateral distance, and playing a smoothing and regulating role in the overall distribution; α3, β3, and γ3 are coefficients describing the overall linear change trend in temperature distribution, characterizing the variation law of temperature with lateral distance and the overall distribution characteristics with spacing.

[0087] Preferably, the specific parameters in the formula are:

[0088] a1=1.0,μ1=10.0,σ1=1.0,a2=1.0,μ2=10.0,σ2=1.0,α1=-5.7×10 -7 ,β1=-0.0002,γ1=-0.014,

[0089] α2=8.6×10 -5 , β2=0.025, γ2=0.979, α3=-0.0069, β3=-1.561, γ3=383.6.

[0090] The temperature distribution model described above allows for the analysis of the impact of different spacings on temperature distribution. This model combines Gaussian distribution terms and quadratic polynomial terms, effectively capturing the variation of temperature across horizontal positions. Furthermore, the introduction of the quadratic function Q(x,d) further demonstrates the interactive effect between horizontal distance and spacing.

[0091] Based on simulation data fitting, a peak temperature model, a mechanical deformation model, and a temperature distribution model are proposed to characterize the impact of the working area spacing on the performance of the micro hotplate. The peak temperature model, through polynomial fitting, describes the relationship where temperature gradually stabilizes as the spacing increases; the mechanical deformation model shows that mechanical deformation decreases with increasing spacing; and the temperature distribution model, combining the lateral coordinate and spacing, further quantifies the temperature gradient change. Through these model analyses, the working area spacing can be optimized to reduce power consumption, achieve uniform temperature distribution, and control mechanical deformation, providing a scientific basis for hotplate design and performance regulation.

[0092] The heating unit 3 includes various array structures. To achieve efficient detection of multiple gases, the micro-hot plate is designed with different heater arrangements, such as... Figure 6 The diagram shows the structure of different heating unit micro-hotplates. In the 4-unit micro-hotplate, the heaters are arranged in a square pattern, while in the 9-unit micro-hotplate, the heaters are arranged in a 3×3 array. Each heater has independent voltage or current input control. By adjusting the input voltage or current of each heating unit, combined with thermal crosstalk effect, precise temperature control is achieved while reducing power consumption.

[0093] By increasing the number of heaters, the selectivity and sensitivity of the micro-hotplate for detecting different gases can be significantly improved, especially in much more complex gas environments where it exhibits higher detection performance. The expanded heating unit design not only improves the sensor's response speed but also provides more flexible and precise temperature control for the detection of various gases.

[0094] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0095] Two identical heaters are integrated on a single SiO2 dielectric thin film, with the heater geometry referenced. Figure 2 The radius of the plate is designed to be 100 μm. Si3N4 material is deposited between the heating electrodes to improve the temperature distribution. The back etching size is 720 μm * 360 μm. The overall planar size of the micro-hot plate is 1500 μm × 1500 μm. The total thickness of the Oxide-Nitride-Oxide sandwich structure is 1.3 μm. Among them, the thickness of the SiO2 support layer 2 is 0.7 μm, and the thickness of Si3N4 and SiO2 in the Si3N4-SiO2 insulating layer 4 is 0.3 μm. The thickness of the Pt heating electrode is 0.2 μm, and the thickness of the Au detection electrode is 0.2 μm.

[0096] When one heater in heating unit 3 is in heating mode, the heat it generates affects the temperature of other heaters through heat conduction. This heat crossover effect may lead to uneven temperature distribution in the heating area. Although the heat crossover effect can be mitigated by increasing the spacing between working areas, utilizing this heat crossover can significantly reduce the overall power consumption of the micro-heatplate.

[0097] Figure 7 This study investigated the effect of different working zone spacings on the temperature distribution at the center of a micro-hotplate under constant voltage input conditions. The results showed that although micro-hotplates with different spacings exhibited a consistent temperature distribution trend, the central region showed a flatter temperature curve when the working zone spacing exceeded 120 μm. When the spacing decreased to below 80 μm, localized hot spots appeared in the central region of the micro-hotplate. Furthermore, shortening the working zone spacing enhanced the thermal cross-contamination effect, further increasing the temperature in the central region of the micro-hotplate.

