Semiconductor gas sensor and manufacturing method thereof

Abstract

The invention relates to the technical field of semiconductor sensors, and discloses a semiconductor gas sensor and a manufacturing method thereof.The semiconductor gas sensor comprises a substrate, a thin film layer and a heating assembly; wherein the thin film layer is arranged at the upper end of the substrate, the heating assembly is embedded in the thin film layer, the thin film layer is provided with a wire bonding hole corresponding to the heating assembly, a part of the heating assembly is exposed through the wire bonding hole, the thin film layer is provided with a through hole, the position of the through hole is kept away from the heating assembly, and the heating assembly is arranged in the through hole. The substrate is provided with a slotted hole, and the through hole is communicated with the slotted hole. Through the thin film structure with the holes, the sensor is higher in packaging adaptability, higher in reliability and better in long-term robustness on the basis of ensuring the structural integrity.

Description

Technical Field

[0001] This application relates to the field of semiconductor sensor technology, and in particular to a semiconductor gas sensor and its manufacturing method. Background Technology

[0002] Platinum-catalyzed hydrogen sensors have been widely used, demonstrating good sensitivity and stability. Platinum catalysts can reduce the amount of hydrogen adhering to surfaces.

[0003] The activation energy of molecules lowers their reaction temperature with oxygen in the air. In an environment with hydrogen (concentration below the explosive critical point), heating a platinum wire to a specific temperature by applying voltage causes the wire's resistance to change with the hydrogen concentration. By designing a suitable platinum wire heater and temperature sensor on a chip, changes in hydrogen concentration can be converted into changes in platinum wire resistance. These changes can then be processed through circuitry and algorithms to accurately sense the external hydrogen concentration. Existing chip-based platinum wire temperature sensors are based on a closed thin-film structure. Issues such as thermal stress and encapsulating compounds during packaging affect the sensor's yield and long-term reliability.

[0004] Existing thin-film sensor chips typically consist of two parts: a platinum wire heater and a platinum wire temperature sensor, placed in two different locations on the chip. During operation, the platinum wire heater is heated to a specific temperature, allowing hydrogen to react with oxygen. By measuring the change in resistance of the heating wire and combining this with the change in resistance of the platinum wire temperature sensor, the concentration of external hydrogen can be accurately determined. Existing MEMS platinum wire temperature sensor chips are manufactured using semiconductor processes and typically consist of a dielectric thin film and a platinum metal thin film. A closed thin-film structure is achieved by patterning the platinum metal thin film and releasing the structure. This structure encounters problems such as thermal stress and encapsulating compounds during packaging, affecting the sensor's yield and long-term reliability. Summary of the Invention

[0005] The purpose of this application is to provide a semiconductor gas sensor to address the technical problems of existing hydrogen sensors during the packaging process, such as thermal stress and encapsulant compounds, which affect the sensor's yield and long-term reliability. Specifically, thermal stress may damage the thin film's mechanical structure and even cause the platinum wire to break; the encapsulant may release gas during heating, and if there is no channel for release, it will accumulate under the thin film, forming a new compound film layer, affecting device performance and long-term stability. This application solves and improves these problems through a novel structural design.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] In a first aspect, the present application provides a semiconductor gas sensor, comprising a substrate, a thin film layer and a heating assembly; wherein the thin film layer is arranged on the upper end of the substrate, the heating assembly is embedded in the interior of the thin film layer, a wire hole is arranged on the thin film layer corresponding to the heating assembly, part of the heating assembly is exposed through the wire hole, a through hole is arranged on the thin film layer, the position of the through hole avoids the heating assembly, a groove hole is arranged on the substrate, and the through hole and the groove hole are communicated.

[0008] Preferably, in the above semiconductor gas sensor, the heating assembly comprises a patterned metal layer.

[0009] Preferably, in the above semiconductor gas sensor, the number of through holes is at least one.

[0010] Preferably, in the above semiconductor gas sensor, the shape of the thin film layer is closed on four sides, and the through hole is arranged at a set position of the thin film layer.

[0011] Preferably, in the above semiconductor gas sensor, the shape of the thin film layer is semi-closed, and the through hole is arranged at a support position of the thin film layer.

[0012] Preferably, in the above semiconductor gas sensor, the substrate is a wafer substrate.

[0013] Preferably, in the above semiconductor gas sensor, the thin film layer is prepared from silicon carbide or silicon oxide.

[0014] Preferably, in the above semiconductor gas sensor, the thin film layer comprises a first dielectric layer and a second dielectric layer, the first dielectric layer is connected with the second dielectric layer, and the heating assembly is completely covered by the first dielectric layer and the second dielectric layer.

