Multi-temperature-zone micro hot plate based on heat crossing and manufacturing method

Abstract

The invention belongs to the technical field of MEMS, and particularly relates to a multi-temperature-zone micro hot plate based on thermal crossing and a manufacturing method. According to the micro hot plate, a plurality of heaters are integrated on a supporting layer, each heater corresponds to one working area, and temperature control is achieved by adjusting the input voltage or current of each heater; the working areas are communicated with one another, the heat cross effect between the working areas is further fully utilized, linkage control over the multiple temperature working areas on the single micro hot plate is achieved, and therefore the working mode that the single micro hot plate and the multiple temperature areas can be coded and controlled is formed. The temperature areas are communicated with one another, the heat cross effect is effectively utilized, and the overall power consumption of the micro hot plate is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of MEMS (Micro-Electro-Mechanical Systems), and particularly relates to a multi-temperature zone micro-hotplate based on thermal crossover and a manufacturing method thereof. Background Art

[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 metal oxide semiconductor gas sensors is based on the response of gas-sensitive functional materials to target gases. Gas-sensitive functional materials usually exhibit the best detection performance at working temperatures of 100°C - 500°C. With the development of micro-electro-mechanical system technology, micro-hotplates (MHP) have been widely used in metal oxide semiconductor gas sensors to provide the working temperature environment required by gas-sensitive functional materials by embedding heating wires in dielectric films.

[0003] Although micro-hotplate-based metal oxide semiconductor gas sensors have significant advantages in providing heating conditions, they still face problems of poor gas selectivity and cross-sensitivity in practical applications, that is, the response of gas-sensitive functional materials to multiple gases is non-unique, making it difficult to accurately distinguish multiple gases. To solve the selectivity problem, existing research mostly adopts the design of integrated sensor arrays to improve the overall selectivity by increasing the number of sensing elements. However, an obvious defect of this method is the significant increase in power consumption. At the same time, although the design of integrating multiple sensors on a single chip can achieve miniaturization and high integration of devices, it is difficult to precisely control the temperature of each working area. Thus, there is an urgent need in this field for an innovative micro-hotplate design to optimize temperature control and balance power consumption, laying a foundation for the development and wide application of subsequent high-performance portable gas sensors. Summary of the Invention

[0004] To overcome the problems in the prior art, the present invention proposes a multi-temperature zone micro-hotplate based on thermal crossover and a manufacturing method thereof.

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

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

[0007] The support layer is located above the silicon-based substrate, and is used to support the upper structure of the micro-hotplate and isolate the heat generated by the heating unit;

[0008] The heating unit is disposed above the support layer and includes a plurality of heaters, each heater corresponding to a working area to form an encodable multi-temperature region; the plurality of heaters share a dielectric film, and heat transfer between the working areas is achieved through the thermal crosstalk effect;

[0009] The insulating layer covers the heating unit and is used for electrical isolation and reduction of heat conduction loss;

[0010] The detection unit is located above the insulating layer and includes a plurality of detection electrodes corresponding one-to-one with the heaters, and is used for sensing and reading the response signal of the gas-sensitive functional material to the target gas.

[0011] Further, the heater adopts a segmented discontinuous and gradually varying width heating electrode.

[0012] Further, the electrode width of the heating electrode gradually increases non-continuously from the edge to the center, and the electrode spacing of the heating electrode is uniform.

[0013] Further, each heater corresponds to a working area, and temperature control is achieved by adjusting the input voltage or current of each heater to form an encodable multi-temperature region, and the temperature regions are interconnected.

[0014] Further, the spacing between the heaters needs to be comprehensively considered and set according to the thermal crosstalk effect on the uniformity of the temperature distribution, power consumption, and mechanical deformation of the micro-hotplate.

[0015] Further, the peak temperature model of the micro-hotplate: the peak temperature T(d) of the micro-hotplate shows a non-linear decreasing trend with the increase of the spacing d, and tends to be stable when the spacing approaches the critical value d critical and is expressed as:

[0016] T(d) = a 4 d 4 + a 3 d 3 + a 2 d 2 + a 1 d + a 0 , d ≤ d critical ;

[0017] wherein, a 4 represents the quartic coefficient and is used to describe the non-linear rapid change of the peak temperature with the increase of the spacing; a 3 represents the cubic coefficient, which reflects the secondary trend correction in the non-linear change; a 2 represents the quadratic coefficient and is used to control the bending degree of the peak temperature decline curve; a 1represents the coefficient of the linear term, which depicts the basic trend of the peak temperature decreasing linearly with the spacing and is directly related to the linear part of the overall change; a 0 represents the constant term, that is, the theoretical peak temperature when the spacing approaches the minimum;

[0018] The corresponding peak temperature is obtained through the spacing d, so as to evaluate the peak temperature and its variation law of the micro - hotplate at different spacings, providing a reference basis for optimizing the structural design and performance regulation of the micro - hotplate.