[0098] Figure 8 The relationship between the peak temperature and mechanical deformation of the micro-hotplate and the spacing between the working areas is shown. As the spacing increases, the peak temperature of the micro-hotplate gradually decreases, reflecting a reduction in the thermal cross-contamination effect. Particularly when the spacing exceeds 120 μm, the thermal cross-contamination between the working areas is significantly reduced, and the peak temperature variation of the micro-hotplate tends to stabilize. Notably, when the spacing between the working areas is shortened to 60 μm, the peak temperature of the micro-hotplate reaches its highest point, but at this point, temperature uniformity is poor. Furthermore, the mechanical deformation of the micro-hotplate is negatively correlated with the spacing between the working areas; within the tested spacing range, the mechanical deformation remains at an acceptable level. Considering power consumption, temperature distribution, and mechanical performance, the optimal spacing between the working areas is designed to be 120 μm. At this distance, the peak temperature of the micro-hotplate is 381 °C, the mechanical deformation is 0.044 μm, and it also exhibits excellent temperature uniformity.

[0099] To improve the thermal performance of the micro-hotplate and reduce heat loss, etched windows are incorporated into its design. These windows utilize the excellent thermal insulation properties of air to more effectively concentrate the heat generated by the heater within the heating area, thereby significantly improving the overall thermal efficiency of the micro-hotplate. For example... Figure 9 The figure shows the temperature distribution of microheat plates with and without etched windows under the same heating voltage. The results show that the temperature in the heating region of the microheat plate with etched windows is significantly higher than that of the microheat plate without etched windows, with a peak temperature difference of 40°C. This indicates that the etched window design can effectively reduce heat loss of the microheat plate and maintain a higher operating temperature in the heating region.

[0100] The 1×2 heater configuration, the smallest unit integrated on a single chip, lays the foundation for building large-scale sensor arrays. Evaluating thermal cross-contamination between working areas is crucial for future applications of large-scale micro-hotplate arrays. The effect of thermal cross-contamination is assessed by monitoring temperature changes in adjacent working areas. Experimental setup as follows... Figure 10 As shown, H1 serves as the heating electrode, and H2 serves as the monitoring electrode. In this configuration, H1 is maintained at a constant temperature, and the temperature change of H2 is monitored to assess the power required to reach a predetermined temperature, thereby quantifying the impact of the thermal cross-effect.

[0101] Table 1 shows a power comparison between dual-working-zone and single-working-zone micro-hotplates at the same operating temperature. Here, H1 and H2 represent the two heaters in the dual-working-zone micro-hotplate, while H... a and H bThis represents the heater in a single-operation-zone micro-hotplate. Although the designs of dual-operation-zone and single-operation-zone micro-hotplates differ in the size of the dielectric film, this difference has a negligible impact on the power required for the heater to reach a specific operating temperature. In a dual-operation-zone micro-hotplate, the temperature of H1 directly affects the power required for H2 to reach a specific temperature. For example, when the temperature of H1 is 100°C, H2 requires 26.07 mW of power to reach an operating temperature of 300°C. However, when the temperature of H1 increases to 400°C, H2 only requires 22.78 mW of power to reach the same temperature. This phenomenon indicates that as the temperature of H1 increases, H2 gains more heat through thermal crossover, thereby reducing the input power required to reach the target temperature. This indirectly demonstrates the effectiveness of thermal crossover between heaters in reducing the power consumption of the micro-hotplate.

[0102] Table 1. Power comparison between dual-working-zone and single-working-zone micro-hotplates at the same operating temperature.