[0015] Preferably, in the above semiconductor gas sensor, a notch is arranged on the first dielectric layer, and part of the heating assembly corresponding to the through hole is exposed through the notch.

[0016] Preferably, in the above semiconductor gas sensor, the heating assembly is prepared from platinum wire.

[0017] In a second aspect, the present application provides a preparation method of the above semiconductor gas sensor, the preparation method comprising:

[0018] Taking a wafer as a substrate;

[0019] Depositing a first dielectric layer on the substrate;

[0020] Depositing metal on the first dielectric layer to form a metal layer;

[0021] patterning the metal layer to obtain a heating component;

[0022] depositing a second dielectric layer on the heating component; wherein the first dielectric layer and the second dielectric layer use the same material and the first dielectric layer and the second dielectric layer are in contact to form the thin film layer;

[0023] preparing a wire hole on the second dielectric layer;

[0024] forming a through hole on the thin film layer by etching;

[0025] etching a slot hole on the back of the substrate in communication with the through hole to obtain the semiconductor gas sensor.

[0026] Preferably, in the above preparation method, the metal deposited on the first dielectric layer comprises platinum gold

[0027] The beneficial effects of the present application are:

[0028] The present application has a more adaptable and higher reliability through the thin film structure with holes, and a better long-term robustness on the basis of ensuring the integrity of the structure. Specifically, the stress changes caused by the thermal expansion and contraction of the gas in the cavity have less impact on the thin film during packaging, and the stress of the thin film itself is more easily released; the gas released by the packaging glue during the heating process can be released through the through hole and the slot hole. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A structure cross-sectional view of a semiconductor gas sensor according to an embodiment of the present application is shown.

[0030] Figure 2 A structure view of a heating component in a semiconductor gas sensor according to an embodiment of the present application is shown.

[0031] Figure 3 A position layout view of a semiconductor gas sensor according to an embodiment of the present application is shown.

[0032] Figure 4 A schematic view of the shape, number and position of the through hole of a semiconductor gas sensor according to an embodiment of the present application is shown, wherein (a) and (b) show different through hole shapes when one through hole is provided, and (c) and (d) show different through hole shapes when two through holes are provided.

[0033] Figure 5 Another cross-sectional structure view of a semiconductor gas sensor according to an embodiment of the present application is shown.

[0034] Figure 6A flow chart of a preparation of a semiconductor gas sensor according to an embodiment of the present application is shown.

[0035] Reference signs:

[0036] 10, substrate; 11, slot hole; 20, thin film layer; 21, wire hole; 22, through hole; 23, first dielectric layer; 24, second dielectric layer; 25, notch; 30, heating component; 31, metal layer. DETAILED DESCRIPTION

[0037] The present application will be described in detail below with specific reference being made to certain embodiments. The advantages and features of the present application will become apparent to those skilled in the art upon examination of the following details. The detailed description of the application is preceded by a description of the background of the application to provide further insight into the inventive concept of the present application. Various modifications and changes can be made thereto without departing from the spirit and scope of the application. It is intended that the definition of the application should be determined with reference to the appropriate claims.

[0038] The specific embodiments of the present application will be further described with reference to the drawings and examples.

[0039] Example 1

[0040] The present application provides a semiconductor gas sensor, which comprises a substrate 10, a thin film layer 20 and a heating component 30. The thin film layer 20 is arranged on the upper end of the substrate 10, and the heating component 30 is embedded in the interior of the thin film layer 20. A wire hole 21 is arranged on the thin film layer 20 corresponding to the heating component, and part of the heating component 30 is exposed through the wire hole 21 to facilitate the wiring of the heating component 30. A through hole 22 is arranged on the thin film layer 20, and the position of the through hole 22 avoids the heating component 30. A slot hole 11 is arranged on the substrate 10, and the through hole is communicated with the slot hole 11.

[0041] In the present embodiment, the heating component 30 is heated after being powered on, so that the surface of the thin film layer 20 reaches the active temperature of the hydrogen catalytic reaction, which is generally 100-300℃. When hydrogen contacts the platinum catalyst, an oxidation reaction occurs, and the heat released in the reaction changes the temperature of the platinum wire, thereby causing a change in the resistance value of the platinum wire. By measuring the resistance change of the heating component 30 (an external detection circuit is connected through the wire hole 21), the hydrogen concentration can be deduced. The through hole 22 and the slot hole 11 form a gas exchange channel to ensure that the gas environment above and below the thin film is consistent, thereby avoiding measurement errors. The gas exchange channel is the core design of the present application, which functions to release the packaging thermal stress, prevent the deformation / breakage of the thin film, simultaneously discharge the volatile substances of the packaging glue, avoid the pollution of the cavity, and balance the gas pressure on both sides of the thin film to maintain the structural stability.