[0019] Furthermore, the mechanical deformation model of the micro - hotplate: the mechanical deformation D(d) shows a downward trend as the spacing d increases, and its relationship is expressed as:

[0020] D(d)=b 4 d 4 +b 3 d 3 +b 2 d 2 +b 1 d + b 0 ,d≤d critical ;

[0021] where, b 4 represents the coefficient of the quartic term, which is used to describe the enhanced trend of the non - linear change of the mechanical deformation as the spacing increases, reflecting the influence of the high - order non - linear part in the process of deformation decrease; b 3 represents the coefficient of the cubic term, which depicts the secondary non - linear trend of the deformation change and is used to adjust the overall smoothness of the deformation curve; b 2 represents the coefficient of the quadratic term, which controls the medium trend of the deformation change and affects the curvature characteristics of the mechanical deformation decreasing with the spacing; b 1 represents the coefficient of the linear term, which depicts the part linearly related to the spacing in the process of deformation decrease and provides support for the linear reference trend of the curve; b 0 represents the constant term, that is, the initial value of the theoretical mechanical deformation at the minimum spacing;

[0022] By inputting the spacing d to calculate the corresponding mechanical deformation, the mechanical response characteristics of the micro - hotplate at different spacings can be analyzed.

[0023] Furthermore, the temperature distribution model of the micro - hotplate: the temperature distribution gradually becomes flat as the spacing d increases, and its relationship is expressed as:

[0024]

[0025] where, x represents the transverse distance; w 1 and w 2 respectively represent the amplitude weights of two Gaussian distributions, which are used to depict the influence intensity of the transverse distance and the spacing on the temperature distribution; μ1 and μ 2 respectively represent the central positions of two Gaussian distributions, corresponding to the peak positions of the temperature distribution; σ 1 and σ 2 respectively represent the standard deviations of the Gaussian distributions, reflecting the expansion width and range of the peak temperature;

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

[0027] Q(x, d)=[α 1 x 2 d 2 +β 1 xd 2 +γ 1 d 2 +[α 2 x 2 d+β 2 xd+γ 2 d]+[α 3 x 2 +β 3 x+γ 3 ;

[0028] In the above formula, α 1 , β 1 , γ 1 are coupling coefficients of high-order non-linear variations related to the spacing and lateral distance in the temperature distribution, reflecting the specific influence of higher-order non-linearity on the temperature distribution; α 2 , β 2 , γ 2 are coefficients used to describe medium non-linear variations in the temperature distribution, reflecting the medium non-linear trend of the temperature distribution with changes in spacing and lateral distance, and playing a smoothing and regulating role in the overall distribution; α 3 , β 3 , γ 3 are coefficients describing the overall linear variation trend in the temperature distribution, characterizing the variation law of temperature in the lateral distance and the overall distribution characteristics with changes in spacing.

[0029] Furthermore, the material used for the support layer is SiO 2 ; the insulating layer includes a high thermal conductivity material Si 3 N 4 and a low thermal conductivity material SiO 2 , forming a Si 3 N 4 -SiO 2 composite film.

[0030] Furthermore, the support layer and the insulating layer form SiO 2 -Si 3 N4 -SiO 2 A composite dielectric film, on which a plurality of rectangular etching windows penetrating the composite dielectric film are distributed.

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

[0032] Step 1: Prepare a silicon-based substrate;

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

[0034] Step 3: Manufacture a heating unit by using a sputtering process and a lithography-lift-off process, and each heater in the heating unit corresponds to a working area;

[0035] Step 4: Chemically vapor deposit Si 3 N 4 ;

[0036] Step 5: Continuously vapor deposit a SiO 3 N 4 layer above Si 2 to form a Si 3 N 4 -SiO 2 composite film;

[0037] Step 6: Introduce an annealing process and a chemical mechanical polishing process to eliminate residual stress and planarize the surface;

[0038] Step 7: Form a detection unit on the insulating layer by using a sputtering process and a lithography-lift-off process, and the detection electrodes in the detection unit correspond to the heaters one by one;

[0039] Step 8: Etch to form a back etching area by wet etching, dry etching or a combination of both, and form a front etching window structure on the front side.

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

[0041] (1) The present invention integrates multiple heaters on a support layer. The heaters adopt a segmented discontinuous gradually varying width heating electrode design. By changing the width of the heating electrode, the temperature distribution uniformity in the working area is improved, and at the same time, the mechanical deformation of the micro-hotplate is reduced, ensuring the structural stability. Due to the thermal cross-effect between working areas, when one working area is in the working state, heat can be effectively transferred to other working areas to achieve thermal compensation, thereby reducing the input power required for other working areas to reach the target temperature and lowering the overall power consumption. In addition, the etching window design in the micro-hotplate utilizes the excellent adiabatic property of air to concentrate heat in the heating area, further reducing heat loss and improving the heat conduction efficiency.

