A MEMS structure measurement system

Abstract

This application discloses a measurement system for MEMS structures, used to measure the sensitivity of a MEMS structure under test. The system includes: a reference MEMS structure for receiving excitation signals and vibrating; the MEMS structure under test for receiving excitation signals and vibrating; a laser vibrometer for measuring the vibration amplitudes of the diaphragms of the reference and the MEMS structures under test; and the sensitivity of the MEMS structure under test is obtained based on the ratio of the vibration amplitude of the reference MEMS structure to the vibration amplitude of the MEMS structure under test, and the sensitivity of the reference MEMS structure. This measurement system for MEMS structures eliminates the need to measure sensitivity in an anechoic chamber.

Description

Technical Field

[0001] The present application relates to the technical field of MEMS (abbreviation of Microelectro Mechanical Systems), and in particular to a measurement system of a MEMS structure. Background Art

[0002] A MEMS microphone is a transducer that converts acoustic energy into electrical energy. One characteristic used to define whether a MEMS microphone is operating properly is sensitivity. The sensitivity of a MEMS microphone is determined by transmitting acoustic energy to the MEMS microphone and then measuring the response of the MEMS microphone and obtaining the output voltage.

[0003] When measuring the sensitivity of a microphone, the method generally used is: using a loudspeaker in an anechoic chamber to apply equal sound pressure to the standard microphone and the microphone to be tested, respectively. Both the standard microphone and the microphone to be tested can convert the sound pressure into an electrical signal. At this time, the sensitivity of the microphone to be tested is measured based on the known sensitivity of the standard microphone and the acquired electrical signal.

[0004] However, this technology requires measuring the sensitivity of the microphone in an anechoic chamber, which limits the measurement site of the microphone and cannot be applied in other places.

[0005] With regard to the problem of measurement site limitations in related technologies, no effective solution has been proposed so far. Summary of the invention

[0006] In view of the problem of limited measurement sites in related technologies, the present application proposes a measurement system for a MEMS structure, which does not require measuring the sensitivity of the MEMS structure in an anechoic chamber.

[0007] The technical solution of this application is implemented as follows:

[0008] According to one aspect of the present application, a MEMS structure measurement system is provided, which is used to measure the sensitivity of a MEMS structure to be measured, comprising:

[0009] A reference MEMS structure is used to receive an excitation signal and vibrate;

[0010] The MEMS structure to be tested is used to receive the excitation signal and vibrate;

[0011] A laser vibrometer, used to measure the vibration amplitude of the diaphragm of the reference MEMS structure and the MEMS structure to be measured;

[0012] The sensitivity of the MEMS structure to be measured is obtained based on the ratio of the vibration amplitude of the reference MEMS structure to the vibration amplitude of the MEMS structure to be measured and the sensitivity of the reference MEMS structure.

[0013] Wherein, the measurement system further comprises:

[0014] A signal generator, used for generating an original excitation signal;

[0015] The power amplifier is used to receive and amplify the original excitation signal and output the excitation signal.

[0016] The reference MEMS structure includes a piezoelectric MEMS microphone, and the MEMS structure to be tested is the same as the reference MEMS structure.

[0017] The original excitation signal is a frequency sweep pulse train signal with a frequency range of 100 Hz to 20 kHz.

[0018] The original excitation signal is a frequency sweep pulse train signal with a frequency range of 100 Hz to 10 kHz.

[0019] The sensitivity range of the piezoelectric MEMS microphone is -70dBV / Pa to -30dBV / Pa.

[0020] Wherein, the sensitivity of the reference MEMS structure is measured by GB T 9401-1988 standard or an equivalent standard.

[0021] Wherein, measuring the vibration amplitude of the diaphragm is equivalent to measuring the displacement, velocity or acceleration of the diaphragm.

[0022] Wherein, measuring the vibration amplitude of the diaphragm is equivalent to measuring the velocity of the diaphragm.

[0023] Wherein, the laser vibrometer includes an out-of-plane, single-point, microscopic Doppler vibrometer.

[0024] In the MEMS structure of the above embodiment, the laser vibrometer has good dynamic response, high linear sensitivity and high precision in measuring the MEMS structure to be measured. Moreover, the laser vibrometer does not need to be in contact with the reference MEMS structure or the MEMS structure to be measured, thus realizing non-contact measurement. Moreover, the laser vibrometer can be used in an ordinary quiet indoor environment, and does not need to be limited to an anechoic chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic diagram of a measurement system for a MEMS structure is shown in accordance with some embodiments. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0028] See also Figure 1 According to an embodiment of the present application, a measurement system for a MEMS structure is provided, which is used to measure the sensitivity of a MEMS structure to be measured. The measurement system is not limited to use in an anechoic chamber, and can be used in a normal quiet indoor environment, thereby improving the measurement efficiency of the MEMS structure and reducing the measurement cost.

[0029] In some embodiments, a measurement system for a MEMS structure includes a signal generator, a power amplifier, a reference MEMS structure, a MEMS structure to be measured, and a laser vibrometer.

[0030] In some embodiments, the signal generator is used to generate an original excitation signal, the original excitation signal is a swept frequency pulse train signal, and the frequency range is 100 Hz to 20 kHz. Preferably, the frequency range is 100 Hz to 10 kHz. The power amplifier is used to receive and amplify the original excitation signal and output the excitation signal.