[0042] The through hole 22 cooperates with the slot hole 11 to improve the packaging reliability and yield of the semiconductor gas sensor, and optimize the sensing accuracy and stability. Specifically, the through hole structure disperses the thermal expansion difference stress between the silicon substrate and the packaging glue during packaging, prevents the film from breaking, and eliminates thermal stress; the slot hole 11 is connected to the outside to discharge volatile compounds released by the packaging glue during heating, avoiding chemical corrosion. The through hole 22 balances the hydrogen concentration, temperature and humidity above and below the film in real time, eliminating the film deformation error caused by the pressure difference; the gas exchange channel ensures that the hydrogen concentration in the cavity is synchronized with the environment, reducing the influence of airflow fluctuations on measurement.

[0043] In some embodiments, as shown in Figure 2 and Figure 3 , the heating assembly 30 includes a patterned metal layer 31.

[0044] For example, the metal layer 31 uses high resistivity platinum Pt or platinum alloy, and forms a serpentine or grid-shaped trace (as shown in Figure 3 ) through photolithography and etching, which greatly increases the effective heating length, and increases the length by 3-5 times under the same area, concentrates heat on the surface sensitive area of the film layer 20, and avoids long straight metal lines through patterned design, uses wavy or fractal edges, disperses thermal expansion stress in multiple directions, and prevents metal layer fracture caused by stress concentration.

[0045] In some embodiments, the line width or pitch of the patterned metal layer 31 can be adjusted, for example, the line width is 5-10 μm, and the pitch is 3-8 μm, so that the resistance value R and the temperature coefficient TCR of the metal layer satisfy: ΔR / R=α·ΔT, where the metal layer is selected as platinum, α≈0.00385 / ℃, to ensure that the resistance change and the hydrogen reaction heat are in a linear relationship, and the linearity is >99%.

[0046] In some embodiments, the number of through holes 22 is at least one. Understandably, the number of through holes 22 can not be limited to 1, but at least 1, which can be n, n is a natural number greater than or equal to 2, and the position of each through hole 22 should avoid the heating assembly 30 when n through holes 22 are set.

[0047] In some embodiments, the shape of the through hole 22 can be any shape, such as Figure 4 , as shown in Figure 4 , the through hole 22 in (a) is circular, and the through hole 22 in (b) is square, and when multiple through holes 22 are provided, the shapes of the multiple through holes 22 can be the same or different. As shown in Figure 4 (c), which shows two through holes 22, which can both be circular, Figure 4(d), which shows two through holes 22, which can be square in shape. In addition, the specific position of the through holes 22 is not specifically limited in the present application, which can be arranged at the middle of the thin film layer 20 (as shown in (a), (b) and (c) of FIG. 1) or at the edge of the thin film layer 20 (as shown in (d) of FIG. 1). Figure 4 Figure 4

[0048] In some embodiments, the shape of the thin film layer 20 can also be arbitrary based on the through holes 22. For example, the shape of the thin film layer 20 can be closed on four sides, and the through holes 22 are arranged at the set positions of the thin film layer 20. The shape of the thin film layer 20 can also be semi-closed, and the through holes are arranged at the support positions of the thin film layer 20.

[0049] In some embodiments, the substrate 10 is a wafer substrate.

[0050] In some embodiments, the thin film layer 20 is made of silicon carbide or silicon oxide.

[0051] It should be noted that the silicon carbide or silicon oxide described above is only an example of the thin film layer 20 and does not constitute a limitation on the present application. The thin film layer 20 serves as an embedded substrate of the platinum wire heater, providing a stable mechanical support structure. Selecting high-hardness materials (SiC hardness ≈ 9.5 Mohs, SiO2 hardness ≈ 7 Mohs) can resist packaging thermal stress and prevent deformation or rupture. The specific selection of silicon carbide or silicon oxide can be determined according to actual conditions. For example, if the sensor operating temperature is greater than 300°C or in a strong corrosive environment, SiC is preferred, and if the operating temperature is < 200°C and low cost is required, SiO2 is preferred.

