A method and system for accelerated batch aging of metal oxide semiconductor gas sensors

Abstract

This invention belongs to the field of semiconductor device manufacturing technology, and particularly relates to a batch accelerated aging method and system for metal oxide semiconductor gas sensors. The method includes the following steps: S1: providing an uncut sensor substrate, on which multiple sensor sensitive units are integrated in an array; S2: placing the sensor substrate on a temperature-controlled aging stage, and forming an electrical connection between the power supply probe and the common electrode interface through a contact connection device; S3: starting the temperature-controlled aging stage to heat the sensor substrate. This invention provides a batch accelerated aging method and system for metal oxide semiconductor gas sensors, aiming to solve the technical problems of low production efficiency, high material costs, large space occupation, and difficulty in ensuring batch consistency in existing semiconductor gas sensor aging processes.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device manufacturing technology, and particularly relates to a method and system for accelerated aging of metal oxide semiconductor gas sensors in batches. Background Technology

[0002] Semiconductor gas sensors, especially planar sensors based on metal oxides (such as SnO2, ZnO, etc.), must undergo a critical "burn-in" process after the sintering preparation of the sensitive material. This process aims to apply continuous electrothermal stress to the sensor, causing the microstructure of the sensitive material to rearrange and the electrical properties to reach a thermodynamically stable state, eliminating early drift introduced during manufacturing, and thus ensuring the consistency and long-term stability of the response characteristics of the finished product.

[0003] In existing technologies, the aging process for planar gas sensors is typically carried out during the packaging stage. The specific process involves: first, dicing the substrate that has been sintered to form independent sensing units; then, wire bonding one or a few sensor units to a socket or support; and finally, manually inserting these pinned semi-finished products one by one into the sockets of a dedicated "aging test fixture." Finally, the fixture filled with sensors is placed in a constant-temperature aging chamber, and the rated operating voltage is applied for a long-term aging process lasting 72 to 120 hours.

[0004] However, the aforementioned traditional aging process has the following significant technical drawbacks: 1. Low production efficiency and long cycle: It relies heavily on manual insertion and removal operations, has a low degree of automation, and has low aging efficiency under a single constant voltage, resulting in a production cycle of several days, which has become a bottleneck restricting production capacity.

[0005] 2. High production costs: A large number of dedicated aging test fixtures and sockets need to be designed and manufactured. These fixtures are easily oxidized and damaged under high temperature environments, making them high-frequency consumables with high maintenance and replacement costs.

[0006] 3. Difficulty in controlling product consistency: Due to differences in contact resistance between different tooling plates and slots, as well as slight unevenness in the temperature field distribution within the large aging chamber, the actual electrothermal stress borne by the same batch of sensors is inconsistent, resulting in a large dispersion in the static resistance and sensitivity of the final product.

[0007] 4. Low space utilization: Due to the physical dimensions of the tooling plate socket, the number of sensors that can be accommodated in a unit volume of aging chamber is limited, resulting in low space utilization in the production workshop. Summary of the Invention

[0008] This invention aims to solve the technical problems of low production efficiency, high material cost, large space occupation, and difficulty in ensuring batch consistency in the existing aging process of semiconductor gas sensors, and provides a batch accelerated aging method and system for metal oxide semiconductor gas sensors.

[0009] To achieve the above objectives, the core technical solution adopted by this invention is as follows: A batch accelerated aging method for metal oxide semiconductor gas sensors, comprising the following steps: S1: Provide an uncut sensor substrate, on which multiple sensor sensing units are integrated in an array. The heating electrodes of the multiple sensor sensing units are connected in parallel through a conductive network inside the sensor substrate and connected to a common electrode interface located at the edge of the sensor substrate. S2: Place the sensor substrate on a temperature-controlled aging bench and make an electrical connection between the power supply probe and the common electrode interface through a contact connection device; S3: Start the temperature-controlled aging bench to heat the sensor substrate, and at the same time apply aging voltage to the common electrode interface through the power supply probe to apply electrothermal stress to multiple sensor sensitive units; In step S3, the process of applying the aging voltage is controlled by a gradient program and includes the following stages performed sequentially: Phase 1: Apply the first aging voltage and maintain it for a first duration. The first aging voltage is higher than the sensor's rated operating voltage for initial stabilization. Second stage: Increase the voltage to the second aging voltage and maintain it for a second duration. The second aging voltage is higher than the first aging voltage and is used for deep activation. The third stage involves reducing the voltage to the third aging voltage and maintaining it for a third duration. The third aging voltage is lower than the second aging voltage and is used for performance convergence.