[0042] (2) Through the controllable multi-temperature region control, the present invention realizes flexible temperature adjustment of each working area of the micro-hotplate. The input voltage or current of each working area can be independently adjusted. Combining with the thermal cross-effect between working areas, each working area is interconnected to achieve the linkage control of multiple temperature working areas on a single micro-hotplate, thus forming a working mode of single micro-hotplate multi-temperature region controllable coding. The array design of the heaters expands the working area of the micro-hotplate, enabling multiple temperature zones to be generated on a single micro-hotplate, allowing the sensor to capture the multiple response characteristics of multiple gases in a single operation and achieving higher detection selectivity and response speed for different gases. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0044] Figure 1 It is a schematic structural diagram of a multi-temperature region micro-hotplate based on thermal cross of the present invention;

[0045] Figure 2 It is a schematic diagram of a segmented discontinuous gradually varying width heater of the present invention;

[0046] Figure 3 It is a schematic diagram of the fitting result of the peak temperature and the working area spacing in the embodiment of the present invention;

[0047] Figure 4 It is a schematic diagram of the fitting result of the mechanical deformation and the working area spacing in the embodiment of the present invention;

[0048] Figure 5 It is a schematic diagram of the fitting result of the temperature distribution and the working area spacing in the embodiment of the present invention;

[0049] Figure 6It is a schematic structural diagram of micro - hotplates of different heating units in an embodiment of the present invention;

[0050] Figure 7 It is a diagram showing the influence of different working spacings on the central temperature distribution of the micro - hotplate in an embodiment of the present invention;

[0051] Figure 8 It is a diagram showing the relationship between the peak temperature and mechanical deformation of the micro - hotplate and the working spacing in an embodiment of the present invention;

[0052] Figure 9 It is a comparative diagram of the temperature distribution of the micro - hotplate with and without an etching window under the same heating voltage in an embodiment of the present invention;

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

[0054] Figure 11 It is a control curve graph of multi - temperature zones of a single micro - hotplate in an embodiment of the present invention;

[0055] Figure 12 It is a temperature distribution curve of the mid - line intercept when the input voltages of three heaters in the micro - hotplate are all 2.3V in an embodiment of the present invention.

[0056] Reference numerals:

[0057] 1, silicon - based substrate; 2, support layer; 3, heating unit; 4, insulating layer; 5, detection unit; 6, front - side etching window; 7, back - side etching area. Detailed implementation manners

[0058] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following, in combination with the accompanying drawings and preferred embodiments, details the specific implementation manners, structures, features, and effects of the technical solutions proposed according to the present invention. The specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

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

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

[0061] The heating unit 3 is disposed above the support layer 2. The heating unit 3 includes a plurality of heaters. The heaters adopt segmented non - continuous gradually changing width heating electrodes. By changing the width of the heating electrodes, the temperature distribution uniformity in the working area is improved. At the same time, the non - continuous gradually changing design helps to reduce local overheating and temperature gradient, thereby reducing the mechanical deformation of the micro - hotplate and ensuring the structural stability. Each heater has an independent voltage or current input control. By regulating the input voltage or current of each heating electrode, the temperature can be controlled to form an encoded multi - temperature region. The thickness of the heater is set to be 100 nm to 500 nm to ensure the optimization of its performance and efficiency.

[0062] The insulating layer 4 covers the heating unit 3; the insulating layer includes a high - thermal - conductivity material Si 3 N 4 and a low - thermal - conductivity material SiO 2 , forming a Si 3 N 4 -SiO 2 composite film for electrical isolation and reducing heat conduction loss. The total thickness of the Si 3 N 4 -SiO 2 composite film is controlled between 0.2 μm and 1 μm.

[0063] The material used for the support layer 2 is SiO 2 , and the insulating layer 4 is a Si 3 N 4 -SiO 2 composite film. Then, the support layer 2 and the insulating layer 4 form an Oxide - Nitride - Oxide sandwich structure to regulate the residual stress of the micro - hotplate. This sandwich structure design can effectively avoid stress mismatch caused by a single dielectric material and reduce the fracture risk of the micro - hotplate.

[0064] The detection unit 5 is located above the insulating layer 4 and includes a plurality of detection electrodes corresponding one - to - one with the heaters for sensing and reading the response signal of the gas - sensitive functional material to the target gas.

[0065] The etching window is located on the sandwich structure formed by the support layer 2 and the insulating layer 4 and includes a plurality of rectangular small etching windows penetrating the sandwich structure for improving the thermal efficiency of the micro - hotplate.

[0066] In this embodiment, the heating unit 3 is composed of a plurality of heaters with the same structure, and the geometric shape of each heater refers to Figure 2 . Among them, W 1 , W 2 , W3 denotes the width of the heating electrode, and the width of the heating electrode increases non - continuously from the edge \(W\) 1 gradually towards the center \(W\) 2 and \(W\) 3 increases non - continuously; \(W\) a denotes the spacing between the heating electrodes, and all the spacings are uniform.

[0067] The electrode width and the electrode spacing are two key parameters of the heater design, and they jointly determine the temperature characteristics of the heating area. For a heater with a constant electrode width and electrode spacing, the power \(P\) distribution on the unit area \(S\) is consistent. According to the formula The heating power density of the concentric - circle heater is evenly distributed within the heating area, where \(\sigma\) represents the heating power density of the heating area. However, the uniform heating power density will result in non - uniform temperature distribution of the micro - hotplate. By changing the electrode width of the heater, the heating power density distribution in the heating area can be optimized, thereby improving the temperature uniformity of the micro - hotplate.

[0068] The heater adopts a segmented non - continuous gradually - changing width design, which makes the width of the heating electrode gradually increase but non - continuously from the edge to the center. By making segmented progressive adjustments to the electrode width, the heating power density distribution of the micro - hotplate is optimized, making the temperature in the heating area more uniform. While improving the temperature distribution uniformity, this design effectively reduces mechanical deformation, which helps to maintain 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 operating, 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 extended to an array layout, increasing the number of heaters. By controlling different working areas separately, specifically, the input voltage or current of each heater can be independently controlled. Combining 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 enhancing the selectivity and efficiency of gas detection.