[0031] In some embodiments, the reference MEMS structure is used to receive an excitation signal and vibrate. The MEMS structure to be tested is used to receive an excitation signal and vibrate. In other words, the reference MEMS structure and the MEMS structure to be tested are used to convert electrical energy into acoustic energy, so that the sensitivity ratio relationship between the reference MEMS structure and the MEMS structure to be tested is obtained by comparing the acoustic energy signals of the reference MEMS structure and the MEMS structure to be tested. In some embodiments, the sensitivity range of the reference MEMS structure is -70dBV / Pa to -30dBV / Pa, measured by GB T 9401-1988 standard or equivalent standards. The reference MEMS structure includes a piezoelectric MEMS microphone. The MEMS structure to be tested has the same basic structure as the reference MEMS structure, and the MEMS structure to be tested may also include a piezoelectric MEMS microphone.

[0032] The laser vibrometer is used to measure the vibration amplitude of the diaphragm of the reference MEMS structure and the MEMS structure to be measured. The laser vibrometer includes out-of-plane, single-point, and microscopic Doppler vibrometers. Measuring the vibration amplitude of the diaphragm is equivalent to measuring the displacement, velocity, or acceleration of the diaphragm. Preferably, the laser vibrometer is used to measure the velocity of the diaphragm.

[0033] In some embodiments, the sensitivity of the MEMS structure to be measured is obtained based on the ratio of the vibration amplitude of the reference MEMS structure to the vibration amplitude of the MEMS structure to be measured and the sensitivity of the reference MEMS structure.

[0034] In principle, the particle velocity in the reference MEMS structure and the MEMS structure to be tested under steady-state conditions is proportional to their respective sound pressures, and the particle velocity is proportional to the generated electrical energy. Therefore, when the same sound pressure is applied to the reference MEMS structure and the MEMS structure to be tested, the reference MEMS structure and the MEMS structure to be tested generate different electrical energies due to their different sensitivities. In other words, under the same sound pressure excitation, the sensitivity of the MEMS structure is proportional to the velocity / amplitude generated. For piezoelectric devices, the process of converting sound energy into electrical energy is the positive piezoelectric effect. In addition, piezoelectric materials also have the inverse piezoelectric effect, which is the process of converting applied electrical energy into sound energy as described in this application. For similar piezoelectric devices with the same piezoelectric material, the efficiency of the positive piezoelectric effect is proportional to the efficiency of the inverse piezoelectric effect. Therefore, the ratio of the vibration amplitude of the reference MEMS structure to the vibration amplitude of the MEMS structure to be tested is equal to the ratio of the sensitivity of the reference MEMS structure to the sensitivity of the MEMS structure to be tested. Thus, the measurement sensitivity is achieved using a laser vibrometer.

[0035] In summary, the laser vibrometer uses the Doppler effect to measure the amplitude (or sound wave) of the reference MEMS structure and the MEMS structure to be measured, respectively, so as to obtain the sensitivity of the MEMS structure to be measured based on the sensitivity of the reference MEMS structure. The advantages of this measurement system are: the laser vibrometer has good dynamic response, high linear sensitivity and high precision in measuring the MEMS structure to be measured. Moreover, the laser vibrometer does not have to be in contact with the reference MEMS structure or the MEMS structure to be measured, thus realizing non-contact measurement. Moreover, the solution of the present application does not require a loudspeaker sound source, so the laser vibrometer can be used in an ordinary quiet indoor environment, and does not have to be limited to an anechoic chamber.

[0036] To sum up, the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A MEMS structure measurement system for measuring the sensitivity of a MEMS structure to be measured. It is characterized in that include: A reference MEMS structure is used to receive an excitation signal and vibrate; The MEMS structure to be tested is used to receive the excitation signal and vibrate; A laser vibrometer, used to measure the vibration amplitude of the diaphragm of the reference MEMS structure and the MEMS structure to be measured; A signal generator, used for generating an original excitation signal; A power amplifier, used for receiving and amplifying the original excitation signal and outputting the excitation signal; Acquire the sensitivity of the MEMS structure to be measured based on the ratio of the vibration amplitude of the reference MEMS structure to the vibration amplitude of the MEMS structure to be measured and the sensitivity of the reference MEMS structure; The reference MEMS structure includes a piezoelectric MEMS microphone, the MEMS structure to be measured is the same as the reference MEMS structure, and measuring the vibration amplitude of the diaphragm is equivalent to measuring the displacement, velocity or acceleration of the diaphragm.

2. The measurement system of the MEMS structure according to claim 1, It is characterized in that The original excitation signal is a frequency sweep pulse train signal with a frequency range of 100 Hz to 20 kHz.

3. The measurement system of the MEMS structure according to claim 2, It is characterized in that The original excitation signal is a frequency sweep pulse train signal with a frequency range of 100 Hz to 10 kHz.

4. The measurement system of the MEMS structure according to claim 3, It is characterized in that The sensitivity range of the piezoelectric MEMS microphone is -70dBV / Pa to -30dBV / Pa.

5. The measurement system of the MEMS structure according to claim 1, It is characterized in that The sensitivity of the reference MEMS structure is measured by GB T 9401-1988 standard or an equivalent standard.

6. The measurement system of the MEMS structure according to claim 1, It is characterized in that Measuring the vibration amplitude of the diaphragm is equivalent to measuring the velocity of the diaphragm.

7. The measurement system of the MEMS structure according to claim 1, It is characterized in that The laser vibrometers include out-of-plane, single-point, microscopic Doppler vibrometers.

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