[0052] In some embodiments, as shown in (a) of FIG. 2, the thin film layer 20 includes a first dielectric layer 23 and a second dielectric layer 24, the first dielectric layer 23 is connected with the second dielectric layer 24, the heating assembly 30 is entirely covered by the first dielectric layer 23 and the second dielectric layer 24, and the first dielectric layer 23 is provided with a notch 25, and the heating assembly 30 is exposed through the notch 25 at the portion corresponding to the through hole 22. Figure 5

[0053] ​​​The heating component 30 is directly exposed to the hydrogen environment entering through the through hole 22 by the gap 25, reducing the medium barrier of hydrogen contacting the heating component, enabling the hydrogen to react with the platinum catalyst more quickly and directly, accelerating the generation of resistance change, thereby improving the response speed and detection sensitivity of the sensor to hydrogen concentration change. The first medium layer 23 and the second medium layer 24 completely wrap the heating component, compared with the original scheme in which the heating component is only embedded in the internal structure of the film layer, the heating component can be more comprehensively fixed, and the deformation or displacement of the heating component 30 caused by temperature change during work is reduced. At the same time, this full-wrapping structure can effectively isolate the heating component from direct contact with external impurities, reducing the risk of contamination or damage of the heating component except for the detection area exposed by the gap, prolonging its service life. The gas exchange channel formed by the through hole 22 and the slot hole 11 still plays a role, ensuring that the gas environment above and below the film layer is consistent. The gap only exposes the heating component in the part corresponding to the through hole, which ensures effective contact between hydrogen and the heating component, avoids unnecessary contact between other parts of the heating component and the gas, reduces irrelevant gas interference, and further improves the accuracy of measurement. The wrapping structure of the two medium layers can more evenly transmit the heat generated by the heating component 30, making the overall temperature distribution of the film layer 20 more stable, avoiding the situation of local temperature being too high or too low, ensuring that the catalytic reaction is stably carried out in the appropriate temperature range, and improving the reliability of the detection result.

[0054] Embodiment 2:

[0055] The embodiment of the present application provides a preparation method of the semiconductor gas sensor as in embodiment 1, which adopts a semiconductor process, deposits a medium structure on a silicon wafer, then deposits a platinum wire and patterns, etches a specific area on the front side to reserve a through hole structure, and finally etches a slot hole through the back structure to prepare the semiconductor gas sensor. As shown in the figure, Figure 5 The preparation method comprises the following steps:

[0056] S1: taking a wafer as a substrate 10;

[0057] S2: depositing a first medium layer 23 on the substrate 10;

[0058] S3: depositing a metal on the first medium layer 23 to form a metal layer 31;

[0059] S4: patterning the metal layer 31 to obtain a heating component 30;

[0060] S5: depositing a second medium layer 24 on the heating component 30; wherein the first medium layer 23 and the second medium layer 24 use the same material and the first medium layer 23 and the second medium layer 24 are in contact to form a film layer 20;

[0061] S6: preparing a wire hole 21 on the second dielectric layer 24;

[0062] S7: forming a through hole 22 on the thin film layer 20 by etching, and etching a part upwardly corresponding to the position of the heating assembly to form a notch 25 on the first dielectric layer 23, so that the part of the bottom end of the heating assembly 30 is exposed through the notch 25 and the through hole;

[0063] S8: etching a slot hole 11 on the back of the substrate 10 to communicate with the through hole 22, and obtaining the semiconductor gas sensor.

[0064] In the above steps S1-S8, the materials of the first dielectric layer 23 and the second dielectric layer 24 are selected as silicon carbide, and the material of the metal layer 31 is selected as platinum metal. The semiconductor gas sensor prepared based on the above steps is compared with the existing sensor chip. Among them, the existing sensor chip is selected as Bosch BME688.

[0065] The zero point offset test and the sensitivity accuracy test will be carried out respectively.

[0066] The purpose of the zero point offset test is to evaluate the long-term working stability of the sensor, that is, the aging characteristics. The test method is: in the environment with constant hydrogen concentration of 0% (i.e. no target gas state); the sensor is continuously powered on, and the output signal value at different time points is recorded; the zero point offset is calculated. The test conditions are: the temperature is set to 25℃±1℃ (constant temperature); the humidity is 50%RH±5%; the sampling interval is 50 hours.

[0067] The same test method and test condition are used for the zero point offset test of the semiconductor gas sensor prepared in the application and the existing sensor chip, and the results are shown in Table 1.