[0070] The spacing between the working areas is set according to the influence of the thermal cross - effect on the performance of the micro - hotplate, ensuring the uniformity of the temperature distribution while reducing power consumption and controlling the mechanical deformation within an acceptable range. Under a constant input voltage or current, appropriately reducing the spacing can enhance the thermal cross - effect, increase the temperature of the working areas, and optimize power consumption. However, too small a spacing will result in local hot spots, affecting temperature uniformity, while too large a spacing will weaken the thermal cross - effect. Considering the temperature distribution, power consumption, and mechanical properties of the micro - hotplate comprehensively, the reasonable setting of the heater spacing achieves the best balance between thermal performance and mechanical performance, significantly improving the overall thermal efficiency of the micro - hotplate.

[0071] The thermal cross - effect between the working areas is a key factor affecting the performance of the micro - hotplate. When the spacing between the working areas is small, the thermal cross - effect is significant, and the heat transfer efficiency between the working areas is high, thus reducing the power consumption required for each working area to reach the set temperature. However, too small a spacing will cause local overheating, resulting in non - uniform temperature distribution and large mechanical deformation. As the spacing increases, the thermal cross - effect gradually weakens, the power consumption increases significantly, but the temperature distribution becomes flatter, and the mechanical deformation also decreases. When the spacing reaches a certain critical spacing d critical After that, the thermal cross - effect almost completely disappears, the performance between the working areas becomes independent, and the peak temperature, mechanical deformation, and temperature distribution all tend to be stable. Therefore, the design of the working area spacing needs to find the best balance between thermal performance and mechanical performance while meeting the constraint conditions of the critical spacing.

[0072] To study the influence of the spacing d between the working areas on the peak temperature, mechanical deformation, and temperature distribution, mathematical models of each parameter are established respectively to quantify their relationship with the spacing. As Figure 3 , Figure 4 , Figure 5 shown, they are the schematic diagrams of the fitting results of the peak temperature, mechanical deformation, and temperature distribution with the working area spacing respectively.

[0073] Peak temperature model: The peak temperature T(d) of the micro - hotplate shows a non - linear decreasing trend with the increase of the spacing d, but it tends to be stable when the spacing approaches the critical value d critical and can be expressed as:

[0074] T(d)=a 4 d 4 +a 3 d 3 +a 2 d 2 +a 1 d+a 0 ,d≤d critical ;

[0075] where, a 4Represents the coefficient of the quartic term, which is used to describe the non-linear rapid change of the peak temperature with the increase of the spacing; a 3 Represents the coefficient of the cubic term, which reflects the secondary trend correction in the non-linear change; a 2 Represents the coefficient of the quadratic term, which is used to control the bending degree of the peak temperature decline curve; a 1 Represents the coefficient of the linear term, which depicts the basic trend of the linear decline of the peak temperature with the spacing, and is directly related to the linear part of the overall change; a 0 Represents the constant term, that is, the theoretical peak temperature when the spacing approaches the minimum.

[0076] Preferably, a 4 = 1.4×10 -6 , a 3 = -4.8×10 -4 , a 2 = 5.9×10 -2 , a 1 = -3.9, a 0 = 5.3×10 2 . By inputting the spacing d, the corresponding peak temperature can be obtained, so as to evaluate the peak temperature and its change law of the micro-heat plate at different spacings, and provide a reference basis for optimizing the structural design and performance regulation of the micro-heat plate.

[0077] Mechanical deformation model: The mechanical deformation D(d) shows a downward trend with the increase of the spacing d, and its relationship can be expressed as:

[0078] D(d) = b 4 d 4 + b 3 d 3 + b 2 d 2 + b 1 d + b 0 , d ≤ d critical ;

[0079] Among them, b 4 Represents the coefficient of the quartic term, which is used to describe the enhanced trend of the non-linear change of the mechanical deformation with the increase of the spacing, and reflects the influence of the high-order non-linear part in the process of deformation decline; b 3 Represents the coefficient of the cubic term, which depicts the secondary non-linear trend of the deformation change and is used to adjust the overall smoothness of the deformation curve; b 2 Represents the coefficient of the quadratic term, which controls the medium trend of the deformation change and affects the curvature characteristics of the mechanical deformation with the decrease of the spacing; b 1 Represents the coefficient of the linear term, which depicts the part linearly related to the spacing in the process of deformation decline and provides support for the linear reference trend of the curve; b 0 Represents the constant term, that is, the initial value of the theoretical mechanical deformation at the minimum spacing;

[0080] Preferably, b 4 = 1.3×10 -10 , b 3 = -3.8×10 -8 , b 2 = 4.5×10 -6 , b 1 = -4.1×10 -4 , b 0 = 7.0×10 -2 , the corresponding mechanical deformation is calculated through the input spacing d, so as to analyze the mechanical response characteristics of the micro-heat plate at different spacings.

