CN107656562B - Temperature control system for MEMS device - Google Patents
Temperature control system for MEMS device Download PDFInfo
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- CN107656562B CN107656562B CN201610594242.7A CN201610594242A CN107656562B CN 107656562 B CN107656562 B CN 107656562B CN 201610594242 A CN201610594242 A CN 201610594242A CN 107656562 B CN107656562 B CN 107656562B
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Abstract
The invention belongs to the technical field of sensors, and particularly relates to a temperature control system for an MEMS device. Temperature detection electrodes and heating electrodes are arranged on the surfaces of an upper substrate and a lower substrate of the MEMS device; the temperature detection circuit transmits the electric signals detected by the temperature detection electrode to the signal processing circuit, the signal processing circuit judges whether the working temperatures of the upper substrate surface and the lower substrate surface of the MEMS device are suitable or not, and the signal processing circuit controls the working temperatures of the upper substrate surface and the lower substrate surface of the MEMS device by controlling the intensity of the control electric signals input to the heating electrode. A temperature control system is provided that eliminates MEMS device temperature performance and temperature hysteresis.
Description
Technical Field
The invention belongs to the technical field of sensors, and particularly relates to a temperature control system for an MEMS device.
Background
Micro-electro-mechanical systems (MEMS) are an important technical field of high-tech development, and are called micro-systems (micro-systems) and micro-machines (micro-machines) in europe and japan, respectively, and refer to a sensor device or a micro-system with a characteristic dimension in a micrometer scale range (1 μm to 1mm) developed by using micro-processing technologies such as photolithography, thin film sputtering, wet etching, dry etching, and bonding. The rapid development of MEMS technology started in the late 80 s of the last century, and its outstanding performance has attracted extensive attention in various aspects, especially after important breakthrough in MEMS fabrication process. Micro-accelerometers, micro-gyroscopes, micro-actuators, micro-optical switches and the like developed based on MEMS technology have been widely applied in the industries of aerospace, seismic exploration, automotive electronics, consumer electronics, medical instruments and the like due to the advantages of small volume, low power consumption, batch production, integration and the like.
MEMS devices have significant advantages in performance, however, due to the limitations of the fabrication process, the materials used for the devices also have certain limitations, and the resulting mismatch in material properties can cause the devices to exhibit different properties at low, normal and high temperatures, which is generally referred to as temperature performance. The MEMS device generally comprises a sensitive structure, an upper substrate, a lower substrate, a metal electrode, a lead plate and the like, wherein the sensitive structure is generally made of silicon, the upper substrate and the lower substrate are made of glass or silicon, and the sensitive structure and the upper substrate and the lower substrate are manufactured into a whole in a bonding mode. The process of silicon and silicon bonding is called as Si-Si bonding process, the development of the Si-Si bonding process in China is late, and the Si-Si bonding process still belongs to a less mature process method compared with the bonding process of silicon and glass at present, so that glass is mostly adopted as a substrate material of an MEMS device in China. The temperature performance of the MEMS device can be theoretically avoided by adopting silicon as the upper substrate material and the lower substrate material, but the temperature performance of the MEMS device still cannot be eliminated due to structural deformation, process errors and other reasons and the change of the performance of the silicon material along with the temperature; however, the glass is used as the upper and lower substrate materials, and the thermal expansion coefficients of the glass and the silicon are different within the working temperature range of the device (-40 ℃ to +70 ℃), so that the structure has a certain thermal stress, and the device has relatively poor temperature performance (bear Wei, northwest industrial university, research on temperature characteristic models of flexible gyros and accelerometers and error compensation models, master academic papers, 2006, 3 months). At present, the temperature performance of the MEMS device is mainly improved by a compensation method, a temperature sensor is generally installed in the device, and the output of the temperature sensor is used as a compensation signal to correct the output signal of the device based on an established device temperature characteristic model. The method can improve the temperature performance of the MEMS device to a certain extent, but the temperature sensor can not accurately test the temperature of the position of the device and can not reflect the temperature difference between the upper substrate and the lower substrate, so that the MEMS device still shows the temperature performance and the temperature hysteresis phenomenon.
Disclosure of Invention
The technical problems solved by the invention are as follows: a temperature control system is provided that is capable of eliminating MEMS device temperature performance and temperature hysteresis.