[0010] Furthermore, the first aging voltage is 1.1 to 1.3 times the rated operating voltage of the sensor; the second aging voltage is 1.4 to 1.8 times the rated operating voltage of the sensor; and the third aging voltage is 1.0 to 1.2 times the rated operating voltage of the sensor.

[0011] Furthermore, in step S3, the heating temperature of the temperature-controlled aging table is set to 200°C to 450°C; the sum of the first duration, the second duration, and the third duration is 24 hours to 48 hours.

[0012] Furthermore, it also includes an online monitoring step: during the execution of step S3, the total current value flowing through the common electrode interface is periodically measured, and the rate of change of the total current value or the total equivalent resistance value of the array calculated based on the total current value is used to determine whether the aging process has reached a stable endpoint; when the rate of change is lower than a preset threshold, the aging is determined to be complete and the application of electrothermal stress is automatically stopped.

[0013] Furthermore, the sensor substrate is a ceramic substrate, and the conductive network and sensor sensing unit are integrally sintered on the ceramic substrate through a screen printing process; the common electrode interface includes at least one pair of metal contacts for connecting the positive and negative terminals of the power supply.

[0014] Furthermore, a batch accelerated aging system for metal-oxide-semiconductor gas sensors is also provided, and a batch accelerated aging method for metal-oxide-semiconductor gas sensors using any one of the above methods includes: A precision temperature-controlled aging stage is used to support sensor substrates and provide a uniform heating environment. The substrate clamping and electrical connection module is located above the precision temperature-controlled aging stage. It includes a clamping mechanism and at least two conductive probes. The clamping mechanism is used to fix the sensor substrate, and the conductive probes are used to directly press the common electrode interface of the sensor substrate. A programmable DC power supply, whose output terminal is electrically connected to a conductive probe, is used to output an adjustable DC voltage; The central control unit is connected to the precision temperature-controlled aging bench and the programmable DC power supply signal, respectively, and is used to control the heating temperature and execute gradient program control to output the aging voltage.

[0015] Furthermore, the substrate clamping and electrical connection module does not include a socket structure for inserting a single sensor; the conductive probe is a gold-plated probe, and its position corresponds to the position of the common electrode interface on the edge of the sensor substrate.

[0016] Furthermore, the precision temperature-controlled aging stage integrates heating elements, temperature sensors, and a PID controller to control the substrate surface temperature within the range of 200°C to 450°C, while ensuring that the temperature uniformity meets preset standards.

[0017] Furthermore, it also includes a monitoring module, which is connected in series with the output circuit of the programmable DC power supply to collect the total current data flowing through the sensor substrate in real time and transmit the data to the central control unit.

[0018] Furthermore, the central control unit is configured to calculate the resistance change rate based on the total current data fed back by the monitoring module, and when the resistance change rate meets the preset convergence condition, automatically control the programmable DC power supply to stop output and control the precision temperature control aging stage to cool down.

[0019] Compared with the prior art, the beneficial effects of this invention are significant and multifaceted: 1. Improved production efficiency: The use of whole-piece aging instead of single-piece plug-in, combined with a unique gradient voltage accelerated aging strategy, significantly shortens the traditional aging cycle of 72-120 hours to 24-48 hours, thus improving efficiency.

[0020] 2. Reduced costs: The expensive and fragile dedicated aging test fixtures and sockets were eliminated, thus eliminating related consumable costs; at the same time, the cumbersome manual plugging and unplugging process was eliminated, reducing manual operation time.

[0021] 3. Improved product consistency: Applying the same voltage across the same substrate via a common conductive network, coupled with uniform heating from a precision temperature control station, reduces the impact of differences in slot contact resistance and spatial temperature gradients. Compared to traditional processes, the static resistance consistency (standard deviation / mean) of the resulting products is improved.

[0022] Improved space utilization: The high-density planar layout at the wafer level allows for a significant increase in the number of sensors that can be aged simultaneously per unit area, thus improving the utilization of production line space. Attached Figure Description

[0023] To enable those skilled in the art to more clearly and comprehensively understand the technical solutions of the present invention, preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the accompanying drawings are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. In the accompanying drawings: Figure 1 This is a flowchart of the batch accelerated aging method provided in the embodiments of the present invention.

[0024] Figure 2 This is a schematic diagram of the structure of the batch accelerated aging system provided in an embodiment of the present invention.

[0025] Figure 3 This is a top view of the sensor substrate (wafer) used in this invention.