[0081] Temperature distribution model: The temperature distribution gradually becomes flat as the spacing d increases, and its relationship can be expressed as:

[0082]

[0083] where x represents the lateral distance; w 1 and w 2 respectively represent the amplitude weights of two Gaussian distributions, used to characterize the influence intensity of the lateral distance and the spacing on the temperature distribution; μ 1 and μ 2 respectively represent the central positions of two Gaussian distributions, corresponding to the peak positions of the temperature distribution; σ 1 and σ 2 respectively represent the standard deviations of the Gaussian distributions, reflecting the expansion width and range of the peak temperature;

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

[0085] Q(x, d) = [α 1 x 2 d 2 + β 1 xd 2 + γ 1 d 2 + [α 2 x 2 d + β 2 xd + γ 2 d] + [α 3 x 2 + β 3 x + γ 3 ;

[0086] In the above formula, α 1 , β 1 , γ 1is the coupling coefficient for the high-order non-linear variation related to the spacing and lateral distance in the temperature distribution, reflecting the specific impact of the high-order non-linearity on the temperature distribution; α 2 , β 2 , γ 2 are the coefficients used to describe the medium non-linear variation in the temperature distribution, reflecting the medium non-linear trend of the temperature distribution with changes in the spacing and lateral distance, and playing a role in smooth adjustment in the overall distribution; α 3 , β 3 , γ 3 are the coefficients describing the overall linear variation trend in the temperature distribution, characterizing the variation law of the temperature in the lateral distance and the overall distribution characteristics with changes in the spacing.

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

[0088] a 1 = 1.0, μ 1 = 10.0, σ 1 = 1.0, a 2 = 1.0, μ 2 = 10.0, σ 2 = 1.0, α 1 = -5.7×10 -7 , β 1 = -0.0002, γ 1 = -0.014,

[0089] α 2 = 8.6×10 -5 , β 2 = 0.025, γ 2 = 0.979, α 3 = -0.0069, β 3 = -1.561, γ 3 = 383.6.

[0090] Through the above temperature distribution model, the influence of different spacings on the temperature distribution can be analyzed. This model combines the Gaussian distribution term and the quadratic polynomial term, and can effectively capture the variation law of the temperature in the lateral position. At the same time, through the introduction of the quadratic function Q(x, d), the interactive influence between the lateral distance and the spacing is further reflected.

[0091] Based on the simulation data fitting, the peak temperature model, mechanical deformation model and temperature distribution model are proposed to characterize the effect of the working area spacing on the performance of the micro-hotplate. The peak temperature model describes the relationship that the temperature gradually tends to be stable as the spacing increases through polynomial fitting; the mechanical deformation model shows that the mechanical deformation decreases as the spacing increases; the temperature distribution model combines the lateral coordinates and spacing to further quantify the temperature gradient change. Through the above model analysis, the working area spacing setting can be optimized to achieve reduced power consumption, uniform temperature distribution and control of mechanical deformation, providing a scientific basis for hot plate design and performance regulation.

[0092] The heating unit 3 includes a variety of array structures. In order to achieve efficient detection of multiple gases, the micro-hotplate is designed with different heater arrangements, such as Figure 6 The figure shows the structure of micro-hotplates with different heating units. The heaters in the 4-unit micro-hotplate are arranged in a square, while the heaters in the 9-unit micro-hotplate 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 and combining the thermal crosstalk effect, precise temperature control can be achieved while reducing power consumption.

[0093] By increasing the number of heaters, the micro-hotplate can significantly improve the detection selectivity and sensitivity of different gases, especially in more complex gas environments. The expanded heating unit design not only improves the sensor's response speed, but also provides more flexible and precise temperature zone control for multiple gas detection.

[0094] The contents involved in the above embodiment are described below in conjunction with a preferred embodiment.

[0095] Two heaters with the same structure are integrated in a SiO 2 The heater geometry on the dielectric film is referenced Figure 2 , whose radius is designed to be 100μm; Si is deposited between the heating electrodes 3 N 4 The material is used to improve the temperature distribution. The back etching size is 720μm*360μm. The overall plane size of the micro-hotplate is 1500μm×1500μm. The total thickness of the oxide-nitride-oxide sandwich structure is 1.3μm. 2 The thickness of the support layer 2 is 0.7 μm, Si 3 N 4 -SiO 2 Si in insulating layer 4 3 N 4 and SiO 2 The thickness of each electrode 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 the heating unit 3 is in the heating state, the heat it generates affects the temperature of other heaters through heat conduction. This thermal cross - effect may lead to non - uniform temperature distribution in the heating area. Although the thermal cross - effect can be weakened by increasing the spacing between working areas, using this thermal cross - effect can significantly reduce the overall power consumption of the micro - hotplate.

[0097] Figure 7 This shows the influence of different working - area spacings on the central temperature distribution of the micro - hotplate under the condition of constant voltage input. The results indicate that although the micro - hotplates with different spacings have consistency in the temperature distribution trend, when the spacing between working areas exceeds 120 μm, the central region shows a more gentle temperature curve. When the spacing is reduced to less than 80 μm, local hot - spot phenomena appear in the central region of the micro - hotplate. In addition, the shortening of the working - area spacing enhances the thermal cross - effect, further increasing the temperature in the central region of the micro - hotplate.