The technical scheme of the invention is as follows: a temperature control system for a MEMS device, characterized by: temperature detection electrodes and heating electrodes are arranged on the surfaces of an upper substrate and a lower substrate of the MEMS device;
the temperature detection circuit transmits the electric signals detected by the temperature detection electrode to the signal processing circuit, the signal processing circuit judges whether the working temperatures of the upper substrate surface and the lower substrate surface of the MEMS device are suitable or not, and the signal processing circuit controls the working temperatures of the upper substrate surface and the lower substrate surface of the MEMS device by controlling the intensity of the control electric signals input to the heating electrode.
As an improvement of the technical scheme, after the temperature detection circuit transmits the electric signals detected by the temperature detection electrode to the signal processing circuit, the signal processing circuit judges whether the working temperatures of the upper substrate surface and the lower substrate surface of the MEMS device have temperature difference or not, and the temperature difference is eliminated by controlling the intensity of the control electric signals input to the heating electrode.
As an improvement of the technical scheme, after the working temperature difference between the upper substrate surface and the lower substrate surface of the MEMS device is eliminated, the signal processing circuit acquires the resistance value of the temperature detection electrode, and the temperature coefficient of the MEMS device is compensated by using the resistance value.
As an improvement of the present technical solution, after the temperature detection circuit transmits the electrical signal detected by the temperature detection electrode to the signal processing circuit, the signal processing circuit judges whether the operating temperatures of the upper and lower substrate surfaces of the MEMS device reach the preset target temperature, and controls the operating temperatures of the upper and lower substrate surfaces of the MEMS device by controlling the intensity of the control electrical signal input to the heating electrode, so that the temperatures of the upper and lower substrate of the MEMS device are the same as the preset target temperature.
The invention has the beneficial effects that: compared with the prior art, the invention has the following advantages:
1. the temperature detection electrode and the heating electrode are prepared on the upper substrate and the lower substrate of the MEMS device and used for detecting and controlling the temperature of the MEMS device, the electrodes are prepared by adopting the MEMS process, the MEMS temperature detection device has the advantages of stable processing process, good repeatability, easiness in batch production, low cost, controllable structural size and the like, and the temperature measurement and control functions can be realized under the condition that the structural size of the device is not increased.
2. The temperature detection electrodes are directly prepared on the upper substrate and the lower substrate, the temperature of the substrates can be accurately measured, and the measured electric signals reflecting the temperature change can be used as compensation signals of device target detection signals on one hand, and can provide reference values for the signal processing circuit on the other hand, so that the accuracy of the intensity of the control electric signals output to the heating electrodes is ensured.
3. The heating electrode can be used for controlling the temperature of the upper substrate and the lower substrate, the temperature of the upper substrate and the temperature of the lower substrate can be accurately controlled according to the signal intensity provided by the signal processing circuit, the temperature of the upper substrate and the temperature of the lower substrate of the MEMS device are ensured to be the same, thermal stress generated by different temperatures is eliminated, and the temperature performance of the device is improved; in addition, the heating electrode can control the device to be at a preset target temperature, so that the MEMS device can be prevented from working at a lower temperature, and the influence of low temperature on the performance of the device is eliminated.
Drawings
FIG. 1 is a schematic structural diagram of a MEMS device;
FIG. 2 is a schematic view of the structure of a temperature detecting electrode and a heating electrode on a substrate;
fig. 3 is a schematic structural diagram of the system.
Detailed Description
As shown in fig. 1, the MEMS device structure of the present invention includes a sensitive layer structure 2, an upper substrate 3 and a lower substrate 1, the sensitive layer structure is a movable structure prepared by wet etching or dry etching, the structure can generate a certain movement state change due to external acceleration, rotation and pressure, the structure is a core structure for detecting a measured object, and the three-layer structure is prepared as a whole by a bonding process.
The MEMS device comprises an upper substrate, a lower substrate, a temperature detection electrode, a heating electrode and a signal detection electrode, wherein the upper substrate and the lower substrate of the MEMS device are respectively prepared by adopting an MEMS process, the temperature detection electrode on the substrate is used for testing the temperature of the substrate, the heating electrode is used for heating the substrate, and the signal detection electrode is used for testing to obtain an electric signal related to a detected object of the MEMS device.
As shown in fig. 2, the temperature detection electrode 5 on the substrate is connected to a lead wire 8 and a lead wire 10, the heating electrode 4 on the substrate is connected to a lead wire 7 and a lead wire 11, and the signal detection electrode 6 on the substrate is connected to a lead wire 9.