[0026] Figure 4 This is a gradient program control curve of the aging voltage changing over time in an embodiment of the present invention. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings: I. Measurement Methods and Evaluation Standards In the following examples and comparative examples, unless otherwise stated, all performance indicators were measured according to the following methods and standards: Gas-sensitive performance test conditions: 1. Test environment: Temperature 25±2℃, relative humidity 50±5% RH.

[0028] 2. Target gas: 100 ppm ethanol (balanced with clean air).

[0029] 3. Testing System: The static gas mixing method testing system (WS-30A gas-sensitive element testing system, Zhengzhou Weisheng Electronic Technology Co., Ltd.) is used.

[0030] Performance parameter definitions: 1. Static resistance (Ra): The resistance value of the sensor after it has stabilized in clean air.

[0031] 2. Sensitivity (S): Defined as S = Ra / Rg, where Rg is the resistance of the sensor in 100 ppm ethanol gas.

[0032] 3. Consistency Assessment (CV): The coefficient of variation (CV) is used to measure batch consistency. The formula is: CV = (Standard Deviation / Mean) × 100%. The smaller the CV value, the better the consistency.

[0033] 4. Aging stability criterion: During the aging process, when the rate of change of the total current flowing through the common electrode is less than 1% over a continuous hour, it is determined to have reached a stable state. III. Specific Implementation Examples Example 1 This embodiment uses a batch of planar semiconductor gas sensors based on SnO2 (tin dioxide) material as an example, with a rated operating voltage of 5.0V. The entire aging process is as follows: Figure 1 As shown, the specific steps are as follows: 1.S1: Provide sensor substrate (preparation stage) A 10cm × 10cm alumina ceramic substrate is provided. The top view of this substrate is as follows. Figure 3 As shown: The substrate integrates 100 (10×10 array) uncut sensor sensitive unit arrays (Unit1...Unit100).

[0035] An internal conductive network (Bus_Line) is pre-fabricated inside the substrate using a screen printing process. This bus connects the heating electrodes of all sensitive units in parallel.

[0036] The conductive network eventually converges and leads out to two common electrode interfaces (Pad_Pos, Pad_Neg) at the edge of the substrate.

[0037] like Figure 3 As shown, the current is input from the positive terminal interface, distributed to each sensitive unit via the parallel conductive bus, and finally converged to the negative terminal interface to form a complete parallel power supply circuit.

[0038] 2.S2: Substrate loading and contact connection like Figure 1 As shown in the preparation stage, the substrate is placed on the temperature control platform of the aging system. The clamping mechanism is activated to accurately clamp the gold-plating probes in the system. Figure 3 The two common electrode interfaces shown establish a reliable physical and electrical connection.

[0039] 3.S3: Applying programmed electrothermal stress Start the central control unit and execute the following: Figure 1 The steps for "applying programmed electrothermal stress" are shown below: Thermal stress: Set the temperature control platform to 400℃ and keep it constant.

[0040] Electrical stress (gradient voltage): controls the aging voltage output of the programmable power supply. The gradient programmable control curve of this voltage over time is shown below. Figure 4 As shown.

[0041] Figure 4 Note: In the graph, the horizontal axis (X-axis) represents aging time (in hours), and the vertical axis (Y-axis) represents the aging voltage applied to the common electrode (in volts V). The curve shows the voltage change process starting from 0V and going through three different level stages.

[0042] The specific control process is as follows: Phase 1 (Initial Stabilization): Corresponding Figure 4 The application period is 0-4 hours. A voltage of 6.0V (1.2 times the rated voltage) is applied and maintained for 4 hours. This stage is used to initially stabilize the microstructure of the material at high temperatures.

[0043] Phase Two (Deep Activation): Corresponding to Figure 4 The voltage is increased to 7.5V (1.5 times the rated voltage) and maintained for 20 hours within a range of 4-24 hours. Figure 4 As shown in the curve, this stage is at the voltage peak, where the high electrothermal stress deeply activates the grain boundary barrier, accelerating the aging process.

[0044] Phase 3 (Performance Convergence): Corresponding to Figure 4 The voltage is reduced to 5.5V (1.1 times the rated voltage) and maintained for 2 hours within a 24-26 hour range. This stage is used to eliminate overshoot caused by high stress, allowing the device performance to converge to the stable operating point.

[0045] 4. Online monitoring and termination like Figure 1As shown in the "Online Monitoring and Feedback" module, the system periodically measures the total current throughout the process. At the end of the third stage (26 hours), the system detects that the rate of change of the total current has met the preset threshold (<1%), automatically cuts off the power supply, and controls the temperature control console to cool down.

[0046] The substrate was then removed and subjected to routine cutting and packaging (soldering pins and adding explosion-proof mesh) to obtain 100 finished sensors.