[0098] Figure 8 This shows the relationship between the peak temperature and mechanical deformation of the micro - hotplate and the working - area spacing. As the spacing increases, the peak temperature of the micro - hotplate gradually decreases, reflecting the weakening of the thermal cross - effect. Especially when the spacing exceeds 120 μm, the thermal cross between working areas is significantly weakened, and the change in the peak temperature of the micro - hotplate tends to be stable. It should be noted that when the spacing between working areas is reduced to 60 μm, the peak temperature of the micro - hotplate reaches the highest, but the temperature uniformity is poor at this time. In addition, the mechanical deformation of the micro - hotplate is negatively correlated with the working - area spacing, and within the tested spacing range, the mechanical deformation remains at an acceptable level. Considering power consumption, temperature distribution, and mechanical properties comprehensively, the optimal spacing between working areas is designed to be 120 μm. At this time, the peak temperature of the micro - hotplate is 381 °C, the mechanical deformation is 0.044 μm, and excellent temperature uniformity is also shown.

[0099] To improve the thermal performance of the micro - hotplate and reduce heat loss, etched windows are introduced in the micro - hotplate design. By utilizing the excellent thermal insulation properties of air, the etched windows can more effectively concentrate the heat generated by the heater in the heating area, thus significantly improving the overall thermal efficiency of the micro - hotplate. As Figure 9 shown, this is the temperature distribution of the micro - hotplate with and without etched windows under the same heating voltage. The results show that the temperature in the heating area of the micro - hotplate with etched windows is significantly higher than that of the micro - hotplate without the etched - window design, and the peak - temperature difference reaches 40 °C. This indicates that the etched - window design can effectively reduce the heat loss of the micro - hotplate and maintain a higher working temperature in the heating area.

[0100] The 1×2 heater configuration is the smallest unit formed by integration on a chip, laying the foundation for building large-scale sensor arrays. Evaluating the thermal crosstalk between working areas is crucial for future applications of large-scale micro-hotplate arrays. The effect of thermal crosstalk is evaluated by monitoring the temperature changes in adjacent working areas. The experimental setup is as Figure 10 shown, where H 1 serves as the heating electrode and H 2 serves as the monitoring electrode. In this configuration, H 1 maintains a constant temperature, and the temperature change of H 2 is monitored to evaluate the power required for it to reach the predetermined temperature, thereby quantifying the impact of the thermal crosstalk effect.

[0101] Table 1 shows the power comparison between dual-working-area and single-working-area micro-hotplates at the same working temperature. Among them, H 1 and H 2 represent the two heaters in the dual-working-area micro-hotplate, while H a and H b represent the heaters in the single-working-area micro-hotplate. Although the designs of the dual-working-area and single-working-area micro-hotplates differ in the size of the dielectric film, this difference has a negligible impact on the power required for the heaters to reach a specific working temperature. In the dual-working-area micro-hotplate, the temperature of H 1 has a direct impact on the power required for H 2 to reach a specific temperature. For example, when the temperature of H 1 is 100 °C, H 2 requires 26.07 mW of power to reach the working temperature of 300 °C. However, when the temperature of H 1 increases to 400 °C, H 2 only requires 22.78 mW of power to reach the same temperature. This phenomenon indicates that as the temperature of H 1 increases, H 2 obtains more heat through thermal crosstalk, thereby reducing the input power required to reach the target temperature. This indirectly proves the effectiveness of thermal crosstalk between heaters in reducing the power consumption of micro-hotplates.

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

[0103]

[0104] Compared with a single-workspace micro-hotplate, the dual-workspace micro-hotplate requires significantly less power to reach the same temperature. Specifically, when both workspaces are operating at 300 °C, the single-workspace design requires 56.74 mW of power, which is 9.36 mW more than the dual-workspace design, meaning an additional 4.68 mW per workspace at the same temperature. This significant power consumption difference highlights the advantage of the thermal cross-effect in reducing overall power consumption. Additionally, the tabular data also shows that even when the input power of H 2 is 0 mW, the temperature of H 2 still rises as the temperature of H 1 increases. This indicates that even without external power input, H2 can reach a relatively high temperature through thermal cross.

[0105] The MOX gas-sensitive functional material shows different responses to gases at different operating temperatures. Achieving multiple temperature regions on a single micro-hotplate can effectively improve the gas selectivity of the sensor. As Figure 11 shown, a single micro-hotplate achieved precise control of multiple temperature zones by fixing the voltage of heater 1 at 2 V and sequentially adjusting the input voltage of heater 2 to 1.2 V, 1.4 V, 1.6 V, 1.8 V, and 2 V. Figure 11 shows that the temperature of heater 1 remained basically constant, while the temperature of heater 2 gradually increased with the increase of its input voltage, forming multiple temperature gradient regions on a single micro-hotplate, and the temperature distribution of each heating region was relatively uniform. Additionally, Figure 11 also demonstrated various temperature configurations for different combinations of heating voltages. By adjusting the input voltage of each heater, the temperature of each workspace can be precisely controlled. This coding-based 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 usually sensitive to multiple gases and tend to exhibit 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 a heater array, and each heater can independently control its input voltage to adjust the temperature of the heating region. Through array design, the micro-hotplate can reach different operating temperatures in different regions. Utilizing the response characteristics of the gas-sensitive functional material at different temperatures, multiple response information can be obtained in a single data reading.