The signal detection electrode 6 on the upper substrate 3 is connected with the corresponding detection electrode on the lower substrate 1 through a lead 9, and an electric signal related to a detected object of the MEMS device can be obtained through testing, and the signal can be expressed as shown in formula (1) without considering the influence of temperature.
Uo＝A×x (1)
In the formula: u shapeoOutputting an electrical signal related to the detected object of the MEMS device; x is the detected object magnitude; a is a transmission coefficient between the detected object and the electric signal output.
The formula (1) is only the device output under ideal conditions, and the MEMS device generally has a certain temperature performance due to the influence of factors such as mismatch of thermal expansion coefficients, material characteristics, process errors, etc., that is, the output of the device varies with temperature. The effect of temperature on the sensitive structural material itself, which is mainly manifested as a change in the transfer coefficient, is taken into account, and the output signal of the MEMS device can be expressed in the form as shown in equation (2).
Uot＝At×x (2)
In the formula: u shapeotOutputting signals of the MEMS device at different temperature points; a. thetThe transmission coefficient between the detected object and the signal output under different temperature conditions.
The influence of temperature on the performance of the MEMS device, in addition to the expression form shown in equation (2), may also affect the signal output of the MEMS device by generating thermal stress on the device due to the different temperatures of the upper substrate 3 and the lower substrate 1 of the device, and under this condition, the output signal may be expressed as shown in equation (3).
Uot＝At×x+Bt×Δt (3)
In the formula: delta t is the temperature difference between the upper substrate 3 and the lower substrate 1 of the MEMS device; b istThe influence coefficient of the temperature difference of the upper substrate and the lower substrate on the output signal of the device is shown.
In summary, to eliminate the influence of temperature on the performance of the MEMS device, on one hand, the temperature of the device needs to be accurately tested, and the tested temperature value is used as a compensation signal to reduce the influence of temperature on the performance of the device; on the other hand, the temperature of the upper substrate 3 and the lower substrate 1 of the device needs to be accurately controlled, and the influence of the temperature difference between the substrates on the performance of the device is eliminated.
The temperature testing of the film electrode prepared by adopting the MEMS process is a mature technology at the present stage, the resistance of the film material can be changed correspondingly under the condition of temperature change, the resistance and the temperature have a good linear relation, and the resistance output of the temperature detection electrode along with the temperature change conforms to a formula (4).
Rt＝R0(1+Ct) (4)
In the formula: c is the conversion coefficient of the resistance and the temperature of the temperature detection electrode; t is the temperature; rtIs the resistance value at t ℃; r0The resistance value was 0 ℃.
The thin film heating electrode can convert direct current or alternating current signals input to the electrode into heat energy, and by the method, control signals can be input to the heating electrode 4 by a signal processing circuit, and the temperature rise magnitude of the upper substrate 3 and the lower substrate 1 can be controlled by adjusting the strength of the control signals. By adopting the mode, on one hand, the temperature of the upper substrate and the lower substrate can be accurately controlled, the temperature difference between the upper substrate 3 and the lower substrate 1 is eliminated, the upper substrate and the lower substrate are kept at the same temperature, and the performance of a device cannot be influenced by the generation of thermal stress; on the other hand, the heating electrode can also enable the MEMS device to work under the condition of being higher than the ambient temperature, and the influence of low temperature on the performance of the device is avoided.
The signal detection electrode 6 on the upper substrate 3 is connected to a signal amplification circuit through a lead 9, and the detection electrode on the lower substrate 1 is also connected to the signal amplification circuit through a corresponding lead, and an electric signal reflecting the object to be measured is obtained by testing and is input to a signal processing circuit. The temperature detection electrode 5 on the upper substrate 3 changes its resistance value due to a temperature change, and the resistance value change is connected to the first temperature detection circuit via the lead 8 and the lead 10, and transmits an electric signal reflecting the temperature of the upper substrate 3 to the signal processing circuit. The temperature detection electrode on the lower substrate 1 is connected with the second temperature detection circuit through corresponding lead wires, and will reflect the temperature of the lower substrate 1The electrical signal is transmitted to a signal processing circuit. The signal processing circuit processes the electric signal reflecting the temperature of the upper substrate 3 and the electric signal reflecting the temperature of the lower substrate 1, the temperature values of the upper substrate 3 and the lower substrate 1 are obtained according to a formula (4), the signal processing circuit outputs a direct current or alternating current control electric signal to the heating electrode of the substrate with lower temperature according to the temperature difference, the heating electrode converts electric energy into heat, the substrate with lower temperature is heated, the temperature of the upper substrate and the temperature of the lower substrate are kept the same, and the condition that B in the formula (3) is eliminatedt× Δ t term on the performance of the MEMS device, and improves the temperature performance of the device after the working temperature difference between the upper and lower substrate surfaces of the MEMS device is eliminated, the signal processing circuit simultaneously takes the electric signal reflecting the temperature of the upper substrate 3 or the lower substrate 1 as a compensation signal to perform temperature compensation on the electric signal of the object to be measured, and further eliminates the influence of the temperature on the performance of the device, so that the A in the formula (3)tThe coefficient does not change along with the temperature, and the temperature coefficient of the MEMS device is compensated.