[0047] Example 2 This embodiment aims to verify the effect under different aging parameters. The only difference from Embodiment 1 is the adjustment of the aging parameters; the rest of the substrate structure remains the same. Figure 3 ) and system connection ( Figure 2 They are all the same.

[0048] Aging temperature: set to 300℃.

[0049] Gradient voltage program: Phase 1: Output 5.5V (1.1 times), maintain for 6 hours.

[0050] Second stage: Output 7.0V (1.4 times), maintain for 24 hours.

[0051] Phase 3: Output 5.0V (1.0 times) and maintain for 6 hours.

[0052] Total aging time: 36 hours.

[0053] IV. Comparative Example Comparative Example 1 (Traditional Process) Using another ceramic substrate produced in the same batch as in Example 1, but without using the whole-sheet aging system of the present invention, a conventional method was employed: 1. Cutting and Packaging: First, the substrate is cut into 100 independent sensor units, and each unit is soldered to a TO-5 metal socket.

[0054] 2. Loading: Operators insert 100 sensors one by one into the sockets of the special test fixture plate in the traditional aging chamber. The manual operation takes about 1.5 hours.

[0055] 3. Aging process: Place the tooling plate into the aging chamber and set the temperature to 400℃. Apply a constant 5.0V (rated voltage) and continue aging for 72 hours.

[0056] 4. Conclusion: Remove the fixture plate, allow it to cool, and then disconnect the sensors one by one. V. Summary and Analysis of Results Data The gas-sensing performance of the finished sensors prepared in Example 1, Example 2 and Comparative Example 1 (50 sensors were randomly selected from each example) was tested, and the results are summarized in Table 1.

[0057] Table 1: Comparison of effect data between the examples and comparative examples Results analysis: 1. Efficiency and Cost: Example 1 adopts... Figure 1 The complete aging process shown reduces the aging cycle from 72 hours in Comparative Example 1 to 26 hours, improving efficiency by more than 60%; and due to the adoption of Figure 2 The socketless probe connection method shown reduces manual operation time from over 90 minutes to less than 5 minutes.

[0058] 2. Consistency: The static resistance CV value of the product in Example 1 (4.2%) was significantly lower than that in Comparative Example 1 (7.8%). This indicates that... Figure 3 A voltage is applied to the common conductive network shown, in conjunction with Figure 4 The gradient voltage strategy shown can effectively eliminate product dispersion caused by uneven socket contact resistance and temperature gradient inside the box, making product performance more uniform.

[0059] 3. Effectiveness: Example 2 shows that even at lower temperatures (300°C), by adjusting the voltage gradient and time, a better consistency effect than the conventional process can be achieved.

[0060] Example 3: Batch Accelerated Aging System This embodiment of the invention also provides a batch accelerated aging system, such as... Figure 2 As shown; the system mainly consists of three parts: a central control unit, a power supply and monitoring module, and an aging platform assembly. The connection relationships and functions of each part are as follows: Central Control Unit (CCU): This is the core of the system. It is responsible for sending "set temperature command" to the precision temperature-controlled aging bench and receiving "temperature feedback". At the same time, it sends "set voltage program" to the programmable DC power supply and receives "real-time current data".

[0061] Power supply and monitoring module: This module includes a programmable DC power supply and a monitoring module. The power supply outputs a gradient DC voltage according to instructions; the monitoring module is connected in series in the circuit to collect the total current data flowing through the substrate in real time and feed it back to the CCU.

[0062] Aging platform components: Precision temperature-controlled aging bench: It integrates heating elements and a PID controller to support the sensor substrate and provide a uniform heat conduction environment.

[0063] Substrate clamping and electrical connection module: Located above the aging stage, this module clamps the substrate using mechanical means. Specifically, it is equipped with two gold-plated conductive probes that directly press against the common electrode interface on the edge of the substrate, such as... Figure 2As shown, this structure completely abandons the traditional socket-type connection. Finally, it should be emphasized that the above embodiments are merely illustrative of the technical concept and preferred implementation of the present invention, and are not intended to exhaustively describe or limit the scope of protection of the present invention. Any person skilled in the art, after understanding the spirit and core technical solutions of the present invention, may make various modifications, equivalent substitutions, or improvements based on the content disclosed in the present invention, without departing from the basic principles of the present invention. These obvious modifications or substitutions should all be considered to be included within the scope of protection claimed by the present invention.

