Micro capacitance measurement method and special device

Abstract

The invention discloses a micro capacitance measurement method and a special device. The device is provided with a sine wave voltage driving source, a current-limiting resistor, a preposed operational amplifier, a feedback resistor, a voltage follower, an amplifying unit, a reference signal generator, a multiplying unit, a low-pass filter, a selective switch and a detection processing unit. The precision and the resolution of the method are high to the micro capacitance measurement.

Description

technical field [0001] The invention relates to electronic measurement technology, in particular to a microcapacitance measurement method. Background technique [0002] In the scientific research and manufacturing of semiconductor microelectronics, materials, biomedicine, and micro-electromechanical systems, the detection of weak capacitance is widely involved. Research and development of weak capacitance monitoring technology and devices has important practical significance. Microcapacitance measurement is basically divided into three types, namely, charge injection method (also known as charge and discharge method), AC excitation method, and AC excitation method with balanced capacitance. [0003] figure 2 It is the schematic diagram of the microcapacitance measurement based on the charge injection method. In the figure, E is the DC voltage source, Cx is the measured microcapacitance, Cas and Cbs are the stray capacitance of the measurement circuit, Z F is the feedback...

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Problems solved by technology

[0004] The disadvantages of the charge injection method are: (1) The voltage at both ends of the capacitor cannot be mutated, and the charge and discharge current of the measured capacitor is relatively large. Due to the limited output current capability of the operational amplifier, the negative input terminal cannot be guaranteed to be a virtual ground, that is, the operational amplifier cannot always work in a linear state. range, the influence of Cbs cannot be completely eliminated; (2) because the voltage source has a certain internal impedance, the influence of Cas cannot be completely eliminated; (3) the switch control signal of the electronic switch causes additional damage to the measured capacitance through the parasitic capacitance of the electronic switch Inject charge; (4) The voltage source cannot be stable when the measured capacitance is large; (5) If the feedback impedance contains capacitance, the detection accuracy will be affected by the capacitance accuracy and excitation frequency

[0006] The disadvantages of the AC excitation method are: (1) The voltage at both ends of the capacitor cannot change abruptly, and the charge and discharge current of the measured capacitor is relatively large. Due to the limited output current capability of the operational amplifier, the negative input terminal cannot be guaranteed to be a virtual ground, that is, the operational amplifier cannot always work in a linear state. range, the influence of Cbs cannot be completely eliminated; (2) because the voltage source has a certain internal impedance, the influence of Cas cannot be completely eliminated; (3) the voltage source cannot be stable when the measured capacitance is large; (4) if the feedback impedance contains Capacitance, the detection accuracy is affected by the capacitance accuracy and excitation accuracy

[0008] The disadvantages of the AC excitation method with balanced capacitors are: (1) The voltage at both ends of the capacitor cannot change suddenly, and the charge and discharge current of the measured capacitor is relatively large. Always work in the linear range, and the influence of Cbs cannot be completely eliminated; (2) Due to the certain internal impedance of the voltage source, the influence of Cas cannot be completely eliminated; (3) The voltage source cannot be stable when the measured capacitance is large; (4) If the feedback impedance contains capacitance, the detection accuracy is affected by the capacitance accuracy and excitation accuracy frequency; (5) A balanced capacitance with high precision and high stability is required

[0009] The patent "Micro-capacitance participating in the measurement circuit" (application number 200810040836.9) proposes a micro-capacitance measurement method based on reference capacitance. The accuracy and stability of the reference capacitance limit the accuracy of micro-capacitance measurement

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