[0107] In the three-heater design, when the same input voltage is applied to all heaters, the thermal cross-effect causes different operating temperatures in each heating region. Figure 12 shows the temperature distribution along the centerline of the micro-hotplate when the input voltage of all heaters is 2.3 V. From Figure 12It can be seen that the heaters show different working temperatures under the same heating voltage. The heater located at the center of the microhotplate has a significantly higher working temperature than the heaters on both sides. This reflects the thermal crosstalk effect between the working areas. The central heater has a higher temperature due to the two-way heat compensation from the heaters on both sides, while the heaters on both sides only receive unidirectional heat compensation from the central heater, resulting in relatively lower temperatures. In addition, the overall temperature distribution in the heating area is relatively uniform, but there is still a certain temperature gradient. The temperature in the area near the center is slightly higher than that in the edge area, which is due to the local temperature fluctuations caused by the thermal crosstalk effect.

[0108] Based on the same inventive concept, an embodiment of the present invention further provides a manufacturing method for implementing a multi-temperature zone microhotplate based on thermal crossover involved above.

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

[0110] Step 1: Prepare a silicon-based substrate 1;

[0111] Select a 6-inch p-type <100> silicon wafer with a thickness of 400 μm and double-sided polishing as the substrate.

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

[0113] Simultaneously grow SiO on both the front and back sides of the silicon wafer by using a thermal oxidation process 2 ; The SiO on the front side 2 plays a supporting role, and the SiO on the back side 2 can be used as a mask for anisotropic etching of the silicon-based substrate 1.

[0114] Step 3: Manufacture a heating unit 3 by using a sputtering process and a lithography-lift-off process. Each heater in the heating unit 3 corresponds to a working area;

[0115] Adopt a sputtering and lithography-lift-off process to prepare titanium / platinum metal of the heating unit 3 on the SiO 2 support layer 2. Each heater in the heating unit 3 corresponds to a working area; Titanium is an adhesion layer with a thickness of 10 nm - 20 nm, which plays a role in tightly connecting with the support layer 2.

[0116] Step 4: Chemically vapor deposit Si 3 N 4 above the heating unit 3;

[0117] Use a plasma-enhanced chemical vapor deposition process to deposit Si 3 N 4 material above the heating unit 3; Si 3 N4 The material completely covers the heating unit 3.

[0118] Step 5: Continue chemical vapor deposition of SiO 3 N 4 above Si to form a Si 2 N 3 -SiO 4 composite insulating layer 4; 2

[0119] Step 6: Introduce an annealing process and a chemical mechanical polishing process to eliminate residual stress and planarize the surface;

[0120] Due to the different thermal expansion coefficients of the silicon dioxide and silicon nitride materials, there is a large residual stress in the composite film. Use a high-temperature annealing process and chemical mechanical grinding to remove the residual stress and planarize the surface.

[0121] Step 7: Form a detection unit 5 above the insulating layer 4 by sputtering and photolithography-lift-off processes, and the detection electrodes in the detection unit 5 correspond to the heaters one by one;

[0122] Sputter the titanium / gold metal of the detection unit on the composite insulating layer. The detection electrodes in the detection unit 5 correspond to the heaters one by one. Titanium is used as an adhesion layer to be tightly connected to the insulating layer, and gold is used as the main detection structure. The detection electrodes as a whole adopt an interdigital structure, that is, the metal electrodes are parallel to each other.

[0123] Step 8: Use wet etching, dry etching or a combination of both to etch to form a back etching region 7, and form a front etching window 6 structure on the front;

[0124] Etch the back of the substrate by combining wet and dry etching until it contacts the silicon dioxide support film on the front to release the enclosed membrane type micro-hotplate structure; in addition, etch on the Oxide-Nitride-Oxide (oxide-nitride-oxide) sandwich structure formed by the support layer 2 and the insulating layer 4 to form an etching window, which includes a plurality of rectangular small etching windows penetrating the composite dielectric film.

[0125] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in 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-based substrate, a supporting layer, a heating unit, an insulating layer, and a detection unit; The support layer is located above the silicon-based substrate and is used to support the upper structure of the micro-hotplate and isolate the heat generated by the heating unit; The heating unit is arranged above the supporting layer, and comprises a plurality of heaters, each heater corresponding to a working area, forming a codable multi-temperature area; the plurality of heaters share a dielectric film, and heat is transferred between the working areas through a thermal cross effect; The insulating layer covers the heating unit and is used for electrical isolation and reducing heat conduction loss; The detection unit is located above the insulating layer, and includes a plurality of detection electrodes corresponding to the heaters one by one, and is used to sense and read the response signal of the gas-sensitive functional material to the target gas.

2. The multi-temperature zone micro-hotplate based on thermal crossover according to claim 1, characterized in that: The heater adopts a segmented, discontinuous, and gradually changing width heating electrode.

3. The multi-temperature zone micro-hotplate based on thermal crossover according to claim 2, characterized in that: The electrode width of the heating electrode increases gradually and discontinuously from the edge to the center, and the electrode spacing of the heating electrode is uniform.

4. The multi-temperature zone micro-hotplate based on thermal crossover according to claim 1, characterized in that: The spacing between the working areas is optimally set according to the combined influence of the thermal cross effect on the peak temperature, mechanical deformation and temperature distribution uniformity of the micro-hotplate.