Claims

1. A batch accelerated aging method for metal oxide semiconductor gas sensors, characterized in that, Includes the following steps: S1: Provide an uncut sensor substrate, on which multiple sensor sensing units are integrated in an array, and the heating electrodes of the multiple sensor sensing units are connected in parallel through a conductive network inside the sensor substrate and connected to a common electrode interface located at the edge of the sensor substrate. S2: Place the sensor substrate on a temperature-controlled aging bench and make an electrical connection between the power supply probe and the common electrode interface through a contact connection device; S3: Start the temperature-controlled aging bench to heat the sensor substrate, and at the same time apply an aging voltage to the common electrode interface through the power supply probe to apply electrothermal stress to the multiple sensor sensitive units; The process of applying the aging voltage in step S3 is controlled by a gradient program and includes the following stages performed sequentially: Phase 1: Apply a first aging voltage and maintain it for a first duration. The first aging voltage is higher than the sensor's rated operating voltage for initial stabilization. Second stage: Increase the voltage to a second aging voltage and maintain it for a second duration. The second aging voltage is higher than the first aging voltage for deep activation. The third stage involves reducing the voltage to a third aging voltage and maintaining it for a third duration. The third aging voltage is lower than the second aging voltage, and this is used for performance convergence.

2. The batch accelerated aging method for a metal oxide semiconductor gas sensor according to claim 1, characterized in that, The first aging voltage is 1.1 to 1.3 times the rated operating voltage of the sensor; the second aging voltage is 1.4 to 1.8 times the rated operating voltage of the sensor; and the third aging voltage is 1.0 to 1.2 times the rated operating voltage of the sensor.

3. The batch accelerated aging method for a metal oxide semiconductor gas sensor according to claim 1, characterized in that, In step S3, the heating temperature of the temperature-controlled aging table is set to 200°C to 450°C; the sum of the first duration, the second duration, and the third duration is 24 hours to 48 hours.

4. The batch accelerated aging method for a metal oxide semiconductor gas sensor according to claim 1, characterized in that, It also includes an online monitoring step: during the execution of step S3, the total current value flowing through the common electrode interface is periodically measured, and the aging process is determined to have reached a stable endpoint based on the total current value or the rate of change of the total equivalent resistance value of the array calculated based on the total current value. When the rate of change is lower than the preset threshold, the aging process is considered complete and the application of electrothermal stress is automatically stopped.

5. The batch accelerated aging method for a metal oxide semiconductor gas sensor according to claim 1, characterized in that, The sensor substrate is a ceramic substrate, and the conductive network and the sensor sensing unit are integrally sintered on the ceramic substrate through a screen printing process; the common electrode interface includes at least one pair of metal contacts for connecting the positive and negative terminals of the power supply.

6. A batch accelerated aging system for metal oxide semiconductor gas sensors, characterized in that, A batch accelerated aging method for a metal oxide semiconductor gas sensor according to any one of claims 1-5 includes: A precision temperature-controlled aging stage is used to support the sensor substrate and provide a uniform heating environment; The substrate clamping and electrical connection module is located above the precision temperature-controlled aging stage and includes a clamping mechanism and at least two conductive probes. The clamping mechanism is used to fix the sensor substrate, and the conductive probes are used to directly press against the common electrode interface of the sensor substrate. A programmable DC power supply, the output of which is electrically connected to the conductive probe, is used to output an adjustable DC voltage; The central control unit is connected to the precision temperature-controlled aging bench and the programmable DC power supply, respectively, and is used to control the heating temperature and execute the gradient program to control the output aging voltage.

7. The batch accelerated aging system for a metal-oxide-semiconductor gas sensor according to claim 6, characterized in that, The substrate clamping and electrical connection module does not include a socket structure for inserting a single sensor; the conductive probe is a gold-plated probe and its position corresponds to the position of the common electrode interface on the edge of the sensor substrate.

8. A batch accelerated aging system for a metal-oxide-semiconductor gas sensor according to claim 6, characterized in that, The precision temperature-controlled aging bench integrates heating elements, temperature sensors, and a PID controller to control the substrate surface temperature within the range of 200°C to 450°C, while ensuring that the temperature uniformity meets preset standards.

9. A batch accelerated aging system for a metal-oxide-semiconductor gas sensor according to claim 6, characterized in that, It also includes a monitoring module, which is connected in series with the output circuit of the programmable DC power supply, for real-time acquisition of the total current data flowing through the sensor substrate and transmitting the data to the central control unit.

10. A batch accelerated aging system for a metal-oxide-semiconductor gas sensor according to claim 9, characterized in that, The central control unit is configured to calculate the resistance change rate based on the total current data fed back by the monitoring module, and when the resistance change rate meets the preset convergence condition, automatically control the programmable DC power supply to stop outputting and control the precision temperature control aging bench to cool down.

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