[0103]

[0104] Compared to single-zone micro-hotplates, dual-zone micro-hotplates require significantly less power to reach the same temperature. Specifically, when both zones operate at 300°C, the single-zone design requires 56.74mW of power, 9.36mW more than the dual-zone design, meaning each zone requires 4.68mW more at the same temperature. This significant power consumption difference highlights the advantage of thermal crossover in reducing overall power consumption. Furthermore, the table data shows that even with 0mW of input power to H2, the temperature of H2 still increases as the temperature of H1 increases. This indicates that even without external power input, H2 can reach a relatively high temperature through thermal crossover.

[0105] MOX gas-sensitive functional materials exhibit varying gas responses at different operating temperatures. Achieving multiple temperature zones on a single micro-hotplate can effectively improve the gas selectivity of the sensor. For example... Figure 11 As shown, a single micro-hot plate achieves precise control of multiple temperature zones by fixing the voltage of heater 1 to 2V and sequentially adjusting the input voltage of heater 2 to 1.2V, 1.4V, 1.6V, 1.8V and 2V. Figure 11 The data shows that the temperature of heater 1 remains relatively constant, while the temperature of heater 2 gradually increases with its input voltage, forming multiple temperature gradient regions on a single micro-hotplate, with relatively uniform temperature distribution in each heating region. Furthermore, Figure 11The document also showcases various temperature configurations with different combinations of heating voltages. By adjusting the input voltage of each heater, the temperature of each working zone can be precisely controlled. This coded temperature control method not only simplifies the operation process but also significantly improves the selectivity and sensitivity of the gas sensor.

[0106] MOX gas sensors are typically sensitive to multiple gases and are prone to cross-sensitivity. Temperature modulation and array design are effective methods to improve the selectivity of MOX gas sensors. The designed single-chip highly integrated micro-hotplate consists of an array of heaters, each of which can independently control its input voltage to regulate the temperature of the heated area. Through array design, the micro-hotplate can achieve different operating temperatures in different areas. By utilizing the response characteristics of gas-sensitive functional materials at different temperatures, multiple response information can be acquired in a single data readout.

[0107] In a three-heater design, when all heaters are subjected to the same input voltage, thermal cross-effects cause each heating zone to exhibit different operating temperatures. Figure 12 This shows the temperature distribution along the centerline of the micro-hotplate when the input voltage for all heaters is 2.3V. From Figure 12 As can be seen, the heaters exhibit different operating temperatures under the same heating voltage, with the heater at the center of the micro-heating plate operating at a significantly higher temperature than the heaters on either side. This reflects the thermal crosstalk effect between the operating areas. The central heater receives bidirectional heat compensation from the heaters on either side, resulting in a higher temperature, while the heaters on either side receive only unidirectional heat compensation from the central heater, leading to relatively lower temperatures. Furthermore, while the overall temperature distribution in the heating area is relatively uniform, a certain temperature gradient still exists, with the temperature near the center slightly higher than the edge areas. This is due to localized temperature fluctuations caused by the thermal crosstalk effect.

[0108] Based on the same inventive concept, embodiments of the present invention also provide a method for manufacturing a multi-temperature zone micro-hot plate based on heat cross-section as described above.

[0109] In one embodiment, a method for manufacturing a multi-temperature zone micro-hot plate based on heat crossover is provided, and the specific manufacturing process is as follows:

[0110] Step 1: Prepare silicon substrate 1;

[0111] Choose a 6-inch p-type material with double-sided polishing and a thickness of 400μm. <100> Silicon wafers are used as substrates.

[0112] Step 2: Form a support layer 2 on the silicon substrate 1 using a thermal oxidation process;

[0113] SiO2 is grown simultaneously on both sides of the silicon wafer using a thermal oxidation process; the SiO2 on the front side serves as a support, while the SiO2 on the back side can be used as a mask for anisotropic etching of the silicon substrate 1.

[0114] Step 3: Fabricate heating unit 3 using sputtering and photolithography-lifting processes. Each heater in heating unit 3 corresponds to a working area.