5. The multi-temperature zone micro-hotplate based on thermal crossover according to claim 4, characterized in that: The peak temperature model of the micro-hotplate: The peak temperature T(d) of the micro-hotplate decreases nonlinearly with the increase of the spacing d. critical tends to be stable, expressed as: <h2 style=";text-align:left;direction:ltr">T(d) = a4d<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> +a3d<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +a2d<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +a1d+a0,d≤d<h2 style=";text-align:left;direction:ltr"> critical <h2 style=";text-align:left;direction:ltr"> ; Among them, a4 represents the quartic term coefficient, which is used to describe the nonlinear rapid change of peak temperature with increasing spacing; a3 represents the cubic term coefficient, which reflects the trend correction of the next level in the nonlinear change; a2 represents the quadratic term coefficient, which is used to control the curvature of the peak temperature drop curve; a1 represents the linear term coefficient, which describes the basic trend of the peak temperature decreasing linearly with the spacing, which is directly related to the linear part of the overall change; a0 represents the constant term, that is, the theoretical peak temperature when the spacing approaches the minimum; The corresponding peak temperature is obtained through the spacing d, so as to evaluate the peak temperature and its variation law of the micro-hotplate at different spacings, and provide a reference for optimizing the structural design and performance regulation of the micro-hotplate.

6. The multi-temperature zone micro-hotplate based on thermal crossover according to claim 4, characterized in that: Mechanical deformation model of the micro-hotplate: The mechanical deformation D(d) decreases with the increase of the spacing d, and the relationship is expressed as: <h2 style=";text-align:left;direction:ltr">D(d) = b4d<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> +b3d<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +b2d<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +b1d+b0,d≤d<h2 style=";text-align:left;direction:ltr"> critical <h2 style=";text-align:left;direction:ltr"> ; Among them, b4 represents the quartic term coefficient, which is used to describe the increasing trend of nonlinear change of mechanical deformation as the spacing increases, reflecting the influence of the high-order nonlinear part in the process of deformation decrease; b3 represents the cubic term coefficient, which describes the sub-order nonlinear trend of deformation change and is used to adjust the overall smoothness of the deformation curve; b2 represents the quadratic term coefficient, which regulates the medium trend of deformation change and affects the curvature characteristics of mechanical deformation as the spacing decreases; b1 represents the linear term coefficient, which depicts the part that is linearly related to the spacing in the process of deformation decrease, providing support for the linear baseline trend of the curve; b0 represents the constant term, that is, the theoretical initial value of mechanical deformation at the minimum spacing; By inputting the spacing d to calculate the corresponding mechanical deformation, the mechanical response characteristics of the micro-hotplate at different spacings can be analyzed.

7. The multi-temperature zone micro-hotplate based on thermal crossover according to claim 4, characterized in that: The temperature distribution model of the micro-hotplate: Temperature distribution As the spacing d increases, it gradually becomes flat, and the relationship is expressed as: Where x represents the lateral distance; w1 and w2 represent the amplitude weights of the two Gaussian distributions, which are used to characterize the influence of the 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, which reflect the extension width and range of the peak temperature. The quadratic function part Q(x,d) is defined as: Q(x,d)=[α1x 2 d 2 +β1xd 2 +γ1d 2 ]+[α2x 2 d+β2xd+γ2d]+[α3x 2 +β3x+γ3]; In the above formula, α1, β1, and γ1 are the coupling coefficients of the higher-order nonlinear changes in the temperature distribution related to the spacing and lateral distance, which reflect the specific influence of the higher-order nonlinearity on the temperature distribution; α2, β2, and γ2 are the coefficients used to describe the moderate nonlinear changes in the temperature distribution, which reflect the moderate nonlinear trend of the temperature distribution with the spacing and lateral distance, and play a role in smoothing the overall distribution; α3, β3, and γ3 are the coefficients describing the overall linear change trend in the temperature distribution, which characterize the variation law of temperature in the lateral distance and the overall distribution characteristics with the spacing.

8. The multi-temperature zone micro-hotplate based on thermal crossover according to claim 1, characterized in that: The material used for the support layer is SiO2; the insulating layer includes Si3N4, a material with high thermal conductivity, and SiO2, a material with low thermal conductivity, to form a Si3N4-SiO2 composite film.

9. The multi-temperature zone micro-hotplate based on thermal crossover according to claim 8, characterized in that: 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.

10. A method for manufacturing a multi-temperature zone micro-hotplate based on thermal cross-coupling as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: Prepare a silicon-based substrate; Step 2: forming a support layer on a silicon-based substrate by a thermal oxidation process; Step 3: Using a sputtering process and a photolithography-stripping process to manufacture a heating unit, each heater in the heating unit corresponds to a working area; Step 4: Chemical vapor deposition of Si3N4 on the heating unit; Step 5: Continue to vapor-deposit SiO2 on the Si3N4 to form a Si3N4-SiO2 composite film; Step 6: Introduce annealing process and chemical mechanical polishing process to eliminate residual force and flatten the surface; Step 7: forming a detection unit on the insulating layer by using a sputtering process and a photolithography-stripping process, wherein the detection electrodes in the detection unit correspond to the heaters one by one; Step 8: Wet etching, dry etching or a combination of both are used to form a back etching area and a front etching window structure on the front side.

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