[0068] Table 1: Zero point offset test results

[0069]

[0070]

[0071] The purpose of the sensitivity accuracy test is to verify the response accuracy of the sensor to the change of hydrogen concentration. The test method is: in the factory calibration, the basic sensitivity is set to 1.0 (normalized reference value); different concentrations of hydrogen are input, such as 0.1%, 0.5%, 1.0% and other gradient concentrations below the lower explosive limit; the output value of the sensor is recorded, and the sensitivity test value is calculated, wherein the sensitivity=(output signal change) / (hydrogen concentration change), and 20 independent tests (data points 1-20) are repeated to ensure statistical significance. The test conditions are: the temperature is set to 25℃, and the hydrogen concentration range is set to 0.1%-2.0% (below LEL).

[0072] The sensitivity precision of the semiconductor gas sensor prepared in the application and the existing sensor chip was tested by using the same test method and test conditions, and the results are shown in Table 2.

[0073] Table 2 Sensitivity precision test results

[0074]

[0075]

[0076] As shown in Table 2, the performance of the semiconductor gas sensor prepared in the application is improved by 30%.

[0077] According to the test results of Table 1 and Table 2, it can be known that:

[0078] 1. Sensitivity: In the tested hydrogen change range, the resistance change range of the temperature sensor is about 25%, which shows good sensitivity.

[0079] 2. Reliability:

[0080] 2-1) The application further improves the reliability of the device in various complex environments by selecting high-performance corrosion-resistant medium materials.

[0081] 2-2) The application adopts a thin film vent structure, which can make the physical environment on both sides of the thin film basically consistent in various temperature and humidity environments. Avoiding physical deformation of the thin film during use due to reasons such as inconsistent pressure, thereby affecting the performance and reliability of the sensor; also avoiding the deposition of a large amount of byproduct gas under the thin film during the packaging process, which may cause chemical corrosion and pollution, and has a potential impact on long-term reliability, and even permanent damage.

[0082] 2-3) Different air flow sizes also have a certain impact on measurement accuracy. The vent design can also ensure that the hydrogen concentration in the cavity and the environment is consistent, thereby making the measurement of the change in thermal conductivity caused by the change in hydrogen concentration more accurate and stable.

[0083] The above embodiments are only used to illustrate the application, and are not intended to limit the application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the application. Therefore, all equivalent technical solutions also belong to the scope of the application, and the patent protection scope of the application should be defined by the claims.

Claims

1. A semiconductor gas sensor, characterized in that, The device includes a substrate, a thin film layer, and a heating component; wherein the thin film layer is disposed on the upper end of the substrate, the heating component is embedded inside the thin film layer, wire holes are provided on the thin film layer corresponding to the heating component to expose part of the heating component, through the wire holes, through the thin film layer, through holes are provided, the through holes are positioned to avoid the heating component, and slots are provided on the substrate, the through holes communicating with the slots.

2. The semiconductor gas sensor as described in claim 1, characterized in that, The heating component includes a patterned metal layer.

3. The semiconductor gas sensor as described in claim 1, characterized in that, The number of through holes is at least one.

4. The semiconductor gas sensor as described in claim 1, characterized in that, The thin film layer is closed on all four sides, and the through holes are located at predetermined positions on the thin film layer.

5. The semiconductor gas sensor as described in claim 1, characterized in that, The thin film layer is semi-closed in shape, and the through hole is provided at the support position of the thin film layer.

6. The semiconductor gas sensor as described in claim 1, characterized in that, The thin film layer includes a first dielectric layer and a second dielectric layer, the first dielectric layer and the second dielectric layer are connected, and the heating component is completely covered by the first dielectric layer and the second dielectric layer.

7. The semiconductor gas sensor as described in claim 6, characterized in that, A notch is provided on the first dielectric layer, and the heating component is exposed through the notch in the portion corresponding to the through hole.

8. The semiconductor gas sensor as described in claim 1, characterized in that, The heating element is made of platinum wire.

9. A method for fabricating a semiconductor gas sensor as described in any one of claims 1 to 7, characterized in that, The preparation method includes: Using wafers as substrates; A first dielectric layer is deposited on the substrate; Deposit metal on the first dielectric layer to form a metal layer; The metal layer is patterned to obtain a heating component; A second dielectric layer is deposited on the heating assembly; wherein the first dielectric layer and the second dielectric layer use the same material and the first dielectric layer and the second dielectric layer are in contact to form the thin film layer; Wire holes are fabricated on the second dielectric layer; Through holes are formed on the thin film layer by etching; The semiconductor gas sensor is fabricated by etching a slot on the back side of the substrate that communicates with the through hole.

10. The preparation method according to claim 9, characterized in that, The metal deposited on the first dielectric layer includes platinum.

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