[0115] Titanium / platinum metal for heating unit 3 is fabricated on SiO2 support layer 2 using sputtering and photolithography-lifting processes. Each heater in heating unit 3 corresponds to a working area. Titanium is used as an adhesion layer with a thickness of 10nm-20nm, which serves to tightly connect with support layer 2.

[0116] Step 4: Chemical vapor deposition of Si3N4 above heating unit 3;

[0117] Si3N4 material was deposited above heating unit 3 using plasma-enhanced chemical vapor deposition; the Si3N4 material completely covered heating unit 3.

[0118] Step 5: Continue vapor deposition of a SiO2 layer on top of Si3N4 to form the Si3N4-SiO2 composite insulating layer 4;

[0119] Step 6: Introduce annealing and chemical mechanical polishing processes to eliminate residual forces and planarize the surface;

[0120] Because silicon dioxide and silicon nitride have different coefficients of thermal expansion, the composite film has large residual stress. High-temperature annealing and chemical mechanical polishing are used to remove residual stress and surface planarization.

[0121] Step 7: Detection unit 5 is formed on the insulating layer 4 using sputtering and photolithography-lifting processes. The detection electrodes in detection unit 5 correspond one-to-one with the heaters.

[0122] Titanium / gold metal for detection units is sputtered onto the composite insulating layer. The detection electrodes in detection unit 5 correspond one-to-one with the heater. Titanium serves as an adhesion layer that is tightly connected to the insulating layer. Gold serves as the main detection structure. The detection electrodes adopt an interdigitated structure, meaning that the metal electrodes are parallel to each other.

[0123] Step 8: Wet etching, dry etching, or a combination of both are used to form the back etching area 7, and a front etching window structure 6 is formed on the front side;

[0124] The back side of the substrate is etched using a combination of wet and dry methods until it contacts the silicon dioxide support film on the front side, in order to release the closed film-type micro-hot plate structure. In addition, etching is performed on the Oxide-Nitride-Oxide sandwich structure formed by the support layer 2 and the insulating layer 4 to form etching windows, which include multiple small rectangular etching windows that penetrate the composite dielectric film.

[0125] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A multi-temperature zone micro-hot plate based on thermal crossover, characterized in that, It includes a silicon substrate, a support layer, a heating unit, an insulating layer, and a detection unit; The support layer is located above the silicon substrate and is used to support the upper structure of the micro-hot plate and isolate the heat generated by the heating unit. The heating unit is disposed above the support layer and includes multiple heaters, each corresponding to a working area, forming a coded multi-temperature region; the multiple heaters share a dielectric film, and heat is transferred between the working areas through the thermal cross-effect. The insulating layer covers the heating unit for electrical isolation and to reduce heat conduction loss; The detection unit is located above the insulating layer and includes multiple detection electrodes that correspond one-to-one with the heater, used to sense and read the response signal of the gas-sensitive functional material to the target gas. The spacing between the working areas is optimized based on the combined effects of thermal cross-contamination on the peak temperature, mechanical deformation, and temperature distribution uniformity of the micro-hot plate. The peak temperature model of the micro-hot plate: peak temperature of the micro-hot plate With spacing The increase in spacing exhibits a non-linear decreasing trend, reaching a critical value. The trend towards stability is represented as: ； in, This represents the coefficient of the fourth term, used to describe the nonlinear and rapid change of peak temperature with increasing spacing; This represents the coefficient of the cubic term, which reflects the secondary trend correction in nonlinear changes; The quadratic coefficient is used to control the curvature of the peak temperature decrease curve; It represents the coefficient of the first term, which depicts the basic trend of the peak temperature decreasing linearly with the distance, and is directly related to the linear part of the overall change; This represents the constant term, which is the theoretical peak temperature when the spacing approaches its minimum. By spacing To obtain the corresponding peak temperature, we can evaluate the peak temperature and its variation law of the micro-hot plate under different spacings, and provide a reference for optimizing the structural design and performance control of the micro-hot plate. The temperature distribution model of the micro-hot plate: Temperature distribution With spacing The increase gradually levels off, and the relationship can be expressed as follows: ； in, Indicates horizontal distance; and These represent the magnitude weights of the two Gaussian distributions, used to characterize the intensity of the influence of lateral distance and spacing on the temperature distribution; and These represent the center positions of the two Gaussian distributions, corresponding to the peak positions of the temperature distributions; and These represent the standard deviations of the Gaussian distribution, reflecting the breadth and range of the peak temperature. Quadratic function part Defined as: ； In the above formula, , , The coupling coefficient of the higher-order nonlinear variation in temperature distribution related to spacing and lateral distance reflects the specific influence of higher-order nonlinearity on temperature distribution; , , The coefficient is used to describe the moderate nonlinear variation in temperature distribution. It reflects the moderate nonlinear trend of temperature distribution with spacing and lateral distance, and plays a smoothing and regulating role in the overall distribution. , , The coefficient describes the overall linear trend of temperature distribution, characterizing the variation law of temperature over lateral distance and the overall distribution characteristics as a function of distance.