In addition, a target temperature may be set in advance for the signal processing circuit, and since the heating electrode has only a function of raising the temperature, the set target temperature is higher than the temperature of the device operating environment. The signal processing circuit calculates the difference between the substrate temperature and the preset target temperature according to the electric signals reflecting the temperatures of the upper substrate 3 and the lower substrate 1, respectively inputs direct current or alternating current control electric signals to the heating electrodes of the upper substrate 3 and the lower substrate 1 through calculation, heats the upper substrate 3 and the lower substrate 1, and adjusts the intensity of the control electric signals input to the heating electrodes by the control circuit, so that the temperatures of the upper substrate 3 and the lower substrate 1 are the same as the preset target temperature. For example: the target temperature can be preset to 40 ℃, when the temperature of the working environment of the MEMS device is-20 ℃, the working temperature of the MEMS device is lower than 40 ℃, the control circuit adopts a corresponding control scheme to control the temperature of the upper substrate 3 and the lower substrate 1 of the MEMS device to 40 ℃, and compared with the working temperature below 0 ℃, the MEMS device has relatively better performance at the working temperature of 40 ℃.
Claims (4)
1. A temperature control system for a MEMS device, characterized by: temperature detection electrodes (5), signal detection electrodes (6) and heating electrodes (4) are arranged on the surfaces of an upper substrate and a lower substrate of the MEMS device, the signal detection electrodes (6) on the surface of the upper substrate and the signal detection electrodes (6) on the surface of the lower substrate are connected with a signal amplification circuit, the temperature detection electrodes (5) on the surface of the upper substrate are connected with a first temperature detection circuit, the temperature detection electrodes (5) on the lower substrate are connected with a second temperature detection circuit, the heating electrodes (4) on the surface of the upper substrate and the heating electrodes (4) on the surface of the lower substrate are connected with a signal processing circuit, and the first temperature detection circuit, the second temperature detection circuit and the signal amplification circuit are connected with the signal processing circuit;
the first temperature detection circuit and the second temperature detection circuit transmit the electric signals detected by the temperature detection electrodes to the signal processing circuit, the signal processing circuit judges whether the working temperatures of the upper substrate surface and the lower substrate surface of the MEMS device are suitable or not, and the signal processing circuit controls the working temperatures of the upper substrate surface and the lower substrate surface of the MEMS device by controlling the intensity of the electric signals input to the heating electrodes.
2. A temperature control system for a MEMS device as claimed in claim 1, wherein: after the temperature detection circuit transmits the electric signals detected by the temperature detection electrodes to the signal processing circuit, the signal processing circuit judges whether the working temperatures of the upper substrate surface and the lower substrate surface of the MEMS device have temperature difference or not, and eliminates the temperature difference by controlling the intensity of the electric signals input to the heating electrodes.
3. A temperature control system for a MEMS device as claimed in claim 2, wherein: after the working temperature difference between the upper substrate surface and the lower substrate surface of the MEMS device is eliminated, the signal processing circuit acquires the resistance value of the temperature detection electrode, and the temperature coefficient of the MEMS device is compensated by using the resistance value.
4. A temperature control system for a MEMS device as claimed in claim 1, wherein: after the temperature detection circuit transmits the electric signals detected by the temperature detection electrode to the signal processing circuit, the signal processing circuit judges whether the working temperatures of the upper substrate surface and the lower substrate surface of the MEMS device reach the preset temperature or not, and controls the working temperatures of the upper substrate surface and the lower substrate surface of the MEMS device by controlling the intensity of the electric signals input to the heating electrode.
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