2. The multi-temperature zone micro-hot plate based on thermal cross-flow according to claim 1, characterized in that, The heater employs segmented, discontinuously tapered heating electrodes.

3. A multi-temperature zone micro-hot plate based on thermal cross-flow according to claim 2, characterized in that, The width of the heating electrode gradually increases from the edge to the center in a non-continuous manner, and the electrode spacing of the heating electrode is uniform.

4. A multi-temperature zone micro-hot plate based on thermal cross-flow according to claim 1, characterized in that, The mechanical deformation model of the micro-hot plate: mechanical deformation With spacing The increase of shows a decreasing trend, and the relationship is expressed as: ； in, The coefficients of the fourth term are used to describe the increasing trend of nonlinear change in mechanical deformation as the spacing increases, reflecting the influence of the higher-order nonlinear components during the deformation reduction process. It represents the coefficient of the cubic term, which characterizes the secondary nonlinear trend of deformation and is used to adjust the overall smoothness of the deformation curve; It represents the coefficient of the quadratic term, which regulates the moderate trend of deformation changes and affects the curvature characteristics of mechanical deformation as the spacing decreases. The coefficient of the first term describes the part of the deformation decrease process that is linearly related to the spacing, providing support for the linear baseline trend of the curve; This represents the constant term, i.e., the initial theoretical mechanical deformation value at the minimum spacing. By inputting the spacing d, the corresponding mechanical deformation is calculated, thereby analyzing the mechanical response characteristics of the micro-hot plate under different spacings.

5. A multi-temperature zone micro-hot plate based on thermal cross-flow according to claim 1, characterized in that, The support layer is made of SiO2; the insulating layer comprises Si3N4, a material with high thermal conductivity, and SiO2, a material with low thermal conductivity, forming a Si3N4-SiO2 composite film.

6. A multi-temperature zone micro-hot plate based on thermal cross-flow according to claim 5, characterized in that, The support layer and the insulating layer form a SiO2-Si3N4-SiO2 composite dielectric film, and multiple rectangular etching windows that penetrate the composite dielectric film are distributed on the composite dielectric film.

7. A method for manufacturing a multi-temperature zone micro-hot plate based on thermal cross-section as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Prepare a silicon substrate; Step 2: Form a support layer on a silicon substrate using a thermal oxidation process; Step 3: Fabricate heating units using sputtering and photolithography-lift processes, with each heater in the heating unit corresponding to a working area; Step 4: Chemical vapor deposition of Si3N4 above the heating unit; Step 5: Continue vapor deposition of SiO2 on top of Si3N4 to form a Si3N4-SiO2 composite film; Step 6: Introduce annealing and chemical mechanical polishing processes to eliminate residual forces and planarize the surface; Step 7: A detection unit is formed on the insulating layer using sputtering and photolithography-lifting processes, with the detection electrodes in the detection unit corresponding one-to-one with the heater; Step 8: Wet etching, dry etching, or a combination of both are used to form the back etching area, and a front etching window structure is formed on the front side.

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